Unable to change ephemeral messages with response_url (with slash commands)

[olavfla]

I'm trying to edit an ephemeral message generated by the respond command in a slack command response, but it just posts it as a new message. Not sure if I'm misreading the docs, but this makes it seem like it can be done.

Reproducible in:

pip freeze | grep slack
python --version
sw_vers && uname -v # or `ver`

The slack_bolt version

slack_bolt==1.22.0
slack_sdk==3.34.0

Python runtime version

Python 3.12.2

OS info

Microsoft Windows [Version 10.0.26100.3194]

Steps to reproduce:

(Share the commands to run, source code, and project settings (e.g., setup.py))

1. Source snippet

app = App(token=os.environ.get("SLACK_BOT_TOKEN"))

# Slash command: /play [url or search term]
# Places the requested socng at the end of the queue
@app.command("/play")
def play_command(ack, respond, command):
    ack()
    text = command.get("text", "").strip()
    if not text:
        respond("Please provide a YouTube URL or search query to play next.")
        return
    try:
        respond({"text":f"Queued: *{text}*", "replace_original":"true"}) #search
        #This function takes some time, so i want to send an acknowledgement to the user in the meantime.
        pcm_path, title, pipe, cancel_callback = (None, "Title", None, None)#download_and_convert(text)
    except Exception as e:
        respond(f"Failed to extract stream URL: {e}")
        return
    # with queue_lock:
    #     url_queue.append((title, pcm_path, cancel_callback))
    #Update with the title from the search result when it's available
    respond({"text":f"Replaced: *{text}*", "replace_original":"true"}) #queued
    # accountability(command["user_id"], title)
    # print(f"Queued {title} as next ({pcm_path})")
    # pipe.join()
    # print(f"Joined {title}")

if __name__ == "__main__":
    handler = SocketModeHandler(app, os.environ.get("SLACK_APP_TOKEN"))
    handler.start()

2. run /play

Expected result:

I expected the first ephemeral message to be replaced by the second one

Actual result:

The second response just posts a new message instead of overwriting the other one.

I have checked the logs to see if the "replace_original" attribute is being included, and it seems like it is. The request body looks like it does in the example for response_urls

DEBUG:slack_sdk.webhook.client:Sending a request - url: https://hooks.slack.com/commands/T071EE57DU2/8570366692821/feHDoUEdcjCTr6UdjDWZDbb5, body: {"text": "Queued: *Polyphia | Look But Don't Touch (feat. Lewis Grant)*", "replace_original": "true"}, headers: {'Content-Type': 'application/json;charset=utf-8', 'User-Agent': 'Python/3.12.2 slackclient/3.34.0 Windows/11'}
DEBUG:slack_sdk.webhook.client:Received the following response - status: 200, headers: {'date': 'Sat, 08 Mar 2025 23:33:03 GMT', 'server': 'Apache', 'vary': 'Accept-Encoding', 'strict-transport-security': 'max-age=31536000; includeSubDomains; preload', 'referrer-policy': 'no-referrer', 'x-slack-unique-id': 'Z8zTrwMpbeGNVSj2mVukFgAAEDw', 'x-slack-backend': 'r', 'access-control-allow-origin': '*', 'x-frame-options': 'SAMEORIGIN', 'content-type': 'text/html', 'content-length': '2', 'via': '1.1 slack-prod.tinyspeck.com, envoy-www-iad-nvnhelnz,envoy-edge-dub-uyzuznti', 'x-envoy-attempt-count': '1', 'x-envoy-upstream-service-time': '115', 'x-backend': 'main_normal main_canary_with_overflow main_control_with_overflow', 'x-server': 'slack-www-hhvm-main-iad-ddkc', 'x-slack-shared-secret-outcome': 'no-match', 'x-edge-backend': 'envoy-www', 'x-slack-edge-shared-secret-outcome': 'no-match', 'connection': 'close'}, body: ok

DEBUG:slack_sdk.webhook.client:Sending a request - url: https://hooks.slack.com/commands/T071EE57DU2/8570366692821/feHDoUEdcjCTr6UdjDWZDbb5, body: {"text": "Replaced: *Polyphia | Look But Don't Touch (feat. Lewis Grant)*", "replace_original": "true"}, headers: {'Content-Type': 'application/json;charset=utf-8', 'User-Agent': 'Python/3.12.2 slackclient/3.34.0 Windows/11'}
DEBUG:slack_sdk.webhook.client:Received the following response - status: 200, headers: {'date': 'Sat, 08 Mar 2025 23:33:06 GMT', 'server': 'Apache', 'vary': 'Accept-Encoding', 'strict-transport-security': 'max-age=31536000; includeSubDomains; preload', 'referrer-policy': 'no-referrer', 'x-slack-unique-id': 'Z8zTsg8I65vyheCsBHeCeAAAgDI', 'x-slack-backend': 'r', 'access-control-allow-origin': '*', 'x-frame-options': 'SAMEORIGIN', 'content-type': 'text/html', 'content-length': '2', 'via': '1.1 slack-prod.tinyspeck.com, envoy-www-iad-vqcbouzg,envoy-edge-dub-szbrifor', 'x-envoy-attempt-count': '1', 'x-envoy-upstream-service-time': '105', 'x-backend': 'main_normal main_canary_with_overflow main_control_with_overflow', 'x-server': 'slack-www-hhvm-main-iad-pxxc', 'x-slack-shared-secret-outcome': 'no-match', 'x-edge-backend': 'envoy-www', 'x-slack-edge-shared-secret-outcome': 'no-match', 'connection': 'close'}, body: ok

Please let me know if this is just me misreading the docs, or if I'm doing something wrong 😊

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[hello-ashleyintech]

Hi, @olavfla! Thanks for submitting this issue 😄

Taking an initial look at your code, do you get different results if you were to pass in a boolean True to replace_original rather than a string "true"?

[olavfla]

Hi, thanks for reviewing my issue.
It still doesn't work if i pass a boolean, but it does change how it looks in the logs:
DEBUG:slack_sdk.webhook.client:Sending a request - url: https://hooks.slack.com/commands/T071EE57DU2/8602511912421/zyddzLIkSDKXxygBSBNWceXW, body: {"text": "Playing next: *VOGEL IM K\u00c4FIG - ATTACK ON TITAN (feat. Stella Siecinska) - // Grissini Project Orchestra*", "replace_original": true}, headers: {'Content-Type': 'application/json;charset=utf-8', 'User-Agent': 'Python/3.12.2 slackclient/3.34.0 Windows/11'}

replace_original is no longer a string when sent.

Based on this, it looks like it's supposed to be a string.

[hello-ashleyintech]

Hi, @olavfla!

Thanks for the reply and additional context! 😄

I spoke with a member of my team and it seems like respond uses the response_url to send ephemeral message to the channel, it seems like it's not possible to reuse the same response_url to update the message using respond. You'll likely need to trigger a new response URL through an action OR use client.chat_update (though not 100% sure this method works with ephemeral messages).

Here are some potential workarounds they proposed:

Synchronous:

1. use respond with the response_url to post an ephemeral message
2. the respond function should return the message data of the ephemeral message
3. use client.chat_update with the channel_id and ts to update the message

Asynchronous (recommended):

1. use respond with the response_url to post an ephemeral message with an action button to update status
2. user clicks button
3. new action event is dispatched
4. the app handles it, and uses the new response_url to update the ephemeral message

Big thanks to @WilliamBergamin for the suggestions 🙇 I hope this helps and let me know if you have additional questions!

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