--- title: "DSPy vs Letta: Which is Better in 2026? | App Stack Builder" description: "DSPy vs Letta compared for 2026 — pricing, free tiers, features, pros & cons. See which agent framework tool is the better fit for your startup." source: https://appstackbuilder.com/compare/dspy-vs-letta retrieved: 2026-10-30 --- ![](https://appstackbuilder.com/logos/dspy.png) vs ![](https://appstackbuilder.com/logos/letta.png) # DSPy vs Letta: Which is Better in 2026? Agent Framework Choosing between [DSPy](https://appstackbuilder.com/tools/dspy) and [Letta](https://appstackbuilder.com/tools/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. DSPy is for: Teams with an evaluation set who want to optimize prompts and LLM pipelines against a metric instead of hand-tuning them. 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 DSPy if you have examples and a metric, and want prompts tuned automatically. Choose Letta if your agent must remember users and past sessions over weeks or months. ## DSPy vs Letta — Side by Side | | DSPy | Letta | | --------------------- | ------------------------------------------------------------------------- | ------------------------------------------------------------------------ | | Category | Agent Framework | Agent Framework | | What it is | Code library: framework for optimizing prompts and LLM programs | Agent server and SDKs: agents with persistent memory | | Languages | Python | Python and TypeScript SDKs | | Licence | MIT | Apache 2.0 | | Managed / paid option | None | Letta API: free tier, Pro $20/month plus usage | | Project status | Active; 3.x | Active | | Pricing | Free | Free · paid from $20/mo | | Starting price | Free tier available | Free tier available | | Free tier | ✓ | ✓ | | Rating | 4.2 | 4.0 | | Best for | Agent Framework — prompt optimization, evaluation-driven, research-backed | Agent Framework — long-term memory, stateful agents, self-host or hosted | ## Pros & Cons ![](https://appstackbuilder.com/logos/dspy.png) [DSPy](https://appstackbuilder.com/tools/dspy) * ✓Replaces prompt tinkering with measurable optimisation * ✓Strong research backing (Stanford) * ✓Composes well with any model provider * ✗A genuinely different mental model to learn * ✗Optimisation runs cost tokens ![](https://appstackbuilder.com/logos/letta.png) [Letta](https://appstackbuilder.com/tools/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 ### DSPy * ✓Signatures and modules replace hand-written prompts * ✓Optimizers, including GEPA, that tune prompts against your metric * ✓Works with most model providers * ✓From Stanford NLP * ✓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 DSPy if… * ✓You have examples and a metric, and want prompts tuned automatically. * ✓Your pipeline keeps breaking when you switch models, and you want to re-optimize instead of rewriting prompts. [DSPy review & pricing ](https://appstackbuilder.com/tools/dspy) ### 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 ](https://appstackbuilder.com/tools/letta) ## Frequently Asked Questions Is DSPy better than Letta?⌄ There’s no single winner; pick on your constraint. Choose DSPy if you have examples and a metric, and want prompts tuned automatically. Choose Letta if your agent must remember users and past sessions over weeks or months. What is the difference between DSPy and Letta?⌄ What it is — DSPy: Code library: framework for optimizing prompts and LLM programs. Letta: Agent server and SDKs: agents with persistent memory. Languages — DSPy: Python. Letta: Python and TypeScript SDKs. Licence — DSPy: MIT. Letta: Apache 2.0\. Managed / paid option — DSPy: None. Letta: Letta API: free tier, Pro $20/month plus usage. Project status — DSPy: Active; 3.x. Letta: Active. DSPy vs Letta: which is cheaper?⌄ DSPy 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, DSPy or Letta?⌄ In our catalog, DSPy rates 4.2 out of 5 and Letta rates 4.0 out of 5, so DSPy has a slight edge on reviews. When should I skip both DSPy and Letta?⌄ Skip DSPy if you don’t have an evaluation set yet. DSPy’s optimizers need one to work. Skip Letta if you only need short-lived task agents. A lighter SDK is simpler. Sources · tool facts checked October 2026 1. 1.[DSPy 3.3.1 release notesnewreleases.io ](https://newreleases.io/project/github/stanfordnlp/dspy/release/3.3.1) 2. 2.[Letta Code (Letta docs)docs.letta.com ](https://docs.letta.com/letta-code) See more options in our guide to the [best agent framework tools for startups](https://appstackbuilder.com/categories/agent-framework). ## Still not sure which to pick? Get a free, AI-powered tech stack — including the best agent framework pick for your budget and team — in 60 seconds. [Build my stack free ](https://appstackbuilder.com/build-stack)