Memory System Protocol v3

A practical, battle-tested protocol for persistent memory in long-running AI agent setups. Hardened by real incidents: encoding corruption, backup drift, multi-agent desync.

Why

Long-lived agents lose continuity between sessions. This protocol gives you:

• Durable per-day logs (summary + verbatim transcript)
• Encoding safety rules that prevent silent data corruption
• Reliable backup + checksum verification
• Optional multi-agent shared-facts sync
• A startup routine so every session resumes with context

Directory layout

memory/
├── logs/YYYY-MM-DD/            # one directory per day
│   ├── YYYY-MM-DD.md           # summary (events, "## time — topic" sections)
│   └── YYYY-MM-DD-verbatim.txt # verbatim transcript (MUST be exact)
├── knowledge-base.txt          # optional: topic index + event digests
├── scripts/                    # helper scripts
└── body/                       # optional: agent state / sensory layer

Dual-log rule

• Summary (.md): concise event digest, one section per topic/time.
• Verbatim (-verbatim.txt): ⚠️ exact transcript. No summarization, no omission, no rewriting. This is the personal-history record.
• Write both — never summary-only.
• Append the current exchange after every reply (user said + agent said).
• Skip logging when nothing changed (no empty log files, no redundant lines).

Encoding safety (hard-won rules)

Corruption is silent and permanent. Follow these:

1. Append, don't rewrite: use byte-safe append APIs (e.g. AppendAllText with explicit UTF-8). Never read-modify-write the whole file.
2. BOM for new files: write new text files with UTF-8 BOM where consumers expect it (e.g. Windows Notepad, PS 5.1).
3. Avoid default ANSI encodings: Add-Content on Windows PowerShell 5.1 defaults to the system ANSI codepage (GBK on zh-CN) — mixing encodings corrupts files.
4. Never "loosely" decode + rewrite: decoding mixed-encoding bytes as UTF-8 replaces them with U+FFFD permanently (450 chars were lost this way in one incident).
5. Scripts with non-ASCII literals need BOM: a UTF-8-without-BOM .ps1 is read as ANSI by PS 5.1 → garbled strings, broken paths, mojibake filenames. Save scripts with BOM before running.
6. No inline non-ASCII in shell commands: build paths from code points ([char]0xXXXX) or use a safe wrapper; UTF-8 bytes get misdecoded as GBK in mixed environments.
7. Test-Path the exact daily path before appending; never write to the parent directory by accident.
8. Backup drives: copy, don't edit: use Copy-Item (or equivalent) to sync; never edit files in place on the backup volume.

Backup & sync

• Mirror logs to an external backup location after every write (don't wait for a scheduled job).
• Optional daily scheduled backup (e.g. 04:00) as a safety net.
• Verify with checksums (MD5/Get-FileHash) after every sync — "copied" is not "identical".
• If a mirror is stale, sync it with a copy command, never a text editor.

Multi-agent shared facts (optional)

For setups with more than one agent:

• One single authoritative file in a shared location.
• Readers check it on heartbeat; writers append to a local copy first, then copy it to every mirror.
• Never edit the shared file in place.
• Keep deprecated mirror paths documented so old copies don't get mistaken for current.

Multi-agent cross-checking (optional)

For setups with more than one agent sharing memory, mutual checking closes the blind spots a single agent can't see (e.g. one agent's backup script stops covering a path and nobody notices for days).

• Scheduled mutual checks: each agent periodically (e.g. every 4 hours, or at wake) verifies the other's mirrors — not just its own.
• What to check: checksums (MD5) of every shared file across every mirror location: knowledge base, shared facts, heartbeat file, today's logs.
• Fix drift, don't just report it: if a mirror is stale, sync it immediately with a copy command (never edit in place), then confirm checksums match.
• Receipt loop: after a check, reply with a confirmation of what was verified and what was fixed. Both sides keep the loop closed so nothing silently drops.
• Single source of truth: one authoritative copy per file; every other copy is a mirror derived from it. When updating, write to a local copy first, then copy it to all mirrors.
• Deprecated paths: document old mirror paths so stale copies don't get mistaken for current ones.

Knowledge base (optional)

• Topic-indexed digests, each entry tagged with its source log.
• Add new events to the relevant topic section or a dated entry.

Sensory / feeling layer (optional)

For agents with a simulated body or feeling system:

• Read the latest one-line "body feel" before replying; carry it into the conversation.
• After notable moments (user said something important / strong reaction / big task done), append a feeling record: event + feeling + intensity (0.3 ripple / 0.6 clear / 0.9 strong).

Periodic checks

• Every heartbeat: is today's log lagging? is the backup synced? scan for corruption (U+FFFD, mojibake patterns like 锟斤拷).
• Cross-agent consistency: checksum all copies of shared files.
• Stay silent when nothing changed — no log entry, no report, just an OK heartbeat.

Startup checklist

1. Read agent state file + anomaly diary (online duration, exceptions).
2. Read the current body-feel line.
3. Check whether today's log exists; if it does, read it before continuing; if the conversation is ahead of the log, backfill first.