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  1. Build microfrontend applications on Workers

    Workers

    You can now deploy microfrontends to Cloudflare, splitting a single application into smaller, independently deployable units that render as one cohesive application. This lets different teams using different frameworks develop, test, and deploy each microfrontend without coordinating releases.

    Microfrontends solve several challenges for large-scale applications:

    • Independent deployments: Teams deploy updates on their own schedule without redeploying the entire application
    • Framework flexibility: Build multi-framework applications (for example, Astro, Remix, and Next.js in one app)
    • Gradual migration: Migrate from a monolith to a distributed architecture incrementally

    Create a microfrontend project:

    Deploy to Cloudflare

    This template automatically creates a router worker with pre-configured routing logic, and lets you configure Service bindings to Workers you have already deployed to your Cloudflare account. The router Worker analyzes incoming requests, matches them against configured routes, and forwards requests to the appropriate microfrontend via service bindings. The router automatically rewrites HTML, CSS, and headers to ensure assets load correctly from each microfrontend's mount path. The router includes advanced features like preloading for faster navigation between microfrontends, smooth page transitions using the View Transitions API, and automatic path rewriting for assets, redirects, and cookies.

    Each microfrontend can be a full-framework application, a static site with Workers Static Assets, or any other Worker-based application.

    Get started with the microfrontends template ↗, or read the microfrontends documentation for implementation details.

  1. Agents SDK v0.3.0, workers-ai-provider v3.0.0, and ai-gateway-provider v3.0.0 with AI SDK v6 support

    Agents Workers

    We've shipped a new release for the Agents SDK ↗ v0.3.0 bringing full compatibility with AI SDK v6 ↗ and introducing the unified tool pattern, dynamic tool approval, and enhanced React hooks with improved tool handling.

    This release includes improved streaming and tool support, dynamic tool approval (for "human in the loop" systems), enhanced React hooks with onToolCall callback, improved error handling for streaming responses, and seamless migration from v5 patterns.

    This makes it ideal for building production AI chat interfaces with Cloudflare Workers AI models, agent workflows, human-in-the-loop systems, or any application requiring reliable tool execution and approval workflows.

    Additionally, we've updated workers-ai-provider v3.0.0, the official provider for Cloudflare Workers AI models, and ai-gateway-provider v3.0.0, the provider for Cloudflare AI Gateway, to be compatible with AI SDK v6.

    Agents SDK v0.3.0

    Unified Tool Pattern

    AI SDK v6 introduces a unified tool pattern where all tools are defined on the server using the tool() function. This replaces the previous client-side AITool pattern.

    Server-Side Tool Definition

    TypeScript
    import { tool } from "ai";
    import { z } from "zod";
    

    // Server: Define ALL tools on the server
    const tools = {
      // Server-executed tool
      getWeather: tool({
        description: "Get weather for a city",
        inputSchema: z.object({ city: z.string() }),
        execute: async ({ city }) => fetchWeather(city)
      }),
    

      // Client-executed tool (no execute = client handles via onToolCall)
      getLocation: tool({
        description: "Get user location from browser",
        inputSchema: z.object({})
        // No execute function
      }),
    

      // Tool requiring approval (dynamic based on input)
      processPayment: tool({
        description: "Process a payment",
        inputSchema: z.object({ amount: z.number() }),
        needsApproval: async ({ amount }) => amount > 100,
        execute: async ({ amount }) => charge(amount)
      })
    };

    Client-Side Tool Handling

    TypeScript
    // Client: Handle client-side tools via onToolCall callback
    import { useAgentChat } from "agents/ai-react";
    

    const { messages, sendMessage, addToolOutput } = useAgentChat({
      agent,
      onToolCall: async ({ toolCall, addToolOutput }) => {
        if (toolCall.toolName === "getLocation") {
          const position = await new Promise((resolve, reject) => {
            navigator.geolocation.getCurrentPosition(resolve, reject);
          });
          addToolOutput({
            toolCallId: toolCall.toolCallId,
            output: {
              lat: position.coords.latitude,
              lng: position.coords.longitude
            }
          });
        }
      }
    });

    Key benefits of the unified tool pattern:

    • Server-defined tools: All tools are defined in one place on the server
    • Dynamic approval: Use needsApproval to conditionally require user confirmation
    • Cleaner client code: Use onToolCall callback instead of managing tool configs
    • Type safety: Full TypeScript support with proper tool typing

    useAgentChat(options)

    Creates a new chat interface with enhanced v6 capabilities.

    TypeScript
    // Basic chat setup with onToolCall
    const { messages, sendMessage, addToolOutput } = useAgentChat({
      agent,
      onToolCall: async ({ toolCall, addToolOutput }) => {
        // Handle client-side tool execution
        await addToolOutput({
          toolCallId: toolCall.toolCallId,
          output: { result: "success" }
        });
      }
    });

    Dynamic Tool Approval

    Use needsApproval on server tools to conditionally require user confirmation:

    TypeScript
    const paymentTool = tool({
      description: "Process a payment",
      inputSchema: z.object({
        amount: z.number(),
        recipient: z.string()
      }),
      needsApproval: async ({ amount }) => amount > 1000,
      execute: async ({ amount, recipient }) => {
        return await processPayment(amount, recipient);
      }
    });

    Tool Confirmation Detection

    The isToolUIPart and getToolName functions now check both static and dynamic tool parts:

    TypeScript
    import { isToolUIPart, getToolName } from "ai";
    

    const pendingToolCallConfirmation = messages.some((m) =>
      m.parts?.some(
        (part) => isToolUIPart(part) && part.state === "input-available",
      ),
    );
    

    // Handle tool confirmation
    if (pendingToolCallConfirmation) {
      await addToolOutput({
        toolCallId: part.toolCallId,
        output: "User approved the action"
      });
    }

    If you need the v5 behavior (static-only checks), use the new functions:

    TypeScript
    import { isStaticToolUIPart, getStaticToolName } from "ai";

    convertToModelMessages() is now async

    The convertToModelMessages() function is now asynchronous. Update all calls to await the result:

    TypeScript
    import { convertToModelMessages } from "ai";
    

    const result = streamText({
      messages: await convertToModelMessages(this.messages),
      model: openai("gpt-4o")
    });

    ModelMessage type

    The CoreMessage type has been removed. Use ModelMessage instead:

    TypeScript
    import { convertToModelMessages, type ModelMessage } from "ai";
    

    const modelMessages: ModelMessage[] = await convertToModelMessages(messages);

    generateObject mode option removed

    The mode option for generateObject has been removed:

    TypeScript
    // Before (v5)
    const result = await generateObject({
      mode: "json",
      model,
      schema,
      prompt
    });
    

    // After (v6)
    const result = await generateObject({
      model,
      schema,
      prompt
    });

    Structured Output with generateText

    While generateObject and streamObject are still functional, the recommended approach is to use generateText/streamText with the Output.object() helper:

    TypeScript
    import { generateText, Output, stepCountIs } from "ai";
    

    const { output } = await generateText({
      model: openai("gpt-4"),
      output: Output.object({
        schema: z.object({ name: z.string() })
      }),
      stopWhen: stepCountIs(2),
      prompt: "Generate a name"
    });

    Note: When using structured output with generateText, you must configure multiple steps with stopWhen because generating the structured output is itself a step.

    workers-ai-provider v3.0.0

    Seamless integration with Cloudflare Workers AI models through the updated workers-ai-provider v3.0.0 with AI SDK v6 support.

    Model Setup with Workers AI

    Use Cloudflare Workers AI models directly in your agent workflows:

    TypeScript
    import { createWorkersAI } from "workers-ai-provider";
    import { useAgentChat } from "agents/ai-react";
    

    // Create Workers AI model (v3.0.0 - enhanced v6 internals)
    const model = createWorkersAI({
      binding: env.AI,
    })("@cf/meta/llama-3.2-3b-instruct");

    Enhanced File and Image Support

    Workers AI models now support v6 file handling with automatic conversion:

    TypeScript
    // Send images and files to Workers AI models
    sendMessage({
      role: "user",
      parts: [
        { type: "text", text: "Analyze this image:" },
        {
          type: "file",
          data: imageBuffer,
          mediaType: "image/jpeg",
        },
      ],
    });
    

    // Workers AI provider automatically converts to proper format

    Streaming with Workers AI

    Enhanced streaming support with automatic warning detection:

    TypeScript
    // Streaming with Workers AI models
    const result = await streamText({
      model: createWorkersAI({ binding: env.AI })("@cf/meta/llama-3.2-3b-instruct"),
      messages: await convertToModelMessages(messages),
      onChunk: (chunk) => {
        // Enhanced streaming with warning handling
        console.log(chunk);
      },
    });

    ai-gateway-provider v3.0.0

    The ai-gateway-provider v3.0.0 now supports AI SDK v6, enabling you to use Cloudflare AI Gateway with multiple AI providers including Anthropic, Azure, AWS Bedrock, Google Vertex, and Perplexity.

    AI Gateway Setup

    Use Cloudflare AI Gateway to add analytics, caching, and rate limiting to your AI applications:

    TypeScript
    import { createAIGateway } from "ai-gateway-provider";
    

    // Create AI Gateway provider (v3.0.0 - enhanced v6 internals)
    const model = createAIGateway({
      gatewayUrl: "https://gateway.ai.cloudflare.com/v1/your-account-id/gateway",
      headers: {
        "Authorization": `Bearer ${env.AI_GATEWAY_TOKEN}`
      }
    })({
      provider: "openai",
      model: "gpt-4o"
    });

    Migration from v5

    Deprecated APIs

    The following APIs are deprecated in favor of the unified tool pattern:

    DeprecatedReplacement
    AITool typeUse AI SDK's tool() function on server
    extractClientToolSchemas()Define tools on server, no client schemas needed
    createToolsFromClientSchemas()Define tools on server with tool()
    toolsRequiringConfirmation optionUse needsApproval on server tools
    experimental_automaticToolResolutionUse onToolCall callback
    tools option in useAgentChatUse onToolCall for client-side execution
    addToolResult()Use addToolOutput()

    Breaking Changes Summary

    1. Unified Tool Pattern: All tools must be defined on the server using tool()
    2. convertToModelMessages() is async: Add await to all calls
    3. CoreMessage removed: Use ModelMessage instead
    4. generateObject mode removed: Remove mode option
    5. isToolUIPart behavior changed: Now checks both static and dynamic tool parts

    Installation

    Update your dependencies to use the latest versions:

    Terminal window
    npm install agents@^0.3.0 workers-ai-provider@^3.0.0 ai-gateway-provider@^3.0.0 ai@^6.0.0 @ai-sdk/react@^3.0.0 @ai-sdk/openai@^3.0.0

    Resources

    Feedback Welcome

    We'd love your feedback! We're particularly interested in feedback on:

    • Migration experience - How smooth was the upgrade from v5 to v6?
    • Unified tool pattern - How does the new server-defined tool pattern work for you?
    • Dynamic tool approval - Does the needsApproval feature meet your needs?
    • AI Gateway integration - How well does the new provider work with your setup?

  1. Static prerendering support for TanStack Start

    Workers

    TanStack Start ↗ apps can now prerender routes to static HTML at build time with access to build time environment variables and bindings, and serve them as static assets. To enable prerendering, configure the prerender option of the TanStack Start plugin in your Vite config:

    vite.config.ts
    import { defineConfig } from "vite";
    import { cloudflare } from "@cloudflare/vite-plugin";
    import { tanstackStart } from "@tanstack/react-start/plugin/vite";
    

    export default defineConfig({
      plugins: [
        cloudflare({ viteEnvironment: { name: "ssr" } }),
        tanstackStart({
          prerender: {
            enabled: true,
          },
        }),
      ],
    });

    This feature requires @tanstack/react-start v1.138.0 or later. See the TanStack Start framework guide for more details.

  1. Build image policies for Workers Builds and Cloudflare Pages

    Workers

    We've published build image policies for Workers Builds and Cloudflare Pages, which establish:

    • Minor version updates: We typically update preinstalled software to the latest available minor version without notice. For tools that don't follow semantic versioning (e.g., Bun or Hugo), we provide 3 months’ notice.
    • Major version updates: Before preinstalled software reaches end-of-life, we update to the next stable LTS version with 3 months’ notice.
    • Build image version deprecation (Pages only): We provide 6 months’ notice before deprecation. Projects on v1 or v2 will be automatically moved to v3 on their specified deprecation dates.

    To prepare for updates, monitor the Cloudflare Changelog ↗, dashboard notifications, and email. You can also override default versions to maintain specific versions.

  1. Retrieve your authentication token with `wrangler auth token`

    Workers

    Wrangler now includes a new wrangler auth token command that retrieves your current authentication token or credentials for use with other tools and scripts.

    Terminal window
    wrangler auth token

    The command returns whichever authentication method is currently configured, in priority order: API token from CLOUDFLARE_API_TOKEN, or OAuth token from wrangler login (automatically refreshed if expired).

    Use the --json flag to get structured output including the token type:

    Terminal window
    wrangler auth token --json

    The JSON output includes the authentication type:

    JSONC
    // API token
    { "type": "api_token", "token": "..." }
    

    // OAuth token
    { "type": "oauth", "token": "..." }
    

    // API key/email (only available with --json)
    { "type": "api_key", "key": "...", "email": "..." }

    API key/email credentials from CLOUDFLARE_API_KEY and CLOUDFLARE_EMAIL require the --json flag since this method uses two values instead of a single token.

  1. Support for ctx.exports in @cloudflare/vitest-pool-workers

    Workers

    The @cloudflare/vitest-pool-workers package now supports the ctx.exports API, allowing you to access your Worker's top-level exports during tests.

    You can access ctx.exports in unit tests by calling createExecutionContext():

    TypeScript
    import { createExecutionContext } from "cloudflare:test";
    import { it, expect } from "vitest";
    

    it("can access ctx.exports", async () => {
      const ctx = createExecutionContext();
      const result = await ctx.exports.MyEntryPoint.myMethod();
      expect(result).toBe("expected value");
    });

    Alternatively, you can import exports directly from cloudflare:workers:

    TypeScript
    import { exports } from "cloudflare:workers";
    import { it, expect } from "vitest";
    

    it("can access imported exports", async () => {
      const result = await exports.MyEntryPoint.myMethod();
      expect(result).toBe("expected value");
    });

    See the context-exports fixture ↗ for a complete example.

  1. Configure your framework for Cloudflare automatically

    Workers

    Wrangler now supports automatic configuration for popular web frameworks in experimental mode, making it even easier to deploy to Cloudflare Workers.

    Previously, if you wanted to deploy an application using a popular web framework like Next.js or Astro, you had to follow tutorials to set up your application for deployment to Cloudflare Workers. This usually involved creating a Wrangler file, installing adapters, or changing configuration options.

    Now wrangler deploy does this for you. Starting with Wrangler 4.55, you can use npx wrangler deploy --x-autoconfig in the directory of any web application using one of the supported frameworks. Wrangler will then proceed to configure and deploy it to your Cloudflare account.

    You can also configure your application without deploying it by using the new npx wrangler setup command. This enables you to easily review what changes we are making so your application is ready for Cloudflare Workers.

    The following application frameworks are supported starting today:

    • Next.js
    • Astro
    • Nuxt
    • TanStack Start
    • SolidStart
    • React Router
    • SvelteKit
    • Docusaurus
    • Qwik
    • Analog

    Automatic configuration also supports static sites by detecting the assets directory and build command. From a single index.html file to the output of a generator like Jekyll or Hugo, you can just run npx wrangler deploy --x-autoconfig to upload to Cloudflare.

    We're really excited to bring you automatic configuration so you can do more with Workers. Please let us know if you run into challenges using this experimentally. We’ve opened a GitHub discussion ↗ and would love to hear your feedback.

  1. New Best Practices guide for Durable Objects

    Durable Objects Workers

    A new Rules of Durable Objects guide is now available, providing opinionated best practices for building effective Durable Objects applications. This guide covers design patterns, storage strategies, concurrency, and common anti-patterns to avoid.

    Key guidance includes:

    • Design around your "atom" of coordination — Create one Durable Object per logical unit (chat room, game session, user) instead of a global singleton that becomes a bottleneck.
    • Use SQLite storage with RPC methods — SQLite-backed Durable Objects with typed RPC methods provide the best developer experience and performance.
    • Understand input and output gates — Learn how Cloudflare's runtime prevents data races by default, how write coalescing works, and when to use blockConcurrencyWhile().
    • Leverage Hibernatable WebSockets — Reduce costs for real-time applications by allowing Durable Objects to sleep while maintaining WebSocket connections.

    The testing documentation has also been updated with modern patterns using @cloudflare/vitest-pool-workers, including examples for testing SQLite storage, alarms, and direct instance access:

    test/counter.test.js
    import { env, runDurableObjectAlarm } from "cloudflare:test";
    import { it, expect } from "vitest";
    

    it("can test Durable Objects with isolated storage", async () => {
      const stub = env.COUNTER.getByName("test");
    

      // Call RPC methods directly on the stub
      await stub.increment();
      expect(await stub.getCount()).toBe(1);
    

      // Trigger alarms immediately without waiting
      await runDurableObjectAlarm(stub);
    });

  1. Billing for SQLite Storage

    Durable Objects Workers

    Storage billing for SQLite-backed Durable Objects will be enabled in January 2026, with a target date of January 7, 2026 (no earlier).

    To view your SQLite storage usage, go to the Durable Objects page

    Go to Durable Objects

    If you do not want to incur costs, please take action such as optimizing queries or deleting unnecessary stored data in order to reduce your SQLite storage usage ahead of the January 7th target. Only usage on and after the billing target date will incur charges.

    Developers on the Workers Paid plan with Durable Object's SQLite storage usage beyond included limits will incur charges according to SQLite storage pricing announced in September 2024 with the public beta ↗. Developers on the Workers Free plan will not be charged.

    Compute billing for SQLite-backed Durable Objects has been enabled since the initial public beta. SQLite-backed Durable Objects currently incur charges for requests and duration, and no changes are being made to compute billing.

    For more information about SQLite storage pricing and limits, refer to the Durable Objects pricing documentation.

  1. Python cold start improvements

    Workers

    Python Workers now feature improved cold start performance, reducing initialization time for new Worker instances. This improvement is particularly noticeable for Workers with larger dependency sets or complex initialization logic.

    Every time you deploy a Python Worker, a memory snapshot is captured after the top level of the Worker is executed. This snapshot captures all imports, including package imports that are often costly to load. The memory snapshot is loaded when the Worker is first started, avoiding the need to reload the Python runtime and all dependencies on each cold start.

    We set up a benchmark that imports common packages (httpx ↗, fastapi ↗ and pydantic ↗) to see how Python Workers stack up against other platforms:

    PlatformMean Cold Start (ms)
    Cloudflare Python Workers1027
    AWS Lambda2502
    Google Cloud Run3069

    These benchmarks run continuously. You can view the results and the methodology on our benchmark page ↗.

    In additional testing, we have found that without any memory snapshot, the cold start for this benchmark takes around 10 seconds, so this change improves cold start performance by roughly a factor of 10.

    To get started with Python Workers, check out our Python Workers overview.

  1. Easy Python package management with Pywrangler

    Workers

    We are introducing a brand new tool called Pywrangler, which simplifies package management in Python Workers by automatically installing Workers-compatible Python packages into your project.

    With Pywrangler, you specify your Worker's Python dependencies in your pyproject.toml file:

    TOML
    [project]
    name = "python-beautifulsoup-worker"
    version = "0.1.0"
    description = "A simple Worker using beautifulsoup4"
    requires-python = ">=3.12"
    dependencies = [
        "beautifulsoup4"
    ]
    

    [dependency-groups]
    dev = [
      "workers-py",
      "workers-runtime-sdk"
    ]

    You can then develop and deploy your Worker using the following commands:

    Terminal window
    uv run pywrangler dev
    uv run pywrangler deploy

    Pywrangler automatically downloads and vendors the necessary packages for your Worker, and these packages are bundled with the Worker when you deploy.

    Consult the Python packages documentation for full details on Pywrangler and Python package management in Workers.

  1. Wrangler config is optional when using Vite plugin

    Workers

    When using the Cloudflare Vite plugin to build and deploy Workers, a Wrangler configuration file is now optional for assets-only (static) sites. If no wrangler.toml, wrangler.json, or wrangler.jsonc file is found, the plugin generates sensible defaults for an assets-only site. The name is based on the package.json or the project directory name, and the compatibility_date uses the latest date supported by your installed Miniflare version.

    This allows easier setup for static sites using Vite. Note that SPAs will still need to set assets.not_found_handling to single-page-application ↗ in order to function correctly.

  1. Configure Workers programmatically using the Vite plugin

    Workers

    The Cloudflare Vite plugin now supports programmatic configuration of Workers without a Wrangler configuration file. You can use the config option to define Worker settings directly in your Vite configuration, or to modify existing configuration loaded from a Wrangler config file. This is particularly useful when integrating with other build tools or frameworks, as it allows them to control Worker configuration without needing users to manage a separate config file.

    The config option

    The Vite plugin's new config option accepts either a partial configuration object or a function that receives the current configuration and returns overrides. This option is applied after any config file is loaded, allowing the plugin to override specific values or define Worker configuration entirely in code.

    Example usage

    Setting config to an object to provide configuration values that merge with defaults and config file settings:

    vite.config.ts
    import { defineConfig } from "vite";
    import { cloudflare } from "@cloudflare/vite-plugin";
    

    export default defineConfig({
      plugins: [
        cloudflare({
          config: {
            name: "my-worker",
            compatibility_flags: ["nodejs_compat"],
            send_email: [
              {
                name: "EMAIL",
              },
            ],
          },
        }),
      ],
    });

    Use a function to modify the existing configuration:

    vite.config.ts
    import { defineConfig } from "vite";
    import { cloudflare } from "@cloudflare/vite-plugin";
    export default defineConfig({
      plugins: [
        cloudflare({
          config: (userConfig) => {
            delete userConfig.compatibility_flags;
          },
        }),
      ],
    });

    Return an object with values to merge:

    vite.config.ts
    import { defineConfig } from "vite";
    import { cloudflare } from "@cloudflare/vite-plugin";
    

    export default defineConfig({
      plugins: [
        cloudflare({
          config: (userConfig) => {
            if (!userConfig.compatibility_flags.includes("no_nodejs_compat")) {
              return { compatibility_flags: ["nodejs_compat"] };
            }
          },
        }),
      ],
    });

    Auxiliary Workers

    Auxiliary Workers also support the config option, enabling multi-Worker architectures without config files.

    Define auxiliary Workers without config files using config inside the auxiliaryWorkers array:

    vite.config.ts
    import { defineConfig } from "vite";
    import { cloudflare } from "@cloudflare/vite-plugin";
    

    export default defineConfig({
      plugins: [
        cloudflare({
          config: {
            name: "entry-worker",
            main: "./src/entry.ts",
            services: [{ binding: "API", service: "api-worker" }],
          },
          auxiliaryWorkers: [
            {
              config: {
                name: "api-worker",
                main: "./src/api.ts",
              },
            },
          ],
        }),
      ],
    });

    For more details and examples, see Programmatic configuration.

  1. One-click Access protection for Workers now creates reusable Cloudflare Access policies

    Workers

    Workers applications now use reusable Cloudflare Access policies to reduce duplication and simplify access management across multiple Workers.

    Previously, enabling Cloudflare Access on a Worker created per-application policies, unique to each application. Now, we create reusable policies that can be shared across applications:

    • Preview URLs: All Workers preview URLs share a single "Cloudflare Workers Preview URLs" policy across your account. This policy is automatically created the first time you enable Access on any preview URL. By sharing a single policy across all preview URLs, you can configure access rules once and have them apply company-wide to all Workers which protect preview URLs. This makes it much easier to manage who can access preview environments without having to update individual policies for each Worker.

    • Production workers.dev URLs: When enabled, each Worker gets its own reusable policy (named <worker-name> - Production) by default. We recognize production services often have different access requirements and having individual policies here makes it easier to configure service-to-service authentication or protect internal dashboards or applications with specific user groups. Keeping these policies separate gives you the flexibility to configure exactly the right access rules for each production service. When you disable Access on a production Worker, the associated policy is automatically cleaned up if it's not being used by other applications.

    This change reduces policy duplication, simplifies cross-company access management for preview environments, and provides the flexibility needed for production services. You can still customize access rules by editing the reusable policies in the Zero Trust dashboard.

    To enable Cloudflare Access on your Worker:

    1. In the Cloudflare dashboard, go to Workers & Pages.
    2. Select your Worker.
    3. Go to Settings > Domains & Routes.
    4. For workers.dev or Preview URLs, click Enable Cloudflare Access.
    5. Optionally, click Manage Cloudflare Access to customize the policy.

    For more information on configuring Cloudflare Access for Workers, refer to the Workers Access documentation.

  1. Agents SDK v0.2.24 with resumable streaming, MCP improvements, and schedule fixes

    Agents Workers

    The latest release of @cloudflare/agents ↗ brings resumable streaming, significant MCP client improvements, and critical fixes for schedules and Durable Object lifecycle management.

    Resumable streaming

    AIChatAgent now supports resumable streaming, allowing clients to reconnect and continue receiving streamed responses without losing data. This is useful for:

    • Long-running AI responses
    • Users on unreliable networks
    • Users switching between devices mid-conversation
    • Background tasks where users navigate away and return
    • Real-time collaboration where multiple clients need to stay in sync

    Streams are maintained across page refreshes, broken connections, and syncing across open tabs and devices.

    Other improvements

    • Default JSON schema validator added to MCP client
    • Schedules ↗ can now safely destroy the agent

    MCP client API improvements

    The MCPClientManager API has been redesigned for better clarity and control:

    • New registerServer() method: Register MCP servers without immediately connecting
    • New connectToServer() method: Establish connections to registered servers
    • Improved reconnect logic: restoreConnectionsFromStorage() now properly handles failed connections
    TypeScript
    // Register a server to Agent
    const { id } = await this.mcp.registerServer({
      name: "my-server",
      url: "https://my-mcp-server.example.com",
    });
    

    // Connect when ready
    await this.mcp.connectToServer(id);
    

    // Discover tools, prompts and resources
    await this.mcp.discoverIfConnected(id);

    The SDK now includes a formalized MCPConnectionState enum with states: idle, connecting, authenticating, connected, discovering, and ready.

    Enhanced MCP discovery

    MCP discovery fetches the available tools, prompts, and resources from an MCP server so your agent knows what capabilities are available. The MCPClientConnection class now includes a dedicated discover() method with improved reliability:

    • Supports cancellation via AbortController
    • Configurable timeout (default 15s)
    • Discovery failures now throw errors immediately instead of silently continuing

    Bug fixes

    • Fixed a bug where schedules ↗ meant to fire immediately with this.schedule(0, ...) or this.schedule(new Date(), ...) would not fire
    • Fixed an issue where schedules that took longer than 30 seconds would occasionally time out
    • Fixed SSE transport now properly forwards session IDs and request headers
    • Fixed AI SDK stream events conversion to UIMessageStreamPart

    Upgrade

    To update to the latest version:

    Terminal window
    npm i agents@latest

  1. Environment variable limits increase for Workers Builds

    Workers

    Workers Builds now supports up to 64 environment variables, and each environment variable can be up to 5 KB in size. The previous limit was 5 KB total across all environment variables.

    This change enables better support for complex build configurations, larger application settings, and more flexible CI/CD workflows.

    For more details, refer to the build limits documentation.

  1. Better local deployment flow for Cloudflare Workers

    Workers

    Until now, if a Worker had been previously deployed via the Cloudflare Dashboard ↗, a subsequent deployment done via the Cloudflare Workers CLI, Wrangler (through the deploy command), would allow the user to override the Worker's dashboard settings without providing details on what dashboard settings would be lost.

    Now instead, wrangler deploy presents a helpful representation of the differences between the local configuration and the remote dashboard settings, and offers to update your local configuration file for you.

    See example below showing a before and after for wrangler deploy when a local configuration is expected to override a Worker's dashboard settings:

    Before

    wrangler deploy run before the improved workflow

    After

    wrangler deploy run after the improved workflow

    Also, if instead Wrangler detects that a deployment would override remote dashboard settings but in an additive way, without modifying or removing any of them, it will simply proceed with the deployment without requesting any user interaction.

    Update to Wrangler v4.50.0 or greater to take advantage of this improved deploy flow.

  1. More SQL aggregate, date and time functions available in Workers Analytics Engine

    Workers Analytics Engine Workers

    You can now perform more powerful queries directly in Workers Analytics Engine ↗ with a major expansion of our SQL function library.

    Workers Analytics Engine allows you to ingest and store high-cardinality data at scale (such as custom analytics) and query your data through a simple SQL API.

    Today, we've expanded Workers Analytics Engine's SQL capabilities with several new functions:

    New aggregate functions: ↗

    • countIf() - count the number of rows which satisfy a provided condition
    • sumIf() - calculate a sum from rows which satisfy a provided condition
    • avgIf() - calculate an average from rows which satisfy a provided condition

    New date and time functions: ↗

    • toYear()
    • toMonth()
    • toDayOfMonth()
    • toDayOfWeek()
    • toHour()
    • toMinute()
    • toSecond()
    • toStartOfYear()
    • toStartOfMonth()
    • toStartOfWeek()
    • toStartOfDay()
    • toStartOfHour()
    • toStartOfFifteenMinutes()
    • toStartOfTenMinutes()
    • toStartOfFiveMinutes()
    • toStartOfMinute()
    • today()
    • toYYYYMM()

    Ready to get started?

    Whether you're building usage-based billing systems, customer analytics dashboards, or other custom analytics, these functions let you get the most out of your data. Get started with Workers Analytics Engine and explore all available functions in our SQL reference documentation.

  1. Select Wrangler environments using the CLOUDFLARE_ENV environment variable

    Workers

    Wrangler now supports using the CLOUDFLARE_ENV environment variable to select the active environment for your Worker commands. This provides a more flexible way to manage environments, especially when working with build tools and CI/CD pipelines.

    What's new

    Environment selection via environment variable:

    • Set CLOUDFLARE_ENV to specify which environment to use for Wrangler commands
    • Works with all Wrangler commands that support the --env flag
    • The --env command line argument takes precedence over the CLOUDFLARE_ENV environment variable

    Example usage

    Terminal window
    # Deploy to the production environment using CLOUDFLARE_ENV
    CLOUDFLARE_ENV=production wrangler deploy
    

    # Upload a version to the staging environment
    CLOUDFLARE_ENV=staging wrangler versions upload
    

    # The --env flag takes precedence over CLOUDFLARE_ENV
    CLOUDFLARE_ENV=dev wrangler deploy --env production
    # This will deploy to production, not dev

    Use with build tools

    The CLOUDFLARE_ENV environment variable is particularly useful when working with build tools like Vite. You can set the environment once during the build process, and it will be used for both building and deploying your Worker:

    Terminal window
    # Set the environment for both build and deploy
    CLOUDFLARE_ENV=production npm run build & wrangler deploy

    When using @cloudflare/vite-plugin, the build process generates a "redirected deploy config" that is flattened to only contain the active environment. Wrangler will validate that the environment specified matches the environment used during the build to prevent accidentally deploying a Worker built for one environment to a different environment.

    Learn more

  1. Workers automatic tracing, now in open beta

    Workers

    Enable automatic tracing on your Workers, giving you detailed metadata and timing information for every operation your Worker performs.

    Tracing example

    Tracing helps you identify performance bottlenecks, resolve errors, and understand how your Worker interacts with other services on the Workers platform. You can now answer questions like:

    • Which calls are slowing down my application?
    • Which queries to my database take the longest?
    • What happened within a request that resulted in an error?

    You can now:

    To get started, set:

    JSONC
    {
      "observability": {
        "tracing": {
          "enabled": true,
        },
      },
    }

    Want to learn more?

  1. D1 can restrict data localization with jurisdictions

    D1 Workers

    You can now set a jurisdiction when creating a D1 database to guarantee where your database runs and stores data. Jurisdictions can help you comply with data localization regulations such as GDPR. Supported jurisdictions include eu and fedramp.

    A jurisdiction can only be set at database creation time via wrangler, REST API or the UI and cannot be added/updated after the database already exists.

    Terminal window
    npx wrangler@latest d1 create db-with-jurisdiction --jurisdiction eu
    curl -X POST "https://api.cloudflare.com/client/v4/accounts/<account_id>/d1/database" \
         -H "Authorization: Bearer $TOKEN" \
         -H "Content-Type: application/json" \
         --data '{"name": "db-with-jurisdiction", "jurisdiction": "eu" }'

    To learn more, visit D1's data location documentation.

  1. Capture Wrangler command output in structured format

    Workers

    You can now capture Wrangler command output in a structured ND-JSON ↗ format by setting the WRANGLER_OUTPUT_FILE_PATH or WRANGLER_OUTPUT_FILE_DIRECTORY environment variables. This feature is particularly useful for CI/CD pipelines and automation tools that need programmatic access to deployment information such as worker names, version IDs, deployment URLs, and error details. Commands that support this feature include wrangler deploy, wrangler versions upload, wrangler versions deploy, and wrangler pages deploy.

  1. Workers WebSocket message size limit increased from 1 MiB to 32 MiB

    Workers Durable Objects Browser Run

    Workers, including those using Durable Objects and Browser Rendering, may now process WebSocket messages up to 32 MiB in size. Previously, this limit was 1 MiB.

    This change allows Workers to handle use cases requiring large message sizes, such as processing Chrome Devtools Protocol messages.

    For more information, please see the Durable Objects startup limits.

  1. Increased Workflows instance and concurrency limits

    Workflows Workers

    We've raised the Cloudflare Workflows account-level limits for all accounts on the Workers paid plan:

    • Instance creation rate increased from 100 workflow instances per 10 seconds to 100 instances per second
    • Concurrency limit increased from 4,500 to 10,000 workflow instances per account

    These increases mean you can create new instances up to 10x faster, and have more workflow instances concurrently executing. To learn more and get started with Workflows, refer to the getting started guide.

    If your application requires a higher limit, fill out the Limit Increase Request Form or contact your account team. Please refer to Workflows pricing for more information.

  1. Access Workers preview URLs from the Build details page

    Workers

    You can now access preview URLs directly from the build details page, making it easier to test your changes when reviewing builds in the dashboard.

    preview button

    What's new

    • A Preview button now appears in the top-right corner of the build details page for successful builds
    • Click it to instantly open the latest preview URL
    • Matches the same experience you're familiar with from Pages