When the model returns multiple tool_use blocks in a single response,
read-only tools (read_file, glob_search, grep_search, WebFetch,
WebSearch, LSP, Git*) now execute concurrently via std:🧵:scope
instead of sequentially.
Architecture:
- Add ToolCall/ToolResult types to ToolExecutor trait
- Add execute_batch() with default sequential fallback
- CliToolExecutor overrides execute_batch to classify tools as
parallel-safe or sequential, then runs parallel-safe tools
concurrently via thread scopes
- run_turn refactored into 3 phases:
1. Pre-hooks + permission checks (sequential, hooks may mutate state)
2. Tool execution (batch, parallel for read-only tools)
3. Post-hooks + session updates (sequential, preserves ordering)
Safety guarantees:
- Pre/post hooks always run sequentially
- Permission checks complete before any tool executes
- Tool results pushed to session in original model order
- Fallback to sequential for single-tool batches
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