[BUG] Image read_file combined with other tool calls produces Anthropic 400 error #1774

Describe the bug
When the model calls read_file on an image (JPG/PNG) in the same turn as another tool call, Zoo Code builds the next user message with the image as a standalone top-level image block placed between the tool_result blocks, instead of nesting it inside the read_file tool_result's content array. The Anthropic API requires all tool_result blocks to be contiguous at the start of the message, so it stops scanning at the image block and rejects the request:

400 {"type":"error","error":{"type":"invalid_request_error","message":"messages.16: `tool_use` ids were found without `tool_result` blocks immediately after: toolu_01UsrBMcBxFtm2TQQ1e2iCQb. Each `tool_use` block must have a corresponding `tool_result` block in the next message."}}

The malformed message is persisted to api_conversation_history.json, so every Retry replays the same broken history and the task is permanently stuck. Starting a new task reproduces it as soon as the model reads an image alongside another tool call again.

Actual message shape written to disk (from ~/Library/Application Support/Code/User/globalStorage/zoocodeorganization.zoo-code/tasks/<id>/api_conversation_history.json, message index 16, base64 elided):

{
  "role": "user",
  "content": [
    { "type": "tool_result", "tool_use_id": "toolu_01HnYZ1DVtTfKgouvT5frb2P",
      "content": "File: ../…/river-and-sun-WORKING.jpg\nNote: Image file (219 KB)" },
    { "type": "image", "source": { "type": "base64", "media_type": "image/jpeg", "data": "<base64 …>" } },
    { "type": "tool_result", "tool_use_id": "toolu_01UsrBMcBxFtm2TQQ1e2iCQb",
      "content": "Command executed in terminal … Exit code: 0 …" },
    { "type": "text", "text": "<environment_details>…" }
  ]
}

Note both tool_result blocks are present — the API error is misleading; the real issue is the image sibling breaking contiguity.

To Reproduce
Steps to reproduce the behavior:

1. Use Anthropic provider (Claude) in Code mode, with native tool calling / multiple tool calls per turn enabled.
2. Have an image file available (e.g. logo.jpg) and set auto-approve for read + execute (or approve both manually — approval state does not matter).
3. Prompt: "In a single response, call read_file on logo.jpg and also run execute_command with ls."
4. Both tools execute successfully and results appear in the UI.
5. The next API request fails with the 400 above. Retry fails identically; the task can no longer continue.

Also reproduced with two image reads plus a third tool call in one turn (message shape [tool_result, tool_result, image, tool_result, image, text…]).

Expected behavior
The image should be nested inside the corresponding tool_result's content array, per the Anthropic Messages API spec:

{ "type": "tool_result", "tool_use_id": "toolu_01HnYZ…",
  "content": [
    { "type": "text", "text": "File: …/logo.jpg\nNote: Image file (219 KB)" },
    { "type": "image", "source": { "type": "base64", "media_type": "image/jpeg", "data": "…" } }
  ] }

All tool_result blocks should then be contiguous at the start of the user message, followed by any text blocks. Manually rewriting the on-disk history this way (moving each image into the preceding tool_result.content) fixed the task immediately, confirming the diagnosis.

Additionally, a retry should not replay a message the API has already rejected as structurally invalid; ideally the history should be validated/repaired before resend.

Screenshots
Screenshot of error taken later. The original error had the 400 error described above.

Video
N/A — deterministic, reproducible with the steps above.

What version of zoo are you running
Zoo Code 3.82.2 (zoocodeorganization.zoo-code-3.82.2)
VS Code 26.6.2, macOS 26.6.2 (25G83)
Provider: Anthropic, model claude-fable-5-1, Code mode

Additional context

• Only occurs when an image read_file is combined with at least one other tool call in the same assistant turn. A lone image read works because the image block ends up after the only tool_result, so contiguity is preserved.
• Files read were outside the workspace (iCloud Drive), but that's incidental — the approval prompt is not involved.
• Workaround for users: instruct the model not to read image files, or to read images in their own turn with no other tool calls; or paste the image into the chat instead.
• Recovery for a stuck task: close the task, edit api_conversation_history.json, move each top-level image block into the content array of the preceding tool_result (converting a string content to [{"type":"text","text":…}] first), reopen the task and retry.
• Likely location: the code path that assembles tool_result blocks for read_file image results when multiple tool uses are being combined into one user message (image blocks appended as siblings rather than as tool_result content).
• Likely dupe of [BUG]Tool results interleaved with image blocks break Anthropic API (tool_use without immediate tool_result) #1307