The Complete
API Toolkit
for Developers
HTTP & WebSocket · Load Testing · API Flows · Database Manager · AI
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Dragon Stack
Engineered for Performance
Synapse Kayser v4.0.0 brings everything a developer needs: HTTP client, API flows, load testing, Database Manager, WebSocket, Markdown and AI — all free.
MCP Server — AI Agent Integration Servidor MCP — Integración con Agentes IA
Synapse Kayser runs an MCP (Model Context Protocol) HTTP+SSE server on port 47821. Connect Claude, Cursor, or any MCP-compatible agent to your collections — the agent can list and execute your requests, including all headers, auth tokens, env vars and pre-request scripts.
Synapse Kayser expone un servidor MCP (Model Context Protocol) HTTP+SSE en el puerto 47821. Conecta Claude, Cursor o cualquier agente compatible — el agente puede listar y ejecutar tus requests con todos los headers, tokens, variables de entorno y scripts de pre-petición.
📖 Full MCP setup guide → 📖 Guía completa de configuración MCP →Nextcloud Sync — Multi-Profile Workspace Nextcloud Sync — Espacio Multi-Perfil
Connect Synapse Kayser to your own Nextcloud server and sync your workspace profiles across machines. Create multiple profiles (work, personal, client), each with its own collections, env vars and settings — switch between them instantly without losing any configuration.
Conecta Synapse Kayser a tu propio servidor Nextcloud y sincroniza tus perfiles entre máquinas. Crea perfiles (trabajo, personal, cliente), cada uno con sus colecciones, variables y configuración — cambia entre ellos al instante sin perder nada.
📖 Nextcloud setup guide → 📖 Guía de configuración Nextcloud →Split Panel — VS Code Style Panel Dividido — Estilo VS Code
Drag any tab to the right edge of the window to open a second panel side-by-side. Work on two requests simultaneously — compare responses, test auth flows in parallel, or keep your login token visible while you test other endpoints. Panels auto-collapse when you move all tabs back.
Arrastra cualquier pestaña al borde derecho para abrir un segundo panel lado a lado. Trabaja en dos requests a la vez — compara respuestas, prueba flujos de auth en paralelo o mantén tu token visible mientras pruebas otros endpoints. Los paneles se colapsan solos cuando quedan vacíos.
Proxy Gateway Manager Gestor de Proxy Gateway
Create and manage multiple local HTTP gateways without leaving the app. Each gateway runs on a custom port, with configurable routes (prefix → target). Toggle Rewrite ON to strip the prefix before forwarding, or Rewrite OFF to keep the full path. Hot start/stop — port freed instantly. Real-time logs with a resizable panel.
Crea y gestiona múltiples gateways HTTP locales sin salir de la app. Cada gateway corre en un puerto personalizado con rutas configurables (prefijo → destino). Activa Rewrite ON para eliminar el prefijo al reenviar, o Rewrite OFF para mantener la ruta completa. Inicio/parada en caliente — puerto liberado al instante. Logs en tiempo real con panel redimensionable.
HTTP Requests
Full REST support with pre-request scripts and assertions. Bearer, OAuth2, and API Key auth for secure agent workflows.
Industrial Load Testing
Stress-test endpoints with configurable worker pools and real-time RAM monitoring. Detect bottlenecks before they hit production.
Kayser AI Engine
Multi-provider support (Groq, OpenAI, Gemini) with persistent keys and independent daily quotas (150/model). No token leakage.
Chained API Flows
Advanced visual automation with loops, variables, and conditional logic. Chain complex business processes with ease.
Bruno Collections
Native read/write for .bru and .yml formats. Keep your collections in Git and sync with your team effortlessly.
AI-Powered Reports
Generate PDF/JSON reports with AI audits, metadata, and persistent feedback notes. Professional documentation made simple.
Database Manager
Connect to PostgreSQL, MySQL, SQL Server, MongoDB and Redis simultaneously. Multiple query tabs per connection, inline cell editing (DBeaver-style), smart SQL autocomplete, multi-row checkboxes, boolean field selects, and improved table alias detection.
Conecta PostgreSQL, MySQL, SQL Server, MongoDB y Redis al mismo tiempo. Múltiples pestañas de query por conexión, edición inline de celdas estilo DBeaver, autocompletado SQL, selección múltiple por fila con checkboxes, campos boolean con select y detección mejorada de alias de tabla.
Compatibility
Bruno-native file support
Read, edit, and save Bruno collections in both formats. Your files, your Git repo, your workflow — no proprietary cloud format.
name: Get User
type: http
seq: 1
}
get {
url: {{base_url}}/users/1
}
headers {
Authorization: Bearer {{token}}
}
// assertions
assert {
res.status: eq 200
}
Read any Bruno collection
Open folders containing .bru or .yml files directly.
Kayser parses both formats with full fidelity — auth, headers, body, assertions, scripts.
Edit and save back
Changes are serialized back to the original file format. Edit a .yml
file, save, and it stays .yml. Full round-trip fidelity preserves
your file structure.
Git-friendly workflow
Because collections are plain text files on disk, you can version-control everything with Git. Team members can share collections without syncing to any cloud service.
Environment variables
Define {{variables}} in your requests and manage
environment files. Switch between dev, staging, and production with a single
selection.
Performance
Load Testing with RAM awareness
Spawn concurrent workers to hammer your API — but intelligently. Kayser monitors your system memory in real-time and alerts you before you run out of RAM.
Configurable worker pools
Set the number of concurrent workers for your load test. The practical limit is your machine's available RAM — Kayser tells you when you're getting close.
Real-time RAM monitoring
During a load test, Kayser continuously checks memory usage. Configurable thresholds trigger visual alerts so you can reduce concurrency before the system starts swapping.
Live metrics dashboard
Watch requests per second, average response time, p95/p99 latencies, error rate, and throughput all update in real-time as your test runs.
RAM Alert: Memory usage at 78% — consider reducing worker count to prevent system slowdown.
Automation
Chained API Flows Engine
Build complex business logic with loops, variables, and conditional step execution. The ultimate flow configurer.
Logical Chaining
Pass data dynamically between any step. Deep variable extraction from JSON/HTML responses.
Advanced Loops
Iterate over arrays and handle repetitive tasks with smart logical blocks.
Granular Audits
Every transformation and logic jump is recorded. Trace your business flow with absolute precision.
Migration
Postman Migration
Export your Postman collection as JSON and import it directly. Kayser converts all your requests, auth configs, and headers to Bruno format — ready to use immediately.
Export from Postman
In Postman, go to your collection → Export → Collection v2.1 JSON. Save the file anywhere on your disk.
Import into Kayser
Open Kayser Test → File → Import Postman Collection → select your JSON file. The migration runs instantly.
Start testing
All requests, folder structure, auth settings, and headers are preserved. Your collection is ready to use in Bruno format.
Audits
AI-Powered Analytics & Notes
Synapse Kayser reports are more than stats. Add persistent notes, metadata, and leverage AI for deep performance diagnostics.
PDF Reports
Clean, professional documents with your branding and detailed step-by-step results. Professional enough to share with clients or management.
Persistent Feedback
Add notes and audits directly to each test result. Notes stay with the report, even after re-opening. Metadata management made simple.
AI Audit Engine
Feed your results to our integrated AI (Groq/Gemini/GPT) for automated bottleneck detection, optimization tips, and deep trend analysis.
Versions & Updates
The last 3 releases. Synapse Kayser evolves fast.
Version 6.5.1 Latest
- Critical fix: installed app failed to start with a database error (NODE_MODULE_VERSION).
- Fix: auto-updater now works on installed builds — app-update.yml is now bundled in the installer.
- Schema explorer in the sidebar: expandable tree per connection (schema/DB → tables/collections, Redis namespaces).
- New Diagram view (ERD): foreign-key relationships between tables, with collapsible nodes.
- Fix crítico: la app instalada fallaba al iniciar con error de base de datos (NODE_MODULE_VERSION).
- Fix: el auto-updater ya funciona en instalaciones — app-update.yml ahora se incluye en el instalador.
- Explorador de esquema en el sidebar: árbol expandible por conexión (schema/DB → tablas/colecciones, namespaces en Redis).
- Nueva vista de Diagrama (ERD): relaciones entre tablas por llave foránea, con nodos colapsables.
- + 5 more changes in full changelog →
- + 5 cambios más en el changelog completo →
Version 6.0.3
- Proxy Gateway Manager: create and manage multiple local HTTP gateways with Express + http-proxy-middleware.
- Configurable routes per gateway: prefix → target with optional pathRewrite to rewrite URLs.
- Hot start/stop of gateways — port is freed immediately when the gateway is stopped.
- Port availability check before starting, with error modal if port is already in use.
- Proxy Gateway Manager: crea y gestiona múltiples gateways HTTP locales con Express + http-proxy-middleware.
- Rutas configurables por gateway: prefijo → destino con opción de pathRewrite para reescribir URLs.
- Inicio/parada de gateways en caliente — el puerto queda libre al detener el gateway.
- Verificación de puerto disponible antes de arrancar, con modal de error si está ocupado.
- + 5 more changes in full changelog →
- + 5 cambios más en el changelog completo →
Version 5.0.0
- Integrated MCP Server: connect any AI agent (Claude, Cursor, etc.) to your HTTP collections on port 47821.
- VS Code-style split panel: open up to 2 requests in parallel, drag tabs between panels.
- Cancel in-flight requests with a visual button from the URL bar.
- MCP configuration button with copy-ready instructions and examples.
- MCP Server integrado: conecta cualquier agente IA (Claude, Cursor, etc.) a tus colecciones HTTP en el puerto 47821.
- Panel dividido estilo VS Code: abre hasta 2 requests en paralelo, arrastra tabs entre paneles.
- Botón de cancelar request en vuelo con indicador visual desde la URL bar.
- Botón de configuración MCP con instrucciones y ejemplos listos para copiar.
- + 3 more changes in full changelog →
- + 3 cambios más en el changelog completo →
How does Synapse Kayser stack up? ¿Cómo se compara Synapse Kayser?
v6.5.1 — scored across 6 categories against Postman, Insomnia and Bruno. v6.5.1 — evaluado en 6 categorías frente a Postman, Insomnia y Bruno.
vs. The Competition vs. La Competencia
| Feature | Característica | Synapse Kayser | Postman | Insomnia | Bruno |
|---|---|---|---|---|---|
| HTTP ClientCliente HTTP | ✓ Full | ✓ | ✓ | ✓ | |
| Load TestingPruebas de Carga | ✓ Unlimited | Partial | ✗ | ✗ | |
| Proxy GatewayProxy Gateway | ✓ Built-in | ✗ | ✗ | ✗ | |
| Database ManagerGestor de BD | ✓ 5 engines | ✗ | ✗ | ✗ | |
| MCP / AI AgentMCP / Agente IA | ✓ Native | Beta | ✗ | ✗ | |
| Cloud SyncSincronización | ✓ Self-hosted | Postman Cloud | Inso Cloud | ✓ Git | |
| 100% Free & Local100% Gratis y Local | ✓ Always | Freemium | Freemium | ✓ | |
| AI Queries & AuditConsultas IA & Auditoría | ✓ Multi-model | Limited | ✗ | ✗ |
Scores are self-assessed at v6.5.1. Synapse Kayser is under active development — ratings will evolve with each release.
Puntuaciones evaluadas internamente en v6.5.1. Synapse Kayser está en desarrollo activo — las calificaciones evolucionarán con cada versión.
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