The rules for secrets, and the same names filled in from a different place on your laptop, in CI and in production.
The rules for secrets
Never in code. Not in a constant, not in a notebook cell, not in a comment.Never in Git. Not even in a "private" repository, and not "just for a minute".Never in a log, an error message, a URL or a screenshot. One key per environment and per purpose. A leaked test key then cannot touch production.Least privilege and spending limits. Give each key only the permissions it needs, and set a monthly spending cap at the provider.Rotate on a schedule, and immediately when in doubt.
Treat any leaked key as compromised
If a key is ever committed, pasted in chat or posted in an issue, revoke it at the provider first , then replace it. Deleting the commit is not enough (Level 0, module 2, Part 9).
Where the values come from
The code asks for the same names everywhere (APP_LLM_API_KEY and so on). What changes is where the values come from:
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Your laptop .env file (not in Git)
CI pipeline encrypted CI secrets
Production secret manager / host settings
Environment APP_LLM_API_KEY=... same names everywhere
Settings class
typed and validated at start-up
secret hidden in logs and repr
missing value: crash early
The code never changes between environments. Only the values around it do.
The same environment-variable names are filled from a different source in each place.
On your laptop: a .env file listed in .gitignore. A committed .env.example shows the names only.In CI (the automatic checks you meet in module 7): the CI service's encrypted secrets.In production: the hosting platform's settings, or a secret manager.
To see an environment variable in action, set one and read it back:
$ export APP_LLM_NAME = big-2
$ python -c "import os; print(os.environ['APP_LLM_NAME'])"
big-2
On Windows Command Prompt use set APP_LLM_NAME=big-2, and in PowerShell use $env:APP_LLM_NAME = "big-2". The variable lasts only for that terminal window.
A .env file is a development convenience
A .env file holds NAME=value lines and is loaded for you when the program starts. It is handy on your laptop. In production, set real environment variables on the host and do not ship a .env file at all. Do not bake secrets into a Docker image either (module 7).