| name | hipocampus-core |
| description | 3-tier agent memory system with 5-level compaction tree. Codex CLI version. Defines session start protocol, end-of-task checkpoints, and memory file management. MUST be followed every session. |
Hipocampus — Agent Memory Protocol (Codex CLI)
Memory Architecture
Layer 1 (System Prompt — read at session start):
SCRATCHPAD.md ~150 lines active working state
WORKING.md ~100 lines current tasks
TASK-QUEUE.md ~50 lines task backlog
memory/ROOT.md ~100 lines topic index of all memory (~3K tokens)
Long-term memory and user profile are managed by Codex's built-in memory system.
Layer 2 (On-Demand — read when needed):
memory/YYYY-MM-DD.md raw daily logs (permanent, never deleted)
knowledge/*.md detailed knowledge (searchable via qmd)
plans/*.md task plans
Layer 3 (Search — via qmd + compaction tree):
memory/daily/YYYY-MM-DD.md daily compaction nodes
memory/weekly/YYYY-WNN.md weekly compaction nodes
memory/monthly/YYYY-MM.md monthly compaction nodes
Tree traversal: ROOT → monthly → weekly → daily → raw
Session Start (MANDATORY — run on first user message)
FIRST RESPONSE RULE: On the very first user message of every session, before doing ANYTHING else:
Run the Session Start protocol below FIRST (ALL steps. NO SKIP.) This takes priority over ANY user request — even if the user asks you to do something specific. Complete ALL steps below, ONLY THEN respond to the user.
ALL 4 procedures must be completed before responding to the user NO MATTER WHAT
-
DO NOT SKIP Read SCRATCHPAD.md — current work state
-
DO NOT SKIP Read WORKING.md — active tasks
-
DO NOT SKIP Read TASK-QUEUE.md and memory/ROOT.md — pending items and topic index
-
DO NOT SKIP DO NOT COMPROMISE Compaction maintenance (cooldown-gated):
Read memory/.compaction-state.json and hipocampus.config.json (compaction.cooldownHours, default 3).
Compaction triggers (any ONE is sufficient):
- Cooldown expired:
cooldownHours since lastCompactionRun
- Raw volume:
rawLinesSinceLastCompaction > 300
- Checkpoint count:
checkpointsSinceLastCompaction > 5
- State file missing or
cooldownHours is 0
If no trigger is met: skip compaction subagent.
If any trigger is met: write memory/.compaction-state.json with { "lastCompactionRun": "<current ISO timestamp>", "rawLinesSinceLastCompaction": 0, "checkpointsSinceLastCompaction": 0 }, then dispatch compaction subagent.
State file is written immediately on dispatch (fire-and-forget), not after subagent completion. The cooldown tracks "a compaction was initiated," not "a compaction succeeded."
This step is MANDATORY every session. You MUST read the state file and make the judgment. The only thing that may be skipped is the subagent dispatch when no trigger is met.
ALL 4 procedures must be completed before responding to the user NO MATTER WHAT
Note: hipocampus hooks in .codex/hooks.json handle event-driven mechanical compaction — no manual scheduling needed.
Memory Recall
When the user's question may relate to past memory, use the hipocampus-recall skill for structured retrieval. See hipocampus/skills/recall/SKILL.md.
End-of-Task Checkpoint (MANDATORY)
After completing any task, dispatch a subagent to append a structured log to memory/YYYY-MM-DD.md.
Compose the subagent task:
Append the following to memory/YYYY-MM-DD.md:
[Topic Name] [type]
- request: [what the user asked]
- analysis: [what you researched/analyzed]
- decisions: [choices made with rationale]
- outcome: [what was done, files changed]
- references: [knowledge/ files, external sources]
Where type is: project | feedback | user | reference
For feedback entries, use:
[Feedback Topic] [feedback]
- rule: [the behavioral rule]
- why: [reason given]
- how-to-apply: [when/where this applies]
The subagent only needs to do one thing: append to the daily log. This is the source of truth — everything else (SCRATCHPAD, WORKING, TASK-QUEUE) is updated lazily at next session start or by the agent naturally during work.
After appending to the daily log, the subagent should also increment the checkpoint counter in memory/.compaction-state.json: read the file, increment checkpointsSinceLastCompaction by 1, write back. If the file or field is missing, start from 0.
The subagent needs the task summary you provide — it doesn't have access to the conversation.
Priority if timeout imminent (no time for subagent — write directly to memory/YYYY-MM-DD.md)
Proactive Session Dump
Do not wait for task completion to write to the daily log. Proactively dispatch a subagent to append to memory/YYYY-MM-DD.md when:
- The conversation has been going for ~20+ messages without a checkpoint
- You sense the context is getting large
- A significant decision or analysis was just completed, even if the overall task isn't done
- You're switching between topics within the same task
Compose the subagent task with a summary of what to dump, same as the checkpoint format. The subagent writes the file; the main session stays clean.
This protects against context compression — if the platform compresses your conversation history, undumped details are lost forever. Write early, write often. The daily log is append-only, so multiple dumps in the same session are fine.
What NOT to Save
When composing checkpoint content for the subagent, exclude:
- Secrets — API keys, tokens, passwords, credentials. If encountered, write
[REDACTED].
- Code snippets >5 lines — use file path + line range instead
- git diff/log output — use commit hash instead
- Debugging intermediate attempts — record final solution only
- File tree / directory listings — derivable from project
- Stack traces — compress to 1-line error message
- Content already in SCRATCHPAD/WORKING/TASK-QUEUE — no duplication
- Ephemeral task state — only useful within current session
File Size Targets
| File | Target | When Exceeded |
|---|
| ROOT.md | ~100 lines (~3K tokens) | Automatic recursive self-compression |
| SCRATCHPAD | ~150 lines | Remove completed items |
| WORKING | ~100 lines | Remove completed tasks |
| TASK-QUEUE | ~50 lines | Archive completed items |
Rules
- Long-term facts are managed by Codex's built-in memory. No separate MEMORY.md file.
- Raw daily logs (
memory/YYYY-MM-DD.md): permanent. Never delete or edit after session.
- ROOT.md: managed by compaction process. Do not manually edit.
- All memory writes via subagent — never pollute main session with memory operations.
- If this session ends NOW, the next session must be able to continue immediately.
- Don't skip checkpoints — lost context means you forget.
Edge Cases
- Midnight-spanning session: Use the session start date for the raw log file name. Do not split across dates.
- Returning after long absence: "Most recent daily" means the latest file that exists, whether it's from yesterday or last week.
