diff --git a/.github/contract-tests/pom.xml b/.github/contract-tests/pom.xml
index 6872d46cf..d70d903a7 100644
--- a/.github/contract-tests/pom.xml
+++ b/.github/contract-tests/pom.xml
@@ -14,7 +14,7 @@
 
     <properties>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-        <gephi-plugins-tests.version>1.1.0</gephi-plugins-tests.version>
+        <gephi-plugins-tests.version>1.2.0</gephi-plugins-tests.version>
     </properties>
 
     <!-- Align the plugin's Gephi/NetBeans dependencies on the current gephi.version, so plugins
@@ -61,6 +61,8 @@
                         <!-- Only test implementations from the plugin's own jar, not the ones its
                              dependencies (e.g. core layout-plugin) register -->
                         <gephi.plugins.tests.jar>${plugin.artifactId}-${plugin.version}.jar</gephi.plugins.tests.jar>
+                        <!-- Where the tests write their warnings (checks that don't fail the build), read by run.sh -->
+                        <gephi.plugins.tests.warnings>${project.build.directory}/contract-warnings.tsv</gephi.plugins.tests.warnings>
                     </systemPropertyVariables>
                     <dependenciesToScan>
                         <dependency>org.gephi:gephi-plugins-tests</dependency>
diff --git a/.github/contract-tests/run.sh b/.github/contract-tests/run.sh
index 724cbed58..2adc2836b 100755
--- a/.github/contract-tests/run.sh
+++ b/.github/contract-tests/run.sh
@@ -6,7 +6,9 @@
 #
 # With no arguments, every module in the root pom.xml's <modules> list is tested. Otherwise only
 # NBM modules under the given folders are; a folder outside the reactor (e.g. a disabled plugin)
-# is skipped with a warning. Modules must be installed in the local Maven repository first
+# is skipped with a warning. Checks that are only advisory (e.g. a layout adding nodes) don't fail
+# the run: they are reported as warning annotations, and in the job summary when running on GitHub
+# Actions. Modules must be installed in the local Maven repository first
 # (mvn install): a module that is missing there, or was rebuilt since, fails instead of testing a
 # stale jar.
 set -euo pipefail
@@ -75,6 +77,44 @@ if [ ${#TARGETS[@]} -eq 0 ]; then
   exit 0
 fi
 
+# Advisory test warnings, one "plugin<TAB>check<TAB>message" entry each
+WARNINGS_FILE="$HARNESS_DIR/target/contract-warnings.tsv"
+WARNINGS=()
+
+# Workflow command data can't contain %, the warnings are single lines already
+annotation_escape() {
+  printf '%s' "$1" | sed -e 's/%/%25/g'
+}
+
+# Plugin names and messages come from the plugin's code, so don't let them format the summary
+markdown_escape() {
+  printf '%s' "$1" | sed -e 's/&/\&amp;/g' -e 's/</\&lt;/g' -e 's/>/\&gt;/g' -e 's/|/\\|/g' -e 's/`/\\`/g'
+}
+
+collect_warnings() {
+  [ -f "$WARNINGS_FILE" ] || return 0
+  local check message
+  while IFS=$'\t' read -r check message; do
+    WARNINGS+=("$1"$'\t'"$check"$'\t'"$message")
+    echo "::warning title=SPI contract test warning::$(annotation_escape "$1: $check: $message")"
+  done < "$WARNINGS_FILE"
+}
+
+# The jars of the modules that depend on the one being tested, installed in the local repository. A plugin split in
+# modules keeps parts of it (e.g. its user interface) in modules that depend on the main one, and the tests look
+# those up too.
+dependent_jars() {
+  local packaging group artifact version basedir repo jar
+  while IFS='|' read -r packaging group artifact version basedir _ repo; do
+    [ "$packaging" = nbm ] || continue
+    [ "$artifact" != "$1" ] || continue
+    grep -q "<artifactId>$1</artifactId>" "$basedir/pom.xml" || continue
+    jar="$repo/${group//.//}/$artifact/$version/$artifact-$version.jar"
+    [ -f "$jar" ] && echo "$jar"
+  done <<< "$PROJECTS"
+  return 0
+}
+
 PASSED=()
 FAILED=()
 for target in "${TARGETS[@]}"; do
@@ -92,20 +132,44 @@ for target in "${TARGETS[@]}"; do
     continue
   fi
 
+  EXTRA_ARGS=()
+  EXTRA_JARS=$(dependent_jars "$artifact" | paste -sd, -)
+  if [ -n "$EXTRA_JARS" ]; then
+    EXTRA_ARGS=(-Dmaven.test.additionalClasspath="$EXTRA_JARS")
+  fi
+
   rm -rf "$HARNESS_DIR/target"
   echo "::group::Contract tests: $gav"
   if mvn -B -ntp -f "$HARNESS_DIR/pom.xml" test -Dgephi.version="$GEPHI_VERSION" \
-      -Dplugin.groupId="$group" -Dplugin.artifactId="$artifact" -Dplugin.version="$version"; then
+      -Dplugin.groupId="$group" -Dplugin.artifactId="$artifact" -Dplugin.version="$version" \
+      ${EXTRA_ARGS[@]+"${EXTRA_ARGS[@]}"}; then
     echo "::endgroup::"
   else
     echo "::endgroup::"
     echo "::error::SPI contract tests failed for $gav"
+    collect_warnings "$gav"
     FAILED+=("$gav")
     continue
   fi
+  collect_warnings "$gav"
   PASSED+=("$gav")
 done
 
+if [ ${#WARNINGS[@]} -gt 0 ] && [ -n "${GITHUB_STEP_SUMMARY:-}" ]; then
+  {
+    echo "### SPI contract test warnings"
+    echo
+    echo "These checks don't fail the build, but are worth a look in review."
+    echo
+    echo "| Plugin | Check | Warning |"
+    echo "| --- | --- | --- |"
+    for warning in "${WARNINGS[@]}"; do
+      IFS=$'\t' read -r gav check message <<< "$warning"
+      echo "| $(markdown_escape "$gav") | $(markdown_escape "$check") | $(markdown_escape "$message") |"
+    done
+  } >> "$GITHUB_STEP_SUMMARY"
+fi
+
 if [ ${#PASSED[@]} -gt 0 ]; then
   echo "SPI contract tests passed for: ${PASSED[*]}"
 fi
diff --git a/AGENTS.md b/AGENTS.md
index 83d1be150..616df2c2c 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -25,7 +25,8 @@ Requires JDK 17 and Maven.
 - Build/test a single plugin module: `mvn -pl modules/<ModuleName> clean package`
 - Run a single module's unit tests only: `mvn -pl modules/<ModuleName> test`
 - Run the SPI contract tests CI runs (from `gephi-plugins-tests`) on a module, after `mvn install`:
-  `.github/contract-tests/run.sh modules/<ModuleName>`
+  `.github/contract-tests/run.sh modules/<ModuleName>`. A failing check fails the run; advisory checks
+  (e.g. a layout adding nodes) only print `::warning::` lines and, in CI, a job summary table.
 - Run Gephi with the module(s) installed (build first): `mvn org.gephi:gephi-maven-plugin:run`
 - IDE run/debug configs are defined in `nbactions.xml`; the IntelliJ debug setup (remote debugger +
   `-Drun.params.debug` VM option) is documented in `README.md`.