diff --git a/apps/server/src/preview/ServerBrowser.test.ts b/apps/server/src/preview/ServerBrowser.test.ts
index 97d75c2c4ecb0..496ac376bd5a8 100644
--- a/apps/server/src/preview/ServerBrowser.test.ts
+++ b/apps/server/src/preview/ServerBrowser.test.ts
@@ -941,9 +941,11 @@ it.live("reports a pending dialog without evaluating the page and resolves it ex
         Effect.sync(() => resolvedEvaluation.resolve({ result: { value: true } })),
       );
       yield* Effect.promise(() => started.promise);
+      // The 4,000-character cap falls between the halves of the emoji.
+      const message = `Delete row?${" ".repeat(3_988)}😀`;
       const dialog = {
         type: () => "confirm",
-        message: () => "Delete row?",
+        message: () => message,
         defaultValue: () => "",
         accept: vi.fn(async () => {
           resolvedEvaluation.resolve({ result: { value: true } });
@@ -958,7 +960,7 @@ it.live("reports a pending dialog without evaluating the page and resolves it ex
         operation: "status",
         input: {},
       });
-      expect(status.dialog).toMatchObject({ type: "confirm", message: "Delete row?" });
+      expect(status.dialog).toMatchObject({ type: "confirm", message: message.slice(0, 3_999) });
       expect(page.title).not.toHaveBeenCalled();
       expect(dialog.dismiss).not.toHaveBeenCalled();
       const reuse = yield* broker
diff --git a/apps/server/src/preview/ServerBrowser.ts b/apps/server/src/preview/ServerBrowser.ts
index 2f681d0c151c9..8d9fded855ed8 100644
--- a/apps/server/src/preview/ServerBrowser.ts
+++ b/apps/server/src/preview/ServerBrowser.ts
@@ -370,6 +370,9 @@ const DOWNLOAD_LIMIT = 20;
 const ABORTED_NAVIGATION_DOWNLOAD_WAIT_MS = 5_000;
 const DOWNLOAD_MAX_BYTES = 1024 * 1024 * 1024;
 
+// Half an emoji serializes to a lone surrogate escape, which provider JSON parsers reject.
+const cutDialogText = (text: string) => text.slice(0, 4_000).replace(/[\uD800-\uDBFF]$/, "");
+
 const tabKey = (threadId: string, tabId: string) => `${threadId}\u0000${tabId}`;
 
 const pushBounded = <A>(
@@ -537,8 +540,8 @@ const make = Effect.gen(function* () {
     tab.dialog
       ? {
           type: tab.dialog.type(),
-          message: tab.dialog.message().slice(0, 4000),
-          defaultValue: tab.dialog.defaultValue().slice(0, 4000),
+          message: cutDialogText(tab.dialog.message()),
+          defaultValue: cutDialogText(tab.dialog.defaultValue()),
         }
       : null;