diff --git a/agent-chat/server.ts b/agent-chat/server.ts
index 82ba05992a31..28a55e7de8df 100644
--- a/agent-chat/server.ts
+++ b/agent-chat/server.ts
@@ -614,8 +614,14 @@ function emitDoneAfterFiles(sess: Session, evt: InternalDoneEvent) {
 
 function sendPrompt(sess: Session, prompt: string, requestId = crypto.randomUUID()) {
   if (sess.transcript) {
-    // Typed into the terminal's agent; the transcript records the prompt.
-    void sess.adapter.send(sess, prompt);
+    // Typed into the terminal's agent; the transcript records the prompt, so
+    // there is no turn generation to unwind and no "done" to emit. The send
+    // can still reject (a replaced agent process, a failed spawn), and that
+    // has to reach the user rather than becoming an unhandled rejection.
+    Promise.resolve(sess.adapter.send(sess, prompt)).catch((err) => {
+      console.error("[agent-chat] send failed", err);
+      sess.emit({ kind: "error", message: safeErrorMessage("send", err) });
+    });
     return;
   }
   emitRouting(sess, { phase: "started", requestId, attempt: 1, provider: sess.provider });
diff --git a/agent-chat/test/server-transcript-send.test.ts b/agent-chat/test/server-transcript-send.test.ts
new file mode 100644
index 000000000000..397ab87d3beb
--- /dev/null
+++ b/agent-chat/test/server-transcript-send.test.ts
@@ -0,0 +1,78 @@
+// A transcript chat view dispatches prompts through the same adapter as any
+// other session, and that adapter can reject: the Pi adapter throws when its
+// process is replaced during startup, and any adapter throws when a spawn
+// fails. The transcript branch of sendPrompt has no turn generation to unwind,
+// so this only checks that the failure reaches the user instead of surfacing
+// as an unhandled rejection.
+import { emitDoneAfterFilesForTest, emitSessionEventForTest, sendPromptForTest } from "../server";
+import type { Adapter, AgentEvent, SessionStatus } from "../types";
+
+function assert(cond: unknown, msg: string): asserts cond {
+  if (!cond) throw new Error(msg);
+}
+
+const unhandled: unknown[] = [];
+const onUnhandled = (reason: unknown) => {
+  unhandled.push(reason);
+};
+process.on("unhandledRejection", onUnhandled);
+
+const adapter = {
+  capabilities: { options: [] },
+  async send() {
+    throw new Error("pi process changed during startup");
+  },
+  stop() {},
+  dispose() {},
+  setOption: async () => {},
+} as unknown as Adapter;
+
+const events: AgentEvent[] = [];
+const sess = {
+  id: "transcript-send-rejection",
+  provider: "pi",
+  cwd: "/tmp",
+  title: "transcript send rejection",
+  autoApprove: true,
+  startOptions: {},
+  status: "idle" as SessionStatus,
+  events,
+  internal: {},
+  adapter,
+  sockets: new Set(),
+  createdAt: Date.now(),
+  transcript: { agent: {} as never, path: "/tmp/transcript.jsonl" },
+  emit(evt: AgentEvent) {
+    if (evt.kind === "done") emitDoneAfterFilesForTest(this as never, evt);
+    else emitSessionEventForTest(this as never, evt);
+  },
+  setStatus(status: SessionStatus) {
+    this.status = status;
+  },
+};
+
+sendPromptForTest(sess as never, "prompt that cannot be delivered");
+// Two turns of the microtask queue: one for the rejection, one for the handler.
+await Promise.resolve();
+await Promise.resolve();
+// An unhandledRejection listener fires on a macrotask, not a microtask.
+await new Promise((resolve) => setTimeout(resolve, 0));
+
+const error = events.find((evt) => evt.kind === "error") as Extract<AgentEvent, { kind: "error" }> | undefined;
+assert(error, `a rejected transcript send must emit an error event: ${JSON.stringify(events)}`);
+// safeReason maps anything outside its allow-list to "unexpected error", so
+// the contract is the sanitized send message the other two call sites emit,
+// not the adapter's own text.
+assert(
+  error.message === "Failed to send message: unexpected error",
+  `the error event should carry the sanitized send message: ${JSON.stringify(error)}`,
+);
+assert(
+  unhandled.length === 0,
+  `a rejected transcript send must not leave an unhandled rejection: ${String(unhandled[0])}`,
+);
+
+process.off("unhandledRejection", onUnhandled);
+console.log("transcript send rejection assertions passed");
+
+export {};