C Repair

AI-assisted detection, repair, and validation for C coding standards, in VS Code. Currently supports CERT® C;

C Repair scans a single C file for CERT® C violations, generates repair candidates with an LLM-driven repair harness, runs validation gates (compile / violation-removal / semantic / regression), and lets you review each fix as a diff before accepting it into your file. The final authority is always you: nothing is applied without an explicit Accept.

Quick start (3 steps)

Install C Repair from the Visual Studio Marketplace (the Get started with C Repair walkthrough opens on first activation), then:

1. Key — C Repair: Connect OpenRouter: approve in the browser, paste the one-time code into the VS Code prompt (works locally, under WSL, and on remotes). Or paste an existing key with C Repair: Set API Key.
2. Bridge — C Repair: Set Up Bridge (one-time; provisions a private Python env from the bundled wheels, then verifies /health).
3. Scan — open a .c file and run C Repair: Scan Current File (or Scan & Fix Current File to also generate repairs and enter the review queue).

How it works

• A small local bridge (FastAPI, spawned by the extension) wraps the repair harness; the extension talks to it over localhost with a per-session token.
• Accepted file = your original file + the hunks you accepted — inferred context (prelude) never leaks into your source.
• Validation results are shown per gate; failing "judgment" gates (violation-removal / semantic / regression) can be overridden explicitly, mechanical gates (compile) cannot.
• Export Repair Report produces a review-evidence Markdown (dispositions, gate evidence, accepted diffs) for PRs and QA.

Costs (BYOK)

Scans and repairs call an LLM through your OpenRouter key. A single-file scan typically costs a few cents; each repair with validation gates costs a few cents more (large files cost more). The status bar shows the session's token usage and an approximate cost after each run. The free model mode (C Repair: Choose Model Mode) costs $0 with reduced quality and shared-pool rate limits — good for trying the flow.

Data handling

The content of the scanned C file (and the inferred context declarations) is sent to OpenRouter and routed to the configured model provider (preset: DeepSeek via DeepInfra) to perform detection, repair, and validation. Do not scan files you are not allowed to share with those services. Everything else stays local: the bridge runs on 127.0.0.1 only, nothing is stored outside your machine, and your API key lives in VS Code's secret storage (never in settings, logs, or command lines).

Requirements

• VS Code 1.85+.
• gcc on PATH (used locally for the compile gate; optional — without it the compile check reports as skipped).
• A Python environment for the local bridge, any ONE of:
  • uv — Set Up Bridge provisions everything automatically (installs uv with your consent when missing);
  • the monorepo dev venv (services/repair-api/.venv) when developing in the repo — detected automatically, takes priority;
  • a manually prepared Python 3.10+ env with repair-api installed, pointed to by crepair.bridge.pythonPath.
• An OpenRouter API key (bring your own key).

Known limitations

• Single .c file at a time — no project-wide analysis.
• One finding per function is repaired (harness constraint).
• Header-dense files are best-effort: external declarations are inferred and shown for review; when the context still does not fully compile, results are marked context incomplete (N symbols still missing) — detection may miss violations there, and zero findings is not a safety guarantee.
• MISRA C is out of scope.

Repairs requiring project-wide changes

A candidate fixes a single function, so some repairs are only a starting point: a fix may change the function's public API (callers must be updated) or depend on facts outside the file (e.g. STR31-C needs the destination buffer's capacity, which often lives in the caller). Passing the validation gates does not guarantee your whole project is correct. Accept such a fix as a base, complete the wider changes yourself, then re-scan to verify — the Getting Started walkthrough (Generate repairs and review → When a repair needs wider changes) walks through this.

Troubleshooting the bridge setup

Commands

Attribution

CERT® is a registered trademark of Carnegie Mellon University. This project is not affiliated with, sponsored, or endorsed by CMU or the Software Engineering Institute. Rule identifiers and titles are referenced for interoperability; this tool does not provide official conformance certification.