Sorry for the off-topic, but what a bliss to see Windows 2000 interface. And what an absolute abomination from hell pretty much all the modern UIs are.
The thing I most want to use this (or some other WASM Linux engine) for is running a coding agent against a virtual operating system directly in my browser.
Claude Code / Codex CLI / etc are all great because they know how to drive Bash and other Linux tools.
The browser is probably the best sandbox we have. Being able to run an agent loop against a WebAssembly Linux would be a very cool trick.
I had a play with v86 a few months ago but didn't quite get to the point where I hooked up the agent to it - here's my WIP: https://tools.simonwillison.net/v86 - it has a text input you can use to send commands to the Linux machine, which is pretty much what you'd need to wire in an agent too.
In that demo try running "cat test.lua" and then "lua test.lua".
Out of interest I tried running my Primes benchmark [1] on both the x86_64 and x86 Alpine and the riscv64 Buildroot, both in Chrome on M1 Mac Mini. Both are 2nd run so that all needed code is already cached locally.
x86_64:
localhost:~# time gcc -O primes.c -o primes
real 0m 3.18s
user 0m 1.30s
sys 0m 1.47s
localhost:~# time ./primes
Starting run
3713160 primes found in 456995 ms
245 bytes of code in countPrimes()
real 7m 37.97s
user 7m 36.98s
sys 0m 0.00s
localhost:~# uname -a
Linux localhost 6.19.3 #17 PREEMPT_DYNAMIC Mon Mar 9 17:12:35 CET 2026 x86_64 Linux
x86 (i.e. 32 bit):
localhost:~# time gcc -O primes.c -o primes
real 0m 2.08s
user 0m 1.43s
sys 0m 0.64s
localhost:~# time ./primes
Starting run
3713160 primes found in 348424 ms
301 bytes of code in countPrimes()
real 5m 48.46s
user 5m 37.55s
sys 0m 10.86s
localhost:~# uname -a
Linux localhost 4.12.0-rc6-g48ec1f0-dirty #21 Fri Aug 4 21:02:28 CEST 2017 i586 Linux
riscv64:
[root@localhost ~]# time gcc -O primes.c -o primes
real 0m 2.08s
user 0m 1.13s
sys 0m 0.93s
[root@localhost ~]# time ./primes
Starting run
3713160 primes found in 180893 ms
216 bytes of code in countPrimes()
real 3m 0.90s
user 3m 0.89s
sys 0m 0.00s
[root@localhost ~]# uname -a
Linux localhost 4.15.0-00049-ga3b1e7a-dirty #11 Thu Nov 8 20:30:26 CET 2018 riscv64 GNU/Linux
Conclusion: as seen also in QEMU (also started by Bellard!), RISC-V is a *lot* easier to emulate than x86. If you're building code specifically to run in emulation, use RISC-V: builds faster, smaller code, runs faster.
Note: quite different gcc versions, with x86_64 being 15.2.0, x86 9.3.0, and riscv64 7.3.0.
> If you're building code specifically to run in emulation, use RISC-V: builds faster, smaller code, runs faster.
I don't really think this bears out in practice. RISC-V is easy to emulate but this does not make it fast to emulate. Emulation performance is largely dominated by other factors where RISC-V does not uniquely dominate.
I've been using the x86_64 Alpine jslinux browser image in Chrome for the last 4 hours - pulling code down via git, building several large packages from source, editing and altering code, and running their test suites. This VM may be 50 times slower than native, but it is rock solid - worked perfectly and is stable. It's simply remarkable.
I am almost sure it was done so carefully that you can extract it from the abominations which are the whatng cartel web engines with a direct to OS abstraction layer that with only some little amount of work.
Is JSLinux still an interpreter, or does it JIT compile these days?
Or are modern JS JITs so good that this is no longer a relevant distinction, i.e. is the performance of a JITted x86 interpreter effectively equivalent to a JITting x86-to-Javascript translator where the result is then itself JIT interpreted?
26 comments
[ 2.8 ms ] story [ 50.0 ms ] threadFor a more open-source version, check out container2wasm (which supports x86_64, riscv64, and AArch64 architectures): https://github.com/container2wasm/container2wasm
From "Show HN: Amla Sandbox – WASM bash shell sandbox for AI agents" (2026) https://news.ycombinator.com/item?id=46825119 :
>>> How to run vscode-container-wasm-gcc-example with c2w, with joelseverin/linux-wasm?
>> linux-wasm is apparently faster than c2w
From "Ghostty compiled to WASM with xterm.js API compatibility" https://news.ycombinator.com/item?id=46118267 :
> From joelseverin/linux-wasm: https://github.com/joelseverin/linux-wasm :
>> Hint: Wasm lacks an MMU, meaning that Linux needs to be built in a NOMMU configuration
From https://news.ycombinator.com/item?id=46229385 :
>> There's a pypi:SystemdUnitParser.
Claude Code / Codex CLI / etc are all great because they know how to drive Bash and other Linux tools.
The browser is probably the best sandbox we have. Being able to run an agent loop against a WebAssembly Linux would be a very cool trick.
I had a play with v86 a few months ago but didn't quite get to the point where I hooked up the agent to it - here's my WIP: https://tools.simonwillison.net/v86 - it has a text input you can use to send commands to the Linux machine, which is pretty much what you'd need to wire in an agent too.
In that demo try running "cat test.lua" and then "lua test.lua".
x86_64:
x86 (i.e. 32 bit): riscv64: Conclusion: as seen also in QEMU (also started by Bellard!), RISC-V is a *lot* easier to emulate than x86. If you're building code specifically to run in emulation, use RISC-V: builds faster, smaller code, runs faster.Note: quite different gcc versions, with x86_64 being 15.2.0, x86 9.3.0, and riscv64 7.3.0.
[1] http://hoult..rg/primes.txt
I don't really think this bears out in practice. RISC-V is easy to emulate but this does not make it fast to emulate. Emulation performance is largely dominated by other factors where RISC-V does not uniquely dominate.
(For APX I have patches at https://lore.kernel.org/qemu-devel/20260301144218.458140-1-p... but I have never tested them on system emulation).
Or are modern JS JITs so good that this is no longer a relevant distinction, i.e. is the performance of a JITted x86 interpreter effectively equivalent to a JITting x86-to-Javascript translator where the result is then itself JIT interpreted?