Pi compose helper

runtime/cli.mjs is a one-request JSON-lines helper. It reads exactly one UTF-8 JSON value from stdin (at most 64 KiB) and writes exactly one JSON result line. The input is complete at EOF; stalled stdin exhausts the total budget and returns timeout. It accepts no command-line input, discovers no models, and never falls back to a model.

Request

{"version":1,"operation":"compose","model":{"provider":"openai-codex","id":"gpt-5.6-luna","thinking":"low"},"input":{"user":"...","assistant":"..."},"label":{"current":"","refresh":true}}

All keys are required and exact. version is 1; operation is compose; thinking is one of minimal, low, medium, high, xhigh, or max. Provider and model IDs are nonempty, control-free strings of at most 256 UTF-8 bytes. Combined input is at most 8192 bytes and the current label at most 120 bytes. Empty input fields are permitted.

The whole operation, including stdin, lazy SDK loading, runtime initialization, and completion, has one 15-second budget. After request validation it uses ModelRuntime.create({ signal, allowModelNetwork: false }), resolves only the requested provider/ID, and makes one completeSimple request with 256 tokens, no retries, and the requested reasoning level. Pi remains the credential authority. The helper does not load sessions, tools, extensions, context files, or auth files itself.

Results

Success is one line no larger than 4096 bytes:

{"version":1,"ok":true,"body":"Plain outcome","label":"Three word label"}

Bodies must contain non-whitespace plain text with no controls or Markdown and no more than 180 Unicode code points. When refresh is false, label is omitted. When it is true, a new label has 3–4 whitespace words and at most 60 bytes; KEEP retains a nonempty current label and is omitted from the result. If Pi returns documented phased text metadata, only final_answer text is parsed; commentary and thinking content are never treated as the result.

Failures are safe, non-diagnostic lines with one of invalid_request, unavailable_model, generation_failed, timeout, or invalid_output. Malformed, unreadable, or oversized input is invalid_request; a stalled input or exhausted total deadline is timeout. No request text, credentials, provider errors, reasoning, stack traces, or raw model output are returned.

The production entrypoint waits for the Node stdout write callback so the one line is flushed, and then exits explicitly. This releases unfinished stdin and provider handles after the result is delivered.

Packaging workaround

Pi coding-agent 0.85.0 publicly imported @earendil-works/pi-server while omitting it from its published manifest; 0.85.1 made the server and client commands source-only and no longer imports it. This package still declares the exact 0.85.1 server package, pinned in lockstep with the other Pi packages, but nothing in the helper or the coding-agent build imports it any more. It does not start a server or use Pi internal runtime APIs. The Nix runtime exposes this entry as steward-pi-helper, an absolute Node 24 wrapper; its package smoke coverage is documented in Nix packaging.