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ADR 0002: Interface and presentation boundary

  • Status: accepted
  • Date: 2026-08-20

Context

The Python-to-Rust transition initially used terminal parity notes to track visible behavior. As the Ratatui TUI and Desktop application evolved, parity with an archived UI stopped being a useful architectural target. Duplicating model, policy, tool, or state logic in each interface would also make authorization and audit behavior inconsistent.

Decision

CLI, TUI, Desktop, gRPC, worker, and SDK crates are interfaces and translations only. Application services own durable behavior behind ports. colossus-presentation maps released typed contracts into bounded semantic documents; renderers choose terminal, plain-text, JSON, or application-specific views without changing policy or state.

Acceptance is based on current semantic and security contracts, not pixel or command parity with Python 0.5. Interface-specific tests remain appropriate for layout, input, transport, restoration, and serialization behavior.

Consequences

  • New interfaces reuse the same application and effect boundaries.
  • Presentation code cannot expose quarantined output or make authorization decisions.
  • TUI and Desktop can change substantially without preserving archived Python chrome.
  • Cross-interface parity tests assert typed behavior; visual and interaction tests stay in the interface that owns them.

See Runtime and ports and Extensions and presentation for the current design.