Install

macOS users can brew install:

  brew install agent-ecosystem/tap/agentsummons

For other install options, including go install, npm, PyPI, and prebuilt binaries, refer to Installation.

Invoke a harness

To start an agent session with your preferred harness, use the agentsummons run command:

  agentsummons run --harness claude-code -p "Summarize this repo" \
  --allowed-tools Read,Grep,Glob --auto-approve

By default, agentsummons acts as a transparent wrapper. Harness stdout/stderr pass through and the harness exit code propagates.

Get a machine-readable result

To get output in a machine-readable format, use the --json flag:

  agentsummons run --harness codex -p "hi" --model gpt-5.6-terra --json

--json swaps to a single result envelope on stdout with the harness output embedded. Use this format for scripts and containers. The envelope stamps the installed harness version and a drift_hint when that version is newer than the flag surface this build was validated against, letting you know to check the output as invocation behavior may have changed.

Check your harnesses

To check installed harness versions against agentsummons before running a session, use the doctor command:

  agentsummons doctor

doctor compares installed harness versions against the validated flag surface without running anything except version commands. It’s a cheap pre-experiment gate. For more details, refer to Flag drift.