feat(tui): actually clear the clipboard after the configured delay

clipboard_clear_delay has been in the default config (45s), settable, and
read by nothing: clipboardSink copied and returned. That made TUI Secret
Mode -- whose entire purpose is to route secrets off the screen -- strictly
less safe than Python's, because it parked them on a session-wide clipboard
indefinitely.

clipboardSink now takes an optional clearAfterSeconds. When set, it schedules
a wipe after the delay, but only if the clipboard still holds the value it
put there, so a value the user copied in the meantime is left alone -- the
same guard Python's copy_to_clipboard(text, timeout) applies via a read-back.
Where the clipboard cannot be read (no paste tool), it clears unconditionally,
because leaving a secret parked is the worse outcome. The timer is unref'd:
it fires while the long-running TUI is up but never holds a process open, so
the one-shot CLI and the agent are unchanged (they pass no delay).

Both TUI clipboard paths -- Secret Mode reveals and the entry 'C' action --
now route through the profile's clipboard_clear_delay.

Tests use a fake wl-copy/wl-paste pair on PATH: the secret is wiped after the
delay, and a value copied over it in the meantime survives.

Co-Authored-By: Claude Opus 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01Tkj4rzKBA3uhfgk7kqjsb8

js/packages/cli/src/sinks.ts

@@ -159,12 +159,28 @@ export async function stdinSink(
   });
 }
 
-const CLIPBOARD_COMMANDS: Array<{ cmd: string; args: string[] }> = [
-  { cmd: "wl-copy", args: [] },
-  { cmd: "xclip", args: ["-selection", "clipboard"] },
-  { cmd: "xsel", args: ["--clipboard", "--input"] },
-  { cmd: "pbcopy", args: [] },
-  { cmd: "clip.exe", args: [] },
+/**
+ * Clipboard tools, each paired with the command that reads the same
+ * selection back. The read command lets a scheduled clear check that the
+ * clipboard still holds *our* secret before wiping it, so it never clobbers
+ * something the user copied in the meantime. `paste: null` means the platform
+ * has a writer but no reliable reader here (Windows `clip.exe`).
+ */
+const CLIPBOARD_TOOLS: Array<{
+  copy: { cmd: string; args: string[] };
+  paste: { cmd: string; args: string[] } | null;
+}> = [
+  { copy: { cmd: "wl-copy", args: [] }, paste: { cmd: "wl-paste", args: ["-n"] } },
+  {
+    copy: { cmd: "xclip", args: ["-selection", "clipboard"] },
+    paste: { cmd: "xclip", args: ["-selection", "clipboard", "-o"] },
+  },
+  {
+    copy: { cmd: "xsel", args: ["--clipboard", "--input"] },
+    paste: { cmd: "xsel", args: ["--clipboard", "--output"] },
+  },
+  { copy: { cmd: "pbcopy", args: [] }, paste: { cmd: "pbpaste", args: [] } },
+  { copy: { cmd: "clip.exe", args: [] }, paste: null },
 ];
 
 /**
@@ -177,6 +193,52 @@ const CLIPBOARD_COMMANDS: Array<{ cmd: string; args: string[] }> = [
  * detach it, ignore its stdio, and treat "stdin accepted and flushed"
  * as success.
  */
+/** Read the current clipboard via a paste tool; null if it cannot be read. */
+function readClipboard(cmd: string, args: string[]): Promise<string | null> {
+  return new Promise((resolve) => {
+    let out = "";
+    const child = spawn(cmd, args, { stdio: ["ignore", "pipe", "ignore"], env: sinkEnv() });
+    child.on("error", () => resolve(null));
+    child.stdout.on("data", (c: Buffer) => {
+      out += c.toString("utf8");
+    });
+    child.on("close", (code) => resolve(code === 0 ? out : null));
+  });
+}
+
+/**
+ * After `delaySeconds`, clear the clipboard — but only if it still holds the
+ * secret we put there, so a value the user copied since is left alone. When
+ * the clipboard cannot be read back (no paste tool, or it failed), clear
+ * unconditionally: leaving a secret parked on a session-wide clipboard is the
+ * worse failure. Mirrors Python's copy_to_clipboard(text, timeout).
+ *
+ * The timer is unref'd: it fires while the (long-running) TUI is still up, but
+ * never keeps a process alive on its own. A one-shot CLI that exits before the
+ * delay will not clear — the same limitation Python's daemon thread has.
+ */
+function scheduleClipboardClear(
+  secret: string,
+  delaySeconds: number,
+  tool: { copy: { cmd: string; args: string[] }; paste: { cmd: string; args: string[] } | null },
+): void {
+  const timer = setTimeout(() => {
+    void (async () => {
+      if (tool.paste) {
+        const current = await readClipboard(tool.paste.cmd, tool.paste.args);
+        // Trailing newline is common from paste tools; compare trimmed.
+        if (current !== null && current.replace(/\n$/, "") !== secret) return;
+      }
+      try {
+        await feedClipboardTool("", tool.copy.cmd, tool.copy.args);
+      } catch {
+        // Best effort: nothing useful to do if the wipe itself fails.
+      }
+    })();
+  }, delaySeconds * 1000);
+  timer.unref?.();
+}
+
 function feedClipboardTool(secret: string, cmd: string, args: string[]): Promise<void> {
   return new Promise((resolve, reject) => {
     const child = spawn(cmd, args, {
@@ -211,13 +273,31 @@ function feedClipboardTool(secret: string, cmd: string, args: string[]): Promise
   });
 }
 
-/** Copy the secret to the system clipboard via the first available tool. */
-export async function clipboardSink(secret: string): Promise<SinkResult> {
+/**
+ * Copy the secret to the system clipboard via the first available tool.
+ *
+ * With `clearAfterSeconds > 0`, schedule a clear that wipes the value after
+ * the delay (see scheduleClipboardClear). The default — no options — leaves
+ * the clipboard untouched afterwards, preserving the behaviour the one-shot
+ * CLI and the agent rely on; only the long-running TUI passes a delay.
+ */
+export async function clipboardSink(
+  secret: string,
+  opts: { clearAfterSeconds?: number } = {},
+): Promise<SinkResult> {
   let lastError: unknown = new Error("no clipboard tool found");
-  for (const { cmd, args } of CLIPBOARD_COMMANDS) {
+  for (const tool of CLIPBOARD_TOOLS) {
     try {
-      await feedClipboardTool(secret, cmd, args);
-      return { sink: "clipboard", detail: `copied via ${cmd}` };
+      await feedClipboardTool(secret, tool.copy.cmd, tool.copy.args);
+      const clear = opts.clearAfterSeconds ?? 0;
+      if (clear > 0) scheduleClipboardClear(secret, clear, tool);
+      return {
+        sink: "clipboard",
+        detail:
+          clear > 0
+            ? `copied via ${tool.copy.cmd}; clears in ${clear}s`
+            : `copied via ${tool.copy.cmd}`,
+      };
     } catch (e) {
       lastError = e;
     }

js/packages/cli/src/tui/menus.ts

@@ -146,6 +146,21 @@ function secretModeOn(s: Session): boolean {
   return Boolean(s.config["secret_mode_enabled"]);
 }
 
+/**
+ * How long a copied secret should sit on the clipboard before being wiped.
+ * 0 (or a non-positive value) disables the auto-clear. Parity with Python's
+ * clipboard_clear_delay.
+ */
+function clipboardClearSeconds(s: Session): number {
+  const raw = Number(s.config["clipboard_clear_delay"] ?? 0);
+  return Number.isFinite(raw) && raw > 0 ? Math.floor(raw) : 0;
+}
+
+/** Copy a secret to the clipboard, honouring the configured auto-clear delay. */
+async function copyToClipboard(s: Session, value: string): Promise<{ detail: string }> {
+  return clipboardSink(value, { clearAfterSeconds: clipboardClearSeconds(s) });
+}
+
 /**
  * Show a secret, honouring Secret Mode.
  *
@@ -155,7 +170,7 @@ function secretModeOn(s: Session): boolean {
 async function reveal(s: Session, value: string, descriptor: string): Promise<void> {
   if (secretModeOn(s)) {
     try {
-      const result = await clipboardSink(value);
+      const result = await copyToClipboard(s, value);
       ok(s.ui, `${descriptor} copied to clipboard (${result.detail}).`);
     } catch (e) {
       fail(s.ui, `Clipboard unavailable: ${(e as Error).message}`);
@@ -630,7 +645,7 @@ async function entryDetails(s: Session, id: string): Promise<void> {
         const secret = materializeSecret(s.vault.index, id, entry, s.vault.mnemonic);
         if (choice === "c") {
           try {
-            const r = await clipboardSink(secret.value);
+            const r = await copyToClipboard(s, secret.value);
             ok(s.ui, `Copied ${secret.descriptor} (${r.detail}).`);
           } catch (e) {
             fail(s.ui, `Clipboard unavailable: ${(e as Error).message}`);