feat(api): folder_indexer.summarize_image via gpt-4o-mini vision

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/core/folder_indexer.py

@@ -41,6 +41,40 @@ async def _llm_text(messages: list) -> object:
     return await llm.ainvoke(messages)
 
 
+async def _llm_vision(messages: list) -> object:
+    """Make the LLM call for vision (image) summarisation.
+
+    Accepts the message list and returns the response directly, mirroring
+    the ``_llm_text`` caller pattern so tests can patch it at the module level.
+    """
+    llm = get_llm(model="gpt-4o-mini", temperature=0.2)
+    return await llm.ainvoke(messages)
+
+
+async def summarize_image(*, image_b64: str, mime: str) -> IndexResult:
+    """Return a compact summary of an image file using vision.
+
+    Parameters
+    ----------
+    image_b64:
+        Base64-encoded image bytes.
+    mime:
+        MIME type of the image, e.g. ``"image/png"``.
+    """
+    template, prompt_obj = get_prompt_or_fallback("folder_file_summary_image", _IMAGE_FALLBACK)
+    messages = [
+        SystemMessage(content=template),
+        HumanMessage(content=[
+            {"type": "text", "text": "Summarise this image."},
+            {"type": "image_url", "image_url": {"url": f"data:{mime};base64,{image_b64}"}},
+        ]),
+    ]
+    response = await _llm_vision(messages)
+    usage = extract_usage(response)
+    summary = (response.content or "").strip()[:500]
+    return IndexResult(summary=summary, tokens_used=usage.get("total", 0))
+
+
 async def summarize_text(*, content: str, ext: str, name: str) -> IndexResult:
     """Return a compact summary of a text file.
 

tests/test_folder_indexer.py

@@ -5,7 +5,7 @@ from unittest.mock import AsyncMock, patch
 
 import pytest
 
-from app.core.folder_indexer import summarize_text, IndexResult
+from app.core.folder_indexer import summarize_text, summarize_image, IndexResult
 
 pytestmark = pytest.mark.asyncio
 
@@ -28,3 +28,26 @@ async def test_summarize_text_truncates_summary_at_500_chars():
     with patch("app.core.folder_indexer._llm_text", new=AsyncMock(return_value=mock_resp)):
         result = await summarize_text(content="x", ext=".md", name="x.md")
     assert len(result.summary) <= 500
+
+
+async def test_summarize_image_uses_vision_content_blocks():
+    mock_resp = AsyncMock()
+    mock_resp.content = "Final logo on white background."
+    mock_resp.usage_metadata = {"total_tokens": 500}
+    captured = {}
+
+    async def fake_llm_vision(messages):
+        captured["messages"] = messages
+        return mock_resp
+
+    with patch("app.core.folder_indexer._llm_vision", new=fake_llm_vision):
+        result = await summarize_image(image_b64="iVBORw0KG", mime="image/png")
+
+    assert "Final logo" in result.summary
+    assert result.tokens_used == 500
+    # last message contains an image content block
+    last = captured["messages"][-1]
+    assert any(
+        isinstance(p, dict) and p.get("type") == "image_url"
+        for p in (last.content if isinstance(last.content, list) else [])
+    )