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.

Model Experience

Context surface	What the model sees	Token effect
Web fetch result, indirectly	Through `dsh-tool-web`, the conversation model sees the final URL, HTTP status, and decoded text or markdown-shaped HTML, or a structured retrieval error. Redirects, headers, and transport mechanics are not added to context unless reflected in an error.	Zero direct tokens. `maxBodyChars` bounds decoded result length before the tool records it; the retained result is resent until compaction.

Known Limitations and Deferred Work

SSRF / private-network protection is deferred — no blocking of private, loopback, link-local, multicast, or otherwise non-public destinations, no DNS-resolve-then-validate, no per-hop re-validation (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.
Only textual content decodes — html/xhtml and text/*-plus-JSON/XML families; a missing Content-Type or any binary type throws WEB_UNSUPPORTED_CONTENT_TYPE, and text-extractable PDF decoding is named deferred work.
Charset comes only from the Content-Type header (UTF-8 default) — an HTML <meta charset> declaration is ignored, and a declared-but-unrecognized charset label throws rather than falling back.