diff --git a/src/theta/analyze.ts b/src/theta/analyze.ts
new file mode 100644
index 000000000..f25dca556
--- /dev/null
+++ b/src/theta/analyze.ts
@@ -0,0 +1,202 @@
+/**
+ * θ₂ ANALYZE: 意図解析、コンテキスト取得
+ *
+ * 観測データを分析し、意図を抽出する。
+ */
+
+import { emitAgentEvent } from "../infra/agent-events.js";
+import {
+  type AnalysisResult,
+  ThetaCycleState,
+  ThetaEvent,
+  ThetaEventType,
+  ThetaPhase,
+} from "./types.js";
+
+// 型のエクスポート
+export type { AnalysisResult };
+
+/**
+ * 分析を実行する
+ *
+ * @param state - θサイクル状態
+ * @returns 更新された状態と分析結果
+ */
+export async function analyze(
+  state: ThetaCycleState,
+): Promise<{ state: ThetaCycleState; result: AnalysisResult }> {
+  const { runId } = state;
+
+  // フェーズ開始イベント
+  emitPhaseEvent(runId, ThetaEventType.PHASE_START, {
+    phase: ThetaPhase.ANALYZE,
+  });
+
+  try {
+    // 入力データの取得
+    const input = state.context.get("observe.input");
+    const metadata = state.context.get("observe.metadata") as Record<string, unknown> | undefined;
+
+    // 意図解析
+    const intent = extractIntent(input);
+    const entities = extractEntities(input);
+    const context = buildContext(input, metadata);
+    const confidence = calculateConfidence(intent, entities);
+
+    const result: AnalysisResult = {
+      intent,
+      entities,
+      context,
+      confidence,
+    };
+
+    // 分析イベント記録
+    const analysisEvent: ThetaEvent = {
+      runId,
+      phase: ThetaPhase.ANALYZE,
+      timestamp: Date.now(),
+      type: ThetaEventType.ANALYSIS,
+      data: {
+        result,
+      },
+    };
+
+    state.events.push(analysisEvent);
+    state.currentPhase = ThetaPhase.ANALYZE;
+    state.context.set("analyze.result", result);
+
+    // Agentイベントを発行
+    emitAgentEvent({
+      runId,
+      stream: "tool",
+      data: {
+        type: "analyze",
+        intent,
+        entities,
+        confidence,
+      },
+    });
+
+    // フェーズ完了イベント
+    emitPhaseEvent(runId, ThetaEventType.PHASE_COMPLETE, {
+      phase: ThetaPhase.ANALYZE,
+      intent,
+      confidence,
+    });
+
+    return { state, result };
+  } catch (error) {
+    // エラーイベント
+    emitPhaseEvent(runId, ThetaEventType.PHASE_ERROR, {
+      phase: ThetaPhase.ANALYZE,
+      error: error instanceof Error ? error.message : String(error),
+    });
+    throw error;
+  }
+}
+
+/**
+ * 入力から意図を抽出する
+ */
+function extractIntent(input: unknown): string {
+  if (typeof input === "string") {
+    // 簡易的な意図抽出（実際はLLM等を使用）
+    const lowerInput = input.toLowerCase();
+    if (lowerInput.includes("create") || lowerInput.includes("new")) {
+      return "create";
+    }
+    if (lowerInput.includes("delete") || lowerInput.includes("remove")) {
+      return "delete";
+    }
+    if (lowerInput.includes("update") || lowerInput.includes("modify")) {
+      return "update";
+    }
+    if (lowerInput.includes("search") || lowerInput.includes("find")) {
+      return "search";
+    }
+    return "unknown";
+  }
+  if (typeof input === "object" && input !== null) {
+    const obj = input as Record<string, unknown>;
+    if (typeof obj.intent === "string") {
+      return obj.intent;
+    }
+  }
+  return "unknown";
+}
+
+/**
+ * 入力からエンティティを抽出する
+ */
+function extractEntities(input: unknown): Record<string, unknown> {
+  const entities: Record<string, unknown> = {};
+
+  if (typeof input === "object" && input !== null) {
+    const obj = input as Record<string, unknown>;
+    // よく使われるエンティティキーを抽出
+    const entityKeys = ["name", "id", "type", "value", "target", "source"];
+    for (const key of entityKeys) {
+      if (key in obj) {
+        entities[key] = obj[key];
+      }
+    }
+  }
+
+  return entities;
+}
+
+/**
+ * コンテキストを構築する
+ */
+function buildContext(input: unknown, metadata?: Record<string, unknown>): Record<string, unknown> {
+  return {
+    inputType: typeof input,
+    hasMetadata: metadata !== undefined,
+    metadataKeys: metadata ? Object.keys(metadata) : [],
+    timestamp: Date.now(),
+  };
+}
+
+/**
+ * 信頼度を計算する
+ */
+function calculateConfidence(intent: string, entities: Record<string, unknown>): number {
+  let score = 0.5; // 基本スコア
+
+  // 意図が特定できている
+  if (intent !== "unknown") {
+    score += 0.2;
+  }
+
+  // エンティティが抽出できている
+  if (Object.keys(entities).length > 0) {
+    score += 0.1 * Math.min(Object.keys(entities).length, 3);
+  }
+
+  return Math.min(score, 1.0);
+}
+
+/**
+ * 分析結果を取得する
+ *
+ * @param state - θサイクル状態
+ * @returns 分析結果
+ */
+export function getAnalysisResult(state: ThetaCycleState): AnalysisResult | undefined {
+  return state.context.get("analyze.result") as AnalysisResult | undefined;
+}
+
+/**
+ * フェーズイベントを発行する
+ */
+function emitPhaseEvent(runId: string, type: ThetaEventType, data: Record<string, unknown>): void {
+  emitAgentEvent({
+    runId,
+    stream: "tool",
+    data: {
+      type: "theta_event",
+      thetaEventType: type,
+      ...data,
+    },
+  });
+}
diff --git a/src/theta/decide.ts b/src/theta/decide.ts
new file mode 100644
index 000000000..544e12272
--- /dev/null
+++ b/src/theta/decide.ts
@@ -0,0 +1,238 @@
+/**
+ * θ₃ DECIDE: 処理方針決定、Agent選択
+ *
+ * 分析結果に基づいて、最適な処理方針とエージェントを選択する。
+ */
+
+import { emitAgentEvent } from "../infra/agent-events.js";
+import {
+  type AnalysisResult,
+  ThetaCycleState,
+  ThetaEvent,
+  ThetaEventType,
+  ThetaPhase,
+} from "./types.js";
+import type { DecisionResult } from "./types.js";
+
+// 型のエクスポート
+export type { DecisionResult };
+
+/**
+ * 利用可能なエージェントの定義
+ */
+interface AgentDefinition {
+  /** エージェントID */
+  id: string;
+  /** 対応する意図 */
+  intents: string[];
+  /** キャパシティ */
+  capacity: number;
+}
+
+/** 利用可能なエージェント一覧 */
+const AVAILABLE_AGENTS: AgentDefinition[] = [
+  { id: "conductor", intents: ["*"], capacity: 10 },
+  { id: "codegen", intents: ["create", "update"], capacity: 5 },
+  { id: "review", intents: ["verify", "check"], capacity: 3 },
+  { id: "deploy", intents: ["deploy", "release"], capacity: 2 },
+];
+
+/**
+ * 処理方針の定義
+ */
+interface StrategyDefinition {
+  /** 戦略ID */
+  id: string;
+  /** 対応する意図 */
+  intents: string[];
+  /** 推奨エージェント */
+  defaultAgent: string;
+  /** 推定実行時間(ms) */
+  estimatedDuration: number;
+}
+
+/** 利用可能な処理方針一覧 */
+const AVAILABLE_STRATEGIES: StrategyDefinition[] = [
+  {
+    id: "direct_execution",
+    intents: ["create", "update", "delete"],
+    defaultAgent: "codegen",
+    estimatedDuration: 5000,
+  },
+  {
+    id: "search_and_retrieve",
+    intents: ["search", "find"],
+    defaultAgent: "conductor",
+    estimatedDuration: 2000,
+  },
+  {
+    id: "verification",
+    intents: ["verify", "check"],
+    defaultAgent: "review",
+    estimatedDuration: 3000,
+  },
+  {
+    id: "deployment",
+    intents: ["deploy", "release"],
+    defaultAgent: "deploy",
+    estimatedDuration: 10000,
+  },
+];
+
+/**
+ * 決定を実行する
+ *
+ * @param state - θサイクル状態
+ * @param analysis - 分析結果
+ * @returns 更新された状態と決定結果
+ */
+export async function decide(
+  state: ThetaCycleState,
+  analysis?: AnalysisResult,
+): Promise<{ state: ThetaCycleState; result: DecisionResult }> {
+  const { runId } = state;
+
+  // フェーズ開始イベント
+  emitPhaseEvent(runId, ThetaEventType.PHASE_START, {
+    phase: ThetaPhase.DECIDE,
+  });
+
+  try {
+    // 分析結果の取得
+    const analysisResult = analysis ?? (state.context.get("analyze.result") as AnalysisResult);
+    if (!analysisResult) {
+      throw new Error("Analysis result not found");
+    }
+
+    // 処理方針の決定
+    const strategy = selectStrategy(analysisResult.intent);
+
+    // エージェントの選択
+    const agent = selectAgent(analysisResult.intent);
+
+    // パラメータの構築
+    const params = buildParams(analysisResult, strategy);
+
+    // 推定実行時間の設定
+    const strategyDef = AVAILABLE_STRATEGIES.find((s) => s.id === strategy);
+    const estimatedDuration = strategyDef?.estimatedDuration;
+
+    const result: DecisionResult = {
+      strategy,
+      agent,
+      params,
+      estimatedDuration,
+    };
+
+    // 決定イベント記録
+    const decisionEvent: ThetaEvent = {
+      runId,
+      phase: ThetaPhase.DECIDE,
+      timestamp: Date.now(),
+      type: ThetaEventType.DECISION,
+      data: {
+        result,
+      },
+    };
+
+    state.events.push(decisionEvent);
+    state.currentPhase = ThetaPhase.DECIDE;
+    state.context.set("decide.result", result);
+
+    // Agentイベントを発行
+    emitAgentEvent({
+      runId,
+      stream: "tool",
+      data: {
+        type: "decide",
+        strategy,
+        agent,
+        params,
+      },
+    });
+
+    // フェーズ完了イベント
+    emitPhaseEvent(runId, ThetaEventType.PHASE_COMPLETE, {
+      phase: ThetaPhase.DECIDE,
+      strategy,
+      agent,
+    });
+
+    return { state, result };
+  } catch (error) {
+    // エラーイベント
+    emitPhaseEvent(runId, ThetaEventType.PHASE_ERROR, {
+      phase: ThetaPhase.DECIDE,
+      error: error instanceof Error ? error.message : String(error),
+    });
+    throw error;
+  }
+}
+
+/**
+ * 意図に基づいて処理方針を選択する
+ */
+function selectStrategy(intent: string): string {
+  const strategy = AVAILABLE_STRATEGIES.find((s) => s.intents.includes(intent));
+  return strategy?.id ?? "default";
+}
+
+/**
+ * 意図に基づいてエージェントを選択する
+ */
+function selectAgent(intent: string): string | undefined {
+  const agent = AVAILABLE_AGENTS.find((a) => a.intents.includes(intent) || a.intents.includes("*"));
+  return agent?.id;
+}
+
+/**
+ * パラメータを構築する
+ */
+function buildParams(analysis: AnalysisResult, strategy: string): Record<string, unknown> {
+  return {
+    intent: analysis.intent,
+    entities: analysis.entities,
+    strategy,
+    confidence: analysis.confidence,
+    timestamp: Date.now(),
+  };
+}
+
+/**
+ * 決定結果を取得する
+ *
+ * @param state - θサイクル状態
+ * @returns 決定結果
+ */
+export function getDecisionResult(state: ThetaCycleState): DecisionResult | undefined {
+  return state.context.get("decide.result") as DecisionResult | undefined;
+}
+
+/**
+ * 利用可能なエージェント一覧を取得する
+ */
+export function getAvailableAgents(): AgentDefinition[] {
+  return [...AVAILABLE_AGENTS];
+}
+
+/**
+ * 利用可能な処理方針一覧を取得する
+ */
+export function getAvailableStrategies(): StrategyDefinition[] {
+  return [...AVAILABLE_STRATEGIES];
+}
+
+/**
+ * フェーズイベントを発行する
+ */
+function emitPhaseEvent(runId: string, type: ThetaEventType, data: Record<string, unknown>): void {
+  emitAgentEvent({
+    runId,
+    stream: "tool",
+    data: {
+      type: "theta_event",
+      thetaEventType: type,
+      ...data,
+    },
+  });
+}
diff --git a/src/theta/execute.ts b/src/theta/execute.ts
new file mode 100644
index 000000000..862de758d
--- /dev/null
+++ b/src/theta/execute.ts
@@ -0,0 +1,253 @@
+/**
+ * θ₄ EXECUTE: 実行(タイムアウト管理)
+ *
+ * 決定された処理方針に基づいて実行を行う。
+ * タイムアウトとリトライを管理する。
+ */
+
+import { emitAgentEvent } from "../infra/agent-events.js";
+import {
+  type DecisionResult,
+  ThetaCycleState,
+  ThetaEvent,
+  ThetaEventType,
+  ThetaPhase,
+} from "./types.js";
+import type { ExecuteOptions, ExecutionResult } from "./types.js";
+
+// 型のエクスポート
+export type { ExecuteOptions, ExecutionResult };
+
+/**
+ * デフォルトの実行オプション
+ */
+const DEFAULT_OPTIONS: ExecuteOptions = {
+  timeout: 30000, // 30秒
+  retries: 3,
+};
+
+/**
+ * 実行を実行する
+ *
+ * @param state - θサイクル状態
+ * @param decision - 決定結果
+ * @param executor - 実行関数
+ * @param options - 実行オプション
+ * @returns 更新された状態と実行結果
+ */
+export async function execute<T = unknown>(
+  state: ThetaCycleState,
+  decision: DecisionResult,
+  executor: (params: Record<string, unknown>) => Promise<T>,
+  options?: Partial<ExecuteOptions>,
+): Promise<{ state: ThetaCycleState; result: ExecutionResult }> {
+  const { runId } = state;
+  const opts = { ...DEFAULT_OPTIONS, ...options };
+
+  // フェーズ開始イベント
+  emitPhaseEvent(runId, ThetaEventType.PHASE_START, {
+    phase: ThetaPhase.EXECUTE,
+    strategy: decision.strategy,
+    agent: decision.agent,
+  });
+
+  const startTime = Date.now();
+
+  try {
+    // リトライ付き実行
+    const data = await executeWithRetry(
+      executor,
+      decision.params,
+      opts.timeout,
+      opts.retries,
+      opts.onProgress,
+    );
+
+    const duration = Date.now() - startTime;
+    const result: ExecutionResult = {
+      success: true,
+      data,
+      duration,
+    };
+
+    // 実行イベント記録
+    const executionEvent: ThetaEvent = {
+      runId,
+      phase: ThetaPhase.EXECUTE,
+      timestamp: Date.now(),
+      type: ThetaEventType.EXECUTION,
+      data: {
+        result,
+      },
+    };
+
+    state.events.push(executionEvent);
+    state.currentPhase = ThetaPhase.EXECUTE;
+    state.context.set("execute.result", result);
+
+    // Agentイベントを発行
+    emitAgentEvent({
+      runId,
+      stream: "tool",
+      data: {
+        type: "execute",
+        success: true,
+        duration,
+      },
+    });
+
+    // フェーズ完了イベント
+    emitPhaseEvent(runId, ThetaEventType.PHASE_COMPLETE, {
+      phase: ThetaPhase.EXECUTE,
+      duration,
+    });
+
+    return { state, result };
+  } catch (error) {
+    const duration = Date.now() - startTime;
+    const execError = error instanceof Error ? error : new Error(String(error));
+
+    const result: ExecutionResult = {
+      success: false,
+      error: execError,
+      duration,
+    };
+
+    // 実行エラーイベント記録
+    const executionEvent: ThetaEvent = {
+      runId,
+      phase: ThetaPhase.EXECUTE,
+      timestamp: Date.now(),
+      type: ThetaEventType.EXECUTION,
+      data: {
+        result,
+      },
+    };
+
+    state.events.push(executionEvent);
+    state.context.set("execute.result", result);
+
+    // エラーイベント
+    emitPhaseEvent(runId, ThetaEventType.PHASE_ERROR, {
+      phase: ThetaPhase.EXECUTE,
+      error: execError.message,
+      duration,
+    });
+
+    return { state, result };
+  }
+}
+
+/**
+ * リトライ付きで実行する
+ */
+async function executeWithRetry<T>(
+  executor: (params: Record<string, unknown>) => Promise<T>,
+  params: Record<string, unknown>,
+  timeout: number,
+  retries: number,
+  onProgress?: (progress: number) => void,
+): Promise<T> {
+  let lastError: Error | null = null;
+
+  for (let attempt = 0; attempt <= retries; attempt++) {
+    try {
+      // 進度通知
+      onProgress?.(attempt / (retries + 1));
+
+      // タイムアウト付き実行
+      const result = await withTimeout(executor(params), timeout);
+      return result;
+    } catch (error) {
+      lastError = error instanceof Error ? error : new Error(String(error));
+
+      // 最後の試行で失敗した場合はエラーを投げる
+      if (attempt >= retries) {
+        throw new Error(`Execution failed after ${retries + 1} attempts: ${lastError.message}`);
+      }
+
+      // 指数バックオフで待機
+      const delay = Math.min(1000 * 2 ** attempt, 10000);
+      await sleep(delay);
+    }
+  }
+
+  throw lastError ?? new Error("Execution failed");
+}
+
+/**
+ * タイムアウト付きで実行する
+ */
+function withTimeout<T>(promise: Promise<T>, timeoutMs: number): Promise<T> {
+  return Promise.race([
+    promise,
+    new Promise<T>((_, reject) =>
+      setTimeout(() => reject(new Error(`Timeout after ${timeoutMs}ms`)), timeoutMs),
+    ),
+  ]);
+}
+
+/**
+ * 指定ミリ秒待機する
+ */
+function sleep(ms: number): Promise<void> {
+  return new Promise((resolve) => setTimeout(resolve, ms));
+}
+
+/**
+ * 実行結果を取得する
+ *
+ * @param state - θサイクル状態
+ * @returns 実行結果
+ */
+export function getExecutionResult(state: ThetaCycleState): ExecutionResult | undefined {
+  return state.context.get("execute.result") as ExecutionResult | undefined;
+}
+
+/**
+ * フェーズイベントを発行する
+ */
+function emitPhaseEvent(runId: string, type: ThetaEventType, data: Record<string, unknown>): void {
+  emitAgentEvent({
+    runId,
+    stream: "tool",
+    data: {
+      type: "theta_event",
+      thetaEventType: type,
+      ...data,
+    },
+  });
+}
+
+/**
+ * バックグラウンド実行を開始する（完了を待たない）
+ *
+ * @param state - θサイクル状態
+ * @param decision - 決定結果
+ * @param executor - 実行関数
+ * @param options - 実行オプション
+ * @returns 実行ID（後で結果を取得するために使用）
+ */
+export function executeBackground<T = unknown>(
+  state: ThetaCycleState,
+  decision: DecisionResult,
+  executor: (params: Record<string, unknown>) => Promise<T>,
+  options?: Partial<ExecuteOptions>,
+): string {
+  const executionId = `bg_${Date.now()}_${Math.random().toString(36).slice(2, 11)}`;
+
+  // 非同期実行（エラーは無視）
+  execute(state, decision, executor, options).catch(() => {
+    // バックグラウンド実行のエラーはログのみ記録
+    emitAgentEvent({
+      runId: state.runId,
+      stream: "error",
+      data: {
+        type: "background_execution_error",
+        executionId,
+      },
+    });
+  });
+
+  return executionId;
+}
diff --git a/src/theta/improve.ts b/src/theta/improve.ts
new file mode 100644
index 000000000..cdb062a90
--- /dev/null
+++ b/src/theta/improve.ts
@@ -0,0 +1,279 @@
+/**
+ * θ₆ IMPROVE: ログ照合、改善提案
+ *
+ * 実行結果を分析し、改善提案を生成する。
+ * 学習サイクルを完結させる。
+ */
+
+import { emitAgentEvent } from "../infra/agent-events.js";
+import { ThetaCycleState, ThetaEvent, ThetaEventType, ThetaPhase } from "./types.js";
+import type { AnalysisResult, ImprovementSuggestion, VerificationResult } from "./types.js";
+
+// 型のエクスポート
+export type { ImprovementSuggestion };
+
+/**
+ * 改善パターンの定義
+ */
+interface ImprovementPattern {
+  /** パターンID */
+  id: string;
+  /** パターンマッチ条件 */
+  match: (context: ThetaCycleState) => boolean;
+  /** 改善提案生成関数 */
+  suggest: (context: ThetaCycleState) => ImprovementSuggestion;
+}
+
+/** デフォルトの改善パターン一覧 */
+const DEFAULT_IMPROVEMENT_PATTERNS: ImprovementPattern[] = [
+  {
+    id: "failed_execution",
+    match: (ctx) => {
+      const result = ctx.context.get("execute.result") as { success?: boolean } | undefined;
+      return result?.success === false;
+    },
+    suggest: () => ({
+      suggestion:
+        "Execution failed. Review error logs and consider retry with different parameters.",
+      target: "execution",
+      priority: "high",
+    }),
+  },
+  {
+    id: "low_quality_score",
+    match: (ctx) => {
+      const result = ctx.context.get("verify.result") as VerificationResult | undefined;
+      return result?.qualityScore !== undefined && result.qualityScore < 0.6;
+    },
+    suggest: (ctx) => {
+      const result = ctx.context.get("verify.result") as VerificationResult | undefined;
+      return {
+        suggestion: `Quality score below threshold (${result?.qualityScore?.toFixed(2)}). Review failed checks: ${result?.failures?.join(", ")}`,
+        target: "quality",
+        priority: "medium",
+      };
+    },
+  },
+  {
+    id: "slow_execution",
+    match: (ctx) => {
+      const result = ctx.context.get("execute.result") as { duration?: number } | undefined;
+      return result?.duration !== undefined && result.duration > 10000; // 10秒超過
+    },
+    suggest: (ctx) => {
+      const result = ctx.context.get("execute.result") as { duration?: number } | undefined;
+      return {
+        suggestion: `Execution took ${result?.duration}ms. Consider optimization or caching.`,
+        target: "performance",
+        priority: "low",
+        metadata: { duration: result?.duration },
+      };
+    },
+  },
+  {
+    id: "unknown_intent",
+    match: (ctx) => {
+      const result = ctx.context.get("analyze.result") as AnalysisResult | undefined;
+      return result?.intent === "unknown";
+    },
+    suggest: () => ({
+      suggestion:
+        "Intent was not recognized. Consider expanding intent patterns or adding training data.",
+      target: "analysis",
+      priority: "medium",
+    }),
+  },
+  {
+    id: "low_confidence",
+    match: (ctx) => {
+      const result = ctx.context.get("analyze.result") as AnalysisResult | undefined;
+      return result?.confidence !== undefined && result.confidence < 0.5;
+    },
+    suggest: (ctx) => {
+      const result = ctx.context.get("analyze.result") as AnalysisResult | undefined;
+      return {
+        suggestion: `Analysis confidence low (${result?.confidence?.toFixed(2)}). Additional context may improve accuracy.`,
+        target: "analysis",
+        priority: "low",
+        metadata: { confidence: result?.confidence },
+      };
+    },
+  },
+  {
+    id: "successful_execution",
+    match: (ctx) => {
+      const execResult = ctx.context.get("execute.result") as { success?: boolean } | undefined;
+      const verifyResult = ctx.context.get("verify.result") as VerificationResult | undefined;
+      return execResult?.success === true && verifyResult?.passed === true;
+    },
+    suggest: () => ({
+      suggestion:
+        "Execution completed successfully. Consider documenting this pattern for future reference.",
+      target: "documentation",
+      priority: "low",
+    }),
+  },
+];
+
+/**
+ * 改善を実行する
+ *
+ * @param state - θサイクル状態
+ * @param customPatterns - カスタム改善パターン（オプション）
+ * @returns 更新された状態と改善提案の配列
+ */
+export async function improve(
+  state: ThetaCycleState,
+  customPatterns?: ImprovementPattern[],
+): Promise<{ state: ThetaCycleState; suggestions: ImprovementSuggestion[] }> {
+  const { runId } = state;
+
+  // フェーズ開始イベント
+  emitPhaseEvent(runId, ThetaEventType.PHASE_START, {
+    phase: ThetaPhase.IMPROVE,
+  });
+
+  try {
+    // 改善パターンの評価
+    const patterns = customPatterns ?? DEFAULT_IMPROVEMENT_PATTERNS;
+    const suggestions: ImprovementSuggestion[] = [];
+
+    for (const pattern of patterns) {
+      if (pattern.match(state)) {
+        suggestions.push(pattern.suggest(state));
+      }
+    }
+
+    // 改善イベント記録
+    const improvementEvent: ThetaEvent = {
+      runId,
+      phase: ThetaPhase.IMPROVE,
+      timestamp: Date.now(),
+      type: ThetaEventType.IMPROVEMENT,
+      data: {
+        suggestions,
+        count: suggestions.length,
+      },
+    };
+
+    state.events.push(improvementEvent);
+    state.currentPhase = ThetaPhase.IMPROVE;
+    state.context.set("improve.suggestions", suggestions);
+
+    // Agentイベントを発行
+    emitAgentEvent({
+      runId,
+      stream: "tool",
+      data: {
+        type: "improve",
+        suggestions,
+        count: suggestions.length,
+      },
+    });
+
+    // フェーズ完了イベント
+    emitPhaseEvent(runId, ThetaEventType.PHASE_COMPLETE, {
+      phase: ThetaPhase.IMPROVE,
+      suggestionCount: suggestions.length,
+    });
+
+    return { state, suggestions };
+  } catch (error) {
+    // エラーイベント
+    emitPhaseEvent(runId, ThetaEventType.PHASE_ERROR, {
+      phase: ThetaPhase.IMPROVE,
+      error: error instanceof Error ? error.message : String(error),
+    });
+    throw error;
+  }
+}
+
+/**
+ * 改善提案を取得する
+ *
+ * @param state - θサイクル状態
+ * @returns 改善提案の配列
+ */
+export function getImprovementSuggestions(state: ThetaCycleState): ImprovementSuggestion[] {
+  return (state.context.get("improve.suggestions") as ImprovementSuggestion[]) ?? [];
+}
+
+/**
+ * 改善パターンを追加する
+ *
+ * @param patterns - 既存パターン配列
+ * @param newPattern - 追加するパターン
+ * @returns 更新されたパターン配列
+ */
+export function addImprovementPattern(
+  patterns: ImprovementPattern[],
+  newPattern: ImprovementPattern,
+): ImprovementPattern[] {
+  return [...patterns, newPattern];
+}
+
+/**
+ * カスタム改善パターンを作成する
+ *
+ * @param id - パターンID
+ * @param match - マッチ条件関数
+ * @param suggest - 改善提案生成関数
+ * @returns 改善パターン定義
+ */
+export function createImprovementPattern(
+  id: string,
+  match: (context: ThetaCycleState) => boolean,
+  suggest: (context: ThetaCycleState) => ImprovementSuggestion,
+): ImprovementPattern {
+  return { id, match, suggest };
+}
+
+/**
+ * サイクル全体のサマリーを生成する
+ *
+ * @param state - θサイクル状態
+ * @returns サマリーオブジェクト
+ */
+export function generateCycleSummary(state: ThetaCycleState): {
+  runId: string;
+  duration: number;
+  phases: ThetaPhase[];
+  eventCount: number;
+  success: boolean;
+  suggestions: ImprovementSuggestion[];
+} {
+  const startTime = state.startTime;
+  const endTime = Date.now();
+  const duration = endTime - startTime;
+
+  const phases = state.events.map((e) => e.phase).filter((p, i, arr) => arr.indexOf(p) === i); // ユニークなフェーズのみ
+
+  const executionResult = state.context.get("execute.result") as { success?: boolean } | undefined;
+  const success = executionResult?.success ?? false;
+
+  const suggestions = getImprovementSuggestions(state);
+
+  return {
+    runId: state.runId,
+    duration,
+    phases,
+    eventCount: state.events.length,
+    success,
+    suggestions,
+  };
+}
+
+/**
+ * フェーズイベントを発行する
+ */
+function emitPhaseEvent(runId: string, type: ThetaEventType, data: Record<string, unknown>): void {
+  emitAgentEvent({
+    runId,
+    stream: "tool",
+    data: {
+      type: "theta_event",
+      thetaEventType: type,
+      ...data,
+    },
+  });
+}
diff --git a/src/theta/index.ts b/src/theta/index.ts
new file mode 100644
index 000000000..acff658c1
--- /dev/null
+++ b/src/theta/index.ts
@@ -0,0 +1,261 @@
+/**
+ * θサイクル (Theta Cycle) - エントリーポイント
+ *
+ * Agent(Intent, World₀) = lim_{n→∞} (θ₆ ∘ θ₅ ∘ θ₄ ∘ θ₃ ∘ θ₂ ∘ θ₁)ⁿ
+ *
+ * 完全なθサイクル実行を提供する。
+ */
+
+// 型定義のエクスポート
+export type {
+  // 共通型
+  ThetaCycleState,
+  ThetaCycleOptions,
+  ThetaEvent,
+  ThetaEventType,
+
+  // 各フェーズ関連
+  ObserveContext,
+  AnalysisResult,
+  DecisionResult,
+  ExecuteOptions,
+  ExecutionResult,
+  VerificationResult,
+  ImprovementSuggestion,
+} from "./types.js";
+
+export { ThetaPhase } from "./types.js";
+
+// θ₁ OBSERVE
+export { observe, handleReaction, getObservations } from "./observe.js";
+
+// θ₂ ANALYZE
+export { analyze, getAnalysisResult } from "./analyze.js";
+
+// θ₃ DECIDE
+export { decide, getDecisionResult, getAvailableAgents, getAvailableStrategies } from "./decide.js";
+
+// θ₄ EXECUTE
+export { execute, executeBackground, getExecutionResult } from "./execute.js";
+
+// θ₅ VERIFY
+export { verify, getVerificationResult, addQualityCheck, createQualityCheck } from "./verify.js";
+
+// θ₆ IMPROVE
+export {
+  improve,
+  getImprovementSuggestions,
+  addImprovementPattern,
+  createImprovementPattern,
+  generateCycleSummary,
+} from "./improve.js";
+
+// 完全なサイクル実行
+import { observe, handleReaction, type ObserveContext } from "./observe.js";
+import { analyze, type AnalysisResult } from "./analyze.js";
+import { decide, type DecisionResult } from "./decide.js";
+import { execute, type ExecuteOptions, type ExecutionResult } from "./execute.js";
+import { verify, type VerificationResult } from "./verify.js";
+import { improve, generateCycleSummary, type ImprovementSuggestion } from "./improve.js";
+import type { ThetaCycleOptions, ThetaCycleState } from "./types.js";
+import { ThetaPhase } from "./types.js";
+
+/**
+ * 新しいθサイクル状態を作成する
+ */
+export function createThetaCycleState(runId: string, options?: ThetaCycleOptions): ThetaCycleState {
+  return {
+    runId,
+    startTime: Date.now(),
+    currentPhase: null,
+    events: [],
+    context: new Map(),
+  };
+}
+
+/**
+ * 完全なθサイクルを実行する
+ *
+ * @param input - 入力データ
+ * @param executor - 実行関数
+ * @param options - サイクルオプション
+ * @returns サイクル結果
+ */
+export async function runThetaCycle<T = unknown>(
+  input: unknown,
+  executor: (params: Record<string, unknown>) => Promise<T>,
+  options?: ThetaCycleOptions & Partial<ExecuteOptions>,
+): Promise<{
+  state: ThetaCycleState;
+  analysis: AnalysisResult;
+  decision: DecisionResult;
+  execution: ExecutionResult;
+  verification: VerificationResult;
+  suggestions: ImprovementSuggestion[];
+}> {
+  const runId = `theta_${Date.now()}_${Math.random().toString(36).slice(2, 11)}`;
+  const state = createThetaCycleState(runId, options);
+
+  // オプションのマージ
+  const timeout = options?.defaultTimeout ?? 30000;
+  const retries = options?.defaultRetries ?? 3;
+
+  // θ₁ OBSERVE
+  const observeState = await observe(state, { input });
+
+  // θ₂ ANALYZE
+  const analyzeResult = await analyze(observeState);
+  const analyzeState = analyzeResult.state;
+
+  // θ₃ DECIDE
+  const decideResult = await decide(analyzeState);
+  const decideState = decideResult.state;
+
+  // θ₄ EXECUTE
+  const executeResult = await execute<T>(decideState, decideResult.result, executor, {
+    timeout,
+    retries,
+  });
+  const executeState = executeResult.state;
+
+  // θ₅ VERIFY
+  const verifyResult = await verify(executeState);
+  const verifyState = verifyResult.state;
+
+  // θ₆ IMPROVE
+  const improveResult = await improve(verifyState);
+  const improveState = improveResult.state;
+
+  // サマリー生成
+  const summary = generateCycleSummary(improveState);
+
+  // オプションのコールバック
+  if (options?.onEvent) {
+    for (const event of improveState.events) {
+      options.onEvent(event);
+    }
+  }
+
+  return {
+    state: improveState,
+    analysis: analyzeResult.result,
+    decision: decideResult.result,
+    execution: executeResult.result,
+    verification: verifyResult.result,
+    suggestions: improveResult.suggestions,
+  };
+}
+
+/**
+ * θサイクルをストリームモードで実行する
+ * 各フェーズの完了時にコールバックを呼び出す
+ *
+ * @param input - 入力データ
+ * @param executor - 実行関数
+ * @param onPhase - フェーズ完了時のコールバック
+ * @param options - サイクルオプション
+ * @returns 最終的なサイクル結果
+ */
+export async function runThetaCycleStream<T = unknown>(
+  input: unknown,
+  executor: (params: Record<string, unknown>) => Promise<T>,
+  onPhase: (phase: ThetaPhase, data: unknown) => void,
+  options?: ThetaCycleOptions & Partial<ExecuteOptions>,
+): Promise<{
+  state: ThetaCycleState;
+  analysis: AnalysisResult;
+  decision: DecisionResult;
+  execution: ExecutionResult;
+  verification: VerificationResult;
+  suggestions: ImprovementSuggestion[];
+}> {
+  const runId = `theta_stream_${Date.now()}_${Math.random().toString(36).slice(2, 11)}`;
+  const state = createThetaCycleState(runId, options);
+
+  const timeout = options?.defaultTimeout ?? 30000;
+  const retries = options?.defaultRetries ?? 3;
+
+  // θ₁ OBSERVE
+  let currentState = await observe(state, { input });
+  onPhase(ThetaPhase.OBSERVE, currentState.events);
+
+  // θ₂ ANALYZE
+  const analyzeResult = await analyze(currentState);
+  currentState = analyzeResult.state;
+  onPhase(ThetaPhase.ANALYZE, analyzeResult.result);
+
+  // θ₃ DECIDE
+  const decideResult = await decide(currentState);
+  currentState = decideResult.state;
+  onPhase(ThetaPhase.DECIDE, decideResult.result);
+
+  // θ₄ EXECUTE
+  const executeResult = await execute<T>(currentState, decideResult.result, executor, {
+    timeout,
+    retries,
+  });
+  currentState = executeResult.state;
+  onPhase(ThetaPhase.EXECUTE, executeResult.result);
+
+  // θ₅ VERIFY
+  const verifyResult = await verify(currentState);
+  currentState = verifyResult.state;
+  onPhase(ThetaPhase.VERIFY, verifyResult.result);
+
+  // θ₆ IMPROVE
+  const improveResult = await improve(currentState);
+  currentState = improveResult.state;
+  onPhase(ThetaPhase.IMPROVE, improveResult.suggestions);
+
+  return {
+    state: currentState,
+    analysis: analyzeResult.result,
+    decision: decideResult.result,
+    execution: executeResult.result,
+    verification: verifyResult.result,
+    suggestions: improveResult.suggestions,
+  };
+}
+
+/**
+ * θサイクルの実行を一時停止/再開するためのチェックポイントを作成する
+ *
+ * @param state - 現在のサイクル状態
+ * @returns シリアライズ可能なチェックポイントデータ
+ */
+export function createCheckpoint(state: ThetaCycleState): {
+  runId: string;
+  startTime: number;
+  currentPhase: ThetaPhase | null;
+  context: Record<string, unknown>;
+  eventCount: number;
+} {
+  return {
+    runId: state.runId,
+    startTime: state.startTime,
+    currentPhase: state.currentPhase,
+    context: Object.fromEntries(state.context.entries()),
+    eventCount: state.events.length,
+  };
+}
+
+/**
+ * チェックポイントからサイクル状態を復元する
+ *
+ * @param checkpoint - チェックポイントデータ
+ * @returns 復元されたサイクル状態
+ */
+export function restoreFromCheckpoint(checkpoint: {
+  runId: string;
+  startTime: number;
+  currentPhase: ThetaPhase | null;
+  context: Record<string, unknown>;
+}): ThetaCycleState {
+  return {
+    runId: checkpoint.runId,
+    startTime: checkpoint.startTime,
+    currentPhase: checkpoint.currentPhase,
+    events: [],
+    context: new Map(Object.entries(checkpoint.context)),
+  };
+}
diff --git a/src/theta/observe.ts b/src/theta/observe.ts
new file mode 100644
index 000000000..f65f2dfc3
--- /dev/null
+++ b/src/theta/observe.ts
@@ -0,0 +1,152 @@
+/**
+ * θ₁ OBSERVE: イベントログ記録、リアクション処理
+ *
+ * 問題理解・分析の最初のフェーズ。
+ * 入力データを観測し、イベントログを記録する。
+ */
+
+import { emitAgentEvent } from "../infra/agent-events.js";
+import {
+  type ObserveContext,
+  ThetaCycleState,
+  ThetaEvent,
+  ThetaEventType,
+  ThetaPhase,
+} from "./types.js";
+
+/**
+ * 観測を実行する
+ *
+ * @param state - θサイクル状態
+ * @param context - 観測コンテキスト
+ * @returns 更新された状態
+ */
+export async function observe(
+  state: ThetaCycleState,
+  context: ObserveContext,
+): Promise<ThetaCycleState> {
+  const { runId } = state;
+
+  // フェーズ開始イベント
+  emitPhaseEvent(runId, ThetaEventType.PHASE_START, {
+    phase: ThetaPhase.OBSERVE,
+    input: context.input,
+  });
+
+  try {
+    // 入力データの観測
+    const observation: ThetaEvent = {
+      runId,
+      phase: ThetaPhase.OBSERVE,
+      timestamp: Date.now(),
+      type: ThetaEventType.OBSERVATION,
+      data: {
+        input: context.input,
+        metadata: context.metadata,
+        sessionKey: context.sessionKey,
+      },
+    };
+
+    // 状態を更新
+    state.events.push(observation);
+    state.currentPhase = ThetaPhase.OBSERVE;
+    state.context.set("observe.input", context.input);
+    state.context.set("observe.metadata", context.metadata);
+
+    // Agentイベントを発行
+    emitAgentEvent({
+      runId,
+      stream: "tool",
+      data: {
+        type: "observe",
+        input: context.input,
+      },
+    });
+
+    // フェーズ完了イベント
+    emitPhaseEvent(runId, ThetaEventType.PHASE_COMPLETE, {
+      phase: ThetaPhase.OBSERVE,
+      observationCount: 1,
+    });
+
+    return state;
+  } catch (error) {
+    // エラーイベント
+    emitPhaseEvent(runId, ThetaEventType.PHASE_ERROR, {
+      phase: ThetaPhase.OBSERVE,
+      error: error instanceof Error ? error.message : String(error),
+    });
+    throw error;
+  }
+}
+
+/**
+ * リアクションを処理する
+ *
+ * @param state - θサイクル状態
+ * @param reaction - リアクションデータ
+ * @returns 更新された状態
+ */
+export async function handleReaction(
+  state: ThetaCycleState,
+  reaction: Record<string, unknown>,
+): Promise<ThetaCycleState> {
+  const { runId } = state;
+
+  // リアクション記録
+  const reactionEvent: ThetaEvent = {
+    runId,
+    phase: ThetaPhase.OBSERVE,
+    timestamp: Date.now(),
+    type: ThetaEventType.OBSERVATION,
+    data: {
+      type: "reaction",
+      reaction,
+    },
+  };
+
+  state.events.push(reactionEvent);
+  state.context.set("observe.reaction", reaction);
+
+  // Agentイベントを発行
+  emitAgentEvent({
+    runId,
+    stream: "tool",
+    data: {
+      type: "reaction",
+      reaction,
+    },
+  });
+
+  return state;
+}
+
+/**
+ * フェーズイベントを発行する
+ */
+function emitPhaseEvent(runId: string, type: ThetaEventType, data: Record<string, unknown>): void {
+  emitAgentEvent({
+    runId,
+    stream: "tool",
+    data: {
+      type: "theta_event",
+      thetaEventType: type,
+      ...data,
+    },
+  });
+}
+
+/**
+ * 観測ログを取得する
+ *
+ * @param state - θサイクル状態
+ * @returns 観測イベントの配列
+ */
+export function getObservations(state: ThetaCycleState): ThetaEvent[] {
+  return state.events.filter(
+    (e) => e.phase === ThetaPhase.OBSERVE && e.type === ThetaEventType.OBSERVATION,
+  );
+}
+
+// 型のエクスポート
+export type { ObserveContext };
diff --git a/src/theta/types.ts b/src/theta/types.ts
new file mode 100644
index 000000000..b2506f87d
--- /dev/null
+++ b/src/theta/types.ts
@@ -0,0 +1,181 @@
+/**
+ * θサイクル (Theta Cycle) の型定義
+ *
+ * Agent(Intent, World₀) = lim_{n→∞} (θ₆ ∘ θ₅ ∘ θ₄ ∘ θ₃ ∘ θ₂ ∘ θ₁)ⁿ
+ */
+
+/**
+ * θサイクルの各フェーズ
+ */
+export enum ThetaPhase {
+  OBSERVE = "θ₁ OBSERVE",
+  ANALYZE = "θ₂ ANALYZE",
+  DECIDE = "θ₃ DECIDE",
+  EXECUTE = "θ₄ EXECUTE",
+  VERIFY = "θ₅ VERIFY",
+  IMPROVE = "θ₆ IMPROVE",
+}
+
+/**
+ * イベントログの型
+ */
+export interface ThetaEvent {
+  /** 実行ID */
+  runId: string;
+  /** フェーズ */
+  phase: ThetaPhase;
+  /** タイムスタンプ */
+  timestamp: number;
+  /** イベント種別 */
+  type: ThetaEventType;
+  /** データ */
+  data: Record<string, unknown>;
+}
+
+/**
+ * イベント種別
+ */
+export enum ThetaEventType {
+  /** フェーズ開始 */
+  PHASE_START = "phase_start",
+  /** フェーズ完了 */
+  PHASE_COMPLETE = "phase_complete",
+  /** フェーズエラー */
+  PHASE_ERROR = "phase_error",
+  /** 観測データ記録 */
+  OBSERVATION = "observation",
+  /** 分析結果 */
+  ANALYSIS = "analysis",
+  /** 決定 */
+  DECISION = "decision",
+  /** 実行結果 */
+  EXECUTION = "execution",
+  /** 検証結果 */
+  VERIFICATION = "verification",
+  /** 改善提案 */
+  IMPROVEMENT = "improvement",
+}
+
+/**
+ * 観測コンテキスト (OBSERVE用)
+ */
+export interface ObserveContext {
+  /** セッションキー */
+  sessionKey?: string;
+  /** 入力データ */
+  input: unknown;
+  /** メタデータ */
+  metadata?: Record<string, unknown>;
+}
+
+/**
+ * 分析結果 (ANALYZE用)
+ */
+export interface AnalysisResult {
+  /** 意図解析結果 */
+  intent: string;
+  /** 抽出されたエンティティ */
+  entities: Record<string, unknown>;
+  /** コンテキスト情報 */
+  context: Record<string, unknown>;
+  /** 信頼度 */
+  confidence: number;
+}
+
+/**
+ * 決定結果 (DECIDE用)
+ */
+export interface DecisionResult {
+  /** 選択された処理方針 */
+  strategy: string;
+  /** 選択されたエージェント */
+  agent?: string;
+  /** パラメータ */
+  params: Record<string, unknown>;
+  /** 推定実行時間(ms) */
+  estimatedDuration?: number;
+}
+
+/**
+ * 実行オプション (EXECUTE用)
+ */
+export interface ExecuteOptions {
+  /** タイムアウト(ms) */
+  timeout: number;
+  /** リトライ回数 */
+  retries: number;
+  /** 进度回调 */
+  onProgress?: (progress: number) => void;
+}
+
+/**
+ * 実行結果 (EXECUTE用)
+ */
+export interface ExecutionResult {
+  /** 成功判定 */
+  success: boolean;
+  /** 結果データ */
+  data?: unknown;
+  /** エラー情報 */
+  error?: Error;
+  /** 実行時間(ms) */
+  duration: number;
+}
+
+/**
+ * 検証結果 (VERIFY用)
+ */
+export interface VerificationResult {
+  /** 検証パス */
+  passed: boolean;
+  /** 品質スコア (0-1) */
+  qualityScore: number;
+  /** 検証項目ごとの結果 */
+  checks: Record<string, boolean>;
+  /** 失敗理由 */
+  failures?: string[];
+}
+
+/**
+ * 改善提案 (IMPROVE用)
+ */
+export interface ImprovementSuggestion {
+  /** 改善内容 */
+  suggestion: string;
+  /** 適用対象 */
+  target: string;
+  /** 優先度 */
+  priority: "low" | "medium" | "high";
+  /** メタデータ */
+  metadata?: Record<string, unknown>;
+}
+
+/**
+ * θサイクルの完全な実行状態
+ */
+export interface ThetaCycleState {
+  /** 実行ID */
+  runId: string;
+  /** 開始時刻 */
+  startTime: number;
+  /** 現在のフェーズ */
+  currentPhase: ThetaPhase | null;
+  /** イベントログ */
+  events: ThetaEvent[];
+  /** コンテキスト */
+  context: Map<string, unknown>;
+}
+
+/**
+ * θサイクルの設定
+ */
+export interface ThetaCycleOptions {
+  /** デフォルトタイムアウト(ms) */
+  defaultTimeout?: number;
+  /** デフォルトリトライ回数 */
+  defaultRetries?: number;
+  /** 詳細ログレベル */
+  verbose?: boolean;
+  /** カスタムイベントハンドラ */
+  onEvent?: (event: ThetaEvent) => void;
+}
diff --git a/src/theta/verify.ts b/src/theta/verify.ts
new file mode 100644
index 000000000..eed1faafb
--- /dev/null
+++ b/src/theta/verify.ts
@@ -0,0 +1,213 @@
+/**
+ * θ₅ VERIFY: 結果検証、品質チェック
+ *
+ * 実行結果を検証し、品質を評価する。
+ */
+
+import { emitAgentEvent } from "../infra/agent-events.js";
+import {
+  type ExecutionResult,
+  ThetaCycleState,
+  ThetaEvent,
+  ThetaEventType,
+  ThetaPhase,
+} from "./types.js";
+import type { VerificationResult } from "./types.js";
+
+// 型のエクスポート
+export type { VerificationResult };
+
+/**
+ * 品質チェック項目の定義
+ */
+interface QualityCheck {
+  /** チェック名 */
+  name: string;
+  /** チェック関数 */
+  check: (result: ExecutionResult) => boolean | Promise<boolean>;
+  /** 重大度 */
+  severity: "critical" | "major" | "minor";
+}
+
+/** デフォルトの品質チェック一覧 */
+const DEFAULT_QUALITY_CHECKS: QualityCheck[] = [
+  {
+    name: "execution_success",
+    check: (result) => result.success,
+    severity: "critical",
+  },
+  {
+    name: "has_output",
+    check: (result) => result.data !== undefined && result.data !== null,
+    severity: "major",
+  },
+  {
+    name: "reasonable_duration",
+    check: (result) => result.duration < 60000, // 1分以内
+    severity: "minor",
+  },
+  {
+    name: "no_critical_errors",
+    check: (result) => {
+      if (!result.error) return true;
+      const errorMsg = result.error.message.toLowerCase();
+      return !errorMsg.includes("critical") && !errorMsg.includes("fatal");
+    },
+    severity: "critical",
+  },
+];
+
+/**
+ * 検証を実行する
+ *
+ * @param state - θサイクル状態
+ * @param customChecks - カスタム品質チェック（オプション）
+ * @returns 更新された状態と検証結果
+ */
+export async function verify(
+  state: ThetaCycleState,
+  customChecks?: QualityCheck[],
+): Promise<{ state: ThetaCycleState; result: VerificationResult }> {
+  const { runId } = state;
+
+  // フェーズ開始イベント
+  emitPhaseEvent(runId, ThetaEventType.PHASE_START, {
+    phase: ThetaPhase.VERIFY,
+  });
+
+  try {
+    // 実行結果の取得
+    const executionResult = state.context.get("execute.result") as ExecutionResult | undefined;
+
+    if (!executionResult) {
+      throw new Error("Execution result not found");
+    }
+
+    // 品質チェックの実行
+    const checks = customChecks ?? DEFAULT_QUALITY_CHECKS;
+    const checkResults: Record<string, boolean> = {};
+    const failures: string[] = [];
+    let totalScore = 0;
+    let totalWeight = 0;
+
+    for (const check of checks) {
+      const passed = await check.check(executionResult);
+      checkResults[check.name] = passed;
+
+      // 重み付け（critical: 5, major: 3, minor: 1）
+      const weight = check.severity === "critical" ? 5 : check.severity === "major" ? 3 : 1;
+      totalWeight += weight;
+
+      if (passed) {
+        totalScore += weight;
+      } else {
+        failures.push(`${check.name} (${check.severity})`);
+      }
+    }
+
+    // 品質スコアの計算 (0-1)
+    const qualityScore = totalWeight > 0 ? totalScore / totalWeight : 0;
+
+    const result: VerificationResult = {
+      passed: qualityScore >= 0.6, // 60%以上でパス
+      qualityScore,
+      checks: checkResults,
+      failures: failures.length > 0 ? failures : undefined,
+    };
+
+    // 検証イベント記録
+    const verificationEvent: ThetaEvent = {
+      runId,
+      phase: ThetaPhase.VERIFY,
+      timestamp: Date.now(),
+      type: ThetaEventType.VERIFICATION,
+      data: {
+        result,
+      },
+    };
+
+    state.events.push(verificationEvent);
+    state.currentPhase = ThetaPhase.VERIFY;
+    state.context.set("verify.result", result);
+
+    // Agentイベントを発行
+    emitAgentEvent({
+      runId,
+      stream: "tool",
+      data: {
+        type: "verify",
+        passed: result.passed,
+        qualityScore: result.qualityScore,
+        failures: result.failures,
+      },
+    });
+
+    // フェーズ完了イベント
+    emitPhaseEvent(runId, ThetaEventType.PHASE_COMPLETE, {
+      phase: ThetaPhase.VERIFY,
+      passed: result.passed,
+      qualityScore: result.qualityScore,
+    });
+
+    return { state, result };
+  } catch (error) {
+    // エラーイベント
+    emitPhaseEvent(runId, ThetaEventType.PHASE_ERROR, {
+      phase: ThetaPhase.VERIFY,
+      error: error instanceof Error ? error.message : String(error),
+    });
+    throw error;
+  }
+}
+
+/**
+ * 検証結果を取得する
+ *
+ * @param state - θサイクル状態
+ * @returns 検証結果
+ */
+export function getVerificationResult(state: ThetaCycleState): VerificationResult | undefined {
+  return state.context.get("verify.result") as VerificationResult | undefined;
+}
+
+/**
+ * 品質チェックを追加する
+ *
+ * @param checks - 既存チェック配列
+ * @param newCheck - 追加するチェック
+ * @returns 更新されたチェック配列
+ */
+export function addQualityCheck(checks: QualityCheck[], newCheck: QualityCheck): QualityCheck[] {
+  return [...checks, newCheck];
+}
+
+/**
+ * カスタム品質チェックを作成する
+ *
+ * @param name - チェック名
+ * @param check - チェック関数
+ * @param severity - 重大度
+ * @returns 品質チェック定義
+ */
+export function createQualityCheck(
+  name: string,
+  check: (result: ExecutionResult) => boolean | Promise<boolean>,
+  severity: "critical" | "major" | "minor" = "major",
+): QualityCheck {
+  return { name, check, severity };
+}
+
+/**
+ * フェーズイベントを発行する
+ */
+function emitPhaseEvent(runId: string, type: ThetaEventType, data: Record<string, unknown>): void {
+  emitAgentEvent({
+    runId,
+    stream: "tool",
+    data: {
+      type: "theta_event",
+      thetaEventType: type,
+      ...data,
+    },
+  });
+}