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.

LangChain vs Letta: Which is Better in 2026?

Name: App Stack Builder
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Agent Framework

Choosing between LangChain 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.

LangChain is for: Python and TypeScript teams that want the largest set of model, vector-store and tool integrations, with LangSmith for tracing and evaluation.

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 LangChain if you want ready-made integrations for many models, vector stores and tools. Choose Letta if your agent must remember users and past sessions over weeks or months.

LangChain vs Letta — Side by Side

	LangChain	Letta
Category	Agent Framework	Agent Framework
What it is	Code library: LLM app and agent framework	Agent server and SDKs: agents with persistent memory
Languages	Python, JavaScript/TypeScript	Python and TypeScript SDKs
Licence	MIT	Apache 2.0
Managed / paid option	LangSmith: free Developer plan, Plus $39/seat/month	Letta API: free tier, Pro $20/month plus usage
Project status	Active; 1.x	Active
Pricing	Free · paid from $39/user/mo	Free · paid from $20/mo
Starting price	Free tier available	Free tier available
Free tier
Rating	4.5	4.0
Best for	Agent Framework — integrations, Python and TypeScript, LangSmith tracing	Agent Framework — long-term memory, stateful agents, self-host or hosted

Pros & Cons

LangChain

Largest ecosystem & integrations
Free open-source core
Python and TypeScript
LangSmith for observability

Abstractions can feel heavy
Fast-moving API surface

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

LangChain

Integrations for most model providers, vector stores and tools
Python and JavaScript/TypeScript libraries
Agents built on the LangGraph runtime since LangChain 1.0
LangSmith for tracing and evals: free Developer plan (5,000 traces a month), Plus at $39 per seat a month
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 LangChain if…

You want ready-made integrations for many models, vector stores and tools.
Your team works in both Python and TypeScript.
You want tracing and evaluation from the same vendor through LangSmith.

LangChain review & pricing

Choose Letta if…

Budget is tight — paid plans start lower ($20/mo vs $39/mo).
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 LangChain better than Letta?⌄

What is the difference between LangChain and Letta?⌄

What it is — LangChain: Code library: LLM app and agent framework. Letta: Agent server and SDKs: agents with persistent memory. Languages — LangChain: Python, JavaScript/TypeScript. Letta: Python and TypeScript SDKs. Licence — LangChain: MIT. Letta: Apache 2.0. Managed / paid option — LangChain: LangSmith: free Developer plan, Plus $39/seat/month. Letta: Letta API: free tier, Pro $20/month plus usage. Project status — LangChain: Active; 1.x. Letta: Active.

LangChain vs Letta: which is cheaper?⌄

LangChain pricing: Free · paid from $39/user/mo. Letta pricing: Free · paid from $20/mo. Confirm current pricing on each tool's official site, as plans change.

Which is rated higher, LangChain or Letta?⌄

In our catalog, LangChain rates 4.5 out of 5 and Letta rates 4.0 out of 5, so LangChain has a slight edge on reviews.

When should I skip both LangChain and Letta?⌄

Skip LangChain if you want a thin library you can read end to end. smolagents and the OpenAI Agents SDK are much smaller. Skip Letta if you only need short-lived task agents. A lighter SDK is simpler.

Sources · tool facts checked October 2026