Savings and statistics

mbx stats shows what sharing builds has saved on this machine and the date counting began. It prints durations such as 50m 59s or 2d 4h.

mbx stats
mbx stats --json

The report combines lifetime savings with a snapshot of the store, its recorded workspaces, and the managed target directories. The Store screen in mbx tui shows the same savings and sharing figures. mbx cache stats is the smaller report on the action store, managed targets, and learned incremental state currently held.

What the numbers mean

Figure	Meaning
Compiler time avoided	Estimated compiler work skipped by cache hits, accumulated across builds.
Cache hits	Compilations served from cache since counting began.
Pruned by mbx	Cumulative bytes collected from managed targets, learned incremental state, generated source trees, and the store, by both automatic sweeps and explicit mbx gc runs. The targets / cache split counts everything but the store as targets.
Automatically pruned	Bytes collected by automatic sweeps, counted from a separate start date.
Requested removals	Bytes removed by confirmed migrations or explicit workspace removals, kept separate from pruning.
Copying avoided	Cumulative output bytes materialized by reflink or hard link rather than copied.
With separate caches	Sum of the logical cache bytes each live recorded workspace can reach, counting shared content once for each workspace.
Duplication avoided	A conservative lower-bound estimate: the separate-cache sum minus the entire shared store, floored at zero.

Read these figures with their limits in mind:

• Compiler time avoided is not elapsed wall-clock time saved, because compilations run in parallel.
• Pruned by mbx, Automatically pruned, and Requested removals are logical file sizes, not physical space reclaimed.
• Copying avoided is not the disk space saved now: files may later change or be deleted.
• Duplication avoided understates sharing. The store also holds objects no live workspace claims, and mbx subtracts those too.

The sharing estimate counts logical cache bytes, not physical filesystem blocks, and leaves out target directories. It covers independent workspaces as well as worktrees. mbx records each checkout it builds, and a recorded workspace counts as live while its checkout is still on disk and mbx has built it in the last 30 days. To attribute bytes to workspaces, mbx walks these checkout records and the cache entries each workspace can reach. The TUI repeats that walk every 30 seconds while the Store screen is open. On an active machine, builds can change the store while mbx is reading it.

mbx keeps the lifetime totals in a savings ledger. Dates use UTC. Until the ledger records anything, the report says no savings recorded yet; reading a report does not start a new ledger. Automatically pruned starts counting at the first ledger update from an mbx version that tracks automatic sweeps separately, and shows not tracked yet until then. Older versions did not distinguish automatic from explicit collection, so mbx does not guess or backfill that history.

JSON report

The versioned JSON report includes version, store, savings, cache, and sharing. Sizes are integer bytes, durations are nanoseconds, and times are Unix timestamps in seconds; an unknown start time is null. Its field names identify estimates and cumulative counters. JSON never contains quips.

A little personality

With the default savings = "quips", the text report and the TUI add a line grounded in the recorded figures, such as “321 compilations served reheated. rustc can finish its coffee.” Set savings = "plain" or savings = "off" to omit the quip. mbx stats and the Store screen still show every figure with either setting.