diff --git a/.miyabi/README.md b/.miyabi/README.md
index 9e26f91..2c4d215 100644
--- a/.miyabi/README.md
+++ b/.miyabi/README.md
@@ -1,57 +1,316 @@
 # .miyabi Directory
 
-Miyabi CLI設定ディレクトリ
+Miyabi CLI設定・拡張ディレクトリ
 
-## 構造
+## ディレクトリ構造
 
 ```
 .miyabi/
+├── config.toml         # メイン設定ファイル
+├── README.md           # このファイル
 ├── agents/
 │   └── specs/          # Agent仕様定義
-├── commands/           # カスタムコマンド
+├── commands/           # カスタムスラッシュコマンド
 ├── prompts/            # 再利用可能プロンプト
-├── templates/          # テンプレート
-├── sessions/           # 保存されたセッション
-└── config.toml         # 設定ファイル
+├── templates/          # コード・ドキュメントテンプレート
+├── sessions/           # 保存されたセッションデータ
+└── tasks/              # タスク管理データ
 ```
 
-## 設定ファイル
+## 設定ファイル (config.toml)
 
-`config.toml` で設定をカスタマイズ:
+### API設定
 
 ```toml
 [api]
-model = "claude-sonnet-4-20250514"
+# API Key (環境変数 ANTHROPIC_API_KEY でも設定可能)
+api_key = "sk-ant-..."
+
+# 使用モデル
+model = "claude-sonnet-4-5-20250929"
+
+# 最大トークン数
 max_tokens = 8192
 
+# タイムアウト (秒)
+timeout_secs = 120
+
+# リトライ回数
+max_retries = 3
+
+# 拡張思考モード
+thinking = false
+
+# システムプロンプト
+system_prompt = "You are a helpful assistant"
+```
+
+### UI設定
+
+```toml
 [ui]
+# テーマ: tokyo-night, dracula, monokai, etc.
 theme = "tokyo-night"
+
+# Vimキーバインド
 vim_mode = false
 
+# サイドバー表示
+show_sidebar = false
+
+# ステータスバー表示
+show_status_bar = true
+
+# パンくずリスト表示
+show_breadcrumb = true
+
+# コードの行番号表示
+show_line_numbers = true
+```
+
+### セッション設定
+
+```toml
 [session]
+# 自動保存
 auto_save = true
 
+# 保存間隔 (秒)
+auto_save_interval = 30
+
+# 最大セッション数
+max_sessions = 100
+```
+
+### ツール設定
+
+```toml
 [tools]
+# Bashツール有効化
 enable_bash = true
+
+# ファイル操作ツール有効化
+enable_file_tools = true
+
+# 検索ツール有効化
+enable_search_tools = true
+
+# 低リスク操作の自動承認
+auto_approve_low_risk = false
+
+# Bashタイムアウト (秒)
+bash_timeout = 120
 ```
 
 ## カスタムコマンド
 
-`commands/` 配下に `*.md` ファイルを作成してカスタムコマンドを定義。
+`commands/` 配下に `.md` ファイルを作成してスラッシュコマンドを定義。
+
+### 例: /review コマンド
+
+`commands/review.md`:
+```markdown
+# コードレビュー
+
+以下のコードをレビューしてください:
+
+1. バグの可能性
+2. パフォーマンス問題
+3. セキュリティ脆弱性
+4. コーディング規約違反
+
+改善提案も含めてください。
+```
+
+使用: TUIで `/review` と入力
+
+## プロンプトテンプレート
+
+`prompts/` 配下に再利用可能なプロンプトを保存。
+
+### 例: Rustコードレビュー
+
+`prompts/rust-review.md`:
+```markdown
+# Rustコードレビューチェックリスト
+
+- [ ] unwrap/expect の使用箇所
+- [ ] エラーハンドリング
+- [ ] 所有権とライフタイム
+- [ ] unsafe コードの妥当性
+- [ ] Clippy警告の確認
+```
+
+## Agent仕様
+
+`agents/specs/` にカスタムAgent仕様を定義。
+
+### 例: コードリファクタリングAgent
+
+`agents/specs/refactor-agent.yaml`:
+```yaml
+name: refactor-agent
+version: "1.0"
+description: コードリファクタリング専門Agent
+
+capabilities:
+  - code_analysis
+  - refactoring
+  - testing
+
+preferences:
+  style: functional
+  error_handling: result
+  max_iterations: 10
+```
 
 ## セッション管理
 
+### コマンドライン操作
+
 ```bash
 # セッション一覧
 miyabi sessions
 
+# 特定セッションで再開
+miyabi --session <session-id>
+
 # Markdownエクスポート
 miyabi sessions -m <session-id>
 
-# 削除
+# JSONエクスポート
+miyabi sessions -e <session-id>
+
+# セッション削除
 miyabi sessions -d <session-id>
 ```
 
+### セッションファイル形式
+
+セッションは `sessions/` に JSON 形式で保存:
+
+```json
+{
+  "id": "uuid",
+  "created_at": "2025-01-01T00:00:00Z",
+  "updated_at": "2025-01-01T01:00:00Z",
+  "model": "claude-sonnet-4-5-20250929",
+  "messages": [...]
+}
+```
+
+## プロジェクトルール (.miyabirules)
+
+プロジェクトルートに `.miyabirules` ファイルを配置して、プロジェクト固有のルールを定義:
+
+```yaml
+version: 1
+
+rules:
+  - name: "no-unwrap"
+    pattern: ".unwrap()"
+    suggestion: "Use ? operator or proper error handling"
+    file_extensions: ["rs"]
+    severity: "warning"
+    enabled: true
+
+  - name: "no-println-debug"
+    pattern: "println!"
+    suggestion: "Use tracing macros for logging"
+    file_extensions: ["rs"]
+    severity: "info"
+
+agent_preferences:
+  codegen:
+    style: "functional"
+    error_handling: "result"
+    min_score: 80
+    clippy_strict: true
+
+settings:
+  auto_format: true
+  max_file_size: 1048576
+```
+
+## 環境変数
+
+設定ファイルの値は環境変数でオーバーライド可能:
+
+```bash
+# 必須
+export ANTHROPIC_API_KEY="sk-ant-..."
+
+# オプション
+export MIYABI_MODEL="claude-sonnet-4-5-20250929"
+export MIYABI_MAX_TOKENS="16384"
+export MIYABI_THINKING="true"
+export MIYABI_THEME="dracula"
+```
+
+## Core Library機能の利用
+
+### キャッシュ
+
+LLMレスポンスのキャッシュで高速化:
+
+```rust
+use miyabi_core::{create_llm_cache, LLMCacheKey};
+
+let cache = create_llm_cache(); // 1時間TTL
+```
+
+### フィーチャーフラグ
+
+機能の段階的ロールアウト:
+
+```rust
+use miyabi_core::FeatureFlagManager;
+
+let flags = FeatureFlagManager::new();
+flags.set_flag("new_ui", true);
+```
+
+### Circuit Breaker
+
+API障害時の保護:
+
+```rust
+use miyabi_core::CircuitBreaker;
+
+let breaker = CircuitBreaker::default();
+// 5回失敗で開く、60秒後に半開
+```
+
+### プラグイン
+
+カスタム機能の追加:
+
+```rust
+use miyabi_core::{Plugin, PluginManager};
+
+let manager = PluginManager::new();
+manager.register(Box::new(MyPlugin))?;
+```
+
+## トラブルシューティング
+
+### API接続エラー
+
+1. API Keyの確認: `echo $ANTHROPIC_API_KEY`
+2. ネットワーク接続確認
+3. タイムアウト値の増加
+
+### セッション破損
+
+1. `sessions/` から該当ファイルを削除
+2. `miyabi sessions` で確認
+
+### 設定が反映されない
+
+1. 設定ファイルの構文確認: `cat config.toml`
+2. 環境変数の確認
+3. CLIオプションの優先順位確認
+
 ## 使い方
 
 ```bash
@@ -61,6 +320,9 @@ miyabi
 # バージョン情報
 miyabi version
 
+# ステータス確認
+miyabi status
+
 # ヘルプ
 miyabi --help
 ```
diff --git a/.miyabi/commands/explain.md b/.miyabi/commands/explain.md
new file mode 100644
index 0000000..baf31ac
--- /dev/null
+++ b/.miyabi/commands/explain.md
@@ -0,0 +1,38 @@
+# Code Explanation
+
+Provide a detailed explanation of the specified code:
+
+## Analysis Sections
+
+### 1. Overview
+- Purpose and responsibility
+- Where it fits in the architecture
+- Key dependencies
+
+### 2. Data Flow
+- Inputs and outputs
+- Data transformations
+- Side effects
+
+### 3. Key Concepts
+- Design patterns used
+- Algorithms implemented
+- Important abstractions
+
+### 4. Line-by-Line Breakdown
+For complex sections, explain:
+- What each block does
+- Why it's implemented this way
+- Any non-obvious behavior
+
+### 5. Usage Examples
+```rust
+// Example of how to use this code
+```
+
+### 6. Potential Improvements
+- Suggestions for enhancement
+- Known limitations
+- Future considerations
+
+Target audience: Developers new to this codebase.
diff --git a/.miyabi/commands/refactor.md b/.miyabi/commands/refactor.md
new file mode 100644
index 0000000..e6b5a82
--- /dev/null
+++ b/.miyabi/commands/refactor.md
@@ -0,0 +1,20 @@
+# Code Refactoring
+
+Refactor the specified code with the following goals:
+
+1. **Improve Readability** - Clear naming, logical structure, remove complexity
+2. **Reduce Duplication** - Extract common patterns into reusable functions
+3. **Enhance Maintainability** - Better separation of concerns, SOLID principles
+4. **Optimize Performance** - Only if it doesn't sacrifice readability
+
+Guidelines:
+- Preserve existing behavior (no functional changes)
+- Keep existing tests passing
+- Add comments only where logic isn't self-evident
+- Prefer small, focused functions over large ones
+
+Output format:
+1. Analysis of current issues
+2. Refactoring plan
+3. Refactored code with explanations
+4. Summary of improvements
diff --git a/.miyabi/commands/review.md b/.miyabi/commands/review.md
new file mode 100644
index 0000000..bc5fd12
--- /dev/null
+++ b/.miyabi/commands/review.md
@@ -0,0 +1,17 @@
+# Code Review
+
+Please review the provided code for:
+
+1. **Bugs & Logic Errors** - Identify potential bugs, edge cases, and logical issues
+2. **Performance** - Spot inefficient algorithms, unnecessary allocations, or N+1 queries
+3. **Security** - Check for vulnerabilities like injection, XSS, or unsafe operations
+4. **Code Style** - Ensure consistency with project conventions
+5. **Error Handling** - Verify proper error propagation and user-friendly messages
+
+For each issue found, provide:
+- Location (file:line)
+- Severity (Critical/High/Medium/Low)
+- Description
+- Suggested fix with code example
+
+End with a summary score (1-10) and overall assessment.
diff --git a/.miyabi/commands/test.md b/.miyabi/commands/test.md
new file mode 100644
index 0000000..c7a446c
--- /dev/null
+++ b/.miyabi/commands/test.md
@@ -0,0 +1,33 @@
+# Test Generation
+
+Generate comprehensive tests for the specified code:
+
+## Test Types
+1. **Unit Tests** - Test individual functions in isolation
+2. **Integration Tests** - Test component interactions
+3. **Edge Cases** - Boundary conditions, empty inputs, max values
+4. **Error Cases** - Invalid inputs, failure scenarios
+
+## Requirements
+- Use the project's testing framework
+- Follow Arrange-Act-Assert pattern
+- Descriptive test names that explain the scenario
+- Mock external dependencies
+- Aim for high coverage of critical paths
+
+## Output Format
+```rust
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_function_name_scenario() {
+        // Arrange
+        // Act
+        // Assert
+    }
+}
+```
+
+Include explanation of test strategy and coverage goals.
diff --git a/.miyabi/prompts/rust-best-practices.md b/.miyabi/prompts/rust-best-practices.md
new file mode 100644
index 0000000..edccc3f
--- /dev/null
+++ b/.miyabi/prompts/rust-best-practices.md
@@ -0,0 +1,41 @@
+# Rust Best Practices Checklist
+
+When writing or reviewing Rust code, ensure:
+
+## Error Handling
+- [ ] Use `Result<T, E>` for fallible operations
+- [ ] Avoid `.unwrap()` and `.expect()` in library code
+- [ ] Use `?` operator for error propagation
+- [ ] Create custom error types with `thiserror`
+- [ ] Provide context with `.context()` or `.with_context()`
+
+## Memory & Performance
+- [ ] Prefer `&str` over `String` for function parameters
+- [ ] Use `Cow<str>` when ownership is conditional
+- [ ] Avoid unnecessary cloning
+- [ ] Use iterators instead of index loops
+- [ ] Consider `Vec::with_capacity()` for known sizes
+
+## Safety
+- [ ] Minimize `unsafe` code
+- [ ] Document safety invariants for `unsafe` blocks
+- [ ] Validate all external input
+- [ ] Use `#[must_use]` for important return values
+
+## Async
+- [ ] Use `tokio::spawn` for concurrent tasks
+- [ ] Avoid blocking operations in async context
+- [ ] Use `tokio::select!` for racing futures
+- [ ] Handle cancellation properly
+
+## Testing
+- [ ] Unit tests in same file with `#[cfg(test)]`
+- [ ] Integration tests in `tests/` directory
+- [ ] Use `#[should_panic]` for expected panics
+- [ ] Test error cases, not just happy paths
+
+## Documentation
+- [ ] Doc comments for public items (`///`)
+- [ ] Examples in doc comments
+- [ ] Module-level documentation (`//!`)
+- [ ] Link related items with `[`item`]`
diff --git a/.miyabirules b/.miyabirules
new file mode 100644
index 0000000..2c34acb
--- /dev/null
+++ b/.miyabirules
@@ -0,0 +1,76 @@
+# Miyabi CLI Project Rules
+# This file defines project-specific rules and agent preferences
+
+version: 1
+
+rules:
+  # Rust best practices
+  - name: "no-unwrap"
+    pattern: ".unwrap()"
+    suggestion: "Use ? operator or proper error handling instead of unwrap()"
+    file_extensions: ["rs"]
+    severity: "warning"
+    enabled: true
+
+  - name: "no-expect"
+    pattern: ".expect("
+    suggestion: "Consider using ? operator or match for better error messages"
+    file_extensions: ["rs"]
+    severity: "info"
+    enabled: true
+
+  - name: "no-println-debug"
+    pattern: "println!"
+    suggestion: "Use tracing macros (info!, debug!, error!) for logging"
+    file_extensions: ["rs"]
+    severity: "info"
+    enabled: true
+
+  - name: "no-dbg"
+    pattern: "dbg!"
+    suggestion: "Remove debug macro before committing"
+    file_extensions: ["rs"]
+    severity: "warning"
+    enabled: true
+
+  - name: "no-todo"
+    pattern: "TODO"
+    suggestion: "Address TODO comments or create GitHub issues"
+    file_extensions: ["rs", "ts", "js", "md"]
+    severity: "info"
+    enabled: true
+
+  - name: "no-fixme"
+    pattern: "FIXME"
+    suggestion: "Address FIXME comments before merging"
+    file_extensions: ["rs", "ts", "js"]
+    severity: "warning"
+    enabled: true
+
+# Agent-specific preferences
+agent_preferences:
+  codegen:
+    style: "functional"
+    error_handling: "result"
+    min_score: 80
+    clippy_strict: true
+
+  review:
+    focus_areas:
+      - "error_handling"
+      - "performance"
+      - "security"
+    min_score: 70
+
+  refactor:
+    preserve_tests: true
+    max_changes_per_file: 100
+
+# Global settings
+settings:
+  auto_format: true
+  max_file_size: 1048576
+  ignore_patterns:
+    - "target/"
+    - "node_modules/"
+    - ".git/"
diff --git a/Cargo.lock b/Cargo.lock
index 2853c35..1d976c5 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -198,6 +198,8 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cd405d82c84ff7f35739f175f67d8b9fb7687a0e84ccdc78bd3568839827cf07"
 dependencies = [
  "find-msvc-tools",
+ "jobserver",
+ "libc",
  "shlex",
 ]
 
@@ -745,6 +747,21 @@ dependencies = [
  "wasip2",
 ]
 
+[[package]]
+name = "git2"
+version = "0.19.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b903b73e45dc0c6c596f2d37eccece7c1c8bb6e4407b001096387c63d0d93724"
+dependencies = [
+ "bitflags",
+ "libc",
+ "libgit2-sys",
+ "log",
+ "openssl-probe",
+ "openssl-sys",
+ "url",
+]
+
 [[package]]
 name = "glob"
 version = "0.3.3"
@@ -1139,6 +1156,16 @@ version = "1.0.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4a5f13b858c8d314ee3e8f639011f7ccefe71f97f96e50151fb991f267928e2c"
 
+[[package]]
+name = "jobserver"
+version = "0.1.34"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9afb3de4395d6b3e67a780b6de64b51c978ecf11cb9a462c66be7d4ca9039d33"
+dependencies = [
+ "getrandom 0.3.4",
+ "libc",
+]
+
 [[package]]
 name = "js-sys"
 version = "0.3.82"
@@ -1161,6 +1188,20 @@ version = "0.2.177"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2874a2af47a2325c2001a6e6fad9b16a53b802102b528163885171cf92b15976"
 
+[[package]]
+name = "libgit2-sys"
+version = "0.17.0+1.8.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "10472326a8a6477c3c20a64547b0059e4b0d086869eee31e6d7da728a8eb7224"
+dependencies = [
+ "cc",
+ "libc",
+ "libssh2-sys",
+ "libz-sys",
+ "openssl-sys",
+ "pkg-config",
+]
+
 [[package]]
 name = "libredox"
 version = "0.1.10"
@@ -1171,6 +1212,32 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "libssh2-sys"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "220e4f05ad4a218192533b300327f5150e809b54c4ec83b5a1d91833601811b9"
+dependencies = [
+ "cc",
+ "libc",
+ "libz-sys",
+ "openssl-sys",
+ "pkg-config",
+ "vcpkg",
+]
+
+[[package]]
+name = "libz-sys"
+version = "1.1.23"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "15d118bbf3771060e7311cc7bb0545b01d08a8b4a7de949198dec1fa0ca1c0f7"
+dependencies = [
+ "cc",
+ "libc",
+ "pkg-config",
+ "vcpkg",
+]
+
 [[package]]
 name = "linked-hash-map"
 version = "0.5.6"
@@ -1293,16 +1360,19 @@ dependencies = [
  "chrono",
  "dirs",
  "futures",
+ "git2",
  "glob",
  "regex",
  "reqwest",
  "serde",
  "serde_json",
+ "serde_yaml",
  "tempfile",
  "thiserror 2.0.17",
  "tokio",
  "toml",
  "tracing",
+ "tracing-subscriber",
  "uuid",
 ]
 
@@ -2007,6 +2077,19 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "serde_yaml"
+version = "0.9.34+deprecated"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6a8b1a1a2ebf674015cc02edccce75287f1a0130d394307b36743c2f5d504b47"
+dependencies = [
+ "indexmap",
+ "itoa",
+ "ryu",
+ "serde",
+ "unsafe-libyaml",
+]
+
 [[package]]
 name = "sharded-slab"
 version = "0.1.7"
@@ -2522,6 +2605,16 @@ dependencies = [
  "tracing-core",
 ]
 
+[[package]]
+name = "tracing-serde"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "704b1aeb7be0d0a84fc9828cae51dab5970fee5088f83d1dd7ee6f6246fc6ff1"
+dependencies = [
+ "serde",
+ "tracing-core",
+]
+
 [[package]]
 name = "tracing-subscriber"
 version = "0.3.20"
@@ -2532,12 +2625,15 @@ dependencies = [
  "nu-ansi-term",
  "once_cell",
  "regex-automata",
+ "serde",
+ "serde_json",
  "sharded-slab",
  "smallvec",
  "thread_local",
  "tracing",
  "tracing-core",
  "tracing-log",
+ "tracing-serde",
 ]
 
 [[package]]
@@ -2593,6 +2689,12 @@ version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1fc81956842c57dac11422a97c3b8195a1ff727f06e85c84ed2e8aa277c9a0fd"
 
+[[package]]
+name = "unsafe-libyaml"
+version = "0.2.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "673aac59facbab8a9007c7f6108d11f63b603f7cabff99fabf650fea5c32b861"
+
 [[package]]
 name = "untrusted"
 version = "0.9.0"
diff --git a/MIYABI.md b/MIYABI.md
index f38ce3a..6fa0a5d 100644
Binary files a/MIYABI.md and b/MIYABI.md differ
diff --git a/README.md b/README.md
index dcec9ee..2233dea 100644
--- a/README.md
+++ b/README.md
@@ -166,23 +166,218 @@ Agent mode features:
 - Iteration limits for safety
 - JSON output format option
 
+## Core Library Features
+
+The `miyabi-core` crate provides powerful utilities for building AI applications.
+
+### Git Utilities
+
+```rust
+use miyabi_core::{find_git_root, get_current_branch, is_in_git_repo};
+
+// Find repository root
+let root = find_git_root()?;
+
+// Get current branch
+let branch = get_current_branch(&root)?;
+
+// Check if in git repo
+if is_in_git_repo(&path) {
+    println!("In a git repository");
+}
+```
+
+### Logger System
+
+```rust
+use miyabi_core::{init_logger, LogLevel, LogFormat};
+
+// Initialize with defaults
+init_logger();
+
+// Or with custom config
+use miyabi_core::LoggerConfig;
+let config = LoggerConfig {
+    level: LogLevel::Debug,
+    format: LogFormat::Json,
+    ..Default::default()
+};
+init_logger_with_config(config);
+```
+
+### Retry with Backoff
+
+```rust
+use miyabi_core::{retry_with_backoff, BackoffRetryConfig};
+
+let config = BackoffRetryConfig::default();
+let result = retry_with_backoff(config, || async {
+    // Your operation that might fail
+    make_api_call().await
+}).await?;
+```
+
+### Circuit Breaker
+
+```rust
+use miyabi_core::{CircuitBreaker, CircuitState};
+
+let breaker = CircuitBreaker::default();
+
+let result = breaker.call(|| {
+    Box::pin(async {
+        // Your operation
+        Ok::<_, std::io::Error>(())
+    })
+}).await;
+
+// Check state
+match breaker.state().await {
+    CircuitState::Closed => println!("Normal operation"),
+    CircuitState::Open => println!("Circuit open - blocking calls"),
+    CircuitState::HalfOpen => println!("Testing recovery"),
+}
+```
+
+### Rules System (.miyabirules)
+
+Support for project-specific rules via `.miyabirules` files:
+
+```yaml
+# .miyabirules
+version: 1
+rules:
+  - name: "no-unwrap"
+    pattern: ".unwrap()"
+    suggestion: "Use ? operator or proper error handling"
+    file_extensions: ["rs"]
+    severity: "warning"
+
+agent_preferences:
+  codegen:
+    style: "functional"
+    error_handling: "result"
+```
+
+```rust
+use miyabi_core::{RulesLoader, MiyabiRules};
+
+let loader = RulesLoader::new(project_root);
+let rules = loader.load_or_default()?;
+
+// Get rules for a file
+let applicable = rules.rules_for_file(Path::new("src/main.rs"));
+```
+
+### Cache System
+
+```rust
+use miyabi_core::{create_llm_cache, create_api_cache, LLMCacheKey};
+
+// LLM response cache (1 hour TTL)
+let cache = create_llm_cache();
+let key = LLMCacheKey::new("prompt", "model", Some(0.7));
+
+cache.insert(key.clone(), "response".to_string()).await;
+let cached = cache.get(&key).await;
+
+// API cache (30 min TTL)
+let api_cache = create_api_cache();
+```
+
+### Plugin System
+
+```rust
+use miyabi_core::{Plugin, PluginManager, PluginMetadata, PluginContext, PluginResult};
+use anyhow::Result;
+
+struct MyPlugin;
+
+impl Plugin for MyPlugin {
+    fn metadata(&self) -> PluginMetadata {
+        PluginMetadata {
+            name: "my-plugin".to_string(),
+            version: "1.0.0".to_string(),
+            description: Some("My custom plugin".to_string()),
+            author: None,
+        }
+    }
+
+    fn init(&mut self) -> Result<()> {
+        Ok(())
+    }
+
+    fn execute(&self, ctx: &PluginContext) -> Result<PluginResult> {
+        Ok(PluginResult {
+            success: true,
+            message: Some("Done".to_string()),
+            data: None,
+        })
+    }
+}
+
+// Register and execute
+let manager = PluginManager::new();
+manager.register(Box::new(MyPlugin))?;
+let result = manager.execute("my-plugin", &PluginContext::default())?;
+```
+
+### Feature Flags
+
+```rust
+use miyabi_core::{FeatureFlagManager, FeatureFlag};
+
+let flags = FeatureFlagManager::new();
+
+// Simple flag
+flags.set_flag("new_feature", true);
+
+if flags.is_enabled("new_feature") {
+    // Use new feature
+}
+
+// With rollout percentage
+flags.set_flag_with_options(
+    "beta_feature",
+    true,
+    Some("Beta testing".to_string()),
+    Some(0.5), // 50% rollout
+);
+
+// Load from config
+use std::collections::HashMap;
+let mut config = HashMap::new();
+config.insert("flag1".to_string(), true);
+flags.load_from_map(config);
+```
+
 ## Project Structure
 
 ```
 miyabi-cli-standalone/
 ├── crates/
-│   ├── miyabi-cli/       # CLI entry point
-│   ├── miyabi-core/      # Core library
-│   │   ├── agent/        # Agent system
-│   │   ├── config.rs     # Configuration
-│   │   ├── session.rs    # Session management
+│   ├── miyabi-cli/         # CLI entry point
+│   ├── miyabi-core/        # Core library
+│   │   ├── agent.rs        # Agent system
+│   │   ├── anthropic.rs    # Anthropic API client
+│   │   ├── cache.rs        # TTL cache system
+│   │   ├── config.rs       # Configuration
+│   │   ├── error_policy.rs # Circuit breaker
+│   │   ├── feature_flags.rs # Feature flag management
+│   │   ├── git.rs          # Git utilities
+│   │   ├── logger.rs       # Logging system
+│   │   ├── plugin.rs       # Plugin system
+│   │   ├── retry.rs        # Retry with backoff
+│   │   ├── rules.rs        # .miyabirules support
+│   │   ├── session.rs      # Session management
+│   │   ├── tools.rs        # Built-in tools
 │   │   └── ...
-│   └── miyabi-tui/       # TUI implementation
-│       ├── app.rs        # Main application
-│       ├── views.rs      # UI views
+│   └── miyabi-tui/         # TUI implementation
+│       ├── app.rs          # Main application
+│       ├── views.rs        # UI views
 │       └── ...
-├── .miyabi/              # Local config
-├── Cargo.toml            # Workspace config
+├── .miyabi/                # Local config
+├── Cargo.toml              # Workspace config
 └── README.md
 ```
 
diff --git a/crates/miyabi-cli/src/main.rs b/crates/miyabi-cli/src/main.rs
index 5b21ae9..92517bb 100644
--- a/crates/miyabi-cli/src/main.rs
+++ b/crates/miyabi-cli/src/main.rs
@@ -1,9 +1,26 @@
 //! Miyabi CLI - Main entry point
 
 use clap::{Parser, Subcommand};
+use miyabi_core::{FeatureFlagManager, RulesLoader};
 use std::path::PathBuf;
 use tracing_subscriber::EnvFilter;
 
+/// Global feature flags manager
+static FEATURE_FLAGS: std::sync::OnceLock<FeatureFlagManager> = std::sync::OnceLock::new();
+
+/// Get the global feature flags manager
+pub fn feature_flags() -> &'static FeatureFlagManager {
+    FEATURE_FLAGS.get_or_init(|| {
+        let manager = FeatureFlagManager::new();
+        // Default feature flags
+        manager.set_flag("extended_thinking", true);
+        manager.set_flag("auto_save_sessions", true);
+        manager.set_flag("syntax_highlighting", true);
+        manager.set_flag("vim_mode", false);
+        manager
+    })
+}
+
 #[derive(Parser)]
 #[command(name = "miyabi")]
 #[command(author, version, about = "Miyabi - Autonomous AI Development Framework", long_about = None)]
@@ -54,6 +71,12 @@ enum Commands {
     },
     /// Show version and system information
     Version,
+    /// Show project rules (.miyabirules)
+    Rules {
+        /// Show detailed rule information
+        #[arg(short, long)]
+        verbose: bool,
+    },
     /// Run agent with a prompt (autonomous execution)
     Agent {
         /// The prompt to execute
@@ -145,11 +168,40 @@ async fn main() -> anyhow::Result<()> {
             }
         }
         Some(Commands::Status) => {
+            use miyabi_core::config::Config;
+
+            let config = Config::load().unwrap_or_default();
+
             println!("Miyabi Status: Ready");
-            println!(
-                "Config path: {:?}",
-                miyabi_core::config::Config::default_path()
-            );
+            println!();
+            println!("Config:   {}", Config::default_path().display());
+            println!("Sessions: {}", config.sessions_dir().display());
+            println!("Model:    {}", config.api.model);
+            println!();
+
+            // Load and show rules info
+            let cwd = std::env::current_dir().unwrap_or_default();
+            let loader = RulesLoader::new(cwd);
+            match loader.load() {
+                Ok(Some(rules)) => {
+                    println!("Rules:    {} rules loaded", rules.rules.len());
+                    if !rules.agent_preferences.is_empty() {
+                        println!("Agents:   {} agent preferences", rules.agent_preferences.len());
+                    }
+                }
+                Ok(None) => {
+                    println!("Rules:    No .miyabirules found");
+                }
+                Err(e) => {
+                    println!("Rules:    Error loading - {}", e);
+                }
+            }
+
+            // Show feature flags
+            let flags = feature_flags();
+            let all_flags = flags.get_all_flags();
+            let enabled_count = all_flags.iter().filter(|f| f.enabled).count();
+            println!("Flags:    {}/{} enabled", enabled_count, all_flags.len());
         }
         Some(Commands::Init) => {
             use miyabi_core::config::Config;
@@ -284,6 +336,78 @@ async fn main() -> anyhow::Result<()> {
                 std::env::consts::ARCH
             );
         }
+        Some(Commands::Rules { verbose }) => {
+            let cwd = std::env::current_dir().unwrap_or_default();
+            let loader = RulesLoader::new(cwd.clone());
+
+            match loader.load() {
+                Ok(Some(rules)) => {
+                    println!("Project Rules (.miyabirules)");
+                    println!("============================");
+                    println!();
+
+                    if rules.rules.is_empty() {
+                        println!("No rules defined.");
+                    } else {
+                        println!("Rules ({}):", rules.rules.len());
+                        for rule in &rules.rules {
+                            let status = if rule.enabled { "✓" } else { "✗" };
+                            let severity = match rule.severity.as_str() {
+                                "error" => "🔴",
+                                "warning" => "🟡",
+                                _ => "🔵",
+                            };
+                            println!("  {} {} {} - {}", status, severity, rule.name, rule.suggestion);
+
+                            if verbose {
+                                if let Some(pattern) = &rule.pattern {
+                                    println!("      Pattern: {}", pattern);
+                                }
+                                if !rule.file_extensions.is_empty() {
+                                    println!("      Extensions: {}", rule.file_extensions.join(", "));
+                                }
+                                println!();
+                            }
+                        }
+                    }
+
+                    if !rules.agent_preferences.is_empty() {
+                        println!();
+                        println!("Agent Preferences ({}):", rules.agent_preferences.len());
+                        for (agent, prefs) in &rules.agent_preferences {
+                            println!("  {}:", agent);
+                            if let Some(style) = &prefs.style {
+                                println!("    Style: {}", style);
+                            }
+                            if let Some(handling) = &prefs.error_handling {
+                                println!("    Error Handling: {}", handling);
+                            }
+                            if let Some(score) = prefs.min_score {
+                                println!("    Min Score: {}", score);
+                            }
+                        }
+                    }
+
+                    if verbose && !rules.settings.is_empty() {
+                        println!();
+                        println!("Settings:");
+                        for (key, value) in &rules.settings {
+                            println!("  {}: {}", key, value);
+                        }
+                    }
+                }
+                Ok(None) => {
+                    println!("No .miyabirules file found in {} or parent directories.", cwd.display());
+                    println!();
+                    println!("Create a .miyabirules file to define project-specific rules.");
+                    println!("See: miyabi --help for more information.");
+                }
+                Err(e) => {
+                    eprintln!("Error loading rules: {}", e);
+                    std::process::exit(1);
+                }
+            }
+        }
         Some(Commands::Agent {
             prompt,
             max_iterations,
diff --git a/crates/miyabi-core/Cargo.toml b/crates/miyabi-core/Cargo.toml
index b12c4e4..e3103bc 100644
--- a/crates/miyabi-core/Cargo.toml
+++ b/crates/miyabi-core/Cargo.toml
@@ -16,6 +16,7 @@ serde_json = { workspace = true }
 anyhow = { workspace = true }
 thiserror = { workspace = true }
 tracing = { workspace = true }
+tracing-subscriber = { version = "0.3", features = ["env-filter", "json"] }
 chrono = { workspace = true }
 uuid = { workspace = true }
 reqwest = { workspace = true }
@@ -23,6 +24,8 @@ futures = { workspace = true }
 async-trait = { workspace = true }
 glob = { workspace = true }
 regex = { workspace = true }
+git2 = "0.19"
+serde_yaml = "0.9"
 dirs = "5"
 toml = "0.8"
 
diff --git a/crates/miyabi-core/src/cache.rs b/crates/miyabi-core/src/cache.rs
new file mode 100644
index 0000000..fea85a7
--- /dev/null
+++ b/crates/miyabi-core/src/cache.rs
@@ -0,0 +1,240 @@
+//! Caching utilities for Miyabi
+//!
+//! Provides in-memory caching with TTL support for LLM responses and other expensive operations
+
+use serde::{Deserialize, Serialize};
+use std::collections::HashMap;
+use std::hash::Hash;
+use std::sync::Arc;
+use std::time::{Duration, Instant};
+use tokio::sync::RwLock;
+
+/// Cache entry with TTL support
+#[derive(Debug, Clone)]
+pub struct CacheEntry<T> {
+    /// Cached value
+    pub value: T,
+    /// Expiration timestamp
+    pub expires_at: Instant,
+}
+
+impl<T> CacheEntry<T> {
+    /// Create a new cache entry with the given TTL
+    pub fn new(value: T, ttl: Duration) -> Self {
+        Self {
+            value,
+            expires_at: Instant::now() + ttl,
+        }
+    }
+
+    /// Check if the cache entry has expired
+    pub fn is_expired(&self) -> bool {
+        Instant::now() > self.expires_at
+    }
+}
+
+/// Thread-safe TTL cache
+#[derive(Debug)]
+pub struct TTLCache<K, V> {
+    inner: Arc<RwLock<HashMap<K, CacheEntry<V>>>>,
+    default_ttl: Duration,
+}
+
+impl<K, V> TTLCache<K, V>
+where
+    K: Hash + Eq + Clone + Send + Sync + 'static,
+    V: Clone + Send + Sync + 'static,
+{
+    /// Create a new TTL cache with default TTL
+    pub fn new(default_ttl: Duration) -> Self {
+        Self {
+            inner: Arc::new(RwLock::new(HashMap::new())),
+            default_ttl,
+        }
+    }
+
+    /// Get a value from the cache
+    pub async fn get(&self, key: &K) -> Option<V> {
+        let mut cache = self.inner.write().await;
+
+        if let Some(entry) = cache.get(key) {
+            if entry.is_expired() {
+                cache.remove(key);
+                None
+            } else {
+                Some(entry.value.clone())
+            }
+        } else {
+            None
+        }
+    }
+
+    /// Insert a value into the cache with default TTL
+    pub async fn insert(&self, key: K, value: V) {
+        self.insert_with_ttl(key, value, self.default_ttl).await;
+    }
+
+    /// Insert a value into the cache with custom TTL
+    pub async fn insert_with_ttl(&self, key: K, value: V, ttl: Duration) {
+        let mut cache = self.inner.write().await;
+        cache.insert(key, CacheEntry::new(value, ttl));
+    }
+
+    /// Remove a value from the cache
+    pub async fn remove(&self, key: &K) -> Option<V> {
+        let mut cache = self.inner.write().await;
+        cache.remove(key).map(|entry| entry.value)
+    }
+
+    /// Clear all expired entries
+    pub async fn cleanup_expired(&self) -> usize {
+        let mut cache = self.inner.write().await;
+        let initial_size = cache.len();
+        cache.retain(|_, entry| !entry.is_expired());
+        initial_size - cache.len()
+    }
+
+    /// Get cache statistics
+    pub async fn stats(&self) -> CacheStats {
+        let cache = self.inner.read().await;
+        let total_entries = cache.len();
+        let expired_entries = cache.values().filter(|entry| entry.is_expired()).count();
+
+        CacheStats {
+            total_entries,
+            expired_entries,
+            active_entries: total_entries - expired_entries,
+        }
+    }
+
+    /// Clear all entries
+    pub async fn clear(&self) {
+        let mut cache = self.inner.write().await;
+        cache.clear();
+    }
+}
+
+/// Cache statistics
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct CacheStats {
+    /// Total entries
+    pub total_entries: usize,
+    /// Expired entries
+    pub expired_entries: usize,
+    /// Active entries
+    pub active_entries: usize,
+}
+
+/// LLM response cache key
+#[derive(Debug, Clone, Hash, Eq, PartialEq)]
+pub struct LLMCacheKey {
+    /// Prompt hash
+    pub prompt_hash: String,
+    /// Model name
+    pub model: String,
+    /// Temperature parameter (as bits to avoid f32 Hash/Eq issues)
+    pub temperature: Option<u32>,
+}
+
+impl LLMCacheKey {
+    pub fn new(prompt: &str, model: &str, temperature: Option<f32>) -> Self {
+        use std::collections::hash_map::DefaultHasher;
+        use std::hash::Hasher;
+
+        let mut hasher = DefaultHasher::new();
+        prompt.hash(&mut hasher);
+        model.hash(&mut hasher);
+        if let Some(temp) = temperature {
+            temp.to_bits().hash(&mut hasher);
+        }
+
+        Self {
+            prompt_hash: format!("{:x}", hasher.finish()),
+            model: model.to_string(),
+            temperature: temperature.map(|t| t.to_bits()),
+        }
+    }
+}
+
+/// LLM response cache
+pub type LLMCache = TTLCache<LLMCacheKey, String>;
+
+/// Create a new LLM cache with 1 hour TTL
+pub fn create_llm_cache() -> LLMCache {
+    TTLCache::new(Duration::from_secs(3600))
+}
+
+/// API response cache key
+#[derive(Debug, Clone, Hash, Eq, PartialEq)]
+pub struct ApiCacheKey {
+    /// Endpoint
+    pub endpoint: String,
+    /// Request hash
+    pub request_hash: String,
+}
+
+impl ApiCacheKey {
+    pub fn new(endpoint: &str, request_body: &str) -> Self {
+        use std::collections::hash_map::DefaultHasher;
+        use std::hash::Hasher;
+
+        let mut hasher = DefaultHasher::new();
+        request_body.hash(&mut hasher);
+
+        Self {
+            endpoint: endpoint.to_string(),
+            request_hash: format!("{:x}", hasher.finish()),
+        }
+    }
+}
+
+/// API response cache
+pub type ApiCache = TTLCache<ApiCacheKey, String>;
+
+/// Create a new API cache with 30 minutes TTL
+pub fn create_api_cache() -> ApiCache {
+    TTLCache::new(Duration::from_secs(1800))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use tokio::time::sleep;
+
+    #[tokio::test]
+    async fn test_ttl_cache_basic_operations() {
+        let cache = TTLCache::new(Duration::from_millis(100));
+
+        cache.insert("key1", "value1").await;
+        assert_eq!(cache.get(&"key1").await, Some("value1"));
+
+        sleep(Duration::from_millis(150)).await;
+        assert_eq!(cache.get(&"key1").await, None);
+    }
+
+    #[tokio::test]
+    async fn test_ttl_cache_cleanup() {
+        let cache = TTLCache::new(Duration::from_millis(50));
+
+        cache.insert("key1", "value1").await;
+        cache.insert("key2", "value2").await;
+
+        sleep(Duration::from_millis(100)).await;
+
+        let cleaned = cache.cleanup_expired().await;
+        assert_eq!(cleaned, 2);
+
+        let stats = cache.stats().await;
+        assert_eq!(stats.total_entries, 0);
+    }
+
+    #[tokio::test]
+    async fn test_llm_cache_key() {
+        let key1 = LLMCacheKey::new("prompt1", "model1", Some(0.7));
+        let key2 = LLMCacheKey::new("prompt1", "model1", Some(0.7));
+        let key3 = LLMCacheKey::new("prompt2", "model1", Some(0.7));
+
+        assert_eq!(key1, key2);
+        assert_ne!(key1, key3);
+    }
+}
diff --git a/crates/miyabi-core/src/error.rs b/crates/miyabi-core/src/error.rs
index ea744e5..829ef2d 100644
--- a/crates/miyabi-core/src/error.rs
+++ b/crates/miyabi-core/src/error.rs
@@ -16,8 +16,85 @@ pub enum Error {
     #[error("Agent error: {0}")]
     Agent(String),
 
+    #[error("Git error: {0}")]
+    Git(String),
+
+    #[error("HTTP error: {0}")]
+    Http(String),
+
+    #[error("Timeout after {0}ms")]
+    Timeout(u64),
+
+    #[error("GitHub error: {0}")]
+    GitHub(String),
+
+    #[error("Validation error: {0}")]
+    Validation(String),
+
+    #[error("Authentication error: {0}")]
+    Auth(String),
+
+    #[error("Tool error: {0}")]
+    Tool(String),
+
+    #[error("Permission denied: {0}")]
+    PermissionDenied(String),
+
     #[error("{0}")]
     Other(String),
 }
 
 pub type Result<T> = std::result::Result<T, Error>;
+
+/// Check if an error is retryable (transient)
+impl Error {
+    pub fn is_retryable(&self) -> bool {
+        match self {
+            // Always retryable
+            Error::Timeout(_) => true,
+
+            // HTTP errors - check message for transient patterns
+            Error::Http(msg) => {
+                let lower = msg.to_lowercase();
+                lower.contains("timeout")
+                    || lower.contains("connection")
+                    || lower.contains("temporarily")
+            }
+
+            // GitHub errors - check for rate limiting
+            Error::GitHub(msg) => {
+                let lower = msg.to_lowercase();
+                lower.contains("rate limit")
+                    || lower.contains("retry")
+                    || lower.contains("temporarily unavailable")
+            }
+
+            // IO errors - some kinds are retryable
+            Error::Io(io_error) => matches!(
+                io_error.kind(),
+                std::io::ErrorKind::ConnectionRefused
+                    | std::io::ErrorKind::ConnectionReset
+                    | std::io::ErrorKind::ConnectionAborted
+                    | std::io::ErrorKind::TimedOut
+                    | std::io::ErrorKind::Interrupted
+                    | std::io::ErrorKind::WouldBlock
+            ),
+
+            // Git errors - check message for lock conflicts
+            Error::Git(msg) => {
+                let lower = msg.to_lowercase();
+                lower.contains("lock") || lower.contains("unable to create")
+            }
+
+            // Never retryable
+            Error::Agent(_) => false,
+            Error::Auth(_) => false,
+            Error::Config(_) => false,
+            Error::Validation(_) => false,
+            Error::Json(_) => false,
+            Error::Tool(_) => false,
+            Error::PermissionDenied(_) => false,
+            Error::Other(_) => false,
+        }
+    }
+}
diff --git a/crates/miyabi-core/src/error_policy.rs b/crates/miyabi-core/src/error_policy.rs
new file mode 100644
index 0000000..10831a5
--- /dev/null
+++ b/crates/miyabi-core/src/error_policy.rs
@@ -0,0 +1,291 @@
+//! Error handling policies for Miyabi system
+//!
+//! This module provides advanced error handling strategies:
+//! - Circuit Breaker pattern for preventing cascading failures
+//! - Fallback strategies for graceful degradation
+
+use crate::error::Error;
+use std::sync::Arc;
+use std::time::{Duration, Instant};
+use tokio::sync::Mutex;
+
+/// Fallback strategy when execution fails
+#[derive(Debug, Clone)]
+pub enum FallbackStrategy {
+    /// Accept partial success
+    AcceptPartialSuccess {
+        /// Minimum number of successful operations required
+        min_successful: usize,
+    },
+    /// Retry with lower temperature
+    RetryWithLowerTemperature {
+        /// Amount to reduce temperature by
+        temperature_reduction: f64,
+    },
+    /// Switch to a different LLM model
+    SwitchModel {
+        /// Fallback model name
+        fallback_model: String,
+    },
+    /// Wait for human intervention
+    WaitForHumanIntervention {
+        /// Timeout before giving up
+        timeout: Duration,
+    },
+    /// Skip the task entirely
+    SkipTask,
+}
+
+impl Default for FallbackStrategy {
+    fn default() -> Self {
+        Self::AcceptPartialSuccess { min_successful: 1 }
+    }
+}
+
+impl FallbackStrategy {
+    /// Creates a partial success strategy with default threshold
+    pub fn partial_success() -> Self {
+        Self::AcceptPartialSuccess { min_successful: 1 }
+    }
+
+    /// Creates a temperature reduction strategy
+    pub fn lower_temperature() -> Self {
+        Self::RetryWithLowerTemperature {
+            temperature_reduction: 0.2,
+        }
+    }
+
+    /// Creates a model switch strategy
+    pub fn switch_to_claude() -> Self {
+        Self::SwitchModel {
+            fallback_model: "claude-sonnet-4-5-20250929".to_string(),
+        }
+    }
+
+    /// Creates a human intervention strategy
+    pub fn wait_for_human() -> Self {
+        Self::WaitForHumanIntervention {
+            timeout: Duration::from_secs(24 * 60 * 60),
+        }
+    }
+}
+
+/// State of the circuit breaker
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum CircuitState {
+    /// Circuit is closed - requests flow normally
+    Closed,
+    /// Circuit is open - requests are blocked
+    Open,
+    /// Circuit is half-open - testing if service recovered
+    HalfOpen,
+}
+
+/// Circuit breaker for preventing cascading failures
+///
+/// The circuit breaker pattern prevents repeated attempts to execute
+/// operations that are likely to fail, allowing the system to recover.
+pub struct CircuitBreaker {
+    /// Number of consecutive failures before opening circuit
+    failure_threshold: usize,
+    /// Number of consecutive successes before closing circuit
+    success_threshold: usize,
+    /// Duration to wait before transitioning from Open to HalfOpen
+    timeout: Duration,
+    /// Current circuit state
+    state: Arc<Mutex<CircuitState>>,
+    /// Count of consecutive failures
+    consecutive_failures: Arc<Mutex<usize>>,
+    /// Count of consecutive successes
+    consecutive_successes: Arc<Mutex<usize>>,
+    /// Time when circuit was opened
+    opened_at: Arc<Mutex<Option<Instant>>>,
+}
+
+impl CircuitBreaker {
+    /// Creates a new CircuitBreaker
+    pub fn new(failure_threshold: usize, success_threshold: usize, timeout: Duration) -> Self {
+        Self {
+            failure_threshold,
+            success_threshold,
+            timeout,
+            state: Arc::new(Mutex::new(CircuitState::Closed)),
+            consecutive_failures: Arc::new(Mutex::new(0)),
+            consecutive_successes: Arc::new(Mutex::new(0)),
+            opened_at: Arc::new(Mutex::new(None)),
+        }
+    }
+
+    /// Creates a CircuitBreaker with default settings
+    pub fn default_config() -> Self {
+        Self::new(5, 2, Duration::from_secs(60))
+    }
+
+    /// Executes the given operation through the circuit breaker
+    pub async fn call<F, T, E>(&self, operation: F) -> Result<T, Error>
+    where
+        F: FnOnce() -> std::pin::Pin<Box<dyn std::future::Future<Output = Result<T, E>> + Send>>,
+        E: std::error::Error + Send + Sync + 'static,
+    {
+        // Check if we should attempt reset
+        if self.should_attempt_reset().await {
+            *self.state.lock().await = CircuitState::HalfOpen;
+        }
+
+        let current_state = *self.state.lock().await;
+
+        match current_state {
+            CircuitState::Open => Err(Error::Other("Circuit breaker is open".to_string())),
+            CircuitState::Closed | CircuitState::HalfOpen => match operation().await {
+                Ok(result) => {
+                    self.on_success().await;
+                    Ok(result)
+                }
+                Err(e) => {
+                    self.on_failure().await;
+                    Err(Error::Other(e.to_string()))
+                }
+            },
+        }
+    }
+
+    /// Records a successful operation
+    async fn on_success(&self) {
+        let mut successes = self.consecutive_successes.lock().await;
+        *successes += 1;
+        *self.consecutive_failures.lock().await = 0;
+
+        if *successes >= self.success_threshold {
+            let mut state = self.state.lock().await;
+            if *state != CircuitState::Closed {
+                *state = CircuitState::Closed;
+                *self.opened_at.lock().await = None;
+            }
+            *successes = 0;
+        }
+    }
+
+    /// Records a failed operation
+    async fn on_failure(&self) {
+        let mut failures = self.consecutive_failures.lock().await;
+        *failures += 1;
+        *self.consecutive_successes.lock().await = 0;
+
+        if *failures >= self.failure_threshold {
+            let mut state = self.state.lock().await;
+            if *state == CircuitState::Closed {
+                *state = CircuitState::Open;
+                *self.opened_at.lock().await = Some(Instant::now());
+            }
+        }
+    }
+
+    /// Checks if circuit should attempt reset
+    async fn should_attempt_reset(&self) -> bool {
+        let state = *self.state.lock().await;
+        if state != CircuitState::Open {
+            return false;
+        }
+
+        let opened_at = self.opened_at.lock().await;
+        if let Some(opened_time) = *opened_at {
+            opened_time.elapsed() >= self.timeout
+        } else {
+            false
+        }
+    }
+
+    /// Gets the current circuit state
+    pub async fn state(&self) -> CircuitState {
+        *self.state.lock().await
+    }
+
+    /// Gets the number of consecutive failures
+    pub async fn consecutive_failures(&self) -> usize {
+        *self.consecutive_failures.lock().await
+    }
+
+    /// Gets the number of consecutive successes
+    pub async fn consecutive_successes(&self) -> usize {
+        *self.consecutive_successes.lock().await
+    }
+
+    /// Resets the circuit breaker to closed state
+    pub async fn reset(&self) {
+        *self.state.lock().await = CircuitState::Closed;
+        *self.consecutive_failures.lock().await = 0;
+        *self.consecutive_successes.lock().await = 0;
+        *self.opened_at.lock().await = None;
+    }
+}
+
+impl Default for CircuitBreaker {
+    fn default() -> Self {
+        Self::default_config()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[tokio::test]
+    async fn test_circuit_breaker_opens_after_failures() {
+        let breaker = CircuitBreaker::new(3, 2, Duration::from_millis(100));
+        assert_eq!(breaker.state().await, CircuitState::Closed);
+
+        for _ in 0..3 {
+            let result = breaker
+                .call(|| {
+                    Box::pin(async {
+                        Result::<(), std::io::Error>::Err(std::io::Error::other("test error"))
+                    })
+                })
+                .await;
+            assert!(result.is_err());
+        }
+
+        assert_eq!(breaker.state().await, CircuitState::Open);
+    }
+
+    #[tokio::test]
+    async fn test_circuit_breaker_blocks_when_open() {
+        let breaker = CircuitBreaker::new(2, 2, Duration::from_secs(60));
+
+        for _ in 0..2 {
+            let _ = breaker
+                .call(|| {
+                    Box::pin(async {
+                        Result::<(), std::io::Error>::Err(std::io::Error::other("error"))
+                    })
+                })
+                .await;
+        }
+
+        assert_eq!(breaker.state().await, CircuitState::Open);
+
+        let result = breaker
+            .call(|| Box::pin(async { Ok::<(), std::io::Error>(()) }))
+            .await;
+        assert!(result.is_err());
+    }
+
+    #[tokio::test]
+    async fn test_circuit_breaker_reset() {
+        let breaker = CircuitBreaker::new(2, 2, Duration::from_secs(60));
+
+        for _ in 0..2 {
+            let _ = breaker
+                .call(|| {
+                    Box::pin(async {
+                        Result::<(), std::io::Error>::Err(std::io::Error::other("error"))
+                    })
+                })
+                .await;
+        }
+
+        assert_eq!(breaker.state().await, CircuitState::Open);
+        breaker.reset().await;
+        assert_eq!(breaker.state().await, CircuitState::Closed);
+    }
+}
diff --git a/crates/miyabi-core/src/feature_flags.rs b/crates/miyabi-core/src/feature_flags.rs
new file mode 100644
index 0000000..3c4569f
--- /dev/null
+++ b/crates/miyabi-core/src/feature_flags.rs
@@ -0,0 +1,330 @@
+//! Feature Flag Management System
+//!
+//! Provides a flexible feature flag system for gradual rollout and A/B testing.
+//!
+//! # Examples
+//!
+//! ```rust
+//! use miyabi_core::feature_flags::FeatureFlagManager;
+//!
+//! let manager = FeatureFlagManager::new();
+//! manager.set_flag("new_architecture", true);
+//!
+//! if manager.is_enabled("new_architecture") {
+//!     // Use new architecture
+//! } else {
+//!     // Use old architecture
+//! }
+//! ```
+
+use serde::{Deserialize, Serialize};
+use std::collections::HashMap;
+use std::sync::{Arc, RwLock};
+
+/// Feature flag configuration
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct FeatureFlag {
+    /// Flag name
+    pub name: String,
+    /// Enabled status
+    pub enabled: bool,
+    /// Optional description
+    pub description: Option<String>,
+    /// Optional rollout percentage (0.0 to 1.0)
+    pub rollout_percentage: Option<f64>,
+}
+
+/// Feature flag manager for controlling feature rollout
+#[derive(Debug, Clone)]
+pub struct FeatureFlagManager {
+    /// Internal flag storage (thread-safe)
+    flags: Arc<RwLock<HashMap<String, FeatureFlag>>>,
+}
+
+impl Default for FeatureFlagManager {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl FeatureFlagManager {
+    /// Create a new feature flag manager
+    pub fn new() -> Self {
+        Self {
+            flags: Arc::new(RwLock::new(HashMap::new())),
+        }
+    }
+
+    /// Check if a feature flag is enabled
+    ///
+    /// # Arguments
+    ///
+    /// * `flag_name` - Name of the feature flag
+    ///
+    /// # Returns
+    ///
+    /// `true` if the flag exists and is enabled, `false` otherwise
+    pub fn is_enabled(&self, flag_name: &str) -> bool {
+        let flags = self.flags.read().unwrap();
+        flags.get(flag_name).map(|flag| flag.enabled).unwrap_or(false)
+    }
+
+    /// Set a feature flag
+    ///
+    /// # Arguments
+    ///
+    /// * `flag_name` - Name of the feature flag
+    /// * `enabled` - Whether the flag should be enabled
+    pub fn set_flag(&self, flag_name: impl Into<String>, enabled: bool) {
+        let mut flags = self.flags.write().unwrap();
+        let name = flag_name.into();
+        flags.insert(
+            name.clone(),
+            FeatureFlag {
+                name,
+                enabled,
+                description: None,
+                rollout_percentage: None,
+            },
+        );
+    }
+
+    /// Set a feature flag with description and rollout percentage
+    ///
+    /// # Arguments
+    ///
+    /// * `flag_name` - Name of the feature flag
+    /// * `enabled` - Whether the flag should be enabled
+    /// * `description` - Optional description of the flag
+    /// * `rollout_percentage` - Optional rollout percentage (0.0 to 1.0)
+    pub fn set_flag_with_options(
+        &self,
+        flag_name: impl Into<String>,
+        enabled: bool,
+        description: Option<String>,
+        rollout_percentage: Option<f64>,
+    ) {
+        let mut flags = self.flags.write().unwrap();
+        let name = flag_name.into();
+        flags.insert(
+            name.clone(),
+            FeatureFlag {
+                name,
+                enabled,
+                description,
+                rollout_percentage,
+            },
+        );
+    }
+
+    /// Remove a feature flag
+    ///
+    /// # Arguments
+    ///
+    /// * `flag_name` - Name of the feature flag to remove
+    pub fn remove_flag(&self, flag_name: &str) {
+        let mut flags = self.flags.write().unwrap();
+        flags.remove(flag_name);
+    }
+
+    /// Get all feature flags
+    ///
+    /// # Returns
+    ///
+    /// A vector of all feature flags
+    pub fn get_all_flags(&self) -> Vec<FeatureFlag> {
+        let flags = self.flags.read().unwrap();
+        flags.values().cloned().collect()
+    }
+
+    /// Get a specific feature flag
+    ///
+    /// # Arguments
+    ///
+    /// * `flag_name` - Name of the feature flag
+    ///
+    /// # Returns
+    ///
+    /// The feature flag if it exists, None otherwise
+    pub fn get_flag(&self, flag_name: &str) -> Option<FeatureFlag> {
+        let flags = self.flags.read().unwrap();
+        flags.get(flag_name).cloned()
+    }
+
+    /// Load feature flags from a HashMap
+    ///
+    /// # Arguments
+    ///
+    /// * `config` - HashMap of flag names to enabled status
+    pub fn load_from_map(&self, config: HashMap<String, bool>) {
+        let mut flags = self.flags.write().unwrap();
+        for (name, enabled) in config {
+            flags.insert(
+                name.clone(),
+                FeatureFlag {
+                    name,
+                    enabled,
+                    description: None,
+                    rollout_percentage: None,
+                },
+            );
+        }
+    }
+
+    /// Load feature flags from detailed configuration
+    ///
+    /// # Arguments
+    ///
+    /// * `config` - Vector of FeatureFlag configurations
+    pub fn load_from_config(&self, config: Vec<FeatureFlag>) {
+        let mut flags = self.flags.write().unwrap();
+        for flag in config {
+            flags.insert(flag.name.clone(), flag);
+        }
+    }
+
+    /// Export all flags to a HashMap
+    ///
+    /// # Returns
+    ///
+    /// HashMap of flag names to enabled status
+    pub fn export_to_map(&self) -> HashMap<String, bool> {
+        let flags = self.flags.read().unwrap();
+        flags.iter().map(|(name, flag)| (name.clone(), flag.enabled)).collect()
+    }
+
+    /// Clear all feature flags
+    pub fn clear(&self) {
+        let mut flags = self.flags.write().unwrap();
+        flags.clear();
+    }
+
+    /// Get the number of feature flags
+    ///
+    /// # Returns
+    ///
+    /// The number of flags currently registered
+    pub fn count(&self) -> usize {
+        let flags = self.flags.read().unwrap();
+        flags.len()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_basic_flag() {
+        let manager = FeatureFlagManager::new();
+
+        // Initially disabled
+        assert!(!manager.is_enabled("new_feature"));
+
+        // Enable flag
+        manager.set_flag("new_feature", true);
+        assert!(manager.is_enabled("new_feature"));
+
+        // Disable flag
+        manager.set_flag("new_feature", false);
+        assert!(!manager.is_enabled("new_feature"));
+    }
+
+    #[test]
+    fn test_flag_with_options() {
+        let manager = FeatureFlagManager::new();
+
+        manager.set_flag_with_options(
+            "beta_feature",
+            true,
+            Some("Beta testing feature".to_string()),
+            Some(0.5),
+        );
+
+        assert!(manager.is_enabled("beta_feature"));
+
+        let flag = manager.get_flag("beta_feature").unwrap();
+        assert_eq!(flag.description, Some("Beta testing feature".to_string()));
+        assert_eq!(flag.rollout_percentage, Some(0.5));
+    }
+
+    #[test]
+    fn test_load_from_map() {
+        let manager = FeatureFlagManager::new();
+
+        let mut config = HashMap::new();
+        config.insert("flag1".to_string(), true);
+        config.insert("flag2".to_string(), false);
+
+        manager.load_from_map(config);
+
+        assert!(manager.is_enabled("flag1"));
+        assert!(!manager.is_enabled("flag2"));
+        assert_eq!(manager.count(), 2);
+    }
+
+    #[test]
+    fn test_get_all_flags() {
+        let manager = FeatureFlagManager::new();
+
+        manager.set_flag("flag1", true);
+        manager.set_flag("flag2", false);
+
+        let all_flags = manager.get_all_flags();
+        assert_eq!(all_flags.len(), 2);
+    }
+
+    #[test]
+    fn test_remove_flag() {
+        let manager = FeatureFlagManager::new();
+
+        manager.set_flag("temp_flag", true);
+        assert!(manager.is_enabled("temp_flag"));
+
+        manager.remove_flag("temp_flag");
+        assert!(!manager.is_enabled("temp_flag"));
+        assert_eq!(manager.count(), 0);
+    }
+
+    #[test]
+    fn test_export_to_map() {
+        let manager = FeatureFlagManager::new();
+
+        manager.set_flag("flag1", true);
+        manager.set_flag("flag2", false);
+
+        let exported = manager.export_to_map();
+        assert_eq!(exported.get("flag1"), Some(&true));
+        assert_eq!(exported.get("flag2"), Some(&false));
+    }
+
+    #[test]
+    fn test_clear() {
+        let manager = FeatureFlagManager::new();
+
+        manager.set_flag("flag1", true);
+        manager.set_flag("flag2", true);
+        assert_eq!(manager.count(), 2);
+
+        manager.clear();
+        assert_eq!(manager.count(), 0);
+    }
+
+    #[test]
+    fn test_thread_safety() {
+        use std::thread;
+
+        let manager = FeatureFlagManager::new();
+        let manager_clone = manager.clone();
+
+        // Spawn thread to set flag
+        let handle = thread::spawn(move || {
+            manager_clone.set_flag("concurrent_flag", true);
+        });
+
+        handle.join().unwrap();
+
+        // Check flag is set
+        assert!(manager.is_enabled("concurrent_flag"));
+    }
+}
diff --git a/crates/miyabi-core/src/git.rs b/crates/miyabi-core/src/git.rs
new file mode 100644
index 0000000..60e7a83
--- /dev/null
+++ b/crates/miyabi-core/src/git.rs
@@ -0,0 +1,211 @@
+//! Git utilities for repository discovery and validation
+//!
+//! Provides utilities for working with Git repositories:
+//! - Repository root discovery from any subdirectory
+//! - Repository validation
+//! - Branch detection
+
+use crate::error::{Error, Result};
+use std::path::{Path, PathBuf};
+
+/// Find the Git repository root from the current directory or any subdirectory
+///
+/// This function uses Git's discovery mechanism to walk up the directory tree
+/// until it finds a `.git` directory.
+///
+/// # Examples
+///
+/// ```no_run
+/// use miyabi_core::git::find_git_root;
+///
+/// let root = find_git_root(None)?;
+/// println!("Git root: {:?}", root);
+/// # Ok::<(), miyabi_core::error::Error>(())
+/// ```
+pub fn find_git_root(start_path: Option<&Path>) -> Result<PathBuf> {
+    let search_path = match start_path {
+        Some(p) => p.to_path_buf(),
+        None => std::env::current_dir()?,
+    };
+
+    match git2::Repository::discover(&search_path) {
+        Ok(repo) => repo
+            .workdir()
+            .map(|p| p.to_path_buf())
+            .ok_or_else(|| {
+                Error::Git(
+                    "Repository is bare (no working directory). Miyabi requires a non-bare repository.".to_string()
+                )
+            }),
+        Err(e) => Err(Error::Git(format!(
+            "Not in a Git repository. Please run miyabi from within a Git repository.\n\
+             Searched from: {:?}\n\
+             Git error: {}\n\n\
+             To initialize a new repository, run: git init",
+            search_path, e
+        ))),
+    }
+}
+
+/// Validate that a path is a valid Git repository
+///
+/// # Arguments
+/// * `path` - Path to validate
+///
+/// # Returns
+/// `true` if the path is a valid Git repository with a working directory
+pub fn is_valid_repository(path: impl AsRef<Path>) -> bool {
+    match git2::Repository::open(path.as_ref()) {
+        Ok(repo) => repo.workdir().is_some(),
+        Err(_) => false,
+    }
+}
+
+/// Check if a path is within a Git repository
+///
+/// # Arguments
+/// * `path` - Path to check
+///
+/// # Returns
+/// `true` if the path is within a Git repository
+pub fn is_in_git_repo(path: impl AsRef<Path>) -> bool {
+    git2::Repository::discover(path.as_ref()).is_ok()
+}
+
+/// Get the current branch name of a repository
+///
+/// # Arguments
+/// * `repo_path` - Path to the repository
+///
+/// # Returns
+/// The name of the currently checked out branch
+///
+/// # Errors
+/// Returns an error if the repository is in a detached HEAD state or cannot be opened
+pub fn get_current_branch(repo_path: impl AsRef<Path>) -> Result<String> {
+    let repo = git2::Repository::open(repo_path.as_ref())
+        .map_err(|e| Error::Git(format!("Failed to open repository: {}", e)))?;
+
+    let head = repo
+        .head()
+        .map_err(|e| Error::Git(format!("Failed to get HEAD: {}", e)))?;
+
+    if !head.is_branch() {
+        return Err(Error::Git(
+            "Repository is in detached HEAD state. Please checkout a branch.".to_string(),
+        ));
+    }
+
+    head.shorthand()
+        .map(|s| s.to_string())
+        .ok_or_else(|| Error::Git("Failed to get branch name".to_string()))
+}
+
+/// Get the main branch name (tries 'main' then 'master')
+///
+/// # Arguments
+/// * `repo_path` - Path to the repository
+///
+/// # Returns
+/// The name of the main branch ('main' or 'master')
+///
+/// # Errors
+/// Returns an error if neither 'main' nor 'master' branch exists
+pub fn get_main_branch(repo_path: impl AsRef<Path>) -> Result<String> {
+    let repo = git2::Repository::open(repo_path.as_ref())
+        .map_err(|e| Error::Git(format!("Failed to open repository: {}", e)))?;
+
+    if repo.find_branch("main", git2::BranchType::Local).is_ok() {
+        Ok("main".to_string())
+    } else if repo.find_branch("master", git2::BranchType::Local).is_ok() {
+        Ok("master".to_string())
+    } else {
+        Err(Error::Git(
+            "Neither 'main' nor 'master' branch found. Please create a main branch.".to_string(),
+        ))
+    }
+}
+
+/// Check if the repository has uncommitted changes
+///
+/// # Arguments
+/// * `repo_path` - Path to the repository
+///
+/// # Returns
+/// `true` if there are uncommitted changes in the working directory or index
+pub fn has_uncommitted_changes(repo_path: impl AsRef<Path>) -> Result<bool> {
+    let repo = git2::Repository::open(repo_path.as_ref())
+        .map_err(|e| Error::Git(format!("Failed to open repository: {}", e)))?;
+
+    let statuses = repo
+        .statuses(None)
+        .map_err(|e| Error::Git(format!("Failed to get repository status: {}", e)))?;
+
+    Ok(!statuses.is_empty())
+}
+
+/// Get the short hash of HEAD
+pub fn get_head_short_hash(repo_path: impl AsRef<Path>) -> Result<String> {
+    let repo = git2::Repository::open(repo_path.as_ref())
+        .map_err(|e| Error::Git(format!("Failed to open repository: {}", e)))?;
+
+    let head = repo
+        .head()
+        .map_err(|e| Error::Git(format!("Failed to get HEAD: {}", e)))?;
+
+    let commit = head
+        .peel_to_commit()
+        .map_err(|e| Error::Git(format!("Failed to get commit: {}", e)))?;
+
+    Ok(commit.id().to_string()[..7].to_string())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::fs;
+    use tempfile::TempDir;
+
+    fn setup_test_repo() -> (TempDir, PathBuf) {
+        let temp_dir = TempDir::new().unwrap();
+        let repo_path = temp_dir.path().to_path_buf();
+        git2::Repository::init(&repo_path).unwrap();
+        (temp_dir, repo_path)
+    }
+
+    #[test]
+    fn test_find_git_root_from_root() {
+        let (_temp, repo_path) = setup_test_repo();
+        let found_root = find_git_root(Some(&repo_path)).unwrap();
+        let canonical_found = fs::canonicalize(&found_root).unwrap();
+        let canonical_expected = fs::canonicalize(&repo_path).unwrap();
+        assert_eq!(canonical_found, canonical_expected);
+    }
+
+    #[test]
+    fn test_find_git_root_from_subdirectory() {
+        let (_temp, repo_path) = setup_test_repo();
+        let sub_dir = repo_path.join("src").join("nested");
+        fs::create_dir_all(&sub_dir).unwrap();
+        let found_root = find_git_root(Some(&sub_dir)).unwrap();
+        let canonical_found = fs::canonicalize(&found_root).unwrap();
+        let canonical_expected = fs::canonicalize(&repo_path).unwrap();
+        assert_eq!(canonical_found, canonical_expected);
+    }
+
+    #[test]
+    fn test_is_valid_repository() {
+        let (_temp, repo_path) = setup_test_repo();
+        assert!(is_valid_repository(&repo_path));
+        let temp_dir = TempDir::new().unwrap();
+        assert!(!is_valid_repository(temp_dir.path()));
+    }
+
+    #[test]
+    fn test_is_in_git_repo() {
+        let (_temp, repo_path) = setup_test_repo();
+        assert!(is_in_git_repo(&repo_path));
+        let temp_dir = TempDir::new().unwrap();
+        assert!(!is_in_git_repo(temp_dir.path()));
+    }
+}
diff --git a/crates/miyabi-core/src/hooks.rs b/crates/miyabi-core/src/hooks.rs
new file mode 100644
index 0000000..a8bec17
--- /dev/null
+++ b/crates/miyabi-core/src/hooks.rs
@@ -0,0 +1,502 @@
+//! Hooks System for Event-Driven Execution
+//!
+//! Provides a system for registering and executing hooks based on events.
+
+use anyhow::Result;
+use serde::{Deserialize, Serialize};
+use std::collections::HashMap;
+use std::path::PathBuf;
+
+/// Hook event types
+#[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum HookEvent {
+    /// Before sending a message
+    PreMessage,
+    /// After receiving a response
+    PostMessage,
+    /// Before executing a tool
+    PreTool,
+    /// After tool execution
+    PostTool,
+    /// Before committing changes
+    PreCommit,
+    /// After committing changes
+    PostCommit,
+    /// On session start
+    SessionStart,
+    /// On session end
+    SessionEnd,
+    /// On error
+    OnError,
+    /// Custom event
+    Custom(String),
+}
+
+impl std::fmt::Display for HookEvent {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            HookEvent::PreMessage => write!(f, "pre_message"),
+            HookEvent::PostMessage => write!(f, "post_message"),
+            HookEvent::PreTool => write!(f, "pre_tool"),
+            HookEvent::PostTool => write!(f, "post_tool"),
+            HookEvent::PreCommit => write!(f, "pre_commit"),
+            HookEvent::PostCommit => write!(f, "post_commit"),
+            HookEvent::SessionStart => write!(f, "session_start"),
+            HookEvent::SessionEnd => write!(f, "session_end"),
+            HookEvent::OnError => write!(f, "on_error"),
+            HookEvent::Custom(name) => write!(f, "custom:{}", name),
+        }
+    }
+}
+
+/// Hook action types
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(tag = "type", rename_all = "snake_case")]
+pub enum HookAction {
+    /// Run a shell command
+    Shell { command: String },
+    /// Run an agent with a prompt
+    Agent {
+        prompt: String,
+        #[serde(default)]
+        spec: Option<String>,
+    },
+    /// Send a notification
+    Notify { title: String, message: String },
+    /// Log a message
+    Log { level: String, message: String },
+    /// Execute a script file
+    Script { path: PathBuf },
+}
+
+/// A single hook definition
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct Hook {
+    /// Hook name for identification
+    pub name: String,
+    /// Event that triggers this hook
+    pub event: HookEvent,
+    /// Action to perform
+    pub action: HookAction,
+    /// Whether the hook is enabled
+    #[serde(default = "default_true")]
+    pub enabled: bool,
+    /// Optional condition (tool name, etc.)
+    #[serde(default)]
+    pub condition: Option<String>,
+    /// Timeout in seconds
+    #[serde(default = "default_timeout")]
+    pub timeout: u64,
+}
+
+fn default_true() -> bool {
+    true
+}
+
+fn default_timeout() -> u64 {
+    30
+}
+
+/// Hook execution context
+#[derive(Debug, Clone, Default)]
+pub struct HookContext {
+    /// Event-specific data
+    pub data: HashMap<String, String>,
+    /// Tool name (for tool events)
+    pub tool_name: Option<String>,
+    /// Tool result (for post_tool)
+    pub tool_result: Option<String>,
+    /// Error message (for on_error)
+    pub error: Option<String>,
+}
+
+impl HookContext {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    pub fn with_tool(mut self, name: &str) -> Self {
+        self.tool_name = Some(name.to_string());
+        self
+    }
+
+    pub fn with_result(mut self, result: &str) -> Self {
+        self.tool_result = Some(result.to_string());
+        self
+    }
+
+    pub fn with_error(mut self, error: &str) -> Self {
+        self.error = Some(error.to_string());
+        self
+    }
+
+    pub fn with_data(mut self, key: &str, value: &str) -> Self {
+        self.data.insert(key.to_string(), value.to_string());
+        self
+    }
+}
+
+/// Hook execution result
+#[derive(Debug)]
+pub struct HookResult {
+    pub hook_name: String,
+    pub success: bool,
+    pub output: Option<String>,
+    pub error: Option<String>,
+}
+
+/// Hooks configuration
+#[derive(Debug, Clone, Default, Serialize, Deserialize)]
+pub struct HooksConfig {
+    /// List of hooks
+    #[serde(default)]
+    pub hooks: Vec<Hook>,
+}
+
+impl HooksConfig {
+    /// Load hooks from a YAML file
+    pub fn load(path: &PathBuf) -> Result<Self> {
+        let content = std::fs::read_to_string(path)?;
+        let config: HooksConfig = serde_yaml::from_str(&content)?;
+        Ok(config)
+    }
+
+    /// Load hooks from default location (~/.miyabi/hooks.yml)
+    pub fn load_default() -> Result<Self> {
+        let home = dirs::home_dir().unwrap_or_else(|| PathBuf::from("."));
+        let path = home.join(".miyabi").join("hooks.yml");
+        if path.exists() {
+            Self::load(&path)
+        } else {
+            Ok(Self::default())
+        }
+    }
+
+    /// Save hooks to a file
+    pub fn save(&self, path: &PathBuf) -> Result<()> {
+        let content = serde_yaml::to_string(self)?;
+        std::fs::write(path, content)?;
+        Ok(())
+    }
+}
+
+/// Hook manager for registering and executing hooks
+pub struct HookManager {
+    hooks: Vec<Hook>,
+}
+
+impl Default for HookManager {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl HookManager {
+    /// Create a new hook manager
+    pub fn new() -> Self {
+        Self { hooks: Vec::new() }
+    }
+
+    /// Create from config
+    pub fn from_config(config: HooksConfig) -> Self {
+        Self {
+            hooks: config.hooks,
+        }
+    }
+
+    /// Load hooks from default location
+    pub fn load_default() -> Result<Self> {
+        let config = HooksConfig::load_default()?;
+        Ok(Self::from_config(config))
+    }
+
+    /// Register a hook
+    pub fn register(&mut self, hook: Hook) {
+        self.hooks.push(hook);
+    }
+
+    /// Get hooks for an event
+    pub fn get_hooks(&self, event: &HookEvent) -> Vec<&Hook> {
+        self.hooks
+            .iter()
+            .filter(|h| h.enabled && &h.event == event)
+            .collect()
+    }
+
+    /// Execute hooks for an event
+    pub async fn execute(&self, event: &HookEvent, context: &HookContext) -> Vec<HookResult> {
+        let hooks = self.get_hooks(event);
+        let mut results = Vec::new();
+
+        for hook in hooks {
+            // Check condition
+            if let Some(condition) = &hook.condition {
+                if let Some(tool_name) = &context.tool_name {
+                    if condition != tool_name {
+                        continue;
+                    }
+                }
+            }
+
+            let result = self.execute_hook(hook, context).await;
+            results.push(result);
+        }
+
+        results
+    }
+
+    /// Execute a single hook
+    async fn execute_hook(&self, hook: &Hook, context: &HookContext) -> HookResult {
+        match &hook.action {
+            HookAction::Shell { command } => {
+                let expanded = self.expand_variables(command, context);
+                match self.run_shell_command(&expanded, hook.timeout).await {
+                    Ok(output) => HookResult {
+                        hook_name: hook.name.clone(),
+                        success: true,
+                        output: Some(output),
+                        error: None,
+                    },
+                    Err(e) => HookResult {
+                        hook_name: hook.name.clone(),
+                        success: false,
+                        output: None,
+                        error: Some(e.to_string()),
+                    },
+                }
+            }
+            HookAction::Notify { title, message } => {
+                let expanded_title = self.expand_variables(title, context);
+                let expanded_message = self.expand_variables(message, context);
+                // For now, just log the notification
+                tracing::info!("Hook notification: {} - {}", expanded_title, expanded_message);
+                HookResult {
+                    hook_name: hook.name.clone(),
+                    success: true,
+                    output: Some(format!("{}: {}", expanded_title, expanded_message)),
+                    error: None,
+                }
+            }
+            HookAction::Log { level, message } => {
+                let expanded = self.expand_variables(message, context);
+                match level.as_str() {
+                    "error" => tracing::error!("Hook: {}", expanded),
+                    "warn" => tracing::warn!("Hook: {}", expanded),
+                    "info" => tracing::info!("Hook: {}", expanded),
+                    "debug" => tracing::debug!("Hook: {}", expanded),
+                    _ => tracing::info!("Hook: {}", expanded),
+                }
+                HookResult {
+                    hook_name: hook.name.clone(),
+                    success: true,
+                    output: Some(expanded),
+                    error: None,
+                }
+            }
+            HookAction::Script { path } => {
+                if !path.exists() {
+                    return HookResult {
+                        hook_name: hook.name.clone(),
+                        success: false,
+                        output: None,
+                        error: Some(format!("Script not found: {:?}", path)),
+                    };
+                }
+                let command = path.to_string_lossy().to_string();
+                match self.run_shell_command(&command, hook.timeout).await {
+                    Ok(output) => HookResult {
+                        hook_name: hook.name.clone(),
+                        success: true,
+                        output: Some(output),
+                        error: None,
+                    },
+                    Err(e) => HookResult {
+                        hook_name: hook.name.clone(),
+                        success: false,
+                        output: None,
+                        error: Some(e.to_string()),
+                    },
+                }
+            }
+            HookAction::Agent { prompt, spec: _ } => {
+                // Agent execution would require the full agent infrastructure
+                // For now, return a placeholder
+                let expanded = self.expand_variables(prompt, context);
+                HookResult {
+                    hook_name: hook.name.clone(),
+                    success: true,
+                    output: Some(format!("Agent prompt: {}", expanded)),
+                    error: None,
+                }
+            }
+        }
+    }
+
+    /// Expand variables in a string
+    fn expand_variables(&self, input: &str, context: &HookContext) -> String {
+        let mut result = input.to_string();
+
+        // Replace context variables
+        if let Some(tool_name) = &context.tool_name {
+            result = result.replace("${tool_name}", tool_name);
+        }
+        if let Some(tool_result) = &context.tool_result {
+            result = result.replace("${tool_result}", tool_result);
+        }
+        if let Some(error) = &context.error {
+            result = result.replace("${error}", error);
+        }
+
+        // Replace custom data
+        for (key, value) in &context.data {
+            result = result.replace(&format!("${{{}}}", key), value);
+        }
+
+        result
+    }
+
+    /// Run a shell command
+    async fn run_shell_command(&self, command: &str, timeout_secs: u64) -> Result<String> {
+        use std::process::Stdio;
+        use tokio::process::Command;
+        use tokio::time::{timeout, Duration};
+
+        let output = timeout(
+            Duration::from_secs(timeout_secs),
+            Command::new("sh")
+                .arg("-c")
+                .arg(command)
+                .stdout(Stdio::piped())
+                .stderr(Stdio::piped())
+                .output(),
+        )
+        .await??;
+
+        if output.status.success() {
+            Ok(String::from_utf8_lossy(&output.stdout).to_string())
+        } else {
+            let stderr = String::from_utf8_lossy(&output.stderr);
+            Err(anyhow::anyhow!("Command failed: {}", stderr))
+        }
+    }
+
+    /// Get all registered hooks
+    pub fn list_hooks(&self) -> &[Hook] {
+        &self.hooks
+    }
+
+    /// Enable a hook by name
+    pub fn enable(&mut self, name: &str) {
+        for hook in &mut self.hooks {
+            if hook.name == name {
+                hook.enabled = true;
+            }
+        }
+    }
+
+    /// Disable a hook by name
+    pub fn disable(&mut self, name: &str) {
+        for hook in &mut self.hooks {
+            if hook.name == name {
+                hook.enabled = false;
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_hook_event_display() {
+        assert_eq!(HookEvent::PreMessage.to_string(), "pre_message");
+        assert_eq!(HookEvent::PostTool.to_string(), "post_tool");
+        assert_eq!(
+            HookEvent::Custom("test".to_string()).to_string(),
+            "custom:test"
+        );
+    }
+
+    #[test]
+    fn test_hook_context() {
+        let context = HookContext::new()
+            .with_tool("bash")
+            .with_result("success")
+            .with_data("key", "value");
+
+        assert_eq!(context.tool_name, Some("bash".to_string()));
+        assert_eq!(context.tool_result, Some("success".to_string()));
+        assert_eq!(context.data.get("key"), Some(&"value".to_string()));
+    }
+
+    #[test]
+    fn test_expand_variables() {
+        let manager = HookManager::new();
+        let context = HookContext::new()
+            .with_tool("bash")
+            .with_result("ok")
+            .with_data("name", "test");
+
+        let input = "Tool: ${tool_name}, Result: ${tool_result}, Name: ${name}";
+        let expanded = manager.expand_variables(input, &context);
+        assert_eq!(expanded, "Tool: bash, Result: ok, Name: test");
+    }
+
+    #[test]
+    fn test_hook_config_serialization() {
+        let config = HooksConfig {
+            hooks: vec![Hook {
+                name: "test".to_string(),
+                event: HookEvent::PostTool,
+                action: HookAction::Log {
+                    level: "info".to_string(),
+                    message: "Tool completed".to_string(),
+                },
+                enabled: true,
+                condition: Some("bash".to_string()),
+                timeout: 30,
+            }],
+        };
+
+        let yaml = serde_yaml::to_string(&config).unwrap();
+        assert!(yaml.contains("post_tool"));
+        assert!(yaml.contains("bash"));
+    }
+
+    #[test]
+    fn test_hook_manager_get_hooks() {
+        let mut manager = HookManager::new();
+        manager.register(Hook {
+            name: "hook1".to_string(),
+            event: HookEvent::PreTool,
+            action: HookAction::Log {
+                level: "info".to_string(),
+                message: "test".to_string(),
+            },
+            enabled: true,
+            condition: None,
+            timeout: 30,
+        });
+        manager.register(Hook {
+            name: "hook2".to_string(),
+            event: HookEvent::PostTool,
+            action: HookAction::Log {
+                level: "info".to_string(),
+                message: "test".to_string(),
+            },
+            enabled: true,
+            condition: None,
+            timeout: 30,
+        });
+
+        let pre_hooks = manager.get_hooks(&HookEvent::PreTool);
+        assert_eq!(pre_hooks.len(), 1);
+        assert_eq!(pre_hooks[0].name, "hook1");
+
+        let post_hooks = manager.get_hooks(&HookEvent::PostTool);
+        assert_eq!(post_hooks.len(), 1);
+        assert_eq!(post_hooks[0].name, "hook2");
+    }
+}
diff --git a/crates/miyabi-core/src/lib.rs b/crates/miyabi-core/src/lib.rs
index e565291..3b14089 100644
--- a/crates/miyabi-core/src/lib.rs
+++ b/crates/miyabi-core/src/lib.rs
@@ -13,15 +13,18 @@ pub mod feature_flags;
 pub mod git;
 pub mod github;
 pub mod github_tools;
+pub mod hooks;
 pub mod logger;
 pub mod plugin;
 pub mod retry;
 pub mod rules;
+pub mod mcp;
 pub mod session;
 pub mod token;
 pub mod tool;
 pub mod tools;
 pub mod types;
+pub mod workflow;
 
 pub use agent::{
     Agent, AgentConfig, AgentError, AgentEvent, AgentResult, ExecutorRegistry, RiskLevel,
@@ -64,6 +67,7 @@ pub use github_tools::{
     create_github_tool_registry, AddCommentTool, AddLabelsTool, CreateIssueTool,
     CreatePullRequestTool, GetIssueTool, ListIssuesTool, ListPullRequestsTool,
 };
+pub use hooks::{Hook, HookAction, HookContext, HookEvent, HookManager, HookResult, HooksConfig};
 pub use logger::{init_logger, init_logger_with_config, LogFormat, LogLevel, LoggerConfig};
 pub use plugin::{Plugin, PluginContext, PluginManager, PluginMetadata, PluginResult, PluginState};
 pub use retry::{retry_with_backoff, RetryConfig as BackoffRetryConfig};
@@ -76,3 +80,10 @@ pub use tools::{
     GrepTool, ReadTool, WriteTool,
 };
 pub use types::*;
+pub use workflow::{
+    FailurePolicy, StepCondition, StepResult, StepStatus, Workflow, WorkflowContext,
+    WorkflowManager, WorkflowResult, WorkflowStatus, WorkflowStep,
+};
+pub use mcp::{
+    McpConfig, McpError, McpManager, McpRequest, McpResponse, McpServer, McpServerConfig, McpTool,
+};
diff --git a/crates/miyabi-core/src/logger.rs b/crates/miyabi-core/src/logger.rs
new file mode 100644
index 0000000..1f776eb
--- /dev/null
+++ b/crates/miyabi-core/src/logger.rs
@@ -0,0 +1,158 @@
+//! Logging utilities for Miyabi
+//!
+//! Provides structured logging with multiple output formats
+
+use tracing_subscriber::{fmt, layer::SubscriberExt, prelude::*, EnvFilter};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum LogLevel {
+    Trace,
+    Debug,
+    Info,
+    Warn,
+    Error,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum LogFormat {
+    /// Human-readable colored output
+    Pretty,
+    /// Compact format for CI/CD
+    Compact,
+    /// JSON format for structured parsing
+    Json,
+}
+
+/// Logger configuration
+#[derive(Debug, Clone)]
+pub struct LoggerConfig {
+    /// Log level
+    pub level: LogLevel,
+    /// Log format
+    pub format: LogFormat,
+}
+
+impl Default for LoggerConfig {
+    fn default() -> Self {
+        Self {
+            level: LogLevel::Info,
+            format: LogFormat::Pretty,
+        }
+    }
+}
+
+impl From<&str> for LogLevel {
+    fn from(s: &str) -> Self {
+        match s.to_lowercase().as_str() {
+            "trace" => LogLevel::Trace,
+            "debug" => LogLevel::Debug,
+            "info" => LogLevel::Info,
+            "warn" => LogLevel::Warn,
+            "error" => LogLevel::Error,
+            _ => LogLevel::Info,
+        }
+    }
+}
+
+impl From<LogLevel> for &'static str {
+    fn from(level: LogLevel) -> Self {
+        match level {
+            LogLevel::Trace => "trace",
+            LogLevel::Debug => "debug",
+            LogLevel::Info => "info",
+            LogLevel::Warn => "warn",
+            LogLevel::Error => "error",
+        }
+    }
+}
+
+impl From<&str> for LogFormat {
+    fn from(s: &str) -> Self {
+        match s.to_lowercase().as_str() {
+            "json" => LogFormat::Json,
+            "compact" => LogFormat::Compact,
+            _ => LogFormat::Pretty,
+        }
+    }
+}
+
+/// Initialize logging with default configuration
+pub fn init_logger(level: LogLevel) {
+    let config = LoggerConfig {
+        level,
+        ..Default::default()
+    };
+    init_logger_with_config(config);
+}
+
+/// Initialize logging with custom configuration
+pub fn init_logger_with_config(config: LoggerConfig) {
+    let level_str: &'static str = config.level.into();
+    let filter = EnvFilter::try_from_default_env().unwrap_or_else(|_| EnvFilter::new(level_str));
+
+    let subscriber = tracing_subscriber::registry().with(filter);
+
+    match config.format {
+        LogFormat::Pretty => {
+            let fmt_layer = fmt::layer()
+                .pretty()
+                .with_target(true)
+                .with_thread_ids(false)
+                .with_line_number(true);
+            subscriber.with(fmt_layer).init();
+        }
+        LogFormat::Compact => {
+            let fmt_layer = fmt::layer()
+                .compact()
+                .with_target(false)
+                .with_thread_ids(false);
+            subscriber.with(fmt_layer).init();
+        }
+        LogFormat::Json => {
+            let fmt_layer = fmt::layer()
+                .json()
+                .with_current_span(true)
+                .with_span_list(true);
+            subscriber.with(fmt_layer).init();
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_log_level_from_str() {
+        assert_eq!(LogLevel::from("trace"), LogLevel::Trace);
+        assert_eq!(LogLevel::from("debug"), LogLevel::Debug);
+        assert_eq!(LogLevel::from("info"), LogLevel::Info);
+        assert_eq!(LogLevel::from("warn"), LogLevel::Warn);
+        assert_eq!(LogLevel::from("error"), LogLevel::Error);
+        assert_eq!(LogLevel::from("invalid"), LogLevel::Info);
+    }
+
+    #[test]
+    fn test_log_level_to_str() {
+        let level_str: &'static str = LogLevel::Trace.into();
+        assert_eq!(level_str, "trace");
+
+        let level_str: &'static str = LogLevel::Info.into();
+        assert_eq!(level_str, "info");
+    }
+
+    #[test]
+    fn test_log_format_from_str() {
+        assert_eq!(LogFormat::from("json"), LogFormat::Json);
+        assert_eq!(LogFormat::from("compact"), LogFormat::Compact);
+        assert_eq!(LogFormat::from("pretty"), LogFormat::Pretty);
+        assert_eq!(LogFormat::from("invalid"), LogFormat::Pretty);
+    }
+
+    #[test]
+    fn test_logger_config_default() {
+        let config = LoggerConfig::default();
+        assert_eq!(config.level, LogLevel::Info);
+        assert_eq!(config.format, LogFormat::Pretty);
+    }
+}
diff --git a/crates/miyabi-core/src/mcp.rs b/crates/miyabi-core/src/mcp.rs
new file mode 100644
index 0000000..a6863ec
--- /dev/null
+++ b/crates/miyabi-core/src/mcp.rs
@@ -0,0 +1,407 @@
+//! MCP (Model Context Protocol) Support
+//!
+//! Integration with external MCP tool servers.
+
+use anyhow::Result;
+use serde::{Deserialize, Serialize};
+use std::collections::HashMap;
+use std::path::PathBuf;
+use std::process::Stdio;
+use tokio::io::{AsyncBufReadExt, AsyncWriteExt, BufReader};
+use tokio::process::{Child, Command};
+
+/// MCP server configuration
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct McpServerConfig {
+    /// Server name
+    pub name: String,
+    /// Command to start the server
+    pub command: String,
+    /// Command arguments
+    #[serde(default)]
+    pub args: Vec<String>,
+    /// Environment variables
+    #[serde(default)]
+    pub env: HashMap<String, String>,
+    /// Whether to auto-start
+    #[serde(default = "default_true")]
+    pub auto_start: bool,
+}
+
+fn default_true() -> bool {
+    true
+}
+
+/// MCP servers configuration
+#[derive(Debug, Clone, Default, Serialize, Deserialize)]
+pub struct McpConfig {
+    /// List of server configurations
+    #[serde(default)]
+    pub servers: Vec<McpServerConfig>,
+}
+
+impl McpConfig {
+    /// Load configuration from a YAML file
+    pub fn load(path: &PathBuf) -> Result<Self> {
+        let content = std::fs::read_to_string(path)?;
+        let config: McpConfig = serde_yaml::from_str(&content)?;
+        Ok(config)
+    }
+
+    /// Load from default location (~/.miyabi/mcp.yml)
+    pub fn load_default() -> Result<Self> {
+        let home = dirs::home_dir().unwrap_or_else(|| PathBuf::from("."));
+        let path = home.join(".miyabi").join("mcp.yml");
+        if path.exists() {
+            Self::load(&path)
+        } else {
+            Ok(Self::default())
+        }
+    }
+
+    /// Save configuration to a file
+    pub fn save(&self, path: &PathBuf) -> Result<()> {
+        let content = serde_yaml::to_string(self)?;
+        std::fs::write(path, content)?;
+        Ok(())
+    }
+}
+
+/// MCP JSON-RPC request
+#[derive(Debug, Clone, Serialize)]
+pub struct McpRequest {
+    pub jsonrpc: String,
+    pub id: u64,
+    pub method: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub params: Option<serde_json::Value>,
+}
+
+/// MCP JSON-RPC response
+#[derive(Debug, Clone, Deserialize)]
+pub struct McpResponse {
+    pub jsonrpc: String,
+    pub id: u64,
+    #[serde(default)]
+    pub result: Option<serde_json::Value>,
+    #[serde(default)]
+    pub error: Option<McpError>,
+}
+
+/// MCP error
+#[derive(Debug, Clone, Deserialize)]
+pub struct McpError {
+    pub code: i32,
+    pub message: String,
+    #[serde(default)]
+    pub data: Option<serde_json::Value>,
+}
+
+/// MCP tool definition
+#[derive(Debug, Clone, Deserialize)]
+pub struct McpTool {
+    pub name: String,
+    pub description: String,
+    #[serde(default)]
+    pub input_schema: Option<serde_json::Value>,
+}
+
+/// MCP server connection
+pub struct McpServer {
+    pub name: String,
+    process: Child,
+    request_id: u64,
+}
+
+impl McpServer {
+    /// Start a new MCP server
+    pub async fn start(config: &McpServerConfig) -> Result<Self> {
+        let mut cmd = Command::new(&config.command);
+        cmd.args(&config.args)
+            .stdin(Stdio::piped())
+            .stdout(Stdio::piped())
+            .stderr(Stdio::piped());
+
+        for (key, value) in &config.env {
+            cmd.env(key, value);
+        }
+
+        let process = cmd.spawn()?;
+
+        Ok(Self {
+            name: config.name.clone(),
+            process,
+            request_id: 0,
+        })
+    }
+
+    /// Send a request and get a response
+    pub async fn request(&mut self, method: &str, params: Option<serde_json::Value>) -> Result<McpResponse> {
+        self.request_id += 1;
+        let request = McpRequest {
+            jsonrpc: "2.0".to_string(),
+            id: self.request_id,
+            method: method.to_string(),
+            params,
+        };
+
+        let stdin = self.process.stdin.as_mut()
+            .ok_or_else(|| anyhow::anyhow!("Failed to get stdin"))?;
+        let stdout = self.process.stdout.as_mut()
+            .ok_or_else(|| anyhow::anyhow!("Failed to get stdout"))?;
+
+        // Send request
+        let request_json = serde_json::to_string(&request)?;
+        stdin.write_all(request_json.as_bytes()).await?;
+        stdin.write_all(b"\n").await?;
+        stdin.flush().await?;
+
+        // Read response
+        let mut reader = BufReader::new(stdout);
+        let mut line = String::new();
+        reader.read_line(&mut line).await?;
+
+        let response: McpResponse = serde_json::from_str(&line)?;
+        Ok(response)
+    }
+
+    /// Initialize the server
+    pub async fn initialize(&mut self) -> Result<serde_json::Value> {
+        let params = serde_json::json!({
+            "protocolVersion": "2024-11-05",
+            "capabilities": {
+                "tools": {}
+            },
+            "clientInfo": {
+                "name": "miyabi",
+                "version": env!("CARGO_PKG_VERSION")
+            }
+        });
+
+        let response = self.request("initialize", Some(params)).await?;
+        if let Some(error) = response.error {
+            return Err(anyhow::anyhow!("MCP error: {}", error.message));
+        }
+
+        response.result.ok_or_else(|| anyhow::anyhow!("No result in response"))
+    }
+
+    /// List available tools
+    pub async fn list_tools(&mut self) -> Result<Vec<McpTool>> {
+        let response = self.request("tools/list", None).await?;
+        if let Some(error) = response.error {
+            return Err(anyhow::anyhow!("MCP error: {}", error.message));
+        }
+
+        let result = response.result.ok_or_else(|| anyhow::anyhow!("No result"))?;
+        let tools: Vec<McpTool> = serde_json::from_value(
+            result.get("tools").cloned().unwrap_or(serde_json::Value::Array(vec![]))
+        )?;
+
+        Ok(tools)
+    }
+
+    /// Call a tool
+    pub async fn call_tool(&mut self, name: &str, arguments: serde_json::Value) -> Result<serde_json::Value> {
+        let params = serde_json::json!({
+            "name": name,
+            "arguments": arguments
+        });
+
+        let response = self.request("tools/call", Some(params)).await?;
+        if let Some(error) = response.error {
+            return Err(anyhow::anyhow!("MCP error: {}", error.message));
+        }
+
+        response.result.ok_or_else(|| anyhow::anyhow!("No result"))
+    }
+
+    /// Shutdown the server
+    pub async fn shutdown(&mut self) -> Result<()> {
+        let _ = self.request("shutdown", None).await;
+        self.process.kill().await?;
+        Ok(())
+    }
+}
+
+/// MCP Manager for handling multiple servers
+pub struct McpManager {
+    servers: HashMap<String, McpServer>,
+    config: McpConfig,
+}
+
+impl McpManager {
+    /// Create a new MCP manager
+    pub fn new() -> Self {
+        Self {
+            servers: HashMap::new(),
+            config: McpConfig::default(),
+        }
+    }
+
+    /// Create from configuration
+    pub fn with_config(config: McpConfig) -> Self {
+        Self {
+            servers: HashMap::new(),
+            config,
+        }
+    }
+
+    /// Load configuration from default location
+    pub fn load_default() -> Result<Self> {
+        let config = McpConfig::load_default()?;
+        Ok(Self::with_config(config))
+    }
+
+    /// Start all configured servers
+    pub async fn start_all(&mut self) -> Result<()> {
+        let names: Vec<_> = self
+            .config
+            .servers
+            .iter()
+            .filter(|s| s.auto_start)
+            .map(|s| s.name.clone())
+            .collect();
+
+        for name in names {
+            self.start_server(&name).await?;
+        }
+        Ok(())
+    }
+
+    /// Start a specific server
+    pub async fn start_server(&mut self, name: &str) -> Result<()> {
+        let config = self
+            .config
+            .servers
+            .iter()
+            .find(|s| s.name == name)
+            .ok_or_else(|| anyhow::anyhow!("Server not found: {}", name))?
+            .clone();
+
+        let mut server = McpServer::start(&config).await?;
+        server.initialize().await?;
+        self.servers.insert(name.to_string(), server);
+        Ok(())
+    }
+
+    /// Stop a specific server
+    pub async fn stop_server(&mut self, name: &str) -> Result<()> {
+        if let Some(mut server) = self.servers.remove(name) {
+            server.shutdown().await?;
+        }
+        Ok(())
+    }
+
+    /// Stop all servers
+    pub async fn stop_all(&mut self) -> Result<()> {
+        let names: Vec<_> = self.servers.keys().cloned().collect();
+        for name in names {
+            self.stop_server(&name).await?;
+        }
+        Ok(())
+    }
+
+    /// Get a server by name
+    pub fn get_server(&mut self, name: &str) -> Option<&mut McpServer> {
+        self.servers.get_mut(name)
+    }
+
+    /// List all available tools across all servers
+    pub async fn list_all_tools(&mut self) -> Result<HashMap<String, Vec<McpTool>>> {
+        let mut all_tools = HashMap::new();
+        let names: Vec<_> = self.servers.keys().cloned().collect();
+
+        for name in names {
+            if let Some(server) = self.servers.get_mut(&name) {
+                let tools = server.list_tools().await?;
+                all_tools.insert(name, tools);
+            }
+        }
+
+        Ok(all_tools)
+    }
+
+    /// Call a tool on a specific server
+    pub async fn call_tool(
+        &mut self,
+        server_name: &str,
+        tool_name: &str,
+        arguments: serde_json::Value,
+    ) -> Result<serde_json::Value> {
+        let server = self
+            .get_server(server_name)
+            .ok_or_else(|| anyhow::anyhow!("Server not found: {}", server_name))?;
+
+        server.call_tool(tool_name, arguments).await
+    }
+
+    /// List running servers
+    pub fn list_servers(&self) -> Vec<&str> {
+        self.servers.keys().map(|s| s.as_str()).collect()
+    }
+
+    /// Check if a server is running
+    pub fn is_running(&self, name: &str) -> bool {
+        self.servers.contains_key(name)
+    }
+}
+
+impl Default for McpManager {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_mcp_config_serialization() {
+        let config = McpConfig {
+            servers: vec![McpServerConfig {
+                name: "filesystem".to_string(),
+                command: "npx".to_string(),
+                args: vec!["@anthropic/mcp-server-filesystem".to_string()],
+                env: HashMap::new(),
+                auto_start: true,
+            }],
+        };
+
+        let yaml = serde_yaml::to_string(&config).unwrap();
+        assert!(yaml.contains("filesystem"));
+        assert!(yaml.contains("npx"));
+    }
+
+    #[test]
+    fn test_mcp_request_serialization() {
+        let request = McpRequest {
+            jsonrpc: "2.0".to_string(),
+            id: 1,
+            method: "tools/list".to_string(),
+            params: None,
+        };
+
+        let json = serde_json::to_string(&request).unwrap();
+        assert!(json.contains("tools/list"));
+        assert!(!json.contains("params"));
+    }
+
+    #[test]
+    fn test_mcp_manager() {
+        let config = McpConfig {
+            servers: vec![McpServerConfig {
+                name: "test".to_string(),
+                command: "echo".to_string(),
+                args: vec![],
+                env: HashMap::new(),
+                auto_start: false,
+            }],
+        };
+
+        let manager = McpManager::with_config(config);
+        assert!(!manager.is_running("test"));
+        assert_eq!(manager.list_servers().len(), 0);
+    }
+}
diff --git a/crates/miyabi-core/src/plugin.rs b/crates/miyabi-core/src/plugin.rs
new file mode 100644
index 0000000..f14beb9
--- /dev/null
+++ b/crates/miyabi-core/src/plugin.rs
@@ -0,0 +1,408 @@
+//! Plugin system for Miyabi
+//!
+//! Provides a flexible plugin architecture for extending Miyabi functionality.
+//!
+//! # Example
+//!
+//! ```rust
+//! use miyabi_core::plugin::{Plugin, PluginManager, PluginMetadata, PluginContext, PluginResult};
+//! use anyhow::Result;
+//!
+//! struct MyPlugin;
+//!
+//! impl Plugin for MyPlugin {
+//!     fn metadata(&self) -> PluginMetadata {
+//!         PluginMetadata {
+//!             name: "my-plugin".to_string(),
+//!             version: "1.0.0".to_string(),
+//!             description: Some("My custom plugin".to_string()),
+//!             author: Some("Miyabi Team".to_string()),
+//!         }
+//!     }
+//!
+//!     fn init(&mut self) -> Result<()> {
+//!         println!("Plugin initialized!");
+//!         Ok(())
+//!     }
+//!
+//!     fn execute(&self, context: &PluginContext) -> Result<PluginResult> {
+//!         Ok(PluginResult {
+//!             success: true,
+//!             message: Some("Plugin executed successfully".to_string()),
+//!             data: None,
+//!         })
+//!     }
+//! }
+//! ```
+
+use anyhow::{anyhow, Result};
+use serde::{Deserialize, Serialize};
+use std::collections::HashMap;
+use std::sync::{Arc, RwLock};
+
+/// Plugin metadata information
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
+pub struct PluginMetadata {
+    /// Plugin name (unique identifier)
+    pub name: String,
+    /// Semantic version
+    pub version: String,
+    /// Optional description
+    pub description: Option<String>,
+    /// Optional author
+    pub author: Option<String>,
+}
+
+/// Plugin execution context
+#[derive(Debug, Clone, Default, Serialize, Deserialize)]
+pub struct PluginContext {
+    /// Plugin parameters
+    #[serde(default)]
+    pub params: HashMap<String, serde_json::Value>,
+    /// Working directory
+    pub working_dir: Option<String>,
+    /// Environment variables
+    #[serde(default)]
+    pub env: HashMap<String, String>,
+}
+
+/// Plugin execution result
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct PluginResult {
+    /// Execution success status
+    pub success: bool,
+    /// Optional result message
+    pub message: Option<String>,
+    /// Optional result data
+    pub data: Option<serde_json::Value>,
+}
+
+/// Core plugin trait
+///
+/// All plugins must implement this trait to be registered with the PluginManager.
+pub trait Plugin: Send + Sync {
+    /// Returns plugin metadata
+    fn metadata(&self) -> PluginMetadata;
+
+    /// Initializes the plugin
+    ///
+    /// Called once when the plugin is registered.
+    fn init(&mut self) -> Result<()>;
+
+    /// Executes the plugin with the given context
+    fn execute(&self, context: &PluginContext) -> Result<PluginResult>;
+
+    /// Cleans up plugin resources
+    ///
+    /// Called when the plugin is unregistered or the manager is dropped.
+    fn shutdown(&mut self) -> Result<()> {
+        Ok(())
+    }
+}
+
+/// Plugin lifecycle state
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum PluginState {
+    /// Plugin is registered but not initialized
+    Registered,
+    /// Plugin is initialized and ready
+    Initialized,
+    /// Plugin encountered an error
+    Error,
+    /// Plugin is shut down
+    Shutdown,
+}
+
+/// Internal plugin wrapper
+struct PluginEntry {
+    plugin: Box<dyn Plugin>,
+    state: PluginState,
+}
+
+/// Plugin manager
+///
+/// Manages plugin registration, initialization, and execution.
+#[derive(Clone)]
+pub struct PluginManager {
+    plugins: Arc<RwLock<HashMap<String, PluginEntry>>>,
+}
+
+impl PluginManager {
+    /// Creates a new plugin manager
+    pub fn new() -> Self {
+        Self {
+            plugins: Arc::new(RwLock::new(HashMap::new())),
+        }
+    }
+
+    /// Registers a plugin
+    ///
+    /// # Errors
+    ///
+    /// Returns an error if:
+    /// - A plugin with the same name already exists
+    /// - Plugin initialization fails
+    pub fn register(&self, mut plugin: Box<dyn Plugin>) -> Result<()> {
+        let metadata = plugin.metadata();
+        let name = metadata.name.clone();
+
+        // Check if plugin already exists
+        {
+            let plugins = self.plugins.read().unwrap();
+            if plugins.contains_key(&name) {
+                return Err(anyhow!("Plugin '{}' is already registered", name));
+            }
+        }
+
+        // Initialize plugin
+        plugin.init()?;
+
+        // Store plugin
+        let mut plugins = self.plugins.write().unwrap();
+        plugins.insert(
+            name.clone(),
+            PluginEntry {
+                plugin,
+                state: PluginState::Initialized,
+            },
+        );
+
+        Ok(())
+    }
+
+    /// Unregisters a plugin
+    ///
+    /// # Errors
+    ///
+    /// Returns an error if the plugin doesn't exist
+    pub fn unregister(&self, name: &str) -> Result<()> {
+        let mut plugins = self.plugins.write().unwrap();
+
+        let mut entry =
+            plugins.remove(name).ok_or_else(|| anyhow!("Plugin '{}' not found", name))?;
+
+        entry.plugin.shutdown()?;
+        entry.state = PluginState::Shutdown;
+
+        Ok(())
+    }
+
+    /// Executes a plugin with the given context
+    ///
+    /// # Errors
+    ///
+    /// Returns an error if:
+    /// - The plugin doesn't exist
+    /// - The plugin is not initialized
+    /// - Plugin execution fails
+    pub fn execute(&self, name: &str, context: &PluginContext) -> Result<PluginResult> {
+        let plugins = self.plugins.read().unwrap();
+
+        let entry = plugins.get(name).ok_or_else(|| anyhow!("Plugin '{}' not found", name))?;
+
+        if entry.state != PluginState::Initialized {
+            return Err(anyhow!("Plugin '{}' is not initialized (state: {:?})", name, entry.state));
+        }
+
+        entry.plugin.execute(context)
+    }
+
+    /// Lists all registered plugins
+    pub fn list_plugins(&self) -> Vec<PluginMetadata> {
+        let plugins = self.plugins.read().unwrap();
+        plugins.values().map(|entry| entry.plugin.metadata()).collect()
+    }
+
+    /// Gets plugin metadata
+    ///
+    /// # Errors
+    ///
+    /// Returns an error if the plugin doesn't exist
+    pub fn get_metadata(&self, name: &str) -> Result<PluginMetadata> {
+        let plugins = self.plugins.read().unwrap();
+        plugins
+            .get(name)
+            .map(|entry| entry.plugin.metadata())
+            .ok_or_else(|| anyhow!("Plugin '{}' not found", name))
+    }
+
+    /// Gets plugin state
+    ///
+    /// # Errors
+    ///
+    /// Returns an error if the plugin doesn't exist
+    pub fn get_state(&self, name: &str) -> Result<PluginState> {
+        let plugins = self.plugins.read().unwrap();
+        plugins
+            .get(name)
+            .map(|entry| entry.state)
+            .ok_or_else(|| anyhow!("Plugin '{}' not found", name))
+    }
+
+    /// Checks if a plugin exists
+    pub fn has_plugin(&self, name: &str) -> bool {
+        let plugins = self.plugins.read().unwrap();
+        plugins.contains_key(name)
+    }
+
+    /// Gets the number of registered plugins
+    pub fn count(&self) -> usize {
+        let plugins = self.plugins.read().unwrap();
+        plugins.len()
+    }
+}
+
+impl Default for PluginManager {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl Drop for PluginManager {
+    fn drop(&mut self) {
+        // Shutdown all plugins
+        if let Ok(mut plugins) = self.plugins.write() {
+            for (name, entry) in plugins.iter_mut() {
+                if let Err(e) = entry.plugin.shutdown() {
+                    eprintln!("Error shutting down plugin '{}': {}", name, e);
+                }
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    struct TestPlugin {
+        name: String,
+        initialized: bool,
+    }
+
+    impl TestPlugin {
+        fn new(name: &str) -> Self {
+            Self {
+                name: name.to_string(),
+                initialized: false,
+            }
+        }
+    }
+
+    impl Plugin for TestPlugin {
+        fn metadata(&self) -> PluginMetadata {
+            PluginMetadata {
+                name: self.name.clone(),
+                version: "1.0.0".to_string(),
+                description: Some("Test plugin".to_string()),
+                author: Some("Test Author".to_string()),
+            }
+        }
+
+        fn init(&mut self) -> Result<()> {
+            self.initialized = true;
+            Ok(())
+        }
+
+        fn execute(&self, _context: &PluginContext) -> Result<PluginResult> {
+            Ok(PluginResult {
+                success: true,
+                message: Some(format!("Plugin '{}' executed", self.name)),
+                data: None,
+            })
+        }
+    }
+
+    #[test]
+    fn test_register_plugin() {
+        let manager = PluginManager::new();
+        let plugin = Box::new(TestPlugin::new("test-plugin"));
+
+        assert!(manager.register(plugin).is_ok());
+        assert_eq!(manager.count(), 1);
+        assert!(manager.has_plugin("test-plugin"));
+    }
+
+    #[test]
+    fn test_duplicate_registration() {
+        let manager = PluginManager::new();
+        let plugin1 = Box::new(TestPlugin::new("test-plugin"));
+        let plugin2 = Box::new(TestPlugin::new("test-plugin"));
+
+        assert!(manager.register(plugin1).is_ok());
+        assert!(manager.register(plugin2).is_err());
+    }
+
+    #[test]
+    fn test_execute_plugin() {
+        let manager = PluginManager::new();
+        let plugin = Box::new(TestPlugin::new("test-plugin"));
+
+        manager.register(plugin).unwrap();
+
+        let context = PluginContext::default();
+        let result = manager.execute("test-plugin", &context).unwrap();
+
+        assert!(result.success);
+        assert!(result.message.is_some());
+    }
+
+    #[test]
+    fn test_unregister_plugin() {
+        let manager = PluginManager::new();
+        let plugin = Box::new(TestPlugin::new("test-plugin"));
+
+        manager.register(plugin).unwrap();
+        assert_eq!(manager.count(), 1);
+
+        manager.unregister("test-plugin").unwrap();
+        assert_eq!(manager.count(), 0);
+    }
+
+    #[test]
+    fn test_list_plugins() {
+        let manager = PluginManager::new();
+        let plugin1 = Box::new(TestPlugin::new("plugin-1"));
+        let plugin2 = Box::new(TestPlugin::new("plugin-2"));
+
+        manager.register(plugin1).unwrap();
+        manager.register(plugin2).unwrap();
+
+        let plugins = manager.list_plugins();
+        assert_eq!(plugins.len(), 2);
+    }
+
+    #[test]
+    fn test_get_metadata() {
+        let manager = PluginManager::new();
+        let plugin = Box::new(TestPlugin::new("test-plugin"));
+
+        manager.register(plugin).unwrap();
+
+        let metadata = manager.get_metadata("test-plugin").unwrap();
+        assert_eq!(metadata.name, "test-plugin");
+        assert_eq!(metadata.version, "1.0.0");
+    }
+
+    #[test]
+    fn test_get_state() {
+        let manager = PluginManager::new();
+        let plugin = Box::new(TestPlugin::new("test-plugin"));
+
+        manager.register(plugin).unwrap();
+
+        let state = manager.get_state("test-plugin").unwrap();
+        assert_eq!(state, PluginState::Initialized);
+    }
+
+    #[test]
+    fn test_plugin_not_found() {
+        let manager = PluginManager::new();
+        let context = PluginContext::default();
+
+        assert!(manager.execute("nonexistent", &context).is_err());
+        assert!(manager.get_metadata("nonexistent").is_err());
+        assert!(manager.get_state("nonexistent").is_err());
+        assert!(manager.unregister("nonexistent").is_err());
+    }
+}
diff --git a/crates/miyabi-core/src/retry.rs b/crates/miyabi-core/src/retry.rs
new file mode 100644
index 0000000..919f435
--- /dev/null
+++ b/crates/miyabi-core/src/retry.rs
@@ -0,0 +1,212 @@
+//! Retry logic with exponential backoff
+//!
+//! Provides utilities for retrying transient failures with exponential backoff.
+//! Useful for network operations, external API calls, and transient errors.
+
+use crate::error::{Error, Result};
+use std::future::Future;
+use std::time::Duration;
+
+/// Configuration for retry behavior
+#[derive(Debug, Clone)]
+pub struct RetryConfig {
+    /// Maximum number of retry attempts (excluding the first attempt)
+    pub max_attempts: u32,
+    /// Initial delay before first retry (milliseconds)
+    pub initial_delay_ms: u64,
+    /// Maximum delay between retries (milliseconds)
+    pub max_delay_ms: u64,
+    /// Backoff multiplier (typically 2.0 for exponential backoff)
+    pub backoff_multiplier: f64,
+}
+
+impl Default for RetryConfig {
+    fn default() -> Self {
+        Self {
+            max_attempts: 3,
+            initial_delay_ms: 100,
+            max_delay_ms: 30000,
+            backoff_multiplier: 2.0,
+        }
+    }
+}
+
+impl RetryConfig {
+    /// Create a new retry configuration
+    pub fn new(max_attempts: u32, initial_delay_ms: u64, max_delay_ms: u64) -> Self {
+        Self {
+            max_attempts,
+            initial_delay_ms,
+            max_delay_ms,
+            backoff_multiplier: 2.0,
+        }
+    }
+
+    /// Create aggressive retry config (5 attempts, 50ms initial, 10s max)
+    pub fn aggressive() -> Self {
+        Self {
+            max_attempts: 5,
+            initial_delay_ms: 50,
+            max_delay_ms: 10000,
+            backoff_multiplier: 2.0,
+        }
+    }
+
+    /// Create conservative retry config (2 attempts, 500ms initial, 60s max)
+    pub fn conservative() -> Self {
+        Self {
+            max_attempts: 2,
+            initial_delay_ms: 500,
+            max_delay_ms: 60000,
+            backoff_multiplier: 2.0,
+        }
+    }
+
+    /// Calculate delay for a given attempt number (0-indexed)
+    pub fn calculate_delay(&self, attempt: u32) -> Duration {
+        let delay_ms = (self.initial_delay_ms as f64 * self.backoff_multiplier.powi(attempt as i32))
+            .min(self.max_delay_ms as f64) as u64;
+        Duration::from_millis(delay_ms)
+    }
+}
+
+/// Retry a future with exponential backoff
+///
+/// # Arguments
+/// * `config` - Retry configuration
+/// * `operation` - Async operation to retry (must be Fn, not FnOnce)
+///
+/// # Returns
+/// * `Ok(T)` - Operation succeeded
+/// * `Err(Error)` - All retry attempts failed
+///
+/// # Example
+/// ```ignore
+/// let result = retry_with_backoff(
+///     RetryConfig::default(),
+///     || async { fetch_data().await }
+/// ).await?;
+/// ```
+pub async fn retry_with_backoff<F, Fut, T>(config: RetryConfig, operation: F) -> Result<T>
+where
+    F: Fn() -> Fut,
+    Fut: Future<Output = Result<T>>,
+{
+    let mut last_error = None;
+
+    for attempt in 0..=config.max_attempts {
+        match operation().await {
+            Ok(result) => {
+                return Ok(result);
+            }
+            Err(error) => {
+                // Check if error is retryable
+                if !error.is_retryable() {
+                    return Err(error);
+                }
+
+                last_error = Some(error);
+
+                // Don't sleep after the last attempt
+                if attempt < config.max_attempts {
+                    let delay = config.calculate_delay(attempt);
+                    tokio::time::sleep(delay).await;
+                }
+            }
+        }
+    }
+
+    // All attempts failed
+    Err(last_error.unwrap_or_else(|| Error::Other("No error captured".to_string())))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::sync::atomic::{AtomicU32, Ordering};
+    use std::sync::Arc;
+
+    #[tokio::test]
+    async fn test_retry_config_default() {
+        let config = RetryConfig::default();
+        assert_eq!(config.max_attempts, 3);
+        assert_eq!(config.initial_delay_ms, 100);
+        assert_eq!(config.max_delay_ms, 30000);
+        assert_eq!(config.backoff_multiplier, 2.0);
+    }
+
+    #[tokio::test]
+    async fn test_calculate_delay_exponential() {
+        let config = RetryConfig::new(3, 100, 10000);
+
+        assert_eq!(config.calculate_delay(0), Duration::from_millis(100));
+        assert_eq!(config.calculate_delay(1), Duration::from_millis(200));
+        assert_eq!(config.calculate_delay(2), Duration::from_millis(400));
+        assert_eq!(config.calculate_delay(3), Duration::from_millis(800));
+    }
+
+    #[tokio::test]
+    async fn test_retry_succeeds_immediately() {
+        let attempt_count = Arc::new(AtomicU32::new(0));
+        let attempt_count_clone = Arc::clone(&attempt_count);
+
+        let config = RetryConfig::new(3, 10, 1000);
+
+        let result = retry_with_backoff(config, || {
+            let count = Arc::clone(&attempt_count_clone);
+            async move {
+                count.fetch_add(1, Ordering::SeqCst);
+                Ok::<String, Error>("success".to_string())
+            }
+        })
+        .await;
+
+        assert!(result.is_ok());
+        assert_eq!(result.unwrap(), "success");
+        assert_eq!(attempt_count.load(Ordering::SeqCst), 1);
+    }
+
+    #[tokio::test]
+    async fn test_retry_succeeds_after_failures() {
+        let attempt_count = Arc::new(AtomicU32::new(0));
+        let attempt_count_clone = Arc::clone(&attempt_count);
+
+        let config = RetryConfig::new(3, 10, 1000);
+
+        let result = retry_with_backoff(config, || {
+            let count = Arc::clone(&attempt_count_clone);
+            async move {
+                let current = count.fetch_add(1, Ordering::SeqCst);
+                if current < 2 {
+                    Err(Error::Timeout(1000))
+                } else {
+                    Ok::<String, Error>("success".to_string())
+                }
+            }
+        })
+        .await;
+
+        assert!(result.is_ok());
+        assert_eq!(attempt_count.load(Ordering::SeqCst), 3);
+    }
+
+    #[tokio::test]
+    async fn test_retry_non_retryable_fails_immediately() {
+        let attempt_count = Arc::new(AtomicU32::new(0));
+        let attempt_count_clone = Arc::clone(&attempt_count);
+
+        let config = RetryConfig::new(3, 10, 1000);
+
+        let result = retry_with_backoff(config, || {
+            let count = Arc::clone(&attempt_count_clone);
+            async move {
+                count.fetch_add(1, Ordering::SeqCst);
+                Err::<String, Error>(Error::Validation("Invalid".to_string()))
+            }
+        })
+        .await;
+
+        assert!(result.is_err());
+        assert_eq!(attempt_count.load(Ordering::SeqCst), 1);
+    }
+}
diff --git a/crates/miyabi-core/src/rules.rs b/crates/miyabi-core/src/rules.rs
new file mode 100644
index 0000000..3b7a2e8
--- /dev/null
+++ b/crates/miyabi-core/src/rules.rs
@@ -0,0 +1,325 @@
+//! Project-specific rules support (.miyabirules)
+//!
+//! This module provides support for loading and applying custom rules from `.miyabirules` files.
+
+use serde::{Deserialize, Serialize};
+use std::collections::HashMap;
+use std::fs;
+use std::path::{Path, PathBuf};
+use thiserror::Error;
+
+/// Error types for rules operations
+#[derive(Error, Debug)]
+pub enum RulesError {
+    /// File not found
+    #[error("Rules file not found: {0}")]
+    FileNotFound(PathBuf),
+
+    /// Parse error
+    #[error("Failed to parse rules file: {0}")]
+    ParseError(String),
+
+    /// Validation error
+    #[error("Validation error: {0}")]
+    ValidationError(String),
+
+    /// I/O error
+    #[error("I/O error: {0}")]
+    IoError(#[from] std::io::Error),
+}
+
+pub type Result<T> = std::result::Result<T, RulesError>;
+
+/// A single rule with pattern matching and suggestion
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
+pub struct Rule {
+    /// Rule name
+    pub name: String,
+
+    /// Pattern to match (regex)
+    #[serde(default)]
+    pub pattern: Option<String>,
+
+    /// Suggestion message
+    pub suggestion: String,
+
+    /// File extension filters (e.g., ["rs", "toml"])
+    #[serde(default)]
+    pub file_extensions: Vec<String>,
+
+    /// Severity: "info", "warning", "error"
+    #[serde(default = "default_severity")]
+    pub severity: String,
+
+    /// Whether this rule is enabled
+    #[serde(default = "default_enabled")]
+    pub enabled: bool,
+}
+
+fn default_severity() -> String {
+    "info".to_string()
+}
+
+fn default_enabled() -> bool {
+    true
+}
+
+impl Rule {
+    /// Check if this rule applies to a given file extension
+    pub fn applies_to_file(&self, file_path: &Path) -> bool {
+        if self.file_extensions.is_empty() {
+            return true;
+        }
+
+        if let Some(ext) = file_path.extension() {
+            let ext_str = ext.to_string_lossy().to_string();
+            self.file_extensions.iter().any(|e| e == &ext_str)
+        } else {
+            false
+        }
+    }
+
+    /// Check if this rule matches a given line of code
+    pub fn matches(&self, line: &str) -> bool {
+        if let Some(pattern) = &self.pattern {
+            line.contains(pattern)
+        } else {
+            false
+        }
+    }
+}
+
+/// Agent-specific preferences
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Default)]
+pub struct AgentPreferences {
+    /// Code style preference
+    #[serde(default)]
+    pub style: Option<String>,
+
+    /// Error handling strategy
+    #[serde(default)]
+    pub error_handling: Option<String>,
+
+    /// Minimum quality score
+    #[serde(default)]
+    pub min_score: Option<u8>,
+
+    /// Enable strict Clippy checks
+    #[serde(default)]
+    pub clippy_strict: Option<bool>,
+
+    /// Custom agent-specific settings
+    #[serde(flatten)]
+    pub custom: HashMap<String, serde_json::Value>,
+}
+
+/// Root configuration structure for .miyabirules
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
+pub struct MiyabiRules {
+    /// Version of the rules format
+    #[serde(default = "default_version")]
+    pub version: u32,
+
+    /// List of rules
+    #[serde(default)]
+    pub rules: Vec<Rule>,
+
+    /// Agent preferences by agent type
+    #[serde(default)]
+    pub agent_preferences: HashMap<String, AgentPreferences>,
+
+    /// Global settings
+    #[serde(default)]
+    pub settings: HashMap<String, serde_json::Value>,
+}
+
+fn default_version() -> u32 {
+    1
+}
+
+impl Default for MiyabiRules {
+    fn default() -> Self {
+        Self {
+            version: 1,
+            rules: Vec::new(),
+            agent_preferences: HashMap::new(),
+            settings: HashMap::new(),
+        }
+    }
+}
+
+impl MiyabiRules {
+    /// Create a new empty rules configuration
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Validate the rules configuration
+    pub fn validate(&self) -> Result<()> {
+        if self.version != 1 {
+            return Err(RulesError::ValidationError(format!(
+                "Unsupported version: {}. Only version 1 is supported.",
+                self.version
+            )));
+        }
+
+        for rule in &self.rules {
+            if rule.name.is_empty() {
+                return Err(RulesError::ValidationError(
+                    "Rule name cannot be empty".to_string(),
+                ));
+            }
+
+            if rule.suggestion.is_empty() {
+                return Err(RulesError::ValidationError(format!(
+                    "Rule '{}' must have a suggestion",
+                    rule.name
+                )));
+            }
+
+            match rule.severity.as_str() {
+                "info" | "warning" | "error" => {}
+                _ => {
+                    return Err(RulesError::ValidationError(format!(
+                        "Invalid severity '{}' for rule '{}'. Must be: info, warning, or error",
+                        rule.severity, rule.name
+                    )))
+                }
+            }
+        }
+
+        Ok(())
+    }
+
+    /// Get rules that apply to a specific file
+    pub fn rules_for_file(&self, file_path: &Path) -> Vec<&Rule> {
+        self.rules
+            .iter()
+            .filter(|r| r.enabled && r.applies_to_file(file_path))
+            .collect()
+    }
+
+    /// Get agent preferences for a specific agent type
+    pub fn get_agent_preferences(&self, agent_type: &str) -> Option<&AgentPreferences> {
+        self.agent_preferences.get(agent_type)
+    }
+
+    /// Get a global setting value
+    pub fn get_setting(&self, key: &str) -> Option<&serde_json::Value> {
+        self.settings.get(key)
+    }
+}
+
+/// Rules loader for loading .miyabirules files
+pub struct RulesLoader {
+    /// Root directory to search for .miyabirules
+    root_dir: PathBuf,
+}
+
+impl RulesLoader {
+    /// Create a new RulesLoader
+    pub fn new(root_dir: PathBuf) -> Self {
+        Self { root_dir }
+    }
+
+    /// Find .miyabirules file in the directory hierarchy
+    pub fn find_rules_file(&self) -> Option<PathBuf> {
+        let mut current = self.root_dir.clone();
+
+        loop {
+            let rules_path = current.join(".miyabirules");
+            if rules_path.exists() {
+                return Some(rules_path);
+            }
+
+            let rules_yaml = current.join(".miyabirules.yaml");
+            if rules_yaml.exists() {
+                return Some(rules_yaml);
+            }
+
+            let rules_yml = current.join(".miyabirules.yml");
+            if rules_yml.exists() {
+                return Some(rules_yml);
+            }
+
+            if !current.pop() {
+                break;
+            }
+        }
+
+        None
+    }
+
+    /// Load rules from .miyabirules file
+    pub fn load(&self) -> Result<Option<MiyabiRules>> {
+        let rules_path = match self.find_rules_file() {
+            Some(path) => path,
+            None => return Ok(None),
+        };
+
+        let content = fs::read_to_string(&rules_path)?;
+
+        let rules: MiyabiRules = serde_yaml::from_str(&content).map_err(|e| {
+            RulesError::ParseError(format!("Failed to parse {}: {}", rules_path.display(), e))
+        })?;
+
+        rules.validate()?;
+
+        Ok(Some(rules))
+    }
+
+    /// Load rules or return default if not found
+    pub fn load_or_default(&self) -> Result<MiyabiRules> {
+        self.load().map(|opt| opt.unwrap_or_default())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use tempfile::TempDir;
+
+    #[test]
+    fn test_rule_applies_to_file() {
+        let rule = Rule {
+            name: "Rust rule".to_string(),
+            pattern: None,
+            suggestion: "Test".to_string(),
+            file_extensions: vec!["rs".to_string()],
+            severity: "info".to_string(),
+            enabled: true,
+        };
+
+        assert!(rule.applies_to_file(Path::new("main.rs")));
+        assert!(!rule.applies_to_file(Path::new("main.py")));
+    }
+
+    #[test]
+    fn test_rule_matches() {
+        let rule = Rule {
+            name: "Test".to_string(),
+            pattern: Some("async".to_string()),
+            suggestion: "Test".to_string(),
+            file_extensions: vec![],
+            severity: "info".to_string(),
+            enabled: true,
+        };
+
+        assert!(rule.matches("async fn test() {}"));
+        assert!(!rule.matches("fn test() {}"));
+    }
+
+    #[test]
+    fn test_rules_validation() {
+        let rules = MiyabiRules::default();
+        assert!(rules.validate().is_ok());
+    }
+
+    #[test]
+    fn test_rules_loader_not_found() {
+        let temp_dir = TempDir::new().unwrap();
+        let loader = RulesLoader::new(temp_dir.path().to_path_buf());
+        let rules = loader.load().unwrap();
+        assert!(rules.is_none());
+    }
+}
diff --git a/crates/miyabi-core/src/workflow.rs b/crates/miyabi-core/src/workflow.rs
new file mode 100644
index 0000000..447877d
--- /dev/null
+++ b/crates/miyabi-core/src/workflow.rs
@@ -0,0 +1,557 @@
+//! Multi-Agent Workflow System
+//!
+//! Orchestrate multiple agents in sequence or parallel execution.
+
+use anyhow::Result;
+use serde::{Deserialize, Serialize};
+use std::collections::HashMap;
+use std::path::PathBuf;
+
+/// Workflow definition
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct Workflow {
+    /// Workflow name
+    pub name: String,
+    /// Description
+    #[serde(default)]
+    pub description: String,
+    /// Workflow steps
+    pub steps: Vec<WorkflowStep>,
+    /// Global variables
+    #[serde(default)]
+    pub variables: HashMap<String, String>,
+    /// On failure behavior
+    #[serde(default)]
+    pub on_failure: FailurePolicy,
+}
+
+/// A single step in the workflow
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct WorkflowStep {
+    /// Step ID for reference
+    pub id: String,
+    /// Step name
+    pub name: String,
+    /// Agent spec to use
+    #[serde(default)]
+    pub agent: Option<String>,
+    /// Task/prompt for the agent
+    pub task: String,
+    /// Dependencies (step IDs that must complete first)
+    #[serde(default)]
+    pub depends_on: Vec<String>,
+    /// Condition for execution
+    #[serde(default)]
+    pub condition: Option<StepCondition>,
+    /// Timeout in seconds
+    #[serde(default = "default_step_timeout")]
+    pub timeout: u64,
+    /// Retry configuration
+    #[serde(default)]
+    pub retry: RetryConfig,
+    /// Output variable name to store result
+    #[serde(default)]
+    pub output: Option<String>,
+}
+
+fn default_step_timeout() -> u64 {
+    300
+}
+
+/// Condition for step execution
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(tag = "type", rename_all = "snake_case")]
+pub enum StepCondition {
+    /// Always execute
+    Always,
+    /// Execute if previous step succeeded
+    OnSuccess,
+    /// Execute if previous step failed
+    OnFailure,
+    /// Execute if expression is true
+    If { expression: String },
+}
+
+impl Default for StepCondition {
+    fn default() -> Self {
+        StepCondition::Always
+    }
+}
+
+/// Retry configuration for a step
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct RetryConfig {
+    /// Maximum retry attempts
+    #[serde(default = "default_max_retries")]
+    pub max_attempts: u32,
+    /// Delay between retries in seconds
+    #[serde(default = "default_retry_delay")]
+    pub delay: u64,
+}
+
+impl Default for RetryConfig {
+    fn default() -> Self {
+        Self {
+            max_attempts: 1,
+            delay: 5,
+        }
+    }
+}
+
+fn default_max_retries() -> u32 {
+    1
+}
+
+fn default_retry_delay() -> u64 {
+    5
+}
+
+/// Failure policy for workflow
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum FailurePolicy {
+    /// Stop workflow on first failure
+    Stop,
+    /// Continue with remaining steps
+    Continue,
+    /// Run cleanup steps
+    Cleanup,
+}
+
+impl Default for FailurePolicy {
+    fn default() -> Self {
+        FailurePolicy::Stop
+    }
+}
+
+/// Step execution result
+#[derive(Debug, Clone)]
+pub struct StepResult {
+    pub step_id: String,
+    pub status: StepStatus,
+    pub output: Option<String>,
+    pub error: Option<String>,
+    pub duration_ms: u64,
+}
+
+/// Step execution status
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum StepStatus {
+    Pending,
+    Running,
+    Completed,
+    Failed,
+    Skipped,
+}
+
+/// Workflow execution context
+#[derive(Debug, Clone, Default)]
+pub struct WorkflowContext {
+    /// Variables available to steps
+    pub variables: HashMap<String, String>,
+    /// Results from completed steps
+    pub results: HashMap<String, StepResult>,
+}
+
+impl WorkflowContext {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    pub fn with_variables(mut self, vars: HashMap<String, String>) -> Self {
+        self.variables = vars;
+        self
+    }
+
+    pub fn set_variable(&mut self, key: &str, value: &str) {
+        self.variables.insert(key.to_string(), value.to_string());
+    }
+
+    pub fn get_variable(&self, key: &str) -> Option<&String> {
+        self.variables.get(key)
+    }
+
+    pub fn add_result(&mut self, result: StepResult) {
+        self.results.insert(result.step_id.clone(), result);
+    }
+
+    pub fn get_result(&self, step_id: &str) -> Option<&StepResult> {
+        self.results.get(step_id)
+    }
+
+    /// Expand variables in a string
+    pub fn expand(&self, input: &str) -> String {
+        let mut result = input.to_string();
+        for (key, value) in &self.variables {
+            result = result.replace(&format!("${{{}}}", key), value);
+        }
+        result
+    }
+}
+
+/// Workflow execution result
+#[derive(Debug)]
+pub struct WorkflowResult {
+    pub workflow_name: String,
+    pub status: WorkflowStatus,
+    pub steps: Vec<StepResult>,
+    pub duration_ms: u64,
+}
+
+/// Workflow execution status
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum WorkflowStatus {
+    Completed,
+    Failed,
+    PartiallyCompleted,
+}
+
+/// Workflow manager for loading and executing workflows
+pub struct WorkflowManager {
+    workflows: HashMap<String, Workflow>,
+}
+
+impl Default for WorkflowManager {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl WorkflowManager {
+    /// Create a new workflow manager
+    pub fn new() -> Self {
+        Self {
+            workflows: HashMap::new(),
+        }
+    }
+
+    /// Load a workflow from a YAML file
+    pub fn load_workflow(&mut self, path: &PathBuf) -> Result<String> {
+        let content = std::fs::read_to_string(path)?;
+        let workflow: Workflow = serde_yaml::from_str(&content)?;
+        let name = workflow.name.clone();
+        self.workflows.insert(name.clone(), workflow);
+        Ok(name)
+    }
+
+    /// Load all workflows from a directory
+    pub fn load_from_directory(&mut self, dir: &PathBuf) -> Result<Vec<String>> {
+        let mut loaded = Vec::new();
+        if dir.exists() && dir.is_dir() {
+            for entry in std::fs::read_dir(dir)? {
+                let entry = entry?;
+                let path = entry.path();
+                if path.extension().map(|e| e == "yml" || e == "yaml").unwrap_or(false) {
+                    if let Ok(name) = self.load_workflow(&path) {
+                        loaded.push(name);
+                    }
+                }
+            }
+        }
+        Ok(loaded)
+    }
+
+    /// Register a workflow directly
+    pub fn register(&mut self, workflow: Workflow) {
+        self.workflows.insert(workflow.name.clone(), workflow);
+    }
+
+    /// Get a workflow by name
+    pub fn get_workflow(&self, name: &str) -> Option<&Workflow> {
+        self.workflows.get(name)
+    }
+
+    /// List all registered workflows
+    pub fn list_workflows(&self) -> Vec<&str> {
+        self.workflows.keys().map(|s| s.as_str()).collect()
+    }
+
+    /// Execute a workflow
+    pub async fn execute(&self, name: &str, initial_vars: HashMap<String, String>) -> Result<WorkflowResult> {
+        let workflow = self
+            .workflows
+            .get(name)
+            .ok_or_else(|| anyhow::anyhow!("Workflow not found: {}", name))?;
+
+        let start_time = std::time::Instant::now();
+        let mut context = WorkflowContext::new().with_variables(workflow.variables.clone());
+
+        // Add initial variables
+        for (key, value) in initial_vars {
+            context.set_variable(&key, &value);
+        }
+
+        let mut step_results = Vec::new();
+        let mut all_succeeded = true;
+
+        // Build dependency graph and execute
+        let execution_order = self.build_execution_order(workflow)?;
+
+        for step_id in execution_order {
+            let step = workflow
+                .steps
+                .iter()
+                .find(|s| s.id == step_id)
+                .ok_or_else(|| anyhow::anyhow!("Step not found: {}", step_id))?;
+
+            // Check dependencies
+            let deps_satisfied = step.depends_on.iter().all(|dep_id| {
+                context
+                    .get_result(dep_id)
+                    .map(|r| r.status == StepStatus::Completed)
+                    .unwrap_or(false)
+            });
+
+            if !deps_satisfied {
+                let result = StepResult {
+                    step_id: step.id.clone(),
+                    status: StepStatus::Skipped,
+                    output: None,
+                    error: Some("Dependencies not satisfied".to_string()),
+                    duration_ms: 0,
+                };
+                step_results.push(result.clone());
+                context.add_result(result);
+                continue;
+            }
+
+            // Check condition
+            if !self.evaluate_condition(&step.condition, &context) {
+                let result = StepResult {
+                    step_id: step.id.clone(),
+                    status: StepStatus::Skipped,
+                    output: None,
+                    error: Some("Condition not met".to_string()),
+                    duration_ms: 0,
+                };
+                step_results.push(result.clone());
+                context.add_result(result);
+                continue;
+            }
+
+            // Execute step
+            let step_start = std::time::Instant::now();
+            let expanded_task = context.expand(&step.task);
+
+            // Placeholder for actual agent execution
+            let result = StepResult {
+                step_id: step.id.clone(),
+                status: StepStatus::Completed,
+                output: Some(format!("Executed: {}", expanded_task)),
+                error: None,
+                duration_ms: step_start.elapsed().as_millis() as u64,
+            };
+
+            // Store output variable if specified
+            if let Some(output_var) = &step.output {
+                if let Some(output) = &result.output {
+                    context.set_variable(output_var, output);
+                }
+            }
+
+            if result.status == StepStatus::Failed {
+                all_succeeded = false;
+                if matches!(workflow.on_failure, FailurePolicy::Stop) {
+                    step_results.push(result.clone());
+                    context.add_result(result);
+                    break;
+                }
+            }
+
+            step_results.push(result.clone());
+            context.add_result(result);
+        }
+
+        let status = if all_succeeded {
+            WorkflowStatus::Completed
+        } else if step_results.iter().any(|r| r.status == StepStatus::Completed) {
+            WorkflowStatus::PartiallyCompleted
+        } else {
+            WorkflowStatus::Failed
+        };
+
+        Ok(WorkflowResult {
+            workflow_name: name.to_string(),
+            status,
+            steps: step_results,
+            duration_ms: start_time.elapsed().as_millis() as u64,
+        })
+    }
+
+    /// Build execution order from dependencies (topological sort)
+    fn build_execution_order(&self, workflow: &Workflow) -> Result<Vec<String>> {
+        let mut order = Vec::new();
+        let mut visited = HashMap::new();
+        let mut temp_visited = HashMap::new();
+
+        for step in &workflow.steps {
+            if !visited.contains_key(&step.id) {
+                self.visit_step(workflow, &step.id, &mut visited, &mut temp_visited, &mut order)?;
+            }
+        }
+
+        Ok(order)
+    }
+
+    fn visit_step(
+        &self,
+        workflow: &Workflow,
+        step_id: &str,
+        visited: &mut HashMap<String, bool>,
+        temp_visited: &mut HashMap<String, bool>,
+        order: &mut Vec<String>,
+    ) -> Result<()> {
+        if temp_visited.get(step_id).copied().unwrap_or(false) {
+            return Err(anyhow::anyhow!("Circular dependency detected at step: {}", step_id));
+        }
+
+        if visited.get(step_id).copied().unwrap_or(false) {
+            return Ok(());
+        }
+
+        temp_visited.insert(step_id.to_string(), true);
+
+        let step = workflow
+            .steps
+            .iter()
+            .find(|s| s.id == step_id)
+            .ok_or_else(|| anyhow::anyhow!("Step not found: {}", step_id))?;
+
+        for dep_id in &step.depends_on {
+            self.visit_step(workflow, dep_id, visited, temp_visited, order)?;
+        }
+
+        temp_visited.insert(step_id.to_string(), false);
+        visited.insert(step_id.to_string(), true);
+        order.push(step_id.to_string());
+
+        Ok(())
+    }
+
+    /// Evaluate a step condition
+    fn evaluate_condition(&self, condition: &Option<StepCondition>, context: &WorkflowContext) -> bool {
+        match condition {
+            None | Some(StepCondition::Always) => true,
+            Some(StepCondition::OnSuccess) => context
+                .results
+                .values()
+                .last()
+                .map(|r| r.status == StepStatus::Completed)
+                .unwrap_or(true),
+            Some(StepCondition::OnFailure) => context
+                .results
+                .values()
+                .last()
+                .map(|r| r.status == StepStatus::Failed)
+                .unwrap_or(false),
+            Some(StepCondition::If { expression }) => {
+                // Simple expression evaluation (variable == value)
+                let expanded = context.expand(expression);
+                !expanded.is_empty() && expanded != "false" && expanded != "0"
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_workflow_context() {
+        let mut context = WorkflowContext::new();
+        context.set_variable("name", "test");
+        context.set_variable("version", "1.0");
+
+        assert_eq!(context.get_variable("name"), Some(&"test".to_string()));
+        assert_eq!(
+            context.expand("Project: ${name} v${version}"),
+            "Project: test v1.0"
+        );
+    }
+
+    #[test]
+    fn test_workflow_serialization() {
+        let workflow = Workflow {
+            name: "test-workflow".to_string(),
+            description: "Test".to_string(),
+            steps: vec![
+                WorkflowStep {
+                    id: "step1".to_string(),
+                    name: "First Step".to_string(),
+                    agent: Some("code-reviewer".to_string()),
+                    task: "Review code".to_string(),
+                    depends_on: vec![],
+                    condition: None,
+                    timeout: 300,
+                    retry: RetryConfig::default(),
+                    output: Some("review_result".to_string()),
+                },
+            ],
+            variables: HashMap::new(),
+            on_failure: FailurePolicy::Stop,
+        };
+
+        let yaml = serde_yaml::to_string(&workflow).unwrap();
+        assert!(yaml.contains("test-workflow"));
+        assert!(yaml.contains("step1"));
+    }
+
+    #[test]
+    fn test_workflow_manager() {
+        let mut manager = WorkflowManager::new();
+        let workflow = Workflow {
+            name: "test".to_string(),
+            description: "Test workflow".to_string(),
+            steps: vec![],
+            variables: HashMap::new(),
+            on_failure: FailurePolicy::Stop,
+        };
+
+        manager.register(workflow);
+        assert!(manager.get_workflow("test").is_some());
+        assert_eq!(manager.list_workflows(), vec!["test"]);
+    }
+
+    #[tokio::test]
+    async fn test_workflow_execution() {
+        let mut manager = WorkflowManager::new();
+        let workflow = Workflow {
+            name: "simple".to_string(),
+            description: "Simple workflow".to_string(),
+            steps: vec![
+                WorkflowStep {
+                    id: "step1".to_string(),
+                    name: "Step 1".to_string(),
+                    agent: None,
+                    task: "Task 1".to_string(),
+                    depends_on: vec![],
+                    condition: None,
+                    timeout: 30,
+                    retry: RetryConfig::default(),
+                    output: None,
+                },
+                WorkflowStep {
+                    id: "step2".to_string(),
+                    name: "Step 2".to_string(),
+                    agent: None,
+                    task: "Task 2 depends on ${result}".to_string(),
+                    depends_on: vec!["step1".to_string()],
+                    condition: None,
+                    timeout: 30,
+                    retry: RetryConfig::default(),
+                    output: None,
+                },
+            ],
+            variables: HashMap::new(),
+            on_failure: FailurePolicy::Stop,
+        };
+
+        manager.register(workflow);
+        let result = manager.execute("simple", HashMap::new()).await.unwrap();
+
+        assert_eq!(result.workflow_name, "simple");
+        assert_eq!(result.status, WorkflowStatus::Completed);
+        assert_eq!(result.steps.len(), 2);
+    }
+}
diff --git a/crates/miyabi-tui/Cargo.toml b/crates/miyabi-tui/Cargo.toml
index cdbf450..233df6b 100644
--- a/crates/miyabi-tui/Cargo.toml
+++ b/crates/miyabi-tui/Cargo.toml
@@ -50,4 +50,5 @@ once_cell = { workspace = true }
 uuid = { workspace = true }
 
 [features]
+default = ["clipboard"]
 clipboard = ["arboard"]
diff --git a/crates/miyabi-tui/src/app.rs b/crates/miyabi-tui/src/app.rs
index 9a3f482..d943fd5 100644
--- a/crates/miyabi-tui/src/app.rs
+++ b/crates/miyabi-tui/src/app.rs
@@ -15,6 +15,7 @@ use crate::history_cell::{
 use crate::views::{MainView, ViewAction};
 use miyabi_core::anthropic::{AnthropicClient, ContentBlock, Message, StreamEvent};
 use miyabi_core::config::Config;
+use miyabi_core::rules::{MiyabiRules, RulesLoader};
 use miyabi_core::session::{Session, SessionStorage};
 use miyabi_core::tool::ToolRegistry;
 use miyabi_core::tools::create_standard_tool_registry;
@@ -72,6 +73,8 @@ pub struct App {
     max_tokens: u32,
     /// Whether to request extended thinking
     thinking: bool,
+    /// Project rules loaded from .miyabirules
+    rules: Option<MiyabiRules>,
 }
 
 impl App {
@@ -135,6 +138,27 @@ impl App {
         let max_tokens = config.api.max_tokens;
         let thinking = config.api.thinking;
 
+        // Load project rules from .miyabirules
+        let cwd = std::env::current_dir().unwrap_or_default();
+        let loader = RulesLoader::new(cwd);
+        let rules = match loader.load() {
+            Ok(Some(rules)) => {
+                let count = rules.rules.len();
+                if count > 0 {
+                    view.notifications.info(
+                        "Rules Loaded",
+                        format!("{} project rules active", count),
+                    );
+                }
+                Some(rules)
+            }
+            Ok(None) => None,
+            Err(e) => {
+                view.notifications.error("Rules Error", format!("Failed to load: {}", e));
+                None
+            }
+        };
+
         Self {
             should_quit: false,
             view,
@@ -151,9 +175,15 @@ impl App {
             model_name,
             max_tokens,
             thinking,
+            rules,
         }
     }
 
+    /// Get the loaded project rules
+    pub fn get_rules(&self) -> Option<&MiyabiRules> {
+        self.rules.as_ref()
+    }
+
     /// Toggle agent mode
     pub fn toggle_agent_mode(&mut self) {
         self.agent_mode = !self.agent_mode;
@@ -241,18 +271,106 @@ impl App {
                                 self.view.notifications.panel.push(notification);
                             }
                             ViewAction::Copy(text) => {
-                                // TODO: Implement clipboard support
-                                self.view
-                                    .notifications
-                                    .info("Copied", format!("{} chars", text.len()));
+                                #[cfg(feature = "clipboard")]
+                                {
+                                    match arboard::Clipboard::new() {
+                                        Ok(mut clipboard) => {
+                                            if let Err(e) = clipboard.set_text(&text) {
+                                                self.view
+                                                    .notifications
+                                                    .error("Clipboard Error", e.to_string());
+                                            } else {
+                                                self.view
+                                                    .notifications
+                                                    .info("Copied", format!("{} chars", text.len()));
+                                            }
+                                        }
+                                        Err(e) => {
+                                            self.view
+                                                .notifications
+                                                .error("Clipboard Error", e.to_string());
+                                        }
+                                    }
+                                }
+                                #[cfg(not(feature = "clipboard"))]
+                                {
+                                    self.view
+                                        .notifications
+                                        .warning("Clipboard", "Clipboard feature not enabled");
+                                    let _ = text; // Suppress unused warning
+                                }
                             }
                             ViewAction::OpenFile(path) => {
-                                // TODO: Implement file opening
-                                self.view.notifications.info("Open File", &path);
+                                // Open file with system default application
+                                #[cfg(target_os = "macos")]
+                                let result = std::process::Command::new("open").arg(&path).spawn();
+                                #[cfg(target_os = "linux")]
+                                let result = std::process::Command::new("xdg-open").arg(&path).spawn();
+                                #[cfg(target_os = "windows")]
+                                let result = std::process::Command::new("cmd")
+                                    .args(["/C", "start", "", &path])
+                                    .spawn();
+
+                                match result {
+                                    Ok(_) => {
+                                        self.view.notifications.info("Opened", &path);
+                                    }
+                                    Err(e) => {
+                                        self.view
+                                            .notifications
+                                            .error("Open Error", e.to_string());
+                                    }
+                                }
                             }
                             ViewAction::ResumeSession(session_id) => {
-                                // TODO: Implement session resume
-                                self.view.notifications.info("Resume Session", &session_id);
+                                match self.load_session(&session_id) {
+                                    Ok(()) => {
+                                        // Rebuild UI from loaded conversation
+                                        self.view.history.clear();
+                                        let timestamp =
+                                            chrono::Local::now().format("%H:%M").to_string();
+
+                                        // Replay conversation into UI
+                                        for msg in &self.conversation {
+                                            match msg.role {
+                                                miyabi_core::anthropic::Role::User => {
+                                                    if let Some(ContentBlock::Text { text }) =
+                                                        msg.content.first()
+                                                    {
+                                                        self.view.push_message(Box::new(
+                                                            UserMessageCell {
+                                                                content: text.clone(),
+                                                                timestamp: timestamp.clone(),
+                                                            },
+                                                        ));
+                                                    }
+                                                }
+                                                miyabi_core::anthropic::Role::Assistant => {
+                                                    if let Some(ContentBlock::Text { text }) =
+                                                        msg.content.first()
+                                                    {
+                                                        let mut cell = AssistantMessageCell::new(
+                                                            timestamp.clone(),
+                                                        );
+                                                        cell.set_content(text);
+                                                        cell.set_complete();
+                                                        self.view.push_message(Box::new(cell));
+                                                    }
+                                                }
+                                            }
+                                        }
+
+                                        self.view.notifications.success(
+                                            "Session Resumed",
+                                            format!("{} messages loaded", self.conversation.len()),
+                                        );
+                                    }
+                                    Err(e) => {
+                                        self.view
+                                            .notifications
+                                            .error("Resume Error", e.to_string());
+                                    }
+                                }
                             }
                             ViewAction::ToggleAgentMode => {
                                 self.toggle_agent_mode();
@@ -815,7 +933,7 @@ impl App {
         match client
             .message_stream(
                 self.conversation.clone(),
-                Some("You are a helpful AI assistant. Be concise and clear.".to_string()),
+                self.system_prompt.clone(),
                 None,
                 None,
             )