lkml-blastradius

The blast radius of every Looker change. Every morning: what changed (LookML deploys, Looker upgrades, Google releases), and which dashboards, Looks, explores and Conversational Analytics agents it hits.

pip install lkml-blastradius
lkblast init    # writes blastradius.yaml + a daily GitHub Actions workflow
lkblast run     # snapshot Looker, compare with yesterday, write the report

Each run takes a metadata snapshot through the Looker API and compares it with the previous one:

Then it reports what changed, old → new, which content it touches, how badly, and why:

Every change is attributed to one of three causes: a LookML deploy in a named project (old → new commit), a Looker upgrade (old → new version) with no deploy, or neither. Changes from Google come from the upgrade line, the matching release notes, and the content validator.

Try it offline

lkblast demo    # two days on a fake Looker (fictional Harborline Supply Co.)
open lkblast-demo/reports/blastradius.html

  2 breaking, 3 numbers may change, 1 cosmetic
  2 new content error(s), 2 open
  Looker upgraded 26.14.2 → 26.16.1
  LookML deployed in core_project, finance_project
  3 new Google release note(s), 2 need attention

The Refund watch Look and the Logistics helper agent are not listed because nothing they use changed.

Run it daily (GitHub Actions + Slack)

1. lkblast init in any repo (it can be an otherwise empty repo).
2. Add repository secrets: LOOKER_BASE_URL, LOOKER_CLIENT_ID, LOOKER_CLIENT_SECRET, and optionally SLACK_WEBHOOK_URL.
3. Push. The workflow runs at 06:00 UTC daily (change the cron in .github/workflows/lkml-blastradius.yml) or on demand from the Actions tab.

Every run writes reports/blastradius.{md,html,json}. The Markdown goes to the job summary, the reports are uploaded as an artifact, and a short summary with a link to the run is posted to Slack. Snapshot history lives in the Actions cache. Each run refreshes it, so it doesn't expire while the job runs daily.

The first run saves a baseline. Impact is reported from the second run on.

API user. Use API credentials of a user that can see all content (an admin, or a role with see_lookml, see_user_dashboards, see_looks, access_data on all models). Content the user can't see is not analyzed. Reading deployed commits needs see_lookml/develop; without it, the report still works but can't tell a LookML deploy from a Looker upgrade.

Options

blastradius.yaml (written by lkblast init; every key is optional):

looker:   {models: [], workers: 8, timeout_seconds: 120}
content:  {dashboards: true, looks: true, looker_agents: true, content_validator: true}
ca_api:   {enabled: false, locations: [global]}   # + GOOGLE_CLOUD_PROJECT, GOOGLE_OAUTH_ACCESS_TOKEN
releases: {enabled: true, lookback_days: 7}
storage:  {dir: .lkblast, keep: 30}
report:   {dir: reports}

lkblast run --fail-on breaking          # exit 1 when something breaks (for alerting)
lkblast compare OLD.json.gz NEW.json.gz # report between any two saved snapshots

To include CA API data agents, set ca_api.enabled: true and provide GOOGLE_CLOUD_PROJECT and an access token in GOOGLE_OAUTH_ACCESS_TOKEN. In Actions, get one with google-github-actions/auth (token_format: access_token). Agents that point at another Looker instance are ignored.

What it does not do

• It reports changes after they reach production (daily). It doesn't check a LookML branch before merge.
• It never runs queries and stores no row data. It can't see a number change that comes from the warehouse data itself.
• It can't see a Google change that alters behavior but not metadata, such as how an agent picks fields. That shows up only as an upgrade line and release notes. Agent answer regression testing is what lookml-agentops does.

API sources

Every Looker endpoint and attribute used is checked against Looker's OpenAPI spec (looker-open-source/sdk-codegen, spec/Looker.4.0.oas.json, 4.0.26.12). The list is in the docstring of looker.py. /agents is marked beta by Looker. CA API fields come from the v1 REST reference. Release-note formats were checked on 2026-10-03 (see releases.py). If Google changes the page layout, the run records a warning and continues.

Development

uv sync && uv run pytest && uv run ruff check src tests && uv run mypy

Apache-2.0. Not affiliated with or endorsed by Google. Looker is a trademark of Google LLC.