diff --git a/src/sandbox/process-output.ts b/src/sandbox/process-output.ts
index 98508bf..c5e7ea6 100644
--- a/src/sandbox/process-output.ts
+++ b/src/sandbox/process-output.ts
@@ -66,12 +66,16 @@ export class ProcessOutput {
     readonly maxBytes: number
   ) {}
 
-  failure(message: string, code = "incomplete_output"): HyperbrowserError {
+  failure(
+    message: string,
+    code = "incomplete_output",
+    details: Record<string, number> = {}
+  ): HyperbrowserError {
     return new HyperbrowserError(message, {
       code,
       service: "runtime",
       retryable: false,
-      details: { process_id: this.processId, last_seq: this.seq },
+      details: { process_id: this.processId, last_seq: this.seq, ...details },
     });
   }
 
@@ -120,8 +124,9 @@ export class ProcessOutput {
     this.size += raw.length;
     if (this.size > this.maxBytes) {
       throw this.failure(
-        "Command output exceeds maxOutputBytes; increase the collection limit or disconnect a detached process",
-        "output_limit_exceeded"
+        `Command output exceeds maxOutputBytes (${this.size} bytes received, limit ${this.maxBytes}); increase the collection limit or disconnect a detached process`,
+        "output_limit_exceeded",
+        { max_output_bytes: this.maxBytes, received_bytes: this.size }
       );
     }
     this.seq = data.seq;
diff --git a/tests/unit/process-collection.test.ts b/tests/unit/process-collection.test.ts
index 276a963..b6af709 100644
--- a/tests/unit/process-collection.test.ts
+++ b/tests/unit/process-collection.test.ts
@@ -147,6 +147,17 @@ describe("sandbox process output collection", () => {
     expect(transport.calls).toHaveLength(1);
   });
 
+  test("output limit error reports the limit and bytes received", async () => {
+    const transport = new FakeTransport([output(1, Buffer.from("too much")), done(1)] as RuntimeSSEEvent[]);
+    const error = await new SandboxProcessesApi(transport.asTransport())
+      .exec("test", { maxOutputBytes: 4 })
+      .then(() => null, (e: unknown) => e);
+    const failure = error as HyperbrowserError;
+    expect(failure.code).toBe("output_limit_exceeded");
+    expect(failure.details).toMatchObject({ max_output_bytes: 4, received_bytes: 8 });
+    expect(failure.message).toContain("8 bytes received, limit 4");
+  });
+
   test("wait timeout keeps the collector alive", async () => {
     const transport = new FakeTransport([output(1, Buffer.from("later")), done(1)]);
     transport.gate = new Gate();