fix(memory): validate merged configuration 🤖🤖🤖

packages/nooa-memory/src/nooa_memory/config.py

@@ -198,5 +198,5 @@ def _validate_owner(cls, value: str | None) -> str | None:
     observability: ObservabilityConfig = ObservabilityConfig()
 
     def merge_with(self, **overrides: object) -> MemoryConfig:
-        """Return a copy with top-level fields overridden."""
-        return self.model_copy(update=overrides)
+        """Return a validated copy with top-level fields overridden."""
+        return type(self).model_validate({**self.model_dump(), **overrides})

packages/nooa-memory/tests/memory/test_memory_config.py

@@ -0,0 +1,36 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+"""Configuration merging obeys the same validation rules as construction."""
+
+import pytest
+from nooa_memory.config import EmbeddingConfig, MemoryConfig
+from pydantic import ValidationError
+
+
+def test_merge_coerces_boolean_without_mutating_original():
+    """Overrides use Pydantic coercion without changing the original configuration."""
+    original = MemoryConfig(enabled=True, path=":memory:")
+    merged = original.merge_with(enabled="false")
+    assert merged.enabled is False
+    assert merged.path == original.path
+    assert original.enabled is True
+
+
+def test_merge_validates_nested_config_as_top_level_replacement():
+    """Nested dictionaries become validated models using top-level replacement semantics."""
+    original = MemoryConfig(embedding=EmbeddingConfig(dim=64, batch_size=3))
+    merged = original.merge_with(embedding={"backend": "hashing", "dim": 16})
+    assert isinstance(merged.embedding, EmbeddingConfig)
+    assert merged.embedding.dim == 16
+    assert merged.embedding.batch_size == EmbeddingConfig().batch_size
+    assert original.embedding.dim == 64
+    assert original.embedding.batch_size == 3
+
+
+@pytest.mark.parametrize(
+    "overrides", [{"owner": "invalid_owner"}, {"embedding": {"backend": "unknown"}}]
+)
+def test_merge_rejects_invalid_configuration(overrides):
+    """Invalid owner and embedding settings fail during the merge, not at later use."""
+    with pytest.raises(ValidationError):
+        MemoryConfig().merge_with(**overrides)