Short answer
These three sound similar but do very different things:
Test Mode — a safe preview. See what Lancer would do without sending anything.
External Mode — hand the bidding off to your own system via webhooks and the API.
Advanced — power-user controls to edit the AI's underlying prompts.
Test Mode
A sandbox. With Test Mode on, nothing is submitted to Upwork and no connects are spent. On any job you can preview the suitability rating and the exact cover letter Lancer would generate — the right way to tune your Knowledge Base and cover letters before going live. Full guide: How to Use Test Mode.
External Mode
For users who want to run their own logic. In a campaign's Integrations tab you can switch it to External: instead of bidding itself, Lancer streams each matching job to your webhook, and your system decides whether to bid by calling the Lancer API. Note: switching a live campaign to External pauses it, and the "new job" Slack/Discord notifications turn off for that campaign. If your system doesn't respond to a job, that lead is simply skipped. See the API, MCP & Integrations section.
Advanced
The campaign's Advanced tab lets power users override the system prompts behind suitability and proposal generation, and review the logs. Most users never need it — your Knowledge Base and cover letter template already control the output. Only touch it if you know exactly what you want to change.