diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0b6f7e784..0d24d4d37 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@
 
 ### Changed
 
+- Raised the configured desktop and shared-types Vitest coverage thresholds to 100% for lines, functions, branches, and statements, with a regression guard against reintroducing a lower owned JavaScript coverage floor.
 - Pinned npm `10.9.9` as the approved lockfile generator, activated it through Node-bundled Corepack before dependency consumption, and fail closed unless its bundled `tar` is at least `7.5.19`; primary CI still consumes the committed lock only through frozen `npm ci` validation, rejects mutable npm resolution in the lock gate, requires integrity evidence for public-registry lock entries, and preserves generator-sensitive root `@esbuild/*` peer metadata.
 
 ### Fixed
@@ -74,4 +75,4 @@
 
 - `ChordsFeature` (코드 분석) 화면에서 각 파트(Role)의 `transpositionPlan`(이조/조옮김 계획)을 표시하는 기능을 추가했습니다.
 - `RangesFeature` (음역대 분석) 화면에서 겹침 경고(Overlap warning) 외에 해당 파트의 채보(Transcription) 가능 노드 수를 요약하여 보여주는 기능을 추가했습니다.
-- 신규 UI 요소에 대한 단위 테스트를 추가했습니다 (`apps/desktop/src/features/chords/index.test.tsx`, `apps/desktop/src/features/ranges/index.test.tsx`).
\ No newline at end of file
+- 신규 UI 요소에 대한 단위 테스트를 추가했습니다 (`apps/desktop/src/features/chords/index.test.tsx`, `apps/desktop/src/features/ranges/index.test.tsx`).
diff --git a/apps/desktop/vite.config.ts b/apps/desktop/vite.config.ts
index f1db6f2b8..122903aa2 100644
--- a/apps/desktop/vite.config.ts
+++ b/apps/desktop/vite.config.ts
@@ -28,10 +28,10 @@ export default defineConfig({
         "src/features/score/scoreStorage.ts"
       ],
       thresholds: {
-        lines: 90,
-        functions: 90,
-        branches: 90,
-        statements: 90
+        lines: 100,
+        functions: 100,
+        branches: 100,
+        statements: 100
       }
     }
   }
diff --git a/docs/engineering/acceptance-criteria.md b/docs/engineering/acceptance-criteria.md
index 6bce19771..ce2f9c0a9 100644
--- a/docs/engineering/acceptance-criteria.md
+++ b/docs/engineering/acceptance-criteria.md
@@ -25,6 +25,11 @@ Run the narrowest passing set that covers touched areas, and do not claim succes
 - `npm run test`
 - `npm audit --workspaces --audit-level=high`
 
+Every repository-configured Vitest coverage gate requires 100% lines, functions,
+branches, and statements for its configured production source set. This applies
+to both the desktop application and the shared-types package; adding another
+owned Vitest source set must not introduce a lower threshold.
+
 When CI/workflow files, supply-chain controls, or release/security docs are changed, also run:
 
 - `python3 scripts/checks/verify_supply_chain.py`
diff --git a/packages/shared-types/test/coverage-policy.test.ts b/packages/shared-types/test/coverage-policy.test.ts
new file mode 100644
index 000000000..48fe23b5b
--- /dev/null
+++ b/packages/shared-types/test/coverage-policy.test.ts
@@ -0,0 +1,12 @@
+import { coverageThresholds } from "../vitest.config";
+
+describe("shared-types coverage policy", () => {
+  it("requires 100% for every configured coverage metric", () => {
+    expect(coverageThresholds).toEqual({
+      lines: 100,
+      functions: 100,
+      branches: 100,
+      statements: 100
+    });
+  });
+});
diff --git a/packages/shared-types/vitest.config.ts b/packages/shared-types/vitest.config.ts
index 14e004545..269601644 100644
--- a/packages/shared-types/vitest.config.ts
+++ b/packages/shared-types/vitest.config.ts
@@ -1,17 +1,19 @@
 import { defineConfig } from "vitest/config";
 
+export const coverageThresholds = {
+  lines: 100,
+  functions: 100,
+  branches: 100,
+  statements: 100
+} as const;
+
 export default defineConfig({
   test: {
     globals: true,
     coverage: {
       provider: "v8",
       include: ["src/index.ts"],
-      thresholds: {
-        lines: 90,
-        functions: 90,
-        branches: 90,
-        statements: 90
-      }
+      thresholds: coverageThresholds
     }
   }
 });