diff --git a/web/src/lib/pty-resume-loading.test.ts b/web/src/lib/pty-resume-loading.test.ts
index 09a2c16a193..72f6e5f779b 100644
--- a/web/src/lib/pty-resume-loading.test.ts
+++ b/web/src/lib/pty-resume-loading.test.ts
@@ -1,5 +1,6 @@
 import { describe, expect, it } from "vitest";
 
+import { PtyResumeSanitizer } from "./pty-resume-sanitizer";
 import {
   PTY_RESUME_LOADING_MAX_MS,
   shouldFinishResumeHydrationOnChunk,
@@ -17,6 +18,40 @@ describe("shouldFinishResumeHydrationOnChunk", () => {
   });
 });
 
+describe("resume hydration gate over the real sanitizer", () => {
+  // Regression: the gate must key off the payload actually written to xterm,
+  // not the raw frame. The sanitizer collapses an erase-only / all-newline /
+  // partial-CSI resume frame to "", so a nonempty raw first frame would
+  // otherwise clear the wait notice while the terminal is still blank.
+  const ESC = String.fromCharCode(27);
+  const CRLF = String.fromCharCode(13, 10);
+  const VISIBLE = `Hello world${CRLF}`;
+
+  const controlOnlyFirstFrames: Array<[string, string]> = [
+    ["erase-only", `${ESC}[2K`],
+    ["all-newline", `${CRLF}${CRLF}`],
+    ["partial-CSI", `${ESC}[`],
+  ];
+
+  it.each(controlOnlyFirstFrames)(
+    "keeps hydrating on a %s first frame, then finishes on visible replay",
+    (_label, firstFrame) => {
+      const sanitizer = new PtyResumeSanitizer();
+
+      // Raw first frame is nonempty, but nothing is written to xterm...
+      expect(firstFrame.length).toBeGreaterThan(0);
+      const firstRendered = sanitizer.next(firstFrame);
+      expect(firstRendered).toBe("");
+      expect(shouldFinishResumeHydrationOnChunk(firstRendered)).toBe(false);
+
+      // ...so the notice only clears once real replay output arrives.
+      const secondRendered = sanitizer.next(VISIBLE);
+      expect(secondRendered.length).toBeGreaterThan(0);
+      expect(shouldFinishResumeHydrationOnChunk(secondRendered)).toBe(true);
+    },
+  );
+});
+
 describe("shouldShowResumeLoadingOverlay", () => {
   it("shows while a resume target is connecting or open and still hydrating", () => {
     expect(
diff --git a/web/src/pages/ChatPage.tsx b/web/src/pages/ChatPage.tsx
index fd18e6133af..529f1d69f93 100644
--- a/web/src/pages/ChatPage.tsx
+++ b/web/src/pages/ChatPage.tsx
@@ -1058,8 +1058,13 @@ export default function ChatPage({ isActive = true }: { isActive?: boolean }) {
           : decoder.decode(new Uint8Array(ev.data as ArrayBuffer), {
               stream: true,
             });
-      term.write(resumeParam ? sanitizer.next(text) : text);
-      noteResumePtyChunk(text);
+      // Gate hydration on the payload actually written to xterm. The
+      // sanitizer can turn a nonempty erase-only / all-newline / partial-CSI
+      // resume frame into "" (pty-resume-sanitizer.ts); keying off raw `text`
+      // would hide the wait notice while the terminal is still blank.
+      const rendered = resumeParam ? sanitizer.next(text) : text;
+      term.write(rendered);
+      noteResumePtyChunk(rendered);
     };
 
     ws.onclose = (ev) => {