fix(web): copy text over plain HTTP

apps/web/src/hooks/useCopyToClipboard.test.ts

@@ -14,6 +14,7 @@ describe("writeTextToClipboard", () => {
   it("reports unavailable clipboard support with structural context", async () => {
     vi.stubGlobal("window", {});
     vi.stubGlobal("navigator", {});
+    vi.stubGlobal("document", undefined);
 
     const error = await writeTextToClipboard("plan contents", "plan").then(
       () => undefined,
@@ -27,6 +28,43 @@ describe("writeTextToClipboard", () => {
     expect((error as Error).message).not.toContain("plan contents");
   });
 
+  it("falls back to a selected textarea when the Clipboard API is unavailable", async () => {
+    const focus = vi.fn();
+    const appendChild = vi.fn();
+    const execCommand = vi.fn(() => true);
+    const remove = vi.fn();
+    const select = vi.fn();
+    const setAttribute = vi.fn();
+    const setSelectionRange = vi.fn();
+    const textarea = {
+      remove,
+      select,
+      setAttribute,
+      setSelectionRange,
+      style: {},
+      value: "",
+    };
+
+    vi.stubGlobal("window", {});
+    vi.stubGlobal("navigator", {});
+    vi.stubGlobal("document", {
+      activeElement: { focus },
+      body: { appendChild },
+      createElement: vi.fn(() => textarea),
+      execCommand,
+    });
+
+    await expect(writeTextToClipboard("remote command", "command")).resolves.toBe(true);
+
+    expect(textarea.value).toBe("remote command");
+    expect(appendChild).toHaveBeenCalledWith(textarea);
+    expect(select).toHaveBeenCalledOnce();
+    expect(setSelectionRange).toHaveBeenCalledWith(0, "remote command".length);
+    expect(execCommand).toHaveBeenCalledWith("copy");
+    expect(remove).toHaveBeenCalledOnce();
+    expect(focus).toHaveBeenCalledOnce();
+  });
+
   it("preserves the exact clipboard failure without exposing copied contents", async () => {
     const cause = new Error("browser clipboard failure");
     const writeText = vi.fn().mockRejectedValue(cause);

apps/web/src/hooks/useCopyToClipboard.ts

@@ -47,19 +47,51 @@ export class ClipboardReadError extends Schema.TaggedErrorClass<ClipboardReadErr
   }
 }
 
+/** Copy fallback for remote web pages served over plain HTTP. */
+function writeTextWithExecCommand(value: string): boolean {
+  if (typeof document === "undefined" || typeof document.execCommand !== "function") return false;
+
+  const textarea = document.createElement("textarea");
+  textarea.value = value;
+  textarea.setAttribute("readonly", "");
+  textarea.setAttribute("aria-hidden", "true");
+  textarea.style.position = "fixed";
+  textarea.style.top = "-9999px";
+  textarea.style.opacity = "0";
+
+  const previouslyFocused = document.activeElement;
+  document.body.appendChild(textarea);
+  try {
+    textarea.select();
+    textarea.setSelectionRange(0, value.length);
+    return document.execCommand("copy");
+  } catch {
+    return false;
+  } finally {
+    textarea.remove();
+    const restoreFocus = (previouslyFocused as { focus?: unknown } | null)?.focus;
+    if (typeof restoreFocus === "function") {
+      restoreFocus.call(previouslyFocused);
+    }
+  }
+}
+
 export async function writeTextToClipboard(value: string, target = "text") {
-  if (
-    typeof window === "undefined" ||
-    typeof navigator === "undefined" ||
-    !navigator.clipboard?.writeText
-  ) {
+  if (typeof window === "undefined") {
     throw new ClipboardApiUnavailableError({
       target,
     });
   }
 
   if (!value) return false;
 
+  if (typeof navigator === "undefined" || !navigator.clipboard?.writeText) {
+    if (writeTextWithExecCommand(value)) return true;
+    throw new ClipboardApiUnavailableError({
+      target,
+    });
+  }
+
   try {
     await navigator.clipboard.writeText(value);
     return true;