fix(agent-init): honour model.context_length override below 64K floor (#8430)

The 64K MINIMUM_CONTEXT_LENGTH gate in agent_init was firing even when
the user had explicitly set model.context_length in config.yaml,
contradicting its own error message ('…or set model.context_length in
config.yaml to override'). Users with locally-hosted 32K models (e.g.
Qwen3-235B-A22B via custom endpoints) hit a dead end: the override path
the error pointed at was never actually consulted.

Fix is the one-liner proposed in the issue: skip the gate when
`agent._config_context_length is not None`. Trust the user when they've
explicitly chosen.

Adds tests/run_agent/test_minimum_context_override.py covering both
the legacy reject-when-no-override path and the new honour-override
path, plus boundary cases.

Closes #8430.

agent/agent_init.py

@@ -1337,10 +1337,15 @@ def init_agent(
     agent.compression_enabled = compression_enabled
 
     # Reject models whose context window is below the minimum required
-    # for reliable tool-calling workflows (64K tokens).
+    # for reliable tool-calling workflows (64K tokens) — unless the user
+    # has *explicitly* set ``model.context_length`` in config.yaml, in
+    # which case we trust them. The error message tells them how to do
+    # this; refusing to honour the override leaves them with no path
+    # forward (#8430).
     from agent.model_metadata import MINIMUM_CONTEXT_LENGTH
     _ctx = getattr(agent.context_compressor, "context_length", 0)
-    if _ctx and _ctx < MINIMUM_CONTEXT_LENGTH:
+    _user_override = getattr(agent, "_config_context_length", None) is not None
+    if _ctx and _ctx < MINIMUM_CONTEXT_LENGTH and not _user_override:
         raise ValueError(
             f"Model {agent.model} has a context window of {_ctx:,} tokens, "
             f"which is below the minimum {MINIMUM_CONTEXT_LENGTH:,} required "

tests/run_agent/test_minimum_context_override.py

@@ -0,0 +1,88 @@
+"""Regression tests for GitHub #8430.
+
+The 64K minimum-context-length gate in ``agent.agent_init`` used to fire
+even when the user had explicitly set ``model.context_length`` in
+``config.yaml``, contradicting its own error message ("…or set
+model.context_length in config.yaml to override"). These tests pin the
+fix: the gate now skips when ``agent._config_context_length`` is not
+None.
+"""
+
+from types import SimpleNamespace
+from unittest.mock import patch
+
+import pytest
+
+from agent import agent_init
+from agent.model_metadata import MINIMUM_CONTEXT_LENGTH
+
+
+def _make_minimal_agent(context_length: int, config_context_length=None):
+    """Build the bare-minimum agent shape the minimum-context gate inspects."""
+    return SimpleNamespace(
+        model="qwen3-235b-a22b",
+        context_compressor=SimpleNamespace(context_length=context_length),
+        _config_context_length=config_context_length,
+    )
+
+
+def _run_gate(agent) -> None:
+    """Inline the agent_init gate exactly as it exists on main."""
+    _ctx = getattr(agent.context_compressor, "context_length", 0)
+    _user_override = getattr(agent, "_config_context_length", None) is not None
+    if _ctx and _ctx < MINIMUM_CONTEXT_LENGTH and not _user_override:
+        raise ValueError(
+            f"Model {agent.model} has a context window of {_ctx:,} tokens, "
+            f"which is below the minimum {MINIMUM_CONTEXT_LENGTH:,} required "
+            f"by Hermes Agent.  Choose a model with at least "
+            f"{MINIMUM_CONTEXT_LENGTH // 1000}K context, or set "
+            f"model.context_length in config.yaml to override."
+        )
+
+
+def test_below_minimum_no_override_raises():
+    """No user override → 32K model is rejected."""
+    agent = _make_minimal_agent(context_length=32_768, config_context_length=None)
+    with pytest.raises(ValueError) as exc_info:
+        _run_gate(agent)
+    err = str(exc_info.value)
+    assert "32,768" in err
+    assert "below the minimum" in err
+
+
+def test_below_minimum_with_explicit_override_is_honoured():
+    """#8430: user explicitly set model.context_length=32768 → respect it."""
+    agent = _make_minimal_agent(context_length=32_768, config_context_length=32_768)
+    # Must not raise.
+    _run_gate(agent)
+
+
+def test_below_minimum_with_smaller_override_is_honoured():
+    """User can dial it below the model's actual ctx if they want (their funeral)."""
+    agent = _make_minimal_agent(context_length=16_000, config_context_length=16_000)
+    _run_gate(agent)
+
+
+def test_at_or_above_minimum_no_override_passes():
+    """Models meeting the minimum pass without an override."""
+    agent = _make_minimal_agent(context_length=128_000, config_context_length=None)
+    _run_gate(agent)
+
+
+def test_zero_context_length_skips_gate():
+    """A zero/unset context_length doesn't trip the gate (existing behaviour)."""
+    agent = _make_minimal_agent(context_length=0, config_context_length=None)
+    _run_gate(agent)
+
+
+def test_gate_lives_at_expected_location():
+    """Smoke test: the production gate string is still where we expect it.
+
+    Catches accidental refactors that remove the override path entirely.
+    """
+    import inspect
+    src = inspect.getsource(agent_init)
+    assert "_config_context_length" in src
+    assert "MINIMUM_CONTEXT_LENGTH" in src
+    # The override guard must appear in the same conditional as MINIMUM_CONTEXT_LENGTH.
+    assert "not _user_override" in src or "_config_context_length is None" in src