A
Lane A
Presently demonstrated or active-program compatible
B
Lane B
Engineering extrapolation (known physics, plausible scaling)
C
Lane C
ASI-contingent (requires superintelligence or radical manufacturing)
D
Lane D
Frontier physics / speculative placeholder (non-baseline for early phases)
Every requirement in this specification is tagged with its maturity lane.
Contributors may advance Lane A or B items without endorsing Lane D concepts.
This framework protects credibility while preserving full multi-century ambition.