fix(delegate): keep child credential pools provider-scoped

[izumi0uu]

What does this PR do?

Fixes delegated subagents accidentally reusing a parent credential pool whose concrete provider does not match the delegated child provider. When delegation is configured for a different provider/model, a mismatched pool lease can call _swap_credential() and overwrite the child runtime back to the pool provider.

This keeps same-provider pool sharing intact for cooldown/rotation state, but refuses concrete provider mismatches before pool resolution and before child leasing.

Related Issue

Fixes #58298

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 🔒 Security fix
• 📝 Documentation update
• ✅ Tests (adding or improving test coverage)
• ♻️ Refactor (no behavior change)
• 🎯 New skill (bundled or hub)

Changes Made

• tools/delegate_tool.py: add a provider-match guard for child credential pools and apply it when resolving parent pool reuse and when leasing in _run_single_child().
• tests/tools/test_delegate.py: cover rejecting a mismatched parent pool and skipping lease/swap/release when a child has a mismatched pool attached.

How to Test

1. Reproduce the pre-fix resolver behavior on upstream/main (5daa5a0f2f218d2f5c8391dffbc47fe57f76232f): a deepseek parent with a zai credential pool returns the parent pool for a deepseek child.
2. Run the after-fix resolver probe: deepseek child + zai parent pool resolves to None and does not return the parent pool.
3. Run the targeted tests listed below.

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):, feat(scope):, etc.)
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature (no unrelated commits)
• I've run pytest tests/ -q and all tests pass
• I've added tests for my changes (required for bug fixes, strongly encouraged for features)
• I've tested on my platform: macOS 15.7.7 (Darwin 24.6.0, arm64)

Documentation & Housekeeping

• I've updated relevant documentation (README, docs/, docstrings) — N/A
• I've updated cli-config.yaml.example if I added/changed config keys — N/A
• I've updated CONTRIBUTING.md or AGENTS.md if I changed architecture or workflows — N/A
• I've considered cross-platform impact (Windows, macOS) per the compatibility guide — provider/pool matching is platform-independent
• I've updated tool descriptions/schemas if I changed tool behavior — N/A

For New Skills

N/A

Screenshots / Logs

python -m compileall -q tools/delegate_tool.py tests/tools/test_delegate.py

scripts/run_tests.sh tests/tools/test_delegate.py -q
=== Summary: 1 files, 153 tests passed, 0 failed (100% complete) in 18.9s (20 workers) ===

scripts/run_tests.sh tests/agent/test_credential_pool_routing.py tests/run_agent/test_fallback_credential_isolation.py -q
=== Summary: 2 files, 18 tests passed, 0 failed (100% complete) in 1.7s (20 workers) ===

[alt-glitch]

This was generated by AI during triage.

Duplicate of #39862 (earliest open) — both add a provider-match guard to _resolve_child_credential_pool and skip the lease/swap in _run_single_child when a child credential pool's provider doesn't match the child runtime, for the same root cause (mismatched parent-pool lease overwriting the child provider). Same code site (tools/delegate_tool.py), same mechanism, same test scenarios.

[teknium1]

Thanks for isolating the post-construction pool attachment and the lease/swap path; current main still has the reported mismatch path at tools/delegate_tool.py:3023 and :1770.

Problems

• The new helper accepts every custom:* pool when the child provider is custom (tools/delegate_tool.py:3011). That does not preserve the endpoint boundary: a child at endpoint A can still lease a custom:endpoint-b pool and have _swap_credential replace its endpoint/key. Main already has the endpoint-aware contract in agent/credential_pool.py:464-499, with coverage in tests/agent/test_credential_pool_provider_boundary.py:16-26.

Suggested changes

• Reuse credential_pool_matches_provider, passing effective_base_url in the resolver and child.base_url in _run_single_child.
• Add resolver and lease-path tests for custom endpoint A versus a custom:endpoint-b pool.

Automated hermes-sweeper review.

[teknium1]

This accepts any custom:* pool for a custom child, including a pool for a different endpoint. Please reuse agent.credential_pool.credential_pool_matches_provider and pass the runtime base URL; its custom-provider branch verifies the exact custom:<name> key.

[izumi0uu]

Addressed in bdbb94d.

I replaced the local matching helper with
agent.credential_pool.credential_pool_matches_provider, passing
effective_base_url from _resolve_child_credential_pool and
child.base_url from _run_single_child.

I also added resolver and lease-path regressions for a child on custom
endpoint A with a custom:endpoint-b pool. Both paths now reject the
mismatched pool before it can be reused, leased, or passed to
_swap_credential.