413 Payload Too Large when reading local image (gpt-5.2-codex + opus-4.5) #12060

Summary

Reading a locally generated PNG through OpenCode API fails with size errors. gpt-5.2-codex returns Cloudflare 413; opus-4.5 returns request_too_large.

Steps to reproduce

1. Generate a PNG on disk (any tool; e.g., render a still image) and note its size.
   Example (optional): bunx remotion still MyComp /tmp/frame-10s.png --frame=240
2. In OpenCode with model gpt-5.2-codex or opus-4.5, read the local PNG via the file-read tool/API (e.g., /tmp/frame-10s.png).
3. Observe the size error once the file exceeds the upstream limit.

Actual

• gpt-5.2-codex:
  Payload Too Large (Cloudflare 413 HTML)
• opus-4.5:
  {"error":{"type":"request_too_large","message":"Request exceeds the maximum size"}}

Expected

• File read succeeds, or
• API returns an explicit file-size limit and/or guidance (e.g., max size or streaming/upload alternative)

Notes

Hypothesis: when the model attempts to upload a local image read from filesystem, the file is too large for upstream limits.