certfix

certfix detects CERT-C issue candidates in C code and generates reviewable fixed-code candidates and patches with LLMs.

certfix is a route-aware LLM-assisted C repair workflow for CERT-C issue candidates. It treats model output as reviewable fixed-code candidates, not trusted source changes.

The goal is not to ask one model to autonomously rewrite a codebase. The goal is to route detection, repair, validation, retry, and review work across local models, API models, programmatic gates, and human review under real-world constraints such as quality, cost, latency, source-code confidentiality, reproducibility, and trust.

certfix does not modify source files in place. A fixed result means the candidate passed the enabled certfix validation gates for that run; it is not a proof of semantic correctness, security correctness, or project integration safety.

certfix complements static analyzers by producing repair candidates, not just diagnostics. Docker is the recommended runtime for normal use. Non-Docker installation and direct llama-server operation are available for advanced or manual use in docs/INSTALLATION.md.

1. Getting Started

certfix uses the same input/output model across API-only, local-only, and hybrid runtime paths:

source folder -> /input:ro -> certfix container -> /output

Source files are mounted read-only and are not modified. Reports, fixed-code candidates, and patches are written to the output folder.

1.1 Prepare Folders

Create or choose a folder containing the C source files to scan, then create an output folder:

my-project/
+-- src/             # scan this folder first
`-- certfix-output/  # generated reports, fixes, and patches

If your C files are not under src/, replace $PWD/src in the commands below with the folder you want to scan. You can mount the project root with $PWD:/input:ro, but using a smaller source folder is recommended for the first run.

When using the published certfix image with docker run, you do not need to copy files from this repository. For Docker Compose, copy the compose file and any supporting llama-server build files required for the route you are testing; see docs/DOCKER.md.

1.2 Choose A Runtime

Option	Use when	Sends source code to API?	Requirements	Start here
A. API-Only	Fastest first run; source can be sent to a provider	Yes	Docker, API key	`certfix-docker api-check`
B. Local-Only	Source code must stay local	No	Docker Compose, NVIDIA GPU, MTP-capable `llama-server`, compatible GGUF model	`certfix-docker local-check`
C. Hybrid	Local detection with API repair/validation	Yes, for API-routed steps	Local-only requirements plus API key	`certfix-docker local-fix --profile local-detection-deepseek-fix-docker`

certfix-docker is the Docker helper used in the commands below; see 3.1 certfix-docker for details.

API-only and hybrid modes send source code to the configured provider for the API-routed steps. Confirm your project data policy before using either mode.

Local-only mode does not send source code to an API provider. You still need to provide or download the model separately.

Option A: API-Only Mode

Use API-only mode when you want the easiest first run and your source can be sent to the configured provider.

Run api-check first. It writes reports and does not generate fix files.

export OPENROUTER_API_KEY=<openrouter-key>
mkdir -p certfix-output

docker run --rm \
  -e OPENROUTER_API_KEY \
  -v "$PWD/src:/input:ro" \
  -v "$PWD/certfix-output:/output" \
  ghcr.io/safe-c-ai/certfix:0.4.1 \
  certfix-docker api-check

certfix check returns exit code 1 when it finds issue candidates. That means the command completed and reported findings; exit code 2 indicates usage, configuration, model, or runtime errors.

After checking the project, run api-fix to generate reviewable fixed-code files and patches:

docker run --rm \
  -e OPENROUTER_API_KEY \
  -v "$PWD/src:/input:ro" \
  -v "$PWD/certfix-output:/output" \
  ghcr.io/safe-c-ai/certfix:0.4.1 \
  certfix-docker api-fix

PowerShell example:

$env:OPENROUTER_API_KEY="<openrouter-key>"
New-Item -ItemType Directory -Force certfix-output

docker run --rm `
  -e OPENROUTER_API_KEY `
  -v "$($PWD.Path)\src:/input:ro" `
  -v "$($PWD.Path)\certfix-output:/output" `
  ghcr.io/safe-c-ai/certfix:0.4.1 `
  certfix-docker api-check

Option B: Local-Only Mode

Use local-only mode when source code must not be sent to an external provider. This is an advanced path because the certfix image does not include llama-server, model weights, or a GPU runtime. The bundled Qwen3.6-27B MTP default requires a large GPU; see docs/DOCKER.md for runtime requirements.

The bundled qwen36-mtp-docker profile targets Qwen3.6-27B MTP by default. The Compose route can use another compatible local model if you provide a matching certfix config/profile and llama-server model settings.

export LLAMA_SERVER_IMAGE=<mtp-capable-llama-server-image>
export SOURCE_DIR="$PWD/src"
export OUTPUT_DIR="$PWD/certfix-output"
export HOST_MODEL_DIR=/path/to/models
export LLAMA_MODEL_PATH=/models/qwen3.6-27b-mtp-ud-q4_k_xl.gguf

docker compose -f docker-compose.local-qwen36.yml up -d llama-server
docker compose -f docker-compose.local-qwen36.yml run --rm certfix certfix-docker local-check

If LLAMA_MODEL_PATH is not set, the compose file falls back to LLAMA_GGUF_REPO and lets llama-server download/cache the configured GGUF. Replace LLAMA_MODEL_PATH with the GGUF file you mounted under /models. The bundled detection route is verified with Qwen3.6-27B MTP. Routing repair/validation to another model is configured in docs/CONFIGURATION.md; non-MTP local runtimes require runtime overrides described in docs/QWEN36_MTP_RUNTIME.md.

Run local-fix after checking when you want fixed-code candidates and patches:

docker compose -f docker-compose.local-qwen36.yml run --rm certfix certfix-docker local-fix

For the full local llama-server Compose flow, model/cache mounts, and host GPU requirements, see docs/DOCKER.md.

Option C: Hybrid Mode

Hybrid mode is an advanced route. It uses the same Compose setup as Local-Only Mode, but switches to a hybrid profile and passes an API key.

The bundled local-detection-deepseek-fix-docker profile uses the default local Qwen3.6 detection route and an API provider for repair/validation. Source code may be sent to the configured provider for those API-routed steps.

export LLAMA_SERVER_IMAGE=<mtp-capable-llama-server-image>
export OPENROUTER_API_KEY=<openrouter-key>
export SOURCE_DIR="$PWD/src"
export OUTPUT_DIR="$PWD/certfix-output"
export HOST_MODEL_DIR=/path/to/models
export LLAMA_MODEL_PATH=/models/qwen3.6-27b-mtp-ud-q4_k_xl.gguf

docker compose -f docker-compose.local-qwen36.yml up -d llama-server
docker compose -f docker-compose.local-qwen36.yml run --rm certfix \
  certfix-docker local-fix --profile local-detection-deepseek-fix-docker

Use the same model mount settings as Option B. If LLAMA_MODEL_PATH is not set, the compose file falls back to LLAMA_GGUF_REPO and lets llama-server download/cache the configured GGUF.

For additional routing profiles and step overrides, see docs/CONFIGURATION.md.

2. Example Output

Given this MEM30-C use-after-free example:

int run_mem30_demo(void) {
    char *p = make_message("primary", 7);
    if (p == NULL) {
        return -1;
    }

    free(p);
    print_label(p);
    return 0;
}

certfix check reports a MEM30-C issue candidate. certfix fix may generate a fixed-code candidate like this:

int run_mem30_demo(void) {
    char *p = make_message("primary", 7);
    if (p == NULL) {
        return -1;
    }

    print_label(p);
    free(p);
    return 0;
}

certfix check writes machine-readable reports:

certfix-output/
+-- reports/
|   +-- check.json
|   +-- check.sarif
|   `-- summary.json

certfix fix adds fixed-code files and patches:

certfix-output/
+-- reports/
|   +-- fixes.json
|   +-- fixes.sarif
|   `-- summary.json
+-- fixes/
|   `-- mem30_use_after_free.fixed.c
`-- patches/
    `-- mem30_use_after_free.c.patch

With certfix fix --comment-merge, certfix keeps the validated comment-stripped artifacts above and adds conservative comment-merged review artifacts. Add --comment-merge-audit when you want an LLM to reject stale or misleading restored comments before those artifacts are written. That audit is an explicit opt-in path that sends the source file's original comments and the restored comments to the configured review model; do not enable it for comments that must not be sent to an API provider.

certfix-output/
+-- reports/
|   `-- comment_merge.json
+-- fixes-commented/
|   `-- mem30_use_after_free.fixed.commented.c
`-- patches-commented/
    `-- mem30_use_after_free.c.commented.patch

LLM output is not guaranteed to be deterministic, so exact output can vary by model, provider, prompt profile, runtime settings, and upstream model updates. See docs/EXAMPLE_OUTPUT.md for a fuller walkthrough.

3. CLI And Configuration

3.1 certfix-docker

certfix-docker is a container helper. It generates a temporary config inside the container, runs certfix doctor, then runs certfix check only or certfix check followed by certfix fix.

Command	Default profile	Flow
`certfix-docker api-check`	`deepseek-v4-flash-openrouter`	config, doctor, check
`certfix-docker api-fix`	`deepseek-v4-flash-openrouter`	config, doctor, check, fix
`certfix-docker local-check`	`qwen36-mtp-docker`	config, doctor, check
`certfix-docker local-fix`	`qwen36-mtp-docker`	config, doctor, check, fix

Common options:

Option	Applies to	Purpose
`--profile <name>`	all `certfix-docker` commands	Generate a different bundled profile before running `doctor`, `check`, or `fix`
`--comment-merge`	`api-fix`, `local-fix`	Add conservative comment-merged review artifacts
`--comment-merge-audit`	`api-fix`, `local-fix`	Ask the configured review model to suppress stale or misleading restored comments before writing comment-merged artifacts

3.2 Raw certfix CLI

The Docker helper is the easiest first-run path. The underlying CLI is still available for manual installation, development, and custom integration.

pip install certfix
certfix config deepseek-v4-flash-openrouter --output .certfix.yaml
certfix doctor
certfix check path/to/source --output-dir certfix-output
certfix fix path/to/source --output-dir certfix-output
certfix fix path/to/source --output-dir certfix-output --comment-merge
certfix fix path/to/source --output-dir certfix-output --comment-merge-audit

For compiler requirements, direct llama-server setup, and non-Docker examples, see docs/INSTALLATION.md.

3.3 Model Routes And Configuration

Docker helper defaults:

api-check / api-fix: DeepSeek V4 Flash through OpenRouter
local-check / local-fix: bundled default Qwen3.6 route through an external llama-server service

certfix supports local, API, and hybrid model routes through .certfix.yaml. Use certfix config <profile> --output .certfix.yaml to write a bundled profile. For the full profile list, include paths, exclusions, advanced routing, and token/context tuning, see docs/CONFIGURATION.md.

3.4 Exit Codes

certfix check:

Code	Meaning
0	No issues found
1	Issues found
2	Usage, configuration, model, or runtime error

certfix fix:

Code	Meaning
0	Command completed and no failed fixes were reported
1	At least one detected issue could not be fixed or failed validation
2	Usage, configuration, model, or runtime error

Use certfix check exit codes for CI violation gating.

4. Limitations

C only.
Supported CERT-C coverage is limited to the 115 bundled rule targets.
CERT-C recommendations are not supported.
Analysis is file/function scoped, not whole-program semantic analysis.
Generated fixes are candidates for review, not guaranteed correct patches.
Fixed-code candidates under fixes/ are comment-stripped.
--comment-merge can add review-only comment-merged artifacts after validation.
--comment-merge-audit uses an LLM to suppress comment-merged artifacts when restored comments appear stale or misleading.
--comment-merge-audit sends the source file's original comments and the restored comments to the configured review model and should not be used with API providers when comments are sensitive.
API-only and hybrid modes may send source code to configured providers.

See docs/LIMITATIONS.md for the full scope and runtime caveats.

5. Documentation

Document	Purpose
docs/INDEX.md	Documentation index
docs/DOCKER.md	API-only, local `llama-server`, and hybrid Docker usage
docs/INSTALLATION.md	Manual installation, compiler setup, and direct runtime setup
docs/FAQ.md	Common questions about runtime/data boundaries, validation, model routing, human review, and benchmarks
docs/EXAMPLE_OUTPUT.md	Before/after example and generated artifact walkthrough
docs/CONFIGURATION.md	Config lookup, bundled profiles, include paths, advanced routing, and token/context tuning
docs/LIMITATIONS.md	Full scope, repair, validation, and runtime limitations
docs/VALIDATION_AND_RETRY.md	Validation gates, retry behavior, and generated fix report fields
docs/SUPPORTED_RULES.md	Supported CERT-C rule target catalog and category coverage
docs/QWEN36_MTP_RUNTIME.md	Local Qwen3.6 MTP `llama-server` setup and verified runtime notes
docs/BENCHMARK_SUMMARY.md	v0.1.0 release-test reference and route-selection benchmark caveats
docs/ARCHITECTURE.md	Release-side architecture and pipeline design
docs/DESIGN_RATIONALE.md	Route-aware, validation-first workflow, model routing, data boundaries, human review boundary, and model evolution
docs/RESEARCH_NOTES.md	Boundary between public release docs and research/archive materials
THIRD_PARTY_NOTICES.md	SARIF, CERT-C, and evaluation dataset attribution and license boundaries

6. License

MIT. See LICENSE.

See THIRD_PARTY_NOTICES.md for bundled standard fixtures and rule metadata notices.

Name		Name	Last commit message	Last commit date
Latest commit History 23 Commits
.github/workflows		.github/workflows
configs		configs
docker		docker
docs		docs
examples/input		examples/input
model-smoke-cases		model-smoke-cases
scripts		scripts
src/certfix		src/certfix
tests		tests
.certfix.yaml.example		.certfix.yaml.example
.dockerignore		.dockerignore
.gitattributes		.gitattributes
.gitignore		.gitignore
AGENTS.md		AGENTS.md
Dockerfile		Dockerfile
LICENSE		LICENSE
README.md		README.md
RELEASE_NOTES.md		RELEASE_NOTES.md
SECURITY.md		SECURITY.md
THIRD_PARTY_NOTICES.md		THIRD_PARTY_NOTICES.md
docker-compose.api.yml		docker-compose.api.yml
docker-compose.local-qwen36.yml		docker-compose.local-qwen36.yml
pyproject.toml		pyproject.toml

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certfix

1. Getting Started

1.1 Prepare Folders

1.2 Choose A Runtime

Option A: API-Only Mode

Option B: Local-Only Mode

Option C: Hybrid Mode

2. Example Output

3. CLI And Configuration

3.1 certfix-docker

3.2 Raw certfix CLI

3.3 Model Routes And Configuration

3.4 Exit Codes

4. Limitations

5. Documentation

6. License

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certfix

1. Getting Started

1.1 Prepare Folders

1.2 Choose A Runtime

Option A: API-Only Mode

Option B: Local-Only Mode

Option C: Hybrid Mode

2. Example Output

3. CLI And Configuration

3.1 certfix-docker

3.2 Raw certfix CLI

3.3 Model Routes And Configuration

3.4 Exit Codes

4. Limitations

5. Documentation

6. License

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