@particle-academy/prism-acp

A provider API client needs an API key and bills per token. A user who pays for a subscription already has working credentials -- in the coding-agent CLI's own store, not in any protocol -- and the way to use them is to run the CLI they belong to. So this package spawns the agent binary and translates, rather than reimplementing the agent against an HTTP API the user has no key for. In subscription mode (the default) it never reads a credential, never holds one, and never puts one on a wire.

Speaks the Agent Client Protocol to a coding-agent CLI the user has already authenticated: Claude through stream-json, Codex through codex app-server. A client -- an editor, a terminal UI, an orchestrator -- gets structured state instead of guessing it from bytes on a pseudo-terminal: session state, streaming assistant output with thought content separable, tool calls with status, token usage and cost. Zero runtime dependencies. The spawned CLI's environment is built allow-list-first and withholds credentials such as ANTHROPIC_API_KEY that would otherwise outrank the CLI's own login. Early: initialize, session/new, session/load, session/prompt and session/cancel work over a pipe; session/set_mode and the client-side fs/* and terminal/* calls do not yet, and the surface will change.

npm install @particle-academy/prism-acp. It drives the agent CLI already on the machine, so the user's existing subscription login is the authentication -- no API key to supply and no adapter program to install. An app that bills per token instead can hand the drivers an API key. Full protocol coverage, driver capabilities and the session-resume rules are in the README.