diff --git a/README.md b/README.md
index a8805b6..6f79162 100644
--- a/README.md
+++ b/README.md
@@ -14,28 +14,28 @@
 
 <!-- mdformat off(no multiline table cells) -->
 
-Format                       | Extensions                          | Validation | Generation
-:--------------------------- | :---------------------------------- | :--------- | :---------
-JPEG                         | `.jpg`, `.jpeg`                     | Yes        | [Yes](formats/jpeg/writer.h)
-PNG                          | `.png`                              | Yes        | [Yes](formats/png/writer.h)
-MP4                          | `.mp4`                              | Yes        | [Yes](formats/bmff/writer.h)
-fMP4 (fragmented MP4)        |                                     | No         | No
-RIFF (e.g., WebP, WAV, AVI)  | `.webp`, `.wav`, `.avi`             | Yes        | [Yes](formats/riff/writer.h)
-TIFF (e.g., TIFF, DNG)       | `.tif`, `.tiff`, `.dng`             | Yes        | [Yes](formats/tiff/writer.h)
-AVIF                         | `.avif`                             | Yes        | [Yes](formats/bmff/writer.h)
-M4A                          | `.m4a`                              | Yes        | [Yes](formats/bmff/writer.h)
-HEIF, HEIC                   | `.heif`, `.heic`                    | Yes        | [Yes](formats/bmff/writer.h)
-MOV                          | `.mov`                              | Yes        | [Yes](formats/bmff/writer.h)
-GIF                          | `.gif`                              | Yes        | [Yes](formats/gif/writer.h)
-MP3                          | `.mp3`                              | Yes        | [Yes](formats/id3/writer.h)
-FLAC                         | `.flac`                             | Yes        | [Yes](formats/id3/writer.h)
-PDF                          | `.pdf`                              | Yes        | [Yes](formats/pdf/writer.h)
-SVG                          |                                     | No         | No
-OGG Vorbis                   |                                     | No         | No
-Text                         |                                     | No         | No
-Live stream video            |                                     | No         | No
-ZIP (e.g., DOCX, PPTX, XLSX) | `.zip`, `.docx`, `.pptx`, `.xlsx`   | Yes        | [Yes](formats/zip/writer.h)
-Fonts                        |                                     | No         | No
+Format                      | Extensions                | Validation | Generation
+:-------------------------- | :------------------------ | :--------- | :---------
+JPEG                        | `.jpg`, `.jpeg`           | Yes        | [Yes](formats/jpeg/writer.h)
+PNG                         | `.png`                    | Yes        | [Yes](formats/png/writer.h)
+MP4                         | `.mp4`                    | Yes        | [Yes](formats/bmff/writer.h)
+fMP4 (fragmented MP4)       |                           | No         | No
+RIFF (e.g., WebP, WAV, AVI) | `.webp`, `.wav`, `.avi`   | Yes        | [Yes](formats/riff/writer.h)
+TIFF (e.g., TIFF, DNG)      | `.tif`, `.tiff`, `.dng`   | Yes        | [Yes](formats/tiff/writer.h)
+AVIF                        | `.avif`                   | Yes        | [Yes](formats/bmff/writer.h)
+M4A                         | `.m4a`                    | Yes        | [Yes](formats/bmff/writer.h)
+HEIF, HEIC                  | `.heif`, `.heic`          | Yes        | [Yes](formats/bmff/writer.h)
+MOV                         | `.mov`                    | Yes        | [Yes](formats/bmff/writer.h)
+GIF                         | `.gif`                    | Yes        | [Yes](formats/gif/writer.h)
+MP3                         | `.mp3`                    | Yes        | [Yes](formats/id3/writer.h)
+FLAC                        | `.flac`                   | Yes        | [Yes](formats/id3/writer.h)
+PDF                         | `.pdf`                    | Yes        | [Yes](formats/pdf/writer.h)
+SVG                         |                           | No         | No
+OGG Vorbis                  |                           | No         | No
+Text                        |                           | No         | No
+Live stream video           |                           | No         | No
+ZIP-based containers        | `.docx`, `.pptx`, `.xlsx` | Yes        | [Yes](formats/zip/writer.h)
+Fonts                       |                           | No         | No
 
 <!-- mdformat on -->
 
diff --git a/generator/generator_factory_test.cc b/generator/generator_factory_test.cc
index 7c8f85e..4de7043 100644
--- a/generator/generator_factory_test.cc
+++ b/generator/generator_factory_test.cc
@@ -91,7 +91,8 @@
                        HasSubstr("template_claim_signer is required")));
 }
 
-TEST(GeneratorFactoryTest, ValidateOptionsRejectsNullUuidGenerator) {
+TEST(GeneratorFactoryTest, ValidateOptionsRejectsNullUuidGenerator)
+__attribute__((no_sanitize("nullability"))) {
   FakeClaimSigner signing_signer;
   FakeClaimSigner template_signer;
   GeneratorOptions options;
@@ -104,7 +105,8 @@
                        HasSubstr("uuid_generator is required")));
 }
 
-TEST(GeneratorFactoryTest, ValidateOptionsRejectsNullHashFactory) {
+TEST(GeneratorFactoryTest, ValidateOptionsRejectsNullHashFactory)
+__attribute__((no_sanitize("nullability"))) {
   FakeClaimSigner signing_signer;
   FakeClaimSigner template_signer;
   GeneratorOptions options;
diff --git a/kokoro/gcp_ubuntu/build_and_test.sh b/kokoro/gcp_ubuntu/build_and_test.sh
index 1ccefa6..7646c03 100755
--- a/kokoro/gcp_ubuntu/build_and_test.sh
+++ b/kokoro/gcp_ubuntu/build_and_test.sh
@@ -23,9 +23,18 @@
 export RUN_INSTRUMENTATION_TESTS="${RUN_INSTRUMENTATION_TESTS:-1}"
 cd "${KOKORO_ARTIFACTS_DIR}/git/staging"
 
+# Use the Bazel caches pre-warmed in the container image, if any.
+bazel_flags=()
+if [[ -n "${BAZEL_REPOSITORY_CACHE:-}" ]]; then
+  bazel_flags+=("--repository_cache=${BAZEL_REPOSITORY_CACHE}")
+fi
+if [[ -n "${BAZEL_DISK_CACHE:-}" ]]; then
+  bazel_flags+=("--disk_cache=${BAZEL_DISK_CACHE}")
+fi
+
 # Run Bazel build and test all targets
-bazel build ...
-bazel test ...
+bazel build "${bazel_flags[@]}" ...
+bazel test "${bazel_flags[@]}" ...
 
 function create_and_start_emulator() {
   local emulator_name=c2pa_emulator
diff --git a/validator/ingredient_result_converter_test.cc b/validator/ingredient_result_converter_test.cc
index e779f92..2ca6772 100644
--- a/validator/ingredient_result_converter_test.cc
+++ b/validator/ingredient_result_converter_test.cc
@@ -75,8 +75,8 @@
     }
   )pb");
 
-  auto result =
-      IngredientResultConverter().Convert(ValidationResult(std::move(input)));
+  auto result = IngredientResultConverter().Convert(
+      ValidationResult(std::move(input), ""));
   ABSL_ASSERT_OK(result);
 
   EXPECT_THAT((*result)->proto(), EqualsProto(R"pb(
@@ -99,8 +99,8 @@
     }
   )pb");
 
-  auto result =
-      IngredientResultConverter().Convert(ValidationResult(std::move(input)));
+  auto result = IngredientResultConverter().Convert(
+      ValidationResult(std::move(input), ""));
   ABSL_ASSERT_OK(result);
 
   EXPECT_THAT((*result)->proto(), EqualsProto(R"pb(
@@ -118,8 +118,8 @@
     active_manifest { label: "legacy_label" }
   )pb");
 
-  auto result =
-      IngredientResultConverter().Convert(ValidationResult(std::move(input)));
+  auto result = IngredientResultConverter().Convert(
+      ValidationResult(std::move(input), ""));
   ABSL_ASSERT_OK(result);
 
   EXPECT_THAT((*result)->proto(), EqualsProto(R"pb(
@@ -154,8 +154,8 @@
     }
   )pb");
 
-  auto result =
-      IngredientResultConverter().Convert(ValidationResult(std::move(input)));
+  auto result = IngredientResultConverter().Convert(
+      ValidationResult(std::move(input), ""));
   ABSL_ASSERT_OK(result);
 
   EXPECT_THAT(
@@ -194,8 +194,8 @@
     }
   )pb");
 
-  auto result =
-      IngredientResultConverter().Convert(ValidationResult(std::move(input)));
+  auto result = IngredientResultConverter().Convert(
+      ValidationResult(std::move(input), ""));
   ABSL_ASSERT_OK(result);
 
   EXPECT_THAT(
@@ -226,8 +226,8 @@
     ingredient_manifests { label: "legacy_ingredient" }
   )pb");
 
-  auto result =
-      IngredientResultConverter().Convert(ValidationResult(std::move(input)));
+  auto result = IngredientResultConverter().Convert(
+      ValidationResult(std::move(input), ""));
   ABSL_ASSERT_OK(result);
 
   EXPECT_THAT(
@@ -252,8 +252,8 @@
     ingredient_manifests { label: "legacy_ingredient" }
   )pb");
 
-  auto result =
-      IngredientResultConverter().Convert(ValidationResult(std::move(input)));
+  auto result = IngredientResultConverter().Convert(
+      ValidationResult(std::move(input), ""));
   ABSL_ASSERT_OK(result);
 
   EXPECT_THAT((*result)->proto(), EqualsProto(R"pb(
@@ -282,8 +282,8 @@
     }
   )pb");
 
-  auto result =
-      IngredientResultConverter().Convert(ValidationResult(std::move(input)));
+  auto result = IngredientResultConverter().Convert(
+      ValidationResult(std::move(input), ""));
   ABSL_ASSERT_OK(result);
 
   EXPECT_THAT((*result)->proto(), EqualsProto(R"pb(
@@ -336,8 +336,8 @@
     }
   )pb");
 
-  auto result =
-      IngredientResultConverter().Convert(ValidationResult(std::move(input)));
+  auto result = IngredientResultConverter().Convert(
+      ValidationResult(std::move(input), ""));
   ABSL_ASSERT_OK(result);
 
   EXPECT_THAT(
@@ -396,8 +396,8 @@
     }
   )pb");
 
-  auto result =
-      IngredientResultConverter().Convert(ValidationResult(std::move(input)));
+  auto result = IngredientResultConverter().Convert(
+      ValidationResult(std::move(input), ""));
   ABSL_ASSERT_OK(result);
 
   EXPECT_THAT(
@@ -442,8 +442,8 @@
     }
   )pb");
 
-  auto result =
-      IngredientResultConverter().Convert(ValidationResult(std::move(input)));
+  auto result = IngredientResultConverter().Convert(
+      ValidationResult(std::move(input), ""));
   ABSL_ASSERT_OK(result);
 
   EXPECT_THAT(
@@ -467,8 +467,8 @@
     ingredient_manifests { label: "urn:c2pa:unreferenced" }
   )pb");
 
-  auto result =
-      IngredientResultConverter().Convert(ValidationResult(std::move(input)));
+  auto result = IngredientResultConverter().Convert(
+      ValidationResult(std::move(input), ""));
   ABSL_ASSERT_OK(result);
 
   EXPECT_THAT((*result)->proto(), EqualsProto(R"pb(
@@ -496,8 +496,8 @@
     }
   )pb");
 
-  auto result =
-      IngredientResultConverter().Convert(ValidationResult(std::move(input)));
+  auto result = IngredientResultConverter().Convert(
+      ValidationResult(std::move(input), ""));
   ABSL_ASSERT_OK(result);
 
   EXPECT_THAT(
@@ -535,8 +535,8 @@
     ingredient_manifests { label: "legacy_label" }
   )pb");
 
-  auto result =
-      IngredientResultConverter().Convert(ValidationResult(std::move(input)));
+  auto result = IngredientResultConverter().Convert(
+      ValidationResult(std::move(input), ""));
   ABSL_ASSERT_OK(result);
 
   EXPECT_THAT(
@@ -568,7 +568,7 @@
       ->set_code("code");
 
   auto result = IngredientResultConverter().Convert(
-      ValidationResult(std::move(validation_result)));
+      ValidationResult(std::move(validation_result), ""));
   ABSL_ASSERT_OK(result);
   EXPECT_EQ((*result)->proto().ingredient_validation_results().spec_version(),
             "2.2.0");
@@ -583,7 +583,7 @@
       ->set_code("code");
 
   auto result = IngredientResultConverter().Convert(
-      ValidationResult(std::move(validation_result)));
+      ValidationResult(std::move(validation_result), ""));
   ABSL_ASSERT_OK(result);
   EXPECT_EQ((*result)->proto().ingredient_validation_results().trust_list_uri(),
             "urn:test");
@@ -637,7 +637,7 @@
   // The converter owns the consumer, so it has to outlive the expectations.
   IngredientResultConverter converter(std::move(consumer));
 
-  auto result = converter.Convert(ValidationResult(std::move(input)));
+  auto result = converter.Convert(ValidationResult(std::move(input), ""));
   ABSL_ASSERT_OK(result);
 
   EXPECT_THAT(
@@ -664,8 +664,8 @@
     }
   )pb");
 
-  auto result =
-      IngredientResultConverter().Convert(ValidationResult(std::move(input)));
+  auto result = IngredientResultConverter().Convert(
+      ValidationResult(std::move(input), ""));
   ABSL_ASSERT_OK(result);
 
   EXPECT_FALSE((*result)->proto().has_digital_source_type());
@@ -684,7 +684,7 @@
   )pb");
 
   EXPECT_THAT(IngredientResultConverter(std::make_unique<FailingConsumer>())
-                  .Convert(ValidationResult(std::move(input))),
+                  .Convert(ValidationResult(std::move(input), "")),
               StatusIs(absl::StatusCode::kInternal));
 }
 
diff --git a/validator/result.h b/validator/result.h
index 14dbb07..d3ba729 100644
--- a/validator/result.h
+++ b/validator/result.h
@@ -32,13 +32,13 @@
 // For now, this is just a wrapper for `ValidationResultProto`.
 class ValidationResult {
  public:
-  explicit ValidationResult(std::unique_ptr<ValidationResultProto> proto,
-                            std::string manifest_store_bytes = "")
+  ValidationResult(std::unique_ptr<ValidationResultProto> proto,
+                   std::string manifest_store_bytes)
       : proto_(std::move(proto)),
         manifest_store_bytes_(std::move(manifest_store_bytes)) {}
 
-  explicit ValidationResult(ValidationResultProto&& proto,
-                            std::string manifest_store_bytes = "")
+  ValidationResult(ValidationResultProto&& proto,
+                   std::string manifest_store_bytes)
       : proto_(std::make_unique<ValidationResultProto>(std::move(proto))),
         manifest_store_bytes_(std::move(manifest_store_bytes)) {}
 
diff --git a/validator/result_test.cc b/validator/result_test.cc
index 2dd0c7c..aedcf4a 100644
--- a/validator/result_test.cc
+++ b/validator/result_test.cc
@@ -36,7 +36,7 @@
 TEST(ValidationResultTest, ToProto) {
   auto proto = std::make_unique<ValidationResultProto>();
   proto->mutable_active_manifest()->set_label("test");
-  ValidationResult result(std::move(proto));
+  ValidationResult result(std::move(proto), "");
   ValidationResultProto expected;
   expected.mutable_active_manifest()->set_label("test");
   EXPECT_THAT(result.proto(), EqualsProto(expected));