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Jarred Sumner
Bun
26.5K posts
user avatar
Jarred Sumner
Bun
@jarredsumner
building @bunjavascript at @anthropicai. formerly: @stripe (twice) @thielfellowship. high school dropout. npm i -g bun
San Francisco, CA
bun.com
Joined May 2014
646
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  • Pinned
    user avatar
    Jarred Sumner
    Bun
    @jarredsumner
    Dec 2, 2025
    People frequently ask: > How is Bun sustainable? If I bet my company’s tech stack on Bun, will Bun still be around in a few years? We didn’t have a great answer to this question, until today
    user avatar
    Bun
    @bunjavascript
    Dec 2, 2025
    Bun is joining Anthropic! bun.com/blog/bun-joins…
    1.2M
  • user avatar
    Jarred Sumner
    Bun
    @jarredsumner
    Jul 26
    Ideal JavaScript runtime architecture: 1) Implement most APIs in native code 2) Declare argument & return types in a code generator 3) Code generate JS <=> native bindings 4) Code generator tells the JIT what to expect This is the JIT half that unblocks the code generator.
    user avatar
    Bun
    @bunjavascript
    Jul 26
    In the next version of Bun bun:ffi gets up to 3x faster
    BUN:FFI • REWRITTEN AS ENGINE-NATIVE FFI IN JAVASCRIPTCORE
up to 3× faster ffi
Symbols & callbacks are engine cells • hot call sites JIT to a bare call; ret • 70× less memory/ symbol
3.0x
3.3x
O bun TinyccO bun •JSC-native
2.3x
1.4x
TINYCC = 1x
noop call 2.27 ns → 763 ps
new CString(
99.5 → 30 ns
yoga layout x1k
opentui benchmark
speedup vs previous TinyCC-based bun:ffi macOS arm64 • opentui: unmodified 347-symbol app
scrollbox 10k opentui benchmark
    59K
  • user avatar
    Jarred Sumner
    Bun
    @jarredsumner
    Jul 26
    this also makes FFI a lot more reliable
    user avatar
    Bun
    @bunjavascript
    Jul 26
    In the next version of Bun bun:ffi gets up to 3x faster
    BUN:FFI • REWRITTEN AS ENGINE-NATIVE FFI IN JAVASCRIPTCORE
up to 3× faster ffi
Symbols & callbacks are engine cells • hot call sites JIT to a bare call; ret • 70× less memory/ symbol
3.0x
3.3x
O bun TinyccO bun •JSC-native
2.3x
1.4x
TINYCC = 1x
noop call 2.27 ns → 763 ps
new CString(
99.5 → 30 ns
yoga layout x1k
opentui benchmark
speedup vs previous TinyCC-based bun:ffi macOS arm64 • opentui: unmodified 347-symbol app
scrollbox 10k opentui benchmark
    43K
  • user avatar
    Jarred Sumner
    Bun
    @jarredsumner
    Jul 25
    ratio improving
    Image
    Image
    user avatar
    Jarred Sumner
    Bun
    @jarredsumner
    Jan 1, 2023
    i wonder what a good ratio is
    54K
  • user avatar
    Jarred Sumner
    Bun
    @jarredsumner
    Jul 24
    It’s a good model
    user avatar
    Claude
    Anthropic
    @claudeai
    Jul 24
    Replying to @claudeai
    On several coding and knowledge work evaluations, Opus 5 is the new state-of-the-art:
    Image
    37K
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