Registry Forwarding Behavior

info

The English user guide is currently in beta preview. Most of the documents have been automatically translated from the Japanese version. Should you find any inaccuracies, please reach out to Flatt Security.

This page describes how Takumi Guard currently forwards requests to each registry and what it responds with. Use it, for example, when you configure a proxy or firewall that restricts outbound traffic.

Subject to change

The behavior described here is what Takumi Guard does today. Changes are announced in the release notes, except where an urgent security fix requires changing it without notice.

Traffic Flow

Takumi Guard does not relay package artifacts. Metadata goes through Takumi Guard, but for an artifact request it returns an HTTP 302 and the client connects directly to the public host to download it. See Package Blocking for the full flow.

Destinations

On a public registry host, the paths listed below sit alongside paths that receive no traffic because Takumi Guard handles them. The two cannot be told apart by host name.

Takumi Guard

Takumi Guard is served on a separate host per ecosystem, and traffic goes to the host for the ecosystem you use.

Host	Ecosystem
npm.flatt.tech	npm
pypi.flatt.tech	PyPI
rubygems.flatt.tech	RubyGems
golang.flatt.tech	Go
packagist.flatt.tech	Packagist

Public Registries (Artifact Download)

Package artifacts are downloaded directly from the host Takumi Guard redirects to.

Host	Paths used	Purpose
registry.npmjs.org	GET /{package}/-/*.tgz GET /@{scope}/{package}/-/*.tgz	npm package artifact
files.pythonhosted.org	GET /packages/**	wheel and sdist artifacts
rubygems.org	GET /gems/*.gem GET /quick/Marshal.4.8/** GET /specs.4.8.gz GET /latest_specs.4.8.gz GET /prerelease_specs.4.8.gz	gem artifact and index
proxy.golang.org	GET /**/@v/*.zip	Go module artifact

For RubyGems, Bundler falls back to the legacy index (/specs.4.8.gz and /quick/Marshal.4.8/) when the Compact Index is unavailable. Takumi Guard redirects those requests too.

For Composer, the artifact host is whatever the package metadata names as its distribution source. A package hosted on GitHub redirects to api.github.com and from there to codeload.github.com. If a dependency is distributed from somewhere else, traffic goes to that host instead. dist.url in https://packagist.flatt.tech/p2/{vendor}/{package}.json shows the source for each dependency.

Traffic Other Than Artifact Redirects

The following traffic also occurs, although it is not an artifact redirect.

Go Checksum Database

Where checksum verification is enabled, the Go toolchain queries the checksum database before fetching a module. Takumi Guard does not proxy this verification, so the client connects directly to sum.golang.org (all paths).

URLs by Ecosystem

The traffic that occurs per ecosystem.

npm

Shared across npm, pnpm, yarn, and bun.

• GET https://npm.flatt.tech/{package}
  • Purpose: Fetch metadata
  • Destination: Takumi Guard
  • Status: 200 / 304
• POST https://npm.flatt.tech/-/npm/v1/security/advisories/bulk
  • Purpose: Query advisories (npm only)
  • Destination: Takumi Guard
  • Status: 200
• POST https://npm.flatt.tech/-/npm/v1/security/audits, /-/npm/v1/security/audits/quick
  • Purpose: Query advisories (pnpm and yarn)
  • Destination: Takumi Guard
  • Status: 200
• GET https://npm.flatt.tech/-/npm/v1/keys, GET https://npm.flatt.tech/-/npm/v1/attestations/{path}
  • Purpose: Verify signing keys and provenance
  • Destination: Takumi Guard
  • Status: 200
• GET https://npm.flatt.tech/-/v1/search
  • Purpose: Search for packages (npm search)
  • Destination: Takumi Guard
  • Status: 200
• GET https://npm.flatt.tech/{package}/-/{file}.tgz
  • Purpose: Request the artifact
  • Destination: Takumi Guard
  • Status: 302 (redirects to registry.npmjs.org)
• GET https://registry.npmjs.org/{package}/-/{file}.tgz
  • Purpose: Download the artifact
  • Destination: Public registry
  • Status: 200

For scoped packages the path is /@{scope}/{package}. yarn, pnpm and bun URL-encode the slash when fetching metadata, sending /@{scope}%2f{package}. %2F is handled the same way, so a path rule needs to match either case.

Using bun

On a first install with no lockfile, the artifact is requested from registry.npmjs.org directly rather than through Takumi Guard. Metadata is still fetched through Takumi Guard, and the hosts involved are the same as above.

PyPI

Shared across pip and uv.

• GET https://pypi.flatt.tech/simple/{project}/
  • Purpose: Fetch metadata
  • Destination: Takumi Guard
  • Status: 200
• GET https://pypi.flatt.tech/files/packages/{hash-path}/{file}
  • Purpose: Request the artifact
  • Destination: Takumi Guard
  • Status: 302 (redirects to files.pythonhosted.org)
• GET https://files.pythonhosted.org/packages/{hash-path}/{file}
  • Purpose: Download the artifact
  • Destination: Public distribution host
  • Status: 200

Using Poetry

A project with the per-repository setup goes through pypi.flatt.tech just like pip and uv. Without it, metadata is not fetched through Takumi Guard and the following requests occur instead.

See poetry in the quickstart for how to configure it.

• GET https://pypi.org/simple/{project}/
  • Purpose: Fetch metadata
  • Destination: Public registry
  • Status: 200
• GET https://pypi.org/pypi/{project}/{version}/json
  • Purpose: Fetch metadata
  • Destination: Public registry
  • Status: 200

RubyGems

Traffic from Bundler.

• GET https://rubygems.flatt.tech/versions
  • Purpose: Fetch the index
  • Destination: Takumi Guard
  • Status: 200 / 206 / 304 (206 for an incremental fetch)
• GET https://rubygems.flatt.tech/info/{gem}
  • Purpose: Fetch metadata
  • Destination: Takumi Guard
  • Status: 200
• GET https://rubygems.flatt.tech/gems/{gem}-{version}.gem
  • Purpose: Request the artifact
  • Destination: Takumi Guard
  • Status: 302 (redirects to rubygems.org)
• GET https://rubygems.org/gems/{gem}-{version}.gem
  • Purpose: Download the artifact
  • Destination: Public registry
  • Status: 200
• GET https://rubygems.flatt.tech/specs.4.8.gz, /latest_specs.4.8.gz, /prerelease_specs.4.8.gz, /quick/Marshal.4.8/{gem}-{version}.gemspec.rz
  • Purpose: Fetch the legacy index, when the Compact Index is unavailable
  • Destination: Takumi Guard
  • Status: 302 (redirects to the same path on rubygems.org)
• GET https://rubygems.org/specs.4.8.gz and the other redirect targets above
  • Purpose: Download the legacy index
  • Destination: Public registry
  • Status: 200

Go

Traffic from the Go toolchain.

• GET https://golang.flatt.tech/sumdb/sum.golang.org/supported
  • Purpose: Check whether the checksum database can be queried through the proxy
  • Destination: Takumi Guard
  • Status: 404 (expected response; the client connects to sum.golang.org directly)
• GET https://golang.flatt.tech/{module}/@v/list
  • Purpose: List versions
  • Destination: Takumi Guard
  • Status: passes the upstream status through
• GET https://golang.flatt.tech/{module}/@latest
  • Purpose: Resolve the latest version (go get module@latest and similar)
  • Destination: Takumi Guard
  • Status: passes the upstream status through
• GET https://golang.flatt.tech/{module}/@v/{version}.info
  • Purpose: Fetch metadata
  • Destination: Takumi Guard
  • Status: passes the upstream status through
• GET https://golang.flatt.tech/{module}/@v/{version}.mod
  • Purpose: Fetch metadata
  • Destination: Takumi Guard
  • Status: passes the upstream status through
• GET https://golang.flatt.tech/{module}/@v/{version}.zip
  • Purpose: Request the artifact
  • Destination: Takumi Guard
  • Status: 302 (redirects to proxy.golang.org)
• GET https://proxy.golang.org/{module}/@v/{version}.zip
  • Purpose: Download the artifact
  • Destination: Public proxy
  • Status: 200
• GET https://sum.golang.org/lookup/{module}@{version}
  • Purpose: Verify checksums
  • Destination: Checksum database
  • Status: 200
• GET https://sum.golang.org/tile/{tile-path}
  • Purpose: Verify checksums
  • Destination: Checksum database
  • Status: 200

Packagist

Traffic from Composer.

• GET https://packagist.flatt.tech/packages.json
  • Purpose: Fetch the repository definition
  • Destination: Takumi Guard
  • Status: 200 / 304
• GET https://packagist.flatt.tech/p2/{vendor}/{package}.json, /p2/{vendor}/{package}~dev.json
  • Purpose: Fetch metadata (Composer 2 fetches both)
  • Destination: Takumi Guard
  • Status: 200 / 304
• POST https://packagist.flatt.tech/api/filter
  • Purpose: Query the packages to install (composer install and composer audit)
  • Destination: Takumi Guard
  • Status: 200
• GET https://packagist.flatt.tech/dist/{vendor}/{package}/{version}/{reference}.{type}
  • Purpose: Request the artifact
  • Destination: Takumi Guard
  • Status: 302 (redirects to the distribution source named in the metadata; api.github.com for a package hosted on GitHub)
• GET https://api.github.com/repos/{owner}/{repo}/zipball/{reference}
  • Purpose: Request the artifact
  • Destination: GitHub
  • Status: 302 (redirects to codeload.github.com)
• GET https://codeload.github.com/{owner}/{repo}/legacy.zip/{reference}
  • Purpose: Download the artifact
  • Destination: GitHub
  • Status: 200
• POST https://packagist.org/downloads/
  • Purpose: Report install statistics (does not affect whether an install succeeds)
  • Destination: Public site
  • Status: 201

Versions verified

This page reflects the following versions, as of September 2026.

• npm v10.8 / v11.19 / v12.0, pnpm v10.33 / v11.25, yarn v1.22 / v4.12 / v4.18, bun v1.4
• pip v22.0 / v26.2, uv v0.12, Poetry v2.4
• Bundler v2.5 / v4.0
• Go v1.23 / v1.27
• Composer v2.10

Reference

Configuring a Proxy or Firewall

The forwarding uses the following destinations besides Takumi Guard. Each is used to download a package artifact or to verify checksums, and installs do not complete if they cannot be reached.

Host	Paths
registry.npmjs.org	/{package}/-/*.tgz /@{scope}/{package}/-/*.tgz
files.pythonhosted.org	/packages/**
rubygems.org	/gems/*.gem /quick/Marshal.4.8/** /specs.4.8.gz /latest_specs.4.8.gz /prerelease_specs.4.8.gz
proxy.golang.org	/**/@v/*.zip
sum.golang.org	All paths

Using Composer

With Composer, the distribution source differs per dependency. You therefore need to check dist.url in https://packagist.flatt.tech/p2/{vendor}/{package}.json and work out the destinations for each dependency.

For a package published on GitHub, for example, the destinations are as follows.

Host	Paths
api.github.com	/repos/*/*/zipball/*
codeload.github.com	/*/*/legacy.zip/*

If a dependency is distributed from somewhere other than GitHub, traffic goes to that source as well.

Private Packages (npm, PyPI, RubyGems, Packagist)

Where a separate registry is configured, the client connects to that registry directly. How it is configured differs per ecosystem.

• Private packages on npm (a registry per scope)
• Private packages on PyPI (an extra index URL)
• Private gems on RubyGems (a source block in the Gemfile)
• Private packages on Packagist (a repository declaration)

Private Modules (Go)

A module matching GOPRIVATE is fetched with git from the host in its module path, going through neither Takumi Guard nor the checksum database. See Using with Private Modules.

Hosts That Receive No Traffic

With Takumi Guard configured, no traffic reaches the following hosts.

Host	Reason
repo.packagist.org	Takumi Guard fetches the metadata on its own side
pypi.org	pip, uv, and a Poetry project with the per-repository setup do not contact it
index.rubygems.org	Bundler does not contact it

packagist.org receives only the install statistics report. An install completes even when that request does not get through.

Support scope

If blocking any of this traffic causes a problem, we will help investigate as far as we can, but it may fall outside the scope of support.