diff --git a/apps/edge/internal/openai/provider_model_rewrite.go b/apps/edge/internal/openai/provider_model_rewrite.go
index 5b2d4f1a..1a93236c 100644
--- a/apps/edge/internal/openai/provider_model_rewrite.go
+++ b/apps/edge/internal/openai/provider_model_rewrite.go
@@ -215,7 +215,9 @@ func prepareHotPathSelectorCanonicalTools(tunnel edgeservice.SubmitProviderTunne
 					},
 				},
 			}}
-			root["tool_choice"] = "required"
+			root["tool_choice"] = map[string]any{
+				"type": "function", "function": map[string]any{"name": hotPathArtifactPairToolName},
+			}
 			delete(root, "parallel_tool_calls")
 			return json.Marshal(root)
 		}
diff --git a/apps/edge/internal/openai/provider_model_rewrite_test.go b/apps/edge/internal/openai/provider_model_rewrite_test.go
index 77d44704..396cc68b 100644
--- a/apps/edge/internal/openai/provider_model_rewrite_test.go
+++ b/apps/edge/internal/openai/provider_model_rewrite_test.go
@@ -394,7 +394,9 @@ func TestHotPathSelectorCanonicalWriteToolReplacesCallerCommandSchema(t *testing
 	if function["name"] != hotPathArtifactPairToolName || properties["plan_content"] == nil || properties["review_content"] == nil || properties["command"] != nil {
 		t.Fatalf("canonical write function=%+v", function)
 	}
-	if request["tool_choice"] != "required" || request["parallel_tool_calls"] != nil {
+	choice := request["tool_choice"].(map[string]any)
+	chosenFunction := choice["function"].(map[string]any)
+	if choice["type"] != "function" || chosenFunction["name"] != hotPathArtifactPairToolName || request["parallel_tool_calls"] != nil {
 		t.Fatalf("pair-write must force one atomic tool call: %+v", request)
 	}
 }
@@ -447,7 +449,8 @@ func TestAnthropicCallerWorkspaceSelectorUsesCanonicalProviderOperation(t *testi
 					t.Fatalf("OpenAI selector tunnel=%+v", prepared)
 				}
 				tool := tools[0].(map[string]any)
-				if tool["name"] != hotPathArtifactPairToolName || request["tool_choice"] != "required" || request["max_output_tokens"] != float64(maxHotPathSelectorOutputTokens) {
+				choice := request["tool_choice"].(map[string]any)
+				if tool["name"] != hotPathArtifactPairToolName || choice["type"] != "function" || choice["name"] != hotPathArtifactPairToolName || request["max_output_tokens"] != float64(maxHotPathSelectorOutputTokens) {
 					t.Fatalf("OpenAI selector request=%+v", request)
 				}
 				if !strings.Contains(request["instructions"].(string), "Operation: pair-write") {
@@ -459,7 +462,9 @@ func TestAnthropicCallerWorkspaceSelectorUsesCanonicalProviderOperation(t *testi
 				t.Fatalf("Gemini selector tunnel=%+v", prepared)
 			}
 			function := tools[0].(map[string]any)["function"].(map[string]any)
-			if function["name"] != hotPathArtifactPairToolName || request["tool_choice"] != "required" || request["max_tokens"] != float64(maxHotPathSelectorOutputTokens) {
+			choice := request["tool_choice"].(map[string]any)
+			chosenFunction := choice["function"].(map[string]any)
+			if function["name"] != hotPathArtifactPairToolName || choice["type"] != "function" || chosenFunction["name"] != hotPathArtifactPairToolName || request["max_tokens"] != float64(maxHotPathSelectorOutputTokens) {
 				t.Fatalf("Gemini selector request=%+v", request)
 			}
 			messages := anySlice(request["messages"])