coding-agent

A way to delegate coding work to Codex, Claude Code, or Pi agents through terminal processes, including background jobs.

In plain words
What is it for?
It helps build features or applications, review pull requests, refactor large projects, and run coding tasks that require repeated file exploration.
Why use it?
It helps hand off feature work, reviews, refactors, and large codebase exploration while keeping the correct terminal setup for each agent.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/understudy-ai/understudy/coding-agent
Any agent
npx skills add understudy-ai/understudy --skill coding-agent
Clone the repo
git clone --depth 1 https://github.com/understudy-ai/understudy

Made for: Claude Code, Codex.

Per session 160 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,730 The whole file, excluding the scripts and references it only reads on demand.
Security scan B 1 finding. Scan, not verified.
Origin 75% copy Near-identical to another mod in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00160 $0.02730
Opus 5 $0.00080 $0.01365
Sonnet 5 $0.00032 $0.00546
Haiku 4.5 $0.00016 $0.00273

Measured yesterday against content hash bedf22709b3f, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade B, and why

coding-agent scanned grade B with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Reads agent configuration directoriesmediumAgent snooping

.claude/, .codex/, .gemini/ hold keys, settings and other credentials a mod has no legitimate need for.

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

This is a copy

75% identical to coding-agent — 95 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

skills/coding-agent/SKILL.md · 296 lines

How it starts

The opening of the file, as written. The whole thing — 296 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Coding Agent (bash-first)

Use bash (with optional background mode) for all coding agent work. Simple and effective.

⚠️ PTY Mode: Codex/Pi/OpenCode yes, Claude Code no

For Codex, Pi, and OpenCode, PTY is still required (interactive terminal apps):

# ✅ Correct for Codex/Pi/OpenCode
bash pty:true 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 background:true on the exec tool

# ❌ Wrong for Claude Code
bash pty:true command:"claude --dangerously-skip-permissions 'task'"

Bash Tool Parameters

Parameter Type Description
command string The shell command to run
pty boolean Use for coding agents! Allocates a pseudo-terminal for interactive CLIs
workdir string Working directory (agent sees only this folder's context)
background boolean Run in background, returns sessionId for monitoring
timeout number Timeout in seconds (kills process on expiry)
elevated boolean Run on host instead of sandbox (if allowed)

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)
send-keys Send key tokens or hex bytes
paste Paste text (with optional bracketed mode)
kill Terminate the session

Read the full file on GitHub · 296 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. yesterday First seen · 296 lines · 160 tokens per session scan B bedf22709b3f

Subscribe to this mod's changes

coding-agent is a skill published in the GitHub repository understudy-ai/understudy (456 stars, last pushed 2mo ago), licensed MIT. It adds 160 tokens to every session and 2,730 once invoked, about $0.0008 per session on Opus 5. A static security scan graded it B with 1 finding (reads agent configuration directories). It is 75% identical to coding-agent, differing in 95 lines, and is treated as a copy.