name: taskcluster
description: >
Interact with Mozilla Taskcluster CI using the taskcluster CLI.
Query task status, view logs, download artifacts, retrigger tasks, and manage task groups.
Use when working with CI tasks from firefox-ci-tc.services.mozilla.com or debugging worker pool issues.
Triggers on "taskcluster", "task status", "task log", "artifacts", "retrigger", "task group".

Taskcluster

Interact with Mozilla Taskcluster CI using the official taskcluster CLI.

Usage

Run from the skill directory:

# Query task status
uv run scripts/tc.py status <TASK_ID>

# Get task logs
uv run scripts/tc.py log <TASK_ID>

# List task artifacts
uv run scripts/tc.py artifacts <TASK_ID>

# Get full task definition
uv run scripts/tc.py definition <TASK_ID>

# Retrigger a task (new task ID, updated timestamps)
uv run scripts/tc.py retrigger <TASK_ID>

# Rerun a task (same task ID)
uv run scripts/tc.py rerun <TASK_ID>

# Cancel a task
uv run scripts/tc.py cancel <TASK_ID>

# List tasks in a group
uv run scripts/tc.py group-list <TASK_GROUP_ID>

# Get task group status
uv run scripts/tc.py group-status <TASK_GROUP_ID>

# Extract task ID from Taskcluster URL
uv run scripts/tc.py status https://firefox-ci-tc.services.mozilla.com/tasks/fuCPrKG2T62-4YH1tWYa7Q

# --- In-Tree Actions (require authentication) ---

# List available actions for a task
uv run scripts/tc.py action-list <TASK_ID>

# Confirm failures - re-run failing tests to determine if intermittent
uv run scripts/tc.py confirm-failures <TASK_ID>

# Backfill - run test on previous pushes to find regression range
uv run scripts/tc.py backfill <TASK_ID>

# Retrigger multiple times (default 5)
uv run scripts/tc.py retrigger-multiple <TASK_ID> --times 10

# Trigger any action by name
uv run scripts/tc.py action <TASK_ID> <ACTION_NAME> --input '{"key": "value"}'

Prerequisites

1. Taskcluster CLI

The skill uses the taskcluster CLI which should be installed via Homebrew:

brew install taskcluster

Check installation:

taskcluster version

2. Authentication (Optional)

Most read-only operations (status, logs, artifacts) work without authentication. For write operations (retrigger, cancel), you need Taskcluster credentials.

Option 1: Environment Variables

export TASKCLUSTER_ROOT_URL=https://firefox-ci-tc.services.mozilla.com
export TASKCLUSTER_CLIENT_ID=your-client-id
export TASKCLUSTER_ACCESS_TOKEN=your-access-token

Option 2: Configuration File

Create ~/.config/taskcluster/credentials.json or use the CLI:

taskcluster signin

Option 3: 1Password CLI

Store credentials in 1Password and configure in config.toml:

cd scripts
cp config.toml.example config.toml

Edit the config.toml to specify your 1Password item and vault.

Common Workflows

Debugging Task Failures

1. Check task status: tc.py status <TASK_ID>
2. View logs: tc.py log <TASK_ID>
3. Inspect full definition: tc.py definition <TASK_ID>
4. Check all tasks in group: tc.py group-list <GROUP_ID>

Working with Treeherder Tasks

When you have a Treeherder URL like:

https://treeherder.mozilla.org/jobs?repo=try&revision=ed901414ea5ec1e188547898b31d133731e77588

1. Use the treeherder skill to get task IDs
2. Use this skill to query individual tasks

Retriggering Failed Tasks

# Retrigger creates a new task with updated timestamps
uv run scripts/tc.py retrigger <TASK_ID>

# Rerun attempts to rerun the same task
uv run scripts/tc.py rerun <TASK_ID>

In-Tree Actions (Confirm Failures, Backfill)

In-tree actions are defined in the Firefox taskgraph and triggered via Taskcluster hooks.
These are the API equivalent of actions available in Treeherder's "Custom Action" menu.

Required scopes: hooks:trigger-hook:project-gecko/in-tree-action-*

# List available actions for a failed task
uv run scripts/tc.py action-list <TASK_ID>

# Confirm failures - re-runs failing tests to determine if intermittent or regression
# This is what Treeherder does when you: Select task > "..." > Custom Action > confirm-failures
uv run scripts/tc.py confirm-failures <TASK_ID>

# Backfill - runs the test on previous pushes to find when a regression started
uv run scripts/tc.py backfill <TASK_ID>

# Retrigger multiple times - useful for stress-testing intermittent failures
uv run scripts/tc.py retrigger-multiple <TASK_ID> --times 10

# Trigger any action by name with custom input
uv run scripts/tc.py action <TASK_ID> retrigger-custom --input '{"path": "test.js"}'

Common use case: Investigating image rollout failures

# 1. Find failed tasks using treeherder skill
uvx --from lumberjackth lj failures 2012615 -t autoland -p windows11-64-24h2 -n 5

# 2. Confirm if failures are intermittent or real regressions
uv run scripts/tc.py confirm-failures <TASK_ID>

# 3. If regression, backfill to find the culprit push
uv run scripts/tc.py backfill <TASK_ID>

URL Support

The skill automatically extracts task IDs from Taskcluster URLs:

# Both of these work identically:
uv run scripts/tc.py status fuCPrKG2T62-4YH1tWYa7Q
uv run scripts/tc.py status https://firefox-ci-tc.services.mozilla.com/tasks/fuCPrKG2T62-4YH1tWYa7Q

Supported URL formats:
- https://firefox-ci-tc.services.mozilla.com/tasks/<TASK_ID>
- https://stage.taskcluster.nonprod.cloudops.mozgcp.net/tasks/<TASK_ID>
- https://community-tc.services.mozilla.com/tasks/<TASK_ID>

Output Formats

All commands return JSON output that can be piped to jq for processing:

# Get only failed tasks from a group
uv run scripts/tc.py group-list <GROUP_ID> | jq '.tasks[] | select(.status.state == "failed")'

# List artifact names
uv run scripts/tc.py artifacts <TASK_ID> | jq '.artifacts[].name'

Related Skills

• treeherder: Query CI job results by revision to get task IDs
• lando: Check landing job status
• os-integrations: Run Firefox mach try commands

References

• references/actions.md - Detailed guide to in-tree actions (confirm-failures, backfill, etc.)
• references/examples.md - Common usage patterns and workflows
• references/integration.md - Integration with other Mozilla tools

Documentation

• Taskcluster Docs: https://docs.taskcluster.net/
• Taskcluster CLI: https://github.com/taskcluster/taskcluster/tree/main/clients/client-shell
• Firefox CI: https://firefox-ci-tc.services.mozilla.com/
• Community Taskcluster: https://community-tc.services.mozilla.com/
• Actions Spec: https://docs.taskcluster.net/docs/manual/using/actions/spec