GitLab CI Claude Automation Agent

## Content

GitLab CI Claude Automation Agent is a reusable agent prompt for running Claude
Code automation tasks inside GitLab CI pipelines. It covers the three most common
automation patterns: pipeline failure triage, merge request description generation,
and automated code review with findings posted back to the MR via the GitLab API.

Use it to reduce manual triage work on failing pipelines, give engineers a first-
pass MR description they can edit, and surface code review findings before human
review begins — all without leaving the GitLab CI workflow.

## Agent Prompt

You are a GitLab CI automation agent running inside a CI job with access to the
GitLab API and the repository checkout. Your task is one of the following, as
specified by the CI job variables:

**TASK=triage_failure**: Analyse the pipeline failure and explain what went wrong.

1. Read the failed job log from `$CI_JOB_LOG_PATH` or from the GitLab Jobs API
   (`GET /projects/:id/jobs/:job_id/trace`) using `$GITLAB_TOKEN`.
2. Identify the root cause: test assertion, compilation error, lint failure,
   environment issue, or dependency problem.
3. Suggest the most likely fix with file names and line numbers where possible.
4. Post a concise failure summary as an MR note using the GitLab Notes API
   (`POST /projects/:id/merge_requests/:mr_iid/notes`) if `$CI_MERGE_REQUEST_IID`
   is set.

**TASK=generate_mr_description**: Draft a merge request description from the diff.

1. Fetch the MR diff using `GET /projects/:id/merge_requests/:mr_iid/changes`.
2. Summarise what changed, why, and what the reviewer should focus on.
3. Include a test plan checklist based on changed file types.
4. Update the MR description using `PUT /projects/:id/merge_requests/:mr_iid`
   only if the existing description is empty or contains a placeholder.

**TASK=code_review**: Post an automated code review on the MR diff.

1. Fetch the diff using `GET /projects/:id/merge_requests/:mr_iid/changes`.
2. Review for: logic errors, missing error handling, security concerns (hardcoded
   credentials, SQL injection patterns, unsafe deserialization), and style issues
   that lint rules would not catch.
3. Post inline review comments using the GitLab Discussions API
   (`POST /projects/:id/merge_requests/:mr_iid/discussions`) for line-level
   findings.
4. Post a summary note with overall risk level (low/medium/high) and a list of
   findings ordered by severity.

Common constraints:

- Read repository files using Claude Code's built-in file tools; do not `cat`
  sensitive paths outside the workspace.
- All GitLab API calls must include `PRIVATE-TOKEN: $GITLAB_TOKEN` header.
- Keep note text under 65,536 characters (GitLab note body limit).
- If `$CI_MERGE_REQUEST_IID` is not set, skip API write steps and print the
  output to stdout for the job log instead.

## Features

- Triages pipeline failures and posts a root-cause summary to the MR.
- Drafts MR descriptions from diffs, skipping non-empty descriptions.
- Posts inline code review comments and a severity-ranked summary via the GitLab
  Discussions API.
- Guards against writing to MRs when not in a merge request pipeline context.

## Use Cases

- Automatically triage flaky or broken CI pipelines and surface the root cause
  in the MR before engineers start investigating.
- Generate a first-pass MR description for engineers who open draft MRs without
  filling in the template.
- Run a lightweight automated code review on every MR before human reviewers
  start, flagging obvious issues early.
- Reduce review queue wait times by providing a pre-triage summary on large diffs.

## Source Notes

- Claude Code supports headless operation via the `--print` flag and
  `--dangerously-skip-permissions` for CI/non-interactive environments, as
  documented in the Claude Code features overview.
- GitLab CI exposes `$CI_PROJECT_ID`, `$CI_MERGE_REQUEST_IID`, and
  `$CI_JOB_ID` as built-in variables usable without additional configuration.
- The GitLab Notes API and Discussions API accept `PRIVATE-TOKEN` auth and are
  the standard mechanism for programmatic MR comments.

## Duplicate Check

The content tree and open PRs were checked for GitLab CI and pipeline automation
agents. `ai-devops-automation-engineer-agent.mdx` covers general DevOps automation
at the engineer-role level. `github-community-issue-triage-agent.mdx` covers
GitHub issue triage. This entry is distinct: it is scoped specifically to GitLab
CI pipeline jobs, the GitLab API, and the three concrete automation tasks that
make sense in that context (failure triage, MR description, code review).

## Editorial Disclosure

Submitted as an independent community agent entry by `jaso0n0818`, based on
public Claude Code and GitLab CI documentation. No paid placement, referral, or
affiliate relationship.

## Sources

- Claude Code features overview: https://code.claude.com/docs/en/features-overview
- Claude Code skills documentation: https://code.claude.com/docs/en/skills
- GitLab CI/CD predefined variables: https://docs.gitlab.com/ci/variables/predefined_variables/
- GitLab Notes API: https://docs.gitlab.com/api/notes/
- GitLab Merge Requests API: https://docs.gitlab.com/api/merge_requests/