skills/common/engineering/implement-issue/SKILL.md

name, description, disable-model-invocation

name	description	disable-model-invocation
implement-issue	Dispatch a child agent in an isolated git worktree to implement a `ready-for-agent` issue end-to-end.	true

Implement Issue

Dispatch a child agent in an isolated git worktree to implement a ready-for-agent issue end-to-end — explore, implement with TDD, run the full quality gate, push a branch, create a PR, comment on the issue, and update labels.

The issue tracker conventions live in docs/agents/issue-tracker.md and the triage label vocabulary in docs/agents/triage-labels.md. Both should have been provided to you already.

Invocation

/skill:implement-issue <N> [--base <branch>] [--force]

• <N> — required, the issue number
• --base <branch> — optional, target base branch (default: repo default branch).
• --force — optional, allow overwriting an existing worktree.

Agent CLI Configuration

The CLI agent for child agents is configured in docs/agents/agent-cli.md. This file is written by /setup-skills Section E and contains:

selected: <agent-name>
binary: <binary-name>
args: "<arguments including @{prompt}>"

Supported agents and their configurations are defined in agents-seed.md in the setup-skills skill directory.

Process

1. Pre-flight checks

Stop on any failure and report clearly what needs fixing. Do not proceed.

1b. Issue exists and is open

If the issue is not found or state is not open, report and stop.

1c. Issue is labeled ready-for-agent

Check that the issue's labels include ready-for-agent. If not, report the current state and point the user to /triage. Stop.

1d. No open blockers

Read the issue body for "Blocked by #M" references. For each referenced issue, check whether it is open:

If any blocker is open, report the blocking issues and stop.

1e. Remote exists and base branch is reachable

Default base is the repo's default branch — infer from git ls-remote --heads origin (look for main or master). Allow an explicit --base <branch> override.

git ls-remote --heads origin <base>

If the remote is unreachable or the base branch doesn't exist, report and stop.

1f. Branch name is free

Derive the branch name from the issue title:

• Format: issue-<N>-<slug>
• Slug: lowercase the title, strip to [a-z0-9-], truncate to ~4–5 short words (max ~50 chars), collapse double hyphens
• If the title yields no usable slug, fall back to issue-<N>

Check that the branch doesn't already exist on the remote:

git ls-remote --heads origin <branch-name>

If it exists, report and stop. (No auto-suffix, no force-push.)

1g. Worktree path is free

The worktree path is a sibling to the main repo: ../<repo-name>-issue-<N>. Check that it doesn't already exist:

ls -d ../<repo-name>-issue-<N>

If it exists, report and stop. Let the user override with --force.

1h. Running inside a tmux session

Confirm $TMUX is set. If not, report "This skill requires a tmux session. Start tmux and rerun." and stop.

1i. Read agent CLI config

Read docs/agents/agent-cli.md and parse the selected, binary, and args fields. If the file is missing or malformed, report:

Agent CLI not configured. Run /setup-skills Section E to configure the CLI agent for child agents.

Stop.

1j. Validate binary on PATH

Confirm the configured binary is on PATH:

command -v <binary>

If the binary is not found, fail with:

Agent '' not found on PATH — rerun /setup-skills to reconfigure.

Stop.

2. Setup

2a. Label the issue in-progress

Change the issue triage labels to in-progress

2b. Create the worktree

git worktree add -b <branch-name> ../<repo-name>-issue-<N> <base>

3. Compose and write the child prompt

Assemble a single prompt that the child agent will receive. Include:

• Issue body — the full markdown body of the issue.
• Comments — all comments, if any
• Standing instruction: "Implement using TDD: write a failing test first, make it pass, refactor. Explore the codebase before writing code. Respect ADRs and the project domain glossary. Set up the project (install dependencies, build) before starting. The issue body may contain Implementation Decisions and Testing Decisions sections — treat these as constraints."
• Context: "Base branch: <base>. Target your PR at <base>. Branch name: <branch-name>."
• Checklist — a numbered checklist the child should work through:
  1. Explore the codebase and read the issue body + comments thoroughly
  2. Install dependencies and build the project
  3. Implement the change using TDD (red-green-refactor)
  4. Run the full project quality gate (infer from package.json, Makefile, Cargo.toml, etc.), fix until green
  5. Commit with conventional commits (feat: for enhancement, fix: for bug) referencing (#<N>)
  6. Push the branch: git push origin <branch-name>
  7. Create a PR with: link to the issue, one-sentence summary, short key-changes list
  8. Comment on the issue with the PR link: "PR opened: <url>"
  9. Change the issue triage label to needs-review
  10. remove the prompt file from /tmp (the child may have already read it)
  11. Print DONE — issue #<N>
• Failure instruction: "If any step fails, report where you stopped and what remains for manual recovery. Print the exact commands needed."

Write the full prompt to a temp file:

cat > /tmp/issue-<N>-prompt.md <<'PROMPT_EOF'
<full-composed-prompt>
PROMPT_EOF

4. Launch the child

4a. Detect runtime environment

Check if mise is available:

command -v mise

If available, use mise x --allow-env='*' -- as the runner prefix. Otherwise, fall back to $SHELL -c.

4b. Compose the agent command

Substitute {prompt} in the configured args with the absolute path to the temp prompt file. The prompt file path is /tmp/issue-<N>-prompt.md:

prompt_file="/tmp/issue-<N>-prompt.md"
substituted_args="${args//\{prompt\}/$prompt_file}"

• If args was non-empty: the agent command is <binary> $substituted_args
• If args was empty (stdin-piping agents): the agent command is cat $prompt_file | <binary>

4c. Compose the full tmux command

Use $substituted_args from step 4b:

tmux new-window -n "issue-<N>-<repo-slug>" -c <absolute-worktree-path> "<runner-prefix> <binary> $substituted_args"

With mise:

tmux new-window -n "issue-<N>-<repo>" -c /path/to/worktree "mise x --allow-env='*' -- $binary $substituted_args"

Without mise (fallback):

tmux new-window -n "issue-<N>-<repo>" -c /path/to/worktree "$SHELL -c '$binary $substituted_args'"

For stdin-piping agents (empty args), use the pipe form:

With mise:

tmux new-window -n "issue-<N>-<repo>" -c /path/to/worktree "mise x --allow-env='*' -- sh -c 'cat $prompt_file | $binary'"

Without mise:

tmux new-window -n "issue-<N>-<repo>" -c /path/to/worktree "$SHELL -c 'cat $prompt_file | $binary'"

The window stays open after the child completes so the user can review the output.

Do not remove the prompt file immediately — the child agent may not have read it yet. The file will be read from /tmp and cleaned up by the OS or the child after use.

5. Print summary

After launching, print:

• Issue number and title
• Worktree path
• Branch name
• Base branch
• Agent used (from docs/agents/agent-cli.md)
• Tmux window name (so the user can find it)
• Cleanup command: git worktree remove <worktree-path> && git worktree prune

The parent's turn ends here. The user can dispatch another issue immediately.