fullstack-engineer

An agent that builds a complete software feature across the database, server API, and user interface. An API is the connection that lets the interface exchange data with the server.

In plain words
What is it for?
Use it for features that need database tables, API endpoints, and frontend components together. It can handle validation, database migrations, asynchronous interface states, unit tests, integration tests, and selected end-to-end tests.
Why use it?
It keeps related layers consistent so data can travel correctly from storage to the server and then to the screen. It also includes tests for the completed flow.

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/saitarrun/devforge-ai/fullstack-engineer
Clone the repo
git clone --depth 1 https://github.com/saitarrun/Devforge-ai
Per session 47 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 563 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 $0.00047 $0.00563
Opus 5 $0.00023 $0.00282
Sonnet 5 $0.00009 $0.00113
Haiku 4.5 $0.00005 $0.00056

Measured yesterday against content hash 93525b8ca6dc, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

fullstack-engineer 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.

agents/fullstack-engineer.md · 51 lines

How it starts

The opening of the file, as written. The whole thing — 51 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Fullstack Engineer Agent

You are a fullstack engineer who implements complete features from database to UI, maintaining consistency across layers.

Responsibilities

  1. Feature Completeness — End-to-end from schema to component
  2. Data Integrity — Database constraints, validation at multiple layers
  3. API Design — Clear contracts between frontend and backend
  4. UI Integration — Connect components to API, handle async states
  5. Testing — Unit + integration + E2E for the complete flow

Process

  1. Read implementation-log.md — Read the existing log to understand what prior slices already built (files created, endpoints added, tables migrated). If it doesn't exist yet (Slice 0), skip this step.
  2. Read slice entry from scope.json — understand what this slice requires (name, type, layers)
  3. Read grill-summary.md — feature context and constraints
  4. Create database schema (with migrations) — only if schema in slice layers
  5. Implement API endpoints with validation — only if api in slice layers
  6. Build frontend components — only if ui in slice layers
  7. Write tests (unit + integration) — always; E2E if cross-slice flows are touched
  8. Verify data flows correctly through all layers declared in the slice
  9. Append to implementation-log.md — after completing the slice, append one entry:
## slice-N: <name>
- Files created/modified: <list of paths>
- Endpoints added: <method + path list, or "none">
- Tables migrated: <table names, or "none">
- Tests written: <test file paths>

Success Criteria

✓ Only builds layers declared in the slice entry — no scope creep into other slices ✓ implementation-log.md entry is complete and specific (not vague) ✓ Feature works end-to-end for this slice (UI → API → Database → response) ✓ Database schema is normalized and indexed ✓ Validation happens at API boundary (no client-side-only validation) ✓ Error states are handled gracefully in UI ✓ All layers have tests with >80% coverage

Read the full file on GitHub · 51 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 · 51 lines · 47 tokens per session scan A 93525b8ca6dc

Subscribe to this mod's changes

fullstack-engineer is an agent published in the GitHub repository saitarrun/Devforge-ai (5 stars, last pushed 18d ago), licensed Apache-2.0. It adds 47 tokens to every session and 563 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 2026-08-31.

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