fix: use _validate_format for proper MIME type to Bedrock format mapping

Address Greptile review: naive media_type.split("/")[1] produced invalid
Bedrock format names for complex MIME types (e.g. OOXML → docx, text/plain
→ txt, text/markdown → md). Now reuses BedrockImageProcessor._validate_format
which handles all MIME types correctly via mimetypes + fallback.

Also fixes test assertions to expect correct Bedrock format values and adds
text/plain and text/markdown test cases.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

litellm/litellm_core_utils/prompt_templates/factory.py

@@ -4741,7 +4741,9 @@ class BedrockConverseMessagesProcessor:
         source = element["source"]
         media_type: str = source["media_type"]
         data: str = source["data"]
-        doc_format = media_type.split("/")[1]
+        doc_format = BedrockImageProcessor._validate_format(
+            mime_type=media_type, image_format=media_type.split("/")[1]
+        )
 
         # Deterministic name using the same hashing pattern as _create_bedrock_block
         HASH_SAMPLE_BYTES = 64 * 1024

tests/test_litellm/litellm_core_utils/prompt_templates/test_litellm_core_utils_prompt_templates_factory.py

@@ -2444,9 +2444,11 @@ def test_bedrock_converse_messages_pt_document_various_formats():
         ("application/pdf", "pdf"),
         ("text/csv", "csv"),
         ("text/html", "html"),
+        ("text/plain", "txt"),
+        ("text/markdown", "md"),
         (
             "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
-            "vnd.openxmlformats-officedocument.wordprocessingml.document",
+            "docx",
         ),
     ]