What is App Stack Builder?

App Stack Builder is a free AI-powered tool that helps founders and developers choose the right tech stack for their projects based on budget, app type, team size, and skill level.

What is the best tech stack for SaaS in 2026?

The best tech stack for SaaS in 2026 typically includes Next.js 16 for frontend, Supabase for database and auth, Vercel for hosting, Stripe for payments, and PostHog for analytics. App Stack Builder can generate a personalized recommendation based on your specific budget and requirements.

Is App Stack Builder free to use?

Yes, App Stack Builder is completely free to use. You can generate unlimited tech stack recommendations without any cost.

What types of apps can I build with the recommended stacks?

App Stack Builder supports various app types including SaaS applications, web apps, mobile apps, e-commerce stores, internal tools, and AI/ML products.

How much does a SaaS tech stack cost per month?

A modern SaaS tech stack can cost anywhere from $0-50/month for bootstrapped startups using free tiers, $100-300/month for growth-stage startups, to $500+/month for enterprise-ready infrastructure. App Stack Builder helps you find the best tools within your specific budget.

What is the best tech stack for solo founders?

For solo founders, we recommend Next.js + Vercel (free), Supabase (free tier), Supabase Auth (free), Stripe (pay as you go), and Plausible or PostHog for analytics. This stack can run your entire SaaS for under $50/month.

Can I export my tech stack recommendations?

Yes, you can export your tech stack recommendations as a PDF document or copy them to your clipboard. You can also share a link to your stack with others.

Langflow vs Letta: Which is Better in 2026?

Name: App Stack Builder
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Agent Framework

Choosing between Langflow and Letta? Both are popular agent framework tools. Below we compare them on pricing, free tiers, features, and pros & cons so you can pick the right fit for your stack.

Langflow is for: Teams who want to build and test agent and RAG flows visually, then serve them as APIs or MCP servers.

Letta is for: Teams building agents that must remember users and context across sessions and restarts, with memory as the core design.

Quick verdict

There’s no single winner; pick on your constraint. Choose Langflow if you want to prototype agent or RAG flows visually before writing code. Choose Letta if your agent must remember users and past sessions over weeks or months.

Langflow vs Letta — Side by Side

	Langflow	Letta
Category	Agent Framework	Agent Framework
What it is	Visual builder for agent and RAG flows	Agent server and SDKs: agents with persistent memory
Languages	Visual editor; Python components	Python and TypeScript SDKs
Licence	MIT	Apache 2.0
Managed / paid option	Self-host or Langflow Desktop	Letta API: free tier, Pro $20/month plus usage
Project status	Active; 1.x	Active
Pricing	Free	Free · paid from $20/mo
Starting price	Free tier available	Free tier available
Free tier
Rating	3.9	4.0
Best for	Agent Framework — visual builder, RAG prototyping, MCP servers	Agent Framework — long-term memory, stateful agents, self-host or hosted

Pros & Cons

Langflow

Fastest way to prototype a chain visually
Exports to code rather than trapping you
Free and self-hostable

Visual editing gets unwieldy past a certain size
Versioning a flow is harder than versioning code

Letta

Memory is the design centre, not an add-on
Agents survive restarts with state intact
Comes from the MemGPT paper

Younger project with a moving API
Memory model is opinionated

Key Features Compared

Langflow

Drag-and-drop builder for agents and RAG flows
Flows served as APIs, and exposable as MCP servers
Works as an MCP client as well
Self-host it, or run Langflow Desktop locally
Owned by IBM through its DataStax acquisition
MIT licence

Letta

Persistent, self-editing agent memory (from the MemGPT research)
Agents keep their state across restarts
Self-hosted server, or the hosted Letta API
Hosted plans: free tier and Pro at $20 a month with pay-as-you-go usage
Letta Code, an open-source coding agent with memory across sessions
Apache 2.0 licence

Choose Langflow if…

You want to prototype agent or RAG flows visually before writing code.
Non-developers on your team need to edit flows.
You want flows exposed as APIs or MCP servers without extra code.

Langflow review & pricing

Choose Letta if…

Your agent must remember users and past sessions over weeks or months.
You want agents that keep state when the process restarts.
You want the choice of self-hosting or a hosted API.

Letta review & pricing

Frequently Asked Questions

Is Langflow better than Letta?⌄

What is the difference between Langflow and Letta?⌄

What it is — Langflow: Visual builder for agent and RAG flows. Letta: Agent server and SDKs: agents with persistent memory. Languages — Langflow: Visual editor; Python components. Letta: Python and TypeScript SDKs. Licence — Langflow: MIT. Letta: Apache 2.0. Managed / paid option — Langflow: Self-host or Langflow Desktop. Letta: Letta API: free tier, Pro $20/month plus usage. Project status — Langflow: Active; 1.x. Letta: Active.

Langflow vs Letta: which is cheaper?⌄

Langflow pricing: Free. Letta pricing: Free · paid from $20/mo. Confirm current pricing on each tool's official site, as plans change.

Which is rated higher, Langflow or Letta?⌄

In our catalog, Langflow rates 3.9 out of 5 and Letta rates 4.0 out of 5, so Letta has a slight edge on reviews.

When should I skip both Langflow and Letta?⌄

Skip Langflow if your flows will grow large and need code review and versioning. A code library such as LangGraph is easier to manage. Skip Letta if you only need short-lived task agents. A lighter SDK is simpler.

Sources · tool facts checked October 2026