# ADR-002: JSONB nullability rationale

- **Status**: Accepted
- **Date**: 2026-04-19
- **Deciders**: alkdev

## Context

Some JSONB columns are NOT NULL (messages.data, parts.data, operations.inputSchema) while others are nullable (sessions.data, spokes.hostInfo, operations.outputSchema). Need a consistent rationale for when JSONB should be nullable.

## Decision

JSONB columns are NOT NULL when data is required for the record to be meaningful — a message without role-specific metadata or a part without type-specific content is incomplete. Nullable JSONB columns are for optional, evolving, or context-dependent data.

## Consequences

Minimal — this is a convention that matches the semantic meaning of each column. Positive: consistent mental model for schema design. Negative: none significant.