Zen /v1/responses (glm-5.3-flash): 422 "Input should be a valid string" when a tool output contains an image — bricks Codex screenshot/browser sessions #48740

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1. github-actions

   assigned

   MrMushrooooom

   on Sep 13, 2026
2. gy6221 commented on Sep 15, 2026

   

   gy6221

   on Sep 15, 2026

   Last edited by gy6221

   More actions

   Additional reproduction that bypasses both cc-switch and the Responses-to-Chat conversion:

   Direct POST https://opencode.ai/zen/go/v1/chat/completions with glm-5.3-flash. The image is already in the final role: "user" content; there is no function_call_output and no /v1/responses request involved.

   Message shape:

   [
     {"role": "system", "content": "s"},
     {"role": "user", "content": "start"},
     {"role": "assistant", "content": null, "tool_calls": [{"id": "c0", "type": "function", "function": {"name": "f", "arguments": "{}"}}]},
     {"role": "tool", "tool_call_id": "c0", "content": "result 0"},
     {"role": "assistant", "content": null, "tool_calls": [{"id": "c1", "type": "function", "function": {"name": "f", "arguments": "{}"}}]},
     {"role": "tool", "tool_call_id": "c1", "content": "result 1"},
     {"role": "assistant", "content": null, "tool_calls": [{"id": "c2", "type": "function", "function": {"name": "f", "arguments": "{}"}}]},
     {"role": "tool", "tool_call_id": "c2", "content": "result 2"},
     {"role": "assistant", "content": null, "tool_calls": [{"id": "c3", "type": "function", "function": {"name": "f", "arguments": "{}"}}]},
     {"role": "tool", "tool_call_id": "c3", "content": "result 3"},
     {
       "role": "user",
       "content": [
         {"type": "text", "text": "screenshot"},
         {
           "type": "image_url",
           "image_url": {
             "url": "data:image/png;base64,...",
             "detail": "original"
           }
         }
       ]
     }
   ]

   Observed intermittently:

   {
     "error": {
       "param": "messages.10.user.content.str",
       "type": "invalid_request_error",
       "message": "Error from provider (Console Go): Upstream request failed: [invalid_request_error] Input should be a valid string"
     }
   }

   Results so far:

   • 4 tool-call/tool-result pairs followed by the image-bearing user message: 1 of 4 requests returned 422.
   • 2 pairs followed by the same message: 1 of 6 requests returned 422 in another run.
   • The same message history without the image returns 200.
   • A text-only content array after the same tool history returns 200.
   • A single tool-call pair followed by the image message has returned 200.
   • Moving the image before the tool-call history has returned 200.

   This means function_call_output is not required to trigger the error, and the issue also reproduces when clients send Chat Completions directly to OpenCode Go. The remaining trigger appears to be a context-dependent combination of multi-turn tool history, an image-bearing user.content array, and the backend/route selected for that session.

   It may therefore be worth broadening the title/scope beyond the Responses-to-Chat conversion path.
3. opencodejr commented on Oct 28, 2026

   

   opencodejrBot

   on Oct 28, 2026

   More actions

   Thanks for the detailed write-up. Narrowing it down to an input_image inside a function_call_output makes this much easier to look into.

   This is a problem with the hosted Zen / OpenCode Go /v1/responses endpoint, not with the OpenCode app. You're calling it from Codex CLI, and the conversion that fails runs on the service side. Its code isn't in this repository, so it can't be fixed or tracked here. Zen and Go service problems like this are handled by the team directly rather than in GitHub issues. Please email help@anoma.ly with:

   • this summary and a link to this issue
   • the sanitized session payloads you offered
   • roughly when it happened (2026-09-13)

   If you've already emailed, the team will get to it, especially now that we've seen it here. Please keep API keys, account details and email addresses out of this public issue and put them only in the email.

   Related issues you linked, for context (all closed):

   • Zen /v1/responses drops array-format assistant content -> 400 "Invalid assistant message: content or tool_calls must be set" #41766: the same Zen /v1/responses conversion path, but it drops array-format assistant content
   • GLM-5.2 via OpenCode Go returns 400: messages.content should be a valid string #32821: the same "content should be a valid string" error with GLM-5.2 on OpenCode Go
   • VS Code extension: pasted images break multi-turn chat with 400 invalid_request_error (content sent as image_url array instead of string) #31870: image parts sent as an array instead of a string, breaking multi-turn chat

   The bot will close this issue in 1 day.
4. opencodejr

   added

   pending close

   triaging

   on Oct 28, 2026
5. opencodejr

   closed this as not plannedon Oct 29, 2026
6. opencodejr commented on Oct 29, 2026

   

   opencodejrBot

   on Oct 29, 2026

   More actions

   Closing this now, @SiliconDawnNo-1: this is a problem with the hosted Zen / OpenCode Go /v1/responses endpoint, which the team handles directly rather than through GitHub issues. If you haven't already, please email help@anoma.ly with the summary from this issue and your sanitized session payloads. Keep keys and account details out of this public thread and put them only in the email. Thanks again for the thorough investigation.