diff --git a/frontend/eslint.config.js b/frontend/eslint.config.js
index 5ef17b59..037353b8 100644
--- a/frontend/eslint.config.js
+++ b/frontend/eslint.config.js
@@ -106,6 +106,31 @@ export default defineConfig(
 			]
 		}
 	},
+	{
+		// Forbid test fixtures (*.test-fixture.svelte) from being imported by
+		// production code. Tree-shaking keeps them out of the production bundle
+		// today (no route reaches them), but a lint rule makes the boundary
+		// explicit so an accidental autocomplete import in a route or component
+		// fails fast. Test files (*.spec.ts / *.test.ts) and the fixtures
+		// themselves are exempt — see the next block. Nora #2 on PR #629
+		// round 3.
+		files: ['**/*.svelte', '**/*.svelte.ts', '**/*.svelte.js', '**/*.ts'],
+		ignores: ['**/*.spec.ts', '**/*.test.ts', '**/*.test-fixture.svelte'],
+		rules: {
+			'no-restricted-imports': [
+				'error',
+				{
+					patterns: [
+						{
+							group: ['**/*.test-fixture.svelte'],
+							message:
+								'Test fixtures (*.test-fixture.svelte) are test-only — do not import from production code. Tracked by #637.'
+						}
+					]
+				}
+			]
+		}
+	},
 	{
 		plugins: { boundaries },
 		settings: {