LangTrace — LangSmith for VS Code
Browse your LangSmith traces, runs, projects, and datasets without leaving the editor.
What it does
LangTrace connects directly to the LangSmith API and surfaces your observability data as a native VS Code sidebar. No context-switching to the browser — inspect traces, debug failing runs, and review prompt inputs/outputs right in your editor.
Features
Projects
- Lists all your LangSmith projects (sessions) in a tree view
- Shows run count, p50 latency, and error rate per project at a glance
- Projects with >10% error rate are highlighted with a warning icon
Runs
- Browse runs for any project — filtered to the last N runs (configurable)
- Each run shows its type icon (LLM / Chain / Tool / Retriever / Embedding), latency, and prompt/completion token counts
- Filter by status (success / error / pending) or search by run name
- Load more runs with a single click
Trace Detail
- Click any run to open a full trace tree in a side panel
- LLM runs render as a chat thread — system, user, and assistant messages displayed as conversation bubbles
- All other runs show syntax-highlighted JSON for inputs and outputs
- Expand / collapse individual steps or use Expand all / Collapse all
- Header shows total latency, prompt↑ and completion↓ token split, and start time
Datasets
- Lists all LangSmith datasets with example count and data type
- Hover tooltip shows created/modified dates and dataset ID
Getting Started
1. Install the extension
Search for LangTrace in the VS Code Extensions panel, or install from the Marketplace.
2. Get a LangSmith API key
- Open smith.langchain.com
- Go to Settings → API Keys → Create API Key
- Copy the key (starts with
ls__)
3. Connect
Open the Command Palette (Ctrl+Shift+P / Cmd+Shift+P) and run:
LangTrace: Set API Key
Paste your key and press Enter. The sidebar will populate immediately.
Commands
| Command |
Description |
LangTrace: Set API Key |
Store your LangSmith API key securely |
LangTrace: Clear API Key |
Remove the stored key |
LangTrace: Refresh |
Re-fetch projects and runs |
LangTrace: Open in Browser |
Open smith.langchain.com |
LangTrace: Filter by Status |
Filter the runs panel by success / error / pending |
LangTrace: Search Runs |
Filter runs by name |
LangTrace: Clear All Filters |
Remove all active filters |
LangTrace: Compare Prompts |
Diff the inputs of two runs side-by-side |
Settings
| Setting |
Default |
Description |
langtrace.pollInterval |
30 |
Auto-refresh interval in seconds (0 to disable) |
langtrace.maxRuns |
50 |
Max runs to fetch per project |
langtrace.baseUrl |
https://api.smith.langchain.com |
API base URL — change for self-hosted LangSmith |
Self-hosted LangSmith
If you run a private LangSmith instance, update the base URL in settings:
"langtrace.baseUrl": "https://your-langsmith.internal"
Disclaimer
This is an unofficial community extension and is not affiliated with, endorsed by, or supported by LangChain, Inc.
License
MIT
