diff --git a/apps/server/src/orchestration-v2/Adapters/CodexAdapterV2.test.ts b/apps/server/src/orchestration-v2/Adapters/CodexAdapterV2.test.ts
index e20edf4c5e723..29931b04291ec 100644
--- a/apps/server/src/orchestration-v2/Adapters/CodexAdapterV2.test.ts
+++ b/apps/server/src/orchestration-v2/Adapters/CodexAdapterV2.test.ts
@@ -4064,6 +4064,58 @@ describe("CodexAdapterV2 post-settle continuation", () => {
     ],
   });
 
+  it.effect("wakes with well-formed text when the cuts split an emoji", () =>
+    Effect.scoped(
+      Effect.gen(function* () {
+        const harness = yield* makeCodexReplayHarness(
+          makeCodexReplayTranscript({
+            scenario: "codex-bg-wake-surrogate",
+            entries: [
+              ...backgroundExecTranscript.entries.slice(0, -1),
+              {
+                type: "emit_inbound",
+                label: "item/completed/command-late",
+                frame: {
+                  method: "item/completed",
+                  params: {
+                    item: {
+                      ...backgroundCommandItem("completed"),
+                      command: `${"c".repeat(199)}🚀`,
+                      aggregatedOutput: `🚀${"x".repeat(999)}\n`,
+                    },
+                    threadId: BG_NATIVE_THREAD,
+                    turnId: BG_NATIVE_TURN,
+                    completedAtMs: 1782622465500,
+                  },
+                },
+              },
+            ],
+          }),
+        );
+        yield* harness.runtime.startTurn(
+          makeCodexTestTurnInput({
+            threadId: harness.threadId,
+            providerThread: harness.providerThread,
+            now: yield* DateTime.now,
+            attemptId: RunAttemptId.make("attempt-codex-bg-wake-surrogate"),
+            text: BG_PROMPT,
+          }),
+        );
+        yield* harness.until(() => harness.continuationRequests.length > 0);
+        assert.isTrue(harness.continuationRequests[0]?.detail?.isWellFormed());
+      }).pipe(
+        Effect.provide(
+          Layer.mergeAll(
+            IdAllocator.layer,
+            McpProviderSessions.layer,
+            NodeServices.layer,
+            NodeCrypto.layer,
+          ),
+        ),
+      ),
+    ),
+  );
+
   it.effect.each([false, true])(
     "keeps commands interrupted after native thread closure (persistent tool: %s)",
     (retainContext) =>
diff --git a/apps/server/src/orchestration-v2/Adapters/CodexAdapterV2.ts b/apps/server/src/orchestration-v2/Adapters/CodexAdapterV2.ts
index 277232830676d..aceb3596ab1f6 100644
--- a/apps/server/src/orchestration-v2/Adapters/CodexAdapterV2.ts
+++ b/apps/server/src/orchestration-v2/Adapters/CodexAdapterV2.ts
@@ -430,17 +430,21 @@ function codexBackgroundCommandDetail(item: {
   readonly exitCode?: number | null | undefined;
   readonly aggregatedOutput?: string | null | undefined;
 }): string {
+  // Codex rejects a turn/start with a lone surrogate and never answers it, so cut on code points.
+  let commandEnd = BACKGROUND_COMMAND_DETAIL_COMMAND_MAX_LENGTH;
+  const finalCommandUnit = item.command.charCodeAt(commandEnd - 1);
+  if (finalCommandUnit >= 0xd800 && finalCommandUnit <= 0xdbff) commandEnd -= 1;
   const command =
     item.command.length > BACKGROUND_COMMAND_DETAIL_COMMAND_MAX_LENGTH
-      ? `${item.command.slice(0, BACKGROUND_COMMAND_DETAIL_COMMAND_MAX_LENGTH)}...`
+      ? `${item.command.slice(0, commandEnd)}...`
       : item.command;
   const exit =
     item.exitCode === null || item.exitCode === undefined ? "" : ` (exit ${item.exitCode})`;
   const output = (item.aggregatedOutput ?? "").trimEnd();
-  const outputTail =
-    output.length > BACKGROUND_COMMAND_DETAIL_OUTPUT_TAIL_MAX_LENGTH
-      ? `...${output.slice(-BACKGROUND_COMMAND_DETAIL_OUTPUT_TAIL_MAX_LENGTH)}`
-      : output;
+  let outputStart = output.length - BACKGROUND_COMMAND_DETAIL_OUTPUT_TAIL_MAX_LENGTH;
+  const firstOutputUnit = output.charCodeAt(outputStart);
+  if (firstOutputUnit >= 0xdc00 && firstOutputUnit <= 0xdfff) outputStart += 1;
+  const outputTail = outputStart > 0 ? `...${output.slice(outputStart)}` : output;
   const header = `Background command completed${exit}: ${command}`;
   return outputTail.length === 0 ? header : `${header}\n\nOutput tail:\n${outputTail}`;
 }