diff --git a/AGENTS.md b/AGENTS.md
index d81b285..4084abb 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -52,3 +52,22 @@ The documentation is the source of truth. Do not invent requirements when an aut
 Prefer small, focused changes. Avoid unrelated refactoring.
 
 When a decision changes the architecture or requirements, update the relevant documentation before or with the implementation.
+
+## Vertical slice completion
+
+Each vertical slice must be complete before it is committed and pushed:
+
+- A new or changed Vue visual component must have a colocated Storybook story or an updated existing story covering its meaningful states.
+- Stories must use representative fixture data and must not introduce production domain behavior solely for visual coverage.
+- Visual slices must pass the web tests, production build, Storybook build, and Storybook interaction/accessibility runner before commit:
+
+	```sh
+	npm run test --workspace=@pokemon-inventory/web
+	npm run build --workspace=@pokemon-inventory/web
+	npm run build-storybook --workspace=@pokemon-inventory/web
+	npm run test-storybook
+	```
+
+- Storybook stories must cover relevant loading, empty, error, selected, disabled, responsive, light/dark theme, and keyboard states when those states exist in the component.
+- Backend-only slices do not require Storybook changes unless they alter a user-facing visual contract.
+- The final commit gate includes the appropriate API/domain/integration tests plus all applicable web and Storybook checks.
diff --git a/docs/TESTING.md b/docs/TESTING.md
index 4060d0f..22e44d4 100644
--- a/docs/TESTING.md
+++ b/docs/TESTING.md
@@ -27,7 +27,18 @@ Test:
 
 ## Component
 
-Test important Vue components and composables.
+Test important Vue components and composables. Every new or changed visual component must include a colocated Storybook story or an update to an existing story before its vertical slice is committed.
+
+For visual slices, run the complete Storybook gate from the repository root:
+
+```sh
+npm run test --workspace=@pokemon-inventory/web
+npm run build --workspace=@pokemon-inventory/web
+npm run build-storybook --workspace=@pokemon-inventory/web
+npm run test-storybook
+```
+
+Stories should use mock fixture data and cover the component states that users can encounter, including keyboard focus, selected, disabled, loading, empty, error, responsive, and light/dark theme behavior where applicable. Do not add production domain behavior just to make a story render.
 
 ## E2E
 
@@ -58,4 +69,6 @@ GitHub Actions should run:
 - accessibility checks
 - build validation
 
+The Storybook build and interaction/accessibility runner are part of the visual-slice commit gate. Backend-only slices may omit them when no visual component or UI contract changes.
+
 Do not weaken or skip tests to obtain a passing build.