chore: import upstream snapshot with attribution

tests/runtime/test_request_contracts_subagent.py

@@ -0,0 +1,27 @@
+"""Regression: the per-turn subagent consult budget must pass chat-config validation.
+
+``subagent_consult_budget`` rides in the request ``config`` (composer stepper)
+but isn't part of any capability's public schema. It must be treated as a
+runtime-only key, not rejected by ``extra="forbid"`` — otherwise a second turn
+with a connected agent errors with "Extra inputs are not permitted".
+"""
+
+from __future__ import annotations
+
+import pytest
+
+from deeptutor.runtime.request_contracts import (
+    validate_capability_config,
+    validate_chat_request_config,
+)
+
+
+def test_chat_config_allows_subagent_consult_budget() -> None:
+    # Must not raise (it's stripped as a runtime-only key before validation).
+    validate_chat_request_config({"subagent_consult_budget": 5})
+    validate_capability_config("chat", {"subagent_consult_budget": 5})
+
+
+def test_chat_config_still_rejects_unknown_keys() -> None:
+    with pytest.raises(ValueError, match="Extra inputs are not permitted"):
+        validate_chat_request_config({"totally_unknown_key": 1})