Bug Report

Description

The delegate_task tool accepts a model parameter in its JSON schema and Python function signature, but the parameter is never forwarded to child agents. Subagents always fall back to the parent agent model, making per-delegation model overrides impossible.

This affects both:

1. Per-call model parameter — passed directly in delegate_task(model={"model": "xxx", "provider": "yyy"})
2. Delegation config — delegation.model in config.yaml (via runtime_provider which returns a bundle without a model field)

Root Cause

In tools/delegate_tool.py (v0.12.0):

1. The delegate_task() function signature does not include a model parameter
2. The single-task dict is built without forwarding model to child agent construction
3. _build_child_agent() has no task_model parameter for per-call model override
4. The effective model resolution (model or parent_agent.model) ignores the task-level model entirely

Impact

• Cannot route specific delegate_task calls to different models
• delegation.model config option is silently ineffective
• Users expecting model-aware delegation get unexpected parent-model fallback

Patch

A complete fix is available (31 lines added, 6 removed across tools/delegate_tool.py, touching 4 locations). Key changes:

1. Add model parameter to delegate_task() signature and tool registry registration
2. Forward model into the task_list dict
3. Add task_model parameter to _build_child_agent()
4. In _build_child_agent(), prioritize task_model over delegation config and parent model
5. Clear the fallback chain when an explicit model is set

Environment

• Hermes Agent v0.12.0
• File: tools/delegate_tool.py