asgard.message.delta

The asgard.message.delta event streams the content of a message. Each event carries a small piece of text, and the idx field is what keeps them in order.

What it is

• When it fires: as the AI generates content, sending it out in pieces
• What it is for: the live typewriter effect
• How often: a message can produce many delta events

The fields that matter

Field	What it is
messageDelta.message.text	The increment: the new piece of text, which may be a character, a phrase or a sentence
messageDelta.message.idx	The position, counting up from 0
messageDelta.message.template	Usually null; it has a value in the complete event

A full example

The example below shows the typewriter effect for one complete message. Say the AI is about to answer with a sentence: it goes out as several delta events, each a character, a phrase or a sentence.

Delta 1 (idx: 0), the first piece

{
    "eventType": "asgard.message.delta",
    "requestId": "6939c5a6c590d90c401e3850a1ff44f3",
    "namespace": "qa-7e301310-a594-4a7b-aa2a-xxxxxxxxxxxx",
    "botProviderName": "bpapi-d97c512f-f8dc-46f6-82f0-xxxxxxxxxxxx",
    "customChannelId": "ch-6xxxxxxxxxxxx",
    "fact": {
        "runInit": null,
        "runDone": null,
        "runError": null,
        "messageStart": null,
        "messageDelta": {
            "message": {
                "messageId": "1834828082242916352",
                "replyToCustomMessageId": "",
                "text": "目前",              // <- only the new text
                "payload": null,
                "isDebug": false,
                "idx": 0,                   // <- the first piece
                "template": null            // <- usually null
            }
        },
        "messageComplete": null
    }
}

Delta 2 (idx: 1), the second piece

{
    "eventType": "asgard.message.delta",
    "requestId": "6939c5a6c590d90c401e3850a1ff44f3",
    "namespace": "qa-7e301310-a594-4a7b-aa2a-xxxxxxxxxxxx",
    "botProviderName": "bpapi-d97c512f-f8dc-46f6-82f0-xxxxxxxxxxxx",
    "customChannelId": "ch-6xxxxxxxxxxxx",
    "fact": {
        "runInit": null,
        "runDone": null,
        "runError": null,
        "messageStart": null,
        "messageDelta": {
            "message": {
                "messageId": "1834828082242916352",
                "replyToCustomMessageId": "",
                "text": "台",               // <- only the new text
                "payload": null,
                "isDebug": false,
                "idx": 1,                   // <- the second piece
                "template": null
            }
        },
        "messageComplete": null
    }
}

Delta 3 (idx: 2), the third piece

{
    "eventType": "asgard.message.delta",
    "requestId": "6939c5a6c590d90c401e3850a1ff44f3",
    "namespace": "qa-7e301310-a594-4a7b-aa2a-xxxxxxxxxxxx",
    "botProviderName": "bpapi-d97c512f-f8dc-46f6-82f0-xxxxxxxxxxxx",
    "customChannelId": "ch-6xxxxxxxxxxxx",
    "fact": {
        "runInit": null,
        "runDone": null,
        "runError": null,
        "messageStart": null,
        "messageDelta": {
            "message": {
                "messageId": "1834828082242916352",
                "replyToCustomMessageId": "",
                "text": "北",               // <- only the new text
                "payload": null,
                "isDebug": false,
                "idx": 2,                   // <- the third piece
                "template": null
            }
        },
        "messageComplete": null
    }
}

Reading the example

What accumulates

As the delta events arrive, the front end accumulates the text like this:

• After delta 1: "目前" (possibly a phrase)
• After delta 2: "目前台" (still accumulating)
• After delta 3: "目前台北" (still accumulating)

What to notice

1. The messageId is the same: every delta belongs to the same message
2. idx counts up: which is what lets you process them in order
3. text is an increment: each one carries the new piece, whether a character, a phrase or a sentence

Worth knowing

• Order matters: process them in idx order
• Accumulate the text: join the text of every delta to produce the typewriter effect
• Watch the cost: the interface updates frequently, so keep an eye on performance