VS 2026 Blazor MSAL Login Loop

[MaddMugsy]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

When trying to run our Blazor WASM site in debug mode from VS2026, it gets stuck in a login loop. We are using MSAL auth with MS Entra ID.

During the login process, the web app will repeatedly hit and break on the "debugger" line below:

export function mono_wasm_runtime_ready (): void {
    INTERNAL.mono_wasm_runtime_is_ready = runtimeHelpers.mono_wasm_runtime_is_ready = true;

    // FIXME: where should this go?
    _next_call_function_res_id = 0;
    _call_function_res_cache = {};
    _debugger_buffer_len = -1;

    // DO NOT REMOVE - magic debugger init function
    if ((<any>globalThis).dotnetDebugger)
        // eslint-disable-next-line no-debugger
        debugger;
}

After it hits that line and I click resume several times, it will login and go to https://localhost:5551/authentication/login-callback, then it will stop at the line with "debugger" in this script:

( () => {
    let r = ["instantiate", "instantiateStreaming", "compile", "compileStreaming"];
    for (let e of r) {
        let t = WebAssembly[e];
        WebAssembly[e] = function(...n) {
            return t.apply(this, n).then(i => {
                if (!(n[0]instanceof WebAssembly.Module))
                    debugger ;return i
            }
            )
        }
    }
}
)();

Then it will try to login again and loop forever.

I was able to resolve this issue disabling the new mono debugger (both checkboxes).

Expected Behavior

Application logs in as normal.

.NET Version

9.0 with VS2026 11109.219

[MackinnonBuck]

Thanks for reaching out, @MaddMugsy.

Could you please provide us with a minimal repro project, hosted as a public GitHub repository, so we can investigate this issue further?

[MaddMugsy]

Sure, I'll start on that now. Note that after updating to the latest VS 2026 version 11111.16 it no longer loops. Instead, after starting debugging, VS 2026 crashes to the desktop before the Blazor client can even finish loading.

Also I messed up the source of the issue - it's MSAL, not Identity.