Topology Says What, Config Says How

Sigil draws a strict line between topology and configuration.

• topology says what the program depends on
• config says how one environment builds the runtime world for those dependencies

Why the Split Matters

When those concerns are mixed together, runtime structure becomes difficult to reason about. Architectural declarations start carrying local ports, production URLs, secret names, and other operational details. Application code then begins to bypass the intended dependency model and reach for raw strings or environment variables directly.

Sigil treats that as a structural weakness, not a mere style issue.

The Rule

Topology files declare logical dependencies and environments. Configuration files build the world for one specific environment around those declared dependencies. Application code refers to declared handles, not raw endpoints.

The compiler reinforces that split by restricting ambient environment access to config modules and by requiring explicit --env selection for topology-aware projects.

Why This Helps

This reduces runtime ambiguity in three ways:

• dependency identity is declared once
• environment-specific binding lives in one predictable place
• application code cannot quietly reconstruct runtime wiring on its own

That makes the project easier to validate and easier to generate against, because the locations of architectural truth are fixed.