Puppeteer: Unknown javascript dialog type: {value}

The browser reported a dialog type outside alert/confirm/prompt/beforeunload.

Error message

Unknown javascript dialog type: {value}

{value} is replaced by the value shown in your error message.

How this error happens

The browser reported a dialog type outside alert, confirm, prompt and beforeunload. A custom transport or incompatible protocol event can supply an invalid type.

The failing block is protocol event data; the correction uses an open page named page.

{
    "type": "custom-dialog",
    "message": "Continue?"
}

How to fix

Use a compatible browser and normal dialog events. Handle the public Dialog object once instead of synthesizing protocol dialog types.

page.once("dialog", async (dialog) => {
    console.log(dialog.type());

    await dialog.accept();
});

await page.evaluate(() => {
    alert("Continue?");
});

Things to keep in mind

The JSON block illustrates invalid event data. An HTML modal or a normal alert cannot manufacture an unknown native dialog type. If valid browser events still trigger the error, isolate the browser or transport failure.

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