Observability
Tracing tools to see inside the 'black box' of LLM execution, crucial for debugging complex agent chains.
| Rank | Model | Price | Summary |
|---|---|---|---|
|
1
|
Freemium | The Default Standard. Its 'Regression Testing' feature now allows you to replay production traffic against new prompt versions to catch regressions before they ship. It remains the deepest integration for complex agentic loops. | |
|
2
|
Open Source | The Open Source Favorite. Offers the best self-hosted tracing experience. Its new 'Model-Based Eval' engine allows you to use cheap models (like Llama 4 Scout) to score the quality of expensive model outputs in real-time. | |
|
3
|
Open Source | The Evaluation Engine. Best for rigorous data science. It specializes in 'Embedding Visualization', allowing you to visualize your RAG retrieval clusters in 3D to understand exactly why the wrong documents were retrieved. | |
|
4
|
Freemium | The Engineer's Choice. From the creators of Weights & Biases. It treats prompts as hyperparameters, bringing traditional ML experiment tracking rigor (A/B testing, versioning) to prompt engineering. | |
|
5
|
Open Source | The Gateway Observer. Because it sits as a proxy, it captures *everything* without SDK integration. Its 'User Journey' view reconstructs entire conversation sessions across days to track long-term agent memory performance. |
Just the Highlights
LangSmith
The Default Standard. Its 'Regression Testing' feature now allows you to replay production traffic against new prompt versions to catch regressions before they ship. It remains the deepest integration for complex agentic loops.
Langfuse
The Open Source Favorite. Offers the best self-hosted tracing experience. Its new 'Model-Based Eval' engine allows you to use cheap models (like Llama 4 Scout) to score the quality of expensive model outputs in real-time.
Arize Phoenix
The Evaluation Engine. Best for rigorous data science. It specializes in 'Embedding Visualization', allowing you to visualize your RAG retrieval clusters in 3D to understand exactly why the wrong documents were retrieved.
W&B Weave
The Engineer's Choice. From the creators of Weights & Biases. It treats prompts as hyperparameters, bringing traditional ML experiment tracking rigor (A/B testing, versioning) to prompt engineering.
Helicone
The Gateway Observer. Because it sits as a proxy, it captures *everything* without SDK integration. Its 'User Journey' view reconstructs entire conversation sessions across days to track long-term agent memory performance.