diff --git a/gui/src/components/AddProviderModal.tsx b/gui/src/components/AddProviderModal.tsx
index 21a7e702f0..979b680976 100644
--- a/gui/src/components/AddProviderModal.tsx
+++ b/gui/src/components/AddProviderModal.tsx
@@ -229,8 +229,12 @@ export default function AddProviderModal({
 
   return (
     <>
-    <div role="dialog" aria-modal="true" aria-label={t("modal.add")} className="modal-overlay" onClick={onClose}>
-      <div ref={dialogRef} className="modal-card" onClick={e => e.stopPropagation()}>
+    {/* The backdrop must not dismiss this modal: a stray click — or a text
+        selection drag that is released outside the card — would wipe every
+        field the user already filled in. Close only via the × button,
+        Escape, or a successful add. */}
+    <div role="dialog" aria-modal="true" aria-label={t("modal.add")} className="modal-overlay">
+      <div ref={dialogRef} className="modal-card">
         <div className="modal-head">
           <h3>{preset ? t("modal.addNamed", { label: preset.label }) : t("modal.add")}</h3>
           <button type="button" className="btn btn-ghost btn-icon" aria-label={t("common.close")} onClick={onClose}><IconX /></button>
diff --git a/gui/tests/add-provider-modal-backdrop.test.tsx b/gui/tests/add-provider-modal-backdrop.test.tsx
new file mode 100644
index 0000000000..df86acf2f0
--- /dev/null
+++ b/gui/tests/add-provider-modal-backdrop.test.tsx
@@ -0,0 +1,155 @@
+import { afterEach, beforeEach, expect, test } from "bun:test";
+import { Window } from "happy-dom";
+import { act } from "react";
+import type { Root } from "react-dom/client";
+import { LanguageProvider } from "../src/i18n/provider";
+import AddProviderModal from "../src/components/AddProviderModal";
+
+/**
+ * The Add Provider modal collects a name, base URL, and API key before the
+ * user saves anything. Dismissing it on a backdrop click — or on a text
+ * selection drag that is released outside the card — unmounts the modal and
+ * wipes all of that input. The backdrop must therefore never close the
+ * modal; only the × button, Escape, and a successful add may.
+ */
+
+const globals = ["document", "window", "navigator", "localStorage", "IS_REACT_ACT_ENVIRONMENT"] as const;
+let previous: Record<(typeof globals)[number], unknown>;
+let win: Window;
+let host: HTMLElement;
+let root: Root | null = null;
+let originalFetch: typeof globalThis.fetch;
+let closeCalls: number;
+
+beforeEach(() => {
+  previous = Object.fromEntries(globals.map((k) => [k, Reflect.get(globalThis, k)])) as typeof previous;
+  originalFetch = globalThis.fetch;
+  win = new Window({ url: "http://localhost/" });
+  Object.defineProperty(win.navigator, "language", { configurable: true, value: "en-US" });
+  Object.defineProperties(globalThis, {
+    document: { configurable: true, value: win.document },
+    window: { configurable: true, value: win },
+    navigator: { configurable: true, value: win.navigator },
+    localStorage: { configurable: true, value: win.localStorage },
+  });
+  (globalThis as typeof globalThis & { IS_REACT_ACT_ENVIRONMENT?: boolean }).IS_REACT_ACT_ENVIRONMENT = true;
+
+  closeCalls = 0;
+  Object.defineProperty(globalThis, "fetch", {
+    configurable: true,
+    value: async (input: RequestInfo | URL) => {
+      const url = new URL(String(input), "http://localhost");
+      if (url.pathname === "/api/oauth/providers") return Response.json({ providers: [] });
+      if (url.pathname === "/api/provider-presets") return Response.json({ providers: [] });
+      if (url.pathname === "/api/usage") return Response.json({ providers: [] });
+      return Response.json({});
+    },
+  });
+
+  host = win.document.createElement("div") as unknown as HTMLElement;
+  win.document.body.appendChild(host as never);
+});
+
+afterEach(async () => {
+  if (root) {
+    const current = root;
+    await act(async () => { current.unmount(); });
+    root = null;
+  }
+  for (const key of globals) {
+    Object.defineProperty(globalThis, key, { configurable: true, value: previous[key] });
+  }
+  Object.defineProperty(globalThis, "fetch", { configurable: true, value: originalFetch });
+  await win.happyDOM?.close?.();
+});
+
+async function mountModal() {
+  const { createRoot } = await import("react-dom/client");
+  await act(async () => {
+    root = createRoot(host);
+    root.render(
+      <LanguageProvider>
+        <AddProviderModal
+          apiBase=""
+          existingNames={[]}
+          initialCustom
+          onClose={() => { closeCalls += 1; }}
+          onAdded={() => {}}
+        />
+      </LanguageProvider>,
+    );
+  });
+  await act(async () => { await new Promise((r) => setTimeout(r, 40)); });
+}
+
+function overlay(): HTMLElement {
+  const el = host.querySelector<HTMLElement>(".modal-overlay");
+  expect(el).toBeTruthy();
+  return el!;
+}
+
+function nameInput(): HTMLInputElement {
+  const el = host.querySelector<HTMLInputElement>(".modal-card input.input");
+  expect(el).toBeTruthy();
+  return el!;
+}
+
+function setInputValue(input: HTMLInputElement, value: string) {
+  const setter = Object.getOwnPropertyDescriptor(win.HTMLInputElement.prototype, "value")!.set!;
+  setter.call(input, value);
+  input.dispatchEvent(new win.Event("input", { bubbles: true }));
+}
+
+function click(target: HTMLElement) {
+  target.dispatchEvent(new win.MouseEvent("click", { bubbles: true }));
+}
+
+test("clicking the backdrop neither closes the modal nor discards entered form data", async () => {
+  await mountModal();
+
+  await act(async () => { setInputValue(nameInput(), "my-provider"); });
+  expect(nameInput().value).toBe("my-provider");
+
+  await act(async () => { click(overlay()); });
+
+  expect(closeCalls).toBe(0);
+  expect(host.querySelector(".modal-overlay")).toBeTruthy();
+  expect(nameInput().value).toBe("my-provider");
+});
+
+test("a text-selection drag released on the backdrop does not close the modal", async () => {
+  await mountModal();
+
+  await act(async () => { setInputValue(nameInput(), "sk-live-key-material"); });
+
+  // Press inside the input (starting a selection drag), release on the overlay.
+  await act(async () => {
+    nameInput().dispatchEvent(new win.MouseEvent("mousedown", { bubbles: true }));
+    overlay().dispatchEvent(new win.MouseEvent("mouseup", { bubbles: true }));
+    click(overlay());
+  });
+
+  expect(closeCalls).toBe(0);
+  expect(host.querySelector(".modal-overlay")).toBeTruthy();
+  expect(nameInput().value).toBe("sk-live-key-material");
+});
+
+test("the close button still closes the modal", async () => {
+  await mountModal();
+
+  const closeButton = host.querySelector<HTMLElement>(".modal-head button[aria-label='Close']");
+  expect(closeButton).toBeTruthy();
+  await act(async () => { click(closeButton!); });
+
+  expect(closeCalls).toBe(1);
+});
+
+test("Escape still closes the modal", async () => {
+  await mountModal();
+
+  await act(async () => {
+    win.dispatchEvent(new win.KeyboardEvent("keydown", { key: "Escape" }));
+  });
+
+  expect(closeCalls).toBe(1);
+});