Follow-up to #32130 and #37094. Backend: collision-safe node-id
sanitization (any invalid character, not just hyphens), topology-aware
layered auto-layout, branch-handle repair for if-else /
question-classifier edges, duplicate-id and graph-cycle validation, a
compacted refine-mode graph prompt (~half the tokens in and out), and an
instruction length cap at the API boundary. Frontend: warn when /refine
cannot load the current draft instead of silently generating from
scratch, cap the session version history, clamp the persisted version
index, guard against empty-graph success envelopes, and give slow
generations more headroom before the client-side abort. New error codes
localised across all 23 locales.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>