What is cratis-chronicle-event-constraints?

A guide to enforcing uniqueness rules when events are appended to the Chronicle event store. The rule is checked inside the append operation, so competing requests cannot both pass a separate, possibly outdated pre-check.

Use it for uniqueness or other state-dependent rules that must hold at event storage time. It also covers specifying the resulting constraint violation in a test.

A command-side check can become stale while another request is writing. An append-time constraint keeps the rule valid when requests race.

cratis-chronicle-event-constraints — Skill for Claude Code and Codex b

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent

npx skills add Cratis/AI --skill cratis-chronicle-event-constraints

Clone the repo

git clone --depth 1 https://github.com/Cratis/AI

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/cratis/ai/cratis-chronicle-event-constraints/github.svg)](https://agentmods.dev/skills/cratis/ai/cratis-chronicle-event-constraints)

Your own site

<a href="https://agentmods.dev/skills/cratis/ai/cratis-chronicle-event-constraints"><img src="https://agentmods.dev/badge/skills/cratis/ai/cratis-chronicle-event-constraints/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/cratis/ai/cratis-chronicle-event-constraints"><img src="https://agentmods.dev/badge/skills/cratis/ai/cratis-chronicle-event-constraints.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 81 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 2,571 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00081	$0.02571
Opus 5	$0.00041	$0.01286
Sonnet 5	$0.00016	$0.00514
Haiku 4.5	$0.00008	$0.00257

Measured yesterday against content hash a920ee671ba2, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

cratis-chronicle-event-constraints scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/cratis-chronicle-event-constraints/SKILL.md · 228 lines

How it starts

The opening of the file, as written. The whole thing — 228 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Chronicle event constraints

A constraint is an append-time invariant. Chronicle evaluates it inside the append, against the event store's own index — so it is the only mechanism that holds when two requests race. A command-side pre-check reads state that may already be stale by the time the append lands; a constraint cannot be.

Constraints are discovered automatically. There is no registration call.

Verified product sources

Package	Version	Purpose
`Cratis.Chronicle` (client)	`16.45.2`	`[Unique]`, `[RemoveConstraint]`, `IConstraint`, `IConstraintBuilder`, `IUniqueConstraintBuilder`, `ConstraintViolation`, `IAppendResult`
`Cratis.Chronicle` code analysis	`16.45.2`	`CHR0017`, `CHR0018`, `CHR0020`
`Cratis.Chronicle.Testing`	`16.45.2`	`EventScenario` and the `IAppendResult` `Should*` assertions

Reverify against the Chronicle repository before claiming support for another version. Never translate an attribute argument order or an assertion name from memory.

Route near misses

The rule rejects command input — a range, a format, a cross-field condition: use cratis-arc-command-validation.
The rule is state-dependent and belongs in the handler under concurrency (the DCB pattern): also cratis-arc-command-validation.
You are creating or changing a read model that the rule reads: use cratis-chronicle-read-model.
You are writing the specification and want the EventScenario mechanics in depth: use cratis-chronicle-event-specifications.

Step 1 — Pick the mechanism

Situation	Use
One event of this type per event source	class-level `[Unique]` on the event type
A property value unique across event sources	property-level `[Unique]` on that property
Release a claimed value when something is removed	`[RemoveConstraint("name")]` on the removal event
The same value must be unique across several event types	`IConstraint` with one `[Unique(name: …)]` name, or a fluent `Unique(…)`
Case-insensitive matching, composite keys, or a scoped constraint	`IConstraint`

Read the full file on GitHub · 228 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

LICENSE 142 B

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

yesterday First seen · 228 lines · 81 tokens per session scan A a920ee671ba2

Subscribe to this mod's changes

cratis-chronicle-event-constraints is a skill published in the GitHub repository Cratis/AI (2 stars, last pushed yesterday), licensed MIT. It adds 81 tokens to every session and 2,571 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-08.

Databases Testing Unit testing agent-skills ai cqrs cratis dotnet event-sourcing

author-test

Generate a test given sample. Parameters: C# SDK repository root; Package name: one of Azure.AI.Projects, Azure.AI.Projects.Agents or Azure.AI.Extensions.OpenAI; the sample to use as a starting point for the test.

Azure/azure-sdk-for-net · 68 tokens

crap-score

Calculates CRAP (Change Risk Anti-Patterns) for a named .NET method, class, or file. USE FOR: explicit CRAP calculation or coverage-and-complexity risk within that named target, including which tests to prioritize. DO NOT USE FOR: project-wide coverage/CRAP, plateaus, or project-wide blockers/priorities…

managedcode/dotnet-skills · 99 tokens

nunit

Write, run, or repair .NET tests that use NUnit. Use when a repo uses NUnit, [Test], [TestCase], [TestFixture], or NUnit3TestAdapter for VSTest or Microsoft.Testing.Platform execution. USE FOR: writing or reviewing NUnit tests; using [Test], [TestCase], [TestFixture], [SetUp], [TearDown] attributes; configuring…

managedcode/dotnet-skills · 146 tokens

maui-unit-testing

Add MAUI app tests around ViewModels, services, platform abstractions, and unit/integration/device boundaries. USE FOR: xUnit, avoiding MauiProgram.CreateMauiApp in unit tests, fakes/mocks, injectable Essentials interfaces, PlatformNotSupportedException, navigation/data services, AppProjectReference, device-test…

dotnet/maui-labs · 84 tokens

coverlet

Use the open-source free coverlet toolchain for .NET code coverage. Use when a repo needs line and branch coverage, collector versus MSBuild driver selection, or CI-safe coverage commands. USE FOR: coverlet setup; CI line or branch coverage; choosing between collector and MSBuild drivers. DO NOT USE FOR: coverage…

managedcode/dotnet-skills · 114 tokens

netarchtest

Use the open-source free NetArchTest.Rules library for architecture rules in .NET unit tests. Use when a repo wants lightweight, fluent architecture assertions for namespaces, dependencies, or layering. USE FOR: the repo uses or wants NetArchTest.Rules; architecture rules should be enforced in automated tests. DO NOT…

managedcode/dotnet-skills · 112 tokens