---
title: Agents SDK v0.8.0: readable state, idempotent schedules, typed AgentClient, and Zod 4
description: Agents SDK v0.8.0 exposes a readable state property on useAgent and AgentClient, makes schedule() idempotent for cron and opt-in for other types, adds full TypeScript inference to AgentClient, and drops Zod v3 in favor of Zod v4.
image: https://developers.cloudflare.com/changelog-preview.png
---
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## Agents SDK v0.8.0: readable state, idempotent schedules, typed AgentClient, and Zod 4
Mar 23, 2026
[ Agents ](https://developers.cloudflare.com/agents/)[ Workers ](https://developers.cloudflare.com/workers/)
The latest release of the [Agents SDK ↗](https://github.com/cloudflare/agents) exposes agent state as a readable property, prevents duplicate schedule rows across Durable Object restarts, brings full TypeScript inference to `AgentClient`, and migrates to Zod 4.
#### Readable `state` on `useAgent` and `AgentClient`
Both `useAgent` (React) and `AgentClient` (vanilla JS) now expose a `state` property that reflects the current agent state. Previously, reading state required manually tracking it through the `onStateUpdate` callback.
**React (`useAgent`)**
* [ JavaScript ](#tab-panel-1236)
* [ TypeScript ](#tab-panel-1237)
JavaScript
```
const agent = useAgent({
agent: "game-agent",
name: "room-123",
});
// Read state directly — no separate useState + onStateUpdate needed
return Score: {agent.state?.score}
;
// Spread for partial updates
agent.setState({ ...agent.state, score: (agent.state?.score ?? 0) + 10 });
```
Explain Code
TypeScript
```
const agent = useAgent({
agent: "game-agent",
name: "room-123",
});
// Read state directly — no separate useState + onStateUpdate needed
return Score: {agent.state?.score}
;
// Spread for partial updates
agent.setState({ ...agent.state, score: (agent.state?.score ?? 0) + 10 });
```
Explain Code
`agent.state` is reactive — the component re-renders when state changes from either the server or a client-side `setState()` call.
**Vanilla JS (`AgentClient`)**
* [ JavaScript ](#tab-panel-1238)
* [ TypeScript ](#tab-panel-1239)
JavaScript
```
const client = new AgentClient({
agent: "game-agent",
name: "room-123",
host: "your-worker.workers.dev",
});
client.setState({ score: 100 });
console.log(client.state); // { score: 100 }
```
TypeScript
```
const client = new AgentClient({
agent: "game-agent",
name: "room-123",
host: "your-worker.workers.dev",
});
client.setState({ score: 100 });
console.log(client.state); // { score: 100 }
```
State starts as `undefined` and is populated when the server sends the initial state on connect (from `initialState`) or when `setState()` is called. Use optional chaining (`agent.state?.field`) for safe access. The `onStateUpdate` callback continues to work as before — the new `state` property is additive.
#### Idempotent `schedule()`
`schedule()` now supports an `idempotent` option that deduplicates by `(type, callback, payload)`, preventing duplicate rows from accumulating when called in places that run on every Durable Object restart such as `onStart()`.
**Cron schedules are idempotent by default.** Calling `schedule("0 * * * *", "tick")` multiple times with the same callback, expression, and payload returns the existing schedule row instead of creating a new one. Pass `{ idempotent: false }` to override.
Delayed and date-scheduled types support opt-in idempotency:
* [ JavaScript ](#tab-panel-1240)
* [ TypeScript ](#tab-panel-1241)
JavaScript
```
import { Agent } from "agents";
class MyAgent extends Agent {
async onStart() {
// Safe across restarts — only one row is created
await this.schedule(60, "maintenance", undefined, { idempotent: true });
}
}
```
TypeScript
```
import { Agent } from "agents";
class MyAgent extends Agent {
async onStart() {
// Safe across restarts — only one row is created
await this.schedule(60, "maintenance", undefined, { idempotent: true });
}
}
```
Two new warnings help catch common foot-guns:
* Calling `schedule()` inside `onStart()` without `{ idempotent: true }` emits a `console.warn` with actionable guidance (once per callback; skipped for cron and when `idempotent` is set explicitly).
* If an alarm cycle processes 10 or more stale one-shot rows for the same callback, the SDK emits a `console.warn` and a `schedule:duplicate_warning` diagnostics channel event.
#### Typed `AgentClient` with `call` inference and `stub` proxy
`AgentClient` now accepts an optional agent type parameter for full type inference on RPC calls, matching the typed experience already available with `useAgent`.
* [ JavaScript ](#tab-panel-1244)
* [ TypeScript ](#tab-panel-1245)
JavaScript
```
const client = new AgentClient({
agent: "my-agent",
host: window.location.host,
});
// Typed call — method name autocompletes, args and return type inferred
const value = await client.call("getValue");
// Typed stub — direct RPC-style proxy
await client.stub.getValue();
await client.stub.add(1, 2);
```
Explain Code
TypeScript
```
const client = new AgentClient({
agent: "my-agent",
host: window.location.host,
});
// Typed call — method name autocompletes, args and return type inferred
const value = await client.call("getValue");
// Typed stub — direct RPC-style proxy
await client.stub.getValue();
await client.stub.add(1, 2);
```
Explain Code
State is automatically inferred from the agent type, so `onStateUpdate` is also typed:
* [ JavaScript ](#tab-panel-1242)
* [ TypeScript ](#tab-panel-1243)
JavaScript
```
const client = new AgentClient({
agent: "my-agent",
host: window.location.host,
onStateUpdate: (state) => {
// state is typed as MyAgent's state type
},
});
```
TypeScript
```
const client = new AgentClient({
agent: "my-agent",
host: window.location.host,
onStateUpdate: (state) => {
// state is typed as MyAgent's state type
},
});
```
Existing untyped usage continues to work without changes. The RPC type utilities (`AgentMethods`, `AgentStub`, `RPCMethods`) are now exported from `agents/client` for advanced typing scenarios.`agents`, `@cloudflare/ai-chat`, and `@cloudflare/codemode` now require `zod ^4.0.0`. Zod v3 is no longer supported.
#### `@cloudflare/ai-chat` fixes
* **Turn serialization** — `onChatMessage()` and `_reply()` work is now queued so user requests, tool continuations, and `saveMessages()` never stream concurrently.
* **Duplicate messages on stop** — Clicking stop during an active stream no longer splits the assistant message into two entries.
* **Duplicate messages after tool calls** — Orphaned client IDs no longer leak into persistent storage.
#### `keepAlive()` and `keepAliveWhile()` are no longer experimental
`keepAlive()` now uses a lightweight in-memory ref count instead of schedule rows. Multiple concurrent callers share a single alarm cycle. The `@experimental` tag has been removed from both `keepAlive()` and `keepAliveWhile()`.
#### `@cloudflare/codemode`: TanStack AI integration
A new entry point `@cloudflare/codemode/tanstack-ai` adds support for [TanStack AI's ↗](https://tanstack.com/ai) `chat()` as an alternative to the Vercel AI SDK's `streamText()`:
* [ JavaScript ](#tab-panel-1246)
* [ TypeScript ](#tab-panel-1247)
JavaScript
```
import {
createCodeTool,
tanstackTools,
} from "@cloudflare/codemode/tanstack-ai";
import { chat } from "@tanstack/ai";
const codeTool = createCodeTool({
tools: [tanstackTools(myServerTools)],
executor,
});
const stream = chat({ adapter, tools: [codeTool], messages });
```
Explain Code
TypeScript
```
import { createCodeTool, tanstackTools } from "@cloudflare/codemode/tanstack-ai";
import { chat } from "@tanstack/ai";
const codeTool = createCodeTool({
tools: [tanstackTools(myServerTools)],
executor,
});
const stream = chat({ adapter, tools: [codeTool], messages });
```
#### Upgrade
To update to the latest version:
Terminal window
```
npm i agents@latest @cloudflare/ai-chat@latest
```