feat(api): add WebSocket stream IDs

[jbeckwith-oai]

Summary

Adds optional WebSocket-only stream_id routing metadata to Responses client events and all server response events. Events sharing a stream ID are processed FIFO and response events echo that identifier.

Source: https://github.com/openai/openai/pull/1282468
OpenAPI commit: 1e5b3b1f1d21b51c5a37d6122c2b3b2d70ef5a1a

Validation

• Castiron public-baseline generation and formatter completed
• Python source compilation passed
• Strict generated-diff quality review passed
• No private inputs, workflow files, or internal-repository changes are included

[openai-sdks]

OkTest Summary

✅ 237/237 SDK tests passed in 11.512s for Python SDK PR #3612.

Test results — 42 files

Test	Result	Time
tests/chat-completions-complex-body.test.ts	✅ Passed	191ms
tests/chat-completions-create.test.ts	✅ Passed	225ms
tests/chat-completions-stream.test.ts	✅ Passed	129ms
tests/files-content-binary.test.ts	✅ Passed	260ms
tests/files-create-multipart.test.ts	✅ Passed	238ms
tests/files-list-pagination.test.ts	✅ Passed	183ms
tests/initialize-config.test.ts	✅ Passed	167ms
tests/instance-isolation.test.ts	✅ Passed	238ms
tests/models-list.test.ts	✅ Passed	226ms
tests/responses-background-lifecycle.test.ts	✅ Passed	238ms
tests/responses-body-method-errors.test.ts	✅ Passed	328ms
tests/responses-cancel-timeout.test.ts	✅ Passed	194ms
tests/responses-cancel.test.ts	✅ Passed	255ms
tests/responses-compact-retries.test.ts	✅ Passed	340ms
tests/responses-compact.test.ts	✅ Passed	308ms
tests/responses-create-advanced-stream.test.ts	✅ Passed	127ms
tests/responses-create-advanced.test.ts	✅ Passed	230ms
tests/responses-create-disconnect.test.ts	✅ Passed	1.096s
tests/responses-create-errors.test.ts	✅ Passed	225ms
tests/responses-create-malformed-api-responses.test.ts	✅ Passed	289ms
tests/responses-create-retries.test.ts	✅ Passed	357ms
tests/responses-create-stream-failures.test.ts	✅ Passed	127ms
tests/responses-create-stream-timeout.test.ts	✅ Passed	222ms
tests/responses-create-stream-wire.test.ts	✅ Passed	3.934s
tests/responses-create-stream.test.ts	✅ Passed	90ms
tests/responses-create-terminal-states.test.ts	✅ Passed	279ms
tests/responses-create-timeout.test.ts	✅ Passed	233ms
tests/responses-create.test.ts	✅ Passed	189ms
tests/responses-delete.test.ts	✅ Passed	243ms
tests/responses-input-items-errors.test.ts	✅ Passed	389ms
tests/responses-input-items-list.test.ts	✅ Passed	331ms
tests/responses-input-items-options.test.ts	✅ Passed	416ms
tests/responses-input-tokens-count-timeout.test.ts	✅ Passed	254ms
tests/responses-input-tokens-count.test.ts	✅ Passed	295ms
tests/responses-malformed-inputs.test.ts	✅ Passed	2.956s
tests/responses-not-found-errors.test.ts	✅ Passed	254ms
tests/responses-parse.test.ts	✅ Passed	426ms
tests/responses-retrieve-retries.test.ts	✅ Passed	320ms
tests/responses-retrieve.test.ts	✅ Passed	249ms
tests/responses-stored-method-errors.test.ts	✅ Passed	567ms
tests/retry-behavior.test.ts	✅ Passed	3.2s
tests/sdk-error-shape.test.ts	✅ Passed	291ms

View OkTest run #31734762287

_{SDK merge (23767b170731) · head (f5d687b53216) · base (721cb1cd1cac) · OkTest (a845fa206fa4)}

[HAYDEN-OAI]

Reviewed the complete generated SDK and OpenAPI diff, including stable and beta synchronous/asynchronous WebSocket request serialization, all server-event variants, discriminated parsing, beta injection events, existing error-dispatch compatibility, and the coordinated upstream schema change. The optional stream_id remains WebSocket-only, preserves existing SSE event inheritance and HTTP request contracts, and is consistently available for multiplexed event routing. No substantive correctness, security, backwards-compatibility, streaming, or reliability issues found.