diff --git a/EvoScientist/image_gen/config.py b/EvoScientist/image_gen/config.py
index 98ea282..805356b 100644
--- a/EvoScientist/image_gen/config.py
+++ b/EvoScientist/image_gen/config.py
@@ -17,7 +17,7 @@ from pathlib import Path
 from typing import Any, Literal
 
 import yaml
-from pydantic import BaseModel, Field, field_validator
+from pydantic import BaseModel, Field, ValidationError, field_validator
 
 IMAGE_GENERATION_SECTION = "image_generation"
 DEFAULT_IMAGE_GENERATION_TIMEOUT_SECONDS = 120.0
@@ -117,4 +117,18 @@ def load_image_generation_settings(
     section = data.get(IMAGE_GENERATION_SECTION)
     if not isinstance(section, dict):
         return ImageGenerationSettings()
-    return ImageGenerationSettings.model_validate(section)
+    try:
+        return ImageGenerationSettings.model_validate(section)
+    except ValidationError as exc:
+        # Never echo input values: a mis-indented yaml can put a literal API
+        # key under the wrong field and pydantic's default message embeds it
+        # verbatim. Report only field locations and error types.
+        from EvoScientist.image_gen.adapters.base import ImageGenError
+
+        details = "; ".join(
+            f"{'.'.join(str(part) for part in error['loc'])}: {error['type']}"
+            for error in exc.errors(include_url=False, include_input=False)
+        )
+        raise ImageGenError(
+            f"invalid {IMAGE_GENERATION_SECTION} section: {details}"
+        ) from None
diff --git a/EvoScientist/model_registry/store.py b/EvoScientist/model_registry/store.py
index 43c52e1..b6550f2 100644
--- a/EvoScientist/model_registry/store.py
+++ b/EvoScientist/model_registry/store.py
@@ -244,16 +244,16 @@ class ModelRuntimeStore:
     def save_registry(
         self,
         *,
-        expected_revision: int,
+        expected_revision: int | None,
         registry: RegistryV4,
         credential_writes: list[CredentialWrite] | None = None,
         validate: SaveValidator | None = None,
     ) -> RegistryV4:
         """Save the registry inside one ``BEGIN IMMEDIATE`` transaction.
 
-        ``expected_revision`` is accepted for API compatibility but ignored:
-        saves are last-write-wins and the stored revision is always
-        ``current + 1``. Credential versions are written first (immutable,
+        ``expected_revision`` (``int`` or ``None``) is accepted for API
+        compatibility but ignored: saves are last-write-wins and the stored
+        revision is always ``current + 1``. Credential versions are written first (immutable,
         with incrementing revisions), then the optional ``validate`` hook
         runs the section 9.2 save-time checks against the post-write state,
         then the registry row is replaced. A bootstrap document atomically
diff --git a/tests/test_image_gen_config.py b/tests/test_image_gen_config.py
index a3e95d2..8344a70 100644
--- a/tests/test_image_gen_config.py
+++ b/tests/test_image_gen_config.py
@@ -2,6 +2,9 @@
 
 import os
 
+import pytest
+
+from EvoScientist.image_gen.adapters.base import ImageGenError
 from EvoScientist.image_gen.config import (
     ImageGenerationSettings,
     ImageModelEntry,
@@ -93,6 +96,26 @@ image_generation:
     assert settings.models[0].resolved_api_key() == "sk-literal"
 
 
+def test_validation_error_never_echoes_config_values(tmp_path):
+    """A malformed section must raise a sanitized error: field locations and
+    error types only, never the offending input values (key-leak red line)."""
+    path = _write_config(
+        tmp_path,
+        """
+image_generation:
+  models:
+    - id: gpt-image-2
+      provider: sk-secret-value-123
+      api_key: sk-secret-value-123
+""",
+    )
+    with pytest.raises(ImageGenError) as excinfo:
+        load_image_generation_settings(config_path=path)
+    message = str(excinfo.value)
+    assert "sk-secret-value-123" not in message
+    assert "provider" in message
+
+
 def test_is_image_generation_model():
     assert is_image_generation_model("gpt-image-2") is True
     assert is_image_generation_model("dall-e-3") is True