refactor: mark implicit startup sidecars deprecated

src/plugins/compat/registry.ts

@@ -206,6 +206,21 @@ export const PLUGIN_COMPAT_RECORDS = [
     diagnostics: ["activation plan compat reason"],
     tests: ["src/plugins/activation-planner.test.ts"],
   },
+  {
+    code: "legacy-implicit-startup-sidecar",
+    status: "deprecated",
+    owner: "plugin-execution",
+    introduced: "2026-04-28",
+    deprecated: "2026-04-28",
+    warningStarts: "2026-04-28",
+    removeAfter: "2026-07-28",
+    replacement:
+      "`activation.onStartup: true` for startup work or `activation.onStartup: false` for inert plugins",
+    docsPath: "/plugins/manifest",
+    surfaces: ["Gateway startup plugin planning", "openclaw.plugin.json activation"],
+    diagnostics: ["plugin compatibility notice"],
+    tests: ["src/plugins/channel-plugin-ids.test.ts", "src/plugins/installed-plugin-index.test.ts"],
+  },
   {
     code: "activation-provider-hint",
     status: "active",

src/plugins/installed-plugin-index-record-builder.ts

@@ -49,10 +49,22 @@ function hasRuntimeContractSurface(record: PluginManifestRecord): boolean {
   );
 }
 
+/**
+ * @deprecated Compatibility classification for plugins that predate explicit
+ * `activation.onStartup`. Every plugin manifest should move to an explicit
+ * startup decision so Gateway boot can avoid importing inert plugins.
+ */
+function isLegacyImplicitStartupSidecar(record: PluginManifestRecord): boolean {
+  return (
+    record.channels.length === 0 &&
+    !hasRuntimeContractSurface(record) &&
+    record.activation?.onStartup === undefined
+  );
+}
+
 function buildStartupInfo(record: PluginManifestRecord): InstalledPluginStartupInfo {
-  const channels = record.channels ?? [];
   return {
-    sidecar: channels.length === 0 && !hasRuntimeContractSurface(record),
+    sidecar: record.activation?.onStartup === true || isLegacyImplicitStartupSidecar(record),
     memory: hasKind(record.kind, "memory"),
     deferConfiguredChannelFullLoadUntilAfterListen:
       record.startupDeferConfiguredChannelFullLoadUntilAfterListen === true,
@@ -65,6 +77,9 @@ function buildStartupInfo(record: PluginManifestRecord): InstalledPluginStartupI
 
 function collectCompatCodes(record: PluginManifestRecord): readonly PluginCompatCode[] {
   const codes: PluginCompatCode[] = [];
+  if (isLegacyImplicitStartupSidecar(record)) {
+    codes.push("legacy-implicit-startup-sidecar");
+  }
   if (record.providerAuthEnvVars && Object.keys(record.providerAuthEnvVars).length > 0) {
     codes.push("provider-auth-env-vars");
   }

src/plugins/installed-plugin-index.test.ts

@@ -263,6 +263,90 @@ describe("installed plugin index", () => {
     });
   });
 
+  it("tags deprecated implicit startup sidecars for legacy plugins", () => {
+    const rootDir = makeTempDir();
+    writeRuntimeEntry(rootDir);
+    writePluginManifest(rootDir, {
+      id: "legacy-sidecar",
+      configSchema: { type: "object" },
+    });
+
+    const index = loadInstalledPluginIndex({
+      candidates: [
+        createPluginCandidate({
+          rootDir,
+        }),
+      ],
+      env: hermeticEnv(),
+    });
+
+    expect(index.plugins[0]).toMatchObject({
+      pluginId: "legacy-sidecar",
+      startup: {
+        sidecar: true,
+      },
+      compat: ["legacy-implicit-startup-sidecar"],
+    });
+  });
+
+  it("does not classify or tag explicit startup opt-outs as deprecated implicit sidecars", () => {
+    const rootDir = makeTempDir();
+    writeRuntimeEntry(rootDir);
+    writePluginManifest(rootDir, {
+      id: "modern-inert",
+      activation: {
+        onStartup: false,
+      },
+      configSchema: { type: "object" },
+    });
+
+    const index = loadInstalledPluginIndex({
+      candidates: [
+        createPluginCandidate({
+          rootDir,
+        }),
+      ],
+      env: hermeticEnv(),
+    });
+
+    expect(index.plugins[0]).toMatchObject({
+      pluginId: "modern-inert",
+      startup: {
+        sidecar: false,
+      },
+      compat: [],
+    });
+  });
+
+  it("classifies explicit startup activation as a gateway startup sidecar", () => {
+    const rootDir = makeTempDir();
+    writeRuntimeEntry(rootDir);
+    writePluginManifest(rootDir, {
+      id: "explicit-startup-provider",
+      providers: ["demo"],
+      activation: {
+        onStartup: true,
+      },
+      configSchema: { type: "object" },
+    });
+
+    const index = loadInstalledPluginIndex({
+      candidates: [
+        createPluginCandidate({
+          rootDir,
+        }),
+      ],
+      env: hermeticEnv(),
+    });
+
+    expect(index.plugins[0]).toMatchObject({
+      pluginId: "explicit-startup-provider",
+      startup: {
+        sidecar: true,
+      },
+    });
+  });
+
   it("keeps bundle format metadata needed for manifest reconstruction", () => {
     const rootDir = makeTempDir();
     fs.mkdirSync(path.join(rootDir, ".claude-plugin"), { recursive: true });