diff --git a/web/src/lib/pty-resume-loading.test.ts b/web/src/lib/pty-resume-loading.test.ts
new file mode 100644
index 00000000000..09a2c16a193
--- /dev/null
+++ b/web/src/lib/pty-resume-loading.test.ts
@@ -0,0 +1,69 @@
+import { describe, expect, it } from "vitest";
+
+import {
+  PTY_RESUME_LOADING_MAX_MS,
+  shouldFinishResumeHydrationOnChunk,
+  shouldShowResumeLoadingOverlay,
+} from "./pty-resume-loading";
+
+describe("shouldFinishResumeHydrationOnChunk", () => {
+  it("finishes on the first non-empty chunk", () => {
+    expect(shouldFinishResumeHydrationOnChunk("")).toBe(false);
+    expect(shouldFinishResumeHydrationOnChunk("hello")).toBe(true);
+  });
+
+  it("keeps a positive hard-cap timeout for wedged resumes", () => {
+    expect(PTY_RESUME_LOADING_MAX_MS).toBeGreaterThan(0);
+  });
+});
+
+describe("shouldShowResumeLoadingOverlay", () => {
+  it("shows while a resume target is connecting or open and still hydrating", () => {
+    expect(
+      shouldShowResumeLoadingOverlay({
+        hasResumeTarget: true,
+        ptyState: "connecting",
+        hydrating: true,
+      }),
+    ).toBe(true);
+    expect(
+      shouldShowResumeLoadingOverlay({
+        hasResumeTarget: true,
+        ptyState: "open",
+        hydrating: true,
+      }),
+    ).toBe(true);
+  });
+
+  it("hides when there is no resume target", () => {
+    expect(
+      shouldShowResumeLoadingOverlay({
+        hasResumeTarget: false,
+        ptyState: "connecting",
+        hydrating: true,
+      }),
+    ).toBe(false);
+  });
+
+  it("hides once hydration finishes", () => {
+    expect(
+      shouldShowResumeLoadingOverlay({
+        hasResumeTarget: true,
+        ptyState: "open",
+        hydrating: false,
+      }),
+    ).toBe(false);
+  });
+
+  it("defers to reconnect / closed / ended overlays", () => {
+    for (const ptyState of ["reconnecting", "closed", "ended"] as const) {
+      expect(
+        shouldShowResumeLoadingOverlay({
+          hasResumeTarget: true,
+          ptyState,
+          hydrating: true,
+        }),
+      ).toBe(false);
+    }
+  });
+});
diff --git a/web/src/lib/pty-resume-loading.ts b/web/src/lib/pty-resume-loading.ts
new file mode 100644
index 00000000000..9a150664d50
--- /dev/null
+++ b/web/src/lib/pty-resume-loading.ts
@@ -0,0 +1,47 @@
+import type { PtyConnectionState } from "@/lib/pty-reconnect";
+
+/**
+ * Hard cap so a wedged resume (never gets PTY payload) cannot leave the
+ * wait notice up forever.
+ */
+export const PTY_RESUME_LOADING_MAX_MS = 30000;
+
+export const PTY_RESUME_LOADING_MESSAGE =
+  "Please wait while the conversation loads…";
+
+export interface ResumeLoadingOverlayInput {
+  hasResumeTarget: boolean;
+  ptyState: PtyConnectionState;
+  hydrating: boolean;
+}
+
+/**
+ * Show a wait notice only while a resumed chat is still blank. Once the
+ * first real PTY payload arrives the terminal has something to show, so
+ * the notice hides and history can stream in underneath.
+ *
+ * Reconnect / ended / closed states keep their own overlays and must not
+ * stack this one on top.
+ */
+export function shouldShowResumeLoadingOverlay({
+  hasResumeTarget,
+  ptyState,
+  hydrating,
+}: ResumeLoadingOverlayInput): boolean {
+  if (!hasResumeTarget || !hydrating) {
+    return false;
+  }
+  if (
+    ptyState === "reconnecting" ||
+    ptyState === "closed" ||
+    ptyState === "ended"
+  ) {
+    return false;
+  }
+  return ptyState === "connecting" || ptyState === "open";
+}
+
+/** First non-empty PTY chunk means the blank window is over. */
+export function shouldFinishResumeHydrationOnChunk(chunkText: string): boolean {
+  return chunkText.length > 0;
+}