The API server's _resolve_media_to_data_urls ran MEDIA_TAG_CLEANUP_RE over the
raw final_response, bypassing the sentinel seam this branch added in
gateway/platforms/base.py. A provider that leaked its end-of-sequence token
glued to the last MEDIA path (MEDIA:/x.png<|eos|>) therefore still produced no
inline image and returned the raw tag to the HTTP client (non-stream and SSE
chat completions) - the exact symptom fixed for the chat platforms. The scan
now stops at _terminal_sentinel_start and drops the control token only when a
tag actually resolved, so unrelated responses stay byte-identical.
_terminal_sentinel_start also recognises a run of repeated exact tokens
(MEDIA:/x.png<|eos|><|eos|>), so a doubled leak no longer hides the attachment
either; mid-text or non-exact sentinels are still not a media boundary.
Review finding: api_server sibling MEDIA surface bypassed _mask_media_scan_text; doubled terminal sentinel still leaked
teknium1
13f908f10d