Diagnostics & agents¶

Understand each finding, consume a stable JSON contract, and keep agent repairs within your declared policy.

Exit code	Meaning
`0`	No unresolved findings.
`1`	Findings need review.
`2`	Invocation, configuration, or I/O failure.

Diagnostic codes¶

Text diagnostics include a sorted, project-relative path, line, column, code, reason, and repair eligibility:

src/example.py:1:1: LMH004 copyright year ends at 2025; expected 2026 [fixable]

Paths use /, including .. for explicitly selected external files.

Code	Meaning	Next step
`LMH001`	Missing header.	Published 0.7.0 requires manual insertion. The unreleased source can use `fix` when a creation year is declared and `fixable` is true.
`LMH002`	Owner mismatch.	Verify the declared ownership manually.
`LMH003`	Invalid, reversed, future, or out-of-policy year.	Review the year policy and source.
`LMH004`	Recognized stale year.	Use `fix` only when `fixable` is true and writes are authorized.
`LMH005`	Missing or mismatched license notice.	Review the configured notice and source.
`LMH006`	Malformed, misplaced, duplicated, or ambiguous layout.	Resolve the layout manually.
`LMH007`	Unsupported encoding or invalid bytes.	Review the file's encoding.
`LMH008`	Unsafe or concurrently changed repair target.	Inspect links, identity, and concurrent writes.
`LMH900`	Command, configuration, or I/O error.	Stop and resolve the error; JSON places it in `error`.

Exit 0 means clean, 1 means unresolved findings, and 2 means an invocation/configuration/I/O failure. A failed repair may follow earlier completed repairs, so inspect changed and the working-tree diff.

JSON output¶

lmh check --output-format json

Successfully parsed JSON-mode commands write only JSON to stdout. Malformed CLI syntax remains a stderr usage error. Schema version 1 is shared by check and fix:

{
  "schema_version": 1,
  "tool_version": "0.7.0",
  "command": "check",
  "config_path": "pyproject.toml",
  "checked": 1,
  "changed": [],
  "diagnostics": [
    {
      "path": "src/example.py",
      "line": 1,
      "column": 1,
      "code": "LMH004",
      "message": "copyright year ends at 2025; expected 2026",
      "fixable": true
    }
  ],
  "expected_header": "# Copyright (C) <FILE_CREATION_YEAR>-2026, Example Organization.\n\n# This program is licensed under the Apache License 2.0.\n# See LICENSE or go to <https://www.apache.org/licenses/LICENSE-2.0> for full license details.\n",
  "error": null
}

expected_header uses the first enabled language's comment marker. Its text and blank lines are shared by all enabled languages. changed lists completed writes; diagnostics lists unresolved findings. Command failures use error instead of an LMH900 diagnostic.

Coding agents¶

Copy this instruction into an agent task:

Read the declared owner, starting year, license, and paths; ask if any are missing.
Run lmh check --output-format json. Exit 1 means findings; exit 2 means stop.
Only run lmh fix when source changes are authorized, then recheck and inspect the
targeted diff. Never infer legal facts or install, commit, or push without permission.

The optional lint-my-headers agent skill uses the same contract. Its retained evaluation results are historical Python-era evidence, not Rust evaluations.

An agent should use fixable and the exit status to guide repairs, and review the actual diff before handoff. Tool output never authorizes choosing an owner, license, or creation year.