fix: require default discovery for metadata reuse

src/plugins/activation-context.ts

@@ -182,15 +182,17 @@ function applyPluginAutoEnableForActivation(params: {
     workspaceDir: params.workspaceDir,
     allowWorkspaceScopedSnapshot: true,
   });
-  const currentManifestRegistry =
-    currentSnapshot?.manifestRegistry ??
-    (normalizePluginsConfig(params.config.plugins).loadPaths.length === 0
+  const defaultDiscoverySnapshot =
+    normalizePluginsConfig(params.config.plugins).loadPaths.length === 0
       ? getCurrentPluginMetadataSnapshot({
           env: params.env,
           workspaceDir: params.workspaceDir,
           allowWorkspaceScopedSnapshot: true,
-        })?.manifestRegistry
-      : undefined);
+          requireDefaultDiscoveryContext: true,
+        })
+      : undefined;
+  const currentManifestRegistry =
+    currentSnapshot?.manifestRegistry ?? defaultDiscoverySnapshot?.manifestRegistry;
   return applyPluginAutoEnable({
     config: params.config,
     env: params.env,

src/plugins/current-plugin-metadata-snapshot.test.ts

@@ -113,6 +113,32 @@ describe("current plugin metadata snapshot", () => {
     ).toBeUndefined();
   });
 
+  it("rejects configless default-discovery reuse for snapshots created with load paths", () => {
+    const config = { plugins: { allow: ["demo"], load: { paths: ["/plugins/one"] } } };
+    const snapshot = createSnapshot({ config });
+    setCurrentPluginMetadataSnapshot(snapshot, { config });
+
+    expect(
+      getCurrentPluginMetadataSnapshot({
+        allowWorkspaceScopedSnapshot: true,
+        requireDefaultDiscoveryContext: true,
+      }),
+    ).toBeUndefined();
+  });
+
+  it("accepts configless default-discovery reuse for snapshots created without load paths", () => {
+    const config = { plugins: { allow: ["demo"] } };
+    const snapshot = createSnapshot({ config });
+    setCurrentPluginMetadataSnapshot(snapshot, { config });
+
+    expect(
+      getCurrentPluginMetadataSnapshot({
+        allowWorkspaceScopedSnapshot: true,
+        requireDefaultDiscoveryContext: true,
+      }),
+    ).toBe(snapshot);
+  });
+
   it("rejects a current snapshot when env-resolved plugin load paths change", () => {
     const config = { plugins: { load: { paths: ["~/plugins"] } } };
     const snapshot = createSnapshot({ config });

src/plugins/current-plugin-metadata-snapshot.ts

@@ -70,6 +70,7 @@ export function getCurrentPluginMetadataSnapshot(
     env?: NodeJS.ProcessEnv;
     workspaceDir?: string;
     allowWorkspaceScopedSnapshot?: boolean;
+    requireDefaultDiscoveryContext?: boolean;
   } = {},
 ): PluginMetadataSnapshot | undefined {
   const {
@@ -110,6 +111,25 @@ export function getCurrentPluginMetadataSnapshot(
       return undefined;
     }
   }
+  if (params.requireDefaultDiscoveryContext === true) {
+    const defaultDiscoveryConfigFingerprint = resolvePluginMetadataControlPlaneFingerprint(
+      {},
+      {
+        env: params.env,
+        index: snapshot.index,
+        policyHash: snapshot.policyHash,
+        workspaceDir: requestedWorkspaceDir,
+      },
+    );
+    const compatibleFingerprints = new Set(compatibleConfigFingerprints ?? []);
+    const fingerprintMatches =
+      configFingerprint === defaultDiscoveryConfigFingerprint ||
+      snapshot.configFingerprint === defaultDiscoveryConfigFingerprint ||
+      compatibleFingerprints.has(defaultDiscoveryConfigFingerprint);
+    if (!fingerprintMatches) {
+      return undefined;
+    }
+  }
   if (snapshot.workspaceDir !== undefined && requestedWorkspaceDir === undefined) {
     return undefined;
   }