seed-test-data

Testing & Quality

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.

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Source SKILL.md: https://github.com/langfuse/langfuse/blob/HEAD/.agents/skills/seed-test-data/SKILL.md

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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)
Async parents whose subtree outlives their own span (subtree wall-clock duration badge)	add `--async-parents` to `trace-tree` (root + hub end immediately while children keep running)
A realistic agent flow over a timeline (graph view + scrubbable timeline)	`pnpm run seed -- agent-timeline --turns 6 --v4` (LangGraph refine loop planner→retriever→generator→critic→loop, staggered in time; add `--timing-only` for the pure timing fallback)
A demo-grade, real-looking agent trace (videos, screenshots, docs)	`pnpm run seed -- support-agent --v4 --id-prefix <hex>` (one fixed, fully handcrafted support-copilot refund run: guardrails, parallel context fan-out, 3-turn ReAct loop with real payloads/costs; deterministic — reseed with a FRESH prefix for a clean take; the prefix is the trace id, so a hex prefix reads like production)
A plain trace with no agentic types (collapsed-by-default graph panel)	add `--plain` to `trace-tree` (SPAN/GENERATION/EVENT only)
An extremely DEEP single-chain trace (tree depth = observation count; layout stress)	`pnpm run seed -- deep-chain --v4` (1401 sequential generations, each the sole child of the previous — the mis-parented-instrumentation shape from LFE-10959 that collapses tree/timeline layouts; `--observations N` to change depth)
A super tough session (v3 legacy session view)	`pnpm run seed -- long-session --traces 300 --observations-per-trace 8`
Diverse v4 session shapes (chat / coding-agent / mixed) for the session-detail view	`pnpm run seed -- session-shapes --shape all` (the `agent` shape has I/O on AGENT/TOOL with no GENERATION — pre-LFE-10520 the "first generation" default rendered empty cards for it; the current "All observations with I/O" default renders it correctly; v4 on by default)
Many traces for list/filter performance	`pnpm run seed -- many-traces --count 100000 --days 14`
Scores with spaces in the name (filter/grammar testing)	`pnpm run seed -- scored-traces --traces 24 --v4`
Lots of scores on every node (dense score badges, tree-row overflow testing)	add `--scores-per-node 12` to `trace-tree` (N distinct scores per observation; try `--depth 2 --breadth 44` for many tall sibling rows)
Varied human-annotation queues (annotate UI / keyboard testing)	`pnpm run seed -- annotation-queue --core-items 12` (creates a "core types" queue covering every score-field render path + an "edge cases" queue with archived/stale/partial scores and observation/session/deleted/completed items)
Huge/malformed/unicode payloads	`pnpm run seed -- trace-tree --payload-bytes 1000000 --payload-style malformed` (styles: json, text, malformed, unicode, bignum, base64)
Big integers beyond 2^53-1 (number-precision testing)	`pnpm run seed -- trace-tree --observations 1 --payload-style bignum`
Huge base64 data-URI in ChatML IO (multimodal crash shape, LFE-10152)	`pnpm run seed -- trace-tree --observations 30 --payload-bytes 20000000 --payload-style base64 --v4` (one unbroken multi-MB base64 token in trace + root-observation IO; max 50 MB)
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 demo@langfuse.com / 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.