Hipocampus — Agent Memory Protocol (OpenCode)

Memory Architecture

Layer 1 (System Prompt — read at session start):
  MEMORY.md        ~50 lines   long-term memory (Core=frozen, Adaptive=compactable)
  USER.md          ~50 lines   user profile and preferences
  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, via Compaction Root in MEMORY.md)

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.

Before starting the steps below: Read MEMORY.md and USER.md first. MEMORY.md contains the Compaction Root section (memory/ROOT.md content). These are NOT auto-loaded on OpenCode — you must read them manually.

ALL 4 procedures must be completed before responding to the user NO MATTER WHAT

1. DO NOT SKIP Read SCRATCHPAD.md — current work state

2. DO NOT SKIP Read WORKING.md — active tasks

3. DO NOT SKIP Read TASK-QUEUE.md — pending items

4. DO NOT SKIP DO NOT COMPROMISE Compaction maintenance (cooldown-gated): Read memory/.compaction-state.json and hipocampus.config.json (compaction.cooldownHours, default 3).

   • Within cooldown: Skip compaction subagent — no dispatch needed.
   • Cooldown expired, file missing, or cooldownHours is 0: Write memory/.compaction-state.json with { "lastCompactionRun": "<current ISO timestamp>" }, then dispatch a subagent to run hipocampus-compaction skill USING SUBAGENTS (chain: Daily→Weekly→Monthly→Root), then run hipocampus compact + qmd update + qmd embed.

   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 cooldown is active. ALL 4 procedures must be completed before responding to the user NO MATTER WHAT

Note: The hipocampus plugin (.opencode/plugins/hipocampus.js) handles event-driven mechanical compaction on session.idle — no HEARTBEAT.md needed.

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]

• 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]

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, MEMORY.md) is updated lazily at next session start or by the agent naturally during work.

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.

File Size Targets

Rules

• MEMORY.md Core section: FROZEN. Never compact, modify, or remove.
• MEMORY.md Adaptive section: compactable. Prune when exceeding target.
• memory/*.md (raw daily logs): PERMANENT. Never delete originals.
• All memory writes via subagent — never pollute main session context.
• Search: see .opencode/skills/hipocampus-search/SKILL.md
• If this session ends NOW, the next session must be able to continue immediately.