diff --git a/internal/server/task_run_json_test.go b/internal/server/task_run_json_test.go
new file mode 100644
index 00000000..db368eca
--- /dev/null
+++ b/internal/server/task_run_json_test.go
@@ -0,0 +1,109 @@
+package server
+
+import (
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"chat-agent-system/internal/bizdev"
+	"chat-agent-system/internal/config"
+	"chat-agent-system/internal/taskrun"
+)
+
+func TestTaskRunResponseMarshalUsesSnakeCase(t *testing.T) {
+	raw, err := json.Marshal(taskRunResponse{
+		RunRecord: taskrun.RunRecord{
+			RunID:        "run_snake",
+			Status:       "failed",
+			ErrorMessage: "dial tcp connection refused",
+			TaskKey:      "user_requirements",
+			WorkspaceID:  "ws_1",
+		},
+		Resumable: false,
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	var body map[string]any
+	if err := json.Unmarshal(raw, &body); err != nil {
+		t.Fatal(err)
+	}
+	for _, key := range []string{"run_id", "status", "error_message", "workspace_id", "task_key", "resumable"} {
+		if _, ok := body[key]; !ok {
+			t.Fatalf("missing %q in %s", key, raw)
+		}
+	}
+	for _, pascal := range []string{"Status", "ErrorMessage", "RunID", "WorkspaceID"} {
+		if _, ok := body[pascal]; ok {
+			t.Fatalf("pascal key %q leaked into %s", pascal, raw)
+		}
+	}
+	if body["status"] != "failed" || body["error_message"] != "dial tcp connection refused" {
+		t.Fatalf("payload=%s", raw)
+	}
+}
+
+func TestGetTaskRunJSONUsesSnakeCase(t *testing.T) {
+	srv := newTestServer(t)
+	ts := httptest.NewServer(srv.Routes())
+	t.Cleanup(ts.Close)
+
+	runID := "run_snake_http"
+	rec := &taskrun.RunRecord{
+		RunID:        runID,
+		SessionID:    "sess-snake",
+		Status:       "failed",
+		ErrorMessage: "dial tcp connection refused",
+		TaskKey:      "intake",
+		UserID:       1,
+	}
+	if _, err := srv.taskRuns.CreateAndStart(
+		t.Context(),
+		runID,
+		rec,
+		bizdev.TaskRunRequest{TaskKey: "intake", ProjectName: "snake-json"},
+		bizdev.StageRunRequest{},
+		"",
+	); err != nil {
+		t.Fatalf("CreateAndStart: %v", err)
+	}
+
+	token := testBearerToken(t, ts.URL, &config.Config{
+		AdminUsername: "admin",
+		AdminPassword: "admin-test-pass",
+	})
+	req, err := http.NewRequest(http.MethodGet, ts.URL+"/api/v1/tasks/runs/"+runID, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	req.Header.Set("Authorization", "Bearer "+token)
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer resp.Body.Close()
+	payload, _ := io.ReadAll(resp.Body)
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("GET status=%d body=%s", resp.StatusCode, payload)
+	}
+	var body map[string]any
+	if err := json.Unmarshal(payload, &body); err != nil {
+		t.Fatalf("decode: %v body=%s", err, payload)
+	}
+	status, _ := body["status"].(string)
+	if status == "" {
+		t.Fatalf("status key missing or empty (pascal leak?): %s", payload)
+	}
+	if _, ok := body["Status"]; ok || strings.Contains(string(payload), `"ErrorMessage"`) {
+		t.Fatalf("pascal keys in GET body: %s", payload)
+	}
+	if _, ok := body["error_message"]; !ok {
+		t.Fatalf("missing error_message: %s", payload)
+	}
+	if _, ok := body["run_id"]; !ok {
+		t.Fatalf("missing run_id: %s", payload)
+	}
+}