* docs: add PRD for design detector hook integration Plans a PostToolUse hook for Claude Code and Codex that runs the existing design detector after every relevant file write and feeds findings back to the agent as advisory system-reminder context. No implementation in this commit; covers UX, technical design, build pipeline changes, distribution, coverage tradeoffs, and rollout. Co-authored-by: Cursor <cursoragent@cursor.com> * docs: revise hook PRD with best-practices review Folds in the P0/P1/P2 findings from an online best-practices critique against the official Claude Code and Codex hook references plus 10+ 2026 community guides and similar prior-art tools (claw-hooks, claude-code-hooks-mastery). Key changes: - Exec form everywhere (Codex snippet was shell form), with Windows rationale. - Default timeout dropped from 10s to 5s. - Re-entrancy guard (CLAUDE_HOOK_DEPTH) and per-file edit counter. - Session-scoped finding dedup promoted from open question to v1. - Per-language inline-ignore syntax map (HTML/JSX/CSS/JS). - Hard-skip rules for sensitive paths and generated/lock files. - Honest framing about Claude Code lacking per-plugin hook disable. - Honest framing about Bash-written files being invisible in v1. - Codex Windows-not-supported call-out, feature flag note, trust ceremony detail. - Optional NDJSON audit log via IMPECCABLE_HOOK_LOG. - Findings cap lowered 8 → 5 with attention-budget rationale. - Versioned envelope ([impeccable@1]) on rendered template. - Expanded test plan, decision log, and stdin payload appendix. Co-authored-by: Cursor <cursoragent@cursor.com> * feat(hooks): ship the design detector hook for Claude Code and Codex Implements docs/hooks-prd.md: a PostToolUse hook that runs the impeccable design detector after every Edit/Write/MultiEdit on a UI file and pushes findings into the agent's next-turn context as a short system reminder. Silent on clean files. Never blocks an edit. Why this matters: today, design slop (side-tab borders, gradient text, purple/cyan palettes, bounce easing, etc.) only gets caught when a human notices or someone explicitly runs /impeccable audit. The hook closes the loop at the moment slop is written. What ships in v1 - skill/scripts/hook.mjs: PostToolUse entry. Reads stdin, runs the detector in-process (no `npx impeccable` cold start), emits hookSpecificOutput.additionalContext when fresh findings exist. - skill/scripts/hook-lib.mjs: extracted helpers (config, cache, filter, render, audit log, runHook orchestrator). 100% unit-testable. - skill/scripts/hook-session-start.mjs: SessionStart greeting, gated by a project-scannable probe + 30-day throttle. - skill/scripts/hook-admin.mjs: backs /impeccable hooks on/off/status/ignore-rule/ignore-file/reset. Hardening built in - Re-entrancy guard (IMPECCABLE_HOOK_DEPTH) so the hook can never recursively spawn itself. - Hard-skip regexes for sensitive paths (.env, .pem, id_rsa, secrets, credentials, .git) and generated/lock/build output. These fire before the file is even read; cannot be turned off via config. - Path-traversal check on the inbound file_path. - Session-scoped dedup keyed by (session, file, rule, line) so the same finding never lands in context twice. Prevents the ~12.5K wasted tokens per chatty session called out in the PRD. - Per-(session, file) edit counter with a one-shot suppression notice on the 7th edit, silent after. - Fail-open contract: every error path returns exit 0 with no stdout. Optional NDJSON audit log via IMPECCABLE_HOOK_LOG. Three kill switches (precedence high to low): 1. IMPECCABLE_HOOK_DISABLED env var (1/true/yes/on, case-insensitive) 2. .impeccable/hook.json `enabled: false` 3. /impeccable hooks off slash command (writes the JSON) Inline ignores are language-aware. `// impeccable: ignore <rule>` for JS/TS, `<!-- impeccable: ignore <rule> -->` for HTML/Vue/Svelte/Astro, `{/* impeccable: ignore <rule> */}` for JSX/TSX, `/* impeccable: ignore <rule> */` for CSS. `*` matches any rule. Directive applies to the next non-blank line. Same shape as ESLint, Stylelint, Biome. Build pipeline - scripts/lib/transformers/hooks.js: per-provider hooks.json builders, plus the slim .codex-plugin/plugin.json manifest. - providers.js: emitHooks: 'claude' for claude-code, emitHooks: 'codex' for codex and agents. Codex also emits emitCodexPlugin. - factory.js: emits hooks/hooks.json next to the skills tree. - build.js: syncs hooks/ into harness roots and into the slim plugin/ subtree; writes .codex-plugin/plugin.json. Build is idempotent (verified: 98 staged files unchanged across two runs). Claude Code wiring uses exec form (command + args) and the ${CLAUDE_PLUGIN_ROOT} placeholder. Matcher: Edit|Write|MultiEdit. `if:` glob filters to UI extensions before spawning Node. PostToolUse timeout 5s, SessionStart timeout 3s. Codex wiring uses ${PLUGIN_ROOT} (Codex's native placeholder), matcher Edit|Write|apply_patch, no `if:` analog (the script does the extension filter). macOS and Linux only; hooks are disabled on Windows in current Codex builds. The trust ceremony and feature flag are documented in README.md. Routing - /impeccable hooks lives outside the 23-command router table on purpose: it is plumbing, not a design skill. The hidden routing slot is added to SKILL.md alongside pin/unpin so the LLM knows to dispatch it. The 23-command count and all stale-count validators remain happy. Tests - tests/hook.test.mjs: 38 unit tests covering env parsing, config load + defaults + malformed, cache round-trip + GC, ignoreRules/minSeverity/inline ignores (all four languages), globbing with **/*/{a,b}, render template with cap + clamp + 0-line prefix drop, audit log NDJSON, payload event-name parameterization, re-entrancy, kill switches, sensitive-path + generated-path + traversal skips, allowlist filter, config ignoreFiles, edit counter cycle including the 7th-edit notice, MultiEdit and apply_patch payload shapes, detector throw swallow, malformed stdin, missing file race. - tests/hook-build.test.mjs: 18 integration tests covering hook manifest shape (matcher, timeouts, exec form, if: glob, placeholders), Codex differences (${PLUGIN_ROOT}, no if:, no SessionStart), Codex plugin manifest (no inline hooks field to avoid the duplicate-file error), routing across the hooksJsonFor table, and presence of all three committed artifacts plus the bundled detector the runtime relative-import path depends on. Full suite: 175 bun tests + 186 node tests, all green. Docs - README.md: new "Design hook" section explaining default behavior, per-project / global / inline disable paths, the JSON schema knobs, the audit log debug flag, and the slop / a11y coverage split. - HARNESSES.md: flips the `hooks` row for Codex from No -> Yes (Claude was already Yes), adds a per-harness hook-surface table with the manifest location and matcher each provider uses. Open questions from the PRD intentionally deferred to v2: Bash-write blind spot, effort-aware suppression, Stop-hook session summary, per-rule severity, async hook mode. None block v1. Co-authored-by: Cursor <cursoragent@cursor.com> * Fix Codex hook scanning: apply_patch paths and co-located stylesheets Parse file targets from Codex apply_patch command bodies, co-scan imported and sibling CSS when UI components are edited, drop the git-sweep PostToolUse group, and align Codex SessionStart manifest and trust docs with the official hooks spec. Co-authored-by: Cursor <cursoragent@cursor.com> * Gitignore hook session cache and drop local test HTML Hook dedup/throttle state in .impeccable/hook.cache.json is per-project runtime data like other .impeccable/ sidecars. Remove an untracked bad-nested-flexbox scratch page from site/public/. Co-authored-by: Cursor <cursoragent@cursor.com> * Fix Claude Code hook: drop Edit-only if filter so Write/MultiEdit fire Claude's if permission rule binds to one tool name, so Edit(*.{…}) never spawned the hook on Write or MultiEdit despite the matcher listing them. Extension filtering now lives in hook-lib on both Claude and Codex. Co-authored-by: Cursor <cursoragent@cursor.com> * Surface Cursor design findings via stop-hook followup Replace dropped postToolUse additional_context with afterFileEdit recording and a one-shot stop followup_message so anti-pattern nudges reach the agent. Co-authored-by: Cursor <cursoragent@cursor.com> * Fix design hook packaging and scans * Fix Cursor hook pending bucket fallback * Fix Sass hook scan coverage * Fix Cursor hook review findings * Fix session start dead hook normalization * Fix hook config and relative scan paths * Remove SessionStart design hook * Remove redundant afterFileEdit normalization * Fix Cursor suppression and module style scans * Fix sensitive path hook filter * Fix disabled Cursor stop hook emission * Refresh hook harness artifacts * Fix Cursor hook manifest install * Add hook ignore-value support * Ignore hook runtime files locally * Fix Codex plugin hook packaging * fix: address PR review bot findings Block numeric hook depth counters from re-entering. Avoid following stylesheet imports from traversal-looking hook targets. * fix: gate ignore-value suggestions by supported rules Only render exact ignore-value commands when the same finding can be suppressed by ignoreValues. * Package Codex plugin as hook-only * Remove Codex plugin packaging * Recover hook install probe plumbing * Remove Codex hook packaging follow-up doc * Remove extra hook docs and skill wording changes * Install real design hooks via skills CLI * Add provider hook smoke runner * Fix Cursor hook delivery with preToolUse gate * Simplify Cursor hook install to preToolUse * Clarify confirmed hook exceptions * Persist hook ignores in shared config * Guard font hook exceptions * Fix hook install after main rebase * Fix hook scan target handling * fix: address hook review findings * Address hook review feedback * Stabilize DeepSeek insert live fixture * Fix Cursor hook Python shell write bypass --------- Co-authored-by: Cursor <cursoragent@cursor.com>
Skill-behavior tests
LLM-backed scenarios that verify how the impeccable skill drives PRODUCT.md / DESIGN.md loading. Each scenario runs against the cheapest tier of each major provider (Anthropic, OpenAI, Google) so a full sweep costs a few cents and finishes in ~2 minutes.
These are the tests you re-run when you refactor anything in SKILL.md's
## Setup section. They fail when the agent stops following the loading
contract.
Run
bun run test:skill-behavior
IMPECCABLE_SKILL_BEHAVIOR_VERBOSE=1 bun run test:skill-behavior # dump per-scenario traces
IMPECCABLE_SKILL_BEHAVIOR_MODELS=claude-sonnet-4-6 bun run test:skill-behavior # scope to one model
Requires .env at repo root with at least one of ANTHROPIC_API_KEY,
OPENAI_API_KEY, GOOGLE_CLOUD_API_KEY. Providers without a key are
skipped, not failed.
How it works
Each scenario:
prepareWorkspace()mints a temp dir, symlinks the canonical skill into<workspace>/.claude/skills/impeccable, and optionally writesPRODUCT.md/DESIGN.mdfixtures.runTurn()inlinesSKILL.md(placeholders neutralized) as the system prompt and runs Vercel AI SDKgenerateTextwith four workspace-scoped tools:bash,read,write,list.- The tools record every call into a
tracethat the test asserts on. - For scenario 4, a second
runTurnreuses turn 1'sresponseMessagesso the model sees a real multi-turn conversation.
The trace is the source of truth, not the model's free-form reply.
Scenarios
| # | Setup | Assertion |
|---|---|---|
| 1 | empty workspace | runs context.mjs (which prints a NO_PRODUCT_MD directive); agent then loads reference/init.md via Read or cat; does not start writing HTML/CSS |
| 2 | PRODUCT.md only (with ## Register: brand) |
runs context.mjs 1-3 times; loads reference/brand.md |
| 3 | PRODUCT.md + DESIGN.md (brand register) | runs context.mjs 1-3 times; loads reference/brand.md; consults the design system (DESIGN.md bundled in output, but CSS / tokens / directory listing also count) |
| 4 | PRODUCT.md + DESIGN.md, context already loaded in turn 1 | turn 2 does not re-run context.mjs; reference/brand.md is loaded across turns 1+2 |
| 5 | PRODUCT.md WITHOUT a ## Register field; task cue says "landing page" |
runs context.mjs (which emits a generic register directive); agent loads reference/brand.md via task-cue cascade |
| 6 | PRODUCT.md + DESIGN.md + a minimal index.html; prompt is /impeccable polish |
loads reference/polish.md |
| 7 | same fixture; prompt is /impeccable audit |
loads reference/audit.md |
| 8 | PRODUCT.md + DESIGN.md + a SvelteKit scaffold (src/app.css, components, +page.svelte); prompt is /impeccable polish src/routes/+page.svelte |
reads at least one project code file (CSS / component / page) — not just the skill's reference files |
| 9 | PRODUCT.md + index.html + a seeded update cache with a newer version (skillVersion copy-mode so context.mjs has a SKILL.md to version-check against); prompt is /impeccable polish index.html |
context.mjs runs and its output carries the UPDATE_AVAILABLE directive (proven via captured bash output); the agent does not auto-run npx impeccable skills update (it must ask first) |
Scenario 9 passed on all three current-lineup providers (claude-sonnet-4-6,
gpt-5.5, gemini-3.1-flash-lite) on 2026-05-28.
Baseline state (2026-05-20, previous cheap tier)
Lineup changed. The default models are now
claude-sonnet-4-6,gpt-5.5, andgemini-3.1-flash-lite(production-tier on Anthropic and OpenAI). The table below was measured on the old cheap tier (claude-haiku-4-5/gpt-5.4-mini) and is kept as the historical record. Re-measure on the current lineup and update this section; the stronger models are expected to clear the scenario 6/7 routing failures that the old gpt tier showed.
Captured after moving sub-command reference loading from step 4 to step 2
of Setup (so the agent loads reference/<command>.md right after
context.mjs, before "doing the work" preempts it), and tightening
step 3 to require at least one project code read even when a sub-command
reference loads first. Use this table when comparing pre/post refactor:
a regression is "more failures than baseline", not "any failures at all".
| Scenario | claude-haiku-4-5 | gpt-5.4-mini | gemini-3.1-flash-lite |
|---|---|---|---|
| 1 (no context) | pass (rare flake — agent stops after context.mjs without loading init.md) |
pass | pass |
| 2 (product only) | pass | pass | pass |
| 3 (product + design) | pass | pass | pass (rare flake — sub-command ref loads but register ref doesn't) |
| 4 (already loaded) | pass | pass | pass |
| 5 (no register field, task-cue cascade) | pass | pass | pass |
6 (polish routing) |
pass | fail | pass |
7 (audit routing) |
pass | fail | pass |
| 8 (existing project, explore design system) | pass | pass | pass |
21-22 / 24 typical. The stable failures are gpt-5.4-mini scenarios 6 and 7:
the model reads index.html (the target file), recognizes "polish" or
"audit" as a familiar action, and proceeds with the work without ever
loading the sub-command reference. Stronger SKILL.md wording (MUST,
"non-optional", reordered earlier) didn't move it; this looks like a
model-floor behavior rather than a skill ambiguity. Claude and Gemini
honor the load.