Session 0017.0 — Transcript

App: vscode-cowriting-plugin Date: 2026-06-10T23-52 → 2026-06-11T06-59 (PST) Type: brainstorming Goal: Brainstorm Feature #17 (diff-view toggle) into its Solution Design — the baseline fork (turn start / last accept / save / pinned) is the load-bearing decision; constraints and non-goals in the issue body. Outcome: Spec graduated — content specs/coauthoring-diff-view.md (F6, v0.1.0, commit 36bc4e3). All forks resolved; INV-18/INV-19 added.

Launch prompt

/goal Brainstorm Feature #17 (diff-view toggle) into its Solution Design — the baseline fork (turn start / last accept / save / pinned) is the load-bearing decision; constraints and non-goals are in the issue body

Plan

Brainstorm Feature #17 (diff-view toggle) into its Solution Design.

Read issue #17 (constraints + non-goals in the body) and the existing F2–F5 specs/code as input.
Work the load-bearing decision first: the baseline fork — what the diff view diffs against (turn start / last accept / save / pinned).
Explore the remaining design forks, write the Solution Design under the content repo's specs/, graduate it at finalize (autonomous default).

Pre-session state

main at 611a180 (PR #16 — proposal threads decide-only fix), in sync with origin. Epic #1 fully shipped (F2 #4 · F3 #6 · F4 #12 · F5 #14).
One dirty file: sandbox/playground.md — a 1-line accidental truncation ("thre" for "thread") left from the operator's manual play before this session. Noted at init; restored at finalize.
Memory resume pointer (f5-cross-rung-shipped): "Next /goal: Brainstorm Feature #17 …" — exactly this session's goal.
No other in-flight sessions; claim of 0017 was uncontended.

Turn-by-turn arc

Init — classified the /goal as brainstorming; claimed session 0017 (--type brainstorming, start 2026-06-10T23-52); seeded the Plan block; verified the CLAUDE.md org-context import; confirmed the baseline (noting the playground stray); resolved app facts (roadmap = this repo; content = vscode-cowriting-plugin-content; no BDD corpus — nothing to consume as gherkin input).
Anchor gate — fetched issue #17 from Gitea (gitea-api.sh, git.benstull.org): type/feature, P2, constraints + firm non-goals in the body. Eligible brainstorming anchor (R3: a feature produces its design first).
Context exploration — read the F4 spec (coauthoring-propose-accept.md) as the form reference, plus model.ts, liveTurn.ts, proposalController.ts, extension.ts, store.ts, and the seam (attributionController.ts:232). The decisive structural fact: INV-9 + INV-10 mean the machine writes the document only through applyAgentEdit, only at accept time — so between machine landings, every buffer change is operator-authored.
The baseline fork (load-bearing) — resolved to a machine-landing–anchored auto-baseline + human pin: initialize at first track, advance on every successful seam application; the diff is operator-authored by construction (new INV-18). The issue's other candidates fell away on the merits: turn-start collapses into accept under F4's propose-by-default (the document doesn't change at turn start); last-save duplicates native compare-with-saved/local-history; fixed session-start mixes machine landings in; a multi-baseline selector is YAGNI (pin covers the operator-chosen epoch).
Secondary forks — snapshot home = extension workspace storage via a vscode-free BaselineStore, never the sidecar (INV-19: no cross-rung contract impact, no .threads/ churn); whose-changes = whole-document diff, no F3 filtering (state-not-history); view primitive = native vscode.diff with readonly cowriting-baseline: left and the live document right (editing continues in the diff view); landing signal = one additive AttributionController.onDidApplyAgentEdit event (one ingress → one signal); keybinding ctrl+alt+d.
Spec written — coauthoring-diff-view.md (F6), the full Solution Design form (handbook §3.3, F4/F5 precedent): BUC/PUC, INV-18/19, architecture (BaselineStore + DiffViewController + seam event), alternatives table, testing strategy (unit + host E2E, no LLM), failure modes (stale-epoch states are visible and pin-recoverable), 4-slice delivery plan, traceability to #17's acceptance.
Self-review — placeholder/consistency/scope/ambiguity pass; one fix (named renderIfOpen as the ensureBaseline hook).
Finalize — restored the playground stray; submitted the spec --status graduated (autonomous default) → content commit 36bc4e3; synced the local content clone; memory updated (f6-diff-view-spec-graduated + index; cleared the stale Next /goal in f5-cross-rung-shipped); published this transcript.

No wrong turns of substance this session; the one mid-course correction was realizing publication of the spec belongs to finalize's submit-spec.sh (not a hand commit/PR), and authoring the spec directly in the content repo's working tree as its canonical home.

Deferred decisions

Autonomous-mode low-confidence calls the driver made and would have liked operator input on. Surfaced at finalize.

Absorb-on-advance semantics (spec §6.7): the baseline advances to a whole-document snapshot at each machine landing, so operator edits made before an accept disappear from the diff ("my changes since the machine last landed", not "my whole session"). The alternative — splicing the accepted replacement into the baseline so older operator edits stay visible — was deferred as an additive refinement (murky edge cases when the machine edits operator-authored-since-baseline text). Confident in the invariant (INV-18 holds either way); less confident the absorb semantics match operator intuition — pin + the epoch-naming diff title are the mitigations.
Default keybinding ctrl+alt+d for cowriting.toggleDiffView (spec §6.7): chosen over cmd+alt+d (macOS Dock toggle) and cmd+k d (taken by compare-with-saved); cheap to change.
Spec authored directly in the content repo working tree (vscode-cowriting-plugin-content/specs/coauthoring-diff-view.md) — its canonical home — rather than a scratch specs/ dir in the plugin repo; finalize's submit-spec.sh publishes from that path.
Restored sandbox/playground.md at finalize (discarded the 1-line pre-session truncation, restoring the committed text) — judged stray damage from manual play, not work; flagged here since discarding an operator working-tree edit is not reversible.

Cut state (end of session)

Repo	State
`vscode-cowriting-plugin`	`main` @ `611a180`, clean, in sync (playground stray restored; no code changes this session)
`vscode-cowriting-plugin-content`	`main` @ `36bc4e3` — specs/coauthoring-diff-view.md added (status: graduated); local clone synced; 4 untracked `issues/*.md` capture drafts remain (Author's to publish)
session-history (`sessions/0017/`)	this transcript, published at finalize

Issue #17: open, unchanged — the spec is its design artifact; the issue closes when F6 ships.
Nothing implemented yet: F6 is spec-only as of this session.

What lands on the operator's plate

Review the graduated spec (autonomous mode skipped the review gate): /Users/benstull/git/benstull.org/benstull/vscode-cowriting-plugin-content/specs/coauthoring-diff-view.md — especially the two deferred calls above (absorb-on-advance semantics; ctrl+alt+d).
The four untracked issues/*.md drafts in the content repo are still yours to commit/publish or discard (capture-session convention).

Prompt the operator can paste into the next session

/goal Plan and execute Feature #17 (F6 diff-view toggle) from the graduated Solution Design at content specs/coauthoring-diff-view.md — 4 slices per §7.2, host-E2E tier, no LLM in CI

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