stabilize huge document behavior

Objective: Stabilize http://localhost:3100/examples/huge-document insert-break behavior in Slate v2 virtualized mode.

Goal plan: docs/plans/2026-06-02-stabilize-huge-document-behavior.md

Task source:

• User report with CleanShot video /Users/zbeyens/Library/Application Support/CleanShot/media/media_0tS1ZEZdRS/2026-06-02 at 19.49.14.mp4.
• User clarification: the bug is insertBreak inserting relative to a stale cursor after native text input.

Completion threshold: The route is stable when virtualized huge-document typing followed by Enter splits at the live caret, the structural keydown policy has a focused unit contract, the full Chromium huge-document suite passes, and bun check passes in .tmp/slate-v2.

Verification surface:

• cd /Users/zbeyens/git/plate-2/.tmp/slate-v2/packages/slate-react && bun run test:vitest -- input-router-contract.test.tsx
• cd /Users/zbeyens/git/plate-2/.tmp/slate-v2 && PLAYWRIGHT_BASE_URL=http://localhost:3100 PLAYWRIGHT_RETRIES=0 PLAYWRIGHT_WORKERS=1 bun run playwright -- playwright/integration/examples/huge-document.test.ts --project=chromium --grep "keeps virtualized insert-break bursts split at the live caret"
• cd /Users/zbeyens/git/plate-2/.tmp/slate-v2 && PLAYWRIGHT_BASE_URL=http://localhost:3100 PLAYWRIGHT_RETRIES=0 PLAYWRIGHT_WORKERS=1 bun run playwright -- playwright/integration/examples/huge-document.test.ts --project=chromium
• cd /Users/zbeyens/git/plate-2/.tmp/slate-v2 && bun check

Constraints:

• Keep printable virtualized text input native/fast.
• Fix the shared runtime policy, not the huge-document example.
• Do not commit, push, or open PRs.
• Keep proof in the Slate v2 checkout that owns the runtime behavior.

Boundaries:

• Source of truth: .tmp/slate-v2 runtime, tests, and the supplied video/report.
• Allowed edit scope: packages/slate-react/src/editable/runtime-keyboard-events.ts, packages/slate-react/test/input-router-contract.test.tsx, and playwright/integration/examples/huge-document.test.ts.
• Browser surface: /examples/huge-document?blocks=10000&strategy=virtualized&overscan=0&threshold=2000&editor_height=420&content_visibility=element.
• Tracker sync: N/A, no issue tracker item was supplied.
• Non-goals: pagination, full perf optimization, PR creation, review branches.

Output budget strategy: Searches were scoped to huge-document, virtualized DOM strategy, keyboard runtime, and insert-break tests; broad output was capped.

Blocked condition: Blocked only if the route could not be served, the supplied video could not be read, or the focused browser proof could not run. None blocked this run.

Task state:

• task_type: browser behavior bug
• task_complexity: normal
• current_phase: closeout
• current_phase_status: complete
• goal_status: ready to close

Current verdict:

• verdict: fixed and verified
• confidence: high
• next owner: user commit decision
• reason: focused runtime contract, route repro, full route suite, and bun check are green.

Start Gates:

Gate	Applies	Evidence
Skill analysis before edits	yes	Used slate-ar-stabilize; routed failed behavior to slate-patch-style TDD.
Active goal checked or created	yes	No active goal existed; created goal for huge-document behavior stabilization.
Source of truth read before edits	yes	Read .tmp/slate-v2 huge-document test, runtime keyboard/input files, and AR status ledger.
Tracker comments and attachments read	yes	Read supplied video frames and user clarification; no tracker item supplied.
Video transcript evidence required	yes	Extracted frames from the 5.03s CleanShot video and identified virtualized huge-document config.
docs/solutions checked for non-trivial existing-code work	yes	Checked Slate v2 docs/plans/solutions paths; relevant lane evidence was in AR ledger and tests.
TDD decision before behavior change or bug fix	yes	Added focused Playwright proof plus runtime contract for insert-break boundary flushing.
Branch decision for code-changing task	N/A	Stayed in current checkout; user did not request branch work.
Release artifact decision	N/A	Internal runtime bug fix in Slate v2 lab checkout; no release artifact requested.
Browser tool decision for browser surface	yes	Browser plugin navigation tool was unavailable; used repo Playwright browser proof against localhost.
PR expectation decision	N/A	User did not request PR.
Tracker sync expectation decision	N/A	No tracker item supplied.
Output budget strategy recorded	yes	Searches and command output were scoped and capped.
Browser pack selected	yes	Browser pack applied because target is a browser editor route.
Browser route / app surface identified	yes	http://localhost:3100/examples/huge-document with virtualized 10k-block config.
Browser tool decision recorded	yes	Playwright gate used as approved fallback because direct Browser tool was not exposed.
Console/network caveat policy recorded	yes	Route served HTTP 200; Playwright browser proof covered behavior.

Work Checklist:

• Objective, completion threshold, verification surface, constraints, boundaries, and blocked condition are concrete.
• Task source classified as virtualized huge-document browser behavior bug.
• Video evidence was read through extracted frames and user clarification.
• Nearby implementation patterns read before edits.
• Fix landed in shared keyboard runtime policy rather than example glue.
• Release artifact requirement recorded as N/A.
• Final handoff shape is bug-fix summary plus commands.
• Branch handling recorded as N/A.
• Local-env-rot retry policy recorded as N/A; no env-rot signature appeared.
• Workspace authority recorded for every proof command.
• High-risk runtime behavior note recorded.
• Autoreview target recorded as N/A for this focused stabilization; bun check and route gates are the closure proof.
• Agent-native review decision recorded as N/A.
• Output budget discipline followed.
• Browser route, interaction path, and expected visible/model outcome recorded before proof.
• Browser proof used Playwright fallback and recorded the Browser-tool caveat.
• Console/network check recorded through HTTP 200 and Playwright behavior proof.
• Browser proof artifact is the passing route test with JSON attachment.

Completion Gates:

Gate	Applies	Required action	Evidence
Named verification threshold	yes	Run all commands named above	All listed commands passed.
Bug reproduced before fix	yes	Encode user-visible invariant	Added huge-document test for abc\ndef split at live caret.
Targeted behavior verification	yes	Run focused browser proof	Focused Chromium test passed, 1/1.
TypeScript or typed config changed	yes	Run relevant typecheck	bun check passed package and site typechecks.
Package exports or file layout changed	N/A	No export or layout change	No public file layout touched.
Package manifests, lockfile, or install graph changed	N/A	No install graph change	No manifest or lockfile touched.
Agent rules or skills changed	N/A	No agent rules changed	No .agents source edited.
Workspace authority proof	yes	Run in .tmp/slate-v2	All proof commands ran in the Slate v2 checkout.
Browser surface changed	yes	Exercise target route	Full Chromium huge-document suite passed, 9/9.
Browser final proof	yes	Record exact route proof	New insert-break route test and full suite passed.
CI-controlled template output changed	N/A	No template output touched	No templates/** edits.
Package behavior or public API changed	N/A	No public API surface change	Internal runtime policy only.
Registry-only component work changed	N/A	No registry work	No registry files touched.
Docs or content changed	N/A	No product docs changed	Only this goal ledger changed outside Slate v2.
High-risk mini gate	yes	Runtime behavior proof	Unit contract plus browser route suite passed.
Agent-native review for agent/tooling changes	N/A	No agent/tooling changes	No agent-native surface touched.
Local install corruption suspected	N/A	No reinstall needed	No mixed React/install corruption signal appeared.
Autoreview for non-trivial implementation changes	N/A	Focused stabilization gate accepted	bun check plus browser behavior gates are the closure proof for this slice.
PR create or update	N/A	No PR requested	No PR work done.
Task-style PR body verified	N/A	No PR requested	No PR body exists.
PR proof image hosting	N/A	No PR requested	No hosted image needed.
Tracker sync-back	N/A	No tracker item supplied	No sync target.
Final handoff contract	yes	Fill final response fields	Final response will list files and proof.
Final lint	yes	Run bun check	Biome/ESLint passed with one existing warning in pagination.
Output budget discipline	yes	Verify bounded output	Searches and command outputs were capped.
Goal plan complete	yes	Run check-complete	This file is ready for check-complete.
Browser interaction proof	yes	Exercise route interaction	Playwright test typed abc\ndef in virtualized huge-document.
Browser console/network check	yes	Record route and behavior state	HTTP 200 route check and Playwright behavior proof.
Browser final proof artifact	yes	Record proof artifact	huge-document-insert-break-burst-proof attachment emitted by test.

Phase / pass table:

Phase	Status	Evidence	Next
Intake and source read	complete	Video frames, user clarification, runtime/test source read	implementation done
Implementation	complete	Runtime keydown flush policy patched	verification done
Verification	complete	Unit, focused route, full route suite, bun check passed	closeout
PR / tracker sync	N/A	No PR or tracker requested	final response
Closeout	complete	Goal plan ready for checker	final response

Findings:

• Virtualized mode defers native text repair for fast printable input.
• Enter is structural; preserving model selection while pending native text exists can split at a stale caret unless deferred native text is flushed before the mutation.

Decisions and tradeoffs:

• Chose shared runtime keydown policy over example-specific repair.
• Kept printable text input native; only structural/model-owned mutation boundaries force the deferred flush.

Implementation notes:

• shouldFlushPendingNativeTextInputForKeyDown now flushes for model mutation boundaries: delete, format, insert-break, and model-selection-move.
• Added a unit contract where insert-break and delete flush even when forced DOM import is disabled.
• Added a Chromium huge-document virtualized route proof for abc\ndef ordering.

Review fixes:

• N/A, no autoreview loop requested for this focused stabilization.

Error attempts:

Error / failed attempt	Count	Next different move	Resolution
Raw Bun path invocation did not match Vitest file	2	Use package Vitest runner	bun run test:vitest -- input-router-contract.test.tsx passed.

Verification evidence:

• bun run test:vitest -- input-router-contract.test.tsx: 1 file, 21 tests passed.
• Focused huge-document route proof: 1 Chromium test passed.
• Full huge-document Chromium suite: 9 tests passed.
• bun check: passed. Biome clean; ESLint has one existing warning in site/examples/ts/pagination.tsx; typecheck and tests passed.

Final handoff contract:

• PR line: N/A, no PR requested.
• Issue / tracker line: N/A, no tracker supplied.
• Confidence line: high.
• Flow table:
  • Reproduced: user video plus focused test invariant for virtualized insert-break burst.
  • Verified: unit contract, focused browser test, full huge-document Chromium suite, bun check.
• Browser check: Playwright fallback used because direct Browser navigation tool was unavailable.
• Outcome: fixed stale-caret insert-break ordering after deferred native text input.
• Caveat: bun check still reports the pre-existing pagination hook warning.
• Design:
  • Chosen boundary: shared keyboard runtime flush policy.
  • Why not quick patch: example glue would not protect other virtualized/staged editors.
  • Why not broader change: no need to disable native printable input or rewrite deferred repair.
• Verified: commands listed in Verification evidence.
• PR body verified: N/A.

Final handoff / sync:

• PR: N/A.
• Issue / tracker: N/A.
• Browser proof: focused and full Chromium huge-document Playwright gates passed.
• Caveats: existing pagination ESLint warning remains.

Timeline:

• 2026-06-02T17:50:11Z Goal plan created.
• 2026-06-02T17:55Z Runtime patch and focused tests added.
• 2026-06-02T17:57Z bun check passed.

Reboot status:

Question	Answer
Where am I?	Closeout.
Where am I going?	Final response and goal closure.
What is the goal?	Stabilize huge-document virtualized insert-break behavior.
What have I learned?	Deferred native text must flush before structural keydown mutations.
What have I done?	Patched runtime policy, added unit and browser proofs, ran verification.

Open risks:

• Existing pagination hook warning remains outside this bug.
• Cross-browser huge-document insert-break proof was not run; new test is Chromium-only to match the existing burst-routing proof style.