Questions about hippo, answered.

Run npm install -g hippo-memory, then hippo init in the project. If the project has a CLAUDE.md, init adds a short block telling Claude to run hippo context --auto when a session starts. It also adds hooks to Claude Code's settings that keep your pinned memories in context, save a task snapshot before compaction, and run hippo sleep when the session ends. hippo init --scan ~ gives every git repo under your home folder a store and installs the same hooks, but adds no block to any CLAUDE.md. The Claude Code plugin (opens in new tab) is the alternative to these hooks; use one, not both.

hippo init adds its instructions to AGENTS.md if the project has one, and Cursor reads that file from the project root. The MCP server gives Cursor's agent tools to recall and store memories once you add hippo mcp to .cursor/mcp.json. Older hippo versions wrote the block to .cursorrules; hippo hook uninstall cursor removes it from there, and from AGENTS.md only when the block there is Cursor's own and unedited (hippo hook install cursor puts it back). A block written for Codex or another agent stays, since Cursor reads it too, and so does an edited block, since hippo cannot tell whose it is. hippo import --cursor .cursor/rules turns your existing rules into memories; it reads an older single .cursorrules file too.

hippo init adds its instructions to your AGENTS.md, which Codex reads before it starts work. Capturing Codex sessions is opt-in: hippo hook install codex wraps the Codex launcher, and hippo hook uninstall codex removes the wrapper.

hippo init detects Claude Code, Codex, Cursor, OpenClaw, OpenCode and Pi, and wires itself into each one's instruction file, hooks or plugin. It only patches instruction files that already exist. Any MCP client can use the MCP server, and other tools can call the CLI or the HTTP API that hippo serve starts.

Yes. hippo mcp runs the server over stdio, and npx -y hippo-memory mcp runs it without a global install. Add it to the MCP config of Claude Desktop, Cursor, Windsurf (now Devin Desktop), Cline or any other client (example above); in Claude Code, run claude mcp add hippo-memory -- hippo mcp. The agent gets tools such as hippo_recall, hippo_remember and hippo_outcome.

mem0 uses a language model to extract memories, OpenAI by default in its open-source library, and memories stored through its hosted MCP server live in your Mem0 account (mem0 docs (opens in new tab), checked 2026-09-28). Hippo stores memories in SQLite on your machine, needs no account and no model, and hippo init wires it into the coding agents it finds. mem0's platform and hippo both mark an older fact superseded when a newer one replaces it. Hippo also lets you mark a recalled memory wrong with hippo outcome --bad, and it drops out of the top results.

No. RAG searches a fixed corpus. Hippo's store changes as your agent works: a memory marked wrong drops out of the top results, a newer fact supersedes the old one, and memories that keep getting recalled last longer while unused ones fade on a half-life. Recall itself is search: BM25, plus embeddings if you install them.

No. Recall runs on BM25 out of the box, with no model and no network call, and a default install has no embedder. Embeddings are an optional install for hybrid search. On LongMemEval-S, where each question gets its own haystack, the benchmark scripts (not hippo recall) fuse BM25 with the free local MiniLM embedder and reach 98.0% recall@5, counting a hit when any answer session is in the top five. On LongMemEval's oracle split with one pooled store, BM25 alone scored 74.0% recall@5 in v0.11. The two runs use different setups, so they are not a before and after.

Yes, for short standing rules such as build commands, code style and things never to do. Claude Code loads CLAUDE.md and its auto memory into every session, and its memory docs (opens in new tab) say that when two rules contradict each other, Claude may pick one arbitrarily. Hippo holds the lessons that pile up, recalls the ones that match the task, and retires the ones marked wrong or replaced. hippo init adds its block to CLAUDE.md, and hippo import --claude CLAUDE.md turns existing notes into memories.

Mark it, and it drops out of the top results. hippo outcome --bad weakens the memories from the last recall, hippo supersede <id> "<new fact>" replaces one with a newer version, and hippo reject <id> --reason "<why>" stops that value from returning at all. On the synthetic E1 test, where every mark is correct, plain BM25 plus the outcome mark cut how often a marked-bad memory stayed in the top five from 71.9% to 0.0%. Real marks are noisier, because --bad marks the whole recall batch.

On your machine, in SQLite: .hippo/hippo.db in each project, plus a global store in ~/.hippo/ for lessons shared across projects, with markdown mirrors you can read and commit. Recall makes no network call by default. Text goes to an outside provider only through features that use one: an API embedder, the Jev or LLM reranker, hippo refine, and the fact extraction hippo sleep runs through Anthropic's API whenever ANTHROPIC_API_KEY is set in its environment. To turn that last one off, set {"extraction":{"enabled":false}} in .hippo/config.json.

Nothing. Hippo is MIT-licensed and needs no account or API key. Optional features that call an outside provider bill through it: the Jev reranker costs about 0.0004 USD a recall, and API embedders and sleep's fact extraction bill your own keys. Memory text handed to your agent uses context tokens, and hippo tokens shows how many.

Judge it by what is tested. 3,500+ tests run against a real database, with no module mocks and no mocked store, and a negative test checks that one tenant cannot read another's memories. It is MIT-licensed and has zero runtime dependencies. What has not been shown yet is whether agents do better work with it: the published numbers measure retrieval.

Not yet. The published numbers measure retrieval: whether the right memory comes back, and whether a memory marked wrong stays out of the results. A paired test that runs real agent sessions with and without hippo is under way. Every measurement, including failed runs and one retracted claim, is indexed in docs/evals (opens in new tab).