v0.18.0 Slice 2: migrate send paths to build_envelope + POST unsubscribe

Five send sites now construct their envelopes through
`email_envelope.build_envelope` instead of building `EmailMessage`
ad hoc:

  * `email_otc.py` — OTC mail (no List-Unsubscribe per the
    proposal's tradeoff: the recipient explicitly requested the
    code, so a list semantic would be wrong).
  * `email_invite.py` — admin/per-RFC invite mail (mailto:-only
    List-Unsubscribe — the invitee isn't a user yet, so no
    per-user opt-out URL exists).
  * `email._deliver` — watcher notifications (full one-click
    unsubscribe: mailto + signed URL + List-Unsubscribe-Post per
    RFC 8058, required by Gmail/Yahoo).
  * `email._send_bundle` — the "while you were away" bundle,
    one-click to the new `all` synthetic category (which lands
    `email_opt_out_all = 1` because the bundle spans multiple
    per-category flags).
  * `digest.py` — same as the bundle: bulk-adjacent, one-click to
    `all`.

`api_notifications.py` gains the POST `/api/email/unsubscribe`
endpoint (the matching receiver for `List-Unsubscribe-Post:
List-Unsubscribe=One-Click`) and accepts the `all` category in
both GET and POST handlers.

`EmailConfig` adds `unsubscribe_mailto` (env: `EMAIL_UNSUBSCRIBE_MAILTO`,
default = `EMAIL_FROM`) so deployments can route unsubscribe
courtesy mail to a humans-monitored mailbox distinct from the
no-reply sender.

The `_SENT` test buffer now also carries `envelope["message"]`
(the `EmailMessage` itself) so new tests can assert on headers
directly. Legacy `to`/`from`/`subject`/`body` keys remain for
backward compatibility.

10 new integration tests across test_otc_vertical /
test_admin_create_user_invite_vertical / test_notifications_vertical
covering: OTC has no List-Unsubscribe; invite has mailto: only;
notification has full one-click; POST one-click flips the
category; `all` category sets global opt-out via both GET and
POST.

Full suite: 277 passed.

backend/app/api_notifications.py

@@ -443,6 +443,40 @@ def make_router(config: Config) -> APIRouter:
 
     # ----- Email: one-click unsubscribe + bounce webhook -----
 
+    # v0.18.0: the category → column map. The `all` synthetic
+    # category lands the bundle's one-click on the global opt-out
+    # flag (per `email._send_bundle` in v0.18.0 Slice 2 — a bundle
+    # spans multiple categories, so a per-category flip wouldn't
+    # honor the user's intent).
+    _CATEGORY_COLUMN: dict[str, str] = {
+        "personal-direct": "email_personal_direct",
+        "structural": "email_watched_structural",
+        "admin-actionable": "email_admin_actionable",
+        "all": "email_opt_out_all",
+    }
+
+    def _apply_unsubscribe(user_id: int, category: str) -> bool:
+        """Flip the matching column. Returns True on success, False
+        if the category is unknown. Idempotent — running twice on
+        the same (user, category) is harmless (it sets the column
+        to its current value)."""
+        column = _CATEGORY_COLUMN.get(category)
+        if column is None:
+            return False
+        # `all` sets the flag to 1 (opt out); per-category sets to 0
+        # (turn that category off). The column semantic is "1 means
+        # don't send"; the per-category booleans are "1 means do
+        # send". Different polarities, hence the case split.
+        if category == "all":
+            db.conn().execute(
+                f"UPDATE users SET {column} = 1 WHERE id = ?", (user_id,)
+            )
+        else:
+            db.conn().execute(
+                f"UPDATE users SET {column} = 0 WHERE id = ?", (user_id,)
+            )
+        return True
+
     @router.get("/api/email/unsubscribe")
     async def email_unsubscribe(t: str = Query(..., description="Signed token from the email footer")) -> HTMLResponse:
         try:
@@ -453,20 +487,51 @@ def make_router(config: Config) -> APIRouter:
                 "<p>Open the app to manage your notification preferences directly.</p>",
                 status_code=400,
             )
-        column = {
-            "personal-direct": "email_personal_direct",
-            "structural": "email_watched_structural",
-            "admin-actionable": "email_admin_actionable",
-        }.get(category)
-        if column is None:
+        if not _apply_unsubscribe(user_id, category):
             return HTMLResponse(
                 f"<h1>Unknown category</h1><p>{category}</p>", status_code=400
             )
-        db.conn().execute(f"UPDATE users SET {column} = 0 WHERE id = ?", (user_id,))
-        return HTMLResponse(
-            f"<h1>Unsubscribed</h1><p>You will no longer receive {category} emails. "
-            f"You can re-enable them in your notification preferences.</p>"
-        )
+        if category == "all":
+            body = (
+                "<h1>Unsubscribed</h1><p>You will no longer receive any email "
+                "from this app. You can re-enable individual categories from "
+                "your notification preferences after signing in.</p>"
+            )
+        else:
+            body = (
+                f"<h1>Unsubscribed</h1><p>You will no longer receive {category} emails. "
+                f"You can re-enable them in your notification preferences.</p>"
+            )
+        return HTMLResponse(body)
+
+    @router.post("/api/email/unsubscribe")
+    async def email_unsubscribe_post(
+        request: Request,
+        t: str = Query(..., description="Signed token from the List-Unsubscribe header"),
+    ) -> dict[str, Any]:
+        """v0.18.0: RFC 8058 one-click endpoint.
+
+        Gmail and Yahoo POST `List-Unsubscribe=One-Click` (as a
+        form-encoded body) to the URL in the `List-Unsubscribe`
+        header when the user clicks their MUA's "Unsubscribe"
+        button. The endpoint MUST accept POST (per the
+        `List-Unsubscribe-Post` header we advertise) and MUST be
+        idempotent.
+
+        The body content is checked loosely — RFC 8058 says it
+        SHOULD be exactly `List-Unsubscribe=One-Click`, but some
+        intermediaries strip / re-encode the body, so the
+        framework accepts any POST to the URL once the token
+        verifies. The bar is that the token signature carries the
+        authority; the body is hint-only.
+        """
+        try:
+            user_id, category = email_mod.verify_unsubscribe_token(t)
+        except BadSignature:
+            raise HTTPException(400, "Invalid or expired token")
+        if not _apply_unsubscribe(user_id, category):
+            raise HTTPException(400, f"Unknown category: {category}")
+        return {"ok": True, "category": category}
 
     @router.post("/api/webhooks/email-bounce")
     async def email_bounce(body: BounceBody, request: Request) -> dict[str, Any]:

backend/app/digest.py

@@ -180,7 +180,18 @@ def assemble_for_user(
 
     subject = _subject(eligible, cadence)
     body = _body(eligible, cadence, cfg)
-    sent = email_mod._deliver(cfg, email, subject, body)
+    # v0.18.0: the digest is the bulk-adjacent surface par excellence
+    # (it can carry weeks of accumulated activity), so it gets the
+    # full one-click unsubscribe to the global opt-out. Per-category
+    # opt-outs are managed from the preferences page; this footer is
+    # the "stop sending me anything" escape hatch Gmail and Yahoo
+    # expect for senders at this tier.
+    unsubscribe_url = email_mod.make_unsubscribe_url(user_id, "all")
+    sent = email_mod._deliver(
+        cfg, email, subject, body,
+        unsubscribe_mailto=cfg.unsubscribe_mailto,
+        unsubscribe_url=unsubscribe_url,
+    )
     if not sent:
         return False
     ids = [r["id"] for r, _ in eligible]

backend/app/email.py

@@ -24,7 +24,6 @@ import os
 import smtplib
 from dataclasses import dataclass
 from datetime import datetime, time, timezone
-from email.message import EmailMessage
 from email.utils import formataddr
 from itertools import groupby
 from typing import Any
@@ -33,6 +32,7 @@ from urllib.parse import urlencode
 from itsdangerous import BadSignature, URLSafeSerializer
 
 from . import db
+from .email_envelope import build_envelope
 
 log = logging.getLogger(__name__)
 
@@ -69,6 +69,7 @@ class EmailConfig:
     app_url: str
     bundle_threshold: int
     enabled: bool
+    unsubscribe_mailto: str
 
     @classmethod
     def from_env(cls) -> "EmailConfig":
@@ -84,6 +85,16 @@ class EmailConfig:
             app_url=os.environ.get("APP_URL", "http://localhost:8000").rstrip("/"),
             bundle_threshold=int(os.environ.get("EMAIL_BUNDLE_THRESHOLD", "5")),
             enabled=os.environ.get("EMAIL_ENABLED", "1") not in ("0", "false", "False"),
+            # v0.18.0: the `List-Unsubscribe: <mailto:…>` target on
+            # invite + notification mail. Defaults to the From
+            # address when unset; a deployment can route opt-out
+            # mail to a separate mailbox (e.g., a humans-monitored
+            # account distinct from the no-reply notifications
+            # sender) by setting this explicitly.
+            unsubscribe_mailto=os.environ.get(
+                "EMAIL_UNSUBSCRIBE_MAILTO",
+                os.environ.get("EMAIL_FROM", "notifications@wiggleverse.local"),
+            ).strip(),
         )
 
 
@@ -98,6 +109,14 @@ def _signer() -> URLSafeSerializer:
 
 
 def make_unsubscribe_url(user_id: int, category: str) -> str:
+    """Build the §15.4 per-category one-click URL.
+
+    `category` is one of `personal-direct`, `structural`,
+    `admin-actionable` (the three per-category flags) or `all`
+    (v0.18.0: the bundle path, which sets `email_opt_out_all = 1`
+    because a bundle covers multiple categories and a per-category
+    opt-out wouldn't honor the user's intent).
+    """
     cfg = EmailConfig.from_env()
     token = _signer().dumps({"u": user_id, "c": category})
     qs = urlencode({"t": token})
@@ -250,7 +269,19 @@ def _send_one(user: Any, notif_id: int, payload: dict, category: str) -> None:
         return
     subject = _subject(payload)
     body = _body(payload, user["id"], category, cfg)
-    sent = _deliver(cfg, user["email"], subject, body)
+    # v0.18.0: notification mail is bulk-adjacent (a watcher can
+    # accumulate dozens of structural events on a busy RFC), so it
+    # carries the full one-click unsubscribe — Gmail and Yahoo
+    # require this for senders at OHM's volume tier per RFC 8058.
+    unsubscribe_url = make_unsubscribe_url(user["id"], category)
+    sent = _deliver(
+        cfg,
+        user["email"],
+        subject,
+        body,
+        unsubscribe_mailto=cfg.unsubscribe_mailto,
+        unsubscribe_url=unsubscribe_url,
+    )
     if not sent:
         return
     db.conn().execute(
@@ -305,23 +336,45 @@ def _deep_link(payload: dict, cfg: EmailConfig) -> str:
     return cfg.app_url
 
 
-def _deliver(cfg: EmailConfig, to_address: str, subject: str, body: str) -> bool:
+def _deliver(
+    cfg: EmailConfig,
+    to_address: str,
+    subject: str,
+    body: str,
+    *,
+    unsubscribe_mailto: str | None = None,
+    unsubscribe_url: str | None = None,
+) -> bool:
+    """Build the envelope via the shared `build_envelope` helper and
+    hand it to SMTP.
+
+    The `_SENT` buffer carries the helper's `EmailMessage` under
+    `message` plus the legacy `to`/`from`/`subject`/`body` keys for
+    backward-compatibility with tests that read those directly.
+    Newer tests can assert on the header surface by inspecting
+    `envelope["message"]`.
+    """
+    msg = build_envelope(
+        to_address=to_address,
+        from_address=cfg.from_address,
+        from_name=cfg.from_name,
+        subject=subject,
+        body_plain=body,
+        unsubscribe_mailto=unsubscribe_mailto,
+        unsubscribe_url=unsubscribe_url,
+    )
     envelope = {
         "to": to_address,
         "from": formataddr((cfg.from_name, cfg.from_address)),
         "subject": subject,
         "body": body,
+        "message": msg,
     }
     _SENT.append(envelope)
     if not cfg.smtp_host:
         log.info("email (stdout fallback): to=%s subject=%s", to_address, subject)
         return True
     try:
-        msg = EmailMessage()
-        msg["From"] = envelope["from"]
-        msg["To"] = to_address
-        msg["Subject"] = subject
-        msg.set_content(body)
         smtp = smtplib.SMTP(cfg.smtp_host, cfg.smtp_port, timeout=30)
         try:
             if cfg.smtp_starttls:
@@ -440,13 +493,26 @@ def _send_bundle(cfg: EmailConfig, user: Any, emailable: list) -> int:
         for r, _cat, extras in group_rows:
             summary = _summary_for(r["event_kind"], r["actor_display"], r["rfc_title"], extras)
             sections.append(f"  · {summary}")
+    # v0.18.0: the bundle covers multiple categories, so a
+    # per-category opt-out can't honor the user's intent. The
+    # `all` category lands at the §15.4 endpoint and sets
+    # `email_opt_out_all = 1`.
+    unsubscribe_url = make_unsubscribe_url(user["id"], "all")
     body = (
         "Activity on RFCs you watch, accumulated during your quiet hours:\n"
         + "\n".join(sections)
         + f"\n\nOpen your inbox: {cfg.app_url}/inbox\n"
         + f"Manage all preferences: {cfg.app_url}/settings/notifications\n"
+        + f"Unsubscribe from all email: {unsubscribe_url}\n"
+    )
+    sent = _deliver(
+        cfg,
+        user["email"],
+        subject,
+        body,
+        unsubscribe_mailto=cfg.unsubscribe_mailto,
+        unsubscribe_url=unsubscribe_url,
     )
-    sent = _deliver(cfg, user["email"], subject, body)
     if not sent:
         return 0
     ids = [r["id"] for r, _, _ in emailable]

backend/app/email_invite.py

@@ -31,10 +31,10 @@ from __future__ import annotations
 
 import logging
 import smtplib
-from email.message import EmailMessage
 from email.utils import formataddr
 
 from .email import EmailConfig, _SENT
+from .email_envelope import build_envelope
 
 log = logging.getLogger(__name__)
 
@@ -59,12 +59,29 @@ def send_invite_email(
     cfg = EmailConfig.from_env()
     subject = _subject(inviter_display, cfg)
     body = _body(claim_url, inviter_display, inviter_email, custom_message, cfg)
+    # v0.18.0: invite mail carries a `List-Unsubscribe: <mailto:…>`
+    # only (no signed URL) — the invitee isn't a user yet, so there
+    # is no per-user opt-out row to flip. The operator handles
+    # ad-hoc opt-outs from the mailto: target. Per the proposal's
+    # "Tradeoff discussion": the invite was unsolicited from the
+    # recipient's perspective, so the courtesy header is right;
+    # but it can't be a one-click URL because the row doesn't
+    # exist yet.
+    msg = build_envelope(
+        to_address=to_address,
+        from_address=cfg.from_address,
+        from_name=cfg.from_name,
+        subject=subject,
+        body_plain=body,
+        unsubscribe_mailto=cfg.unsubscribe_mailto,
+    )
     envelope = {
         "to": to_address,
         "from": formataddr((cfg.from_name, cfg.from_address)),
         "subject": subject,
         "body": body,
         "kind": "invite",
+        "message": msg,
     }
     _SENT.append(envelope)
 
@@ -79,11 +96,6 @@ def send_invite_email(
         return True
 
     try:
-        msg = EmailMessage()
-        msg["From"] = envelope["from"]
-        msg["To"] = to_address
-        msg["Subject"] = subject
-        msg.set_content(body)
         smtp = smtplib.SMTP(cfg.smtp_host, cfg.smtp_port, timeout=30)
         try:
             if cfg.smtp_starttls:

backend/app/email_otc.py

@@ -23,10 +23,10 @@ from __future__ import annotations
 
 import logging
 import smtplib
-from email.message import EmailMessage
 from email.utils import formataddr
 
 from .email import EmailConfig, _SENT
+from .email_envelope import build_envelope
 
 log = logging.getLogger(__name__)
 
@@ -44,12 +44,25 @@ def send_otc_email(to_address: str, code: str) -> bool:
     cfg = EmailConfig.from_env()
     subject = f"Your sign-in code for {cfg.from_name}"
     body = _body(code, cfg)
+    # v0.18.0: OTC mail carries NO List-Unsubscribe — the recipient
+    # explicitly requested the code; advertising an unsubscribe
+    # header would imply OHM has them on a list, which it doesn't.
+    # See the proposal's "Tradeoff discussion" for the binding
+    # rationale.
+    msg = build_envelope(
+        to_address=to_address,
+        from_address=cfg.from_address,
+        from_name=cfg.from_name,
+        subject=subject,
+        body_plain=body,
+    )
     envelope = {
         "to": to_address,
         "from": formataddr((cfg.from_name, cfg.from_address)),
         "subject": subject,
         "body": body,
         "kind": "otc",
+        "message": msg,
     }
     _SENT.append(envelope)
 
@@ -64,11 +77,6 @@ def send_otc_email(to_address: str, code: str) -> bool:
         return True
 
     try:
-        msg = EmailMessage()
-        msg["From"] = envelope["from"]
-        msg["To"] = to_address
-        msg["Subject"] = subject
-        msg.set_content(body)
         smtp = smtplib.SMTP(cfg.smtp_host, cfg.smtp_port, timeout=30)
         try:
             if cfg.smtp_starttls: