Environment Variables, Secrets, and Build-Time Configuration
Phase 32 objective: containerize the existing architecture without moving durable state, secrets, or business responsibilities into the container layer.
Three categories Build configuration determines compiled output. Runtime configuration is read when the container starts. Secrets must be injected at runtime by the platform or secret manager and never baked into image layers.
NEXT_PUBLIC_* Public browser config - never secret
Next.js caveat NEXT_PUBLIC_* values may become part of browser bundles and are not secrets. Public configuration often needs to be known at build time, while server-only environment variables can remain runtime configuration.
Docker rule Never COPY .env into a production image. Use .dockerignore and platform secret injection.
Security work starts with trust boundaries and abuse cases. A feature is incomplete until unauthorized and malformed paths are deliberately exercised.
Restate the goal of “Environment Variables Secrets and Build Time Config” as one observable behavior. Write the success signal before touching code.
Trace the boundary map: asset → trust boundary → attacker input → control → verified denial/allow. Mark the one boundary this lesson changes.
Inspect the current repository state and record the exact files, route, table, or runtime involved. Avoid creating an abstraction before you can name the existing owner.
Implement the smallest vertical slice. Add one coherent change, run the narrowest verification command, and read the output before continuing.
Connect the slice to TaskFlow’s phase artifact: Dockerfiles and compose/dev verification that build and run TaskFlow services from clean inputs.. Verify behavior from the outside as a user or API client would.
Create one controlled failure that is safe to reproduce. Predict the symptom first, capture evidence, locate the earliest broken boundary, then fix only that cause.
Close the reference and rebuild or explain the core change from memory. Record what you would monitor or test before trusting the same change in production.
Threat: authenticated User B changes the URL to User A's task id.
Expected control: API loads the resource scope and denies the action.
Evidence: 403 response + unchanged database row + security-safe log.Do not copy this as a finished answer. Predict what each boundary does, type the smallest useful slice, run it, then compare the result with your prediction.
Return to the nearest observable boundary: input, network, process log, database, or rendered UI. Compare actual evidence with the predicted path.
Change one variable at a time and reproduce the original failure after the fix; otherwise you have correlation, not diagnosis.
Without copying the final source, create a second small scenario that applies “Environment Variables Secrets and Build Time Config” to a different TaskFlow resource or input. Write the acceptance criteria first, implement it, and provide the evidence that each criterion is satisfied.
Write a .dockerignore first so local node_modules, Git history, secrets, and build output do not enter context.
Use the smallest change that demonstrates this lesson. Stop after it works and capture evidence.Huge build context invalidating caches
Predict the symptom before causing the failure. Then locate the earliest boundary where reality diverges from expectation.Why does this responsibility live here, what input does it trust, what output proves success, and what would go wrong if another layer owned it?
If your explanation is vague, repeat the boundary trace before moving on.Close the reference. Reproduce the core idea from memory or explain the exact request/data flow aloud. Then check your diff or notes for accidental shortcuts that bypass validation, authorization, error handling, or verification earned in earlier phases.