release: 2.51.0

[stainless-app]

Automated Release PR

2.51.0 (2026-07-30)

Full Changelog: v2.50.0...v2.51.0

Features

• api: fast tier (8808ed2)

Bug Fixes

• api: add fast tier to helper methods (6064126)

---

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[openai-sdks]

OkTest Summary

✅ 237/237 SDK tests passed in 12.137s for Python SDK PR #3553.

Test results — 42 files

Test	Result	Time
tests/chat-completions-complex-body.test.ts	✅ Passed	177ms
tests/chat-completions-create.test.ts	✅ Passed	233ms
tests/chat-completions-stream.test.ts	✅ Passed	137ms
tests/files-content-binary.test.ts	✅ Passed	260ms
tests/files-create-multipart.test.ts	✅ Passed	235ms
tests/files-list-pagination.test.ts	✅ Passed	186ms
tests/initialize-config.test.ts	✅ Passed	156ms
tests/instance-isolation.test.ts	✅ Passed	253ms
tests/models-list.test.ts	✅ Passed	200ms
tests/responses-background-lifecycle.test.ts	✅ Passed	271ms
tests/responses-body-method-errors.test.ts	✅ Passed	405ms
tests/responses-cancel-timeout.test.ts	✅ Passed	224ms
tests/responses-cancel.test.ts	✅ Passed	307ms
tests/responses-compact-retries.test.ts	✅ Passed	391ms
tests/responses-compact.test.ts	✅ Passed	270ms
tests/responses-create-advanced-stream.test.ts	✅ Passed	370ms
tests/responses-create-advanced.test.ts	✅ Passed	298ms
tests/responses-create-disconnect.test.ts	✅ Passed	1.236s
tests/responses-create-errors.test.ts	✅ Passed	187ms
tests/responses-create-malformed-api-responses.test.ts	✅ Passed	256ms
tests/responses-create-retries.test.ts	✅ Passed	400ms
tests/responses-create-stream-failures.test.ts	✅ Passed	148ms
tests/responses-create-stream-timeout.test.ts	✅ Passed	239ms
tests/responses-create-stream-wire.test.ts	✅ Passed	3.987s
tests/responses-create-stream.test.ts	✅ Passed	114ms
tests/responses-create-terminal-states.test.ts	✅ Passed	270ms
tests/responses-create-timeout.test.ts	✅ Passed	238ms
tests/responses-create.test.ts	✅ Passed	265ms
tests/responses-delete.test.ts	✅ Passed	234ms
tests/responses-input-items-errors.test.ts	✅ Passed	336ms
tests/responses-input-items-list.test.ts	✅ Passed	331ms
tests/responses-input-items-options.test.ts	✅ Passed	410ms
tests/responses-input-tokens-count-timeout.test.ts	✅ Passed	252ms
tests/responses-input-tokens-count.test.ts	✅ Passed	236ms
tests/responses-malformed-inputs.test.ts	✅ Passed	3.033s
tests/responses-not-found-errors.test.ts	✅ Passed	287ms
tests/responses-parse.test.ts	✅ Passed	452ms
tests/responses-retrieve-retries.test.ts	✅ Passed	334ms
tests/responses-retrieve.test.ts	✅ Passed	312ms
tests/responses-stored-method-errors.test.ts	✅ Passed	667ms
tests/retry-behavior.test.ts	✅ Passed	3.208s
tests/sdk-error-shape.test.ts	✅ Passed	442ms

View OkTest run #30565423161

_{SDK merge (7168301297ea) · head (fa6635277f11) · base (4f404262955c) · OkTest (91635c6a2723)}

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Propagate fast tier to chat helper signatures

The new literal is only added to the generated create() surfaces, but the chat helper APIs still expose the old enum (parse() at line 118, stream() at line 1574, and async equivalents at lines 1729/3185) while forwarding service_tier through to create(). In typed code, client.chat.completions.parse(..., service_tier="fast") or .stream(..., service_tier="fast") is still rejected even though this change documents Fast mode support for Chat Completions.

Useful? React with 👍 / 👎.

[chatgpt-codex-connector]

Propagate fast tier to responses helpers

The standard responses.create() overloads now accept service_tier="fast", but the Responses helper signatures still use the old literal set (stream() overload/implementation at lines 1108/1151 and parse() at line 1313, plus async at lines 2943/2986/3147). Typed users who opt in via client.responses.stream(..., service_tier="fast") or .parse(...) still get an invalid-literal error even though these helpers send the same request parameter.

Useful? React with 👍 / 👎.

[stainless-app]

🤖 Release is at https://github.com/openai/openai-python/releases/tag/v2.51.0 🌻