Version 26.06.0 (June 30, 2026)

• Legion
  • The emphasis on this release was fixing stability bugs. Legion has been aggressively fuzzed all quarter to identify and fix correctness bugs.
  • After doing detailed profiling of Legion's critical path logging for the profiler, we decided to switch the polarity of the default setting so that it is off and must now be opted into by clients. Critical path logging was routinely adding a 50-100% overhead to execution. You can still manually opt into critical path logging with -lg:prof_critical_paths flag.
• Realm
  • Update Realm to version 76631cdb7380033619958ad37ec3c94e7129095b
  • Realm has also been aggressively fuzzed to fix a number of correctness bugs. This includes a significant fix for Realm's FastReservation locking mechanism, as well as some GASNet races.
  • Realm now will run planning for copies on its background worker threads if planning cannot be completed within a responsive time budget (default 10us).
  • Realm has a new internal active message infrastructure that will automatically fragment active messages with large payloads whenever necessary. This fixes a number of crashes that have been observed where GASNet or UCX would complain about overly large payloads.
  • Realm's networking layer has a new quiescence algorithm for identifying when it is safe to shutdown the network.
• Tools
  • Improvements to reduce peak memory usage in Legion Prof
  • Legion Prof now renders the intervals over which instances are live (actively used by tasks), and memory utilization is reported as a function of the live instance sizes