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.

July 2026

What’s New

Runtime Manager agent:

This release of Mule runtime 4.12.1 includes Runtime Manager agent 2.7.16. See Runtime Manager Agent 2.7.16 Release Notes.

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.

General improvements:

The Mule Troubleshooting plugin now includes additional diagnostic sections in the Diagnostic Information Analysis File (DIAF). See Mule Troubleshooting Plugin for more information.
- System Info: Reports host-level diagnostics including OS details, CPU metrics, memory, and disk input and output statistics.
- JVM Agents: Lists agents attached at JVM startup via -javaagent, -agentpath, or -agentlib arguments.
- Connectors State: Shows connector configuration states, connection pools, errors, and TLS details.
- Cluster Info: Reports clustering configuration and distributed lock diagnostics.

Fixed Issues

Patch release version: 4.12.1

This patch update addresses these Mule issues:

Issue Resolution ID

Issue Resolution	ID
Clustered applications deployed with two or more replicas no longer fail to start with a `NullPointerException` error during cluster node discovery.	W-22843942
Cluster node IDs are no longer generated with negative values.	W-22294724
Graceful shutdown no longer times out when a global error handler runs for a flow.	W-22434375
Long-running internal tasks no longer use the shared `forkJoin` pool during parallel flow shutdown and bootstrap configuration, preventing thread starvation.	W-22279521
Race conditions in `outerFluxCompletionScheduler` no longer occur during graceful shutdown.	W-22343018
Mule no longer hangs during shutdown when a parameter validation exception occurs during flow execution.	W-22248534
Connectivity testing of configurations in clustered deployments no longer uses distributed locks, preventing deadlocks.	W-22248198
Fatal errors such as `StackOverflowError` are now logged instead of being consumed by internal error handling.	W-22496803
Object Store retrieved from the registry in `OAuthHandler` is now properly initialized and started.	W-22373641
SDK parameter validation errors now raise the `MULE:VALIDATION` error type instead of `MULE:UNKNOWN`.	W-22276522
`ConcurrentModificationException` errors no longer occur when multiple plugins with shared dependencies are deployed simultaneously.	W-21193046
The error type in the EE cache scope is now correctly reported as `MULE:RETRY_EXHAUSTED` instead of `EE:RETRY_EXHAUSTED` when until-successful exhausts its retries.	W-21525972
Test Connection for the HTTP listener now correctly reports a failure when an unresolvable hostname is configured in the host field.	W-21921687
HTTP Server now supports upgrade requests to h2c even when the request contains a non-empty body.	W-22506085
Duplicate XSD elements are no longer generated for connection providers declared at both the extension and configuration levels.	W-20824537
Shutdown validation for dynamic configurations can now be skipped by enabling the `mule.forcefulShutdown.dynamicConfig.disableStoppingCheck` system property.	W-22772644
Flows with a scheduler source are no longer left in an invalid state after a flow restart.	W-22918240
Stopping a flow no longer waits unnecessarily when no events are being processed.	W-22969411
Project versions defined with properties are now resolved recursively.	W-22845430
Extension packager validation no longer fails for operations annotated with `@Validator` that use a `CompletionCallback` operation.	W-22817376
Events that are dropped within a processing hook are now properly completed and terminated.	W-22470584
In-memory Object Store partitions are now created correctly when an application is deployed to a cluster with the Object Store plugin enabled.	W-17714668
Deserialization errors no longer occur in the Object Store during a runtime patch upgrade.	W-20880559
Applications deployed with a serialized AST now include all Mule error types in the error type repository.	W-22399271
Applications that use HTTP request attributes no longer fail annotation processing due to default constructor validation.	W-22385620
The Netty HTTP listener now rejects `HTTP/1.1` requests that have a missing or duplicate host header, in compliance with RFC 9112.	W-23052713
The maximum size of the dynamic `flow-ref` cache is now configurable through the `mule.flowRef.dynamicCacheMaxSize` system property, which defaults to 20.	W-22219018
API Gateway contract persistence can now be disabled by setting the `anypoint.platform.contracts_persistence_enabled` system property to `false`, avoiding errors when persisting large numbers of contracts.	W-22568982
Large Anypoint Platform authentication failure responses no longer cause excessive log bloat.	W-21882516
SDK sources that don’t implement `Reconnectable` are no longer restarted during graceful shutdown.	W-21563258
OpenTelemetry flow statistics now report metrics correctly for applications with more than one flow.	W-23051614
The artifact type (domain, policy, or application) is now included as an OpenTelemetry resource attribute.	W-21768636
OpenTelemetry metric attribute names now use a consistent notation.	W-21921584
The `mule.openTelemetry.logging.exporter.resource.container.service.name` system property is now available to set the service name that the Mule container reports for OpenTelemetry telemetry.	W-22861497
Event dumps now include a state for events that are waiting on a non-blocking operation.	W-22142952
The Netty library is upgraded to 4.2.15.Final.	W-22831076
The c3p0 library is upgraded to 0.14.1.	W-22990155
The Bitronix Transaction Manager library is upgraded to 3.0.2.	W-22405007
The Reactor Netty library is upgraded to 1.3.6.	W-3300013
The Jackson Core library is upgraded to 2.21.1.	W-22839747
The Apache Neethi library is upgraded to 3.2.1.	W-22839752
The OpenTelemetry API library is upgraded to 1.62.0.	W-22849469
The Spring Framework is upgraded to 6.2.19.	W-22939417

Clustered applications deployed with two or more replicas no longer fail to start with a NullPointerException error during cluster node discovery.

W-22843942

Cluster node IDs are no longer generated with negative values.

W-22294724

Graceful shutdown no longer times out when a global error handler runs for a flow.

W-22434375

Long-running internal tasks no longer use the shared forkJoin pool during parallel flow shutdown and bootstrap configuration, preventing thread starvation.

W-22279521

Race conditions in outerFluxCompletionScheduler no longer occur during graceful shutdown.

W-22343018

Mule no longer hangs during shutdown when a parameter validation exception occurs during flow execution.

W-22248534

Connectivity testing of configurations in clustered deployments no longer uses distributed locks, preventing deadlocks.

W-22248198

Fatal errors such as StackOverflowError are now logged instead of being consumed by internal error handling.

W-22496803

Object Store retrieved from the registry in OAuthHandler is now properly initialized and started.

W-22373641

SDK parameter validation errors now raise the MULE:VALIDATION error type instead of MULE:UNKNOWN.

W-22276522

ConcurrentModificationException errors no longer occur when multiple plugins with shared dependencies are deployed simultaneously.

W-21193046

The error type in the EE cache scope is now correctly reported as MULE:RETRY_EXHAUSTED instead of EE:RETRY_EXHAUSTED when until-successful exhausts its retries.

W-21525972

Test Connection for the HTTP listener now correctly reports a failure when an unresolvable hostname is configured in the host field.

W-21921687

HTTP Server now supports upgrade requests to h2c even when the request contains a non-empty body.

W-22506085

Duplicate XSD elements are no longer generated for connection providers declared at both the extension and configuration levels.

W-20824537

Shutdown validation for dynamic configurations can now be skipped by enabling the mule.forcefulShutdown.dynamicConfig.disableStoppingCheck system property.

W-22772644

Flows with a scheduler source are no longer left in an invalid state after a flow restart.

W-22918240

Stopping a flow no longer waits unnecessarily when no events are being processed.

W-22969411

Project versions defined with properties are now resolved recursively.

W-22845430

Extension packager validation no longer fails for operations annotated with @Validator that use a CompletionCallback operation.

W-22817376

Events that are dropped within a processing hook are now properly completed and terminated.

W-22470584

In-memory Object Store partitions are now created correctly when an application is deployed to a cluster with the Object Store plugin enabled.

W-17714668

Deserialization errors no longer occur in the Object Store during a runtime patch upgrade.

W-20880559

Applications deployed with a serialized AST now include all Mule error types in the error type repository.

W-22399271

Applications that use HTTP request attributes no longer fail annotation processing due to default constructor validation.

W-22385620

The Netty HTTP listener now rejects HTTP/1.1 requests that have a missing or duplicate host header, in compliance with RFC 9112.

W-23052713

The maximum size of the dynamic flow-ref cache is now configurable through the mule.flowRef.dynamicCacheMaxSize system property, which defaults to 20.

W-22219018

API Gateway contract persistence can now be disabled by setting the anypoint.platform.contracts_persistence_enabled system property to false, avoiding errors when persisting large numbers of contracts.

W-22568982

Large Anypoint Platform authentication failure responses no longer cause excessive log bloat.

W-21882516

SDK sources that don’t implement Reconnectable are no longer restarted during graceful shutdown.

W-21563258

OpenTelemetry flow statistics now report metrics correctly for applications with more than one flow.

W-23051614

The artifact type (domain, policy, or application) is now included as an OpenTelemetry resource attribute.

W-21768636

OpenTelemetry metric attribute names now use a consistent notation.

W-21921584

The mule.openTelemetry.logging.exporter.resource.container.service.name system property is now available to set the service name that the Mule container reports for OpenTelemetry telemetry.

W-22861497

Event dumps now include a state for events that are waiting on a non-blocking operation.

W-22142952

The Netty library is upgraded to 4.2.15.Final.

W-22831076

The c3p0 library is upgraded to 0.14.1.

W-22990155

The Bitronix Transaction Manager library is upgraded to 3.0.2.

W-22405007

The Reactor Netty library is upgraded to 1.3.6.

W-3300013

The Jackson Core library is upgraded to 2.21.1.

W-22839747

The Apache Neethi library is upgraded to 3.2.1.

W-22839752

The OpenTelemetry API library is upgraded to 1.62.0.

W-22849469

The Spring Framework is upgraded to 6.2.19.

W-22939417

DataWeave 2.12.1 is bundled with the Mule 4.12.1 release. This patch release addresses these DataWeave issues:

Issue Resolution ID

Issue Resolution	ID
Scope resolution errors no longer occur when importing Java classes with self-referential array properties.	W-22914494
`StackOverflowError` errors no longer occur when computing or converting type metadata for self-referencing recursive types.	W-21712344

Scope resolution errors no longer occur when importing Java classes with self-referential array properties.

W-22914494

StackOverflowError errors no longer occur when computing or converting type metadata for self-referencing recursive types.

W-21712344

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:

Scope Visibility:

DataWeave now supports private, internal, and @VisibleTo annotations for controlling directive access. This enables better code encapsulation and visibility management across DataWeave modules. See Scope Visibility in DataWeave.

Component Metadata:

DataWeave introduces dw::meta::Component and related component types for working with component descriptors. This provides enhanced metadata handling capabilities. See Component (dw::meta::Component) and Component Types (dw::meta::Component).

General Improvements:

The UNLIMITED_CONTEXT math variable now has the precision=0 and roundingMode=HALF_UP properties.
The Maven plugin for DataWeave now includes guidance for configuring cryptographic taint analysis during compilation.
The DataWeave extension plugin now provides editor support for scope visibility validation and diagnostics.
DataWeave incorporates new system properties. See DataWeave System 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.

Mule Runtime Engine 4.12.0 Release Notes

July 2026

What’s New

Fixed Issues

June 2, 2026

What’s New

DataWeave Features

Fixed Issues

Bundled Components

Upgrade

Considerations for Mule Extension Developers

See Also