Bug Description

When configuring delegation.model and delegation.provider in config.yaml, subagents spawned via delegate_task ignore the override and always use the parent agent's model and provider.

Steps to Reproduce

1. Configure delegation in ~/.hermes/config.yaml:

delegation:
  model: deepseek-v4-flash
  provider: deepseek
  base_url: https://api.deepseek.com/v1
  api_key: sk-<redacted>

2. Run a simple delegate_task test:

delegate_task(goal="Tell me your model name", toolsets=[])

3. Observe the result: model: glm-5.1 (parent model) instead of deepseek-v4-flash.

Expected Behavior

Subagent should use deepseek-v4-flash via api.deepseek.com/v1 as configured in the delegation section.

Actual Behavior

Subagent always inherits the parent's model (glm-5.1) and provider (zai).

Investigation

I traced through the code and found:

What works correctly

• _load_config() returns the correct delegation config with base_url, api_key, model, provider
• _resolve_delegation_credentials() correctly returns:

  {"model": "deepseek-v4-flash", "provider": "custom", "base_url": "https://api.deepseek.com/v1", "api_key": "sk-...", "api_mode": "chat_completions"}

• These values are passed to _build_child_agent() as override_provider, override_base_url, override_api_key
• _build_child_agent() computes effective_model = creds["model"] (correct: "deepseek-v4-flash")
• AIAgent.__init__() receives the correct model, base_url, api_key, provider parameters

What goes wrong

The agent log shows the subagent ended up on provider=copilot-acp model=glm-5.1:

ERROR [subagent-0] API call failed after 3 retries. Could not start Copilot ACP command 'copilot'. | provider=copilot-acp model=glm-5.1

The parent agent runs on zai/glm-5.1 (NOT copilot-acp), yet the child somehow gets provider=copilot-acp. The ACP transport inheritance in _build_child_agent (lines 1032-1053) should be cleared when override_provider is set (line 1045-1047), but the result suggests it is not being cleared properly.

Even after the most recent test (where the parent is on plain zai transport), the subagent still returns "model": "glm-5.1" — suggesting the delegation credentials may be resolved but then overwritten somewhere in AIAgent.__init__() or the fallback chain.

Additional note

When base_url and api_key were empty strings ('') in config (the default), _resolve_delegation_credentials takes the if configured_base_url: branch as falsy, falls through to if not configured_provider: which also falls through, and returns all None values — meaning the child inherits everything from the parent. The ${ENV_VAR} syntax was not expanded in the delegation section even though _expand_env_vars exists in the config loader. This may be a separate issue.

Environment

• OS: macOS 26.3.1
• Hermes Agent: latest (installed via curl script)
• Parent model: zai/glm-5.1
• Configured delegation model: deepseek/deepseek-v4-flash
• DeepSeek API verified reachable via curl (returns valid completions)

Config (sanitized)

model:
  default: zai/glm-5.1
  provider: zai
  base_url: https://open.bigmodel.cn/api/coding/paas/v4

delegation:
  model: deepseek-v4-flash
  provider: deepseek
  base_url: https://api.deepseek.com/v1
  api_key: sk-<redacted>
  inherit_mcp_toolsets: true
  max_iterations: 50
  child_timeout_seconds: 600
  max_concurrent_children: 3
  max_spawn_depth: 1
  orchestrator_enabled: true