> Canonical page: https://posttrainllm.com/artifacts/memory64-browser-behemoth

Browser memory artifact Report artifact 2026-05-31

# Memory64 Browser Behemoth Allocation

The Memory64 work is a useful public artifact because it has a crisp blocker, a measurable unlock, and a compatibility lesson: browsers can train larger local models, but feature detection matters.

- Memory64
- browser
- WASM

## Headline Numbers

Evidence class applies to each value: measured = retained evaluation or runtime result; historical = recorded result not freshly reproduced; derived = calculated or decided from records; observed = current artifact state; not-measured = an explicit evidence gap.

Allocated params

 473M browser tab, Memory64 build historical

Allocation time

 3.7s measured Behemoth allocation historical

Train step

 82.2s single sanity step after allocation historical

## Competitive Context

**System**

**Metric**

**Score**

**Size / Class**

**Comparable?**

**Readout**

 posttrainllm Memory64 build browser allocation ceiling 473M params >4GB heap path Direct Shows the browser can allocate beyond the old wasm32 limit on supported runtimes.

 posttrainllm wasm32 build browser allocation ceiling OOM around 4GB 32-bit heap path Direct Baseline failure mode that Memory64 fixes.

Direct rows share this artifact's eval setup. Directional rows are useful market context but should not be read as leaderboard claims.

## Memory ceiling

**Build**

**Outcome**

**Why**

 WASM32 OOM around 4GB heap 32-bit pointer ceiling

 WASM Memory64 473M params allocated 64-bit memory address path

## Release Blockers

### Browser support variability

Memory64 descriptor spelling and support differ across browser versions.

 Unblock: Keep runtime feature detection and clear fallback copy.

## Evidence

- [Devlog writeup](https://posttrainllm.com/devlog)
- [Browser playground](https://posttrainllm.com/playground)

## Next Release Action

Keep this as a public technical artifact; do not make it active factory work unless a browser-run specialist needs it.