🐛 Fix line splitting in `format_sse_event` to comply with SSE spec by Zawwarsami16 · Pull Request #15515 · fastapi/fastapi

Zawwarsami16 · 2026-05-14T07:42:17Z

What's happening

format_sse_event in fastapi/sse.py uses str.splitlines() to split data_str (and comment) into SSE lines. splitlines() is wrong on two counts here:

Drops trailing empty strings. "Hello\n".splitlines() is ["Hello"], so the trailing data: line gets eaten — corrupting any payload that ends with a newline. This is the bug in the linked issue.
Treats 8 extra characters as line breaks. \v, \f, \x1c, \x1d, \x1e, \x85, U+2028, U+2029 — per the Python docs. SSE only recognizes \n, \r\n, and \r per the spec, so a payload like "A B" was being silently split into two data: lines.

The fix

A small helper, _split_sse_lines, normalizes \r\n and lone \r to \n, then splits on \n. That preserves trailing empties (because split("\n") keeps them), and only recognizes the three line terminators that SSE actually defines.

def _split_sse_lines(value: str) -> list[str]:
    return value.replace(\"\\r\\n\", \"\\n\").replace(\"\\r\", \"\\n\").split(\"\\n\")

Both data: and comment: branches now go through the helper.

Tests

8 new unit tests in tests/test_sse.py that directly exercise format_sse_event:

Test	Input	Output
`preserves_trailing_newline`	`\"Hello\\n\"`	`b\"data: Hello\\ndata: \\n\\n\"`
`preserves_trailing_double_newline`	`\"Hello\\n\\n\"`	`b\"data: Hello\\ndata: \\ndata: \\n\\n\"`
`single_newline_data`	`\"\\n\"`	`b\"data: \\ndata: \\n\\n\"`
`crlf_normalizes_to_lf`	`\"Hello\\r\\nWorld\"`	`b\"data: Hello\\ndata: World\\n\\n\"`
`bare_cr_treated_as_line_break`	`\"Hello\\rWorld\"`	`b\"data: Hello\\ndata: World\\n\\n\"`
`unicode_line_separator_not_split`	`\"A\\u2028B\"`	`b\"data: A\\u2028B\\n\\n\"` (NOT split)
`vertical_tab_not_split`	`\"A\\vB\"`	`b\"data: A\\vB\\n\\n\"` (NOT split)
`comment_preserves_trailing_newline`	`comment=\"hi\\n\"`	`b\": hi\\n: \\n\\n\"`

The U+2028 / \\v tests are the regression catchers — they distinguish a correct fix (split(\"\\n\") after normalizing) from the naive fix (splitlines()) and from a wrong fix that splits on every Unicode line break.

All 26 tests in tests/test_sse.py pass:

```
tests/test_sse.py .......................... [100%]
26 passed in 1.94s
```

No production code outside format_sse_event was touched.

…g in format_sse_event splitlines() drops trailing empty strings and treats 8 extra characters (\v, \f, \x1c-\x1e, \x85, U+2028, U+2029) as line breaks. SSE only recognizes \n, \r\n, and \r per the spec, and trailing empty data lines are part of the payload — silently dropping them corrupts the stream. Both the data: and the comment branch were affected. Adds 8 unit tests covering trailing-newline preservation, CRLF/CR normalization, and the splitlines() quirks (U+2028, vertical tab) staying inside the payload. Closes fastapi#15500

codspeed · 2026-05-14T07:44:29Z

Merging this PR will not alter performance

✅ 24 untouched benchmarks

_{Comparing Zawwarsami16:fix/sse-trailing-newlines (871cfe7) with master (31ce3cb)}

YuriiMotov

LGTM in general!
I would only simplify comments and tests a bit (see suggested changes) - IMO, comments are too verbose.

Also tested with more real-live tests (see in the details)

Details

from collections.abc import AsyncIterable

from fastapi import FastAPI
from fastapi.sse import EventSourceResponse, ServerSentEvent
from fastapi.testclient import TestClient

app = FastAPI()


multiline_items = [
    "Hello\n",
    "\n",
    "Hello\n\n",
    "Hello\r\nWorld",
    "A\u2028B",
]


@app.get("/multiline-items/stream-json", response_class=EventSourceResponse)
async def sse_multiline_items_json() -> AsyncIterable[str]:
    for item in multiline_items:
        yield item


@app.get("/multiline-items/stream-raw", response_class=EventSourceResponse)
async def sse_multiline_items_raw():
    for item in multiline_items:
        yield ServerSentEvent(raw_data=item)


def test_sse_multiline_items_json() -> None:

    client = TestClient(app)
    response = client.get("/multiline-items/stream-json")
    assert response.status_code == 200
    assert response.headers["content-type"] == "text/event-stream; charset=utf-8"

    assert response.text == (
        'data: "Hello\\n"\n'
        "\n"
        'data: "\\n"\n'
        "\n"
        'data: "Hello\\n\\n"\n'
        "\n"
        'data: "Hello\\r\\nWorld"\n'
        "\n"
        'data: "A\u2028B"\n'
        "\n"
    )


def test_sse_multiline_items_raw() -> None:

    client = TestClient(app)
    response = client.get("/multiline-items/stream-raw")
    assert response.status_code == 200
    assert response.headers["content-type"] == "text/event-stream; charset=utf-8"

    assert response.text == (
        "data: Hello\n"
        "data: \n"
        "\n"
        "data: \n"
        "data: \n"
        "\n"
        "data: Hello\n"
        "data: \n"
        "data: \n"
        "\n"
        "data: Hello\n"
        "data: World\n"
        "\n"
        "data: A\u2028B\n"
        "\n"
    )

@Zawwarsami16, thanks!

Zawwarsami16 · 2026-05-27T19:31:25Z

Thanks @YuriiMotov — pushed 866e577 addressing all three:

Shortened the comment in _split_sse_lines to a two-line summary.
Folded the per-case data tests into one @pytest.mark.parametrize and rewrote the literal U+2028 as \u2028 so VS Code stops flagging the file.
Added test_format_sse_event_keeps_empty_data_line from fix(sse): preserve empty data lines when formatting SSE #15618 — format_sse_event(data_str="") now has explicit coverage that it emits b"data: \n\n".

tests/test_sse.py is green locally (27 passed in 1.18s).

YuriiMotov

LGTM!

Also tested with more real-live tests (see in the details)

Details

from collections.abc import AsyncIterable

from fastapi import FastAPI
from fastapi.sse import EventSourceResponse, ServerSentEvent
from fastapi.testclient import TestClient

app = FastAPI()


multiline_items = [
    "Hello\n",
    "\n",
    "Hello\n\n",
    "Hello\r\nWorld",
    "A\u2028B",
]


@app.get("/multiline-items/stream-json", response_class=EventSourceResponse)
async def sse_multiline_items_json() -> AsyncIterable[str]:
    for item in multiline_items:
        yield item


@app.get("/multiline-items/stream-raw", response_class=EventSourceResponse)
async def sse_multiline_items_raw():
    for item in multiline_items:
        yield ServerSentEvent(raw_data=item)


def test_sse_multiline_items_json() -> None:

    client = TestClient(app)
    response = client.get("/multiline-items/stream-json")
    assert response.status_code == 200
    assert response.headers["content-type"] == "text/event-stream; charset=utf-8"

    assert response.text == (
        'data: "Hello\\n"\n'
        "\n"
        'data: "\\n"\n'
        "\n"
        'data: "Hello\\n\\n"\n'
        "\n"
        'data: "Hello\\r\\nWorld"\n'
        "\n"
        'data: "A\u2028B"\n'
        "\n"
    )


def test_sse_multiline_items_raw() -> None:

    client = TestClient(app)
    response = client.get("/multiline-items/stream-raw")
    assert response.status_code == 200
    assert response.headers["content-type"] == "text/event-stream; charset=utf-8"

    assert response.text == (
        "data: Hello\n"
        "data: \n"
        "\n"
        "data: \n"
        "data: \n"
        "\n"
        "data: Hello\n"
        "data: \n"
        "data: \n"
        "\n"
        "data: Hello\n"
        "data: World\n"
        "\n"
        "data: A\u2028B\n"
        "\n"
    )

@Zawwarsami16, thank you!
Passing this to Sebastian for the final review

tiangolo

Thank you! 🚀

This will be available in FastAPI 0.140.12, released in the next few hours. 🎉

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MR [#16077](https://github.com/fastapi/fastapi/pull/16077) by [@tiangolo](https://github.com/tiangolo). - 👷 Add OpenAPI dependency benchmarks. MR [#16075](https://github.com/fastapi/fastapi/pull/16075) by [@tiangolo](https://github.com/tiangolo). ### [`v0.140.6`](https://github.com/fastapi/fastapi/releases/tag/0.140.6) [Compare Source](https://github.com/fastapi/fastapi/compare/0.140.5...0.140.6) ##### Refactors - ⚡️ Avoid flattening dependencies for request parameters, mainly for OpenAPI. MR [#16073](https://github.com/fastapi/fastapi/pull/16073) by [@tiangolo](https://github.com/tiangolo). ### [`v0.140.5`](https://github.com/fastapi/fastapi/releases/tag/0.140.5) [Compare Source](https://github.com/fastapi/fastapi/compare/0.140.4...0.140.5) ##### Refactors - ⚡️ Avoid flattening dependencies for body fields. MR [#16071](https://github.com/fastapi/fastapi/pull/16071) by [@tiangolo](https://github.com/tiangolo). ### [`v0.140.4`](https://github.com/fastapi/fastapi/releases/tag/0.140.4) [Compare Source](https://github.com/fastapi/fastapi/compare/0.140.3...0.140.4) ##### Refactors - ⚡️ Skip unused dependency repeat bookkeeping. MR [#16069](https://github.com/fastapi/fastapi/pull/16069) by [@tiangolo](https://github.com/tiangolo). ### [`v0.140.3`](https://github.com/fastapi/fastapi/releases/tag/0.140.3) [Compare Source](https://github.com/fastapi/fastapi/compare/0.140.2...0.140.3) ##### Refactors - ⚡️ Avoid repeated dependency flattening in OpenAPI. MR [#16067](https://github.com/fastapi/fastapi/pull/16067) by [@tiangolo](https://github.com/tiangolo). ### [`v0.140.2`](https://github.com/fastapi/fastapi/releases/tag/0.140.2) [Compare Source](https://github.com/fastapi/fastapi/compare/0.140.1...0.140.2) ##### Refactors - ⚡️ Stop retaining flat dependency trees. MR [#16065](https://github.com/fastapi/fastapi/pull/16065) by [@tiangolo](https://github.com/tiangolo). ##### Internal - 👷 Add new memory benchmark. MR [#16064](https://github.com/fastapi/fastapi/pull/16064) by [@tiangolo](https://github.com/tiangolo). ### [`v0.140.1`](https://github.com/fastapi/fastapi/releases/tag/0.140.1) [Compare Source](https://github.com/fastapi/fastapi/compare/0.140.0...0.140.1) ##### Refactors - ♻️ Update the lru\_cache limit for dependencies to account for large apps. MR [#16062](https://github.com/fastapi/fastapi/pull/16062) by [@tiangolo](https://github.com/tiangolo). ### [`v0.140.0`](https://github.com/fastapi/fastapi/releases/tag/0.140.0) [Compare Source](https://github.com/fastapi/fastapi/compare/0.139.2...0.140.0) ##### Refactors - ⚡️ Reduce memory usage in dependencies. MR [#16049](https://github.com/fastapi/fastapi/pull/16049) by [@tiangolo](https://github.com/tiangolo). ##### Docs - 📝 Fix links in docs. MR [#15967](https://github.com/fastapi/fastapi/pull/15967) by [@YuriiMotov](https://github.com/YuriiMotov). - 📝 Add Library Skills documentation. MR [#16041](https://github.com/fastapi/fastapi/pull/16041) by [@tiangolo](https://github.com/tiangolo). - 📝 Update docs to use uv projects by default. MR [#16032](https://github.com/fastapi/fastapi/pull/16032) by [@tiangolo](https://github.com/tiangolo). - 📝 Restructure FastAPI People and related pages. MR [#16015](https://github.com/fastapi/fastapi/pull/16015) by [@tiangolo](https://github.com/tiangolo). ##### Internal - 👷 Add CI memory benchmark. MR [#16046](https://github.com/fastapi/fastapi/pull/16046) by [@tiangolo](https://github.com/tiangolo). - 👥 Update FastAPI People - Sponsors. MR [#16027](https://github.com/fastapi/fastapi/pull/16027) by [@tiangolo](https://github.com/tiangolo). - 🔥 Remove now-obsolete scripts to generate data for FastAPI People. MR [#16016](https://github.com/fastapi/fastapi/pull/16016) by [@tiangolo](https://github.com/tiangolo). ### [`v0.139.2`](https://github.com/fastapi/fastapi/releases/tag/0.139.2) [Compare Source](https://github.com/fastapi/fastapi/compare/0.139.1...0.139.2) ##### Fixes - 🐛 Refactor router route building to make it thread-safe, mainly relevant for tests running in parallel threads (uncommon). MR [#16013](https://github.com/fastapi/fastapi/pull/16013) by [@tiangolo](https://github.com/tiangolo). ### [`v0.139.1`](https://github.com/fastapi/fastapi/releases/tag/0.139.1) [Compare Source](https://github.com/fastapi/fastapi/compare/0.139.0...0.139.1) ##### Fixes - 🐛 Fix frontend fallback support for doted paths like `/users/john.doe`. MR [#16011](https://github.com/fastapi/fastapi/pull/16011) by [@tiangolo](https://github.com/tiangolo). ##### Docs - 📝 Fix topic repository list not being displayed and `skip_users` not being applied. MR [#15995](https://github.com/fastapi/fastapi/pull/15995) by [@YuriiMotov](https://github.com/YuriiMotov). ##### Translations - 🌐 Update translations for tr (update-outdated). MR [#16005](https://github.com/fastapi/fastapi/pull/16005) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for zh-hant (update-outdated). MR [#15996](https://github.com/fastapi/fastapi/pull/15996) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for fr (update-outdated). MR [#16006](https://github.com/fastapi/fastapi/pull/16006) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for de (update-outdated). MR [#15999](https://github.com/fastapi/fastapi/pull/15999) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for ko (update-outdated). MR [#16004](https://github.com/fastapi/fastapi/pull/16004) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for zh (update-outdated). MR [#16001](https://github.com/fastapi/fastapi/pull/16001) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for uk (update-outdated). MR [#16003](https://github.com/fastapi/fastapi/pull/16003) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for ja (update-outdated). MR [#15998](https://github.com/fastapi/fastapi/pull/15998) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for pt (update-outdated). MR [#16000](https://github.com/fastapi/fastapi/pull/16000) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for es (update-outdated). MR [#15997](https://github.com/fastapi/fastapi/pull/15997) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for ru (update-outdated). MR [#16002](https://github.com/fastapi/fastapi/pull/16002) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for hi (add-missing). MR [#15990](https://github.com/fastapi/fastapi/pull/15990) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for hi (add-missing). MR [#15925](https://github.com/fastapi/fastapi/pull/15925) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for hi (add-missing). MR [#15797](https://github.com/fastapi/fastapi/pull/15797) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update `llm-prompt.md` for Hindi. MR [#15810](https://github.com/fastapi/fastapi/pull/15810) by [@YuriiMotov](https://github.com/YuriiMotov). - 🌐 Fix language-specific translation prompt for Russian language. MR [#15924](https://github.com/fastapi/fastapi/pull/15924) by [@YuriiMotov](https://github.com/YuriiMotov). ##### Internal - ⬆ Bump the python-packages group across 1 directory with 6 updates. MR [#15981](https://github.com/fastapi/fastapi/pull/15981) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump typing-extensions from 4.15.0 to 4.16.0. MR [#15982](https://github.com/fastapi/fastapi/pull/15982) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump the github-actions group across 1 directory with 4 updates. MR [#15983](https://github.com/fastapi/fastapi/pull/15983) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump pre-commit hooks. MR [#15985](https://github.com/fastapi/fastapi/pull/15985) by [@tiangolo](https://github.com/tiangolo). - 👷 Use `FASTAPI_LATEST_CHANGES` token in `bump-pre-commit-hooks` workflow. MR [#15984](https://github.com/fastapi/fastapi/pull/15984) by [@YuriiMotov](https://github.com/YuriiMotov). - 👷 Add GH workflow to bump pre-commit hook versions. MR [#15873](https://github.com/fastapi/fastapi/pull/15873) by [@YuriiMotov](https://github.com/YuriiMotov). - 🔧 Set Dependabot schedule interval to "monthly". MR [#15874](https://github.com/fastapi/fastapi/pull/15874) by [@YuriiMotov](https://github.com/YuriiMotov). - ⬆ Bump CodSpeedHQ/action from 4.17.6 to 4.18.1 in the github-actions group. MR [#15950](https://github.com/fastapi/fastapi/pull/15950) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump the python-packages group with 8 updates. MR [#15952](https://github.com/fastapi/fastapi/pull/15952) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - 🔧 Update sponsors: add TutorCruncher. MR [#15947](https://github.com/fastapi/fastapi/pull/15947) by [@tiangolo](https://github.com/tiangolo). - 👷 Fix notify translations checkout target. MR [#15933](https://github.com/fastapi/fastapi/pull/15933) by [@tiangolo](https://github.com/tiangolo). - 👷 Fix latest-changes checkout target. MR [#15932](https://github.com/fastapi/fastapi/pull/15932) by [@tiangolo](https://github.com/tiangolo). - 🔧 Update sponsors: remove RapidProxy. MR [#15929](https://github.com/fastapi/fastapi/pull/15929) by [@tiangolo](https://github.com/tiangolo). - ⬆️ Update issue-manager to 0.8.1. MR [#15928](https://github.com/fastapi/fastapi/pull/15928) by [@tiangolo](https://github.com/tiangolo). - ⬆️ Update latest-changes to 0.6.1. MR [#15926](https://github.com/fastapi/fastapi/pull/15926) by [@tiangolo](https://github.com/tiangolo). ### [`v0.139.0`](https://github.com/fastapi/fastapi/releases/tag/0.139.0) [Compare Source](https://github.com/fastapi/fastapi/compare/0.138.2...0.139.0) ##### Features - ✨ Support dependencies in `app.frontend()`, e.g. for automatic cookie authentication for the frontend. MR [#15908](https://github.com/fastapi/fastapi/pull/15908) by [@tiangolo](https://github.com/tiangolo). ##### Translations - 🌐 Update translations for fr (update-outdated). MR [#15897](https://github.com/fastapi/fastapi/pull/15897) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for ja (update-outdated). MR [#15895](https://github.com/fastapi/fastapi/pull/15895) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for zh-hant (update-outdated). MR [#15896](https://github.com/fastapi/fastapi/pull/15896) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for de (update-outdated). MR [#15899](https://github.com/fastapi/fastapi/pull/15899) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for es (update-outdated). MR [#15892](https://github.com/fastapi/fastapi/pull/15892) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for tr (update-outdated). MR [#15891](https://github.com/fastapi/fastapi/pull/15891) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for pt (update-outdated). MR [#15893](https://github.com/fastapi/fastapi/pull/15893) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for zh (update-outdated). MR [#15898](https://github.com/fastapi/fastapi/pull/15898) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for uk (update-outdated). MR [#15900](https://github.com/fastapi/fastapi/pull/15900) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for ko (update-outdated). MR [#15890](https://github.com/fastapi/fastapi/pull/15890) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for ru (update-outdated). MR [#15894](https://github.com/fastapi/fastapi/pull/15894) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for ko (add-missing). MR [#15888](https://github.com/fastapi/fastapi/pull/15888) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for es (add-missing). MR [#15880](https://github.com/fastapi/fastapi/pull/15880) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for zh-hant (add-missing). MR [#15889](https://github.com/fastapi/fastapi/pull/15889) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for pt (add-missing). MR [#15883](https://github.com/fastapi/fastapi/pull/15883) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for zh (add-missing). MR [#15885](https://github.com/fastapi/fastapi/pull/15885) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for ja (add-missing). MR [#15882](https://github.com/fastapi/fastapi/pull/15882) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for tr (add-missing). MR [#15887](https://github.com/fastapi/fastapi/pull/15887) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for uk (add-missing). MR [#15886](https://github.com/fastapi/fastapi/pull/15886) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for fr (add-missing). MR [#15881](https://github.com/fastapi/fastapi/pull/15881) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for de (add-missing). MR [#15884](https://github.com/fastapi/fastapi/pull/15884) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for ru (add-missing). MR [#15879](https://github.com/fastapi/fastapi/pull/15879) by [@tiangolo](https://github.com/tiangolo). ##### Internal - 👥 Update FastAPI People - Experts. MR [#15909](https://github.com/fastapi/fastapi/pull/15909) by [@tiangolo](https://github.com/tiangolo). - 👥 Update FastAPI GitHub topic repositories. MR [#15906](https://github.com/fastapi/fastapi/pull/15906) by [@tiangolo](https://github.com/tiangolo). - 👥 Update FastAPI People - Contributors and Translators. MR [#15878](https://github.com/fastapi/fastapi/pull/15878) by [@tiangolo](https://github.com/tiangolo). - 👷 Remove not needed `allow-unsafe-pr-checkout: true`. MR [#15876](https://github.com/fastapi/fastapi/pull/15876) by [@YuriiMotov](https://github.com/YuriiMotov). - ⬆ Bump the github-actions group with 5 updates. MR [#15872](https://github.com/fastapi/fastapi/pull/15872) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump the python-packages group across 1 directory with 10 updates. MR [#15870](https://github.com/fastapi/fastapi/pull/15870) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump CodSpeedHQ/action from 4.17.0 to 4.17.5 in the github-actions group. MR [#15826](https://github.com/fastapi/fastapi/pull/15826) by [@dependabot\[bot\]](https://github.com/apps/dependabot). ### [`v0.138.2`](https://github.com/fastapi/fastapi/releases/tag/0.138.2) [Compare Source](https://github.com/fastapi/fastapi/compare/0.138.1...0.138.2) ##### Refactors - ♻️ Make `app.frontend()` return 404 for methods other than `GET` or `HEAD` with no static file matches. MR [#15863](https://github.com/fastapi/fastapi/pull/15863) by [@tiangolo](https://github.com/tiangolo). ##### Internal - 🔧 Update sponsors: remove Stainless. MR [#15862](https://github.com/fastapi/fastapi/pull/15862) by [@tiangolo](https://github.com/tiangolo). - ♻️ Refactor how sponsors data is handled for banners. MR [#15852](https://github.com/fastapi/fastapi/pull/15852) by [@tiangolo](https://github.com/tiangolo). ### [`v0.138.1`](https://github.com/fastapi/fastapi/releases/tag/0.138.1) [Compare Source](https://github.com/fastapi/fastapi/compare/0.138.0...0.138.1) ##### Refactors - ♻️ Refactor Library Skills, make info easier to find for agents. MR [#15841](https://github.com/fastapi/fastapi/pull/15841) by [@tiangolo](https://github.com/tiangolo). ##### Internal - 👷 Simplify pull request workflow triggers. MR [#15836](https://github.com/fastapi/fastapi/pull/15836) by [@tiangolo](https://github.com/tiangolo). - 👷 Update issue-manager to 0.7.1. MR [#15833](https://github.com/fastapi/fastapi/pull/15833) by [@tiangolo](https://github.com/tiangolo). - ⬆️ Update issue-manager to 0.7.0. MR [#15831](https://github.com/fastapi/fastapi/pull/15831) by [@tiangolo](https://github.com/tiangolo). - 🔧 Update sponsors: Add TestMu again. MR [#15830](https://github.com/fastapi/fastapi/pull/15830) by [@tiangolo](https://github.com/tiangolo). - 🔒️ Update zizmor workflow security checks. MR [#15820](https://github.com/fastapi/fastapi/pull/15820) by [@tiangolo](https://github.com/tiangolo). - ⬆ Bump pydantic-settings from 2.14.1 to 2.14.2. MR [#15799](https://github.com/fastapi/fastapi/pull/15799) by [@dependabot\[bot\]](https://github.com/apps/dependabot). ### [`v0.138.0`](https://github.com/fastapi/fastapi/releases/tag/0.138.0) [Compare Source](https://github.com/fastapi/fastapi/compare/0.137.2...0.138.0) ##### Features - ✨ Add support for `app.frontend("/", directory="dist")` and `router.frontend("/", directory="dist")`. MR [#15800](https://github.com/fastapi/fastapi/pull/15800) by [@tiangolo](https://github.com/tiangolo). - Read the docs: [Frontend](https://fastapi.tiangolo.com/tutorial/frontend/). ##### Docs - 📝 Fix typo in release notes. MR [#15807](https://github.com/fastapi/fastapi/pull/15807) by [@tiangolo](https://github.com/tiangolo). - 📝 Add `app.frontend()` instructions to Agent Library Skill. MR [#15805](https://github.com/fastapi/fastapi/pull/15805) by [@tiangolo](https://github.com/tiangolo). - 📝 Update release notes link. MR [#15802](https://github.com/fastapi/fastapi/pull/15802) by [@tiangolo](https://github.com/tiangolo). - ✏️ Update white space characters in bigger apps. MR [#15801](https://github.com/fastapi/fastapi/pull/15801) by [@tiangolo](https://github.com/tiangolo). - ✏️ Fix grammar, typos, and broken links in docs. MR [#15694](https://github.com/fastapi/fastapi/pull/15694) by [@YuriiMotov](https://github.com/YuriiMotov). ##### Translations - 🌐 Enable Hindi docs translations. MR [#15554](https://github.com/fastapi/fastapi/pull/15554) by [@YuriiMotov](https://github.com/YuriiMotov). ##### Internal - 🐛 Fix failing test, update format for raised errors. MR [#15804](https://github.com/fastapi/fastapi/pull/15804) by [@tiangolo](https://github.com/tiangolo). - 👷 Fix test-alls-green. MR [#15803](https://github.com/fastapi/fastapi/pull/15803) by [@tiangolo](https://github.com/tiangolo). - 🔧 Enable checking `release-notes.md` for typos. MR [#15796](https://github.com/fastapi/fastapi/pull/15796) by [@YuriiMotov](https://github.com/YuriiMotov). - 📝 Tweak wording about deploying to FastAPI Cloud. MR [#15793](https://github.com/fastapi/fastapi/pull/15793) by [@tiangolo](https://github.com/tiangolo). - 🔨 Use `gpt-5.5` model in `translate.py`, specify `-chat` to avoid warnings. MR [#15792](https://github.com/fastapi/fastapi/pull/15792) by [@YuriiMotov](https://github.com/YuriiMotov). ### [`v0.137.2`](https://github.com/fastapi/fastapi/releases/tag/0.137.2) [Compare Source](https://github.com/fastapi/fastapi/compare/0.137.1...0.137.2) ##### Features - ✨ Add `iter_route_contexts()` for advanced use cases that used to use `router.routes` (e.g. Jupyverse). MR [#15785](https://github.com/fastapi/fastapi/pull/15785) by [@tiangolo](https://github.com/tiangolo). ##### Translations - 🌐 Fix broken Markdown in Korean custom response docs. MR [#15774](https://github.com/fastapi/fastapi/pull/15774) by [@kooqooo](https://github.com/kooqooo). - 🌐 Update translations for fr (update-outdated). MR [#15761](https://github.com/fastapi/fastapi/pull/15761) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for zh-hant (update-outdated). MR [#15760](https://github.com/fastapi/fastapi/pull/15760) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for de (update-outdated). MR [#15759](https://github.com/fastapi/fastapi/pull/15759) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for ko (update-outdated). MR [#15757](https://github.com/fastapi/fastapi/pull/15757) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for uk (update-outdated). MR [#15756](https://github.com/fastapi/fastapi/pull/15756) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for zh (update-outdated). MR [#15755](https://github.com/fastapi/fastapi/pull/15755) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for tr (update-outdated). MR [#15754](https://github.com/fastapi/fastapi/pull/15754) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for pt (update-outdated). MR [#15753](https://github.com/fastapi/fastapi/pull/15753) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for es (update-outdated). MR [#15752](https://github.com/fastapi/fastapi/pull/15752) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for ja (update-outdated). MR [#15751](https://github.com/fastapi/fastapi/pull/15751) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for ru (update-outdated). MR [#15758](https://github.com/fastapi/fastapi/pull/15758) by [@tiangolo](https://github.com/tiangolo). ##### Internal - 🔧 Update sponsors: add BairesDev. MR [#15787](https://github.com/fastapi/fastapi/pull/15787) by [@tiangolo](https://github.com/tiangolo). - 🔨 Update sponsors script to simplify previews. MR [#15786](https://github.com/fastapi/fastapi/pull/15786) by [@tiangolo](https://github.com/tiangolo). - ⬆ Bump the python-packages group across 1 directory with 7 updates. MR [#15777](https://github.com/fastapi/fastapi/pull/15777) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump cryptography from 46.0.7 to 48.0.1. MR [#15779](https://github.com/fastapi/fastapi/pull/15779) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump aiohttp from 3.14.0 to 3.14.1. MR [#15781](https://github.com/fastapi/fastapi/pull/15781) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump starlette from 1.2.1 to 1.3.1. MR [#15780](https://github.com/fastapi/fastapi/pull/15780) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump astral-sh/setup-uv from 8.1.0 to 8.2.0 in the github-actions group. MR [#15776](https://github.com/fastapi/fastapi/pull/15776) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump <https://github.com/crate-ci/typos> from v1.47.1 to v1.47.2 in the pre-commit group. MR [#15775](https://github.com/fastapi/fastapi/pull/15775) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump python-multipart from 0.0.30 to 0.0.32. MR [#15778](https://github.com/fastapi/fastapi/pull/15778) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⏪️ Revert removing scripts, only remove `coverage.sh`. MR [#15772](https://github.com/fastapi/fastapi/pull/15772) by [@tiangolo](https://github.com/tiangolo). - 🔥 Remove unused scripts. MR [#15771](https://github.com/fastapi/fastapi/pull/15771) by [@tiangolo](https://github.com/tiangolo). - 🔧 Add ty configs to check docs sources. MR [#15770](https://github.com/fastapi/fastapi/pull/15770) by [@tiangolo](https://github.com/tiangolo). - 🔧 Add ty configs to check docs sources. MR [#15769](https://github.com/fastapi/fastapi/pull/15769) by [@tiangolo](https://github.com/tiangolo). ### [`v0.137.1`](https://github.com/fastapi/fastapi/releases/tag/0.137.1) [Compare Source](https://github.com/fastapi/fastapi/compare/0.137.0...0.137.1) ##### Fixes - 🚨 Fix typing checks for APIRoute. MR [#15765](https://github.com/fastapi/fastapi/pull/15765) by [@tiangolo](https://github.com/tiangolo). - 🐛 Fix bug, allow empty path in path operation in prefixless router. MR [#15763](https://github.com/fastapi/fastapi/pull/15763) by [@tiangolo](https://github.com/tiangolo). ### [`v0.137.0`](https://github.com/fastapi/fastapi/releases/tag/0.137.0) [Compare Source](https://github.com/fastapi/fastapi/compare/0.136.3...0.137.0) ##### Breaking Changes - ♻️ Refactor internals to preserve `APIRouter` and `APIRoute` instances. MR [#15745](https://github.com/fastapi/fastapi/pull/15745) by [@tiangolo](https://github.com/tiangolo). Unblocks ✨ SO MANY THINGS ✨ Before this, `router.include_router(other_router)` would take each path operation from `other_router` and "clone" it, or recreate it from scratch. This would mean that in the end there was only one top level router, part of the app. The way it is structured here is that there are a few additional classes to handle intermediate metadata for router and route inclusion. That way the information of "router X includes Y and Y includes Z" is stored somewhere, without affecting (recreating / clonning) the final route. ##### Non Objectives Dependencies for 404: previously I intended to support dependencies that would be executed even for 404, but that would conflict with the fact that a router could *not* find a match, but the next router *did* find a match. Executing dependencies in the router that did not find a match would not make sense, they could consume the request, body, etc. This original idea was discarded. ##### Specific Breaking Changes Now `router.routes` is no longer a plain list of `APIRoute` objects, it can contain these intermediate objects that can contain additional routers, forming a tree. Any logic that depended on iterating on the `router.routes` directly would be affected, that logic cannot expect to be able to extract data from a plain list of routes, as it's no longer a plain list but a tree. Additionally, any logic that iterated on `router.routes` to modify them would now also see these new objects, and would not see all the routes in the app. `router.routes` should be considered an internal implementation detail, only passed around to the FastAPI functions that need it. ##### Features - Adding routes (path operations) after a router is included now works, they are reflected as they are not copied. - Including `subrouter` in `mainrouter` can be done before adding routes (path operations) to `subrouter`, because now the the entire object is stored instead of copying the routes. - As routes are not copied, in some cases that might save some memory. ##### Alpha Features This is not documented yet, so it's not officially supported yet and could change in the future. But, as `APIRoute` and `APIRouter` instances are now preserved, they could be customized. `APIRouter` has two new methods, `.matches()` and `.handle()`, counterpart to the existing ones in `APIRoute`. With this a router could customize how it matches and handles requests. For example, it could match only requests that include some specific header, for example for handling versions in headers. Still, for now, consider this very experimental and potentially changing and breaking in the future. ##### Future Features Enabled - Custom `APIRoute` subclasses (undocumented, but alraedy works as desccribed above) - Custom `APIRouter` subclasses (undocumented, but already works as described above) - Dependencies per router - Exception handlers per router - Middleware per router - Other features planned ##### Docs - 📝 Update release notes. MR [#15747](https://github.com/fastapi/fastapi/pull/15747) by [@tiangolo](https://github.com/tiangolo). - 📝 Update FastAPI Cloud deployment instructions. MR [#15724](https://github.com/fastapi/fastapi/pull/15724) by [@alejsdev](https://github.com/alejsdev). - ✏️ Use `Annotated` in inline example in `docs/en/docs/tutorial/body-multiple-params.md`. MR [#15591](https://github.com/fastapi/fastapi/pull/15591) by [@TheArchons](https://github.com/TheArchons). - 📝 Remove "NGINX Unit" from the list of ASGI-servers in docs. MR [#15475](https://github.com/fastapi/fastapi/pull/15475) by [@angryfoxx](https://github.com/angryfoxx). - 📝 Update `docs/en/docs/tutorial/security/oauth2-jwt.md`. MR [#14781](https://github.com/fastapi/fastapi/pull/14781) by [@zadevhub](https://github.com/zadevhub). ##### Translations - 🌐 Update translations for zh-hant (update-outdated). MR [#15671](https://github.com/fastapi/fastapi/pull/15671) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for es (update-outdated). MR [#15670](https://github.com/fastapi/fastapi/pull/15670) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for fr (update-outdated). MR [#15669](https://github.com/fastapi/fastapi/pull/15669) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for ja (update-outdated). MR [#15668](https://github.com/fastapi/fastapi/pull/15668) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for pt (update-outdated). MR [#15667](https://github.com/fastapi/fastapi/pull/15667) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for tr (update-outdated). MR [#15666](https://github.com/fastapi/fastapi/pull/15666) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for zh (update-outdated). MR [#15665](https://github.com/fastapi/fastapi/pull/15665) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for ko (update-outdated). MR [#15664](https://github.com/fastapi/fastapi/pull/15664) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for de (update-outdated). MR [#15673](https://github.com/fastapi/fastapi/pull/15673) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for uk (update-outdated). MR [#15672](https://github.com/fastapi/fastapi/pull/15672) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for ru (update-outdated). MR [#15674](https://github.com/fastapi/fastapi/pull/15674) by [@tiangolo](https://github.com/tiangolo). ##### Internal - 🔧 Update sponsors: remove TalorData. MR [#15744](https://github.com/fastapi/fastapi/pull/15744) by [@tiangolo](https://github.com/tiangolo). - 🔧 Update sponsors: remove ExoFlare. MR [#15736](https://github.com/fastapi/fastapi/pull/15736) by [@tiangolo](https://github.com/tiangolo). - 🔧 Update sponsors: remove InterviewPal. MR [#15735](https://github.com/fastapi/fastapi/pull/15735) by [@tiangolo](https://github.com/tiangolo). - 🔧 Update sponsors: remove Liblab. MR [#15731](https://github.com/fastapi/fastapi/pull/15731) by [@tiangolo](https://github.com/tiangolo). - 🔧 Update sponsors: remove Scalar. MR [#15730](https://github.com/fastapi/fastapi/pull/15730) by [@tiangolo](https://github.com/tiangolo). - ⬆ Bump the python-packages group across 1 directory with 6 updates. MR [#15721](https://github.com/fastapi/fastapi/pull/15721) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump python-multipart from 0.0.29 to 0.0.30. MR [#15723](https://github.com/fastapi/fastapi/pull/15723) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump the github-actions group with 3 updates. MR [#15720](https://github.com/fastapi/fastapi/pull/15720) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump starlette from 1.1.0 to 1.2.1. MR [#15722](https://github.com/fastapi/fastapi/pull/15722) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump <https://github.com/crate-ci/typos> from v1.46.0 to v1.47.1 in the pre-commit group. MR [#15719](https://github.com/fastapi/fastapi/pull/15719) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - 🔧 Update sponsors, add Rapidproxy. MR [#15689](https://github.com/fastapi/fastapi/pull/15689) by [@tiangolo](https://github.com/tiangolo). - 🔧 Update sponsors: Remove TestMu. MR [#15688](https://github.com/fastapi/fastapi/pull/15688) by [@tiangolo](https://github.com/tiangolo). - ⬆ Bump the python-packages group across 1 directory with 11 updates. MR [#15683](https://github.com/fastapi/fastapi/pull/15683) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump aiohttp from 3.13.4 to 3.14.0. MR [#15681](https://github.com/fastapi/fastapi/pull/15681) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump the github-actions group with 2 updates. MR [#15682](https://github.com/fastapi/fastapi/pull/15682) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump starlette from 1.0.0 to 1.1.0. MR [#15684](https://github.com/fastapi/fastapi/pull/15684) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - 👥 Update FastAPI People - Experts. MR [#15677](https://github.com/fastapi/fastapi/pull/15677) by [@tiangolo](https://github.com/tiangolo). - 👥 Update FastAPI GitHub topic repositories. MR [#15675](https://github.com/fastapi/fastapi/pull/15675) by [@tiangolo](https://github.com/tiangolo). - 👥 Update FastAPI People - Contributors and Translators. MR [#15662](https://github.com/fastapi/fastapi/pull/15662) by [@tiangolo](https://github.com/tiangolo). - 👷 Automate release preparation. MR [#15661](https://github.com/fastapi/fastapi/pull/15661) by [@tiangolo](https://github.com/tiangolo). - 🔥 Remove slim package stub, deprecated for a while. MR [#15649](https://github.com/fastapi/fastapi/pull/15649) by [@tiangolo](https://github.com/tiangolo). - ⬆ Bump authlib from 1.6.11 to 1.7.2. MR [#15512](https://github.com/fastapi/fastapi/pull/15512) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump pymdown-extensions from 10.21.2 to 10.21.3. MR [#15569](https://github.com/fastapi/fastapi/pull/15569) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump CodSpeedHQ/action from 4.14.0 to 4.15.1. MR [#15513](https://github.com/fastapi/fastapi/pull/15513) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump python-multipart from 0.0.26 to 0.0.29. MR [#15595](https://github.com/fastapi/fastapi/pull/15595) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - 🔒️ Improve GitHub actions security. MR [#15607](https://github.com/fastapi/fastapi/pull/15607) by [@YuriiMotov](https://github.com/YuriiMotov). - ⚰️ Remove ruff and coverage ignores for non-existing files. MR [#15610](https://github.com/fastapi/fastapi/pull/15610) by [@YuriiMotov](https://github.com/YuriiMotov). - ✅ Use custom `changing_dir` instead of `CLIRunner.isolated_filesystem` to set working dir. MR [#15616](https://github.com/fastapi/fastapi/pull/15616) by [@YuriiMotov](https://github.com/YuriiMotov). - ✅ Add `httpx2` test dependency to avoid deprecation warning. MR [#15603](https://github.com/fastapi/fastapi/pull/15603) by [@YuriiMotov](https://github.com/YuriiMotov). - ⬆ Bump the python-packages group with 15 updates. MR [#15594](https://github.com/fastapi/fastapi/pull/15594) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - 👷 Configure Dependabot to group updates and update weekly. MR [#15560](https://github.com/fastapi/fastapi/pull/15560) by [@YuriiMotov](https://github.com/YuriiMotov). ### [`v0.136.3`](https://github.com/fastapi/fastapi/releases/tag/0.136.3) [Compare Source](https://github.com/fastapi/fastapi/compare/0.136.1...0.136.3) ##### Refactors - ♻️ Do not accept underscore headers when using `convert_underscores=True` (the default). MR [#15589](https://github.com/fastapi/fastapi/pull/15589) by [@tiangolo](https://github.com/tiangolo). ### [`v0.136.1`](https://github.com/fastapi/fastapi/releases/tag/0.136.1) [Compare Source](https://github.com/fastapi/fastapi/compare/0.136.0...0.136.1) ##### Upgrades - ⬆️ Update Pydantic v2 code to address deprecations. MR [#15101](https://github.com/fastapi/fastapi/pull/15101) by [@svlandeg](https://github.com/svlandeg). ##### Internal - 🔨 Tweak translation script. MR [#15174](https://github.com/fastapi/fastapi/pull/15174) by [@YuriiMotov](https://github.com/YuriiMotov). - ⬆ Bump mkdocs-material from 9.7.1 to 9.7.6. MR [#15408](https://github.com/fastapi/fastapi/pull/15408) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump inline-snapshot from 0.31.1 to 0.32.6. MR [#15409](https://github.com/fastapi/fastapi/pull/15409) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump pytest-codspeed from 4.3.0 to 4.4.0. MR [#15407](https://github.com/fastapi/fastapi/pull/15407) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump pytest-cov from 7.0.0 to 7.1.0. MR [#15406](https://github.com/fastapi/fastapi/pull/15406) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump cloudflare/wrangler-action from 3.14.1 to 3.15.0. MR [#15405](https://github.com/fastapi/fastapi/pull/15405) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump mypy from 1.19.1 to 1.20.1. MR [#15410](https://github.com/fastapi/fastapi/pull/15410) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump python-dotenv from 1.2.1 to 1.2.2. MR [#15400](https://github.com/fastapi/fastapi/pull/15400) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump starlette from 0.52.1 to 1.0.0. MR [#15397](https://github.com/fastapi/fastapi/pull/15397) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump pygithub from 2.8.1 to 2.9.1. MR [#15396](https://github.com/fastapi/fastapi/pull/15396) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump pyjwt from 2.12.0 to 2.12.1. MR [#15393](https://github.com/fastapi/fastapi/pull/15393) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump zizmor from 1.23.1 to 1.24.1. MR [#15394](https://github.com/fastapi/fastapi/pull/15394) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump strawberry-graphql from 0.312.3 to 0.314.3. MR [#15395](https://github.com/fastapi/fastapi/pull/15395) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump python-multipart from 0.0.22 to 0.0.26. MR [#15360](https://github.com/fastapi/fastapi/pull/15360) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump authlib from 1.6.9 to 1.6.11. MR [#15373](https://github.com/fastapi/fastapi/pull/15373) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump aiohttp from 3.13.3 to 3.13.4. MR [#15282](https://github.com/fastapi/fastapi/pull/15282) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump pygments from 2.19.2 to 2.20.0. MR [#15263](https://github.com/fastapi/fastapi/pull/15263) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump pymdown-extensions from 10.20.1 to 10.21.2. MR [#15391](https://github.com/fastapi/fastapi/pull/15391) by [@YuriiMotov](https://github.com/YuriiMotov). - ⬆ Bump pillow from 12.1.1 to 12.2.0. MR [#15333](https://github.com/fastapi/fastapi/pull/15333) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump pytest from 9.0.2 to 9.0.3. MR [#15334](https://github.com/fastapi/fastapi/pull/15334) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump actions/upload-artifact from 7.0.0 to 7.0.1. MR [#15374](https://github.com/fastapi/fastapi/pull/15374) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump actions/cache from 5.0.4 to 5.0.5. MR [#15385](https://github.com/fastapi/fastapi/pull/15385) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - 🔧 Update sponsors: remove Zuplo. MR [#15369](https://github.com/fastapi/fastapi/pull/15369) by [@tiangolo](https://github.com/tiangolo). - 🔧 Update sponsors: remove Speakeasy. MR [#15368](https://github.com/fastapi/fastapi/pull/15368) by [@tiangolo](https://github.com/tiangolo). - 🔒️ Add zizmor and fix audit findings. MR [#15316](https://github.com/fastapi/fastapi/pull/15316) by [@YuriiMotov](https://github.com/YuriiMotov). ### [`v0.136.0`](https://github.com/fastapi/fastapi/releases/tag/0.136.0) [Compare Source](https://github.com/fastapi/fastapi/compare/0.135.4...0.136.0) ##### Upgrades - ⬆️ Support free-threaded Python 3.14t. MR [#15149](https://github.com/fastapi/fastapi/pull/15149) by [@svlandeg](https://github.com/svlandeg). ### [`v0.135.4`](https://github.com/fastapi/fastapi/releases/tag/0.135.4) [Compare Source](https://github.com/fastapi/fastapi/compare/0.135.3...0.135.4) ##### Refactors - 🔥 Remove April Fool's `@app.vibe()` 🤪. MR [#15363](https://github.com/fastapi/fastapi/pull/15363) by [@tiangolo](https://github.com/tiangolo). ##### Internal - ⬆ Bump cryptography from 46.0.5 to 46.0.7. MR [#15314](https://github.com/fastapi/fastapi/pull/15314) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump strawberry-graphql from 0.307.1 to 0.312.3. MR [#15309](https://github.com/fastapi/fastapi/pull/15309) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - 🔨 Add pre-commit hook to ensure latest release header has date. MR [#15293](https://github.com/fastapi/fastapi/pull/15293) by [@YuriiMotov](https://github.com/YuriiMotov). ### [`v0.135.3`](https://github.com/fastapi/fastapi/releases/tag/0.135.3) [Compare Source](https://github.com/fastapi/fastapi/compare/0.135.2...0.135.3) ##### Features - ✨ Add support for `@app.vibe()`. MR [#15280](https://github.com/fastapi/fastapi/pull/15280) by [@tiangolo](https://github.com/tiangolo). - New docs: [Vibe Coding](https://fastapi.tiangolo.com/advanced/vibe/). ##### Docs - ✏️ Fix typo for `client_secret` in OAuth2 form docstrings. MR [#14946](https://github.com/fastapi/fastapi/pull/14946) by [@bysiber](https://github.com/bysiber). ##### Internal - 👥 Update FastAPI People - Experts. MR [#15279](https://github.com/fastapi/fastapi/pull/15279) by [@tiangolo](https://github.com/tiangolo). - ⬆ Bump orjson from 3.11.7 to 3.11.8. MR [#15276](https://github.com/fastapi/fastapi/pull/15276) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - ⬆ Bump ruff from 0.15.0 to 0.15.8. MR [#15277](https://github.com/fastapi/fastapi/pull/15277) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - 👥 Update FastAPI GitHub topic repositories. MR [#15274](https://github.com/fastapi/fastapi/pull/15274) by [@tiangolo](https://github.com/tiangolo). - ⬆ Bump fastmcp from 2.14.5 to 3.2.0. MR [#15267](https://github.com/fastapi/fastapi/pull/15267) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - 👥 Update FastAPI People - Contributors and Translators. MR [#15270](https://github.com/fastapi/fastapi/pull/15270) by [@tiangolo](https://github.com/tiangolo). - ⬆ Bump requests from 2.32.5 to 2.33.0. MR [#15228](https://github.com/fastapi/fastapi/pull/15228) by [@dependabot\[bot\]](https://github.com/apps/dependabot). - 👷 Add ty check to `lint.sh`. MR [#15136](https://github.com/fastapi/fastapi/pull/15136) by [@svlandeg](https://github.com/svlandeg). ### [`v0.135.2`](https://github.com/fastapi/fastapi/releases/tag/0.135.2) [Compare Source](https://github.com/fastapi/fastapi/compare/0.135.1...0.135.2) ##### Upgrades - ⬆️ Increase lower bound to `pydantic >=2.9.0.` and fix the test suite. MR [#15139](https://github.com/fastapi/fastapi/pull/15139) by [@svlandeg](https://github.com/svlandeg). ##### Docs - 📝 Add missing last release notes dates. MR [#15202](https://github.com/fastapi/fastapi/pull/15202) by [@tiangolo](https://github.com/tiangolo). - 📝 Update docs for contributors and team members regarding translation MRs. MR [#15200](https://github.com/fastapi/fastapi/pull/15200) by [@YuriiMotov](https://github.com/YuriiMotov). - 💄 Fix code blocks in reference docs overflowing table width. MR [#15094](https://github.com/fastapi/fastapi/pull/15094) by [@YuriiMotov](https://github.com/YuriiMotov). - 📝 Fix duplicated words in docstrings. MR [#15116](https://github.com/fastapi/fastapi/pull/15116) by [@AhsanSheraz](https://github.com/AhsanSheraz). - 📝 Add docs for `pyproject.toml` with `entrypoint`. MR [#15075](https://github.com/fastapi/fastapi/pull/15075) by [@tiangolo](https://github.com/tiangolo). - 📝 Update links in docs to no longer use the classes external-link and internal-link. MR [#15061](https://github.com/fastapi/fastapi/pull/15061) by [@tiangolo](https://github.com/tiangolo). - 🔨 Add JS and CSS handling for automatic `target=_blank` for links in docs. MR [#15063](https://github.com/fastapi/fastapi/pull/15063) by [@tiangolo](https://github.com/tiangolo). - 💄 Update styles for internal and external links in new tab. MR [#15058](https://github.com/fastapi/fastapi/pull/15058) by [@tiangolo](https://github.com/tiangolo). - 📝 Add documentation for the FastAPI VS Code extension. MR [#15008](https://github.com/fastapi/fastapi/pull/15008) by [@savannahostrowski](https://github.com/savannahostrowski). - 📝 Fix doctrings for `max_digits` and `decimal_places`. MR [#14944](https://github.com/fastapi/fastapi/pull/14944) by [@YuriiMotov](https://github.com/YuriiMotov). - 📝 Add dates to release notes. MR [#15001](https://github.com/fastapi/fastapi/pull/15001) by [@YuriiMotov](https://github.com/YuriiMotov). ##### Translations - 🌐 Update translations for zh (update-outdated). MR [#15177](https://github.com/fastapi/fastapi/pull/15177) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for zh-hant (update-outdated). MR [#15178](https://github.com/fastapi/fastapi/pull/15178) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for zh-hant (add-missing). MR [#15176](https://github.com/fastapi/fastapi/pull/15176) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for zh (add-missing). MR [#15175](https://github.com/fastapi/fastapi/pull/15175) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for ja (update-outdated). MR [#15171](https://github.com/fastapi/fastapi/pull/15171) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for ko (update-outdated). MR [#15170](https://github.com/fastapi/fastapi/pull/15170) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for tr (update-outdated). MR [#15172](https://github.com/fastapi/fastapi/pull/15172) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for ko (add-missing). MR [#15168](https://github.com/fastapi/fastapi/pull/15168) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for ja (add-missing). MR [#15167](https://github.com/fastapi/fastapi/pull/15167) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for tr (add-missing). MR [#15169](https://github.com/fastapi/fastapi/pull/15169) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for fr (update-outdated). MR [#15165](https://github.com/fastapi/fastapi/pull/15165) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for fr (add-missing). MR [#15163](https://github.com/fastapi/fastapi/pull/15163) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for uk (update-outdated). MR [#15160](https://github.com/fastapi/fastapi/pull/15160) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for uk (add-missing). MR [#15158](https://github.com/fastapi/fastapi/pull/15158) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for pt (add-missing). MR [#15157](https://github.com/fastapi/fastapi/pull/15157) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for pt (update-outdated). MR [#15159](https://github.com/fastapi/fastapi/pull/15159) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for es (update-outdated). MR [#15155](https://github.com/fastapi/fastapi/pull/15155) by [@tiangolo](https://github.com/tiangolo). - 🌐 Update translations for es (add-missing). MR [#15154](https:/…

Zawwarsami16 and others added 2 commits May 14, 2026 03:41

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YuriiMotov changed the title ~~fix(sse): preserve trailing newlines + use spec-correct line splitting in format_sse_event~~ 🐛 Fix line splitting in format_sse_event to comply with SSE spec May 18, 2026

YuriiMotov added the bug Something isn't working label May 18, 2026

Sujit-1509 mentioned this pull request May 26, 2026

Fix line splitting in format_sse_event to comply with SSE spec #15608

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YuriiMotov added the waiting label May 26, 2026

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fix(sse): preserve empty data lines when formatting SSE #15618

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address review: shorten comment, parametrize tests, add empty-data case

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Merge branch 'master' into fix/sse-trailing-newlines

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hbrooks mentioned this pull request May 28, 2026

🐛 Fix line splitting in format_sse_event to comply with SSE spec ellipsis-dev-test/fastapi#3

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Comment thread tests/test_sse.py

Add test for empty data value

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YuriiMotov mentioned this pull request Jul 7, 2026

fix(sse): emit data field for empty SSE data payload #15948

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This was referenced Jul 26, 2026

Fix SSE data payload dropping trailing newlines #16055

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fix(sse): preserve empty data strings and trailing newlines in format_sse_event #16081

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Merge branch 'master' into fix/sse-trailing-newlines

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pre-commit-ci-lite Bot and others added 3 commits July 28, 2026 10:33

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🔄 Merge branch 'master' into pr/Zawwarsami16/15515

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✅ Remove duplicate SSE empty-data test

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tiangolo merged commit 0f3e7bd into fastapi:master Jul 28, 2026
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🐛 Fix line splitting in `format_sse_event` to comply with SSE spec - #15515

🐛 Fix line splitting in `format_sse_event` to comply with SSE spec#15515
tiangolo merged 9 commits into
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Zawwarsami16 commented May 14, 2026

What's happening

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codspeed Bot commented May 14, 2026 •

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Zawwarsami16 commented May 27, 2026 •

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