setup-agent-backend

name	setup-agent-backend
description	Configure a specific agent backend (claude_code, codex, opencode, anthropic, openai, google, ollama). Verifies the backend is reachable, runs a one-shot ping, and emits the `agent:` (+ optional `llm:`) block to inline into WORKFLOW.md. Called by other skills; rarely invoked directly.
version	1.0.0

setup-agent-backend

Configure a specific agent backend for Sinfonia. Returns a YAML snippet that other skills (setup-workflow, setup-state-machine) inline into the generated WORKFLOW.md.

When to use

• Invoked by setup-workflow during fresh project setup.
• Invoked by setup-state-machine when a state needs a different backend from the global default.
• Invoked directly by an operator who wants to switch a deployed Sinfonia to a new backend.

Procedure

1. Ask which backend

Offer:

Backend	Best for
claude_code	Anthropic's Claude Code CLI is installed; want subscription pricing
codex	OpenAI's Codex CLI is installed
opencode	sst/opencode is installed; want a multi-provider router (75+ providers, incl. local Ollama+LSP)
anthropic	direct Anthropic API; want raw control
openai	direct OpenAI API
google	direct Google AI / Gemini API
ollama	local Ollama daemon; no cloud costs

2. Verify the backend is reachable

Backend	Verification
claude_code	claude --version returns a version; which claude is non-empty
codex	codex --version returns a version
opencode	opencode --version returns a version (per 02-opencode-backend.md §4)
anthropic	$ANTHROPIC_API_KEY is non-empty; ping https://api.anthropic.com/v1/messages with a 1-token prompt
openai	$OPENAI_API_KEY is non-empty; ping /v1/chat/completions
google	$GOOGLE_API_KEY is non-empty; ping generativelanguage.googleapis.com/v1beta/models
ollama	curl -fsSL http://localhost:11434/api/tags returns 200

If verification fails, stop and surface the error. Do NOT emit a YAML block that points at an unreachable backend.

3. Auth setup

Backend	Auth flow
claude_code	claude /login (interactive — opens a browser). Operator runs this themselves.
codex	codex auth (interactive). Operator runs this themselves.
opencode	opencode auth login (interactive — picks one of OpenCode's 75+ providers). Operator runs this themselves.
anthropic / openai / google	Set the corresponding API key env var. The skill prompts for the name + verifies it's non-empty.
ollama	No auth.

4. One-shot ping (CLI backends only)

For claude_code, codex, opencode: run a one-shot test prompt and assert a non-empty response:

echo 'echo hello' | claude --quiet --prompt-stdin 2>&1 | tee /tmp/agent-ping.log
test -s /tmp/agent-ping.log  # non-empty

Adapt for the chosen backend (OpenCode uses --format json; see 02-opencode-backend.md §5 for the actual flag set).

5. Emit the YAML block

Render the appropriate template:

• templates/agent-claude-code.liquid
• templates/agent-codex.liquid
• templates/agent-opencode.liquid
• templates/agent-anthropic.liquid
• templates/agent-openai.liquid
• templates/agent-google.liquid
• templates/agent-ollama.liquid

Return the rendered snippet to the calling skill.

Templates

One template per backend, each emitting the agent: and (where applicable) llm: block.

See also

• crates/sinfonia/src/agent/opencode.rs rustdoc — the verified OpenCode flag set (relevant if you're configuring opencode).
• docs/SPEC.md §18.2 — the canonical backend table.