Gambit is an open-source, developer-first framework that 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.

Watch the demo video.

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 demo

Downloads example files (hello decks plus the examples/ gallery) and sets environment variables.

To start onboarding with the simulator, run:

npx @bolt-foundry/gambit-simulator serve gambit/hello.deck.md
open http://localhost:8000/debug

Use the Build tab to draft your own workspace decks and scenarios.

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 via the simulator package):

npx @bolt-foundry/gambit-simulator 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.
• Context often arrives as a single giant fetch or RAG blob, so costs climb and\ hallucinations slip in.
• Input/outputs are rarely typed, which makes orchestration brittle and hard to\ 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.
• Mix LLM and compute tasks interchangeably and effortlessly inside the same\ deck tree.
• Feed models only what they need per step; inject references and cards instead\ of dumping every document.
• Keep orchestration logic local and testable; run decks offline with\ 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 <command>

Run a deck once:

npx @bolt-foundry/gambit run <deck> --context <json|string> --message <json|string>

--context replaces the old --init flag. The CLI still accepts --init as a deprecated alias for now so existing scripts keep working.

Drop into a REPL (streams by default):

npx @bolt-foundry/gambit repl <deck>

Run a persona against a root deck (scenario):

npx @bolt-foundry/gambit scenario <root-deck> --test-deck <persona-deck>

Grade a saved session:

npx @bolt-foundry/gambit grade <grader-deck> --state <file>

Start the Debug UI server with the simulator package:

npx @bolt-foundry/gambit-simulator serve <deck> --port 8000

Tracing and state: 

--trace <file> for JSONL traces\ --verbose to print events\ --state <file> to persist a session.

Worker sandbox defaults

• Deck-executing CLI surfaces default to worker sandbox execution.
• Use --no-worker-sandbox (or --legacy-exec) to force legacy in-process execution.
• --worker-sandbox explicitly forces worker execution on.
• --sandbox / --no-sandbox are deprecated aliases.
• gambit.toml equivalent: toml [execution] worker_sandbox = false # same as --no-worker-sandbox # legacy_exec = true # equivalent rollback toggle

The npm launcher (npx @bolt-foundry/gambit ...) runs the Gambit CLI binary for your platform, so these defaults and flags apply there as well.

Using the Simulator

The simulator is the local Debug UI that streams runs and renders traces. It now lives in @bolt-foundry/gambit-simulator, not the framework package.

Run with npx (no install):

npx @bolt-foundry/gambit-simulator <command>

Start it:

npx @bolt-foundry/gambit-simulator serve <deck> --port 8000

Then open:

http://localhost:8000/

It also serves:

http://localhost:8000/test
http://localhost:8000/grade
http://localhost:8000/verify (enabled by default; disable with GAMBIT_SIMULATOR_VERIFY_TAB=0)

To seed deterministic Verify fixtures for local iteration:

cd packages/gambit
deno task verify:seed-fixture

The Debug UI shows transcript lanes plus a trace/tools feed. If the deck has an\ contextSchema, the UI renders a schema-driven form with defaults and a raw JSON\ tab. Local-first state is stored under .gambit/ (sessions, traces, notes).

Build Chat Provider (Workbench)

Workbench build chat defaults to Codex CLI (codex-cli/default). To run build chat through Claude Code CLI instead (no OpenRouter path), set:

export GAMBIT_SIMULATOR_BUILD_CHAT_PROVIDER=claude-code-cli

Optional overrides:

export GAMBIT_SIMULATOR_BUILD_CHAT_MODEL=claude-code-cli/default
export GAMBIT_SIMULATOR_BUILD_CHAT_MODEL_FORCE=claude-code-cli/sonnet

When the simulator is running, you can also switch providers in the Workbench header (left of New chat).

Using the Library

Use the library when you want TypeScript decks/cards or custom compute steps.

Import the helpers from JSR:

import { defineDeck, defineCard } from "jsr:@bolt-foundry/gambit";

Related

• reviews/2026-04-15-AAR-raw-response-items.md

Define contextSchema/responseSchema with Zod to validate IO, and implement\ run/execute for compute decks. To call a child deck from code, use\ ctx.spawnAndWait({ path, input }). Emit structured trace events with\ ctx.log(...).

Runtime defaults for programmatic runDeck

runDeck from @bolt-foundry/gambit now uses CLI-equivalent provider/model defaults (alias expansion, provider routing, fallback behavior).

Before (direct-provider setup in each caller):

import { createOpenRouterProvider, runDeck } from "jsr:@bolt-foundry/gambit";

const provider = createOpenRouterProvider({
  apiKey: Deno.env.get("OPENROUTER_API_KEY")!,
});
await runDeck({
  path: "./root.deck.md",
  input: { message: "hi" },
  modelProvider: provider,
});

After (defaulted wrapper):

import { runDeck } from "jsr:@bolt-foundry/gambit";

await runDeck({
  path: "./root.deck.md",
  input: { message: "hi" },
});

Per-runtime override (shared runtime object):

import { createDefaultedRuntime, runDeck } from "jsr:@bolt-foundry/gambit";

const runtime = await createDefaultedRuntime({
  fallbackProvider: "codex-cli",
});

await runDeck({
  runtime,
  path: "./root.deck.md",
  input: { message: "hi" },
});

Replacement mapping:

• Legacy direct core passthrough export: runDeck -> runDeckCore
• Defaulted wrapper export: runDeck
• Runtime builder: createDefaultedRuntime

---

Author your first deck

Minimal Markdown deck (model-powered): hello_world.deck.md

+++
label = "hello_world"

[modelParams]
model = "openai/gpt-4o-mini"
temperature = 0
+++

You are a concise assistant. Greet the user and echo the input.

Run it:

npx @bolt-foundry/gambit run ./hello_world.deck.md --context '"Gambit"' --stream

Compute deck in TypeScript (no model call): echo.deck.ts

// echo.deck.ts
import { defineDeck } from "jsr:@bolt-foundry/gambit";
import { z } from "zod";

export default defineDeck({
  label: "echo",
  contextSchema: z.object({ text: z.string() }),
  responseSchema: z.object({ text: z.string(), length: z.number() }),
  run(ctx) {
    return { text: ctx.input.text, length: ctx.input.text.length };
  },
});

Run it:

npx @bolt-foundry/gambit run ./echo.deck.ts --context '{"text":"ping"}'

Deck with a child action (calls a TypeScript tool): agent_with_time.deck.md

+++
label = "agent_with_time"
modelParams = { model = "openai/gpt-4o-mini", temperature = 0 }
[[actions]]
name = "get_time"
path = "./get_time.deck.ts"
description = "Return the current ISO timestamp."
+++

A tiny agent that calls get_time, then replies with the timestamp and the input.

And the child action: get_time.deck.ts

// get_time.deck.ts
import { defineDeck } from "jsr:@bolt-foundry/gambit";
import { z } from "zod";

export default defineDeck({
  label: "get_time",
  contextSchema: z.object({}), // no args
  responseSchema: z.object({ iso: z.string() }),
  run() {
    return { iso: new Date().toISOString() };
  },
});

Run it:

npx @bolt-foundry/gambit run ./agent_with_time.deck.md --context '"hello"' --stream

Legacy respond-flow demo (historical compatibility)

packages/gambit/examples/respond_flow/ is kept as a legacy compatibility example for historical transcript/grader behavior. New decks should return schema-valid assistant output directly instead of calling gambit_respond.

cd packages/gambit
npx @bolt-foundry/gambit-simulator serve ./examples/respond_flow/decks/root.deck.ts --port 8000

Then:

1. Open http://localhost:8000/test, pick the Escalation persona, and run it. Leave the “Use scenario deck input for init” toggle on to see persona data seed the init form automatically.
2. Switch to the Debug tab to inspect the session; this scenario still emits legacy gambit_respond payloads for compatibility testing.
3. Head to the Calibrate tab and run the Respond payload grader to validate historical non-root respond-output handling.

Deno

If you prefer Deno, use the Deno commands below.

Quickstart:

export OPENROUTER_API_KEY=...
deno run -A jsr:@bolt-foundry/gambit/cli demo

Run a deck:

deno run -A jsr:@bolt-foundry/gambit/cli run <deck> --context <json|string> --message <json|string>

Start the Debug UI:

deno run -A jsr:@bolt-foundry/gambit-simulator/cli serve <deck> --port 8000