Show HN: Gambit, an open-source agent harness for building reliable AI agents

Summary

Gambit Gambit helps you build reliable LLM workflows by composing small, typed “decks” with clear inputs/outputs and guardrails. Run decks locally, stream traces, and debug with a built-in UI. Quickstart Requirements: Node.js 18+ and OPENROUTER_API_KEY (set OPENROUTER_BASE_URL if you proxy OpenRouter-style APIs). Run the CLI directly with npx (no install): export OPENROUTER_API_KEY=... npx @bolt-foundry/gambit init Downloads example files (hello decks plus the examples/ gallery) and sets environment variables. Run an example in the terminal ( repl ): npx @bolt-foundry/gambit repl gambit/hello.deck.md This example just says "hello" and repeats your message back to you. Run an example in the browser ( serve ): npx @bolt-foundry/gambit serve gambit/hello.deck.md open http://localhost:8000/debug Status quo Most teams wire one long prompt to several tools and hope the model routes correctly. correctly. Context often arrives as a single giant fetch or RAG blob, so costs climb and hallucinations slip in. hallucinations slip in. Input/outputs are rarely typed, which makes orchestration brittle and hard to test offline. test offline. Debugging leans on provider logs instead of local traces, so reproducing failures is slow. Our vision Treat each step as a small deck with explicit inputs/outputs and guardrails; model calls are just one kind of action. model calls are just one kind of action. Mix LLM and compute tasks interchangeably and effortlessly inside the same deck tree. deck tree. Feed models only what they need per step; inject references and cards instead of dumping every document. of dumping every document. Keep orchestration logic local and testable; run decks offline with predictable traces. predictable traces. Ship with built-in observability (streaming, REPL, debug UI) so debugging feels like regular software, not guesswork. Using the CLI Use the CLI to run decks locally, stream output, and capture traces/state. Run with npx (no install): npx @bolt-foundry/gambit ...