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Acrux Core vs LangSmith: prompts, gateway, and tracing

· 4 min read
The Acrux Core Team
LLM-ops platform

If you're building on LLMs, you eventually need four things: prompts you can change without redeploying, a reliable path to model providers, visibility into what each call did, and a way to tell whether a change helped. LangSmith and Acrux Core both address this space from different starting points. This is an honest look at where they overlap and where they differ.

note

LangSmith is a mature, widely used product from the LangChain team. This post compares product shape, not quality — the goal is to help you pick the tool that fits how you work.

The one-line difference​

LangSmith grew up around tracing and evaluation, with deep ties to the LangChain/LangGraph ecosystem, and later added prompt management.

Acrux Core is built around a runtime gateway plus prompt versioning as the spine, with tracing, a tool catalog, and evaluation layered on the same team-scoped model — one continuous line from authoring to measurement.

Prompt versioning​

Both let you store prompts and version them.

  • Acrux Core treats every version as immutable and uses aliases (production, staging) that you move between versions. Your app fetches my-prompt@production at runtime via the SDK; promoting a new version changes behavior with no redeploy. Prompts can also bind a default model.
  • LangSmith offers a prompt hub with commits and tags, and is especially convenient if you're already pulling prompts through LangChain.

If "change the live prompt without shipping code" is a core workflow, Acrux Core's alias model is built around exactly that.

The model gateway​

This is the biggest structural difference.

  • Acrux Core ships an OpenAI-compatible gateway: one endpoint in front of OpenAI, Anthropic, Gemini, and any OpenAI-compatible provider (OpenRouter, Together, local servers). You bring your own keys (encrypted at rest), register public model names, and get routing, cost accounting, caching, virtual keys, and budgets. Your app can even send a stored-prompt reference and let the gateway render and route in one call.
  • LangSmith does not position itself as a proxy/gateway; you typically call providers directly (often through LangChain) and send traces to LangSmith.

If you want a single audited, cost-visible path to every provider, that's a first-class feature in Acrux Core rather than something you assemble yourself.

Tracing​

  • LangSmith has deep, mature tracing — rich support for nested runs, and automatic instrumentation when you use LangChain/LangGraph.
  • Acrux Core traces every gateway call automatically (model, tokens, latency, cost) and accepts your own OTel-shaped spans via the SDK's trace() for whole chains. Traces can be grouped into sessions, and feedback attaches to traces and spans.

For LangChain-heavy apps, LangSmith's automatic instrumentation is hard to beat. For framework-agnostic apps, Acrux Core gives you tracing for free the moment you route through the gateway.

Tools​

  • Acrux Core has a tool catalog: callable functions versioned exactly like prompts, attached to a prompt version, with a client-side runToolLoop in the SDK or a gateway-run HTTP executor.
  • LangSmith leans on LangChain's large library of tool integrations.

Different philosophies: a governed, versioned in-house catalog versus a broad ecosystem of ready-made integrations.

Evaluation​

Both support datasets and experiments.

  • Acrux Core builds datasets from real production feedback (thumbs up/down + comments on traces), then runs experiments that sweep version × model grids with an automatic production baseline.
  • LangSmith has a rich, well-established evaluation suite with many built-in and custom evaluators.

LangSmith's eval tooling is broader today; Acrux Core's angle is tight coupling between the feedback you already collect and the datasets you evaluate against.

Hosting​

  • Acrux Core is a standard Postgres + Node stack you can self-host; BYOK keeps provider keys under your control.
  • LangSmith is primarily a managed cloud service (with enterprise self-hosting options).

Which should you pick?​

  • Choose LangSmith if you're deep in the LangChain/LangGraph ecosystem and want the most mature tracing and evaluation available today.
  • Choose Acrux Core if you want prompts, a provider gateway, tracing, tools, and evaluation as one integrated, self-hostable platform — and you value runtime prompt swaps and a single cost-visible path to every model.

Want to try the integrated story? The Quickstart gets you from sign-up to a traced, gateway-routed call in about ten minutes.