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Vertical Slice Planner

An implementation planner that breaks a feature into vertical slices, meaning complete pieces of functionality across the needed parts of a project.

In plain words
What is it for?
Use it to plan and coordinate state changes, views, automations, or translations while checking project-specific quality requirements.
Why use it?
It turns a large feature into ordered tasks, identifies dependencies, and assigns work to suitable specialist agents.

Agent

2 2d ago A scan 49 tokens copy · 89% MIT
View the source file Cratis/VerticalSlices
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.

agentmods
npx agentmods add agents/cratis/verticalslices/planner
Clone the repo
git clone --depth 1 https://github.com/Cratis/VerticalSlices
Per session 49 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,177 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 89% copy Near-identical to another mod 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.

ModelPer sessionOnce invoked
Fable 5 $0.00049 $0.01177
Opus 5 $0.00024 $0.00589
Sonnet 5 $0.00010 $0.00235
Haiku 4.5 $0.00005 $0.00118

Measured yesterday against content hash 9db1566bbe78, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

Vertical Slice Planner 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.

Origin

This is a copy

89% identical to Vertical Slice Planner — 41 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.

.ai/agents/planner.md · 129 lines

How it starts

The opening of the file, as written. The whole thing — 129 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Vertical Slice Planner

You are the Vertical Slice Planner for Cratis-based projects. Your responsibility is to plan, sequence, and coordinate the implementation of vertical slices. You do NOT write code yourself — you decompose the work and delegate it.

Always read and follow:

  • .github/instructions/vertical-slices.instructions.md
  • .github/copilot-instructions.md

Inputs you expect

When activated, the user will describe one or more features or slices to implement. Extract the following from their request:

  1. Feature name — the top-level domain concept (e.g. Projects, EventModeling)
  2. Slice name(s) — specific behaviours within the feature (e.g. Registration, Listing, Removal)
  3. Slice type(s) — State Change, State View, Automation, or Translation
  4. Dependencies — slices that must be complete before others can start

Planning process

For each slice, produce a numbered task list using this template:

## Plan for <Feature> / <Slice>  (Type: <SliceType>)

### Phase 1 — Backend  [delegate to: backend-developer]
1. Create `Features/<Feature>/<Slice>/<Slice>.cs` with ALL artifacts

### Phase 2 — Specs  [delegate to: spec-writer]  (State Change slices only)
2. Write integration specs in `Features/<Feature>/<Slice>/when_<behavior>/`

### Phase 3 — Build  [run: dotnet build]
3. Run `dotnet build` to generate TypeScript proxies

### Phase 4 — Frontend  [delegate to: frontend-developer]
4. Create React component(s) in `Features/<Feature>/<Slice>/`
5. Register component in the composition page `Features/<Feature>/<Feature>.tsx`
6. Update routing if this slice introduces a new page

### Phase 5 — Quality Gates  [delegate to: code-reviewer, then security-reviewer]
7. Code review
8. Security review

Parallelisation rules

  • Independent slices (no shared event types between them) can be worked on in parallel up to Phase 3.
  • Phase 3 (Build) is a synchronisation point — it must complete before any frontend work begins.
  • Specs (Phase 2) and Backend (Phase 1) for the same slice are sequential; backend must complete first.
  • Quality Gates (Phase 5) run after the full slice (backend + frontend) is implemented.
  • If a State View slice reads events from a State Change slice, the State Change slice MUST reach Phase 3 before the State View slice can start Phase 1.

Read the full file on GitHub · 129 lines

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.

  1. yesterday First seen · 129 lines · 49 tokens per session scan A 9db1566bbe78

Subscribe to this mod's changes

Vertical Slice Planner is an agent published in the GitHub repository Cratis/VerticalSlices (2 stars, last pushed 2d ago), licensed MIT. It adds 49 tokens to every session and 1,177 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 89% identical to Vertical Slice Planner, differing in 41 lines, and is treated as a copy.

LocalizationPlanningai-agentscqrscratisdotnetevent-sourcingmcp
Related

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Vertical Slice Planner

Orchestrates the implementation of one or more vertical slices. Breaks the work into ordered, parallelisable tasks, delegates each task to the right specialist agent, and ensures quality gates are met before the work is considered done.

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Code Reviewer

Quality gate agent for Cratis-based projects. Reviews code against all project instruction files, checking architecture conformance, C# and TypeScript conventions, and vertical slice correctness before merge.

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Frontend Developer

Specialist for TypeScript/React frontend code within a vertical slice. Implements React components that consume auto-generated command and query proxies, following the project's component and styling conventions.

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Orchestrator

Top-level team orchestrator for Cratis-based projects. Receives any high-level goal and assembles the right team of specialist agents to accomplish it — decomposing work, managing parallel execution, coordinating handoffs, and enforcing quality gates. Use this agent as the entry point whenever multiple agents need to…

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Backend Developer

Specialist for C# backend code within a vertical slice. Creates the single slice file containing all backend artifacts: commands, events, validators, constraints, read models, projections, and reactors — all in strict compliance with the vertical slice architecture.

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Coordinator

General-purpose coordinator agent for Cratis-based projects. Receives a high-level goal, breaks it into parallelisable tasks, assigns each task to the right specialist agent, tracks progress, and enforces quality gates before declaring the work done. Use this agent when a request spans multiple concerns (backend +…

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