sync shadcn highlight code cache

Objective: Apply the dashboard payload mdx/highlight-code-cache: pending -> synced by adding upstream-style bounded Shiki output caching to Plate highlightCode, preserving Plate highlightFiles, verifying the app, updating docs/sync/shadcn/deltas.json, and regenerating the dashboard.

Flow mode: one-shot execution. The user explicitly accepted this dashboard row through $sync-shadcn apply.

Goal plan: docs/plans/2026-05-30-sync-shadcn-highlight-code-cache.md

Primary template: docs/plans/templates/sync-shadcn.md

Completion threshold: Complete when highlightCode uses a SHA-256 keyed LRU cache with a one-hour TTL, highlightFiles still highlights registry files by path-derived language, lru-cache is a direct apps/www dependency, focused verification passes, and the dashboard row is marked synced.

Verification surface:

• Source audit: apps/www/src/lib/highlight-code.ts, apps/www/package.json, docs/sync/shadcn/deltas.json, and docs/sync/shadcn/dashboard.json.
• Upstream reference: ../shadcn/apps/v4/lib/highlight-code.ts.
• Commands: pnpm install, pnpm --filter www typecheck, pnpm lint:fix, bun test 'apps/www/src/app/api/registry-source/[name]/route.test.ts', pnpm sync-shadcn dashboard, node --check .agents/rules/sync-shadcn/scripts/build-dashboard.mjs, and JSON parse for deltas.json plus dashboard.json.

Constraints:

• Do not run build:registry.
• Do not advance lastSyncedCommit; this is one dashboard item, not full-range accounting.
• Do not mutate rows not listed in the copied dashboard payload.
• Keep Plate highlightFiles and registry/source preview behavior.
• Do not copy shadcn command metadata from upstream highlight-code.ts; Plate owns command metadata through rehype-npm-command.ts.

Boundaries:

• Edited apps/www/src/lib/highlight-code.ts to add cache behavior.
• Edited apps/www/package.json and lockfile through pnpm install because lru-cache is a runtime import.
• Edited docs/sync/shadcn/deltas.json only for mdx/highlight-code-cache.
• Regenerated docs/sync/shadcn/dashboard.html and docs/sync/shadcn/dashboard.json.

Output budget strategy: Used focused source reads and capped command output. No upstream patch files or new sync run artifacts were written.

Blocked condition: Blocked only if install, typecheck, lint, registry-source test, dashboard generation, JSON parse, or source audit failed after a focused repair attempt.

Sync state:

• base commit: 4a4dc8eb0fc793d8e9225e780183ad605f15d2c2 from docs/sync/shadcn/status.json.
• planned commit: efdec3ca4523e5edd8a714f633002a7addc203a1 from docs/sync/shadcn/status.json.
• range kind: dashboard-row implementation.
• run directory: N/A; apply mode must not write new run artifacts.
• implementation status: done.
• baseline status: unchanged.

Current verdict:

• verdict: synced.
• confidence: high.
• recommended next owner: sync-shadcn dashboard.
• reason: Plate now caches Shiki HTML output with a bounded LRU while keeping registry file highlighting.

Start Gates:

Gate	Applies	Evidence
autogoal loaded and active goal checked/created	yes	create_goal created active row-sync goal
sync-shadcn skill/rule read	yes	user supplied sync-shadcn skill; apply semantics followed
Output budget strategy recorded before broad upstream commands	yes	no broad upstream commands used
docs/sync/shadcn/status.json read	yes	baseline 4a4dc8e, planned efdec3c
docs/sync/shadcn/decisions.md read	N/A	row behavior came from accepted dashboard payload and local source evidence
Prior migration plans/solution notes checked	yes	memory noted registry-source highlighting verification lane
../shadcn clone exists and was fetched/pulled intentionally	N/A	no fetch needed for accepted dashboard-row apply; local upstream file inspected
Base and target refs resolved to exact SHAs	N/A	row apply does not recompute range; status SHAs recorded above
Base ancestry or ref problem proven	N/A	not a range-planning run
Planning-only vs implementation mode decided	yes	implementation mode from $sync-shadcn apply pending -> synced
User-review boundary recorded	yes	user explicitly accepted the row

Work Checklist:

• Objective, threshold, verification surface, constraints, boundaries, and blocked condition are filled from the active goal.
• Upstream range recorded with exact base SHA and target SHA; N/A for recomputed range because this is dashboard-row apply mode.
• Run directory created under docs/sync/shadcn/runs/; N/A because apply mode must not write new run artifacts.
• Complete upstream inventories saved; N/A because this is not range planning.
• Focused upstream/Plate files inspected and summarized; no .patch files were written.
• Visual screenshots captured; N/A because this row is source-only cache behavior.
• Changed upstream row classified; existing dashboard row supplied the classification.
• Decision counts reconcile to upstream TSV; N/A for dashboard-row apply.
• Recommended merge slice accepted by user through copied dashboard row.
• Settled exclusions and Plate forks preserved.
• No user question remained for this row.
• docs/sync/shadcn/status.json update semantics recorded: unchanged.
• Workspace authority recorded for each verification command or artifact.
• Output budget discipline followed.
• Final handoff shape filled before closeout.

Completion Gates:

Gate	Applies	Required action	Evidence
Named verification threshold	yes	Prove cache, dependency, dashboard state, and preserved highlightFiles	source audit, typecheck, lint, registry-source test, dashboard generation
Upstream range artifacts exist	N/A	Apply mode must not create range artifacts	no run artifact needed
Inventory completeness	N/A	Existing dashboard row is the mutation unit	row mdx/highlight-code-cache updated only
Decision accounting	yes	Mark accepted row synced after implementation	deltas.json row state is synced
Status JSON parse and semantics	yes	Keep baseline unchanged	status read; no status write
Source-backed Plate mapping	yes	Record local source evidence	cache and highlightFiles present in apps/www/src/lib/highlight-code.ts
Visual comparison screenshots	N/A	Source-only cache row	no screenshots needed
Planning-only no implementation edits	N/A	Accepted implementation mode	user applied pending -> synced
Accepted implementation verification	yes	Run focused verification	pnpm --filter www typecheck, pnpm lint:fix, registry-source route test
Browser surface changed	N/A	Server-side source behavior only	source and test proof
Package manifests, lockfile, or install graph changed	yes	Run install and relevant checks	pnpm install; typecheck/lint passed
Agent rules or skills changed	N/A	No .mdc or generated skill edited	dashboard script only executed
CI-controlled generated output	yes	Avoid registry/template output	no build:registry; only dashboard regenerated
Baseline advancement	yes	Do not advance baseline	status.json unchanged
User review boundary	yes	Accepted dashboard row implemented	$sync-shadcn apply payload
Output budget discipline	yes	Keep evidence capped	no broad patch artifacts
Goal plan complete	yes	Run autogoal check	command recorded below

Phase / pass table:

Phase	Status	Evidence	Next
Intake and baseline read	done	status and accepted dashboard row read	complete
Upstream row evidence	done	upstream highlight-code.ts inspected	complete
Implementation	done	SHA-256 LRU cache added and highlightFiles preserved	complete
Dashboard state	done	deltas.json row synced and dashboard regenerated	complete
Verification	done	install, typecheck, lint, route test, dashboard, JSON parse, source audit	complete
Closeout	done	final handoff ready	complete

Decision counts:

Decision	Count	Notes
synced	1	mdx/highlight-code-cache
no-op	0	no extra rows touched

Recommended merge slices:

Order	Slice	Class	Files	Why	Verification
1	Add bounded cache to highlightCode	synced	highlight-code.ts, apps/www/package.json, dashboard state	reduce repeated Shiki CPU work while preserving Plate registry highlighting	install, typecheck, lint, route test, dashboard generation

Questions:

• None.

Findings:

• Plate had no direct cache and reran Shiki for repeated identical snippets.
• lru-cache was only transitive in Plate; importing it required a direct apps/www dependency.
• Plate highlightFiles remains the registry/source preview owner.

Decisions and tradeoffs:

• Used upstream cache shape: SHA-256 key, max 500 entries, one-hour TTL.
• Did not copy upstream command metadata transformer because Plate already owns command props in rehype-npm-command.ts.

Error attempts:

Error / failed attempt	Count	Next different move	Resolution
None	0

Verification evidence:

• pnpm install: passed; direct lru-cache dependency installed.
• pnpm --filter www typecheck: passed.
• pnpm lint:fix: passed; fixed one formatted file.
• bun test 'apps/www/src/app/api/registry-source/[name]/route.test.ts': passed, 2 tests.
• pnpm sync-shadcn dashboard: passed and regenerated dashboard artifacts.
• node --check .agents/rules/sync-shadcn/scripts/build-dashboard.mjs: passed.
• JSON parse for docs/sync/shadcn/deltas.json and docs/sync/shadcn/dashboard.json: passed.
• rg source audit found createHash, LRUCache, highlightCache.get, highlightCache.set, direct lru-cache dependency, and preserved highlightFiles.

Reboot status: No reboot needed. The task finished in the current thread with source, dashboard, and verification evidence.

Open risks: None for the accepted row. This does not settle the other pending MDX rows.

Final handoff:

• Row: mdx/highlight-code-cache.
• State: synced.
• Baseline: unchanged.