# Common Trust Core The Common Trust Core is the single, unmodified body of logic (`kernel.py`) that runs identically across every deployment. The [[Detection Rules|rules]], [[Proven Invariants|invariants]], and [[Four-State Trust Machine|state machine]] all live here, and **nothing in this core changes from site to site**. > [!important] One core, many sites > Portability does not come from forking the kernel per customer. It comes from holding the core fixed and varying only a thin per-site profile — see [[Profile-Based Portability]]. The same core was validated unmodified across all four [[Cross-Domain Validation|domains]]. Keeping the core invariant is what makes [[Deterministic Detection]] meaningful: if behaviour differed per deployment, no cross-domain claim would be defensible. The frozen core is also the unit that gets hashed and version-locked under the [[Frozen Evidence Baseline]]. ## Why this is the moat A fixed, proven core that ports across domains with only profile changes is a structural [[Data Moat|defensibility]] argument: each validated domain strengthens trust in the *same* artefact rather than a new fork. It also lowers [[Deployment Velocity|deployment cost]] — onboarding a site is a profiling exercise, not an engineering rewrite. Compare the [[Switching Cost Design]] logic: once the trust core is embedded at the [[Fail-Closed Trust Gate]], replacing it means re-validating safety from scratch. --- Related: [[Integrity Kernel MOC]] · [[Profile-Based Portability]] · [[Deterministic Detection]] · [[Cross-Domain Validation]] · [[Data Moat]] · [[Switching Cost Design]]