pi-vcc

Algorithmic conversation compactor for Pi. No LLM calls — produces a brief transcript via extraction and formatting.

Inspired by VCC (View-oriented Conversation Compiler).

Why pi-vcc

	Pi default	pi-vcc
Method	LLM-generated summary	Algorithmic extraction, no LLM
Determinism	Non-deterministic, can hallucinate	Same input = same output, always
Token reduction	Varies	35-99% on real sessions (higher on longer sessions)
Compaction latency	Waits for LLM call	30-470ms, no API calls
History after compaction	Gone — agent only sees summary	Active lineage searchable via vcc_recall (scope:"all" available)
Repeated compactions	Each rewrite risks losing more	Sections merge and accumulate
Cost	Burns tokens on summarization call	Zero — no API calls
Structure	Free-form prose	Brief transcript + 4 semantic sections

Real session metrics

Measured on real session JSONLs under ~/.pi/agent/sessions (chars = rendered message text).

Session	Messages	Before	After	Reduction	Time
Session A	2,943	997,162	7,959	99.2%	64ms
Session B	1,703	428,334	7,762	98.2%	29ms
Session C	1,657	424,183	9,577	97.7%	54ms
Session D	1,004	2,258,477	4,439	99.8%	30ms
Session E	486	295,006	11,163	96.2%	30ms
Session F	46	5,234	3,364	35.7%	5ms
Session G	27	8,595	2,489	71.0%	2ms

Features

• No LLM — purely algorithmic, zero extra API cost
• Brief transcript — chronological conversation flow, each tool call collapsed to a one-liner with (#N) refs, text truncated to keep it compact
• 5 semantic sections — session goal, files & changes, commits, outstanding context, user preferences
• Bounded merge — rolling sections re-capped after merge instead of growing unbounded
• Lossless recall — vcc_recall reads raw session JSONL, so active-lineage history stays searchable across compactions
• Scoped recall — default search is active lineage; use scope:"all" / scope:all to intentionally search across all lineages
• Regex search — vcc_recall supports regex patterns (hook|inject, fail.*build) and OR-ranked multi-word queries
• Result ranking — search results ranked by term relevance, rare terms weighted higher than common ones
• /pi-vcc-recall — slash command to search history directly, results shown as collapsible message and auto-fed to agent as context
• Fallback cut — still works when Pi core returns nothing to summarize
• /pi-vcc — manual compaction on demand

Install

pi install npm:@sting8k/pi-vcc

Or from GitHub:

pi install https://github.com/sting8k/pi-vcc

Or try without installing:

pi -e https://github.com/sting8k/pi-vcc

Usage

Once installed, pi-vcc registers a session_before_compact hook.

• Run /pi-vcc to trigger pi-vcc compaction manually.
• By default, /compact and auto-threshold compactions still go through pi core (LLM-based). Set overrideDefaultCompaction: true in the config to let pi-vcc handle all compaction paths.
• To search older active-lineage history after compaction, use vcc_recall.
• To intentionally search across all lineages, pass scope:"all" to vcc_recall or run /pi-vcc-recall <query> scope:all.
• To search and feed results to agent yourself, run /pi-vcc-recall <query> [page:N].
  • Tip: type /recall and Pi will autocomplete to /pi-vcc-recall.

How compaction works

Pi splits the conversation at the last user message. Everything after — the kept tail — stays intact and untouched. pi-vcc only summarizes the older portion before that cut point.

Compacted message structure

[Session Goal]
- Fix the authentication bug in login flow
- [Scope change]
- Also update the session token refresh logic

[Files And Changes]
- Modified: src/auth/session.ts
- Created: tests/auth-refresh.test.ts

[Commits]
- a1b2c3d: fix(auth): refresh token after password reset

[Outstanding Context]
- lint check still failing on line 42

[User Preferences]
- Prefer Vietnamese responses
- Always run tests before committing

[user]
Fix the auth bug, users can't log in after password reset

[assistant]
Root cause is a missing token refresh after password reset...
* bash "bun test tests/auth.test.ts" (#12)
* edit "src/auth/session.ts" (#14)
* bash "bun test tests/auth.test.ts" (#16)
...(28 earlier lines omitted)

Sections appear only when relevant — a session with no git commits won't have [Commits].

Sections:

Section	Description
[Session Goal]	Initial goal + scope changes (regex-based extraction)
[Files And Changes]	Modified/created files from tool calls (capped, paths trimmed to common root)
[Commits]	Git commits made during the session (last 8, hash + first line)
[Outstanding Context]	Unresolved items — errors, pending questions
[User Preferences]	Regex-extracted from user messages (always, never, prefer...)
Brief transcript	Chronological conversation flow — rolling window of ~120 recent lines, tool calls collapsed to one-liners with (#N) refs

Merge policy:

• Session Goal, User Preferences: concise sticky sections
• Outstanding Context: fresh-only (replaced each compaction)
• Files And Changes, Commits: unique union across compactions
• Brief transcript: rolling window, older lines drop off

Recall (Lossless History)

Pi's default compaction discards old messages permanently. After compaction, the agent only sees the summary.

vcc_recall bypasses this by reading the raw session JSONL file directly. By default it searches only the active conversation lineage, regardless of how many compactions have happened. Use scope:"all" only when you intentionally want to include off-lineage branches.

Search

Queries support regex and multi-word OR logic ranked by relevance:

vcc_recall({ query: "auth token" })                         // active-lineage OR search, ranked
vcc_recall({ query: "auth token", page: 2 })                // paginated (5 results/page)
vcc_recall({ query: "hook|inject" })                         // regex pattern
vcc_recall({ query: "fail.*build" })                         // regex pattern
vcc_recall({ query: "auth token", scope: "all" })           // search all lineages

Manual slash command:

/pi-vcc-recall auth token scope:all

Browse

Without a query, returns the last 25 entries as brief summaries:

vcc_recall()
vcc_recall({ scope: "all" })  // browse recent entries across all lineages

Expand

Returns full untruncated content for specific indices found via search:

vcc_recall({ expand: [41, 42] })                 // active-lineage expand
vcc_recall({ expand: [41, 42], scope: "all" })   // expand across all lineages

Typical workflow: search → find relevant entry indices → expand those indices for full content.

Some tool results are truncated by Pi core at save time. expand returns everything in the JSONL but can't recover what Pi already cut.

Pipeline

1. Normalize — raw Pi messages → uniform blocks (user, assistant, tool_call, tool_result, thinking)
2. Filter noise — strip system messages, empty blocks
3. Build sections — extract goal, file paths, blockers, preferences
4. Brief transcript — chronological conversation flow, tool calls collapsed to one-liners, text truncated
5. Format — render into bracketed sections + transcript
6. Merge — if previous summary exists: sticky sections merge, volatile sections replace, transcript rolls

Config

Config lives at ~/.pi/agent/pi-vcc-config.json (auto-scaffolded on first load with safe defaults):

{
  "overrideDefaultCompaction": false,
  "debug": false
}

• overrideDefaultCompaction (default false): when false, pi-vcc only runs for /pi-vcc; /compact and auto-threshold compactions fall through to pi core. Set true to make pi-vcc handle all compaction paths.
• debug (default false): when true, each compaction writes detailed info to /tmp/pi-vcc-debug.json — message counts, cut boundary, summary preview, sections.

Related Work

• VCC — the original transcript-preserving conversation compiler
• Pi — the AI coding agent this extension is built for

License

MIT