Safari 26.2 Regression Causing Dynamic Web TWAIN v19.3 Auto-Reconnect Failure on macOS

Symptom

After upgrading to Safari 26.2 on macOS, a compatibility issue was observed with Dynamic Web TWAIN v19.3.

When a site installs or updates the Dynamic Web TWAIN v19.3 Service for the first time, the automatic connection and reconnect mechanism fails. A browser refresh is required to restore normal behavior.

Issue characteristics

• Only occurs in Safari 26.2
• Does not occur in Safari 26.1 or earlier versions
• Does not occur in Dynamic Web TWAIN versions prior to 19.3

Reason

Dynamic Web TWAIN 19.3 introduced a new configuration in reconnect requests: targetAddressSpace: "loopback", following the Chrome Local Network Access documentation to explicitly indicate that the request targets the loopback address (127.0.0.1).

In Safari 26.1 and earlier, this configuration is ignored and requests are sent normally.

In Safari 26.2, fetch throws a TypeError when this configuration is present, causing the request to fail before being sent. As a result, reconnect cannot be implemented even though the Dynamsoft Service is installed and running.

Update

The WebKit team has identified this issue as a regression in Safari 26.2 and has already fixed it. The fix will be included in an upcoming Safari release.

Original post creation date: Dec 31, 2025

Last modified date: Dec 31, 2025