diff --git a/document-parser/infra/settings.py b/document-parser/infra/settings.py
index ebb596c..60cc3c5 100644
--- a/document-parser/infra/settings.py
+++ b/document-parser/infra/settings.py
@@ -25,6 +25,27 @@ class Settings:
         default_factory=lambda: ["http://localhost:3000", "http://localhost:5173"]
     )
 
+    def __post_init__(self) -> None:
+        errors: list[str] = []
+        if self.document_timeout <= 0:
+            errors.append(f"document_timeout must be > 0 (got {self.document_timeout})")
+        if self.conversion_timeout <= 0:
+            errors.append(f"conversion_timeout must be > 0 (got {self.conversion_timeout})")
+        if self.max_concurrent_analyses < 1:
+            errors.append(
+                f"max_concurrent_analyses must be >= 1 (got {self.max_concurrent_analyses})"
+            )
+        if self.max_page_count < 0:
+            errors.append(f"max_page_count must be >= 0 (got {self.max_page_count})")
+        if self.max_file_size < 0:
+            errors.append(f"max_file_size must be >= 0 (got {self.max_file_size})")
+        if self.default_table_mode not in ("accurate", "fast"):
+            errors.append(
+                f"default_table_mode must be 'accurate' or 'fast' (got '{self.default_table_mode}')"
+            )
+        if errors:
+            raise ValueError("Invalid settings:\n  " + "\n  ".join(errors))
+
     @classmethod
     def from_env(cls) -> Settings:
         """Build a Settings instance from environment variables."""
diff --git a/document-parser/tests/test_settings.py b/document-parser/tests/test_settings.py
index 1b8837c..aa27233 100644
--- a/document-parser/tests/test_settings.py
+++ b/document-parser/tests/test_settings.py
@@ -29,6 +29,57 @@ class TestSettingsDefaults:
             s.upload_dir = "/other"  # type: ignore[misc]
 
 
+class TestSettingsValidation:
+    def test_negative_document_timeout_rejected(self):
+        import pytest
+
+        with pytest.raises(ValueError, match="document_timeout must be > 0"):
+            Settings(document_timeout=-1.0)
+
+    def test_zero_document_timeout_rejected(self):
+        import pytest
+
+        with pytest.raises(ValueError, match="document_timeout must be > 0"):
+            Settings(document_timeout=0)
+
+    def test_negative_conversion_timeout_rejected(self):
+        import pytest
+
+        with pytest.raises(ValueError, match="conversion_timeout must be > 0"):
+            Settings(conversion_timeout=-1)
+
+    def test_zero_max_concurrent_rejected(self):
+        import pytest
+
+        with pytest.raises(ValueError, match="max_concurrent_analyses must be >= 1"):
+            Settings(max_concurrent_analyses=0)
+
+    def test_negative_max_page_count_rejected(self):
+        import pytest
+
+        with pytest.raises(ValueError, match="max_page_count must be >= 0"):
+            Settings(max_page_count=-1)
+
+    def test_negative_max_file_size_rejected(self):
+        import pytest
+
+        with pytest.raises(ValueError, match="max_file_size must be >= 0"):
+            Settings(max_file_size=-1)
+
+    def test_invalid_table_mode_rejected(self):
+        import pytest
+
+        with pytest.raises(ValueError, match="default_table_mode must be"):
+            Settings(default_table_mode="turbo")
+
+    def test_multiple_errors_reported(self):
+        import pytest
+
+        with pytest.raises(ValueError, match="document_timeout") as exc_info:
+            Settings(document_timeout=-1, conversion_timeout=-1)
+        assert "conversion_timeout" in str(exc_info.value)
+
+
 class TestSettingsFromEnv:
     def test_reads_env_vars(self, monkeypatch):
         monkeypatch.setenv("APP_VERSION", "1.2.3")