Add optional header field to ask_user across all SDKs

[patniko]

What & why

Companion to github/copilot-agent-runtime#10078, which adds a short, model-populated header to the ask_user tool — surfaced on the user_input.requested event and the userInput.request RPC, mirroring Anthropic's AskUserQuestion.header. Hosts can render it as a dialog title instead of synthesizing one from the question.

This PR adds header to the hand-written userInput.request handler request type that integrators implement, in every language, plus README docs:

Language	Hand-written handler type	README
Node	src/types.ts UserInputRequest, src/client.ts	✅
Python	copilot/session.py UserInputRequest TypedDict + handler	✅
Go	types.go (public + wire structs), client.go mapping	✅
.NET	Types.cs UserInputRequest, Client.cs RPC param	—
Rust	handler.rs trait, session.rs dispatch	✅
Java	rpc/UserInputRequest (+getHeader/setHeader), RpcHandlerDispatcher	—

The field is optional everywhere; existing callers are unaffected.

Generated event type — intentionally not touched here

The generated UserInputRequestedData (the user_input.requested event payload) is produced by codegen from the @github/copilot schema. It is left untouched so the Codegen Check stays green. It will gain header automatically once:

1. The runtime change ships and @github/copilot is bumped to that version.
2. npm run generate (ts/csharp/python/go/rust) and cd java && mvn generate-sources -Pcodegen are run.
3. E2E snapshots under test/snapshots/ask_user/ are re-recorded (the CLI doesn't emit header yet).

⚠️ Breaking (Rust only)

UserInputHandler::handle gains a header: Option<String> parameter (positional trait method). All in-repo implementors (example + tests) are updated.

Verification

Node typecheck ✅ · Go go build ./... ✅ · .NET dotnet build ✅ · Rust cargo build + cargo test --no-run ✅ · Python py_compile ✅. Java not compiled (no JDK in this environment); edits follow the existing record/fluent-setter/dispatcher patterns.

[github-actions]

Cross-SDK Consistency Review

The code changes across all six SDKs look well-aligned — all SDKs correctly add the optional header field to the UserInputRequest type and pass it through to the handler. ✅

Two minor README documentation gaps were flagged with inline comments:

SDK	Code	README
Node.js	✅	✅
Python	✅	✅
Go	✅	✅
.NET	✅	⚠️ dotnet/README.md line 807 lists other fields but is missing // request.Header - ...
Rust	✅	✅
Java	✅	⚠️ java/README.md has no UserInputRequest/ask_user section at all

The PR description already calls these out with — — just confirming the specific locations. The .NET fix is a one-liner. The Java gap is pre-existing and potentially its own follow-up.

Everything else (type definitions, wire struct mappings, handler dispatch, nullability/optionality treatment) is consistent across all languages.

Generated by SDK Consistency Review Agent for issue #1624 · sonnet46 1.3M · ◷

[github-actions]

Generated by SDK Consistency Review Agent for issue #1624 · sonnet46 1.3M

[github-actions]

The .NET code is updated here, but dotnet/README.md line 807 still documents only question, choices, and allowFreeform in the OnUserInputRequest example. All other SDK READMEs (Node, Python, Go, Rust) were updated to mention header — .NET is the odd one out.

Suggested addition at dotnet/README.md line 808 (after // request.Question - ...):

        // request.Header - Optional short title summarizing the question (suitable as a dialog title)

[github-actions]

The Java code correctly gains header, but the Java README (java/README.md) has no UserInputRequest / ask_user documentation section at all — unlike every other SDK README. This pre-existing gap is now more visible since the other READMEs all show the new field.

Consider adding a "User Input Requests" section to java/README.md (modelled after the Node/Python/Go/.NET equivalents) that documents the onUserInputRequest handler, including the new header field. For example:

var session = client.createSession(new SessionConfig()
    .setModel("gpt-5")
    .setOnUserInputRequest((request, invocation) -> {
        // request.getQuestion()      - The question to ask
        // request.getHeader()        - Optional short title suitable as a dialog title
        // request.getChoices()       - Optional list of choices for multiple choice
        // request.isAllowFreeform()  - Whether freeform input is allowed (default: true)
        return CompletableFuture.completedFuture(
            new UserInputResponse().setAnswer("User's answer here").setWasFreeform(true)
        );
    })).get();