Mule Runtime Engine 4.12.0 Release Notes

Mule runtime engine (Mule) is a lightweight integration engine that runs Mule applications and supports domains and policies.

This version of Mule provides important enhancements and fixes. Deploy all your new and existing applications to the latest version to benefit from the improvements.

For guidance with the patching process, see Apply Patch Updates.

June 2, 2026

What’s New

The 4.12.0 version of Mule runtime introduces these enhancements:

OpenTelemetry Direct Telemetry Stream:

Mule 4.12 adds OpenTelemetry metrics support to Direct Telemetry Stream, including message processing, flow inventory, error tracking, runtime alerts, and JVM instrumentation metrics. See OpenTelemetry Support in Mule Runtime for a detailed description of the feature.

Feature Flagging Mechanism:

Mule 4.12 incorporates new feature flags. See Feature Flagging Mechanism for a detailed description of each feature flag and configuration instructions.

Runtime Manager agent:

This release of Mule runtime 4.12.0 includes Runtime Manager agent 2.7.15. See Runtime Manager Agent 2.7.15 Release Notes.

General improvements:

To build applications for Mule runtime engine 4.12.0, use Mule Maven Plugin 4.10.0 or later. See Mule Maven Plugin 4.10.0 Release Notes.

DataWeave Features

The 2.12.0 version of DataWeave introduces these new features and enhancements:

General improvements:

DataWeave incorporates new system properties. See DataWeave System Properties.
The UNLIMITED_CONTEXT math variable now has the precision=0 and roundingMode=HALF_UP properties.

Fixed Issues

The release addresses these Mule issues and incorporates all patch updates from the 4.12.0 Mule release through June 2026:

Issue Resolution ID

Issue Resolution	ID
Upstream HTTP requests are now cancelled when a downstream client disconnects, preventing unnecessary data transfer.	W-20084343
The Netty HTTP client no longer throws `NullPointerException` when handling Expect 100-Continue responses.	W-21513490
Sensitive headers are no longer forwarded when an HTTP request is redirected to a different host. This can be configured with `FILTER_SENSITIVE_HEADERS_ON_REDIRECT`.	W-21045658
The Apache CXF library is upgraded to 3.6.8.	W-20541600
Cluster encryption now uses the configured algorithm correctly instead of defaulting to Blowfish.	W-21666905
Race conditions during policy redeployment that caused Mule to stop processing events permanently no longer occur.	W-22343705
Redelivery policy logging now includes additional context for troubleshooting.	W-20636028
The Tanuki Java Service Wrapper is upgraded to 3.6.4.	W-17051070
The RAML parser is upgraded to 1.1.10.	W-21768014
The OpenTelemetry SDK is upgraded to 1.60.1.	W-21808539
Persistent ObjectStore or Batch data serialized before a patch upgrade now deserializes correctly after upgrading.	W-22623626
`OutOfMemory` errors no longer occur when establishing SSL connections with HTTP endpoints.	W-22547971

Upstream HTTP requests are now cancelled when a downstream client disconnects, preventing unnecessary data transfer.

W-20084343

The Netty HTTP client no longer throws NullPointerException when handling Expect 100-Continue responses.

W-21513490

Sensitive headers are no longer forwarded when an HTTP request is redirected to a different host. This can be configured with FILTER_SENSITIVE_HEADERS_ON_REDIRECT.

W-21045658

The Apache CXF library is upgraded to 3.6.8.

W-20541600

Cluster encryption now uses the configured algorithm correctly instead of defaulting to Blowfish.

W-21666905

Race conditions during policy redeployment that caused Mule to stop processing events permanently no longer occur.

W-22343705

Redelivery policy logging now includes additional context for troubleshooting.

W-20636028

The Tanuki Java Service Wrapper is upgraded to 3.6.4.

W-17051070

The RAML parser is upgraded to 1.1.10.

W-21768014

The OpenTelemetry SDK is upgraded to 1.60.1.

W-21808539

Persistent ObjectStore or Batch data serialized before a patch upgrade now deserializes correctly after upgrading.

W-22623626

OutOfMemory errors no longer occur when establishing SSL connections with HTTP endpoints.

W-22547971

DataWeave 2.12.0 is bundled with the Mule 4.12.0 release. This release addresses these DataWeave issues:

Issue Resolution ID

Issue Resolution	ID
DataWeave now supports the `private` modifier on `fun`, `var`, `ns`, and `type` declarations to hide them from importers.	W-21148967
`internal` is no longer a reserved word and can now be used as an identifier in DataWeave scripts.	W-21508044
The compiler now reports an error when overloads of the same function declare different visibility modifiers.	W-21362539
`StackOverflowError` no longer occurs in the type checker when resolving intersections of unbound type parameters.	W-20124753
Runtime errors no longer occur when invoking overloaded functions across modules.	W-21811015
Spurious type-check errors no longer occur when an optional key-value pair is assigned to a required one.	W-21351058
`deferred` values passed to the `write` function now terminate correctly.	W-20925604
Out-of-memory errors no longer occur when reading large text or CDATA sections with the indexed XML reader.	W-21006104
The Java module bean introspection cache no longer causes memory leaks.	W-22419118

DataWeave now supports the private modifier on fun, var, ns, and type declarations to hide them from importers.

W-21148967

internal is no longer a reserved word and can now be used as an identifier in DataWeave scripts.

W-21508044

The compiler now reports an error when overloads of the same function declare different visibility modifiers.

W-21362539

StackOverflowError no longer occurs in the type checker when resolving intersections of unbound type parameters.

W-20124753

Runtime errors no longer occur when invoking overloaded functions across modules.

W-21811015

Spurious type-check errors no longer occur when an optional key-value pair is assigned to a required one.

W-21351058

deferred values passed to the write function now terminate correctly.

W-20925604

Out-of-memory errors no longer occur when reading large text or CDATA sections with the indexed XML reader.

W-21006104

The Java module bean introspection cache no longer causes memory leaks.

W-22419118

Bundled Components

DataWeave version 2.12.0
Runtime Manager Agent plugin version 2.7.15

Upgrade

If you’re upgrading to this version of Mule from an earlier Mule 4.x version, see Mule Upgrades and Patch Updates.

To ensure optimal performance with this version of Mule and avoid unexpected issues, update these modules and extensions to their latest version at the time of this release:

Module or Extension	Version
APIkit for Mule 4	1.11.17
APIkit for OData	2.4.0
APIkit for OData 4	1.6.0
APIkit for SOAP	2.1.0
APIkit for GraphQL	1.2.0
Spring module	2.1.2
MUnit plugin	3.7.1

Considerations for Mule Extension Developers

When you build a Mule extension, if you update the version of your parent pom.xml file to 1.4.0 or later, ensure that the dependencies in your pom.xml file don’t override dependencies in the parent pom.xml file. Declare only the dependencies you need. If you declare a dependency that’s already in the parent pom.xml file, don’t specify a version, so that it uses the version from the parent pom.xml file.