Softwr

Software Development · head to head

Bun vs LangSmith

Bun logo

Bun

Software Development

JavaScript runtime, bundler, test runner and package manager unified in single toolchain

From
Free
Rated
-
Full reviewWebsite
LangSmith logo

LangSmith

Software Development

Know what your agents are really doing

From
Free
Rated
-
Full reviewWebsite

The short version

  • Each has a real cost: Bun linux requires kernel 5.6 or higher (5.1 minimum but with compatibility issues); older systems not supported; LangSmith usage-based pricing applies beyond included traces; LCU charges at $1.50/LCU and LSU at $1.00/LSU
  • Prices and features above were last checked on 29 August 2026.

Where they differ

Only the attributes on which Bun and LangSmith actually diverge.

Attributes where Bun and LangSmith differ
AttributeBunLangSmith
Pricing modelopen-sourcefreemium
PlatformsmacOS, Windows, Linux, FreeBSD, AndroidWeb

Identical on both: starting price (Free), free tier (Yes), user rating (Not yet rated), category (Software Development).

What people use each for

The jobs each tool is most often brought in to do.

Bun

  • High-performance JavaScript services prioritising startup time and memory efficiencynot LangSmith
  • Single-file executable deployment without Node runtime dependenciesnot LangSmith
  • Monorepo management with workspace supportnot LangSmith
  • Full-stack development with unified toolchainnot LangSmith
  • Systems programming and shell scripting with JavaScriptnot LangSmith

LangSmith

  • Tracing agent execution step-by-step in productionnot Bun
  • Detecting agent failures affecting latency and costnot Bun
  • Monitoring token usage and latency percentilesnot Bun
  • Clustering traces to identify failure modesnot Bun
  • Self-hosting traces within VPC for data residencynot Bun

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

Bun

  • Linux requires kernel 5.6 or higher (5.1 minimum but with compatibility issues); older systems not supported
  • Native Node.js addons not supported directly; requires FFI workarounds for C libraries
  • Ecosystem less mature than Node.js; fewer third-party packages optimised for Bun
  • Windows support newer and less mature than Linux/macOS; occasional edge cases

LangSmith

  • Usage-based pricing applies beyond included traces; LCU charges at $1.50/LCU and LSU at $1.00/LSU
  • Free tier limited to 1 seat and 5,000 traces per month

Pricing, plan by plan

Bun

Free

No published plan breakdown. See the Bun review.

LangSmith

Free
  • DeveloperFree
    • 1 seat maximum
    • 5,000 base traces monthly
  • Plus$39/month
    • Unlimited seats
    • 10,000 base traces monthly
    • 1 free small serverless deployment
  • Enterprise$null/mo
    • Custom pricing
    • Self-hosted and hybrid options
    • Custom SSO, ABAC, RBAC

Which should you pick?

Choose Bun if

  • You want to start without paying.
  • You work on macOS, Windows, Linux, FreeBSD, Android.
Bun review

Choose LangSmith if

  • You want to start without paying.
LangSmith review

Questions people ask

Is Bun or LangSmith better?
Neither clearly leads. Bun starts at Free and LangSmith at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Bun or LangSmith?
Bun starts at Free and LangSmith at Free.
Does Bun or LangSmith run on more platforms?
Bun runs on macOS, Windows, Linux, FreeBSD, Android. LangSmith runs on Web.
Can I use Bun for free?
Both have a free tier, so you can try either at no cost before committing.
What is Bun best used for?
Bun is most often used for high-performance javascript services prioritising startup time and memory efficiency, single-file executable deployment without node runtime dependencies, monorepo management with workspace support, full-stack development with unified toolchain. Of those, high-performance javascript services prioritising startup time and memory efficiency and single-file executable deployment without node runtime dependencies are not what LangSmith is typically brought in for.

Answered from the vendors’ own pages

Bun: Is Bun free?

Yes, Bun is free and open-source software; no pricing tiers or subscription costs exist for the core runtime and tooling.

Source
LangSmith: What does LangSmith cost?

LangSmith Developer plan is free with up to 5,000 base traces monthly. Plus plan costs $39/month per seat with 10,000 base traces included. Enterprise pricing is custom.

Source
Bun: How much does Bun cost for production use?

Bun itself has no production licensing costs; you only pay for infrastructure (servers, compute) to run applications built with Bun.

Source
LangSmith: How does LangSmith usage-based pricing work?

Beyond included traces, LangSmith charges $1.50 per LCU (LangChain Compute Unit) for computational work and $1.00 per LSU (LangChain Storage Unit) for data storage.

Source
Bun: Does Bun offer commercial support or service tiers?

Bun's free open-source model does not include published commercial support tiers; enterprise support arrangements would require direct contact with Anthropic.

Source
LangSmith: Is there a free tier for LangSmith?

Yes, the Developer plan is free with limits on seat count (1 seat maximum) and trace volume (5,000 base traces per month).

Source
Bun: Can I use Bun in production without paying?

Yes, Bun is free to use in production since it is open-source software with no licensing fees, though you must cover your own operational costs.

Source
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