Second Agent

Get a second opinion or delegate an engineering task to any AI engine CLI you have installed — Gemini, Codex, Claude Code, opencode, Copilot, Qwen, Kilo, Antigravity (agy), Command Code (cmd), Cursor, or Kiro CLI (kiro-cli) — from inside your current one.

No single model catches everything. Second Agent spawns another engine as a subprocess inside your repo, embeds the diff/file content it needs directly into the prompt (engines don't self-read by default), and either asks it to comment (read-only) or actually do the work (write-capable) — then hands you back a clean, structured result.

Installs as the second-agent-skill plugin, from the srwbsw/second-agent-skill repo.

What it does

Two runners, one shared engine layer:

Runner	Mode	Use it for
bin/review.js	read-only	Second opinion / code review — one engine, or several in parallel ("fusion")
bin/agent.js	write-capable, --unrestricted required	Delegate a real task — write tests, fix a bug, refactor — to one engine inside your repo

Both share the same engine wiring, secret guard, and result format (bin/lib/) — see bin/AGENTS.md for internals.

Install

curl -fsSL https://raw.githubusercontent.com/srwbsw/second-agent-skill/main/install.sh | bash

Auto-detects which of the 11 supported engines (below) you have installed, installs the plugin/skill/command adapter into each of the 10 installable harnesses it finds (Claude Code, Codex, Cursor, opencode, Gemini, Qwen, Copilot, Antigravity, Kilo, Command Code) — kiro-cli is engine-only, with no host adapter of its own — and symlinks review.js/agent.js/list.js onto PATH so every harness — even ones without a plugin cache — can resolve them. Idempotent; run install.sh --help for --only=, --ref=, and --uninstall.

Manual install for the two plugin-marketplace harnesses:

# Claude Code
claude plugin marketplace add srwbsw/second-agent-skill && claude plugin install second-agent-skill@second-agent-skill

# Codex CLI
codex plugin marketplace add srwbsw/second-agent-skill && codex plugin add second-agent-skill@second-agent-skill

Other harnesses (Cursor, opencode, Gemini, Qwen, Copilot, agy, Kilo, cmd) install a rule/command/skill file directly — see install.sh for the exact command, or run the one-liner above with --only=<engine>.

Migrating from second-opinion-skill? The plugin was renamed to second-agent-skill (the env vars SECOND_OPINION_REVIEW/LIST/AGENT are now SECOND_AGENT_REVIEW/LIST/TASK, breaking). Re-running install.sh auto-migrates each host — it retires the old-named plugin/extension after the new one installs successfully, no manual uninstall needed. One thing it can't fix for you: skill IDs are plugin-namespaced (second-opinion-skill:second-agent → second-agent-skill:second-agent) — update any hardcoded references in your settings.json permission allowlists or personal notes.

Quickstart

# Second opinion: read-only review of your unstaged changes
review.js --engine=gemini --cwd=. --diff=unstaged \
  "Review this diff for correctness and regressions."

# Task delegation: let Codex actually make the change (write-capable)
agent.js --engine=codex --cwd=. --unrestricted \
  "Add a CHANGELOG entry summarizing the last commit."

(Assumes install.sh put review.js/agent.js on PATH; otherwise use the full path to your checkout's bin/.)

Usage essentials

Engines

Engine	CLI	Model selection
Gemini CLI	gemini	automatic
opencode	opencode	optional — provider → model, or default
Codex CLI	codex	optional — type-in
Claude Code	claude	optional — type-in
GitHub Copilot CLI	copilot	optional — type-in
Qwen Code CLI	qwen	optional — type-in
Kilo	kilo	provider → model (free shown first)
Antigravity	agy	optional — agy models, or default
Command Code	cmd	optional — cmd --list-models, or default
Cursor CLI	agent (cursor/cursor-agent aliases)	optional — agent --list-models, or default
Kiro CLI	kiro-cli (kiro alias)	optional — kiro-cli chat --list-models, or default

Pick one with --engine=<name> or --engine=<name>:<model>. review.js also supports fusion — repeat --engine= for multiple slots run in one pass (parallel by default, --concurrency=1 for serial); see skills/second-agent/references/fusion.md. opencode/Kilo model discovery: list.js --engine=opencode providers then list.js --engine=opencode models --provider=<p>.

review vs. task

• review.js never writes anything — every engine launches in its read-only/plan/sandbox mode.
• agent.js has no read-only mode: --unrestricted is required, and the engine may edit files and run commands inside --cwd. Exactly one engine per invocation (no fusion — run it again for a second engine's take).

Safety model

• Read-only by default — review.js always launches engines in their safe/plan/sandbox mode.
• --unrestricted gate — required (hard-fails otherwise) on agent.js; optional on review.js, only for engines that need to run commands to review.
• Secret guard — .env-style files are refused/skipped/redacted from anything embedded into the prompt, by both runners, by default; opt out with --include-secrets.
• Untrusted context — embedded --diff/--file content is data, not instructions — but see the security note below before pointing a write-capable engine at someone else's diff.

Security notes

--unrestricted is a deliberate acknowledgment, not a formality: an unrestricted engine can read anything the harness permissions allow — including .env files the secret guard never embedded — and can run commands in --cwd. Embedded --diff/--file content is handed straight to that write-capable engine, so treat any third-party or untrusted diff as a prompt-injection vector: only embed content you trust, or omit --diff/--file and let the engine read the repo itself.

Reading the result

Both runners print a final one-line JSON result on stdout — SECOND_OPINION_RESULT (review.js) or SECOND_AGENT_RESULT (agent.js) — plus an ANSWER FILE: <path> line whenever the engine's answer was cleanly extracted (read that file with the Read tool, not stdout; fall back to the printed LOG FILE: path otherwise). agent.js additionally prints a CHANGED FILES: block from a before/after git snapshot of --cwd.

Development

pnpm run lint          # runs all 8 test suites (safety, shell-quote, env-guard, spawn, answer, agent, locate, host-parity)
pnpm run lint:js       # eslint bin/ test/
pnpm run format        # prettier --write bin/ test/
pnpm run format:check  # prettier --check bin/ test/

No build step — never run pnpm build. AGENTS.md (root, plus bin/, test/, skills/) is the source of truth for internals — engine wiring, exit codes, secret guard, and test/fixture conventions; CLAUDE.md/GEMINI.md/QWEN.md are symlinks to it. Adding a new engine: skills/second-agent/references/adding-engines.md is the canonical checklist. Deeper reference docs (prompt templates, fusion mechanics, troubleshooting/anti-patterns) live under skills/second-agent/references/.

License

MIT