Add web search capabilities

README.md

@@ -76,9 +76,38 @@ Each bot is one JSON file in `config/` (see `config/default.json` for the templa
 | `max_tokens`       | number | `1000`      | Maximum output tokens per reply. **Thinking tokens count toward this limit** — raise it (e.g. `4000`+) whenever `thinking` is `"adaptive"`, or a turn can spend the whole budget on reasoning and produce no text. |
 | `thinking`         | string | *(omitted)* | Reasoning mode: `"adaptive"` (the model decides when and how much to think) or `"disabled"`. Omit the key entirely to use the model's own API default. If the configured model doesn't support the chosen mode, the API rejects the request with a 400 — owners/admins see the raw error, regular users get the generic fallback. Check [Anthropic's model docs](https://platform.claude.com/docs/en/build-with-claude/adaptive-thinking) for per-model support. |
 | `thinking_display` | string | *(omitted)* | `"summarized"` or `"omitted"`. Only valid together with `"thinking": "adaptive"`. Controls whether the API returns a readable summary of the reasoning (logged, never sent to chat). Thinking is billed the same either way; when omitted, the API's per-model default applies. |
+| `web_search`       | object | *(omitted)* | Enables Anthropic's server-side web search (and, optionally, web fetch), sandboxed to a domain allowlist. Omit the key entirely to leave both tools off — an absent block sends byte-identical requests to before. See [Web search / fetch](#web-search--fetch) below. |
 
 Every reply logs one accounting line — `[usage] model=... in=... out=... thinking=... stop=...` — so thinking spend (billed even when its text is omitted) stays visible in `journalctl`/`docker compose logs`. A `stop=max_tokens` line is accompanied by an error-level warning that the reply was truncated.
 
+### Web search / fetch
+
+The `web_search` block wires in Anthropic's server-side `web_search` (and optionally `web_fetch`) tools, mirroring how `mcp_servers` wires in MCP toolsets: the engine provides the generic mechanism, and the per-bot config carries the policy. **No domains are hardcoded in the engine** — each profile declares its own allowlist. When the model decides a question needs current information, it runs a search server-side; results and any fetch targets are confined to the domains you list.
+
+```json
+"web_search": {
+  "allowed_domains": [
+    "example.com/help",
+    "docs.example.com"
+  ],
+  "max_uses": 3,
+  "fetch": true,
+  "max_content_tokens": 50000
+}
+```
+
+| Field                | Type     | Description |
+| -------------------- | -------- | ----------- |
+| `allowed_domains`    | string[] | Search results and fetch targets are restricted to these. Each entry is a **domain with an optional path prefix and no scheme** — `example.com` or `example.com/help`. Mutually exclusive with `blocked_domains`. |
+| `blocked_domains`    | string[] | Excludes these domains instead of allowlisting. Mutually exclusive with `allowed_domains` (setting both fails validation at boot, since the API 400s). |
+| `max_uses`           | number   | Caps how many searches the model may run per turn. Omit for no cap. |
+| `fetch`              | bool     | Also enable `web_fetch`, which pulls full page content for URLs already surfaced by a search or pasted by the user (it cannot fetch model-invented URLs). Shares the same allow/block list. Citations are always on when fetch is enabled, so fetched passages are sourceable. |
+| `max_content_tokens` | number   | Caps the tokens a single `web_fetch` may pull into context. Only meaningful with `fetch: true`. |
+
+The allowlist is a **hard, server-side sandbox**, not a prompt request — off-list results are dropped and an off-list fetch target returns `url_not_allowed`, which is the exfiltration mitigation Anthropic recommends for bots processing untrusted input. Keep the list tight. Note that `web_fetch` cannot read JavaScript-rendered pages, so for dynamic sites the search snippet (plus citations) is the reliable signal and a full fetch is a bonus, not a dependency.
+
+Web search is **not free** — Anthropic bills per search (plus the tokens the results add) — so scope the allowlist and `max_uses` deliberately, and lean on a prompt that tells the bot to search only when a question actually turns on current or authoritative information. Search activity logs as `[web] ...` lines, and long multi-search turns are handled transparently (the engine follows Anthropic's `pause_turn` continuations up to a small cap, so a slow search doesn't truncate the reply).
+
 > [!TIP]
 > For deep request/response debugging, the Anthropic Go SDK ships `option.WithDebugLog(...)` (dumps full HTTP bodies with auth headers redacted). It is not wired into the bot — dev-only, add it temporarily to the client constructor if you ever need wire-level traces.