diff --git a/cameleer-server-core/src/main/java/com/cameleer/server/core/runtime/DirtyStateCalculator.java b/cameleer-server-core/src/main/java/com/cameleer/server/core/runtime/DirtyStateCalculator.java
new file mode 100644
index 00000000..f9a32ad6
--- /dev/null
+++ b/cameleer-server-core/src/main/java/com/cameleer/server/core/runtime/DirtyStateCalculator.java
@@ -0,0 +1,70 @@
+package com.cameleer.server.core.runtime;
+
+import com.cameleer.common.model.ApplicationConfig;
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.node.ObjectNode;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeSet;
+import java.util.UUID;
+
+/**
+ * Compares the app's current desired state (JAR + agent config + container config) to the
+ * config snapshot from the last successful deployment, producing a structured dirty result.
+ *
+ * <p>Pure logic — no IO, no Spring. Safe to unit-test as a POJO.</p>
+ */
+public class DirtyStateCalculator {
+
+    private static final ObjectMapper MAPPER = new ObjectMapper();
+
+    public DirtyStateResult compute(UUID desiredJarVersionId,
+                                    ApplicationConfig desiredAgentConfig,
+                                    Map<String, Object> desiredContainerConfig,
+                                    DeploymentConfigSnapshot snapshot) {
+        List<DirtyStateResult.Difference> diffs = new ArrayList<>();
+
+        if (snapshot == null) {
+            diffs.add(new DirtyStateResult.Difference("snapshot", "(none)", "(none)"));
+            return new DirtyStateResult(true, diffs);
+        }
+
+        if (!Objects.equals(desiredJarVersionId, snapshot.jarVersionId())) {
+            diffs.add(new DirtyStateResult.Difference("jarVersionId",
+                    String.valueOf(desiredJarVersionId), String.valueOf(snapshot.jarVersionId())));
+        }
+
+        compareJson("agentConfig", MAPPER.valueToTree(desiredAgentConfig),
+                MAPPER.valueToTree(snapshot.agentConfig()), diffs);
+        compareJson("containerConfig", MAPPER.valueToTree(desiredContainerConfig),
+                MAPPER.valueToTree(snapshot.containerConfig()), diffs);
+
+        return new DirtyStateResult(!diffs.isEmpty(), diffs);
+    }
+
+    private void compareJson(String prefix, JsonNode desired, JsonNode deployed,
+                             List<DirtyStateResult.Difference> diffs) {
+        if (!(desired instanceof ObjectNode desiredObj) || !(deployed instanceof ObjectNode deployedObj)) {
+            if (!Objects.equals(desired, deployed)) {
+                diffs.add(new DirtyStateResult.Difference(prefix,
+                        String.valueOf(desired), String.valueOf(deployed)));
+            }
+            return;
+        }
+        TreeSet<String> keys = new TreeSet<>();
+        desiredObj.fieldNames().forEachRemaining(keys::add);
+        deployedObj.fieldNames().forEachRemaining(keys::add);
+        for (String key : keys) {
+            JsonNode d = desiredObj.get(key);
+            JsonNode p = deployedObj.get(key);
+            if (!Objects.equals(d, p)) {
+                diffs.add(new DirtyStateResult.Difference(prefix + "." + key,
+                        String.valueOf(d), String.valueOf(p)));
+            }
+        }
+    }
+}
diff --git a/cameleer-server-core/src/main/java/com/cameleer/server/core/runtime/DirtyStateResult.java b/cameleer-server-core/src/main/java/com/cameleer/server/core/runtime/DirtyStateResult.java
new file mode 100644
index 00000000..8af70fed
--- /dev/null
+++ b/cameleer-server-core/src/main/java/com/cameleer/server/core/runtime/DirtyStateResult.java
@@ -0,0 +1,7 @@
+package com.cameleer.server.core.runtime;
+
+import java.util.List;
+
+public record DirtyStateResult(boolean dirty, List<Difference> differences) {
+    public record Difference(String field, String staged, String deployed) {}
+}
diff --git a/cameleer-server-core/src/test/java/com/cameleer/server/core/runtime/DirtyStateCalculatorTest.java b/cameleer-server-core/src/test/java/com/cameleer/server/core/runtime/DirtyStateCalculatorTest.java
new file mode 100644
index 00000000..ba9ec733
--- /dev/null
+++ b/cameleer-server-core/src/test/java/com/cameleer/server/core/runtime/DirtyStateCalculatorTest.java
@@ -0,0 +1,91 @@
+package com.cameleer.server.core.runtime;
+
+import com.cameleer.common.model.ApplicationConfig;
+import org.junit.jupiter.api.Test;
+
+import java.util.Map;
+import java.util.UUID;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class DirtyStateCalculatorTest {
+
+    @Test
+    void noSnapshot_meansEverythingDirty() {
+        DirtyStateCalculator calc = new DirtyStateCalculator();
+
+        ApplicationConfig desiredAgent = new ApplicationConfig();
+        desiredAgent.setSamplingRate(1.0);
+        Map<String, Object> desiredContainer = Map.of("memoryLimitMb", 512);
+
+        DirtyStateResult result = calc.compute(UUID.randomUUID(), desiredAgent, desiredContainer, null);
+
+        assertThat(result.dirty()).isTrue();
+        assertThat(result.differences()).extracting(DirtyStateResult.Difference::field)
+                .contains("snapshot");
+    }
+
+    @Test
+    void identicalSnapshot_isClean() {
+        DirtyStateCalculator calc = new DirtyStateCalculator();
+
+        ApplicationConfig cfg = new ApplicationConfig();
+        cfg.setSamplingRate(0.5);
+        Map<String, Object> container = Map.of("memoryLimitMb", 512);
+
+        UUID jarId = UUID.randomUUID();
+        DeploymentConfigSnapshot snap = new DeploymentConfigSnapshot(jarId, cfg, container);
+        DirtyStateResult result = calc.compute(jarId, cfg, container, snap);
+
+        assertThat(result.dirty()).isFalse();
+        assertThat(result.differences()).isEmpty();
+    }
+
+    @Test
+    void differentJar_marksJarField() {
+        DirtyStateCalculator calc = new DirtyStateCalculator();
+        ApplicationConfig cfg = new ApplicationConfig();
+        Map<String, Object> container = Map.of();
+        UUID v1 = UUID.randomUUID();
+        UUID v2 = UUID.randomUUID();
+        DeploymentConfigSnapshot snap = new DeploymentConfigSnapshot(v1, cfg, container);
+
+        DirtyStateResult result = calc.compute(v2, cfg, container, snap);
+
+        assertThat(result.dirty()).isTrue();
+        assertThat(result.differences()).extracting(DirtyStateResult.Difference::field)
+                .contains("jarVersionId");
+    }
+
+    @Test
+    void differentSamplingRate_marksAgentField() {
+        DirtyStateCalculator calc = new DirtyStateCalculator();
+
+        ApplicationConfig deployedCfg = new ApplicationConfig();
+        deployedCfg.setSamplingRate(0.5);
+        ApplicationConfig desiredCfg = new ApplicationConfig();
+        desiredCfg.setSamplingRate(1.0);
+        UUID jarId = UUID.randomUUID();
+        DeploymentConfigSnapshot snap = new DeploymentConfigSnapshot(jarId, deployedCfg, Map.of());
+
+        DirtyStateResult result = calc.compute(jarId, desiredCfg, Map.of(), snap);
+
+        assertThat(result.dirty()).isTrue();
+        assertThat(result.differences()).extracting(DirtyStateResult.Difference::field)
+                .contains("agentConfig.samplingRate");
+    }
+
+    @Test
+    void differentContainerMemory_marksContainerField() {
+        DirtyStateCalculator calc = new DirtyStateCalculator();
+        ApplicationConfig cfg = new ApplicationConfig();
+        UUID jarId = UUID.randomUUID();
+        DeploymentConfigSnapshot snap = new DeploymentConfigSnapshot(jarId, cfg, Map.of("memoryLimitMb", 512));
+
+        DirtyStateResult result = calc.compute(jarId, cfg, Map.of("memoryLimitMb", 1024), snap);
+
+        assertThat(result.dirty()).isTrue();
+        assertThat(result.differences()).extracting(DirtyStateResult.Difference::field)
+                .contains("containerConfig.memoryLimitMb");
+    }
+}