dsh-crw

fastCRW-backed web_search and web_fetch for DeepSeek Harness.

The harness treats web access as a capability seam (ctx.web) with pluggable providers. This package registers two of them under the id crw, so the model keeps the exact same web_search / web_fetch tools and only the backend changes.

Why

The base composition ships web_search on, and web_fetch off. Its own config says why:

> Fetch stays disabled and no fetch provider is mounted: that provider defers > SSRF protection and the model would choose the request target.

That is a fair call. The in-box HTTP fetch provider runs fetch() in the harness process, and its README names the gap outright: no blocking of private, loopback, link-local or multicast destinations, no DNS-resolve-then-validate. A model that picks http://169.254.169.254/ gets your cloud metadata endpoint.

fastCRW resolves and validates the target server-side and refuses private ranges, so the harness process never opens a connection the model chose. That is what makes turning fetch on reasonable, and it is why fetch: true lives in this bundle rather than upstream.

The second reason is that plain HTTP is not how the open web reads any more:

fastCRW escalates per page from plain HTTP through its browser tiers only when a page needs one, so the common case stays fast and the hard case still answers. Not every wall falls: an interactive Cloudflare challenge still wins sometimes.

Install

export CRW_API_KEY=...          # fastcrw.com, 500 free credits, no card
dsh plugin --profile default add dsh-crw
dsh --profile default

Get a key at fastcrw.com. The free tier is a one-time 500 credits and needs no card; one page is one credit.

To install straight from this repo instead, pin a commit and allow the build. A git install fetches sources, so pnpm has to run this package's prepare script to produce lib/, and pnpm 10+ requires you to say so explicitly:

# $DSH_HOME/profiles/<name>/pnpm-workspace.yaml
allowBuilds:
  dsh-crw: true

dsh plugin --profile default add github:us/dsh-crw#<sha>

That allowance runs this package's build on your machine at install time, so pin the commit rather than tracking the branch.

Verify the layer before booting:

dsh --profile default --dump-config    # shows a "# == dsh-crw" layer

What the bundle does

The shipped cordis.patch.yml applies three changes over @deepseek-ai/dsh-base:

• points web.searchProvider and web.fetchProvider at crw
• turns on tool-web's fetch and raises both timeouts, since a page behind a

JS or anti-bot wall escalates through browser tiers before it answers

• mounts this plugin, reading $CRW_API_KEY

The base layer's own DeepSeek search provider stays mounted, so switching search back is one line in your profile's cordis.patch.yml:

- id: web
  config:
    searchProvider: deepseek-official
    fetchProvider: crw

Config

- id: crw
  name: dsh-crw
  config:
    apiKey: !!js process.env.CRW_API_KEY
    answer: false

Self-hosting

fastCRW is AGPL-3.0 and the engine is one binary, so the whole web layer can stay on your own machine:

crw serve

- id: crw
  name: dsh-crw
  config:
    baseURL: http://127.0.0.1:3002

A self-hosted endpoint takes no credential, so apiKey may be empty. The provider only insists on a key when it is pointed at the cloud endpoint.

Mapping notes

• Search. POST /v1/search. Each result maps to a WebSearchSource: url,

title, and snippet from the result's snippet or, failing that, its description. A result without a URL is dropped rather than given an invented one. With answer on, the synthesized answer becomes the seam's content. The seam owns the final maxResults truncation.

• Fetch. POST /v1/scrape with formats: ['markdown']. The body kind is

text, not html: fastCRW already returns markdown, and html would send it back through the tool's turndown pass to convert converted output.

• Non-2xx targets. fastCRW reports a 404 target as success: false while

still returning what it got. The seam's contract is the other way round, so an envelope carrying a status code is always a result. A WebError is reserved for failing to retrieve the resource at all: a rejected URL, a bad key, an exhausted balance.

• No renderer hint is sent. fastCRW's escalation ladder decides per page

whether plain HTTP is enough.

Development

bun install
bun test
bun run build

License

MIT.