Langsmith Trace Analyzer

LangSmith Trace Analyzer

Use this skill to move from raw LangSmith traces to actionable debugging/evaluation insights.

Quick Start

# Install dependencies
uv pip install langsmith langsmith-fetch

# Auth
export LANGSMITH_API_KEY=

Fast workflow

1. Download traces with scripts/download_traces.py (or scripts/download_traces.ts).
2. Analyze downloaded JSON with scripts/analyze_traces.py.
3. Load targeted references only when needed:

• references/filtering-querying.md for query/filter syntax
• references/analysis-patterns.md for deeper diagnostics
• references/benchmark-analysis.md for benchmark-specific workflows

Decision Guide

1. Known trace IDs

Use langsmith-fetch trace directly, or --trace-ids in downloader scripts.

1. Need to discover traces first

Use LangSmith SDK list_runs/listRuns with filters, then download selected trace IDs.

1. Need aggregate insights

Run analyze_traces.py for summary stats, patterns, and passed-vs-failed comparisons.

Core Workflows

1) Download and organize traces

Python:

uv run skills/langsmith-trace-analyzer/scripts/download_traces.py \
  --project "my-project" \
  --filter "job_id=abc123" \
  --last-hours 24 \
  --limit 100 \
  --output ./traces \
  --organize

TypeScript:

ts-node skills/langsmith-trace-analyzer/scripts/download_traces.ts \
  --project "my-project" \
  --filter "job_id=abc123" \
  --last-hours 24 \
  --limit 100 \
  --output ./traces

Output layout:

traces/
├── manifest.json
└── by-outcome/
    ├── passed/
    ├── failed/
    └── error/
        ├── GraphRecursionError/
        ├── TimeoutError/
        └── DaytonaError/

Notes:

• Python script supports --organize/--no-organize.
• Both scripts use SDK filtering plus langsmith-fetch for full trace payload export.

2) Analyze downloaded traces

# Markdown report
uv run skills/langsmith-trace-analyzer/scripts/analyze_traces.py ./traces --output report.md

# JSON output
uv run skills/langsmith-trace-analyzer/scripts/analyze_traces.py ./traces --json

# Compare passed vs failed (expects by-outcome folders)
uv run skills/langsmith-trace-analyzer/scripts/analyze_traces.py ./traces --compare --output comparison.md

The analyzer reports:

• message/tool-call/token/duration summaries
• top tool usage
• anomaly patterns (high message count, repeated tools, quick failures)
• passed-vs-failed metric deltas when comparison is enabled

3) Query traces correctly (SDK)

Use official LangSmith run filter syntax via filter and/or start_time:

from datetime import datetime, timedelta, timezone
from langsmith import Client

client = Client()

start = datetime.now(timezone.utc) - timedelta(hours=24)
filter_query = 'and(eq(metadata_key, "job_id"), eq(metadata_value, "abc123"))'

runs = client.list_runs(
    project_name="my-project",
    is_root=True,
    start_time=start,
    filter=filter_query,
)

For TypeScript:

import { Client } from "langsmith";

const client = new Client();
for await (const run of client.listRuns({
  projectName: "my-project",
  isRoot: true,
  filter: 'and(eq(metadata_key, "job_id"), eq(metadata_value, "abc123"))',
})) {
  console.log(run.id, run.status);
}

Accuracy and Schema Notes

• LangSmith run fields are commonly top-level (status, error, total_tokens, start_time, end_time).
• Some exported traces also include nested metadata (metadata or extra.metadata) and/or messages.
• analyze_traces.py is resilient to multiple payload shapes, including raw array payloads.
• For full conversation content, prefer downloaded trace payloads over bare list_runs results.

Troubleshooting

| Issue | Likely Cause | Action | |---|---|---| | LANGSMITH_API_KEY missing | Auth not configured | export LANGSMITH_API_KEY= | | No runs returned | Wrong project/filter/time range | Verify project name and filter syntax | | Empty/partial message arrays | Run schema differs or incomplete data | Use downloaded trace JSON and inspect status/error fields | | JSON parse error on downloaded files | Bad/incomplete export | Re-download trace; use --format raw paths in scripts | | Re-downloading same traces repeatedly | Existing files in nested folders | Use current scripts (they check existing files across output tree) |

Safety for Open Source

• Do not commit downloaded trace artifacts (manifest.json, trace JSON dumps) unless sanitized.
• Trace payloads can contain user prompts, outputs, metadata, and other sensitive runtime data.
• Keep this skill repository focused on scripts/templates, not production trace exports.

Resources

scripts/

• scripts/download_traces.py: Python downloader + organizer
• scripts/download_traces.ts: TypeScript downloader + organizer
• scripts/analyze_traces.py: Offline analysis and reporting

references/

• references/filtering-querying.md: LangSmith query/filter examples
• references/analysis-patterns.md: Diagnostic patterns and heuristics
• references/benchmark-analysis.md: Benchmark-oriented analysis

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: Lubu-Labs
• Source: Lubu-Labs/langchain-agent-skills
• License: MIT

Install and usage instructions live in the source repository linked above.