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

An anonymous public HTTP(S) `WebFetchProvider` for the harness [web capability seam](../web/README.md) (`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`](../../timeout/timeout-policy/README.md), 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](../../../docs/rfc/implemented/architecture/2026-06-24-web-capability-seam.md). Until it lands, this provider is an SSRF primitive and **must not be enabled** in a deployment that can reach sensitive internal network targets.