Tagged architecture

2 pieces

• September 3, 2026 · 6 min read

  Every Reused Module Is Untested Until You Run It Against the New Envelope

  A reused module carries a correctness argument scoped to its old environment. Ariane 5 lost a launcher to a conversion that was safe within Ariane 4's velocity range, and the Therac-25 killed three people reusing code whose assumption about hardware interlocks was no longer true.

• August 19, 2026 · 6 min read

  Boeing 737 MAX and MCAS: The Single Sensor Nobody Fault Injected

  MCAS depended on one angle of attack sensor for a function Boeing's own assessment classified as hazardous, a classification that normally precludes single sensor dependence. The safety analysis also understated the system's authority by more than four times. This is a system safety failure, not a missing unit test.