Skill: aposd-verifying-correctness

Before "Done" — scope check

Design quality ≠ correctness. Well-designed code can still have bugs, missing requirements, or safety issues.

Run every dimension check before claiming done — "I think I covered everything" without explicit mapping is exactly the gap this skill exists to close.

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Dimension Detection & Checks

For each dimension: detect if it applies, then verify.

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1. Requirements Coverage

Detect: Were requirements stated? (explicit list, user request, spec)

If YES, verify:

• RC-1: List each requirement explicitly
• RC-2: For each: point to code that implements it
• RC-3: Any requirement without code? → Not done
• RC-4: Any code without requirement? → Scope creep or missing requirement

Red flag: "I think I covered everything" without explicit mapping

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2. Concurrency Safety

Detect: Any of these present?

• Multiple threads/processes accessing same data
• Async/await patterns
• Shared mutable state (class attributes, globals)
• "Thread-safe" in requirements or docstring
• Web handlers, queue workers, background tasks

If YES, verify:

• CS-1: All shared mutable state identified
• CS-2: Each access point protected (lock, atomic, queue, immutable)
• CS-3: No time-of-check to time-of-use (TOCTOU) gaps
• CS-4: Lock ordering consistent (if multiple locks)

Red flag: "It's probably fine" or "Python GIL handles it"

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3. Error Handling

Detect: Can any operation fail?

• I/O (file, network, database)
• External calls (APIs, subprocesses)
• Resource acquisition (memory, connections)
• User input processing
• Parsing/deserialization

If YES, verify:

• EH-1: Each failure point has explicit handling OR propagates
• EH-2: No bare except: or except Exception: pass
• EH-3: Error messages actionable (what failed, why, how to fix)
• EH-4: Partial failures handled (rollback, cleanup, consistent state)
• EH-5: No error path silently continues as if nothing happened (catch-log-continue, default returns on failure, swallowed callbacks all create silent failures — each error path either surfaces to the caller or is observable via logs/metrics/alerts)

Red flag: "Errors are rare" or "caller handles it" without checking caller

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4. Resource Management

Detect: Does code acquire resources?

• File handles, sockets, connections
• Locks, semaphores
• Memory allocations (large buffers, caches)
• External service handles
• Background threads/processes

If YES, verify:

• RM-1: Every acquire has corresponding release
• RM-2: Release happens in finally/context manager/destructor
• RM-3: Release happens on error paths too
• RM-4: No resource leaks on repeated calls
• RM-5: Bounded growth (caches have limits, queues have limits)

Red flag: "It cleans up eventually" or daemon threads without shutdown

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5. Boundary Conditions

Detect: Does code handle variable-size input?

• Collections (lists, dicts, sets)
• Strings, byte arrays
• Numeric ranges
• Optional/nullable values

If YES, verify:

• BC-1: Empty input: What happens with [], "", None, 0?
• BC-2: Single item: Edge case often different from N items
• BC-3: Maximum size: What if input is huge? Memory? Time?
• BC-4: Invalid values: Negative numbers, NaN, special characters?
• BC-5: Type boundaries: int overflow, float precision?

Red flag: "Nobody would pass that" or "that's an edge case"

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6. Security (if applicable)

Detect: Does code handle untrusted input?

• User-provided data (forms, API requests)
• File contents from external sources
• URLs, paths, identifiers from users
• Data that becomes SQL, shell, HTML, or code

If YES, verify:

• SE-1: Input validated before use
• SE-2: No string concatenation for SQL/shell/HTML (use parameterized)
• SE-3: Path traversal prevented (no ../ exploitation)
• SE-4: Secrets not logged or exposed in errors
• SE-5: Auth/authz checked before action, not after

Red flag: "It's internal only" (internals get exposed)

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CHECKER: every ID'd item above is a checklist item. The Output Format below is the report — one PASS/FAIL/N/A line per dimension with the evidence lines it asks for; individual items appear under their dimension only when they fail (ID — evidence — location); close with one line N items checked, M pass, K n/a.

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Output Format

When verifying, output:

## Correctness Verification

### Requirements: [PASS/FAIL/N/A]
- Requirement 1 → implemented in X
- Requirement 2 → implemented in Y

### Concurrency: [PASS/FAIL/N/A]
- Shared state: [list]
- Protection: [how]

### Errors: [PASS/FAIL/N/A]
- Failure points: [list]
- Handling: [approach]

### Resources: [PASS/FAIL/N/A]
- Acquired: [list]
- Released: [how]

### Boundaries: [PASS/FAIL/N/A]
- Edge cases: [list]
- Handling: [approach]

### Security: [PASS/FAIL/N/A]
- Untrusted input: [list]
- Validation: [approach]
- FAIL items only: [ID — evidence — location]   (same line under every dimension that has failures)

N items checked, M pass, K n/a

**Verdict:** [DONE / NOT DONE - list blockers]