Vision → Loop → Evidence

The LangDrift protocol has three pillars, in this order:

The solid path is the canonical model. The dotted inputs show the information needed to interpret observed Loop movement as a Drift Event.

Vision

Vision is the intended product direction. Protocol version 1 represents it with three Markdown document families:

• research
• prd
• context

A Vision Target is an explicit identity used as the comparison target for a Drift Event. The event stores that identity in vision_target_id.

Loop

Loop is the work and decision cycle that follows intent. Its Markdown document families are:

• triage
• design-document
• spec
• ticket

Observed movement comes from this cycle. The protocol connects artifacts through explicit identifiers rather than inferring relationships from prose or repository structure.

Evidence

Evidence makes observations, decisions, and interpretations auditable. Its document and event families are:

• adr
• audit
• record
• drift

A Record is a normalized observed fact. A Drift Event is a separate interpretation of observed movement against a Vision Target, supported by Evidence.

Drift is derived

Drift is derived from the Loop; it is not a pillar and it is not automatically negative. The Evidence schema stores Drift Event envelopes because their references and reasoning must remain auditable.

expected means the movement matches recorded intent. unexpected means it does not. Neither state says whether the movement is beneficial or harmful.