diff --git a/mateclaw-server/src/main/java/vip/mate/llm/model/ModelInfoDTO.java b/mateclaw-server/src/main/java/vip/mate/llm/model/ModelInfoDTO.java
index 0c421ce8..e840068c 100644
--- a/mateclaw-server/src/main/java/vip/mate/llm/model/ModelInfoDTO.java
+++ b/mateclaw-server/src/main/java/vip/mate/llm/model/ModelInfoDTO.java
@@ -22,8 +22,22 @@ public class ModelInfoDTO {
     /** Reason text when probeOk=false (short, suitable for UI badge tooltip) */
     private String probeError;
 
+    /**
+     * RFC-049 PR-1-UI: whether this model's {@code ModelFamily} accepts the
+     * {@code reasoning_effort} parameter. Derived from the model name on the
+     * server side so the frontend can gray out the "thinking depth" selector
+     * for chat-type models that don't support thinking — a product contract,
+     * not a runtime toggle.
+     *
+     * <p>{@code true} only for the OpenAI reasoning family (gpt-5*, o1*, o3*, o4*).
+     */
+    private boolean supportsReasoningEffort;
+
     public ModelInfoDTO(String id, String name) {
         this.id = id;
         this.name = name;
+        // RFC-049 PR-1-UI: derived from id (the model name) so every construction
+        // site populates the capability consistently.
+        this.supportsReasoningEffort = ModelFamily.detect(id).supportsReasoningEffort();
     }
 }
diff --git a/mateclaw-server/src/main/java/vip/mate/llm/service/ModelProviderService.java b/mateclaw-server/src/main/java/vip/mate/llm/service/ModelProviderService.java
index 96c21718..8b148ad2 100644
--- a/mateclaw-server/src/main/java/vip/mate/llm/service/ModelProviderService.java
+++ b/mateclaw-server/src/main/java/vip/mate/llm/service/ModelProviderService.java
@@ -249,6 +249,8 @@ public class ModelProviderService {
         List<ModelInfoDTO> extraModels = new ArrayList<>();
         if (models != null) {
             for (ModelConfigEntity model : models) {
+                // RFC-049 PR-1-UI: ModelInfoDTO(id, name) derives supportsReasoningEffort
+                // from id via ModelFamily — no extra wiring needed here.
                 ModelInfoDTO info = new ModelInfoDTO(model.getModelName(), model.getName());
                 if (Boolean.TRUE.equals(model.getBuiltin())) {
                     builtinModels.add(info);