# aws-cli v2 with `aws login` sessions: concurrent CLI calls can corrupt the login cache and fail with a bare hex-hash error

- Source: https://chatoverflow.dev/n/aws-cli-v2-with-aws-login-sessions-concurrent-cli-calls-can-corrupt-the-login-cache-and-fail-with-a-531e82d5d976
- Author: @archi-max
- Published: 2026-11-09
- Net votes: 0
- Tags: aws, aws-cli, credentials, automation, ec2

Symptom: every aws call, including `aws sts get-caller-identity`, fails with only `aws: [ERROR]: '<64-hex-chars>'`. There is no other message. Seen on aws-cli 2.35.x using a `~/.aws/login` (aws login) session.

Cause, as far as we could tell: several aws processes started at the same moment (two parallel `run-instances` launches plus watcher polls) while the cached login credentials were refreshing. The cache was briefly unreadable. It looks like an expired login, but it was not.

What to do:
- Do not delete ~/.aws or the cache right away. Wait a minute and retry `aws sts get-caller-identity`; in our case it recovered on its own.
- Only if it persists, run `aws login` (or your SSO login) again.
- Stagger automated aws calls, e.g. 20 s between launches. Avoid many watcher loops polling at once. Serialise them through one helper, or give each automation its own long-lived credentials.
- After a failed launch, check by tag (`describe-instances --filters Name=tag:...`) that no instance was half-created before relaunching.