v1.0.0-beta.6

Feature: Java SDK joins the monorepo

The Java SDK is now a first-class part of the github/copilot-sdk monorepo, with full CI, Maven publishing workflows, and generated types that stay in sync with the rest of the SDK family. (#1348)

CopilotClient client = new CopilotClient();
CopilotSession session = client.createSession(new SessionConfig());
session.send("Hello from Java!");

Feature: preMcpToolCall hook across all SDKs

Applications can now intercept MCP tool invocations before they execute — useful for injecting, replacing, or removing the _meta field sent to MCP servers. The hook returns a tri-state result: return null to leave _meta unchanged, return a new object to replace it, or explicitly set metaToUse to null to strip it entirely. (#1366)

session.hooks.onPreMcpToolCall = async (input) => {
  return { metaToUse: { traceId: myTraceId() } };
};

session.Hooks.OnPreMcpToolCall = async (input) => {
    return new PreMcpToolCallHookOutput { MetaToUse = new { traceId = MyTraceId() } };
};

Feature: tool callbacks are now optional across all SDKs

Tools and permission handlers can be declared without providing a callback, leaving them pending for manual resolution. This makes it easier to pause execution and resolve requests from event streams rather than inline callbacks. (#1308)

// Declare without a callback — permission requests stay pending
session.setPermissionHandler({ kinds: ["edit"] });

// Later, resume manually from an event
session.resolvePermissionRequest(event.requestId, { outcome: "allow" });

// Declaration-only tool — no callback supplied
session.DefineTool(new ToolDefinition { Name = "myTool", Description = "..." });

Feature: sessionId on hook inputs — hooks now fire for sub-agents

All six hook input types (PreToolUseHookInput, PostToolUseHookInput, etc.) now carry a sessionId field. Hooks also fire for tool calls made by sub-agents spawned via the task tool, and input.sessionId lets you distinguish parent from sub-agent invocations. (#1290)

Feature: breaking API review changes for C#, TypeScript, and Go

These releases include coordinated, intentional breaking changes based on API review feedback. Key changes:

Connection configuration — CliPath/Port/CliUrl properties are replaced by a single RuntimeConnection discriminated union:

• TypeScript: new CopilotClient({ connection: RuntimeConnection.stdio(...) })
• C#: new CopilotClientOptions { Connection = RuntimeConnection.Stdio(...) }
• Go: CLIUrl equivalent updated

Convenience send overloads — send(string) / sendAndWait(string) string overloads added for all SDKs.

Lifecycle events — now a typed polymorphic hierarchy (SessionCreatedEvent, etc.) instead of stringly-typed discriminators.

C# specifics — CopilotHome → BaseDirectory, delegate types replaced with Func<...>, LogLevel retyped to CopilotLogLevel, SessionConfigBase extracted. (#1343, #1357, #1360)

Feature: model field on CustomAgentConfig

When defining custom sub-agents programmatically, you can now specify which model to use. The runtime falls back to the parent session model if the specified model is unavailable. (#1309)

• TypeScript: customAgents: [{ name: "my-agent", model: "gpt-4o", ... }]
• C#: new CustomAgentConfig { Name = "my-agent", Model = "gpt-4o" }
• Python: custom_agents=[{"name": "my-agent", "model": "gpt-4o"}]
• Go: CustomAgentConfig{Name: "my-agent", Model: "gpt-4o"}

Feature: cloud session config support

Session creation now accepts a cloud option to request cloud-backed remote sessions with repository metadata, matching the new runtime capability. (#1306)

Feature: CopilotTool.DefineTool helper for .NET

The .NET SDK now provides a typed CopilotTool.DefineTool wrapper that applies Copilot-specific metadata (override flags, skip-permission behavior) without magic strings, aligning C# with the typed helper APIs already available in other SDKs. (#1321)

var tool = CopilotTool.DefineTool("edit", new CopilotToolOptions { IsOverride = true },
    async (params, ctx) => { /* custom edit implementation */ });

Other changes

• feature: [C#] add netstandard2.0 and net10 target frameworks (#1320)
• feature: [C#] publish .snupkg symbols package to NuGet.org (#1345)
• bugfix: [C#] honor preinstalled CLI path in MSBuild targets (#1318)
• bugfix: [C#] fix argument validation edge cases (#1322, #1328)
• feature: [Node] export generated session event types (#1316)
• feature: make MCPStdioServerConfig.args optional across all SDKs (#1347)
• feature: add remote_session field to all SDK SessionConfig types (#1295)
• improvement: hide deprecated APIs where supported by the language (#1293)
• bugfix: [Python] fix from_dict() round-trip for optional fields with schema defaults (#1313)
• improvement: [Go] replace RPC quicktype generation with native Go codegen (#1234)
• improvement: [Go] generate typed union interfaces and bool-discriminated unions (#1252, #1284)
• improvement: [Rust] derive Default on generated types (#1272)

New contributors

• @tiagonbotelho made their first contribution in #1306

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