diff --git a/internal/api/server_routes.go b/internal/api/server_routes.go
index d57af9c70..6102b83b4 100644
--- a/internal/api/server_routes.go
+++ b/internal/api/server_routes.go
@@ -675,6 +675,9 @@ func (s *Server) handleHomeCodexClientModels(c *gin.Context) {
 			model["display_name"] = entry.displayName
 			model["description"] = entry.displayName
 		}
+		if entry.maxCompletionTokens > 0 {
+			model["max_completion_tokens"] = entry.maxCompletionTokens
+		}
 		models = append(models, model)
 	}
 
diff --git a/internal/api/server_test.go b/internal/api/server_test.go
index 21f78281c..30df27914 100644
--- a/internal/api/server_test.go
+++ b/internal/api/server_test.go
@@ -1832,15 +1832,16 @@ func TestModelsWithClientVersionReturnsCodexCatalog(t *testing.T) {
 	clientID := "test-client-version-catalog"
 	modelRegistry.RegisterClient(clientID, "openai", []*registry.ModelInfo{
 		{
-			ID:            "gpt-5.5",
-			Object:        "model",
-			Created:       1776902400,
-			OwnedBy:       "openai",
-			Type:          "openai",
-			DisplayName:   "GPT 5.5",
-			Description:   "Frontier model for complex coding, research, and real-world work.",
-			ContextLength: 272000,
-			Thinking:      &registry.ThinkingSupport{Levels: []string{"low", "medium", "high", "xhigh"}},
+			ID:                  "gpt-5.5",
+			Object:              "model",
+			Created:             1776902400,
+			OwnedBy:             "openai",
+			Type:                "openai",
+			DisplayName:         "GPT 5.5",
+			Description:         "Frontier model for complex coding, research, and real-world work.",
+			ContextLength:       272000,
+			MaxCompletionTokens: 64000,
+			Thinking:            &registry.ThinkingSupport{Levels: []string{"low", "medium", "high", "xhigh"}},
 		},
 		{
 			ID:            "custom-codex-model-test",
@@ -1908,6 +1909,9 @@ func TestModelsWithClientVersionReturnsCodexCatalog(t *testing.T) {
 	if _, ok := gpt55["minimal_client_version"]; !ok {
 		t.Fatal("expected minimal_client_version in codex catalog")
 	}
+	if got, _ := gpt55["max_tokens"].(float64); got != 64000 {
+		t.Fatalf("gpt-5.5 max_tokens = %v, want 64000", gpt55["max_tokens"])
+	}
 	serviceTiers, ok := gpt55["service_tiers"].([]any)
 	if !ok || len(serviceTiers) != 1 {
 		t.Fatalf("expected gpt-5.5 priority service tier, got %#v", gpt55["service_tiers"])
diff --git a/internal/client/codex/models/models.go b/internal/client/codex/models/models.go
index 3dd684f57..1c9e5794c 100644
--- a/internal/client/codex/models/models.go
+++ b/internal/client/codex/models/models.go
@@ -61,6 +61,7 @@ func buildCodexClientModels(models []map[string]any, providersForModel Providers
 			entry := cloneCodexClientModelMap(template)
 			applyCodexClientDisplayName(entry, model)
 			applyCodexClientMaxContextLengthOverride(entry, model)
+			applyCodexClientMaxTokens(entry, model)
 			applyCodexClientSearchToolSupport(entry, id, true, providersForModel)
 			sanitizeCodexClientReasoningMetadata(entry)
 			applyCodexClientVisibilityOverride(entry, id)
@@ -73,6 +74,7 @@ func buildCodexClientModels(models []map[string]any, providersForModel Providers
 
 		entry := cloneCodexClientModelMap(defaultTemplate)
 		applyCodexClientModelMetadata(entry, id, model, optimizeMultiAgentV2)
+		applyCodexClientMaxTokens(entry, model)
 		applyCodexClientSearchToolSupport(entry, id, false, providersForModel)
 		sanitizeCodexClientReasoningMetadata(entry)
 		applyCodexClientVisibilityOverride(entry, id)
@@ -193,6 +195,12 @@ func applyCodexClientMaxContextLengthOverride(entry map[string]any, model map[st
 	}
 }
 
+func applyCodexClientMaxTokens(entry map[string]any, model map[string]any) {
+	if maxCompletionTokens := intModelValue(model, "max_completion_tokens"); maxCompletionTokens > 0 {
+		entry["max_tokens"] = maxCompletionTokens
+	}
+}
+
 func applyCodexClientSearchToolSupport(entry map[string]any, id string, templateModel bool, providersForModel ProvidersForModelFunc) {
 	supportsSearch, _ := entry["supports_search_tool"].(bool)
 	if !supportsSearch {
diff --git a/internal/client/codex/models/models_test.go b/internal/client/codex/models/models_test.go
index f009ca7cf..6500a8f7a 100644
--- a/internal/client/codex/models/models_test.go
+++ b/internal/client/codex/models/models_test.go
@@ -363,3 +363,38 @@ func TestCodexClientModelsResponseAppliesMaxContextLengthOverride(t *testing.T)
 		}
 	}
 }
+
+func TestCodexClientModelsResponseMapsMaxCompletionTokensToMaxTokens(t *testing.T) {
+	const wantTemplateLimit = 64000
+	const wantSynthesizedLimit = 32000
+
+	resp := BuildResponse([]map[string]any{
+		{"id": "gpt-5.5", "max_completion_tokens": wantTemplateLimit},
+		{"id": "custom-output-limit-model", "max_completion_tokens": wantSynthesizedLimit},
+	}, nil, false)
+	models, ok := resp["models"].([]map[string]any)
+	if !ok {
+		t.Fatalf("models type = %T, want []map[string]any", resp["models"])
+	}
+
+	bySlug := make(map[string]map[string]any, len(models))
+	for _, model := range models {
+		bySlug[stringModelValue(model, "slug")] = model
+	}
+
+	for _, testCase := range []struct {
+		slug string
+		want int
+	}{
+		{slug: "gpt-5.5", want: wantTemplateLimit},
+		{slug: "custom-output-limit-model", want: wantSynthesizedLimit},
+	} {
+		entry := bySlug[testCase.slug]
+		if entry == nil {
+			t.Fatalf("missing model %q", testCase.slug)
+		}
+		if got := intModelValue(entry, "max_tokens"); got != testCase.want {
+			t.Errorf("%s max_tokens = %d, want %d", testCase.slug, got, testCase.want)
+		}
+	}
+}