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CephalonEngine

Cephalon engineering standards

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This document is the consolidated standards baseline for code, packaging, documentation, testing, and quality gates that apply to the Cephalon engine and every shipped Cephalon.* package, host adapter, companion pack, and tooling surface.

Cross-references: project-memory.md, architecture.md, architecture-patterns-research.md, architecture/design-patterns-reference.md, compatibility.md, package-publishing.md, engine-surface-maturity-audit.md, conformance-matrix.md, reference-docs.md, benchmarking.md, dotnet11-readiness.md, long-range-direction.md.

How to use this document

Section titled “How to use this document”

This page does not replace any of the more detailed docs above. It is the one place a contributor or AI agent can read first to understand what “high quality” means in this repository before they ship code, docs, packaging, or planning changes. Each section ends with the doc that owns the deeper truth so this page stays a navigable index, not a duplicate source.

First-class engine qualities

Section titled “First-class engine qualities”

Every shipped surface must consider the following qualities deliberately, not as later hardening chores. They are listed once here so future ADRs, planning cards, and reviews can reference a stable set of dimensions.

  • Performance. Hot paths have benchmarks; benchmark drift is part of release validation; allocations and JIT shape are checked when claims justify it.
  • Security. Supply-chain trust, secret hygiene, transport security, and least-privilege defaults are part of the contract, not appendix material.
  • Usability (developer experience). Consumer code shrinks as the engine grows; APIs feel obvious; docs and IntelliSense agree.
  • Reliability. Failure modes are explicit; retries, timeouts, circuit breakers, bulkheads, and rate limits are first-class settings.
  • Maintainability. Source, docs, and planning truth move together; engine-internal abstractions stay small and additive.
  • Scalability. Cell-based, edge-aware, and distributed-by-default placement is supported by the same primitives whether the deployment is single-instance or multi-region.
  • Flexibility. Architecture, transport, host, and policy choices live in engine composition, not in consumer-app rewrites.
  • Compatibility. Public packages stay binary-stable across minor versions; breaking changes go through deliberate, versioned obsoletion.
  • Data integrity. Outbox, durable execution, CDC, event-sourcing, and saga choreography contracts keep replay-safe semantics first.
  • Availability. Health, readiness, dependency-health probes, and degradation modes are observable through the runtime catalog surface.
  • Auditability. Behavior, governance, tenancy, agent-tool, and rollout decisions emit truthful runtime metadata so audits do not require log archaeology.
  • Compliance. Multi-tenancy, governance, sovereignty routing, retention, and data-handling decisions stay declarative and inspectable.

These qualities are listed in the same order in project-memory.md. When a planning card claims to advance one of them, name the dimension explicitly in the card so reviewers can check the claim.

Library and API design

Section titled “Library and API design”

Cephalon ships reusable libraries that other teams take dependencies on. That changes the design constraints from “what works for our app” to “what other teams can rely on for years.” The dominant external reference is Microsoft’s Framework Design Guidelines; Cephalon applies those guidelines consistently across the Cephalon.* family.

Authoritative external sources:

Cephalon-specific application:

  • public types that are part of the engine contract live under Cephalon.Abstractions or one of the explicitly named contract packages; implementation-only types stay internal unless the contract actually needs them
  • prefer constructor injection over property injection; constructors stay lightweight; expensive work happens in explicit Initialize/Start methods or in hosted lifetime callbacks
  • prefer stable Add{Group} registration entry points (e.g., AddCephalonEngine, AddCephalonAspNetCore, AddBehaviorEventingBridge) over implicit discovery; explicit ordering beats ambient registration magic
  • prefer extension methods on stable surfaces (IServiceCollection, IBehaviorTopologyBuilder, IRestBehaviorEndpointGroupBuilder, etc.) for module/host-facing API ergonomics
  • avoid public mutable state on shared services; expose immutable descriptors and registry contracts instead
  • avoid leaking System.Text.Json, Microsoft.Extensions.*, or other implementation libraries through public contracts when they are not part of the intended contract; if the implementation library is the contract, document that explicitly
  • naming follows the Microsoft naming guidelines: PascalCase for public members, async methods end in Async, interfaces start with I, contributors/registries/catalogs use those exact suffixes consistently
  • new public surface uses XML doc comments; doc generation is on by default in Directory.Build.props

Deeper truth:

Code quality gates

Section titled “Code quality gates”

The repo enforces baseline quality gates through MSBuild defaults so contributors and AI seats cannot accidentally drop them.

Directory.Build.props (current shipped baseline):

  • <ImplicitUsings>enable</ImplicitUsings>
  • <Nullable>enable</Nullable>
  • <AnalysisLevel>latest-recommended</AnalysisLevel>
  • <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
  • <GenerateDocumentationFile>true</GenerateDocumentationFile>
  • <NoWarn>$(NoWarn);CS1591</NoWarn> (missing XML doc comment is not a hard error, but XML docs are still expected on public contracts)

Additional standards:

  • Directory.Packages.props enables Central Package Management; do not put <PackageReference Version="..." /> inside individual project files
  • analyzer suppressions live next to the code being suppressed and include a // reason: ... comment so the suppression is reviewable
  • nullable annotations on public surface are part of the contract; weakening a nullable annotation on a public member is a binary break
  • async methods accept CancellationToken whenever they perform IO, host work, or could plausibly need cancellation later; cancellation tokens default to default only when the surface is intentionally non-cancelable

Performance and allocation discipline:

  • hot paths use Memory<T> / Span<T> / ReadOnlySpan<T> instead of array allocations where the API allows
  • avoid ToList() / ToArray() materialization in framework code unless the caller asked for materialization
  • avoid LINQ allocation traps inside per-request paths
  • benchmarks for known hot paths live under benchmarks/ and are wired into release validation; see benchmarking.md

Diagnostics standards:

  • engine-emitted diagnostics use stable diagnostic ids (Cephalon.* numbered ids); ids are assigned once and never reused
  • Cephalon.Behaviors, Cephalon.Engine, governance, tenancy, CDC, eventing, and resilience surfaces all share the same numbered-diagnostic discipline

Compatibility discipline

Section titled “Compatibility discipline”

Cephalon is a framework, not a single application. That changes the compatibility expectations.

  • public packages stay binary-stable across minor versions; binary breaks are deliberate, versioned, and documented
  • prefer additive changes plus opt-in settings over silent contract churn
  • treat package dependencies as part of the public contract; tightening a transitive minimum version can be a breaking change
  • use [Obsolete] with a clear migration message before removing a public member; obsoletion is the floor for known breaking changes
  • run Microsoft.DotNet.PackageValidation baselines so accidental binary breaks are caught at packaging time, not at consumer adoption time

The deeper compatibility-and-alignment contract lives in compatibility.md. Do not duplicate that contract here — read it before changing public surface, package metadata, or framework baselines.

Packaging standards

Section titled “Packaging standards”

Cephalon ships under a coherent, layered Cephalon.* package family. Package taxonomy is part of the framework’s discoverability and upgrade safety, not a release afterthought.

Shared metadata (already inherited via Directory.Build.props):

  • Authors = Cephalon
  • PackageLicenseExpression = MIT
  • PackageProjectUrl, RepositoryUrl, RepositoryType = git, PublishRepositoryUrl = true
  • shared PACKAGE.md readme by default; package-specific PACKAGE.md allowed when the package needs its own
  • baseline package version 0.1.0-preview until the family enters its first stable cut

Required publishing hygiene:

  • Source Link is enabled on all packable Cephalon.* projects
  • symbol packages (.snupkg) ship alongside primary .nupkg
  • PackageValidationBaselineVersion is configured for stable packages so accidental binary breaks fail packaging
  • vulnerability scans (dotnet list package --vulnerable --include-transitive) run as part of release validation
  • prefer trusted publishing (NuGet trusted-publishing flow + GitHub OIDC) over long-lived API keys when the release flow is formalized

Splitting policy:

  • split a package only when its assembly is independently useful to consumers
  • avoid one-megapackage that bundles unrelated functionality; avoid micro-fragmenting a coherent surface across many trivially-small packages
  • when a package is split, the split is documented in compatibility.md and the family taxonomy stays consistent with the shipped names listed in docs/components/README.md

Authoritative external sources:

Deeper truth:

Documentation standards

Section titled “Documentation standards”

Cephalon uses two documentation layers on purpose. Neither layer replaces the other.

  • hand-authored Markdown under README.md and docs/ is the primary human-facing product and adoption documentation; it explains ownership, usage, architecture, and adoption. Component pages under docs/components/* are the per-package map.
  • XML doc comments on public contracts are the API explanation layer used by IntelliSense and the Cephalon.ReferenceDocs publishing path. They explain supported public API behavior precisely enough for reference generation.

Rules that apply to every change:

  • when source changes, the related hand-authored docs change in the same slice; no source patches that leave docs drifting
  • when a public/runtime/package surface changes, review source + component docs + compatibility docs + readiness/validation docs + planning docs together as one change surface
  • when in doubt about the engine’s runtime intent, treat hand-authored docs as the primary contract and docs/reference/* as the generated API layer underneath them
  • repository-facing docs, commit messages, and planning artefacts stay in English so the durable record reads consistently

Deeper truth:

Testing standards

Section titled “Testing standards”

The repo distinguishes deterministic engine tests, host integration tests, sample/runtime tests, and benchmark guardrails on purpose.

  • engine-core and abstraction tests are deterministic and isolated; they do not rely on filesystem ordering, configuration leakage from samples, or environment variables
  • host integration tests for ASP.NET Core and Worker hosts use real host configurations and content roots; do not silently rely on whatever config files happen to be copied into a test output folder
  • sample and showcase tests target real sample content roots explicitly so the harness keeps testing the actual sample, not whatever transient output state existed at run time
  • benchmarks live under benchmarks/ and use BenchmarkInProcessShortRunConfig for the smoke path so release validation can run them quickly without losing meaningful signal
  • guardrail benchmarks for hot paths participate in scripts/validate-release.ps1

Test-style conventions:

  • prefer xUnit; assertion style stays consistent inside a test project
  • prefer one assertion concept per test; use Assert.Multiple or fluent assertions only when the test really expresses one combined concept
  • name tests after the behavior under test and the expected outcome; avoid Test_Method_Test1-style names

Authoritative external reference:

Security and supply-chain standards

Section titled “Security and supply-chain standards”

Security is a framework concern, not an application concern. Cephalon’s standards therefore stay strict by default.

  • secrets, tokens, and signing keys never live in repo-tracked files; secrets are injected through environment, host config, or trusted-publishing flows
  • transport security defaults assume TLS; HTTP-only modes are explicit opt-in for development scenarios
  • vulnerability scans run on every release validation pass; transitive vulnerabilities are part of the report
  • analyzer-only signals are readiness, not support; trim/AOT/single-file claims still need the manifest, project settings, validation coverage, workflow automation, and docs to all agree (see dotnet11-readiness.md)
  • when the planned scripts/validate-deployment-mode-claims.ps1 validation harness ships, its claim-truthful verdict is the authoritative gate for promoting trim, Native AOT, or single-file support from not-claimed to claimed; analyzer-only signals or local publish experiments do not widen the contract by themselves (see deployment-mode-support.md)
  • governance, tenancy, multi-tenancy, identity, and policy decisions stay declarative and inspectable through the engine’s runtime catalogs so audits do not require log archaeology

Authoritative external sources:

Planning and governance standards

Section titled “Planning and governance standards”

The standards above apply to every change. They are kept in sync with planning artefacts, GitHub Project tracking, and the durable record through:

When a change advances one of the engine quality dimensions listed at the top of this page, name the dimension in the matching planning card and in the commit message so reviewers can check the claim against this standard.

Maintenance posture

Section titled “Maintenance posture”

This document is meant to be the durable index of Cephalon engineering standards. Update it when:

  • the shipping framework or readiness lane changes (refresh the relevant cross-link, especially dotnet11-readiness.md)
  • a new quality gate is introduced (analyzer pack, validation lane, vulnerability scan tier, package-validation baseline tier)
  • a new Microsoft library design guideline materially changes recommended practice
  • the package family taxonomy or splitting policy changes
  • the testing or benchmarking discipline materially evolves

Prefer rewriting the affected section in place over appending. Long-range standards rarely benefit from change history living inside the standards page itself; meaningful history belongs in commits, planning cards, and architecture review snapshots.