↳ pi-branch-cost-footer

Branch-scoped cost & token usage in the pi footer

The footer that follows you down the branch — not the whole session.

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pi's built-in footer shows whole-session token usage and cost — it sums every entry in the JSONL tree, including the sibling branches you forked away from in /tree. If you explore three approaches from the same turn, the footer keeps quietly adding all three into one ballooning $ figure.

This extension replaces that footer with one that sums only the current branch — ctx.sessionManager.getBranch() walks the active leaf up to the root — so the cost reflects the path you're actually on. Jump between branches in /tree and the numbers update to match.

~/projects/my-app (feature/auth) • refactor-oauth
↳ ↑12.4k ↓3.1k R48k W2.0k CH94.2% $0.0421 8.3%/200k          (anthropic) anthropic/claude-sonnet-4 • xhigh

The leading ↳ marks this as the branch-scoped footer, so you can always tell it apart from the default at a glance. Toggle it off with /branch-cost to compare against the whole-session total.

Why

pi sessions are a tree, not a list. Every /fork and every /tree jump leaves the old path intact in the file. The built-in footer is honest about that — it reports the whole tree — but when you're heads-down on one branch, "how much has this line of work cost?" is the question you actually want answered.

pi-branch-cost-footer answers it. It's a drop-in: zero config, on by default, and a faithful replica of the built-in footer — only the accounting scope changes.

# /tree — jump from feature/auth to feature/payments
~/projects/my-app (feature/payments) • refactor-oauth
↳ ↑5.1k ↓0.9k R22k W1.0k CH91.7% $0.0113 2.6%/200k          (anthropic) anthropic/claude-sonnet-4 • xhigh

Same session file — different branch, different cost.

Features

• Branch-scoped totals — input, output, cache-read, cache-write, cache-hit rate, and $ cost all sum from the active branch only.
• Faithful layout — matches the built-in footer: pwd (git-branch) • session-name on line 1, the stats line on line 2, extension statuses on line 3 when present.
• Live on branch switches — re-renders when you navigate in /tree; subscribes to out-of-band git branch changes too.
• Context usage — ctx%/window with the same warning/error color thresholds as the built-in footer; ?/window while unknown (e.g. right after compaction).
• Multi-provider aware — prefixes the model with (provider) when more than one provider is available, like the built-in footer.
• Thinking-level aware — appends • <level> (e.g. • xhigh) to the model when it supports reasoning, and • thinking off when off. Read live from pi.getThinkingLevel(), so it updates as you cycle thinking effort.
• Subscription-aware — appends (sub) to cost when the active model is an OAuth subscription.
• Toggle — /branch-cost switches between this footer and pi's default, so you can compare side by side.
• Zero config — on by default; nothing to set up.

The footer line

Segment	Meaning
↳	Marks this as the branch-scoped footer (accent-colored)
↑	Cumulative input tokens on this branch
↓	Cumulative output tokens on this branch
R	Cumulative cache-read tokens on this branch
W	Cumulative cache-write tokens on this branch
CH	Latest cache-hit rate
$	Cumulative cost on this branch ( (sub) if on an OAuth subscription)
x%/window	Context usage, colored when high; ?/window while unknown
(provider) model • thinking X	Active model, prefixed with provider when several are available; • <level> (e.g. • xhigh) appended when the model supports reasoning — • thinking off when off

Segments are omitted when zero (matching the built-in footer), so a fresh branch with no assistant turns shows just ↳, the context %, and the model.

Installation

Option 1: pi install (recommended)

pi install npm:pi-branch-cost-footer

Or install directly from GitHub:

pi install https://github.com/monotykamary/pi-branch-cost-footer

Option 2: manual

git clone git@github.com:monotykamary/pi-branch-cost-footer.git
pi -e /path/to/pi-branch-cost-footer

Option 3: project-local

To enable it for a single project (not globally), install it locally and trust the project:

pi install -l https://github.com/monotykamary/pi-branch-cost-footer

Usage

Once installed and pi is running in a trusted project, the branch-scoped footer is active automatically.

• Switch branches — open /tree, navigate to any point, and continue. The footer recomputes from the new active branch on the next render.
• Compare with the default — run /branch-cost to restore pi's built-in whole-session footer; run it again to come back. A notification confirms each switch.

How branch scope is computed

ctx.sessionManager.getBranch() returns the entries from the current leaf up to the root — the active path. The extension walks those entries and sums usage.input, usage.output, usage.cacheRead, usage.cacheWrite, and usage.cost.total from every assistant message. Entries on abandoned sibling branches are never counted.

Because getBranch() is root → leaf, shared ancestors count toward every branch that descends from them. If you branch off a turn that already cost $5, the new branch starts at $5 — that's "cumulative on the branch," the same accounting /session-style tools usually intend.

Compatibility

This is a near-perfect replica of the built-in footer with one deliberate difference (the scope) and one cosmetic omission caused by what's reachable from the footer context:

• The (auto) tag on context % is omitted — the auto-compact setting isn't reachable from the footer context.

The model's • thinking X suffix is included. The active thinking level isn't on ctx, but it is on the ExtensionAPI — pi.getThinkingLevel() — and the footer factory closes over pi. It's read fresh on every render, and the TUI already re-renders when the thinking effort changes (its editor-border update calls requestRender), so the suffix updates dynamically as you cycle levels — no extra event subscription needed.

The branch-scoped cost and token totals are exact.

Development

pnpm install
pnpm test          # vitest
pnpm lint:dead     # knip

The extension is loaded by pi as TypeScript directly (no build step). Tests stub @earendil-works/pi-tui and drive the footer with a plain theme to exercise the layout and accounting logic. @earendil-works/pi-ai and @earendil-works/pi-coding-agent are type-only imports, erased at runtime and provided by pi itself.

License

MIT