feat(buzz-agent): expose provider-native web search tools

[potgieterdl]

Motivation

Buzz Desktop's default managed-agent runtime is buzz-agent. When it is configured with a direct Anthropic API key or an OpenRouter API key, provider-hosted web search is not exposed to the model.

Observed on Windows with the same research prompt:

• Anthropic Sonnet through Buzz Agent uses the local buzz-dev-mcp shell and curl.
• OpenRouter (tried with DeepSeek V4 Flash) through Buzz Agent does the same.
• Using native harness for Claude Code and Codex runtimes use their provider-native hosted web tools.

The distinction matters: buzz-acp is the relay/ACP bridge used with multiple runtimes; the missing capability is specifically in the built-in buzz-agent provider client. This may be intentional because hosted search has separate cost and policy implications, but users currently have no setting to allow it.

Current source behavior:

• Desktop defaults to buzz-agent and gives it buzz-dev-mcp: runtime catalog.
• Anthropic tools are serialized only from MCP ToolDef values; no Anthropic web_search_* server tool is added: anthropic_body.
• OpenRouter requests likewise expose only function tools; no openrouter:web_search server tool is added.
• The response parsers do not preserve hosted-search result/citation structures such as Anthropic server_tool_use / web_search_tool_result or OpenRouter url_citation annotations.

An API key authenticates the request but does not enable hosted search by itself; the client must declare the provider's server tool.

Proposed solution

Add an explicit per-agent setting such as Allow provider-hosted web search, preserving today's behavior when disabled.

When enabled, buzz-agent should:

• add the provider-specific hosted-search tool where supported (Anthropic web_search_*, OpenRouter openrouter:web_search, and OpenAI Responses web_search);
• let the model decide when to search;
• preserve citations and server-tool usage in the returned answer/history;
• handle provider-specific continuation states such as Anthropic pause_turn;
• expose a bounded maximum-use option and make additional search cost clear in the UI.

Unsupported providers/models should fail clearly or leave the tool unavailable rather than silently implying that an API key includes internet access.

Alternatives considered

• Use Claude Code or Codex instead of Buzz Agent. This works, but does not help users choosing Buzz Agent specifically for BYOK/provider flexibility.
• Use curl through the local shell. This depends on local network policy and loses provider-hosted search controls and structured citations.
• Add a web-search MCP server. Viable, but adds separate configuration and credentials for a capability already offered by several configured providers.
• For OpenRouter, use the deprecated :online model variant/web plugin. The recommended interface is now tools: [{"type":"openrouter:web_search"}].

Additional context

Provider documentation:

• Anthropic web search tool
• OpenRouter web search server tool

Closest related issues, but different scope:

• Docs: how to connect an external MCP server (Olostep) to Buzz agents? #4515 documents connecting an external web-search/scraping MCP server.
• desktop: no per-agent MCP injection channel for preset/custom ACP runtimes (omp, hermes) #4550 concerns MCP injection for preset/custom ACP runtimes.
• feat(examples): add a provider-agnostic Last30Days agent #4158 notes that evidence acquisition is an explicit backend capability for a proposed research agent.

No issue or PR specifically covering provider-native hosted search in buzz-agent was found after searching open and closed items for web_search, “native search”, openrouter:web_search, server_tool_use, and related terms.