How we make this list: we compare pricing pages, product documentation and public user reviews. Ratings come from G2, Capterra or Trustpilot, with the date we checked them.
Key takeaways
- Braintrust Pro costs $249 per month with a free Starter tier covering 1 GB of data and 10,000 scores, and it meters on scores.
- Open-source options like Langfuse, Arize Phoenix, Promptfoo, and DeepEval cover tracing and evals at no licence cost.
- LangSmith is deepest for LangChain and LangGraph teams, while Arize AX covers tracing plus evals in one platform.
- The 2026 shift is from single-turn output scoring to multi-step trajectory scoring for agents.
Quick comparison
| Tool | Best for | Starting price | Free plan |
|---|
 LangSmith | LangChain and LangGraph teams | $39/seat/month | Yes |
 Arize AX | Unified observability and evals | $50/month | Yes |
 Langfuse | Open-source tracing and evals | $29.99/month | Yes |
 Confident AI | Pytest-native eval testing | $200/month | Yes |
 Promptfoo | Code-first prompt checks | $0 | Yes |
 Comet Opik | Budget open-source evals | $19/month | Yes |
 Maxim AI | Agent simulation testing | $29/seat/month | Yes |
 Weights & Biases Weave | Experiment tracking teams | $60/month | Yes |
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The best braintrust alternatives
Starting price$39/seat/month
Free planYes
LangSmith is the commercial platform behind LangChain, and its strength is the agent lifecycle: tracing for LangGraph workflows is best in class, and the product now spans deployment and evaluation in one place. Teams get native tracing, datasets, a Prompt Hub, custom evaluators, and annotation queues. For teams committed to LangChain, no rival integrates as deeply.
Pricing starts with a free Developer tier covering 5,000 base traces monthly, then Plus at $39 per seat per month with 10,000 base traces included. Trace overage and extended retention get expensive fast, and self-hosting appears only at Enterprise. For LangChain-native agent work, LangSmith is the deepest pick.
What we like- Best LangGraph tracing
- Datasets and Prompt Hub
- Annotation queues
Watch out for- Per-seat cost grows fast
- Trace overage gets expensive
- Self-host only at Enterprise
Starting price$50/month
Free planYes
Arize AX unifies observability and evaluation in one platform, with OpenTelemetry-based tracing, evaluation logic shared with its open-source Phoenix project, and day-0 support for frontier models. Teams running classic ML plus LLMs get one system for both, with a self-hosted enterprise option. For unified eval-to-production observability, Arize AX leads.
Pro starts at $50 per month, with a free tier covering 25,000 spans monthly, 1 GB storage, and 15-day retention. Production-scale pricing runs higher, and the interface carries its classic ML heritage. For OpenTelemetry-native teams, Arize AX is the top choice.
What we like- Observability plus evaluation in one platform
- Day-0 frontier-model support
- Self-hosted enterprise option
Watch out for- Platform cost at scale
- Classic ML heritage shows in UI
- Setup planning needed
Starting price$29.99/month
Free planYes
Langfuse is the leading open-source tracing platform with built-in evals, covering tracing, datasets, experiments, LLM-as-judge scorers, and prompt management, with free self-hosting and a free Hobby cloud tier. Teams that want infrastructure they control without vendor lock-in start here. Note that Langfuse was among platforms acquired or sunset between May 2025 and April 2026, so confirm the current roadmap before committing.
Cloud pricing runs Core at $29.99 per month and Pro at $199 per month, with Enterprise custom. For self-hosted trace and dataset infrastructure, Langfuse remains the reference.
What we like- MIT-core tracing
- Datasets and experiments
- LLM-as-judge scorers
- Free self-hosting
Watch out for- Cloud Core and Pro pricing adds up
- Self-hosting needs operations
- Acquired, roadmap in flux
Starting price$200/month
Free planYes
Confident AI, built on the open-source DeepEval framework, is the most developer-first evaluation suite here, with pytest-native CI integration, trajectory and tool-call scoring, multi-turn simulation, online evals on live traffic, and an AI governance gate. Its 50-plus research-backed metrics cover RAG and agent quality, and the evaluation-first CI workflow fits teams that gate deploys on eval results. For eval-driven development in code, Confident AI leads.
Starter costs $200 per month with unlimited seats, and the free tier covers 5 test runs weekly, 1 GB of trace spans, and 2 seats. For pytest-native eval testing, Confident AI is the pick.
What we like- Pytest-native CI workflow
- 50-plus research-backed metrics
- Trajectory and tool-call scoring
Watch out for- Highest entry paid tier here
- Developer-first interface
- Cloud features need paid plan
Starting price$0
Free planYes
Promptfoo is the free, open-source CLI for code-first prompt and model checks, with YAML-driven evals, custom assertions, model comparisons, and CI checks. It excels at red-teaming and adversarial testing, letting teams run hundreds of prompt variants against assertions in CI. For teams that want evals in code with no licence cost, Promptfoo is unbeatable.
It is CLI-first with no production monitoring platform and no hosted tracing story of its own, so it pairs with a tracing tool rather than replacing one. For code-first prompt checks, Promptfoo wins.
What we like- Free and open source
- Config-as-code evals
- Red-teaming and adversarial testing
Watch out for- CLI-first, no production monitoring
- No hosted tracing story
- Setup is code-heavy
Starting price$19/month
Free planYes
Comet Opik gives teams an Apache-2.0 core with unlimited self-hosted spans, seats, and retention, plus a free cloud tier for up to 10 team members. Pro Cloud costs $19 per month, the cheapest paid tier in this group. For budget-conscious teams that want a genuine open-source option with a clear cloud upgrade path, Opik is the value pick.
The ecosystem is smaller than LangSmith or Arize, and advanced cloud features sit behind the paid tier. For budget open-source evals, Opik leads.
What we like- Apache-2.0 core
- Unlimited self-hosted spans, seats, and retention
- Cheapest paid cloud tier here
Watch out for- Smaller ecosystem than LangSmith or Arize
- Cloud features behind paid tier
- Newer platform
Starting price$29/seat/month
Free planYes
Maxim AI specializes in agent simulation and pre-release testing, letting teams simulate multi-turn agent behavior before release rather than only scoring finished outputs. Its simulation-based training and evaluation approach fits the 2026 shift toward trajectory scoring. The Developer plan is free forever, with Professional at $29 per seat per month billed monthly.
Per-seat pricing grows with team size, and production tracing runs thinner than LangSmith or Arize. For pre-release agent simulation, Maxim AI is the standout.
What we like- Agent simulation and pre-release testing
- Simulation-based training
- Free Developer plan
Watch out for- Per-seat pricing
- Simulation focus over production tracing
- Newer platform
#8
Weights & Biases Weave
Best for: Experiment tracking teams
Visit wandb.ai
Starting price$60/month
Free planYes
Weights & Biases Weave extends the best-known ML experiment tracking platform into LLM tracing and evaluation, so teams already tracking experiments and fine-tuning get evals in the same system. Pro costs $60 per month billed monthly, with a 30-day Pro trial and a free tier. For teams that already live in Weights & Biases, Weave is the natural eval addition.
Note that Weights & Biases was among platforms acquired or sunset between May 2025 and April 2026, so confirm current ownership and roadmap before committing. For experiment-tracking teams, Weave still fits best.
What we like- Deep experiment tracking heritage
- Tracing plus evals
- 30-day Pro trial
Watch out for- Per-user cost at scale
- ML-experiment focus over pure evals
- Setup planning
How we chose
We compared evaluation depth, tracing quality, agent trajectory scoring, CI integration, self-hosting options, and pricing for each tool, then checked them against recent AI evaluation platform comparisons with data verified in 2026. Tools made the list only if teams can run LLM or agent evaluations today with a published or widely reported offering. Where pricing sits behind a quote or varies by listing, we used See website rather than printing a contested figure. We also weighed ownership status separately, since several platforms in this space were acquired or sunset in 2025 and 2026. We also checked framework fit, since LangChain-native teams gain more from LangSmith than from a framework-neutral tool, while teams spanning many providers gain more from OpenTelemetry-based tracing. Run a two-week trial on real production traces before committing to any paid plan, and compare scores across vendors first.
Different teams hit different bottlenecks. If the problem is comparing prompt versions rigorously, Braintrust or Confident AI fits. If the problem is debugging agent traces, LangSmith or Arize AX fits. If the problem is cost or control, Langfuse, Arize Phoenix, Promptfoo, or Opik fits. If the problem is pre-release agent behavior, Maxim AI fits. Most mature teams end up with two tools: one for evals in CI and one for production tracing, rather than forcing one platform to cover both jobs well.
Also confirm how each vendor meters usage before signing. Braintrust meters on scores, LangSmith meters on traces and seats, Arize meters on spans, and Confident AI meters on test runs. A team running high-volume agent evals can blow past a cheap headline price on overage, so model your monthly scores, spans, and traces against each pricing page before committing. Also test human annotation workflows during the trial, since automated scores alone miss nuance: annotation queues, reviewer agreement, and feedback loops decide whether eval results actually improve the product or only decorate a dashboard.
Frequently asked questions
What is Braintrust and what does it cost?
Braintrust is an eval-driven development platform for LLM and agent teams, covering prompt comparisons, datasets, custom scorers, CI gates, and trace review. The free Starter tier includes 1 GB of processed data and 10,000 scores per month with unlimited users and projects, while Pro costs $249 per month with 5 GB and 50,000 scores included. Braintrust meters on scores, not just traces, which fits teams running lots of evaluation. Also note that older comparisons cited Braintrust Pro at $450 per month, while current listings show $249 per month, so confirm the current pricing page before budgeting.
Which Braintrust alternative is best for open source?
Langfuse leads for open-source tracing with built-in evals and free self-hosting, while Arize Phoenix offers source-available tracing under an Elastic License. Promptfoo covers code-first evals free under MIT, and Comet Opik offers an Apache-2.0 core with unlimited self-hosted spans. For a fully open core, Langfuse and Opik are the strongest picks.
Which Braintrust alternative is best for LangChain teams?
LangSmith is the deepest pick for LangChain and LangGraph teams, with best-in-class LangGraph tracing, datasets, Prompt Hub, and annotation queues. Plus costs $39 per seat per month. Teams committed to the LangChain ecosystem should shortlist LangSmith first, and weigh trace overage costs at volume.
What is trajectory scoring and why does it matter in 2026?
Trajectory scoring evaluates multi-step agent behavior, including tool calls, reasoning steps, and final output, rather than only the final answer. The core shift in 2026 is from single-turn output scoring to trajectory scoring, since agent failures often hide in intermediate steps. Confident AI, Maxim AI, and Arize AX all support trajectory or simulation-based scoring.
Should I worry about platform acquisitions in this space?
Yes, check before committing: Humanloop, Weights & Biases, Langfuse, and Galileo were acquired or sunset between May 2025 and April 2026. Confirm current ownership, roadmap, and data export options for any platform you shortlist, and prefer tools with open-source cores or clear export paths if continuity matters. Also confirm data retention limits, since free tiers often keep traces for only 14 or 15 days, and longer retention usually costs extra. A short retention window can erase the failure history you need for debugging.
Sources we checked (8)
- https://www.langchain.com/langsmith
- https://arize.com
- https://langfuse.com
- https://www.confident-ai.com
- https://promptfoo.dev
- https://www.comet.com/site/products/opik/
- https://www.getmaxim.ai
- https://wandb.ai
Is your product missing or out of date?
We review this list regularly. Vendors can request a listing, send updated pricing or ask about featured placement.
Shihab Mia · Founder, Rankite
Shihab has 5+ years in B2B and SaaS SEO. He writes Rankite's software buying guides from pricing pages, documentation and public user reviews. More about Shihab.