diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 816633c..379afba 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -58,4 +58,4 @@ jobs:
         run: npm run build
 
       - name: Run backend tests
-        run: npm run test:backend || echo "Backend tests not yet configured"
+        run: npm run test:backend
diff --git a/.gitignore b/.gitignore
index 6d22b85..3ba83de 100644
--- a/.gitignore
+++ b/.gitignore
@@ -15,3 +15,6 @@ coverage/
 # Deployment
 deploy/
 deploy.tar.gz
+
+# Serena (AIエージェント用ローカル設定。各自の環境に閉じるため追跡しない)
+.serena/
diff --git a/.serena/.gitignore b/.serena/.gitignore
deleted file mode 100644
index 14d86ad..0000000
--- a/.serena/.gitignore
+++ /dev/null
@@ -1 +0,0 @@
-/cache
diff --git a/.serena/project.yml b/.serena/project.yml
deleted file mode 100644
index a4b2187..0000000
--- a/.serena/project.yml
+++ /dev/null
@@ -1,68 +0,0 @@
-# language of the project (csharp, python, rust, java, typescript, go, cpp, or ruby)
-#  * For C, use cpp
-#  * For JavaScript, use typescript
-# Special requirements:
-#  * csharp: Requires the presence of a .sln file in the project folder.
-language: typescript
-
-# whether to use the project's gitignore file to ignore files
-# Added on 2025-04-07
-ignore_all_files_in_gitignore: true
-# list of additional paths to ignore
-# same syntax as gitignore, so you can use * and **
-# Was previously called `ignored_dirs`, please update your config if you are using that.
-# Added (renamed) on 2025-04-07
-ignored_paths: []
-
-# whether the project is in read-only mode
-# If set to true, all editing tools will be disabled and attempts to use them will result in an error
-# Added on 2025-04-18
-read_only: false
-
-
-# list of tool names to exclude. We recommend not excluding any tools, see the readme for more details.
-# Below is the complete list of tools for convenience.
-# To make sure you have the latest list of tools, and to view their descriptions, 
-# execute `uv run scripts/print_tool_overview.py`.
-#
-#  * `activate_project`: Activates a project by name.
-#  * `check_onboarding_performed`: Checks whether project onboarding was already performed.
-#  * `create_text_file`: Creates/overwrites a file in the project directory.
-#  * `delete_lines`: Deletes a range of lines within a file.
-#  * `delete_memory`: Deletes a memory from Serena's project-specific memory store.
-#  * `execute_shell_command`: Executes a shell command.
-#  * `find_referencing_code_snippets`: Finds code snippets in which the symbol at the given location is referenced.
-#  * `find_referencing_symbols`: Finds symbols that reference the symbol at the given location (optionally filtered by type).
-#  * `find_symbol`: Performs a global (or local) search for symbols with/containing a given name/substring (optionally filtered by type).
-#  * `get_current_config`: Prints the current configuration of the agent, including the active and available projects, tools, contexts, and modes.
-#  * `get_symbols_overview`: Gets an overview of the top-level symbols defined in a given file.
-#  * `initial_instructions`: Gets the initial instructions for the current project.
-#     Should only be used in settings where the system prompt cannot be set,
-#     e.g. in clients you have no control over, like Claude Desktop.
-#  * `insert_after_symbol`: Inserts content after the end of the definition of a given symbol.
-#  * `insert_at_line`: Inserts content at a given line in a file.
-#  * `insert_before_symbol`: Inserts content before the beginning of the definition of a given symbol.
-#  * `list_dir`: Lists files and directories in the given directory (optionally with recursion).
-#  * `list_memories`: Lists memories in Serena's project-specific memory store.
-#  * `onboarding`: Performs onboarding (identifying the project structure and essential tasks, e.g. for testing or building).
-#  * `prepare_for_new_conversation`: Provides instructions for preparing for a new conversation (in order to continue with the necessary context).
-#  * `read_file`: Reads a file within the project directory.
-#  * `read_memory`: Reads the memory with the given name from Serena's project-specific memory store.
-#  * `remove_project`: Removes a project from the Serena configuration.
-#  * `replace_lines`: Replaces a range of lines within a file with new content.
-#  * `replace_symbol_body`: Replaces the full definition of a symbol.
-#  * `restart_language_server`: Restarts the language server, may be necessary when edits not through Serena happen.
-#  * `search_for_pattern`: Performs a search for a pattern in the project.
-#  * `summarize_changes`: Provides instructions for summarizing the changes made to the codebase.
-#  * `switch_modes`: Activates modes by providing a list of their names
-#  * `think_about_collected_information`: Thinking tool for pondering the completeness of collected information.
-#  * `think_about_task_adherence`: Thinking tool for determining whether the agent is still on track with the current task.
-#  * `think_about_whether_you_are_done`: Thinking tool for determining whether the task is truly completed.
-#  * `write_memory`: Writes a named memory (for future reference) to Serena's project-specific memory store.
-excluded_tools: []
-
-# initial prompt for the project. It will always be given to the LLM upon activating the project
-# (contrary to the memories, which are loaded on demand).
-initial_prompt: ""
-
-project_name: "shift"
diff --git a/codecov.yml b/codecov.yml
index 6ab4360..670b533 100644
--- a/codecov.yml
+++ b/codecov.yml
@@ -1,6 +1,8 @@
 codecov:
   require_ci_to_pass: yes
 
+# 暫定設定: 表示レンジ・閾値は現状に合わせた値。実測ベースへの調整は
+# docs/refactoring/phase-5-e2e-ci.md で対応する。
 coverage:
   precision: 2
   round: down
diff --git a/jest.config.ts b/jest.config.ts
index c0c8728..5309b67 100644
--- a/jest.config.ts
+++ b/jest.config.ts
@@ -42,7 +42,8 @@ const config: Config = {
     '/js/modules/'
   ],
   coverageThreshold: {
-    // Global thresholds (very low since frontend tests don't have coverage yet)
+    // 暫定値: フロントエンドはまだカバレッジ計測対象外のため非常に低く設定している。
+    // 実測ベースへの引き上げは docs/refactoring/phase-5-e2e-ci.md で対応する。
     global: {
       statements: 3,
       branches: 1,
diff --git a/playwright.config.ts b/playwright.config.ts
index 0da95d6..6a29235 100644
--- a/playwright.config.ts
+++ b/playwright.config.ts
@@ -8,7 +8,7 @@ export default defineConfig({
   workers: process.env.CI ? 1 : undefined,
   reporter: 'html',
   use: {
-    baseURL: 'http://localhost:8080',
+    baseURL: 'http://localhost:3000',
     trace: 'on-first-retry',
     screenshot: 'only-on-failure',
   },
@@ -22,7 +22,7 @@ export default defineConfig({
 
   webServer: {
     command: 'npm run dev',
-    url: 'http://localhost:8080',
+    url: 'http://localhost:3000',
     reuseExistingServer: !process.env.CI,
     timeout: 120000,
   },