Show HN: Hippo, biologically inspired memory for AI agents
github.com
github.com
The brain persists across sessions: stop the robot, restart it, synaptic weights reload and it continues from where it left off. Decay happens naturally through R-STDP — synapses that don't contribute to reward weaken over time. No explicit forgetting mechanism needed.
Currently running on a Unitree Go2 (MuJoCo) and a 100€ Freenove robot dog (Raspberry Pi 4, real hardware). Same architecture, different bodies.
github.com/MarcHesse/mhflocke
I've been playing around with doing that with a cron job for a "dream" sequence.
I really want to get them out of main context asap, and where they belong, into skills.
What you want is a context mipmap.
Then there was the Claude article describing using filesystem hierarchy to organize markdown knowledge, which apparently beats RAG.
I've long held the belief that if you want to simulate human behaviour, you need human-like memory storage, because so much of our behaviour is influenced by how our memories work. Even something as stupid as walking into between rooms and forgetting why you went there, is a behaviour that would otherwise have to be simulated directly but can be indirectly simulated by the memory of why an Agent is moving from room to room having a chance of disappearing.
Now, as for how useful this will be for something that isn't trying to directly simulate a human and is trying to be "superintelligent", I'm not entirely sure, but I am excited that someone is exploring it.
https://ieeexplore.ieee.org/abstract/document/5952114 https://ieeexplore.ieee.org/abstract/document/5548405 https://ieeexplore.ieee.org/abstract/document/5953964
I never did get many citations for these, maybe I just wasn't very good at "marketing" my papers.
I've been working on a related problem from the other direction: Claude Code and Codex already persist full session transcripts, but there's no good way to search across them. So I built ccrider (https://github.com/neilberkman/ccrider). It indexes existing sessions into SQLite FTS5 and exposes an MCP server so agents can query their own conversation history without a separate memory layer. Basically treating it as a retrieval problem rather than a storage problem.
The "biological" memory strength shouldn't just be a time thing, and even then, the time of the AI agent should only be conformed to the AI's lifetime and not the actual clock. Look up https://stackoverflow.com/questions/3523442/difference-betwe... monotonic clock. If you want a decay, it shouldn't be related to an actual clock, but it's work time.
But memory is more about triggers than it is about anything else. So you should absolutely have memory triggers based on location. Something like a path hash. So whever an agent is working and remembering things it should be tightly compacted to that location; only where a "compaction" happens should these memories become more and more generalized to locations.
The types of memory that often are more prominent are like this, whether it's sports or GUIs, physical location triggers much more intrinsics than conscious memory. Focus on how to trigger recall based on project paths, filenames in the path, file path names, etc.
I feel like much of my life is virtual, non-localised. Writing missives to the four corners of the wind here and elsewhere; gaming online; research/chats with LLMs or on the web, email with people.
My physical location is often not important - a continuing context from non-physical aspects of my existence matters more.
That said, one of the things that's hard for me about digital life is the lack of waymarks - I used to be quite "geographical" in my thinking. Like "oh the part I found interesting was on the left page after the RGB diagram", I'd find that and also find my train of thought and extend it. Now, information can be in any myriad of freeform places across at least 3 devices and in emails, notebooks, bookmarks, chat histories, and of course my brain. When some ready syncretism of those things happens it feels like we'll make better advances. Personal agents can be a part of that.
As this repo notes is "The secret to good memory isn't remembering more. It's knowing what to forget." But knowing what is likely to be important in the future implies a working model of the future and your place in it. It's a fully AGI complete problem: "Given my current state and goals, what am I going to find important conditioned on the likelihood of any particular future...". Anyone working with these agents knows they are hopelessly bad at modeling their own capabilities much less projecting that forward.
You have some novel approaches here which I have learned a lot from! Your hypershpere physics approach is fascinating - it's a different approach than I took, but it accomplishes some tasks without an LLM. Your importance-based eviction system can significantly reduce the size of the ephemeral session state before it gets processed to persistent memory by the LLM, and your half-life knowledge decay mechanism is more elegant than the temporal approach I took.
If I am finally allowed to post a show hn, I'll post a few details, but our projects mostly solve different things and are complimentary. I can certainly use some things in Hippo to improve my system, maybe there is something that would interest you in mine -- Memforge (https://github.com/salishforge/memforge) if you're interested.
They do, the missing piece is a tool to access them. See comment about my tool that addresses this: https://news.ycombinator.com/item?id=47668270
I personally don't think a memory system should try to "select what to forget", but to store everythign and live with the contradictions inherent in history. Having said that, we need to ascribe a certain confidence to each memory at storage time, where something uncertain is described as such, and when contradicting information gets stored, it reduces the confidence even further -- this on top of time decay and retreival bumps in confidence. E. T. Jaynes argued that this could be achieved in machines through Bayesian updating, say a beta distribution is stored for each memory and upon storing knowledge that confirms this memory, the beta distribution is updated to have more confidence (the original is the prior).
If every memory has a Bayesian prior denoting confidence, and this is surfaced when recalling, then the LLM itself can decide how to sythesize the different memories. Together with a "remembered on" field, the LLM can grok that the database schema was changed, or a certain design pattern was discarded (for example).
(Full disclosure, I have developed a memory system myself which I will post here in a couple days, with a slightly different target audience than hippo).
we're building swarm-like agent memory agents share memories across rooms and nodes. Reading Steiner + Time Leap Capsules (yeah, Steins;Gate easter eggs lol).
your consolidation and decay mechanics are close to what we want. might integrate similar approach.
Here's a post I wrote about how we can start to potentially mimic mechanisms
https://n0tls.com/2026-03-14-musings.html
Would love to compare notes, I'm also looking at linguistic phenomena through an LLM lens
https://n0tls.com/2026-03-19-more-musings.html
Hoping to wrap up some of the kaggle eval work and move back to researching more neuropsych.