Axial
Repository F# setup
open System
open System.IO
open System.Threading
open System.Threading.Tasks
open Axial
open Axial.Layers
open Axial.Console
open Axial.FileSystem
open Axial.Hosting
open Axial.Hosting.Browser
open Axial.Hosting.Node
open Axial.HttpClient
open Axial.PlatformService
open Axial.Process
open Axial.State
open Axial.Telemetry
open Axial.Telemetry.JavaScript

Browser Hosting

Axial.Hosting.Browser is a JavaScript-only Fable package. It connects a root App to browser ownership without pretending the browser has a dependable process-shutdown phase.

dotnet add package Axial.Hosting.Browser

The package's .NET target asset exists for Fable project compilation. Calling its entry points outside Fable browser JavaScript fails immediately.

UI-Owned Mount

Mount the application when the UI root or feature is created:

open Axial.Hosting.Browser

let running =
    BrowserApp.mount browserEnvironment application
When the owner unmounts, request stop and allow cleanup to finish: 
    let! _ = running.Stop()
    return ()
}
React hooks, Elmish program ownership, custom elements, and other UI frameworks can call the same pair. The hosting package does not depend on one framework.

AbortSignal Ownership

Use startWithSignal when the owner already exposes an AbortSignal:

open Fable.Core.JsInterop

let controller: obj = emitJsExpr () "new AbortController()"
let signal: AbortSignal = emitJsExpr controller "$0.signal"

let running =
    BrowserApp.startWithSignal
        signal
        browserEnvironment
        application

// Later:
emitJsStatement controller "$0.abort()"
The structural `AbortSignal` binding avoids requiring a particular browser-binding package. An already-aborted signal requests stop immediately. The event listener is removed after application completion.

Page Lifecycle Is Not Application Shutdown

The adapter deliberately does not stop applications on visibilitychange, pagehide, or beforeunload:

  • a hidden tab can become visible again;
  • pagehide may place the page in the back/forward cache;
  • browsers do not guarantee time for asynchronous unload cleanup.

The UI owner should stop work when its actual ownership ends. For data that must survive page termination, use the browser's persistence or delivery mechanisms rather than relying on Flow finalizers during unload.

Outcomes

Browsers have no process exit code. Observe running.Completion and translate the structured Exit into application state, a fatal-error screen, or an error-reporting adapter:

async {
    let! exit = running.Completion

    match exit with
    | Exit.Success () -> ()
    | Exit.Failure Cause.Interrupt -> () // normal unmount
    | Exit.Failure cause -> showFatalError cause
}
|> Async.StartImmediate
Do not flatten typed failures, interruption, and defects into the same UI message before the application edge decides how each should be handled.