KHR_interactivity portable behavior graphs

Document status: reviewed. Canonical source.

Summary

KHR_interactivity adds portable, self-contained behavior graphs to glTF. Graph nodes model events, control flow, value operations and state while companion extensions add optional capabilities. The design explicitly considers constrained execution and graceful handling of unavailable companion operations.

Evidence

The current specification is a Release Candidate. It defines directed acyclic graphs, strictly typed value sockets, retained custom variables, static and dynamic implementation limits, and no-op replacement for unsupported extension operations. Its full runtime remains Turing-complete because operations may repeatedly activate flow, so time and execution budgets are still necessary. The 16 July 2026 announcement says it was submitted for ratification; that does not make it a ratified extension.

NUIF relevance

NUIF should use a separate behavior/state graph rather than embedding arbitrary scripts into visual nodes. The core behavior profile should remain declarative, bounded and capability-aware; richer runtime logic belongs in extensions or host application code.