langsmith

LangSmith Tool

Use this tool to debug AI chains, inspect past runs, manage datasets, and analyze token costs in LangSmith.

Prerequisites

uv tool install langsmith-cli
/plugin marketplace add gigaverse-app/langsmith-cli

See Installation Guide if install fails or for alternative methods.

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🚨 MANDATORY Rules — Read These First

1. Always use --json

ALWAYS pass --json as the FIRST argument. Without it you get Rich terminal tables — unparseable, useless to agents.

# ✅ CORRECT
langsmith-cli --json runs list --project my-project --limit 5

# ❌ WRONG — Rich table output, cannot be parsed
langsmith-cli runs list --project my-project --limit 5

2. Always use --output for data extraction — never shell redirection

# ✅ CORRECT — atomic write, errors visible, non-zero exit on failure
langsmith-cli --json runs list --project my-project --output runs.jsonl
python3 -c "import json; runs = [json.loads(l) for l in open('runs.jsonl')]"

# ❌ WRONG — errors go to stderr silently, you get empty/corrupt file
langsmith-cli --json runs list --project my-project > runs.json

# ❌ WRONG — heredoc overrides pipe stdin, python3 reads empty stdin
langsmith-cli --json runs get <id> --fields outputs | python3 << 'EOF'
import sys, json; data = json.load(sys.stdin)  # stdin is EMPTY
EOF

Use python3 -c "..." (no heredoc) if you must pipe inline.

3. Cache-First Workflow — ALWAYS check cache before any API call

Step 1: langsmith-cli runs cache list
         ↓
Step 2: Is the project listed with recent data?
   YES → Use `runs cache grep` directly. Zero API calls. STOP.
   NO  → Tell user: "Project X is not in cache. Downloading in background."
         Run `langsmith-cli --json runs cache download ...` in background,
         poll TaskOutput(block=false) for progress, use cache grep when done.

Red flags — STOP if you're about to:

• Query the API (runs list, --fetch N) when the project is already cached
• Run runs cache download without first checking runs cache list
• Download a project already listed in runs cache list
• Run runs cache download without --json — Rich output is swallowed when captured to a file, leaving you with zero progress visibility
• Use --fetch N after a cache download — --fetch always hits the API, never the cache

Background download + progress tracking:

# ✅ CORRECT — --json emits {"event":"progress","project":"...","new_runs":N} to stderr per batch
langsmith-cli --json runs cache download --project "dev/my-project" --last 30d
# Run in background, poll TaskOutput(block=false), relay new_runs count to user
# Final stdout: {"event":"download_complete","total_new_runs":N}

4. Always use --fields to reduce token usage

langsmith-cli --json runs list --fields id,name,status,start_time
langsmith-cli --json runs get <id> --fields inputs,outputs,error

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Quick Command Reference

Task	Command
List recent runs	langsmith-cli --json runs list --project <name> --limit 10 --fields id,name,status
Get a single run	langsmith-cli --json runs get <id> --fields inputs,outputs,error
Get run + child outputs	langsmith-cli --json runs get <id> --follow-children --fields id,name,inputs,outputs
Get latest run	langsmith-cli --json runs get-latest --project <name> --fields inputs,outputs
Get latest error	langsmith-cli --json runs get-latest --project <name> --failed --fields id,name,error
Search run content	langsmith-cli --json runs list --grep "pattern" --grep-in outputs --limit 20
Search cached runs	langsmith-cli runs cache grep "pattern" -E --grep-in outputs --project <name>
Download cache	langsmith-cli --json runs cache download --project <name> --last 7d
List cache	langsmith-cli runs cache list
Discover cache schema	langsmith-cli --json runs cache schema --project <name> --include outputs
Analyze token costs	langsmith-cli --json runs usage --from-cache --breakdown model --active-only
List projects	langsmith-cli --json projects list --name-pattern "dev/*" --fields name
Count runs	langsmith-cli --json runs list --project <name> --count
Run stats	langsmith-cli --json runs stats --project <name>
List datasets	langsmith-cli --json datasets list --fields id,name
List prompts	langsmith-cli --json prompts list --fields repo_handle,description
List feedback for a run	langsmith-cli --json feedback list --run-id <run-id>
Create feedback	langsmith-cli --json feedback create <run-id> --key correctness --score 0.9
List annotation queues	langsmith-cli --json annotation-queues list
Get annotation queue	langsmith-cli --json annotation-queues get <queue-id>
View experiment results	langsmith-cli --json experiments results <experiment-name>
Open run in browser	Construct URL manually — see LangSmith URLs section below

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📚 When to Read Reference Files

When your task matches one of the sections below, you MUST load that reference file before proceeding — don't load them speculatively for unrelated tasks.

→ Read references/runs.md when:

• You need the full flag list for runs list, runs get, runs get-latest, runs search, runs sample, runs analyze, runs tags, runs fields, runs export
• You need to use --trace-filter, --tree-filter, --sort-by, --roots, --run-type, --tag, --model, --min-latency, --max-latency
• You need to filter runs by metadata: --metadata key=value (supports wildcards key=val* and regex key=/pattern/)
• You need to paginate, export to files, or watch live runs

→ Read references/search.md when:

• You need to choose between --query (server-side, fast, first 250 chars) vs --grep (client-side, all content, regex)
• You need to write FQL filter expressions (eq, gt, has, and, search, metadata_key/metadata_value)
• You need to search by content with regex, Hebrew/Unicode characters, or multi-field patterns
• You need common search+filter patterns (find errors, filter by tag, combine filters)
• You want to avoid writing inline scripts — the CLI often handles it natively

→ Read references/cost-analysis.md when:

• You need to analyze token usage or costs for a project or event window
• You need to break down costs by model, provider, or gateway
• You need to find missing model pricing and apply a pricing YAML
• You need hourly/daily cost distribution or cost attribution for a channel/community
• You need to use runs usage, runs pricing, runs cache download + --from-cache
• You need the Key Flags for offline analysis (--from-cache, --group-by, --breakdown, --apply-pricing)

→ Read references/projects.md when:

• You need to create, update, or delete projects
• You need to filter projects by name pattern/regex across environments

→ Read references/datasets.md and references/examples.md when:

• You need to create or manage evaluation datasets
• You need to add, update, or delete examples
• You need to push JSONL to a dataset or create examples from runs

→ Read references/prompts.md when:

• You need to pull, push, or version prompt templates
• You need to list prompt commits or compare versions

→ Use feedback commands when:

• You need to list, get, create, or delete feedback scores on runs
• Commands: feedback list [--run-id <id>] [--key <key>] [--limit N], feedback get <id>, feedback create <run-id> --key <key> [--score N] [--comment <str>], feedback delete <id> [--confirm]

→ Use annotation-queues commands when:

• You need to manage human review queues (list, create, update, delete)
• Commands: annotation-queues list, annotation-queues get <id>, annotation-queues create <name> [--description <str>], annotation-queues update <id> [--name <str>] [--description <str>], annotation-queues delete <id> [--confirm]

→ Use experiments commands when:

• You need to view run stats and feedback scores for a named experiment (project)
• Commands: experiments results <experiment-name>

→ Read references/fql.md when:

• You need to write a complex --filter expression and want operator reference
• You need metadata_key/metadata_value filter syntax

→ Read docs/examples.md when:

• You want end-to-end workflow examples (debugging, dataset management, production monitoring)
• You want common patterns without having to piece together flags yourself
• You need to search for recognized entities in extraction chain outputs (e.g. find all runs where "Niklas" was recognized as a known entity in extracted_entities) — there's a complete recipe covering cache download, Python JSONL scanning, deduplication of sub-runs, and llm_recognition filtering

→ Read references/cache-recipes.md when:

• You need to discover the nested structure of cached run data (inputs/outputs schema)
• You want to query cached JSONL data with Python one-liners or DuckDB SQL
• You need to extract, sort, or aggregate structured outputs from cached runs
• You need to find specific entities, values, or patterns in nested output fields

→ Read references/troubleshooting.md when:

• CLI commands fail, return unexpected results, or produce authentication errors
• You see rate limit errors and want strategies to work around them

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LangSmith URLs

runs open generates broken URLs. Build trace URLs manually using the project's id and tenant_id:

# Step 1: Get org ID (tenant_id) and project ID
langsmith-cli --json projects get "dev/my-project" --fields id,tenant_id

# Step 2: Build the URL
# https://smith.langchain.com/o/{tenant_id}/projects/p/{project_id}?peek={run_id}&peeked_trace={trace_id}

Example:

org_id = "b658ea18-0431-42c0-8d03-337d43fed8cf"   # tenant_id from projects get
proj_id = "730acc6c-ec97-4f08-915e-7d3f7f775300"  # id from projects get

url = f"https://smith.langchain.com/o/{org_id}/projects/p/{proj_id}?peek={run_id}&peeked_trace={trace_id}"

• peek = the specific run ID to open in the side panel
• peeked_trace = the trace (root run) ID it belongs to
• Both IDs come from your search results (run.id and run.trace_id)

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Key Flags Cheat Sheet

# Multi-project matching
--project-name-pattern "prd/*"    # wildcard
--project-name-regex "^(prd|stg)" # regex

# Time windows (combinable)
--since 2026-01-15 --before 2026-01-29
--last 7d
--since 2026-01-15 --last 14d     # forward window

# Content search
--query "text"                    # server-side, fast, first ~250 chars only
--grep "pattern" --grep-regex --grep-in inputs,outputs  # client-side, all content

# Metadata filter (server-side, supports wildcards and regex)
--metadata channel_id=Gigaverse_Daily_Standup*
--metadata channel_id=/^Gigaverse/

# Reduce output size
--fields id,name,status,start_time
--roots                           # root traces only (cleaner)
--limit 10 --fetch 500            # fetch 500 from API, return top 10 matches