Introducing the Azure Functions serverless agents runtime (preview)
We're thrilled to announce the Azure Functions serverless agents runtime, now in public preview. It brings a new, markdown-first programming model for building AI agents as a first-class workload on Azure Functions, with the event-driven triggers, scale-to-zero economics, and operational integrations you know and love from the platform. A few things you could build in a matter of minutes: A daily briefing agent that wakes up on a timer, scours the web, and drops a summary in your Outlook inbox every morning. A Teams chat agent that triggers on every message and answers your team's questions, looking up data across your connected systems. An on-call troubleshooting agent that investigates incidents by querying logs in Azure Data Explorer and reports back what it found. Each one is a single markdown file with instructions plus a trigger, and deployed like any other function app and running on the Flex Consumption plan. Why a serverless agents runtime Building production agents today usually means stitching together a framework, a hosting layer, message queues, identity, secrets, observability, and a long list of per-service integrations. Most of that work is plumbing, not the agent. Azure Functions has spent years making event-driven compute simple: declare a trigger, write the handler, get autoscale and managed identity for free. The serverless agents runtime applies that same model to agents: Agents are the unit of work. You define behavior in natural language, not boilerplate. Trigger agents from almost any event. HTTP requests, timers, queues, database changes, Teams messages, Outlook mail, and more. Tools, MCP servers, connectors, and sandboxed execution are declared, not coded. Deploy and operate like any function app. Flex Consumption for scale-to-zero and per-second billing, managed identity, VNet integration, Application Insights, and the same deployment tools you already use. Markdown-first: what an agent looks like An agent is a .agent.md file. Your app can have multiple agents, each with its own metadata that declares the trigger. The markdown body becomes the agent's instructions. Here's a timer-triggered agent that summarizes the day's tech news and emails it: --- name: Daily Tech News Email description: Fetches top tech news and emails a summary daily. trigger: type: timer_trigger args: schedule: "0 0 15 * * *" --- You are a news assistant. When triggered, do the following: 1. Scour the web for today's top tech news headlines. Use reputable sources; Include links to the original articles. 2. Summarize the top stories in a concise, well-formatted HTML email body. 3. Email the summary to $TO_EMAIL with the subject "Daily Tech News Summary" followed by today's date. That's the whole function. Drop the file into your app, deploy, and it runs on the schedule. No framework wiring, no service-specific integration code. Your agents can share configuration and capabilities through a few files alongside the agent definitions. agents.config.yaml declares system tools and the default model. mcp.json lists the MCP servers your agents can call, including MCP-enabled Azure connections. A /tools folder holds custom Python tools and a /skills folder holds reusable prompt fragments. Everything here is optional and available to every agent automatically when present. In this example, the agent uses a Container Apps dynamic session to browse the web with Playwright, and a Microsoft Office 365 connection (exposed as an MCP server) to send the email: # agents.config.yaml system_tools: dynamic_sessions_code_interpreter: endpoint: $ACA_SESSION_POOL_ENDPOINT model: $AZURE_OPENAI_DEPLOYMENT // mcp.json { "servers": { "office365": { "type": "http", "url": "$MICROSOFT_365_CONNECTION_MCP_ENDPOINT", "auth": { "scope": "https://apihub.azure.com/.default" } } } } The function app's managed identity authenticates to the connection's MCP endpoint, so there are no secrets to manage. Any Azure connector that supports MCP, or any remote MCP server, can be added the same way. Any of these global settings can be overridden per agent in the agent's metadata. What you get in the preview Triggers across the Azure Functions catalog. HTTP, Timer, Queue, Service Bus, Event Hubs, Cosmos DB, Blob, Event Grid, plus new connection-backed triggers like Teams messages, Outlook mail, and calendar events. 1,400+ Azure connectors as tools. Create a connection, enable its MCP endpoint, and an agent can send mail, post to Teams, create records, query data, all without integration code or auth plumbing. Any remote MCP server as tools. Use any remote MCP server. Sandboxed code and browser automation. Run code or a Playwright-powered browser in Azure Container Apps dynamic sessions, isolated per agent session. Built-in chat UI, HTTP API, and MCP server endpoint with no extra code. Custom Python tools in a tools/ folder and reusable skills in a skills/ folder, shared across agents. Pluggable model providers. Microsoft Foundry, Azure OpenAI, and OpenAI out of the box. Where this fits The serverless agents runtime is designed for the agents most enterprises actually need to build: Scheduled background agents that summarize, monitor, or reconcile on a timer. Event-driven assistants that react to messages, emails, alerts, and database changes. Cross-system agents that tie multiple SaaS and enterprise apps together through connections. Trigger with a Teams message, look up the customer in Salesforce, send an email, and update a database record, all from one agent. Conversational front-ends that pair an HTTP or chat-UI entry point with the same agents your event triggers invoke. Agents as MCP servers that other agents and MCP clients can integrate with directly. We want your feedback The serverless agents runtime is in public preview, and we're actively building it out with input from real customer workloads. Tell us what you build, what's missing, and where the model should go next. Get started Docs: aka.ms/azure-functions-agents-docs Building agents on Azure Functions has never been easier. We can't wait to see what you create with the serverless agents runtime!Azure Functions MCP Extension: What's New at Build 2026
The Azure Functions MCP extension has had a breakout year! Since its initial preview, the extension has grown from a single trigger type into a full-featured platform for building remote MCP servers: with tool, resource, and prompt triggers across multiple languages, MCP Apps for interactive UIs, built-in MCP authentication, and feature enhancements. Here's what's new and what it means for developers building MCP servers on Azure Functions. The full MCP primitive set: Tools, resources, and prompts When the MCP extension first shipped, it supported tool triggers. Declare a function as an MCP tool, and any MCP client can discover and call it. That was the starting point. Since then, we've shipped the remaining MCP primitives: Resource triggers: expose a function as an MCP resource. Prompt triggers: expose a function as an MCP prompt, letting clients request structured prompt templates from your server. Like tool triggers, resource and prompt triggers are supported in multiple languages including .NET, Java, Python, TypeScript, and JavaScript. MCP Apps: interactive UI from your MCP server MCP Apps let your tools return interactive user interfaces instead of plain text. Combine tool triggers with resource triggers, and your MCP server can serve rich, rendered experiences to MCP-aware clients. The Azure Functions MCP extension supports MCP Apps natively, meaning the same function app that exposes tools and resources can also serve UI components. The launch blog post on the Azure Apps Blog walked through the pattern in detail. For .NET developers, the new fluent builder API (available in the latest NuGet release) makes it easier to compose MCP Apps by chaining tool and resource definitions in a declarative style. MCP authentication The extension supports built-in MCP authentication, implementing the requirements of the MCP auth spec. All samples in the aka.ms/remote-mcp repo enable built-in MCP auth by default with Microsoft Entra ID as the identity provider. Samples have also been updated to demonstrate how to exchange tokens in the On-Behalf-Of (OBO) flow, so your MCP tools can access downstream APIs using the invoking user's identity. Auth configuration in the Azure portal: Preview at Build is a one-click experience in the Azure portal for configuring built-in MCP auth. No more manual app registration creating, configuration and wiring to the server. Just open your server app on the portal and click to enable MCP auth. Try it out! Feature enhancements Beyond the headline primitives and auth, the extension has shipped a steady stream of capabilities the past few months. The following are the notable additions. Structured content Structured content lets you return machine-readable JSON metadata alongside your tool's response via the `structuredContent` field. Clients that support it can programmatically consume the data (e.g. parse fields, render tables, drive downstream logic) rather than just displaying text. Clients that don't support it still get the regular content blocks as a fallback. Rich content types Tools aren't limited to returning plain text. The extension supports the full set of MCP content block types, e.g. `TextContent`, `ImageContent`, `AudioContent`, `ResourceLink`, and `EmbeddedResource`, so your tools can return images, audio clips, references to resources, and inline file content alongside text. Input and output schemas `WithInputSchema` and `WithOutputSchema` give you explicit control over the JSON schemas advertised for your tools. This is especially useful when the auto-generated schema from function parameters doesn't capture the full contract. For example, when your tool accepts a complex nested object or returns a specific shape that clients depend on. Input and output schemas are currently supported in .NET, with support for other languages coming soon. builder.ConfigureMcpTool("SearchDocs") .WithOutputSchema(""" { "type": "object", "properties": { "results": { "type": "array", "items": { "type": "string" } }, "query": { "type": "string" } }, "required": ["results", "query"] } """); Fluent configuration APIs in .NET A set of fluent builder APIs that let you configure MCP primitives declaratively in `Program.cs`: ConfigureMcpTool: add properties, metadata, input/output schemas, or promote a tool to an MCP App ConfigureMcpResource: attach metadata to resources ConfigureMcpPrompt: define prompt arguments and metadata builder.ConfigureMcpTool("sayhello") .WithProperty("name", McpToolPropertyType.String, "Name of the user", required: true) .WithMetadata("ui", new { resourceUri = "ui://index.html" }); What's next Usage of the MCP extension has grown steadily since its preview launch. Tool execution volume has increased 15x over the past several months as more customers move from experimentation to production. As adoption grows, so do the expectations. Developers building production MCP servers are hitting real friction around auth complexity, client configuration, and observability. We're continuing to invest in the extension to address these gaps and help customers be more successful building and hosting MCP servers on Azure Functions. Here's where we're focusing next. Continued auth simplification Auth remains the biggest barrier to getting an MCP server into production. We'll work on: Smoother client setup: making it easier to connect any MCP client to an authenticated Azure Functions MCP server, not just VS Code. Simplified OBO flow: streamlining the experience of On-Behalf-Of authentication so developers can delegate user identity to downstream services with less configuration. Our goal: the secure path should be the easy path. Deeper integration with Microsoft Foundry We'll build tighter integration between Azure Functions MCP servers and Microsoft Foundry. This includes surfacing MCP servers in Foundry Toolbox, a new feature introduced to help Foundry agents discover and consume tools from a single endpoint. Developers will be able to publish an MCP server from Functions and have it available to Foundry agents through Toolbox without manual endpoint configuration. Continued feature enhancement We prioritize based on feedback from the community raised in our GitHub repo. For example, support for streaming output and pagination are top items in our backlog today based on user demand. We also track the MCP spec's evolution closely and will continue shipping support for strategic features as they land. Examples of proposals we're following: MCP Tasks: the Tasks extension (SEP-2663) defines a standard pattern for async, long-running tool calls with durable task handles. This replaces hand-rolled polling patterns and aligns well with Functions' execute-and-return model. Stateless MCP: SEP-2575 proposes removing the mandatory initialization handshake, which is a natural fit for serverless platforms like Azure Functions where fresh instances can handle any request. Have something you'd like us to prioritize? Let us know by filing a request on GitHub. Get started Samples: Samples showcasing most up-to-date features: aka.ms/remote-mcp Documentation: Model Context Protocol for Azure Functions MCP Extension GitHub repo: Azure Functions MCP ExtensionWrite Logic Apps in C#: introducing the Logic Apps Standard SDK
The workflow you always wished you could write in code If you build on Logic Apps Standard, you already know the deal: the runtime is excellent at the unglamorous parts of integration - connecting to systems, retrying, scaling, keeping run history you can actually debug. What you sometimes wanted was a different front door. You're a .NET developer. You live in C#, source control, and pull requests. And for a long time, authoring a workflow meant leaving all of that behind for a visual designer and a JSON file. That's the gap the new Logic Apps Standard SDK closes. It lets you define Logic Apps Standard workflows in code - strongly typed, IntelliSense-guided C# - without giving up a single thing the runtime already does for you. What is the Logic Apps Standard SDK? The Logic Apps Standard SDK (Microsoft.Azure.Workflows.Sdk) is a NuGet package that gives you a fluent, code-first way to build workflow definitions in C#. Instead of dragging actions onto a canvas, you compose a workflow with method chaining: a trigger, then the actions that follow it, all the way to a response. Worth saying clearly, because people ask: this is a new way to define workflows - not a new runtime. The workflows you write with the SDK compile down to the same definitions and run on the same Logic Apps Standard runtime you use today. Same connectors. Same hosting. Same rich run history and monitoring. You're changing the authoring experience, not the engine underneath it. Why this matters for developers When your workflow lives in C#, it behaves like the rest of your code. A few things fall out of that almost for free: Type safety and IntelliSense - connector operations, triggers, and outputs are discoverable as you type, and the compiler catches mistakes before you run anything. Real source control and reviews - workflows diff like code, get reviewed in pull requests, and version alongside the services they orchestrate. Familiar tooling - refactor, debug with F5, and lean on the .NET ecosystem you already know. Extensibility on your terms — Compose your workflow declaratively with the fluent builder, then drop into plain imperative C# wherever a step needs logic that might be too complex to implement declaratively - loops, branching, a call into your own library, all encapsulated in a step of your workflow - without leaving the file or the language. And it isn't limited to one style of work. The SDK covers both enterprise integration workflows - the connect-systems-and-move-data scenarios Logic Apps is known for - and agentic workflows, where a conversational or autonomous AI agent drives the steps. Both are first-class in the same SDK, built from the same building blocks. There's one more angle worth calling out, because it's becoming hard to ignore: coding agents are simply better at writing imperative code than declarative JSON. And the reason is the same set of guardrails that helps you. Strong typing and a compilation step mean the code an agent produces is syntactically correct out of the gate — the type system and the compiler do the checking, so you don't have to. Layer unit tests on top and you've covered north of 90% of what matters; what's left is integration testing. Getting an LLM to the same level of accuracy against declarative JSON means building dedicated tooling to stand in for everything the compiler gives you for free. With code-first workflows, those guardrails are just there — which makes this a natural fit for an agent-assisted way of building. Getting started Everything here lives in the Logic Apps extension for VS Code. You'll want the Logic Apps Standard VS Code extension version 5.961.10 or later, which includes all the components you need to create code first workflows. Beyond that, the prerequisites are the ones you'd expect - VS Code with the Logic Apps extension, an Azure subscription you can create resources in, and a working comfort with C# and .NET. From a clean start, you're a handful of steps from a running workflow: Create the workspace — launch the Logic Apps extension and choose Create new Logic Apps workspace. Pick a folder, name the workspace and project, and when prompted for the workflow type, choose Logic Apps codeful - that's the code-first option that uses the SDK. Pick a workflow kind - name your first workflow and choose how it runs: Stateful, Autonomous agents (Preview), or Conversational agents (Preview). The agent options are where the agentic scenarios live. Enable connectors - when prompted, select Use connectors from Azure, choose your subscription and resource group, and pick Connection Keys for authentication. Managed identity is still in development, so connection keys are the way in for now. Find your way around - the project opens with Program.cs, which builds and starts the host, plus a workflow file (like workflow1.cs) where your trigger and actions are defined. The SDK compiles those definitions and runs them on the Logic Apps runtime. Run it - press F5 (or right-click Program.cs and pick Overview). The runtime starts locally and an overview page opens where you can fire triggers, watch run history, and inspect inputs and outputs. That last part is worth dwelling on: run history for SDK workflows uses the same rich visual view as designer-built ones. You author in code, but you monitor and troubleshoot exactly as you always have. A look at the capabilities Connectors and triggers Every workflow starts with a trigger and runs a series of actions. The SDK exposes both through two entry points - WorkflowTriggers and WorkflowActions - each split into BuiltIn and Managed. Built-in triggers and actions run directly in the runtime: HTTP request, recurrence, and the conversational agent trigger; actions like Compose, HTTP, Response, and custom code. Managed connectors give you the full Logic Apps connector catalog - Service Bus, SharePoint, SQL, and hundreds more - typed and ready to call. The managed surface is generated from the same connector definitions the designer uses, so the operations you know are right there: // Built-in trigger var trigger = WorkflowTriggers.BuiltIn.CreateHttpTrigger(); // Managed connector action — full catalog, strongly typed var getItems = WorkflowActions.Managed .Sharepointonline("sharepoint") .GetItems( dataset: () => "https://contoso.sharepoint.com", table: () => "orders-list-id") .WithName("GetOrders"); The fluent API streamlines the definition This is where it comes together. You compose a workflow by chaining operations with .Then(...). The shape of your code mirrors the shape of your workflow - read it top to bottom and you read the execution path. trigger .Then(validateOrder) .Then(getOrders) .Then(sendResponse); Control flow is part of the same fluent model. Built-in structures like Condition (if/else) and ForEach - along with Switch, Until, Scope, and Terminate - are just actions you chain in, each taking a small factory for the branch or loop body: var checkTotal = WorkflowActions.BuiltIn.Control.Condition( expression: () => order.Total > 1000, trueBranch: () => requireApproval, falseBranch: () => autoApprove ).WithName("CheckOrderValue"); And ForEach takes the collection to iterate and a factory that builds the body for each item: var processLines = WorkflowActions.BuiltIn.Control.ForEach( items: () => order.LineItems, actions: (item) => new WorkflowBuiltInActions() .Compose(inputs: () => $"Line: {item}").WithName("HandleLine") ).WithName("ProcessLineItems"); Need parallel branches that fan back in? The same Then pattern handles branching and join - no JSON wiring, no run-after blocks to hand-edit. Extending workflows with custom code Some logic doesn't belong in a connector or an expression - it's just code. The CustomCode action lets you drop a real C# method into the middle of a workflow. It receives a WorkflowContext, so you can read the trigger payload or any earlier action's results and return a strongly typed value the next step can use: var enrich = WorkflowActions.BuiltIn.CustomCode<string>(async (context) => { var trigger = await context.GetTriggerResults(); var order = await context.GetActionResults("GetOrders"); // your logic, your libraries, your types return "enriched"; }).WithName("EnrichOrder"); That's the escape hatch that keeps you in flow: when a step needs custom transformation, validation, or a call into your own libraries, you write a method instead of bending an expression to do something it was never meant to. Handling failures: try/catch with run-after Real workflows have to deal with things going wrong, and the SDK gives you the same try/catch shape Logic Apps has always had - expressed in code. The .Then(...) overload takes a FlowStatus[] run-after condition, so a handler runs only when the step before it ends in a status you name. Wrap the risky work in a Scope (your try), then chain a handler that runs after it Failed or TimedOut (your catch): var tryProcess = WorkflowActions.BuiltIn.Control.Scope(() => callPaymentApi.Then(saveOrder) ).WithName("ProcessPayment"); var handleFailure = WorkflowActions.BuiltIn .Compose(inputs: () => "Payment failed — compensating") .WithName("HandleFailure"); trigger .Then(tryProcess) .Then(handleFailure, runAfter: new[] { FlowStatus.Failed, FlowStatus.TimedOut }); The status set is the whole vocabulary: Succeeded, Failed, Skipped, and TimedOut. Combine them however a step needs - a cleanup action that should run no matter what can list every status; a finally is just the union. The same idea scales to fan-in. When several parallel branches converge, the per-predecessor RunAfter overload lets the join wait on each branch independently - so you can require some to succeed and tolerate others failing: leftChain .Join(rightChain) .Then(merge, runAfter: new[] { new RunAfter(leftChain, FlowStatus.Succeeded), new RunAfter(rightChain, FlowStatus.Succeeded), }); Putting it together Here's a small but complete shape - an HTTP-triggered order workflow that validates input, branches on order value, loops over line items, runs custom code, and replies. The core steps live in a Scope so a single failure handler can catch anything that goes wrong, and a clean reply only runs when the work succeeds. Notice it's all one readable chain: namespace LogicApps { using Microsoft.Azure.Workflows.Sdk; using Microsoft.Azure.Workflows.Sdk.Connectors.Msnweather; using System.Net; public class OrderWorkflow : IWorkflowProvider { /// <summary> /// Gets the HTTP request/response workflow definition. /// </summary> public FlowDefinition[] GetWorkflows() { // --- Trigger ---------------------------------------------------- var trigger = WorkflowTriggers.BuiltIn.CreateHttpTrigger(); // --- Managed connector action (full catalog, strongly typed) ---- // Reused verbatim from the confirmed stateful1.cs pattern. var getWeather = WorkflowActions.Managed.Msnweather("msnweather").CurrentWeather( location: () => "98058", units: () => unitsInput.Imperial).WithName("GetWeather"); // --- Custom code: real C# in the middle of the workflow --------- var enrich = WorkflowActions.BuiltIn.CustomCode<string>(async (context) => { var triggerResults = await context.GetTriggerResults(); var weather = await context.GetActionResults("GetWeather"); // your logic, your libraries, your types return "enriched"; }).WithName("EnrichOrder"); // --- ForEach over a collection (control flow via .Control) ------- var processLines = WorkflowActions.BuiltIn.Control.ForEach( items: () => trigger.TriggerOutput.Body["lineItems"], actions: (item) => WorkflowActions.BuiltIn .Compose(inputs: () => $"Line: {item}").WithName("HandleLine") ).WithName("ProcessLineItems"); // --- Condition (if/else) (control flow via .Control) ------------ var checkTotal = WorkflowActions.BuiltIn.Control.Condition( expression: () => true, trueBranch: () => processLines, falseBranch: () => WorkflowActions.BuiltIn .Compose(inputs: () => "Auto-approved").WithName("AutoApprove") ).WithName("CheckOrderValue"); // --- Scope groups the core steps so one handler catches failures - var processOrder = WorkflowActions.BuiltIn.Control.Scope(() => checkTotal .Then(getWeather) .Then(enrich) ).WithName("ProcessOrder"); // --- Responses -------------------------------------------------- var ok = WorkflowActions.BuiltIn.Response( responseBody: () => "Order processed").WithName("Reply"); var failed = WorkflowActions.BuiltIn.Response( statusCode: () => HttpStatusCode.InternalServerError, responseBody: () => "Order failed").WithName("ReplyFailed"); // --- Assemble --------------------------------------------------- // Happy path runs after the Scope Succeeded; the handler runs after // Failed or TimedOut. trigger .Then(processOrder) .Then(ok, runAfter: new[] { FlowStatus.Succeeded }) .Then(failed, runAfter: new[] { FlowStatus.Failed, FlowStatus.TimedOut }); return new[] { WorkflowFactory.CreateStatefulWorkflow("OrderWorkflow", trigger) }; } } } That last stretch is the best-practice shape in miniature: the happy-path Reply runs only after the Scope Succeeded, while a separate handler catches Failed or TimedOut and returns a 500 - no exception plumbing, just run-after conditions. You implement IWorkflowProvider, hand your trigger graph to WorkflowFactory as a stateful, stateless, or agent workflow, and the host registers it. Run it with F5 and the Logic Apps runtime starts locally - same as any Standard project. Before you build: preview realities I'd rather you go in clear-eyed. While the SDK is in public preview, keep these in mind: Service Provider connectors aren't supported yet - that connector type is coming in a future release. Dynamic schemas aren't supported - support is planned. Custom code supports callback methods only - inline lambdas aren't available in this version. Define and name actions before referencing them - name an action before using it as a dependency elsewhere. Managed identity authentication is in development - use connection keys for connectors in the meantime. Try it, and tell us what you think If you've ever wanted your workflows to live where the rest of your code lives - in C#, in source control, in your pull requests - this is for you. Install the Logic Apps extension for VS Code, create a Logic Apps codeful project, and build your first workflow in code. This is a preview, which means your feedback genuinely shapes where it goes - which capabilities come next, where the rough edges are. Bring issues, feature requests and feedback to our GitHub page. I read it. Let's make code-first workflows something you actually want to use.Announcing Go support in Azure Functions (Preview)
We're excited to announce that Azure Functions now supports Go as a first-class language, available today in public preview on the Flex Consumption plan. Go developers can now build event-driven, serverless applications using idiomatic Go, the standard toolchain they already love, and the full breadth of Azure Functions triggers, bindings, and operational capabilities. TL;DR: Write Functions in Go using a new code-first programming model and SDK (azure-functions-golang-worker). Use triggers across HTTP, Timer, Service Bus, Event Hubs, Event Grid, Cosmos DB, and Blob Storage. Why Go on Azure Functions Go has become a default choice for cloud-native APIs, platform services, networking tools, and high-throughput integration workloads. Until now, teams that standardized on Go on Azure had to either: Use Azure Functions through the custom handlers protocol, missing out on a first-class developer experience, or Build and operate their own serving, scaling, and eventing infrastructure on containers or VMs. With first-class Go support, those teams get the productivity of Go plus the operational leverage of serverless: automatic scaling, pay-per-use billing, integrated triggers across the Azure ecosystem, and built-in observability, without leaving the Go ecosystem. What's in the preview A new Go programming model and SDK: a code-first, idiomatic way to register Functions and declare triggers using functional options. Support for popular triggers: HTTP, Timer, Service Bus (queues and topics), Event Hubs, Event Grid, Cosmos DB, and Blob Storage. More to come. Native Go build pipeline: go build produces a single static binary that the Functions host invokes directly. No function.json, no interop shims at request time. Integrated observability: Application Insights logging, metrics, and distributed tracing. End-to-end tooling: local development with a preview build of Azure Functions Core Tools. Deployment via Core Tools, zip deploy, or GitHub Actions. Flex Consumption: fast elastic scale, scale-to-zero, per-second billing, VNet integration, and always-ready instances. A quick look at the programming model The Go model is code-first: you register functions and declare triggers in Go, with compile-time checks and full IDE support. No separate JSON metadata to keep in sync. Here's a minimal HTTP-triggered Function: package main import ( "fmt" "net/http" "github.com/azure/azure-functions-golang-worker/sdk" "github.com/azure/azure-functions-golang-worker/worker" ) func main() { app := sdk.FunctionApp() app.HTTP("hello", hello, sdk.WithMethods("GET", "POST"), sdk.WithAuth("anonymous"), ) worker.Start(app) } func hello(w http.ResponseWriter, r *http.Request) { name := r.URL.Query().Get("name") if name == "" { name = "world" } fmt.Fprintf(w, "Hello, %s!", name) } Notice the HTTP handler is a plain http.HandlerFunc, the same signature you'd use with net/http or any Go web framework. There's nothing Functions-specific to learn at the handler level. Registering other triggers The same pattern works across triggers. Non-HTTP handlers take a context.Context plus a typed payload: import ( "context" "log" "github.com/azure/azure-functions-golang-worker/sdk" "github.com/azure/azure-functions-golang-worker/sdk/bindings" ) // Timer: runs every 10 seconds func onTimer(ctx context.Context, t bindings.TimerInfo) error { log.Printf("timer fired; past due=%v", t.IsPastDue) return nil } app.Timer("cleanup", onTimer, sdk.WithSchedule("*/10 * * * * *"), ) // Service Bus queue func onOrder(ctx context.Context, msg bindings.ServiceBusMessage) error { log.Printf("order %s: %s", msg.MessageId, string(msg.Body)) return nil } app.ServiceBusQueue("processOrder", onOrder, sdk.WithQueueName("orders"), sdk.WithConnection("ServiceBusConnection"), ) // Event Hubs func onEvent(ctx context.Context, e bindings.EventHubMessage) error { log.Printf("event seq=%d body=%s", e.SequenceNumber, string(e.Body)) return nil } app.EventHub("ingest", onEvent, sdk.WithEventHubName("telemetry"), sdk.WithConnection("EventHubConnection"), ) // Cosmos DB change feed func onChange(ctx context.Context, docs []bindings.CosmosDocument) error { for _, d := range docs { log.Printf("doc %s: %s", d.ID, string(d.Data)) } return nil } app.CosmosDB("onChange", onChange, sdk.WithDatabase("ToDoList"), sdk.WithContainer("Items"), sdk.WithConnection("CosmosDBConnection"), ) // Event Grid func onGridEvent(ctx context.Context, e bindings.EventGridEvent) error { log.Printf("%s: %s", e.EventType, e.Subject) return nil } app.EventGrid("onEvent", onGridEvent) Extension triggers: real Azure SDK clients For triggers like Blob Storage, the Go SDK injects a fully-typed Azure SDK client directly into your handler. You opt in with a blank import, so your binary only includes the extensions you actually use: import ( "context" "io" "log" "github.com/Azure/azure-sdk-for-go/sdk/storage/azblob/blob" "github.com/azure/azure-functions-golang-worker/sdk" _ "github.com/azure/azure-functions-golang-worker/triggers/blob" // registers blob trigger client factory "github.com/azure/azure-functions-golang-worker/worker" ) func onUpload(ctx context.Context, client *blob.Client) error { log.Printf("blob: %s", client.URL()) resp, err := client.DownloadStream(ctx, nil) if err != nil { return err } defer resp.Body.Close() data, err := io.ReadAll(resp.Body) if err != nil { return err } log.Printf("size=%d", len(data)) return nil } app.Blob("onUpload", onUpload, sdk.WithPath("uploads/{name}"), sdk.WithConnection("AzureWebJobsStorage"), sdk.WithSource("EventGrid"), ) The handler receives a *blob.Client from github.com/Azure/azure-sdk-for-go/sdk/storage/azblob/blob, the same client you'd use in any other Go app. Because it's a real SDK client, you can DownloadStream blobs of any size without buffering the whole payload through the worker. Dependencies stay isolated per extension, so apps that don't use Blob never pull in azblob or azidentity. Project layout A Go function app is just a regular Go module plus the standard Functions config files: my-function-app/ ├── host.json ├── local.settings.json ├── go.mod ├── go.sum └── main.go No function.json and no generated metadata. Triggers are declared in main.go. go build, go test, and go mod tidy all just work. Get started Quickstart Install the preview tooling, scaffold your first Go function app, run it locally, and deploy to Flex Consumption. We can't wait to see what you build. Welcome to Functions, Gophers.Introducing On-demand Sandboxes for Azure Durable Task Scheduler (Private Preview)
Maybe it needs a native toolchain. Maybe it runs untrusted customer or LLM-generated code. Maybe it needs Python from a .NET orchestrator, or bursty compute that should scale to zero when the work is done. Today, we're thrilled to announce On-demand Sandboxes for Azure Durable Task Scheduler, now available in private preview. On-demand Sandboxes lets you move those individual workflow steps to managed, isolated compute while your orchestrator stays exactly where it is. Tell DTS which steps should run in isolation, provide a container image with the step code, and DTS handles provisioning, scaling, and teardown. No infrastructure to manage, no idle costs, no orchestrator changes. Sign up for On-demand Sandboxes Private Preview Today → Availability: On-demand Sandboxes targets the standalone Durable Task SDKs used outside the Azure Functions host — for apps running on Azure Container Apps, Azure Kubernetes Service, App Service, or anywhere else you self-host. The private preview supports the .NET and Python Durable Task SDKs, with additional language SDKs and Azure Functions support coming soon. What is Azure Durable Task Scheduler? The Durable Task Scheduler is a fully managed backend for durable execution on Azure. It can serve as the backend for a Durable Function App using the Durable Functions extension, or as the backend for an app leveraging the Durable Task SDKs in other compute environments, such as Azure Container Apps, Azure Kubernetes Service, or Azure App Service. For a deeper introduction, see the Durable Task Scheduler overview or the full Durable Task documentation. Why On-demand Sandboxes? Most activities belong in-process. They're fast, simple, and co-located with your orchestrator. But sometimes you hit a step that doesn't fit: it needs a native binary, a different language runtime, per-invocation isolation, or bursty compute you don't want to keep warm. On-demand Sandboxes gives you a way to handle those exceptions without spinning up dedicated infrastructure or managing scaling policies in Azure Kubernetes Service or Azure Container Apps. Activity-level granularity. Move individual steps to managed compute, not your whole app. Per-activity or per-invocation isolation. Each execution runs in a clean, microVM-backed sandbox. Ideal for untrusted code, customer plugins, or LLM-generated logic. Cross-runtime flexibility. Run a Python inference step from a .NET orchestrator. No compromise on either side. Scale-to-zero. Pay for CPU and memory per second of execution, not infrastructure that waits. No orchestrator changes. Your orchestration code and hosting model don't change at all. Here are a few scenarios where On-demand Sandboxes shines: Native toolchains. Package ffmpeg, LibreOffice, or Pandoc in a container without dragging them into your main app. CPU-heavy preprocessing. OCR, layout extraction, or image processing can scale independently of the rest of your workflow. Cross-runtime workflows. A .NET orchestrator dispatches a Python inference step. No compromises. Sandboxed code execution. Run customer plugins or LLM-generated code with a clean boundary on every invocation. Multi-tenant isolation. Tenant-specific steps get dedicated boundaries while everything else stays in-process. Bursty event-driven workloads. Steps that spike hard but rarely may not justify always-on infrastructure. Sub-second cold starts mean you get capacity when you need it without paying to keep it warm. How it works On-demand Sandboxes uses a two-part model: a worker profile in your orchestrator app that tells DTS which activities to offload, and a worker image that contains those activity implementations. Your orchestrator still calls activities the same way it always has; the decision to run one activity in a sandbox lives in the profile configuration. 1. Declare a sandbox worker profile In the app that hosts your orchestrator, define a sandbox worker profile. The profile gives DTS the container image, resource shape, concurrency setting, and activity names that should run in a sandbox: using Microsoft.DurableTask.Worker.AzureManaged.Sandbox; [SandboxWorkerProfile("code-executor")] internal sealed class CodeSandboxWorkerProfile : ISandboxWorkerProfile { public void Configure(SandboxOptions options) { options.ContainerImage = Environment.GetEnvironmentVariable("DTS_SANDBOX_IMAGE") ?? throw new InvalidOperationException("DTS_SANDBOX_IMAGE is required."); options.Cpu = "1000m"; options.Memory = "2048Mi"; options.MaxConcurrentActivities = 1; options.AddActivity(TaskNames.ExecuteCode); } } Then enable on-demand sandbox discovery when you configure the Durable Task worker in the main app: workerBuilder.AddTasks(tasks => tasks.AddAllGeneratedTasks()); workerBuilder.UseDurableTaskScheduler(options => { options.EndpointAddress = Environment.GetEnvironmentVariable("DTS_ENDPOINT"); options.TaskHubName = Environment.GetEnvironmentVariable("DTS_TASK_HUB"); options.Credential = credential; }); workerBuilder.EnableSandboxes(); Here's what the profile configuration does: SandboxWorkerProfile: a friendly profile id for this sandbox setup. It groups the activity, image, and resource settings for monitoring and reuse across deployments. ContainerImage: the container image (from your registry) that contains the activity implementations. Cpu / Memory: the resource shape for each worker instance. Sized per your activity's needs. MaxConcurrentActivities: how many activities a single worker instance can process concurrently. AddActivity: the specific activity to offload. Only activities added to a sandbox worker profile execute in DTS-managed isolated compute; everything else stays in-process. The orchestrator call site doesn't change: ExecuteCodeOutput execution = await context.CallActivityAsync<ExecuteCodeOutput>( TaskNames.ExecuteCode, new ExecuteCodeInput(pythonCode, input.CsvData)); ExecuteCode is not registered in the main app's in-process activity list. When the orchestrator calls it, DTS uses the codegen profile to route the work to the sandbox image. 2. Build the worker image The worker image is a container you own. In most apps, this worker lives in a separate project from the orchestrator host so it can have its own entry point, dependencies, and container image. It registers the activity implementations it can run and opts in to managed execution with UseSandboxWorker(): builder.Services.AddDurableTaskWorker(workerBuilder => { workerBuilder.AddTasks(tasks => { tasks.AddActivity<ExecuteCodeActivity>(); }); workerBuilder.UseSandboxWorker(); }); UseSandboxWorker() is the key line. It signals that this worker runs in DTS-managed compute. The sandbox worker does not need to configure the DTS endpoint, task hub, profile id, or credentials; DTS injects the runtime settings when it starts the container. The activity implementations themselves are standard Durable Task activities. There's nothing special about the activity code: it can call a runtime with different dependencies, such as Python and pandas, while running in an isolated container instead of in your main app's process. Package the image like any containerized service, including whatever runtimes and native tools the activity needs. Push it to your container registry (e.g., Azure Container Registry) and reference the image in the worker profile's ContainerImage option. View logs in the DTS dashboard Once your sandbox activities are running, you can view their execution logs directly in the Durable Task Scheduler dashboard. The dashboard shows real-time output from your managed workers, including stdout, stderr, and activity lifecycle events. This gives you full visibility into what's happening inside the sandbox without needing to configure external log sinks or set up your own observability pipeline. Demo Get started On-demand Sandboxes is in private preview. To get access, sign up here. We'll enable the feature on your scheduler and help you get your first sandbox activity running. Once you're in, the workflow is straightforward: declare a sandbox worker profile in your orchestrator app, build and push a worker image, and DTS takes care of the rest. Sign up for On-demand Sandboxes Private Preview Today → Documentation: Durable Task Scheduler overview Samples: Azure-Samples/Durable-Task-Scheduler Pricing: Azure Durable Task Scheduler pricing Questions, feedback, or ideas? Open an issue in the Durable-Task-Scheduler GitHub repo. We'd love to hear from you.Introducing Azure Container Apps Sandboxes: Secure Infrastructure for Agentic Workloads
Today we are announcing the public preview of Azure Container Apps Sandboxes - a new first-class resource type that gives you fast, secure, ephemeral compute environments with built-in suspend and resume. This is the underlying infrastructure on which products like Cloud sandboxes in GitHub Copilot, Foundry Hosted Agents, and Azure Container Apps Express are built, you now have the opportunity to build your solutions leveraging this infrastructure. Azure Container Apps Sandboxes unlocks two massive opportunities. For platform developers and ISVs, sandboxes give you the same isolated compute fabric that powers many Microsoft products. You get the building blocks to create your own multi-tenant platform on proven, enterprise-scale infrastructure. For AI agents, sandboxes become a self-configurable tool that lets agents extend their own capabilities on the fly. An agent can spin up a fresh sandbox in milliseconds and use it to execute untrusted code, compile source, test HTTP requests against a live app, launch a browser session, or tackle whatever needs a quick and scalable infrastructure. On one side it empowers humans to build platforms, on the other it empowers agents to build their own capabilities. Both get enterprise-grade isolation, instant startup, and snapshot-based persistence out of the box. We'll walk through the resource model, sandbox lifecycle, the features that set Sandboxes apart - like snapshots, lifecycle policies, network egress controls, volumes, and managed identities - and show you how to get started with the portal and CLI. What Are Container Apps Sandboxes? Container Apps Sandboxes are secure, isolated compute environments that start in sub-second time, scale to thousands, and cost nothing when idle. Each sandbox runs in its own hardware-isolated microVM boundary - fully separated from the host, the platform, and every other sandbox. You bring your own Open Container Initiative (OCI) image, and Sandboxes handle the rest: provisioning from prewarmed pools, strong multi-tenant isolation, and snapshot-based suspend/resume that preserves full memory and disk state across sessions. There are many ways Sandboxes can help you build your next project - here are a few: Your own build & test systems - wire a Sandbox into your CI/CD flow to run builds while your laptop stays cool. Agents that can run anything safely - an agent spawns a sandbox, executes work inside it, and returns the output with no agent host privileges required. Agent swarms - decompose a research question, spawn N sandbox workers in parallel (each pinned to its own image and egress policy), and synthesize the result. Early access customers are already unlocking significant benefits by leveraging Azure Container Apps Sandboxes. "With Azure Container Apps sandboxes, SitecoreAI can safely enable agents to take real action. The combination of multi-tenant isolation, rapid scale-out, and full automation allows Sitecore to run long-lived, autonomous agents that securely execute code, manage workflows, and interact with enterprise systems within secure, governed environments. With this foundation, we can build agents that do real work: assembling content, personalizing experiences, and optimizing campaigns in production. Agents that operate continuously, learn from results, and improve over time, so our customers get better outcomes without giving up control." - Mo Cherif, VP of AI and Innovation, Sitecore "We got early access to Azure Container Apps Sandboxes, and got the first prototype integrated with Atlas AI in hours, and it's already shaping a new Atlas AI capability that we plan to launch in preview in Q3. It gives every Atlas AI agent a safe, sandboxed workspace (file system, terminal, code execution) on a customer's live data in Cognite Data Fusion. The value: Industrial process, reliability, and production engineers spend days and weeks on questions like "which wells are underperforming and why?" These questions are tractable but expensive, so they are asked rarely and decisions are made on gut feel. With this, an agent pulls the data, runs the analysis, cross-references maintenance and inspection records, and returns a cited draft in minutes. Sandboxes make it practical: Aligned feature set, per-customer isolation, pause/resume across multi-day investigations, scale-to-zero economics." - Kelvin Sundli, Product manager, Atlas AI, Cognite Resource Model: Sandbox Groups and Sandboxes The top-level ARM resource is Microsoft.App/SandboxGroups. A Sandbox Group is the management boundary for a collection of sandboxes that share configuration - think of it like a Container Apps Environment, but purpose-built for sandboxes. When you create a Sandbox Group, you specify: Subscription, Resource Group, and Region Sandbox defaults (optional): default CPU, memory, disk, max sandbox count, and default idle timeout Networking: optionally deploy into a custom VNet with a dedicated subnet for private networking Identity: System or user assigned Entra identity. Individual sandboxes are created within a Sandbox Group. Each sandbox has its own source (disk image or snapshot), resource tier, lifecycle policy, network egress policy, environment variables, ports, volumes, and connections. Sandbox Lifecycle Sandboxes have a well-defined lifecycle with the following states: State Description Creating Provisioning the sandbox from a disk image or snapshot Running Actively executing - backed by a live microVM Idle System-suspended after inactivity; can auto-resume on the next request Suspended Full state (memory + disk) preserved as a snapshot; no compute costs Resuming Restoring from a suspended or idle state - sub-second for most workloads Stopped User-initiated stop; can be resumed Stopping Graceful shutdown in progress Deleting Teardown in progress The key insight here is the distinction between Idle and Suspended. When a sandbox goes idle (e.g., no traffic for a configured timeout), the system can automatically suspend it and capture a snapshot. When a new request arrives, the sandbox resumes transparently. This gives you scale-to-zero economics with stateful compute - something that wasn't possible before without significant custom engineering. Disk Images: Bring Your Own Container Sandboxes boot from Disk Images - Open Container Initiative (OCI) images converted into an optimized root filesystem format. You point to any OCI image (public or private registry), and the platform builds a bootable disk image from it. You can start with public, pre-built images maintained by the platform (for example, Ubuntu base images), or bring your own private images. For private registries, you can authenticate with username/token or use a user-assigned managed identity for Azure Container Registry (ACR) – integrated with Azure as you expect. Snapshots: Full-State Persistence Snapshots capture the complete state of a running sandbox - memory, disk, and all running processes. When you resume a sandbox from a snapshot, every process, open file handle, and in-memory data structure is restored exactly as it was. A snapshot captures the full state of a running sandbox: memory pages, disk, processes. Two ways to make one - automatically on suspend, or manually on demand. Three things they're great for: Checkpointing mid-task so a long-running agent can resume exactly where it left off Cloning an environment that's already warm - dependencies installed, caches populated, services running Shipping a "ready-to-go" state that resumes in sub-second instead of cold-booting Snapshots are free during the preview, after which they will be stored as Azure Blob Storage at standard rates. Each snapshot records the source sandbox, resource allocation (CPU, memory, disk), and container metadata - so what you get back is exactly what you snapshotted. Resource Tiers Every sandbox is assigned to a resource tier that determines its CPU, memory, and disk allocation: Tier CPU Memory Disk XS 0.25 vCPU 0.5 GB 5 GB S 0.5 vCPU 1 GB 10 GB M (default) 1vCPU 2 GB 20 GB L 2 vCPU 4 GB 40 GB XL 4 vCPU 8 GB 80 GB When creating a sandbox from a snapshot, the resource tier is inherited from the snapshot and cannot be changed - this ensures the restored environment has the exact resources it was running with when the snapshot was taken. Lifecycle Policies: Auto-Suspend and Auto-Delete Every sandbox can be configured with lifecycle policies that automate state transitions and cleanup: Auto-Suspend Idle timeout: How long a sandbox can sit idle before being suspended (configurable: 1m, 2m, 5m, 10m, 30m, 60m) Suspend mode: Disk + Memory (default): Full snapshot including memory state - resume picks up exactly where you left off, with all processes and in-memory data intact. Disk: Only the disk is preserved; the VM restarts fresh on resume. Useful when you only need file persistence, not process continuity. Auto-Delete Automatically delete sandboxes after a configurable number of days of inactivity Prevents accumulation of abandoned sandboxes that consume snapshot storage These lifecycle policies are what make Sandboxes economically viable at scale. A platform serving thousands of tenants can configure aggressive idle timeouts (say, 60 seconds) with Memory suspend mode, and each tenant's sandbox disappears from the billing meter almost immediately - but resumes in sub-second time the moment they return. Network Egress Policy For scenarios involving untrusted code - AI agents executing LLM-generated scripts, multi-tenant SaaS with user-submitted workloads - controlling outbound network access is critical. Sandboxes provide a per-sandbox Network Egress Policy: Default action: Allow or Deny all outbound traffic Host rules: Domain-pattern rules (e.g., *.github.com → Allow) to permit specific destinations Custom CIDR rules: Network-level rules for IP ranges (e.g., 10.0.0.0/8 → Deny) Skip egress proxy: Option to bypass the egress proxy entirely when custom VNet routing handles policy enforcement This means you can run a sandbox in a deny-by-default posture and allowlist only the specific endpoints it needs (your API server, a package registry, etc.) - without setting up NSGs or firewall appliances. Managed Volumes: Persistent and Shared Storage Sandboxes support two types of mountable volumes, both managed by Microsoft: Volume Type Backed By Best For Managed Azure Blob Azure Blob Storage Shared data across sandboxes, file uploads/downloads, persistent artifacts Managed Data Disk Azure Disk Storage High-performance storage for databases, build caches, large working sets - only available to one sandbox at a time Blob volumes come with a built-in file explorer in the portal - you can browse, upload, download, create folders, and drag-and-drop files directly. Data Disk volumes provide dedicated block storage with configurable sizes. Secrets and Identity Secrets Sandbox Groups support key-value secrets scoped to the group. Secrets can be created, edited, and referenced by sandboxes within the group. These secrets can be used in egress policies to modify requests with transform or header-injection rules, without exposing the secrets to code running inside the sandbox. Managed Identity Sandbox Groups support both system-assigned and user-assigned managed identities, with full RBAC role assignment management. This means your sandboxes can authenticate to Azure services (Key Vault, Storage, Cosmos DB, etc.) without managing credentials - the same identity model you use everywhere else in Azure. MCP Connectors and Triggers ACA Sandboxes now supports managed connectors through the Model Context Protocol (MCP), giving sandboxes access to external APIs - including Microsoft 365, Salesforce, ServiceNow, GitHub, and 1,400+ other systems - without managing credentials directly. Attach a Connector Gateway to your sandbox group, and every sandbox in the group can call external APIs through a standardized MCP interface at runtime. Pair connectors with triggers to build event-driven automation: route an Outlook email to a sandbox that triages it with an AI agent, or react to a SharePoint file upload by extracting and processing the document all without writing glue code. Triggers can fire a shell command inside a sandbox or invoke an HTTP endpoint the sandbox exposes, so your automation shapes fit naturally around your workload. The integration is built on the new Connector Namespace service (az connector-namespace), the same runtime behind Logic Apps and Power Platform connectors, now available as a programmable layer for sandboxes. See the end-to-end samples for runnable azd up-deployable examples covering email triage and document automation scenarios. The Portal Experience Azure Container Apps Sandboxes are only available in the new Azure Container Apps portal that provides a rich, IDE-like experience for working with sandboxes. Creating a Sandbox The portal offers multiple creation paths: Standard Sandbox - full configuration control over source, resources, lifecycle, networking, and volumes GitHub Copilot Sandbox - preset, Copilot CLI ready to go, GitHub credentials can be wired through the Access Token before the sandbox is created Claude Sandbox - Claude CLI pre-installed, ready for agentic coding inside the sandbox Using Coding Agents (Copilot CLI / Claude Code) If you live inside Copilot CLI or Claude Code, you don't need to learn a new CLI. Install the azure-sandbox skill once and your agent picks up the right skills: # GitHub Copilot CLI # Add as a plugin marketplace /plugin marketplace add microsoft/azure-container-apps # Install all skills /plugin install sandboxes@Azure-Container-Apps # Claude Code claude plugin add microsoft/azure-container-apps The skill runs prerequisite checks silently (az --version, az account show, node --version, aca --version), prompts only if something's missing, and maps natural-language asks to the right aca commands. Bundled runbooks cover Copilot CLI BYOK (bring your own Azure OpenAI key), the deploy-a-web-app walkthrough, and shell setup. Sandbox Detail Page Once your sandbox is running, the detail page gives you immediate access to the sandbox terminal and additional details, such as - Network Audit - real-time egress traffic log showing allowed and denied requests Monitor - live CPU, memory, disk, and network utilization charts Connectors - attached connections with an "Add" action Volumes - mounted volumes with an "Add" action Log Stream - streaming container logs Processes - running process list inside the sandbox Files - file explorer to browse the sandbox filesystem The toolbar actions let you manage the state of the sandbox - Resume or Stop. In the Ellipsis menu (⁝) you can find additional settings to manage network Egress Policy and ingress (Add port), take a Snapshot of the sandbox, Commit (save disk state as a new disk image), set Lifecycle Policy or permanently Delete the sandbox. Finally, you can see additional Details in a side panel. Getting Started with the CLI and Python SDK All sandbox and sandbox-group operations go through the aca CLI. There are no az containerapp sandbox commands, - az is only used for az login, az account show, and resource-group management. Install (CLI) # Mac, Linux curl -fsSL https://aka.ms/aca-cli-install | sh # Windows irm https://aka.ms/aca-cli-install-ps | iex Run aca --help to get started. Install (Python SDK) pip install azure-containerapps-sandbox For more details, quick start and examples on ACA CLI and Python SDK, please go to https://sandboxes.azure.com Evolution from Dynamic Sessions If you've used Azure Container Apps Dynamic Sessions, Sandboxes are the next evolution of that capability. Everything Sessions can do, Sandboxes can do - and significantly more: Capability Dynamic Sessions Sandboxes Sub-second startup ✓ ✓ Strong isolation ✓ ✓ Custom container images ✓ ✓ Custom VNet integration ✓ (Partial) ✓ Suspend/resume with Memory and Disk snapshots - ✓ Lifecycle policies (auto-suspend, auto-delete) - ✓ Network egress policy (per-sandbox) - ✓ Persistent managed volumes (Blob, Data Disk) - ✓ Managed identity (system + user-assigned) - ✓ Secrets management - ✓ Configurable resource tiers - ✓ Direct access to sandbox in Portal experience - ✓ We will continue to support Dynamic Sessions, but all new investment goes into Sandboxes. If you're building new workloads on isolated ephemeral compute, start with Sandboxes. How It All Fits Together ACA Sandboxes is a platform primitive. It's the foundation on which multiple Microsoft products are already built - including ACA Express, Cloud sandboxes in GitHub Copilot, and Foundry Hosted Agents. When you build on Sandboxes, you're building on the same infrastructure that powers Microsoft's own portfolio. This is the evolution of what we shared with Project Legion in 2024. Legion described the internal infrastructure; Sandboxes exposes it as a customer-facing primitive that you can use directly. What's Next • Deeper Azure integrations - first-class connectivity with Azure networking, identity, storage, and AI services • Enhanced SDK and CLI - richer programmatic experiences for managing sandboxes at scale • More Microsoft services built on Sandboxes - this is just the beginning Get Started Today • Portal: https://sandboxes.azure.com/ • Documentation: Azure Container Apps Sandboxes • Pricing: Azure Container Apps Pricing (per-second vCPU/memory billing, scale-to-zero, snapshots at Blob Storage rates) We'd love to hear your feedback. You can ask questions, or file issues on the Azure Container Apps GitHub (prefix with [Sandbox] for Sandboxes-specific issues).What's new in Azure Container Apps at Build'26
Azure Container Apps (ACA) is a fully managed serverless container platform that enables developers to build and deploy microservices and modern applications without requiring container expertise or needing infrastructure management. ACA provides built-in autoscaling (including scale to zero), per-second billing, advanced networking, built-in observability, and simplified developer experiences across multiple programming languages and frameworks. The world of application development is shifting rapidly. Agentic AI is fundamentally changing the requirements of cloud platforms - more code is being written by AI, more apps are being deployed by agents, and more deployment stacks are being assembled autonomously. Platforms are aligning to two concurrent demands: hosting intelligent agents as first-class workloads, and giving those same agents access to empty, secure compute pools as tools they can invoke on demand. At the same time, the proliferation of AI-generated code means that platforms must offer strong isolation for untrusted workloads, instant provisioning for rapid iteration, and production-grade defaults that make the right thing the easy thing - for both humans and agents. Azure Container Apps is purpose-built for this new reality. Whether you're a developer shipping a web app in minutes or an agent spinning up ephemeral sandboxes for code execution, ACA provides the serverless foundation that meets both audiences where they are. Customers across industries are betting on ACA as the compute foundation for their AI and cloud-native workloads: Replit runs its agent-driven software creation platform on Azure, enabling enterprises like Hexaware to securely build and deploy AI-generated applications at scale with seamless procurement through Azure Marketplace. LayerX built its Ai Workforce document processing platform on Azure Container Apps, Azure OpenAI, Azure AI Search, and Cosmos DB - helping clients like Mitsui & Co. save 570 hours annually by automating manual document tasks. SJR built GX Manager with Microsoft Foundry to automate website personalization at scale - delivering production-grade, data-grounded content in seconds instead of hours of manual curation. August AI powers an AI health companion serving over 3.5 million customers on Azure infrastructure, scoring 100% on the U.S. Medical Licensing Examination and delivering potentially life-saving medical support. Photon Education created Classwise on Azure OpenAI and Foundry with Defender for Cloud security, enabling teachers to prepare lessons faster and engage students more effectively in inclusive learning environments. Microsoft Foundry Agent Service is built directly on Azure Container Apps, serving over 20,000 customers with a dedicated agent runtime that handles fast startup, tool execution, long-running operations, and enterprise-grade isolation at scale. Following the features announced at Ignite'25 and our continued momentum through early 2026, we're excited to share what's new at Build'26. This release deepens our commitment to the agentic era with new primitives for secure ephemeral compute, the fastest path from container to production, a reimagined portal experience, and continued investment in security, observability, and developer productivity. Azure Container Apps Sandboxes (Public Preview) Teams building agentic applications, multi-tenant platforms, development environments, and CI/CD systems have often had to stitch together custom infrastructure to run untrusted code safely, preserve state across sessions, and handle bursty demand without paying for idle capacity. Azure Container Apps Sandboxes addresses that challenge with a new first-class resource type that provides fast, secure, ephemeral compute environments with built-in suspend and resume capabilities. Each sandbox runs in its own hardware-isolated microVM boundary, supports standard OCI container images, and starts in sub-second time. Sandboxes can preserve memory, disk state, and preloaded libraries in a snapshot, so workloads resume quickly from the same point without incurring a cold-start reload penalty. Why Sandboxes are perfect for agents Agents can safely run AI-generated code in isolated environments with instant startup. Agents also accumulate context, intermediate results, and working state during long-running tasks. With sandbox snapshots, agents get persistent, isolated workspaces that survive across task boundaries - they can suspend and resume as needed, preserving full execution context including memory and disk. Key capabilities Sub-second startup - provision and execute immediately Hardware-isolated microVMs - strong security boundary for untrusted code Snapshot and resume - full state preservation (memory + disk) across sessions OCI container image support - bring any container Scale to zero, scale to thousands - consumption pricing with per-second billing This is the underlying infrastructure on which products like Cloud Sandbox in GitHub Copilot, Foundry Hosted Agents, and Azure Container Apps Express are built. ACA Sandboxes joins the Container Apps family alongside Apps, Jobs, Functions, and Dynamic Sessions as a foundational building block for the next generation of cloud and AI application workloads. Learn more about Azure Container Apps Sandboxes at https://aka.ms/aca/sandboxes Azure Container Apps Express (Public Preview) We recently launched Azure Container Apps Express in public preview - the simplest and fastest way to launch and scale powerful applications on Azure, from zero to hyperscale, without infrastructure decisions. It represents the first Azure compute platform purpose-built for agent and developer use alike. Express is based on years of experience running Azure Container Apps at scale. We've learned that most developers working on web apps, APIs, and agents want to deploy quickly, have automatic scaling, and avoid dealing with complex infrastructure. Express provides these capabilities - it sets up your environment in seconds, handles any amount of traffic, and removes complicated settings. This helps teams move from writing code to having a production-ready app in minutes, not hours. What makes Express different Instant provisioning - your app is running in seconds, not minutes Sub-second cold starts - fast enough for interactive UIs and on-demand agent endpoints Scale to and from zero - automatic, no configuration required Per-second billing - pay only for what you use, no environment provisioning fee Production-ready defaults - autoscaling, managed identity, secrets management, custom domains, container registry integration, revision management, and built-in observability Purpose-built for custom agents Agents need to spin up application endpoints on demand - fast, reliably, and without pre-provisioning infrastructure. Express is purpose-built for this pattern: it provisions in seconds, scales from zero instantly when an agent triggers a workload, and scales back down when the task is complete. Whether an agent is deploying a tool-use endpoint, standing up a temporary API for a multi-step workflow, or launching a web UI for human-in-the-loop review, Express gives it a production-grade, internet-reachable application with zero operational overhead. It's the fastest path from "an agent decided to deploy something" to "it's live and serving traffic." Learn more about Azure Container Apps Express at https://aka.ms/aca/express/launch-blog New Azure Container Apps Portal You open the Azure portal and want to deploy a Container App. Ten minutes later you're three blades deep, toggling settings you don't understand, wondering which workload profile is best before you even have an app. We built a different portal. One where deploying a container app takes less time than reading this paragraph. One where creating an Azure Container App is a single click. And one where experimental features ship weekly, not quarterly. Smart defaults, advanced when you need Developers care about outcomes - where their app is running and how to reach it - not starting with a configuration form. The new portal offers three creation modes to keep setup simple: Simple "one-click create" - auto-generates a unique name and provisions your app. Provide the container image and egress settings. That's it - no environment type selection, networking decisions, or container registry configuration. Advanced create - unlocks everything: custom VNets with subnet selection, managed identity for registry auth, lifecycle policies, egress controls, environment variables, custom scale rules, and more. It's a toggle at the top of the same form, not a separate workflow. Express App (Preview) - the new kind of ACA application that provisions and starts almost instantly. Observe quickly, act faster The app overview page surfaces critical information at a glance - including a unified Log Stream that brings app and system logs together in one place. Getting to the root cause now takes fewer clicks, and next steps are always one click away. Faster releases, direct feedback loop Azure Container Apps Express (Preview) and Azure Container Apps Sandboxes (Preview) are currently available only in this new portal. We ship weekly - often more. Upcoming Portal Features in settings give you an easy way to opt in to early access features and share feedback directly. Security: Defender for Cloud Serverless Containers Posture and Confidential Compute Security remains a top priority as enterprises run more sensitive and regulated workloads on Azure Container Apps. At Build'26, we're announcing two key security milestones. Public Preview: Defender for Cloud Serverless Containers Posture on Azure Container Apps Customers can now bring Azure Container Apps environments into Microsoft Defender for Cloud's Serverless Containers Posture experience, helping security teams extend posture management across more of their container estate from a single workflow. This makes it easier to gain visibility into Container Apps resources and assess risks across areas such as identity, networking, and container or image configuration. With this capability, teams can more consistently evaluate risk across container environments and use attack path analysis to identify potential exposure faster. The result is a more unified security posture, less manual effort, and stronger confidence when securing Container Apps deployments. Serverless Containers Posture is available as part of the Defender CSPM plan. Learn more at the Defender for Cloud documentation. General Availability: Confidential Compute for Azure Container Apps Confidential Compute in Azure Container Apps is now generally available, providing hardware-backed Trusted Execution Environments (TEEs) through workload profiles. This extends protection to data in use - in addition to data at rest and in transit - enabling teams to run higher-trust workloads with stronger isolation for sensitive data. With confidential computing now GA, Azure Container Apps becomes more viable for regulated, financial, healthcare, and other high-trust scenarios where organizations need hardware-enforced isolation that protects in-memory data, including from the underlying infrastructure. There is no extra charge for confidential compute workload profiles. Learn more at the Azure Confidential Computing documentation. Observability: HTTP Traffic Logs and OpenTelemetry Destinations Knowing what's happening inside your application is essential to running production workloads with confidence. At Build'26, we're announcing two enhancements that give teams deeper visibility and more flexibility in where they send telemetry. Monitor HTTP traffic in Azure Container Apps Azure Container Apps now adds a dedicated Azure Monitor diagnostic setting category - ContainerAppHTTPLogs - that exposes detailed HTTP access logs for incoming traffic. This capability is designed for high-volume request data, enabling teams to troubleshoot ingress and request-flow issues with much greater precision. With HTTP traffic logs, you can now investigate: Failed requests and error codes Latency patterns and outliers Retries and WebSocket disconnects Routing behavior and backend connectivity The result is faster issue resolution, less operational friction, and stronger confidence in running high-traffic, business-critical applications. Standard Azure Monitor log volume charges apply. Learn more at Azure Monitor pricing. Additional OpenTelemetry Destinations: New Relic, Dynatrace, Elastic Azure Container Apps enhances its managed OpenTelemetry (OTel) capabilities by expanding support for third-party observability platforms. This update introduces additional endpoint options for commonly used monitoring tools - New Relic, Dynatrace, and Elastic - extending the existing managed OpenTelemetry experience. Teams can now use a more consistent OpenTelemetry-based pipeline across Azure Monitor, Datadog, New Relic, Dynatrace, Elastic, and any OTLP-compatible endpoint, with less configuration overhead and more flexibility to route logs, metrics, and traces where they need them - without deploying or managing their own collectors. No extra charge applies. Learn more at the OpenTelemetry agents documentation. Additional Enhancements and Ecosystem Updates Beyond the headline announcements, Azure Container Apps continues to evolve with a steady cadence of improvements across the platform. Override Scale Rules in Azure Functions on Azure Container Apps Azure Functions on Container Apps has traditionally used platform-managed scaling, where triggers are automatically translated into KEDA scale rules. With the new allowScalingRuleOverride property, customers can now choose to override platform-managed scaling and define their own custom KEDA scaling rules. This enhancement is especially useful for scenarios where automatically generated KEDA rules lead to unintended scaling behavior, where workloads require custom thresholds or concurrency tuning, or where teams need standardized scaling policies across services. It works with any of the 60+ KEDA scalers - Service Bus, Kafka, PostgreSQL, HTTP concurrency, Cron, and more. Heroku Migration to Azure Container Apps With Heroku entering maintenance mode, Azure Container Apps is a natural landing zone for Heroku workloads. New guidance and tooling makes the migration path straightforward - from understanding why ACA is the right next step to a practical migration guide for hands-on implementation. Dapr v1.16 Platform Upgrade Azure Container Apps completed a staged platform upgrade to Dapr v1.16.4, bringing modernized actor scheduling, improved scalability for reminders, and updated TLS/security internals. The upgrade is fully platform-managed, with minimal customer action required for most workloads. Running AI Models on ACA Serverless GPUs The community continues to push the boundaries of what's possible with serverless GPUs on ACA. Recent highlights include running Gemma 4 with Ollama for fully private, self-hosted inference, and deploying ComfyUI for text-to-image and text-to-video workloads - all with scale-to-zero and per-second billing. Hosting Remote MCP Servers on ACA Azure Container Apps is emerging as the preferred platform for hosting Model Context Protocol (MCP) servers. With serverless scaling, idle billing, HTTP/1.1 and HTTP/2 support, and managed identity integration, ACA provides a production-ready environment for exposing tools and APIs to AI agents. Multiple tutorials and guides are now available for deploying MCP servers on ACA, including integration with Azure API Management. App Modernization with GitHub Copilot GitHub Copilot App Modernization can dramatically reduce the time required to modernize legacy applications and deploy them to ACA. A recent walkthrough demonstrated upgrading a classic ASP.NET MVC app on .NET Framework to .NET 10 and deploying it to Azure Container Apps in hours - with managed identity and Key Vault integration enabled by default. Azure Skills Repository for Container Apps The new Azure Skills repository includes comprehensive skills specifically for Azure Container Apps - covering troubleshooting, best practices, architecture patterns, security, deployment, and integration. These skills are designed to be used by AI agents and developer tools like GitHub Copilot CLI, providing rich context for building, deploying, and operating ACA workloads. It's another example of how the ACA ecosystem is evolving to be agent-native. Docker Compose for Agents Docker Compose for Agents on Container Apps (public preview) brings the familiar Compose workflow to agentic applications. Declare models, agents, and MCP tools in a single compose.yaml file and deploy unchanged from laptop to cloud - supporting LangGraph, Vercel AI SDK, Spring AI, CrewAI, and other frameworks. Learn more at the Compose for Agents documentation. What's Next Azure Container Apps is redefining how developers and agents build, deploy, and operate intelligent applications. With Sandboxes for secure ephemeral compute, Express for instant provisioning, a reimagined portal for streamlined management, and continued investment in security and observability - ACA provides the ideal foundation for the agentic era. The features announced at Build'26 deepen our commitment to making Azure Container Apps the platform where both humans and AI agents can ship production workloads with confidence, speed, and minimal operational overhead. Also, if you're at Build, come see us at the following sessions: Breakout 221: Idea to production-ready agent in seconds on AI-native runtime Demo 312: Multi-agents in action with 3 AI agents, 3 frameworks, tools & models Lab 580: Build and deploy reasoning agents with NVIDIA Nemotron and Foundry Lightning Talk 453: Building an End‑to‑End Enterprise AI Platform on Azure Or come visit us at the Azure Application Services booth #44. Visit our GitHub page for feedback, feature requests, or questions. Check out our roadmap to see what we're working on next. We look forward to hearing from you!Introducing Azure Container Apps Express!
Three years ago, a 15-second cold start was industry-leading. Today, developers and AI agents expect sub-second. The speed bar has moved, and the tooling needs to move with it. After running Azure Container Apps for years, we've learned something important: for most developers, the ACA environment is an unnecessary construct. It adds provisioning time, configuration surface, and cognitive overhead — when all you really want is to run your app with scaling, networking, and operations handled for you. At the same time, a new class of workloads has emerged. Agent-first platforms — systems where AI agents deploy endpoints on demand, spin up tool-use APIs, and tear them down when work is done — demand an even more radical focus on speed and simplicity. Every second of provisioning delay is wasted agent productivity. Today, we're launching Azure Container Apps Express in Public Preview — the fastest, simplest way to go from a container image to an internet-reachable app on Azure, ready for many production-style workloads. What Is ACA Express? ACA Express removes the infrastructure decisions. There's no environment to provision, no networking to configure, no scaling rules to write. You bring a container image, Express handles everything else. Behind the scenes, Express runs your container on pre-provisioned capacity with sensible defaults baked in — so you skip environment setup without giving up ACA's serverless model. There's more coming in this space soon — keep watching. Here's what that means in practice: Instant provisioning — your app is running in seconds, not minutes Sub-second cold starts — fast enough for interactive UIs and on-demand agent endpoints Scale to and from zero — automatic, no configuration required (full scaling controls coming soon) Per-second billing — pay only for what you use Production-ready defaults — ingress, secrets, environment variables, and observability are built in Express is purpose-built for two audiences: developers who want to ship fast (SaaS apps, APIs, web dashboards, prototypes) and agents that deploy on demand (MCP servers, tool-use endpoints, multi-step workflow APIs, human-in-the-loop UIs). If you've ever waited for an ACA environment to provision, only to realize you didn't need half of the configuration options it asked you for — Express is your answer. What You Can Do Today Note: West Central US is currently the only available region. We will expand to new regions through the coming days. Express is in Public Preview starting today. It's a deliberate early ship — there's a meaningful feature gap compared to the existing Azure Container Apps offering, and we're filling it fast. New capabilities are landing on a rapid cadence throughout the preview, and by Microsoft Build in June, Express should be close to feature-complete. For the current list of supported features, known gaps, and what's on the way, see the Express documentation. We'd rather put valuable technology in your hands early and iterate with you than wait behind closed doors for perfection. Who Is Express For? Scenario Why Express SaaS apps and APIs Deploy and scale without infrastructure planning AI app frontends Chat UIs and copilot frontends that scale with usage spikes MCP servers Expose API endpoints for AI agents in seconds Agent workflows Spin up endpoints on demand, tear down when done Prototypes and startups Go from idea to production in minutes Web dashboards Internal tools with instant availability Get Started Express is available now in Public Preview. Try it: Azure Container Apps Express overview — concepts, capabilities, and the current feature support matrix Deploy your first app with the Azure CLI — step-by-step quickstart New Azure Container Apps Portal — create and manage Express apps alongside your existing Container Apps resources Have questions? Check the Azure Container Apps Express FAQ for answers to common questions about pricing, limits, regions, and the road to GA. We're building Express in the open and we want to hear from you. Tell us what features matter most, what works, and what doesn't — reach out on the Azure Container Apps GitHub or in the comments below.Even simpler to Safely Execute AI-generated Code with Azure Container Apps Dynamic Sessions
AI agents are writing code. The question is: where does that code run? If it runs in your process, a single hallucinated import os; os.remove('/') can ruin your day. Azure Container Apps dynamic sessions solve this with on-demand sandboxed environments - Hyper-V isolated, fully managed, and ready in milliseconds. Thanks to your feedback, Dynamic Sessions are now easier to use with AI via MCP. Agents can quickly start a session interpreter and safely run code - all using a built-in MCP endpoint. Additionally - new starter samples show how to invoke dynamic sessions from Microsoft Agent Framework with code interpreter and with a custom container for even more versatility. What Are Dynamic Sessions? A session pool maintains a reservoir of pre-warmed, isolated sandboxes. When your app needs one, it’s allocated instantly via REST API. When idle, it’s destroyed automatically after provided session cool down period. What you get: Strong isolation - Each session runs in its own Hyper-V sandbox - enterprise-grade security Millisecond startup -Pre-warmed pool eliminates cold starts Fully managed - No infra to maintain - automatic lifecycle, cleanup, scaling Simple access - Single HTTP endpoint, session identified by a unique ID Scalable - Hundreds to thousands of concurrent sessions Two Session Types 1. Code Interpreter — Run Untrusted Code Safely Code interpreter sessions accept inline code, run it in a Hyper-V sandbox, and return the output. Sessions support network egress and persistent file systems within the session lifetime. Three runtimes are available: Python - Ships with popular libraries pre-installed (NumPy, pandas, matplotlib, etc.). Ideal for AI-generated data analysis, math computation, and chart generation. Node.js - Comes with common npm packages. Great for server-side JavaScript execution, data transformation, and scripting. Shell - A full Linux shell environment where agents can run arbitrary commands, install packages, start processes, manage files, and chain multi-step workflows. Unlike Python/Node.js interpreters, shell sessions expose a complete OS - ideal for agent-driven DevOps, build/test environments, CLI tool execution, and multi-process pipelines. 2. Custom Containers — Bring Your Own Runtime Custom container sessions let you run your own container image in the same isolated, on-demand model. Define your image, and Container Apps handles the pooling, scaling, and lifecycle. Typical use cases are hosting proprietary runtimes, custom code interpreters, and specialized tool chains. This sample (Azure Samples) dives deeper into Customer Containers with Microsoft agent Framework orchestration. MCP Support for Dynamic Sessions Dynamic sessions also support Model Context Protocol (MCP) on both shell and Python session types. This turns a session pool into a remote MCP server that AI agents can connect to - enabling tool execution, file system access, and shell commands in a secure, ephemeral environment. With an MCP-enabled shell session, an Azure Foundry agent can spin up a Flask app, run system commands, or install packages - all in an isolated container that vanishes when done. The MCP server is enabled with a single property on the session pool (isMCPServerEnabled: true), and the resulting endpoint + API key can be plugged directly into Azure Foundry as a connected tool. For a step-by-step walkthrough, see How to add an MCP tool to your Azure Foundry agent using dynamic sessions. Deep Dive: Building an AI Travel Agent with Code Interpreter Sessions Let’s walk through a sample implementation - a travel planning agent that uses dynamic sessions for both static code execution (weather research) and LLM-generated code execution (charting). Full source: github.com/jkalis-MS/AIAgent-ACA-DynamicSession Architecture Travel Agent Architecture Component Purpose Microsoft Agent Framework Agent runtime with middleware, telemetry, and DevUI Azure OpenAI (GPT-4o) LLM for conversation and code generation ACA Session Pools Sandboxed Python code interpreter Azure Container Apps Hosts the agent in a container Application Insights Observability for agent spans The agent implements with two variants switchable in the Agent Framework DevUI - tools in ACA Dynamic Session (sandbox) and tools running locally (no isolation) - making the security value immediately visible. Scenario A: Static Code in a Sandbox - Weather Research The agent sends pre-written Python code to the session pool to fetch live weather data. The code runs with network egress enabled, calls the Open-Meteo API, and returns formatted results - all without touching the host process. import requests from azure.identity import DefaultAzureCredential credential = DefaultAzureCredential() token = credential.get_token("https://dynamicsessions.io/.default") response = requests.post( f"{pool_endpoint}/code/execute?api-version=2024-02-02-preview&identifier=weather-session-1", headers={"Authorization": f"Bearer {token.token}"}, json={"properties": { "codeInputType": "inline", "executionType": "synchronous", "code": weather_code, # Python that calls Open-Meteo API }}, ) result = response.json()["properties"]["stdout"] Scenario B: LLM-Generated Code in a Sandbox - Dynamic Charting This is where it gets interesting. The user asks “plot a chart comparing Miami and Tokyo weather.” The agent: Fetches weather data Asks Azure OpenAI to generate matplotlib code using a tightly-scoped system prompt Safety-checks the generated code for forbidden imports (subprocess, os.system, etc.) Wraps the code with data injection and sends it to the sandbox Downloads the resulting PNG from the sandbox’s /mnt/data/ directory from openai import AzureOpenAI # 1. LLM generates chart code client = AzureOpenAI(azure_endpoint=endpoint, api_key=key, api_version="2024-12-01-preview") generated_code = client.chat.completions.create( model="gpt-4o", messages=[{"role": "system", "content": CODE_GEN_PROMPT}, {"role": "user", "content": f"Weather data: {weather_json}"}], temperature=0.2, ).choices[0].message.content # 2. Execute in sandbox requests.post( f"{pool_endpoint}/code/execute?api-version=2024-02-02-preview&identifier=chart-session-1", headers={"Authorization": f"Bearer {token.token}"}, json={"properties": { "codeInputType": "inline", "executionType": "synchronous", "code": f"import json, matplotlib\nmatplotlib.use('Agg')\nimport matplotlib.pyplot as plt\nweather_data = json.loads('{weather_json}')\n{generated_code}", }}, ) # 3. Download the chart img = requests.get( f"{pool_endpoint}/files/content/chart.png?api-version=2024-02-02-preview&identifier=chart-session-1", headers={"Authorization": f"Bearer {token.token}"}, ).content The result is a dark-themed dual-subplot chart comparing maximal and minimal temperature forecast chart example rendered by the Chart Weather tool in Dynamic Session: Authentication The agent uses DefaultAzureCredential locally and ManagedIdentityCredential when deployed. Tokens are cached and refreshed automatically: from azure.identity import DefaultAzureCredential token = DefaultAzureCredential().get_token("https://dynamicsessions.io/.default") auth_header = f"Bearer {token.token}" # Uses ManagedIdentityCredential automatically when deployed to Container Apps Observability The agent uses Application Insights for end-to-end tracing. The Microsoft Agent Framework exposes OpenTelemetry spans for invoke_agent, chat, and execute tool - wired to Azure Monitor with custom exporters: from azure.monitor.opentelemetry import configure_azure_monitor from agent_framework.observability import create_resource, enable_instrumentation # Configure Azure Monitor first configure_azure_monitor( connection_string="InstrumentationKey=...", resource=create_resource(), # Uses OTEL_SERVICE_NAME, etc. enable_live_metrics=True, ) # Then activate Agent Framework's telemetry code paths, optional if ENABLE_INSTRUMENTATION and/or ENABLE_SENSITIVE_DATA are set in env vars enable_instrumentation(enable_sensitive_data=False) This gives you traces for every agent invocation, tool execution (including sandbox timing), and LLM call - visible in the Application Insights transaction search and end-to-end transaction view in the new Agents blade in Application Insights. You can also open a detailed dashboard by clicking Explore in Grafana. Session pools emit their own metrics and logs for monitoring sandbox utilization and performance. Combined with the agent-level Application Insights traces, you can get full visibility from the user prompt → agent → LLM → sandbox execution → response across both your application and the infrastructure running untrusted code. Deploy with One Command The project includes full Bicep infrastructure-as-code. A single azd up provisions Azure OpenAI, Container Apps, Session Pool (with egress enabled), Container Registry, Application Insights, and all role assignments. azd auth login azd up Next Steps Dynamic sessions documentation – Microsoft Learn MCP + Shell sessions tutorial - How to add an MCP tool to your Foundry agent Custom container sessions sample - github.com/Azure-Samples/dynamic-sessions-custom-container AI Agent + Dynamic Sessions - github.com/jkalis-MS/AIAgent-ACA-DynamicSessionThe Agent that investigates itself
Azure SRE Agent handles tens of thousands of incident investigations each week for internal Microsoft services and external teams running it for their own systems. Last month, one of those incidents was about the agent itself. Our KV cache hit rate alert started firing. Cached token percentage was dropping across the fleet. We didn't open dashboards. We simply asked the agent. It spawned parallel subagents, searched logs, read through its own source code, and produced the analysis. First finding: Claude Haiku at 0% cache hits. The agent checked the input distribution and found that the average call was ~180 tokens, well below Anthropic’s 4,096-token minimum for Haiku prompt caching. Structurally, these requests could never be cached. They were false positives. The real regression was in Claude Opus: cache hit rate fell from ~70% to ~48% over a week. The agent correlated the drop against the deployment history and traced it to a single PR that restructured prompt ordering, breaking the common prefix that caching relies on. It submitted two fixes: one to exclude all uncacheable requests from the alert, and the other to restore prefix stability in the prompt pipeline. That investigation is how we develop now. We rarely start with dashboards or manual log queries. We start by asking the agent. Three months earlier, it could not have done any of this. The breakthrough was not building better playbooks. It was harness engineering: enabling the agent to discover context as the investigation unfolded. This post is about the architecture decisions that made it possible. Where we started In our last post, Context Engineering for Reliable AI Agents: Lessons from Building Azure SRE Agent, we described how moving to a single generalist agent unlocked more complex investigations. The resolution rates were climbing, and for many internal teams, the agent could now autonomously investigate and mitigate roughly 50% of incidents. We were moving in the right direction. But the scores weren't uniform, and when we dug into why, the pattern was uncomfortable. The high-performing scenarios shared a trait: they'd been built with heavy human scaffolding. They relied on custom response plans for specific incident types, hand-built subagents for known failure modes, and pre-written log queries exposed as opaque tools. We weren’t measuring the agent’s reasoning – we were measuring how much engineering had gone into the scenario beforehand. On anything new, the agent had nowhere to start. We found these gaps through manual review. Every week, engineers read through lower-scored investigation threads and pushed fixes: tighten a prompt, fix a tool schema, add a guardrail. Each fix was real. But we could only review fifty threads a week. The agent was handling ten thousand. We were debugging at human speed. The gap between those two numbers was where our blind spots lived. We needed an agent powerful enough to take this toil off us. An agent which could investigate itself. Dogfooding wasn't a philosophy - it was the only way to scale. The Inversion: Three bets The problem we faced was structural - and the KV cache investigation shows it clearly. The cache rate drop was visible in telemetry, but the cause was not. The agent had to correlate telemetry with deployment history, inspect the relevant code, and reason over the diff that broke prefix stability. We kept hitting the same gap in different forms: logs pointing in multiple directions, failure modes in uninstrumented paths, regressions that only made sense at the commit level. Telemetry showed symptoms, but not what actually changed. We'd been building the agent to reason over telemetry. We needed it to reason over the system itself. The instinct when agents fail is to restrict them: pre-write the queries, pre-fetch the context, pre-curate the tools. It feels like control. In practice, it creates a ceiling. The agent can only handle what engineers anticipated in advance. The answer is an agent that can discover what it needs as the investigation unfolds. In the KV cache incident, each step, from metric anomaly to deployment history to a specific diff, followed from what the previous step revealed. It was not a pre-scripted path. Navigating towards the right context with progressive discovery is key to creating deep agents which can handle novel scenarios. Three architectural decisions made this possible – and each one compounded on the last. Bet 1: The Filesystem as the Agent's World Our first bet was to give the agent a filesystem as its workspace instead of a custom API layer. Everything it reasons over – source code, runbooks, query schemas, past investigation notes – is exposed as files. It interacts with that world using read_file, grep, find, and shell. No SearchCodebase API. No RetrieveMemory endpoint. This is an old Unix idea: reduce heterogeneous resources to a single interface. Coding agents already work this way. It turns out the same pattern works for an SRE agent. Frontier models are trained on developer workflows: navigating repositories, grepping logs, patching files, running commands. The filesystem is not an abstraction layered on top of that prior. It matches it. When we materialized the agent’s world as a repo-like workspace, our human "Intent Met" score - whether the agent's investigation addressed the actual root cause as judged by the on-call engineer - rose from 45% to 75% on novel incidents. But interface design is only half the story. The other half is what you put inside it. Code Repositories: the highest-leverage context Teams had prewritten log queries because they did not trust the agent to generate correct ones. That distrust was justified. Models hallucinate table names, guess column schemas, and write queries against the wrong cluster. But the answer was not tighter restriction. It was better grounding. The repo is the schema. Everything else is derived from it. When the agent reads the code that produces the logs, query construction stops being guesswork. It knows the exact exceptions thrown, and the conditions under which each path executes. Stack traces start making sense, and logs become legible. But beyond query grounding, code access unlocked three new capabilities that telemetry alone could not provide: Ground truth over documentation. Docs drift and dashboards show symptoms. The code is what the service actually does. In practice, most investigations only made sense when logs were read alongside implementation. Point-in-time investigation. The agent checks out the exact commit at incident time, not current HEAD, so it can correlate the failure against the actual diffs. That's what cracked the KV cache investigation: a PR broke prefix stability, and the diff was the only place this was visible. Without commit history, you can't distinguish a code regression from external factors. Reasoning even where telemetry is absent. Some code paths are not well instrumented. The agent can still trace logic through source and explain behavior even when logs do not exist. This is especially valuable in novel failure modes – the ones most likely to be missed precisely because no one thought to instrument them. Memory as a filesystem, not a vector store Our first memory system used RAG over past session learnings. It had a circular dependency: a limited agent learned from limited sessions and produced limited knowledge. Garbage in, garbage out. But the deeper problem was retrieval. In SRE Context, embedding similarity is a weak proxy for relevance. “KV cache regression” and “prompt prefix instability” may be distant in embedding space yet still describe the same causal chain. We tried re-ranking, query expansion, and hybrid search. None fixed the core mismatch between semantic similarity and diagnostic relevance. We replaced RAG with structured Markdown files that the agent reads and writes through its standard tool interface. The model names each file semantically: overview.md for a service summary, team.md for ownership and escalation paths, logs.md for cluster access and query patterns, debugging.md for failure modes and prior learnings. Each carry just enough context to orient the agent, with links to deeper files when needed. The key design choice was to let the model navigate memory, not retrieve it through query matching. The agent starts from a structured entry point and follows the evidence toward what matters. RAG assumes you know the right query before you know what you need. File traversal lets relevance emerge as context accumulates. This removed chunking, overlap tuning, and re-ranking entirely. It also proved more accurate, because frontier models are better at following context than embeddings are at guessing relevance. As a side benefit, memory state can be snapshotted periodically. One problem remains unsolved: staleness. When two sessions write conflicting patterns to debugging.md, the model must reconcile them. When a service changes behavior, old entries can become misleading. We rely on timestamps and explicit deprecation notes, but we do not have a systemic solution yet. This is an active area of work, and anyone building memory at scale will run into it. The sandbox as epistemic boundary The filesystem also defines what the agent can see. If something is not in the sandbox, the agent cannot reason about it. We treat that as a feature, not a limitation. Security boundaries and epistemic boundaries are enforced by the same mechanism. Inside that boundary, the agent has full execution: arbitrary bash, python, jq, and package installs through pip or apt. That scope unlocks capabilities we never would have built as custom tools. It opens PRs with gh cli, like the prompt-ordering fix from KV cache incident. It pushes Grafana dashboards, like a cache-hit-rate dashboard we now track by model. It installs domain-specific CLI tools mid-investigation when needed. No bespoke integration required, just a shell. The recurring lesson was simple: a generally capable agent in the right execution environment outperforms a specialized agent with bespoke tooling. Custom tools accumulate maintenance costs. Shell commands compose for free. Bet 2: Context Layering Code access tells the agent what a service does. It does not tell the agent what it can access, which resources its tools are scoped to, or where an investigation should begin. This gap surfaced immediately. Users would ask "which team do you handle incidents for?" and the agent had no answer. Tools alone are not enough. An integration also needs ambient context so the model knows what exists, how it is configured, and when to use it. We fixed this with context hooks: structured context injected at prompt construction time to orient the agent before it takes action. Connectors - what can I access? A manifest of wired systems such as Log Analytics, Outlook, and Grafana, along with their configuration. Repositories - what does this system do? Serialized repo trees, plus files like AGENTS.md, Copilot.md, and CLAUDE.md with team-specific instructions. Knowledge map - what have I learned before? A two-tier memory index with a top-level file linking to deeper scenario-specific files, so the model can drill down only when needed. Azure resource topology - where do things live? A serialized map of relationships across subscriptions, resource groups, and regions, so investigations start in the right scope. Together, these context hooks turn a cold start into an informed one. That matters because a bad early choice does not just waste tokens. It sends the investigation down the wrong trajectory. A capable agent still needs to know what exists, what matters, and where to start. Bet 3: Frugal Context Management Layered context creates a new problem: budget. Serialized repo trees, resource topology, connector manifests, and a memory index fill context fast. Once the agent starts reading source files and logs, complex incidents hit context limits. We needed our context usage to be deliberately frugal. Tool result compression via the filesystem Large tool outputs are expensive because they consume context before the agent has extracted any value from them. In many cases, only a small slice or a derived summary of that output is actually useful. Our framework exposes these results as files to the agent. The agent can then use tools like grep, jq, or python to process them outside the model interface, so that only the final result enters context. The filesystem isn't just a capability abstraction - it's also a budget management primitive. Context Pruning and Auto Compact Long investigations accumulate dead weight. As hypotheses narrow, earlier context becomes noise. We handle this with two compaction strategies. Context Pruning runs mid-session. When context usage crosses a threshold, we trim or drop stale tool calls and outputs - keeping the window focused on what still matters. Auto-Compact kicks in when a session approaches its context limit. The framework summarizes findings and working hypotheses, then resumes from that summary. From the user's perspective, there's no visible limit. Long investigations just work. Parallel subagents The KV cache investigation required reasoning along two independent hypotheses: whether the alert definition was sound, and whether cache behavior had actually regressed. The agent spawned parallel subagents for each task, each operating in its own context window. Once both finished, it merged their conclusions. This pattern generalizes to any task with independent components. It speeds up the search, keeps intermediate work from consuming the main context window, and prevents one hypothesis from biasing another. The Feedback loop These architectural bets have enabled us to close the original scaling gap. Instead of debugging the agent at human speed, we could finally start using it to fix itself. As an example, we were hitting various LLM errors: timeouts, 429s (too many requests), failures in the middle of response streaming, 400s from code bugs that produced malformed payloads. These paper cuts would cause investigations to stall midway and some conversations broke entirely. So, we set up a daily monitoring task for these failures. The agent searches for the last 24 hours of errors, clusters the top hitters, traces each to its root cause in the codebase, and submits a PR. We review it manually before merging. Over two weeks, the errors were reduced by more than 80%. Over the last month, we have successfully used our agent across a wide range of scenarios: Analyzed our user churn rate and built dashboards we now review weekly. Correlated which builds needed the most hotfixes, surfacing flaky areas of the codebase. Ran security analysis and found vulnerabilities in the read path. Helped fill out parts of its own Responsible AI review, with strict human review. Handles customer-reported issues and LiveSite alerts end to end. Whenever it gets stuck, we talk to it and teach it, ask it to update its memory, and it doesn't fail that class of problem again. The title of this post is literal. The agent investigating itself is not a metaphor. It is a real workflow, driven by scheduled tasks, incident triggers, and direct conversations with users. What We Learned We spent months building scaffolding to compensate for what the agent could not do. The breakthrough was removing it. Every prewritten query was a place we told the model not to think. Every curated tool was a decision made on its behalf. Every pre-fetched context was a guess about what would matter before we understood the problem. The inversion was simple but hard to accept: stop pre-computing the answer space. Give the model a structured starting point, a filesystem it knows how to navigate, context hooks that tell it what it can access, and budget management that keeps it sharp through long investigations. The agent that investigates itself is both the proof and the product of this approach. It finds its own bugs, traces them to root causes in its own code, and submits its own fixes. Not because we designed it to. Because we designed it to reason over systems, and it happens to be one. We are still learning. Staleness is unsolved, budget tuning remains largely empirical, and we regularly discover assumptions baked into context that quietly constrain the agent. But we have crossed a new threshold: from an agent that follows your playbook to one that writes the next one. Thanks to visagarwal for co-authoring this post.
