deepseek-harness/packages/web/web-fetch-local

@deepseek-ai/dsh-web-fetch-local

An anonymous public HTTP(S) WebFetchProvider for the harness web capability seam (ctx.web). It retrieves a concrete URL and returns a status code plus bounded decoded content.

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. It is a function/namespace plugin (inject: ['web']).

Responsibility split

The provider owns safe resource retrieval: URL validation, HTTP transport, redirect policy, a resource-backstop timeout, abort propagation, byte caps, charset decoding, content-type classification, and binary rejection. @deepseek-ai/dsh-tool-web owns presentation (HTML→markdown, truncation formatting). A non-2xx HTTP response is a result (status code + decoded body), not an error; WebError is reserved for failures to safely retrieve or represent the resource.

The provider's timeoutMs/maxTimeoutMs is a resource backstop for direct ctx.web.fetch() callers and misconfigured deployments — it is NOT the model-facing tool-call budget. The tool-call budget for web_fetch is deployment policy owned by @deepseek-ai/dsh-timeout-policy, which arms a per-call deadline on exec.signal. A shipped web-tool deployment sets the provider backstop above the tool-timeout budget, so the tool-call policy normally wins for model calls (returning TOOL_TIMEOUT); when the outer deadline signal reaches this provider first, it classifies as WEB_ABORTED and the outer wrapper replaces the result with TOOL_TIMEOUT. The provider's own WEB_FETCH_TIMEOUT only fires for a direct seam caller whose own budget elapsed.

Transport hygiene

• Accepts only http: and https: URLs; rejects credentials in URLs (WEB_BLOCKED_URL) and over-long/malformed URLs (WEB_INVALID_URL).
• Enforces a max URL length, response byte cap (WEB_FETCH_TOO_LARGE), decoded body character cap, timeout (WEB_FETCH_TIMEOUT), and redirect hop cap.
• Propagates the caller's abort signal (WEB_ABORTED) into the network request and the streaming read.
• Follows only same-origin redirects; a cross-origin redirect fails with WEB_REDIRECT_BLOCKED, requiring a fresh tool call (the model of Claude Code's WebFetch).
• Sends an explicit product User-Agent, never a browser disguise.
• Rejects unsupported (e.g. binary) content types with WEB_UNSUPPORTED_CONTENT_TYPE.

Config

Key	Default	Meaning
maxUrlLength	2048	Maximum accepted request URL length.
maxResponseBytes	5_000_000	Maximum response body size in bytes.
maxBodyChars	100_000	Maximum decoded body length in characters.
timeoutMs	30_000	Default fetch timeout — a resource backstop for direct ctx.web.fetch() callers, not the model-facing tool-call budget (that is dsh-timeout-policy).
maxTimeoutMs	120_000	Upper bound for a per-request timeout override (direct callers).
maxRedirects	5	Maximum same-origin redirect hops (0 follows none).
userAgent	deepseek-harness/…	User-Agent header.

The numeric limits are validated at plugin construction: every cap except maxRedirects must be a positive finite number, and maxRedirects must be a non-negative integer. An invalid value throws rather than silently constructing a provider with nonsensical limits.

Security note

SSRF / private-network protection (blocking private, loopback, link-local, multicast, and otherwise non-public destinations, with DNS-resolve-then-validate and per-hop re-validation) is deferred — see the web capability seam RFC. Until it lands, this provider is an SSRF primitive and must not be enabled in a deployment that can reach sensitive internal network targets.