sub-agent

Delegate a self-contained task to a coding assistant through a non-interactive background process. Use for feature development, code review, refactoring, and tasks requiring substantial file exploration.

SKILL.md

Quality

Evals

Security

Sub-Agent (opensquilla process tools)

Generic "spawn a sub-Agent" entry point for delegating self-contained tasks to Codex / Claude Code / OpenCode / Pi via background process. Use this playbook for self-contained coding and file-editing tasks.

Use OpenSquilla's exec_command and process tools for coding agent work. exec_command starts both short and long commands; use yield_time_ms=0 for a long run and keep the returned execution handle. OpenSquilla does not expose a bash tool; do not use the legacy bash tool-call DSL.

Non-Interactive CLI Mode

OpenSquilla's process tools do not expose a pty parameter. Prefer non-interactive command modes that run and exit cleanly:

# ✅ Correct for Codex/Pi/OpenCode
exec_command(command="codex exec 'Your prompt'")

For Claude Code (claude CLI), use --print --permission-mode bypassPermissions instead. --dangerously-skip-permissions with PTY can exit after the confirmation dialog. --print mode keeps full tool access and avoids interactive confirmation:

# ✅ Correct for Claude Code (no PTY needed)
cd /path/to/project && claude --permission-mode bypassPermissions --print 'Your task'

# For background execution: use exec_command(yield_time_ms=0, ...)

# ❌ Wrong for Claude Code
exec_command(command="claude --dangerously-skip-permissions 'task'")

OpenSquilla Tool Parameters

Tool	Key parameters	Description
`exec_command`	`command`, `workdir`, `timeout`, `yield_time_ms`	Start a shell command; use `yield_time_ms=0` for a long run and keep the returned execution handle.
`process`	`action`, `session_id`, `data`, `offset`, `limit`	Poll, log, write to, or stop a background process.

Process Tool Actions (for background sessions)

Action	Description
`list`	List all running/recent sessions
`poll`	Check if session is still running
`log`	Get session output (with optional offset/limit)
`write`	Send raw data to stdin
`submit`	Send data + newline (like typing and pressing Enter)
`eof`	Close stdin
`remove`	Remove a finished session from the process list
`kill`	Terminate the session

Quick Start: One-Shot Tasks

For quick prompts/chats, create a temp git repo and run:

# Quick chat (Codex needs a git repo!)
SCRATCH=$(mktemp -d) && cd $SCRATCH && git init && codex exec "Your prompt here"

# Or in a real project
exec_command(workdir="~/Projects/myproject", command="codex exec 'Add error handling to the API calls'")

Why git init? Codex refuses to run outside a trusted git directory. Creating a temp repo solves this for scratch work.

The Pattern: workdir + exec_command + process

For longer tasks, use exec_command(yield_time_ms=0, ...):

# Start agent in target directory.
exec_command(yield_time_ms=0, workdir="~/project", command="codex exec --full-auto 'Build a snake game'")
# Returns an execution handle (the current compatibility field is `session_id`)

# Wait for it to finish — blocks until the process exits (or the timeout
# elapses, in which case just call wait again). Prefer this over polling in a
# loop: a looped process(action="poll") burns a full turn + tokens each time.
process(action="wait", session_id="XXX")

# Peek at output without blocking (optional, for progress)
process(action="log", session_id="XXX")

# Send input (if agent asks a question)
process(action="write", session_id="XXX", data="y")

# Submit with Enter (like typing "yes" and pressing Enter)
process(action="submit", session_id="XXX", data="yes")

# Kill if needed
process(action="kill", session_id="XXX")

Why workdir matters: Agent wakes up in a focused directory, doesn't wander off reading unrelated files (like your soul.md 😅).

Codex CLI

Model: gpt-5.2-codex is the default (set in ~/.codex/config.toml)

Flags

Flag	Effect
`exec "prompt"`	One-shot execution, exits when done
`--full-auto`	Sandboxed but auto-approves in workspace
`--yolo`	NO sandbox, NO approvals (fastest, most dangerous)

Building/Creating

# Quick one-shot
exec_command(workdir="~/project", command="codex exec --full-auto 'Build a dark mode toggle'")

# Background for longer work
exec_command(yield_time_ms=0, workdir="~/project", command="codex exec --full-auto 'Refactor the auth module'")

Reviewing PRs

⚠️ CRITICAL: Never review PRs in OpenSquilla's own project folder! Clone to temp folder or use git worktree.

# Clone to temp for safe review
REVIEW_DIR=$(mktemp -d)
git clone https://github.com/user/repo.git $REVIEW_DIR
cd $REVIEW_DIR && gh pr checkout 130
exec_command(workdir="$REVIEW_DIR", command="codex review --base origin/main")
# Clean up after: trash $REVIEW_DIR

# Or use git worktree (keeps main intact)
git worktree add /tmp/pr-130-review pr-130-branch
exec_command(workdir="/tmp/pr-130-review", command="codex review --base main")

Batch PR Reviews (parallel army!)

# Fetch all PR refs first
git fetch origin '+refs/pull/*/head:refs/remotes/origin/pr/*'

# Deploy the army - one Codex per PR
exec_command(yield_time_ms=0, workdir="~/project", command="codex exec 'Review PR #86. git diff origin/main...origin/pr/86'")
exec_command(yield_time_ms=0, workdir="~/project", command="codex exec 'Review PR #87. git diff origin/main...origin/pr/87'")

# Monitor all
process(action="list")

# Post results to GitHub
gh pr comment <PR#> --body "<review content>"

Claude Code

# Foreground
exec_command(workdir="~/project", command="claude --permission-mode bypassPermissions --print 'Your task'")

# Background
exec_command(yield_time_ms=0, workdir="~/project", command="claude --permission-mode bypassPermissions --print 'Your task'")

OpenCode

exec_command(workdir="~/project", command="opencode run 'Your task'")

Pi Coding Agent

# Install: npm install -g @mariozechner/pi-coding-agent
exec_command(workdir="~/project", command="pi -p 'Your task'")

# Non-interactive mode
exec_command(command="pi -p 'Summarize src/'")

# Different provider/model
exec_command(command="pi --provider openai --model gpt-4o-mini -p 'Your task'")

Note: Pi now has Anthropic prompt caching enabled (PR #584, merged Jan 2026)!

Parallel Issue Fixing with git worktrees

For fixing multiple issues in parallel, use git worktrees:

# 1. Create worktrees for each issue
git worktree add -b fix/issue-78 /tmp/issue-78 main
git worktree add -b fix/issue-99 /tmp/issue-99 main

# 2. Launch Codex in each
exec_command(yield_time_ms=0, workdir="/tmp/issue-78", command="pnpm install && codex exec --full-auto 'Fix issue #78: <description>. Commit and push.'")
exec_command(yield_time_ms=0, workdir="/tmp/issue-99", command="pnpm install && codex exec --full-auto 'Fix issue #99 from the approved ticket summary. Implement only the in-scope edits and commit after review.'")

# 3. Monitor progress
process(action="list")
process(action="log", session_id="XXX")

# 4. Create PRs after fixes
cd /tmp/issue-78 && git push -u origin fix/issue-78
gh pr create --repo user/repo --head fix/issue-78 --title "fix: ..." --body "..."

# 5. Cleanup
git worktree remove /tmp/issue-78
git worktree remove /tmp/issue-99

⚠️ Rules

Use the right execution mode per agent:
- Codex/Pi/OpenCode: non-interactive command mode (codex exec, opencode run, pi -p)
- Claude Code: --print --permission-mode bypassPermissions (no PTY required)
Respect tool choice - if user asks for Codex, use Codex.
- Orchestrator mode: do NOT hand-code patches yourself.
- If an agent fails/hangs, respawn it or ask the user for direction, but don't silently take over.
Be patient - don't kill sessions because they're "slow"
Monitor with process:log - check progress without interfering
--full-auto for building - auto-approves changes
vanilla for reviewing - no special flags needed
Parallel is OK - run many Codex processes at once for batch work
NEVER start Codex inside your OpenSquilla state directory ($OPENSQUILLA_STATE_DIR, default ~/.opensquilla/state) - keep agent state separate from project worktrees.
NEVER checkout branches inside the live OpenSquilla runtime state/workspace directories - use an explicit project worktree.

Progress Updates (Critical)

When you spawn coding agents in the background, keep the user in the loop.

Send 1 short message when you start (what's running + where).
Then only update again when something changes:
- a milestone completes (build finished, tests passed)
- the agent asks a question / needs input
- you hit an error or need user action
- the agent finishes (include what changed + where)
If you kill a session, immediately say you killed it and why.

This prevents the user from seeing only "Agent failed before reply" and having no idea what happened.

Auto-Notify on Completion

For long-running background tasks, ask the agent to print a clear completion line so progress is visible in process(action="log", ...) output:

... your task here.

When completely finished, send a brief status update in this session.

Example:

exec_command(yield_time_ms=0, workdir="~/project", command="codex exec --full-auto 'Build a REST API for todos.

When completely finished, print: Done: Built todos REST API with CRUD endpoints'")

This makes completion visible in the background process log.

Learnings (Jan 2026)

Prefer non-interactive modes: Coding agents are easiest to supervise when they print progress and exit cleanly.
Git repo required: Codex won't run outside a git directory. Use mktemp -d && git init for scratch work.
exec is your friend: codex exec "prompt" runs and exits cleanly - perfect for one-shots.
submit vs write: Use submit to send input + Enter, write for raw data without newline.
Sass works: Codex responds well to playful prompts. Asked it to write a haiku about being second fiddle to a space lobster, got: "Second chair, I code / Space lobster sets the tempo / Keys glow, I follow" 🦞

Repository: TokenRhythm/opensquilla
Path: src/opensquilla/skills/bundled/sub-agent/SKILL.md
Commit: 943b784

Last updated: 5 days ago
First committed: 3 months ago

Is this your skill?

If you maintain this skill, you can claim it as your own. Once claimed, you can manage eval scenarios, bundle related skills, attach documentation or rules, and ensure cross-agent compatibility.