For example running

uv pip install numpy --verbose

with the following env variables set

UV_INDEX_URL=https://VssSessionToken@pkgs.dev.azure.com/project-name/_packaging/feed-name/pypi/simple/
UV_KEYRING_PROVIDER=subprocess

the first time fails but rerunning it again works correctly.

UV version 0.1.38 but has been an issue since support for this type of auth landed in #2976

Redacted log of non working execution

❯ uv pip install numpy --verbose
INFO Found a virtualenv through CONDA_PREFIX at: C:\Users\username\Miniconda3\envs\testuv
DEBUG Probing interpreter info for: \\?\C:\Users\username\Miniconda3\envs\testuv\python.exe
DEBUG Found Python 3.12.3 for: \\?\C:\Users\username\Miniconda3\envs\testuv\python.exe
DEBUG Using Python 3.12.3 environment at C:\Users\username\Miniconda3\envs\testuv\python.exe
DEBUG Trying to lock if free: C:\Users\username\AppData\Local\Temp\uv-53f2e5d017b1b435.lock
TRACE Caching credentials for https://VssSessionToken@pkgs.dev.azure.com/project-name/_packaging/feed-name/pypi/simple/
DEBUG Using registry request timeout of 30s
DEBUG Solving with target Python version 3.12.3
DEBUG Adding direct dependency: numpy*
INFO add_decision: root @ 0a0.dev0
TRACE Fetching metadata for numpy from https://VssSessionToken@pkgs.dev.azure.com/project-name/_packaging/feed-name/pypi/simple/numpy/
TRACE No cache entry exists for \\?\C:\Users\username\AppData\Local\uv\cache\simple-v7\cf3a2cb28c077ae5\numpy.rkyv
DEBUG No cache entry for: https://pkgs.dev.azure.com/project-name/_packaging/feed-name/pypi/simple/numpy/
TRACE Sending fresh GET request for https://pkgs.dev.azure.com/project-name/_packaging/feed-name/pypi/simple/numpy/
TRACE Handling request for https://VssSessionToken@pkgs.dev.azure.com/project-name/_packaging/feed-name/pypi/simple/numpy/
TRACE Request for https://VssSessionToken@pkgs.dev.azure.com/project-name/_packaging/feed-name/pypi/simple/numpy/ is missing a password, looking for credentials
TRACE No password in cache for realm VssSessionToken@https://pkgs.dev.azure.com
DEBUG Checking keyring for credentials for VssSessionToken@https://pkgs.dev.azure.com/project-name/_packaging/feed-name/pypi/simple/numpy/
TRACE Checking keyring for URL https://pkgs.dev.azure.com/project-name/_packaging/feed-name/pypi/simple/numpy/
DEBUG Found credentials in keyring for https://pkgs.dev.azure.com/project-name/_packaging/feed-name/pypi/simple/numpy/
TRACE checkout waiting for idle connection: ("https", pkgs.dev.azure.com)
DEBUG starting new connection: https://pkgs.dev.azure.com/
TRACE Http::connect; scheme=Some("https"), host=Some("pkgs.dev.azure.com"), port=None
DEBUG resolving host="pkgs.dev.azure.com"
DEBUG connecting to [2620:1ec:21::20]:443
DEBUG connected to [2620:1ec:21::20]:443
DEBUG No cached session for DnsName("pkgs.dev.azure.com")
DEBUG Not resuming any session
TRACE Sending ClientHello Message {
    ...
}
TRACE We got ServerHello ServerHelloPayload {
    ...
}
DEBUG ALPN protocol is Some(b"http/1.1")
DEBUG Using ciphersuite TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
DEBUG Server supports tickets
DEBUG Server may staple OCSP response
TRACE Server stapled OCSP response is [...]
DEBUG ECDHE curve is EcParameters { curve_type: NamedCurve, named_group: secp384r1 }
TRACE Server cert is CertificateChain([CertificateDer(...)])
DEBUG Server DNS name is DnsName("pkgs.dev.azure.com")
TRACE Unvalidated OCSP response: [...]
TRACE http1 handshake complete, spawning background dispatcher task
TRACE checkout dropped for ("https", pkgs.dev.azure.com)
TRACE put; add idle connection for ("https", pkgs.dev.azure.com)
DEBUG pooling idle connection for ("https", pkgs.dev.azure.com)
DEBUG Sending warning alert CloseNotify
error: HTTP status client error (401 Unauthorized) for url (https://pkgs.dev.azure.com/project-name/_packaging/feed-name/pypi/simple/numpy/)

Redacted log of working execution

❯ uv pip install numpy --verbose
INFO Found a virtualenv through CONDA_PREFIX at: C:\Users\username\Miniconda3\envs\testuv
DEBUG Cached interpreter info for Python 3.12.3, skipping probing: C:\Users\username\Miniconda3\envs\testuv\python.exe
DEBUG Using Python 3.12.3 environment at C:\Users\username\Miniconda3\envs\testuv\python.exe

DEBUG Trying to lock if free: C:\Users\username\AppData\Local\Temp\uv-53f2e5d017b1b435.lock
TRACE Caching credentials for https://VssSessionToken@pkgs.dev.azure.com/project-name/_packaging/feed-name/pypi/simple/
DEBUG Using registry request timeout of 30s
DEBUG Solving with target Python version 3.12.3
DEBUG Adding direct dependency: numpy*
INFO add_decision: root @ 0a0.dev0
TRACE Fetching metadata for numpy from https://VssSessionToken@pkgs.dev.azure.com/project-name/_packaging/feed-name/pypi/simple/numpy/
TRACE No cache entry exists for \\?\C:\Users\username\AppData\Local\uv\cache\simple-v7\cf3a2cb28c077ae5\numpy.rkyv
DEBUG No cache entry for: https://pkgs.dev.azure.com/project-name/_packaging/feed-name/pypi/simple/numpy/
TRACE Sending fresh GET request for https://pkgs.dev.azure.com/project-name/_packaging/feed-name/pypi/simple/numpy/
TRACE Handling request for https://VssSessionToken@pkgs.dev.azure.com/project-name/_packaging/feed-name/pypi/simple/numpy/
TRACE Request for https://VssSessionToken@pkgs.dev.azure.com/project-name/_packaging/feed-name/pypi/simple/numpy/ is missing a password, looking for credentials
TRACE No password in cache for realm VssSessionToken@https://pkgs.dev.azure.com
DEBUG Checking keyring for credentials for VssSessionToken@https://pkgs.dev.azure.com/project-name/_packaging/feed-name/pypi/simple/numpy/
TRACE Checking keyring for URL https://pkgs.dev.azure.com/project-name/_packaging/feed-name/pypi/simple/numpy/
DEBUG Found credentials in keyring for https://pkgs.dev.azure.com/project-name/_packaging/feed-name/pypi/simple/numpy/
TRACE checkout waiting for idle connection: ("https", pkgs.dev.azure.com)
DEBUG starting new connection: https://pkgs.dev.azure.com/
TRACE Http::connect; scheme=Some("https"), host=Some("pkgs.dev.azure.com"), port=None
DEBUG resolving host="pkgs.dev.azure.com"
DEBUG connecting to [2620:1ec:21::20]:443
DEBUG connected to [2620:1ec:21::20]:443
DEBUG No cached session for DnsName("pkgs.dev.azure.com")
DEBUG Not resuming any session
TRACE Sending ClientHello Message {
    ...
}
TRACE We got ServerHello ServerHelloPayload {
    ...
}
DEBUG ALPN protocol is Some(b"http/1.1")
DEBUG Using ciphersuite TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
DEBUG Server supports tickets
DEBUG Server may staple OCSP response
TRACE Server stapled OCSP response is [...]
DEBUG ECDHE curve is EcParameters { curve_type: NamedCurve, named_group: secp384r1 }
TRACE Server cert is CertificateChain([CertificateDer(...)])
DEBUG Server DNS name is DnsName("pkgs.dev.azure.com")
TRACE Unvalidated OCSP response: [...]
TRACE http1 handshake complete, spawning background dispatcher task
TRACE checkout dropped for ("https", pkgs.dev.azure.com)
TRACE Updating cached credentials for https://pkgs.dev.azure.com/project-name/_packaging/feed-name/pypi/simple/numpy/ to Credentials { username: Username(Some("VssSessionToken")), password: Some("...") }
TRACE cached request https://pkgs.dev.azure.com/project-name/_packaging/feed-name/pypi/simple/numpy/ is not storable because its response has a 'no-store' cache-control directive
TRACE attempting to decode a frame
TRACE frame decoded from buffer
...