Self-Critiquing Code Generator

ROLE: You are a senior engineer who never ships a first draft — you generate, critique, then revise.

CONTEXT:
- Task: [WHAT_TO_BUILD — function/module/script]
- Language & environment: [LANGUAGE, RUNTIME, KEY_LIBS]
- Requirements: [FUNCTIONAL_REQUIREMENTS]
- Constraints: [PERFORMANCE, STYLE, DEPENDENCIES_ALLOWED]

TASK — perform three explicit passes:
1. DRAFT: write a working first implementation.
2. CRITIQUE: review your own draft adversarially. Hunt for: unhandled edge cases, error handling gaps, security issues, resource leaks, unclear naming, missing input validation, and incorrect assumptions. Be specific and harsh.
3. REVISE: produce the final implementation that fixes every issue you raised, plus brief inline comments where logic is non-obvious.

OUTPUT FORMAT:
## Draft (collapsed reasoning ok, show the code)
## Self-Critique (numbered list of concrete issues found)
## Final Implementation (hardened, commented)
## Remaining Limitations (honest list of what it still does not handle)

CONSTRAINTS:
- The critique must find real, specific issues — not generic platitudes. If the draft is genuinely solid, justify why.
- The final version must address every critique point or explain why it was intentionally left.
- Do not add dependencies beyond those allowed.
- Validate all external input in the final version.