diff --git a/packages/utils/src/postmortem.ts b/packages/utils/src/postmortem.ts
index 33dabe3d3..c2784c1e4 100644
--- a/packages/utils/src/postmortem.ts
+++ b/packages/utils/src/postmortem.ts
@@ -27,6 +27,7 @@ const callbackList: ((reason: Reason) => Promise<void> | void)[] = [];
 // Tracks cleanup run state (to prevent recursion/reentry issues)
 let cleanupStage: "idle" | "running" | "complete" = "idle";
 const CLEANUP_DEADLINE_MS = 10_000;
+let cleanupPromise: Promise<void> | undefined;
 let stdioDisconnectRegistrations = 0;
 
 /**
@@ -41,7 +42,7 @@ function runCleanup(reason: Reason): Promise<void> {
 			cleanupStage = "running";
 			break;
 		case "running":
-			return Promise.resolve();
+			return cleanupPromise ?? Promise.resolve();
 		case "complete":
 			return Promise.resolve();
 	}
@@ -68,9 +69,10 @@ function runCleanup(reason: Reason): Promise<void> {
 		deadline.resolve();
 	}, CLEANUP_DEADLINE_MS);
 	deadlineTimer.unref();
-	return Promise.race([cleanupSettled, deadline.promise]).finally(() => {
+	cleanupPromise = Promise.race([cleanupSettled, deadline.promise]).finally(() => {
 		clearTimeout(deadlineTimer);
 	});
+	return cleanupPromise;
 }
 
 // Register signal and error event handlers to trigger cleanup before exit.
@@ -92,6 +94,11 @@ export function classifyBrokenPipe(err: Error): BrokenPipeSource | undefined {
 	return undefined;
 }
 
+/** Whether an EPIPE came from an IPC `send()` to an optional worker. */
+export function isIpcSendEpipe(err: Error): boolean {
+	return classifyBrokenPipe(err) === "ipc-send";
+}
+
 /**
  * Treat unhandled stdout EPIPE rejections as a graceful peer disconnect.
  *
diff --git a/packages/utils/test/postmortem-epipe.test.ts b/packages/utils/test/postmortem-epipe.test.ts
index 25fdcd8a1..c6df49a9f 100644
--- a/packages/utils/test/postmortem-epipe.test.ts
+++ b/packages/utils/test/postmortem-epipe.test.ts
@@ -2,6 +2,7 @@ import { describe, expect, it } from "bun:test";
 import { postmortem } from "@oh-my-pi/pi-utils";
 
 const childFlag = "--stdio-epipe-child";
+const raceChildFlag = "--stdio-epipe-race-child";
 const childFlagIndex = process.argv.indexOf(childFlag);
 if (childFlagIndex >= 0) {
 	const marker = process.argv[childFlagIndex + 1];
@@ -17,6 +18,33 @@ if (childFlagIndex >= 0) {
 	const keepAlive = Promise.withResolvers<void>();
 	await keepAlive.promise;
 }
+else if (process.argv.includes(raceChildFlag)) {
+	const marker = process.argv[process.argv.indexOf(raceChildFlag) + 1];
+	if (!marker) throw new Error("Missing cleanup marker path");
+	let cleanupComplete = false;
+	let exitAttempted = false;
+	const exit = process.exit;
+	process.exit = ((code?: number) => {
+		if (!exitAttempted) {
+			exitAttempted = true;
+			void Bun.write(marker, cleanupComplete ? "after cleanup" : "before cleanup").then(() => exit(code));
+		}
+		return undefined as never;
+	}) as typeof process.exit;
+	postmortem.registerStdioDisconnectHandling();
+	postmortem.register("stdio-epipe-race-test", async () => {
+		process.stderr.write("cleanup started\n");
+		void Promise.reject(Object.assign(new Error("broken pipe"), { code: "EPIPE", syscall: "write" }));
+		await new Response(Bun.stdin.stream()).text();
+		cleanupComplete = true;
+	});
+	let rejectionCount = 0;
+	process.on("unhandledRejection", () => {
+		if (++rejectionCount === 2) process.stderr.write("second rejection observed\n");
+	});
+	void Promise.reject(Object.assign(new Error("broken pipe"), { code: "EPIPE", syscall: "write" }));
+	await new Promise<void>(() => {});
+}
 
 describe("postmortem broken-pipe handling", () => {
 	function makeErr(props: { code?: string; syscall?: string; message?: string }): Error {
@@ -28,6 +56,8 @@ describe("postmortem broken-pipe handling", () => {
 	it("classifies worker IPC and stdio EPIPE errors", () => {
 		expect(postmortem.classifyBrokenPipe(makeErr({ code: "EPIPE", syscall: "send" }))).toBe("ipc-send");
 		expect(postmortem.classifyBrokenPipe(makeErr({ code: "EPIPE", syscall: "write" }))).toBe("stdio-write");
+		expect(postmortem.isIpcSendEpipe(makeErr({ code: "EPIPE", syscall: "send" }))).toBe(true);
+		expect(postmortem.isIpcSendEpipe(makeErr({ code: "EPIPE", syscall: "write" }))).toBe(false);
 	});
 
 	it("does not classify unrelated errors as recoverable broken pipes", () => {
@@ -66,4 +96,40 @@ describe("postmortem broken-pipe handling", () => {
 				.catch(() => {});
 		}
 	});
+
+	it("keeps waiting for active cleanup when another stdio EPIPE arrives", async () => {
+		const marker = `/tmp/omp-postmortem-stdio-race-${process.pid}-${Date.now()}`;
+		const child = Bun.spawn([process.execPath, import.meta.path, raceChildFlag, marker], {
+			stdin: "pipe",
+			stdout: "pipe",
+			stderr: "pipe",
+		});
+		try {
+			const decoder = new TextDecoder();
+			const stderrReader = child.stderr.getReader();
+			let stderr = "";
+			while (!stderr.includes("second rejection observed\n")) {
+				const chunk = await stderrReader.read();
+				if (chunk.done) throw new Error("Child exited before observing the second rejection");
+				stderr += decoder.decode(chunk.value);
+			}
+			stderrReader.releaseLock();
+			expect(stderr).toContain("cleanup started\n");
+			child.stdin.end();
+			const [exitCode, stdout] = await Promise.all([child.exited, new Response(child.stdout).text()]);
+			expect(stdout).toBe("");
+			expect(exitCode).toBe(0);
+			expect(await Bun.file(marker).text()).toBe("after cleanup");
+		} finally {
+			try {
+				child.stdin.end();
+			} catch {
+				// Already closed after completing teardown.
+			}
+			await child.exited;
+			await Bun.file(marker)
+				.delete()
+				.catch(() => {});
+		}
+	});
 });