LLM Observability — Detailed Feature Comparison

Date: 2026-02-25 | Model: google/gemini-3-pro-preview

O(Strong) / △(Medium) / X(None or Not Applicable)

Core Tracing & Logging

Feature	Description	W&B Weave	LangSmith	Langfuse	Braintrust	MLflow	Arize Phoenix
Full Request/Response Tracing	Complete capture of LLM input prompts, output responses, and parameters	O	O	O	O	O	O
Nested Span & Tree View	Hierarchical span tracing with parent-child tree visualization	O	O	O	O	O	O
Streaming Support	Real-time tracing of streaming LLM responses	△	O	△	O	△	△
Multimodal Tracing	Tracing and rendering of image, audio, and other non-text inputs/outputs	O	△	△	△	△	X
Auto-Instrumentation	One-line automatic trace collection (decorators, autolog, etc.)	O	O	O	O	O	O
Metadata & Tags Filtering	Custom metadata and tag attachment with search and filtering	O	O	O	O	O	O
Token Counting & Estimation	Accurate per-tokenizer input/output/cached token counting	O	O	O	O	O	△
OpenTelemetry Standard	OTEL-standard trace export/import compatibility	O	O	O	O	O	O

Agent & RAG Specifics

Feature	Description	W&B Weave	LangSmith	Langfuse	Braintrust	MLflow	Arize Phoenix
RAG Retrieval Visualizer	UI display of retrieved document chunks with content and relevance scores	O	O	△	△	△	O
Tool/Function Call Rendering	Parsed view of tool/function call inputs and return values	O	O	O	O	O	O
Agent Execution Graph	DAG/graph visualization of agent workflows with loops and branches	O	O	O	O	△	O
Intermediate Step State	Storage and display of agent intermediate reasoning (Chain-of-Thought)	O	O	O	O	O	O
Session/Thread Replay	Replay of user session or conversation thread as a complete flow	X	O	O	△	O	△
Failed Step Highlighting	Automatic highlighting of failed steps in agent traces	△	O	O	O	O	O
MCP Integration	Model Context Protocol server/client integration and tracing	O	O	O	X	X	O

Evaluation & Quality

Feature	Description	W&B Weave	LangSmith	Langfuse	Braintrust	MLflow	Arize Phoenix
LLM-as-a-Judge Wizard	GUI-based LLM judge builder without requiring code	O	O	O	O	O	△
Custom Eval Scorers	User-defined code-based evaluation function authoring and execution	O	O	O	O	O	O
Dataset Management & Curation	Evaluation dataset creation, versioning, and trace-to-dataset conversion	X	O	O	X	O	O
Prompt Optimization / DSPy Support	Automatic prompt optimization or candidate suggestion (e.g. DSPy integration)	X	△	△	X	O	O
Regression Testing	Automatic quality regression detection on model/prompt changes	O	O	O	O	△	O
Comparison View (Side-by-side)	Side-by-side comparison of model/prompt outputs	X	O	O	X	O	O
Annotation Queues	Team-based annotation workflows with queue management and reviewer assignment	△	O	O	△	△	X
Online Evaluation	Real-time automatic evaluation on live production traffic	O	O	O	O	O	O

Guardrails & Safety

Feature	Description	W&B Weave	LangSmith	Langfuse	Braintrust	MLflow	Arize Phoenix
PII/Sensitive Data Masking	Automatic PII and sensitive data detection and masking	X	△	O	X	O	X
Hallucination Detection	Dedicated guardrail for detecting hallucinated content	O	O	△	△	O	O
Topic/Jailbreak Guardrails	Blocking of forbidden topics and jailbreak attempt detection	O	O	△	X	X	X
Policy Management as Code	Guardrail rules defined and managed as code	O	X	△	X	△	X

Analytics & Dashboard

Feature	Description	W&B Weave	LangSmith	Langfuse	Braintrust	MLflow	Arize Phoenix
Cost Analysis & Attribution	Cost tracking with per-user/team/project attribution	O	O	O	O	X	△
Token Usage Analytics	Input/output token usage breakdown and trends	O	O	O	O	O	O
Latency Heatmap & P99	Latency distribution visualization with percentile monitoring	O	O	O	X	O	O
Error Rate Monitoring	Error rate tracking and alerting	O	O	O	O	O	O
Embedding Space Visualization	UMAP/t-SNE embedding clustering and visualization	X	X	X	X	X	O
Custom Metrics & Dashboard	User-defined custom metric tracking with dashboard widgets	O	O	O	O	O	O

Development Lifecycle

Feature	Description	W&B Weave	LangSmith	Langfuse	Braintrust	MLflow	Arize Phoenix
Prompt Management (CMS)	Prompt versioning with non-developer editing and deployment capabilities	O	O	O	O	O	O
Playground & Sandbox	Interactive prompt and parameter testing environment	O	O	O	O	△	O
Experiment Tracking	A/B test and experiment management with hyperparameter logging	O	O	O	O	O	O
Fine-tuning Integration	Fine-tuning data export and pipeline integration	O	△	△	X	△	X
Version Control & Rollback	Prompt and model version management with rollback capability	O	O	O	O	O	△

Integration & DX

Feature	Description	W&B Weave	LangSmith	Langfuse	Braintrust	MLflow	Arize Phoenix
SDK Support (Py/JS/Go)	Official SDK support across Python, JavaScript/TypeScript, and Go	X	O	O	X	△	O
Gateway/Proxy Mode	Proxy-based tracing without SDK installation (URL change only)	X	X	X	O	O	X
Popular Frameworks	Built-in support for LangChain, LlamaIndex, AutoGen, CrewAI, etc.	O	O	O	O	O	O
API & Webhooks	REST/GraphQL API and webhook integration for external systems	O	O	O	O	△	O
CI/CD Integration	Integration with CI/CD pipelines (GitHub Actions, etc.) for automated eval and deployment	O	O	O	O	△	△

Enterprise & Infrastructure

Feature	Description	W&B Weave	LangSmith	Langfuse	Braintrust	MLflow	Arize Phoenix
Deployment Options	Multi-tenant SaaS, dedicated SaaS, and self-hosted/VPC deployment options	O	O	O	O	O	O
Open Source	Open-source code availability and community	△	X	O	X	O	O
Data Sovereignty & Compliance	Data region selection with SOC 2/HIPAA/GDPR compliance	X	△	O	△	O	O
RBAC & SSO	Role-based access control with SSO/SAML authentication	O	O	O	△	△	O
Audit Logs	User and system action audit trail	O	△	O	△	△	X
Data Warehouse Export	Automated export to Snowflake, BigQuery, S3, etc.	O	△	O	O	O	△