Borrowing it
Nothing to install: this file belongs to Cratis/VerticalSlices. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/Cratis/VerticalSlices/main/.ai/skills/diagnose-slice/SKILL.mdgit clone --depth 1 https://github.com/Cratis/VerticalSlicesWrote 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.
[](https://agentmods.dev/skills/cratis/verticalslices/diagnose-slice)<a href="https://agentmods.dev/skills/cratis/verticalslices/diagnose-slice"><img src="https://agentmods.dev/badge/skills/cratis/verticalslices/diagnose-slice/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.
<a href="https://agentmods.dev/skills/cratis/verticalslices/diagnose-slice"><img src="https://agentmods.dev/badge/skills/cratis/verticalslices/diagnose-slice.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00083 | $0.01205 |
| Opus 5.5 | $0.00033 | $0.00482 |
| Sonnet 5.5 | $0.00017 | $0.00241 |
| Haiku 4.5 | $0.00008 | $0.00120 |
Grade A, and why
diagnose-slice 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 1mo ago.
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.
This is a copy
100% identical to diagnose-slice — 28 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 49 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Symptom → likely cause → fix for the common ways a Cratis application slice misbehaves. Each row routes to the rule/skill that owns the detail — start there. Reproduce a real defect with a spec before and after the fix.
Backend / Chronicle
| Symptom | Likely cause | Fix → |
|---|---|---|
| Read model query returns empty / stale | projection not wired: event→read-model property names differ (AutoMap only maps matching names), or a default value masks missing wiring | add-projection, cratis-readmodel; [SetFrom<T>] for name diffs; no default values on [ReadModel] props |
| App crashes on startup with a projection error | duplicate [FromEvent<T>] for the same event on one read model |
add-projection (one [FromEvent<T>] per event) |
| Command always "not successful" with no validation errors | [Roles]/authorization: an unauthorized result isn't successful and carries no validation errors |
auth-and-identity, cratis-command; assert ShouldNotBeAuthorized() |
| Command rejected unexpectedly | a CommandValidator/ConceptValidator rule, or Provide() short-circuited with ValidationResult.Error |
add-business-rule, cratis-command |
| Handler returns HTTP 500 instead of rejecting | threw from Provide()/Handle() for a business rule (that's an exception, not a rejection) |
return Result<TEvent, ValidationResult> — add-business-rule |
| Reactor's returned events never appended | returned EventForEventSourceId on a Chronicle version before reactor support |
return event objects, or ReactorSideEffect for another target — reactors.md |
| Projection/reactor stops processing ("quarantined") | a handler threw; the partition paused and the observer quarantined (does not auto-resume) | read the failure off the server first — inspect-running-chronicle; then fix the handler (make it idempotent) and replay — reactors.md |
| Duplicate side effect on replay | non-idempotent reactor without [OnceOnly] |
mark the handler [OnceOnly] — reactors.md |
| Chronicle analyzer warns on an event property | a nullable event property | model the optional fact as a separate event — vertical-slices.md, event-modeling |
| A read model needs a field from another slice | wrong stream boundary / missing event | re-model (information completeness) — event-modeling; never cross-read another read model at runtime |
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.
- 1mo ago First seen · 49 lines · 83 tokens per session scan A 45839e11e7aa
diagnose-slice is a skill published in the GitHub repository Cratis/VerticalSlices (2 stars, last pushed 1mo ago), licensed MIT. It adds 83 tokens to every session and 1,205 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 100% identical to diagnose-slice, differing in 28 lines, and is treated as a copy.
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