diff --git a/packages/core-shared/src/conformance/define-feature.test.ts b/packages/core-shared/src/conformance/define-feature.test.ts
new file mode 100644
index 0000000..3510c41
--- /dev/null
+++ b/packages/core-shared/src/conformance/define-feature.test.ts
@@ -0,0 +1,45 @@
+import { describe, it, expectTypeOf } from "vitest";
+import { defineFeature, type FeatureManifest } from "@/conformance/define-feature";
+
+describe("defineFeature", () => {
+  it("preserves literal types of a manifest declared with `as const`", () => {
+    const manifest = defineFeature({
+      name: "auth",
+      requiredCores: ["audit"],
+      useCases: {
+        signIn: {
+          mutates: false,
+          audits: [],
+          publishes: [],
+          consumes: [],
+        },
+        signUp: {
+          mutates: true,
+          audits: ["user.created"],
+          publishes: ["auth.signed-up"],
+          consumes: [],
+        },
+      },
+      realtimeChannels: [],
+      jobs: [],
+    } as const);
+
+    // Literal preservation: name is the literal "auth", not string
+    expectTypeOf(manifest.name).toEqualTypeOf<"auth">();
+    // Use-case keys preserved
+    expectTypeOf(manifest.useCases.signUp.audits).toEqualTypeOf<readonly ["user.created"]>();
+    expectTypeOf(manifest.useCases.signUp.mutates).toEqualTypeOf<true>();
+    expectTypeOf(manifest.useCases.signIn.mutates).toEqualTypeOf<false>();
+  });
+
+  it("FeatureManifest type accepts the shape", () => {
+    const manifest = defineFeature({
+      name: "blog",
+      requiredCores: [],
+      useCases: {},
+      realtimeChannels: [],
+      jobs: [],
+    } as const);
+    expectTypeOf(manifest).toMatchTypeOf<FeatureManifest>();
+  });
+});
diff --git a/packages/core-shared/src/conformance/define-feature.ts b/packages/core-shared/src/conformance/define-feature.ts
new file mode 100644
index 0000000..91ee653
--- /dev/null
+++ b/packages/core-shared/src/conformance/define-feature.ts
@@ -0,0 +1,38 @@
+/**
+ * Per-use-case manifest entry. Declares what the use case does at the contract
+ * level: whether it mutates state, what audit events it emits, what cross-feature
+ * events it publishes or consumes. The conformance system reads these to
+ * derive binding-slot types and to verify code against manifest declarations.
+ */
+export type UseCaseManifest = {
+  readonly mutates: boolean;
+  readonly audits: readonly string[];
+  readonly publishes: readonly string[];
+  readonly consumes: readonly string[];
+};
+
+/**
+ * The feature-level manifest. One per feature package, conventionally exported
+ * as `<featureName>Manifest` from `src/feature.manifest.ts`.
+ */
+export type FeatureManifest = {
+  readonly name: string;
+  readonly requiredCores: readonly string[];
+  readonly useCases: { readonly [k: string]: UseCaseManifest };
+  readonly realtimeChannels: readonly string[];
+  readonly jobs: readonly string[];
+};
+
+/**
+ * Identity helper that exists purely to widen the input type to satisfy
+ * `FeatureManifest` while preserving the literal types of the `as const`
+ * input. Downstream types (`ProductionUseCase<I, O, M>`) consume the
+ * preserved literals to derive binding-slot brand requirements.
+ *
+ * Usage:
+ *
+ *   export const authManifest = defineFeature({ name: "auth", ... } as const);
+ */
+export function defineFeature<const M extends FeatureManifest>(manifest: M): M {
+  return manifest;
+}