v0.3.0-preview.0

What's Changed

• Add Go submodule version tags for reproducible builds by @Copilot in #33
• Correct backtick code block formatting by @leereilly in #43
• Add minor updates to python sdk by @sugatoray in #45
• Add tests to verify forward compatibility for unknown session event types by @Copilot in #35
• fix(go): ensure reliable session event handler unsubscription by @nathfavour in #24
• Fix Go e2e tests not running in CI by @SteveSandersonMS in #47
• Fix JSON-RPC pipe reads >64KB by handling short reads by @Copilot in #31
• Update @github/copilot to 0.0.387 by @devm33 in #54
• Fix escape issue in client.ts by @doggy8088 in #56
• Allow issue triage workflow to run for all users by @Copilot in #32
• Improve abort tests across all SDKs; add Go unsubscribe tests by @SteveSandersonMS in #48
• Add config dir to session options by @devm33 in #15
• Update some snapshots; remove redundant ones by @SteveSandersonMS in #52
• feat: add skillDirectories and disabledSkills to all SDKs by @friggeri in #57
• Fix and unskip some skills E2E tests by @SteveSandersonMS in #69
• Use STJ's polymorphism support instead of custom converter by @stephentoub in #70
• Update CONTRIBUTING.md to clarify contribution types by @SteveSandersonMS in #68
• Copilot SDK Cookbook by @aaronpowell in #80
• Add getting started tutorial by @burkeholland in #63
• Update README title and add demos folder by @ashleywolf in #75
• Move docs to correct folder by @patniko in #82
• Move examples and demos docs by @patniko in #83
• Moving files into the correct locations by @aaronpowell in #84
• Update README structure and add samples folder by @ashleywolf in #85
• feat: add status, auth, and models metadata APIs to all SDKs by @friggeri in #77
• Adding FAQ section to the README by @aaronpowell in #86
• Make the .NET library NativeAOT compatible by @stephentoub in #81
• Fix code formatting by @SteveSandersonMS in #90
• fix: correct broken links in cookbook documentation by @GeekTrainer in #93
• Fix .NET SDK prerequisites in CONTRIBUTING.md by @Copilot in #87
• fix: remove temporary README.md replacement step from publish workflow by @patniko in #108
• Modify npm init command for module type by @sinedied in #132
• Document external CLI server connection by @Copilot in #103
• Add agentic workflow for cross-SDK consistency enforcement by @Copilot in #95
• Bump Python minimum version to 3.9+ by @Copilot in #151
• Add missing list_sessions() method to Python SDK client by @Copilot in #153
• Re-run uv lock and fix Python tests by @friggeri in #157
• Document image attachment support in SDK READMEs by @Copilot in #150
• Bump githubnext/gh-aw from 0.36.0 to 0.37.1 by @dependabot[bot] in #66
• Adding .NET to the devcontainer by @aaronpowell in #88
• Use Pydantic for weather parameters in get_weather by @adityagesh in #120
• Add uv sync as alternative installation option by @harupy in #146
• feat: Infinite Sessions by @jmoseley in #76
• Fix BYOK FAQ: clarify it refers to API keys, not encryption keys by @mohamedaminehamdi in #174
• Include community SDKs in README by @brunoborges in #178
• docs: add MCP server usage documentation by @AnassKartit in #98
• Add download badges to README by @Copilot in #156
• docs: add .NET example for interactive weather assistant by @vicperdana in #119
• chore: Update generated events to match schemas. by @jmoseley in #208
• Add ListSessions and DeleteSession methods to Go SDK by @Copilot in #213
• Remove samples directory, link to awesome-copilot resources by @Copilot in #210
• Hide StreamJsonRpc implementation detail behind IOException by @Copilot in #202
• Simplify Node.js example by @SteveSandersonMS in #221
• Bump actions/download-artifact from 6.0.0 to 7.0.0 by @dependabot[bot] in #65
• Bump actions/checkout from 5.0.1 to 6.0.1 by @dependabot[bot] in #67
• Fixes #227 - Premium requests consumed while running py dev test by @vivganes in #228
• Bump githubnext/gh-aw from 0.37.13 to 0.37.31 by @dependabot[bot] in #240
• Consistently use Dataclasses in Python SDK by @Copilot in #216
• Fix .NET CLI server mode code samples - add missing UseStdio = false by @Copilot in #232
• Configure Copilot agent environment to match devcontainer by @Copilot in #236
• Add provider info to docs by @patniko in #257
• Fix formatting and update README structure by @doggy8088 in #258
• Update docs to reflect you need version for Azure Foundry by @patniko in #260
• Optimize CI: Split into separate workflows with native path filtering by @Copilot in #259
• Add githubToken and useLoggedInUser options to all SDK clients by @friggeri in #237
• feat: add hooks and user input handlers to all SDKs with e2e tests by @friggeri in #269
• Add lsp config for dotnet. by @jmoseley in #234
• docs: add hooks, user input, and auth options to SDK READMEs by @friggeri in #270
• Add paths-ignore filters to SDK test workflows by @Copilot in #271
• feat(nodejs): add typed event filtering to session.on() by @friggeri in #272
• Add dependabot monitoring for npm, pip, gomod, and nuget by @Copilot in #273
• Set default vscode formatter for Go by @qmuntal in #295
• [go] Honor ClientOptions.UseStdio = false by @qmuntal in #296
• [go] Honor empty ClientOptions.Env by @qmuntal in #297
• Bump githubnext/gh-aw from 0.37.31 to 0.38.2 by @dependabot[bot] in #274
• Bump @types/node from 25.0.3 to 25.1.0 in /test/harness by @dependabot[bot] in #275
• Bump openai from 6.15.0 to 6.17.0 in /test/harness by @dependabot[bot] in #276
• Consolidate path filters in SDK test workflows per GitHub Actions spec by @Copilot in #303
• feat: add reasoning_effort support to all SDK clients by @friggeri in #302
• Cache list_models across all SDK languages to prevent rate limiting under concurrency by @Copilot in #300
• [go] rewrite interface{} to any by @qmuntal in #298
• Removing cookbook from sdk repo by @aaronpowell in #316
• Cleanup Go Client implementation by @qmuntal in #321
• Fix ask-user test snapshots by @qmuntal in #319
• Add a new line after model generating final response when tool call completes by @moonshade9 in #307
• Replace Literal model type with string in Python SessionConfig by @Copilot in #325
• Clarify FAQ: BYOK works without GitHub Copilot subscription by @lossyrob in #336
• [go] make e2e and jsonrpc internal packages by @qmuntal in #339
• Fail CI if snaps...

v0.2.2

Feature: session filesystem support across all four SDKs

The sessionFs feature introduced earlier in Node.js is now available across .NET, Go, and Python too, so you can redirect session-scoped storage (events, checkpoints, temp files, workspace state) to your own backing store instead of the runtime's default local filesystem. This is especially useful for serverless and multi-tenant hosts. (#1036)

// TypeScript
const client = new CopilotClient({
  sessionFs: { initialCwd: "/", sessionStatePath: "/s", conventions: "posix" },
});

const session = await client.createSession({
    createSessionFsHandler: () => ({ readFile: async () => "...", writeFile: async () => { /* ... */ }, /* ... */ })
});

// C#
var client = new CopilotClient(new CopilotClientOptions {
    SessionFs = new()
    {
        InitialCwd = "/",
        SessionStatePath = "/",
        Conventions = SessionFsSetProviderRequestConventions.Posix
    }
});

var session = await client.CreateSessionAsync(new SessionConfig
{
    CreateSessionFsHandler = _ => new MySessionFsHandler(/* ... */) // e.g., map to in-memory storage, etc
});

For a full end-to-end sample of a multi-user hosted system using sessionFs, see https://github.com/github/copilot-sdk-server-sample

Feature: override model capabilities when creating a session or switching models

All SDKs can now override individual model capabilities such as vision support without replacing the full capabilities object. This makes BYOK and custom-provider scenarios easier, and lets you change behavior mid-session with setModel/SetModelAsync. (#1029)

const session = await client.createSession({
  modelCapabilities: { supports: { vision: false } },
});
await session.setModel("claude-sonnet-4.5", { modelCapabilities: { supports: { vision: true } } });

await session.SetModelAsync("claude-sonnet-4.5", reasoningEffort: null,
    modelCapabilities: new ModelCapabilitiesOverride { Supports = new ModelCapabilitiesOverrideSupports { Vision = true } });

Feature: enableConfigDiscovery for automatic MCP and skill discovery

All SDKs now expose enableConfigDiscovery, allowing the runtime to automatically discover MCP server configs and skill directories from the working directory and merge them with any explicitly supplied configuration. Explicit values still win on name collisions. (#1044)

const session = await client.createSession({
  enableConfigDiscovery: true,
});

var session = await client.CreateSessionAsync(new SessionConfig {
    EnableConfigDiscovery = true,
});

Improvement: safer per-event data types in Go

The Go SDK no longer flattens all session event payloads into one giant optional struct. event.Data is now a per-event typed interface, so adding a new event type no longer risks silently changing the shape of existing ones. (#1037)

switch d := event.Data.(type) {
case *copilot.AssistantMessageData:
    fmt.Println(d.Content)
}

⚠️ Breaking change (Go): event.Data is now a SessionEventData interface rather than a flat struct, so consumers must use type assertions or type switches. This update also applies some Go-style initialism renames such as Ui → UI and Uri → URI.

Other changes

• bugfix: [.NET] [Go] ignore unknown hook types from newer CLI versions instead of failing the session, improving forward compatibility with runtime updates (#1013)
• improvement: [Go] harden the internal JSON-RPC transport and framing logic, including stricter protocol validation and better handling of exact error payload JSON (#949)

v0.2.2-preview.0

Other changes

• bugfix: [C#] [Go] tolerate unknown hook types to prevent session hang (#1013)

  When the CLI invokes a hook type the SDK doesn't recognize (e.g. postToolUseFailure), .NET and Go were returning a JSON-RPC error that caused the CLI to terminate the session — appearing as a hang. Unknown hook types are now silently ignored, matching the existing Node.js behavior.

Note

🔒 Integrity filter blocked 43 items

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To allow these resources, lower min-integrity in your GitHub frontmatter:

tools:
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    min-integrity: approved  # merged | approved | unapproved | none

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v0.2.1

Feature: commands and UI elicitation across all four SDKs

Register slash commands that CLI users can invoke and drive interactive input dialogs from any SDK language. This feature was previously Node.js-only; it now ships in Python, Go, and .NET as well. (#906, #908, #960)

const session = await client.createSession({
  onPermissionRequest: approveAll,
  commands: [{
    name: "summarize",
    description: "Summarize the conversation",
    handler: async (context) => { /* ... */ },
  }],
  onElicitationRequest: async (context) => {
    if (context.type === "confirm") return { action: "confirm" };
  },
});

// Drive dialogs from the session
const confirmed = await session.ui.confirm({ message: "Proceed?" });
const choice = await session.ui.select({ message: "Pick one", options: ["A", "B"] });

var session = await client.CreateSessionAsync(new SessionConfig {
    OnPermissionRequest = PermissionHandler.ApproveAll,
    Commands = [
        new CommandDefinition {
            Name = "summarize",
            Description = "Summarize the conversation",
            Handler = async (context) => { /* ... */ },
        }
    ],
});

// Drive dialogs from the session
var confirmed = await session.Ui.ConfirmAsync(new ConfirmOptions { Message = "Proceed?" });

⚠️ Breaking change (Node.js): The onElicitationRequest handler signature changed from two arguments (request, invocation) to a single ElicitationContext that combines both. Update callers to use context.sessionId and context.message directly.

Feature: session.getMetadata across all SDKs

Efficiently fetch metadata for a single session by ID without listing all sessions. Returns undefined/null (not an error) when the session is not found. (#899)

• TypeScript: const meta = await client.getSessionMetadata(sessionId);
• C#: var meta = await client.GetSessionMetadataAsync(sessionId);
• Python: meta = await client.get_session_metadata(session_id)
• Go: meta, err := client.GetSessionMetadata(ctx, sessionID)

Feature: sessionFs for virtualizing per-session storage (Node SDK)

Supply a custom sessionFs adapter in Node SDK session config to redirect the runtime's per-session storage (event log, large output files) to any backing store — useful for serverless deployments or custom persistence layers. (#917)

Other changes

• bugfix: structured tool results (with toolTelemetry, resultType, etc.) now sent via RPC as objects instead of being stringified, preserving metadata for Node, Go, and Python SDKs (#970)
• feature: [Python] CopilotClient and CopilotSession now support async with for automatic resource cleanup (#475)
• improvement: [Python] copilot.types module removed; import types directly from copilot (#871)
• improvement: [Python] workspace_path now accepts any os.PathLike and session.workspace_path returns a pathlib.Path (#901)
• improvement: [Go] simplified rpc package API: renamed structs drop the redundant Rpc infix (e.g. ModelRpcApi → ModelApi) (#905)
• fix: [Go] Session.SetModel now takes a pointer for optional options instead of a variadic argument (#904)

New contributors

• @Sumanth007 made their first contribution in #475
• @jongalloway made their first contribution in #957
• @Morabbin made their first contribution in #970
• @schneidafunk made their first contribution in #998

Note

🔒 Integrity filter blocked 2 items

The following items were blocked because they don't meet the GitHub integrity level.

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To allow these resources, lower min-integrity in your GitHub frontmatter:

tools:
  github:
    min-integrity: approved  # merged | approved | unapproved | none

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v0.2.1-preview.2

Feature: onElicitationRequest callback for elicitation provider support

[Node] SDK clients can now act as elicitation providers by registering an onElicitationRequest callback in SessionConfig. The SDK negotiates the requestElicitation capability with the runtime, listens for broadcast elicitation.requested events, invokes the handler, and responds automatically. (#908)

const session = await client.createSession({
  onElicitationRequest: async (request) => {
    // respond to structured user input requests broadcast by the CLI runtime
    return { type: "string", value: "user response" };
  },
});

Feature: getSessionMetadata API across all SDKs

All SDKs now expose an efficient O(1) lookup of a single session's metadata by ID — no need to call listSessions and filter client-side. (#899)

• TypeScript: await client.getSessionMetadata(sessionId) — returns SessionMetadata | undefined
• C#: await client.GetSessionMetadataAsync(sessionId) — returns SessionMetadata?
• Python: await client.get_session_metadata(session_id) — returns SessionMetadata | None
• Go: client.GetSessionMetadata(ctx, sessionID) — returns (*SessionMetadata, error)

Feature: async context manager support for Python client and session

[Python] CopilotClient and CopilotSession now implement the async context manager protocol for automatic resource cleanup. (#475)

async with CopilotClient() as client:
    async with await client.create_session() as session:
        response = await session.get_response("Hello")

Other changes

• bugfix: [Node, Go, Python] structured ToolResultObject values were stringified before RPC, causing toolTelemetry and resultType to be silently lost on the server side (#970)
• improvement: [All] update bundled runtime to 1.0.15-2, resolving a regression with postToolUse hooks (#978)

New contributors

• @Sumanth007 made their first contribution in #475
• @Morabbin made their first contribution in #970

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v0.2.1-preview.1

Change: ephemeral events no longer included in getMessages()

Following a runtime update to 1.0.12, events like session.idle are now truly ephemeral — they are only observable via live event listeners and are not returned by session.getMessages() / get_messages(). This makes session resume behave consistently whether the session was previously active in-process or is being resumed from disk. (#927)

If your code calls getMessages() and checks for a session.idle event to determine whether a turn is complete, switch to using a live event listener instead:

session.on("session.idle", () => {
  // turn is complete
});

session.OnSessionIdle += (e) => {
    // turn is complete
};

Other changes

• improvement: [All] COPILOT_CLI_PATH env var is now read from the effective environment configured on the client (e.g. via options.env), not just the process environment — consistent across all SDKs (#925)

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v0.2.1-preview.0

Feature: commands and UI elicitation support for Node.js

The Node.js SDK now supports registering slash commands and prompting users with interactive dialogs. Pass commands in session config to handle CLI slash commands; use session.ui to show confirm, select, or text-input prompts. The feature was already available in other SDKs. (#906)

const session = await client.createSession({
  commands: [{
    name: "deploy",
    handler: async (params) => ({ text: `Deploying to \$\{params.args}...` })
  }]
});

const confirmed = await session.ui.confirm({ title: "Proceed?", message: "This will deploy to production." });
const env = await session.ui.select({ title: "Environment", options: [{ value: "prod" }, { value: "staging" }] });
const note = await session.ui.input({ title: "Release note" });

Feature: custom model listing for BYOK mode

All four SDKs now accept an onListModels callback in client options. When provided, client.listModels() calls your handler instead of querying the CLI — useful for BYOK setups where you want to expose your provider's available models. (#730)

const client = new CopilotClient({
  onListModels: async () => [{ id: "gpt-4o", displayName: "GPT-4o", vendor: "OpenAI" }]
});

var client = new CopilotClient(new CopilotClientOptions {
    OnListModels = async (ct) => [new ModelInfo { Id = "gpt-4o", DisplayName = "GPT-4o" }]
});

• Python: on_list_models=lambda: [ModelInfo(id="gpt-4o", display_name="GPT-4o")]
• Go: OnListModels: func(ctx context.Context) ([]copilot.ModelInfo, error) { ... }

Feature: blob attachments for inline image data

A new blob attachment type lets you send base64-encoded content directly to a session without writing it to disk first — useful when images are already in memory (screenshots, API responses, generated images). (#731)

await session.sendMessage("Describe this screenshot", {
  attachments: [{ type: "blob", data: base64Data, mimeType: "image/png", displayName: "screen.png" }]
});

await session.send_message("Describe this screenshot", attachments=[
    BlobAttachment(type="blob", data=base64_data, mime_type="image/png", display_name="screen.png")
])

Other changes

• feature: [All] tools can now set skipPermission: true to bypass per-use permission prompts for safe tools (#808)
• bugfix: [Node] add CJS compatibility so the SDK can be require()d in VS Code extensions and other CommonJS contexts (#546)
• bugfix: [Node] cliPath is now ignored when cliUrl is already set (#787)
• bugfix: [C#] fix SessionEvent.ToJson() failing for events with JsonElement-backed members (e.g. tool.execution_start, session.shutdown) (#868)
• bugfix: [C#] unknown session event types no longer throw; they are returned as UnknownSessionEvent preserving the raw JSON (#881)
• bugfix: [C#] fix AOT serialization crash when a CancellationToken fires during a JSON-RPC operation (#783)
• improvement: [C#] optional RPC parameters are now optional method parameters, preventing source-breaking changes when new optional params are added by the runtime (#733)
• bugfix: [Go] all enum constants are now consistently named using the TypeNameValue convention (e.g. SessionEventTypeSessionIdle, ModeInteractive) — breaking change: update any references using the old unprefixed names (#883)
• improvement: [Go] Rpc suffix removed from struct names in the rpc package (e.g. ModelRpcApi → ModelApi) (#905)
• bugfix: [Go] Session.SetModel now takes *SetModelOptions instead of a variadic argument (#904)
• bugfix: [Python] workspace_path in CopilotSession now accepts any os.PathLike value, not just strings (#901)
• improvement: [Python] telemetry, jsonrpc, and sdk_protocol_version modules are now marked as private (#884)

New contributors

• @darthmolen made their first contribution in #546
• @MackinnonBuck made their first contribution in #731
• @kirankashyap made their first contribution in #740
• @PureWeen made their first contribution in #783
• @stefansedich made their first contribution in #784
• @sergiou87 made their first contribution in #787
• @MRayermannMSFT made their first contribution in #808
• @xoofx made their first contribution in #868
• @jamesmontemagno made their first contribution in #879
• @Ron537 made their first contribution in #881
• @edburns made their first contribution in #889

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v0.2.0

This is a big update with a broad round of API refinements, new capabilities, and cross-SDK consistency improvements that have shipped incrementally through preview releases since v0.1.32.

Highlights

Fine-grained system prompt customization

A new "customize" mode for systemMessage lets you surgically edit individual sections of the Copilot system prompt — without replacing the entire thing. Ten sections are configurable: identity, tone, tool_efficiency, environment_context, code_change_rules, guidelines, safety, tool_instructions, custom_instructions, and last_instructions.

Each section supports four static actions (replace, remove, append, prepend) and a transform callback that receives the current rendered content and returns modified text — useful for regex mutations, conditional edits, or logging what the prompt contains. (#816)

const session = await client.createSession({
  onPermissionRequest: approveAll,
  systemMessage: {
    mode: "customize",
    sections: {
      identity: {
        action: (current) => current.replace("GitHub Copilot", "Acme Assistant"),
      },
      tone: { action: "replace", content: "Be concise and professional." },
      code_change_rules: { action: "remove" },
    },
  },
});

var session = await client.CreateSessionAsync(new SessionConfig {
    OnPermissionRequest = PermissionHandler.ApproveAll,
    SystemMessage = new SystemMessageConfig {
        Mode = SystemMessageMode.Customize,
        Sections = new Dictionary<string, SectionOverride> {
            ["identity"] = new() {
                Transform = current => Task.FromResult(current.Replace("GitHub Copilot", "Acme Assistant")),
            },
            ["tone"] = new() { Action = SectionOverrideAction.Replace, Content = "Be concise and professional." },
            ["code_change_rules"] = new() { Action = SectionOverrideAction.Remove },
        },
    },
});

OpenTelemetry support across all SDKs

All four SDK languages now support distributed tracing with the Copilot CLI. Set telemetry in your client options to configure an OTLP exporter; W3C trace context is automatically propagated on session.create, session.resume, and session.send, and restored in tool handlers so tool execution is linked to the originating trace. (#785)

const client = new CopilotClient({
  telemetry: {
    otlpEndpoint: "http://localhost:4318",
    sourceName: "my-app",
  },
});

var client = new CopilotClient(new CopilotClientOptions {
    Telemetry = new TelemetryConfig {
        OtlpEndpoint = "http://localhost:4318",
        SourceName = "my-app",
    },
});

• Python: CopilotClient(SubprocessConfig(telemetry={"otlp_endpoint": "http://localhost:4318", "source_name": "my-app"}))
• Go: copilot.NewClient(&copilot.ClientOptions{Telemetry: &copilot.TelemetryConfig{OTLPEndpoint: "http://localhost:4318", SourceName: "my-app"}})

Blob attachments for inline binary data

A new blob attachment type lets you send images or other binary content directly to a session without writing to disk — useful when data is already in memory (screenshots, API responses, generated images). (#731)

await session.send({
  prompt: "What's in this image?",
  attachments: [{ type: "blob", data: base64Str, mimeType: "image/png" }],
});

await session.SendAsync(new MessageOptions {
    Prompt = "What's in this image?",
    Attachments = [new UserMessageDataAttachmentsItemBlob { Data = base64Str, MimeType = "image/png" }],
});

Pre-select a custom agent at session creation

You can now specify which custom agent should be active when a session starts, eliminating the need for a separate session.rpc.agent.select() call. (#722)

const session = await client.createSession({
  customAgents: [
    { name: "researcher", prompt: "You are a research assistant." },
    { name: "editor", prompt: "You are a code editor." },
  ],
  agent: "researcher",
  onPermissionRequest: approveAll,
});

var session = await client.CreateSessionAsync(new SessionConfig {
    CustomAgents = [
        new CustomAgentConfig { Name = "researcher", Prompt = "You are a research assistant." },
        new CustomAgentConfig { Name = "editor", Prompt = "You are a code editor." },
    ],
    Agent = "researcher",
    OnPermissionRequest = PermissionHandler.ApproveAll,
});

---

New features

• skipPermission on tool definitions — Tools can now be registered with skipPermission: true to bypass the confirmation prompt for low-risk operations like read-only queries. Available in all four SDKs. (#808)
• reasoningEffort when switching models — All SDKs now accept an optional reasoningEffort parameter in setModel() for models that support it. (#712)
• Custom model listing for BYOK — Applications using bring-your-own-key providers can supply onListModels in client options to override client.listModels() with their own model list. (#730)
• no-result permission outcome — Permission handlers can now return "no-result" so extensions can attach to sessions without actively answering permission requests. (#802)
• SessionConfig.onEvent catch-all — A new onEvent handler on session config is registered before the RPC is issued, guaranteeing that early events like session.start are never dropped. (#664)
• Node.js CJS compatibility — The Node.js SDK now ships both ESM and CJS builds, fixing crashes in VS Code extensions and other tools bundled with esbuild's format: "cjs". No changes needed in consumer code. (#546)
• Experimental API annotations — APIs marked experimental in the schema (agent, fleet, compaction groups) are now annotated in all four SDKs: [Experimental] in C#, /** @experimental */ in TypeScript, and comments in Python and Go. (#875)
• System notifications and session log APIs — Updated to match the latest CLI runtime, adding system.notification events and a session log RPC API. (#737)

Improvements

• [.NET, Go] Serialize event dispatch so handlers are invoked in registration order with no concurrent calls (#791)
• [Go] Detach CLI process lifespan from the context passed to Client.Start so cancellation no longer kills the child process (#689)
• [Go] Stop RPC client logging expected EOF errors (#609)
• [.NET] Emit XML doc comments from schema descriptions in generated RPC code (#724)
• [.NET] Use lazy property initialization in generated RPC classes (#725)
• [.NET] Add DebuggerDisplay attribute to SessionEvent for easier debugging (#726)
• [.NET] Optional RPC params are now represented as optional method params for forward-compatible generated code (#733)
• [.NET] Replace Task.WhenAny + Task.Delay timeout pattern with .WaitAsync(TimeSpan) (#805)
• [.NET] Add NuGet package icon (#688)
• [Node] Don't resolve cliPath when cliUrl is already set (#787)

New RPC methods

We've added low-level RPC methods to control a lot more of what's going on in the session. These are emerging APIs that don't yet have friendly wrappers, and some may be flagged as experimental or subject to change.

• session.rpc.skills.list(), .enable(name), .disable(name), .reload()
• session.rpc.mcp.list(), .enable(name), .disable(name), .reload()
• session.rpc.extensions.list(), .enable(name), .disable(name), .reload()
• session.rpc.plugins.list()
• session.rpc.ui.elicitation(...) — structured user input
• session.rpc.shell.exec(command), .kill(pid)
• session.log(message, level, ephemeral)

In an forthcoming update, we'll add friendlier wrappers for these.

Bug fixes

• [.NET] Fix SessionEvent.ToJson() failing for events with JsonElement-backed payloads (assistant.message, tool.execution_start, etc.) (#868)
• [.NET] Add fallback TypeInfoResolver for StreamJsonRpc.RequestId to fix NativeAOT compatibility (#783)
• [.NET] Fix codegen for discriminated unions nested within other types (#736)
• [.NET] Handle unknown session event types gracefully instead of throwing (#881)

---

⚠️ Breaking changes

All SDKs

• autoRestart removed — The autoRestart option has been deprecated across all SDKs (it was never fully implemented). The property still exists but has no effect and will be removed in a future release. Remove any references to autoRestart from your client options. (#803)

Python

The Pyth...

v0.1.33-preview.4

Feature: fine-grained system prompt customization

A new "customize" mode for systemMessage lets you selectively override individual sections of the Copilot system prompt — without replacing the entire prompt. This sits between "append" (add to the end) and "replace" (replace everything). (#816)

Ten sections are configurable: identity, tone, tool_efficiency, environment_context, code_change_rules, guidelines, safety, tool_instructions, custom_instructions, and last_instructions.

Each section supports four static actions (replace, remove, append, prepend) and a transform action — a callback that receives the current rendered section content and returns the modified version, enabling regex mutations, logging, or conditional edits.

const session = await client.createSession({
  systemMessage: {
    mode: "customize",
    sections: {
      identity: {
        // transform: read current content and return modified content
        action: (current) => current.replace("GitHub Copilot", "Acme Assistant"),
      },
      tone: { action: "replace", content: "Be concise and professional." },
      code_change_rules: { action: "remove" },
    },
  },
});

var session = await client.CreateSessionAsync(new SessionOptions {
    SystemMessage = new SystemMessageOptions {
        Mode = SystemMessageMode.Customize,
        Sections = new Dictionary(string, SectionOverride) {
            ["identity"] = new() {
                Transform = current => current.Replace("GitHub Copilot", "Acme Assistant"),
            },
            ["tone"] = new() { Action = "replace", Content = "Be concise and professional." },
            ["code_change_rules"] = new() { Action = "remove" },
        },
    },
});

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v0.1.33-preview.3

Feature: OpenTelemetry support across all SDKs

All four SDK languages now support distributed tracing with the Copilot CLI. Set telemetry in your client options to configure an OTLP exporter; W3C trace context is then propagated on session.create, session.resume, and session.send, and restored in tool handlers so tool execution is linked to the originating trace. (#785)

const client = new CopilotClient({
  telemetry: {
    otlpEndpoint: "(localhost/redacted)
    sourceName: "my-app",
  },
});

var client = new CopilotClient(new CopilotClientOptions {
    Telemetry = new TelemetryConfig {
        OtlpEndpoint = "(localhost/redacted)
        SourceName = "my-app",
    },
});

Feature: blob attachment type for inline base64 data

A new blob attachment type lets you send images or other binary content directly to a session without writing to disk first — useful when data is already in memory (screenshots, API responses, generated images). (#731)

await session.send("What's in this image?", {
  attachments: [{ type: "blob", data: base64Str, mimeType: "image/png" }],
});

await session.SendAsync("What's in this image?", new MessageOptions {
    Attachments = [new BlobAttachment { Data = base64Str, MimeType = "image/png" }],
});

Feature: Node.js CommonJS (CJS) compatibility

The Node.js SDK now ships both ESM and CJS builds, fixing crashes in VS Code extensions and other tools bundled with esbuild's format: "cjs". No changes needed in consumer code — Node automatically selects the right format. (#546)

Feature: reasoningEffort when switching models

All SDKs now accept an optional reasoningEffort parameter in setModel() for models that support it. (#712)

await session.setModel("claude-sonnet-4.6", { reasoningEffort: "high" });

await session.SetModelAsync("claude-sonnet-4.6", reasoningEffort: "high");

• Python: await session.set_model("claude-sonnet-4.6", reasoning_effort="high")
• Go: session.SetModel(ctx, "claude-sonnet-4.6", &copilot.SetModelOptions{ReasoningEffort: "high"})

Feature: skipPermission flag on tool definitions

Tools can now be registered with skipPermission: true (or SkipPermission in .NET) to bypass the permission confirmation step for low-risk tools such as read-only queries. (#808)

session.defineTool("query_db", { skipPermission: true }, async (params) => {
  // read-only, no permission prompt
});

session.DefineTool("query_db", new ToolOptions { SkipPermission = true }, async (params) => {
    // read-only, no permission prompt
});

Feature: experimental API annotations

APIs marked experimental in the schema (agent, fleet, and compaction groups) are now annotated in all four SDK languages: [Experimental] in C#, /** @experimental */ in TypeScript, and comments in Python and Go. Experimental APIs will continue to evolve. (#875)

Other changes

• feature: [Python] CopilotClient constructor now accepts typed config objects instead of individual keyword arguments (#793)
• feature: [Python] updated CopilotSession.send() and send_and_wait() signatures for cleaner API surface (#814)
• feature: [Python] add typed overloads for CopilotClient.on() event registration (#589)
• improvement: [.NET, Go] serialize event dispatch so handlers are invoked in registration order with no concurrent calls (#791)
• improvement: [Go] detach CLI process lifespan from the context passed to Client.Start so cancellation no longer kills the child process (#689)
• improvement: [Go] LogOptions.Ephemeral changed from bool to *bool for proper three-state semantics; use copilot.Bool(true) (#827)
• improvement: [Go] stop RPC client logging expected EOF errors (#609)
• bugfix: [C#] fix SessionEvent.ToJson() failing for events with JsonElement-backed payloads (assistant.message, tool.execution_start, etc.) (#868)
• bugfix: [.NET] add fallback TypeInfoResolver for StreamJsonRpc.RequestId to fix NativeAOT compatibility (#783)
• improvement: [.NET] replace Task.WhenAny + Task.Delay timeout pattern with .WaitAsync(TimeSpan) (#805)
• improvement: remove autoRestart option across all SDKs (was never fully implemented; APIs are now marked obsolete and will be removed soon) (#803)

New contributors

• @darthmolen made their first contribution in #546
• @MackinnonBuck made their first contribution in #731
• @PureWeen made their first contribution in #783
• @stefansedich made their first contribution in #784
• @MRayermannMSFT made their first contribution in #808
• @xoofx made their first contribution in #868
• @jamesmontemagno made their first contribution in #879
• @edburns made their first contribution in #889

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