[brainsparker]

I work at You.com. This follows up on #534 and @xhd0728's note there: Tavily stays the default, and this adds youcom as one more opt-in websearch_backend, keyed only (YDC_API_KEY). It is modeled on the Serply backend from #531.

What changes

• servers/retriever/src/websearch_backends/youcom_backend.py: new YoucomWebSearchBackend. It sends POST https://ydc-index.io/v1/search with X-API-Key, maps results.web[] to passages (snippets joined, description as fallback, empty results dropped), and trims to top_k.
• Errors: 401/403 raise ToolError (bad key), 402 raises ToolError (out of credits), 429 retries and waits for Retry-After when the server sends it, otherwise the usual exponential backoff. Other failures retry like the other backends and return [] at the end.
• websearch_backends/__init__.py: registers youcom.
• servers/retriever/parameter.yaml: adds youcom to the options comment and a youcom block with the same fields Serply uses. websearch_backend stays tavily.
• .env.dev: adds YDC_API_KEY=. AGENTS.md: lists youcom among the backends.
• The User-Agent is youdotcom-integration/openbmb-ultrarag, so we can see on our side how much traffic comes from UltraRAG. Happy to change it to UltraRAG like Serply if you prefer.

To use it: set YDC_API_KEY and websearch_backend: youcom. Keys come from https://you.com/platform?utm_source=openbmb-ultrarag&utm_medium=oss_integration&utm_campaign=2026-10-oss-integrations&utm_content=pr_body

Tests

tests/servers/retriever/test_youcom_websearch_backend.py runs against a local aiohttp server, the same way the Serply test does. It covers:

• the request body, key and User-Agent;
• snippet and description handling, top_k, and empty results;
• the env var key;
• a missing key;
• 401/403/402 failing at once with no retry;
• 429 honoring Retry-After;
• 429 running out of retries.

$ pytest -q tests/servers/retriever/test_youcom_websearch_backend.py tests/servers/retriever/test_serply_websearch_backend.py
10 passed

ruff format is clean. ruff check reports the same rule groups it already reports on serply_backend.py (typing aliases, broad except). I kept the file's style matching the other backends instead of changing it.

On keyless mode: I left it out because #534 said keyed-only was fine. If you want it later, it would be a small follow-up.