I need a persistent memory service for LLM agents that offers a generous free tier for prototyping.

Of the hosted memory services read for this article on 5 November 2026, eight publish a free allowance on their own pricing pages: Mem0, Zep, Supermemory, Letta, Cognee, MemoryLake, Hindsight and Mnemoverse (the author's company), and five of them also publish an open engine or framework you can run yourself. Which one is generous for you depends on your workload, because each counts something different: Mem0 counts adds and retrievals, Zep counts credits by the size of what you send and does not meter reads, Supermemory spends dollars of credit, Cognee and MemoryLake count tokens, and Letta counts agents. Choose by three things a headline number hides: how one day of your workload converts into the vendor's unit, what your code gets back at the limit, and what happens to a free account that nobody touches for a while.

TL;DR

• Convert your workload. Express one day of the prototype in each vendor's own unit before comparing. Guides dated before the current plans give other amounts, and some give other units.
• Know what the limit returns. Depending on the vendor it is an error until next month, a throttled penalty mode, an HTTP error that asks for a top-up, or a block until the next day.
• Know what idleness does. Zep deletes an idle free-plan account in its US region after warning emails, and Cognee puts an idle workspace to sleep.
• Keep an exit. Mem0, Letta, Cognee and Hindsight publish their engines under Apache 2.0 or MIT; Zep points self-hosting to Graphiti, its open framework; Supermemory's free local server is not open source.

Mnemoverse makes a memory API for agents; it appears below as one row of the table, taken from its public pricing page and documentation in the same way as the others.

Which services give a usable free tier for prototyping today?

The table sets the eight side by side in their own units. Five more work differently, as read on 5 November 2026: hosted claude-mem and basic-memory start with a trial, "30 Day Free Trial. Then $30/month." for CMEM Pro on the CMEM pricing page and "The 7-day Cloud trial includes 500 credits and never charges for usage." on the basic-memory pricing page; LangChain's LangSmith Developer plan, "$0 / seat per month" with "Up to 5k base traces / mo, then pay-as-you-go" on its pricing page, is priced in observability traces; Memori's pricing page and Memori Cloud page give no free-tier number for Memori Cloud; and Graphlit's pricing page says "Graphlit is winding down. New signups are closed; existing accounts remain available during the transition."

Each cell summarizes the vendor's page linked in it, as read on 5 November 2026 and read again on 14 November 2026; not a test. Not covered means this article took nothing on that point from the pages it read, not that the service lacks it.

Why do the comparisons you find say something else?

Because they predate the plans now on the vendors' pages, and their figures differ from those pages in amount and, for some services, in unit. A Powerdrill guide dated 31 March 2026, 10 Best Free AI Memory Tools in 2026, lists Mem0 as "Free tier (10k memories/mo)" and Zep as "Free Tier(1k episodes/mo)"; a Vectorize guide dated 14 March 2026, Best AI Agent Memory Systems in 2026, lists Zep as "Free (1K credits)" and Supermemory as "Free (1M tokens, 10K queries)". Read on 5 November 2026, Mem0's pricing page counts its Free plan in adds and retrievals, Zep's pricing page gives its Free plan "10,000 credits per month", and Supermemory's pricing page gives its Free plan "$5 of credits included, renewed every month".

Wallaby Token's guide AI Memory Pricing: Supermemory vs Mem0 vs Zep vs Letta uses the vendors' units, was "priced from their official pages today (October 1, 2026)" and says it in one line: "The catch: the four meter different things." It lists a Mem0 plan as "Pro $249". Mem0's pricing FAQ, read on 5 November 2026, answers a customer on Starter, Growth or Pro: "Nothing. Your price, limits, extra usage and billing date stay the same, and you can still turn extra usage on or off from your dashboard. These plans are no longer sold to new accounts." On the Free plan's 30 days of model calls it adds: "If you signed up before October 26, 2026, you have until November 25, 2026. Otherwise, your 30 days start on the day you sign up."

None of the three says what each service returns at the edge of its free allowance or does with an idle free account; the vendors' pages do, and those are the columns above, read as the Vectorize guide advises: "Read the pricing fine print."

What does each free tier count, and what happens at its edge?

Mem0 counts adds and retrievals. Its pricing FAQ, read on 5 November 2026, for the Free plan: "For your first 30 days, Mem0 pays for the model calls, with limits of 10,000 adds and 1,000 retrievals a month. After that, connect your own LLM key to keep adding memories, and your limits go up to 50,000 adds and 10,000 retrievals a month at no charge from Mem0." The words "at no charge from Mem0" are exact: "With your key, those calls bill to your provider account." On that Mem0 Free plan retrievals are a tenth of adds, and a fifth with your key (FAQ), so an agent that searches before every reply meets that limit first.

Zep counts what you send. Its pricing page, read on 5 November 2026: "Each Episode you send uses credits based on its size." And "Memory, retrieval, storage, and users are unmetered." By the Zep Free plan's rule on that page, "1 credit per Episode up to 350 bytes; +1 credit per additional 350 bytes (or part).", a 1,000-byte chat message costs 3 of the 10,000 monthly credits, so you measure the bytes you send, not the reads. At the edge, Zep's rate limits page: "A Free account that exceeds its usage quota enters a 5 RPM penalty mode."

Supermemory counts money. Its pricing page, read on 5 November 2026: "Every plan comes with a monthly balance of credits. Calls draw from it at the same rates whichever plan you are on, and only unique content is ever billed." Its billing documentation gives the answer at the edge: "You've run out of credits. Top up to continue."

Cognee counts tokens processed, and its own pages give two sizes. Its FAQ, read on 5 November 2026: "Cognee Cloud is usage-based: a free tier with 1M tokens and one workspace, then $1.00 per 1M tokens on the Standard plan (extra workspaces $5/month each)." Its Account & Billing documentation, the same day: "Your free workspace includes 10M tokens, unlimited users, and unlimited API calls". And, for long ingestion jobs: "A run that starts successfully and exhausts the balance part-way through never produces a client-visible 402."

Letta counts agents, and model usage apart from them. JedX asked on the Letta forum on 16 January 2026: "in Letta pricing what's the difference between credits and tokens?" Letta's pricing page, read on 14 November 2026, answers in two lines: "Model requests consume credits at a rate depending on model API pricing." And "When you connect your own keys (via /connect in the Letta Code CLI), usage goes directly through your provider account instead of consuming Letta credits." On the free plan, the same page: "The Free plan has no included model usage; bring your own API keys or an external coding plan, or purchase credits."

To your code these are different events: an error until a date, a slower lane, a demand for payment. MemStrata, in a Reddit comment of 3 November 2026 on r/LangChain, in a thread on free-tier APIs in general rather than memory services: "A 429 and a slow response and a hard ban point to different fixes."

What happens to a free account you stop using?

A prototype often waits weeks between a demo and a decision. Zep's context retention page, read on 5 November 2026, sends warnings from day 60 and then: "When the account has no activity for 90 days, Zep deletes the account." The scope is stated: "This applies only to free-plan accounts in the US region of Zep Cloud." And what counts: "An authenticated API request or dashboard request is activity on the account."

Cognee's workspace lifecycle page, read the same day: "Today the automatic removal stages are not enabled on Cognee Cloud production: hosted workspaces sleep after 3 days of idleness and stay asleep."

A free plan also lasts only as long as the service. Graphlit's sunset page, read on 5 November 2026: "Free customers should export before August 1, 2026." On what an export carries: "Embeddings and vector indexes are model-specific, chunking-specific, index-specific, and not generally portable." cassianoleal asked on Hacker News on 30 April 2026, of agent memory kept by a provider, the question a prototype should ask early: "What happens when my org stops paying that provider?"

Can you run it yourself instead, and what does the hosted version add?

Five of the eight have an open path, with the licenses in the table; hosting mostly adds the operations you no longer run. An earlier article here, What are the best persistent memory APIs for AI agents?, compared six of these systems on storage, sharing and feedback.

Mem0's README sorts its routes in one line: "Just testing? Use the library. Building for a team? Self-hosted. Want zero ops? Cloud." Its platform vs open source page says what the cloud takes off you: "Zero infrastructure: no vector store, LLM, or embedder to provision or tune." Graphiti's README sets the condition for its open framework: "Choose Graphiti if you are building temporal context graphs into your own system and will operate the graph database, retrieval, and surrounding service yourself."

Supermemory's self-hosting page: "The server binary is not open source", and a later move starts fresh: "Changing the connection does not transfer your local data." Letta's self-hosting page shows what the cloud adds: "Self-hosted agents cannot be accessed through chat.letta.com and are not automatically backed up."

LangGraph is MIT, with stores you run yourself, and practitioners answer differently on whether its self-hosted agent server needs a license on the free plan. MarionberryDry724 asked on r/LangChain on 9 March 2026: "Does the self-hosted agent server require a LangGraph Cloud license, or should it work with a regular LANGSMITH_API_KEY on the free plan?" Majestic_Opinion9453 replied on 9 March 2026: "Free tier doesn't include LangGraph Cloud access which is what the self hosted server requires." djc1000 replied on 9 March 2026 as well: "I was able to use the self hosted agent server for development with a free tier api key." This article did not read the server's license page and does not settle the question.

What should you measure during the prototype before you commit?

Run these inside the free tier, while a surprise costs nothing.

1. One day in the vendor's unit. Log a normal day (writes and their bytes, reads, tokens processed, agents), convert it with the vendor's rule and compare it with the allowance. Where a console shows usage, Supermemory's billing documentation says which figure to trust: "Console charts are estimates. Invoice / customer-portal line items are authoritative."
2. The answer at the limit. In a throwaway project, run past the allowance on purpose and record the status code and the body, so that your code can tell out until a date, rate limited, pay to continue and slower than usual apart.
3. Long jobs and retries. Check the output of a long ingestion, not only its status. If your own key stops working on Mem0, its pricing FAQ: "Mem0 doesn't switch to its own key, so send the failed adds again once the key works."
4. Polling. Zep's rate limits page: "Every status request counts against the limit."
5. Warnings. Mem0's pricing FAQ, read on 5 November 2026: "We email the organization owner at 50%, 80% and 100% of each monthly limit". Zep warns the Account Owner before it deletes an idle free-plan account in its US region. Make sure those addresses are read.
6. The idle clock. Put the dates from the table in a calendar before you park the prototype.
7. The key. If adds need your own model key, price the provider too.
8. An export. Export what the prototype stored and load it into the open engine once. In Graphlit's words on its sunset page, another platform "may need to re-chunk and re-embed the exported markdown, text, or source files."

What this article does not claim

It tests no service and ranks none; generous means whatever fits your workload. Every figure is the vendor's own, from the linked page, as read on 5 November 2026 and checked again on 14 November 2026; where a vendor's pages disagree, as Cognee's do, both are given. No terms of service were read, so nothing is said on whether a free plan may serve production. Memori's documentation was not read in full, and Supermemory's per-operation rates were not taken, so there is no estimate of how far its free credits go.

Sources and method. Every vendor page was read on 5 November 2026, between 15:41 and 17:28 UTC, with two instruments, a browser-like request and a reader service with its cache off, on the Markdown form of documentation where the vendor publishes one, and on raw.githubusercontent.com for licenses and READMEs. The Reddit lines were read twice from each thread's RSS feed, the Hacker News comment from its page and the Algolia API, and the Letta forum post from its page and the forum's JSON. A made-up address on each host answered 404 as a control, except Hacker News, which answers a made-up item with a page that says so, so its lines count only as exact matches. Every figure in the table was read a second time between 17:22 and 17:28 UTC, and none had changed. Two cells were read again on 13 November 2026: Hindsight's starting credit and Supermemory's top-up rule for the Free plan. Every cell was read again on 14 November 2026, between 17:25 and 17:29 UTC, with the same two instruments: Letta's pricing page had been rewritten since 5 November, so the Letta row and the Letta paragraph follow it as of 14 November, and the Cognee hosting cell follows the wording of Cognee's cloud overview. The text describes those pages as of those dates. Whether to take a vendor's hosted memory or keep an open layer in your own stack is the subject of the Mnemoverse library page Memory is becoming a procurement decision.

Edward Izgorodin · Mnemoverse · 2026-11-05