--file flag hardcodes text/plain for all attachments breaking image uploads #34318

Activity

1. github-actions

   assigned

   StarpTech

   on Jun 28, 2026
2. github-actions commented on Jun 28, 2026

   

   github-actionsBot

   on Jun 28, 2026 – with GitHub Actions

   Contributor

   More actions

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

   • bug: run --file hardcodes text/plain MIME type for all files #16723: run --file hardcodes text/plain MIME type for all files
   • bug: --file flag hardcodes all attachments as text/plain, breaking image/vision uploads #25353: --file flag hardcodes all attachments as text/plain, breaking image/vision uploads
   • CLI: --file flag attaches images with incorrect MIME type, breaking multimodal support #24698: CLI --file flag attaches images with incorrect MIME type, breaking multimodal support

   If your issue is different, please add more context explaining how it differs from the above.
3. akaguny commented on Aug 11, 2026

   

   akaguny

   on Aug 11, 2026

   More actions

   Still reproducible in v1.18.16 (latest release, 2026-08-10).

   Reproduction on Linux, opencode v1.18.16, custom OpenAI-compatible provider (RouterAI) with a vision model declared as attachment: true + modalities: {input: ["text", "image"]}:

   opencode run "What is written in the attached image?" \
     --model routerai/qwen/qwen3-vl-30b-a3b-instruct \
     -f /tmp/vision_test.png
   

   Result: the model responds "The model does not support image input." and the server log shows:

   message=file mime=text/plain
   

   The root cause is still exactly as described here: in packages/opencode/src/cli/cmd/run.ts, local (non---attach) mode hardcodes the MIME type:

   const mime = !args.attach
     ? isDirectory
       ? "application/x-directory"
       : "text/plain"          // <- FSUtil.mimeType(path) result on the line above is discarded
     : content && text !== undefined && Buffer.from(text, "utf8").equals(content)
       ? "text/plain"
       : detected

   FSUtil.mimeType() (mime-types lookup()) already returns image/png correctly for the same path — the value just never gets used in local mode.

   Two fix PRs (#34319, #34369) were closed unmerged; the bug has been open since 2025 (#16723, #24698, #25353, #38952). Suggested one-line fix:

   const mime = isDirectory ? "application/x-directory" : detected

   Worth noting: with attachment + modalities declared in the provider config, the TUI attachment path and the server API (POST /session/{id}/message with a data:image/png;base64,... file part) both deliver images correctly — only the run --file CLI path is affected.
4. neriousy commented on Oct 1, 2026

   

   neriousy

   on Oct 1, 2026

   Member

   More actions

   In OpenCode v2, opencode run --file keeps the detected type for images and PDFs, so they reach the model as real image/PDF attachments. Only other UTF-8 text files are sent as text/plain.

   Fixed in #35526.

   Closing as completed. If something doesn't work on v2, please open a new issue.
5. neriousy

   closed this as completedon Oct 1, 2026