deepseek-harness/packages/web/web-search-deepseek

@deepseek-ai/dsh-web-search-deepseek

A DeepSeek-backed WebSearchProvider for the harness web capability seam (ctx.web). It calls DeepSeek's Anthropic-compatible Messages API (POST {baseURL}/messages) with the native web_search_20250305 server tool enabled, and maps the structured web_search_tool_result blocks DeepSeek returns into the seam's normalized WebSearchResult.

This is an implementation package: it registers a provider into ctx.web, it does not own the key and it does not register a model-facing tool. Like @deepseek-ai/dsh-llm-deepseek, it is a function/namespace plugin (inject: ['web']). The Anthropic wire shape is a provider-private detail — it does not make this provider depend on ctx.llm.

How it differs from a dedicated search endpoint

Exa and Perplexity expose dedicated search endpoints; DeepSeek does not. Instead this provider issues a full Messages model call carrying the web_search server tool, so one search costs a complete model turn in latency and tokens — heavier than a pure retrieval endpoint. DeepSeek runs the search server-side and returns structured web_search_tool_result blocks; the provider parses those blocks and never scrapes URLs out of model prose.

Strict mode: if the response carries no web_search_tool_result block (native search did not trigger), the provider throws WebError WEB_PROVIDER_ERROR rather than degrading to prose-scraping — honest and debuggable.

It reuses $DEEPSEEK_API_KEY (no new secret) but not $DEEPSEEK_BASE_URL: the search endpoint is the Anthropic-compatible base (https://api.deepseek.com/anthropic/v1), distinct from the chat-completions base (https://api.deepseek.com) the LLM adapter uses.

Config

Key	Default	Meaning
apiKey	$DEEPSEEK_API_KEY	DeepSeek API key. Empty/absent → provider status() reports missing-credential. Sent as both x-api-key and Authorization: Bearer (official vs Anthropic-compatible proxy).
baseURL	https://api.deepseek.com/anthropic/v1	Anthropic-compatible endpoint base; /messages is appended. Use a separate env var such as $DEEPSEEK_SEARCH_BASE_URL when overriding it; do not reuse $DEEPSEEK_BASE_URL, which belongs to the chat-completions LLM adapter. An unparseable value makes status() report misconfigured.
model	deepseek-v4-flash	Anthropic-format model name.
apiVersion	2023-06-01	anthropic-version header value.
maxTokens	4096	Positive-integer upper bound on generated tokens for the Messages request.
maxUses	5	Positive-integer maximum web_search server-tool uses per request.

- id: web-search-deepseek
  name: '@deepseek-ai/dsh-web-search-deepseek'
  config:
    apiKey: !!js process.env.DEEPSEEK_API_KEY
    baseURL: !!js process.env.DEEPSEEK_SEARCH_BASE_URL

Mapping

DeepSeek returns no provider-generated answer surface this provider trusts as content, so content is omitted. sources[] is built from the web_search_result items inside web_search_tool_result blocks: url ← url, title ← title, publishedAt ← page_age. The per-source snippet lives separately in a text block's citations[] (a cited_text keyed by url), so the provider joins the two — a result with no citation excerpt simply has no snippet. Results are deduped by url (a maxUses > 1 request can surface the same URL across searches). DeepSeek's web_search has no result-count knob (only maxUses), so maxResults is enforced by the seam (truncating sources[] and setting truncated). Provider failures surface as WebError WEB_PROVIDER_ERROR; an aborted request surfaces as WEB_ABORTED.

Known Limitations and Deferred Work

• One search costs a full Messages model turn — latency plus generated tokens, with up to maxUses server-side searches; DeepSeek exposes no dedicated retrieval endpoint.
• Over-returned sources still cost tokens — with no result-count knob on the wire, maxResults is enforced only post-hoc by seam truncation.
• Uncited results carry no snippet — a source gains one only when a text block citation (cited_text) matches its URL.
• Abort classification is error-shape-based — only a DOMException named AbortError maps to WEB_ABORTED; an abort carrying a custom reason (e.g. dsh-timeout's TimeoutReason) surfaces as WEB_PROVIDER_ERROR.