seed-test-data

name

seed-test-data

description

Seed local Langfuse test data with one command: large/branching observation trees (v3 and v4 events), long sessions, bulk traces for list performance. Use whenever a task needs ClickHouse/Postgres test data — e.g. "seed a complex trace", "make a tough session", "fill the trace list", "test v4 events UI", or when debugging trace/session/list rendering or performance. Never write ad-hoc seed scripts or raw ClickHouse inserts.

Seed Test Data

One-shot deterministic test data for local Langfuse. The CLI handles env loading, preflight checks, ClickHouse/Postgres writes, readback verification, and prints UI deep links plus a machine-readable JSON summary (last stdout line).

If anything fails, run doctor first

pnpm run seed -- doctor

Prints PASS/WARN/FAIL per dependency (Postgres, migrations, project, ClickHouse, v4 dev tables, Redis, MinIO, web app) with the exact fix command for every failure. Do not debug Docker/ClickHouse manually before running this.

Need → command

I need...	Command
A very complex observation tree (v3)	pnpm run seed -- trace-tree --observations 5000 --depth 12 --breadth 500
The same tree readable in the v4 events UI	add --v4 (writes events_full; events_core fills via MV)
A super tough session (v3 legacy session view)	pnpm run seed -- long-session --traces 300 --observations-per-trace 8
Many traces for list/filter performance	pnpm run seed -- many-traces --count 100000 --days 14
Huge/malformed/unicode payloads	pnpm run seed -- trace-tree --payload-bytes 1000000 --payload-style malformed (styles: json, text, malformed, unicode)
See all scenarios and flags	pnpm run seed -- list --json
Predict without writing	add --dry-run

Contract

• Last stdout line is a JSON summary: traceIds, sessionIds, counts, verified (ClickHouse readback), links (UI deep links). Use --json to suppress progress logs. Non-zero exit = data did not land; the error includes a fix: line.
• Deterministic: same --seed (default 42) and flags → same ids (ids never contain dates), with timestamps anchored to the current UTC day. Re-running within the same day overwrites in place; a later-day re-run updates the same ids with re-anchored timestamps (the previous day's rows persist under their old dates until then). Independent copies come only from --id-prefix.
• Default project is the seeded 7a88fb47-b4e2-43b8-a06c-a5ce950dc53a (login [e-mail] / password); override with --project.
• Open the printed links in the browser to verify visually. The v4 events-backed UI is the per-user "Fast (Preview)" sidebar toggle, or LANGFUSE_MIGRATION_V4_WRITE_MODE=events_only server-side.

Extending

Add a scenario in packages/shared/scripts/seeder/scenarios/: a plain function using the deterministic Rng (never Math.random), register it in scenarios/index.ts, and update the table in packages/shared/scripts/seeder/AGENTS.md and this skill. Scenario names, flags, and JSON keys are additive-only contracts. Design rationale: packages/shared/scripts/seeder/README.md.