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Running Qwen3.8 Flash-Next (125B MoE, IQ3\_XXS) on the Strata engine across a mixed rig — RTX 5060 Ti + 3090 + 2x 3060, 262k context. After upgrading 0.1.39 -> 0.1.40.1, nvidia-smi showed a lot of VRAM just sitting there unused. My first thought: is Strata leaving VRAM on the table (a bug)?

1) v0.1.40.1 leaves ~10.7 GiB of VRAM unused (live nvidia-smi)

|GPU|Total (MiB)|Used|Free|
|:-|:-|:-|:-|
|RTX 5060 Ti|16,311|15,514|337|
|RTX 3060|12,288|5,580|6,332|
|RTX 3090|24,576|23,799|328|
|RTX 3060|12,288|7,912|4,000|
|Total|65,463|52,805|10,997|

\~51.6 GiB used, \~10.7 GiB free of 63.9 GiB — and the free VRAM sits mostly on the two 3060s (6.3 + 4.0 GiB). So Strata really is not filling the cards. Bug?

2) It's caching ~24% fewer experts

The model is fixed: 48 MoE layers x 512 experts = 24,576 cacheable experts (plus 48 always-on shared experts). "Resident experts" is how many Strata keeps on-GPU.

|Engine|Resident experts (GSQ-RCO)|Resident experts (orca)|
|:-|:-|:-|
|0.1.36|23,354|\-|
|0.1.38|23,170|22,131|
|0.1.39|23,168|22,145|
|0.1.40.1|17,515|18,586|

That's -24% (GSQ-RCO) and -16% (orca) resident experts on 0.1.40.1 — which is where the free VRAM comes from.

3) ...but the cache hit rate barely moved, and generation actually improved

|Engine|Cache hit rate|Gen tok/s|
|:-|:-|:-|
|0.1.36|99.7%|65.4|
|0.1.38|99.9%|69.2|
|0.1.39|99.7%|\~87|
|0.1.40.1|98.1%|104|

Hit rate dropped \~1.6 points while resident experts dropped 24%. Decode went up.

Why it is not a bug (according to Flash Next)

The experts Strata dropped are cold — the profile ranks experts by routed mass, and the tail carries <2% of traffic. Caching them buys \~0% hit rate. Spilling a cold expert over PCIe costs nothing when it is hit 0.1% of the time. The cards that stay partly empty (the 3060s) are the ones whose layers rarely route to their cached experts; filling them with cold experts would buy nothing.

So the "unused VRAM" is headroom, and the experts that used to fill it were dead weight.

(Naming note: the engine banner prints "0.1.40" because the build's CMake project version was never bumped, but the checked-out release in the running binary is v0.1.40.1 — the latest.)

(Caveat: the gen jump is partly the engine, partly because 0.1.40.1 ran at a lower 250 W power cap than the 370 W runs — but decode improved despite the lower cap, so the engine gain is real. Hit rate is measured live-serve; gen for 0.1.39 is a live-serve mean, the rest are matched-harness benches. nvidia-smi reflects the live server, so the VRAM totals are for 0.1.40.1.)