Tilt

Tilt: Kubernetes Dev Toolkit

Tilt automates the local Kubernetes development loop: watch files, build images, deploy to cluster. Configuration lives in a Tiltfile (Starlark, a Python dialect). A resource bundles an image build + k8s deploy (or a local command) into a single manageable unit.

CLI Operations

The commands an agent uses to interact with a running Tilt instance.

Lifecycle

Task	Command
Start dev environment	tilt up [-- <Tiltfile args>]
Start with terminal log streaming	tilt up --stream
Start specific resources only	tilt up frontend backend
Run in CI/batch mode (exits on success/failure)	tilt ci --timeout 30m
Stop and delete deployed resources	tilt down
Change runtime Tiltfile args	tilt args -- --flag value
Change runtime args (clear all)	tilt args --clear

On Ctrl+C from tilt up: K8s and Docker Compose resources keep running. Local serve_cmd processes stop. Use tilt down to clean up.

Viewing Logs

Task	Command
Stream all logs	tilt logs -f
Stream logs for one resource	tilt logs -f <resource>
Show only errors	tilt logs --level error
Show build logs only	tilt logs --source build
Show runtime logs only	tilt logs --source runtime
Logs since 5 minutes ago	tilt logs --since 5m
Last 100 lines	tilt logs --tail 100
JSON output (for parsing)	tilt logs --json

Resource Management

Task	Command
List all resources	tilt get uiresources
Resource status as JSON	tilt get uiresources -o json
Describe a resource in detail	tilt describe uiresource <name>
Force rebuild a resource	tilt trigger <resource>
Enable a disabled resource	tilt enable <resource>
Disable a resource	tilt disable <resource>
Wait for resource readiness	tilt wait --for=condition=Ready uiresource/<name>

Inspection & Debugging

Task	Command
Diagnostics (versions, cluster)	tilt doctor
Inspect file watches	tilt get filewatches
Describe a specific file watch	tilt describe filewatch <name>
Full engine state dump (JSON)	tilt dump engine
Full UI state dump	tilt dump webview
Test Docker build as Tilt would	tilt docker -- build <args>
List API resource types	tilt api-resources

The Tilt API server runs on localhost:10350 by default. All tilt get/describe/trigger commands talk to it.

Build Strategy Selector

Situation	Function	Key detail
Standard Dockerfile	docker_build(ref, context)	Watches context dir, auto-injects into k8s
Custom toolchain (Bazel, ko, Buildpacks)	custom_build(ref, cmd, deps)	Must tag with $EXPECTED_REF env var
Non-Docker builder (Buildah, kaniko)	custom_build(..., skips_local_docker=True)	Builder handles push independently
Docker Compose services	docker_compose(configPaths)	Manages compose lifecycle
Helm charts	k8s_yaml(helm('./chart'))	Renders locally, deploys to cluster
Kustomize overlays	k8s_yaml(kustomize('./overlay'))	Renders locally, deploys to cluster

Live Update Decision Tree

Live update replaces full image rebuilds with in-place container file syncs, seconds instead of minutes.

Step	Purpose	Ordering
fall_back_on(files)	Force full rebuild when these files change	Must come first
sync(local, remote)	Copy changed files into running container	After fall_back_on
run(cmd, trigger=files)	Execute command in container (e.g., install deps)	After sync
restart_container()	Restart the container process	Must come last

docker_build('myapp', '.', live_update=[
    fall_back_on(['requirements.txt']),
    sync('./src', '/app/src'),
    run('pip install -r requirements.txt', trigger=['requirements.txt']),
])

When live update breaks: Changes to files outside the docker_build context trigger a full rebuild. Changes outside any sync() path also trigger a full rebuild. First tilt up always does a full build, live update requires a running container.

Resource Configuration

# Kubernetes resource with port forwarding and dependencies
k8s_resource('frontend',
    port_forwards=['3000:3000'],
    resource_deps=['api', 'database'],
    labels=['web'],
    trigger_mode=TRIGGER_MODE_MANUAL,
)

# Local resource (build tool, test runner, code generator)
local_resource('codegen',
    cmd='make generate',
    deps=['./proto'],
    labels=['tools'],
)

# Local server (runs continuously)
local_resource('storybook',
    serve_cmd='npm run storybook',
    deps=['./src/components'],
    allow_parallel=True,
    readiness_probe=probe(http_get=http_get_action(port=6006)),
)

Parallelism: Local resources run serially by default. Set allow_parallel=True for independent resources. Image builds default to 3 concurrent, adjust with update_settings(max_parallel_updates=N).

Dependencies: resource_deps gates on first-ever readiness only, once a dependency is ready once, dependents unlock permanently for that session.

Debugging Flow

Service crashing?     → tilt logs -f <resource> --source runtime
Build failing?        → tilt logs -f <resource> --source build
                        tilt docker -- build <args>  (reproduces Tilt's exact build)
Wrong files rebuild?  → tilt get filewatches
                        tilt describe filewatch <name>
                        Check .tiltignore, watch_settings(ignore=), ignore= param
Force a rebuild?      → tilt trigger <resource>
Resource stuck?       → tilt describe uiresource <name>
                        Check resource_deps chain
                        For CRDs: pod_readiness='ignore'
General diagnostics?  → tilt doctor
Full state dump?      → tilt dump engine | jq .

Top 10 Pitfalls

Pitfall	Fix
local() calls don't track file deps	Wrap with read_file() or add watch_file()
Live update paths outside docker_build context	Ensure sync local paths fall within context dir
Local resources block each other	Set allow_parallel=True on independent resources
resource_deps doesn't re-gate on updates	It only checks first-ever readiness, not current version
Starlark has no while/try-except/class/recursion	Use for loops, fail() for errors, dicts for state
.tiltignore doesn't affect Docker build context	Use .dockerignore to exclude from both rebuild triggers AND context
$EXPECTED_REF not used in custom_build	Build script MUST tag the image with this env var
run() trigger files not in a sync() step	Trigger paths must also be covered by a sync step
First tilt up always does full build	Live update cannot work until a container is running
CRD pods stuck in pending	Set pod_readiness='ignore' on CRD resources

Additional Resources

Reference Files

For detailed API signatures and advanced patterns, consult:

• references/api-reference.md: Complete Tiltfile API catalog organized by category, Starlark language notes, ignore mechanism comparison
• references/patterns.md: Multi-service architectures, environment config, CI integration, performance optimization, programmatic Tilt interaction, extension ecosystem

Anti-Patterns

Anti-Pattern	Fix
Starting or stopping Tilt without consent	Ask before changing long-running dev environments
Treating tilt up as a build command	Use tilt ci for batch verification
Live update without fallbacks	Put build/dependency files in fall_back_on
Debugging from Kubernetes YAML only	Inspect uiresources, file watches, and logs
Using local() for watched shell work	Use local_resource with explicit deps

What This Skill is NOT

• Not a Kubernetes primer.
• Not permission to run, restart, or tear down a dev environment.
• Not a substitute for reading tilt doctor and resource logs.