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bonsai keeps your Go binary small the way you keep a tree small: deliberate pruning. It builds your target, works out which dependencies are actually driving its size and your minimum Go version, and tells you how much each one would save if you cut it — including the transitive ones you never imported directly.

The thing it’s built around: “this dep is 8 MB, so dropping it saves 8 MB” is almost never true. Most of that weight is shared with other dependencies that aren’t going anywhere. What matters is how much only it keeps alive. bonsai gives you that number so the call stays yours.

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The mental model in one minute

bonsai treats your binary like a memory heap and your dependencies like objects on it. A dependency’s honest cost isn’t its own size — it’s its retained size: itself plus everything that becomes unreachable if it goes away. Shared weight is credited to nobody, because it doesn’t disappear when just one of its holders leaves.

Everything bonsai reports is a reading off that one idea. If you only remember one thing: rank by what a cut actually frees, not by what’s biggest.