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+# Session 0015.0 — Transcript
+
+> App: vscode-cowriting-plugin
+> Start: 2026-06-10T22-37 (PST) · End: 2026-06-10T23-29 (PST)
+> Type: planning-and-executing
+> Driver: Claude (Opus 4.8) · Operator: Ben Stull
+> Posture: autonomous (yolo, default)
+
+## Launch prompt
+
+```
+Implement Feature #14 (F5 cross-rung format + round-trip) per the graduated spec vscode-cowriting-plugin-content/specs/coauthoring-cross-rung-format.md — plan just-in-time from its §7.2 slices, then execute; done = contract + schema published, unit + host E2E green (round-trip, merge, fail-safe, unknown-field preservation all exercised).
+```
+
+## Pre-state
+
+- `main` clean and pushed; F4 (#12) shipped in session 0012; F5 spec graduated
+  in session 0014 (`coauthoring-cross-rung-format.md`, all six forks resolved).
+- Anchor: Feature #14 with an approved Solution Design — R2/R3 gate satisfied.
+- No other sessions in flight (claim peek clean).
+
+## Plan
+
+Full plan: `docs/superpowers/plans/2026-06-10-f5-cross-rung-format.md`
+(13 tasks; archived to content `plans/` at finalize). Slices → tasks:
+
+- SLICE-1 (T1–T3): ajv devDep; `schemas/coauthoring-sidecar.schema.json` +
+  `scripts/validate-sidecar.mjs` + schema unit suite; contract doc
+  `specs/coauthoring-sidecar-contract.md` in the content repo (INV-14).
+- SLICE-2 (T4–T8): Provenance `email`/`agent.onBehalfOf`; serializer
+  unknown-field preservation (INV-15); `isNewerMajor` + store write-refusal
+  backstop; `gitUserEmail` identity helper; `VersionGuard` read-only gating
+  across all three controllers (INV-16, PUC-4).
+- SLICE-3 (T9): pure `mergeArtifacts` + unit tests of every documented case
+  (INV-17).
+- SLICE-4 (T10–T11): `scripts/crossrung-reply.mjs` stand-in + byte-fidelity
+  unit test; host E2E round-trip (PUC-2) + newer-major fail-safe (PUC-4).
+- SLICE-5 (T12–T13): README pointers; full gate; PR + merge.
+
+Execution mode: inline (superpowers:executing-plans).
+
+## Session arc
+
+1. **Init** — claimed 0015; baseline verified clean (`main` == `origin/main`
+   after pulling our own claim commit); spec read end-to-end; codebase
+   surveyed (model/store/controllers/E2E idioms).
+2. **Plan** — just-in-time plan written from spec §7.2 (13 TDD tasks).
+3. **SLICE-1** — ajv devDep (`0ddeaba`); JSON Schema 2020-12 + ajv validator
+   script + `expectValidSidecar` test helper, schema suite green (`7c4d3ed`);
+   **contract v1.0 published** to content repo
+   (`specs/coauthoring-sidecar-contract.md`, `856553a`, pushed) — normative,
+   status `living`, with serialization rules, field tables, INV-15/16
+   compatibility rules, INV-17 merge rules, conforming-writer checklist,
+   changelog.
+4. **SLICE-2** — Provenance `email` + `agent.onBehalfOf` w/ optional-omission
+   (`da172a3`); `withUnknowns()` unknown-field preservation at every
+   serializer level, byte-stable (`a6b16f0`); `isNewerMajor` +
+   `CoauthorStore.update` INV-16 throw backstop (`746071a`); `gitUserEmail`
+   (vscode-free, exec git config, fail-open, cached) wired into both
+   controllers' `currentAuthor()` (`ef4ec8d`); `VersionGuard` shared across
+   the three controllers, gating every write gesture, one warning per doc,
+   exposed on `CowritingApi` (`ef7d940`).
+5. **SLICE-3** — `mergeArtifacts` pure reference implementation: union-by-id,
+   thread shell/messages split, updatedAt-then-lexicographic resolution,
+   conflicts surfaced, differing-major throw (`452f5d1`). One test-expectation
+   fix mid-task: the divergent-message test asserted a human-intuitive winner;
+   the deterministic tie-break legitimately picks the other side — corrected
+   to assert determinism + symmetry.
+6. **SLICE-4** — `crossrung-reply.mjs` stand-in (self-contained foreign
+   writer; independent contract serialization; validates before/after;
+   refuses newer majors) with byte-fidelity unit test vs the reference
+   serializer — passed first try (`e0c127c`); host E2E: editor thread →
+   stand-in reply (ELECTRON_RUN_AS_NODE) → external-change → message renders
+   at re-resolved anchor (PUC-2); v2 sidecar → warning + bytes untouched
+   through edit/save (PUC-4) (`5de59fd`).
+7. **SLICE-5 + ship** — README cross-rung section (`abb9c88`); full gate
+   green: typecheck · **98/98 vitest** · build · **18+3 host E2E**. Pushed,
+   **PR #15** created via Gitea API and merged (`4651410`); **issue #14
+   auto-closed**; branch deleted.
+8. **Operator play feedback** — operator hit the dead "Reply…" input on a
+   proposal thread (no submit command wired for `cowriting.proposals`).
+   Answered (proposals are decide-only, INV-12; discussion = coauthoring
+   thread) and fixed: `canReply=false` + test-facing `RenderedProposal.canReply`
+   + E2E assertion; gate green; **PR #16** merged (`611a180`).
+9. **Operator question (open)** — "show the operator's changes better from a
+   diff perspective; easy toggle current ↔ diff view?" Answered with today's
+   options (git Open Changes/gutter; F4 proposal diffs; attribution toggle)
+   and named the gap: attribution is state-not-history, so a my-changes diff
+   needs a baseline snapshot + virtual doc provider + toggle command. Offered
+   to capture as a Feature issue; **no answer at finalize** — recorded in
+   memory as the open idea.
+10. **Finalize** (goal hook fired on achievement) — plan archived to content
+    `plans/2026-06-10-f5-cross-rung-format.md` (`57f5827`); memory
+    `f5-cross-rung-shipped.md` written + indexed; this transcript published.
+
+## Cut state
+
+- Plugin repo `main` @ `611a180` (PR #15 + #16 merged), pushed, no open PRs.
+  Working tree clean except `sandbox/playground.md` (operator's play scratch
+  — deliberately untouched).
+- Content repo `main` @ `57f5827` (contract + archived plan), pushed.
+  Untracked `issues/*.md` capture drafts predate this session (Author's).
+- Issue #14 closed. **Epic #1 fully shipped** (F2 · F3 · F4 · F5).
+- Pipeline (§9): VS Code extension — no deploy stage/PPE/browser surface; the
+  app's required tier is host E2E, run green. Nothing deferred.
+
+## Deferred decisions
+
+- Inline execution chosen over subagent-driven (tasks share heavy
+  `model.ts`/serializer context; single coherent feature).
+- Thread-shell divergence rule: lexicographically-larger stable-stringify
+  (makes "resolved" beat "open" deterministically) — documented in the
+  contract; revisit at team rung if too naive.
+- INV-15 implemented at the serializer level only (spec §6.2 wording);
+  controller record-rebuild paths own their records.
+- Stand-in writer deliberately re-implements contract serialization
+  (executable documentation); byte-fidelity unit test is the drift tripwire.
+- Merge tie-break is deterministic but not human-intuitive (lexicographic on
+  stable-stringify); the divergent-message test was corrected to assert
+  determinism + symmetry rather than a particular winner.
+- Diff-view feature idea NOT filed as an issue (operator hadn't confirmed);
+  recorded in memory instead.
+
+## Operator plate
+
+- Reload the extension dev host to pick up the PR #16 fix (rebuild first if
+  not running `npm run watch`).
+- Decide on the diff-view toggle idea: capture as a Feature issue, or drop.
+- `sandbox/playground.md` left dirty for you.
+
+## Next-session prompt
+
+```
+/goal Open a capture session for the diff-view toggle feature (operator's own changes as a toggleable diff vs a turn/accept baseline — sketch in memory f5-cross-rung-shipped), filing it as a typed Feature issue on benstull/vscode-cowriting-plugin
+```
+
+(Alternative frontier: the rfc-app#46 Gitea-substrate brainstorming — different
+repo — which consumes the F5 contract as its input.)
diff --git a/sessions/0015/SESSION-0015.0-TRANSCRIPT-2026-06-10T22-37--INPROGRESS.md b/sessions/0015/SESSION-0015.0-TRANSCRIPT-2026-06-10T22-37--INPROGRESS.md
deleted file mode 100644
index acb4040..0000000
--- a/sessions/0015/SESSION-0015.0-TRANSCRIPT-2026-06-10T22-37--INPROGRESS.md
+++ /dev/null
@@ -1,23 +0,0 @@
-# Session 0015.0 — Transcript
-
-> App: vscode-cowriting-plugin
-> Start: 2026-06-10T22-37 (PST)
-> Type: planning-and-executing
-> Status: **PLACEHOLDER — claimed at session start; finalized at session end.**
->
-> This file reserves session ID 0015 for vscode-cowriting-plugin. The driver replaces this
-> body with the full transcript and renames the file to its final
-> SESSION-0015.0-TRANSCRIPT-2026-06-10T22-37--<end>.md form at session end.
-
-## Launch prompt
-
-```
-Implement Feature #14 (F5 cross-rung format + round-trip) per the graduated spec vscode-cowriting-plugin-content/specs/coauthoring-cross-rung-format.md — plan just-in-time from its §7.2 slices, then execute; done = contract + schema published, unit + host E2E green (round-trip, merge, fail-safe, unknown-field preservation all exercised).
-
-```
-
-## Deferred decisions
-
-_Autonomous-mode low-confidence calls the driver made and would have
-liked operator input on. Appended as the session runs; surfaced at
-finalize. Empty if none._