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babysitter-sdk — the core engine

**Package:** @a5c-ai/babysitter-sdk · **Metapackage:** @a5c-ai/babysitter · **Version:** 6.0.0 · **Maturity:** GA / core

**babysitter-sdk is the event-sourced orchestration engine at the center of the whole ecosystem. It is what makes Babysitter deterministic and obedient: your workflow is real code, the orchestrator can only do what that code permits, and every step is recorded in an immutable journal.**

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On this page

• What it is
• What it contains
• The metapackage
• Who depends on it
• A minimal example
• Next steps

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What it is

The SDK is described in its own package as "storage and run-registry primitives for event-sourced babysitter workflows." In practice it is both the **core library** and the **implementation behind the core CLI**.

The defining behaviors:

• **Process as code.** A process is an async function process(inputs, ctx). The orchestrator executes only what that function asks for — there is no out-of-band agency.
• **Event sourcing.** State lives as an append-only sequence of events in an immutable journal under ~/.a5c/runs/. The current state is a replay of those events, which gives you **deterministic replay** and **resume from any point**.
• **Mandatory stop + gate enforcement.** After each step the engine stops, asks the process what is permitted next, and either permits the next task or halts until a gate passes. This is the obedience mechanism — *gates block progression; they are not suggestions.*

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What it contains

**Entrypoints (bins):** babysitter, babysitter-sdk, babysitter-mcp-server.

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The metapackage

@a5c-ai/babysitter is the **metapackage** — "metapackage for installing all babysitter npm packages." It is the recommended human-facing install and ships the babysitter bin shim. Most users install this rather than reaching for babysitter-sdk directly:

npm install -g @a5c-ai/babysitter
babysitter --version

Reach for @a5c-ai/babysitter-sdk directly only when you are **authoring processes or embedding Babysitter in your own code**:

npm install @a5c-ai/babysitter-sdk

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Who depends on it

Effectively everything: every Babysitter process, the babysitter CLI, and the adapters, hooks, and genty layers all consume the SDK. Atlas supplies metadata *to* the runtime; the SDK is the runtime.

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A minimal example

A process is ordinary code. The orchestrator runs the tasks you declare, in the order your code allows, stopping after each one:

// process.js — illustrative shape
async function process(inputs, ctx) {
  const research = await ctx.task('research', { prompt: `Analyze ${inputs.repo}` });

  const impl = await ctx.task('implement', {
    prompt: 'Implement the change',
    dependsOn: [research],
  });

  // A gate is just code logic — it blocks progression until satisfied.
  let score = await ctx.task('score', { prompt: 'Score the result 0-100' });
  if (score < 80) {
    await ctx.task('refine', { prompt: 'Improve until the score clears the gate' });
  }

  // Park for human approval — durable, survives restarts (tasks/Breakpoints Adapter).
  await ctx.breakpoint('approve-release', { summary: impl.summary });
  return { done: true };
}

Every ctx.task, ctx.breakpoint, and decision above becomes journal events under ~/.a5c/runs/<runId>/. The quality gate (score < 80) is just one piece of code logic — one capability, not the headline.

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Next steps

• **See how the engine connects to everything else:** Architecture & How It Fits Together
• **Run it:** Installation → Quickstart
• **Author processes:** Process Definitions and the Custom Process tutorial
• **Understand the model:** Two-Loops Architecture and Journal System