Scripting and CI

One prompt, one answer

-p runs a single turn and exits. Only the final answer goes to stdout; progress goes to stderr, so you can pipe or capture the answer cleanly.

anchor -p "why does the build fail?"
anchor -p "summarize the changes on this branch" > summary.md

Piped input is added to the prompt, or is the prompt when there’s no argument:

git diff | anchor -p "review this change"
cat error.log | anchor -p

An @path in the prompt is only attached in the interactive REPL. In -p it stays plain text, and the model reads the file itself if it needs it.

Approvals in -p

Nobody can answer a prompt in -p mode, so anything that would ask is refused, and the refusal is reported on stderr. Read-only work, such as reading files or running git diff, works as usual.

Commands and MCP tools you’ve answered “always” to in an interactive session in the same directory are saved and run without asking, so a -p run can use npm test once you’ve allowed npm.

To allow specific things for one run, pass --allow once for each: a program, an MCP tool (mcp__server__tool), or edits for file writes in the directory. A command runs only when every program in it is allowed. Nothing is saved.

anchor -p --allow edits --allow npm "fix the failing test" --until "npm test"

To allow everything that would ask, pass --yolo. Hard denials and secret masking still apply either way.

Limits

--max-rounds <n> stops the run after n model requests, counted across all --until rounds. Each sub-agent gets the same limit of its own; one that reaches it stops and reports what it has. --timeout <seconds> stops it after that long, including time spent running the check but not time spent starting MCP servers: startup gets a separate limit of the same length, and a server that hasn’t connected by then is skipped. Both end the run with a distinct exit code and result status, so a calling program can tell them apart from a failure.

anchor -p --yolo "fix the failing test" --until "npm test" --max-rounds 40 --timeout 900

Project MCP servers you’ve never approved interactively are skipped in -p mode.

Exit codes

Code	Meaning
`0`	The turn completed (and the `--until` check passed, if set).
`1`	An error, such as a provider or network failure.
`2`	A usage error in the command line.
`3`	The loop guard stopped a turn that was going in circles.
`4`	The `--until` check never passed.
`5`	The run reached `--max-rounds`.
`124`	The run reached `--timeout`.
`130`	Cancelled with Ctrl+C.

JSON output

With --json, every event is written to stdout as one JSON object per line, ending with a result line:

anchor -p "list the TODOs" --json

{"type":"tool_start","id":"call_1","name":"grep","summary":"TODO"}
{"type":"tool_end","id":"call_1","name":"grep","ok":true,"result":"src/a.cs:12: // TODO ..."}
{"type":"text","text":"There are 3 TODOs:"}
{"type":"usage","input":5210,"output":84,"cached":2304}
{"type":"turn_end","reason":"completed","detail":null}
{"type":"result","status":"completed","text":"There are 3 TODOs: ...","check":null,"files_changed":[],"session":"20260928-225355-be7b","usage":{"input":5210,"output":84,"cached":2304}}

Every event type is in the JSON reference.

In CI

A GitHub Actions step that asks anchor to fix lint errors until the linter passes:

- name: Fix lint
  env:
    ANTHROPIC_API_KEY: ${{ secrets.ANTHROPIC_API_KEY }}
  run: |
    curl -fsSL https://raw.githubusercontent.com/fuseraft/anchor/main/install.sh | bash
    ~/.local/bin/anchor -p --yolo "fix the lint errors" --until "npm run lint"

Editors and other tools

anchor --json without -p is a line protocol for driving anchor from an editor or another program: send requests on stdin, read events on stdout, and answer approval prompts yourself. See the JSON reference.