feat(evolution): auto-trigger + quality gate + actor marking (U6, R5/R6)

U6 of the complex task quality loop plan.

R5 (auto evolution trigger + quality gate):
- EvolutionConfig (Pydantic v2): success_sample_rate=0.1, min_confidence=0.5,
  min_examples=3, observe_only=True, cross_workspace_sharing=False
- Success path gated by success_sample_rate; failure path always runs (100%)
- Observe-only mode records reflections without feeding optimizer (RV14:
  avoids noise-driven prompt degradation during initial rollout)
- PromptOptimizer.can_optimize() consumption gate: sample count >= min_examples
  AND mean quality >= min_confidence
- PitfallDetector confidence threshold: low-confidence warnings marked
  observe-only; confidence = failure_rate * min(1.0, total/3) linear ramp
  (ponytail: upgrade to Wilson interval)

R6 (actor marking + cross-workspace sharing):
- All evolution artifacts (EvolutionLogEntry, Module, PitfallWarning) carry
  actor field; defaults to result.agent_name
- can_share_artifact(): same-workspace always allowed; cross-workspace requires
  explicit opt-in via EvolutionConfig.cross_workspace_sharing=True

KTD-8: gave_up_after_reflections treated as failure path (triggers 100%
evolution) even when stream wrapper marks status as COMPLETED. Detection via
output_data.trace_outcome or error_message substring (ponytail: heuristic;
upgrade path is a dedicated TaskResult.trace_outcome field).

Backward compat: all gates conditional on auto_evolution_config is not None;
existing EvolutionMixin usage without config preserves prior behavior.

Tests: tests/unit/test_evolution_auto_trigger.py (37 tests) covers R5/R6
scenarios - sample rate gate, observe-only, consumption gate, pitfall
confidence, actor marking, cross-workspace sharing, gave_up_after_reflections,
error handling, fire-and-forget, backpressure cap, AE3 happy path.

src/agentkit/evolution/__init__.py

@@ -11,6 +11,7 @@ from agentkit.evolution.prompt_optimizer import (
 )
 from agentkit.evolution.strategy_tuner import StrategyTuner
 from agentkit.evolution.ab_tester import ABTester
+from agentkit.evolution.config import EvolutionConfig
 from agentkit.evolution.evolution_store import (
     EvolutionStore,
     EvolutionStoreProtocol,
@@ -30,6 +31,7 @@ __all__ = [
     "Module",
     "StrategyTuner",
     "ABTester",
+    "EvolutionConfig",
     "EvolutionStore",
     "EvolutionStoreProtocol",
     "PersistentEvolutionStore",

src/agentkit/evolution/config.py

@@ -0,0 +1,43 @@
+"""EvolutionConfig - auto-evolution trigger configuration (U6, R5/R6).
+
+R5: success sample rate gates success-path evolution at evolve_after_task() entry;
+    failure path always runs (100%). Quality gates (min_confidence, min_examples)
+    prevent noise-driven prompt degradation.
+R6: actor marking on all evolution artifacts; cross-workspace sharing defaults off.
+"""
+
+from __future__ import annotations
+
+from pydantic import BaseModel, ConfigDict, Field
+
+
+class EvolutionConfig(BaseModel):
+    """Configuration for auto-evolution triggering and quality gates.
+
+    Attributes:
+        success_sample_rate: Fraction of success-path tasks that trigger evolution
+            (``random.random() < rate``). Failure path always runs (100%).
+            Default 0.1 — 1 in 10 successful tasks feed evolution.
+        min_confidence: Minimum confidence for pitfall ingestion and optimizer
+            consumption. Low-confidence pitfalls are marked observe-only.
+        min_examples: Minimum sample count before PromptOptimizer may consume
+            them. Pairs with min_confidence as a two-part consumption gate.
+        observe_only: When True, reflections/examples are recorded but NOT fed
+            to the optimizer. Avoids noise-driven prompt degradation (RV14)
+            during initial rollout. Set False once signal quality is validated.
+        cross_workspace_sharing: When False (default), evolution artifacts
+            (pitfalls, optimized prompts) are NOT shared across agent/expert
+            workspaces. Same-workspace sharing is always on. Cross-workspace
+            requires explicit opt-in (R6 trust boundary).
+        actor_marking: When True, stamp the producing agent/expert identity on
+            all evolution artifacts for traceability (R6).
+    """
+
+    model_config = ConfigDict(extra="forbid")
+
+    success_sample_rate: float = Field(default=0.1, ge=0.0, le=1.0)
+    min_confidence: float = Field(default=0.5, ge=0.0, le=1.0)
+    min_examples: int = Field(default=3, ge=1)
+    observe_only: bool = True
+    cross_workspace_sharing: bool = False
+    actor_marking: bool = True

src/agentkit/evolution/lifecycle.py

@@ -4,14 +4,16 @@
 """
 
 import logging
+import random
 from dataclasses import dataclass, field
 from datetime import datetime, timezone
 from typing import Any
 
 from sqlalchemy.exc import DBAPIError
 
-from agentkit.core.protocol import EvolutionEvent, TaskMessage, TaskResult
+from agentkit.core.protocol import EvolutionEvent, TaskMessage, TaskResult, TaskStatus
 from agentkit.evolution.ab_tester import ABTestConfig, ABTestResult, ABTester
+from agentkit.evolution.config import EvolutionConfig
 from agentkit.evolution.evolution_store import EvolutionStore
 from agentkit.evolution.llm_reflector import LLMReflector
 from agentkit.evolution.prompt_optimizer import (
@@ -39,6 +41,7 @@ class SoulEvolutionConfig:
 @dataclass
 class EvolutionLogEntry:
     """进化日志条目"""
+
     task_id: str
     reflection: Reflection | None = None
     optimized_module: Module | None = None
@@ -47,6 +50,12 @@ class EvolutionLogEntry:
     rolled_back: bool = False
     event_id: str | None = None
     created_at: datetime = field(default_factory=lambda: datetime.now(timezone.utc))
+    # R6: actor marking — which agent/expert produced this evolution artifact
+    actor: str = ""
+    # R5: whether this entry was gated by the success sample rate
+    sampled: bool = True
+    # R5: observe-only entries record but do not mutate prompts
+    observe_only: bool = False
 
 
 class EvolutionMixin:
@@ -73,15 +82,14 @@ class EvolutionMixin:
         auxiliary_model: str | None = None,
         strategy_tuning_enabled: bool = False,
         evolution_config: SoulEvolutionConfig | None = None,
+        auto_evolution_config: EvolutionConfig | None = None,
     ):
         if reflector is not EvolutionMixin._UNSET:
             # 显式传入了 reflector 参数（包括 None）
             self._reflector = reflector
         elif reflector_type is not None:
             # 未传入 reflector，但指定了 reflector_type → 自动创建
-            self._reflector = self._create_reflector(
-                reflector_type, llm_gateway, auxiliary_model
-            )
+            self._reflector = self._create_reflector(reflector_type, llm_gateway, auxiliary_model)
         else:
             # 都未指定：保持向后兼容，reflector 为 None
             self._reflector = None
@@ -93,6 +101,8 @@ class EvolutionMixin:
         self._current_module: Module | None = None
         self._strategy_tuning_enabled = strategy_tuning_enabled
         self._evolution_config = evolution_config
+        # U6/R5/R6: auto-evolution config (sample rate, quality gates, actor marking)
+        self._auto_evolution_config = auto_evolution_config
         self.pending_soul_updates: dict[str, list] = {}
 
     @staticmethod
@@ -133,19 +143,43 @@ class EvolutionMixin:
         task: TaskMessage,
         result: TaskResult,
         memory_store: MemoryStore | None = None,
+        actor: str | None = None,
     ) -> EvolutionLogEntry:
         """任务完成后执行进化流程。
 
         流程：
-        1. Reflector 反思 → 得到 Reflection
-        2. Soul 进化检查（如果 memory_store 可用）
-        3. 如果 Reflection 有改进建议 → PromptOptimizer 优化
-        4. 如果优化产生了新 Prompt → ABTester 验证
-        5. 如果 AB 测试通过 → EvolutionStore 应用变更
-        6. 如果 AB 测试失败 → 回滚
-        7. 如果策略调优启用 → StrategyTuner 调优
+        1. R5 成功采样门控（仅 auto_evolution_config 配置时生效）
+        2. Reflector 反思 → 得到 Reflection
+        3. Soul 进化检查（如果 memory_store 可用）
+        4. 如果 Reflection 有改进建议 → PromptOptimizer 优化
+        5. 如果优化产生了新 Prompt → ABTester 验证
+        6. 如果 AB 测试通过 → EvolutionStore 应用变更
+        7. 如果 AB 测试失败 → 回滚
+        8. 如果策略调优启用 → StrategyTuner 调优
+
+        R5: 成功路径按 success_sample_rate 采样；失败路径始终执行（100%）。
+        R6: 所有进化产物携带 actor 标记。
+        KTD-8: gave_up_after_reflections 视为失败路径。
         """
-        log_entry = EvolutionLogEntry(task_id=task.task_id)
+        # R6: actor marking — defaults to the agent that produced the result
+        resolved_actor = actor or result.agent_name or ""
+        log_entry = EvolutionLogEntry(task_id=task.task_id, actor=resolved_actor)
+
+        cfg = self._auto_evolution_config
+
+        # R5: success sample rate gate — only when auto_evolution_config is set.
+        # Failure path always runs (100%). KTD-8: gave_up_after_reflections = failure.
+        is_failure = self._is_failure_path(result)
+        if cfg is not None and not is_failure:
+            if random.random() >= cfg.success_sample_rate:
+                logger.debug(
+                    "Success-path evolution skipped for task %s (sample rate %.2f)",
+                    task.task_id,
+                    cfg.success_sample_rate,
+                )
+                log_entry.sampled = False
+                self._evolution_log.append(log_entry)
+                return log_entry
 
         # Step 1: 反思
         if self._reflector is None:
@@ -177,16 +211,46 @@ class EvolutionMixin:
             self._evolution_log.append(log_entry)
             return log_entry
 
+        # R5: observe-only mode — record reflection but do NOT feed optimizer.
+        # Avoids noise-driven prompt degradation during initial rollout (RV14).
+        if cfg is not None and cfg.observe_only:
+            logger.debug(
+                "Observe-only mode: recording reflection without feeding optimizer for task %s",
+                task.task_id,
+            )
+            log_entry.observe_only = True
+            self._evolution_log.append(log_entry)
+            return log_entry
+
+        # R5: consumption gate — sample count >= min_examples AND confidence达标.
+        min_conf = cfg.min_confidence if cfg is not None else 0.5
+        min_examples = cfg.min_examples if cfg is not None else 3
+        if hasattr(self._prompt_optimizer, "can_optimize"):
+            if not self._prompt_optimizer.can_optimize(
+                min_confidence=min_conf, min_examples=min_examples
+            ):
+                logger.debug(
+                    "Optimizer consumption gate not met for task %s, skipping optimization",
+                    task.task_id,
+                )
+                self._evolution_log.append(log_entry)
+                return log_entry
+
         # 将反思结果作为训练样本
         self._prompt_optimizer.add_example(
             input_data=task.input_data,
             output_data=result.output_data or {},
             quality_score=reflection.quality_score,
+            actor=resolved_actor,
         )
 
         # Pass trace and reflection to LLMPromptOptimizer if available
         optimized = await self._optimize_with_context(self._current_module, reflection)
 
+        # R6: stamp actor on optimized module
+        if cfg is None or cfg.actor_marking:
+            optimized.actor = resolved_actor
+
         # 检查是否真正产生了变化
         if optimized.name == self._current_module.name and not optimized.demos:
             logger.debug("Optimization produced no meaningful changes")
@@ -240,9 +304,43 @@ class EvolutionMixin:
         self._evolution_log.append(log_entry)
         return log_entry
 
-    async def _optimize_with_context(
-        self, module: Module, reflection: Reflection
-    ) -> Module:
+    def _is_failure_path(self, result: TaskResult) -> bool:
+        """Determine if a result should trigger failure-path evolution (100%).
+
+        KTD-8: ``gave_up_after_reflections`` (U5) is treated as failure even when
+        the stream wrapper marks status as COMPLETED, because the reflexion loop
+        exhausted without producing a verified answer.
+
+        ponytail: string-matching on output_data/error_message is a heuristic;
+        upgrade path is a dedicated TaskResult.trace_outcome field.
+        """
+        if result.status != TaskStatus.COMPLETED:
+            return True
+        # KTD-8: detect gave_up_after_reflections signal carried in output or error
+        if result.output_data and isinstance(result.output_data, dict):
+            if result.output_data.get("trace_outcome") == "gave_up_after_reflections":
+                return True
+        if result.error_message and "gave_up_after_reflections" in result.error_message:
+            return True
+        return False
+
+    def can_share_artifact(self, source_actor: str, target_actor: str) -> bool:
+        """R6: check if an evolution artifact can be shared between workspaces.
+
+        Same-workspace sharing is always on. Cross-workspace sharing requires
+        explicit opt-in via ``EvolutionConfig.cross_workspace_sharing=True``.
+
+        Trust boundary: evolution products are agent-produced and must be
+        validated before entering the shared store.
+        """
+        if source_actor == target_actor:
+            return True
+        cfg = self._auto_evolution_config
+        if cfg is not None and cfg.cross_workspace_sharing:
+            return True
+        return False
+
+    async def _optimize_with_context(self, module: Module, reflection: Reflection) -> Module:
         """Run optimization, passing reflection context if optimizer supports it"""
         from agentkit.evolution.prompt_optimizer import LLMPromptOptimizer
 
@@ -263,11 +361,13 @@ class EvolutionMixin:
 
         # Create test if not exists
         if test_id not in self._ab_tester._tests:
-            self._ab_tester.create_test(ABTestConfig(
+            self._ab_tester.create_test(
+                ABTestConfig(
                     test_id=test_id,
                     agent_name=result.agent_name,
                     change_type="prompt",
-            ))
+                )
+            )
 
         # Assign group deterministically based on task_id
         group = self._ab_tester.assign_group(test_id, task_id=task.task_id)
@@ -318,6 +418,9 @@ class EvolutionMixin:
                 "rolled_back": entry.rolled_back,
                 "event_id": entry.event_id,
                 "created_at": entry.created_at.isoformat(),
+                "actor": entry.actor,
+                "sampled": entry.sampled,
+                "observe_only": entry.observe_only,
             }
             if entry.reflection:
                 record["reflection"] = {
@@ -444,9 +547,7 @@ class EvolutionMixin:
         # 按 pattern 分类累积反思（patterns为空时使用默认category）
         categories = reflection.patterns if reflection.patterns else ["default"]
         for pattern in categories:
-            self.record_reflection(
-                pattern, reflection, task_type=task_type, score=score
-            )
+            self.record_reflection(pattern, reflection, task_type=task_type, score=score)
 
         # 检查是否有类别满足触发条件
         for category, reflections in list(self.pending_soul_updates.items()):
@@ -455,9 +556,7 @@ class EvolutionMixin:
             quality_gradient_triggered = False
             if len(scores) >= 3:
                 last_3 = scores[-3:]
-                declines = [
-                    last_3[i] - last_3[i - 1] for i in range(1, len(last_3))
-                ]
+                declines = [last_3[i] - last_3[i - 1] for i in range(1, len(last_3))]
                 if all(d <= config.quality_gradient_threshold for d in declines):
                     quality_gradient_triggered = True
 
@@ -467,7 +566,7 @@ class EvolutionMixin:
             for r in reflections:
                 age_seconds = (now - r["timestamp"]).total_seconds()
                 age_hours = age_seconds / 3600.0
-                effective_count += config.time_decay_factor ** age_hours
+                effective_count += config.time_decay_factor**age_hours
             # Round to avoid floating-point precision issues
             # (e.g. 3 recent reflections should yield exactly 3.0)
             effective_count = round(effective_count, 6)
@@ -506,8 +605,7 @@ class EvolutionMixin:
 
                 if update_result.get("success"):
                     logger.info(
-                        f"Soul evolved: category={category}, "
-                        f"version={update_result.get('version')}"
+                        f"Soul evolved: category={category}, version={update_result.get('version')}"
                     )
                     # 清除已处理的类别
                     del self.pending_soul_updates[category]

src/agentkit/evolution/pitfall_detector.py

@@ -33,6 +33,9 @@ class PitfallWarning:
         failure_rate: 历史失败率（0.0 ~ 1.0）
         historical_failures: 历史失败原因列表
         suggestion: 优化建议
+        confidence: 置信度（0.0 ~ 1.0），综合 failure_rate 和样本量计算
+        actor: 产生此预警对应的 agent/expert 标识（R6 actor marking）
+        observe_only: 低置信度预警标记为 observe-only，记录但不驱动优化
     """
 
     step_name: str
@@ -40,6 +43,12 @@ class PitfallWarning:
     failure_rate: float
     historical_failures: list[str] = field(default_factory=list)
     suggestion: str = ""
+    # U6/R5: confidence score for quality gate before ingestion
+    confidence: float = 0.0
+    # U6/R6: actor marking — which agent/expert produced the underlying experiences
+    actor: str = ""
+    # U6/R5: low-confidence warnings are marked observe-only (not discarded)
+    observe_only: bool = False
 
 
 class ExperienceStoreProtocol(Protocol):
@@ -51,8 +60,7 @@ class ExperienceStoreProtocol(Protocol):
         top_k: int = 5,
         task_type: str | None = None,
         search_multiplier: int = 5,
-    ) -> list[Any]:
-        ...
+    ) -> list[Any]: ...
 
 
 # 预警级别阈值
@@ -89,27 +97,33 @@ class PitfallDetector:
         experience_store: ExperienceStoreProtocol,
         similarity_threshold: float = 0.3,
         max_search_results: int = 50,
+        min_confidence: float = 0.0,
     ):
         """
         Args:
             experience_store: 经验存储实例（ExperienceStore 或 InMemoryExperienceStore）
             similarity_threshold: 步骤名称关键词匹配的最小相似度阈值
             max_search_results: 从经验存储检索的最大结果数
+            min_confidence: 置信度阈值（U6/R5）。低于此值的预警标记为 observe_only。
+                默认 0.0 表示不过滤（保持向后兼容）。
         """
         self._store = experience_store
         self._similarity_threshold = similarity_threshold
         self._max_search_results = max_search_results
+        self._min_confidence = min_confidence
 
     async def check_pitfalls(
         self,
         task_type: str,
         planned_steps: list[Any],
+        actor: str = "",
     ) -> list[PitfallWarning]:
         """检查计划步骤中的潜在陷阱
 
         Args:
             task_type: 任务类型
             planned_steps: 计划步骤列表（PlanStep 对象或具有 name/description 属性的对象）
+            actor: 产生此检测请求的 agent/expert 标识（R6 actor marking）
 
         Returns:
             按严重程度排序的预警列表（HIGH → MEDIUM → LOW）
@@ -127,7 +141,7 @@ class PitfallDetector:
         step_failure_stats = self._extract_step_failure_stats(all_experiences)
 
         # 3. 匹配当前计划步骤并生成预警
-        warnings = self._match_and_warn(planned_steps, step_failure_stats)
+        warnings = self._match_and_warn(planned_steps, step_failure_stats, actor=actor)
 
         # 4. 按严重程度排序（HIGH → MEDIUM → LOW），同级别按失败率降序
         warnings.sort(key=lambda w: (_warning_level_order(w.warning_level), -w.failure_rate))
@@ -208,8 +222,8 @@ class PitfallDetector:
                         s.failure_reasons.append(error)
 
             # 收集优化建议 — only add to steps that are part of this experience
-            if hasattr(exp, 'optimization_tips') and exp.optimization_tips:
-                experience_steps = set(exp.steps) if hasattr(exp, 'steps') and exp.steps else set()
+            if hasattr(exp, "optimization_tips") and exp.optimization_tips:
+                experience_steps = set(exp.steps) if hasattr(exp, "steps") and exp.steps else set()
                 for step_name, s in stats.items():
                     if experience_steps and step_name in experience_steps:
                         s.optimization_tips.extend(exp.optimization_tips)
@@ -220,6 +234,7 @@ class PitfallDetector:
         self,
         planned_steps: list[Any],
         step_failure_stats: dict[str, _StepFailureStats],
+        actor: str = "",
     ) -> list[PitfallWarning]:
         """将计划步骤与失败统计进行匹配，生成预警"""
         warnings: list[PitfallWarning] = []
@@ -236,9 +251,7 @@ class PitfallDetector:
             best_similarity = 0.0
 
             for stats_step_name, stats in step_failure_stats.items():
-                similarity = _compute_name_similarity(
-                    step_name, step_description, stats_step_name
-                )
+                similarity = _compute_name_similarity(step_name, step_description, stats_step_name)
                 if similarity > best_similarity:
                     best_similarity = similarity
                     best_match = stats
@@ -254,18 +267,29 @@ class PitfallDetector:
                 else 0.0
             )
 
+            # U6/R5: compute confidence from failure_rate and sample size.
+            # ponytail: linear ramp to 3 samples; upgrade to Wilson interval
+            # if precision matters at low sample counts.
+            confidence = _compute_confidence(failure_rate, best_match.total_occurrences)
+
             # 分配预警级别
             warning_level = _determine_warning_level(failure_rate)
 
             # 生成建议
             suggestion = _build_suggestion(best_match, failure_rate)
 
+            # U6/R5: low-confidence warnings are marked observe-only (not discarded)
+            observe_only = self._min_confidence > 0.0 and confidence < self._min_confidence
+
             warning = PitfallWarning(
                 step_name=step_name,
                 warning_level=warning_level,
                 failure_rate=round(failure_rate, 4),
                 historical_failures=best_match.failure_reasons[:5],  # 最多保留 5 条
                 suggestion=suggestion,
+                confidence=round(confidence, 4),
+                actor=actor,
+                observe_only=observe_only,
             )
             warnings.append(warning)
 
@@ -321,12 +345,48 @@ def _compute_name_similarity(
     return len(intersection) / len(union)
 
 
-_STOP_WORDS = frozenset({
-    "a", "an", "the", "and", "or", "but", "in", "on", "at", "to", "for",
-    "of", "with", "by", "from", "is", "are", "was", "were", "be", "been",
-    "being", "have", "has", "had", "do", "does", "did", "will", "would",
-    "could", "should", "may", "might", "can", "shall", "not", "no",
-})
+_STOP_WORDS = frozenset(
+    {
+        "a",
+        "an",
+        "the",
+        "and",
+        "or",
+        "but",
+        "in",
+        "on",
+        "at",
+        "to",
+        "for",
+        "of",
+        "with",
+        "by",
+        "from",
+        "is",
+        "are",
+        "was",
+        "were",
+        "be",
+        "been",
+        "being",
+        "have",
+        "has",
+        "had",
+        "do",
+        "does",
+        "did",
+        "will",
+        "would",
+        "could",
+        "should",
+        "may",
+        "might",
+        "can",
+        "shall",
+        "not",
+        "no",
+    }
+)
 
 
 def _extract_keywords(text: str) -> frozenset[str]:
@@ -337,10 +397,7 @@ def _extract_keywords(text: str) -> frozenset[str]:
     # 统一分隔符
     normalized = text.lower().replace("_", " ").replace("-", " ")
     words = normalized.split()
-    return frozenset(
-        w for w in words
-        if len(w) > 1 and w not in _STOP_WORDS
-    )
+    return frozenset(w for w in words if len(w) > 1 and w not in _STOP_WORDS)
 
 
 def _determine_warning_level(failure_rate: float) -> WarningLevel:
@@ -357,6 +414,33 @@ def _determine_warning_level(failure_rate: float) -> WarningLevel:
     return WarningLevel.LOW
 
 
+# U6/R5: minimum sample count for full confidence
+_CONFIDENCE_FULL_SAMPLES = 3
+
+
+def _compute_confidence(failure_rate: float, total_occurrences: int) -> float:
+    """Compute confidence score for a pitfall warning.
+
+    Combines failure_rate with sample size: small samples reduce confidence
+    linearly. A warning based on 1 occurrence is low-confidence even if the
+    failure_rate is high; 3+ occurrences yield full confidence.
+
+    ponytail: linear ramp is a naive heuristic; upgrade path is a Wilson
+    score interval for statistically rigorous low-sample confidence bounds.
+
+    Args:
+        failure_rate: Historical failure rate (0.0 ~ 1.0).
+        total_occurrences: Total number of times this step was observed.
+
+    Returns:
+        Confidence score (0.0 ~ 1.0).
+    """
+    if total_occurrences <= 0:
+        return 0.0
+    sample_factor = min(1.0, total_occurrences / _CONFIDENCE_FULL_SAMPLES)
+    return failure_rate * sample_factor
+
+
 def _warning_level_order(level: WarningLevel) -> int:
     """预警级别排序值（越小越严重）"""
     return {

src/agentkit/evolution/prompt_optimizer.py

@@ -21,6 +21,7 @@ logger = logging.getLogger(__name__)
 @dataclass
 class Signature:
     """Prompt 签名 - 定义输入/输出字段"""
+
     input_fields: dict[str, str]  # name -> description
     output_fields: dict[str, str]  # name -> description
     instruction: str = ""
@@ -41,10 +42,13 @@ class Signature:
 @dataclass
 class Module:
     """可组合的 Prompt 策略模块"""
+
     name: str
     signature: Signature
     template: str = ""
     demos: list[dict[str, Any]] = field(default_factory=list)
+    # U6/R6: actor marking — which agent/expert produced this optimized module
+    actor: str = ""
 
     def render(self, **kwargs) -> str:
         parts = []
@@ -80,18 +84,42 @@ class BootstrapPromptOptimizer:
         input_data: dict,
         output_data: dict,
         quality_score: float,
+        actor: str = "",
     ) -> None:
         """添加训练样本"""
         example = {
             "input": input_data,
             "output": output_data,
             "quality_score": quality_score,
+            "actor": actor,
         }
         if quality_score >= 0.7:
             self._success_examples.append(example)
         else:
             self._failure_examples.append(example)
 
+    def can_optimize(self, min_confidence: float = 0.5, min_examples: int | None = None) -> bool:
+        """U6/R5: consumption gate — sample count and confidence达标.
+
+        Returns True only when:
+        1. Success example count >= min_examples (default: constructor's
+           ``min_examples_for_optimization``)
+        2. Mean quality score of success examples >= min_confidence
+
+        ponytail: mean-quality gate is redundant with the >= 0.7 success
+        threshold in add_example when min_confidence <= 0.7; upgrade path
+        is a diversity-weighted confidence metric if noise becomes an issue.
+        """
+        threshold = min_examples if min_examples is not None else self._min_examples
+        if len(self._success_examples) < threshold:
+            return False
+        if not self._success_examples:
+            return False
+        mean_quality = sum(ex["quality_score"] for ex in self._success_examples) / len(
+            self._success_examples
+        )
+        return mean_quality >= min_confidence
+
     async def optimize(self, module: Module) -> Module:
         """优化 Module 的 Prompt
 
@@ -110,15 +138,17 @@ class BootstrapPromptOptimizer:
             key=lambda x: x["quality_score"],
             reverse=True,
         )
-        best_demos = sorted_examples[:self._max_demos]
+        best_demos = sorted_examples[: self._max_demos]
 
         # 构建 few-shot 示例
         demos = []
         for example in best_demos:
-            demos.append({
+            demos.append(
+                {
                     "input": str(example["input"]),
                     "output": str(example["output"]),
-            })
+                }
+            )
 
         # 优化指令（基于失败案例的反面教材）
         optimized_instruction = module.signature.instruction
@@ -127,9 +157,8 @@ class BootstrapPromptOptimizer:
             for ex in self._failure_examples[-3:]:
                 failure_patterns.add(str(ex["input"])[:100])
             if failure_patterns:
-                optimized_instruction += (
-                    f"\n\nAvoid these patterns:\n"
-                    + "\n".join(f"- {p}" for p in failure_patterns)
+                optimized_instruction += "\n\nAvoid these patterns:\n" + "\n".join(
+                    f"- {p}" for p in failure_patterns
                 )
 
         # 创建优化后的 Module
@@ -186,9 +215,16 @@ class LLMPromptOptimizer:
         input_data: dict,
         output_data: dict,
         quality_score: float,
+        actor: str = "",
     ) -> None:
         """添加训练样本（委托给 bootstrap 优化器）"""
-        self._bootstrap.add_example(input_data, output_data, quality_score)
+        self._bootstrap.add_example(input_data, output_data, quality_score, actor=actor)
+
+    def can_optimize(self, min_confidence: float = 0.5, min_examples: int | None = None) -> bool:
+        """U6/R5: consumption gate — delegates to bootstrap optimizer."""
+        return self._bootstrap.can_optimize(
+            min_confidence=min_confidence, min_examples=min_examples
+        )
 
     async def optimize(self, module: Module, trace: Any = None, reflection: Any = None) -> Module:
         """使用 LLM 优化 Module 的 Prompt

tests/unit/test_evolution_auto_trigger.py

@@ -0,0 +1,879 @@
+"""Tests for U6: auto evolution trigger + quality gate + actor marking.
+
+Covers R5 (success sample rate, quality thresholds, observe-only) and
+R6 (actor marking, cross-workspace sharing gate).
+
+Test scenarios:
+- Happy path (AE3): failure -> evolution fires (100%); success -> fires at 0.1 rate
+- Observe-only mode: recorded but not fed to optimizer
+- Backpressure cap reached: evolution task dropped + logged
+- Low-confidence pitfall: marked observe-only
+- Evolution task error: caught, does not fail the stream
+- PromptOptimizer sample count < 3: skip optimization
+- Actor marking present on all artifacts
+- Cross-workspace sharing rejected without opt-in
+- gave_up_after_reflections triggers failure-path evolution
+"""
+
+from __future__ import annotations
+
+import asyncio
+from datetime import datetime, timezone
+from unittest.mock import patch
+
+import pytest
+
+from agentkit.core.protocol import TaskMessage, TaskResult, TaskStatus
+from agentkit.evolution.config import EvolutionConfig
+from agentkit.evolution.experience_schema import TaskExperience
+from agentkit.evolution.experience_store import InMemoryExperienceStore
+from agentkit.evolution.lifecycle import EvolutionMixin
+from agentkit.evolution.pitfall_detector import (
+    PitfallDetector,
+    WarningLevel,
+    _compute_confidence,
+)
+from agentkit.evolution.prompt_optimizer import Module, PromptOptimizer, Signature
+from agentkit.evolution.reflector import Reflection, Reflector
+
+
+# ── Helpers ──────────────────────────────────────────────
+
+
+def _make_task(
+    task_id: str = "test-001",
+    agent_name: str = "evolving_agent",
+) -> TaskMessage:
+    return TaskMessage(
+        task_id=task_id,
+        agent_name=agent_name,
+        task_type="echo",
+        priority=0,
+        input_data={"query": "hello"},
+        callback_url=None,
+        created_at=datetime.now(timezone.utc),
+    )
+
+
+def _make_result(
+    status: str = TaskStatus.COMPLETED,
+    output_data: dict | None = None,
+    error_message: str | None = None,
+    agent_name: str = "evolving_agent",
+    task_id: str = "test-001",
+) -> TaskResult:
+    return TaskResult(
+        task_id=task_id,
+        agent_name=agent_name,
+        status=status,
+        output_data=output_data if output_data is not None else {"key": "value"},
+        error_message=error_message,
+        started_at=datetime.now(timezone.utc),
+        completed_at=datetime.now(timezone.utc),
+        metrics={"elapsed_seconds": 5.0},
+    )
+
+
+def _make_failure_result(
+    agent_name: str = "evolving_agent",
+    task_id: str = "test-001",
+) -> TaskResult:
+    return _make_result(
+        status=TaskStatus.FAILED,
+        output_data=None,
+        error_message="task failed",
+        agent_name=agent_name,
+        task_id=task_id,
+    )
+
+
+def _make_module() -> Module:
+    return Module(
+        name="test_module",
+        signature=Signature(
+            input_fields={"query": "search query"},
+            output_fields={"result": "search result"},
+            instruction="Find the best result.",
+        ),
+    )
+
+
+class LowQualityReflector(Reflector):
+    """Always produces failure outcome with improvement suggestions."""
+
+    async def reflect(self, task: TaskMessage, result: TaskResult) -> Reflection:
+        return Reflection(
+            task_id=task.task_id,
+            agent_name=result.agent_name,
+            outcome="failure",
+            quality_score=0.2,
+            patterns=["slow_execution"],
+            insights=["Low quality score indicates potential issues"],
+            suggestions=["Consider prompt optimization for this task type"],
+        )
+
+
+class SuccessReflector(Reflector):
+    """Always produces success outcome with suggestions (for testing success-path)."""
+
+    async def reflect(self, task: TaskMessage, result: TaskResult) -> Reflection:
+        return Reflection(
+            task_id=task.task_id,
+            agent_name=result.agent_name,
+            outcome="success",
+            quality_score=0.9,
+            patterns=["fast_execution"],
+            insights=["Good execution"],
+            suggestions=["Consider caching results for similar queries"],
+        )
+
+
+class ErrorReflector(Reflector):
+    """Always raises during reflection."""
+
+    async def reflect(self, task: TaskMessage, result: TaskResult) -> Reflection:
+        raise RuntimeError("reflector crashed")
+
+
+def _make_experience(
+    task_type: str = "code_review",
+    outcome: str = "failure",
+    steps_summary: str | list = "",
+    success_rate: float = 0.0,
+) -> TaskExperience:
+    return TaskExperience(
+        experience_id="",
+        task_type=task_type,
+        goal="test goal",
+        steps_summary=steps_summary,
+        outcome=outcome,
+        duration_seconds=10.0,
+        success_rate=success_rate,
+        failure_reasons=[],
+        optimization_tips=[],
+        created_at=datetime.now(timezone.utc),
+    )
+
+
+# ── R5: Success sample rate gate ─────────────────────────
+
+
+class TestSuccessSampleRate:
+    """R5: success-path evolution gated by success_sample_rate; failure always runs."""
+
+    async def test_failure_always_triggers_evolution(self):
+        """Failure path always triggers evolution regardless of sample rate."""
+        cfg = EvolutionConfig(success_sample_rate=0.0, observe_only=False)
+        reflector = LowQualityReflector()
+        mixin = EvolutionMixin(reflector=reflector, auto_evolution_config=cfg)
+        mixin.set_current_module(_make_module())
+
+        task = _make_task()
+        result = _make_failure_result()
+        entry = await mixin.evolve_after_task(task, result)
+
+        assert entry.sampled is True
+        assert entry.reflection is not None
+        assert entry.reflection.outcome == "failure"
+
+    async def test_success_skipped_when_rate_zero(self):
+        """Success path skipped when success_sample_rate=0.0."""
+        cfg = EvolutionConfig(success_sample_rate=0.0, observe_only=False)
+        reflector = SuccessReflector()
+        mixin = EvolutionMixin(reflector=reflector, auto_evolution_config=cfg)
+
+        task = _make_task()
+        result = _make_result(status=TaskStatus.COMPLETED)
+        entry = await mixin.evolve_after_task(task, result)
+
+        assert entry.sampled is False
+        assert entry.reflection is None  # evolution skipped before reflection
+
+    async def test_success_runs_when_rate_one(self):
+        """Success path runs when success_sample_rate=1.0."""
+        cfg = EvolutionConfig(success_sample_rate=1.0, observe_only=False)
+        reflector = SuccessReflector()
+        mixin = EvolutionMixin(reflector=reflector, auto_evolution_config=cfg)
+
+        task = _make_task()
+        result = _make_result(status=TaskStatus.COMPLETED)
+        entry = await mixin.evolve_after_task(task, result)
+
+        assert entry.sampled is True
+        assert entry.reflection is not None
+        assert entry.reflection.outcome == "success"
+
+    async def test_success_sampled_at_rate_boundary(self):
+        """At rate=0.1, random < 0.1 runs; random >= 0.1 skips."""
+        cfg = EvolutionConfig(success_sample_rate=0.1, observe_only=False)
+        reflector = SuccessReflector()
+
+        # random < 0.1 -> evolution runs
+        mixin_run = EvolutionMixin(reflector=reflector, auto_evolution_config=cfg)
+        with patch("agentkit.evolution.lifecycle.random.random", return_value=0.05):
+            entry = await mixin_run.evolve_after_task(
+                _make_task(), _make_result(status=TaskStatus.COMPLETED)
+            )
+        assert entry.sampled is True
+        assert entry.reflection is not None
+
+        # random >= 0.1 -> evolution skipped
+        mixin_skip = EvolutionMixin(reflector=reflector, auto_evolution_config=cfg)
+        with patch("agentkit.evolution.lifecycle.random.random", return_value=0.15):
+            entry = await mixin_skip.evolve_after_task(
+                _make_task(), _make_result(status=TaskStatus.COMPLETED)
+            )
+        assert entry.sampled is False
+        assert entry.reflection is None
+
+    async def test_no_config_preserves_backward_compat(self):
+        """Without auto_evolution_config, no sample gate applies (backward compat)."""
+        reflector = SuccessReflector()
+        mixin = EvolutionMixin(reflector=reflector)
+
+        task = _make_task()
+        result = _make_result(status=TaskStatus.COMPLETED)
+        entry = await mixin.evolve_after_task(task, result)
+
+        assert entry.sampled is True
+        assert entry.reflection is not None
+
+
+# ── R5: Observe-only mode ────────────────────────────────
+
+
+class TestObserveOnly:
+    """R5: observe-only mode records but does not feed optimizer."""
+
+    async def test_observe_only_records_without_optimizing(self):
+        """Observe-only: reflection recorded, optimizer not fed."""
+        cfg = EvolutionConfig(success_sample_rate=1.0, observe_only=True, min_confidence=0.0)
+        reflector = LowQualityReflector()
+        optimizer = PromptOptimizer(max_demos=3, min_examples_for_optimization=1)
+        mixin = EvolutionMixin(
+            reflector=reflector,
+            prompt_optimizer=optimizer,
+            auto_evolution_config=cfg,
+        )
+        mixin.set_current_module(_make_module())
+
+        task = _make_task()
+        result = _make_failure_result()
+        entry = await mixin.evolve_after_task(task, result)
+
+        assert entry.observe_only is True
+        assert entry.reflection is not None
+        assert entry.optimized_module is None
+        # Optimizer should NOT have been fed
+        success_count, _ = optimizer.example_count
+        assert success_count == 0
+
+    async def test_observe_only_false_allows_optimization(self):
+        """When observe_only=False, optimization can proceed (if gates pass)."""
+        cfg = EvolutionConfig(success_sample_rate=1.0, observe_only=False, min_confidence=0.0)
+        reflector = LowQualityReflector()
+        optimizer = PromptOptimizer(max_demos=3, min_examples_for_optimization=1)
+        # Pre-fill enough success examples to pass consumption gate
+        for i in range(3):
+            optimizer.add_example(
+                input_data={"query": f"q_{i}"},
+                output_data={"result": f"r_{i}"},
+                quality_score=0.9,
+            )
+        mixin = EvolutionMixin(
+            reflector=reflector,
+            prompt_optimizer=optimizer,
+            auto_evolution_config=cfg,
+        )
+        mixin.set_current_module(_make_module())
+
+        task = _make_task()
+        result = _make_failure_result()
+        entry = await mixin.evolve_after_task(task, result)
+
+        assert entry.observe_only is False
+        assert entry.optimized_module is not None
+
+
+# ── R5: PromptOptimizer consumption gate ─────────────────
+
+
+class TestConsumptionGate:
+    """R5: optimizer consumption gate — sample count >= min_examples AND confidence."""
+
+    async def test_sample_count_below_threshold_skips_optimization(self):
+        """PromptOptimizer sample count < min_examples -> skip optimization."""
+        cfg = EvolutionConfig(
+            success_sample_rate=1.0,
+            observe_only=False,
+            min_examples=3,
+            min_confidence=0.0,
+        )
+        reflector = LowQualityReflector()
+        optimizer = PromptOptimizer(max_demos=3, min_examples_for_optimization=3)
+        # Only 2 success examples — below threshold
+        for i in range(2):
+            optimizer.add_example(
+                input_data={"query": f"q_{i}"},
+                output_data={"result": f"r_{i}"},
+                quality_score=0.9,
+            )
+        mixin = EvolutionMixin(
+            reflector=reflector,
+            prompt_optimizer=optimizer,
+            auto_evolution_config=cfg,
+        )
+        mixin.set_current_module(_make_module())
+
+        task = _make_task()
+        result = _make_failure_result()
+        entry = await mixin.evolve_after_task(task, result)
+
+        assert entry.optimized_module is None  # gate not met
+
+    def test_can_optimize_returns_false_below_threshold(self):
+        """can_optimize() returns False when sample count < min_examples."""
+        optimizer = PromptOptimizer(max_demos=3, min_examples_for_optimization=3)
+        assert optimizer.can_optimize(min_confidence=0.5) is False
+
+    def test_can_optimize_returns_true_above_threshold(self):
+        """can_optimize() returns True when sample count and confidence met."""
+        optimizer = PromptOptimizer(max_demos=3, min_examples_for_optimization=3)
+        for i in range(3):
+            optimizer.add_example(
+                input_data={"query": f"q_{i}"},
+                output_data={"result": f"r_{i}"},
+                quality_score=0.9,
+            )
+        assert optimizer.can_optimize(min_confidence=0.5) is True
+
+    def test_can_optimize_returns_false_low_confidence(self):
+        """can_optimize() returns False when mean quality < min_confidence."""
+        optimizer = PromptOptimizer(max_demos=3, min_examples_for_optimization=3)
+        for i in range(3):
+            optimizer.add_example(
+                input_data={"query": f"q_{i}"},
+                output_data={"result": f"r_{i}"},
+                quality_score=0.3,  # below 0.5 threshold
+            )
+        # These go to failure_examples (quality < 0.7), so success_examples is empty
+        assert optimizer.can_optimize(min_confidence=0.5) is False
+
+
+# ── R5: Pitfall confidence threshold ─────────────────────
+
+
+class TestPitfallConfidence:
+    """R5: low-confidence pitfalls marked observe-only."""
+
+    def test_compute_confidence_high_sample_high_rate(self):
+        """3+ occurrences with high failure_rate -> high confidence."""
+        conf = _compute_confidence(failure_rate=0.6, total_occurrences=5)
+        assert conf == pytest.approx(0.6)
+
+    def test_compute_confidence_low_sample(self):
+        """1 occurrence -> confidence scaled down by 1/3."""
+        conf = _compute_confidence(failure_rate=0.6, total_occurrences=1)
+        assert conf == pytest.approx(0.6 * (1.0 / 3.0))
+
+    def test_compute_confidence_zero_samples(self):
+        """0 occurrences -> zero confidence."""
+        assert _compute_confidence(failure_rate=0.5, total_occurrences=0) == 0.0
+
+    async def test_low_confidence_pitfall_marked_observe_only(self):
+        """Pitfall with confidence < min_confidence is marked observe-only."""
+        store = InMemoryExperienceStore(decay_rate=0.01, alpha=0.7)
+        # Only 1 failure experience -> low sample -> low confidence
+        await store.record_experience(
+            _make_experience(
+                task_type="testing",
+                outcome="failure",
+                steps_summary=[
+                    {"step_name": "Run Tests", "outcome": "failure", "error": "Flaky"},
+                ],
+            )
+        )
+
+        detector = PitfallDetector(
+            experience_store=store,
+            similarity_threshold=0.3,
+            min_confidence=0.5,
+        )
+
+        from agentkit.core.plan_schema import PlanStep, PlanStepStatus
+
+        steps = [
+            PlanStep(
+                step_id="s1",
+                name="Run Tests",
+                description="Run tests",
+                status=PlanStepStatus.PENDING,
+            )
+        ]
+        warnings = await detector.check_pitfalls(
+            task_type="testing", planned_steps=steps, actor="test_agent"
+        )
+
+        assert len(warnings) == 1
+        assert warnings[0].observe_only is True
+        assert warnings[0].confidence < 0.5
+        assert warnings[0].actor == "test_agent"
+
+    async def test_high_confidence_pitfall_not_observe_only(self):
+        """Pitfall with confidence >= min_confidence is not observe-only."""
+        store = InMemoryExperienceStore(decay_rate=0.01, alpha=0.7)
+        # 3+ failure experiences -> full sample factor -> high confidence
+        for _ in range(4):
+            await store.record_experience(
+                _make_experience(
+                    task_type="deployment",
+                    outcome="failure",
+                    steps_summary=[
+                        {"step_name": "Deploy", "outcome": "failure", "error": "OOM"},
+                    ],
+                )
+            )
+
+        detector = PitfallDetector(
+            experience_store=store,
+            similarity_threshold=0.3,
+            min_confidence=0.5,
+        )
+
+        from agentkit.core.plan_schema import PlanStep, PlanStepStatus
+
+        steps = [
+            PlanStep(
+                step_id="s1", name="Deploy", description="Deploy app", status=PlanStepStatus.PENDING
+            )
+        ]
+        warnings = await detector.check_pitfalls(task_type="deployment", planned_steps=steps)
+
+        assert len(warnings) == 1
+        assert warnings[0].observe_only is False
+        assert warnings[0].confidence >= 0.5
+
+
+# ── R6: Actor marking ────────────────────────────────────
+
+
+class TestActorMarking:
+    """R6: actor marking on all evolution artifacts."""
+
+    async def test_log_entry_carries_actor(self):
+        """EvolutionLogEntry carries the actor identity."""
+        cfg = EvolutionConfig(success_sample_rate=1.0, observe_only=False)
+        reflector = LowQualityReflector()
+        mixin = EvolutionMixin(reflector=reflector, auto_evolution_config=cfg)
+
+        task = _make_task(agent_name="backend_engineer")
+        result = _make_failure_result(agent_name="backend_engineer")
+        entry = await mixin.evolve_after_task(task, result, actor="backend_engineer")
+
+        assert entry.actor == "backend_engineer"
+
+    async def test_actor_defaults_to_result_agent_name(self):
+        """Actor defaults to result.agent_name when not explicitly provided."""
+        cfg = EvolutionConfig(success_sample_rate=1.0, observe_only=True)
+        reflector = LowQualityReflector()
+        mixin = EvolutionMixin(reflector=reflector, auto_evolution_config=cfg)
+
+        task = _make_task(agent_name="qa_engineer")
+        result = _make_failure_result(agent_name="qa_engineer")
+        entry = await mixin.evolve_after_task(task, result)
+
+        assert entry.actor == "qa_engineer"
+
+    async def test_actor_marked_on_optimized_module(self):
+        """Optimized Module carries the actor identity."""
+        cfg = EvolutionConfig(success_sample_rate=1.0, observe_only=False, min_confidence=0.0)
+        reflector = LowQualityReflector()
+        optimizer = PromptOptimizer(max_demos=3, min_examples_for_optimization=1)
+        for i in range(3):
+            optimizer.add_example(
+                input_data={"query": f"q_{i}"},
+                output_data={"result": f"r_{i}"},
+                quality_score=0.9,
+            )
+        mixin = EvolutionMixin(
+            reflector=reflector,
+            prompt_optimizer=optimizer,
+            auto_evolution_config=cfg,
+        )
+        mixin.set_current_module(_make_module())
+
+        task = _make_task(agent_name="tech_lead")
+        result = _make_failure_result(agent_name="tech_lead")
+        entry = await mixin.evolve_after_task(task, result, actor="tech_lead")
+
+        assert entry.optimized_module is not None
+        assert entry.optimized_module.actor == "tech_lead"
+
+    async def test_actor_in_history(self):
+        """get_evolution_history includes actor field."""
+        cfg = EvolutionConfig(success_sample_rate=1.0, observe_only=True)
+        reflector = LowQualityReflector()
+        mixin = EvolutionMixin(reflector=reflector, auto_evolution_config=cfg)
+
+        await mixin.evolve_after_task(
+            _make_task(), _make_failure_result(), actor="frontend_engineer"
+        )
+        history = mixin.get_evolution_history()
+        assert len(history) == 1
+        assert history[0]["actor"] == "frontend_engineer"
+
+    async def test_pitfall_warning_carries_actor(self):
+        """PitfallWarning carries the actor identity."""
+        store = InMemoryExperienceStore(decay_rate=0.01, alpha=0.7)
+        await store.record_experience(
+            _make_experience(
+                task_type="testing",
+                outcome="failure",
+                steps_summary=[
+                    {"step_name": "Run Tests", "outcome": "failure", "error": "Error"},
+                ],
+            )
+        )
+        detector = PitfallDetector(experience_store=store, similarity_threshold=0.3)
+
+        from agentkit.core.plan_schema import PlanStep, PlanStepStatus
+
+        steps = [
+            PlanStep(
+                step_id="s1",
+                name="Run Tests",
+                description="Run tests",
+                status=PlanStepStatus.PENDING,
+            )
+        ]
+        warnings = await detector.check_pitfalls(
+            task_type="testing", planned_steps=steps, actor="code_reviewer"
+        )
+        assert len(warnings) == 1
+        assert warnings[0].actor == "code_reviewer"
+
+
+# ── R6: Cross-workspace sharing ──────────────────────────
+
+
+class TestCrossWorkspaceSharing:
+    """R6: cross-workspace sharing defaults off; same-workspace always on."""
+
+    def test_same_workspace_sharing_always_allowed(self):
+        """Same-actor sharing is always allowed."""
+        mixin = EvolutionMixin(reflector=Reflector())
+        assert mixin.can_share_artifact("agent_a", "agent_a") is True
+
+    def test_cross_workspace_sharing_default_off(self):
+        """Cross-workspace sharing rejected without opt-in (default)."""
+        cfg = EvolutionConfig(cross_workspace_sharing=False)
+        mixin = EvolutionMixin(reflector=Reflector(), auto_evolution_config=cfg)
+        assert mixin.can_share_artifact("agent_a", "agent_b") is False
+
+    def test_cross_workspace_sharing_with_opt_in(self):
+        """Cross-workspace sharing allowed when explicitly opted in."""
+        cfg = EvolutionConfig(cross_workspace_sharing=True)
+        mixin = EvolutionMixin(reflector=Reflector(), auto_evolution_config=cfg)
+        assert mixin.can_share_artifact("agent_a", "agent_b") is True
+
+    def test_no_config_cross_workspace_rejected(self):
+        """Without config, cross-workspace sharing is rejected (safe default)."""
+        mixin = EvolutionMixin(reflector=Reflector())
+        assert mixin.can_share_artifact("agent_a", "agent_b") is False
+
+
+# ── KTD-8: gave_up_after_reflections ─────────────────────
+
+
+class TestGaveUpAfterReflections:
+    """KTD-8: gave_up_after_reflections triggers failure-path evolution."""
+
+    async def test_gave_up_treated_as_failure(self):
+        """gave_up_after_reflections in output_data triggers failure path."""
+        cfg = EvolutionConfig(success_sample_rate=0.0, observe_only=True)
+        reflector = LowQualityReflector()
+        mixin = EvolutionMixin(reflector=reflector, auto_evolution_config=cfg)
+
+        task = _make_task()
+        # status=COMPLETED but trace_outcome=gave_up_after_reflections
+        result = _make_result(
+            status=TaskStatus.COMPLETED,
+            output_data={"trace_outcome": "gave_up_after_reflections"},
+        )
+        entry = await mixin.evolve_after_task(task, result)
+
+        # Even though success_sample_rate=0.0, failure path always runs
+        assert entry.sampled is True
+        assert entry.reflection is not None
+
+    async def test_gave_up_in_error_message_treated_as_failure(self):
+        """gave_up_after_reflections in error_message triggers failure path."""
+        cfg = EvolutionConfig(success_sample_rate=0.0, observe_only=True)
+        reflector = LowQualityReflector()
+        mixin = EvolutionMixin(reflector=reflector, auto_evolution_config=cfg)
+
+        task = _make_task()
+        result = _make_result(
+            status=TaskStatus.COMPLETED,
+            output_data={"content": "some output"},
+            error_message="gave_up_after_reflections: exhausted reinjections",
+        )
+        entry = await mixin.evolve_after_task(task, result)
+
+        assert entry.sampled is True
+        assert entry.reflection is not None
+
+    def test_is_failure_path_normal_success(self):
+        """Normal success (COMPLETED, no gave_up signal) is not failure path."""
+        mixin = EvolutionMixin(reflector=Reflector())
+        result = _make_result(status=TaskStatus.COMPLETED, output_data={"key": "val"})
+        assert mixin._is_failure_path(result) is False
+
+    def test_is_failure_path_failed_status(self):
+        """FAILED status is failure path."""
+        mixin = EvolutionMixin(reflector=Reflector())
+        result = _make_result(status=TaskStatus.FAILED, output_data=None)
+        assert mixin._is_failure_path(result) is True
+
+    def test_is_failure_path_cancelled_status(self):
+        """CANCELLED status is failure path."""
+        mixin = EvolutionMixin(reflector=Reflector())
+        result = _make_result(status=TaskStatus.CANCELLED, output_data=None)
+        assert mixin._is_failure_path(result) is True
+
+
+# ── Error handling: evolution does not fail the stream ───
+
+
+class TestEvolutionErrorHandling:
+    """Evolution task error is caught and does not propagate to the caller.
+
+    The _evolve_safe wrapper in config_driven.py catches all exceptions from
+    evolve_after_task. These tests verify that pattern.
+    """
+
+    async def test_evolve_safe_swallows_reflector_error(self):
+        """_evolve_safe pattern: reflector error is caught, not propagated."""
+
+        class SafeWrapper(EvolutionMixin):
+            """Simulates the _evolve_safe pattern from ConfigDrivenAgent."""
+
+            async def _evolve_safe(self, task: TaskMessage, result: TaskResult) -> None:
+                try:
+                    await self.evolve_after_task(task, result)
+                except Exception:
+                    pass  # swallowed, matching config_driven.py:_evolve_safe
+
+        mixin = SafeWrapper(reflector=ErrorReflector())
+        # Should not raise
+        await mixin._evolve_safe(_make_task(), _make_failure_result())
+
+    async def test_apply_change_error_does_not_crash_evolution(self):
+        """_apply_change errors are caught internally (existing behavior)."""
+        cfg = EvolutionConfig(success_sample_rate=1.0, observe_only=False, min_confidence=0.0)
+        reflector = LowQualityReflector()
+        optimizer = PromptOptimizer(max_demos=3, min_examples_for_optimization=1)
+        for i in range(3):
+            optimizer.add_example(
+                input_data={"query": f"q_{i}"},
+                output_data={"result": f"r_{i}"},
+                quality_score=0.9,
+            )
+        mixin = EvolutionMixin(
+            reflector=reflector,
+            prompt_optimizer=optimizer,
+            auto_evolution_config=cfg,
+        )
+        mixin.set_current_module(_make_module())
+
+        # Should complete without raising even if internal steps have issues
+        entry = await mixin.evolve_after_task(_make_task(), _make_failure_result())
+        assert entry is not None
+
+
+# ── Integration: fire-and-forget via asyncio.create_task ─
+
+
+class TestFireAndForgetIntegration:
+    """Evolution fires via U2's execute_stream hooks (fire-and-forget pattern).
+
+    Validates that evolve_after_task works correctly when scheduled as a
+    fire-and-forget asyncio task, matching _trigger_evolution_hooks behavior.
+    """
+
+    async def test_evolve_after_task_completes_as_asyncio_task(self):
+        """evolve_after_task completes when scheduled via asyncio.create_task."""
+        cfg = EvolutionConfig(success_sample_rate=1.0, observe_only=True)
+        reflector = LowQualityReflector()
+        mixin = EvolutionMixin(reflector=reflector, auto_evolution_config=cfg)
+
+        task = _make_task()
+        result = _make_failure_result()
+
+        # Schedule as fire-and-forget task (mirrors _schedule_evolution)
+        async def _evolve():
+            await mixin.evolve_after_task(task, result)
+
+        t = asyncio.create_task(_evolve())
+        await t  # wait for completion
+
+        history = mixin.get_evolution_history()
+        assert len(history) == 1
+        assert history[0]["reflection"] is not None
+
+    async def test_concurrent_evolution_tasks_isolated(self):
+        """Multiple concurrent evolution tasks don't interfere."""
+        cfg = EvolutionConfig(success_sample_rate=1.0, observe_only=True)
+        reflector = LowQualityReflector()
+        mixin = EvolutionMixin(reflector=reflector, auto_evolution_config=cfg)
+
+        async def _run_one(task_id: str):
+            await mixin.evolve_after_task(
+                _make_task(task_id=task_id),
+                _make_failure_result(task_id=task_id),
+            )
+
+        await asyncio.gather(
+            _run_one("task-a"),
+            _run_one("task-b"),
+            _run_one("task-c"),
+        )
+
+        history = mixin.get_evolution_history()
+        assert len(history) == 3
+        task_ids = {h["task_id"] for h in history}
+        assert task_ids == {"task-a", "task-b", "task-c"}
+
+
+# ── Backpressure cap (U2 _schedule_evolution) ────────────
+
+
+class TestBackpressureCap:
+    """Backpressure cap reached -> evolution task dropped + logged.
+
+    Tests U2's _schedule_evolution backpressure, which U6's auto-trigger relies on.
+    """
+
+    async def test_evolution_task_dropped_when_cap_reached(self):
+        """When pending tasks reach cap, new evolution tasks are dropped."""
+        import agentkit.core.config_driven as cd
+
+        # Save original state to restore after test
+        try:
+            # Create blocking coroutines that won't complete during the test
+            block_event = asyncio.Event()
+
+            async def _blocking_evolve() -> None:
+                await block_event.wait()
+
+            cap = 4
+            # Fill up to cap
+            for _ in range(cap):
+                cd._schedule_evolution(_blocking_evolve(), cap=cap)
+
+            assert len(cd._pending_evolution_tasks) == cap
+
+            # Track dropped count before (access via module — int is immutable)
+            dropped_before = cd._evolution_dropped_count
+
+            # Try to schedule one more -> should be dropped
+            cd._schedule_evolution(_blocking_evolve(), cap=cap)
+
+            assert len(cd._pending_evolution_tasks) == cap  # still at cap
+            assert cd._evolution_dropped_count == dropped_before + 1
+
+            # Release the blocking tasks so they can complete and be cleaned up
+            block_event.set()
+            # Let the event loop process task completions
+            await asyncio.sleep(0.05)
+        finally:
+            # Restore: clean up any remaining tasks
+            block_event = asyncio.Event()
+            block_event.set()
+            # Wait for any stragglers
+            if cd._pending_evolution_tasks:
+                await asyncio.gather(*cd._pending_evolution_tasks, return_exceptions=True)
+            cd._pending_evolution_tasks.clear()
+
+
+# ── AE3: Happy path — pitfall detection ──────────────────
+
+
+class TestAE3HappyPath:
+    """AE3: task fails -> evolution fires (100%) -> Reflector records ->
+    PitfallDetector detects; task succeeds -> evolution fires at 0.1 rate.
+    """
+
+    async def test_failure_triggers_evolution_and_pitfall_detection(self):
+        """Full happy path: failure -> evolution -> pitfall detection."""
+        # 1. Evolution fires on failure (100%)
+        cfg = EvolutionConfig(success_sample_rate=0.0, observe_only=True)
+        reflector = LowQualityReflector()
+        mixin = EvolutionMixin(reflector=reflector, auto_evolution_config=cfg)
+
+        task = _make_task()
+        result = _make_failure_result()
+        entry = await mixin.evolve_after_task(task, result)
+        assert entry.reflection is not None
+        assert entry.reflection.outcome == "failure"
+
+        # 2. PitfallDetector detects high-failure-rate step
+        store = InMemoryExperienceStore(decay_rate=0.01, alpha=0.7)
+        for _ in range(6):
+            await store.record_experience(
+                _make_experience(
+                    task_type="order_processing",
+                    outcome="failure",
+                    steps_summary=[
+                        {"step_name": "Call API", "outcome": "failure", "error": "timeout"},
+                    ],
+                )
+            )
+        for _ in range(4):
+            await store.record_experience(
+                _make_experience(
+                    task_type="order_processing",
+                    outcome="success",
+                    success_rate=1.0,
+                    steps_summary=[
+                        {"step_name": "Call API", "outcome": "success"},
+                    ],
+                )
+            )
+
+        detector = PitfallDetector(experience_store=store, similarity_threshold=0.3)
+        from agentkit.core.plan_schema import PlanStep, PlanStepStatus
+
+        steps = [
+            PlanStep(
+                step_id="s1",
+                name="Call API",
+                description="Call external API",
+                status=PlanStepStatus.PENDING,
+            )
+        ]
+        warnings = await detector.check_pitfalls(task_type="order_processing", planned_steps=steps)
+
+        assert len(warnings) == 1
+        assert warnings[0].warning_level == WarningLevel.HIGH
+        assert warnings[0].failure_rate >= 0.5
+
+    async def test_success_sampled_at_0_1_rate(self):
+        """Success path: with rate=0.1, ~10% of tasks trigger evolution."""
+        cfg = EvolutionConfig(success_sample_rate=0.1, observe_only=True)
+        reflector = SuccessReflector()
+
+        triggered = 0
+        total = 100
+        for _ in range(total):
+            mixin = EvolutionMixin(reflector=reflector, auto_evolution_config=cfg)
+            entry = await mixin.evolve_after_task(
+                _make_task(), _make_result(status=TaskStatus.COMPLETED)
+            )
+            if entry.reflection is not None:
+                triggered += 1
+
+        # With rate=0.1 over 100 trials, expect ~10 (allow wide tolerance)
+        # ponytail: statistical test; flaky at extreme bounds. Upgrade to
+        # deterministic mock if CI reliability becomes an issue.
+        assert 1 <= triggered <= 25