apache/maven · warning

The following goals are not marked as thread-safe in {}:

Error message

The following goals are not marked as thread-safe in {}:

What it means

The debug-enabled branch of BuilderCommon's thread-safety check: when -X is active and the plan contains non-thread-safe plugins, Maven logs 'The following goals are not marked as thread-safe in <project>:' followed by one line per unsafe MojoDescriptor id (executionPlan.getNonThreadSafeMojos()). It is the precise, goal-level version of the plugin-level list shown without -X.

Source

Thrown at impl/maven-core/src/main/java/org/apache/maven/lifecycle/internal/builder/BuilderCommon.java:127

                lifeCycleExecutionPlanCalculator.calculateExecutionPlan(session, project, taskSegment.getTasks());

        lifecycleDebugLogger.debugProjectPlan(project, executionPlan);

        if (session.getRequest().getDegreeOfConcurrency() > 1
                && session.getProjects().size() > 1) {
            final Set<Plugin> unsafePlugins = executionPlan.getNonThreadSafePlugins();
            if (!unsafePlugins.isEmpty()) {
                for (String s : MultilineMessageHelper.format(
                        "Your build is requesting parallel execution, but this project contains the following "
                                + "plugin(s) that have goals not marked as thread-safe to support parallel execution.",
                        "While this /may/ work fine, please look for plugin updates and/or "
                                + "request plugins be made thread-safe.",
                        "If reporting an issue, report it against the plugin in question, not against Apache Maven.")) {
                    logger.warn(s);
                }
                if (logger.isDebugEnabled()) {
                    final Set<MojoDescriptor> unsafeGoals = executionPlan.getNonThreadSafeMojos();
                    logger.warn("The following goals are not marked as thread-safe in " + project.getName() + ":");
                    for (MojoDescriptor unsafeGoal : unsafeGoals) {
                        logger.warn("  " + unsafeGoal.getId());
                    }
                } else {
                    logger.warn("The following plugins are not marked as thread-safe in " + project.getName() + ":");
                    for (Plugin unsafePlugin : unsafePlugins) {
                        logger.warn("  " + unsafePlugin.getId());
                    }
                    logger.warn("");
                    logger.warn("Enable verbose output (-X) to see precisely which goals are not marked as"
                            + " thread-safe.");
                }
                logger.warn(MultilineMessageHelper.separatorLine());
            }
        }

        final String defaulModelId = DefaultLifecycleRegistry.DEFAULT_LIFECYCLE_MODELID;

View on GitHub (pinned to e4093d4e12)

Solutions

1. Use the listed goal ids to pin/upgrade exactly those plugin versions in pluginManagement.
2. Re-run without -T for the modules that execute those goals if they cannot be upgraded.
3. Bind those goals to a forked or sequential part of the build so they never run concurrently.
4. For your own plugin, add org.apache.maven.plugins.annotations.Mojo(threadSafe = true) once verified.

Example fix

# before
mvn -T 1C package   # warn: plugins not marked thread-safe

# after: identify exact goals, then pin fixed versions
mvn -X -T 1C package | grep -A20 'not marked as thread-safe'
# -> maven-pmd-plugin:3.13.0:pmd  => upgrade to 3.27.0 in pluginManagement

# guard: capture goal-level report once, gate CI on it being empty
mvn -X -T 1C package 2>&1 | grep -A50 'goals are not marked as thread-safe' | tee /tmp/unsafe.txt
test ! -s /tmp/unsafe.txt

When it happens

Trigger: Same parallel session conditions as the parent warning (degreeOfConcurrency > 1, multiple projects, non-empty getNonThreadSafePlugins()) plus logger.isDebugEnabled() — i.e. Maven invoked with -X or -e/-debug output.

Common situations: Diagnosing which exact goals break a -T build after seeing the plugin-level warning; CI debug logs showing goal ids like 'maven-javadoc-plugin:3.x:jar (attach-javadocs)'.

Related errors

• Your build is requesting parallel execution, but this projec
• The following plugins are not marked as thread-safe in {}:
• Enable verbose output (-X) to see precisely which goals are
• Invalid threads core multiplier value: '{}'. Value must be p
• Invalid threads value: '{}'. Value must be positive.

AI-assisted analysis of apache/maven@e4093d4e12 (2026-08-21). Data as JSON: /api/errors/47b17474c2308a00. Report an issue: GitHub.