Expose typed message sources across all SDKs

[jmoseley]

Applications need to distinguish automated messages from human input when using ordinary session.send. The runtime already accepts source, but the SDKs' high-level send APIs did not expose it.

Add an optional MessageSource API across all six SDKs. Unset source remains omitted, preserving existing human-message payloads. Explicit values serialize as "user" or "system".

SDK	API
Node.js/TypeScript	Exported MessageSource union and MessageOptions.source
Python	Exported MessageSource literal type and source= on send / send_and_wait
Go	MessageSourceUser / MessageSourceSystem and MessageOptions.Source
.NET	Nullable MessageOptions.Source with MessageSource.User / System
Java	Nullable fluent MessageOptions.setSource(MessageSource.USER / SYSTEM)
Rust	MessageOptions::with_source and handwritten rpc::SendRequest::with_source with MessageSource::{User, System}

Send-and-wait methods forward the same option without changing completion or error handling. Java and .NET clones retain source. Rust's raw request builder sets its existing crate-visible field; generated RPC code stays untouched. Each language README includes usage guidance.

This does not change runtime/schema files, CLI pins, dependencies, billing flags, hooks, delivery modes, or system-prompt configuration. Both human and automated messages still use ordinary session.send, not the dedicated notification API.

Coverage

Focused regressions cover default omission, explicit user/system serialization, companion options and tracing where supported, clone preservation, idle completion without assistant output, and genuine errors. Existing waiter behavior remains covered.

• Node.js: 23 focused tests, project typecheck, targeted formatting/lint.
• Python: 21 session tests, targeted Ruff and type checks.
• Go: focused source/wait/header/tracing tests, also under the race detector; gofmt.
• .NET: 26 targeted tests, all SDK target builds, formatting.
• Java: 64 targeted tests (19 new cases), Spotless, Java 17 bytecode / Java 25 overlay.
• Rust: 34 targeted source/send/tracing tests, all-target compilation, focused Clippy, formatting, and compiled README examples.

[Copilot]

Copilot review overview

🟢 Approval recommended

The implementation is compatible, focused, documented, and comprehensively tested.

Review tier: Balanced
Findings: None

What changed in this PR

Adds typed Rust message provenance while preserving existing wire behavior.

Changes:

• Adds MessageSource::{User, System} and builders for both send APIs.
• Serializes explicit sources while omitting unset values.
• Documents and thoroughly tests payload, waiting, error, and tracing behavior.

File	Description
rust/​src/​types.rs	Defines typed sources and extends MessageOptions.
rust/​src/​session.rs	Adds source to outgoing requests when set.
rust/​src/​rpc.rs	Adds the raw RPC request builder.
rust/​tests/​session_test.rs	Covers serialization and behavioral compatibility.
rust/​README.md	Documents both supported send paths.

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

[github-actions]

SDK Consistency Review — PR #2550 (MessageSource)

Reviewed the authoritative diff (get_files + get_diff) across all six SDKs. This PR adds a MessageSource (user | system) field to the message-send API, and it is implemented consistently across every language:

SDK	Type	Field on MessageOptions/equivalent	Wire field	Default when unset
Node.js/TS	export type MessageSource = "user" | "system"	source?: MessageSource	source	omitted
Python	MessageSource = Literal["user", "system"]	source: MessageSource | None (kwarg on send/send_and_wait)	source (only added to params if not None)	omitted
Go	type MessageSource string w/ MessageSourceUser/MessageSourceSystem consts	Source MessageSource on MessageOptions	source,omitempty	omitted (empty string)
.NET	enum MessageSource { User, System } w/ JsonStringEnumConverter	MessageSource? Source on MessageOptions	Source (nullable, serializer omits when null)	omitted
Java	enum MessageSource { USER, SYSTEM } w/ @JsonValue/@JsonCreator	MessageSource source w/ getter/fluent setter on MessageOptions, propagated to SendMessageRequest	source	omitted (null)
Rust	pub enum MessageSource { User, System } (#[non_exhaustive], serde lowercase)	pub source: Option<MessageSource> + with_source() builder on MessageOptions; also a SendRequest::with_source() helper in rpc.rs	source (only inserted into JSON if Some)	omitted

Observations:

• Naming follows each language's idiom correctly (camelCase field in TS/Java, snake_case in Python/Rust, PascalCase property in Go/.NET, with wire-level JSON key uniformly source/"user"/"system").
• Semantics are identical everywhere: Source is independent of Mode/AgentMode, defaults to omitted (runtime treats as user message) when unset.
• Tests were added in parallel for every SDK (message_source_test.go, MessageSourceTest.java, message-source.test.ts, test_session.py additions, session_test.rs, .NET lifetime/clone tests) and each README was updated with matching documentation.
• Minor non-issue: Rust additionally exposes a SendRequest::with_source() helper in the low-level rpc.rs (generated RPC layer) alongside the higher-level MessageOptions::with_source() — this is Rust-specific plumbing for the generated request type and doesn't need a mirror in other SDKs.

No cross-language inconsistencies found. This is a clean, well-synchronized feature addition across all six SDKs — no changes requested.

Generated by SDK Consistency Review Agent for #2550 · copilot · sonnet50 · 24.9 AIC · ⌖ 12.9 AIC · ⊞ 9.7K · ◷