Reference: `runtimes/*.yaml`

Each YAML file under runtimes/ defines one runtime adapter. File stem = runtime id used in agent runtime: fields.

Fields

Field	Type	Required	Notes
`binary`	string	yes	CLI binary name (resolved on `$PATH`) or absolute path.
`supports_mcp`	bool	no, default `false`	Must be `true` for participation in the mailbox. All shipped runtimes set this.
`session_resume`	string	no	Parsed-but-inert metadata, kept for back-compat. The actual resume strategy is hard-coded per runtime in `agent-wrapper.sh`: claude-code spawns with a deterministic UUIDv5 derived from `teamctl:<project>:<agent>` (`--session-id` to create, `--resume` to attach existing); codex reopens its newest session via `resume --last` scoped to the per-agent `CODEX_HOME`; opencode continues via `-c` scoped to the per-agent `OPENCODE_DB`; gemini has no equivalent. Setting this in a custom adapter is a no-op today.
`default_model`	string	no	Used when an agent doesn’t set its own `model:`.
`env`	map<string,string>	no	Merged into the agent’s environment on launch.

Shipped adapters

claude-code.yaml: Anthropic’s Claude Code CLI.
codex.yaml: OpenAI’s Codex CLI.
gemini.yaml: Google’s Gemini CLI.
opencode.yaml: OpenCode, the provider-agnostic terminal agent.

Example

# runtimes/aider.yaml: hypothetical adapter for aider
binary: aider
supports_mcp: true
default_model: sonnet
env:
  AIDER_CHAT_HISTORY_FILE: ""

session_resume was an early field for declaring resume strategy. It’s still parsed (back-compat) but inert: leave it out of new adapters. claude-code agents now auto-resume via deterministic UUIDv5 session ids; other runtimes either resume natively or don’t.

You’d also need an aider) case in bin/agent-wrapper.sh that knows how to pass aider’s own MCP-config and system-instruction flags. The shipped cases show the range: claude-code and gemini take the rendered JSON via --mcp-config, while codex and opencode have no such flag — codex’s MCP servers are rendered as [mcp_servers.*] tables into a per-agent CODEX_HOME/config.toml, and opencode’s ride the mcp block of a per-agent OPENCODE_CONFIG json.