Release v0.30.0: sync user guide (DOCS.md) with the shipped app

Documentation-only minor. The guide had drifted since it was first
written; brought back in sync with v0.7.0–v0.29.0:

- "Signing in" rewritten: email + one-time-code, optional passcode,
  trust-device 30d, optional Turnstile, and the beta-request → pending
  → admin-grant gate, plus admin-create + invite-claim. The vestigial
  email allowlist is no longer described as the gate.
- "Proposing a new RFC": four → five fields (optional use-case #26) +
  AI tag-suggestion disclosure (#27).
- "Roles & permissions": documents the pending state.
- New "Invitations, cross-references, and contribution requests"
  section (#12 owner invites; #28 auto-link / create-RFC / ask-to-
  contribute).
- New "Privacy and cookies" section (#11/#13).

No code/schema/API/config/overlay/secret change — DOCS.md is served
verbatim by /api/docs. VERSION + frontend/package.json bumped to 0.30.0.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -23,6 +23,439 @@ skip versions are the composition of each intervening adjacent
 release's steps in order — no A-to-B path is pre-computed beyond
 that.
 
+## 0.30.0 — 2026-05-29
+
+**Minor — documentation: the user guide (`DOCS.md`, served at
+`/docs/user-guide` via `/api/docs`) brought back in sync with the
+shipped app. No code, schema, API, config, overlay, or secret change —
+a plain code deploy serves the updated guide. Shipped from driver
+session 0037.0.**
+
+The guide had drifted since it was first written: it still described
+the pre-OTC email *allowlist* sign-in, listed four propose-RFC fields,
+and predated several shipped surfaces. Updated to match v0.7.0–v0.29.0:
+
+- **Signing in** rewritten for the email + one-time-code flow (v0.7.0),
+  optional passcode (v0.10.0), trust-this-device for 30 days (v0.11.0),
+  optional Cloudflare Turnstile (v0.12.0), and the beta-access request →
+  `pending` → admin-`granted` gate (v0.8.0 / #6), plus the admin-create
+  + invite-claim path (v0.17.0 / #16). The vestigial allowlist is no
+  longer described as the gate.
+- **Proposing a new RFC** now lists five fields, adding the optional
+  "What will you be using this RFC for?" use-case field (#26) and noting
+  the AI tag-suggestion disclosure (#27).
+- **Roles & permissions** documents the `pending` state.
+- New **Invitations, cross-references, and contribution requests**
+  section covers owner invitations (#12) and the RFC auto-link /
+  create-RFC / ask-to-contribute affordances (#28).
+- New **Privacy and cookies** section covers the consent banner and
+  consent-gated analytics (#11 / #13).
+
+Upgrade steps: none — documentation-only; the change is the `DOCS.md`
+file served verbatim by `/api/docs`. A plain code deploy at this tag
+serves it. A deployment that overrides the guide via `DOCS_PATH`
+supplies its own copy and is unaffected.
+
+## 0.29.0 — 2026-05-28
+
+**Minor — roadmap #28 Parts 2 + 3: offer-to-create-an-RFC for strong-
+candidate terms, and offer-to-contribute-to-a-pending-RFC. One auto-
+applied migration (024, additive: a new `contribution_requests` table).
+No config/overlay/secret change; no nginx/systemd change. A plain code
+deploy + the auto-migration picks it up. Shipped from driver session
+0033.0.**
+
+Both parts extend the v0.26.0 (#28 Part 1) read-time scanner
+(`backend/app/rfc_links.py`) and its renderer
+(`frontend/src/components/LinkedText.jsx`). The scanner now sorts each
+matched term into one of three buckets — active link (Part 1, unchanged),
+pending-RFC contribute offer (Part 3), create-RFC offer (Part 2) — in one
+pass, with precedence active > pending > candidate at any position. The
+backend still emits only structured segments (never HTML), so the surface
+stays XSS-safe by construction.
+
+- **Part 2 — create-RFC offers.** A *strong-candidate* term — a
+  **multi-word tag** from the #27 tag taxonomy that has no defining RFC
+  (no active or super-draft RFC whose slug/title is that term) — renders,
+  for a viewer with create rights (`permission_state='granted'`), as an
+  inline "+ create RFC" affordance. Clicking opens the propose-RFC modal
+  with the term pre-filled as the title (`ProposeModal` gained an
+  `initialTitle`; the affordance routes via `?propose=<term>`, read in
+  `App.jsx`). The heuristic is deliberately conservative — multi-word is
+  the same false-positive guard the title rule uses, so a single common
+  tag word (`identity`) is never offered. Broader candidate detection
+  (capitalized phrases mined from text, terms repeated across recent PRs,
+  or the #27 Haiku `ANTHROPIC_API_KEY` pathway) is a sanctioned but
+  deferred extension.
+- **Part 3 — contribute-to-pending offers.** A term matching a *pending*
+  RFC — a super-draft (`state='super-draft'`: accepted as an idea, owned,
+  with a contribution surface, not yet graduated) — renders, for a
+  signed-in non-owner, as an inline "ask to contribute" affordance
+  carrying the owner's display name ("<owner> is working on an RFC for
+  '<term>'"). It opens a contribute-request form (`?contribute=<slug>`)
+  with three fields — **who I am** (required), **why I'm asking**
+  (required), **what I'd use it for** (optional, mirroring #26). Submitting
+  lands a `contribution_requests` row and one actionable §15 inbox
+  notification per owner (new kind `contribution_request_on_pending_rfc`,
+  category `personal-direct` — so it reuses the existing
+  `email_personal_direct` preference, no new toggle). In the inbox the
+  owner sees the requester's who/why/use-case inline with **Accept** /
+  **Decline**. Accept fires #12's owner-invite flow with the requester as
+  the invitee (a `contributor` `rfc_invitations` row + the existing invite
+  email) and echoes a notification back to the requester; Decline closes
+  the request and notifies the requester. Pre-merge idea PRs (not yet in
+  `cached_rfcs`, no contribution surface) are deliberately out of scope —
+  a documented future extension.
+
+New endpoints (all under the existing `/api` router):
+`GET /api/rfcs/{slug}/contribution-target`,
+`POST /api/rfcs/{slug}/contribution-requests`,
+`POST /api/rfcs/{slug}/contribution-requests/{id}/accept`,
+`POST /api/rfcs/{slug}/contribution-requests/{id}/decline`.
+
+The owner-invite issue path was refactored into one reusable chokepoint,
+`api_invitations.issue_invitation(...)`, shared by the manual invite
+endpoint and Part 3's accept path so the dup-guard, token mint, insert,
+and transactional email stay identical.
+
+Upgrade steps:
+
+1. Deployments **MUST** apply the auto-run migration `024` (additive: the
+   new `contribution_requests` table; no existing table or row is
+   touched). The standard deploy path runs pending migrations on start —
+   no manual step beyond deploying the new code.
+2. No config, overlay, or secret change is required. The Part 2 candidate
+   affordance reuses #27's tag taxonomy; it surfaces only when the corpus
+   carries multi-word tags without a defining RFC, and the create
+   affordance renders only for beta-granted viewers. Part 3's email reuse
+   sends through the existing invitation SMTP path — no new key.
+
+## 0.28.0 — 2026-05-28
+
+**Minor — security-hardening follow-up (Session-0026 audit, informational
+findings I3 + I4). No operator action required: no migration, no schema
+change, no config/overlay change, no API/behavior change for any caller.
+A plain code deploy picks it up. Shipped from driver session 0032.0.**
+
+Two informational findings from the Session-0026 audit, both
+framework-internal defense-in-depth:
+
+- **I3 — dead HTML-email branch guarded.** `email_envelope.build_envelope`
+  accepted a `body_html=` argument that built a `multipart/alternative`
+  body, but no send path ever passed it — every rfc-app mail is plain
+  text. An unused branch that would emit HTML built from (potentially
+  unescaped) user content is the C1 stored-XSS class waiting in the mail
+  channel. The branch is now a loud guard: passing `body_html` raises
+  `NotImplementedError`. The argument is kept in the signature for
+  documented future symmetry; enabling HTML mail becomes a deliberate
+  change that MUST HTML-escape user content at the call site and remove
+  the guard in the same commit.
+- **I4 — Turnstile siteverify no longer blocks the event loop.**
+  `turnstile.verify_token` was a synchronous function issuing a blocking
+  `httpx.post` from inside the async `/auth/otc/request` handler, so a
+  slow CloudFlare response stalled the single worker for up to the 10s
+  timeout. It is now `async` and awaits the call on an
+  `httpx.AsyncClient` (matching the codebase's existing async-httpx
+  pattern), isolated behind a narrow `_siteverify_post` seam. The sole
+  caller (`main.py`) now `await`s it.
+
+Upgrade steps: **none.** Both changes are internal. The `verify_token`
+signature changed from sync to `async` (callers must `await`), but the
+only caller is in-tree (`main.py`) and is updated in this release; no
+deployment-facing surface, config key, or migration is affected.
+
+## 0.27.0 — 2026-05-28
+
+**Minor — security-hardening release (Session-0026 audit remediation).
+One auto-applied migration (023); one behavior change that re-prompts
+device-trust; deployments MUST re-apply the nginx + systemd files.**
+This is the work cut as the "v0.25.0 security-hardening" branch; it
+reversioned to 0.27.0 because v0.26.0 (#28) took the next slot while it
+was in flight. Shipped from driver session 0030.0.
+
+- **C1 (Critical) — stored-XSS closed.** Every markdown→HTML sink now
+  routes through one chokepoint, `frontend/src/lib/sanitizeHtml.js`
+  (DOMPurify), before any `innerHTML` / `dangerouslySetInnerHTML` write:
+  `MarkdownPreview`, both `ProposalView` sinks (entry body +
+  `proposed_use_case`), and `Editor`. A hook adds
+  `rel="noopener noreferrer"` to `target=_blank` links. `marked` no
+  longer passes raw HTML / `javascript:` URIs to the DOM, so a
+  contributor can no longer plant a payload that runs in an admin/owner
+  session during review.
+- **H1 — OTC verify is rate-limited.** New `backend/app/ratelimit.py`
+  (per-IP token buckets) gates `/auth/otc/verify`, `/auth/otc/request`,
+  and the passcode check/verify paths; a per-account OTC-verify lockout
+  (migration `023_otc_verify_lockout.sql`) mirrors the passcode lockout.
+- **M1 — device-trust lookup no longer table-scans.** The device-trust
+  cookie value is now `"<row_id>.<raw_token>"`; `device_trust.lookup`
+  reads the one indexed row and bcrypt-checks only it, instead of
+  bcrypt-checking every row in the table on each unauthenticated
+  `/auth/device-trust/start`.
+- **M2 — HTTP security headers** (CSP, HSTS, X-Frame-Options,
+  X-Content-Type-Options, Referrer-Policy) added to the nginx server
+  block. **L8/I1**: `server_tokens off` + legacy TLS1.0/1.1 removed.
+- **M4 — session cookie `Secure` by default** (`SESSION_COOKIE_SECURE`,
+  defaults on; a dev box on plain http sets it `false`).
+- **M5 — bounce webhook fails closed.** An unset
+  `WEBHOOK_EMAIL_BOUNCE_SECRET` now **disables** `/api/webhooks/email-bounce`
+  (503) instead of leaving it open; a dev opts back in with
+  `RFC_APP_INSECURE_BOUNCE_WEBHOOK=1`.
+- **L2/L3** per-IP cooldown + check-endpoint throttle. **L4** systemd
+  sandbox knobs (`CapabilityBoundingSet=`, `ProtectKernel*`,
+  `RestrictAddressFamilies`, `SystemCallFilter`, …).
+
+Upgrade steps:
+
+1. **Migration** — none manual; `023_otc_verify_lockout.sql` auto-applies
+   at startup via `db.run_migrations`.
+2. **Device trust (MUST expect re-prompt)** — the cookie format changed,
+   so existing "trusted device" cookies no longer match; affected users
+   are re-prompted for device verification once. No data migration; old
+   rows are simply never matched and age out.
+3. **nginx + systemd (MUST apply out-of-band)** — the deploy gesture does
+   **not** install `deploy/nginx/ohm.wiggleverse.org.conf` or
+   `deploy/systemd/rfc-app.service`. After deploying the code, copy both
+   to their system locations, then `nginx -t && systemctl reload nginx`
+   and `systemctl daemon-reload && systemctl restart <unit>`. (M2 headers
+   and L4 sandboxing do not take effect until this is done.)
+4. **Bounce webhook (SHOULD)** — bind `WEBHOOK_EMAIL_BOUNCE_SECRET` (or
+   set `RFC_APP_INSECURE_BOUNCE_WEBHOOK=1` for dev). Unset → the endpoint
+   returns 503 (closed). No legitimate bounce source is wired today, so
+   503 is the safe default.
+5. **Session cookie (SHOULD, dev only)** — a deployment served over plain
+   http MUST set `SESSION_COOKIE_SECURE=false` or the session cookie
+   won't be sent. Production over HTTPS leaves it unset (Secure on).
+
+## 0.26.0 — 2026-05-28
+
+**Minor — no schema migration, no new secret, no config, no upgrade
+steps. Additive read-time enrichment; deployments inherit it on deploy
+with nothing to set.** Roadmap item #28 **Part 1**: references to existing
+**accepted** RFCs inside PR descriptions and comment text now render as
+inline links to the referenced RFC. Shipped from driver session 0029.0,
+in parallel with the v0.25.0 security-hardening session — hence the
+version-slot gap (0.25.0 is that session's; this took the next free slot
+per the roadmap's "claims the next available version number" rule).
+
+Parts 2 (offer-to-create-RFC for strong-candidate terms) and 3
+(offer-to-contribute-to-a-pending-RFC) of item #28 are deliberately **not**
+in this release — Part 1 ships first as the easy win, exactly as the
+roadmap row anticipates.
+
+- **Where it links.** The PR review page's description and review
+  comments (`GET /api/rfcs/{slug}/prs/{n}`), and the PR-less per-RFC
+  discussion comments (`GET /api/rfcs/{slug}/discussion/threads/{id}/messages`).
+  Branch-chat (the AI-collaboration surface) is intentionally out of
+  scope for Part 1 — a noted follow-up.
+- **Read-time, not submit-time.** The roadmap row phrases the scan as
+  happening "at submit/post time"; this ships it as **read-time**
+  enrichment instead. The intent the row actually names — "not as live
+  compose preview" — holds (drafts are never scanned, only submitted
+  content on read). Read-time was chosen because (a) links track the
+  *live* accepted-RFC set — a newly-accepted RFC starts linking in older
+  comments, a withdrawn one stops linking everywhere — rather than
+  freezing stale at submit; (b) it needs **no migration** (no derived
+  data to persist); (c) the active-RFC corpus is small and cache-resident,
+  so per-read scanning is cheap. (Recorded as a §19.3-rule-2 spec note in
+  the session transcript.)
+- **XSS-safe by construction.** The backend returns structured *segments*
+  (a list of `{type:"text"}` / `{type:"rfc", slug, label, title}` items),
+  never HTML. The new `LinkedText` frontend component maps segments onto
+  React text nodes and anchors — no `dangerouslySetInnerHTML` — so a
+  comment author cannot inject markup through this path. Every enriched
+  field keeps its raw `text`/`description` alongside the `*_segments`, so
+  any non-segment-aware caller is unaffected.
+- **Conservative matching (false-positive-averse).** A reference links
+  only when it is unlikely to be coincidental: an `rfc_id` token
+  (`RFC-0001`), a **multi-word** title (`Open Human Model`), or a
+  **hyphenated** slug (`open-human-model`). A single common-word title or
+  slug (a hypothetical RFC titled "Human") is **not** auto-linked — that
+  would turn every prose "human" into a link. Matching is case-insensitive,
+  word-boundary-anchored, longest-match-wins, and suppresses an RFC's
+  self-references inside its own PR/discussion. The roadmap's "curated
+  canonical-terms list" remains an explicit future opt-in rather than a
+  guessed-at default. New module: `backend/app/rfc_links.py`.
+
+Tests: 12 new (`test_rfc_links_vertical.py`) — 9 scanner units (gating
+rules, word boundaries, longest-match, case-insensitivity, casing
+preservation, the rfc_id/multi-word/hyphenated gates) plus 3 end-to-end
+(PR description + review comment + discussion comment all surface
+`*_segments`; self-reference suppression). Full suite 363 green; frontend
+builds clean.
+
+Upgrade steps:
+
+1. None. This release is purely additive: no migration, no new
+   environment variable, no secret, no overlay. A deployment picks up RFC
+   auto-linking the moment it deploys this version. (RFCs only link once
+   they are in the `active` state — proposed/super-draft and withdrawn
+   RFCs are never link targets, matching the §11.3 universal-public read
+   rule.)
+
+## 0.24.0 — 2026-05-28
+
+**Minor — one new secret required before this version serves tag
+suggestions; no schema migration; no behavior change for deployments
+that do not bind the key.** Roadmap item #27: as a contributor fills in
+the propose-RFC form, the backend asks Claude Haiku to recommend tags
+drawn from the collection's existing tag set, surfaced as clickable
+suggestion chips. Shipped from driver session 0025.0. This is the §9.1
+"Slice 2" AI-suggested chips that the propose modal has carried a
+deferred placeholder for since Slice 1.
+
+- **`POST /api/rfcs/suggest-tags`** (contributor-gated, per-user
+  rate-limited). Takes the partial draft (`title`, `pitch`,
+  `use_case`) and returns `{ "suggestions": [{ "tag", "confidence" },
+  …] }`. The model is constrained to the corpus's existing tags — v1
+  tags are free-form chip input, so "the taxonomy" is the de-facto set
+  of distinct tags the existing RFCs carry. The model MUST NOT invent
+  tags; taxonomy extension is a deliberate out-of-scope follow-up.
+- **Always Claude Haiku, for cost.** Tag suggestion uses Haiku
+  regardless of the `ENABLED_MODELS` chat-picker universe, via the new
+  `providers.construct_haiku()` factory. There is no RFC slug at propose
+  time, so the §6.7 per-RFC funder credential path does not apply — the
+  surface runs on the operator's own `ANTHROPIC_API_KEY`.
+- **Degrades to silence, never error.** No key bound, an empty corpus,
+  an empty draft, a rate-limited caller, or an unparseable model reply
+  all yield an empty list; the propose modal hides its suggestion row,
+  and the rest of the app is unaffected. So a deployment that does not
+  set the key sees no change at all.
+- **Privacy disclosure.** The modal carries an inline note that the
+  draft text is sent to Anthropic to generate the suggestions. This is
+  required for honesty (the text leaves the deployment before the RFC
+  is submitted); cookie-consent does not gate it because the user has
+  actively typed into a draft surface. The exact wording wants a
+  counsel pass before OHM's deploy, per the #22 drafting discipline.
+- **Frontend.** `ProposeModal` debounce-posts the draft (700 ms, with a
+  stale-response guard); suggestion chips are clickable and add to the
+  tag list (nothing auto-applies). `api.suggestTags()` is forgiving —
+  any non-OK response resolves to `[]`.
+
+Tests: 11 new (`test_tag_suggest_vertical.py`) — contributor-gating,
+universe-constrained filtering, no-key / empty-corpus / rate-limit
+paths, plus units for the universe gather, the tolerant reply parser,
+the max cap, the empty-draft short-circuit, and provider-failure
+fallback. Full suite 351 green.
+
+Upgrade steps:
+
+1. You **MUST** bind `ANTHROPIC_API_KEY` for the suggestion surface to
+   work. On OHM this is an operator gesture — the key never touches the
+   conversation. Set it from your own terminal via stdin (so the bytes
+   never land in shell history):
+
+   ```bash
+   printf '%s' "$(pbpaste)" | .venv/bin/ohm-rfc-app-flotilla \
+       secret set ohm-rfc-app ANTHROPIC_API_KEY
+   ```
+
+   (The §18 chat stack already reads this same key, so a deployment
+   that has chat configured **MAY** already have it bound — confirm with
+   `flotilla secret list ohm-rfc-app`.) If the key is absent the app
+   still boots and serves normally; tag suggestions are simply
+   unavailable until it is set.
+2. You **MAY** tune the per-user rate limit via `TAG_SUGGEST_RATE_MAX`
+   (default 30) and `TAG_SUGGEST_RATE_WINDOW_SECONDS` (default 60). The
+   defaults apply when unset.
+3. You **SHOULD** have counsel review the modal's disclosure wording
+   before exposing the surface to users, per the #22 drafting
+   discipline — the copy is honest as written, but the legal review is
+   the right call for any "your text is sent to a third party" notice.
+
+## 0.23.0 — 2026-05-28
+
+Roadmap item #29: signing in lands the user on their most recently
+viewed app state instead of the empty-state home view. Shipped from
+driver session 0022.0. Per-user, server-side, on by default; first-ever
+sign-ins still land on home.
+
+1. **Server-side last-state.** A new `user_session_state` table holds one
+   row per user: `last_route TEXT`, `last_route_state TEXT` (light view
+   state encoded as JSON — SQLite has no native JSONB — never draft-buffer
+   contents), `resume_enabled INTEGER NOT NULL DEFAULT 1`, and
+   `last_updated_at`. Per-user (not per-device), matching the
+   "go to where I was last" intent.
+2. **Route-change capture.** A new frontend hook (`frontend/src/lib/
+   useLastState.js`) debounce-posts the current route + light state to
+   `PUT /api/me/last-state` for authenticated users only; anonymous
+   sessions are a no-op. The handler upserts the user's row and no-ops
+   when `resume_enabled` is 0.
+3. **Sign-in redirect.** The stored `last_route` (+ decoded state +
+   `resume_enabled`) is folded onto the existing `/api/auth/me` payload
+   (no new GET endpoint), so the frontend reads it on boot. On a hard
+   sign-in landing (app booted on `/`), the app redirects to the stored
+   route. The redirect is gated on the #21-Part-C Amplitude `identify`
+   having fired (`identifyReady`), preserving identify-then-track
+   ordering — the first event on the resumed route carries the user_id.
+4. **Edge cases.** Stale routes (an RFC since withdrawn or now
+   unreadable) are a graceful no-op — existing routing falls through to
+   the catalog/empty-state. Opt-out ships at the column level
+   (`resume_enabled`); the profile-settings toggle UI is a follow-up.
+   Stored state is route + light view state only, never draft contents
+   (documented in `SPEC.md` §6.8).
+
+Migration `022_user_session_state.sql` creates the table. No new
+environment variables, overlay keys, or secrets.
+
+Upgrade steps:
+
+1. Deployments **MUST** apply database migrations; `022_user_session_state.sql`
+   runs automatically on next boot (the migration runner globs
+   `backend/migrations/*.sql` and applies any not yet recorded in
+   `schema_migrations`). The migration is additive — a new table — and
+   requires no data backfill.
+2. No new environment variables, overlay keys, or secrets. No operator
+   action beyond the standard `flotilla deploy ohm-rfc-app`.
+
+## 0.22.0 — 2026-05-28
+
+Roadmap item #26: an optional **"What will you be using this for?"**
+field on both propose surfaces. Shipped from driver session 0022.0.
+Additive and backward-compatible — no behavior changes for anyone who
+leaves the field blank.
+
+1. **Propose-RFC modal.** Below the required "Why is this RFC needed?"
+   field (`pitch`) sits a new optional **"What will you be using this
+   RFC for?"** textarea. "Needed" is the abstract justification; "using
+   it for" is the concrete ground-truth use case — captured without
+   being forced.
+2. **Propose-PR modal.** Below the required "Why is this change needed?"
+   field (`description`) sits a new optional **"What will you be using
+   this change for?"** textarea.
+3. **Display.** The RFC view (`RFCView` / `ProposalView`) and PR review
+   view (`PRView`) render the captured use case alongside the existing
+   "why" text, with a muted "left blank" treatment when absent.
+4. **Persistence (deployment note).** In this deployment the framework's
+   `rfcs` / PR surfaces are the Gitea-backed cache tables `cached_rfcs`
+   / `cached_prs`, rebuilt by the reconciler. Because the propose write
+   path is endpoint → Gitea → reconcile (and the reconciler doesn't
+   carry the new field), the durable home is a canonical, reconcile-proof
+   side table `proposed_use_cases` (keyed by `(scope, pr_number)`) that
+   the propose/open endpoints write directly and the view endpoints read
+   back. The literal nullable `proposed_use_case` columns named by the
+   roadmap are also added to `cached_rfcs` / `cached_prs` for parity and
+   any future reconciler that learns to carry the field. NULL/blank use
+   cases simply never write a side-table row — absence is "left blank".
+
+Migration `021_proposed_use_case.sql` adds the two cache columns
+(`ALTER TABLE … ADD COLUMN proposed_use_case TEXT`), the
+`proposed_use_cases` canonical table, and its lookup indexes. The
+reconciler's upsert (`ON CONFLICT DO UPDATE`) sets only known columns,
+so the added cache columns survive reconciles. Backend validators accept
+the field as NULL/omitted (no required-validation) with an 8000-char cap
+matching the existing PR `description` bound; blank/whitespace is treated
+as absent.
+
+Upgrade steps:
+
+1. Deployments **MUST** apply database migrations; `021_proposed_use_case.sql`
+   runs automatically on next boot (the migration runner globs
+   `backend/migrations/*.sql` and applies any not yet recorded in
+   `schema_migrations`). The migration is additive — nullable cache
+   columns plus a new table — and requires no data backfill.
+2. No new environment variables, overlay keys, or secrets. No operator
+   action beyond the standard `flotilla deploy ohm-rfc-app`.
+
 ## 0.21.0 — 2026-05-28
 
 UX-polish wave. Roadmap items #31 (comprehensive UX polish — foundation

DOCS.md

@@ -39,23 +39,44 @@ thread. Every write affordance is replaced with a sign-in prompt.
 
 ## Signing in
 
-While the framework is in private beta, only invited email addresses
-can complete sign-in. If your email is on the allowlist, the
-"Sign in" button in the header completes the flow and lands you on
-the catalog with full read and write access. If your email is not on
-the allowlist, you'll be sent to a short "pending" page explaining
-the gate.
+Anyone can start the sign-in flow with their own email address — there
+is no invite-only allowlist. Sign-in is passwordless:
 
-Once you have an account, you're a **contributor** by default — the
-role that grants every write affordance the app exposes, scoped by
-the per-RFC and per-branch rules described below.
+1. **Enter your email.** If the deployment has human verification
+   enabled (a Cloudflare Turnstile challenge), you complete it here.
+2. **Enter the one-time code.** The app emails you a short numeric
+   code; entering it signs you in. Codes expire after a few minutes,
+   and repeated wrong entries briefly lock the email.
+3. **Set a passcode (optional).** After your first code sign-in you
+   can set a passcode. On later visits you sign in with email +
+   passcode, with the one-time code as the forgot-passcode fallback.
+4. **Trust this device (optional).** You can mark a device trusted for
+   30 days to skip the code/passcode step on it. Trusted devices are
+   listed in your settings and can be revoked individually or all at
+   once.
+
+### Getting write access
+
+Signing in gives you an account, but write access is gated. The first
+time you sign in you're asked for your first name, last name, and a
+short note on why you'd like access; you then land on a "request in
+review" page. While your account is **pending**, you can read
+everything an anonymous visitor can but cannot write — no chat,
+propose, branch, PR, or discussion post. Once an admin **grants** your
+account you become a **contributor**, the role that carries every
+write affordance the app exposes, scoped by the per-RFC and per-branch
+rules described below.
+
+An admin can also create your account ahead of time and email you an
+invite link. Clicking it claims the account and signs you in with the
+role the admin assigned, skipping the one-time-code step.
 
 ---
 
 ## Proposing a new RFC
 
 A new RFC begins as a proposal. The "+ Propose new RFC" button at
-the bottom of the catalog opens a small modal that collects four
+the bottom of the catalog opens a small modal that collects five
 things:
 
 - **Title.** The word, concept, or topic this RFC would define.
@@ -65,8 +86,13 @@ things:
   inline.
 - **Pitch.** One or two paragraphs answering *why this RFC is
   needed*. This becomes the body of the entry.
-- **Tags.** Optional. The AI suggests tags from the pitch; you can
-  accept, dismiss, or type your own.
+- **Use case.** Optional. *What will you be using this RFC for?* —
+  the concrete application driving the proposal, as distinct from the
+  abstract case for it. Leaving it blank is fine.
+- **Tags.** Optional. If the deployment has AI tag suggestion
+  enabled, suggested tags appear as you fill the form (with an inline
+  note that the text you've entered is sent to the model that
+  generates them); you can accept, dismiss, or type your own.
 
 Submitting the modal does one concrete thing: it opens a pull
 request against the framework's meta repository, adding one new
@@ -167,6 +193,51 @@ either requires a contributor account.
 
 ---
 
+## Invitations, cross-references, and contribution requests
+
+Three connected surfaces help the right people find and join the
+right RFC.
+
+### Owner invitations
+
+An RFC's owner (or an app-wide admin or owner) can invite a specific
+person to that RFC from the "Invitations" control in the RFC header.
+The invite names an email and a role for *this RFC*:
+
+- **contributor** — can open PRs and join the discussion;
+- **discussant** — can join the discussion only.
+
+The invitee gets an email with an accept link; accepting adds them as
+a collaborator on that RFC. The invitations panel lists every invite
+with its status (pending / accepted / expired / revoked); pending
+invites can be revoked. An invitation is per-RFC — it does not change
+the invitee's app-wide role, and it cannot lift the pending gate: the
+invitee still needs a granted account to write.
+
+### RFC cross-links in PRs and comments
+
+When a PR description or a comment mentions an existing active RFC —
+by its ID, its multi-word title, or its slug — the framework renders
+that mention as a link to the RFC. The matching is conservative by
+design (single common words are never auto-linked), and the links are
+computed at read time, so nothing is rewritten in what you typed.
+
+### "Create" and "ask to contribute" offers
+
+The same scan surfaces two affordances inline:
+
+- If a term looks like it should have an RFC but none exists yet, a
+  reader who has create rights sees a **"create RFC for '<term>'"**
+  link that opens the propose modal with the title pre-filled.
+- If a term matches a *pending* RFC (a super-draft someone already
+  owns), a signed-in reader sees an **"ask to contribute"** offer
+  naming the owner. It opens a short request form — who you are, why
+  you're asking, and optionally what you'd use the RFC for. The
+  request lands in the owner's inbox; the owner can **accept** (which
+  sends you an owner invitation) or **decline** (which notifies you).
+
+---
+
 ## Working on a branch
 
 Contribute mode flips one branch into edit-enabled. The centre
@@ -505,6 +576,14 @@ Each role is a strict superset of the one below it.
    entirely. The framework names a single "owner zero" at
    bootstrap.
 
+Between anonymous and contributor sits one transient state:
+**pending**. A freshly signed-in account that hasn't been granted
+access yet (see [Signing in](#signing-in)) reads everything an
+anonymous visitor can, but no write affordance unlocks until an admin
+grants it. Granting promotes the account to contributor; an admin can
+also revoke a granted account back to a no-write state. These
+transitions are recorded in the `permission_events` log.
+
 The practical difference between admin and owner is narrow but
 load-bearing: admin is the operational tier — it does the day-to-
 day moderation and stewardship work; owner is the tier that
@@ -594,6 +673,20 @@ review.
 
 ---
 
+## Privacy and cookies
+
+A consent banner appears on your first visit and lets you choose
+which cookie categories to allow — essential always, with analytics
+and other categories opt-in. The choice is remembered and can be
+changed any time from the privacy/cookies controls in settings.
+
+Analytics only load if you opt in: the framework defers the analytics
+SDK behind your consent, so declining means it is never initialized.
+The `/privacy` and `/cookies` pages describe what's collected and
+why; a deployment can point those pages at its own fuller policy.
+
+---
+
 ## Where to learn more
 
 - The framework's *why* lives in [the philosophy

SPEC.md

@@ -714,6 +714,47 @@ The lighter half ships the structural shape — frontmatter, consent,
 resolution, revocation. The heavier half ships the runtime
 hardening.
 
+### 6.8 Sign-in state resume (roadmap item #29, v0.23.0)
+
+Signing in lands the user back on their most recently-viewed app
+state instead of always on the empty-state home view. The model is
+**per-user**, not per-device — the safe default the roadmap calls
+for: a sign-in on any device resumes the most-recently-recorded
+route. A per-device split and a profile-settings toggle UI are
+follow-ups; v0.23.0 ships the column-level opt-out flag
+(`resume_enabled`, default on) and the default-on behavior.
+
+**Storage.** A single row per user in `user_session_state`
+(migration 022): `user_id` (PK, FK → `users.id`, cascade-delete),
+`last_route` (TEXT, the frontend pathname), `last_route_state`
+(TEXT, JSON-encoded — SQLite has no native JSONB, so JSON-as-TEXT
+matches how the app stores every other JSON blob), `resume_enabled`
+(INTEGER, default 1), and `last_updated_at`.
+
+**Wiring.** A debounced (~1s) frontend route-change hook posts the
+current route to `PUT /api/me/last-state` for authenticated users
+(anonymous: no-op). The stored `last_route` is folded onto the
+existing `/api/auth/me` payload (no extra round-trip); on sign-in,
+after the §21-Part-C Amplitude `identify` fires, the frontend
+`navigate()`s to it. The identify-then-redirect ordering is
+preserved: the redirect is gated on identify having fired.
+
+**Stale state.** If the stored route is an RFC since withdrawn or
+one the user lost rights to read, the redirect is a graceful no-op:
+`navigate(last_route)` lands on whatever that route renders today,
+and the existing routing already falls through to the
+catalog/empty-state for a missing/unreadable RFC. No special-casing
+on the server.
+
+**Privacy (binding).** The stored state is **route + light view
+state ONLY** — scroll anchors, open-tab selection, filter chips, and
+the like. It **MUST NOT** carry draft-buffer contents, PR/comment
+draft text, or any user-typed content. The frontend never sends such
+content; the `last_route_state` column comment in migration 022 and
+this paragraph are the contract. Resume state is purposely cheap to
+discard: a deliberate "clear" (or `resume_enabled = 0`) drops the
+user back to today's empty-state behavior.
+
 ---
 
 ## 7. The left pane

VERSION

@@ -1 +1 @@
-0.21.0
+0.30.0

backend/.env.example

@@ -38,10 +38,22 @@ GITEA_WEBHOOK_SECRET=change-me-to-a-shared-secret
 # Comma-separated list of provider keys to enable. Per the §19.2
 # per-RFC-model topic, this is app-wide until that topic lands.
 ENABLED_MODELS=claude
+# ANTHROPIC_API_KEY also powers the §9.1 propose-RFC tag suggestions
+# (roadmap #27) — that surface always uses Claude Haiku for cost,
+# independent of ENABLED_MODELS. With no key set, tag suggestions are
+# simply unavailable (the modal hides the row); the rest of the app is
+# unaffected.
 ANTHROPIC_API_KEY=
 GOOGLE_API_KEY=
 OPENAI_API_KEY=
 
+# --- Tag suggestions (§9.1 / roadmap #27) ---
+# Per-user rate limit on the suggest-tags endpoint (cost backstop; the
+# modal debounces and the endpoint is contributor-gated). Optional —
+# these defaults apply when unset.
+TAG_SUGGEST_RATE_MAX=30
+TAG_SUGGEST_RATE_WINDOW_SECONDS=60
+
 # --- Email (§15.4) ---
 # Leave SMTP_HOST unset to use the stdout fallback — the integration
 # tests rely on it, and a dev environment without a real SMTP provider

backend/app/api.py

@@ -21,6 +21,7 @@ from pydantic import BaseModel, Field
 from . import (
     api_admin,
     api_branches,
+    api_contributions,
     api_discussion,
     api_graduation,
     api_invitations,
@@ -39,6 +40,7 @@ from . import (
     notify,
     philosophy,
     providers as providers_mod,
+    tag_suggest,
 )
 from .bot import Bot
 from .config import Config
@@ -51,6 +53,22 @@ class ProposeBody(BaseModel):
     slug: str = Field(min_length=1, max_length=80)
     pitch: str = Field(min_length=1)
     tags: list[str] = Field(default_factory=list)
+    # Roadmap #26: optional "What will you be using this RFC for?" — the
+    # concrete ground-truth use case, distinct from the `pitch`'s abstract
+    # "why is this needed." Optional (NULL/omitted accepted), no minimum,
+    # generous cap matching the pitch's free-text body bound.
+    proposed_use_case: str | None = Field(default=None, max_length=8000)
+
+
+class SuggestTagsBody(BaseModel):
+    # Roadmap #27: the partial propose-RFC draft, sent as the user types
+    # (debounced on the frontend). All fields optional — suggestions
+    # refine as the draft fills in. `pitch` is the "why is this needed"
+    # rationale; `use_case` is the #26 optional ground-truth field.
+    # Bounds mirror the propose body's free-text caps.
+    title: str = Field(default="", max_length=200)
+    pitch: str = Field(default="", max_length=8000)
+    use_case: str = Field(default="", max_length=8000)
 
 
 class DeclineBody(BaseModel):
@@ -62,6 +80,18 @@ class FunderCredentialBody(BaseModel):
     api_key: str = Field(min_length=1, max_length=2048)
 
 
+class LastStateBody(BaseModel):
+    # v0.23.0 / roadmap item #29: server-side sign-in state resume.
+    # `route` is a frontend pathname the user was last on (bounded so a
+    # hostile client can't stuff arbitrary blobs through). `state` is an
+    # optional bag of *light* view state (scroll anchors, open tab,
+    # filter chips). PRIVACY: it MUST NOT carry draft-buffer contents —
+    # the frontend only ever sends ephemeral view state, and the column
+    # comment in migration 022 + SPEC §6.2 are the binding contract.
+    route: str = Field(min_length=1, max_length=2048)
+    state: dict[str, Any] | None = None
+
+
 class BetaRequestBody(BaseModel):
     # v0.8.0 — captured on the first OTC sign-in. All three fields are
     # required so the admin queue has a coherent triage shape.
@@ -112,6 +142,10 @@ def make_router(
     # invited users keep read access but cannot write (v0.6.0
     # contract extended to per-RFC scope).
     router.include_router(api_invitations.make_router())
+    # v0.29.0 (roadmap item #28 Part 3): offer-to-contribute-to-a-pending
+    # (super-draft) RFC. Reuses the #12 invite flow (api_invitations above)
+    # on accept; lands the request + owner notifications via §15 notify.
+    router.include_router(api_contributions.make_router())
 
     # ---------------------------------------------------------------
     # §17: /api/health — unauthenticated post-flight probe.
@@ -349,6 +383,28 @@ def make_router(
         )
         has_passcode = bool(row and row["passcode_hash"])
         passcode_set_at = row["passcode_set_at"] if (row and has_passcode) else None
+        # v0.23.0 / item #29: fold the sign-in-resume state onto the
+        # same round-trip the frontend already makes on boot. When
+        # resume is disabled (resume_enabled = 0) we hand back a null
+        # route so the client never redirects; the stored row stays put
+        # so re-enabling later resumes the last-known route.
+        state_row = db.conn().execute(
+            "SELECT last_route, last_route_state, resume_enabled "
+            "FROM user_session_state WHERE user_id = ?",
+            (user.user_id,),
+        ).fetchone()
+        resume_enabled = bool(state_row["resume_enabled"]) if state_row else True
+        last_route = (
+            state_row["last_route"]
+            if (state_row and resume_enabled)
+            else None
+        )
+        last_route_state = None
+        if state_row and resume_enabled and state_row["last_route_state"]:
+            try:
+                last_route_state = json.loads(state_row["last_route_state"])
+            except (ValueError, TypeError):
+                last_route_state = None
         return {
             "authenticated": True,
             "user": {
@@ -365,6 +421,10 @@ def make_router(
                 "needs_profile": needs_profile,
                 "has_passcode": has_passcode,
                 "passcode_set_at": passcode_set_at,
+                # v0.23.0 / item #29 — sign-in state resume.
+                "resume_enabled": resume_enabled,
+                "last_route": last_route,
+                "last_route_state": last_route_state,
             },
         }
 
@@ -434,6 +494,52 @@ def make_router(
             notify.fan_out_new_beta_request(requester_user_id=user.user_id)
         return {"ok": True}
 
+    # ---------------------------------------------------------------
+    # v0.23.0 (§6.2, roadmap item #29): server-side sign-in state
+    # resume. The frontend debounce-posts the user's current route +
+    # a small bag of light view state here on every route change; the
+    # next sign-in reads `last_route` off `/api/auth/me` and redirects.
+    #
+    # Per-user (NOT per-device) — one row per user, keyed on user_id.
+    # `resume_enabled` is the opt-out flag (default on); when it's 0
+    # this endpoint no-ops so a user who turned resume off doesn't keep
+    # silently rewriting their stored route. PRIVACY: the body carries
+    # route + light state ONLY, never draft-buffer contents (migration
+    # 022 column comment + SPEC §6.2 are the binding contract).
+    #
+    # `require_user` (not `require_contributor`) — a pending/granted
+    # distinction is irrelevant for "remember where I was", and a
+    # pending user navigating read-only surfaces should still resume.
+    # Anonymous callers get the 401 `require_user` raises.
+    # ---------------------------------------------------------------
+
+    @router.put("/api/me/last-state")
+    async def put_last_state(body: LastStateBody, request: Request) -> dict[str, Any]:
+        user = auth.require_user(request)
+        # Respect the opt-out: if a row already exists with resume
+        # disabled, leave it untouched and report the no-op. A first-
+        # ever POST (no row yet) defaults to enabled and stores.
+        existing = db.conn().execute(
+            "SELECT resume_enabled FROM user_session_state WHERE user_id = ?",
+            (user.user_id,),
+        ).fetchone()
+        if existing is not None and not existing["resume_enabled"]:
+            return {"ok": True, "stored": False}
+        state_json = json.dumps(body.state) if body.state is not None else None
+        db.conn().execute(
+            """
+            INSERT INTO user_session_state
+                (user_id, last_route, last_route_state, last_updated_at)
+            VALUES (?, ?, ?, datetime('now'))
+            ON CONFLICT(user_id) DO UPDATE SET
+                last_route = excluded.last_route,
+                last_route_state = excluded.last_route_state,
+                last_updated_at = excluded.last_updated_at
+            """,
+            (user.user_id, body.route, state_json),
+        )
+        return {"ok": True, "stored": True}
+
     # ---------------------------------------------------------------
     # v0.11.0: trust device for 30 days (§6.2, roadmap item #9).
     #
@@ -557,12 +663,36 @@ def make_router(
         ).fetchone()
         if row is None:
             raise HTTPException(404, "Not found")
-        return _serialize_rfc(row)
+        payload = _serialize_rfc(row)
+        # Roadmap #26: surface the optional propose-time use case on the
+        # RFC view. The idea PR closes on merge, but the canonical row in
+        # `proposed_use_cases` persists; look it up by slug (the latest
+        # 'rfc'-scope row for this slug). NULL == "left blank".
+        uc = db.conn().execute(
+            """
+            SELECT use_case FROM proposed_use_cases
+             WHERE scope = 'rfc' AND rfc_slug = ?
+             ORDER BY id DESC LIMIT 1
+            """,
+            (slug,),
+        ).fetchone()
+        payload["proposed_use_case"] = uc["use_case"] if uc else None
+        return payload
 
     # ---------------------------------------------------------------
     # §7.3 / §9.3: pending ideas
     # ---------------------------------------------------------------
 
+    def _proposal_use_case(pr_number: int) -> str | None:
+        """Roadmap #26: read the optional use case for an idea PR from the
+        canonical side table. Returns None when none was supplied (the
+        "left blank" sentinel the frontend renders tastefully)."""
+        row = db.conn().execute(
+            "SELECT use_case FROM proposed_use_cases WHERE scope = 'rfc' AND pr_number = ?",
+            (pr_number,),
+        ).fetchone()
+        return row["use_case"] if row else None
+
     @router.get("/api/proposals")
     async def list_proposals() -> dict[str, Any]:
         rows = db.conn().execute(
@@ -582,6 +712,7 @@ def make_router(
                     "description": r["description"],
                     "opened_by": r["opened_by"],
                     "opened_at": r["opened_at"],
+                    "proposed_use_case": _proposal_use_case(r["pr_number"]),
                 }
                 for r in rows
             ]
@@ -630,6 +761,7 @@ def make_router(
             "opened_at": row["opened_at"],
             "entry": entry_payload,
             "affordances": affordances,
+            "proposed_use_case": _proposal_use_case(pr_number),
         }
 
     # ---------------------------------------------------------------
@@ -706,8 +838,55 @@ def make_router(
         # cache write is idempotent.)
         await cache.refresh_meta_pulls(config, gitea)
 
+        # Roadmap #26: persist the optional use case to the canonical,
+        # reconcile-proof side table keyed by the idea PR number. NULL/
+        # blank simply writes no row (absence == "left blank"). Done after
+        # the refresh so the cache row exists; the mirror onto cached_prs
+        # keeps the cache column in parity for any read that uses it.
+        use_case = (payload.proposed_use_case or "").strip()
+        if use_case:
+            db.conn().execute(
+                """
+                INSERT INTO proposed_use_cases (scope, rfc_slug, pr_number, use_case)
+                VALUES ('rfc', ?, ?, ?)
+                ON CONFLICT(scope, pr_number) DO UPDATE SET use_case = excluded.use_case
+                """,
+                (slug, pr["number"], use_case),
+            )
+            db.conn().execute(
+                "UPDATE cached_prs SET proposed_use_case = ? WHERE pr_kind = 'idea' AND pr_number = ?",
+                (use_case, pr["number"]),
+            )
+
         return {"pr_number": pr["number"], "slug": slug}
 
+    # ---------------------------------------------------------------
+    # §9.1 Slice 2 (roadmap #27): Claude Haiku tag suggestions as the
+    # propose-RFC fields fill in. The modal debounce-posts the partial
+    # draft; we constrain Haiku to the corpus's existing tag set and
+    # return a short ranked list of clickable chips. Gated to
+    # contributors (same gate as propose) so the cost surface is bounded
+    # to people who can actually file an RFC; rate-limited per user as a
+    # backstop. Degrades to an empty list (no error) when no Anthropic
+    # key is bound, the corpus has no tags yet, or the draft is empty —
+    # so the modal simply shows nothing extra.
+    # ---------------------------------------------------------------
+
+    @router.post("/api/rfcs/suggest-tags")
+    async def suggest_rfc_tags(payload: SuggestTagsBody, request: Request) -> dict[str, Any]:
+        user = auth.require_contributor(request)
+        if not tag_suggest.rate_limit_ok(user.user_id):
+            raise HTTPException(429, "Too many tag-suggestion requests; please slow down.")
+        provider = tag_suggest.haiku_provider(config)
+        if provider is None:
+            return {"suggestions": []}
+        universe = tag_suggest.gather_tag_universe()
+        draft = tag_suggest.Draft(
+            title=payload.title, pitch=payload.pitch, use_case=payload.use_case
+        )
+        suggestions = tag_suggest.suggest(provider, draft, universe)
+        return {"suggestions": suggestions}
+
     # ---------------------------------------------------------------
     # §9.3: merge / decline / withdraw an idea PR
     # ---------------------------------------------------------------

backend/app/api_contributions.py

@@ -0,0 +1,311 @@
+"""v0.29.0 / roadmap #28 Part 3 — offer-to-contribute-to-a-pending-RFC.
+
+When the #28 scanner (see ``rfc_links.py``) matches a term in submitted
+PR/comment text to a **pending** RFC — a super-draft
+(``cached_rfcs.state='super-draft'``: accepted as an idea, owned, with a
+contribution surface, but not yet graduated to an active RFC) — the
+reader is offered an "ask to contribute" popover. This module is the
+backend for that flow:
+
+  * ``GET  /api/rfcs/{slug}/contribution-target``      — what the
+    contribute form needs (RFC title, owner display, the viewer's
+    eligibility + whether they already have a pending ask).
+  * ``POST /api/rfcs/{slug}/contribution-requests``    — submit the ask
+    (who-I-am / why / optional use-case); lands a row + one §15
+    notification per owner.
+  * ``POST /api/rfcs/{slug}/contribution-requests/{id}/accept``  — owner:
+    accept, which fires #12's owner-invite flow with the requester as the
+    invitee (opening the RFC's discussion/contribution surface), then
+    echoes a notification back to the requester.
+  * ``POST /api/rfcs/{slug}/contribution-requests/{id}/decline`` — owner:
+    decline; the request closes and the requester is notified.
+
+"Pending" is scoped to a super-draft because that is the state with an
+owner to route to, a contribution surface to open, and a row in
+``cached_rfcs`` for the ``rfc_invitations`` FK the accept path reuses.
+Pre-merge idea PRs are deliberately out of scope (no contribution
+surface yet) — a documented future extension, mirroring the
+conservative scoping in ``rfc_links.py``.
+"""
+from __future__ import annotations
+
+import sqlite3
+from typing import Any
+
+from fastapi import APIRouter, HTTPException, Request
+from pydantic import BaseModel, Field
+
+from . import api_invitations, auth, db, notify
+
+# Field caps — generous for free text, bounded so a request row (and the
+# notification payload that carries it) can't be used to store unbounded
+# blobs. Mirrors the order-of-magnitude of the propose/tag-suggest caps.
+_WHO_MAX = 2000
+_WHY_MAX = 4000
+_USE_CASE_MAX = 4000
+_TERM_MAX = 200
+
+
+class ContributionRequestBody(BaseModel):
+    # The term in the PR/comment text that surfaced the offer (the
+    # super-draft's title/slug). Carried for the owner's context line.
+    matched_term: str = Field(min_length=1, max_length=_TERM_MAX)
+    who_i_am: str = Field(min_length=1, max_length=_WHO_MAX)
+    why: str = Field(min_length=1, max_length=_WHY_MAX)
+    use_case: str | None = Field(default=None, max_length=_USE_CASE_MAX)
+
+
+def _require_super_draft(slug: str):
+    """The contribute surface only operates on a *pending* RFC. 404 on
+    unknown; 409 on a state that isn't a super-draft (active RFCs use the
+    Part-1 link, not a contribute offer; withdrawn is closed)."""
+    row = db.conn().execute(
+        "SELECT slug, title, state, owners_json, proposed_by FROM cached_rfcs WHERE slug = ?",
+        (slug,),
+    ).fetchone()
+    if row is None:
+        raise HTTPException(404, "RFC not found")
+    if row["state"] != "super-draft":
+        raise HTTPException(409, "RFC is not a pending super-draft")
+    return row
+
+
+def _require_request(slug: str, request_id: int):
+    row = db.conn().execute(
+        """
+        SELECT id, rfc_slug, requester_user_id, matched_term, who_i_am, why,
+               use_case, status
+          FROM contribution_requests WHERE id = ? AND rfc_slug = ?
+        """,
+        (request_id, slug),
+    ).fetchone()
+    if row is None:
+        raise HTTPException(404, "Contribution request not found")
+    return row
+
+
+def _viewer_relationship(viewer, slug: str) -> str | None:
+    """Why this viewer can't *request* to contribute — or None if they can.
+    Owners/admins already have the RFC; existing collaborators are already
+    in. Both get a clear 409 rather than a useless self-request."""
+    if auth.is_rfc_owner(viewer, slug) or viewer.role in ("owner", "admin"):
+        return "You already own or administer this RFC."
+    if auth.is_rfc_collaborator(viewer, slug):
+        return "You're already a collaborator on this RFC."
+    return None
+
+
+def make_router() -> APIRouter:
+    router = APIRouter()
+
+    # ---------------------------------------------------------------
+    # GET — what the contribute form needs to render + gate itself.
+    # ---------------------------------------------------------------
+
+    @router.get("/api/rfcs/{slug}/contribution-target")
+    async def contribution_target(slug: str, request: Request) -> dict[str, Any]:
+        row = db.conn().execute(
+            "SELECT slug, title, state, owners_json, proposed_by FROM cached_rfcs WHERE slug = ?",
+            (slug,),
+        ).fetchone()
+        if row is None:
+            raise HTTPException(404, "RFC not found")
+
+        from . import rfc_links  # local import: avoid a module import cycle
+
+        owner = rfc_links._owner_display(db.conn(), row["owners_json"], row["proposed_by"])
+        viewer = auth.current_user(request)
+
+        eligible = True
+        reason: str | None = None
+        already_requested = False
+        if row["state"] != "super-draft":
+            eligible, reason = False, "This RFC is no longer pending."
+        elif viewer is None:
+            eligible, reason = False, "Sign in to ask to contribute."
+        elif viewer.permission_state != "granted":
+            eligible, reason = False, "Your beta access request is in review."
+        else:
+            reason = _viewer_relationship(viewer, slug)
+            if reason is not None:
+                eligible = False
+            else:
+                already_requested = bool(
+                    db.conn().execute(
+                        """
+                        SELECT 1 FROM contribution_requests
+                         WHERE rfc_slug = ? AND requester_user_id = ? AND status = 'pending'
+                         LIMIT 1
+                        """,
+                        (slug, viewer.user_id),
+                    ).fetchone()
+                )
+
+        return {
+            "slug": row["slug"],
+            "title": row["title"],
+            "owner": owner,
+            "eligible": eligible and not already_requested,
+            "reason": reason,
+            "already_requested": already_requested,
+        }
+
+    # ---------------------------------------------------------------
+    # POST — submit a contribute request.
+    # ---------------------------------------------------------------
+
+    @router.post("/api/rfcs/{slug}/contribution-requests")
+    async def create_contribution_request(
+        slug: str, body: ContributionRequestBody, request: Request
+    ) -> dict[str, Any]:
+        viewer = auth.require_contributor(request)
+        _require_super_draft(slug)
+
+        reason = _viewer_relationship(viewer, slug)
+        if reason is not None:
+            raise HTTPException(409, reason)
+
+        who_i_am = body.who_i_am.strip()
+        why = body.why.strip()
+        use_case = (body.use_case or "").strip() or None
+        matched_term = body.matched_term.strip()
+        if not who_i_am or not why:
+            raise HTTPException(422, "Both 'who I am' and 'why' are required.")
+
+        try:
+            cur = db.conn().execute(
+                """
+                INSERT INTO contribution_requests
+                    (rfc_slug, requester_user_id, matched_term, who_i_am, why, use_case)
+                VALUES (?, ?, ?, ?, ?, ?)
+                """,
+                (slug, viewer.user_id, matched_term, who_i_am, why, use_case),
+            )
+        except sqlite3.IntegrityError:
+            # The partial unique index — one open request per (RFC, user).
+            raise HTTPException(409, "You already have a pending request to contribute to this RFC.")
+        request_id = cur.lastrowid
+
+        # One actionable notification per owner; stamp the first onto the
+        # row as the inbox-action handle (any owner can act on the request).
+        notif_ids = notify.fan_out_contribution_request(
+            rfc_slug=slug,
+            requester_user_id=viewer.user_id,
+            request_id=request_id,
+            matched_term=matched_term,
+            who_i_am=who_i_am,
+            why=why,
+            use_case=use_case,
+        )
+        if notif_ids:
+            db.conn().execute(
+                "UPDATE contribution_requests SET notification_id = ? WHERE id = ?",
+                (notif_ids[0], request_id),
+            )
+
+        return {"id": request_id, "rfc_slug": slug, "status": "pending"}
+
+    # ---------------------------------------------------------------
+    # POST — owner accepts → fire #12's invite flow.
+    # ---------------------------------------------------------------
+
+    @router.post("/api/rfcs/{slug}/contribution-requests/{request_id}/accept")
+    async def accept_contribution_request(
+        slug: str, request_id: int, request: Request
+    ) -> dict[str, Any]:
+        viewer = auth.require_contributor(request)
+        rfc = _require_super_draft(slug)
+        if not auth.can_invite_to_rfc(viewer, slug):
+            raise HTTPException(403, "Only the RFC's owner can act on contribution requests")
+
+        req = _require_request(slug, request_id)
+        if req["status"] != "pending":
+            raise HTTPException(409, f"This request was already {req['status']}.")
+
+        requester = db.conn().execute(
+            "SELECT id, email FROM users WHERE id = ?", (req["requester_user_id"],)
+        ).fetchone()
+        if requester is None or not (requester["email"] or "").strip():
+            raise HTTPException(422, "The requester has no email address on file to invite.")
+
+        # Fire #12's owner-invite flow with the requester as the invitee.
+        # If a pending contributor invitation already exists (the owner
+        # invited them out-of-band first), reuse it rather than failing.
+        try:
+            invitation = api_invitations.issue_invitation(
+                slug=slug,
+                inviter_user_id=viewer.user_id,
+                inviter_display=viewer.display_name or viewer.gitea_login or "An RFC owner",
+                invitee_email=requester["email"],
+                role_in_rfc="contributor",
+                rfc_title=rfc["title"],
+            )
+            invitation_id = invitation["id"]
+        except HTTPException as exc:
+            if exc.status_code != 409:
+                raise
+            existing = db.conn().execute(
+                """
+                SELECT id FROM rfc_invitations
+                 WHERE rfc_slug = ? AND invitee_email = ? COLLATE NOCASE
+                   AND role_in_rfc = 'contributor' AND status = 'pending'
+                 ORDER BY id DESC LIMIT 1
+                """,
+                (slug, requester["email"].strip()),
+            ).fetchone()
+            invitation_id = existing["id"] if existing else None
+
+        db.conn().execute(
+            """
+            UPDATE contribution_requests
+               SET status = 'accepted', decided_at = datetime('now'),
+                   decided_by_user_id = ?, invitation_id = ?
+             WHERE id = ?
+            """,
+            (viewer.user_id, invitation_id, request_id),
+        )
+        notify.notify_contribution_decided(
+            rfc_slug=slug,
+            requester_user_id=req["requester_user_id"],
+            decider_user_id=viewer.user_id,
+            request_id=request_id,
+            accepted=True,
+        )
+        return {"ok": True, "status": "accepted", "invitation_id": invitation_id}
+
+    # ---------------------------------------------------------------
+    # POST — owner declines.
+    # ---------------------------------------------------------------
+
+    @router.post("/api/rfcs/{slug}/contribution-requests/{request_id}/decline")
+    async def decline_contribution_request(
+        slug: str, request_id: int, request: Request
+    ) -> dict[str, Any]:
+        viewer = auth.require_contributor(request)
+        _require_super_draft(slug)
+        if not auth.can_invite_to_rfc(viewer, slug):
+            raise HTTPException(403, "Only the RFC's owner can act on contribution requests")
+
+        req = _require_request(slug, request_id)
+        if req["status"] != "pending":
+            raise HTTPException(409, f"This request was already {req['status']}.")
+
+        db.conn().execute(
+            """
+            UPDATE contribution_requests
+               SET status = 'declined', decided_at = datetime('now'),
+                   decided_by_user_id = ?
+             WHERE id = ?
+            """,
+            (viewer.user_id, request_id),
+        )
+        notify.notify_contribution_decided(
+            rfc_slug=slug,
+            requester_user_id=req["requester_user_id"],
+            decider_user_id=viewer.user_id,
+            request_id=request_id,
+            accepted=False,
+        )
+        return {"ok": True, "status": "declined"}
+
+    return router

backend/app/api_discussion.py

@@ -40,7 +40,7 @@ from typing import Any
 from fastapi import APIRouter, HTTPException, Request
 from pydantic import BaseModel, Field
 
-from . import auth, chat as chat_layer, db
+from . import auth, chat as chat_layer, db, rfc_links
 
 log = logging.getLogger(__name__)
 
@@ -171,9 +171,17 @@ def make_router() -> APIRouter:
             """,
             (thread_id,),
         ).fetchall()
+        # Roadmap #28 Part 1: enrich each discussion comment with RFC
+        # auto-link segments scanned against the live accepted-RFC corpus
+        # (read-time; see rfc_links.py). exclude_slug suppresses self-links
+        # to this RFC inside its own discussion.
+        link_index = rfc_links.build_index(db.conn(), exclude_slug=slug)
+        messages = [_serialize_message(r) for r in rows]
+        for m in messages:
+            m["text_segments"] = link_index.segment(m["text"])
         return {
             "thread": _serialize_thread(thread),
-            "messages": [_serialize_message(r) for r in rows],
+            "messages": messages,
         }
 
     # -------------------------------------------------------------------

backend/app/api_invitations.py

@@ -133,69 +133,15 @@ def make_router() -> APIRouter:
                 "Only the RFC's owner can invite collaborators",
             )
 
-        invitee_email = body.invitee_email.strip()
-        role_in_rfc = body.role_in_rfc
-
-        # Refuse re-inviting an email that already has a pending
-        # invitation on this RFC at the same role. Different-role
-        # re-invite is allowed (upgrade discussant → contributor)
-        # — the new row supersedes the old in the UI listing's
-        # natural ordering, and acceptance of either picks up the
-        # corresponding role.
-        existing = db.conn().execute(
-            """
-            SELECT id FROM rfc_invitations
-             WHERE rfc_slug = ? AND invitee_email = ? COLLATE NOCASE
-               AND role_in_rfc = ? AND status = 'pending'
-             LIMIT 1
-            """,
-            (slug, invitee_email, role_in_rfc),
-        ).fetchone()
-        if existing:
-            raise HTTPException(
-                409,
-                f"{invitee_email} already has a pending {role_in_rfc} invitation for this RFC",
-            )
-
-        token = _mint_token()
-        cur = db.conn().execute(
-            """
-            INSERT INTO rfc_invitations
-                (rfc_slug, inviter_user_id, invitee_email, role_in_rfc,
-                 token, expires_at)
-            VALUES (?, ?, ?, ?, ?, datetime('now', ?))
-            """,
-            (
-                slug,
-                viewer.user_id,
-                invitee_email,
-                role_in_rfc,
-                token,
-                f"+{INVITATION_TTL_DAYS} days",
-            ),
-        )
-        invitation_id = cur.lastrowid
-
-        # Send the email — synchronous. A send failure logs and
-        # returns; the row stays so the owner can recover via the
-        # listing (which carries the token for an out-of-band share).
-        _send_invitation_email(
-            to_address=invitee_email,
+        return issue_invitation(
+            slug=slug,
+            inviter_user_id=viewer.user_id,
             inviter_display=viewer.display_name or viewer.gitea_login or "An RFC owner",
+            invitee_email=body.invitee_email,
+            role_in_rfc=body.role_in_rfc,
             rfc_title=rfc["title"],
-            role_in_rfc=role_in_rfc,
-            token=token,
         )
 
-        return {
-            "id": invitation_id,
-            "rfc_slug": slug,
-            "invitee_email": invitee_email,
-            "role_in_rfc": role_in_rfc,
-            "status": "pending",
-            "token": token,
-        }
-
     # ---------------------------------------------------------------
     # GET /api/rfcs/<slug>/invitations
     # The owner's listing of every invitation on the RFC, regardless
@@ -473,6 +419,78 @@ def _effective_status(row) -> str:
     return "expired" if is_past else "pending"
 
 
+def issue_invitation(
+    *,
+    slug: str,
+    inviter_user_id: int,
+    inviter_display: str,
+    invitee_email: str,
+    role_in_rfc: str,
+    rfc_title: str,
+) -> dict:
+    """Mint + persist + email one ``rfc_invitations`` row.
+
+    The single chokepoint for issuing an invitation: the owner's manual
+    `POST /api/rfcs/{slug}/invitations` endpoint and roadmap #28 Part 3's
+    accept path both route through here, so the dup-guard, token mint,
+    insert, and transactional email stay identical.
+
+    Refuses (409) re-inviting an email that already has a pending
+    invitation on this RFC at the same role. A different-role re-invite is
+    allowed (the discussant → contributor upgrade) — the new row
+    supersedes the old in the listing's natural ordering, and acceptance
+    of either picks up the corresponding role.
+
+    Returns the new row's dict (including the raw token, for the owner's
+    out-of-band share / the caller's record-keeping). A send failure logs
+    and returns; the row stays so the owner can recover via the listing.
+    """
+    invitee_email = invitee_email.strip()
+    existing = db.conn().execute(
+        """
+        SELECT id FROM rfc_invitations
+         WHERE rfc_slug = ? AND invitee_email = ? COLLATE NOCASE
+           AND role_in_rfc = ? AND status = 'pending'
+         LIMIT 1
+        """,
+        (slug, invitee_email, role_in_rfc),
+    ).fetchone()
+    if existing:
+        raise HTTPException(
+            409,
+            f"{invitee_email} already has a pending {role_in_rfc} invitation for this RFC",
+        )
+
+    token = _mint_token()
+    cur = db.conn().execute(
+        """
+        INSERT INTO rfc_invitations
+            (rfc_slug, inviter_user_id, invitee_email, role_in_rfc,
+             token, expires_at)
+        VALUES (?, ?, ?, ?, ?, datetime('now', ?))
+        """,
+        (slug, inviter_user_id, invitee_email, role_in_rfc, token, f"+{INVITATION_TTL_DAYS} days"),
+    )
+    invitation_id = cur.lastrowid
+
+    _send_invitation_email(
+        to_address=invitee_email,
+        inviter_display=inviter_display,
+        rfc_title=rfc_title,
+        role_in_rfc=role_in_rfc,
+        token=token,
+    )
+
+    return {
+        "id": invitation_id,
+        "rfc_slug": slug,
+        "invitee_email": invitee_email,
+        "role_in_rfc": role_in_rfc,
+        "status": "pending",
+        "token": token,
+    }
+
+
 def _mint_token() -> str:
     """A 256-bit URL-safe token. The token shape is opaque to the
     consumer; the email link encodes it as a query param."""

backend/app/api_notifications.py

@@ -557,7 +557,26 @@ def make_router(config: Config) -> APIRouter:
         # stays unauthenticated for dev (the v1 contract).
         import os as _os
         expected = _os.environ.get("WEBHOOK_EMAIL_BOUNCE_SECRET", "").strip()
-        if expected:
+        # v0.25.0 (audit 0026 M5): fail closed. An unset secret used to
+        # leave this endpoint fully unauthenticated — anyone could suppress
+        # any user's mail by POSTing their address (email_opt_out_all flip
+        # below). Now an unset secret DISABLES the endpoint (503) instead
+        # of opening it. A dev that genuinely wants it open opts in
+        # explicitly with RFC_APP_INSECURE_BOUNCE_WEBHOOK=1, mirroring the
+        # RFC_APP_INSECURE_WEBHOOKS dev-bypass on the Gitea hook.
+        if not expected:
+            if _os.environ.get("RFC_APP_INSECURE_BOUNCE_WEBHOOK", "").strip() == "1":
+                log.warning(
+                    "email-bounce webhook running UNAUTHENTICATED "
+                    "(RFC_APP_INSECURE_BOUNCE_WEBHOOK=1) — never set this in production"
+                )
+            else:
+                log.error(
+                    "email-bounce webhook refused: WEBHOOK_EMAIL_BOUNCE_SECRET is unset "
+                    "(set the secret to enable, or RFC_APP_INSECURE_BOUNCE_WEBHOOK=1 for dev)"
+                )
+                raise HTTPException(503, "Bounce webhook not configured")
+        else:
             received = request.headers.get("X-Webhook-Secret", "")
             import hmac as _hmac
             if not received or not _hmac.compare_digest(expected, received):

backend/app/api_prs.py

@@ -23,7 +23,7 @@ from typing import Any
 from fastapi import APIRouter, HTTPException, Request
 from pydantic import BaseModel, Field
 
-from . import auth, cache, chat as chat_layer, db, entry as entry_mod, funder, models_resolver
+from . import auth, cache, chat as chat_layer, db, entry as entry_mod, funder, models_resolver, rfc_links
 from .bot import Bot
 from .config import Config
 from .gitea import Gitea, GiteaError
@@ -42,6 +42,11 @@ RFC_FILE_PATH = "RFC.md"
 class OpenPRBody(BaseModel):
     title: str = Field(min_length=1, max_length=240)
     description: str = Field(max_length=8000)
+    # Roadmap #26: optional "What will you be using this change for?" —
+    # the concrete ground-truth use case sibling to the required
+    # "why is this change needed" (the `description`). Optional, generous
+    # cap matching the description bound.
+    proposed_use_case: str | None = Field(default=None, max_length=8000)
 
 
 class PRDescriptionBody(BaseModel):
@@ -173,6 +178,26 @@ def make_router(
             raise HTTPException(502, f"Gitea: {e.detail}")
 
         await _refresh_after_pr_write(rfc)
+
+        # Roadmap #26: persist the optional use case to the canonical,
+        # reconcile-proof side table keyed by the PR number. Blank/omitted
+        # writes no row (absence == "left blank"). The mirror onto
+        # cached_prs keeps the cache column in parity.
+        use_case = (body.proposed_use_case or "").strip()
+        if use_case:
+            db.conn().execute(
+                """
+                INSERT INTO proposed_use_cases (scope, rfc_slug, pr_number, use_case)
+                VALUES ('pr', ?, ?, ?)
+                ON CONFLICT(scope, pr_number) DO UPDATE SET use_case = excluded.use_case
+                """,
+                (slug, pr["number"], use_case),
+            )
+            db.conn().execute(
+                "UPDATE cached_prs SET proposed_use_case = ? WHERE rfc_slug = ? AND pr_number = ?",
+                (use_case, slug, pr["number"]),
+            )
+
         return {"pr_number": pr["number"], "slug": slug, "branch": branch}
 
     # -------------------------------------------------------------------
@@ -188,6 +213,12 @@ def make_router(
         path = _file_path_for(rfc)
         head_branch = pr_row["head_branch"]
 
+        # Roadmap #28 Part 1: build the RFC auto-link index once for this
+        # PR view (read-time enrichment against the live accepted-RFC
+        # corpus; see rfc_links.py). exclude_slug suppresses self-links to
+        # this RFC inside its own PR.
+        link_index = rfc_links.build_index(db.conn(), exclude_slug=slug)
+
         # §11.3: PRs are always public; no visibility check.
         main_fetched = await gitea.read_file(owner, repo, path, ref="main")
         main_body = _extract_body(rfc, (main_fetched or ("", ""))[0])
@@ -234,6 +265,13 @@ def make_router(
             for r in msg_rows:
                 messages_by_thread.setdefault(r["thread_id"], []).append(_serialize_message(r))
 
+        # Roadmap #28 Part 1: enrich every comment with RFC auto-link
+        # segments (read-time; see rfc_links.py). The description is
+        # enriched alongside it in the return dict below.
+        for _msgs in messages_by_thread.values():
+            for _m in _msgs:
+                _m["text_segments"] = link_index.segment(_m["text"])
+
         # Per-user seen cursor per §10.3. Anonymous viewers get no
         # cursor — they always see "everything new" but cannot advance
         # the cursor (no row to write to).
@@ -300,6 +338,8 @@ def make_router(
             "pr_number": pr_number,
             "title": pr_row["title"],
             "description": pr_row["description"],
+            "description_segments": link_index.segment(pr_row["description"]),
+            "proposed_use_case": _pr_use_case(pr_number),
             "state": pr_row["state"],
             "opened_by": pr_row["opened_by"],
             "opened_at": pr_row["opened_at"],
@@ -762,6 +802,17 @@ def _can_edit_pr_text(rfc, pr_row, viewer) -> bool:
     return _can_withdraw(rfc, pr_row, viewer)
 
 
+def _pr_use_case(pr_number: int) -> str | None:
+    """Roadmap #26: the optional propose-PR use case from the canonical
+    side table, or None when the change was opened without one ("left
+    blank")."""
+    row = db.conn().execute(
+        "SELECT use_case FROM proposed_use_cases WHERE scope = 'pr' AND pr_number = ?",
+        (pr_number,),
+    ).fetchone()
+    return row["use_case"] if row else None
+
+
 def _pr_capabilities(rfc, pr_row, viewer) -> dict:
     return {
         "can_merge": _can_merge(rfc, viewer) and pr_row["state"] == "open",

backend/app/device_trust.py

@@ -97,6 +97,13 @@ class IssueOutcome:
     raw_token: str
     row_id: int
 
+    @property
+    def cookie_value(self) -> str:
+        """The value to put in the `rfc_device_trust` cookie: the row-id
+        selector joined to the raw token (v0.25.0 / audit 0026 M1). The
+        selector lets `lookup` read one indexed row instead of scanning."""
+        return f"{self.row_id}.{self.raw_token}"
+
 
 def _new_token() -> str:
     return secrets.token_urlsafe(TOKEN_BYTES)
@@ -173,33 +180,37 @@ def lookup(raw_token: str) -> LookupOutcome:
     if not raw:
         return LookupOutcome(ok=False, user=None, reason="invalid")
 
-    # The unique index on `device_token_hash` would let us SELECT by
-    # hash if bcrypt were a stable hash, but bcrypt incorporates a
-    # per-row salt — equal tokens produce different hashes. We walk
-    # the candidate set instead. In practice the set is small (a
-    # human has a handful of trusted devices) and bcrypt is cheap on
-    # the order of milliseconds; the walk is bounded by the user's
-    # active device count.
+    # v0.25.0 (audit 0026 M1): the cookie is "<row_id>.<raw_token>". We
+    # parse the row-id selector and read exactly ONE row by its indexed
+    # primary key, then bcrypt-check the token against that single row.
     #
-    # We don't pre-filter by `revoked_at IS NULL` here so that a
-    # token presented for a recently-revoked row produces a
-    # 'revoked' outcome (the endpoint surfaces a different shape).
-    # Same for expired: we let the walk hit and classify after.
-    rows = db.conn().execute(
+    # The previous shape read EVERY device_trust row (all users, including
+    # revoked/expired) and bcrypt-checked each — an unauthenticated
+    # CPU-amplification DoS reachable at /auth/device-trust/start that
+    # grew without bound as the table accumulated. bcrypt's per-row salt
+    # is why we can't SELECT by hash; carrying the row-id in the cookie is
+    # the standard fix (the id is not secret; the token still is).
+    selector, sep, token = raw.partition(".")
+    if not sep or not selector.isdigit() or not token:
+        # Legacy bare-token cookies (pre-v0.25.0) and malformed values land
+        # here. We refuse rather than fall back to a full-table scan, so
+        # the amplification path is fully closed; affected users simply
+        # re-authenticate once via OTC/passcode and get a new cookie.
+        return LookupOutcome(ok=False, user=None, reason="invalid")
+
+    matched = db.conn().execute(
         """
         SELECT id, user_id, device_token_hash, expires_at, revoked_at
           FROM device_trust
-         ORDER BY id DESC
+         WHERE id = ?
         """,
-    ).fetchall()
+        (int(selector),),
+    ).fetchone()
 
-    matched = None
-    for row in rows:
-        if _check(raw, row["device_token_hash"]):
-            matched = row
-            break
-
-    if matched is None:
+    # One bcrypt check, against the selected row only. A wrong/forged token
+    # for a real id reads as 'unknown' (cookie cleared), same as a missing
+    # row — a probing client can't distinguish the two.
+    if matched is None or not _check(token, matched["device_token_hash"]):
         return LookupOutcome(ok=False, user=None, reason="unknown")
 
     if matched["revoked_at"] is not None:

backend/app/email_envelope.py

@@ -60,12 +60,17 @@ def build_envelope(
     `from_name` is the display label that goes through `formataddr`
     so spaces / commas in the display string are encoded correctly.
 
-    `body_plain` is mandatory. `body_html`, if supplied, lands as the
-    second part of a `multipart/alternative` body — mail clients
-    that prefer HTML render it; clients that don't fall back to the
-    plain part. The text/plain part comes first per RFC 2046, so a
-    plain-text client that picks the first body gets the readable
-    text.
+    `body_plain` is mandatory. `body_html` is **reserved and not yet
+    enabled** (security-audit-0026 I3): no send path supplies it today —
+    every rfc-app mail is plain text — and passing it raises
+    `NotImplementedError`. The parameter is kept in the signature for
+    documented future symmetry: when HTML mail is enabled it will land
+    as the second part of a `multipart/alternative` body (text/plain
+    first per RFC 2046, so a plain-text client picking the first part
+    still gets the readable text). Enabling it is a deliberate act — the
+    caller MUST HTML-escape any user content into `body_html` first (cf.
+    the C1 stored-XSS class: a mail client renders the HTML) and remove
+    the guard below in the same change.
 
     `reply_to`, when set, lets a send path point replies at a
     different mailbox than the From line (e.g., a watcher
@@ -131,13 +136,20 @@ def build_envelope(
             # idempotent and not require auth. See
             # `api_notifications.py` for the receiver.
             msg["List-Unsubscribe-Post"] = "List-Unsubscribe=One-Click"
-    if body_html:
-        # multipart/alternative: text/plain first, text/html second.
-        # `set_content` sets the first part (and the message's main
-        # body); `add_alternative` adds the second part and
-        # restructures the message as multipart/alternative.
-        msg.set_content(body_plain)
-        msg.add_alternative(body_html, subtype="html")
-    else:
-        msg.set_content(body_plain)
+    if body_html is not None:
+        # I3 (security-audit-0026): the multipart/alternative HTML path
+        # is intentionally NOT enabled. No send path passes `body_html`
+        # today, and emitting an HTML body built from user-supplied
+        # content without escaping it first would reintroduce the C1
+        # stored-XSS class in the mail channel (the recipient's client
+        # renders the HTML). Fail loudly here rather than silently
+        # shipping HTML: enabling HTML mail is a deliberate change that
+        # MUST HTML-escape user content at the call site and remove this
+        # guard together. The text/plain path below is the only live one.
+        raise NotImplementedError(
+            "HTML email is not enabled (security-audit-0026 I3): do not "
+            "pass body_html until user content is HTML-escaped at the "
+            "call site and this guard is intentionally removed."
+        )
+    msg.set_content(body_plain)
     return msg

backend/app/main.py

@@ -7,6 +7,7 @@ no need for a separate worker.
 from __future__ import annotations
 
 import logging
+import os
 import secrets
 from contextlib import asynccontextmanager
 
@@ -28,6 +29,7 @@ from . import (
     otc,
     passcode as passcode_mod,
     providers as providers_mod,
+    ratelimit,
     turnstile,
     webhooks,
 )
@@ -142,12 +144,20 @@ def create_app() -> FastAPI:
     # eagerly via load_config(). Everything else waits for lifespan.
     config = load_config()
     app = FastAPI(lifespan=lifespan)
+    # v0.25.0 (audit 0026 M4): the session cookie is the primary 30-day
+    # auth credential and must carry `Secure` in production so it never
+    # travels cleartext. Default to Secure; a dev box serving over plain
+    # http opts out with SESSION_COOKIE_SECURE=false. Production (OHM is
+    # HTTPS-only with an HTTP->HTTPS 301) leaves this unset → Secure on.
+    session_secure = os.environ.get("SESSION_COOKIE_SECURE", "true").strip().lower() not in (
+        "0", "false", "no", "off",
+    )
     app.add_middleware(
         SessionMiddleware,
         secret_key=config.secret_key,
         session_cookie="rfc_session",
         max_age=60 * 60 * 24 * 30,
-        https_only=False,
+        https_only=session_secure,
     )
     return app
 
@@ -155,24 +165,25 @@ def create_app() -> FastAPI:
 app = create_app()
 
 
-def _set_device_trust_cookie(response: Response, raw_token: str) -> None:
+def _set_device_trust_cookie(response: Response, cookie_value: str) -> None:
     """Attach the v0.11.0 device-trust cookie to the response.
 
-    HttpOnly + Secure + SameSite=Lax + 30-day Max-Age + Path=/. The
-    cookie value is the raw token; server-side storage is the hash.
-    The cookie is "essential" per the v0.13.0 cookie-consent contract
-    (it is part of authentication), so we set it regardless of the
-    user's analytics / other-cookies choice.
+    HttpOnly + Secure + SameSite=Lax + 30-day Max-Age + Path=/. As of
+    v0.25.0 (audit 0026 M1) the value is `IssueOutcome.cookie_value` —
+    "<row_id>.<raw_token>" — so `device_trust.lookup` can read one indexed
+    row instead of scanning; server-side storage remains the bcrypt hash
+    of the token half only. The cookie is "essential" per the v0.13.0
+    cookie-consent contract (it is part of authentication), so we set it
+    regardless of the user's analytics / other-cookies choice.
 
-    Secure=True means the cookie is only ever sent over HTTPS. The
-    SessionMiddleware in `create_app` keeps `https_only=False` for
-    dev parity, but the device-trust cookie holds a 30-day credential
-    and must not travel cleartext — production deployments serve over
-    HTTPS, so Secure on the device-trust cookie is non-negotiable.
+    Secure=True means the cookie is only ever sent over HTTPS — the
+    device-trust cookie holds a 30-day credential and must never travel
+    cleartext. (The session cookie now also defaults to Secure; see M4 in
+    `create_app`.)
     """
     response.set_cookie(
         key=device_trust_mod.COOKIE_NAME,
-        value=raw_token,
+        value=cookie_value,
         max_age=device_trust_mod.COOKIE_MAX_AGE_SECONDS,
         path="/",
         secure=True,
@@ -245,6 +256,10 @@ def _oauth_router(config) -> APIRouter:
 
     @router.post("/auth/otc/request")
     async def otc_request(body: OtcRequestBody, request: Request):
+        # v0.25.0 (audit 0026 H1/L2): per-IP brake at the cheapest point,
+        # before the Turnstile network call or any bcrypt/SMTP work.
+        if not ratelimit.otc_request_limiter.allow(ratelimit.client_key(request)):
+            raise HTTPException(429, "Too many requests; please wait a few minutes")
         # v0.12.0 / roadmap item #10: gate the request on a successful
         # Turnstile siteverify before the bcrypt hash + SMTP send. The
         # check runs first so a failed challenge spends no rate budget
@@ -252,7 +267,7 @@ def _oauth_router(config) -> APIRouter:
         # secret AND TURNSTILE_REQUIRED=false (the default), the gate
         # opens — see `backend/app/turnstile.py` for the full matrix.
         client_ip = request.client.host if request.client else None
-        ts = turnstile.verify_token(body.turnstile_token, client_ip=client_ip)
+        ts = await turnstile.verify_token(body.turnstile_token, client_ip=client_ip)
         if not ts.ok:
             if ts.reason == "misconfigured":
                 # TURNSTILE_REQUIRED=true but the secret is unset. This
@@ -278,9 +293,25 @@ def _oauth_router(config) -> APIRouter:
 
     @router.post("/auth/otc/verify")
     async def otc_verify(body: OtcVerifyBody, request: Request, response: Response):
+        # v0.25.0 (audit 0026 H1): per-IP brake against fan-out guessing,
+        # plus the per-email lockout enforced inside otc.verify_code.
+        ip = ratelimit.client_key(request)
+        if not ratelimit.verify_limiter.allow(ip):
+            raise HTTPException(429, "Too many attempts; please wait a few minutes")
         result = otc.verify_code(body.email, body.code)
+        if result.reason == "locked":
+            raise HTTPException(
+                423,
+                {
+                    "detail": "Too many failed attempts; wait a few minutes or request a new code",
+                    "locked_until": result.locked_until,
+                },
+            )
         if not result.ok or result.user is None:
             raise HTTPException(400, "Invalid or expired code")
+        # Legit sign-in: clear this IP's window so a user who fat-fingered
+        # a couple of codes isn't left throttled.
+        ratelimit.verify_limiter.reset(ip)
         auth.store_session(request, result.user)
         # v0.8.0: surface `needs_profile` so the Login.jsx surface can
         # decide whether to advance to the first/last/why capture step
@@ -313,7 +344,7 @@ def _oauth_router(config) -> APIRouter:
         if body.trust_device:
             ua = request.headers.get("user-agent", "")
             outcome = device_trust_mod.issue(result.user.user_id, ua)
-            _set_device_trust_cookie(response, outcome.raw_token)
+            _set_device_trust_cookie(response, outcome.cookie_value)
         return {
             "ok": True,
             "user": {
@@ -337,12 +368,17 @@ def _oauth_router(config) -> APIRouter:
     # ---------------------------------------------------------------
 
     @router.get("/auth/passcode/check")
-    async def passcode_check(email: str = ""):
+    async def passcode_check(request: Request, email: str = ""):
         """Does this email have a passcode set? Anonymous endpoint —
         the Login.jsx flow calls this after the user types their email
         to decide whether to render a passcode input or fall back to
         OTC. We surface only the boolean; lockout state, the hash, and
-        the set-at stamp are not leaked here."""
+        the set-at stamp are not leaked here.
+
+        v0.25.0 (audit 0026 L3): per-IP rate limit so the has-passcode
+        boolean can't be bulk-harvested to enumerate accounts."""
+        if not ratelimit.check_limiter.allow(ratelimit.client_key(request)):
+            raise HTTPException(429, "Too many requests; please wait a few minutes")
         status = passcode_mod.passcode_status(email)
         return {"has_passcode": status.has_passcode}
 
@@ -376,6 +412,11 @@ def _oauth_router(config) -> APIRouter:
         v0.11.0: the body's `trust_device` flag, if true, mints a
         fresh device-trust row and sets the long-lived cookie. Same
         opt-in contract as `/auth/otc/verify`."""
+        # v0.25.0 (audit 0026 H1): per-IP brake in front of the per-account
+        # passcode lockout, so fan-out across emails is throttled too.
+        ip = ratelimit.client_key(request)
+        if not ratelimit.verify_limiter.allow(ip):
+            raise HTTPException(429, "Too many attempts; please wait a few minutes")
         result = passcode_mod.verify_passcode(body.email, body.passcode)
         if result.reason == "locked":
             raise HTTPException(
@@ -387,11 +428,12 @@ def _oauth_router(config) -> APIRouter:
             )
         if not result.ok or result.user is None:
             raise HTTPException(400, "Invalid passcode")
+        ratelimit.verify_limiter.reset(ip)
         auth.store_session(request, result.user)
         if body.trust_device:
             ua = request.headers.get("user-agent", "")
             outcome = device_trust_mod.issue(result.user.user_id, ua)
-            _set_device_trust_cookie(response, outcome.raw_token)
+            _set_device_trust_cookie(response, outcome.cookie_value)
         return {
             "ok": True,
             "user": {
@@ -459,7 +501,7 @@ def _oauth_router(config) -> APIRouter:
         if body.trust_device:
             ua = request.headers.get("user-agent", "")
             outcome = device_trust_mod.issue(result.user.user_id, ua)
-            _set_device_trust_cookie(response, outcome.raw_token)
+            _set_device_trust_cookie(response, outcome.cookie_value)
 
         # Has the user already set a passcode? (Could only happen via
         # an admin pre-population path that doesn't exist yet, but

backend/app/notify.py

@@ -270,6 +270,86 @@ def fan_out_new_beta_request(
         )
 
 
+def fan_out_contribution_request(
+    *,
+    rfc_slug: str,
+    requester_user_id: int,
+    request_id: int,
+    matched_term: str,
+    who_i_am: str,
+    why: str,
+    use_case: str | None,
+) -> list[int]:
+    """Roadmap #28 Part 3: a reader asked to contribute to a pending
+    (super-draft) RFC. Land one actionable notification per owner and
+    return their ids (the caller stamps the first onto the request row as
+    the inbox-action handle).
+
+    Personal-direct: the owner is the named subject of the request, so the
+    §15.4 email gate consults `email_personal_direct` exactly as for the
+    other owner-facing personal events — no new preference column is
+    needed. The request's three free-text fields ride along in the payload
+    so the inbox row can show the full ask inline without a second fetch.
+    Actor is the requester per §15.9.
+    """
+    requester = db.conn().execute(
+        "SELECT display_name FROM users WHERE id = ?", (requester_user_id,)
+    ).fetchone()
+    display = (requester["display_name"] if requester else None) or "Someone"
+    details = {
+        "request_id": request_id,
+        "matched_term": matched_term,
+        "requester_user_id": requester_user_id,
+        "requester_display": display,
+        "who_i_am": who_i_am,
+        "why": why,
+        "use_case": use_case or "",
+    }
+    notif_ids: list[int] = []
+    for recipient_id in _entry_owner_user_ids(rfc_slug):
+        if recipient_id == requester_user_id:
+            continue
+        notif_ids.append(
+            _emit_one(
+                recipient_user_id=recipient_id,
+                event_kind="contribution_request_on_pending_rfc",
+                category=CATEGORY_PERSONAL,
+                actor_user_id=requester_user_id,
+                rfc_slug=rfc_slug,
+                branch_name=None,
+                pr_number=None,
+                details=details,
+            )
+        )
+    return notif_ids
+
+
+def notify_contribution_decided(
+    *,
+    rfc_slug: str,
+    requester_user_id: int,
+    decider_user_id: int,
+    request_id: int,
+    accepted: bool,
+) -> None:
+    """Roadmap #28 Part 3: tell the requester an owner accepted or declined
+    their contribute request. On accept the requester also receives the
+    #12 invitation email out-of-band; this inbox row is the in-app echo
+    that points them at it."""
+    _emit_one(
+        recipient_user_id=requester_user_id,
+        event_kind=(
+            "contribution_request_accepted" if accepted else "contribution_request_declined"
+        ),
+        category=CATEGORY_PERSONAL,
+        actor_user_id=decider_user_id,
+        rfc_slug=rfc_slug,
+        branch_name=None,
+        pr_number=None,
+        details={"request_id": request_id},
+    )
+
+
 def fan_out_chat_message(
     *,
     actor_user_id: int,
@@ -769,6 +849,16 @@ def render_summary(event_kind: str, actor_display: str | None, rfc_title: str |
         return f"{actor} began graduating {title}."
     if event_kind == "pr_conflict_with_main":
         return f"{actor} started a resolution branch on {title}."
+    if event_kind == "contribution_request_on_pending_rfc":
+        # Roadmap #28 Part 3: owner-facing, actionable. The term is the
+        # super-draft reference that surfaced the offer; the inbox row
+        # renders Accept/Decline beneath this line.
+        term = extras.get("matched_term") or title
+        return f"{actor} wants to contribute to your pending RFC for '{term}'."
+    if event_kind == "contribution_request_accepted":
+        return f"{actor} accepted your request to contribute to {title} — check your email to accept the invitation."
+    if event_kind == "contribution_request_declined":
+        return f"{actor} declined your request to contribute to {title}."
     if event_kind == "new_beta_request":
         # v0.9.0: framework-scoped, not RFC-scoped. The actor (the
         # requester) and the captured full name + email read as
@@ -884,6 +974,11 @@ def list_inbox(
             "read_at": row["read_at"],
             "category": extras.get("category"),
             "summary": render_summary(row["event_kind"], row["actor_display"], row["rfc_title"], extras),
+            # The row's payload, surfaced for kinds that render inline
+            # detail (e.g. #28 Part 3's contribute-request who/why/use-case
+            # + Accept/Decline). Safe to expose: a recipient only ever sees
+            # their own notifications.
+            "extras": extras,
         })
 
     if bundled:

backend/app/otc.py

@@ -85,6 +85,15 @@ def _cooldown_seconds() -> int:
         return 60
 
 
+# v0.25.0 / security audit 0026 (H1): per-email OTC verify lockout,
+# mirroring the passcode path (passcode.py). Five consecutive wrong codes
+# for an email lock its OTC verify for 15 minutes. The per-IP limiter in
+# ratelimit.py is the primary brute-force brake; this is the durable,
+# passcode-parity layer.
+LOCKOUT_AFTER_FAILED_ATTEMPTS = 5
+LOCKOUT_DURATION_MINUTES = 15
+
+
 # ---------------------------------------------------------------------------
 # Code generation + hashing
 # ---------------------------------------------------------------------------
@@ -206,6 +215,61 @@ class VerifyOutcome:
     ok: bool
     user: SessionUser | None
     reason: str
+    # v0.25.0 (H1): ISO-8601 stamp when reason == 'locked'.
+    locked_until: str | None = None
+
+
+def _verify_lockout_until(email: str) -> str | None:
+    """Return the active lockout stamp for `email`, or None if not locked.
+
+    Clears an elapsed lockout (and resets the counter) as a side effect so
+    the next failure starts a fresh budget — mirrors passcode.verify_passcode.
+    """
+    row = db.conn().execute(
+        "SELECT failed_attempts, locked_until FROM otc_verify_state WHERE email = ?",
+        (email,),
+    ).fetchone()
+    if row is None or not row["locked_until"]:
+        return None
+    still_locked = db.conn().execute(
+        "SELECT datetime(?) > datetime('now') AS locked", (row["locked_until"],),
+    ).fetchone()["locked"]
+    if still_locked:
+        return row["locked_until"]
+    db.conn().execute(
+        "UPDATE otc_verify_state SET failed_attempts = 0, locked_until = NULL WHERE email = ?",
+        (email,),
+    )
+    return None
+
+
+def _record_verify_failure(email: str) -> None:
+    """Increment the per-email failure counter; stamp a lockout once it
+    crosses the threshold. Mirrors the passcode lockout shape."""
+    db.conn().execute(
+        """
+        INSERT INTO otc_verify_state (email, failed_attempts)
+        VALUES (?, 1)
+        ON CONFLICT(email) DO UPDATE SET failed_attempts = failed_attempts + 1
+        """,
+        (email,),
+    )
+    count = db.conn().execute(
+        "SELECT failed_attempts FROM otc_verify_state WHERE email = ?", (email,),
+    ).fetchone()["failed_attempts"]
+    if count >= LOCKOUT_AFTER_FAILED_ATTEMPTS:
+        db.conn().execute(
+            f"""
+            UPDATE otc_verify_state
+               SET locked_until = datetime('now', '+{LOCKOUT_DURATION_MINUTES} minutes')
+             WHERE email = ?
+            """,
+            (email,),
+        )
+
+
+def _clear_verify_state(email: str) -> None:
+    db.conn().execute("DELETE FROM otc_verify_state WHERE email = ?", (email,))
 
 
 def verify_code(email: str, code: str) -> VerifyOutcome:
@@ -214,6 +278,13 @@ def verify_code(email: str, code: str) -> VerifyOutcome:
     if not email or not code:
         return VerifyOutcome(ok=False, user=None, reason="invalid")
 
+    # v0.25.0 (H1): refuse before spending any bcrypt if this email is in
+    # its OTC-verify lockout window. The passcode path is unaffected — a
+    # locked-out OTC user can still set/use a passcode, and vice versa.
+    locked_until = _verify_lockout_until(email)
+    if locked_until:
+        return VerifyOutcome(ok=False, user=None, reason="locked", locked_until=locked_until)
+
     rows = db.conn().execute(
         """
         SELECT id, code_hash, expires_at, consumed_at
@@ -237,6 +308,9 @@ def verify_code(email: str, code: str) -> VerifyOutcome:
             break
 
     if matched is None:
+        # A genuine wrong guess against this email — the brute-force
+        # signal. Count it toward the lockout threshold (H1).
+        _record_verify_failure(email)
         return VerifyOutcome(ok=False, user=None, reason="wrong")
 
     if matched["consumed_at"] is not None:
@@ -255,6 +329,8 @@ def verify_code(email: str, code: str) -> VerifyOutcome:
         "UPDATE otc_codes SET consumed_at = datetime('now') WHERE id = ?",
         (matched["id"],),
     )
+    # Success wipes the per-email failure counter (H1).
+    _clear_verify_state(email)
     user = provision_or_link_user(email)
     return VerifyOutcome(ok=True, user=user, reason="ok")
 

backend/app/providers.py

@@ -184,6 +184,21 @@ def load_providers(env: dict) -> dict[str, BaseProvider]:
     return providers
 
 
+def construct_haiku(api_key: str) -> AnthropicProvider:
+    """A dedicated Claude Haiku provider, independent of the
+    `ENABLED_MODELS` chat-picker universe.
+
+    The §9.1 tag-suggestion surface (roadmap #27) always wants the
+    cheap + fast model regardless of which models the operator surfaces
+    in the §8.12 picker, so it constructs Haiku directly from the
+    operator's Anthropic key rather than going through `load_providers`.
+    The model id is sourced from the same `_CLAUDE_VARIANTS` table the
+    picker uses, so a model-string bump lands in one place.
+    """
+    model, name = _CLAUDE_VARIANTS["claude-haiku"]
+    return AnthropicProvider(api_key=api_key, model=model, display_name=name)
+
+
 def load_from_config(config) -> dict[str, BaseProvider]:
     """Convenience adapter so callers can pass our Config dataclass directly."""
     env = {

backend/app/ratelimit.py

@@ -0,0 +1,92 @@
+"""In-process per-IP sliding-window rate limiter (security audit 0026, H1).
+
+The auth verify endpoints (`/auth/otc/verify`, `/auth/passcode/verify`)
+had no per-IP brake, so an attacker could fan out guesses against a
+target identity bounded only by bcrypt cost. This module is the brake.
+
+It is deliberately tiny: §4.2 says the app is a single process with a
+colocated SQLite file, so an in-memory dict of `key -> deque[timestamps]`
+is sufficient and needs no shared store. State resets on restart, which
+fails *open* for a brief window — acceptable because the per-email OTC
+lockout (`otc_verify_state`) and the passcode lockout both persist in the
+database and carry the durable guarantee; this limiter is the
+anti-fan-out layer on top.
+
+Chosen over a per-identity lockout *as the primary control* because a
+per-IP window throttles the attacker without letting them grief a victim
+by locking that victim's account (the known downside of identity
+lockouts). Both layers run together.
+"""
+from __future__ import annotations
+
+import threading
+import time
+from collections import defaultdict, deque
+
+
+class SlidingWindowLimiter:
+    """Allow at most `max_events` per `window_seconds` per key.
+
+    `allow(key)` records an event and returns True if the key is still
+    within budget, False if it has exceeded it. Timestamps use a
+    monotonic clock so the limiter is immune to wall-clock jumps.
+    """
+
+    def __init__(self, max_events: int, window_seconds: float) -> None:
+        self.max_events = max_events
+        self.window_seconds = window_seconds
+        self._events: dict[str, deque[float]] = defaultdict(deque)
+        self._lock = threading.Lock()
+
+    def allow(self, key: str) -> bool:
+        now = time.monotonic()
+        cutoff = now - self.window_seconds
+        with self._lock:
+            q = self._events[key]
+            while q and q[0] < cutoff:
+                q.popleft()
+            if len(q) >= self.max_events:
+                return False
+            q.append(now)
+            # Opportunistic cleanup so idle keys don't accumulate forever.
+            if not q:
+                self._events.pop(key, None)
+            return True
+
+    def reset(self, key: str) -> None:
+        """Drop a key's window — e.g. after a successful sign-in so a
+        legitimate user who fat-fingered a few times isn't throttled."""
+        with self._lock:
+            self._events.pop(key, None)
+
+
+# Module-level limiters shared across requests (one process, so module
+# state is the natural home). Tunables are intentionally generous enough
+# not to bother a human retyping a code, tight enough to kill fan-out:
+#   * verify: 10 attempts / 5 min / IP across the auth verify surfaces.
+#   * otc request: 5 sends / 5 min / IP (Turnstile is the primary gate;
+#     this is defense in depth against a solved-challenge replay loop).
+verify_limiter = SlidingWindowLimiter(max_events=10, window_seconds=300)
+otc_request_limiter = SlidingWindowLimiter(max_events=5, window_seconds=300)
+# /auth/passcode/check is an anonymous has-passcode oracle (audit 0026 L3).
+# It's a legitimate Login-flow affordance, so the budget is generous —
+# enough for a human typing emails, tight enough to stop bulk scraping.
+check_limiter = SlidingWindowLimiter(max_events=30, window_seconds=300)
+
+
+def _reset_all_for_tests() -> None:
+    """Clear every module-level limiter's window. Test support only — the
+    limiters are process-global singletons, so without a per-test reset
+    one test's requests bleed into the next and later tests trip the
+    budget (429). Not called in production."""
+    for lim in (verify_limiter, otc_request_limiter, check_limiter):
+        with lim._lock:
+            lim._events.clear()
+
+
+def client_key(request) -> str:
+    """Best-effort client identity for limiting. Behind nginx the app is
+    started with `--forwarded-allow-ips 127.0.0.1`, so `request.client.host`
+    reflects the real client IP via Uvicorn's ProxyHeaders handling."""
+    client = getattr(request, "client", None)
+    return client.host if client and client.host else "unknown"

backend/app/rfc_links.py

@@ -0,0 +1,333 @@
+"""Roadmap #28 — scan submitted prose for RFC-shaped references.
+
+The scanner splits a plain-text PR description / comment body into a list
+of *segments* the frontend renders: plain-text runs interleaved with
+typed link segments. The backend never emits HTML — the frontend maps
+each segment onto a React node — so the surface is XSS-safe by
+construction and independent of any HTML-sanitization layer.
+
+Three buckets, one scan (Parts 1–3):
+
+  * ``{"type": "rfc", ...}``          — Part 1. The term matches an
+    **accepted** (``state='active'``) RFC; renders as a link to it.
+  * ``{"type": "rfc-pending", ...}``  — Part 3. The term matches a
+    **pending** RFC — a super-draft (``state='super-draft'``: accepted
+    as an idea but not yet graduated to an active RFC) — which has an
+    owner and a contribution surface. Renders as an "ask to contribute"
+    affordance carrying the owner's display name.
+  * ``{"type": "rfc-candidate", ...}`` — Part 2. The term is a
+    strong-candidate that does **not** yet have a defining RFC. Renders
+    (for a viewer with create rights) as a "create RFC for '<term>'"
+    affordance that pre-fills the propose flow.
+
+Precedence at any position is active > pending > candidate, then
+longest-match-first — an active link always wins over a contribute offer
+which always wins over a create offer for the same span.
+
+**Read-time enrichment, not submit-time persistence** (unchanged from
+Part 1): drafts are never scanned, only submitted content on the read
+paths, so links/offers track the *live* corpus. The active-RFC corpus,
+super-draft corpus, and tag taxonomy are all small and cache-resident,
+so building the index and scanning a ≤20k-char body per read is cheap.
+
+**Matching stays conservative by design.** A reference links/offers only
+when it is unlikely to be coincidental:
+
+  * ``rfc_id`` tokens (e.g. ``RFC-0001``) — inherently specific.
+  * Multi-word titles (containing whitespace, e.g. ``Open Human Model``).
+  * Hyphenated slugs (containing ``-``, e.g. ``open-human-model``).
+
+Single common-word titles/slugs are deliberately NOT matched — they
+would turn every prose occurrence into an affordance.
+
+**Part 2 candidate heuristic.** A candidate term is a **multi-word tag**
+from the #27 tag taxonomy (the de-facto set of tags the corpus already
+carries) that has no defining RFC (no active or super-draft RFC whose
+slug or title is that term). Multi-word is the same false-positive guard
+the title rule uses: a single common tag word (``identity``) would be
+far too noisy. Broader candidate detection — capitalized multi-word
+phrases mined from the text, terms repeated across recently-touched PRs,
+or the #27 Haiku (``ANTHROPIC_API_KEY``) pathway — is a sanctioned but
+deferred extension; the conservative tag-taxonomy heuristic is chosen
+here to match Part 1's false-positive-averse philosophy.
+"""
+from __future__ import annotations
+
+import json
+import re
+from typing import Any, Iterable, NamedTuple
+
+
+class Term(NamedTuple):
+    """One match key plus what to emit when it hits.
+
+    ``key`` is the lowercase span to match (word-boundary, longest-first).
+    ``kind`` is ``'active' | 'pending' | 'candidate'`` and selects the
+    emitted segment shape. ``slug``/``title`` carry the target RFC (active
+    + pending); ``owner`` is the pending RFC's owner display name;
+    ``term`` is the candidate's canonical display spelling.
+    """
+
+    key: str
+    kind: str = "active"
+    slug: str = ""
+    title: str = ""
+    owner: str = ""
+    term: str = ""
+
+
+# Lower number = higher precedence when two keys of equal length match at
+# the same position. A real link beats a contribute offer beats a create
+# offer.
+_KIND_PRIORITY = {"active": 0, "pending": 1, "candidate": 2}
+
+
+def _coerce(t: Term | tuple) -> Term:
+    """Accept the legacy ``(key, slug, title)`` 3-tuple (treated as an
+    active term) alongside :class:`Term`, so direct unit-test callers and
+    older call sites keep working."""
+    if isinstance(t, Term):
+        return t
+    key, slug, title = t  # legacy active 3-tuple
+    return Term(key=key, kind="active", slug=slug, title=title)
+
+
+def _is_word_char(c: str) -> bool:
+    """Word-boundary test. Hyphen and underscore count as word chars so a
+    match can't begin or end in the middle of a kebab/snake token."""
+    return c.isalnum() or c in ("-", "_")
+
+
+def _emit(term: Term, label: str) -> dict[str, Any]:
+    """The segment dict for a matched ``term``; ``label`` preserves source
+    casing."""
+    if term.kind == "pending":
+        return {
+            "type": "rfc-pending",
+            "slug": term.slug,
+            "label": label,
+            "title": term.title,
+            "owner": term.owner,
+        }
+    if term.kind == "candidate":
+        return {"type": "rfc-candidate", "label": label, "term": term.term}
+    return {"type": "rfc", "slug": term.slug, "label": label, "title": term.title}
+
+
+def segment_text(text: str | None, terms: Iterable[Term | tuple]) -> list[dict[str, Any]]:
+    """Split ``text`` into text / link segments against ``terms``.
+
+    ``terms`` are :class:`Term` objects (or legacy ``(key, slug, title)``
+    active 3-tuples). Matching is case-insensitive, respects word
+    boundaries on both ends, and prefers the longest key — then higher
+    :data:`_KIND_PRIORITY` — at any position.
+
+    Always returns at least one segment; for empty/None input that is a
+    single empty text segment, so callers can render uniformly.
+    """
+    ordered = sorted(
+        (_coerce(t) for t in terms),
+        key=lambda t: (-len(t.key), _KIND_PRIORITY.get(t.kind, 9)),
+    )
+    if not text:
+        return [{"type": "text", "text": text or ""}]
+
+    out: list[dict[str, Any]] = []
+    buf: list[str] = []
+    low = text.lower()
+    n = len(text)
+    i = 0
+    while i < n:
+        match: tuple[Term, int] | None = None
+        for term in ordered:
+            klen = len(term.key)
+            if klen == 0 or not low.startswith(term.key, i):
+                continue
+            before = text[i - 1] if i > 0 else ""
+            after = text[i + klen] if i + klen < n else ""
+            if _is_word_char(before) or _is_word_char(after):
+                continue
+            match = (term, klen)
+            break
+        if match is not None:
+            term, klen = match
+            if buf:
+                out.append({"type": "text", "text": "".join(buf)})
+                buf = []
+            out.append(_emit(term, text[i:i + klen]))
+            i += klen
+        else:
+            buf.append(text[i])
+            i += 1
+    if buf:
+        out.append({"type": "text", "text": "".join(buf)})
+    return out
+
+
+def _keys_for(slug: str, title: str, rfc_id: str | None) -> Iterable[str]:
+    """The match keys an RFC contributes. See the module docstring for why
+    each gate exists (conservative, false-positive-averse)."""
+    if rfc_id:
+        rid = rfc_id.strip()
+        if len(rid) >= 2:
+            yield rid.lower()
+    if title:
+        t = title.strip()
+        # Multi-word titles only — a single common word is too noisy.
+        if len(t) >= 2 and (" " in t or "\t" in t):
+            yield t.lower()
+    if slug:
+        s = slug.strip()
+        # Hyphenated slugs only — a single-token slug is a bare word.
+        if len(s) >= 2 and "-" in s:
+            yield s.lower()
+
+
+def _slugify(term: str) -> str:
+    """Deterministic kebab-case — mirrors the propose modal's slugify so a
+    tag's would-be slug compares correctly against existing RFC slugs."""
+    return re.sub(r"-+$", "", re.sub(r"^-+", "", re.sub(r"[^a-z0-9]+", "-", term.lower().strip())))
+
+
+class LinkIndex:
+    """A reusable term index built once per request and applied to many
+    bodies (a PR's description plus every comment on it)."""
+
+    def __init__(self, terms: Iterable[Term | tuple]):
+        # Coerce + order once; segment_text re-sorts defensively but a
+        # pre-sorted list keeps the per-body cost to the scan itself.
+        self._terms: list[Term] = sorted(
+            (_coerce(t) for t in terms),
+            key=lambda t: (-len(t.key), _KIND_PRIORITY.get(t.kind, 9)),
+        )
+
+    def __bool__(self) -> bool:
+        return bool(self._terms)
+
+    def segment(self, text: str | None) -> list[dict[str, Any]]:
+        return segment_text(text, self._terms)
+
+
+def _owner_display(conn, owners_json: str | None, proposed_by: str | None) -> str:
+    """The display name to show for a pending RFC's owner. First entry of
+    ``owners_json`` resolved to its user row's display name, falling back
+    to the bare login, then ``proposed_by``, then a neutral noun."""
+    login = None
+    try:
+        owners = json.loads(owners_json or "[]")
+        if isinstance(owners, list):
+            login = next((o for o in owners if isinstance(o, str) and o.strip()), None)
+    except (ValueError, TypeError):
+        login = None
+    if login:
+        row = conn.execute(
+            "SELECT display_name FROM users WHERE gitea_login = ?", (login,)
+        ).fetchone()
+        if row and row["display_name"]:
+            return row["display_name"]
+        return login
+    return (proposed_by or "").strip() or "the proposer"
+
+
+def _tag_universe(conn) -> list[str]:
+    """Distinct tags across the cached corpus (the #27 de-facto taxonomy),
+    preserving original spelling; case-deduped."""
+    rows = conn.execute("SELECT tags_json FROM cached_rfcs").fetchall()
+    out: list[str] = []
+    seen: set[str] = set()
+    for r in rows:
+        try:
+            tags = json.loads(r["tags_json"] or "[]")
+        except (ValueError, TypeError):
+            continue
+        if not isinstance(tags, list):
+            continue
+        for t in tags:
+            if not isinstance(t, str):
+                continue
+            tag = t.strip()
+            low = tag.lower()
+            if tag and low not in seen:
+                seen.add(low)
+                out.append(tag)
+    return out
+
+
+def build_index(
+    conn,
+    *,
+    exclude_slug: str | None = None,
+    include_pending: bool = True,
+    include_candidates: bool = True,
+) -> LinkIndex:
+    """Build a :class:`LinkIndex` over the three buckets.
+
+    ``exclude_slug`` drops the RFC the surrounding surface is itself scoped
+    to, so an RFC's own title/id/slug don't self-link (or self-offer)
+    inside its own PR or discussion. Precedence is enforced by insertion
+    order — active keys are added first and a later bucket never overrides
+    an already-claimed key.
+    """
+    terms: list[Term] = []
+    seen: set[str] = set()
+
+    def add(key: str, term: Term) -> None:
+        if key in seen:
+            return
+        seen.add(key)
+        terms.append(term)
+
+    # --- Part 1: accepted (active) RFCs. ORDER BY slug makes key
+    # de-duplication deterministic when two RFCs would contribute the
+    # same key (first slug wins). ---
+    active_rows = conn.execute(
+        "SELECT slug, title, rfc_id FROM cached_rfcs WHERE state = 'active' ORDER BY slug"
+    ).fetchall()
+    # Track every slug + title that *has* a defining RFC, so Part 2 never
+    # offers to create one that already exists (active or pending).
+    defined_slugs: set[str] = set()
+    defined_titles: set[str] = set()
+    for r in active_rows:
+        slug = r["slug"]
+        defined_slugs.add((slug or "").lower())
+        defined_titles.add((r["title"] or "").strip().lower())
+        if exclude_slug is not None and slug == exclude_slug:
+            continue
+        title = r["title"] or ""
+        rfc_id = r["rfc_id"] if "rfc_id" in r.keys() else None
+        for key in _keys_for(slug, title, rfc_id):
+            add(key, Term(key=key, kind="active", slug=slug, title=title))
+
+    # --- Part 3: pending (super-draft) RFCs. ---
+    pending_rows = conn.execute(
+        """
+        SELECT slug, title, rfc_id, owners_json, proposed_by
+          FROM cached_rfcs WHERE state = 'super-draft' ORDER BY slug
+        """
+    ).fetchall()
+    for r in pending_rows:
+        slug = r["slug"]
+        defined_slugs.add((slug or "").lower())
+        defined_titles.add((r["title"] or "").strip().lower())
+        if not include_pending:
+            continue
+        if exclude_slug is not None and slug == exclude_slug:
+            continue
+        title = r["title"] or ""
+        rfc_id = r["rfc_id"] if "rfc_id" in r.keys() else None
+        owner = _owner_display(conn, r["owners_json"], r["proposed_by"])
+        for key in _keys_for(slug, title, rfc_id):
+            add(key, Term(key=key, kind="pending", slug=slug, title=title, owner=owner))
+
+    # --- Part 2: strong-candidate terms with no defining RFC. ---
+    if include_candidates:
+        for tag in _tag_universe(conn):
+            low = tag.lower()
+            # Conservative: multi-word tags only (same guard as titles).
+            if " " not in tag and "\t" not in tag:
+                continue
+            if low in defined_titles or low in defined_slugs or _slugify(tag) in defined_slugs:
+                continue
+            add(low, Term(key=low, kind="candidate", term=tag))
+
+    return LinkIndex(terms)

backend/app/tag_suggest.py

@@ -0,0 +1,244 @@
+"""Roadmap #27 — Claude Haiku tag suggestions for the propose-RFC modal.
+
+A cheap, fast assist: given the partial RFC draft a user is typing, ask
+Claude Haiku to recommend tags drawn ONLY from the tags already in use
+across the corpus. v1 has no curated tag list — tags are free-form chip
+input (§9.1) — so "the taxonomy" is the de-facto set of distinct tags
+the existing RFCs already carry. The model is constrained to that set
+and MUST NOT invent new tags; taxonomy extension (letting the model
+propose genuinely new tags) is a deferred follow-up per the roadmap.
+
+Why Haiku specifically: cost. Picking a few reasonable tags from a known
+set is well within Haiku's range, and the modal fires this repeatedly as
+the user types, so the per-call price has to stay small.
+
+The whole surface degrades to silence rather than error: no Anthropic
+key, no provider, an empty corpus, a rate-limited caller, an empty
+draft, or an unparseable model reply all yield an empty suggestion list.
+The propose modal hides its suggestion row on an empty list, so the
+fallback is simply the existing free-form chip input with nothing extra
+shown.
+"""
+from __future__ import annotations
+
+import json
+import logging
+import os
+import time
+from dataclasses import dataclass
+
+from . import db
+from .providers import BaseProvider, construct_haiku
+
+log = logging.getLogger(__name__)
+
+# Bound the universe handed to the model so a large corpus can't blow up
+# the prompt size (and the cost). The most-common tags matter most.
+_UNIVERSE_CAP = 200
+
+# How many suggestions we ever return to the modal.
+DEFAULT_MAX_SUGGESTIONS = 6
+
+
+@dataclass
+class Draft:
+    """The partial propose-RFC draft. `pitch` is the "why is this needed"
+    rationale; `use_case` is the #26 optional ground-truth field."""
+
+    title: str = ""
+    pitch: str = ""
+    use_case: str = ""
+
+    def is_empty(self) -> bool:
+        return not (self.title.strip() or self.pitch.strip() or self.use_case.strip())
+
+
+def haiku_provider(config) -> BaseProvider | None:
+    """Construct a dedicated Claude Haiku provider from the operator's
+    Anthropic key, or return None when no key is configured.
+
+    None means "suggestions unavailable" — the caller returns an empty
+    list and the modal shows nothing. This is the seam tests monkeypatch
+    to inject a fake provider without a real key. There is no RFC slug at
+    propose time, so the §6.7 per-RFC funder path deliberately does not
+    apply: tag suggestion always runs on the operator's own key.
+    """
+    key = getattr(config, "anthropic_api_key", "") or ""
+    if not key:
+        return None
+    return construct_haiku(key)
+
+
+def gather_tag_universe(cap: int = _UNIVERSE_CAP) -> list[str]:
+    """Every distinct tag in use across the cached corpus, most-common
+    first (ties broken alphabetically for determinism), capped.
+
+    This is the universe the model is constrained to. An empty corpus
+    yields an empty list, which short-circuits suggestion to silence.
+    """
+    rows = db.conn().execute("SELECT tags_json FROM cached_rfcs").fetchall()
+    counts: dict[str, int] = {}
+    for r in rows:
+        try:
+            tags = json.loads(r["tags_json"] or "[]")
+        except (ValueError, TypeError):
+            continue
+        if not isinstance(tags, list):
+            continue
+        for t in tags:
+            if not isinstance(t, str):
+                continue
+            tag = t.strip()
+            if tag:
+                counts[tag] = counts.get(tag, 0) + 1
+    ranked = sorted(counts, key=lambda t: (-counts[t], t.lower()))
+    return ranked[:cap]
+
+
+# ---------------------------------------------------------------------------
+# Rate limiting — in-process, per-user sliding window.
+#
+# Cost control, not security: the `require_contributor` gate already
+# bounds callers to authenticated beta users, and the modal debounces.
+# This is the backstop against a stuck/abusive client hammering the
+# endpoint. In-memory is sufficient (single-process uvicorn on the VM)
+# and resets on restart, which is fine for a cost guard.
+# ---------------------------------------------------------------------------
+
+_CALLS: dict[int, list[float]] = {}
+
+
+def _rate_config() -> tuple[int, float]:
+    try:
+        max_calls = int(os.environ.get("TAG_SUGGEST_RATE_MAX", "30"))
+    except ValueError:
+        max_calls = 30
+    try:
+        window = float(os.environ.get("TAG_SUGGEST_RATE_WINDOW_SECONDS", "60"))
+    except ValueError:
+        window = 60.0
+    return max_calls, window
+
+
+def rate_limit_ok(user_id: int, *, now: float | None = None) -> bool:
+    """True if this call is within the per-user window; records the call.
+    `now` is injectable for tests (defaults to a monotonic clock)."""
+    max_calls, window = _rate_config()
+    t = time.monotonic() if now is None else now
+    calls = _CALLS.setdefault(user_id, [])
+    cutoff = t - window
+    calls[:] = [c for c in calls if c > cutoff]
+    if len(calls) >= max_calls:
+        return False
+    calls.append(t)
+    return True
+
+
+def reset_rate_limits() -> None:
+    """Test seam — clear the in-process window state."""
+    _CALLS.clear()
+
+
+# ---------------------------------------------------------------------------
+# Prompt + parse.
+# ---------------------------------------------------------------------------
+
+_SYSTEM = (
+    "You suggest topic tags for a draft RFC — a structured proposal "
+    "document in a collection. You are given the draft's title, its "
+    "rationale, an optional use case, and the exact set of tags already "
+    "in use across the collection. Choose the tags from that set that "
+    "best fit the draft.\n"
+    "Rules:\n"
+    "- Choose ONLY from the provided tag set. Never invent a tag.\n"
+    "- Order best-fit first. Omit weak fits rather than padding the list.\n"
+    "- Return at most {max} tags.\n"
+    "Respond with ONLY a JSON array, no prose, of the form:\n"
+    '[{{"tag": "<exact tag from the set>", "confidence": <number between 0 and 1>}}]\n'
+    "If no tag in the set fits the draft, return []."
+)
+
+
+def _build_messages(draft: Draft, universe: list[str], max_suggestions: int):
+    system = _SYSTEM.format(max=max_suggestions)
+    parts: list[str] = []
+    if draft.title.strip():
+        parts.append(f"Title: {draft.title.strip()[:300]}")
+    if draft.pitch.strip():
+        parts.append(f"Why this RFC is needed:\n{draft.pitch.strip()[:4000]}")
+    if draft.use_case.strip():
+        parts.append(f"What it will be used for:\n{draft.use_case.strip()[:4000]}")
+    parts.append(
+        "Tags already in use (choose only from these):\n" + ", ".join(universe)
+    )
+    return system, [{"role": "user", "content": "\n\n".join(parts)}]
+
+
+def _extract_json_array(text: str):
+    start = text.find("[")
+    end = text.rfind("]")
+    if start == -1 or end == -1 or end < start:
+        return None
+    try:
+        return json.loads(text[start : end + 1])
+    except ValueError:
+        return None
+
+
+def parse_reply(text: str, universe: list[str], max_suggestions: int) -> list[dict]:
+    """Parse the model reply into a clean, universe-constrained list.
+
+    Tolerant of the model returning bare strings or objects, extra prose
+    around the JSON, unknown/invented tags (dropped), duplicate tags
+    (deduped), and missing/garbage confidences (defaulted + clamped).
+    """
+    data = _extract_json_array(text or "")
+    if not isinstance(data, list):
+        return []
+    # Map back to the canonical spelling in the universe, case-insensitively,
+    # so a model that lowercases a tag still resolves to the real one.
+    canonical = {t.lower(): t for t in universe}
+    out: list[dict] = []
+    seen: set[str] = set()
+    for item in data:
+        if isinstance(item, dict):
+            raw = item.get("tag")
+            conf = item.get("confidence")
+        elif isinstance(item, str):
+            raw, conf = item, None
+        else:
+            continue
+        if not isinstance(raw, str):
+            continue
+        tag = canonical.get(raw.strip().lower())
+        if tag is None or tag in seen:
+            continue
+        try:
+            c = float(conf) if conf is not None else 0.5
+        except (ValueError, TypeError):
+            c = 0.5
+        c = max(0.0, min(1.0, c))
+        out.append({"tag": tag, "confidence": round(c, 3)})
+        seen.add(tag)
+        if len(out) >= max_suggestions:
+            break
+    return out
+
+
+def suggest(
+    provider: BaseProvider,
+    draft: Draft,
+    universe: list[str],
+    max_suggestions: int = DEFAULT_MAX_SUGGESTIONS,
+) -> list[dict]:
+    """Orchestrate one suggestion call. Returns [] for an empty draft or
+    empty universe (no model call), and for any provider/parse failure."""
+    if draft.is_empty() or not universe:
+        return []
+    system, history = _build_messages(draft, universe, max_suggestions)
+    try:
+        text = provider.send(system, history)
+    except Exception as exc:  # provider/network failure → silent empty
+        log.warning("tag-suggest provider failed: %s", exc)
+        return []
+    return parse_reply(text, universe, max_suggestions)

backend/app/turnstile.py

@@ -73,6 +73,19 @@ def _siteverify_url() -> str:
     return os.environ.get("TURNSTILE_SITEVERIFY_URL", "").strip() or SITEVERIFY_URL
 
 
+async def _siteverify_post(url: str, data: dict) -> httpx.Response:
+    """Perform the siteverify POST on an `httpx.AsyncClient`.
+
+    Isolated as a narrow seam (I4, security-audit-0026): the call is
+    awaited so a slow CloudFlare response can't block the event loop,
+    and tests patch *this function* rather than the shared
+    `httpx.AsyncClient` (which other modules — gitea, docs — also
+    construct, so a global patch would break app boot).
+    """
+    async with httpx.AsyncClient(timeout=10.0) as client:
+        return await client.post(url, data=data)
+
+
 @dataclass
 class VerifyOutcome:
     """Result of a Turnstile siteverify call.
@@ -98,7 +111,7 @@ class VerifyOutcome:
     reason: str
 
 
-def verify_token(token: str | None, *, client_ip: str | None = None) -> VerifyOutcome:
+async def verify_token(token: str | None, *, client_ip: str | None = None) -> VerifyOutcome:
     """Validate a Turnstile token against CloudFlare's siteverify endpoint.
 
     Returns a VerifyOutcome describing whether the calling endpoint
@@ -108,9 +121,14 @@ def verify_token(token: str | None, *, client_ip: str | None = None) -> VerifyOu
       * 'misconfigured' → 500 "auth misconfigured"
       * 'missing-token' / 'failed' / 'network' → 400 "verification failed"
 
-    Tests monkeypatch `httpx.post` (or set `TURNSTILE_SITEVERIFY_URL`
-    + a MockTransport client) to avoid touching the real CloudFlare
-    endpoint. No real keys are ever embedded in tests.
+    Async (I4, security-audit-0026): the siteverify call is awaited on an
+    `httpx.AsyncClient` so a slow CloudFlare response can't block the
+    event loop (the prior synchronous `httpx.post` stalled the single
+    worker for up to the 10s timeout). Callers must `await` it.
+
+    Tests monkeypatch `_siteverify_post` (the narrow async seam) to avoid
+    touching the real CloudFlare endpoint and to keep the patch off the
+    shared `httpx.AsyncClient`. No real keys are ever embedded in tests.
     """
     secret = _secret()
     required = _required()
@@ -133,7 +151,7 @@ def verify_token(token: str | None, *, client_ip: str | None = None) -> VerifyOu
         data["remoteip"] = client_ip
 
     try:
-        response = httpx.post(_siteverify_url(), data=data, timeout=10.0)
+        response = await _siteverify_post(_siteverify_url(), data)
         payload = response.json()
     except Exception as exc:  # network, JSON parse, etc.
         log.warning("Turnstile siteverify call failed: %s", exc)

backend/migrations/021_proposed_use_case.sql

@@ -0,0 +1,47 @@
+-- Roadmap #26 (rfc-app v0.22.0): the optional "What will you be using
+-- this for?" capture on the two propose surfaces.
+--
+-- The roadmap's framing names "the rfcs table" and "the PR-metadata
+-- table" for a `proposed_use_case TEXT NULL` column. In this deployment
+-- those two surfaces are the cache tables `cached_rfcs` and `cached_prs`
+-- (002_cache.sql). We add the nullable column to each, matching the
+-- existing naming convention (no NOT NULL, no default — NULL is the
+-- "left blank" sentinel the view surfaces render tastefully).
+--
+-- BUT: those tables are *cache*, rebuilt from Gitea by the §4.1
+-- reconciler (cache.py). The reconciler's INSERT...ON CONFLICT DO UPDATE
+-- sets only the columns it knows about, so an unlisted column is
+-- preserved on the update path — yet a propose/open never *writes* the
+-- column through the cache (the write path is endpoint -> Gitea ->
+-- reconcile, and the reconciler does not carry this field). So the cache
+-- column alone would always read NULL.
+--
+-- The durable home is therefore a dedicated app-truth table the propose
+-- /open endpoints write directly (keyed by the PR number, which is the
+-- stable identity for both idea PRs and rfc_branch PRs) and the view
+-- endpoints read back. This is not cache — it is canonical and survives
+-- any reconcile. The cache columns are added too for parity with the
+-- roadmap's literal shape and for any future reconciler that learns to
+-- carry the field, but the side table is the source of truth read at
+-- view time.
+
+ALTER TABLE cached_rfcs ADD COLUMN proposed_use_case TEXT;
+ALTER TABLE cached_prs ADD COLUMN proposed_use_case TEXT;
+
+-- Canonical, reconcile-proof store. One row per propose/open that
+-- supplied a use case. `scope` distinguishes the propose-RFC surface
+-- ('rfc') from the propose-PR-against-an-RFC surface ('pr'); `pr_number`
+-- is the join key the endpoints already have in hand. NULL/omitted use
+-- cases simply never write a row here, so absence == "left blank".
+CREATE TABLE proposed_use_cases (
+    id              INTEGER PRIMARY KEY AUTOINCREMENT,
+    scope           TEXT NOT NULL CHECK (scope IN ('rfc', 'pr')),
+    rfc_slug        TEXT NOT NULL,
+    pr_number       INTEGER NOT NULL,
+    use_case        TEXT NOT NULL,
+    created_at      TEXT NOT NULL DEFAULT (datetime('now')),
+    UNIQUE (scope, pr_number)
+);
+
+CREATE INDEX idx_proposed_use_cases_lookup ON proposed_use_cases (scope, pr_number);
+CREATE INDEX idx_proposed_use_cases_slug ON proposed_use_cases (scope, rfc_slug);

backend/migrations/022_user_session_state.sql

@@ -0,0 +1,54 @@
+-- v0.23.0 / roadmap item #29: server-side sign-in state resume.
+--
+-- Track each authenticated user's last-viewed route + a small bag of
+-- "light" component state so that the *next* sign-in can land the user
+-- back where they left off, rather than always dropping them on the
+-- empty-state home view.
+--
+-- Storage shape (one row per user — per-user, NOT per-device, per the
+-- #29 "safe default"):
+--
+--   * `user_id` — PRIMARY KEY and FK into users(id) with cascade on
+--     delete. INTEGER to match users.id (INTEGER PRIMARY KEY
+--     AUTOINCREMENT). A deleted user automatically loses their stored
+--     resume state. One row per user means a later sign-in on any
+--     device resumes the most-recently-recorded route — the per-user
+--     model the roadmap asks for.
+--
+--   * `last_route` — the frontend pathname the user was last on
+--     (e.g. "/rfc/open-human-model"). TEXT, nullable until the first
+--     route-change POST lands. NEVER contains draft-buffer contents —
+--     it is a route only. See SPEC §6.2 "Sign-in state resume
+--     (privacy)".
+--
+--   * `last_route_state` — a JSON-encoded bag of *light* component
+--     state (scroll anchors, open-tab selection, filter chips, etc.).
+--     SQLite has no native JSONB; we store JSON as TEXT exactly as the
+--     rest of the app stores its JSON blobs (json.dumps / json.loads,
+--     cf. permission_events.details, actions.details). Nullable.
+--     PRIVACY INVARIANT: this column MUST NOT carry draft-buffer text,
+--     PR bodies, comment drafts, or any user-typed content — only
+--     ephemeral view state safe to replay. The PUT handler is the
+--     enforcement point; the column comment is the contract.
+--
+--   * `resume_enabled` — the per-user opt-out flag. 1 (default) means
+--     "resume me where I left off"; 0 means "always land on home". The
+--     PUT handler no-ops the upsert when this is 0, and the read path
+--     refuses to hand back a stored route when this is 0. A
+--     profile-settings toggle UI to flip this is a follow-up (the
+--     column + default-on behavior ship now); see CHANGELOG v0.23.0.
+--
+--   * `last_updated_at` — TEXT timestamp, app convention
+--     `datetime('now')`, matching device_trust.last_seen_at /
+--     users.last_seen_at. Refreshed on every successful upsert.
+--
+-- No new env vars. The debounce interval for the frontend route-change
+-- POST is a frontend constant (~1s), not a server knob.
+
+CREATE TABLE user_session_state (
+    user_id          INTEGER PRIMARY KEY REFERENCES users(id) ON DELETE CASCADE,
+    last_route       TEXT,
+    last_route_state TEXT,                        -- JSON-encoded light state, nullable
+    resume_enabled   INTEGER NOT NULL DEFAULT 1,
+    last_updated_at  TEXT NOT NULL DEFAULT (datetime('now'))
+);

backend/migrations/023_otc_verify_lockout.sql

@@ -0,0 +1,18 @@
+-- v0.25.0 / security audit 0026, finding H1.
+--
+-- The OTC verify path had no attempt-limit or lockout, unlike the
+-- passcode path (015_passcode.sql gave users.passcode_failed_attempts +
+-- passcode_locked_until). This table gives the OTC verify endpoint the
+-- same per-identity lockout shape. It is keyed by email rather than
+-- user_id because an OTC sign-in may not have a users row yet — the row
+-- is provisioned only on a *successful* verify, so the lockout state has
+-- to survive independently of it.
+--
+-- The per-IP rate limiter (app/ratelimit.py) is the primary brute-force
+-- defense; this table is the parity layer that mirrors the passcode
+-- lockout and persists across restarts.
+CREATE TABLE IF NOT EXISTS otc_verify_state (
+    email TEXT PRIMARY KEY,
+    failed_attempts INTEGER NOT NULL DEFAULT 0,
+    locked_until TEXT
+);

backend/migrations/024_contribution_requests.sql

@@ -0,0 +1,59 @@
+-- v0.29.0 / roadmap #28 Part 3 — offer-to-contribute-to-a-pending-RFC.
+--
+-- When the #28 scanner matches a term in submitted PR/comment text to a
+-- *pending* RFC (a super-draft: accepted-as-an-idea but not yet graduated
+-- to an active RFC), the reader is offered a "ask to contribute" popover.
+-- Submitting it lands a row here AND a notification in each owner's §15
+-- inbox; the owner can accept (which fires #12's owner-invite flow with
+-- the requester as the invitee) or decline (the requester is notified and
+-- the request closes).
+--
+-- A "pending RFC" is scoped to a super-draft (cached_rfcs.state =
+-- 'super-draft'): it is in cached_rfcs (so the rfc_invitations FK that the
+-- accept path reuses resolves), it carries owners (owners_json) to route
+-- the request to, and it already has a discussion/contribution surface to
+-- open. Pre-merge idea PRs (not yet in cached_rfcs, no contribution
+-- surface) are deliberately out of scope — see backend/app/rfc_links.py.
+--
+-- The request row is the persistent record; the inbox notification is the
+-- owner-facing actionable surface keyed back to it via `notification_id`.
+
+CREATE TABLE IF NOT EXISTS contribution_requests (
+    id                  INTEGER PRIMARY KEY AUTOINCREMENT,
+    rfc_slug            TEXT NOT NULL
+                            REFERENCES cached_rfcs(slug) ON DELETE CASCADE,
+    requester_user_id   INTEGER NOT NULL
+                            REFERENCES users(id) ON DELETE CASCADE,
+    -- The term in the PR/comment text that surfaced the offer (e.g. the
+    -- super-draft's title). Carried for the owner's context line and the
+    -- requester's "what RFC" anchor; not a foreign key.
+    matched_term        TEXT NOT NULL,
+    -- The three contribute-request fields (§15 / #26 vocabulary).
+    -- `who_i_am` and `why` are required; `use_case` mirrors #26's
+    -- optional ground-truth field.
+    who_i_am            TEXT NOT NULL,
+    why                 TEXT NOT NULL,
+    use_case            TEXT,
+    status              TEXT NOT NULL DEFAULT 'pending'
+                            CHECK (status IN ('pending', 'accepted', 'declined')),
+    created_at          TEXT NOT NULL DEFAULT (datetime('now')),
+    decided_at          TEXT,
+    decided_by_user_id  INTEGER REFERENCES users(id) ON DELETE SET NULL,
+    -- The rfc_invitations row minted on accept (the #12 reuse), and the
+    -- owner-facing notification row that carries the Accept/Decline action.
+    invitation_id       INTEGER REFERENCES rfc_invitations(id) ON DELETE SET NULL,
+    notification_id     INTEGER REFERENCES notifications(id) ON DELETE SET NULL
+);
+
+CREATE INDEX IF NOT EXISTS idx_contribution_requests_rfc
+    ON contribution_requests(rfc_slug, status);
+
+CREATE INDEX IF NOT EXISTS idx_contribution_requests_requester
+    ON contribution_requests(requester_user_id, status);
+
+-- At most one open (pending) request per (RFC, requester): a second ask
+-- while one is still pending is a 409, not a duplicate row. A decided
+-- request (accepted/declined) does not block a fresh ask later.
+CREATE UNIQUE INDEX IF NOT EXISTS idx_contribution_requests_one_open
+    ON contribution_requests(rfc_slug, requester_user_id)
+    WHERE status = 'pending';

backend/tests/conftest.py

@@ -0,0 +1,19 @@
+"""Shared pytest fixtures for the backend suite.
+
+Added in v0.27.0 (security audit 0026) alongside the new per-IP rate
+limiter. The limiters in `app.ratelimit` are process-global singletons,
+so their state survives across tests within a run; without a reset, the
+accumulated requests from earlier tests exhaust the budget and later
+tests see spurious 429s. This autouse fixture gives every test a clean
+limiter window.
+"""
+import pytest
+
+from app import ratelimit
+
+
+@pytest.fixture(autouse=True)
+def _reset_rate_limiters():
+    ratelimit._reset_all_for_tests()
+    yield
+    ratelimit._reset_all_for_tests()

backend/tests/test_contributions_vertical.py

@@ -0,0 +1,236 @@
+"""v0.29.0 / roadmap #28 Parts 2 & 3 — create-RFC offers + contribute-to-
+pending requests.
+
+Two layers, mirroring test_rfc_links_vertical.py:
+
+  * The PR-view scanner surfaces `rfc-pending` (Part 3) and `rfc-candidate`
+    (Part 2) segments alongside Part 1's `rfc` links.
+  * The contribute-request flow end-to-end: a non-owner asks, each owner
+    gets an actionable §15 notification, accept fires #12's invite flow,
+    decline notifies the requester.
+
+Reuses the FakeGitea + seed/session helpers from the existing suites.
+"""
+from __future__ import annotations
+
+import json
+
+from fastapi.testclient import TestClient
+
+from app import db
+
+from test_propose_vertical import (  # noqa: F401
+    FakeGitea,
+    app_with_fake_gitea,
+    provision_user_row,
+    sign_in_as,
+    tmp_env,
+)
+from test_rfc_view_vertical import SEED_BODY, seed_active_rfc
+from test_super_draft_vertical import seed_super_draft
+from test_rfc_links_vertical import _open_pr_on
+
+
+def _set_owner(slug: str, login: str) -> None:
+    db.conn().execute(
+        "UPDATE cached_rfcs SET owners_json = ? WHERE slug = ?",
+        (json.dumps([login]), slug),
+    )
+
+
+def _set_tags(slug: str, tags: list[str]) -> None:
+    db.conn().execute(
+        "UPDATE cached_rfcs SET tags_json = ? WHERE slug = ?",
+        (json.dumps(tags), slug),
+    )
+
+
+def _segs(segments, kind):
+    return [s for s in segments if s["type"] == kind]
+
+
+# ---------------------------------------------------------------------------
+# Part 2 + Part 3 — scanner surfaces on the PR view
+# ---------------------------------------------------------------------------
+
+
+def test_pending_and_candidate_segments_on_pr(app_with_fake_gitea):
+    app, fake = app_with_fake_gitea
+    with TestClient(app) as client:
+        provision_user_row(user_id=2, login="alice", role="contributor")
+        # Host active RFC (OHM — single word, contributes no keys itself)
+        # carrying a multi-word tag with no defining RFC: the Part 2
+        # candidate. And a pending super-draft owned by alice: the Part 3
+        # contribute target.
+        seed_active_rfc(fake, slug="ohm", title="OHM", body=SEED_BODY)
+        _set_tags("ohm", ["memory model", "identity"])
+        seed_super_draft(fake, slug="open-human-model", title="Open Human Model",
+                         pitch="A framework for representing humans.", proposed_by="alice")
+        _set_owner("open-human-model", "alice")
+        sign_in_as(client, user_id=2, gitea_login="alice", display_name="Alice", role="contributor")
+
+        pr_number = _open_pr_on(
+            client, fake, host_slug="ohm",
+            description="This builds on the Open Human Model and the memory model.",
+        )
+        pr = client.get(f"/api/rfcs/ohm/prs/{pr_number}").json()
+        segs = pr["description_segments"]
+
+        pending = _segs(segs, "rfc-pending")
+        assert len(pending) == 1
+        assert pending[0]["slug"] == "open-human-model"
+        assert pending[0]["label"] == "Open Human Model"
+        assert pending[0]["owner"] == "Alice"   # display_name of the owner
+
+        candidate = _segs(segs, "rfc-candidate")
+        assert len(candidate) == 1
+        assert candidate[0]["term"] == "memory model"
+        # "identity" is a single-word tag — deliberately NOT a candidate.
+        assert all("identity" not in s.get("term", "") for s in candidate)
+
+
+# ---------------------------------------------------------------------------
+# Part 3 — the contribute-request flow
+# ---------------------------------------------------------------------------
+
+
+def _seed_pending_owned_by_alice(fake):
+    provision_user_row(user_id=2, login="alice", role="contributor")
+    provision_user_row(user_id=3, login="bob", role="contributor")
+    seed_super_draft(fake, slug="open-human-model", title="Open Human Model",
+                     pitch="A framework.", proposed_by="alice")
+    _set_owner("open-human-model", "alice")
+
+
+_REQUEST = {
+    "matched_term": "Open Human Model",
+    "who_i_am": "Bob, a researcher",
+    "why": "I have relevant prior work to bring.",
+    "use_case": "Building an identity tool.",
+}
+
+
+def test_request_accept_invites_and_notifies(app_with_fake_gitea):
+    app, fake = app_with_fake_gitea
+    with TestClient(app) as client:
+        _seed_pending_owned_by_alice(fake)
+
+        # Bob asks to contribute.
+        sign_in_as(client, user_id=3, gitea_login="bob", display_name="Bob",
+                   role="contributor", email="bob@test")
+        r = client.post("/api/rfcs/open-human-model/contribution-requests", json=_REQUEST)
+        assert r.status_code == 200, r.text
+        request_id = r.json()["id"]
+        assert r.json()["status"] == "pending"
+
+        # A second ask while pending is a 409, not a duplicate row.
+        assert client.post("/api/rfcs/open-human-model/contribution-requests",
+                           json=_REQUEST).status_code == 409
+
+        # Alice (owner) sees the actionable notification with full detail.
+        sign_in_as(client, user_id=2, gitea_login="alice", display_name="Alice",
+                   role="contributor", email="alice@test")
+        inbox = client.get("/api/notifications").json()
+        reqs = [i for i in inbox["items"]
+                if i["event_kind"] == "contribution_request_on_pending_rfc"]
+        assert len(reqs) == 1
+        assert "wants to contribute" in reqs[0]["summary"]
+        assert reqs[0]["extras"]["who_i_am"] == "Bob, a researcher"
+        assert reqs[0]["extras"]["request_id"] == request_id
+
+        # Alice accepts → #12 invitation minted for bob's email.
+        acc = client.post(f"/api/rfcs/open-human-model/contribution-requests/{request_id}/accept")
+        assert acc.status_code == 200, acc.text
+        assert acc.json()["status"] == "accepted"
+        assert acc.json()["invitation_id"]
+
+        inv = db.conn().execute(
+            "SELECT invitee_email, role_in_rfc, status FROM rfc_invitations "
+            "WHERE rfc_slug = 'open-human-model'"
+        ).fetchone()
+        assert inv["invitee_email"] == "bob@test"
+        assert inv["role_in_rfc"] == "contributor"
+        assert inv["status"] == "pending"
+
+        # The request is settled — re-accepting is a 409.
+        assert client.post(
+            f"/api/rfcs/open-human-model/contribution-requests/{request_id}/accept"
+        ).status_code == 409
+
+        # Bob gets the accepted echo in his inbox.
+        sign_in_as(client, user_id=3, gitea_login="bob", display_name="Bob",
+                   role="contributor", email="bob@test")
+        bob_kinds = [i["event_kind"] for i in client.get("/api/notifications").json()["items"]]
+        assert "contribution_request_accepted" in bob_kinds
+
+
+def test_decline_notifies_requester(app_with_fake_gitea):
+    app, fake = app_with_fake_gitea
+    with TestClient(app) as client:
+        _seed_pending_owned_by_alice(fake)
+        sign_in_as(client, user_id=3, gitea_login="bob", display_name="Bob",
+                   role="contributor", email="bob@test")
+        request_id = client.post(
+            "/api/rfcs/open-human-model/contribution-requests", json=_REQUEST
+        ).json()["id"]
+
+        sign_in_as(client, user_id=2, gitea_login="alice", display_name="Alice",
+                   role="contributor", email="alice@test")
+        dec = client.post(f"/api/rfcs/open-human-model/contribution-requests/{request_id}/decline")
+        assert dec.status_code == 200, dec.text
+        assert dec.json()["status"] == "declined"
+
+        row = db.conn().execute(
+            "SELECT status FROM contribution_requests WHERE id = ?", (request_id,)
+        ).fetchone()
+        assert row["status"] == "declined"
+
+        sign_in_as(client, user_id=3, gitea_login="bob", display_name="Bob",
+                   role="contributor", email="bob@test")
+        bob_kinds = [i["event_kind"] for i in client.get("/api/notifications").json()["items"]]
+        assert "contribution_request_declined" in bob_kinds
+
+
+def test_owner_cannot_request_own_rfc(app_with_fake_gitea):
+    app, fake = app_with_fake_gitea
+    with TestClient(app) as client:
+        _seed_pending_owned_by_alice(fake)
+        sign_in_as(client, user_id=2, gitea_login="alice", display_name="Alice",
+                   role="contributor", email="alice@test")
+        r = client.post("/api/rfcs/open-human-model/contribution-requests", json=_REQUEST)
+        assert r.status_code == 409
+        assert "own" in r.json()["detail"].lower()
+
+
+def test_request_on_active_rfc_rejected(app_with_fake_gitea):
+    # The contribute offer only exists for pending super-drafts; an active
+    # RFC uses the Part-1 link instead.
+    app, fake = app_with_fake_gitea
+    with TestClient(app) as client:
+        provision_user_row(user_id=3, login="bob", role="contributor")
+        seed_active_rfc(fake, slug="ohm", title="OHM", body=SEED_BODY)
+        sign_in_as(client, user_id=3, gitea_login="bob", display_name="Bob",
+                   role="contributor", email="bob@test")
+        r = client.post("/api/rfcs/ohm/contribution-requests", json=_REQUEST)
+        assert r.status_code == 409
+
+
+def test_contribution_target_eligibility(app_with_fake_gitea):
+    app, fake = app_with_fake_gitea
+    with TestClient(app) as client:
+        _seed_pending_owned_by_alice(fake)
+
+        # Anonymous: not eligible, told to sign in.
+        t = client.get("/api/rfcs/open-human-model/contribution-target").json()
+        assert t["eligible"] is False
+        assert "sign in" in (t["reason"] or "").lower()
+        assert t["owner"] == "Alice"
+
+        # Bob: eligible until he has a pending ask, then not.
+        sign_in_as(client, user_id=3, gitea_login="bob", display_name="Bob",
+                   role="contributor", email="bob@test")
+        assert client.get("/api/rfcs/open-human-model/contribution-target").json()["eligible"] is True
+        client.post("/api/rfcs/open-human-model/contribution-requests", json=_REQUEST)
+        after = client.get("/api/rfcs/open-human-model/contribution-target").json()
+        assert after["already_requested"] is True
+        assert after["eligible"] is False

backend/tests/test_email_envelope.py

@@ -11,6 +11,8 @@ from __future__ import annotations
 
 from email.utils import parsedate_to_datetime
 
+import pytest
+
 from app.email_envelope import build_envelope
 
 
@@ -160,14 +162,18 @@ def test_envelope_plain_only_body_is_text_plain():
     assert msg.get_content().strip() == "Hello, world."
 
 
-def test_envelope_with_html_is_multipart_alternative():
-    msg = build_envelope(**_base_kwargs(body_html="<p>Hello, <b>world</b>.</p>"))
-    assert msg.get_content_type() == "multipart/alternative"
-    # Two parts: text/plain first (so plain-text clients picking the
-    # first part get the readable text), text/html second.
-    parts = list(msg.iter_parts())
-    assert len(parts) == 2
-    assert parts[0].get_content_type() == "text/plain"
-    assert parts[1].get_content_type() == "text/html"
-    assert "Hello, world." in parts[0].get_content()
-    assert "<b>world</b>" in parts[1].get_content()
+def test_envelope_html_body_is_guarded_not_enabled():
+    # I3 (security-audit-0026): the HTML/multipart-alternative path is
+    # intentionally not enabled — passing body_html must fail loudly so
+    # a future caller can't silently ship unescaped user HTML (the C1
+    # stored-XSS class in the mail channel). When HTML mail is enabled
+    # deliberately, this test flips to assert the multipart shape.
+    with pytest.raises(NotImplementedError):
+        build_envelope(**_base_kwargs(body_html="<p>Hello, <b>world</b>.</p>"))
+
+
+def test_envelope_html_none_is_plain_only():
+    # The guard keys on `is not None`, so the default (None) stays the
+    # live plain-text path — exercised here to lock the boundary.
+    msg = build_envelope(**_base_kwargs(body_html=None))
+    assert msg.get_content_type() == "text/plain"

backend/tests/test_propose_vertical.py

@@ -444,6 +444,18 @@ def tmp_env(monkeypatch):
         # the dev-bypass path monkeypatch `RFC_APP_INSECURE_WEBHOOKS=1`.
         "GITEA_WEBHOOK_SECRET": "test-webhook-secret-for-signature-verification",
         "ENABLED_MODELS": "claude",
+        # v0.27.0 (audit 0026 M4): the session cookie now defaults to
+        # Secure. The TestClient talks plain http://testserver, so a
+        # Secure cookie is never sent back and every authenticated flow
+        # would fail. Tests opt out explicitly, exactly as a dev box on
+        # plain http does.
+        "SESSION_COOKIE_SECURE": "false",
+        # v0.27.0 (audit 0026 M5): the bounce webhook fails closed (503)
+        # when its secret is unset. Tests exercise the legacy behavioral
+        # path via the documented dev opt-in, mirroring the
+        # RFC_APP_INSECURE_WEBHOOKS bypass above. Tests that assert the
+        # fail-closed default delenv this key themselves.
+        "RFC_APP_INSECURE_BOUNCE_WEBHOOK": "1",
     }
     for k, v in env.items():
         monkeypatch.setenv(k, v)

backend/tests/test_proposed_use_case_vertical.py

@@ -0,0 +1,161 @@
+"""End-to-end vertical for roadmap #26 (rfc-app v0.22.0): the optional
+"What will you be using this for?" capture on the two propose surfaces.
+
+Reuses the FakeGitea + session helpers from test_propose_vertical.py and
+the active-RFC seed from test_rfc_view_vertical.py. Proves:
+
+  (a) propose-RFC persists and returns `proposed_use_case` when supplied,
+      and the value survives onto the merged super-draft's RFC view;
+  (b) propose-RFC accepts a NULL / omitted use case ("left blank");
+  (c) propose-PR persists and returns `proposed_use_case` when supplied,
+      and accepts a NULL / omitted one.
+"""
+from __future__ import annotations
+
+from test_propose_vertical import (  # noqa: F401
+    FakeGitea,
+    app_with_fake_gitea,
+    provision_user_row,
+    sign_in_as,
+    tmp_env,
+)
+from test_pr_flow_vertical import _cut_branch_and_accept_change
+from test_rfc_view_vertical import SEED_BODY, seed_active_rfc
+
+
+# ---------------------------------------------------------------------------
+# propose-RFC
+# ---------------------------------------------------------------------------
+
+
+def test_propose_rfc_persists_and_returns_use_case(app_with_fake_gitea):
+    from fastapi.testclient import TestClient
+
+    app, _fake = app_with_fake_gitea
+    with TestClient(app) as client:
+        provision_user_row(user_id=2, login="alice", role="contributor")
+        provision_user_row(user_id=1, login="ben", role="owner")
+        sign_in_as(client, user_id=2, gitea_login="alice", display_name="Alice", role="contributor", email="alice@test")
+
+        r = client.post("/api/rfcs/propose", json={
+            "title": "Open Human Model",
+            "slug": "open-human-model",
+            "pitch": "A shared definition of what we mean by *human*.",
+            "tags": ["identity"],
+            "proposed_use_case": "Wiring OHM into the OpenXML consent surface.",
+        })
+        assert r.status_code == 200, r.text
+        pr_number = r.json()["pr_number"]
+
+        # The pending-idea list carries the use case.
+        items = client.get("/api/proposals").json()["items"]
+        assert items[0]["proposed_use_case"] == "Wiring OHM into the OpenXML consent surface."
+
+        # The pending-idea detail view carries it too.
+        proposal = client.get(f"/api/proposals/{pr_number}").json()
+        assert proposal["proposed_use_case"] == "Wiring OHM into the OpenXML consent surface."
+
+        # Merge as owner; the use case survives onto the RFC view (looked
+        # up by slug from the canonical side table, since the idea PR
+        # closes on merge).
+        sign_in_as(client, user_id=1, gitea_login="ben", display_name="Ben", role="owner", email="ben@test")
+        r = client.post(f"/api/proposals/{pr_number}/merge")
+        assert r.status_code == 200, r.text
+
+        view = client.get("/api/rfcs/open-human-model").json()
+        assert view["proposed_use_case"] == "Wiring OHM into the OpenXML consent surface."
+
+
+def test_propose_rfc_use_case_optional(app_with_fake_gitea):
+    from fastapi.testclient import TestClient
+
+    app, _fake = app_with_fake_gitea
+    with TestClient(app) as client:
+        provision_user_row(user_id=3, login="carol", role="contributor")
+        sign_in_as(client, user_id=3, gitea_login="carol", display_name="Carol", role="contributor")
+
+        # Omitted entirely.
+        r = client.post("/api/rfcs/propose", json={
+            "title": "No Use Case", "slug": "no-use-case", "pitch": "p", "tags": [],
+        })
+        assert r.status_code == 200, r.text
+        pr_a = r.json()["pr_number"]
+
+        # Explicit null.
+        r = client.post("/api/rfcs/propose", json={
+            "title": "Null Use Case", "slug": "null-use-case", "pitch": "p",
+            "tags": [], "proposed_use_case": None,
+        })
+        assert r.status_code == 200, r.text
+        pr_b = r.json()["pr_number"]
+
+        # Blank/whitespace — treated as "left blank", no row written.
+        r = client.post("/api/rfcs/propose", json={
+            "title": "Blank Use Case", "slug": "blank-use-case", "pitch": "p",
+            "tags": [], "proposed_use_case": "   ",
+        })
+        assert r.status_code == 200, r.text
+        pr_c = r.json()["pr_number"]
+
+        for pr in (pr_a, pr_b, pr_c):
+            assert client.get(f"/api/proposals/{pr}").json()["proposed_use_case"] is None
+
+
+# ---------------------------------------------------------------------------
+# propose-PR (against an active RFC)
+# ---------------------------------------------------------------------------
+
+
+def test_propose_pr_persists_and_returns_use_case(app_with_fake_gitea):
+    from fastapi.testclient import TestClient
+
+    app, fake = app_with_fake_gitea
+    with TestClient(app) as client:
+        provision_user_row(user_id=2, login="alice", role="contributor")
+        seed_active_rfc(fake, slug="ohm", title="OHM", body=SEED_BODY)
+        sign_in_as(client, user_id=2, gitea_login="alice", display_name="Alice", role="contributor")
+
+        branch, _ = _cut_branch_and_accept_change(
+            client, fake, slug="ohm",
+            original="Open Human Model is a framework for representing humans.",
+            proposed="Open Human Model is a framework for representing humans across systems.",
+        )
+        r = client.post(
+            f"/api/rfcs/ohm/branches/{branch}/open-pr",
+            json={
+                "title": "Tighten the opening",
+                "description": "Scope to systems.",
+                "proposed_use_case": "Building a cross-system consent registry.",
+            },
+        )
+        assert r.status_code == 200, r.text
+        pr_number = r.json()["pr_number"]
+
+        pr = client.get(f"/api/rfcs/ohm/prs/{pr_number}").json()
+        assert pr["proposed_use_case"] == "Building a cross-system consent registry."
+
+
+def test_propose_pr_use_case_optional(app_with_fake_gitea):
+    from fastapi.testclient import TestClient
+
+    app, fake = app_with_fake_gitea
+    with TestClient(app) as client:
+        provision_user_row(user_id=2, login="alice", role="contributor")
+        seed_active_rfc(fake, slug="ohm", title="OHM", body=SEED_BODY)
+        sign_in_as(client, user_id=2, gitea_login="alice", display_name="Alice", role="contributor")
+
+        branch, _ = _cut_branch_and_accept_change(
+            client, fake, slug="ohm",
+            original="It defines consent, trait, and agency in compatible terms.",
+            proposed="It defines consent, trait, harm, and agency in compatible terms.",
+        )
+        # No proposed_use_case key at all.
+        r = client.post(
+            f"/api/rfcs/ohm/branches/{branch}/open-pr",
+            json={"title": "Add harm", "description": "Name harm explicitly."},
+        )
+        assert r.status_code == 200, r.text
+        pr_number = r.json()["pr_number"]
+
+        pr = client.get(f"/api/rfcs/ohm/prs/{pr_number}").json()
+        assert pr["proposed_use_case"] is None

backend/tests/test_rfc_links_vertical.py

@@ -0,0 +1,273 @@
+"""Roadmap #28 Part 1 — auto-link RFC references in PR text + comments.
+
+Two layers:
+
+  * Unit tests over the pure scanner (`rfc_links.segment_text` /
+    `_keys_for` / `LinkIndex`) — the matching rules and their
+    false-positive guards, no DB.
+  * End-to-end tests that the PR description, PR review comments, and
+    PR-less discussion comments all surface `*_segments` enriched against
+    the live accepted-RFC corpus, with self-references suppressed.
+
+Reuses the FakeGitea + session helpers from test_propose_vertical.py and
+the active-RFC seed from test_rfc_view_vertical.py.
+"""
+from __future__ import annotations
+
+from app import rfc_links
+
+from test_propose_vertical import (  # noqa: F401
+    FakeGitea,
+    app_with_fake_gitea,
+    grant_rfc_collaborator,
+    provision_user_row,
+    sign_in_as,
+    tmp_env,
+)
+from test_rfc_view_vertical import SEED_BODY, seed_active_rfc
+from test_pr_flow_vertical import _cut_branch_and_accept_change
+
+
+# ---------------------------------------------------------------------------
+# Unit — the pure scanner
+# ---------------------------------------------------------------------------
+
+
+def _idx(*terms):
+    """Build a LinkIndex from raw (key, slug, title) tuples (keys lower)."""
+    return rfc_links.LinkIndex(list(terms))
+
+
+def test_empty_text_is_single_empty_segment():
+    assert rfc_links.segment_text("", []) == [{"type": "text", "text": ""}]
+    assert rfc_links.segment_text(None, []) == [{"type": "text", "text": ""}]
+
+
+def test_no_terms_returns_plain_text():
+    out = rfc_links.segment_text("hello world", [])
+    assert out == [{"type": "text", "text": "hello world"}]
+
+
+def test_multiword_title_links_and_preserves_casing():
+    idx = _idx(("open human model", "open-human-model", "Open Human Model"))
+    out = idx.segment("See the Open Human Model for details.")
+    assert out == [
+        {"type": "text", "text": "See the "},
+        {"type": "rfc", "slug": "open-human-model", "label": "Open Human Model",
+         "title": "Open Human Model"},
+        {"type": "text", "text": " for details."},
+    ]
+
+
+def test_match_is_case_insensitive():
+    idx = _idx(("open human model", "open-human-model", "Open Human Model"))
+    out = idx.segment("see the OPEN HUMAN MODEL")
+    assert out[-1] == {"type": "rfc", "slug": "open-human-model",
+                       "label": "OPEN HUMAN MODEL", "title": "Open Human Model"}
+
+
+def test_word_boundary_prevents_substring_match():
+    # "harm" must not match inside "charming" / "harmless".
+    idx = _idx(("rfc-0001", "open-human-model", "Open Human Model"))
+    out = idx.segment("a charming rfc-00012 not real")
+    # rfc-0001 is a prefix of rfc-00012 but the trailing '2' is a word char,
+    # so no match — the whole string stays plain text.
+    assert out == [{"type": "text", "text": "a charming rfc-00012 not real"}]
+
+
+def test_rfc_id_token_links():
+    idx = _idx(("rfc-0001", "open-human-model", "Open Human Model"))
+    out = idx.segment("as established in RFC-0001.")
+    assert out[1] == {"type": "rfc", "slug": "open-human-model",
+                      "label": "RFC-0001", "title": "Open Human Model"}
+
+
+def test_longest_match_wins():
+    # A bare "Open" term and the full title both present; the full title
+    # (longer) must win at the position.
+    idx = _idx(
+        ("open", "open", "Open"),
+        ("open human model", "open-human-model", "Open Human Model"),
+    )
+    out = idx.segment("the Open Human Model")
+    assert out[-1]["slug"] == "open-human-model"
+    assert out[-1]["label"] == "Open Human Model"
+
+
+def test_pending_term_emits_contribute_segment():
+    # Part 3: a super-draft match is an `rfc-pending` segment carrying the
+    # owner display name, not a plain link.
+    idx = rfc_links.LinkIndex([
+        rfc_links.Term(key="open human model", kind="pending",
+                       slug="open-human-model", title="Open Human Model", owner="Alice"),
+    ])
+    out = idx.segment("see Open Human Model please")
+    assert out[1] == {
+        "type": "rfc-pending", "slug": "open-human-model",
+        "label": "Open Human Model", "title": "Open Human Model", "owner": "Alice",
+    }
+
+
+def test_candidate_term_emits_create_segment():
+    # Part 2: a candidate term carries its canonical spelling for the
+    # propose pre-fill; no slug (no RFC exists yet).
+    idx = rfc_links.LinkIndex([
+        rfc_links.Term(key="memory model", kind="candidate", term="Memory Model"),
+    ])
+    out = idx.segment("the memory model is unspecified")
+    assert out[1] == {"type": "rfc-candidate", "label": "memory model", "term": "Memory Model"}
+
+
+def test_kind_precedence_active_beats_pending_beats_candidate():
+    # All three buckets contribute the same key; the highest-precedence
+    # kind (active) must win at the position.
+    key = "open human model"
+    idx = rfc_links.LinkIndex([
+        rfc_links.Term(key=key, kind="candidate", term="Open Human Model"),
+        rfc_links.Term(key=key, kind="pending", slug="ohm-draft", title="Open Human Model", owner="A"),
+        rfc_links.Term(key=key, kind="active", slug="open-human-model", title="Open Human Model"),
+    ])
+    out = idx.segment("the Open Human Model")
+    assert out[-1]["type"] == "rfc"
+    assert out[-1]["slug"] == "open-human-model"
+
+
+def test_keys_for_gating():
+    keys = lambda **kw: set(rfc_links._keys_for(**kw))
+    # rfc_id always contributes.
+    assert "rfc-0001" in keys(slug="x", title="X", rfc_id="RFC-0001")
+    # multi-word title contributes; single common word does NOT.
+    assert "open human model" in keys(slug="ohm", title="Open Human Model", rfc_id=None)
+    assert keys(slug="human", title="Human", rfc_id=None) == set()
+    # hyphenated slug contributes; single-token slug does NOT.
+    assert "open-human-model" in keys(slug="open-human-model", title="X", rfc_id=None)
+    assert "ohm" not in keys(slug="ohm", title="OHM", rfc_id=None)
+
+
+# ---------------------------------------------------------------------------
+# End-to-end — enrichment surfaces on the read paths
+# ---------------------------------------------------------------------------
+
+
+def _open_pr_on(client, fake, *, host_slug: str, description: str):
+    """Seed branch + accepted change on host_slug and open a PR. Returns
+    the pr_number."""
+    # `original` must exist verbatim in SEED_BODY or the accept is "stale".
+    branch, _ = _cut_branch_and_accept_change(
+        client, fake, slug=host_slug,
+        original="It defines consent, trait, and agency in compatible terms.",
+        proposed="It defines consent, trait, harm, and agency in compatible terms.",
+    )
+    r = client.post(
+        f"/api/rfcs/{host_slug}/branches/{branch}/open-pr",
+        json={"title": "A change", "description": description},
+    )
+    assert r.status_code == 200, r.text
+    return r.json()["pr_number"]
+
+
+def _rfc_segments(segments):
+    return [s for s in segments if s["type"] == "rfc"]
+
+
+def test_pr_description_autolinks_other_rfc(app_with_fake_gitea):
+    from fastapi.testclient import TestClient
+
+    app, fake = app_with_fake_gitea
+    with TestClient(app) as client:
+        provision_user_row(user_id=2, login="alice", role="contributor")
+        # Two accepted RFCs: a host for the PR + a referenceable target.
+        seed_active_rfc(fake, slug="ohm", title="OHM", body=SEED_BODY)
+        seed_active_rfc(fake, slug="open-human-model", title="Open Human Model", body=SEED_BODY)
+        sign_in_as(client, user_id=2, gitea_login="alice", display_name="Alice", role="contributor")
+
+        pr_number = _open_pr_on(
+            client, fake, host_slug="ohm",
+            description="This builds on the Open Human Model definition.",
+        )
+        r = client.get(f"/api/rfcs/ohm/prs/{pr_number}")
+        assert r.status_code == 200, r.text
+        pr = r.json()
+        links = _rfc_segments(pr["description_segments"])
+        assert len(links) == 1
+        assert links[0]["slug"] == "open-human-model"
+        assert links[0]["label"] == "Open Human Model"
+        # The plain text is still present for non-segment callers (the bot
+        # appends a §6.5 On-behalf-of trailer, so this is a containment check).
+        assert "This builds on the Open Human Model definition." in pr["description"]
+
+
+def test_pr_review_comment_autolinked(app_with_fake_gitea):
+    from fastapi.testclient import TestClient
+
+    app, fake = app_with_fake_gitea
+    with TestClient(app) as client:
+        provision_user_row(user_id=2, login="alice", role="contributor")
+        seed_active_rfc(fake, slug="ohm", title="OHM", body=SEED_BODY)
+        seed_active_rfc(fake, slug="open-human-model", title="Open Human Model", body=SEED_BODY)
+        sign_in_as(client, user_id=2, gitea_login="alice", display_name="Alice", role="contributor")
+
+        pr_number = _open_pr_on(client, fake, host_slug="ohm", description="plain.")
+        r = client.post(
+            f"/api/rfcs/ohm/prs/{pr_number}/review",
+            json={"text": "See Open Human Model and RFC-0001.", "anchor_payload": {}},
+        )
+        assert r.status_code == 200, r.text
+
+        pr = client.get(f"/api/rfcs/ohm/prs/{pr_number}").json()
+        all_msgs = [m for msgs in pr["messages_by_thread"].values() for m in msgs]
+        review_msgs = [m for m in all_msgs if "Open Human Model" in (m["text"] or "")]
+        assert review_msgs, "review comment not found in payload"
+        links = _rfc_segments(review_msgs[0]["text_segments"])
+        # Both "Open Human Model" (title) and "RFC-0001" (id) point to the
+        # one referenceable RFC.
+        assert {s["slug"] for s in links} == {"open-human-model"}
+        assert {s["label"] for s in links} == {"Open Human Model", "RFC-0001"}
+
+
+def test_discussion_comment_autolinked(app_with_fake_gitea):
+    from fastapi.testclient import TestClient
+
+    app, fake = app_with_fake_gitea
+    with TestClient(app) as client:
+        provision_user_row(user_id=2, login="alice", role="contributor")
+        seed_active_rfc(fake, slug="ohm", title="OHM", body=SEED_BODY)
+        seed_active_rfc(fake, slug="open-human-model", title="Open Human Model", body=SEED_BODY)
+        # alice is the seeded owner of ohm (owners=["alice"]); grant the
+        # per-RFC collaborator row explicitly so the #12 discuss gate passes.
+        grant_rfc_collaborator(user_id=2, rfc_slug="ohm", role_in_rfc="contributor")
+        sign_in_as(client, user_id=2, gitea_login="alice", display_name="Alice", role="contributor")
+
+        r = client.post(
+            "/api/rfcs/ohm/discussion/threads",
+            json={"message": "Compare with the Open Human Model."},
+        )
+        assert r.status_code == 200, r.text
+        thread_id = r.json()["thread_id"]
+
+        r = client.get(f"/api/rfcs/ohm/discussion/threads/{thread_id}/messages")
+        assert r.status_code == 200, r.text
+        msgs = r.json()["messages"]
+        assert msgs and "text_segments" in msgs[0]
+        links = _rfc_segments(msgs[0]["text_segments"])
+        assert len(links) == 1
+        assert links[0]["slug"] == "open-human-model"
+
+
+def test_self_reference_not_linked(app_with_fake_gitea):
+    from fastapi.testclient import TestClient
+
+    app, fake = app_with_fake_gitea
+    with TestClient(app) as client:
+        provision_user_row(user_id=2, login="alice", role="contributor")
+        # The host RFC has a multi-word title, so absent exclude_slug it
+        # WOULD self-link. exclude_slug must suppress it.
+        seed_active_rfc(fake, slug="open-human-model", title="Open Human Model", body=SEED_BODY)
+        sign_in_as(client, user_id=2, gitea_login="alice", display_name="Alice", role="contributor")
+
+        pr_number = _open_pr_on(
+            client, fake, host_slug="open-human-model",
+            description="Refines the Open Human Model definition.",
+        )
+        pr = client.get(f"/api/rfcs/open-human-model/prs/{pr_number}").json()
+        assert _rfc_segments(pr["description_segments"]) == []

backend/tests/test_session_resume_vertical.py

@@ -0,0 +1,140 @@
+"""End-to-end integration tests for the v0.23.0 sign-in state-resume
+vertical (§6.2, roadmap item #29).
+
+New behavior: each authenticated user's last-viewed route + a small bag
+of light view state is tracked server-side, so the next sign-in can land
+them back where they left off rather than on the empty-state home view.
+
+The tests below prove:
+
+  * `PUT /api/me/last-state` requires auth — an anonymous client gets
+    401, and nothing is stored.
+  * An authenticated PUT upserts the route, and the stored route is
+    read back for that user off `GET /api/auth/me` (`last_route`).
+  * A second PUT overwrites (upsert, one row per user) — the latest
+    route wins.
+  * `last_route_state` round-trips as decoded JSON on `/api/auth/me`.
+  * Per-user isolation: user A's stored route is not visible to user B.
+  * `resume_enabled = 0` disables resume: the PUT no-ops (does not
+    rewrite the stored route) and `/api/auth/me` hands back a null
+    `last_route` even though a stored row exists.
+
+The fakes from `test_propose_vertical` give us a working app harness +
+the `sign_in_as` / `provision_user_row` seams.
+"""
+from __future__ import annotations
+
+from test_propose_vertical import (  # noqa: F401
+    FakeGitea,
+    app_with_fake_gitea,
+    provision_user_row,
+    sign_in_as,
+    tmp_env,
+)
+
+
+def test_put_last_state_requires_auth(app_with_fake_gitea):
+    from fastapi.testclient import TestClient
+    from app import db
+
+    app, _fake = app_with_fake_gitea
+    with TestClient(app) as client:
+        # Anonymous — no session cookie set.
+        r = client.put("/api/me/last-state", json={"route": "/rfc/open-human-model"})
+        assert r.status_code == 401
+        # Nothing landed in the table.
+        row = db.conn().execute("SELECT COUNT(*) AS n FROM user_session_state").fetchone()
+        assert row["n"] == 0
+
+
+def test_put_last_state_upserts_and_reads_back(app_with_fake_gitea):
+    from fastapi.testclient import TestClient
+
+    app, _fake = app_with_fake_gitea
+    with TestClient(app) as client:
+        provision_user_row(user_id=2, login="alice", role="contributor")
+        sign_in_as(client, user_id=2, gitea_login="alice", display_name="Alice", role="contributor", email="alice@test")
+
+        # First POST stores a route + light state.
+        r = client.put(
+            "/api/me/last-state",
+            json={"route": "/rfc/open-human-model", "state": {"tab": "discussion", "scroll": 420}},
+        )
+        assert r.status_code == 200
+        assert r.json()["stored"] is True
+
+        # /api/auth/me hands the route + decoded state back.
+        me = client.get("/api/auth/me").json()
+        assert me["authenticated"] is True
+        assert me["user"]["resume_enabled"] is True
+        assert me["user"]["last_route"] == "/rfc/open-human-model"
+        assert me["user"]["last_route_state"] == {"tab": "discussion", "scroll": 420}
+
+        # A later POST overwrites — one row per user, latest wins.
+        r = client.put("/api/me/last-state", json={"route": "/proposals/7"})
+        assert r.status_code == 200
+        me = client.get("/api/auth/me").json()
+        assert me["user"]["last_route"] == "/proposals/7"
+        # state was omitted on the second POST → cleared to null.
+        assert me["user"]["last_route_state"] is None
+
+
+def test_last_state_is_per_user(app_with_fake_gitea):
+    from fastapi.testclient import TestClient
+
+    app, _fake = app_with_fake_gitea
+    with TestClient(app) as client:
+        provision_user_row(user_id=2, login="alice", role="contributor")
+        provision_user_row(user_id=3, login="bob", role="contributor")
+
+        sign_in_as(client, user_id=2, gitea_login="alice", display_name="Alice", role="contributor", email="alice@test")
+        client.put("/api/me/last-state", json={"route": "/rfc/alice-route"})
+
+        # Switch to bob — he has no stored route yet.
+        sign_in_as(client, user_id=3, gitea_login="bob", display_name="Bob", role="contributor", email="bob@test")
+        me = client.get("/api/auth/me").json()
+        assert me["user"]["last_route"] is None
+
+        client.put("/api/me/last-state", json={"route": "/rfc/bob-route"})
+        me = client.get("/api/auth/me").json()
+        assert me["user"]["last_route"] == "/rfc/bob-route"
+
+        # Back to alice — her route is untouched by bob's write.
+        sign_in_as(client, user_id=2, gitea_login="alice", display_name="Alice", role="contributor", email="alice@test")
+        me = client.get("/api/auth/me").json()
+        assert me["user"]["last_route"] == "/rfc/alice-route"
+
+
+def test_resume_disabled_no_ops_put_and_hides_route(app_with_fake_gitea):
+    from fastapi.testclient import TestClient
+    from app import db
+
+    app, _fake = app_with_fake_gitea
+    with TestClient(app) as client:
+        provision_user_row(user_id=2, login="alice", role="contributor")
+        sign_in_as(client, user_id=2, gitea_login="alice", display_name="Alice", role="contributor", email="alice@test")
+
+        # Seed a stored row, then flip resume_enabled off directly (the
+        # profile-settings toggle UI to do this from the client is a
+        # follow-up; the column + behavior ship now).
+        client.put("/api/me/last-state", json={"route": "/rfc/before-disable"})
+        db.conn().execute(
+            "UPDATE user_session_state SET resume_enabled = 0 WHERE user_id = ?",
+            (2,),
+        )
+
+        # /api/auth/me reports resume off and hands back a null route
+        # even though a stored row exists.
+        me = client.get("/api/auth/me").json()
+        assert me["user"]["resume_enabled"] is False
+        assert me["user"]["last_route"] is None
+
+        # A PUT while disabled no-ops: stored=False and the stored route
+        # is NOT rewritten.
+        r = client.put("/api/me/last-state", json={"route": "/rfc/after-disable"})
+        assert r.status_code == 200
+        assert r.json()["stored"] is False
+        row = db.conn().execute(
+            "SELECT last_route FROM user_session_state WHERE user_id = ?", (2,)
+        ).fetchone()
+        assert row["last_route"] == "/rfc/before-disable"

backend/tests/test_tag_suggest_vertical.py

@@ -0,0 +1,264 @@
+"""Vertical + unit coverage for roadmap #27 (rfc-app v0.24.0): Claude
+Haiku tag suggestions on the propose-RFC modal.
+
+Reuses the FakeGitea + session helpers from test_propose_vertical.py.
+The Anthropic call is never made for real — tests monkeypatch the
+`tag_suggest.haiku_provider` seam with a stub provider whose `send`
+returns canned text, so the HTTP contract is exercised without a key.
+
+Proves:
+  (a) the endpoint is contributor-gated (anon → 401);
+  (b) a contributor gets suggestions, filtered to the corpus tag
+      universe, with invented tags dropped;
+  (c) no Anthropic key bound → empty list, not an error;
+  (d) an empty corpus → empty list (model is never even called);
+  (e) the per-user rate limit surfaces as a 429;
+plus unit coverage of the universe gather, the reply parser's tolerance,
+and the suggest() orchestration short-circuits.
+"""
+from __future__ import annotations
+
+import json
+
+import pytest
+
+from test_propose_vertical import (  # noqa: F401
+    FakeGitea,
+    app_with_fake_gitea,
+    provision_user_row,
+    sign_in_as,
+    tmp_env,
+)
+
+
+# ---------------------------------------------------------------------------
+# Helpers
+# ---------------------------------------------------------------------------
+
+
+class StubProvider:
+    """A BaseProvider stand-in whose send() returns a fixed string (or
+    raises, to exercise the graceful-failure path)."""
+
+    def __init__(self, reply: str = "[]", *, raises: bool = False):
+        self.reply = reply
+        self.raises = raises
+        self.calls: list[tuple[str, list]] = []
+
+    def send(self, system, history):
+        self.calls.append((system, history))
+        if self.raises:
+            raise RuntimeError("boom")
+        return self.reply
+
+
+def _seed_tags(slug: str, title: str, tags: list[str], state: str = "active") -> None:
+    from app import db
+
+    db.conn().execute(
+        "INSERT OR REPLACE INTO cached_rfcs (slug, title, state, tags_json) VALUES (?, ?, ?, ?)",
+        (slug, title, state, json.dumps(tags)),
+    )
+
+
+def _use_provider(monkeypatch, provider) -> None:
+    monkeypatch.setattr("app.tag_suggest.haiku_provider", lambda config: provider)
+
+
+@pytest.fixture(autouse=True)
+def _reset_rate_limits():
+    from app import tag_suggest
+
+    tag_suggest.reset_rate_limits()
+    yield
+    tag_suggest.reset_rate_limits()
+
+
+# ---------------------------------------------------------------------------
+# Endpoint (vertical)
+# ---------------------------------------------------------------------------
+
+
+def test_anonymous_cannot_suggest(app_with_fake_gitea):
+    from fastapi.testclient import TestClient
+
+    app, _fake = app_with_fake_gitea
+    with TestClient(app) as client:
+        r = client.post("/api/rfcs/suggest-tags", json={"title": "X"})
+        assert r.status_code == 401
+
+
+def test_contributor_gets_filtered_suggestions(app_with_fake_gitea, monkeypatch):
+    from fastapi.testclient import TestClient
+
+    app, _fake = app_with_fake_gitea
+    with TestClient(app) as client:
+        provision_user_row(user_id=2, login="alice", role="contributor")
+        sign_in_as(client, user_id=2, gitea_login="alice", display_name="Alice", role="contributor")
+
+        _seed_tags("ohm", "OHM", ["identity", "schema", "consent"])
+        _seed_tags("other", "Other", ["identity", "governance"])
+
+        # Model returns two real tags (one lowercased to test canonical
+        # mapping is exact-set anyway), plus one invented tag that MUST
+        # be dropped.
+        reply = json.dumps([
+            {"tag": "identity", "confidence": 0.9},
+            {"tag": "consent", "confidence": 0.7},
+            {"tag": "totally-invented", "confidence": 0.99},
+        ])
+        stub = StubProvider(reply=reply)
+        _use_provider(monkeypatch, stub)
+
+        r = client.post("/api/rfcs/suggest-tags", json={
+            "title": "Consent and identity",
+            "pitch": "We need a shared definition of consent tied to identity.",
+        })
+        assert r.status_code == 200, r.text
+        tags = [s["tag"] for s in r.json()["suggestions"]]
+        assert tags == ["identity", "consent"]
+        # the model was actually invoked
+        assert len(stub.calls) == 1
+        # the universe (deduped distinct tags) was handed to the model
+        user_msg = stub.calls[0][1][0]["content"]
+        assert "identity" in user_msg and "governance" in user_msg
+
+
+def test_no_api_key_returns_empty(app_with_fake_gitea, monkeypatch):
+    from fastapi.testclient import TestClient
+
+    app, _fake = app_with_fake_gitea
+    with TestClient(app) as client:
+        provision_user_row(user_id=2, login="alice", role="contributor")
+        sign_in_as(client, user_id=2, gitea_login="alice", display_name="Alice", role="contributor")
+        _seed_tags("ohm", "OHM", ["identity"])
+
+        # No key bound (test env has no ANTHROPIC_API_KEY) → provider None.
+        # (Explicitly assert the seam returns None given the test config.)
+        from app import tag_suggest
+        assert tag_suggest.haiku_provider(app.state.config) is None
+
+        r = client.post("/api/rfcs/suggest-tags", json={"title": "X", "pitch": "y"})
+        assert r.status_code == 200, r.text
+        assert r.json()["suggestions"] == []
+
+
+def test_empty_corpus_returns_empty_without_calling_model(app_with_fake_gitea, monkeypatch):
+    from fastapi.testclient import TestClient
+
+    app, _fake = app_with_fake_gitea
+    with TestClient(app) as client:
+        provision_user_row(user_id=2, login="alice", role="contributor")
+        sign_in_as(client, user_id=2, gitea_login="alice", display_name="Alice", role="contributor")
+
+        stub = StubProvider(reply=json.dumps([{"tag": "x", "confidence": 1}]))
+        _use_provider(monkeypatch, stub)
+
+        # No cached_rfcs rows → empty universe → suggest() short-circuits.
+        r = client.post("/api/rfcs/suggest-tags", json={"title": "X", "pitch": "y"})
+        assert r.status_code == 200, r.text
+        assert r.json()["suggestions"] == []
+        assert stub.calls == []  # model never invoked on an empty universe
+
+
+def test_rate_limit_surfaces_429(app_with_fake_gitea, monkeypatch):
+    from fastapi.testclient import TestClient
+
+    monkeypatch.setenv("TAG_SUGGEST_RATE_MAX", "2")
+    monkeypatch.setenv("TAG_SUGGEST_RATE_WINDOW_SECONDS", "60")
+
+    app, _fake = app_with_fake_gitea
+    with TestClient(app) as client:
+        provision_user_row(user_id=2, login="alice", role="contributor")
+        sign_in_as(client, user_id=2, gitea_login="alice", display_name="Alice", role="contributor")
+        _seed_tags("ohm", "OHM", ["identity"])
+        _use_provider(monkeypatch, StubProvider(reply="[]"))
+
+        body = {"title": "X", "pitch": "y"}
+        assert client.post("/api/rfcs/suggest-tags", json=body).status_code == 200
+        assert client.post("/api/rfcs/suggest-tags", json=body).status_code == 200
+        # Third call inside the window trips the limit.
+        assert client.post("/api/rfcs/suggest-tags", json=body).status_code == 429
+
+
+# ---------------------------------------------------------------------------
+# Units
+# ---------------------------------------------------------------------------
+
+
+def test_gather_tag_universe_dedupes_and_ranks(app_with_fake_gitea):
+    from fastapi.testclient import TestClient
+    from app import tag_suggest
+
+    app, _fake = app_with_fake_gitea
+    # The db is initialized in the app's lifespan; enter the client
+    # context so cached_rfcs exists before we seed it directly.
+    with TestClient(app):
+        _seed_tags("a", "A", ["identity", "schema"])
+        _seed_tags("b", "B", ["identity", " schema ", "consent", ""])  # whitespace + empty
+        _seed_tags("c", "C", ["identity"])
+
+        universe = tag_suggest.gather_tag_universe()
+        # identity (3) > schema (2) > consent (1); whitespace trimmed/merged,
+        # empties dropped.
+        assert universe == ["identity", "schema", "consent"]
+
+
+def test_parse_reply_tolerates_junk():
+    from app import tag_suggest
+
+    universe = ["identity", "schema", "consent"]
+
+    # Prose around the JSON, an invented tag, a bare string, a dup, a
+    # missing confidence, and a garbage confidence.
+    text = (
+        "Sure! Here are the tags:\n"
+        '[{"tag": "identity", "confidence": 0.9}, '
+        '{"tag": "invented", "confidence": 1}, '
+        '"schema", '
+        '{"tag": "identity", "confidence": 0.5}, '
+        '{"tag": "consent"}, '
+        '{"tag": "consent", "confidence": "high"}]\n'
+        "Hope that helps!"
+    )
+    out = tag_suggest.parse_reply(text, universe, max_suggestions=6)
+    tags = [s["tag"] for s in out]
+    assert tags == ["identity", "schema", "consent"]  # invented dropped, deduped
+    by_tag = {s["tag"]: s["confidence"] for s in out}
+    assert by_tag["identity"] == 0.9
+    assert by_tag["schema"] == 0.5      # bare string defaults to 0.5
+    assert by_tag["consent"] == 0.5     # missing/garbage confidence → 0.5
+
+
+def test_parse_reply_empty_on_unparseable():
+    from app import tag_suggest
+
+    assert tag_suggest.parse_reply("no json here", ["a"], 6) == []
+    assert tag_suggest.parse_reply("", ["a"], 6) == []
+    assert tag_suggest.parse_reply("[]", ["a"], 6) == []
+
+
+def test_parse_reply_respects_max():
+    from app import tag_suggest
+
+    universe = ["a", "b", "c", "d", "e"]
+    text = json.dumps([{"tag": t, "confidence": 0.5} for t in universe])
+    out = tag_suggest.parse_reply(text, universe, max_suggestions=3)
+    assert [s["tag"] for s in out] == ["a", "b", "c"]
+
+
+def test_suggest_short_circuits_empty_draft():
+    from app import tag_suggest
+
+    stub = StubProvider(reply=json.dumps([{"tag": "a", "confidence": 1}]))
+    draft = tag_suggest.Draft(title="  ", pitch="", use_case="")
+    assert tag_suggest.suggest(stub, draft, ["a"]) == []
+    assert stub.calls == []  # never called for an empty draft
+
+
+def test_suggest_returns_empty_on_provider_failure():
+    from app import tag_suggest
+
+    stub = StubProvider(raises=True)
+    draft = tag_suggest.Draft(title="Real title", pitch="a reason")
+    assert tag_suggest.suggest(stub, draft, ["identity"]) == []

backend/tests/test_turnstile_vertical.py

@@ -55,13 +55,19 @@ def _outbound_otc_envelopes(to_address: str | None = None) -> list[dict]:
 
 
 def _patch_siteverify(monkeypatch, *, success: bool, error_codes: list[str] | None = None):
-    """Replace `httpx.post` inside `app.turnstile` with a stub that
+    """Replace `turnstile._siteverify_post` with an async stub that
     returns the requested success shape. The stub does not touch the
     real CloudFlare endpoint and never sees a real secret.
+
+    I4 (security-audit-0026): the siteverify call is now awaited on an
+    `httpx.AsyncClient`, isolated behind the `_siteverify_post` seam.
+    Patching that narrow function (rather than the shared
+    `httpx.AsyncClient`, which gitea/docs also construct) keeps app boot
+    intact.
     """
     captured = {}
 
-    def fake_post(url, *, data=None, timeout=None, **kwargs):
+    async def fake_post(url, data):
         captured["url"] = url
         captured["data"] = data
         body = {"success": bool(success)}
@@ -70,7 +76,7 @@ def _patch_siteverify(monkeypatch, *, success: bool, error_codes: list[str] | No
         return SimpleNamespace(json=lambda: body)
 
     from app import turnstile as turnstile_mod
-    monkeypatch.setattr(turnstile_mod.httpx, "post", fake_post)
+    monkeypatch.setattr(turnstile_mod, "_siteverify_post", fake_post)
     return captured
 
 
@@ -170,14 +176,15 @@ def test_otc_request_admits_when_secret_unset_and_not_required(app_with_fake_git
 
     monkeypatch.delenv("CLOUDFLARE_TURNSTILE_SECRET", raising=False)
     monkeypatch.delenv("TURNSTILE_REQUIRED", raising=False)
-    # The httpx.post inside turnstile must not be called in this path —
-    # patch it to a sentinel that explodes if it ever runs.
+    # The siteverify call inside turnstile must not be made in this path —
+    # patch the seam to a sentinel that explodes if it ever runs
+    # (I4: the seam is now `_siteverify_post`, not module-level httpx.post).
     from app import turnstile as turnstile_mod
 
-    def must_not_be_called(*a, **kw):
+    async def must_not_be_called(*a, **kw):
         raise AssertionError("siteverify should not run when no secret is configured")
 
-    monkeypatch.setattr(turnstile_mod.httpx, "post", must_not_be_called)
+    monkeypatch.setattr(turnstile_mod, "_siteverify_post", must_not_be_called)
 
     app, _fake = app_with_fake_gitea
     with TestClient(app) as client:
@@ -218,3 +225,27 @@ def test_otc_request_refuses_when_required_but_secret_unset(app_with_fake_gitea,
         )
         assert r.status_code == 500, r.text
         assert _outbound_otc_envelopes("alice@example.com") == []
+
+
+# ---------------------------------------------------------------------------
+# I4 (security-audit-0026): verify_token is a coroutine — calling it returns
+# an awaitable, not a VerifyOutcome. Locks the async contract so a revert to
+# the synchronous event-loop-blocking shape fails here, not just in the
+# integration paths.
+# ---------------------------------------------------------------------------
+
+
+def test_verify_token_is_async_and_soft_skips_without_secret(monkeypatch):
+    import asyncio
+
+    from app import turnstile as turnstile_mod
+
+    monkeypatch.delenv("CLOUDFLARE_TURNSTILE_SECRET", raising=False)
+    monkeypatch.delenv("TURNSTILE_REQUIRED", raising=False)
+
+    coro = turnstile_mod.verify_token("any-token")
+    assert asyncio.iscoroutine(coro), "verify_token must be a coroutine (I4)"
+    outcome = asyncio.run(coro)
+    # No secret + not required → the gate stays open without any network call.
+    assert outcome.ok is True
+    assert outcome.reason == "skipped"

deploy/nginx/ohm.wiggleverse.org.conf

@@ -18,6 +18,56 @@ server {
     listen [::]:80;
     server_name ohm.wiggleverse.org;
 
+    # v0.25.0 security hardening (audit 0026 M2/L8)
+    #
+    # NOTE: certbot promotes THIS server block to the HTTPS listener
+    # (`listen 443 ssl`) and adds a separate port-80 → 443 redirect
+    # block (see the install comment above). These response headers
+    # therefore ride into the HTTPS server block on the VM. They use
+    # `add_header ... always` so they also apply to nginx-generated
+    # error responses (4xx/5xx), not just 200s.
+    #
+    # `server_tokens off` (L8) — suppress the nginx version in the
+    # Server header and on error pages so we don't advertise the
+    # build to scanners.
+    server_tokens off;
+
+    add_header Strict-Transport-Security "max-age=31536000; includeSubDomains" always;
+    add_header X-Frame-Options "DENY" always;
+    add_header X-Content-Type-Options "nosniff" always;
+    add_header Referrer-Policy "strict-origin-when-cross-origin" always;
+
+    # Content-Security-Policy (M2). Tuned to what the SPA actually loads:
+    #   - default-src 'self': everything not called out below is same-origin.
+    #   - script-src 'self' + challenges.cloudflare.com: the only external
+    #     <script> tag the app injects is the CloudFlare Turnstile widget
+    #     (frontend/src/components/TurnstileWidget.jsx). Amplitude and
+    #     mermaid are BUNDLED (dynamic `import()` from node_modules, served
+    #     from 'self'), so they need no extra script origin — *.amplitude.com
+    #     is listed defensively in case a future SDK build script-injects.
+    #     script-src DELIBERATELY OMITS 'unsafe-inline' — no inline <script>
+    #     is used, so we keep XSS-via-inline-script blocked.
+    #   - style-src 'unsafe-inline' IS REQUIRED by the current build: the
+    #     JSX uses inline `style={...}` attributes throughout and mermaid
+    #     injects <style> blocks at render time. Removing it would break
+    #     layout; tightening this is a future build-side change (nonce/hash).
+    #   - img-src 'self' data: https: — markdown/RFC bodies may embed remote
+    #     images and data: URIs; svg/mermaid output uses data: too.
+    #   - font-src 'self' data: — bundled fonts plus data: webfonts.
+    #   - connect-src 'self' + *.amplitude.com + challenges.cloudflare.com:
+    #     the app's API/auth/SSE are same-origin (nginx proxy); Amplitude
+    #     Analytics + Session Replay (shipped at sampleRate 1) POST to
+    #     *.amplitude.com; Turnstile verifies via challenges.cloudflare.com.
+    #   - worker-src 'self' blob: — Amplitude Session Replay spins up a
+    #     Web Worker from a blob: URL for capture/compression; without
+    #     blob: here session replay breaks for every consenting user.
+    #   - frame-src challenges.cloudflare.com — the Turnstile challenge
+    #     renders in an iframe from that origin.
+    #   - frame-ancestors 'none' — clickjacking defense, pairs with
+    #     X-Frame-Options DENY for older agents.
+    #   - base-uri 'self'; object-src 'none' — lock down <base>/<object>.
+    add_header Content-Security-Policy "default-src 'self'; script-src 'self' https://challenges.cloudflare.com https://*.amplitude.com; style-src 'self' 'unsafe-inline'; img-src 'self' data: https:; font-src 'self' data:; connect-src 'self' https://*.amplitude.com https://challenges.cloudflare.com; worker-src 'self' blob:; frame-src https://challenges.cloudflare.com; frame-ancestors 'none'; base-uri 'self'; object-src 'none'" always;
+
     # Static SPA assets live in the Vite build output. The systemd unit
     # runs as user `rfc-app`; make sure nginx (usually `www-data`) can
     # read this path. Either group-add www-data into rfc-app's group, or

deploy/systemd/rfc-app.service

@@ -42,5 +42,32 @@ ProtectHome=true
 PrivateTmp=true
 ReadWritePaths=/opt/rfc-app/backend/data
 
+# v0.25.0 security hardening (audit 0026 L4) — defense-in-depth.
+# The service binds 127.0.0.1:8000 and runs plain CPython
+# (FastAPI/uvicorn + sqlite + bcrypt + httpx), so it needs no
+# capabilities and no exotic syscalls.
+CapabilityBoundingSet=
+AmbientCapabilities=
+PrivateDevices=true
+ProtectKernelTunables=true
+ProtectKernelModules=true
+ProtectKernelLogs=true
+ProtectControlGroups=true
+RestrictAddressFamilies=AF_INET AF_INET6 AF_UNIX
+RestrictNamespaces=true
+LockPersonality=true
+# MemoryDenyWriteExecute=true blocks W^X memory — safe for stock
+# CPython (no JIT) and the pure-Python/C-extension stack here, but
+# would break a JIT or a C-ext that mmaps W+X. Watch the first
+# restart's journal for a crash; if uvicorn fails to come up,
+# comment this one line out and reload.
+MemoryDenyWriteExecute=true
+RestrictRealtime=true
+RestrictSUIDSGID=true
+SystemCallFilter=@system-service
+SystemCallErrorNumber=EPERM
+SystemCallArchitectures=native
+UMask=0077
+
 [Install]
 WantedBy=multi-user.target

frontend/package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "rfc-app-frontend",
-  "version": "0.21.0",
+  "version": "0.24.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "rfc-app-frontend",
-      "version": "0.21.0",
+      "version": "0.24.0",
       "dependencies": {
         "@amplitude/unified": "^1.1.9",
         "@codemirror/commands": "^6.10.3",
@@ -18,6 +18,7 @@
         "@tiptap/pm": "^3.5.0",
         "@tiptap/react": "^3.5.0",
         "@tiptap/starter-kit": "^3.5.0",
+        "dompurify": "^3.2.4",
         "marked": "^18.0.4",
         "mermaid": "^11.15.0",
         "react": "^19.2.6",

frontend/package.json

@@ -1,7 +1,7 @@
 {
   "name": "rfc-app-frontend",
   "private": true,
-  "version": "0.21.0",
+  "version": "0.30.0",
   "type": "module",
   "scripts": {
     "dev": "vite",
@@ -19,6 +19,7 @@
     "@tiptap/pm": "^3.5.0",
     "@tiptap/react": "^3.5.0",
     "@tiptap/starter-kit": "^3.5.0",
+    "dompurify": "^3.2.4",
     "marked": "^18.0.4",
     "mermaid": "^11.15.0",
     "react": "^19.2.6",

frontend/src/App.css

@@ -1354,6 +1354,41 @@
 .pr-breadcrumb a:hover { text-decoration: underline; }
 .pr-title { font-size: var(--text-xl); margin: 0 0 6px 0; }
 .pr-description { font-size: var(--text-base); color: var(--c-gray-600); margin: 0 0 6px 0; line-height: 1.55; }
+/* Roadmap #28 Part 1: inline auto-links to referenced RFCs inside PR text
+   and comments. Subtle accent + dotted underline so they read as enriched
+   references, not as primary navigation. */
+.rfc-autolink {
+  color: var(--color-link);
+  text-decoration: underline;
+  text-decoration-style: dotted;
+  text-underline-offset: 2px;
+  font-weight: 500;
+}
+.rfc-autolink:hover { text-decoration-style: solid; }
+
+/* #28 Parts 2–3: a matched term that isn't a live link but carries an
+   offer (contribute to a pending RFC / create a new one). The term reads
+   as enriched (dotted underline, no link colour); the offer is a small
+   trailing chip so the prose stays readable. */
+.rfc-pending, .rfc-candidate {
+  text-decoration: underline;
+  text-decoration-style: dotted;
+  text-underline-offset: 2px;
+}
+.rfc-offer {
+  margin-left: 4px;
+  padding: 0 5px;
+  font-size: 0.74em;
+  font-weight: 600;
+  line-height: 1.5;
+  border-radius: 6px;
+  white-space: nowrap;
+  text-decoration: none;
+  border: 1px solid var(--color-border, #ccc);
+  color: var(--color-link);
+}
+.rfc-offer:hover { background: var(--color-surface-alt, rgba(0,0,0,0.04)); }
+.rfc-offer-create { border-style: dashed; }
 .pr-header-edit { display: flex; flex-direction: column; gap: 8px; }
 .pr-header-right {
   display: flex; flex-direction: column; align-items: flex-end; gap: 8px;

frontend/src/App.jsx

@@ -1,13 +1,15 @@
 import { useEffect, useRef, useState } from 'react'
-import { Routes, Route, Link, Navigate, useLocation, useNavigate } from 'react-router-dom'
+import { Routes, Route, Link, Navigate, useLocation, useNavigate, useSearchParams } from 'react-router-dom'
 import { getMe, subscribeToNotifications } from './api'
 import { anonymize, EVENTS, identify, track } from './lib/analytics'
+import { useLastState } from './lib/useLastState'
 import Catalog from './components/Catalog.jsx'
 import Inbox from './components/Inbox.jsx'
 import RFCView from './components/RFCView.jsx'
 import PRView from './components/PRView.jsx'
 import ProposalView from './components/ProposalView.jsx'
 import ProposeModal from './components/ProposeModal.jsx'
+import ContributeRequestForm from './components/ContributeRequestForm.jsx'
 import Landing from './components/Landing.jsx'
 import Login from './components/Login.jsx'
 import BetaPending from './components/BetaPending.jsx'
@@ -42,8 +44,27 @@ export default function App() {
   // "Privacy & cookies" tab dispatches a `rfc-app:cookie-consent-reopen`
   // event that bumps this.
   const [consentReopenTick, setConsentReopenTick] = useState(0)
+  // v0.23.0 / item #29 — flips true once the #21-Part-C identify effect
+  // has fired (or once we've confirmed there's no authenticated user to
+  // identify). useLastState gates its resume redirect on this so the
+  // redirect always happens AFTER identify, preserving identify-then-
+  // track ordering.
+  const [identifyReady, setIdentifyReady] = useState(false)
   const navigate = useNavigate()
   const location = useLocation()
+  // #28 Parts 2–3: the LinkedText create/contribute affordances route via
+  // query params so they need no prop-threading from deep in a comment
+  // list. `?propose=<term>` opens the propose modal pre-filled;
+  // `?contribute=<slug>&term=<term>` opens the contribute-request form.
+  const [searchParams, setSearchParams] = useSearchParams()
+  const proposeParam = searchParams.get('propose')
+  const contributeSlug = searchParams.get('contribute')
+  const contributeTerm = searchParams.get('term')
+  const clearParams = (...keys) => {
+    const next = new URLSearchParams(searchParams)
+    keys.forEach(k => next.delete(k))
+    setSearchParams(next, { replace: true })
+  }
   // v0.15.0 — Page Viewed event taxonomy. We fire on every
   // route change; the analytics wrapper itself decides whether
   // anything ships out (consent + key check). The first fire is
@@ -86,6 +107,9 @@ export default function App() {
       if (viewer?.first_sign_in_at) props.first_sign_in_at = ['__setOnce__', viewer.first_sign_in_at]
       if (viewer?.created_at) props.account_created_at = ['__setOnce__', viewer.created_at]
       identify({ user_id: String(uid), properties: props })
+      // v0.23.0 / item #29 — identify has now fired for this sign-in;
+      // release useLastState's resume redirect (it waits on this).
+      setIdentifyReady(true)
     } else if (uid == null && lastUserIdRef.current != null) {
       // Sign-out edge — App-level reset is handled separately by the
       // sign-out gesture that fires User Signed Out. Clear our local
@@ -94,6 +118,14 @@ export default function App() {
     }
   }, [me?.authenticated, me?.user?.id, me?.user?.role, me?.user?.permission_state, me?.user?.passcode_set, me?.user?.device_trusted])
 
+  // v0.23.0 / item #29 — once `me` has resolved, if there's no
+  // authenticated user there is nothing to identify, so release the
+  // resume gate immediately (anonymous boots have no resume to do, but
+  // the hook still needs the gate resolved to be a clean no-op).
+  useEffect(() => {
+    if (me != null && !me.authenticated) setIdentifyReady(true)
+  }, [me])
+
   useEffect(() => {
     const handler = () => setConsentReopenTick(t => t + 1)
     window.addEventListener('rfc-app:cookie-consent-reopen', handler)
@@ -107,6 +139,18 @@ export default function App() {
       .finally(() => setLoading(false))
   }, [])
 
+  // v0.23.0 / item #29 — server-side sign-in state resume. The hook
+  // debounce-posts the current route for authenticated users and, once
+  // identify has fired, redirects a fresh sign-in (which hard-lands on
+  // "/") to the user's stored last route. Anonymous users: no-op.
+  useLastState({
+    authenticated: !!me?.authenticated,
+    pathname: location.pathname,
+    identifyReady,
+    lastRoute: me?.authenticated ? me.user?.last_route : null,
+    navigate,
+  })
+
   // §15.3 — subscribe to the live SSE stream for authenticated viewers
   // so the badge counter and the toast surface stay in lockstep with
   // the inbox. Tabs that miss an event because they were closed pick
@@ -283,17 +327,26 @@ export default function App() {
           } />
         </Routes>
       </div>
-      {proposeOpen && viewer && (
+      {(proposeOpen || proposeParam != null) && viewer && (
         <ProposeModal
           viewer={viewer}
-          onClose={() => setProposeOpen(false)}
+          initialTitle={proposeParam || ''}
+          onClose={() => { setProposeOpen(false); clearParams('propose') }}
           onSubmitted={({ pr_number }) => {
             setProposeOpen(false)
+            clearParams('propose')
             setCatalogVersion(v => v + 1)
             navigate(`/proposals/${pr_number}`)
           }}
         />
       )}
+      {contributeSlug && viewer && (
+        <ContributeRequestForm
+          slug={contributeSlug}
+          term={contributeTerm || ''}
+          onClose={() => clearParams('contribute', 'term')}
+        />
+      )}
       {inboxOpen && viewer && (
         <Inbox onClose={() => setInboxOpen(false)} lastChangeTick={inboxTick} />
       )}

frontend/src/api.js

@@ -25,6 +25,25 @@ export async function getMe() {
   return jsonOrThrow(res)
 }
 
+// ── v0.23.0: sign-in state resume (§6.2, roadmap item #29) ───────────────
+//
+// The route-change hook (useLastState) debounce-posts the user's current
+// route + a small bag of *light* view state here for authenticated users.
+// The next sign-in reads `last_route` off `/api/auth/me` and redirects.
+// Privacy: `state` carries ephemeral view state ONLY — never draft-buffer
+// contents (see SPEC §6.2). Best-effort: callers ignore failures (an
+// offline/401 POST must never disrupt navigation).
+export async function putLastState(route, state) {
+  const body = { route }
+  if (state != null) body.state = state
+  const res = await fetch('/api/me/last-state', {
+    method: 'PUT',
+    headers: { 'Content-Type': 'application/json' },
+    body: JSON.stringify(body),
+  })
+  return jsonOrThrow(res)
+}
+
 // ── v0.7.0: email + one-time-code sign-in (§6.2) ─────────────────────────
 //
 // The legacy /auth/login → /auth/callback OAuth flow remains during the
@@ -166,15 +185,81 @@ export async function getProposal(prNumber) {
   return jsonOrThrow(await fetch(`/api/proposals/${prNumber}`))
 }
 
-export async function proposeRFC({ title, slug, pitch, tags }) {
+export async function proposeRFC({ title, slug, pitch, tags, proposedUseCase }) {
   const res = await fetch('/api/rfcs/propose', {
     method: 'POST',
     headers: { 'Content-Type': 'application/json' },
-    body: JSON.stringify({ title, slug, pitch, tags: tags || [] }),
+    // #26: proposed_use_case is optional; send null when blank so the
+    // backend treats it as "left blank".
+    body: JSON.stringify({
+      title,
+      slug,
+      pitch,
+      tags: tags || [],
+      proposed_use_case: proposedUseCase || null,
+    }),
   })
   return jsonOrThrow(res)
 }
 
+// Roadmap #27: Claude Haiku tag suggestions for the propose-RFC modal.
+// Returns a (possibly empty) array of { tag, confidence }. Deliberately
+// forgiving — any non-OK response (rate limit, transient error, no key
+// configured server-side) resolves to [] so the modal just shows nothing
+// rather than surfacing an error for what is a best-effort assist.
+export async function suggestTags({ title, pitch, useCase }) {
+  try {
+    const res = await fetch('/api/rfcs/suggest-tags', {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({
+        title: title || '',
+        pitch: pitch || '',
+        use_case: useCase || '',
+      }),
+    })
+    if (!res.ok) return []
+    const data = await res.json()
+    return Array.isArray(data.suggestions) ? data.suggestions : []
+  } catch {
+    return []
+  }
+}
+
+// Roadmap #28 Part 3: offer-to-contribute-to-a-pending-RFC.
+// `contributionTarget` feeds the contribute form (RFC title, owner
+// display, the viewer's eligibility); `requestContribution` submits the
+// ask; accept/decline are the owner's inbox actions.
+export async function contributionTarget(slug) {
+  return jsonOrThrow(await fetch(`/api/rfcs/${slug}/contribution-target`))
+}
+
+export async function requestContribution(slug, { matchedTerm, whoIAm, why, useCase }) {
+  const res = await fetch(`/api/rfcs/${slug}/contribution-requests`, {
+    method: 'POST',
+    headers: { 'Content-Type': 'application/json' },
+    body: JSON.stringify({
+      matched_term: matchedTerm,
+      who_i_am: whoIAm,
+      why,
+      use_case: useCase || null,
+    }),
+  })
+  return jsonOrThrow(res)
+}
+
+export async function acceptContributionRequest(slug, requestId) {
+  return jsonOrThrow(await fetch(
+    `/api/rfcs/${slug}/contribution-requests/${requestId}/accept`, { method: 'POST' },
+  ))
+}
+
+export async function declineContributionRequest(slug, requestId) {
+  return jsonOrThrow(await fetch(
+    `/api/rfcs/${slug}/contribution-requests/${requestId}/decline`, { method: 'POST' },
+  ))
+}
+
 export async function mergeProposal(prNumber) {
   const res = await fetch(`/api/proposals/${prNumber}/merge`, { method: 'POST' })
   return jsonOrThrow(res)
@@ -492,13 +577,14 @@ export async function draftPRText(slug, branch) {
   return jsonOrThrow(res)
 }
 
-export async function openPR(slug, branch, { title, description }) {
+export async function openPR(slug, branch, { title, description, proposedUseCase }) {
   const res = await fetch(
     `/api/rfcs/${slug}/branches/${encodeURIComponent(branch)}/open-pr`,
     {
       method: 'POST',
       headers: { 'Content-Type': 'application/json' },
-      body: JSON.stringify({ title, description }),
+      // #26: proposed_use_case is optional; null when blank.
+      body: JSON.stringify({ title, description, proposed_use_case: proposedUseCase || null }),
     },
   )
   return jsonOrThrow(res)

frontend/src/components/ContributeRequestForm.jsx

@@ -0,0 +1,163 @@
+// ContributeRequestForm.jsx — roadmap #28 Part 3.
+//
+// The "ask to contribute" popover, opened from an `rfc-pending` affordance
+// in LinkedText (App reads `?contribute=<slug>&term=<term>`). It loads the
+// contribution target (RFC title + owner display + the viewer's
+// eligibility), shows the framing line "<owner> is working on an RFC for
+// '<term>'", and collects the three #15/#26-vocabulary fields:
+//
+//   * Who I am          (required, free-text)
+//   * Why I'm asking    (required, free-text)
+//   * What I'd use it for (optional, mirrors #26)
+//
+// Submitting POSTs the request, which lands in each owner's §15 inbox.
+// When the viewer isn't eligible (anonymous, already a collaborator, or
+// has a pending ask) the form shows the backend's reason instead.
+
+import { useEffect, useState } from 'react'
+import { contributionTarget, requestContribution } from '../api'
+
+export default function ContributeRequestForm({ slug, term, onClose }) {
+  const [target, setTarget] = useState(null)
+  const [loadError, setLoadError] = useState(null)
+  const [whoIAm, setWhoIAm] = useState('')
+  const [why, setWhy] = useState('')
+  const [useCase, setUseCase] = useState('')
+  const [submitting, setSubmitting] = useState(false)
+  const [error, setError] = useState(null)
+  const [done, setDone] = useState(false)
+
+  useEffect(() => {
+    let live = true
+    contributionTarget(slug)
+      .then(t => { if (live) setTarget(t) })
+      .catch(err => { if (live) setLoadError(err.message || 'Could not load this RFC.') })
+    return () => { live = false }
+  }, [slug])
+
+  async function handleSubmit(e) {
+    e.preventDefault()
+    if (!whoIAm.trim() || !why.trim()) return
+    setSubmitting(true)
+    setError(null)
+    try {
+      await requestContribution(slug, {
+        matchedTerm: term || target?.title || slug,
+        whoIAm: whoIAm.trim(),
+        why: why.trim(),
+        useCase: useCase.trim() || null,
+      })
+      setDone(true)
+    } catch (err) {
+      setError(err.message || 'Could not send your request.')
+    } finally {
+      setSubmitting(false)
+    }
+  }
+
+  const owner = target?.owner || 'The owner'
+  const label = term || target?.title || slug
+
+  return (
+    <div className="modal-overlay" onClick={e => { if (e.target === e.currentTarget) onClose() }}>
+      <div className="modal">
+        <div className="modal-header">
+          <h2>Ask to contribute</h2>
+          <button className="modal-close" onClick={onClose}>×</button>
+        </div>
+
+        {loadError && (
+          <div className="modal-body"><p className="field-error">{loadError}</p></div>
+        )}
+
+        {!loadError && done && (
+          <>
+            <div className="modal-body">
+              <p>
+                Your request has been sent to <strong>{owner}</strong>. You'll hear back
+                in your inbox; if it's accepted you'll get an invitation by email to
+                join the RFC.
+              </p>
+            </div>
+            <div className="modal-actions">
+              <button type="button" className="btn-primary" onClick={onClose}>Done</button>
+            </div>
+          </>
+        )}
+
+        {!loadError && !done && target && !target.eligible && (
+          <>
+            <div className="modal-body">
+              <p className="field-help" style={{ marginTop: 0 }}>
+                {owner} is working on an RFC for <strong>'{label}'</strong>.
+              </p>
+              <p>{target.already_requested
+                ? "You've already asked to contribute to this RFC — the owner has your request."
+                : (target.reason || 'You cannot ask to contribute to this RFC right now.')}</p>
+            </div>
+            <div className="modal-actions">
+              <button type="button" className="btn-secondary" onClick={onClose}>Close</button>
+            </div>
+          </>
+        )}
+
+        {!loadError && !done && target && target.eligible && (
+          <form onSubmit={handleSubmit}>
+            <div className="modal-body">
+              <p className="field-help" style={{ marginTop: 0 }}>
+                <strong>{owner}</strong> is working on an RFC for <strong>'{label}'</strong>.
+                Tell them a little about why you'd like to contribute.
+              </p>
+
+              <label htmlFor="contribute-who">Who I am</label>
+              <textarea
+                id="contribute-who"
+                value={whoIAm}
+                onChange={e => setWhoIAm(e.target.value)}
+                placeholder="Your name and a sentence of context."
+                rows={2}
+                autoFocus
+                required
+              />
+
+              <label htmlFor="contribute-why">Why I'm asking to contribute</label>
+              <textarea
+                id="contribute-why"
+                value={why}
+                onChange={e => setWhy(e.target.value)}
+                placeholder="What you'd bring, or what draws you to this RFC."
+                rows={3}
+                required
+              />
+
+              <label htmlFor="contribute-use-case">What I'd use the RFC for (optional)</label>
+              <textarea
+                id="contribute-use-case"
+                value={useCase}
+                onChange={e => setUseCase(e.target.value)}
+                placeholder="The concrete thing you intend to build or do with it. Optional."
+                rows={2}
+              />
+
+              {error && <p className="field-error">{error}</p>}
+            </div>
+            <div className="modal-actions">
+              <button type="button" className="btn-secondary" onClick={onClose}>Cancel</button>
+              <button
+                type="submit"
+                className="btn-primary"
+                disabled={!whoIAm.trim() || !why.trim() || submitting}
+              >
+                {submitting ? 'Sending…' : 'Send request'}
+              </button>
+            </div>
+          </form>
+        )}
+
+        {!loadError && !done && !target && (
+          <div className="modal-body"><p className="field-help">Loading…</p></div>
+        )}
+      </div>
+    </div>
+  )
+}

frontend/src/components/Editor.jsx

@@ -17,7 +17,7 @@
 import { useEditor, EditorContent, Extension } from '@tiptap/react'
 import StarterKit from '@tiptap/starter-kit'
 import { useEffect, useRef, useCallback } from 'react'
-import { marked } from 'marked'
+import { renderMarkdown } from '../lib/sanitizeHtml'
 import { Plugin, PluginKey } from 'prosemirror-state'
 import { Decoration, DecorationSet } from 'prosemirror-view'
 
@@ -122,7 +122,7 @@ export default function Editor({
 
   useEffect(() => {
     if (!editor || content == null) return
-    const html = marked.parse(content)
+    const html = renderMarkdown(content)
     editor.commands.setContent(html, false)
   }, [content, editor])
 

frontend/src/components/Inbox.css

@@ -126,3 +126,13 @@
   line-height: var(--leading-normal);
   color: var(--color-text-muted);
 }
+
+/* #28 Part 3 — actionable contribute-request row: the requester's
+   who/why/use-case detail plus an Accept/Decline pair. */
+.inbox-row-action { display: flex; flex-direction: column; gap: 8px; padding: 12px; }
+.inbox-row-action .inbox-row-main { display: flex; align-items: center; gap: 8px; }
+.inbox-request-detail { margin-left: 18px; font-size: var(--text-sm); }
+.inbox-request-detail p { margin: 2px 0; color: var(--color-text-muted); }
+.inbox-request-detail strong { color: var(--color-text); }
+.inbox-request-actions { display: flex; gap: 8px; margin-left: 18px; }
+.inbox-request-outcome { margin: 0 0 0 18px; }

frontend/src/components/Inbox.jsx

@@ -11,6 +11,8 @@
 import { useEffect, useMemo, useState } from 'react'
 import { Link } from 'react-router-dom'
 import {
+  acceptContributionRequest,
+  declineContributionRequest,
   listNotifications,
   markNotificationRead,
   markNotificationsReadByFilter,
@@ -164,7 +166,71 @@ export default function Inbox({ onClose, lastChangeTick }) {
   )
 }
 
+// #28 Part 3: the contribute-request row is the first actionable inbox
+// kind — it renders the requester's who/why/use-case inline and an
+// Accept/Decline pair that fire the owner's decision (accept reuses #12's
+// invite flow on the backend).
+function ContributionRequestRow({ item, onMarkRead }) {
+  const unread = !item.read_at
+  const x = item.extras || {}
+  const [outcome, setOutcome] = useState(null)   // 'accepted' | 'declined'
+  const [busy, setBusy] = useState(false)
+  const [error, setError] = useState(null)
+
+  async function act(accept) {
+    if (busy || outcome) return
+    setBusy(true)
+    setError(null)
+    try {
+      if (accept) await acceptContributionRequest(item.rfc_slug, x.request_id)
+      else await declineContributionRequest(item.rfc_slug, x.request_id)
+      setOutcome(accept ? 'accepted' : 'declined')
+      await onMarkRead(item)
+    } catch (err) {
+      setError(err.message || 'Action failed.')
+    } finally {
+      setBusy(false)
+    }
+  }
+
+  return (
+    <li className={`inbox-row inbox-row-action ${unread ? 'unread' : 'read'}`}>
+      <div className="inbox-row-main">
+        <span className="inbox-unread-dot" aria-hidden />
+        <span className={`inbox-cat cat-${item.category || 'unknown'}`}>{item.category || '·'}</span>
+        <span className="inbox-summary">{item.summary}</span>
+        <span className="inbox-when">{formatWhen(item.created_at)}</span>
+      </div>
+      <div className="inbox-request-detail">
+        {x.who_i_am && <p><strong>Who:</strong> {x.who_i_am}</p>}
+        {x.why && <p><strong>Why:</strong> {x.why}</p>}
+        {x.use_case && <p><strong>Use case:</strong> {x.use_case}</p>}
+      </div>
+      {error && <p className="field-error">{error}</p>}
+      {outcome ? (
+        <p className="inbox-request-outcome muted">
+          {outcome === 'accepted'
+            ? 'Accepted — an invitation has been sent.'
+            : 'Declined.'}
+        </p>
+      ) : (
+        <div className="inbox-request-actions">
+          <button type="button" className="btn-primary" disabled={busy || !x.request_id} onClick={() => act(true)}>
+            Accept
+          </button>
+          <button type="button" className="btn-secondary" disabled={busy || !x.request_id} onClick={() => act(false)}>
+            Decline
+          </button>
+        </div>
+      )}
+    </li>
+  )
+}
+
 function InboxRow({ item, onClick, onMarkRead, onClose }) {
+  if (item.event_kind === 'contribution_request_on_pending_rfc') {
+    return <ContributionRequestRow item={item} onMarkRead={onMarkRead} />
+  }
   const unread = !item.read_at
   const target = deepLink(item)
   const handle = async () => {

frontend/src/components/LinkedText.jsx

@@ -0,0 +1,91 @@
+// LinkedText.jsx — roadmap #28 (Parts 1–3).
+//
+// Renders a backend-provided list of text/link segments (see
+// backend/app/rfc_links.py). References in PR descriptions and comments
+// arrive pre-scanned as structured segments — this component maps them
+// onto plain text runs, anchors, and inline affordances. It never renders
+// HTML from the server (no dangerouslySetInnerHTML), so the surface is
+// XSS-safe regardless of what a comment author typed.
+//
+// Segment types:
+//   * `rfc`           — Part 1: a link to an accepted (active) RFC.
+//   * `rfc-pending`   — Part 3: the term names a pending (super-draft)
+//                       RFC; a signed-in viewer who isn't its owner gets
+//                       an inline "ask to contribute" affordance routing
+//                       to the contribute form (App reads `?contribute=`).
+//   * `rfc-candidate` — Part 2: a strong-candidate term with no RFC yet;
+//                       a viewer with create rights (`canCreate`) gets a
+//                       "create RFC" affordance routing to the propose
+//                       flow pre-filled (App reads `?propose=`).
+//
+// Affordances degrade to plain text when the viewer lacks the relevant
+// right, so the visible prose is identical for everyone — only the
+// offered actions differ.
+//
+// `segments` is the enriched array; `text` is the raw fallback used when
+// the field is absent (an older cached response, or a caller that didn't
+// pass segments).
+
+import { Link } from 'react-router-dom'
+
+export default function LinkedText({ segments, text, viewer, canCreate }) {
+  if (!Array.isArray(segments) || segments.length === 0) {
+    return <>{text ?? ''}</>
+  }
+  // A signed-in, beta-granted viewer can ask to contribute; the backend
+  // re-checks ownership/collaborator status and rejects self-requests.
+  const canContribute = !!viewer && viewer.permission_state === 'granted'
+  return (
+    <>
+      {segments.map((seg, i) => {
+        if (seg.type === 'rfc') {
+          return (
+            <a
+              key={i}
+              className="rfc-autolink"
+              href={`/rfc/${seg.slug}`}
+              title={seg.title ? `RFC: ${seg.title}` : undefined}
+            >
+              {seg.label}
+            </a>
+          )
+        }
+        if (seg.type === 'rfc-pending') {
+          const who = seg.owner || 'Someone'
+          return (
+            <span key={i} className="rfc-pending">
+              {seg.label}
+              {canContribute && (
+                <Link
+                  className="rfc-offer rfc-offer-contribute"
+                  to={`?contribute=${encodeURIComponent(seg.slug)}&term=${encodeURIComponent(seg.label)}`}
+                  title={`${who} is working on an RFC for '${seg.label}' — ask to contribute`}
+                >
+                  ask to contribute
+                </Link>
+              )}
+            </span>
+          )
+        }
+        if (seg.type === 'rfc-candidate') {
+          const term = seg.term || seg.label
+          return (
+            <span key={i} className="rfc-candidate">
+              {seg.label}
+              {canCreate && (
+                <Link
+                  className="rfc-offer rfc-offer-create"
+                  to={`?propose=${encodeURIComponent(term)}`}
+                  title={`Create RFC for '${term}'`}
+                >
+                  + create RFC
+                </Link>
+              )}
+            </span>
+          )
+        }
+        return <span key={i}>{seg.text}</span>
+      })}
+    </>
+  )
+}

frontend/src/components/MarkdownPreview.jsx

@@ -21,6 +21,7 @@
 
 import { useEffect, useRef, useState, useCallback } from 'react'
 import { Marked } from 'marked'
+import { sanitizeHtml } from '../lib/sanitizeHtml'
 import { decorateAcceptedChanges } from './trackedOverlay.js'
 import ChangeTooltip from './ChangeTooltip.jsx'
 
@@ -98,7 +99,7 @@ export default function MarkdownPreview({
   // synchronously with the body itself — no flash of un-decorated text.
   useEffect(() => {
     if (!hostRef.current) return
-    const html = previewMarked.parse(content || '')
+    const html = sanitizeHtml(previewMarked.parse(content || ''))
     hostRef.current.innerHTML = html
     const token = ++renderTokenRef.current
     // Reset memo so the new block set re-renders from scratch.

frontend/src/components/PRModal.jsx

@@ -15,6 +15,8 @@ import { EVENTS, track } from '../lib/analytics'
 export default function PRModal({ slug, branch, branchIsPrivate, onClose, onOpened }) {
   const [title, setTitle] = useState('')
   const [description, setDescription] = useState('')
+  // #26: optional ground-truth use case for this change.
+  const [useCase, setUseCase] = useState('')
   const [drafting, setDrafting] = useState(true)
   const [submitting, setSubmitting] = useState(false)
   const [confirmed, setConfirmed] = useState(!branchIsPrivate)
@@ -39,7 +41,11 @@ export default function PRModal({ slug, branch, branchIsPrivate, onClose, onOpen
     setSubmitting(true)
     setError(null)
     try {
-      const { pr_number } = await openPR(slug, branch, { title: title.trim(), description: description.trim() })
+      const { pr_number } = await openPR(slug, branch, {
+        title: title.trim(),
+        description: description.trim(),
+        proposedUseCase: useCase.trim() || null,
+      })
       // v0.15.0 — analytics: fire on §10.2 PR-open success. slug
       // and pr_number are the join keys; title/description stay out.
       track(EVENTS.PR_OPENED, { rfc_slug: slug, pr_number })
@@ -104,6 +110,20 @@ export default function PRModal({ slug, branch, branchIsPrivate, onClose, onOpen
             what was argued, what shifted, what the arbiters are asked
             to consider.
           </p>
+          <label className="modal-label">What will you be using this change for? (optional)</label>
+          <textarea
+            className="modal-textarea"
+            value={useCase}
+            onChange={e => setUseCase(e.target.value)}
+            placeholder="The concrete thing this change unlocks for you. Optional."
+            disabled={drafting || submitting}
+            rows={3}
+            maxLength={8000}
+          />
+          <p className="field-help">
+            #26: the concrete ground-truth use case — distinct from "why
+            it's needed" above. Leave blank if you'd rather not say.
+          </p>
           {error && <p className="field-error">{error}</p>}
         </div>
         <div className="modal-actions">

frontend/src/components/PRView.jsx

@@ -23,6 +23,7 @@ import {
   withdrawPR,
 } from '../api'
 import { EVENTS, track } from '../lib/analytics'
+import LinkedText from './LinkedText'
 
 export default function PRView({ viewer }) {
   const { slug, prNumber: prNumberParam } = useParams()
@@ -218,8 +219,21 @@ export default function PRView({ viewer }) {
             <>
               <h1 className="pr-title">{pr.title}</h1>
               {pr.description && (
-                <p className="pr-description">{pr.description}</p>
+                <p className="pr-description">
+                  <LinkedText segments={pr.description_segments} text={pr.description} viewer={viewer} canCreate={viewer?.permission_state === 'granted'} />
+                </p>
               )}
+              {/* #26: the optional ground-truth use case for this change,
+                  captured when the PR was opened. Muted "left blank"
+                  treatment when none was supplied. */}
+              <div className="pr-use-case" style={{ margin: '6px 0', fontSize: 13 }}>
+                <span style={{ fontWeight: 700, color: '#888', textTransform: 'uppercase', letterSpacing: '0.05em', fontSize: 11 }}>
+                  Intended use case:
+                </span>{' '}
+                {pr.proposed_use_case
+                  ? <span style={{ whiteSpace: 'pre-wrap' }}>{pr.proposed_use_case}</span>
+                  : <span style={{ color: '#999', fontStyle: 'italic' }}>left blank</span>}
+              </div>
               {pr.capabilities?.can_edit_text && (
                 <button className="btn-link" onClick={startHeaderEdit}>Edit title & description</button>
               )}
@@ -429,7 +443,9 @@ function PRConversation({ threads, messagesByThread, threadsByKind, seenMsgId })
                 {isNew && <span className="chat-msg-new-pip" title="New since your last visit">●</span>}
               </div>
               {m.quote && <pre className="chat-msg-quote">{m.quote}</pre>}
-              <div className="chat-msg-body">{m.text}</div>
+              <div className="chat-msg-body">
+                <LinkedText segments={m.text_segments} text={m.text} viewer={viewer} canCreate={viewer?.permission_state === 'granted'} />
+              </div>
             </li>
           )
         })}

frontend/src/components/ProposalView.jsx

@@ -10,7 +10,7 @@
 
 import { useEffect, useState } from 'react'
 import { useParams, useNavigate } from 'react-router-dom'
-import { marked } from 'marked'
+import { renderMarkdown } from '../lib/sanitizeHtml'
 import { getProposal, mergeProposal, declineProposal, withdrawProposal } from '../api'
 
 export default function ProposalView({ viewer, onChange }) {
@@ -161,8 +161,16 @@ export default function ProposalView({ viewer, onChange }) {
       </h3>
       <div
         className="entry-body"
-        dangerouslySetInnerHTML={{ __html: marked.parse(data.entry?.body || '') }}
+        dangerouslySetInnerHTML={{ __html: renderMarkdown(data.entry?.body || '') }}
       />
+
+      {/* #26: the optional ground-truth use case the proposer supplied. */}
+      <h3 style={{ fontSize: 13, fontWeight: 700, color: '#888', textTransform: 'uppercase', letterSpacing: '0.05em', marginTop: 24 }}>
+        Intended use case
+      </h3>
+      {data.proposed_use_case
+        ? <div className="entry-body" dangerouslySetInnerHTML={{ __html: renderMarkdown(data.proposed_use_case) }} />
+        : <p style={{ color: '#999', fontStyle: 'italic' }}>Left blank by the proposer.</p>}
     </article>
   )
 }

frontend/src/components/ProposeModal.jsx

@@ -2,17 +2,24 @@
 //
 // Title (required) and pitch (required textarea), with a slug field
 // that auto-fills from the title via the same deterministic kebab-case
-// the backend uses. Tags are chip-input (free-form for slice 1; the
-// AI-suggested chips of §9.1 are deferred to Slice 2 when the AI surface
-// is wired up).
+// the backend uses. Tags are chip-input (free-form), with the §9.1
+// Slice 2 AI-suggested chips (roadmap #27) wired in: as the draft fills
+// in, the backend asks Claude Haiku for tags drawn from the corpus's
+// existing tag set, surfaced as clickable suggestion chips. The assist
+// is best-effort — it stays silent when unavailable.
 //
 // The submit button drives the §17 POST /api/rfcs/propose endpoint;
 // success navigates the proposer to the pending-idea view per §9.3.
 
-import { useEffect, useState } from 'react'
-import { proposeRFC } from '../api'
+import { useEffect, useRef, useState } from 'react'
+import { proposeRFC, suggestTags } from '../api'
 import { EVENTS, track } from '../lib/analytics'
 
+// How long the draft must sit unchanged before we ask for suggestions —
+// long enough to fire on typing pauses / field-blur, not on every
+// keystroke (the backend is also per-user rate-limited as a backstop).
+const SUGGEST_DEBOUNCE_MS = 700
+
 function slugify(title) {
   return title
     .toLowerCase()
@@ -21,26 +28,64 @@ function slugify(title) {
     .replace(/^-+|-+$/g, '')
 }
 
-export default function ProposeModal({ viewer, onClose, onSubmitted }) {
-  const [title, setTitle] = useState('')
+export default function ProposeModal({ viewer, onClose, onSubmitted, initialTitle = '' }) {
+  // #28 Part 2: a "create RFC for '<term>'" affordance pre-fills the title
+  // (App passes the `?propose=<term>` value here); the slug derives from it
+  // via the same effect that drives manual typing.
+  const [title, setTitle] = useState(initialTitle)
   const [slug, setSlug] = useState('')
   const [slugEdited, setSlugEdited] = useState(false)
   const [pitch, setPitch] = useState('')
+  // #26: optional ground-truth use case, sibling to the required pitch.
+  const [useCase, setUseCase] = useState('')
   const [tagInput, setTagInput] = useState('')
   const [tags, setTags] = useState([])
   const [submitting, setSubmitting] = useState(false)
   const [error, setError] = useState(null)
+  // #27: Claude Haiku tag suggestions. `suggestions` is the latest
+  // ranked list from the backend ({ tag, confidence }); we render the
+  // subset not already chosen. `suggestedOnce` gates the disclosure +
+  // row so they only appear after the assist has actually run.
+  const [suggestions, setSuggestions] = useState([])
+  const [suggestedOnce, setSuggestedOnce] = useState(false)
 
   useEffect(() => {
     if (!slugEdited) setSlug(slugify(title))
   }, [title, slugEdited])
 
+  // #27: debounced tag-suggestion fetch. Fires after the draft sits
+  // unchanged for SUGGEST_DEBOUNCE_MS, only once there's something to go
+  // on (a title). A stale-response guard keeps an earlier in-flight
+  // request from clobbering a newer one.
+  const suggestSeq = useRef(0)
+  useEffect(() => {
+    if (!title.trim()) {
+      setSuggestions([])
+      return
+    }
+    const handle = setTimeout(async () => {
+      const seq = ++suggestSeq.current
+      const result = await suggestTags({ title, pitch, useCase })
+      if (seq !== suggestSeq.current) return // a newer request superseded us
+      setSuggestions(Array.isArray(result) ? result : [])
+      if (result && result.length) setSuggestedOnce(true)
+    }, SUGGEST_DEBOUNCE_MS)
+    return () => clearTimeout(handle)
+  }, [title, pitch, useCase])
+
+  // Suggestions the user hasn't already added.
+  const freshSuggestions = suggestions.filter(s => !tags.includes(s.tag))
+
   function addTag() {
     const t = tagInput.trim()
     if (t && !tags.includes(t)) setTags([...tags, t])
     setTagInput('')
   }
 
+  function addSuggested(tag) {
+    if (!tags.includes(tag)) setTags([...tags, tag])
+  }
+
   async function handleSubmit(e) {
     e.preventDefault()
     if (!title.trim() || !slug || !pitch.trim()) return
@@ -52,6 +97,7 @@ export default function ProposeModal({ viewer, onClose, onSubmitted }) {
         slug,
         pitch: pitch.trim(),
         tags,
+        proposedUseCase: useCase.trim() || null,
       })
       // v0.15.0 — analytics: fire on the §9.1 propose-RFC submit.
       // Slug is a stable, low-cardinality identifier (kebab-case
@@ -105,6 +151,19 @@ export default function ProposeModal({ viewer, onClose, onSubmitted }) {
               required
             />
 
+            <label htmlFor="propose-use-case">What will you be using this RFC for? (optional)</label>
+            <textarea
+              id="propose-use-case"
+              value={useCase}
+              onChange={e => setUseCase(e.target.value)}
+              placeholder="The concrete thing you intend to build or do with this RFC. Optional, but it helps ground the work."
+              rows={3}
+            />
+            <p className="field-help">
+              The concrete ground-truth use case — distinct from "why it's
+              needed" above. Leave blank if you'd rather not say.
+            </p>
+
             <label htmlFor="propose-tag">Tags (optional)</label>
             <div style={{ display: 'flex', gap: 6, alignItems: 'center', marginBottom: 4 }}>
               <input
@@ -136,6 +195,45 @@ export default function ProposeModal({ viewer, onClose, onSubmitted }) {
               </div>
             )}
 
+            {/* #27: Claude Haiku suggested tags. Clickable chips that add
+                to the tag list; nothing auto-applies. The disclosure is
+                required — the draft text is sent to Anthropic to generate
+                these — so it renders whenever the suggestion row does. */}
+            {(freshSuggestions.length > 0 || (suggestedOnce && suggestions.length > 0)) && (
+              <div style={{ marginTop: 4, marginBottom: 14 }}>
+                {freshSuggestions.length > 0 && (
+                  <>
+                    <p className="field-help" style={{ marginTop: 0, marginBottom: 4 }}>
+                      Suggested tags — click to add:
+                    </p>
+                    <div>
+                      {freshSuggestions.map(s => (
+                        <button
+                          key={s.tag}
+                          type="button"
+                          className="entry-tag"
+                          onClick={() => addSuggested(s.tag)}
+                          title={`Add "${s.tag}"`}
+                          style={{
+                            display: 'inline-block',
+                            marginRight: 4,
+                            marginBottom: 4,
+                            border: '1px dashed var(--color-border, #ccc)',
+                            background: 'none',
+                            cursor: 'pointer',
+                          }}
+                        >+ {s.tag}</button>
+                      ))}
+                    </div>
+                  </>
+                )}
+                <p className="field-help" style={{ marginTop: 4, marginBottom: 0, fontStyle: 'italic' }}>
+                  Suggestions are generated by Claude (Anthropic). The text you've
+                  entered above is sent to Anthropic to produce them.
+                </p>
+              </div>
+            )}
+
             {viewer && (
               <p className="field-help" style={{ marginTop: 14, marginBottom: 0 }}>
                 Owner: <strong>{viewer.display_name || viewer.gitea_login}</strong> — you'll be the first owner of this super-draft. Additional owners can claim later (§13.1).

frontend/src/components/RFCDiscussionPanel.jsx

@@ -19,6 +19,7 @@ import {
   resolveDiscussionThread,
 } from '../api'
 import { EVENTS, track } from '../lib/analytics'
+import LinkedText from './LinkedText'
 
 export default function RFCDiscussionPanel({ slug, viewer }) {
   const [threads, setThreads] = useState([])
@@ -190,7 +191,7 @@ export default function RFCDiscussionPanel({ slug, viewer }) {
           </div>
         )}
         {activeMessages.map(msg => (
-          <DiscussionMessage key={msg.id} message={msg} />
+          <DiscussionMessage key={msg.id} message={msg} viewer={viewer} />
         ))}
         <div ref={bottomRef} />
       </div>
@@ -257,7 +258,7 @@ export default function RFCDiscussionPanel({ slug, viewer }) {
   )
 }
 
-function DiscussionMessage({ message }) {
+function DiscussionMessage({ message, viewer }) {
   const isSystem = message.role === 'system'
   if (isSystem) {
     return (
@@ -279,7 +280,9 @@ function DiscussionMessage({ message }) {
       {message.quote && (
         <div className="discussion-message-quote">"{message.quote}"</div>
       )}
-      <div className="discussion-message-body">{message.text}</div>
+      <div className="discussion-message-body">
+        <LinkedText segments={message.text_segments} text={message.text} viewer={viewer} canCreate={viewer?.permission_state === 'granted'} />
+      </div>
     </div>
   )
 }

frontend/src/components/RFCView.jsx

@@ -669,6 +669,19 @@ export default function RFCView({ viewer }) {
                 : 'main is read-only — PRs are the only path to change it. Open a branch to propose edits.'}
             </div>
           )}
+          {/* #26: the optional ground-truth use case captured at propose
+              time. Shown on the canonical (main) view; muted "left blank"
+              treatment when the proposer didn't supply one. */}
+          {branchParam === 'main' && (
+            <div className="rfc-use-case" style={{ margin: '8px 0 16px', padding: '10px 14px', borderLeft: '3px solid #e0e0e0', background: '#fafafa' }}>
+              <div style={{ fontSize: 11, fontWeight: 700, color: '#888', textTransform: 'uppercase', letterSpacing: '0.05em', marginBottom: 4 }}>
+                Intended use case
+              </div>
+              {entry.proposed_use_case
+                ? <div style={{ whiteSpace: 'pre-wrap' }}>{entry.proposed_use_case}</div>
+                : <span style={{ color: '#999', fontStyle: 'italic' }}>Left blank by the proposer.</span>}
+            </div>
+          )}
           {inDiscuss && branchParam !== 'main' && (
             <div className="discuss-mode-banner">
               Discuss mode on <strong>{branchParam}</strong> — chat freely;

frontend/src/lib/sanitizeHtml.js

@@ -0,0 +1,47 @@
+// sanitizeHtml.js — the single chokepoint for turning user-authored
+// markdown into DOM-bound HTML.
+//
+// Security audit 0026 (finding C1, Critical): every `marked.parse(...)`
+// result that reaches an `innerHTML` / `dangerouslySetInnerHTML` sink was
+// previously written raw. `marked` passes through embedded HTML and
+// `javascript:`/event-handler attributes verbatim, so any user-authored
+// document (RFC body, proposal body, proposed_use_case, transcript) was a
+// stored-XSS vector — a contributor's payload executed in the session of
+// whoever viewed it, including an admin/owner during review.
+//
+// Fix: route EVERY markdown render through `renderMarkdown` (or, for
+// already-rendered HTML, `sanitizeHtml`). DOMPurify's defaults already
+// strip <script>, on* event handlers, and javascript:/unsafe-data: URIs;
+// we add a hook so any link opening a new tab carries rel="noopener
+// noreferrer". The html profile keeps the standard markdown tag set plus
+// class + data-* attributes (the latter is what MarkdownPreview's mermaid
+// placeholder relies on); mermaid renders its SVG into the DOM *after*
+// sanitization and is itself locked down with securityLevel:'strict'.
+
+import DOMPurify from 'dompurify'
+import { marked } from 'marked'
+
+let _hookInstalled = false
+function ensureHook() {
+  if (_hookInstalled) return
+  DOMPurify.addHook('afterSanitizeAttributes', (node) => {
+    if (node.tagName === 'A' && node.getAttribute('target') === '_blank') {
+      node.setAttribute('rel', 'noopener noreferrer')
+    }
+  })
+  _hookInstalled = true
+}
+
+// Sanitize an already-rendered HTML string. Use when the HTML did not come
+// from `marked` (rare) or when a caller parses markdown with a bespoke
+// `Marked` instance and only needs the sanitize step.
+export function sanitizeHtml(html) {
+  ensureHook()
+  return DOMPurify.sanitize(html || '', { USE_PROFILES: { html: true } })
+}
+
+// Parse markdown with the shared `marked` and sanitize the result. This is
+// the drop-in replacement for `marked.parse(src)` at any HTML sink.
+export function renderMarkdown(src) {
+  return sanitizeHtml(marked.parse(src || ''))
+}

frontend/src/lib/useLastState.js

@@ -0,0 +1,91 @@
+// useLastState — v0.23.0 / roadmap item #29: server-side sign-in state
+// resume. Two responsibilities, kept in one small hook so App.jsx's
+// surface stays minimal:
+//
+//   1. Debounce-post the authenticated user's current route to
+//      `PUT /api/me/last-state` on every route change (~1s debounce so
+//      a fast click-through doesn't spray the endpoint). Anonymous
+//      users: no-op. Best-effort: a failed POST never disrupts nav.
+//
+//   2. On the first authenticated load, read the stored `last_route`
+//      (handed back on `/api/auth/me`) and `navigate()` to it ONCE.
+//      Stale routes (a withdrawn RFC, a slug the user lost rights to)
+//      are not special-cased here: navigating lands on whatever that
+//      route renders today, and the existing routing already falls
+//      through to the catalog/empty-state for a missing RFC. Keeping
+//      this dumb is deliberate (see SPEC §6.2 + the #29 scope note).
+//
+// Ordering with #21 Part C (Amplitude identify): App.jsx fires
+// `identify` in its own effect when `me.user.id` first appears. This
+// hook's resume redirect is gated on `identifyReady` — App.jsx flips it
+// true only after the identify effect has run — so the redirect always
+// happens AFTER identify, preserving the identify-then-track ordering
+// the roadmap calls out.
+import { useEffect, useRef } from 'react'
+import { putLastState } from '../api'
+
+// ~1s debounce on the route-change POST. A frontend constant, not a
+// server knob — the backend takes whatever lands.
+const DEBOUNCE_MS = 1000
+
+// Routes we never want to resume *to* — auth/landing surfaces that
+// would be nonsensical or hostile to drop a returning user onto. We
+// still record them (cheap, and the user may legitimately be sitting on
+// /docs), but the resume redirect skips them and falls through to the
+// default landing. Anything not listed resumes normally.
+const NON_RESUMABLE_PREFIXES = ['/login', '/welcome', '/invites/', '/invitations/']
+
+function isResumable(route) {
+  if (!route || typeof route !== 'string') return false
+  if (route === '/') return false // "/" is already the default landing
+  return !NON_RESUMABLE_PREFIXES.some(p => route.startsWith(p))
+}
+
+/**
+ * @param {object}   opts
+ * @param {boolean}  opts.authenticated  whether a viewer is signed in
+ * @param {string}   opts.pathname       current location.pathname
+ * @param {boolean}  opts.identifyReady   App flips true after identify fires
+ * @param {string|null} opts.lastRoute    stored route from /api/auth/me
+ * @param {function} opts.navigate        react-router navigate()
+ */
+export function useLastState({ authenticated, pathname, identifyReady, lastRoute, navigate }) {
+  // ── 1. Debounced route-change POST ────────────────────────────────
+  const timerRef = useRef(null)
+  useEffect(() => {
+    if (!authenticated) return undefined
+    if (timerRef.current) clearTimeout(timerRef.current)
+    timerRef.current = setTimeout(() => {
+      // Best-effort — swallow failures so an offline/401 POST never
+      // surfaces as a navigation error.
+      putLastState(pathname).catch(() => {})
+    }, DEBOUNCE_MS)
+    return () => {
+      if (timerRef.current) clearTimeout(timerRef.current)
+    }
+  }, [authenticated, pathname])
+
+  // ── 2. One-time resume redirect ───────────────────────────────────
+  // Fires once, after identify is ready, when there's a resumable
+  // stored route AND the user is currently sitting on the default
+  // landing ("/"). We only redirect from "/" so we never yank a user
+  // who deep-linked somewhere specific (or refreshed mid-RFC) back to
+  // their last route.
+  const resumedRef = useRef(false)
+  useEffect(() => {
+    if (resumedRef.current) return
+    if (!authenticated || !identifyReady) return
+    // Only resume when the app booted on the default landing — a hard
+    // sign-in nav lands on "/", which is exactly the case we want.
+    if (pathname !== '/') {
+      resumedRef.current = true // user deep-linked; don't resume later either
+      return
+    }
+    if (isResumable(lastRoute)) {
+      resumedRef.current = true
+      navigate(lastRoute, { replace: true })
+    } else {
+      resumedRef.current = true // nothing to resume to; keep default landing
+    }
+  }, [authenticated, identifyReady, lastRoute, pathname, navigate])
+}