fix: thread agenthub_config through chat_model_factory new path

[cotovanu-cristian]

Summary

When agents run with command=\"debug\" (or any non-runtime context), the LLM gateway calls were shipping X-UiPath-AgentHub-Config: agentsruntime instead of the computed agentsplayground. Every debug session was billed against the runtime quota.

The bug

chat_model_factory.get_chat_model accepted an agenthub_config parameter whose docstring said it was "ignored by the new factory" — and it was. On the use_new_llm_clients=True path, the value was dropped before delegating to uipath_langchain_client.factory.get_chat_model, which built a fresh PlatformSettings whose agenthub_config defaults to \"agentsruntime\" upstream.

The local _AgentHubConfigDefaultMixin (added in #825/#830) clears that default for direct-construction users — from uipath_langchain.chat import UiPathChat etc. — but the factory path bypassed it entirely, so uipath-agents callers in agent_graph_builder/llm_utils.py:create_llm had their carefully computed value silently discarded.

Trace for uipath debug agent.json:

get_execution_type(ctx) → AgentExecutionType.PLAYGROUND
get_agenthub_config(PLAYGROUND) → \"agentsplayground\"  ✓
get_chat_model(model, agenthub_config=\"agentsplayground\")  → dropped on floor
get_chat_model_factory(client_settings=None)
  └─ PlatformSettings()  → agenthub_config=\"agentsruntime\"  ✗

The fix

In chat_model_factory.get_chat_model, when agenthub_config is provided on the new path:

• Build client_settings via get_default_client_settings() if the caller didn't supply one.
• Set client_settings.agenthub_config = agenthub_config before delegating.
• Caller-supplied client_settings instances are mutated, not replaced, so other fields survive.
• agenthub_config=None is a pass-through — preserves existing env-var / direct-construction paths governed by the mixin.

hasattr guard mirrors the pattern in _AgentHubConfigDefaultMixin._clear_agenthub_config_default, since the UiPathBaseSettings ABC doesn't expose agenthub_config (only the concrete PlatformBaseSettings does).

What changed

File	Change
src/uipath_langchain/chat/chat_model_factory.py	+12/-2 — fix + docstring update
tests/chat/test_chat_model_factory_agenthub.py	+123 — 4 new tests
pyproject.toml	0.10.18 → 0.10.19
uv.lock	regenerated

Tests added (4)

1. Tracer — get_chat_model(agenthub_config=\"agentsplayground\", use_new_llm_clients=True) results in client_settings.agenthub_config == \"agentsplayground\" reaching the upstream factory. Was failing before the fix; proves the bug.
2. Pass-through — agenthub_config=None does not synthesize a client_settings; preserves env-var / mixin paths.
3. Caller settings preserved — explicit client_settings is mutated, not replaced; non-agenthub_config fields survive.
4. Legacy path regression guard — use_new_llm_clients=False still threads agenthub_config to the legacy factory.

Existing tests/chat/test_agenthub_config_default.py (39 tests for direct-construction mixin behavior) still passes — the fix is additive, the mixin is still load-bearing for direct constructors.

Full chat suite: 239 passed.

Out of scope / follow-ups

• ClaudeSDKRuntime and GatewayProxy defaults in uipath-agents-python/src/uipath_agents/claude_sdk/{runtime.py:90,gateway_proxy.py:168} — same agenthub_config: str = \"agentsruntime\" anti-pattern. Currently masked by AgentsClaudeSDKRuntime overriding both. Worth fixing but lives in a different repo/package.
• Upstream PlatformSettings.agenthub_config = \"agentsruntime\" default in uipath_langchain_client — would be a cleaner fix to set default=None upstream, but cross-package coordination. This PR neutralizes the symptom for the agents path without needing it.

Test plan

• New tests pass: uv run pytest tests/chat/test_chat_model_factory_agenthub.py
• Existing mixin tests still pass: uv run pytest tests/chat/test_agenthub_config_default.py
• Full chat suite passes: uv run pytest tests/chat/ (239 passed)
• mypy clean on changed source: uv run mypy src/uipath_langchain/chat/chat_model_factory.py
• ruff clean on changed files
• Manual verification: run uv run uipath debug agent.json '{}' against a real tenant; confirm LLM gateway requests carry X-UiPath-AgentHub-Config: agentsplayground

🤖 Generated with Claude Code

[cotovanu-cristian]

closing as it's included in #835