feat: cap max_call_duration at 20 min via typed workflow_configurations request

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

api/tests/test_campaign_call_dispatcher.py

@@ -845,9 +845,7 @@ class TestAcquireConcurrentSlotScoping:
         )
 
     @pytest.mark.asyncio
-    async def test_no_campaign_max_concurrency_skips_scope(
-        self, mock_call_concurrency
-    ):
+    async def test_no_campaign_max_concurrency_skips_scope(self, mock_call_concurrency):
         dispatcher = CampaignCallDispatcher()
         campaign = self._campaign({})
 

api/tests/test_workflow_configurations_schema.py

@@ -0,0 +1,61 @@
+import pytest
+from pydantic import ValidationError
+
+from api.schemas.workflow_configurations import (
+    DEFAULT_MAX_CALL_DURATION_SECONDS,
+    MAX_CALL_DURATION_SECONDS,
+    WorkflowConfigurationDefaults,
+)
+
+
+def test_max_call_duration_default_within_bounds():
+    config = WorkflowConfigurationDefaults()
+    assert config.max_call_duration == DEFAULT_MAX_CALL_DURATION_SECONDS
+
+
+def test_max_call_duration_accepts_cap():
+    config = WorkflowConfigurationDefaults(max_call_duration=MAX_CALL_DURATION_SECONDS)
+    assert config.max_call_duration == MAX_CALL_DURATION_SECONDS
+
+
+def test_max_call_duration_rejects_over_cap():
+    with pytest.raises(ValidationError):
+        WorkflowConfigurationDefaults(max_call_duration=MAX_CALL_DURATION_SECONDS + 1)
+
+
+def test_max_call_duration_rejects_non_positive():
+    with pytest.raises(ValidationError):
+        WorkflowConfigurationDefaults(max_call_duration=0)
+
+
+def test_null_values_treated_as_unset():
+    """Stored configs / older clients send explicit JSON nulls for keys the
+    user never configured; they must validate as defaults, not fail."""
+    config = WorkflowConfigurationDefaults.model_validate(
+        {
+            "max_call_duration": None,
+            "turn_start_strategy": None,
+            "turn_start_min_words": None,
+        }
+    )
+    assert config.max_call_duration == DEFAULT_MAX_CALL_DURATION_SECONDS
+    # Nulls count as unset, so a sparse round-trip drops them entirely.
+    assert config.model_dump(exclude_unset=True) == {}
+
+
+def test_exclude_unset_round_trip_stays_sparse():
+    config = WorkflowConfigurationDefaults.model_validate(
+        {"max_call_duration": 600, "custom_extra_key": {"a": 1}}
+    )
+    assert config.model_dump(exclude_unset=True) == {
+        "max_call_duration": 600,
+        "custom_extra_key": {"a": 1},
+    }
+
+
+def test_cap_stays_within_concurrency_stale_timeout():
+    """A call outliving the rate limiter's stale window has its concurrency
+    slot purged mid-call, so the cap must never exceed it."""
+    from api.services.campaign.rate_limiter import rate_limiter
+
+    assert MAX_CALL_DURATION_SECONDS <= rate_limiter.stale_call_timeout