diff --git a/src/lib/application.ts b/src/lib/application.ts
index 75b5cd214..8bd1302be 100644
--- a/src/lib/application.ts
+++ b/src/lib/application.ts
@@ -41,6 +41,7 @@ import { fileURLToPath } from "url";
 import { createRequire } from "module";
 import { Outputs } from "./output/output.js";
 import { validateMergeModuleWith } from "./validation/unusedMergeModuleWith.js";
+import { validateFilePaths } from "./validation/filePaths.js";
 import { diagnostic, diagnostics } from "./utils/loggers.js";
 import { ValidatingFileRegistry } from "./utils/ValidatingFileRegistry.js";
 import { Internationalization } from "./internationalization/internationalization.js";
@@ -703,6 +704,10 @@ export class Application extends AbstractComponent<
             validateMergeModuleWith(project, this.logger);
         }
 
+        if (checks.invalidPath) {
+            validateFilePaths(project, this.logger);
+        }
+
         this.trigger(Application.EVENT_VALIDATE_PROJECT, project);
 
         this.logger.verbose(`Validation took ${Date.now() - start}ms`);
diff --git a/src/lib/models/FileRegistry.ts b/src/lib/models/FileRegistry.ts
index 6cda93a04..96f646efb 100644
--- a/src/lib/models/FileRegistry.ts
+++ b/src/lib/models/FileRegistry.ts
@@ -121,6 +121,20 @@ export class FileRegistry {
         return this.names.get(id);
     }
 
+    /**
+     * Iterate over all registered media file paths, yielding entries
+     * that do NOT have an associated reflection.
+     */
+    getMediaPaths(): Iterable<NormalizedPath> {
+        const result: NormalizedPath[] = [];
+        for (const [id, path] of this.mediaToPath.entries()) {
+            if (!this.mediaToReflection.has(id)) {
+                result.push(path);
+            }
+        }
+        return result;
+    }
+
     getNameToAbsoluteMap(): ReadonlyMap<string, string> {
         const result = new Map<string, string>();
         for (const [id, name] of this.names.entries()) {
diff --git a/src/lib/output/plugins/AssetsPlugin.ts b/src/lib/output/plugins/AssetsPlugin.ts
index 71b53d35b..0422907a3 100644
--- a/src/lib/output/plugins/AssetsPlugin.ts
+++ b/src/lib/output/plugins/AssetsPlugin.ts
@@ -125,10 +125,6 @@ export class AssetsPlugin extends RendererComponent {
             for (const [fileName, absolute] of toCopy.entries()) {
                 if (isFile(absolute)) {
                     copySync(absolute, join(media, fileName));
-                } else {
-                    this.application.logger.warn(
-                        i18n.relative_path_0_is_not_a_file_and_will_not_be_copied_to_output(absolute),
-                    );
                 }
             }
         }
diff --git a/src/lib/validation/filePaths.ts b/src/lib/validation/filePaths.ts
new file mode 100644
index 000000000..f102513fa
--- /dev/null
+++ b/src/lib/validation/filePaths.ts
@@ -0,0 +1,16 @@
+import type { ProjectReflection } from "../models/index.js";
+import { i18n, type Logger } from "#utils";
+import { isFile } from "../utils/fs.js";
+
+export function validateFilePaths(
+    project: ProjectReflection,
+    logger: Logger,
+): void {
+    for (const absolute of project.files.getMediaPaths()) {
+        if (!isFile(absolute)) {
+            logger.validationWarning(
+                i18n.relative_path_0_is_not_a_file_and_will_not_be_copied_to_output(absolute),
+            );
+        }
+    }
+}
diff --git a/src/test/validation.test.ts b/src/test/validation.test.ts
index 905672c25..5f1d29f5a 100644
--- a/src/test/validation.test.ts
+++ b/src/test/validation.test.ts
@@ -2,10 +2,12 @@ import { ok } from "assert";
 import { join } from "path";
 import { validateDocumentation } from "../lib/validation/documentation.js";
 import { validateExports } from "../lib/validation/exports.js";
+import { validateFilePaths } from "../lib/validation/filePaths.js";
 import { getConverter2App, getConverter2Program, getConverter2Project } from "./programs.js";
 import { TestLogger } from "./TestLogger.js";
 import { fileURLToPath } from "url";
 import { validateMergeModuleWith } from "../lib/validation/unusedMergeModuleWith.js";
+import { normalizePath } from "#node-utils";
 
 function convertValidationFile(...files: [string, ...string[]]) {
     return getConverter2Project(files, "validation");
@@ -233,3 +235,47 @@ describe("validateMergeModuleWith", () => {
         );
     });
 });
+
+describe("validateFilePaths", () => {
+    it("Should warn if a registered path is a directory", () => {
+        const project = convertValidationFile("variable.ts");
+        // Register a directory path (the converter2 directory itself) without a reflection association
+        const dirPath = normalizePath(
+            join(fileURLToPath(import.meta.url), "../converter2"),
+        );
+        project.files.registerAbsolute(dirPath);
+
+        const logger = new TestLogger();
+        validateFilePaths(project, logger);
+
+        logger.expectMessage(
+            `warn: The relative path ${dirPath} is not a file and will not be copied to the output directory`,
+        );
+    });
+
+    it("Should not warn for registered files", () => {
+        const project = convertValidationFile("variable.ts");
+        const filePath = normalizePath(
+            join(fileURLToPath(import.meta.url), "../converter2/validation/variable.ts"),
+        );
+        project.files.registerAbsolute(filePath);
+
+        const logger = new TestLogger();
+        validateFilePaths(project, logger);
+
+        logger.expectNoOtherMessages();
+    });
+
+    it("Should not warn for directories with a reflection association", () => {
+        const project = convertValidationFile("variable.ts");
+        const dirPath = normalizePath(
+            join(fileURLToPath(import.meta.url), "../converter2"),
+        );
+        project.files.registerReflectionPath(dirPath, project);
+
+        const logger = new TestLogger();
+        validateFilePaths(project, logger);
+
+        logger.expectNoOtherMessages();
+    });
+});