Sysprose

An open-source, pure-browser modeler for a SysML v2–style notation. Author a system as text or as diagrams, validate it against a rule engine, and verify it from a terminal: each requirement read as the assume/guarantee pair its own clauses state, decided by an SMT solver or reported honestly as undecided; state machines walked exhaustively rather than one run at a time; and verdicts written back into the file, where they go stale the moment the design changes.

The modeler itself needs JavaScript. The documentation does not:

All reference documentation
Conformance scorecard — what was measured, and what was not
User guide
Command-line reference
Model checking, read against this tool
Source on GitHub

Sysprose implements a SysML v2–style notation and is a candidate, not a certified or conformance-tested implementation. SysML is a trademark of the Object Management Group.