@@ -265,7 +265,8 @@ private AIConfig buildConfig(
       String graphKey) {
     Supplier<LDAIConfigTracker> factory = trackerFactory(
         key, parsed.getVariationKey(), parsed.getVersion(),
-        parsed.getModel(), parsed.getProvider(), context, graphKey);
+        parsed.getModel(), parsed.getProvider(),
+        parsed.getModelKey(), parsed.getModelVersion(), context, graphKey);
     switch (mode) {
       case AGENT:
         return new AIAgentConfig(
@@ -330,7 +331,7 @@ private AIConfig buildConfigFromDefault(
       String graphKey) {
     // Default configs still get real trackers — the configKey was requested even if no flag was found.
     // variationKey is null because no flag evaluation occurred.
-    Supplier<LDAIConfigTracker> factory = trackerFactory(key, null, null, null, null, context, graphKey);
+    Supplier<LDAIConfigTracker> factory = trackerFactory(key, null, null, null, null, null, null, context, graphKey);
     switch (mode) {
       case AGENT: {
         AIAgentConfigDefault agent = (AIAgentConfigDefault) defaultValue;
@@ -386,21 +387,14 @@ private Supplier<LDAIConfigTracker> trackerFactory(
       Integer version,
       com.launchdarkly.sdk.server.ai.datamodel.LDAIConfigTypes.Model model,
       com.launchdarkly.sdk.server.ai.datamodel.LDAIConfigTypes.Provider provider,
-      LDContext context) {
-    return trackerFactory(configKey, variationKey, version, model, provider, context, null);
-  }
-
-  private Supplier<LDAIConfigTracker> trackerFactory(
-      String configKey,
-      String variationKey,
-      Integer version,
-      com.launchdarkly.sdk.server.ai.datamodel.LDAIConfigTypes.Model model,
-      com.launchdarkly.sdk.server.ai.datamodel.LDAIConfigTypes.Provider provider,
+      String modelKey,
+      Integer modelVersion,
       LDContext context,
       String graphKey) {
     String modelName = model != null && model.getName() != null ? model.getName() : "";
     String providerName = provider != null && provider.getName() != null ? provider.getName() : "";
     int ver = version != null ? version : 1;
+    int mVer = modelVersion != null ? modelVersion : 1;
     return () -> new LDAIConfigTrackerImpl(
         client,
         UUID.randomUUID().toString(),
@@ -409,6 +403,8 @@ private Supplier<LDAIConfigTracker> trackerFactory(
         ver,
         modelName,
         providerName,
+        modelKey,
+        mVer,
         context,
         graphKey,
         logger);
 
@@ -217,7 +217,10 @@ public static final class Model {
     private final Map<String, Object> parameters;
     private final Map<String, Object> custom;
 
-    private Model(String name, Map<String, Object> parameters, Map<String, Object> custom) {
+    private Model(
+        String name,
+        Map<String, Object> parameters,
+        Map<String, Object> custom) {
       this.name = name;
       this.parameters = parameters;
       this.custom = custom;
 
@@ -599,6 +599,8 @@ public static final class TrackData {
     private final int version;
     private final String modelName;
     private final String providerName;
+    private final String modelKey;
+    private final int modelVersion;
     private final String graphKey;
 
     /**
@@ -610,6 +612,8 @@ public static final class TrackData {
      * @param version the config version
      * @param modelName the model name, or empty string when unknown
      * @param providerName the provider name, or empty string when unknown
+     * @param modelKey the stable model key, or {@code null} when unknown
+     * @param modelVersion the model version
      * @param graphKey the agent graph key, or {@code null} when not part of a graph
      */
     public TrackData(
@@ -619,13 +623,17 @@ public TrackData(
         int version,
         String modelName,
         String providerName,
+        String modelKey,
+        int modelVersion,
         String graphKey) {
       this.runId = Objects.requireNonNull(runId, "runId");
       this.configKey = Objects.requireNonNull(configKey, "configKey");
       this.variationKey = variationKey;
       this.version = version;
       this.modelName = modelName == null ? "" : modelName;
       this.providerName = providerName == null ? "" : providerName;
+      this.modelKey = modelKey == null || modelKey.trim().isEmpty() ? null : modelKey;
+      this.modelVersion = modelVersion;
       this.graphKey = graphKey;
     }
 
@@ -683,6 +691,24 @@ public String getProviderName() {
       return providerName;
     }
 
+    /**
+     * Returns the stable model key.
+     *
+     * @return the model key, or {@code null} when unknown
+     */
+    public String getModelKey() {
+      return modelKey;
+    }
+
+    /**
+     * Returns the model version.
+     *
+     * @return the model version
+     */
+    public int getModelVersion() {
+      return modelVersion;
+    }
+
     /**
      * Returns the agent graph key.
      *
@@ -695,7 +721,7 @@ public String getGraphKey() {
     /**
      * Builds an {@link LDValue} representation of this track data using camelCase keys.
      * <p>
-     * {@code variationKey} and {@code graphKey} are omitted when {@code null}.
+     * {@code variationKey}, {@code modelKey}, and {@code graphKey} are omitted when {@code null}.
      *
      * @return an {@link LDValue} object containing all non-null fields
      */
@@ -705,10 +731,14 @@ public LDValue toLDValue() {
           .put("configKey", configKey)
           .put("version", version)
           .put("modelName", modelName)
-          .put("providerName", providerName);
+          .put("providerName", providerName)
+          .put("modelVersion", modelVersion);
       if (variationKey != null) {
         b.put("variationKey", variationKey);
       }
+      if (modelKey != null) {
+        b.put("modelKey", modelKey);
+      }
       if (graphKey != null) {
         b.put("graphKey", graphKey);
       }
 
@@ -37,6 +37,8 @@ public final class AIConfigFlagValue {
   private final Map<String, Tool> tools;
   private final JudgeConfiguration judgeConfiguration;
   private final String evaluationMetricKey;
+  private final String modelKey;
+  private final Integer modelVersion;
 
   private AIConfigFlagValue(Builder b) {
     this.enabled = b.enabled;
@@ -50,6 +52,8 @@ private AIConfigFlagValue(Builder b) {
     this.tools = b.tools == null ? null : Collections.unmodifiableMap(b.tools);
     this.judgeConfiguration = b.judgeConfiguration;
     this.evaluationMetricKey = b.evaluationMetricKey;
+    this.modelKey = b.modelKey;
+    this.modelVersion = b.modelVersion;
   }
 
   /**
@@ -97,6 +101,26 @@ public Mode getMode() {
     return mode;
   }
 
+  /**
+   * Returns the {@code _ldMeta.modelKey}. Lives under {@code _ldMeta} rather than {@code model}
+   * itself, to avoid {@code modelVersion} reading as the underlying LLM's own version
+   * (e.g. "GPT-5.4").
+   *
+   * @return the model key, or {@code null} if absent
+   */
+  public String getModelKey() {
+    return modelKey;
+  }
+
+  /**
+   * Returns the {@code _ldMeta.modelVersion}.
+   *
+   * @return the model version, or {@code null} if absent
+   */
+  public Integer getModelVersion() {
+    return modelVersion;
+  }
+
   /**
    * Returns the model configuration.
    *
@@ -184,6 +208,8 @@ public static final class Builder {
     private Map<String, Tool> tools;
     private JudgeConfiguration judgeConfiguration;
     private String evaluationMetricKey;
+    private String modelKey;
+    private Integer modelVersion;
 
     private Builder() {
     }
@@ -221,6 +247,28 @@ public Builder version(Integer v) {
       return this;
     }
 
+    /**
+     * Sets the model key, parsed from {@code _ldMeta.modelKey}.
+     *
+     * @param v the model key
+     * @return this builder
+     */
+    public Builder modelKey(String v) {
+      this.modelKey = v;
+      return this;
+    }
+
+    /**
+     * Sets the model version, parsed from {@code _ldMeta.modelVersion}.
+     *
+     * @param v the model version
+     * @return this builder
+     */
+    public Builder modelVersion(Integer v) {
+      this.modelVersion = v;
+      return this;
+    }
+
     /**
      * Sets the mode.
      *
 
@@ -42,7 +42,8 @@ public static AIConfigFlagValue parse(LDValue value) {
       return builder.build();
     }
 
-    parseMeta(value.get("_ldMeta"), builder);
+    LDValue meta = value.get("_ldMeta");
+    parseMeta(meta, builder);
     builder.model(parseModel(value.get("model")));
     builder.provider(parseProvider(value.get("provider")));
     builder.messages(parseMessages(value.get("messages")));
@@ -54,8 +55,13 @@ public static AIConfigFlagValue parse(LDValue value) {
     return builder.build();
   }
 
+  // modelKey/modelVersion are parsed here alongside the rest of _ldMeta (enabled, variationKey,
+  // version, mode) rather than inside parseModel, so they're stored the same way as every other
+  // _ldMeta field instead of a one-off path. They also live under _ldMeta rather than model
+  // itself, to avoid modelVersion reading as the underlying LLM's own version (e.g. "GPT-5.4").
   private static void parseMeta(LDValue meta, AIConfigFlagValue.Builder builder) {
     if (meta == null || meta.getType() != LDValueType.OBJECT) {
+      builder.modelVersion(1);
       return;
     }
     LDValue enabled = meta.get("enabled");
@@ -68,6 +74,10 @@ private static void parseMeta(LDValue meta, AIConfigFlagValue.Builder builder) {
       builder.version(version.intValue());
     }
     builder.mode(Mode.fromWireValue(asStringOrNull(meta.get("mode"))));
+
+    LDValue modelVersion = meta.get("modelVersion");
+    builder.modelVersion(modelVersion.getType() == LDValueType.NUMBER ? modelVersion.intValue() : 1);
+    builder.modelKey(trimToNull(asStringOrNull(meta.get("modelKey"))));
   }
 
   /**
 
@@ -58,6 +58,8 @@ public final class LDAIConfigTrackerImpl implements LDAIConfigTracker {
   private final int version;
   private final String modelName;   // empty string when unknown
   private final String providerName; // empty string when unknown
+  private final String modelKey;    // nullable
+  private final int modelVersion;
   private final String graphKey;    // nullable
 
   // Computed once at construction
@@ -86,6 +88,8 @@ public final class LDAIConfigTrackerImpl implements LDAIConfigTracker {
    * @param version the config version
    * @param modelName the model name, or empty string when unknown
    * @param providerName the provider name, or empty string when unknown
+   * @param modelKey the stable model key, or {@code null} when unknown
+   * @param modelVersion the model version
    * @param context the evaluation context; must not be {@code null}
    * @param graphKey the agent graph key, or {@code null} when not part of a graph
    * @param logger the logger; must not be {@code null}
@@ -98,6 +102,8 @@ public LDAIConfigTrackerImpl(
       int version,
       String modelName,
       String providerName,
+      String modelKey,
+      int modelVersion,
       LDContext context,
       String graphKey,
       LDLogger logger) {
@@ -108,6 +114,8 @@ public LDAIConfigTrackerImpl(
     this.version = version;
     this.modelName = modelName == null ? "" : modelName;
     this.providerName = providerName == null ? "" : providerName;
+    this.modelKey = modelKey == null || modelKey.trim().isEmpty() ? null : modelKey;
+    this.modelVersion = modelVersion;
     this.context = Objects.requireNonNull(context, "context");
     this.graphKey = graphKey;
     this.logger = Objects.requireNonNull(logger, "logger");
@@ -137,14 +145,25 @@ public static LDAIConfigTrackerImpl fromResumptionToken(
         d.getVersion(),
         "", // modelName not carried in token
         "", // providerName not carried in token
+        null, // modelKey not carried in token
+        1, // modelVersion not carried in token
         context,
         d.getGraphKey(),
         logger);
   }
 
   @Override
   public TrackData getTrackData() {
-    return new TrackData(runId, configKey, variationKey, version, modelName, providerName, graphKey);
+    return new TrackData(
+        runId,
+        configKey,
+        variationKey,
+        version,
+        modelName,
+        providerName,
+        modelKey,
+        modelVersion,
+        graphKey);
   }
 
   @Override
@@ -377,10 +396,14 @@ private ObjectBuilder baseData() {
         .put("configKey", configKey)
         .put("version", version)
         .put("modelName", modelName)
-        .put("providerName", providerName);
+        .put("providerName", providerName)
+        .put("modelVersion", modelVersion);
     if (variationKey != null) {
       b.put("variationKey", variationKey);
     }
+    if (modelKey != null) {
+      b.put("modelKey", modelKey);
+    }
     if (graphKey != null) {
       b.put("graphKey", graphKey);
     }
 
@@ -134,6 +134,33 @@ public void completionConfigReturnsTypedConfigFromVariation() {
     assertThat(config.getMessages().get(0).getRole(), is(Message.Role.SYSTEM));
   }
 
+  @Test
+  public void completionConfigPropagatesModelMetadataToTracker() {
+    String json = "{\"_ldMeta\":{\"enabled\":true,\"mode\":\"completion\","
+        + "\"modelKey\":\"custom-gpt\",\"modelVersion\":7},"
+        + "\"model\":{\"name\":\"gpt-4\"}}";
+    when(client.jsonValueVariation(anyString(), any(), any())).thenReturn(LDValue.parse(json));
+
+    AICompletionConfig config = ai.completionConfig("key", context, null, null);
+
+    // modelKey/modelVersion are intentionally not exposed on Model; they surface only via the
+    // tracker's stamped event data, mirroring variationKey/version.
+    assertThat(config.createTracker().getTrackData().getModelKey(), is("custom-gpt"));
+    assertThat(config.createTracker().getTrackData().getModelVersion(), is(7));
+  }
+
+  @Test
+  public void completionConfigDefaultsMissingModelMetadata() {
+    String json = "{\"_ldMeta\":{\"enabled\":true,\"mode\":\"completion\"},"
+        + "\"model\":{\"name\":\"gpt-4\"}}";
+    when(client.jsonValueVariation(anyString(), any(), any())).thenReturn(LDValue.parse(json));
+
+    AICompletionConfig config = ai.completionConfig("key", context, null, null);
+
+    assertThat(config.createTracker().getTrackData().getModelKey(), is(nullValue()));
+    assertThat(config.createTracker().getTrackData().getModelVersion(), is(1));
+  }
+
   @Test
   public void interpolationExposesContextAsLdctx() {
     String json = "{\"_ldMeta\":{\"enabled\":true,\"mode\":\"completion\"},"