fix(llm): accept local .avif attachments like base64 AVIF

docs/documentation/agent_design/llms/modalities.md

@@ -74,7 +74,7 @@ Given the LLM powering your agent, you can pass image inputs to your multimodal
 ```
 The `attachment` parameter can be a single `str` or a `list[str]`. We currently support the following:
 
-- Both file and web URLs of the following types: `jpeg`, `png`, `gif`, and `webp`
+- Both file and web URLs of the following types: `jpeg`, `png`, `gif`, `webp`, and `avif` (OpenAI, Anthropic and Gemini do not accept `avif`, but some OpenAI-compatible servers do)
 - `byte64` encoded string of the image
 
 A web URL without a file extension (for example a CDN link) is passed to the provider as an image. A URL whose extension names an audio, video, text or Office document file (such as `.mp3`, `.mp4` or `.docx`) raises a `ValueError`, since those formats are not supported as attachments yet. With `trust_urls=True`, such a URL is HEAD-probed first and accepted when the server reports an image or PDF, for example a thumbnail service that renders a frame from a `.mp4` path.

packages/railtracks/src/railtracks/llm/message.py

@@ -31,6 +31,7 @@
     ".png": "image/png",
     ".gif": "image/gif",
     ".webp": "image/webp",
+    ".avif": "image/avif",
     ".pdf": "application/pdf",
 }
 

packages/railtracks/tests/unit_tests/llm/test_message.py

@@ -175,6 +175,7 @@ class TestAttachment:
             (".png", "png"),
             (".gif", "gif"),
             (".webp", "webp"),
+            (".avif", "avif"),
             (".PNG", "png"),
         ],
     )
@@ -258,6 +259,13 @@ def test_url(self):
         # Image URLs are passed to the provider as-is; no fetch at construction.
         assert attachment.encoding is None
 
+    def test_url_avif(self):
+        attachment = Attachment("https://example.com/photo.avif")
+        assert attachment.type == "url"
+        assert attachment.modality == "image"
+        assert attachment.mime_type == "image/avif"
+        assert attachment.encoding is None
+
     def test_url_with_query_string(self):
         url = "https://example.com/photo.png?token=abc&x=1"
         attachment = Attachment(url)