[BUG] anthropic `tool_use` blocks missing `tool_result blocks` - Complete system failure

[drzraf]

Describe the bug
tool_use blocks missing tool_result blocks - Complete system failure

To Reproduce
Steps (from the original bug report)

• Start Roo agent in Debug mode (or any mode)
• Issue a request requiring 4+ parallel tool calls (e.g., "search codebase for X and read files Y, Z,
• Wait for tools to execute
• Error occurs when agent attempts next API call

Frequency: ~100% reproducible with 4+ parallel tools

Simpler personal reproducer:

• triggers Claude to use read_multiple_file tools against more than one image
• API failure in a loop

(I strongly believe this is the same underlying root cause)

The system sends API requests with tool_use blocks but missing or incomplete tool_result blocks, violating Anthropic's API contract and causing immediate failure.

Expected behavior
All tool_use blocks should have corresponding tool_result blocks in the next user message per Anthropic API requirements.

Root Cause Analysis
Primary Diagnosis (80% confidence): Message history reconstruction bug

When rebuilding conversation history for the API request:

1. Agent executes 4 tools in parallel ✅
2. All 4 tool_use blocks recorded in assistant message ✅
3. BUG: Tool results missing/incomplete when constructing next user message ❌
4. Malformed API request sent ❌
5. Anthropic API rejects request ❌

What version of zoo are you running
latest

Additional context
Original bug report: RooCodeInc/Roo-Code#11777
remote draft PR: RooCodeInc/Roo-Code#12183