fix: guard Slack cmdarg decode

src/slack/monitor/slash.command-arg-menus.test.ts

@@ -197,4 +197,27 @@ describe("Slack native command argument menus", () => {
       }),
     );
   });
+
+  it("treats malformed percent-encoding as an invalid button (no throw)", async () => {
+    const { actions, postEphemeral, ctx, account } = createHarness();
+    registerSlackMonitorSlashCommands({ ctx: ctx as never, account: account as never });
+
+    const handler = actions.get("clawdbot_cmdarg");
+    if (!handler) throw new Error("Missing arg-menu action handler");
+
+    await handler({
+      ack: vi.fn().mockResolvedValue(undefined),
+      action: { value: "cmdarg|%E0%A4%A|mode|on|U1" },
+      body: { user: { id: "U1" }, channel: { id: "C1" } },
+    });
+
+    expect(postEphemeral).toHaveBeenCalledWith(
+      expect.objectContaining({
+        token: "bot-token",
+        channel: "C1",
+        user: "U1",
+        text: "Sorry, that button is no longer valid.",
+      }),
+    );
+  });
 });

src/slack/monitor/slash.ts

@@ -72,11 +72,23 @@ function parseSlackCommandArgValue(raw?: string | null): {
   if (parts.length !== 5 || parts[0] !== SLACK_COMMAND_ARG_VALUE_PREFIX) return null;
   const [, command, arg, value, userId] = parts;
   if (!command || !arg || !value || !userId) return null;
+  const decode = (text: string) => {
+    try {
+      return decodeURIComponent(text);
+    } catch {
+      return null;
+    }
+  };
+  const decodedCommand = decode(command);
+  const decodedArg = decode(arg);
+  const decodedValue = decode(value);
+  const decodedUserId = decode(userId);
+  if (!decodedCommand || !decodedArg || !decodedValue || !decodedUserId) return null;
   return {
-    command: decodeURIComponent(command),
-    arg: decodeURIComponent(arg),
-    value: decodeURIComponent(value),
-    userId: decodeURIComponent(userId),
+    command: decodedCommand,
+    arg: decodedArg,
+    value: decodedValue,
+    userId: decodedUserId,
   };
 }