[FEATURE]: Add TinyFish BYOK web search and fetch #29927

Feature hasn't been suggested before.

• I have verified this feature I'm about to request hasn't been suggested before.

Problem

websearch is currently only available through the OpenCode provider or specific hosted search flags like Exa. This makes web access feel tied to OpenCode Zen / hosted infrastructure, even though users could bring their own web API key.

Request

Add first-class TinyFish BYOK support for web search and fetch.

The ideal UX is a /web command where a user can paste their TinyFish API key. Once connected, OpenCode should enable the existing websearch and webfetch tools using TinyFish.

Why TinyFish

TinyFish Search and Fetch are free on every plan and use 0 credits. The free plan is rate-limited, but users can still get an API key and use Search/Fetch without paying per request or consuming credits.

Search returns structured web results for agents. Fetch renders pages in a real browser and returns clean extracted content, including JavaScript-heavy pages.

Why this belongs in OpenCode

Web access is a core agent capability. Users on free/non-Zen setups should have a built-in way to use free Search/Fetch through their own TinyFish key instead of wiring MCP/custom tools manually.

This keeps the capability discoverable and consistent with the existing websearch / webfetch tool UX.

Proposed behavior

• /web prompts for a TinyFish API key
• OpenCode stores it using existing auth storage
• websearch becomes available when TinyFish is configured
• webfetch routes through TinyFish when configured
• Existing OpenCode/Exa/Parallel behavior stays unchanged

Related but distinct from #10704, which focuses on provider-hosted search. This request is specifically for TinyFish BYOK search/fetch. Also related to #29752 because generic websearch provider config could be part of the implementation direction.

I’m happy to open a PR for this if the maintainers are open to the direction.