Research Idea Decision Context Contract

Decision context is a read-only explanation of selection, deferral, closure, and reopening. Read one idea through GET /api/topics/{topic_id}/ideas/{idea_id}/decisions or one Decision Record through GET /api/topics/{topic_id}/idea-decisions/{decision_record_id}.

The response includes mutated: false, topic identity, the requested idea or decision id, decisions, involved ideas, decision-linked transitions, reopen_history, index_revision, and diagnostics. Each decision includes its stable decision_record_id, every explicitly recorded option, selected idea ids, option_set_complete, rationale, consequences, actor refs, decision time, supporting refs, transition refs, and missing_fields.

Each option includes idea_id, outcome, ordering, rationale, consequence, supporting refs, nested lightweight idea identity, and any directly linked disposition reason_code, transition_ref, and transition rationale. Option membership is authoritative. Generation siblings are not added unless the Decision Record recorded them as options.

Historical data may have no option set, an incomplete option set, or missing rationale. The response preserves available objects, sets option_set_complete: false, lists missing_fields, and emits idea_decision_context_incomplete. Clients show that diagnostic and do not invent alternatives or reasons. A closed idea keeps its closure transition and reason after a later reopen; the later transition also appears in reopen_history.