Read: invalid image payload from file attachment poisons subsequent turns #15264

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1. github-actions

   assigned

   thdxr

   on Feb 26, 2026
2. github-actions

   added

   coreAnything pertaining to core functionality of the application (opencode server stuff)Anything pertaining to core functionality of the application (opencode server stuff)

   on Feb 26, 2026
3. github-actions commented on Feb 26, 2026

   

   github-actionsBot

   on Feb 26, 2026 – with GitHub Actions

   Contributor

   More actions

   This issue might be a duplicate of existing issues. Please check:

   • Trying to read an invalid image file bricks the session #9512: Trying to read an invalid image file bricks the session — same root cause (invalid image bytes cause a provider error that poisons subsequent turns in the session)
4. kapaandyy commented on Mar 23, 2026

   

   kapaandyy

   on Mar 23, 2026

   More actions

   Additional reproduction scenario: file extension vs actual MIME type mismatch

   @thdxr I hit the exact same "poisons subsequent turns" issue, but with a more specific root cause worth noting:

   What happened

   1. Used bash tool to call Gemini API for image generation. Gemini returned mimeType=image/jpeg data.
   2. The AI-written script saved the JPEG data with a .png extension: /tmp/nano_banana_test.png
   3. AI then called the read tool on this .png file
   4. OpenCode's read tool correctly detected the attachment mime as image/jpeg (stored correctly in the DB with "mime":"image/jpeg" and "url":"data:image/jpeg;base64,...")
   5. However, when assembling the API request for the next turn, OpenCode used media_type: image/png (inferred from the .png file extension), overriding the correctly detected mime
   6. Anthropic API returned 400: "The image was specified using the image/png media type, but the image appears to be a image/jpeg image"
   7. Session permanently stuck - every subsequent turn re-sends the poisoned tool_result

   Key insight

   The bug is in the provider adapter layer: when converting stored attachments into API request payloads, OpenCode re-infers the media type from the file path extension instead of using the already-correct mime field from the stored attachment data.

   Environment

   • OpenCode v1.2.27
   • macOS (arm64)
   • Anthropic claude-opus-4-6
   • Workaround: manually cleaned the SQLite DB (opencode.db) - removed the image attachment from the part data and deleted the error messages
5. zeke

   added a commit that references this issue on Apr 5, 2026

   fix(read): reject unsupported image formats before sending to provider

   ...

   This issue will close once commit b28b36a is merged into the 'dev' branch.

   b28b36a
6. thdxr

   assigned

   rekram1-node

   and unassigned

   thdxr

   on Apr 26, 2026
7. rekram1-node

   closed this as completedin #21114on May 1, 2026