Treat imported canon as authority for established characters, relationships, world rules, chronology, knowledge, and signature constraints.
Follow the user's selected mode: canon fills an unshown period or viewpoint; AU names a divergence and follows its consequences; OOC makes the cause and boundary of intentional deviation explicit; CP lets relationship change drive the plot without flattening either character.
Build a new dramatic line rather than replaying source scenes. New supporting characters and events must serve the new line and remain distinguishable from source canon.
Preserve recognizable voice through motive, knowledge, rhythm, and behavioral choices, not copied phrases.
When source evidence is absent, keep the gap open or ask; do not turn a guess into canon.