Validate Type Safety

Final verification gate before marking any TypeScript work complete. Combines type checking with reward hacking detection, test verification, and linting. ALL 5 steps must pass.

Tooling Detection

Before running any commands, detect the project's package manager and linting tool. Do NOT hardcode bun, npm, or trunk — detect from what's available.

Package Manager

Check for lockfiles in the project root:

If multiple exist, prefer in the order listed above. Store as $PM_RUN (e.g., bun run).

Linter

Check for linting tools in this order:

If none found, skip Step 5 and note it in the output.

Type Check Command

Look for a type-check or typecheck script in package.json:

• If found: ${PM_RUN} type-check (or typecheck)
• If not found: npx tsc --noEmit (fallback)

For monorepos, check if the root package.json has a workspace-level type-check script first.

Validation Steps

Step 0: tsconfig Strictness Check (Informational)

Read the project's tsconfig.json (or the tsconfig covering changed files in a monorepo). Verify:

• "strict": true is set — WARN if missing
• "noUncheckedIndexedAccess": true — INFO if missing (recommended)
• "noImplicitReturns": true — INFO if missing (recommended)
• "exactOptionalPropertyTypes": true — INFO if missing (recommended)

For monorepos: use the Glob tool to find tsconfig.json files, then identify which one covers the changed files (check include/exclude paths and references).

This step is informational only — it does not cause a FAIL verdict, but findings are reported.

Step 1: Run TypeScript Type Check

${PM_RUN} type-check  # or detected equivalent

Expected: Zero errors, exit code 0.

If errors exist, they MUST be fixed. Do not proceed to Step 2 until type-check passes.

Step 2: Run Reward Hacking Scan

Execute the /scan-reward-hacking skill on the changed files.

Expected: PASS verdict with no unfixed CRITICAL or HIGH severity patterns.

Step 3: Verify Test Inclusion

Check that test files are NOT excluded from type checking. Use Grep to search tsconfig files (in changed packages for monorepos):

• Pattern: \.test\.ts or \.spec\.ts in exclude arrays of tsconfig files
• Pattern: test directories in exclude arrays

Expected: No tsconfig files exclude test files from type checking.

Step 4: Run Tests

${PM_RUN} test

For monorepos with many packages, if the project has a --filter or --scope option, run tests only for affected packages when possible.

Expected: All tests pass. Type fixes should not break functionality.

Step 5: Lint Check

# Use detected linter command from Tooling Detection
trunk check --ci --upstream origin/main  # or biome/eslint equivalent

Expected: Zero lint errors.

If no linter was detected, skip this step and note it in the output.

Optional: Type Coverage Metric

If type-coverage is available (check with which type-coverage or npx type-coverage --help), report the numeric coverage score:

npx type-coverage --at-least 0

This is informational only — does not affect the verdict.

Output Format

Present results in this format:

## Type Safety Validation Results

### Tooling Detected
- Package manager: {bun|pnpm|yarn|npm}
- Linter: {trunk|biome|eslint|none}
- Type check command: {detected command}

### Step 0: tsconfig Strictness (Informational)
- strict: true — {YES / MISSING}
- noUncheckedIndexedAccess — {YES / missing (recommended)}
- noImplicitReturns — {YES / missing (recommended)}
- exactOptionalPropertyTypes — {YES / missing (recommended)}

### Step 1: TypeScript Type Check
- Status: PASS / FAIL
- Errors: {count} (list if any)

### Step 2: Reward Hacking Scan
- Status: PASS / FAIL
- Critical: {count}
- High: {count}
- (Details if any issues found)

### Step 3: Test File Inclusion
- Status: PASS / FAIL
- tsconfig files excluding tests: {count} (list if any)

### Step 4: Tests
- Status: PASS / FAIL
- Failed tests: {count} (list if any)

### Step 5: Lint Check
- Status: PASS / FAIL / SKIPPED (no linter detected)
- Errors: {count} (list if any)

### Type Coverage (if available)
- Coverage: {X}% ({Y}/{Z} types)

---

## Overall Verdict: PASS / FAIL

{If FAIL, list all items that must be fixed}

Verdict Criteria

PASS requires ALL of the following:

• Type check exits with code 0
• No CRITICAL or HIGH severity reward hacking patterns
• No tsconfig files exclude test files (in changed packages)
• All tests pass
• Lint check passes (or no linter detected)

FAIL if ANY check fails.

If Validation Fails

Do NOT mark the work as complete. Instead:

1. Fix all issues identified in the validation
2. Re-run validation after fixes
3. Only mark complete when validation passes

Fast-Fail Mode

For efficiency, stop on the first failing step. Report which step failed and what needs fixing. Re-run the full validation after fixes are applied.

Integration with Other Skills

• Called by /implement-plan as part of quality gates
• Called by /oneshot Phase 4 (Validate + Quality Gates)
• Invokes /scan-reward-hacking internally for Step 2