Memory Compaction

Memory Compaction — Budget-Aware Memory Skill

Keep memory small without making it forget.

Activation

When this skill activates for a compaction pass, output:

Checking memory budgets before saving.

Never rewrite a memory file without first writing a snapshot.

Context Guard

Budget Check Protocol

Before writing any save to a budgeted file:

1. Read compaction/compaction-policy.md for the file's budget and newest-tier size.
2. Measure the current file (lines or chars per the policy unit).
3. If under budget → save normally, no compaction.
4. If over budget → run the Compaction Protocol below, then save.

Compaction Protocol

Step 1: Snapshot

• Run date to get the current timestamp.
• Copy the target file to compaction/snapshots/[basename]-[YYYY-MM-DD].md (use only the filename without its directory — e.g. main-memory, not main/main-memory — so snapshots never create nested subdirectories inside compaction/snapshots/).
• If a snapshot for today already exists, append -HHMMSS (seconds included) to avoid overwriting. If a same-second collision is still possible, use a sequential suffix (-v2, -v3).

Step 2: Split Into Tiers

• Newest tier — the last N entries per the policy. Never touched.
• Mid-age tier — entries between newest and oldest. Light summarization only.
• Oldest tier — everything older. Target for heavy compaction.

Deterministic boundary: the newest tier is the last N entries named in the policy. The oldest tier is everything below the newest tier, down to 30% of the file's total line count (rounded to whole entries). Anything between is the mid-age tier. This keeps compaction results consistent across sessions.

Step 3: Compact the Oldest Tier

• Read every entry in the oldest tier.
• Distill into a dense summary that keeps:
  • Verified facts, paths, commands, and settings
  • Decisions and the reasons behind them
  • User preferences and recurring corrections
• Drop:
  • Redundant or duplicated statements
  • Resolved chatter and one-off context
  • Filler and transitional notes
• Never include secrets, tokens, passwords, or credentials in the summary.

Step 4: Rewrite

• Replace the verbose oldest-tier entries with a single block:

## Compacted History
*Distilled from [N] entries on [YYYY-MM-DD]. Full detail in compaction/snapshots/[file]-[date].md.*

- [fact / decision / preference, one dense bullet each]

• Keep the mid-age and newest tiers in place.
• Append the new save below.

Step 5: Verify and Report

• Confirm the file is now under budget.
• Confirm no fact, decision, or preference was lost (compare against snapshot if unsure).
• Report:

Compacted [N] entries ([X] lines) into a [Y]-line history block.
[file] is now [Z]/[budget] lines. Snapshot: compaction/snapshots/[file]-[date].md

Restore Protocol

When the user says restore compaction [snapshot]:

1. Confirm the snapshot exists in compaction/snapshots/.
2. Show the user the snapshot date and size.
3. Ask for confirmation before overwriting the current file.
4. Replace the current file with the snapshot contents.

Safety Rules

1. Snapshot before every compaction — no exceptions.
2. Never compact the newest tier.
3. Preserve all facts, decisions, and preferences.
4. Never summarize secrets into a shared Compacted History block.
5. Confirm before first compaction of a user-customized file.
6. Compaction is summarization, not deletion — knowledge moves to a denser form, it does not disappear.

A good compaction is one the user never notices, except that memory stopped overflowing.