Reference

Limits

Sizes, budgets and timeouts to design around.

Design within these limits from the start. Most problems with new apps come from going over one of them.

Package

Item	Limit
App file	One HTML file, under 2 MB
Glasses module	WebAssembly 1.0, up to 128 KB
Memory	Exactly one 64 KiB page as both minimum and maximum, including an 8 KiB stack
Name	1 to 31 printable ASCII characters, the same in the manifest and the Rust code

Item	Limit
Callbacks	500,000 instructions per call to `app_init`, `app_render`, `app_event` or `app_stop`
Not available	WASI, threads, SIMD, bulk memory, reference types, a start section, and files or sockets on the glasses

Per frame. Several budgets are shared with MIRA’s own interface, so leave headroom.

Item	Limit
Canvas	640 × 480, 16 gray levels
Drawing calls	512, shared with MIRA’s interface
Text calls	64, shared with MIRA’s interface
Image calls	64, with up to 131,072 image pixels in total
4-bit image memory	32 KiB, shared with MIRA’s interface
1-bit masks	Up to 32 × 32 each, 16 slots shared with MIRA’s interface

A call that doesn’t fit a budget is skipped rather than drawn partly.

Item	Limit
Phone to glasses	3,500 bytes of JSON per message
Glasses to phone	4,096 bytes of JSON per message
Realtime	380-byte scenes to the glasses, 379-byte controls back
Phone requests	8 in flight, 384-byte payloads, 8-second timeout

Item	Limit
Network	10 MB request and response bodies, 8 requests at a time
Microphone	16 kHz mono, 16-bit samples, in frames of about 100 to 256 ms. At most 256 ms waits while your page is busy.