An AI prompt engineering studio with a modular component vault, semantic search, community packs, and multi-step prompt chaining.
No authentication required. Build, compile, and test prompts instantly.
Google OAuth protected workspace with component vaults, semantic search, prompt packs, and chaining.
Browse and compose prompts using reusable Persona, Protocol, Format, and Template components.
View the final assembled prompt before execution, with full visibility into generated context.
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Add your API Key and initiate chat through it.
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You can chain multiple steps using different Prompts.
Most developers prompt AI models in one unstructured shot. The model has to infer intent, guess output format, and handle everything in a single bloated context window.
Measured result: A resume rewrite task in a single prompt consumed 41,000 tokens. The same task broken into three focused, structured prompts consumed 18,000 tokens — a 56% reduction — with more precise output.
Prompt Builder is built around that insight. It gives you a structured, reusable, composable system for building prompts — not a blank text box.
Prompt Builder has two tiers:
A stateless prompt compiler. No auth required.
- 5 workflow templates — Summarise, Extract, Classify, Draft, Analyse
- PDF to Markdown parser — client-side via pdfjs-dist
- Live token counter — raw content vs compiled prompt size
- Live Sandbox — run against Gemini, GPT-4o Mini, or Claude Haiku with your own API key
- Real token telemetry from API response headers
- Prompt history via IndexedDB
A full prompt engineering environment with auth, a component vault, semantic search, and chaining.
Prompts are built from composable primitives stored in a PostgreSQL database:
| Layer | Purpose |
|---|---|
| Persona | Defines who the model is — role, expertise, communication style |
| Protocol | Defines how it thinks — reasoning steps, constraints, rules |
| Format | Defines output structure — markdown, tables, JSON, reports |
| Template | The task itself — with {{variable}} placeholders |
39 public vault components across all layers, ready to use out of the box.
Type in the Task Template area and the studio automatically suggests relevant components from the vault using cosine similarity search powered by pgvector and Gemini embeddings (768-dimensional). Results update with a 1500ms debounce and show similarity scores.
Discover and share Prompt Packs — curated bundles of components that represent a complete workflow preset (e.g. Code Review, Documentation Writer, Bug Analyser).
- Browse public packs with category filters and semantic search
- Load any pack directly into the studio with all components pre-selected
- Save packs to your personal library
- Create your own packs from the studio or community page
- Use count tracking per pack
Build multi-step prompt pipelines where each step's output feeds into the next via {{previous_output}}.
Example — Bug Report chain:
- Step 1: Analyse the bug description → structured root cause analysis
- Step 2:
Based on: {{previous_output}}→ write a concrete fix - Step 3:
Review this fix: {{previous_output}}→ edge cases and approval verdict
Each step streams output in real time. Progress bar tracks completion. Chains are saved locally and reloadable.
Run compiled prompts directly in the studio against three models — Gemini, GPT-4o Mini, Claude Haiku. Supports follow-up messages, conversation threading, and resumable chat sessions. Real token metrics per response.
Browser (Next.js App Router)
│
├── /api/execute ← BYOK streaming proxy (edge runtime)
├── /api/components ← Vault CRUD + semantic search
├── /api/packs ← Pack CRUD + save + use count
│
└── Supabase
├── prompt_components (pgvector 768d, HNSW index, RLS)
└── prompt_packs (pgvector 768d, RLS)
user_saved_packs
API key security: Keys are stored in sessionStorage only — never written to a database, never logged server-side. The Next.js edge route acts as a passthrough proxy. Keys are cleared when the tab closes.
Auth: Google OAuth via Supabase. Middleware protects /advanced, /manage, and /community. RLS policies enforce row-level ownership at the database layer, with a redundant ownership check in each API route.
| Layer | Technology |
|---|---|
| Frontend | Next.js 15 (App Router), React |
| Styling | Tailwind CSS v4 |
| Database | Supabase (PostgreSQL + pgvector) |
| Auth | Supabase Google OAuth + @supabase/ssr |
| Embeddings | Gemini Embedding API (768d) |
| Vector Search | pgvector — HNSW index, cosine similarity |
| AI Proxy | Next.js Edge Route — Vercel AI SDK |
| Providers | Gemini, GPT-4o Mini, Claude Haiku |
| Local Storage | localForage (IndexedDB) |
| Deployment | Vercel |
git clone https://github.com/themechbro/promptbuilder
cd promptbuilder
npm installCreate .env.local:
NEXT_PUBLIC_SUPABASE_URL=your_supabase_url
NEXT_PUBLIC_SUPABASE_ANON_KEY=your_supabase_anon_key
GEMINI_API_KEY=your_gemini_api_key
NEXT_PUBLIC_GA_ID=your_ga4_idnpm run devOpen http://localhost:3000.
The Standard Workbench works without any environment variables. The Advanced Studio requires Supabase credentials and a Gemini API key for embedding generation.
create table prompt_components (
id uuid primary key default gen_random_uuid(),
type component_type not null, -- persona | protocol | format | template | taxonomy
name text not null,
slug text not null,
version text not null default '1.0.0',
content text not null,
metadata jsonb default '{}',
embedding vector(768), -- Gemini embedding for semantic search
is_public boolean default false,
created_by uuid references auth.users(id),
created_at timestamptz default now(),
updated_at timestamptz default now(),
unique (created_by, type, slug)
);HNSW index (m=16, ef_construction=64) for sub-millisecond approximate nearest neighbour search. Row-level security on all operations.
| Version | Description |
|---|---|
| v1.2.4 | Standard workbench — stateless, no auth |
| v2.0.0 | Advanced Studio — modular vault, Google OAuth, 4-layer canvas |
| v2.1.0 | Live Sandbox — streaming, conversation threading, chat history |
| v2.2.0 | Semantic search — pgvector + Gemini embeddings, suggestion UI |
| v2.3.0 | Community Hub — Prompt Packs, vault management |
| v2.3.1 | UI polish — Architecture Layers, modals, output tab |
| v2.4.0 | Prompt Chaining — linear pipeline, streaming per step |
- grpc/grpc-java — race condition fix in client connection handling (merged)
- Microsoft PromptKit — active contributor