CMP sources

walkerOS provides ready-made source packages for popular Consent Management Platforms. Each source listens for CMP events and automatically calls elb('walker consent', state), with no manual event listener code needed.

CMP	Package
CookieFirst	@walkeros/web-source-cmp-cookiefirst
CookiePro / OneTrust	@walkeros/web-source-cmp-cookiepro
Usercentrics	@walkeros/web-source-cmp-usercentrics

Conditional activation with require

Some sources and destinations shouldn't act on lifecycle events right away. They may depend on consent status being resolved first, or need information provided by other sources (like session IDs). The require option solves this by gating on() delivery (for sources) or initialization (for destinations) until specific collector events have fired.

Add require to any source or destination config to gate it on the listed events:

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In this example the CMP source initializes immediately and fires elb('walker consent', state) once the user makes a choice. That consent event unblocks the session source, the dataLayer source, and the GA4 destination, all at once.

How require works

1. Sources are registered immediately and their Instance.init() runs eagerly after registration. require does not block init — it gates on() delivery. Lifecycle events targeted at a source with unmet require are buffered in Instance.queueOn.
2. Destinations with require are held as pending during initialization until their listed events fire.
3. A require entry is satisfied by the collector's current recorded state, not only by a future event. So order does not matter: a step activates whether the required state (such as a CMP applying consent) was recorded before or after the step registered. The collector reconciles every pending step against current state at each state change, at the run barrier, and once after all sources have registered.
4. Sources whose require just emptied have their queued lifecycle events replayed via source.on(type, data). Destinations whose require just emptied are registered and become eligible to initialize/send; any previously queued events are preserved and delivered once the collector is allowed to push, so no data is lost.

Key points

• CMP sources must not have require: they need to fire consent immediately, so the collector should be able to call on('consent', …) on them right away
• Accepted values: any collector event type, such as "consent", "session", "user", "run", "config", "globals", etc.
• AND logic: require: ["consent", "session"] waits for both events
• Cascading: a CMP source fires consent → session source's require clears, its queued on('consent', …) replays, it fires session → a dataLayer source waiting for ["session"] clears next

How CMP sources work

1. Detecting if the CMP is already loaded and reading existing consent
2. Listening for CMP-specific events on consent changes
3. Mapping CMP categories to walkerOS consent groups via categoryMap
4. Calling elb('walker consent', state) with the mapped state

CMP and session sources perform their initial consent read during init(), not in the source factory. The factory stays side-effect free; the consent emit happens once the collector runs the source's init(). Combined with the current-state require matching above, this means a require:["consent"] step activates reliably regardless of which source provided the consent or when.

All CMP sources support explicitOnly (default: true) to filter out implicit/default consent and only process active user choices.

For more details on how consent works in walkerOS, see the consent management guide.