pi-context-tree is a pi package that turns the session tree into a git-style workflow with a rich context panel. It keeps the working context small, fresh, and relevant, folds side-work back as clean reviewed commits, and never lets lossy auto-summaries touch your source material.

Never mutates your session JSONL — every change is append-only and recoverable, verified by byte-for-byte golden tests against real pi.

Why

As the context window fills, retrieval degrades measurably and non-uniformly — attention is a fixed budget and every token competes for a slice:

• Context rot (Chroma 2025, cited in Anthropic's context-engineering guidance) — answer quality drops with input length, even on trivial tasks.
• NoLiMa (ICML 2025) — of 13 models claiming ≥128k windows, 11 fall below half their short-context score by 32k tokens.

So pruning is a quality feature, not just a cost one. pi-context-tree treats the session like a git repo: a small trunk (master), side-work on branches, and master only ever receives clean, human-reviewed commits — never a lossy auto-summary. (Heuristic: keep the trunk in a 5–15% band.)

Why not pi's built-in /fork, /tree, and /compact?

You can already split and navigate context natively — but the moves that keep the trunk clean aren't there. That's the gap this fills:

| You want to… | Native pi | pi-context-tree | |---|---|---| | explore a side-quest, then bring back only the answer | /fork + /tree split and navigate; leaving a branch auto-summarizes (lossy, unconfirmed) | /branch + /merge --squash fold back a human-confirmed decision record — the noisy turns stay on the branch, recoverable | | reclaim a bloated tool result | /compact rewrites the whole context into a lossy summary you can't undo | /crop surgically stubs one fat result (or a whole Q&A turn) — append-only and recoverable | | see what's filling the window and act on it | /tree switches branches | /panel adds per-node token costs, a top-consumers view, decision cards, and one-key crop/branch/merge |

Features

| | | |---|---| | /branch <name> [model] | Label the current point and fork off — optionally onto a cheaper model for the side-quest. The trunk model is restored on merge. | | /merge | Close a branch — bare /merge squashes to a human-confirmed ◆ decision record (--pick for the mode selector); also discard and tournament (winner record + epitaphs for the losers). | | /crop | Stub fat tool/MCP results, or drop a whole Q&A turn — append-only, always recoverable. --top crops the biggest result inline; or review in the panel; or headless --auto --apply. | | /undo | One-key revert of the last mutation — re-open a squashed/discarded branch, restore a crop, or undo a /branch. Append-only: nothing is deleted. | | /panel (Ctrl+Q) | Full-screen TUI: the tree with per-node token costs, branch status colors, top context consumers, all decision records (/decisions --export to markdown), and an entry inspector. | | Ambient health gauge | A green→red bar above your prompt with a ▲ trend + jump attribution — ctx 38% ▲ +24% (chrome.snapshot) tells you what to crop. Honest while estimating (band + ~est, never a fake-precise %). Plus a hashed title and a 40% nudge. | | pitree | A standalone, read-only forest CLI across all your pi projects, with dangling-branch detection. |

Demo

The full-screen context panel — the tree with token costs, branch status colors, the health gauge, and one-keystroke actions:

Prefer to click around? Open the interactive TUI mockup in a browser — the keybindings match the implementation.

Requirements

• pi (the coding agent) — built and tested against @earendil-works/*@0.79.1 (newer pi usually works too; see Status).
• Node.js ≥ 22.19.

pi install handles everything else; pi provides its core packages to the extension at runtime.

Status & compatibility

Maturity: v0.1.0 — the first public release. Every command and panel view works against pi 0.79.1, covered by golden and real-TUI tests (see Development). Bug reports and feedback are very welcome.

pi version: built and tested against @earendil-works/*@0.79.1. The extension declares a permissive peer dependency on pi, so it also loads against newer pi — a new pi release doesn't require an update, and most just keep working. A non-blocking CI lane runs the full integration suite against pi@latest on every push as an early warning for breaking changes; if it (or your own session) breaks on a newer pi, please open an issue.

Install

# from npm (recommended — versioned releases):
pi install npm:pi-context-tree

# …or straight from GitHub (tracks the default branch):
pi install git:github.com/navbytes/pi-context-tree

# update: re-run the install  ·  uninstall:
pi remove npm:pi-context-tree

Pin a version for reproducibility: pi install npm:[email protected] (or git:…@v0.1.0 from GitHub). The bare forms track the latest release / the default branch. See Status & compatibility.

# load packages/extension from source (don't combine with the installed package — duplicate commands):
pi remove git:github.com/navbytes/pi-context-tree   # if previously installed
pi -e /path/to/pi-context-tree

# standalone forest CLI (read-only, never writes) — install globally from npm:
npm install -g @pi-context-tree/pitree
pitree [dir] [--dangling] [--json]
pitree ui                                            # session picker → read-only panel

Quickstart

The core loop, end to end:

# 1. install into pi (survives restarts; re-run to update)
pi install npm:pi-context-tree

# 2. inside a pi session, fork off for a side-quest
/branch fix-flaky-test               # add a model id (e.g. haiku-4.5) to run the branch on a cheaper one

#    …do the noisy exploration…

# 3. fold just the conclusion back to the trunk as a reviewed decision record
/merge            # bare /merge = squash → opens $EDITOR; save to confirm, quit empty to abort

# 4. see and prune what's in context any time
/panel            # browse the tree;  /crop --top to stub the biggest tool dump

# changed your mind? one-key, append-only revert of the last branch/merge/crop
/undo

New to the workflow? The hands-on USAGE guide walks the full loop with worked examples.

Usage

/branch <name> [model]

Labels the current point (mirrored into pi's native labels — it doubles as a checkpoint) and opens a branch, optionally switching to a cheaper model for the side-quest. The trunk model is recorded and restored on merge.

/branch fix-flaky-test               # branch at the current leaf
/branch fix-flaky-test haiku-4.5     # …and run the branch on haiku (bare id or provider/id; Tab completes)

/merge [--pick | --no-llm | --discard | --tournament] [note…]

Closes the nearest open branch at or above the leaf. Bare /merge squashes — the 99% path, straight to the editor draft. --pick opens a selector with every mode; or pass a mode directly:

• squash (the default) — the branch model drafts a decision record from the branch transcript; it opens in your editor. Nothing lands until you save — closing the editor empty aborts everything. The confirmed record becomes one ◆ decision record at the branch label; the noisy turns stay on the branch (history is append-only, never deleted).
• squash --no-llm — same flow, but you write the record into the template yourself (no LLM call).
• --discard [note] — back to the label, nothing injected, branch marked rejected. The note lands on the close marker.
• --tournament — needs open sibling branches forked from the same point. The current branch wins: ONE combined record (winner + one-line drafted epitaphs for each loser), per-sibling close markers. Epitaphs keep the trunk model from re-proposing rejected approaches.

Merging never triggers pi's lossy summarize-on-leave — you never end up with both a summary and a decision record.

/crop [--top] [--auto] [--apply] [--dry-run] [--min-tokens N] [--older-than N] [--keep glob]

Surgically stubs out fat tool/MCP results. Interactive by default: opens the panel's crop view with rule-based pre-marking when --auto is given. --auto --apply skips the panel entirely (scriptable; the only mode available where pi has no TUI). --dry-run always wins — it reports and writes nothing.

/crop --top is the one-shot path: it names the single biggest unprotected result and asks ✂ chrome.snapshot ~61k → crop? [y/N] — one trusted decision instead of the blind rules sweep.

Auto rules: ≥ --min-tokens (default 10k), older than --older-than assistant turns (default 2), never the latest result per tool (cropping those needs an explicit double-mark in the panel), never --keep matches.

Two granularities, one mechanism. The crop panel has a t toggle:

• result mode (default) — stub individual fat tool/MCP results, replaced by [cropped: tool arg, ~tokens, sha8].
• turn mode — remove a whole Q&A turn (a user question + every answer/tool entry it spawned) together. Removing only the answer would orphan tool_call/tool_result pairs and break user/assistant alternation, so turns drop as a unit. A removed turn collapses to one label-free [dropped turn — N entries, ~tokens, recoverable: sha8] note. The current/leaf turn is protected; ◆ decision records can never be swept up. Turn removal is panel-only.

Both branch at an anchor and leave the originals untouched on the previous branch — recoverable forever, nothing is ever deleted.

/undo

One-key revert of the last pi-context-tree mutation — append-only, nothing is deleted. It navigates the leaf back to the anchor the mutation recorded, and a confirm names exactly what reverts:

• after a squash / discard → re-opens the branch at its tip (the decision record stays in history, off-path);
• after a crop → restores the original fat result or Q&A turn;
• after a /branch → drops back to where you branched.

It reverts the last active mutation (the most recent still on your path) — run it again to peel back further. This is the safety net that makes cropping and merging feel reversible.

/panel (also Ctrl+Q) and /decisions [--export path]

The full-screen context panel (an overlay over pi). /decisions opens it straight on the decisions view (and prints a text listing where no TUI is available, e.g. RPC mode); /decisions --export [path] writes every trunk record to portable markdown (default ctree-decisions.md) to paste into a PR / ADR / Slack. The panel stays up across actions: pick a mutation (jump/branch/merge/crop-apply), it executes in command context after re-validating the session, and the panel reopens with fresh state until you close it. Ctrl+Q opens view-only in 0.79.1 (shortcuts get no command context and pi has no command-invoke API) — use /panel for mutations.

The context panel

A full-screen overlay with five keyboard-driven views — tree (every entry with its token cost and branch status), consumers (what's eating the window), decisions (◆ records as cards), crop, and inspect. You act from where you see the problem: b branch, m merge, c crop, ⏎ jump/fold. The screenshot above is the tree view.

Full keymap, glyph legend, and reading guide → USAGE §5 — The context panel.

Ambient UI (outside the panel)

A context-health gauge bar pinned above the prompt (CONTEXT ▓▓░ … N% band, green→red, band ticks at 5/15/40%). It carries a ▲ trend when context is filling fast and attributes jumps — ctx 38% ▲ +24% (chrome.snapshot) names what just bloated the window, right where you'll see it. While pi is still estimating (right after a session loads) it stays honest: the band word + a coarse ~est, never a fake-precise percent. Plus a footer status ⎇ branch · ctx N% band, a terminal title color-hashed per branch, a one-time nudge when context crosses 40%, and a philosophy warning on /compact.

pitree — the standalone forest CLI

pitree [dir] [--dangling] [--json]   # scan ~/.pi/agent/sessions across all projects (read-only)
pitree ui                            # session picker → the read-only panel

Flags dangling branches (open forks with no close marker) across every project. It never writes — enforced by a test.

How it works

• Append-only, always. Every mutation (/merge, /crop) writes new ctree/* entries; existing session JSONL lines are never edited or deleted, so originals are recoverable forever.
• Human-confirmed merges. The only summarization is branch→decision-record, and it always passes through your editor before entering the trunk. /merge integrates with (never fights) pi's native summarize-on-leave and never double-writes a summary and a decision record.
• Layered, pi-light core. core imports nothing of pi (pure parsing/tree/estimation/planning); tui builds the panel on pi-tui; only the extension adapter touches pi's API. See the architecture doc for the verified pi APIs (with file:line references) and the load-bearing design decisions.

FAQ

Ctrl+Q doesn't open the panel. It's view-only in pi 0.79.1 (shortcuts get no command context) — use /panel to mutate. If even view-only won't open, a terminal multiplexer may be intercepting the key; run /panel directly.

My commands appear twice. You have both the installed package and a -e dev tree loaded. Remove one — pi remove git:github.com/navbytes/pi-context-tree, or stop passing -e.

The gauge says "est" or shows a ~. pi reports zero context usage right after a session loads, so until your first fresh turn the gauge shows the band word + a coarse ~Nk est (no fake-precise percent on a guess); it switches to pi's exact number once a turn lands.

Where did /undo put me? /undo re-opens the last branch/crop by navigating your leaf back to where the mutation started — nothing is deleted. After undoing a squash you're back on the branch (the decision record is still in history, just off your current path); type and keep working, or /undo again to peel back the previous mutation.

Does this ever rewrite or delete my session? No — every change is append-only. /merge and /crop add new entries and the originals stay recoverable on the previous branch, verified by byte-for-byte golden tests against real pi.

How do I pin a version? pi install npm:[email protected] installs a specific release from npm (or git:…@v0.1.0 from GitHub). The bare npm: / git: forms track the latest published release / the default branch and update whenever you reinstall.

Development

npm install
npm test            # builds core/tui/pitree dist, then vitest in all workspaces
npm run check       # tsc --noEmit ×4 packages + biome
npm run fixtures    # regenerate committed fixtures (deterministic, byte-identical)

Layout: core (parser, tree, estimator, crop planner, panel view-model — zero pi deps) · tui (ContextPanel on pi-tui) · extension (the pi-facing surface, loaded from source via jiti) · pitree (standalone CLI/panel).

Testing. TDD throughout; packages/core/src/testkit.ts exports the deterministic SessionBuilder used by tests and fixtures. Golden integration tests (packages/extension/test/golden/) run the real pinned pi in --mode rpc against a mock OpenAI endpoint and pin the resulting session JSONL byte-for-byte. A real-TUI test boots pi in a pseudo-terminal via expect(1) and walks the panel keymap. Both self-skip when pi/expect are missing; re-record intended golden changes with UPDATE_GOLDENS=1 npm test -w @pi-context-tree/extension.

CI (.github/workflows/ci.yml): lint+types+unit per push · integration against the pinned pi (keyless) · a non-blocking pi@latest drift lane.

See CONTRIBUTING.md for the full conventions and the dev loop.

Roadmap

• Upstream a branchWithFilteredHistory API to pi (replaces the crop reconstruction-block compromise with true per-entry filtered history).
• Mutating actions from Ctrl+Q once pi exposes a command-invoke API (view-only today).
• v2 (out of v1 scope): web dashboard, RPC-attach mutation for the standalone panel, scope-selector export, global zoom-out view.

Documentation

• USAGE.md — hands-on guide (install, the core loop, commands by example, panel keys, recipes). Start here.
• pi-context-tree-spec.md — PRD/TRD v0.3 + the evidence/positioning section.
• pi-context-tree-architecture.md — verified pi APIs (file:line) + design decisions.
• pi-context-tree-mockup.html — interactive TUI mockup (open in a browser).

Contributing

Contributions are welcome! Please read CONTRIBUTING.md for the TDD / append-only / conventional-commit conventions, and see CHANGELOG.md for release notes. Bug reports and feature requests use the issue templates.

License

MIT © Naveen (navbytes).

Acknowledgements

Built for pi by earendil-works. The git-style context model and the "context is the new code" framing come from the Context Engineering deck that originated this project; the design philosophy is grounded in the context-rot and NoLiMa research cited above.