n8n-io/n8n · warning · UnsupportedOperationError

Operation not supported: drag

Error message

Operation not supported: drag

What it means

Thrown as UnsupportedOperationError('drag', 'agent-browser') by the agent-browser adapter's drag() stub. The agent-browser CLI has no drag command, so the adapter explicitly rejects the operation rather than silently no-op'ing. UnsupportedOperationError extends McpBrowserError and carries a hint that the operation is not available for agent-browser sessions.

Source

Thrown at packages/@n8n/mcp-browser/src/adapters/agent-browser.ts:399

		const resp = await this.run(['eval', script]);
		if (!resp.success) throw new Error(resp.error ?? 'select failed');
		return Array.isArray(resp.data) ? (resp.data as string[]) : values;
	}

	async hover(pageId: string, target: ElementTarget): Promise<void> {
		await this.switchToTab(pageId);
		await this.runAction(['hover', this.resolveTarget(target)]);
	}

	async press(pageId: string, keys: string): Promise<void> {
		AgentBrowserAdapter.assertSafeArg(keys, 'key');
		await this.switchToTab(pageId);
		await this.runAction(['press', keys]);
	}

	async drag(_pageId: string, _from: ElementTarget, _to: ElementTarget): Promise<void> {
		await Promise.resolve();
		throw new UnsupportedOperationError('drag', this.name);
	}

	async scroll(pageId: string, target?: ElementTarget, options?: ScrollOptions): Promise<void> {
		await this.switchToTab(pageId);
		if (target) {
			await this.runAction(['scrollintoview', this.resolveTarget(target)]);
		} else {
			await this.runAction([
				'scroll',
				options?.direction ?? 'down',
				String(options?.amount ?? 300),
			]);
		}
	}

	async upload(
		_pageId: string,
		_target: ElementTarget | undefined,

View on GitHub (pinned to 5ac6606e81)

Solutions

1. Check adapter.name === 'agent-browser' before calling drag, and either skip the action or switch to the Playwright adapter.
2. Emulate drag with a sequence of hover + mouse-down-equivalent clicks if the page supports it.
3. Gate drag behind a capability check surfaced to the LLM so it doesn't emit unsupported actions.

Example fix

// before
await adapter.drag(pageId, from, to);

// after — guard by adapter capability
if (adapter.name === 'playwright') {
  await adapter.drag(pageId, from, to);
} else {
  // emulate, or surface 'unsupported' to the caller
}

function adapterSupportsDrag(name: string): boolean {
  return name === 'playwright';
}

function supportsDrag(adapter: Adapter): boolean {
  return adapter.name !== 'agent-browser';
}

When it happens

Trigger: Calling adapter.drag(pageId, fromTarget, toTarget) on an AgentBrowserAdapter instance. The method awaits a resolved promise (to satisfy the async signature) then throws synchronously, so the rejection is immediate.

Common situations: A tool/orchestrator layer calls drag() generically across adapters without checking capability; a caller migrated from the Playwright adapter (which supports drag) to agent-browser; an LLM tool emitted a drag action against an agent-browser session.

Related errors

• Operation not supported: upload
• Operation not supported: dialog
• Operation not supported: pdf
• agent-browser failed
• Page not found: ${pageId}

AI-assisted analysis of n8n-io/n8n@5ac6606e81 (2026-08-12). Data as JSON: /api/errors/7f6bde4c4a6dd677. Report an issue: GitHub.