Viaduct vs Langtail

A side-by-side comparison built from both listings. Blank cells mean the company has not given that detail; we never guess.

Viaduct compared with Langtail
Detail	Viaduct	Langtail
What it does	Free C4 modeling tool with an MCP server for software teams to share architecture context with AI development tools	Prompt management platform for building, testing, and deploying AI prompts collaboratively
Stage	Not given	Not given
Founded	Not given	2023
Based in	LT	CZ
Pricing model	Freemium	Not given
Pricing	Browser: Free with account. Desktop: €10 a month after 7-day free trial, one licence covers 3 machines. Enterprise: custom pricing.	Free plan: $0/month with unlimited users, 2 prompts or assistants, 1,000 logs per month, 30 days data retention. Pro: $99/month + VAT for 1 user, 20 prompts or assistants, unlimited logs, 90 days data retention. Team: $499/month + VAT for 10 users, unlimited prompts or assistants, unlimited logs, 1
Key features	System context, container, component, and code diagrams Live collaboration on models MCP server for AI coding agents Change sets for scoped agent work Organization SSO JSON import and export OpenAPI contract export Desktop app for macOS, Windows, Linux AI assistant for model descriptions Installable PWA	Spreadsheet-like interface for managing prompts with no coding required Natural language evaluation, pattern matching, and custom code testing Experiment with models and parameters to optimize prompts Data-driven insights from prompt performance and user interactions AI Firewall preventing prompt injections and DoS attacks Support for multiple LLM providers TypeScript SDK and OpenAPI support Self-hosting option for maximum security
What makes it different	Model elements exist once and appear on every level they belong to Endpoints are real OpenAPI documents, not diagram labels Desktop app keeps all data local and offline-capable Free browser version with no paywall or feature limits AI agents read and write architecture through MCP	Prevents unpredictable LLM outputs through proper prompt management and testing Non-technical teams can manage prompts with intuitive spreadsheet interface Built-in AI Firewall for security and safety of AI outputs Works seamlessly with all major LLM providers
Community votes	0	0
DR (Domain Rating by Ahrefs)	20 no change since last check	29 no change since last check
Trust Flow (Majestic)	10	6
Citation Flow (Majestic)	28	34
Referring domains (Majestic)	74	275

5 details filled in for both companies.

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