[BUG] Claude Code Web default environment prevents fetching of github release artifacts

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

When I start a Claude Code Web session in the default environment, it has trouble fetching release artifacts from GitHub. This is problematic because it prevents uv from installing required Python versions for projects that need a Python version that's not preinstalled in the default CCWeb environment.

uv says the following when trying to download a Python version:

error: Failed to install cpython-3.14.2-linux-x86_64-gnu
  Caused by: Request failed after 3 retries
  Caused by: Failed to download https://github.com/astral-sh/python-build-standalone/...
  Caused by: tunnel error: unsuccessful

while directing CC to fetch the url (https://github.com/astral-sh/python-build-standalone/releases/download/20260114/cpython-3.14.2%2B20260114-x86_64-unknown-linux-gnu-install_only_stripped.tar.gz) directly yields:

Exit code 56
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed

  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0HTTP/1.1 200 OK
date: Tue, 20 Jan 2026 14:51:34 GMT
server: envoy

HTTP/2 302 
date: Tue, 20 Jan 2026 14:51:16 GMT
content-type: text/html; charset=utf-8
content-length: 0
vary: X-PJAX, X-PJAX-Container, Turbo-Visit, Turbo-Frame, X-Requested-With,Accept-Encoding, Accept, X-Requested-With
location: https://release-assets.githubusercontent.com/github-production-release-asset/162334160/2db4a11b-0728-4a6f-83fc-a39e07cd29b8?sp=r&sv=2018-11-09&sr=b&spr=https&se=2026-01-20T15%3A25%3A59Z&rscd=attachment%3B+filename%3Dcpython-3.14.2%2B20260114-x86_64-unknown-linux-gnu-install_only_stripped.tar.gz&rsct=application%2Foctet-stream&skoid=96c2d410-5711-43a1-aedd-ab1947aa7ab0&sktid=398a6654-997b-47e9-b12b-9515b896b4de&skt=2026-01-20T14%3A25%3A29Z&ske=2026-01-20T15%3A25%3A59Z&sks=b&skv=2018-11-09&sig=b2EIqhKA87RKHeAl9u0f5kW8xlAl4SZoQeI7f9LxjEA%3D&jwt=eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJpc3MiOiJnaXRodWIuY29tIiwiYXVkIjoicmVsZWFzZS1hc3NldHMuZ2l0aHVidXNlcmNvbnRlbnQuY29tIiwia2V5Ijoia2V5MSIsImV4cCI6MTc2ODkyMjQ3NiwibmJmIjoxNzY4OTIwNjc2LCJwYXRoIjoicmVsZWFzZWFzc2V0cHJvZHVjdGlvbi5ibG9iLmNvcmUud2luZG93cy5uZXQifQ.5-2ElaIf-A0BHc8wYgj2MXDtKdzqD5coL_ByYnXZfEo&response-content-disposition=attachment%3B%20filename%3Dcpython-3.14.2%2B20260114-x86_64-unknown-linux-gnu-install_only_stripped.tar.gz&response-content-type=application%2Foctet-stream
cache-control: no-cache
######## A bunch of security headers omitted here ########
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0

  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
curl: (56) CONNECT tunnel failed, response 403

server: github.com
x-github-request-id: 1000:38A595:15C725:1F433F:696F9677

HTTP/1.1 403 Forbidden
x-deny-reason: host_not_allowed
content-length: 16
content-type: text/plain
date: Tue, 20 Jan 2026 14:51:34 GMT
server: envoy
connection: close

What Should Happen?

The default network profile should allow uv to download Python versions.

Error Messages/Logs

Steps to Reproduce

Create a new CCWeb session, asking Claude to:

Try to fetch https://github.com/astral-sh/python-build-standalone/releases/download/20260114/cpython-3.14.2%2B20260114-x86_64-unknown-linux-gnu-install_only_stripped.tar.gz

Or, alternatively, to:

Use uv to install Python 3.14 (`uv python install 3.14`)

Claude Model

None

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

N/A

Platform

Anthropic API

Operating System

Other

Terminal/Shell

Non-interactive/CI environment

Additional Information

_No response_

    "@react-icons/all-files": "https://github.com/react-icons/react-icons/releases/download/v5.5.0/react-icons-all-files-5.5.0.tgz",

Exit code 1
Scope: all 5 workspace projects
Lockfile is up to date, resolution step is skipped
Progress: resolved 1, reused 0, downloaded 0, added 0
Packages: +2345
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Progress: resolved 2345, reused 0, downloaded 0, added 0
Packages are hard linked from the content-addressable store to the virtual store.
  Content-addressable store is at: /root/.local/share/pnpm/store/v3
  Virtual store is at:             node_modules/.pnpm
Progress: resolved 2345, reused 15, downloaded 30, added 30
 ERR_PNPM_FETCH_403  GET https://github.com/react-icons/react-icons/releases/download/v5.5.0/react-icons-all-files-5.5.0.tgz: Forbidden - 403

No authorization header was set for the request.

No authorization settings were found in the configs.
Try to log in to the registry by running "pnpm login"
or add the auth tokens manually to the ~/.npmrc file.

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed

  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
curl: (22) The requested URL returned error: 403
error: failed to download ruby-3.4.7.tar.gz

BUILD FAILED (Ubuntu 24.04 on x86_64 using ruby-build 20260121