Three different mechanisms pass env vars (interpolation, .env files, environment: blocks) and each fails in its own way. Identify which layer is silently dropping your value.
${VAR} in compose.yaml substitutes at CONFIG parse time (from your shell/.env file); the environment: block sets what the CONTAINER sees. Setting the shell var changes interpolation, not the container's env, and vice versa.
Compose reads .env from the project directory (where you run the command, by default) — not the compose file's folder. Shell vars override .env values, and .env doesn't affect already-created containers until recreate.
up -d reuses unchanged containers: env changes need an explicit recreate (up -d --force-recreate or compose down/up).
docker exec <ct> env | grep -i <var> ; docker inspect <ct> --format '{{json .Config.Env}}' | python3 -m json.tooldocker compose config # renders the final config with all substitutions applieddocker compose up -d --force-recreate # env only applies at container creation# services:
# app:
# env_file: ./.env.production # loads KEY=VALUE lines into the containerdocker compose config is the ground truth — if the value is wrong there, the container was never the problem. Lists/quotes in .env files aren't parsed like shell: no quotes, no spaces around =.
It's interpolated from the shell and the .env file in the compose project dir at command time — not from the container's or image's environment. Print it with docker compose config to see the substitution result.
No. Environment is baked in at container creation. Recreate with docker compose up -d --force-recreate (or down/up) after changing .env or environment:.
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