# Sub Agent

> Delegate a self-contained task to a sub-Agent (Codex, Claude Code, or Pi via background process). The original use case was coding tasks — building features, reviewing PRs, refactoring — but the skill is the generic "spawn a sub-Agent with full tool surface" slot used by meta-skill DAG steps for any LLM-driven sub-task (policy review, trace parsing, report synthesis, document generation). Renamed from ``coding-agent`` to reflect actual usage; the wrapped CLIs (codex / claude / pi) still bias toward coding workloads. Use when: (1) building/creating new features or apps, (2) reviewing PRs (spawn in temp dir), (3) refactoring large codebases, (4) iterative tasks that need file exploration, (5) meta-skill steps requiring full tool/LLM agency. NOT for: simple one-liner fixes (just edit), reading code (use read tool), thread-bound ACP harness requests in chat (for example spawn/run Codex or Claude Code in a Discord thread; use sessions_spawn with runtime:"acp"), or any work in ~/clawd workspace (never spawn agents

- Skill: `gabrielmoreira/sub-agent` (Agent Skill)
- Install (CLI): `npx skillmds@latest add gabrielmoreira/sub-agent`
- Raw SKILL.md: https://api.skillmd.com/api/skills/gabrielmoreira/sub-agent/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: AI & ML
- Author: gabrielmoreira (https://skillmd.com/u/gabrielmoreira)
- Updated: 2026-09-09
- Page: https://skillmd.com/skills/gabrielmoreira/sub-agent

---


# 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.
Wrapping CLIs are coding-oriented, but the skill itself is used as
the generic sub-Agent slot by meta-skill DAGs for any LLM-driven
sub-task (file edits, document generation, policy review, etc.).

Use opensquilla's `exec_command`, `background_process`, and `process` tools for coding agent work. 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:

```bash
# ✅ 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:

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

# For background execution: use background_process

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

### OpenSquilla Tool Parameters

| Tool | Key parameters | Description |
| ---- | -------------- | ----------- |
| `exec_command` | `command`, `workdir`, `timeout` | Run a foreground shell command. |
| `background_process` | `command`, `workdir`, `timeout` | Start a long-running command and return `session_id`. |
| `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:

```bash
# 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 + background_process

For longer tasks, use `background_process`:

```bash
# Start agent in target directory.
background_process(workdir="~/project", command="codex exec --full-auto 'Build a snake game'")
# Returns session_id for tracking

# 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

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

# Background for longer work
background_process(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.

```bash
# 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!)

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

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

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

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

---

## OpenCode

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

---

## Pi Coding Agent

```bash
# 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:

```bash
# 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
background_process(workdir="/tmp/issue-78", command="pnpm install && codex exec --full-auto 'Fix issue #78: <description>. Commit and push.'")
background_process(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

1. **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)
2. **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.
3. **Be patient** - don't kill sessions because they're "slow"
4. **Monitor with process:log** - check progress without interfering
5. **--full-auto for building** - auto-approves changes
6. **vanilla for reviewing** - no special flags needed
7. **Parallel is OK** - run many Codex processes at once for batch work
8. **NEVER start Codex inside your OpenSquilla state directory** (`$OPENSQUILLA_STATE_DIR`, default `~/.opensquilla/state`) - keep agent state separate from project worktrees.
9. **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:**

```bash
background_process(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"_ 🦞