``provider_tools`` reached the effective provider only for the OpenAI preset,
so a DeepSeek ``provider_tools`` in TOML was dropped on the way — and the preset
defaulted to none, leaving search unavailable for every convention.
DeepSeek now defaults to ``[{type="web_search"}]`` like OpenAI does (``[]``
turns it off) and its list reaches the agent: the Anthropic convention runs the
hosted search inside the response, the Responses and chat conventions get the
local ``web_search`` tool (see ``config.routing.local_web_search``).
Only DeepSeek's Anthropic-compatible surface runs a hosted ``web_search``: the
Responses and chat-completions surfaces answer "I can't browse the web" with
``{"type": "web_search"}`` and with the server-tool shape alike, so a DeepSeek
provider that talks them had no search at all.
``config.routing.local_web_search`` decides per provider: a DeepSeek provider
whose ``provider_tools`` ask for ``web_search`` and whose convention is not
``anthropic`` gets the local tool (``tools/net/search.py``), which asks the
search-capable endpoint behind the scenes and hands the model one ``title —
url`` line per hit — read a page with ``fetch``, the bodies stay server-side.
DeepSeek's preset asks for no hosted tool by default, so this stays opt-in.
NCBM