LangSmith Alternatives (2026): 7 Tools Compared

Oren CohenPublished October 6, 2026Sources reviewed October 6, 20267 min read

The main LangSmith alternatives in 2026: Langfuse and Opik for open source, Arize Phoenix for OpenTelemetry-native tracing, Braintrust for evaluation depth, and W&B Weave or Datadog if you already use them. Converra is different: it adds verified fixes on top of any of them.

Converra is our product, so it is labeled as a complement rather than ranked against the others. Every vendor statement below comes from that vendor's own documentation or pricing page, checked on October 6, 2026.

The short version

Pick the replacement by what you need most: self-hosting (Langfuse, Opik, Phoenix), evaluation depth (Braintrust), or a platform you already run (Weave, Datadog). None of them returns a per-deploy verdict on whether a fix worked; that is the gap Converra fills alongside any of them.

Why teams look for a LangSmith alternative

The common reasons are self-hosting (LangSmith's self-hosted option is an Enterprise add-on), per-seat pricing as a team grows, wanting a fully open-source stack, or standardizing on a platform the company already uses for monitoring or ML.

LangSmith itself is moving fast: Engine now proposes code fixes as pull requests from production issues. If code-level fix proposals are what you need, compare the current Engine before switching. See the LangSmith vs Converra comparison for detail.

How we compared

We read each vendor's current documentation, pricing, and license on October 6, 2026, and compared the same things: how tracing works, evaluation and simulation, whether the tool proposes fixes, how prompts reach production, whether anything measures a change after release, hosting, and starting price.

We did not run hands-on benchmarks, and the order below groups tools by the need they serve rather than by a quality score. Prices change often; check each vendor's pricing page before deciding.

Best open-source match

Langfuse

Open-source tracing, evaluation, and prompt management, acquired by ClickHouse in January 2026 and still MIT-licensed outside enterprise folders.

Best for: teams that want to self-host tracing and evals for free, or keep trace data in their own infrastructure.

Free self-hosting; cloud plans from free to $2,499 per month
LLM-as-a-judge on live traffic, annotation queues, and experiments with CI checks
Prompt versions served by label, with rollback by moving the label

No built-in fix generation; its guides use an external coding agent
Multi-turn simulation is a cookbook, not a built-in feature

Converra vs Langfuse

Best all-in-one open source

Opik by Comet

Apache-2.0 platform for tracing, evaluation, prompt management, and production monitoring, with built-in user simulation and an agent optimizer.

Best for: teams that want the widest open-source feature set, including simulation and fix suggestions, at a low entry price.

Apache 2.0 license; self-host free with the full feature set
Built-in multi-turn evaluation with a simulated user
Diagnostics groups matching failures into issues with a likely root cause and suggested fix
Pro Cloud from $19 per month

Diagnostics requires the Ollie assistant and consumes its tokens
No documented promotion of prompts to production or post-release verdict

Best for OpenTelemetry-native tracing

Arize Phoenix

Arize's source-available tracing and evaluation tool built on OpenTelemetry and OpenInference, with Arize AX as the managed product.

Best for: teams that want free self-hosted tracing on open standards, with an upgrade path to a managed platform.

Built on OpenTelemetry with OpenInference instrumentation for many agent frameworks
LLM, code-based, and human evaluations, with datasets and experiments
Prompt versions with production, staging, and development tags
Arize AX adds the Alyx agent and prompt optimization

Elastic License 2.0, which is source-available rather than OSI open source
Fix proposals live mainly in the managed Arize AX product

Best evaluation-first platform

Braintrust

Evaluation and observability platform whose Loop agent can analyze logs and edit prompts, scorers, and datasets.

Best for: teams whose center of gravity is evals, with experiments, scorers, and playgrounds across many AI features.

Topics and Patterns surface recurring problems in production traces
Loop edits prompts, scorers, and datasets, pausing for approval by default
Prompt environments loaded directly from code

Patterns is in public preview
User simulation comes through a partner; Pro is $249 per month

Converra vs Braintrust

Best for W&B and CoreWeave users

W&B Weave

Weights & Biases' observability and evaluation tool for production agents, now part of CoreWeave.

Best for: teams already on Weights & Biases or CoreWeave who want production monitoring next to their training stack.

Agent tracing built on OpenTelemetry and the GenAI semantic conventions
Signals score production agent behavior automatically, with alerts
Versions prompts, datasets, and model configurations

Priced by ingested data volume; Pro starts at $60 per month
No documented assistant that proposes fixes

Best inside an existing Datadog stack

Datadog LLM Observability

Agent tracing, evaluations, experiments, and prompt management inside the Datadog platform.

Best for: teams already standardized on Datadog that want agent telemetry next to infrastructure and APM.

Auto-instrumentation for Python, Node.js, and Java
Insights give each recurring problem a root cause and a recommended fix, and resolve it when it stops appearing
Managed prompts with versions, plus experiments on versioned datasets

SaaS only; no self-hosted option found
Pricing not listed on the public pricing page we reviewed; check with Datadog

Complements, not replaces

Converra

Not a tracing tool. Converra reads your traces, diagnoses recurring failures, tests prompt or configuration fixes head-to-head against the current agent, ships what you approve, and returns a production verdict.

Best for: teams that keep their tracing tool and want fixes tested before release and judged on live traffic as verified, not fixed, or confounded.

Connectors for LangSmith and Langfuse; other data through its SDK or traces API
Head-to-head multi-turn simulation against the current agent, with regression scenarios
A production verdict on every fix it ships

Does not replace tracing, datasets, or prompt management
Built for conversational agents; LangSmith single-turn traces are skipped

How the loop works

LangSmith alternatives at a glance

One row per tool, on the dimensions that usually decide the choice. A dash means the vendor documentation we reviewed did not describe the capability.

LangSmith alternatives compared, as of October 6, 2026
Tool	License and hosting	Proposes fixes	Starting paid price
Langfuse	MIT (except enterprise folders); free self-hosting	No; external agent in guides	$29 per month (Core)
Opik	Apache 2.0; free self-hosting	Yes, Diagnostics with Ollie	$19 per month (Pro Cloud)
Arize Phoenix	Elastic License 2.0; free self-hosting	In Arize AX (Alyx)	AX Pro $50 per month
Braintrust	SaaS; Enterprise self-hosted data plane	Yes, Loop and Patterns	$249 per month (Pro)
W&B Weave	SaaS, dedicated, or self-managed	—	$60 per month (Pro)
Datadog	SaaS only	Yes, Insights recommend fixes	Check with Datadog
Converra	Managed; Enterprise on-prem or VPC option	Yes, tested head-to-head before release	See pricing page

Tool: Langfuse
License and hosting: MIT (except enterprise folders); free self-hosting
Proposes fixes: No; external agent in guides
Starting paid price: $29 per month (Core)

Tool: Opik
License and hosting: Apache 2.0; free self-hosting
Proposes fixes: Yes, Diagnostics with Ollie
Starting paid price: $19 per month (Pro Cloud)

Tool: Arize Phoenix
License and hosting: Elastic License 2.0; free self-hosting
Proposes fixes: In Arize AX (Alyx)
Starting paid price: AX Pro $50 per month

Tool: Braintrust
License and hosting: SaaS; Enterprise self-hosted data plane
Proposes fixes: Yes, Loop and Patterns
Starting paid price: $249 per month (Pro)

Tool: W&B Weave
License and hosting: SaaS, dedicated, or self-managed
Proposes fixes: —
Starting paid price: $60 per month (Pro)

Tool: Datadog
License and hosting: SaaS only
Proposes fixes: Yes, Insights recommend fixes
Starting paid price: Check with Datadog

Tool: Converra
License and hosting: Managed; Enterprise on-prem or VPC option
Proposes fixes: Yes, tested head-to-head before release
Starting paid price: See pricing page

What none of these do: say whether the fix worked

Several tools now find recurring failures and propose fixes. After a change ships, LangSmith Engine reopens an issue if it recurs, Datadog Insights resolve when a problem stops appearing, and Braintrust lets you track whether a problem declined. None of the documentation we reviewed describes a verdict tied to a specific deployment that also accounts for other changes in the same window.

That is the job Converra does next to whichever tracing tool you pick: it measures the targeted failure on live traffic after a fix ships and marks it verified, not fixed, or confounded. The guide to verifying a fix after deployment explains why trend lines and reopened issues are not the same thing.

Why Helicone is not on this list

Helicone was acquired by Mintlify in March 2026 and says its services will remain live in maintenance mode, with security patches and bug fixes. It still works as a self-hosted gateway, but it is a poor choice for a new long-term commitment.

Sources

Frequently asked questions

What is the best open-source alternative to LangSmith?

Langfuse and Opik are the closest open-source alternatives: Langfuse is MIT-licensed outside its enterprise folders and Opik is Apache 2.0, and both self-host for free. Arize Phoenix is free to self-host but uses the Elastic License 2.0.

Which LangSmith alternative can propose fixes?

Opik's Diagnostics, Braintrust's Loop and Patterns, Datadog's Insights, and Arize AX's Alyx all propose fixes in some form. Converra generates prompt or configuration fixes and tests them head-to-head against the current agent before release.

Is Converra a LangSmith alternative?

Not for tracing. Converra reads LangSmith traces and adds fix generation, head-to-head simulation, and a production verdict. You keep LangSmith or one of the tools above for tracing.

Can I self-host a LangSmith alternative for free?

Yes. Langfuse, Opik, and Arize Phoenix can all be self-hosted at no license cost. Braintrust and LangSmith offer self-hosting only on Enterprise plans, and Datadog is SaaS only.

How current is this comparison?

Vendor documentation and prices were checked on October 6, 2026. These products change monthly, so confirm anything decisive on the vendor's own site.

Written by

Oren Cohen

Founder of Converra. Previously founded Buildup (acquired by Stanley Black & Decker) and, as VP Product Growth at Totango, owned AI end-to-end from design through production.

Whatever you trace with, verify the fix

Converra connects to LangSmith or Langfuse, diagnoses recurring failures, tests fixes against your current agent, ships what you approve, and returns a production verdict: verified, not fixed, or confounded.

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