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Building on Letronna
Which way into Letronna fits your program, and what each one gives it.
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Each way in is a process your program starts and talks to on stdin and stdout. Letronna's approvals, rules and hooks apply to all of them, as they do in the terminal.
Pick one
- Your program wants an answer. Use
letronna -p. It runs one task in the project folder and prints the result, as text or JSON. - Your program is an editor. Use
letronna acp. The editor shows the turn as it runs and answers the approvals itself. - Your program is another agent. Use
letronna mcp serve. It keeps its own model and loop, and calls Letronna's tools when it needs them.
From a script
letronna -p never stops to ask, so choose a mode that allows what the task needs. For an answer your program can parse, ask for JSON:
letronna -p --output json "how many files are in this folder?"To get the answer itself in a shape you choose, give it a JSON Schema. The answer is printed alone, or as value with --output json:
letronna -p --json-schema schema.json "list the TODOs in src"To keep one run going and send it more messages, use --input-format stream-json. Every option is on Scripts and one-shot runs.
From an editor
The editor starts this command and speaks the Agent Client Protocol to it:
letronna acpEach prompt runs as an ordinary Letronna session, in the same list as the others. A call that needs a yes goes to the editor with the terminal's answers: once, always in this session, or no. Every mode but Auto is offered. See Zed and JetBrains.
From another agent
Add this command to the other agent as an MCP server:
letronna mcp serveIt offers these tools:
| Tool | Does |
|---|---|
web_fetch | reads a web page |
browse, use_page | open and work a page in Letronna's browser |
search_web | searches the web |
make_image, speak, transcribe, make_video | make and read media on the hosted models |
Calls are answered one at a time, in order; start a second server to run more at once. A tool that needs a yes is refused unless the server was started with --yes, and your deny and ask rules still refuse with it. --allow-turn adds letronna_turn, which runs a whole Letronna turn on a prompt and returns its answer.
The media tools spend your credit: see Hosted models and credit.