diff --git a/e2e/captureSnapshot/session-detail.ts b/e2e/captureSnapshot/session-detail.ts
index 2c1dd14..2ddf8ad 100644
--- a/e2e/captureSnapshot/session-detail.ts
+++ b/e2e/captureSnapshot/session-detail.ts
@@ -86,5 +86,22 @@ export const sessionDetailCapture = defineCapture({
         }
       },
     },
+
+    {
+      name: "sidechain-task-modal",
+      setup: async (page) => {
+        const sidechainTaskButton = page
+          .locator('[data-testid="sidechain-task-button"]')
+          .first();
+        if (await sidechainTaskButton.isVisible()) {
+          await sidechainTaskButton.click();
+          await page.waitForTimeout(1000);
+
+          // モーダルが開いたことを確認
+          const modal = page.locator('[data-testid="sidechain-task-modal"]');
+          await modal.waitFor({ state: "visible", timeout: 3000 });
+        }
+      },
+    },
   ],
 });
diff --git a/src/app/projects/[projectId]/sessions/[sessionId]/components/conversationModal/SidechainConversationModal.tsx b/src/app/projects/[projectId]/sessions/[sessionId]/components/conversationModal/SidechainConversationModal.tsx
index e9bfae6..12b526a 100644
--- a/src/app/projects/[projectId]/sessions/[sessionId]/components/conversationModal/SidechainConversationModal.tsx
+++ b/src/app/projects/[projectId]/sessions/[sessionId]/components/conversationModal/SidechainConversationModal.tsx
@@ -67,6 +67,7 @@ export const SidechainConversationModal: FC<
           variant="outline"
           size="sm"
           className="w-full mb-3 items-center justify-start"
+          data-testid="sidechain-task-button"
         >
           <div className="flex items-center gap-2 overflow-hidden">
             <Eye className="h-4 w-4 flex-shrink-0" />
@@ -76,7 +77,10 @@ export const SidechainConversationModal: FC<
           </div>
         </Button>
       </DialogTrigger>
-      <DialogContent className="w-[95vw] md:w-[90vw] max-h-[80vh] overflow-hidden flex flex-col px-2 md:px-8">
+      <DialogContent
+        className="w-[95vw] md:w-[90vw] max-h-[80vh] overflow-hidden flex flex-col px-2 md:px-8"
+        data-testid="sidechain-task-modal"
+      >
         <DialogHeader>
           <DialogTitle>
             {title.length > 100 ? `${title.slice(0, 100)}...` : title}
diff --git a/src/server/core/git/presentation/GitController.ts b/src/server/core/git/presentation/GitController.ts
index 200830a..4f90a35 100644
--- a/src/server/core/git/presentation/GitController.ts
+++ b/src/server/core/git/presentation/GitController.ts
@@ -1,4 +1,4 @@
-import { Context, Effect, Layer } from "effect";
+import { Context, Effect, Either, Layer } from "effect";
 import type { ControllerResponse } from "../../../lib/effect/toEffectResponse";
 import type { InferEffect } from "../../../lib/effect/types";
 import { ProjectRepository } from "../../project/infrastructure/ProjectRepository";
@@ -23,9 +23,19 @@ const LayerImpl = Effect.gen(function* () {
       }
 
       const projectPath = project.meta.projectPath;
-      const branches = yield* gitService.getBranches(projectPath);
+      const branches = yield* Effect.either(
+        gitService.getBranches(projectPath),
+      );
+
+      if (Either.isLeft(branches)) {
+        return {
+          response: [],
+          status: 200,
+        } as const satisfies ControllerResponse;
+      }
+
       return {
-        response: branches,
+        response: branches.right,
         status: 200,
       } as const satisfies ControllerResponse;
     });
@@ -45,9 +55,17 @@ const LayerImpl = Effect.gen(function* () {
 
       const projectPath = project.meta.projectPath;
 
-      const commits = yield* gitService.getCommits(projectPath);
+      const commits = yield* Effect.either(gitService.getCommits(projectPath));
+
+      if (Either.isLeft(commits)) {
+        return {
+          response: [],
+          status: 200,
+        } as const satisfies ControllerResponse;
+      }
+
       return {
-        response: commits,
+        response: commits.right,
         status: 200,
       } as const satisfies ControllerResponse;
     });