ADR-0001: Hybrid Kernel Model

Status

Accepted

Context

VibeOS requires:

  • strong isolation for risky components
  • low overhead on kernel hot paths
  • room for compatibility runtimes and service-oriented evolution

A pure monolithic kernel conflicts with the security and compatibility goals. A pure microkernel increases risk for early implementation complexity and performance regressions if IPC and service orchestration are not yet mature.

Decision

VibeOS adopts a hybrid microkernel-inspired modular architecture:

  • kernel core remains small and primitive-oriented
  • user-space services host drivers, filesystems, policy engines, and compatibility runtimes by default
  • privileged execution is allowed only for boot-critical, interrupt-critical, or benchmark-justified components

Consequences

Positive:

  • smaller trusted computing base than a monolithic design
  • safer placement for compatibility layers
  • controlled path for restartable services

Negative:

  • architectural governance burden increases
  • IPC performance becomes a first-order success factor
  • some subsystems may need later relocation based on measurement

Implementation notes

  • placement exceptions require benchmark evidence
  • subsystem contracts must be explicit and versioned
  • the first design review in Phase 2 must verify that early bootstrap code does not create accidental permanent kernel dependencies