Performance and size

Viva is built for small binaries and low idle cost. Those are design targets, not claims. Every result below comes from a report in the repository, on the machine and build named in it. Treat them as baselines for that machine rather than promises about yours.

Budgets

For a minimal native application:

Budget	Target
Stripped executable	at most 4 MiB (review above 8 MiB)
Warm start to first interactive frame	at most 50 ms
Idle resident memory	at most 15 MiB
Idle CPU, GPU submissions and presents	effectively zero
Framework goroutines while idle	at most 2
An unchanged frame	no layout, no scene rebuild, no GPU submit

When goals conflict, the order is low memory, then runtime performance, then small artifacts, then correctness, then ergonomics and cross-platform consistency, and last the optional browser target.

What has been measured

M0 is the minimal macOS window: a Metal clear and present with no components. Measured on Apple silicon, macOS 15.5, Go 1.26.5, built with -trimpath -ldflags='-s -w -buildid='.

Metric	Result	Target	Verdict
Stripped executable	1,697,506 bytes	at most 4 MiB	pass
Settled CPU	0.0%	effectively zero	pass
Idle GPU submissions	0 after initial present	zero	pass
Physical footprint after a real Metal present	26.3–26.8 MiB	at most 15 MiB	miss
First scheduled frame	123.075–373.643 ms	at most 50 ms warm	miss

The report is explicit about both misses. An earlier 15 MiB figure was taken before any Metal command was submitted, and was rejected as a baseline. The fixed cost of AppKit and Metal has not yet been separated from Viva’s own, so the footprint target stands but is not met. The full reports, with machine details and reproduction commands, are in the repository’s docs/benchmarks/.

The retained scene (M1) drains an unchanged 10,000-node scene in 2.012 ns with no allocations, and updates one node of 10,000 in 12.39 ns with no allocations.

What to avoid in your own code

Viva can only keep the idle cost at zero if the application does too.

• Do not repaint on a timer. Call Invalidator.Invalidate when state changes, and let the window sleep otherwise.
• Do not allocate in Paint. It runs on every repaint, and the framework’s own steady-state paths are written to allocate as little as possible, close to nothing. Reuse buffers and keep per-frame work proportional to what changed.
• Keep callbacks short. They run on the window thread. Do slow work on another goroutine and publish the result through OnWake.
• Link only what you use. Optional subsystems live in their own packages and build tags, so an unused one adds no code to your binary.

Reproducing

The benchmarks/ directory holds the scripts behind the macOS and Linux baselines, and every report names the command that produced it. viva build reports a program’s size on its own, separate from anything around it.