web.md

The web browser (--html / --serve / --web)

A second frontend over the same data — the TUI in your web browser, deliberately mirroring it: the same lazygit-style sidebar and detail tabs, the same eighth-block cost bars, the same keymap. It's curses-free, so it also works where the TUI can't.

One self-contained file: --html

opentab --html writes the whole browser as one self-contained HTML file (default opentab-report.html) — no server, no dependencies, works from disk or any static host.

• The same sidebar (Years appear with >1 year of data), the same per-scope detail tabs, Trends (T) and the price table (P) as overlays, live range scoping (R) and colour themes (C).
• Driven by the TUI keys (j/k, Tab, h/l, Esc, $, w, p/t, T, P, R) or the mouse; every table sorts on a header click.
• Every view is a shareable deep link (#/m/2026-06, #/s/<session>, …) and the browser's back button steps out.
• $ toggles the what-if estimate instantly — both cost snapshots travel in the page, so it's a client-side swap, never a reprice.
• w arms a what-if model — the TUI's w, mirrored (see below).
• Combine with --demo for a page you can publish: opentab --demo --html demo.html.

w — the what-if model

w opens a picker with two tiers — the models you've actually used (the ones with a real list price), and, one Tab away, the whole models.dev catalog, cheapest-for-your-mix first with its eff $/M blend (j/k move · f filters, word-anchored fuzzy · h/l, Tab, or a click switch the tier tabs · Enter arms · Esc cancels) — and arms one as a comparison target: "what if the expensive model had done the subagents' work too?". Used few models? The catalog tier is the point — it opens directly when nothing you've used is priceable.

It is session-scoped, exactly as in the TUI. Open a session and:

• its Subagents tab shows the whole tree — root row included — with each node's Cost beside a What-if column: that node's tokens at the target's list rates. Under it, the session comparison: TOTAL (list rates) your models $310.46 → all at anthropic/claude-opus-4-5 $104.34 saved $206.12 (66%);
• its Overview carries the same three figures (Your models / All at target / Change) — so a session that delegated nothing (no tree to table) still answers. Both read one reducer, so they can't disagree.

Both sides are priced at list rates — the only apples-to-apples basis for a rate substitution — and the baseline is computed from the session's per-model token splits, so every token is priced at the model that actually produced it. That is why arming a model a single-model session already used is exactly a $0 change, and why a subscription backend (which records $0) never reports a 100% saving. The Cost column keeps its ordinary meaning — recorded spend, $-estimated where nothing was recorded — so it does not add up to the TOTAL. There is deliberately no per-node Δ: a node can mix models, so it has no honest baseline of its own.

Everything else on the page — the sidebar, the rollups, Trends, Prices — keeps showing your actual spend, and $ keeps working as always. w again clears the target; it works in --demo too, and it is never remembered between visits (unlike the theme and the price pins).

The static file omits the per-session Turns/Tools/Context tabs (embedding them would mean scanning every session up front) — that's what the server is for.

Served live: --serve and --web

opentab --serve serves the same browser on http://localhost:8321 (--port) and adds what a static file can't have: the per-session Turns timeline and Tools attribution fetched live on drill-in, plus a refresh button that re-reads your data.

opentab --web is the same thing but also opens it in your default web browser — cross-platform: open on macOS, xdg-open on Linux, the shell association on Windows. On a headless box with no browser it just serves.

Security

The server binds to localhost only by default — the page shows prompt titles, project paths, and spend. If you want it reachable from another machine, put it behind something like Tailscale (--bind, which warns beyond localhost), never a public interface.

Themes

The web page and the TUI share one theme source: C opens the same picker in both, the bundled palettes (Catppuccin Mocha/Latte, Tokyo Night/Day, Gruvbox, Nord, Dracula, Rosé Pine, …) render identically, and the page remembers the viewer's choice in localStorage.