Summary

When a tool call is interrupted or fails in a specific way, OpenClaw saves a malformed tool_use block to the session history (missing the required input field). This corrupts the session permanently — all subsequent requests fail with a validation error from Claude's API, resulting in blank responses.

Steps to reproduce

1. Use OpenClaw with a Claude model via the Antigravity provider
2. Trigger multiple tool calls (e.g., browser automation, exec commands)
3. During a tool call, interrupt the process (timeout, network issue, or manual interruption)
4. The tool call gets saved to the session .jsonl file with a malformed structure
5. Send any new message — it will "think" but return a blank response
6. Check the session file or logs for the error: messages.X.content.Y.tool_use.input: Field required

Expected behavior

• OpenClaw should validate tool call structures before saving to the session file
• Malformed tool calls should not be persisted
• If a corrupted message exists, OpenClaw should detect and recover (or at least warn the user)

Actual behavior

• Malformed tool_use block is saved to session (missing input field)
• Every subsequent API request includes the corrupted history
• Claude API rejects with: messages.X.content.Y.tool_use.input: Field required
• User sees "thinking" indicator but blank response
• Error cascades — each retry adds another error message to the session, making it worse

Environment

• OpenClaw version: 2026.1.29
• OS: macOS 26.2 (arm64)
• Install method: npm (npm i -g openclaw@latest)
• Model: google-antigravity/claude-opus-4-5-thinking
• Node: v24.8.0

Logs or screenshots

Error in session file:

messages.237.content.1.tool_use.input: Field required

Corrupted message structure (note missing input on second toolCall):

{
  "id": "e775c1a3",
  "message": {
    "role": "assistant",
    "content": [
      {"type": "text", "text": "..."},
      {"type": "tool_use", "id": "toolu_123", "name": "browser", "input": {...}},
      {"type": "tool_use", "id": "toolu_456", "name": "exec"}
    ]
  }
}

Note: The second tool_use block is missing the required input field.

Frequency: Happened twice in one day during normal usage (browser automation and exec commands).

Workaround

Manually repair the session file by removing the corrupted message and all descendants:

# Find the corrupted line and truncate the session
# Backup first, then remove from the corrupted message onwards

Suggested Fix

1. Validate before saving: Check that all tool_use blocks have required fields (id, name, input) before persisting to the session file
2. Graceful recovery: If API returns this specific validation error, auto-rollback to last known good state
3. Session checkpoints: Periodic snapshots that can be restored

This issue was identified with AI assistance (Claude via OpenClaw). The analysis and reproduction steps have been verified by the user.