LLM Commit Messages

Worktrunk generates commit messages by building a templated prompt and piping it to an external command. This integrates with wt merge, wt step commit, and wt step squash.

Setup

Any command that reads a prompt from stdin and outputs a commit message works. Add to ~/.config/worktrunk/config.toml:

Claude Code

[commit.generation]
command = "CLAUDECODE= MAX_THINKING_TOKENS=0 claude -p --model=haiku --tools='' --disable-slash-commands --setting-sources='' --system-prompt=''"

CLAUDECODE= unsets the nesting guard so claude -p works from within a Claude Code session. The other flags disable tools, skills, settings, and system prompt for fast text-only output. See Claude Code docs for installation.

Codex

[commit.generation]
command = "codex exec -m gpt-5.1-codex-mini -c model_reasoning_effort='low' -c system_prompt='' --sandbox=read-only --json - | jq -sr '[.[] | select(.item.type? == \"agent_message\")] | last.item.text'"

Uses the fast mini model with low reasoning effort and an empty system prompt for faster output. Requires jq for JSON parsing. See Codex CLI docs.

Other tools

# opencode — use a fast model variant
command = "opencode run -m anthropic/claude-haiku-4.5 --variant fast"

# llm
command = "llm -m claude-haiku-4.5"

# aichat
command = "aichat -m claude:claude-haiku-4.5"

How it works

When worktrunk needs a commit message, it builds a prompt from a template and pipes it to the configured command via shell (sh -c). Environment variables can be set inline in the command string.

Usage

These examples assume a feature worktree with changes to commit.

wt merge

Squashes all changes (uncommitted + existing commits) into one commit with an LLM-generated message, then merges to the default branch:

$ wt merge
◎ Squashing 3 commits into a single commit (5 files, +48)...
◎ Generating squash commit message...
   feat(auth): Implement JWT authentication system
   ...

wt step commit

Stages and commits with LLM-generated message:

$ wt step commit

wt step squash

Squashes branch commits into one with LLM-generated message:

$ wt step squash

See wt merge and wt step for full documentation.

Branch summaries (experimental)

With summary = true and a [commit.generation] command configured, Worktrunk generates LLM branch summaries — one-line descriptions of each branch's changes since the default branch.

Summaries appear in:

• wt switch interactive picker — preview tab 5
• wt list --full — the Summary column (see wt list)

Enable in user config:

[list]
summary = true

Disabled by default — when enabled, each branch's diff is sent to the configured LLM for summarization. Results are cached until the diff changes.

Prompt templates

Worktrunk uses minijinja templates (Jinja2-like syntax) to build prompts. There are sensible defaults, but templates are fully customizable.

Custom templates

Override the defaults with inline templates:

[commit.generation]
command = "llm -m claude-haiku-4.5"

template = """
Write a commit message for this diff. One line, under 50 chars.

Branch: {{ branch }}
Diff:
{{ git_diff }}
"""

squash-template = """
Combine these {{ commits | length }} commits into one message:
{% for c in commits %}
- {{ c }}
{% endfor %}

Diff:
{{ git_diff }}
"""

Template variables

Template syntax

Templates use minijinja, which supports:

• Variables: {{ branch }}, {{ repo | upper }}
• Filters: {{ commits | length }}, {{ repo | upper }}
• Conditionals: {% if recent_commits %}...{% endif %}
• Loops: {% for c in commits %}{{ c }}{% endfor %}
• Loop variables: {{ loop.index }}, {{ loop.length }}
• Whitespace control: {%- ... -%} strips surrounding whitespace

See wt config create --help for the full default templates.

Fallback behavior

When no LLM is configured, worktrunk generates deterministic messages based on changed filenames (e.g., "Changes to auth.rs & config.rs").