# LangSmith Alternatives 2027: 9 Paid, Free & Open-Source

Source: https://zekaiwork.com/alternatives/langsmith/
Prices checked: 2026-11-13 (Zekai Price Ledger)

The best LangSmith alternatives in 2027 are Braintrust (best overall, $249/mo), Langfuse (best free plan: 50k units a month, 2 users) and Opik (best open source, Apache-2.0). LangSmith itself starts at $39/seat/mo. Zekai checked these prices on vendor pages on 13 Nov 2026; 6 more are compared below, including 1 with a free plan and 4 open source.

| Tool | Type | Starting price | Free plan limit | Licence | Best for | Price checked | Links |
|---|---|---|---|---|---|---|---|
| LangSmith (the tool being replaced) | — | $39/seat/mo | 5k base traces a month, 1 seat | — | — | 2026-11-13 | [pricing](https://www.langchain.com/pricing) |
| Langfuse | Open source | $29/mo (hosted) | No limit (self-hosted) | MIT | Self-hosted tracing with flat pricing | 2026-11-13 | [site](https://langfuse.com) [pricing](https://langfuse.com/pricing) [code](https://github.com/langfuse/langfuse) [Zekai page](https://zekaiwork.com/free-open-source/langfuse/) |
| Braintrust | Free plan + paid | $249/mo | Starter: $10 model credits, 1 GB processed data, 10k scores, 14-day retention, unlimited users | — | Eval-first teams shipping prompts weekly | 2026-11-13 | [site](https://www.braintrust.dev) [pricing](https://www.braintrust.dev/pricing) [Zekai page](https://zekaiwork.com/ai-tools/braintrust/) |
| Opik | Open source | $19/mo (hosted) | No limit (self-hosted) | Apache-2.0 | Cheapest hosted tracing plus open source | 2026-11-13 | [site](https://www.comet.com/site/products/opik/) [pricing](https://www.comet.com/site/pricing/) [code](https://github.com/comet-ml/opik) [Zekai page](https://zekaiwork.com/free-open-source/opik/) |
| Datadog Agent Observability | Free plan + paid | $160/mo | Free: 40K LLM spans a month, 15-day trace retention | — | Teams already monitoring infrastructure on Datadog | 2026-11-13 | [site](https://www.datadoghq.com/product/llm-observability/) [pricing](https://www.datadoghq.com/pricing/?product=llm-observability) [Zekai page](https://zekaiwork.com/ai-tools/datadog/) |
| Arize Phoenix | Open source | $50/mo (hosted) | No limit (self-hosted) | Elastic-2.0 (not OSI-approved) | OpenTelemetry-native tracing you can run locally | 2026-11-13 | [site](https://phoenix.arize.com) [pricing](https://arize.com/pricing/) [code](https://github.com/Arize-ai/phoenix) [Zekai page](https://zekaiwork.com/free-open-source/arize-phoenix/) |
| Helicone | Open source | $79/mo (hosted) | No limit (self-hosted) | Apache-2.0 | Proxy-style request logging with gateway caching | 2026-11-13 | [site](https://www.helicone.ai) [pricing](https://www.helicone.ai/pricing) [code](https://github.com/Helicone/helicone) [Zekai page](https://zekaiwork.com/free-open-source/helicone/) |
| W&B Weave | Open source | $60/mo (hosted) | No limit (self-hosted) | Apache-2.0 | Teams that also track model training runs | 2026-11-13 | [site](https://wandb.ai/site/weave/) [pricing](https://wandb.ai/site/pricing/) [code](https://github.com/wandb/weave) [Zekai page](https://zekaiwork.com/free-open-source/wandb-weave/) |
| Laminar | Open source | $30/mo (hosted) | No limit (self-hosted) | Apache-2.0 | Agent trace search with browser session recording | 2026-11-13 | [site](https://laminar.sh) [pricing](https://laminar.sh/pricing) [code](https://github.com/lmnr-ai/lmnr) |
| Lunary | Paid | $20/user/mo | No free plan | — | Small teams wanting prompt management and human reviews | 2026-11-13 | [site](https://lunary.ai) [pricing](https://lunary.ai/pricing) |

## How each alternative compares with LangSmith

- **Langfuse** (Open source, $29/mo (hosted), checked 2026-11-13): Paid plans bill per usage unit (100k units included, then $8 per 100k) with unlimited users from $29/mo, whereas LangSmith Plus charges $39 per seat plus per-trace overage; Langfuse can also be self-hosted. Switch if your team has many seats but modest trace volume and wants flat monthly pricing or self-hosting. Stay with LangSmith if you already build on LangGraph and want Fleet, Sandboxes and Agent Server deployment inside one vendor.
- **Braintrust** (Free plan + paid, $249/mo, checked 2026-11-13): Starter gives unlimited users and projects at $0, but meters scores (10k a month) and processed data (1 GB) instead of traces; LangSmith Developer is limited to 1 seat. Switch if several engineers and PMs must share one eval workspace and you want to avoid per-seat charges. Stay with LangSmith if you want a small trace-based bill at $39 per seat rather than a $249 flat Pro fee.
- **Opik** (Open source, $19/mo (hosted), checked 2026-11-13): Pro Cloud costs $19 a month for up to 50 team members and 100k spans; the OSS build is Apache-2.0 and adds Test Suites with assertions and an Agent Playground. Switch if you need a low fixed monthly bill for a large team and want a permissively licensed self-host option. Stay with LangSmith if you rely on LangSmith Fleet, Sandboxes or Engine for agent deployment beyond tracing and evals.
- **Datadog Agent Observability** (Free plan + paid, $160/mo, checked 2026-11-13): Bills only on LLM spans (100K a month in Pro) and links agent traces to backend services, infrastructure and real user sessions; LangSmith meters all base traces. Switch if your backend is already monitored in Datadog and you want agent traces beside infrastructure and session data. Stay with LangSmith if you only need LLM tracing and datasets and do not want an infrastructure monitoring contract.
- **Arize Phoenix** (Open source, $50/mo (hosted), checked 2026-11-13): Phoenix is source-available under Elastic License 2.0, which is not OSI-approved, and the hosted AX Pro plan is $50 a month with unlimited users and unlimited evals, against LangSmith's per-seat $39. Switch if you want unlimited users and evals on a $50 flat hosted plan, or a local-first tracing tool you can run from a notebook. Stay with LangSmith if your agents run on LangGraph and you want Agent Server deployment and Sandboxes from the same vendor as tracing.
- **Helicone** (Open source, $79/mo (hosted), checked 2026-11-13): Counts requests rather than traces (10,000 free) and includes a gateway with caching, rate limits and automatic fallbacks; Pro has unlimited seats at $79 a month plus usage. Switch if you want a request-logging gateway with caching and provider fallbacks and a flat team price instead of per-seat billing. Stay with LangSmith if you need full agent trace trees, online evaluators and annotation queues from the tool you already use for LangChain apps.
- **W&B Weave** (Open source, $60/mo (hosted), checked 2026-11-13): Sits beside W&B experiment tracking, artifacts and model registry, with Weave data ingestion metered in GB (1 GB free) and extra ingestion at $0.10 per MB on Free. Switch if your team already tracks training runs in Weights & Biases and wants agent traces and evals in the same workspace. Stay with LangSmith if you need trace-count pricing, Fleet or Agent Server deployment rather than data-volume metering.
- **Laminar** (Open source, $30/mo (hosted), checked 2026-11-13): Prices by GB of trace data ($2 per GB over 3 GB on Starter) and records browser sessions beside traces; Starter has unlimited seats and projects, unlike LangSmith's per-seat billing. Switch if you run browser-using agents and want session recordings plus unlimited seats on a $30 Starter plan. Stay with LangSmith if you need LangGraph Studio, prompt hub and the 5k-trace Developer plan with community support.
- **Lunary** (Paid, $20/user/mo, checked 2026-11-13): Team plan is $20 per user with 50,000 events a month, 300 AI Playground queries and 1-year history; self-hosting is listed only under Enterprise, and the page shows no free plan for new workspaces. Switch if you want a cheaper per-seat price than $39 and need chat replays, topic classification and human reviews for a small team. Stay with LangSmith if you want a free Developer plan to start on and trace-based pricing with LangGraph-native deployment.

## Open-source options in detail

- **Langfuse** (https://github.com/langfuse/langfuse): Licence: MIT; Last release: 2026-11-12
- **Opik** (https://github.com/comet-ml/opik): Licence: Apache-2.0; Last release: 2026-11-06
- **Arize Phoenix** (https://github.com/Arize-ai/phoenix): Licence: Elastic-2.0 (not OSI-approved); Last release: 2026-11-11
- **Helicone** (https://github.com/Helicone/helicone): Licence: Apache-2.0; Last release: 2025-08-21
- **W&B Weave** (https://github.com/wandb/weave): Licence: Apache-2.0; Last release: 2026-11-05
- **Laminar** (https://github.com/lmnr-ai/lmnr): Licence: Apache-2.0; Last release: 2026-11-10

## Questions

### What is the best alternative to LangSmith in 2027?
Braintrust is the best overall LangSmith alternative on this page ($249/mo). For no cost, Langfuse has a free plan (Hobby: 50k units a month, 2 users, 30 days data access). To self-host, Opik is open source (Apache-2.0).

### Is there a free version of LangSmith?
Yes. LangSmith has a free plan: 5k base traces a month, 1 seat. Paid plans start at $39/seat/mo, checked on 13 Nov 2026.

### Is there a 100% free alternative to LangSmith?
Yes. Langfuse, Opik, Arize Phoenix, Helicone, W&B Weave, Laminar are open source and free to self-host. Braintrust, Datadog Agent Observability have a free plan with limits, shown in the table.

### What is cheaper than LangSmith?
Datadog Agent Observability starts at $160/mo, against $39/seat/mo for LangSmith, as listed on each vendor's pricing page on 13 Nov 2026.

### How much do LangSmith alternatives cost for a team of 5?
If each of 5 people buys the entry paid plan, at the prices Zekai checked on 13 Nov 2026, the monthly cost is Opik $95/mo, Lunary $100/mo, Langfuse $145/mo, against LangSmith $195/mo for LangSmith. Team and business plans can cost more per seat. The Zekai Cost Finder on this page recalculates for any team size.

### Which is better, Braintrust or LangSmith?
Starter gives unlimited users and projects at $0, but meters scores (10k a month) and processed data (1 GB) instead of traces; LangSmith Developer is limited to 1 seat. Choose Braintrust if several engineers and PMs must share one eval workspace and you want to avoid per-seat charges. Stay with LangSmith if you want a small trace-based bill at $39 per seat rather than a $249 flat Pro fee.

### Why are people leaving LangSmith?
The documented reasons are: Workspaces now have an hourly cap on persisted bytes, defaulting to 100 GB, and ingestion is rejected once a workspace exceeds it (2 Nov 2026); Multipart and OTel batch ingestion now enforce short-term usage limits, so over-limit traces receive an HTTP 429 response (26 Oct 2026). Each is sourced in the section above.

### What is the best LangSmith alternative?
Langfuse is the most searched rival and is open source with a free cloud tier. Braintrust suits eval-heavy teams, Opik and Laminar are low-cost hosted options, and Datadog suits teams already using it.

## Related on Zekai

- [AI for Software Development](https://zekaiwork.com/professions/ai-software-development-code-automation/)

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Live table, team cost finder and price alerts: https://zekaiwork.com/alternatives/langsmith/