pi-memory

Memory extension for pi with semantic search powered by qmd.

Thanks to https://github.com/skyfallsin/pi-mem for inspiration.

Persistent memory across coding sessions — long-term facts, daily logs, and a scratchpad checklist. Core memory works as plain markdown files. Optional qmd integration adds keyword, semantic, and hybrid search across all memory files, plus automatic selective injection of relevant past memories into every turn.

Installation

# Install from npm (recommended)
pi install npm:pi-memory

# Install from local checkout
pi install ./pi-memory

# Optional (enables `memory_search` + selective injection, requires Bun)
command -v qmd >/dev/null 2>&1 || bun install -g https://github.com/tobi/qmd

Or copy to your extensions directory:

cp -r pi-memory ~/.pi/agent/extensions/pi-memory

Optional: Enable search with qmd

When qmd is installed, the extension automatically creates the pi-memory collection and path contexts on first session start.

Note: memory_search semantic/deep modes require vector embeddings. If you see a warning like “need embeddings”, run qmd embed once and retry.

If you prefer manual setup:

qmd collection add ~/.pi/agent/memory --name pi-memory
qmd context add /daily "Daily append-only work logs organized by date" -c pi-memory
qmd context add / "Curated long-term memory: decisions, preferences, facts, lessons" -c pi-memory
qmd embed

Without qmd, all core tools (write/read/scratchpad) work normally. Only memory_search and selective injection require qmd.

Tools

Tool	Description
memory_write	Write to MEMORY.md (long-term) or daily log
memory_read	Read any memory file or list daily logs
scratchpad	Add/done/undo/clear/list checklist items
memory_search	Search across all memory files (requires qmd)

memory_search modes

Mode	Speed	Method	Best for
keyword	~30ms	BM25	Specific terms, dates, names, #tags, [[links]]
semantic	~2s	Vector search	Related concepts, different wording
deep	~10s	Hybrid + reranking	When other modes miss

If the first search doesn't find what you need, try rephrasing or switching modes.

File layout

~/.pi/agent/memory/
  MEMORY.md              # Curated long-term memory
  SCRATCHPAD.md           # Checklist of things to fix/remember
  daily/
    2026-02-15.md         # Daily append-only log
    2026-02-14.md
    ...

How it works

Context injection

Before every agent turn, the following are injected into the system prompt (in priority order):

1. Open scratchpad items (up to 2K chars)
2. Today's daily log (up to 3K chars, tail)
3. Relevant memories via qmd search (up to 2.5K chars) — searches using the user's current prompt to surface related past context
4. MEMORY.md (up to 4K chars, middle-truncated)
5. Yesterday's daily log (up to 3K chars, tail — lowest priority, trimmed first)

Total injection is capped at 16K chars. When qmd is unavailable, step 3 is skipped and the rest works as before.

Selective injection

When qmd is available, the extension automatically searches memory using the user's prompt before each turn. The top 3 keyword results are injected alongside the standard context. This surfaces relevant past decisions, preferences, and notes — even from daily logs older than yesterday — without the agent needing to explicitly call memory_search.

The search has a 3-second timeout and fails silently. If qmd is down or the query returns nothing, injection falls back to the standard behavior.

Tags and links

Use #tags and [[wiki-links]] in memory content to improve searchability:

#decision [[database-choice]] Chose PostgreSQL for all backend services.
#preference [[editor]] User prefers Neovim with LazyVim config.
#lesson [[api-versioning]] URL prefix versioning (/v1/) avoids CDN cache issues.

These are content conventions, not enforced metadata. qmd's full-text indexing makes them searchable for free.

Session handoff

When the context window compacts, the extension automatically captures a handoff entry in today's daily log:

<!-- HANDOFF 2026-02-15 14:30:00 [a1b2c3d4] -->
## Session Handoff
**Open scratchpad items:**
- [ ] Fix auth bug
- [ ] Review PR #42
**Recent daily log context:**
...last 15 lines of today's log...

This ensures in-progress context survives compaction and is visible in the next turn (via today's daily log injection).

Other behavior

• Persistence: Memory files are plain markdown on disk — readable, editable, and git-friendly.
• Tool response previews: Write/scratchpad tools return size-capped previews instead of full file contents.
• qmd auto-setup: On first session start with qmd available, the extension creates the collection and path contexts automatically.
• qmd re-indexing: After every write, a debounced qmd update runs in the background (fire-and-forget, non-blocking) unless disabled via PI_MEMORY_QMD_UPDATE.
• qmd embeddings: Semantic/deep search needs vector embeddings. If you see “need embeddings” warnings, run qmd embed once and retry.
• Graceful degradation: If qmd is not installed, core tools work fine. memory_search returns install instructions.

Configuration

Variable	Values	Default	Description
PI_MEMORY_QMD_UPDATE	background, manual, off	background	Controls automatic qmd update after writes
PI_MEMORY_NO_SEARCH	1	unset	Disable selective injection (for A/B testing)

Running tests

# Unit tests (no LLM, no qmd — fast, deterministic)
bun test/unit.ts

# End-to-end tests (requires pi + API key, optionally qmd)
bun test/e2e.ts

# Recall effectiveness eval (requires pi + API key + qmd)
bun test/eval-recall.ts

# Pin provider/model for cheaper eval runs
PI_E2E_PROVIDER=openai PI_E2E_MODEL=gpt-4o-mini bun test/eval-recall.ts

# Multiple runs for statistical robustness
EVAL_RUNS=3 bun test/eval-recall.ts

All tests back up and restore existing memory files.

Test levels

Level	File	Requirements	What it tests
Unit	test/unit.ts	None	Context builder, truncation, handoff, scratchpad parsing
E2E	test/e2e.ts	pi + API key	Tool registration, write/recall, scratchpad lifecycle, search
Eval	test/eval-recall.ts	pi + API key + qmd	Recall accuracy with vs without selective injection

Development

This is a single-file extension (index.ts). No build step required — pi loads TypeScript directly.

# Test with pi directly
pi -p -e ./index.ts "remember: I prefer dark mode"

# Verify memory was written
cat ~/.pi/agent/memory/MEMORY.md

Publishing (maintainers)

# Confirm package name is available
npm view pi-memory

# Bump version (choose patch/minor/major)
npm version patch

# Publish to npm (public)
npm publish --access public

# Verify install
pi install npm:pi-memory

Changelog

0.2.0

• Selective injection: Before each turn, the user's prompt is searched against memory via qmd. Top results are injected into the system prompt alongside standard context, surfacing relevant past decisions without explicit tool calls.
• qmd auto-setup: The extension automatically creates the pi-memory collection and path contexts on session start when qmd is available. No manual qmd collection add needed.
• Tags and links: memory_write and context injection now encourage #tags and [[wiki-links]] as searchable content conventions.
• Session handoff on compaction: session_before_compact automatically writes a handoff entry to today's daily log with open scratchpad items and recent context, preserving in-progress state across context compaction.
• Improved memory_search description: Encourages iterative search (rephrasing, mode-switching) and mentions tags/links in keyword mode.
• Context priority reordering: Injection order is now scratchpad > today > search results > MEMORY.md > yesterday (previously MEMORY.md was first). MEMORY.md budget reduced from 6K to 4K to make room for search results (2.5K).
• PI_MEMORY_NO_SEARCH env var: Disable selective injection for A/B testing.
• Unit tests: Added test/unit.ts with 18 deterministic tests (no LLM/qmd needed).
• Recall eval: Added test/eval-recall.ts for measuring recall effectiveness with/without selective injection.

0.1.0

• Initial release: memory_write, memory_read, scratchpad, memory_search tools.
• Context injection of MEMORY.md, scratchpad, and today/yesterday daily logs.
• qmd integration for keyword, semantic, and hybrid search.
• Debounced background qmd update after writes.