git:20260928.0195e54 to git:20260929.57c87f2

+ What is measured: decay and sleep are design choices. In hippo's mechanism audit, decay had no measurable effect against decay switched off (-0.7 points [-1.4, 0.1] on a 20-session synthetic test, too short for a 365-day half-life to act), and sleep lowered LongMemEval hit@5 by 3.6 points [-5.8, -1.4] under the audit's declared scorer (https://github.com/kitfunso/hippo-memory/blob/master/docs/evals/2026-09-23-mechanism-audit-round2-result.md). On that synthetic test, outcome marks and retrieval strengthening measured helping; supersession is not measured yet. hippo has not been shown to improve agent task success: the published numbers measure retrieval.

+ Retrieval, corpus first: on LongMemEval-S (500 questions, each scored against its own ~48-session haystack), `hippo recall` on a default install puts an answer session in its top 5 for 85.6% of questions inside its default 4,000-token budget, and 87.6% with the optional MiniLM embedder. With the budget lifted it scores 96.8%, but then it returns every candidate, so that figure measures the ranking (https://github.com/kitfunso/hippo-memory/blob/master/docs/evals/2026-09-28-recall-cli-longmemeval-result.md). The benchmark scripts, which are not `hippo recall`, reach R@5 98.0% at their best of five settings with the free local MiniLM embedder, and 99.8% with voyage-3-large (opt-in, paid), counting a hit when any answer session is in the top 5. Counting a hit only when every answer session is in the top 5, over the 470 questions that have an answer, MiniLM scores 86.8 to 88.5%. On the older LongMemEval oracle split with pooled retrieval, BM25 only and no embeddings (v0.11), R@5 was 74.0%.

+ Install: `npm install -g hippo-memory`, then `hippo init` in one project. It creates the project's `.hippo/` store, seeded from the last 30 days of git history, and adds hippo's instructions to the agent files already there (CLAUDE.md, and AGENTS.md, which Codex, Cursor, OpenClaw, OpenCode and Pi read); it never creates either file. When the project uses Claude Code it adds 7 hook entries to `~/.claude/settings.json`, and when it uses OpenCode, a plugin in `~/.config/opencode/plugins/`. It sets up a daily 6:15am run (crontab on Linux and macOS, a scheduled task on Windows), and its first run imports the project's Claude Code auto memory. `--no-hooks`, `--no-schedule` and `--no-learn` leave those parts out. An optional second step sets up many repos at once: every git repo in a folder and up to three levels below it gets its own store, seeded from a year of its git history, plus the same user-level hooks and the daily run, and no instruction file is patched. That command is `hippo init --scan ~`. `npx -y hippo-memory mcp` runs the MCP server without a global install.

+ - [Comparison tables](https://github.com/kitfunso/hippo-memory#comparison): hippo against nine other memory tools, plain facts first, then design bets