diff --git a/packages/plugin/src/boundaries.test.ts b/packages/plugin/src/boundaries.test.ts
index b0834956d6..6d15281c6b 100644
--- a/packages/plugin/src/boundaries.test.ts
+++ b/packages/plugin/src/boundaries.test.ts
@@ -283,6 +283,10 @@ describe("lifecycle hook SDK types", () => {
         server.addHook("workspace.create.before", async ({ request }) => ({ ...request, title: "Changed" }));
         server.addHook("workspace.create.before", async () => {});
         server.addHook("agent.open.before", async () => {});
+        server.addHook("agent.open.before", async ({ request }) => {
+          const { metadata, ...withoutMetadata } = request;
+          return withoutMetadata;
+        });
         server.addHook("agent.turn.after", async ({ agent, outcome, timeline }, { paseo, signal }) => {
           const kind: "completed" | "failed" | "canceled" = outcome.kind;
           // @ts-expect-error Notification payloads have no creation request.
diff --git a/packages/plugin/src/server/lifecycle.ts b/packages/plugin/src/server/lifecycle.ts
index 256ff45c0f..89f1b62412 100644
--- a/packages/plugin/src/server/lifecycle.ts
+++ b/packages/plugin/src/server/lifecycle.ts
@@ -132,10 +132,17 @@ export interface PluginHookRequests {
   "workspace.create.before": Omit<WorkspaceCreateRequest, "type" | "requestId">;
 }
 
+/** What a hook may return: a field it leaves out stays as it was. */
+type PluginHookRequestResults = Omit<PluginHookRequests, "agent.open.before"> & {
+  "agent.open.before": Omit<PluginSessionOpenRequest, "metadata"> & {
+    metadata?: Readonly<Record<string, JsonValue>>;
+  };
+};
+
 export type PluginHooks = {
   [Name in keyof PluginHookRequests]: {
     request: PluginHookRequests[Name];
-    result: PluginHookRequests[Name];
+    result: PluginHookRequestResults[Name];
   };
 } & { [Name in keyof PluginHookEvents]: { payload: PluginHookEvents[Name] } } & {
   "worktree.create.after": { payload: { worktree: PluginHookWorktree } };
diff --git a/packages/server/src/server/plugins/lifecycle/handlers.test.ts b/packages/server/src/server/plugins/lifecycle/handlers.test.ts
index 5b9996d4af..e9b3ab4d74 100644
--- a/packages/server/src/server/plugins/lifecycle/handlers.test.ts
+++ b/packages/server/src/server/plugins/lifecycle/handlers.test.ts
@@ -101,6 +101,30 @@ test("session-open hooks reject changes to session identity instead of silently
   ).rejects.toThrow("agent.open.before hooks can only change env");
 });
 
+test("a create hook that omits metadata passes on what an earlier hook added", async () => {
+  const hooks = new PluginHookHandlers(() => {});
+  hooks.addHook("agent.create.before", async ({ request }) => ({
+    ...request,
+    metadata: { ...request.metadata, "new.plugin": { ticket: 42 } },
+  }));
+  hooks.addHook("agent.create.before", async ({ request }) => ({
+    config: request.config,
+    env: request.env,
+  }));
+  const seen: unknown[] = [];
+  hooks.addHook("agent.create.before", async ({ request }) => {
+    seen.push(request.metadata);
+  });
+  const result = await hooks.invoke(
+    "operation",
+    "agent.create.before",
+    { config: { provider: "codex", cwd: "/project" }, env: {}, metadata: { original: true } },
+    paseo,
+  );
+  expect(result).toMatchObject({ metadata: { original: true, "new.plugin": { ticket: 42 } } });
+  expect(seen).toEqual([{ original: true, "new.plugin": { ticket: 42 } }]);
+});
+
 test("a session-open hook that returns its own object without metadata leaves metadata unchanged", async () => {
   const hooks = new PluginHookHandlers(() => {});
   hooks.addHook("agent.open.before", async ({ request }) => ({
diff --git a/packages/server/src/server/plugins/lifecycle/index.ts b/packages/server/src/server/plugins/lifecycle/index.ts
index e78226f61b..eb6684a2fa 100644
--- a/packages/server/src/server/plugins/lifecycle/index.ts
+++ b/packages/server/src/server/plugins/lifecycle/index.ts
@@ -249,6 +249,8 @@ export async function validateBeforeResult<Name extends keyof PluginWireBeforeRe
     if (previous.config.cwd !== next.config.cwd) {
       throw new Error("agent.create.before hooks cannot change the workspace directory");
     }
+    // Omitted means unchanged: the next hook sees what this one was handed.
+    return { ...result, metadata: next.metadata ?? previous.metadata };
   }
   if (name === "worktree.create.before") {
     const previous = beforeSchemas["worktree.create.before"].parse(input);