# Intent.Common.Drift The drift check that compares a designer's model with hand-written code, shared by every module that contributes a designer to it. Intent.Domain.Guardrails.Contracts and Intent.Services.Guardrails.Contracts contribute the Domain and Services designers, and install this module with them; it isn't installed on its own. The module knows no designer. A contributing module supplies, for its designer, the facts the model states and how to read them from the model, the templates whose generated types are compared with the code, and the designer's text in the files below. This module supplies everything else: - **The recipe engine.** Each designer's recipe file, `guardrails/.drift.json` beside the application's `.application.config`, says where each fact is in the code and how to read its value. It is read against a C# index of the code (without comments, layout or disabled code) and, for other files, their text. - **The structure comparison.** Each type a contributing template generates is compared with its file on disk, on what its element can state. - **The drift report.** Every Software Factory run writes `DriftReport.mdx` to `.cache/guardrails//`, in the folder that holds the solution's `.isln`, when there is something to act on, and fails the run with one error while the model and the code disagree. It remembers, per machine, what the model and the code looked like when they last agreed (`.model.json`), so a change made in the model first is left to the Software Factory. - **Recipe validation, on demand.** Each contributing module's ValidateDriftRecipes module task returns, as JSON, what every recipe reads from the code. Each contributing module's README describes its designer's facts, what is compared, and its technology guides. ## Files for AI agents The module writes four files, each covering every designer contributed in the application: - `guardrails-model-sync.md` into the application's rules folder (the `AI.Context.Instructions` output): an always-on rule to update the model in the same change as the code, run the Software Factory and resolve the drift it reports. - `skills/sync-model/SKILL.md` (the `AI.Context.Skills` output): the `/sync-model` skill, which resolves each drift row by updating the model, the code, a recipe or the exceptions. Beside it, `skills/sync-model/references/intent-drift.md` says how to resolve a row about a modelled interaction. - `skills/configure-drift-check/SKILL.md`: the `/configure-drift-check` skill, which documents the recipe file format and every fact each designer states, and writes and extends the recipe files for whatever technology the code uses. Each contributing module writes its technology guides beside it. - `skills/validate-drift-recipes/SKILL.md`: the `/validate-drift-recipes` skill, which runs each designer's ValidateDriftRecipes module task and checks what each recipe reads against the code. None of them is written until a module contributes a designer. ## Contributing a designer A module contributes one designer with a `DriftDesigner`: the designer's name (which names its recipe file and report), its id, its order in the files above, its kinds of fact, a function reading the facts and one reading the elements by id, the id of its ValidateDriftRecipes task, and its text in the files above (`DriftGuidance`). Each `FactKind` names its recipe key, its report label, its placeholders with what each names, which of them name the fact's own element, and the model's vocabulary for its value. - The module's drift report template implements `IDriftDesignerSource`, returning its `DriftDesigner`, and delegates to `DriftReportRunner`: it takes the runner's `ReportFile` as its file, and answers `CanRunTemplate` from the runner's `CanRun`. The files above find every template of the run that implements `IDriftDesignerSource`. - The module's ValidateDriftRecipes module task delegates `Execute` to `RecipeValidationTask.Execute`, passing its `DriftDesigner`. - Each template whose generated C# file is compared with the code implements `IDriftStructureSource`, naming the designer, and records what its element can state on each type it builds, with `Modellable` under `Modellable.MetadataKey`. - `DriftReportRunner.ReportPath` gives a designer's report path as guidance names it. The contributing module compiles against this module without shipping it: a project reference that isn't copied to output, and a `` on Intent.Common.Drift in its `.imodspec`. Two copies of this module's assembly would leave the contribution implementing interfaces the loaded copy doesn't know. One module contributes each designer. The code index reads C#; other files are read as text.