Device Message says: Failed to receive a message: Failed to load just created webxdc instance

An error message suddenly appeared in device messages:

:cross_mark: Failed to receive a message: Failed to load just created webxdc instance: Message Msg#17977 does not exist. Core version v2.48.0. Please report this bug to delta@merlinux.eu or https://support.delta.chat/.

Delta Chat version

Core version v2.48.0.
Happens on Desktop as well as Android.

Expected behavior

I expect no error to appear

Actual behavior

Device message shows the following new message:

Failed to receive a message: Failed to load just created webxdc instance:
Message Msg#17977 does not exist. Core version v2.48.0.
and it asks to post this here.

Steps to reproduce the problem

  1. open delta chat
  2. find the error as new message in Device messages

Debug logs

Logs
2026-04-12T17:33:57.276Z	core/event            	INFO	""	11	"src/receive_imf.rs:520: Receiving message \"0c0c88cd-0f4f-4bef-bb86-1610e9e23a05@localhost\", seen=false..."
2026-04-12T17:33:57.277Z	core/event            	INFO	""	11	"src/receive_imf.rs:1446: Encrypted group message. Chat assignment = GroupChat { grpid: \"XXXXXXXXXXX\" }."
2026-04-12T17:33:57.293Z	core/event            	INFO	""	11	"src/receive_imf.rs:2362: Message has 1 parts and is assigned to chat #Chat#150, timestamp=1776014590."
2026-04-12T17:33:57.295Z	core/event            	INFO	""	11	"src/imap.rs:1409: Passing message UID 9835 to receive_imf()."
2026-04-12T17:33:57.354Z	core/event            	INFO	""	11	"src/receive_imf.rs:520: Receiving message \"f7e89baa-2358-47ea-9dd6-e590bfa18123@localhost\", seen=false..."
2026-04-12T17:33:57.354Z	core/event            	INFO	""	11	"src/receive_imf.rs:1446: Encrypted group message. Chat assignment = GroupChat { grpid: \"XXXXXXXXXXX\" }."
2026-04-12T17:33:57.370Z	core/event            	INFO	""	11	"src/receive_imf.rs:2362: Message has 1 parts and is assigned to chat #Chat#150, timestamp=1776014886."
2026-04-12T17:33:57.370Z	core/event            	INFO	""	11	"src/contact.rs:2157: Recently seen loop waiting for 0h 4m 9s or interrupt"
2026-04-12T17:33:57.370Z	core/event            	INFO	""	11	"src/imap.rs:1454: Successfully received 157 UIDs."
2026-04-12T17:33:57.370Z	core/event            	INFO	""	11	"src/imap.rs:810: 159 mails read from \"INBOX\"."
2026-04-12T17:33:57.370Z	core/event            	INFO	""	11	"src/imap.rs:819: available_post_msgs: 2, download_later: 2."
2026-04-12T17:33:57.376Z	core/event            	INFO	""	11	"src/download.rs:202: Downloading message INBOX/9706 fully..."
2026-04-12T17:33:57.376Z	core/event            	INFO	""	11	"src/imap.rs:1319: Starting UID FETCH of message set \"9706\"."
2026-04-12T17:33:58.048Z	core/event            	INFO	""	11	"src/imap.rs:1409: Passing message UID 9706 to receive_imf()."
2026-04-12T17:33:58.201Z	core/event            	INFO	""	11	"src/mimeparser.rs:1603: added blobfile: \"$BLOBDIR/4458XXXXXXXXXXXXXXXXXXXXXXXXXXX.xdc\""
2026-04-12T17:33:58.203Z	core/event            	INFO	""	11	"src/receive_imf.rs:520: Receiving message \"4571870c-cb3d-432e-9b41-1dbf7a31b471@localhost\", seen=false..."
2026-04-12T17:33:58.203Z	core/event            	INFO	""	11	"src/receive_imf.rs:1287: Message 4571870c-cb3d-432e-9b41-1dbf7a31b471@localhost is a post-message (pre-message exists already, so trash after replacing attachment)."
2026-04-12T17:33:58.205Z	core/event            	WARNING	""	11	"src/receive_imf.rs:2505: handle_post_message: 4571870c-cb3d-432e-9b41-1dbf7a31b471@localhost: Pre-message was not downloaded yet so treat as normal message."
2026-04-12T17:33:58.207Z	core/event            	INFO	""	11	"src/receive_imf.rs:2362: Message has 1 parts and is assigned to chat #Chat#Trash, timestamp=1775960014."
2026-04-12T17:33:58.207Z	core/event            	WARNING	""	11	"src/imap.rs:1416: receive_imf error: Failed to load just created webxdc instance: Message Msg#17977 does not exist."
2026-04-12T17:33:58.207Z	core/event            	INFO	""	11	"src/imap.rs:1454: Successfully received 1 UIDs."
2026-04-12T17:33:58.207Z	core/event            	INFO	""	11	"src/download.rs:202: Downloading message INBOX/9768 fully..."
2026-04-12T17:33:58.207Z	core/event            	INFO	""	11	"src/imap.rs:1319: Starting UID FETCH of message set \"9768\"."
2026-04-12T17:33:58.830Z	core/event            	INFO	""	11	"src/imap.rs:1409: Passing message UID 9768 to receive_imf()."
2026-04-12T17:33:58.943Z	core/event            	INFO	""	11	"src/mimeparser.rs:1603: added blobfile: \"$BLOBDIR/0c3aXXXXXXXXXXXXXXXXXXXXXXXXXXX.png\""
2026-04-12T17:33:58.945Z	core/event            	INFO	""	11	"src/receive_imf.rs:520: Receiving message \"95617269-6c18-478c-8205-a74da9bfcb41@localhost\", seen=true..."
2026-04-12T17:33:58.945Z	core/event            	INFO	""	11	"src/receive_imf.rs:1287: Message 95617269-6c18-478c-8205-a74da9bfcb41@localhost is a post-message (pre-message exists already, so trash after replacing attachment)."
2026-04-12T17:33:58.949Z	core/event            	INFO	""	11	"src/receive_imf.rs:2362: Message has 1 parts and is assigned to chat #Chat#Trash, timestamp=1775960014."
2026-04-12T17:33:58.949Z	core/event            	INFO	""	11	"src/imap.rs:1454: Successfully received 1 UIDs."
2026-04-12T17:33:59.033Z	core/event            	INFO	""	11	"src/imap/idle.rs:47: Transport 1: Skip IDLE in \"INBOX\" because we got interrupt."
2026-04-12T17:33:59.033Z	core/event            	INFO	""	11	"src/sql.rs:944: Start housekeeping..."
2026-04-12T17:33:59.035Z	core/event            	INFO	""	11	"src/sql.rs:1005: 301 files in use."
2026-04-12T17:33:59.035Z	core/event            	INFO	""	11	"src/sql.rs:1065: Housekeeping: Keeping new unreferenced file #1: \"4458XXXXXXXXXXXXXXXXXXXXXXXXXXX.xdc\"."
2026-04-12T17:33:59.040Z	core/event            	INFO	""	11	"src/sql.rs:780: Incremental vacuum freed 0 pages."
2026-04-12T17:33:59.058Z	core/event            	INFO	""	11	"src/sql.rs:687: wal_checkpoint: Total time: 18.405514ms. Writers blocked for: 1.625881ms. Readers blocked for: 1.479908ms."
2026-04-12T17:33:59.065Z	core/event            	INFO	""	11	"src/sql.rs:912: Housekeeping done."
2026-04-12T17:33:59.101Z	core/event            	INFO	""	11	"src/imap.rs:1162: Marked messages 9708:9715,9719:9727,9729:9737,9739:9755,9757:9766,9776,9784:9785,9788:9792,9802,9807:9823 in folder INBOX as seen."
2026-04-12T17:33:59.103Z	core/event            	INFO	""	11	"src/imap.rs:576: Transport 1: No new emails in folder \"INBOX\"."
2026-04-12T17:33:59.150Z	core/event            	INFO	""	11	"src/imap/select_folder.rs:41: Expunge messages in \"INBOX\"."
2026-04-12T17:33:59.186Z	core/event            	INFO	""	11	"src/imap/select_folder.rs:44: Close/expunge succeeded."
2026-04-12T17:33:59.234Z	core/event            	INFO	""	11	"src/imap/select_folder.rs:82: Transport 1: Selected folder \"INBOX\"."
2026-04-12T17:33:59.311Z	core/event            	INFO	""	11	"src/imap/idle.rs:67: Transport 1: IDLE entering wait-on-remote state in folder \"INBOX\"."


This is a known issue in 2.48.0, it will be fixed in 2.49+.
The fix is fix: assign webxdc updates from post-message to webxdc instance by link2xt · Pull Request #8095 · chatmail/core · GitHub

Workaround for the sender is to send webxdc first, and only then start using it, instead of opening it while it is in the draft mode.