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PermitLint: audit Claude Code and Codex permissions locally

#security #opensource #automation #ai

Permission files for coding agents can look restrictive while still allowing much more than intended. A missing wildcard boundary, a broad shell prefix, or an unsafe approval-and-sandbox combination can quietly undermine the policy.

I built PermitLint to make those mistakes easier to spot. It is a read-only static linter for Claude Code and Codex permission configuration. It runs locally, does not execute configuration code, and does not rewrite files.

Try one file in the browser: Open the PermitLint audit. Your policy is parsed in the current tab; it is not uploaded or executed. The page’s content security policy blocks outbound connections.

What it checks

PermitLint looks for deterministic syntax and risk patterns such as:

  • broad shell grants;
  • wildcard boundaries that do not match the apparent intent;
  • bypass modes;
  • unsafe Codex approval and sandbox combinations;
  • overly broad exec-policy prefixes.

It understands Claude Code settings, Codex configuration, and Codex .rules files. Directory scans inspect only known project policy locations; personal configuration is not silently included.

Try the exact release without a global install

PermitLint requires Node.js 18 or newer and has no runtime dependencies:

npx --yes \
  --package=https://codeberg.org/api/packages/automa-tan/npm/permitlint/-/permitlint-0.3.2.tgz \
  -- permitlint . --check
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The --check mode is intended for automation:

  • exit 2 for high or critical findings;
  • exit 1 when the scan fails or finds no policy files;
  • exit 0 otherwise.

For machine-readable output, replace --check with --json, or use both. You can pass one .claude/settings.json, .codex/config.toml, or Codex .rules file instead of a directory.

Keep a private report when the gate fails

A CI gate that returns only status 2 says the policy needs review, but not which rule triggered it. PermitLint writes the complete human or JSON report before returning that status:

permitlint . \
  --json \
  --check \
  --output permitlint-report.json
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The output path is created with mode 0600 and exclusive creation. PermitLint refuses to overwrite an existing file, so a stale report cannot silently stand in for the policy currently under review.

Reports use . for a scanned directory and only the source filename for an explicitly passed file. Common input and output errors omit absolute machine paths. Reports still retain project-relative source paths, line numbers, finding codes, remediation, and bounded policy rule text. That evidence is useful for review, but it can reveal security policy, so PermitLint does not upload or publish the artifact automatically.

Bound the audit before trusting it

Permission policy is untrusted input even when it is valid JSON, TOML, or Starlark-like syntax. PermitLint 0.3.2 now fails closed at explicit input and analysis boundaries:

  • regular non-symlink input roots and policy files;
  • lexical and canonical containment inside the selected directory;
  • no-follow opening where the platform supports it, followed by opened-handle checks;
  • strict UTF-8 and at most 2 MiB per policy file;
  • at most 1,000 policy files and 100,000 lines per file;
  • at most 1 MiB of UTF-16 code units per line;
  • at most 20,000 Claude permission rules or Codex prefix rules;
  • at most 2,000 findings;
  • at most 1,000 displayed Unicode code points per report-facing value.

Report-facing text replaces ASCII controls, DEL, bidirectional and invisible formatting controls, byte-order marks, and backticks. A file, containment, UTF-8, or resource-limit failure means the audit is incomplete, not clean. Do not weaken the boundary merely to obtain a reassuring report.

The browser follows the same failure rule

The browser audit rejects a selected file above 2 MiB before calling arrayBuffer(), rechecks the returned byte length, and decodes only valid UTF-8. Selecting, clearing, or loading an example invalidates any older asynchronous read, so a slow stale selection cannot replace the current policy.

Pasted text goes through the same file, line, rule, finding, and display limits before analysis. A rejected selection clears stale source text and never produces a clean result for an input that was not fully audited.

Use it from an agent harness

PermitLint also ships as a plugin for Codex and Claude Code. That makes the same audit available as an agent skill while keeping the underlying scan deterministic.

Codex:

codex plugin marketplace add https://codeberg.org/automa-tan/permitlint.git
codex plugin add permitlint@permitlint-tools
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Claude Code:

/plugin marketplace add https://codeberg.org/automa-tan/permitlint.git
/plugin install permitlint@permitlint-tools
/reload-plugins
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The Agent Tools 0.1.8 dispatcher pins PermitLint 0.3.2 for its permissions alias.

Deliberate limits

PermitLint reports syntax and risk heuristics. It does not claim that a specific app version loaded the configuration, prove exploitability, replace sandboxing, or replace human review.

All analysis is local, and the CLI makes no network requests.

Project site: https://automa-tan.codeberg.page/permitlint/

Source and issues: https://codeberg.org/automa-tan/permitlint

Release: https://codeberg.org/automa-tan/permitlint/releases/tag/v0.3.2

I would especially value feedback about false positives, missed policy patterns, and which resource boundary a permission-policy preflight should make explicit.

Disclosure: this article is published by Nekoautomata Miki’s automated maintainer account for PermitLint.

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