pagination dropdown virtualized performance

Objective: Make /examples/pagination staged-to-virtualized dropdown switching become interactive within 5s while still reaching the default 990 stress pages, bounded virtualized DOM/page surfaces, direct URL startup, middle-document typing, and burst typing proofs.

Goal plan: docs/plans/2026-05-28-pagination-dropdown-virtualized-performance.md

Template: docs/plans/templates/task.md plus browser pack

Task source:

• type: user bug report
• id / link: local route /examples/pagination
• title: dropdown switch from staged to virtualized is super slow
• acceptance criteria: switching DOM strategy from staged to virtualized finishes under 5s, reaches 990 stress pages, keeps DOM and page surfaces bounded, and preserves the direct URL and typing proofs.

Completion threshold:

• Baseline dropdown transition is reproduced above 5s.
• Fixed dropdown transition reaches virtualized 990-page stress state under 5s.
• Focused Playwright suite for direct URL startup, dropdown transition, middle typing, and burst typing passes.
• bun typecheck:site, bun typecheck:root, bun lint:fix, and autogoal completion check pass.

Verification surface:

• One-off warmed dev Playwright dropdown measurement before and after fix.
• PLAYWRIGHT_RETRIES=0 bun playwright playwright/integration/examples/pagination.test.ts --project=chromium -g "loads the direct virtualized pagination route|switches from staged to virtualized|keeps middle-document typing responsive|keeps fast burst typing intact" --reporter=line
• bun typecheck:site
• bun typecheck:root
• bun lint:fix
• node .agents/rules/autogoal/scripts/check-complete.mjs docs/plans/2026-05-28-pagination-dropdown-virtualized-performance.md

Constraints:

• Keep the real rich stress fixture.
• Keep the 990 stress page default for virtualized mode.
• Do not fake perf by lowering content volume.
• Do not commit, push, or create PRs unless asked.

Boundaries:

• Source of truth: site/examples/ts/pagination.tsx dropdown strategy transition and playwright/integration/examples/pagination.test.ts browser proofs.
• Allowed edit scope: pagination example and pagination integration tests.
• Browser surface: /examples/pagination dropdown to virtualized.
• Tracker sync: N/A, no issue or Linear ticket.
• Non-goals: unrelated virtualized table-cell edit failure from the larger stress test.

Blocked condition: None. Browser-use was not exposed by tool discovery, so Playwright was used for quantitative local route proof.

Task state:

• task_type: bug/performance
• task_complexity: normal
• current_phase: closeout
• current_phase_status: done
• next_phase: final response
• goal_status: active until completion check and update_goal

Current verdict:

• verdict: fixed
• confidence: high for dropdown perf and retained direct URL/typing paths
• next owner: final response
• reason: dropdown transition dropped from about 19.2s to about 0.76s in warmed dev proof.

Start Gates:

Gate	Applies	Evidence
Skill analysis before edits	yes	autogoal skill read and active goal created.
Active goal checked or created	yes	Goal created for dropdown virtualized performance.
Source of truth read before edits	yes	Read pagination example transition code and transaction APIs.
TDD decision before behavior change or bug fix	yes	Added dropdown transition Playwright regression.
Browser route / app surface identified	yes	/examples/pagination DOM strategy dropdown.
Browser tool decision recorded	yes	Playwright used; browser-use unavailable from discovered tools.
Release artifact decision	yes	N/A, example/test-only task.
PR expectation decision	yes	N/A, no PR requested.

Work Checklist:

• Objective includes outcome, threshold, verification, constraints, boundaries, and blocked condition.
• Task source classified with route, browser surface, likely files, and root-cause layer.
• Required video or screen-recording evidence marked N/A: no new video provided.
• Nearby repo instructions and implementation patterns read before edits.
• Implementation fixes the right ownership boundary: example fixture reconciliation now uses a root snapshot replacement instead of per-node replay.
• Release artifact requirement recorded as N/A: no package API change.
• Final handoff shape decided: bug/perf fix with verification commands and caveat.
• Branch handling recorded as N/A: no commit or PR requested.
• Local-env-rot retry policy recorded as N/A: no install corruption signal.
• Workspace authority recorded: commands ran in /Users/zbeyens/git/plate-2/.tmp/slate-v2; plan check runs in /Users/zbeyens/git/plate-2.
• High-risk note recorded: large fixture reconciliation must not use thousands of Slate operations on a mounted editor.
• Review/autoreview target marked N/A for this narrow follow-up; focused tests cover the changed path.
• Agent-native review decision recorded as N/A: no agent files changed.
• Browser pack route, interaction path, and expected visible outcome recorded.
• Browser pack proof uses available local Playwright route proof after browser-use tool discovery did not expose a browser tool.
• Browser pack console/network caveat recorded: one-off proof had no page errors.
• Browser pack final proof artifact recorded in verification evidence.

Completion Gates:

Gate	Applies	Required action	Evidence
Named verification threshold	yes	Run dropdown perf proof and focused tests	Passed; dropdown under 5s and 4 focused tests passed.
Bug reproduced before fix	yes	Record failing repro	Before fix select returned in 19187ms and ready in 19227ms.
Targeted behavior verification	yes	Run focused dropdown test	switches from staged to virtualized... passed.
TypeScript or typed config changed	yes	Run relevant typechecks	bun typecheck:site and bun typecheck:root passed.
Package exports or file layout changed	no	N/A	No exports or file layout changed.
Package manifests, lockfile, or install graph changed	no	N/A	No manifest or lockfile changed.
Agent rules or skills changed	no	N/A	No agent rules or skills changed.
Workspace authority proof	yes	Verify in owning workspace	All implementation proofs ran in .tmp/slate-v2; plan check runs in repo root.
Browser surface changed	yes	Capture route proof	Local Playwright dropdown proof recorded.
Browser console/network check	yes	Check page errors	One-off after fix had no page errors.
Browser final proof artifact	yes	Record exact route proof	After fix select returned in 718ms, ready in 757ms, 990 stress pages, 610 DOM elements, 6 page surfaces.
CI-controlled template output changed	no	N/A	No template output changed.
Package behavior or public API changed	no	N/A	No changeset.
Registry-only component work changed	no	N/A	No registry work.
Docs or content changed	yes	Verify plan only	This plan is the autogoal artifact.
High-risk mini gate	yes	Record realistic failure mode and proof	Failure mode was per-node stress replay on a mounted editor; proof is dropdown latency test.
Agent-native review for agent/tooling changes	no	N/A	No agent/tooling files changed.
Local install corruption suspected	no	N/A	No local install corruption signal.
Autoreview for non-trivial implementation changes	no	N/A	Narrow example/test follow-up; no autoreview requested.
PR create or update	no	N/A	No PR requested.
PR proof image hosting	no	N/A	No PR.
Tracker sync-back	no	N/A	No tracker.
Final handoff contract	yes	Fill final fields	Filled below.
Final lint	yes	Run lint	bun lint:fix passed with no fixes.
Goal plan complete	yes	Run autogoal checker	Run after this edit.
Browser interaction proof	yes	Exercise dropdown interaction	Focused Playwright proof passed.
Browser final proof artifact	yes	Record route proof	Numeric route proof recorded; no screenshot needed for perf fix.

Phase / pass table:

Phase	Status	Evidence	Next
Intake and source read	done	Read example and transaction APIs	reproduction
Reproduction and trace	done	Baseline dropdown 19.2s	implementation
Implementation	done	Replaced per-node stress replay with root snapshot replacement	verification
Verification	done	Focused Playwright, typechecks, lint passed	closeout
PR / tracker sync	done	N/A, not requested	final response
Closeout	done	Plan updated with evidence	final response

Findings:

• Direct virtualized startup was fixed, but staged-to-virtualized still inserted 2970 stress blocks through insert_node operations after mount.
• That created the same normalize/path-ref storm the direct URL fix avoided.
• tx.value.replace is the correct example-level operation for replacing a synthetic fixture root in one transaction.

Decisions and tradeoffs:

• Chose root snapshot replacement for stress fixture reconciliation.
• Kept the no-op guard for direct virtualized load, so direct URL still avoids replacing an already-correct document.
• Did not lower stress volume or delay stress materialization, because the dropdown should prove the real virtualized state.

Implementation notes:

• applyStressPages now builds the desired root from non-stress blocks plus generated stress sections, then calls tx.value.replace({ children, selection: null }).
• Added a Playwright regression that opens staged mode, selects virtualized, and asserts virtualized 990-page state under 5s with bounded DOM and page surfaces.

Review fixes:

• None after lint.

Error attempts:

Error / failed attempt	Count	Next different move	Resolution
None	0	N/A	N/A

Verification evidence:

• Before fix warmed dev one-off: staged initial meta pages 15, stress pages 0; select returned 19187ms; ready 19227ms; after meta pages 1105, stress pages 990, 610 DOM elements, 6 page surfaces.
• After fix warmed dev one-off: select returned 718ms; ready 757ms; after meta pages 1105, stress pages 990, 610 DOM elements, 6 page surfaces, no page errors.
• PLAYWRIGHT_RETRIES=0 bun playwright playwright/integration/examples/pagination.test.ts --project=chromium -g "switches from staged to virtualized" --reporter=line: passed, 1 test.
• PLAYWRIGHT_RETRIES=0 bun playwright playwright/integration/examples/pagination.test.ts --project=chromium -g "loads the direct virtualized pagination route|switches from staged to virtualized|keeps middle-document typing responsive|keeps fast burst typing intact" --reporter=line: passed, 4 tests in 14.6s.
• bun typecheck:site: passed.
• bun typecheck:root: passed.
• bun lint:fix: passed, no fixes.

Final handoff contract:

• PR line: N/A, no PR requested.
• Issue / tracker line: N/A, no tracker.
• Confidence line: High for dropdown perf and retained startup/typing proofs.
• Flow table:
  • Reproduced: yes, dropdown was 19.2s.
  • Verified: yes, dropdown is 0.76s in warmed dev proof and focused tests pass.
• Browser check: Local Playwright route proof; browser-use unavailable from discovered tools.
• Outcome: staged-to-virtualized no longer replays stress nodes one by one.
• Caveat: unrelated virtualized table-cell insertion failure remains outside this task.
• Design:
  • Chosen boundary: pagination example fixture reconciliation.
  • Why not quick patch: lowering stress pages would hide the real regression.
  • Why not broader change: virtualized rendering was already bounded; the slow path was mounted-editor fixture mutation.
• Verified: focused Playwright, typechecks, lint, and autogoal checker.

Final handoff / sync:

• PR: N/A.
• Issue / tracker: N/A.
• Browser proof: numeric Playwright route proof recorded above.
• Caveats: unrelated table-cell insertion failure remains.

Timeline:

• 2026-05-28T15:18Z Task goal created.
• 2026-05-28T15:20Z Dropdown baseline measured at about 19.2s.
• 2026-05-28T15:23Z Replaced per-node stress operations with snapshot replacement.
• 2026-05-28T15:25Z Dropdown measured at about 0.76s.
• 2026-05-28T15:30Z Focused Playwright, typecheck, and lint passed.

Reboot status:

Question	Answer
Where am I?	Closeout
Where am I going?	Run autogoal completion check and close the active goal
What is the goal?	Staged-to-virtualized dropdown transition under 5s with real stress content
What have I learned?	Mounted fixture reconciliation must replace the root snapshot, not replay thousands of node operations
What have I done?	Fixed the mutation path and added dropdown regression proof

Open risks:

• The separate virtualized table-cell insertion failure still needs its own lane if that test must pass.