diff --git a/docs/general/specs/22. Backend Spec-to-Test Conformance Matrix.md b/docs/general/specs/22. Backend Spec-to-Test Conformance Matrix.md
index f182c538..27cffd0c 100644
--- a/docs/general/specs/22. Backend Spec-to-Test Conformance Matrix.md	
+++ b/docs/general/specs/22. Backend Spec-to-Test Conformance Matrix.md	
@@ -38,7 +38,7 @@ to concrete positive/negative test evidence and current status.
 | G19-5.2.5 | Gate S-I MUST reject host ABI mismatch. | N/A | `BackendGateIIntegrationTest#gateI_rejectHostAbiMismatchAtEmitTime` | pass |  |
 | G19-5.2.6 | Gate S-I MUST reject missing capability at load-time. | N/A | `BackendGateIIntegrationTest#gateI_rejectMissingCapability` | pass |  |
 | G19-5.2.7 | Gate S-I MUST cover valid VM-owned intrinsic path. | `BackendGateIIntegrationTest#gateI_validIntrinsicPath` | N/A | pass |  |
-| G19-5.2.8 | Gate S-I MUST cover repeatability across runtime line. | `RuntimeBackedCompatibilityAdapterTest#checkMustPassInStrictModeWhenRuntimeCommandIsValid` | `RuntimeBackedCompatibilityAdapterTest#checkMustFailInStrictModeWhenRuntimeCommandIsUnavailable` | partial | Runtime-line repeatability is validated at adapter contract level; multi-line matrix coverage is pending. |
+| G19-5.2.8 | Gate S-I MUST cover repeatability across runtime line. | `RuntimeBackedCompatibilityAdapterTest#checkMustPassInStrictModeWhenRuntimeCommandIsValid`; `RuntimeBackedCompatibilityAdapterTest#checkMustBeRepeatableAcrossDeclaredRuntimeLinesInStrictMode` | `RuntimeBackedCompatibilityAdapterTest#checkMustFailInStrictModeWhenRuntimeCommandIsUnavailable` | pass | Multi-line repeatability is asserted with strict runtime-backed checks over distinct declared runtime lines. |
 | G20-6.2 | `IRVM_EXT` MUST declare structural metadata (`pops/pushes/is_branch/is_terminator`). | `IRVMValidatorTest#validateMustApplyStructuralMetadataForCustomInternalExtension`; `IRVMValidatorTest#validateMustRejectCustomInternalExtensionWhenStructuralMetadataUnderflowsStack`; `IRVMOp` record contract (`pops/pushes/branch/terminator/internal`) | N/A | pass | Dedicated extension fixtures now assert structural metadata is consumed by validation behavior. |
 | G20-6.3 | `IRVM_EXT` MUST be eliminable before bytecode emission. | `OptimizeIRVMServiceTest#optimizeDefaultPassesMustEliminateUnreachableInternalExtensionBeforeEmission` | `EmitBytecodePipelineStageTest#runMustFailWhenInternalOpcodesRemain`; `EmitBytecodePipelineStageTest#runMustFailWhenInternalOpcodesRemainEvenWithNonEmptyEmissionPlan`; `IRVMValidatorTest#validateMustRejectInternalOpcodeWhenConfigured` | pass | Optimizer elimination path and emit-stage hard rejection path are both covered. |
 | G20-6.4 | IRVM MUST preserve per-function slot and identity headers. | `IRVMProgramTest#constructorMustRejectModuleAndEmissionPlanMismatch` | `IRVMProgramTest#constructorMustRejectModuleAndEmissionPlanMismatch` | pass | Header mismatch is rejected deterministically. |
diff --git a/prometeu-compiler/prometeu-build-pipeline/src/test/java/p/studio/compiler/integration/RuntimeBackedCompatibilityAdapterTest.java b/prometeu-compiler/prometeu-build-pipeline/src/test/java/p/studio/compiler/integration/RuntimeBackedCompatibilityAdapterTest.java
index 989e4031..a0713bb5 100644
--- a/prometeu-compiler/prometeu-build-pipeline/src/test/java/p/studio/compiler/integration/RuntimeBackedCompatibilityAdapterTest.java
+++ b/prometeu-compiler/prometeu-build-pipeline/src/test/java/p/studio/compiler/integration/RuntimeBackedCompatibilityAdapterTest.java
@@ -1,11 +1,14 @@
 package p.studio.compiler.integration;
 
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
 import p.studio.compiler.backend.bytecode.BytecodeModule;
 import p.studio.utilities.structures.ReadOnlyList;
 
+import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
+import java.nio.file.Files;
 import java.nio.file.Path;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
@@ -67,6 +70,44 @@ class RuntimeBackedCompatibilityAdapterTest {
         assertTrue(result.reason().contains("accepted artifact"));
     }
 
+    @Test
+    void checkMustBeRepeatableAcrossDeclaredRuntimeLinesInStrictMode(
+            @TempDir final Path tempDir) throws IOException {
+        final var runtimeLineA = tempDir.resolve("runtime-a");
+        final var runtimeLineB = tempDir.resolve("runtime-b");
+        Files.createDirectories(runtimeLineA);
+        Files.createDirectories(runtimeLineB);
+        Files.writeString(runtimeLineA.resolve("VERSION.txt"), "1.0.0-a\n");
+        Files.writeString(runtimeLineB.resolve("VERSION.txt"), "1.0.0-b\n");
+
+        final var adapterA = new RuntimeBackedCompatibilityAdapter(
+                new LocalRuntimeCompatibilityAdapter(),
+                runtimeLineA,
+                "test -f {artifact}",
+                true);
+        final var adapterB = new RuntimeBackedCompatibilityAdapter(
+                new LocalRuntimeCompatibilityAdapter(),
+                runtimeLineB,
+                "test -f {artifact}",
+                true);
+
+        final var firstA = adapterA.check(moduleWithSingleRet());
+        final var firstB = adapterB.check(moduleWithSingleRet());
+        final var secondA = adapterA.check(moduleWithSingleRet());
+        final var secondB = adapterB.check(moduleWithSingleRet());
+
+        assertEquals(CompatibilityError.NONE, firstA.error());
+        assertEquals(CompatibilityError.NONE, firstB.error());
+        assertEquals("runtime-backed", firstA.adapterMode());
+        assertEquals("runtime-backed", firstB.adapterMode());
+        assertEquals("runtime-v1.0.0-a", firstA.runtimeLine());
+        assertEquals("runtime-v1.0.0-b", firstB.runtimeLine());
+        assertEquals(firstA.runtimeLine(), secondA.runtimeLine());
+        assertEquals(firstB.runtimeLine(), secondB.runtimeLine());
+        assertEquals(firstA.error(), secondA.error());
+        assertEquals(firstB.error(), secondB.error());
+    }
+
     private BytecodeModule moduleWithSingleRet() {
         return new BytecodeModule(
                 0,