resonate-basic-durable-world-usage-typescript

Resonate Basic Durable World Usage

SDK version: This skill reflects @resonatehq/sdk v0.11.4 (current on npm).

Two execution engines (v0.11.0+): The SDK now ships two engines. This skill documents the generator engine (imported from @resonatehq/sdk), which uses function* / yield* and is the basis of all existing Resonate examples. An async/await engine (imported from @resonatehq/sdk/async) was added in v0.11.0 and is documented in resonate-async-await-engine-typescript.

Overview

The Durable World is inside generator functions where you write durable, recoverable execution logic using the Context object. Every operation checkpoints progress, enabling automatic recovery after failures.

Key distinction: Durable World code uses ctx (Context). Ephemeral World code uses resonate (Client).

Mental Model

Generator Function (function*)
       ↓
   yield* ctx.run()      ← Checkpoint
       ↓
   yield* ctx.sleep()    ← Checkpoint + Suspend
       ↓
   yield* ctx.rpc()      ← Checkpoint + Cross Process
       ↓
   return result         ← Final Checkpoint

Every yield* is a durable checkpoint.

If the process crashes, the execution replays from the last checkpoint using stored results.

Core Syntax Rules

1. Use function* (Generator Functions)

// ✅ CORRECT - Generator function
function* myWorkflow(ctx: Context, arg: string) {
  // Durable code here
}

// ❌ WRONG - Async function
async function myWorkflow(ctx: Context, arg: string) {
  // Not durable!
}

// ❌ WRONG - Async generator
async function* myWorkflow(ctx: Context, arg: string) {
  // Invalid syntax for Resonate
}

2. Always yield* Context Calls

function* myWorkflow(ctx: Context) {
  // ✅ CORRECT
  const result = yield* ctx.run(someFunc, "arg");

  // ❌ WRONG - Missing yield*
  const result = ctx.run(someFunc, "arg");

  // ❌ WRONG - Using await
  const result = await ctx.run(someFunc, "arg");
}

3. First Parameter is Always Context