PostToolUse Quality Hooks: Auto-Format and Typecheck After Edits

[dean0x]

Summary

Add PostToolUse hooks that automatically run fast quality checks after file edits — formatting, type checking, console.log detection. Distinct from PreToolUse enforcement (#98) which blocks unwanted actions; PostToolUse hooks run AFTER successful tool execution and provide advisory feedback.

Motivation (from Harness Alpha Analysis)

Harness Alpha implements 7 PostToolUse hooks that catch issues at edit-time rather than waiting for end-of-workflow review:

Hook	Trigger	Action
post-edit-format	After Edit/Write on .js/.ts	Auto-format with Biome or Prettier (async)
post-edit-typecheck	After Edit/Write on .ts	Run tsc --noEmit on changed file (async)
post-edit-console-warn	After Edit/Write	Warn if console.log was introduced
quality-gate	After Edit/Write	Fast quality checklist (async, non-blocking)
build-complete	After Bash (build commands)	Analyze build output for warnings
pr-created	After Bash (gh pr create)	Log PR URL and suggest review command
observe	After any tool	Capture observations for learning (async)

Why This Is Different from #98

Aspect	#98 (PreToolUse)	This Issue (PostToolUse)
Timing	Before tool runs	After tool completes
Purpose	Block unwanted actions	Catch quality issues
Effect	Prevents execution (exit 2)	Advisory feedback
Blocking?	Yes (gate)	No (inform)
Example	"Reviewer can't Write"	"Your edit introduced a type error"

Why This Matters for DevFlow

Currently, quality issues accumulate during implementation and are caught either by:

• Scrutinizer (end of /implement — late feedback)
• Manual npm run build / tsc (user-initiated)
• Self-review (/self-review — explicit command)

PostToolUse hooks catch issues immediately — before the agent moves on. This prevents cascading errors where one type error leads to workarounds in subsequent edits.

Technical Approach

Phase 1: Core Hooks (High Value, Low Risk)

1. Auto-Format Hook

# scripts/hooks/post-edit-format.sh
# Triggers: PostToolUse on Edit/Write for .ts/.tsx/.js/.jsx
# Detects: Biome (biome.json) → Prettier (.prettierrc) → skip
# Runs: async, non-blocking, 5-second timeout
# Output: Silent on success, warn on format diff

2. TypeScript Check Hook

# scripts/hooks/post-edit-typecheck.sh
# Triggers: PostToolUse on Edit/Write for .ts/.tsx
# Runs: tsc --noEmit --pretty on the changed file
# Output: Warn with error details if type errors found
# Async: Yes, non-blocking

3. Console.log Detection Hook

# scripts/hooks/post-edit-console-warn.sh
# Triggers: PostToolUse on Edit/Write
# Checks: Did the edit introduce console.log/console.debug/console.warn?
# Output: Advisory warning (not blocking)

Phase 2: Extended Hooks (Future)

• Build analysis after Bash commands containing build keywords
• PR creation logging and review command suggestion
• Test result capture after Bash test commands

Integration with Existing Infrastructure

• Hook profiles (Research Report: Harness Alpha Competitive Analysis — 13 Enhancement Opportunities #107 item 2): PostToolUse hooks should respect DEVFLOW_HOOK_PROFILE when implemented
• Memory hooks: PostToolUse hooks are independent of session memory hooks (different lifecycle events)
• Ambient mode: PostToolUse hooks are always-on regardless of ambient classification (they're quality enforcement, not intent-based)

CLI Management

devflow init --quality-hooks    # Enable PostToolUse quality hooks
devflow init --no-quality-hooks # Skip (default for now)

Register in settings.json under hooks.PostToolUse[].

Effort & Impact

• Effort: Medium (3 hook scripts + CLI integration + tests)
• Impact: High — catches errors at edit-time instead of end-of-workflow
• Risk: Low — hooks are async and non-blocking; worst case is a false positive warning

Cross-Reference

• Distinct from PreToolUse Hook Enforcement System #98 (PreToolUse enforcement — blocking, policy-based)
• Complements Scrutinizer (which catches issues at end-of-workflow)
• Relates to Research Report: Harness Alpha Competitive Analysis — 13 Enhancement Opportunities #107 item 2 (Hook Profile Gating — PostToolUse hooks should be profile-gated)