vercel-labs/agent-browser · error

The "switch" action requires a target tab id or label.

Error message

The "switch" action requires a target tab id or label.

What it means

The eve 'tabs' tool switch action maps to 'agent-browser tab <target>' where target is a tab id or label. Unlike 'new' and 'close', which have sensible defaults, switching has nothing to default to, so execute() throws when action is 'switch' and target is undefined.

Solutions

1. List tabs first (action: 'list') and pass a concrete id or label
2. Pass the label you created the tab with: tools.tabs({ action: 'switch', target: 'checkout' })
3. For creating-and-switching use action 'new' with a label instead

Example fix

// before
await tools.tabs({ action: "switch" });

// after
const list = await tools.tabs({ action: "list" });
await tools.tabs({ action: "switch", target: list[0].id });

if (input.action === "switch" && input.target === undefined) {
  const tabs = await tools.tabs({ action: "list" });
  if (tabs.length === 1) return tabs[0]; // nothing to switch to
  throw new Error("switch requires a tab id or label from the list");
}

function canSwitchTab(i: { action: string; target?: string }): boolean {
  return i.action !== "switch" || i.target !== undefined;
}

When it happens

Trigger: Calling tabs with { action: 'switch' } and no target; label stored in an undefined variable; confusing 'switch' with 'new' (which needs neither).

Common situations: Agents assuming switch-to-latest semantics; flows where the tab list was fetched earlier and the id was dropped.

Related errors

• Provide a direction to scroll, or a selector to scroll into…
• Provide at least one of: selector, text, urlPattern…
• The " " action requires a value.
• The "attr" property requires an attribute name.
• The "goto" action requires a url.

AI-assisted analysis of vercel-labs/agent-browser@548b159b30 (2026-08-16). Data as JSON: /api/errors/0c6d16ea643f7a81. Report an issue: GitHub.

Appendix: source

Thrown at packages/@agent-browser/eve/extension/tools/tabs.ts:33

    target: z
      .string()
      .optional()
      .describe('Tab id ("t2") or label. Required for "switch"; "close" defaults to the active tab.'),
    url: z.string().optional().describe('URL to open when action is "new".'),
  }),
  async execute({ action, label, target, url }, ctx) {
    switch (action) {
      case "list":
        return await runBrowser(ctx, ["tab"]);
      case "new": {
        const args = ["tab", "new"];
        if (label !== undefined) args.push("--label", label);
        if (url !== undefined) args.push(url);
        return await runBrowser(ctx, args);
      }
      case "switch":
        if (target === undefined) {
          throw new Error('The "switch" action requires a target tab id or label.');
        }
        return await runBrowser(ctx, ["tab", target]);
      case "close":
        return await runBrowser(ctx, target === undefined ? ["tab", "close"] : ["tab", "close", target]);
    }
  },
});

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