feat(proxy): run web search locally when upstream lacks it

[orangeboyChen]

What this does

Anthropic (web_search_20260209) and the Responses API (web_search_preview) both delegate web search to the provider. CodeBuddy has no equivalent, so requests carrying those tools either failed or silently lost the tool.

When a client declares a search tool and the new setting is on, the proxy swaps it for a plain web_search function, runs the query through a local search backend, and appends the results as a tool message. The model answers normally and the client never sees the substitution.

Settings

Adds 启用本地 WebSearch / Enable local web search to the console, described as performing WebSearch locally in Codebuddy2API. It renders as a switch rather than a text input.

The option only appears when SEARXNG_URL is set — hiding the label keeps it out of both the rendered form and the save payload, so an unconfigured deployment cannot enable a feature with nothing behind it. getActiveConfig re-checks per request, so a deployment that later drops the variable stops advertising the tool.

Pluggable backends

Search sits behind a WebSearchProvider interface (lib/server/search/) with SearXNG as the first implementation. Adding another backend means adding one provider file and one entry in resolveProvider — the proxy loop does not change. Configuration is env-only, since a search instance is deployment infrastructure rather than a per-request preference:

SEARXNG_URL, SEARXNG_API_KEY, SEARXNG_ENGINES,
SEARXNG_LANGUAGE, SEARXNG_MAX_RESULTS, SEARXNG_TIMEOUT_MS

Behavior notes

• Anthropic's dated server-tool types, Responses' web_search_preview, and a plain function named web_search are all recognised.
• The loop buffers upstream responses, so a streaming client gets a synthesized SSE stream once the loop finishes; usage is summed across iterations.
• Guards against runaway loops: iteration cap, and forced tool_choice is relaxed to auto after the first turn. If the budget is spent while the model still wants to search, the tool is withdrawn for one final call so the request terminates with an answer instead of an unresolved tool call.
• Turns that mix a search call with an unrelated one are handed back to the client, which resolves the other call and re-submits — the proxy can only produce a result for the search.
• Search failures become tool-result text rather than exceptions, so the model still sees the turn and can say the search failed.

Verification

lint, format:check, typecheck, build, and the full suite (344 tests, 23 files) pass. Coverage 94.2% statements / 87.9% branches against the 90/90/70 thresholds; patch branch coverage 93.0% against the 90% target.

[codecov]

Codecov Report

❌ Patch coverage is 95.77039% with 14 lines in your changes missing coverage. Please review.
✅ Project coverage is 95.01%. Comparing base (80bb2b8) to head (73e3e59).
⚠️ Report is 2 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #127      +/-   ##
==========================================
+ Coverage   94.95%   95.01%   +0.05%     
==========================================
  Files          22       26       +4     
  Lines        4620     4950     +330     
  Branches     1325     1432     +107     
==========================================
+ Hits         4387     4703     +316     
- Misses        233      247      +14     

Flag	Coverage Δ
unittests	95.01% <95.77%> (+0.05%)	⬆️

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