hippo is short for hippocampus, the part of a brain that turns the day into long-term memory during sleep. Coding agents have none: every session starts from zero, and each agent is an island. Every night hippo goes through the day's Claude Code, Codex, DeepSeek Harness (dsh), OpenCode, Muse Code and Command Code sessions and turns what went wrong into rules. A second model with a fresh context checks each one against what actually happened. Keep a rule, and the next session starts with it.
A day, a night, the next morning
day Claude Code 10:07 you: "no, previews use the staging database, not production"
Claude Code 13:32 you: "dont point previews at the production database again, staging only"
night 03:30 proposed rule Use the staging database for previews, never production
reviewer confirmed, against turn 3 of both sessions
proposed fix Auth sessions.md: last 7 days -> now 24 hours
reviewer rejected: "nothing in the evidence shows the 24 hour lifetime was deployed"
morning Inbox keep it (you did not write the rule)
Codex $ hippo brief --task "Run a preview of the album page against the database"
rules:
- Run previews and manual checks against the staging database (npm run preview -- --db staging), never production.
Why this is not a memory file an agent keeps for itself:
- Built from what happened. hippo reads every session on the machine, not what an agent chose to write down. On the maintainer's machine that is 5,078 sessions and 784,867 turns, indexed in 162 seconds.
- You never write the rule. Correct an agent twice and hippo proposes it. You keep it or dismiss it.
- It cannot make things up. A second model must confirm every change against the evidence, and
hippo revert undoes any change by its receipt. On the repo's eval set with a real model it fixed 3 of 7 planted errors and damaged 0 of 8 correct notes; on the maintainer's own notes it has fixed 7 wrong statements, each checked by hand.
- Small. A session gets about 1.5 KB: the notes that matter to its task, not the whole pile.
| Agent | How it gets the memory |
|---|
| Claude Code | At session start, through hippo hooks install or the plugin. |
DeepSeek Harness (dsh) | At session start, through its plugin. |
| OpenCode | In the system prompt of each request, through its plugin. |
| Codex | At session start and first prompt, through hippo hooks install --agent codex once you trust the hooks in Codex. |
| Muse Code | Not given the notes yet. Its sessions are read like the others. |
| Command Code | Not given the notes yet. Its sessions are read like the others. |
Install
macOS (Apple silicon or Intel) or Linux (x86_64 or arm64), one line, no sudo (installs to ~/.local/bin):
curl -fsSL https://raw.githubusercontent.com/VanitasCaesar1/hippo/main/install.sh | sh
Inside Claude Code, as a plugin (then run /hippo:setup):
/plugin marketplace add VanitasCaesar1/hippo
/plugin install hippo@hippo
With Rust 1.89 or later: cargo install --locked --git https://github.com/VanitasCaesar1/hippo hippo.
Inside DeepSeek Harness (dsh), as a plugin that gives sessions the same start block and lets the model call hippo ask and hippo show day: dsh plugin --profile web add "github:VanitasCaesar1/hippo#v0.4.1&path:/plugins/dsh" (details).
Inside OpenCode 2, as a plugin that does the same: add { "package": "github:VanitasCaesar1/hippo#v0.4.1::path:plugins/opencode" } to plugins in ~/.config/opencode/opencode.json (details).
The first two minutes
hippo # lists the agent history it finds; nothing is written yet
hippo start --yes # indexes it (history only, nothing sent), then shows your last active day
hippo card # that day as a 1200 x 675 PNG to share, and the same lines as text
The overview gives the day's sessions and sub-agents, the agents' work time, how long they waited on you, the pull requests they merged, the times you corrected them (the first one quoted), the busiest sessions, and four commands to try next. It reads ~/.claude*/projects, ~/.codex/sessions and ~/.dsh/sessions; hippo start --add-root <dir> adds another folder.
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