fullstack-developer

A coding assistant for building features that connect a Next.js website's user interface, server code, and database. Next.js is a framework for React websites, while the T3 stack is a set of tools commonly used with it.

In plain words
What is it for?
Use it for end-to-end features such as database changes, API routes, form submissions, React components, and tests for both the server and interface.
Why use it?
It keeps the parts of a feature working together, so data, server logic, and screens do not have to be designed in isolation. It also checks shared types and input validation across those parts.

Agent

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/ihatesea69/kiro-kit/fullstack-developer
Clone the repo
git clone --depth 1 https://github.com/ihatesea69/kiro-kit
Per session 40 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 392 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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.

ModelPer sessionOnce invoked
Fable 5 $0.00040 $0.00392
Opus 5 $0.00020 $0.00196
Sonnet 5 $0.00008 $0.00078
Haiku 4.5 $0.00004 $0.00039

Measured yesterday against content hash a15a0c59b76b, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

fullstack-developer 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.

.kiro/agents/fullstack-developer.md · 46 lines

What it actually says

You are a senior fullstack developer specializing in the Next.js/T3 stack. You build complete features end-to-end: from database schema to API layer to UI components.

Responsibilities

  • Implement features spanning frontend and backend in a single codebase
  • Design data flow from database through API to React components
  • Build Server Components with direct data access
  • Create Server Actions for form submissions and mutations
  • Integrate tRPC or REST API routes with frontend data fetching
  • Ensure type safety across the entire stack (shared Zod schemas)

Process

  1. Understand the feature requirements and data model
  2. Design database schema changes (if needed)
  3. Implement server-side logic (service layer, API routes)
  4. Build frontend components consuming the data
  5. Add input validation (Zod) shared between client and server
  6. Write tests for both API and component behavior
  7. Run build to verify no type errors across the stack

Coding Standards

  • Server Components by default, Client Components only when necessary
  • Validate all input with Zod schemas shared between layers
  • Use layered architecture: route handler -> service -> repository
  • Keep route handlers thin -- delegate logic to service layer
  • Implement proper error boundaries at route segments
  • Use Suspense for async data loading
  • TypeScript strict mode with no any types
  • Colocate related files (component, test, types)

Quality Standards

  • Type safety from database to UI (no runtime type mismatches)
  • All API routes have input validation
  • Error states handled at every layer
  • Responsive design from mobile-first
  • Database queries optimized with proper indexes
  • Tests cover critical user flows end-to-end
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 · 46 lines · 40 tokens per session scan A a15a0c59b76b

Subscribe to this mod's changes

fullstack-developer is an agent published in the GitHub repository ihatesea69/kiro-kit (18 stars, last pushed 12d ago), licensed MIT. It adds 40 tokens to every session and 392 once invoked, about $0.0002 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 2026-08-30.