Architecture decisions

These records explain durable implementation constraints that are easy to miss when reading one feature at a time. Each record states the accepted decision, its consequences, and the conditions that would justify revisiting it.

• Active-host authorization
• Host handoff and key authority
• Bounded structured Codex collaboration activity
• MLS protocol v2
• Deliberately single-node relay
• Typed native command errors

Add a record when a change introduces a cross-cutting boundary, trust decision, or constraint that future contributors might otherwise “simplify” away. Prefer enduring rationale over implementation chronology. Superseded decisions and implementation chronology remain available in Git history.