Event Translation — Juggler and BiDi to CDP

Foxbridge subscribes to Juggler/BiDi events and translates them into CDP events that Puppeteer expects. This page documents every translation.

Target Events

Juggler Event	CDP Event(s)	Notes
`Browser.attachedToTarget`	`Target.attachedToTarget` (x2)	Dual-session model: emits TAB then PAGE attachment
`Browser.detachedFromTarget`	`Target.targetDestroyed`, `Target.detachedFromTarget`	Cleans up both tab and page sessions

Dual-Session Model

Puppeteer expects two CDP sessions per tab (matching Chrome’s architecture):

Tab session — represents the browser-level target
Page session — represents the content-level target, routes to Juggler

When setAutoAttach is called on a tab session, foxbridge emits the page attachment. Targets that arrive before setAutoAttach are queued and emitted retroactively.

Juggler Event	CDP Event(s)
`Page.navigationCommitted`	`Page.lifecycleEvent` (init, commit), `Page.frameNavigated`
`Page.eventFired` (load)	`Page.loadEventFired`, `Page.lifecycleEvent` (load), `Page.frameStoppedLoading`
`Page.eventFired` (DOMContentLoaded)	`Page.domContentEventFired`, `Page.lifecycleEvent` (DOMContentLoaded)

Foxbridge filters intermediate about:blank navigations that Juggler emits during redirects — Chrome does not emit these, and they confuse Puppeteer’s loader tracking.

Execution Context Events

Juggler Event	CDP Event
`Runtime.executionContextCreated`	`Runtime.executionContextCreated`
`Runtime.executionContextDestroyed`	`Runtime.executionContextDestroyed`
`Runtime.executionContextsCleared`	`Runtime.executionContextsCleared`

Context IDs are translated from Juggler’s string IDs to CDP’s numeric IDs. A bidirectional map (ctxMap) tracks the mapping. When a new default context is created, foxbridge re-emits any registered isolated world contexts so Puppeteer’s utility world stays functional.

Frame Events

Juggler Event	CDP Event
`Page.frameAttached`	`Page.frameAttached`
`Page.frameDetached`	`Page.frameDetached`

The main frame’s ID (where parentFrameId is empty) is stored in the session for use by Page.navigate and Page.getFrameTree.

Dialog Events

Juggler Event	CDP Event
`Page.dialogOpened`	`Page.javascriptDialogOpening`
`Page.dialogClosed`	`Page.javascriptDialogClosed`

Dialog IDs are tracked so Page.handleJavaScriptDialog can reference the correct dialog.

Console Events

Juggler Event	CDP Event
`Runtime.console`	`Runtime.consoleAPICalled`

Network Events

Juggler Event	CDP Event
`Network.requestWillBeSent`	`Network.requestWillBeSent`
`Network.responseReceived`	`Network.responseReceived`
`Network.requestFinished`	`Network.loadingFinished`
`Network.requestFailed`	`Network.loadingFailed`
`Browser.requestIntercepted`	`Fetch.requestPaused` + `Network.requestWillBeSent`

WebSocket URLs (ws://, wss://) also trigger Network.webSocketCreated. Request interception events are delivered to the correct page session by matching the frameId.

BiDi-Specific Differences

When running with the BiDi backend, foxbridge emits Runtime.executionContextsCleared on navigation (since BiDi lacks an explicit equivalent). Context destruction also cleans up all derived isolated world mappings pointing to the same realm.