Summary

Fixes #19447

When the parent agent uses a composite toolset like hermes-cli (which bundles 44+ tools), calling delegate_task(toolsets=["web"]) resulted in zero tools because the intersection compared toolset names rather than the tools within them: "web" ∉ {"hermes-cli"}.

Changes

tools/delegate_tool.py

• Add _expand_parent_toolsets() helper that collects all tool names from parent toolsets, then recognises any individual toolset whose tools are a subset of the parent's available tools
• Call it before the intersection on the if toolsets: branch so individual toolset names (e.g. web, terminal, browser) are recognised when parent uses a composite like hermes-cli

tests/tools/test_delegate_composite_toolsets.py (new)

• 5 unit tests covering: composite expansion, individual toolsets unchanged, empty set, unknown toolset passthrough, end-to-end intersection

How it works

def _expand_parent_toolsets(parent_toolsets):
    # 1. Collect all tool names from parent toolsets
    # 2. For each toolset in TOOLSETS, if its tools ⊆ parent_tool_names, add it
    # 3. Return expanded set (original names preserved)

Test results

• 160/161 delegate tests pass (1 pre-existing flaky timing test)
• 5/5 new composite expansion tests pass