fix: use StreamingResponse for chat completions SSE

sse_starlette's EventSourceResponse added \r\n line endings that
Open WebUI couldn't parse. Switched to plain StreamingResponse with
manual SSE formatting matching OpenAI's exact format.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -7,6 +7,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [2.0.4] - 2026-02-05
+
+### Fixed
+
+- **Open WebUI streaming compatibility** - Replaced `sse_starlette` `EventSourceResponse` with plain `StreamingResponse` for chat completions; `sse_starlette` added `\r\n` line endings and extra SSE fields that Open WebUI couldn't parse
+
 ## [2.0.3] - 2026-02-05
 
 ### Fixed

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "tatlock"
-version = "2.0.3"
+version = "2.0.4"
 description = "OpenAI-compatible API with Ollama backend"
 requires-python = ">=3.12"
 dependencies = []

src/chat/router.py

@@ -7,7 +7,7 @@ import logging
 from typing import AsyncGenerator
 
 from fastapi import APIRouter
-from sse_starlette.sse import EventSourceResponse
+from starlette.responses import StreamingResponse
 
 from src.chat import service
 from src.chat.schemas import (
@@ -22,36 +22,33 @@ router = APIRouter(prefix="/chat", tags=["chat"])
 
 async def _stream_response(
     request: ChatCompletionRequest,
-) -> AsyncGenerator[dict, None]:
+) -> AsyncGenerator[str, None]:
     """
     Generate SSE stream for chat completion.
 
-    EventSourceResponse adds "data: " prefix automatically.
+    Yields raw SSE-formatted strings matching OpenAI's format exactly:
-    We just yield the dict/string content.
+    data: {json}\n\n
     """
     try:
         async for chunk in service.create_chat_completion_stream(request):
-            # Yield dict - EventSourceResponse will format as SSE
+            yield f"data: {chunk.model_dump_json()}\n\n"
-            yield {"data": chunk.model_dump_json()}
 
-        # Send [DONE] message
+        yield "data: [DONE]\n\n"
-        yield {"data": "[DONE]"}
 
     except Exception as e:
         logger.error(f"Error in streaming response: {e}")
-        error_data = {"error": {"message": str(e), "type": "internal_error"}}
+        error_data = json.dumps({"error": {"message": str(e), "type": "internal_error"}})
-        yield {"data": json.dumps(error_data)}
+        yield f"data: {error_data}\n\n"
 
 
 @router.post("/completions", response_model=ChatCompletionResponse)
 async def create_chat_completion(
     request: ChatCompletionRequest,
-) -> ChatCompletionResponse | EventSourceResponse:
+) -> ChatCompletionResponse | StreamingResponse:
     """
     Create chat completion (OpenAI-compatible).
 
     Supports both regular and streaming responses.
-    Currently returns mock lorem ipsum responses.
 
     Args:
         request: Chat completion request
@@ -63,6 +60,13 @@ async def create_chat_completion(
 
     if request.stream:
         logger.info("Streaming response requested")
-        return EventSourceResponse(_stream_response(request))
+        return StreamingResponse(
+            _stream_response(request),
+            media_type="text/event-stream",
+            headers={
+                "Cache-Control": "no-store",
+                "X-Accel-Buffering": "no",
+            },
+        )
 
     return await service.create_chat_completion(request)