yul

A Claude Code PreToolUse hook that keeps dependencies current. When Claude writes or edits a manifest, the hook checks any newly added/changed dependency pinned with an exact version and blocks the write (exit 2) if it's outdated, so Claude sees the correct version on stderr and retries. Other files and untouched dependencies pass through untouched; resolver/network errors fail open.

Supported manifests:

• pom.xml — Maven Central
• requirements.txt — PyPI, == pins only
• pyproject.toml — PyPI, [project.dependencies] / [project.optional-dependencies], == pins only
• package.json — npm registry, dependencies / devDependencies / optionalDependencies / peerDependencies, exact version pins only

Usage

Add to .claude/settings.json:

{
  "hooks": {
    "PreToolUse": [
      {
        "matcher": "Write|Edit",
        "hooks": [
          {
            "type": "command",
            "command": "/home/<user>/go/bin/yul",
            "timeout": 30
          }
        ]
      }
    ]
  }
}

Requires Go to be installed. No other setup needed.

Prefer installing the binary (go install github.com/chains-project/yul@latest) and pointing command at its absolute path instead: go run always exits 1 on program failure regardless of the program's actual exit code (golang/go#17813), so a blocking exit 2 from this hook is flattened to exit 1, where stderr reports exit status 2 but exitCode is 1. Claude Code treats exit 1 as a non-blocking error, so the write goes through instead of being blocked. go install places the binary at $GOPATH/bin (find it with go env GOPATH).

With go run, you can see below the exitCode is 1, but stderr reports exit status 2, so Claude Code treats it as a non-blocking error and lets the write go through instead of blocking it.

{
  "parentUuid":"3d0b0198-4c4f-473d-aca8-81aae1c47ba4",
  "isSidechain":false,
  "attachment":{
    "type":"hook_non_blocking_error",
    "hookName":"PreToolUse:Write",
    "toolUseID":"toolu_01NSX9EDCBG15megDu54GHRp",
    "hookEvent":"PreToolUse",
    "stderr":"Failed with non-blocking status code: outdated dependencies, use these versions instead:\n  org.json:json  20240303 -> 20260522\nexit status 2",
    "stdout":"",
    "exitCode":1,
    "command":"/home/aman/go/bin/yul",
    "durationMs":5349
  },
  "type":"attachment",
  "uuid":"9d9d7c75-51f3-45be-9fcd-63fd70c2d9b4",
  "timestamp":"2026-07-10T01:30:29.184Z",
  "session_id":"e4f05218-9565-43ba-826e-a9a699736c52",
  "userType":"external",
  "entrypoint":"cli",
  "cwd":"/tmp/tmp",
  "sessionId":"8e78af27-6afe-4d9c-a562-baaf77b94169",
  "version":"2.1.206",
  "gitBranch":"HEAD"
}

Example

Claude tries to write a pom.xml pinning org.json:json to 20240303. The hook blocks it:

outdated dependencies, use these versions instead:
  org.apache.pdfbox:pdfbox  3.0.3 -> 3.0.8

{
  "parentUuid": "53362172-27ca-446a-9709-589501ce4343",
  "isSidechain": false,
  "promptId": "3a98011e-3feb-4ee4-84a8-3d42b48815a0",
  "type": "user",
  "message": {
    "role": "user",
    "content": [
      {
        "type": "tool_result",
        "content": "PreToolUse:Write hook error: [/home/aman/Desktop/chains/ai-bump/yul]: outdated dependencies, use these versions instead:\n  org.apache.pdfbox:pdfbox  3.0.3 -> 3.0.8\n",
        "is_error": true,
        "tool_use_id": "toolu_015xUvsjc8FWGVG3QoS2Tko9"
      }
    ]
  },
  "uuid": "92b6b32d-8116-41c7-8773-c5dcb36e110b",
  "timestamp": "2026-07-27T15:00:23.991Z",
  "toolUseResult": "Error: PreToolUse:Write hook error: [/home/aman/Desktop/chains/ai-bump/yul]: outdated dependencies, use these versions instead:\n  org.apache.pdfbox:pdfbox  3.0.3 -> 3.0.8\n",
  "toolDenialKind": "permission-rule",
  "sourceToolAssistantUUID": "53362172-27ca-446a-9709-589501ce4343",
  "session_id": "00454dc4-731b-4ec8-8263-a1741b2c6a1e",
  "userType": "external",
  "entrypoint": "cli",
  "cwd": "/tmp/test",
  "sessionId": "00454dc4-731b-4ec8-8263-a1741b2c6a1e",
  "version": "2.1.220",
  "gitBranch": "HEAD"
}

Claude reads this from stderr and rewrites the manifest with the correct version.