diff --git a/CHANGELOG.md b/CHANGELOG.md
index feb7b21..c6b7c28 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,29 @@ All notable changes to selectools will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.19.3] - 2026-03-31
+
+### Added
+
+#### Stability Markers Applied to All Public APIs
+
+Every public class and function exported from `selectools` now carries a stability marker:
+
+**`@stable`** (API frozen — breaking changes require a major version bump):
+`Role`, `Message`, `ToolCall`, `AgentResult`, `StepType`, `TraceStep`, `AgentTrace`, `Agent`, `AgentConfig`, `AgentObserver`, `AsyncAgentObserver`, `LoggingObserver`, `ConversationMemory`, `Tool`, `ToolParameter`, `ToolRegistry`, `tool`, `ToolPolicy`, `PolicyDecision`, `PolicyResult`, `OpenAIProvider`, `AnthropicProvider`, `GeminiProvider`, `OllamaProvider`, `FallbackProvider`, `TestCase`, `CaseResult`, `CaseVerdict`, `EvalSuite`, `EvalReport`, `AuditLogger`, `PrivacyLevel`, `CancellationToken`, `InMemoryCache`, `Cache`, `CacheKeyBuilder`, `CacheStats`, `SessionStore`, `JsonFileSessionStore`, `SQLiteSessionStore`, `KnowledgeMemory`, `KnowledgeEntry`, `KnowledgeStore`, `FileKnowledgeStore`, `SQLiteKnowledgeStore`, `Guardrail`, `GuardrailAction`, `GuardrailResult`, `GuardrailsPipeline`, `PIIGuardrail`, `ToxicityGuardrail`, `TopicGuardrail`, `FormatGuardrail`, `LengthGuardrail`, `TokenEstimate`, `estimate_tokens`, `estimate_run_tokens`, `AgentUsage`, `UsageStats`, `AgentAnalytics`, `Entity`, `EntityMemory`, `KnowledgeGraphMemory`
+
+**`@beta`** (API may change in a minor release):
+`trace_to_html`, `SimpleStepObserver`, `LocalProvider`, `RedisSessionStore`, `AgentGraph`, `SupervisorAgent`, `GraphState`, `MergePolicy`, `ContextMode`, `InterruptRequest`, `Scatter`, `CheckpointStore`, `InMemoryCheckpointStore`, `FileCheckpointStore`, `SQLiteCheckpointStore`, `PostgresCheckpointStore`, `Pipeline`, `Step`, `StepResult`, `step`, `parallel`, `branch`, `retry`, `cache_step`, `PlanAndExecuteAgent`, `ReflectiveAgent`, `DebateAgent`, `TeamLeadAgent`, `compose`
+
+Introspect programmatically:
+```python
+from selectools import Agent, AgentGraph
+print(Agent.__stability__)      # "stable"
+print(AgentGraph.__stability__) # "beta"
+```
+
+**Tests:** 3135 | **Examples:** 75 | **Models:** 152
+
 ## [0.19.2] - 2026-03-31
 
 ### Added
diff --git a/README.md b/README.md
index 83dfc55..0c79197 100644
--- a/README.md
+++ b/README.md
@@ -26,6 +26,22 @@ result = AgentGraph.chain(planner, writer, reviewer).run("Write a blog post")
 
 ## What's New in v0.19
 
+### v0.19.3 — Stability Markers Applied to All Public APIs
+
+Every public class and function exported from `selectools` now carries a stability marker:
+
+```python
+from selectools import Agent, AgentGraph, PlanAndExecuteAgent
+
+print(Agent.__stability__)               # "stable"
+print(AgentGraph.__stability__)          # "beta"
+print(PlanAndExecuteAgent.__stability__) # "beta"
+```
+
+**`@stable`** — 60+ core symbols (Agent, AgentConfig, providers, memory, tools, evals, guardrails, sessions, knowledge, cache, cancellation)
+
+**`@beta`** — 30+ newer symbols (AgentGraph, SupervisorAgent, Pipeline, @step, parallel, branch, all four patterns, compose)
+
 ### v0.19.2 — Enterprise Hardening
 
 ```python
diff --git a/ROADMAP.md b/ROADMAP.md
index 79ba944..d0c7f4f 100644
--- a/ROADMAP.md
+++ b/ROADMAP.md
@@ -55,6 +55,10 @@ Security audit → Stability markers (@stable/@beta/@deprecated) → Deprecation
 → Property-based tests (Hypothesis) → Concurrency smoke suite → 5 production simulations
 → 3135 tests, 75 examples
 
+v0.19.3 ✅ Stability Markers Applied to All Public APIs
+@stable on 60+ core symbols → @beta on 30+ orchestration/pipeline/patterns symbols
+→ Full stability introspection via .__stability__ on every exported class and function
+
 v0.20.0 🟡 Visual Agent Builder
 Zero-install web UI → Drag-drop graph builder → YAML/Python export → Live test execution
 
@@ -184,6 +188,29 @@ Focus: Production readiness and developer trust signals before the Visual Agent
 | **Production simulations** (5 new)    | ✅      | High   | Medium |
 
 
+---
+
+## v0.19.3: Stability Markers Applied ✅
+
+Focus: Apply `@stable` and `@beta` markers to every public symbol in the library, completing the stability annotation work started in v0.19.2.
+
+### Stable APIs (60+ symbols)
+
+Core types, providers, agent, memory, tools, evals, guardrails, sessions, knowledge, cache, cancellation, token estimation, analytics, audit — all marked `@stable`. Breaking changes to these require a major version bump.
+
+### Beta APIs (30+ symbols)
+
+Orchestration (`AgentGraph`, `SupervisorAgent`), pipelines (`Pipeline`, `@step`, `parallel`, `branch`), patterns (`PlanAndExecuteAgent`, `ReflectiveAgent`, `DebateAgent`, `TeamLeadAgent`), and composition (`compose`) — marked `@beta`. These may change in a minor release.
+
+### Introspection
+
+```python
+from selectools import Agent, AgentGraph, PlanAndExecuteAgent
+print(Agent.__stability__)              # "stable"
+print(AgentGraph.__stability__)         # "beta"
+print(PlanAndExecuteAgent.__stability__)  # "beta"
+```
+
 ---
 
 ## v0.20.0: Visual Agent Builder 🟡
diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index feb7b21..c6b7c28 100644
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -5,6 +5,29 @@ All notable changes to selectools will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.19.3] - 2026-03-31
+
+### Added
+
+#### Stability Markers Applied to All Public APIs
+
+Every public class and function exported from `selectools` now carries a stability marker:
+
+**`@stable`** (API frozen — breaking changes require a major version bump):
+`Role`, `Message`, `ToolCall`, `AgentResult`, `StepType`, `TraceStep`, `AgentTrace`, `Agent`, `AgentConfig`, `AgentObserver`, `AsyncAgentObserver`, `LoggingObserver`, `ConversationMemory`, `Tool`, `ToolParameter`, `ToolRegistry`, `tool`, `ToolPolicy`, `PolicyDecision`, `PolicyResult`, `OpenAIProvider`, `AnthropicProvider`, `GeminiProvider`, `OllamaProvider`, `FallbackProvider`, `TestCase`, `CaseResult`, `CaseVerdict`, `EvalSuite`, `EvalReport`, `AuditLogger`, `PrivacyLevel`, `CancellationToken`, `InMemoryCache`, `Cache`, `CacheKeyBuilder`, `CacheStats`, `SessionStore`, `JsonFileSessionStore`, `SQLiteSessionStore`, `KnowledgeMemory`, `KnowledgeEntry`, `KnowledgeStore`, `FileKnowledgeStore`, `SQLiteKnowledgeStore`, `Guardrail`, `GuardrailAction`, `GuardrailResult`, `GuardrailsPipeline`, `PIIGuardrail`, `ToxicityGuardrail`, `TopicGuardrail`, `FormatGuardrail`, `LengthGuardrail`, `TokenEstimate`, `estimate_tokens`, `estimate_run_tokens`, `AgentUsage`, `UsageStats`, `AgentAnalytics`, `Entity`, `EntityMemory`, `KnowledgeGraphMemory`
+
+**`@beta`** (API may change in a minor release):
+`trace_to_html`, `SimpleStepObserver`, `LocalProvider`, `RedisSessionStore`, `AgentGraph`, `SupervisorAgent`, `GraphState`, `MergePolicy`, `ContextMode`, `InterruptRequest`, `Scatter`, `CheckpointStore`, `InMemoryCheckpointStore`, `FileCheckpointStore`, `SQLiteCheckpointStore`, `PostgresCheckpointStore`, `Pipeline`, `Step`, `StepResult`, `step`, `parallel`, `branch`, `retry`, `cache_step`, `PlanAndExecuteAgent`, `ReflectiveAgent`, `DebateAgent`, `TeamLeadAgent`, `compose`
+
+Introspect programmatically:
+```python
+from selectools import Agent, AgentGraph
+print(Agent.__stability__)      # "stable"
+print(AgentGraph.__stability__) # "beta"
+```
+
+**Tests:** 3135 | **Examples:** 75 | **Models:** 152
+
 ## [0.19.2] - 2026-03-31
 
 ### Added
diff --git a/pyproject.toml b/pyproject.toml
index 3061b7c..cc2ccf9 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "selectools"
-version = "0.19.2"
+version = "0.19.3"
 description = "Production-ready AI agents with tool calling, structured output, execution traces, and RAG. Provider-agnostic (OpenAI, Anthropic, Gemini, Ollama) with fallback chains, batch processing, tool policies, streaming, caching, and cost tracking."
 readme = "README.md"
 requires-python = ">=3.9"
diff --git a/src/selectools/__init__.py b/src/selectools/__init__.py
index d2ad20e..3e73690 100644
--- a/src/selectools/__init__.py
+++ b/src/selectools/__init__.py
@@ -1,6 +1,6 @@
 """Public exports for the selectools package."""
 
-__version__ = "0.19.2"
+__version__ = "0.19.3"
 
 # Import submodules (lazy loading for optional dependencies)
 from . import embeddings, evals, guardrails, models, patterns, rag, toolbox
diff --git a/src/selectools/agent/config.py b/src/selectools/agent/config.py
index 29224c6..82589c6 100644
--- a/src/selectools/agent/config.py
+++ b/src/selectools/agent/config.py
@@ -7,6 +7,8 @@
 from dataclasses import dataclass, field
 from typing import TYPE_CHECKING, Any, Callable, Coroutine, Dict, List, Optional, Union
 
+from ..stability import stable
+
 if TYPE_CHECKING:
     from ..cache import Cache
     from ..cancellation import CancellationToken
@@ -30,6 +32,7 @@
 ]
 
 
+@stable
 @dataclass
 class AgentConfig:
     """
diff --git a/src/selectools/agent/core.py b/src/selectools/agent/core.py
index 90f966b..8334b37 100644
--- a/src/selectools/agent/core.py
+++ b/src/selectools/agent/core.py
@@ -18,6 +18,7 @@
 from ..prompt import PromptBuilder
 from ..providers.base import Provider, ProviderError
 from ..providers.openai_provider import OpenAIProvider
+from ..stability import stable
 from ..structured import (
     ResponseFormat,
     build_schema_instruction,
@@ -57,6 +58,7 @@ class _RunContext:
     terminal_tool_result: Optional[str] = None
 
 
+@stable
 class Agent(_ToolExecutorMixin, _ProviderCallerMixin, _LifecycleMixin, _MemoryManagerMixin):
     """
     Provider-agnostic AI agent that iteratively calls tools to accomplish tasks.
diff --git a/src/selectools/analytics.py b/src/selectools/analytics.py
index 74aad23..48ffb1b 100644
--- a/src/selectools/analytics.py
+++ b/src/selectools/analytics.py
@@ -10,6 +10,8 @@
 from pathlib import Path
 from typing import Any, Dict
 
+from .stability import stable
+
 
 @dataclass
 class ToolMetrics:
@@ -81,6 +83,7 @@ def to_dict(self) -> dict:
         }
 
 
+@stable
 class AgentAnalytics:
     """
     Analytics tracker for agent tool usage.
diff --git a/src/selectools/audit.py b/src/selectools/audit.py
index 35a68d8..e0bce57 100644
--- a/src/selectools/audit.py
+++ b/src/selectools/audit.py
@@ -24,10 +24,12 @@
 from typing import Any, Dict, List, Optional
 
 from .observer import AgentObserver
+from .stability import stable
 from .types import AgentResult, Message
 from .usage import UsageStats
 
 
+@stable
 class PrivacyLevel(str, Enum):
     """Controls how tool arguments are recorded in audit logs."""
 
@@ -37,6 +39,7 @@ class PrivacyLevel(str, Enum):
     NONE = "none"
 
 
+@stable
 class AuditLogger(AgentObserver):
     """JSONL audit logger that implements the AgentObserver protocol.
 
diff --git a/src/selectools/cache.py b/src/selectools/cache.py
index 6d928ce..764b269 100644
--- a/src/selectools/cache.py
+++ b/src/selectools/cache.py
@@ -20,12 +20,14 @@
     from .tools.base import Tool
     from .types import Message
 
+from .stability import stable
 
 # ---------------------------------------------------------------------------
 # CacheStats
 # ---------------------------------------------------------------------------
 
 
+@stable
 @dataclass
 class CacheStats:
     """Tracks cache performance metrics."""
@@ -69,6 +71,7 @@ class _CacheEntry:
 # ---------------------------------------------------------------------------
 
 
+@stable
 @runtime_checkable
 class Cache(Protocol):
     """
@@ -109,6 +112,7 @@ def stats(self) -> CacheStats:
 # ---------------------------------------------------------------------------
 
 
+@stable
 class InMemoryCache:
     """
     Thread-safe in-memory LRU cache with per-entry TTL.
@@ -216,6 +220,7 @@ def __repr__(self) -> str:
 # ---------------------------------------------------------------------------
 
 
+@stable
 class CacheKeyBuilder:
     """
     Builds deterministic cache keys from LLM request parameters.
diff --git a/src/selectools/cancellation.py b/src/selectools/cancellation.py
index 5656ae8..0e320ab 100644
--- a/src/selectools/cancellation.py
+++ b/src/selectools/cancellation.py
@@ -10,8 +10,10 @@
 import threading
 
 from .exceptions import CancellationError
+from .stability import stable
 
 
+@stable
 class CancellationToken:
     """Thread-safe signal for cancelling an agent run.
 
diff --git a/src/selectools/compose.py b/src/selectools/compose.py
index ed3fc03..63d847c 100644
--- a/src/selectools/compose.py
+++ b/src/selectools/compose.py
@@ -23,10 +23,12 @@ def extract(data: dict, field: str) -> str: ...
 
 from typing import Any, Callable, List, Optional, Sequence
 
+from .stability import beta
 from .tools.base import Tool
 from .tools.decorators import tool as tool_decorator
 
 
+@beta
 def compose(
     *tools_or_fns: Any,
     name: Optional[str] = None,
diff --git a/src/selectools/entity_memory.py b/src/selectools/entity_memory.py
index 7cc58be..c41776a 100644
--- a/src/selectools/entity_memory.py
+++ b/src/selectools/entity_memory.py
@@ -14,9 +14,11 @@
 from dataclasses import dataclass, field
 from typing import Any, Dict, List, Optional
 
+from .stability import stable
 from .types import Message, Role
 
 
+@stable
 @dataclass
 class Entity:
     """A named entity extracted from conversation.
@@ -69,6 +71,7 @@ def from_dict(cls, data: Dict[str, Any]) -> "Entity":
 )
 
 
+@stable
 class EntityMemory:
     """Maintains a registry of entities mentioned in conversation.
 
diff --git a/src/selectools/evals/report.py b/src/selectools/evals/report.py
index 4deb6db..c8a2bc9 100644
--- a/src/selectools/evals/report.py
+++ b/src/selectools/evals/report.py
@@ -9,9 +9,11 @@
 from pathlib import Path
 from typing import Any, Dict, List, Optional, Union
 
+from ..stability import stable
 from .types import CaseResult, CaseVerdict, EvalMetadata
 
 
+@stable
 @dataclass
 class EvalReport:
     """Aggregated evaluation results with statistics."""
diff --git a/src/selectools/evals/suite.py b/src/selectools/evals/suite.py
index d25b8fd..616a696 100644
--- a/src/selectools/evals/suite.py
+++ b/src/selectools/evals/suite.py
@@ -11,11 +11,13 @@
 
 from .. import __version__
 from ..agent import Agent
+from ..stability import stable
 from .evaluators import DEFAULT_EVALUATORS
 from .report import EvalReport
 from .types import CaseResult, CaseVerdict, EvalFailure, EvalMetadata, TestCase
 
 
+@stable
 class EvalSuite:
     """Evaluate an agent against a list of test cases.
 
diff --git a/src/selectools/evals/types.py b/src/selectools/evals/types.py
index c05b0cc..6e6a33e 100644
--- a/src/selectools/evals/types.py
+++ b/src/selectools/evals/types.py
@@ -6,7 +6,10 @@
 from enum import Enum
 from typing import Any, Callable, Dict, List, Optional
 
+from selectools.stability import stable
 
+
+@stable
 class CaseVerdict(str, Enum):
     """Verdict for a single evaluated test case."""
 
@@ -16,6 +19,7 @@ class CaseVerdict(str, Enum):
     SKIP = "skip"
 
 
+@stable
 @dataclass
 class TestCase:
     """A single test case for agent evaluation.
@@ -125,6 +129,7 @@ class EvalFailure:
     message: str
 
 
+@stable
 @dataclass
 class CaseResult:
     """Result of evaluating a single TestCase."""
diff --git a/src/selectools/guardrails/base.py b/src/selectools/guardrails/base.py
index fe8051d..7138063 100644
--- a/src/selectools/guardrails/base.py
+++ b/src/selectools/guardrails/base.py
@@ -12,7 +12,10 @@
 from enum import Enum
 from typing import Optional
 
+from selectools.stability import stable
 
+
+@stable
 class GuardrailAction(str, Enum):
     """Action to take when a guardrail check fails."""
 
@@ -21,6 +24,7 @@ class GuardrailAction(str, Enum):
     WARN = "warn"
 
 
+@stable
 @dataclass
 class GuardrailResult:
     """Result of a single guardrail check.
@@ -40,6 +44,7 @@ class GuardrailResult:
     guardrail_name: Optional[str] = None
 
 
+@stable
 class Guardrail:
     """Base class for all guardrails.
 
diff --git a/src/selectools/guardrails/format.py b/src/selectools/guardrails/format.py
index 2ef987c..2276ccf 100644
--- a/src/selectools/guardrails/format.py
+++ b/src/selectools/guardrails/format.py
@@ -10,9 +10,12 @@
 import json
 from typing import List, Optional
 
+from selectools.stability import stable
+
 from .base import Guardrail, GuardrailAction, GuardrailResult
 
 
+@stable
 class FormatGuardrail(Guardrail):
     """Validate that content matches expected format constraints.
 
diff --git a/src/selectools/guardrails/length.py b/src/selectools/guardrails/length.py
index e5a770c..1cdca1e 100644
--- a/src/selectools/guardrails/length.py
+++ b/src/selectools/guardrails/length.py
@@ -9,9 +9,12 @@
 import re
 from typing import Optional
 
+from selectools.stability import stable
+
 from .base import Guardrail, GuardrailAction, GuardrailResult
 
 
+@stable
 class LengthGuardrail(Guardrail):
     """Enforce content length constraints.
 
diff --git a/src/selectools/guardrails/pii.py b/src/selectools/guardrails/pii.py
index 17b2ba5..15f6be8 100644
--- a/src/selectools/guardrails/pii.py
+++ b/src/selectools/guardrails/pii.py
@@ -11,6 +11,8 @@
 from dataclasses import dataclass
 from typing import Dict, List, Optional
 
+from selectools.stability import stable
+
 from .base import Guardrail, GuardrailAction, GuardrailResult
 
 _BUILTIN_PATTERNS: Dict[str, re.Pattern[str]] = {
@@ -34,6 +36,7 @@ class PIIMatch:
     end: int
 
 
+@stable
 class PIIGuardrail(Guardrail):
     """Detect (and optionally redact) PII in content.
 
diff --git a/src/selectools/guardrails/pipeline.py b/src/selectools/guardrails/pipeline.py
index 5abdefe..377178c 100644
--- a/src/selectools/guardrails/pipeline.py
+++ b/src/selectools/guardrails/pipeline.py
@@ -12,11 +12,14 @@
 from dataclasses import dataclass, field
 from typing import List, Optional
 
+from selectools.stability import stable
+
 from .base import Guardrail, GuardrailAction, GuardrailError, GuardrailResult
 
 logger = logging.getLogger("selectools.guardrails")
 
 
+@stable
 @dataclass
 class GuardrailsPipeline:
     """Ordered pipeline of input and output guardrails.
diff --git a/src/selectools/guardrails/topic.py b/src/selectools/guardrails/topic.py
index 7cbb870..b6ad6a1 100644
--- a/src/selectools/guardrails/topic.py
+++ b/src/selectools/guardrails/topic.py
@@ -11,9 +11,12 @@
 import unicodedata
 from typing import List, Optional
 
+from selectools.stability import stable
+
 from .base import Guardrail, GuardrailAction, GuardrailResult
 
 
+@stable
 class TopicGuardrail(Guardrail):
     """Reject content that mentions denied topics.
 
diff --git a/src/selectools/guardrails/toxicity.py b/src/selectools/guardrails/toxicity.py
index 0ceac61..0262768 100644
--- a/src/selectools/guardrails/toxicity.py
+++ b/src/selectools/guardrails/toxicity.py
@@ -11,6 +11,8 @@
 import re
 from typing import List, Optional, Set
 
+from selectools.stability import stable
+
 from .base import Guardrail, GuardrailAction, GuardrailResult
 
 _DEFAULT_BLOCKLIST: Set[str] = {
@@ -33,6 +35,7 @@
 }
 
 
+@stable
 class ToxicityGuardrail(Guardrail):
     """Block content that exceeds a toxicity threshold.
 
diff --git a/src/selectools/knowledge.py b/src/selectools/knowledge.py
index 6bba340..eb02589 100644
--- a/src/selectools/knowledge.py
+++ b/src/selectools/knowledge.py
@@ -19,11 +19,14 @@
 from datetime import datetime, timedelta, timezone
 from typing import Any, Dict, List, Optional, Protocol, runtime_checkable
 
+from .stability import stable
+
 # ======================================================================
 # KnowledgeEntry — structured entry for the new store-based API
 # ======================================================================
 
 
+@stable
 @dataclass
 class KnowledgeEntry:
     """A single piece of knowledge stored by the agent.
@@ -66,6 +69,7 @@ def is_expired(self) -> bool:
 # ======================================================================
 
 
+@stable
 @runtime_checkable
 class KnowledgeStore(Protocol):
     """Protocol for knowledge storage backends.
@@ -113,6 +117,7 @@ def prune(
 # ======================================================================
 
 
+@stable
 class FileKnowledgeStore:
     """File-based knowledge store (backward-compatible with the original KnowledgeMemory).
 
@@ -279,6 +284,7 @@ def prune(
 # ======================================================================
 
 
+@stable
 class SQLiteKnowledgeStore:
     """SQLite-backed knowledge store for production single-process use.
 
@@ -442,6 +448,7 @@ def prune(
 # ======================================================================
 
 
+@stable
 class KnowledgeMemory:
     """Maintains cross-session knowledge with daily logs and persistent facts.
 
diff --git a/src/selectools/knowledge_graph.py b/src/selectools/knowledge_graph.py
index 38120ff..537e6ff 100644
--- a/src/selectools/knowledge_graph.py
+++ b/src/selectools/knowledge_graph.py
@@ -14,6 +14,7 @@
 from dataclasses import dataclass, field
 from typing import Any, Dict, List, Optional, Protocol, runtime_checkable
 
+from .stability import stable
 from .types import Message, Role
 
 
@@ -301,6 +302,7 @@ def _prune(self, conn: sqlite3.Connection) -> None:
 )
 
 
+@stable
 class KnowledgeGraphMemory:
     """Maintains a knowledge graph of relationship triples from conversation.
 
diff --git a/src/selectools/memory.py b/src/selectools/memory.py
index 6b65f12..dfb822a 100644
--- a/src/selectools/memory.py
+++ b/src/selectools/memory.py
@@ -8,9 +8,11 @@
 from dataclasses import replace
 from typing import Any, Dict, List, Optional
 
+from .stability import stable
 from .types import Message, Role
 
 
+@stable
 class ConversationMemory:
     """
     Maintains conversation history with configurable limits.
diff --git a/src/selectools/observer.py b/src/selectools/observer.py
index e50a3da..52b45e0 100644
--- a/src/selectools/observer.py
+++ b/src/selectools/observer.py
@@ -35,10 +35,12 @@ def on_tool_end(self, run_id, call_id, tool_name, result, duration_ms):
 import time
 from typing import Any, Callable, Dict, List, Optional
 
+from .stability import beta, stable
 from .types import AgentResult, Message
 from .usage import UsageStats
 
 
+@stable
 class AgentObserver:
     """Base class for agent lifecycle observers.
 
@@ -602,6 +604,7 @@ def on_supervisor_replan(
 # ======================================================================
 
 
+@stable
 class LoggingObserver(AgentObserver):
     """Observer that writes structured JSON events to Python's logging module.
 
@@ -1021,6 +1024,7 @@ def on_eval_end(
         )
 
 
+@stable
 class AsyncAgentObserver(AgentObserver):
     """Base class for async agent lifecycle observers.
 
@@ -1420,6 +1424,7 @@ async def a_on_supervisor_replan(self, run_id: str, stall_count: int, new_plan:
 # ======================================================================
 
 
+@beta
 class SimpleStepObserver(AgentObserver):
     """Observer that routes all lifecycle events to a single callback.
 
diff --git a/src/selectools/orchestration/checkpoint.py b/src/selectools/orchestration/checkpoint.py
index d611a56..41aa3e8 100644
--- a/src/selectools/orchestration/checkpoint.py
+++ b/src/selectools/orchestration/checkpoint.py
@@ -32,6 +32,7 @@
 from datetime import datetime, timezone
 from typing import Dict, List, Optional, Protocol, Tuple, runtime_checkable
 
+from ..stability import beta
 from .state import GraphState
 
 
@@ -56,6 +57,7 @@ class CheckpointMetadata:
     created_at: datetime
 
 
+@beta
 @runtime_checkable
 class CheckpointStore(Protocol):
     """Protocol for checkpoint backends.
@@ -117,6 +119,7 @@ def _deserialize_checkpoint(data: Dict) -> Tuple[GraphState, int]:
 # ------------------------------------------------------------------
 
 
+@beta
 class InMemoryCheckpointStore:
     """Thread-safe in-memory checkpoint store.
 
@@ -172,6 +175,7 @@ def delete(self, checkpoint_id: str) -> bool:
 # ------------------------------------------------------------------
 
 
+@beta
 class FileCheckpointStore:
     """File-based checkpoint store.
 
@@ -290,6 +294,7 @@ def delete(self, checkpoint_id: str) -> bool:
 """
 
 
+@beta
 class SQLiteCheckpointStore:
     """SQLite-backed checkpoint store with WAL mode for concurrent access.
 
diff --git a/src/selectools/orchestration/graph.py b/src/selectools/orchestration/graph.py
index ad89d22..0692b22 100644
--- a/src/selectools/orchestration/graph.py
+++ b/src/selectools/orchestration/graph.py
@@ -37,6 +37,7 @@
 )
 
 from ..exceptions import GraphExecutionError
+from ..stability import beta
 from ..trace import AgentTrace, StepType, TraceStep
 from ..types import AgentResult, Message, Role
 from ..usage import UsageStats
@@ -164,6 +165,7 @@ def _merge_usage(base: UsageStats, added: Any) -> UsageStats:
     )
 
 
+@beta
 class AgentGraph:
     """Directed graph of agent nodes with routing, parallelism, and HITL support.
 
diff --git a/src/selectools/orchestration/state.py b/src/selectools/orchestration/state.py
index 054bf97..b70d1d1 100644
--- a/src/selectools/orchestration/state.py
+++ b/src/selectools/orchestration/state.py
@@ -17,10 +17,12 @@
 if TYPE_CHECKING:
     from ..types import AgentResult, Message
 
+from ..stability import beta
 
 STATE_KEY_LAST_OUTPUT: str = "__last_output__"
 
 
+@beta
 class MergePolicy(str, Enum):
     """Policy for merging parallel branch states.
 
@@ -34,6 +36,7 @@ class MergePolicy(str, Enum):
     APPEND = "append"
 
 
+@beta
 class ContextMode(str, Enum):
     """Controls what conversation history is forwarded to a node's agent.
 
@@ -51,6 +54,7 @@ class ContextMode(str, Enum):
     CUSTOM = "custom"
 
 
+@beta
 @dataclass
 class GraphState:
     """Shared context passed between nodes in an AgentGraph.
@@ -153,6 +157,7 @@ def from_prompt(cls, prompt: str) -> "GraphState":
         return cls(messages=[Message(role=Role.USER, content=prompt)])
 
 
+@beta
 @dataclass
 class InterruptRequest:
     """Yielded from generator nodes to pause execution for human input.
@@ -173,6 +178,7 @@ class InterruptRequest:
     interrupt_key: str = ""
 
 
+@beta
 @dataclass
 class Scatter:
     """Returned from routing functions to create dynamic parallel branches.
diff --git a/src/selectools/orchestration/supervisor.py b/src/selectools/orchestration/supervisor.py
index c8f5655..b813252 100644
--- a/src/selectools/orchestration/supervisor.py
+++ b/src/selectools/orchestration/supervisor.py
@@ -45,6 +45,7 @@
     from ..types import AgentResult
     from .checkpoint import CheckpointStore
 
+from ..stability import beta
 from ..types import Message, Role
 from ..usage import UsageStats
 from .graph import AgentGraph, ErrorPolicy, GraphResult, _merge_usage
@@ -168,6 +169,7 @@ def _safe_json_parse(text: str, default: Any = None) -> Any:
     return default
 
 
+@beta
 class SupervisorAgent:
     """High-level multi-agent coordinator.
 
diff --git a/src/selectools/patterns/debate.py b/src/selectools/patterns/debate.py
index 3929811..4ccbd0e 100644
--- a/src/selectools/patterns/debate.py
+++ b/src/selectools/patterns/debate.py
@@ -16,6 +16,7 @@
     from ..cancellation import CancellationToken
     from ..observer import AgentObserver
 
+from ..stability import beta
 from ..types import Message, Role
 
 
@@ -39,6 +40,7 @@ def total_rounds(self) -> int:
         return len(self.rounds)
 
 
+@beta
 class DebateAgent:
     """Multi-agent debate: agents argue → judge synthesizes conclusion.
 
diff --git a/src/selectools/patterns/plan_and_execute.py b/src/selectools/patterns/plan_and_execute.py
index 3b5d708..5c3c008 100644
--- a/src/selectools/patterns/plan_and_execute.py
+++ b/src/selectools/patterns/plan_and_execute.py
@@ -22,6 +22,7 @@
 from ..orchestration.graph import GraphResult
 from ..orchestration.state import GraphState
 from ..orchestration.supervisor import _safe_json_parse
+from ..stability import beta
 from ..trace import AgentTrace
 from ..types import Message, Role
 from ..usage import UsageStats
@@ -63,6 +64,7 @@ class PlanStep:
 """
 
 
+@beta
 class PlanAndExecuteAgent:
     """Planner generates a structured plan; executor agents handle each step.
 
diff --git a/src/selectools/patterns/reflective.py b/src/selectools/patterns/reflective.py
index 129aab7..868a4bb 100644
--- a/src/selectools/patterns/reflective.py
+++ b/src/selectools/patterns/reflective.py
@@ -17,6 +17,7 @@
     from ..cancellation import CancellationToken
     from ..observer import AgentObserver
 
+from ..stability import beta
 from ..types import Message, Role
 
 
@@ -43,6 +44,7 @@ def total_rounds(self) -> int:
         return len(self.rounds)
 
 
+@beta
 class ReflectiveAgent:
     """Actor-Critic loop: actor drafts, critic evaluates, actor revises.
 
diff --git a/src/selectools/patterns/team_lead.py b/src/selectools/patterns/team_lead.py
index 4dfff8a..a0ad531 100644
--- a/src/selectools/patterns/team_lead.py
+++ b/src/selectools/patterns/team_lead.py
@@ -24,6 +24,7 @@
 from ..orchestration.graph import AgentGraph
 from ..orchestration.state import ContextMode, GraphState
 from ..orchestration.supervisor import _safe_json_parse
+from ..stability import beta
 from ..types import Message, Role
 
 
@@ -79,6 +80,7 @@ def total_assignments(self) -> int:
 """
 
 
+@beta
 class TeamLeadAgent:
     """Team lead delegates subtasks to agents and coordinates results.
 
diff --git a/src/selectools/pipeline.py b/src/selectools/pipeline.py
index 2effcf9..ca1a9b5 100644
--- a/src/selectools/pipeline.py
+++ b/src/selectools/pipeline.py
@@ -36,6 +36,8 @@ def translate(text: str, lang: str = "es") -> str:
 from functools import wraps
 from typing import Any, Callable, Dict, List, Optional, Sequence, Tuple, Union
 
+from selectools.stability import beta
+
 
 def _filter_kwargs(fn: Callable, kwargs: Dict[str, Any]) -> Dict[str, Any]:
     """Return only the kwargs that *fn* accepts.
@@ -94,6 +96,7 @@ def _get_type_hints(fn: Callable) -> Dict[str, Any]:
 # ---------------------------------------------------------------------------
 
 
+@beta
 @dataclass
 class StepResult:
     """Result of a single step or pipeline execution.
@@ -109,6 +112,7 @@ class StepResult:
     steps_run: int = 0
 
 
+@beta
 class Step:
     """A callable wrapper around a plain function with composition support.
 
@@ -167,6 +171,7 @@ def __repr__(self) -> str:  # noqa: D105
         return f"Step({self.name!r})"
 
 
+@beta
 def step(
     fn: Optional[Callable] = None,
     *,
@@ -215,6 +220,7 @@ def _ensure_step(fn: Any) -> Step:
 # ---------------------------------------------------------------------------
 
 
+@beta
 class Pipeline:
     """A sequence of steps executed in order.
 
@@ -522,6 +528,7 @@ def __call__(self, state: Any) -> Any:
 # ---------------------------------------------------------------------------
 
 
+@beta
 def parallel(*steps_or_fns: Union[Step, Callable]) -> Step:
     """Run multiple steps in parallel on the same input, return dict of results.
 
@@ -571,6 +578,7 @@ async def _run(s: Step) -> Tuple[str, Any]:
 # ---------------------------------------------------------------------------
 
 
+@beta
 def branch(
     router: Optional[Callable] = None,
     **named_steps: Union[Step, Callable],
@@ -629,6 +637,7 @@ def _branch_fn(input: Any, **kwargs: Any) -> Any:
 # ---------------------------------------------------------------------------
 
 
+@beta
 def retry(step_or_fn: Union[Step, Callable], attempts: int = 3) -> Step:
     """Wrap a step with retry logic.
 
@@ -644,6 +653,7 @@ def retry(step_or_fn: Union[Step, Callable], attempts: int = 3) -> Step:
     return Step(wrapped.fn, name=wrapped.name, retry=attempts, on_error="raise")
 
 
+@beta
 def cache_step(
     step_or_fn: Union[Step, Callable],
     ttl: int = 300,
diff --git a/src/selectools/policy.py b/src/selectools/policy.py
index b5f64f0..1d700b2 100644
--- a/src/selectools/policy.py
+++ b/src/selectools/policy.py
@@ -13,13 +13,17 @@
 from pathlib import Path
 from typing import Any, Dict, List, Optional, Union
 
+from selectools.stability import stable
 
+
+@stable
 class PolicyDecision(str, Enum):
     ALLOW = "allow"
     REVIEW = "review"
     DENY = "deny"
 
 
+@stable
 @dataclass
 class PolicyResult:
     """Outcome of evaluating a tool call against the policy."""
@@ -29,6 +33,7 @@ class PolicyResult:
     matched_rule: str = ""
 
 
+@stable
 @dataclass
 class ToolPolicy:
     """Declarative allow / review / deny rules for tool execution.
diff --git a/src/selectools/providers/anthropic_provider.py b/src/selectools/providers/anthropic_provider.py
index ecc024f..ad75ea9 100644
--- a/src/selectools/providers/anthropic_provider.py
+++ b/src/selectools/providers/anthropic_provider.py
@@ -17,11 +17,13 @@
 from ..exceptions import ProviderConfigurationError
 from ..models import Anthropic as AnthropicModels
 from ..pricing import calculate_cost
+from ..stability import stable
 from ..types import Message, Role, ToolCall
 from ..usage import UsageStats
 from .base import Provider, ProviderError
 
 
+@stable
 class AnthropicProvider(Provider):
     """Anthropic Messages API adapter."""
 
diff --git a/src/selectools/providers/fallback.py b/src/selectools/providers/fallback.py
index f9dd66e..69ad8ba 100644
--- a/src/selectools/providers/fallback.py
+++ b/src/selectools/providers/fallback.py
@@ -24,6 +24,7 @@
     cast,
 )
 
+from ..stability import stable
 from ..types import Message, ToolCall
 from .base import Provider, ProviderError
 
@@ -43,6 +44,7 @@ def _is_retriable(exc: Exception) -> bool:
     return any(s in msg for s in _RETRIABLE_SUBSTRINGS) or bool(_RETRIABLE_STATUS_CODES.search(msg))
 
 
+@stable
 class FallbackProvider:
     """Wraps multiple providers with automatic failover.
 
diff --git a/src/selectools/providers/gemini_provider.py b/src/selectools/providers/gemini_provider.py
index 0e815ca..eb92583 100644
--- a/src/selectools/providers/gemini_provider.py
+++ b/src/selectools/providers/gemini_provider.py
@@ -19,11 +19,13 @@
 from ..exceptions import ProviderConfigurationError
 from ..models import Gemini as GeminiModels
 from ..pricing import calculate_cost
+from ..stability import stable
 from ..types import Message, Role, ToolCall
 from ..usage import UsageStats
 from .base import Provider, ProviderError
 
 
+@stable
 class GeminiProvider(Provider):
     """
     Google Gemini adapter using the new google-genai SDK.
diff --git a/src/selectools/providers/ollama_provider.py b/src/selectools/providers/ollama_provider.py
index 962289f..c15765a 100644
--- a/src/selectools/providers/ollama_provider.py
+++ b/src/selectools/providers/ollama_provider.py
@@ -9,11 +9,13 @@
 from typing import Any, Dict
 
 from ..models import Ollama as OllamaModels
+from ..stability import stable
 from ..types import ToolCall
 from ._openai_compat import _OpenAICompatibleBase
 from .base import ProviderError
 
 
+@stable
 class OllamaProvider(_OpenAICompatibleBase):
     """
     Adapter for Ollama local models using OpenAI-compatible API.
diff --git a/src/selectools/providers/openai_provider.py b/src/selectools/providers/openai_provider.py
index e501d66..85028fd 100644
--- a/src/selectools/providers/openai_provider.py
+++ b/src/selectools/providers/openai_provider.py
@@ -15,6 +15,7 @@
 from ..exceptions import ProviderConfigurationError
 from ..models import OpenAI as OpenAIModels
 from ..pricing import calculate_cost
+from ..stability import stable
 from ._openai_compat import _OpenAICompatibleBase
 from .base import ProviderError
 
@@ -33,6 +34,7 @@ def _uses_max_completion_tokens(model: str) -> bool:
     return any(model.startswith(p) for p in _MAX_COMPLETION_TOKENS_PREFIXES)
 
 
+@stable
 class OpenAIProvider(_OpenAICompatibleBase):
     """Adapter that speaks to OpenAI's Chat Completions API."""
 
diff --git a/src/selectools/providers/stubs.py b/src/selectools/providers/stubs.py
index c5eaa6a..fbb2c67 100644
--- a/src/selectools/providers/stubs.py
+++ b/src/selectools/providers/stubs.py
@@ -8,11 +8,13 @@
 
 from typing import Any, AsyncIterable, Iterable, List, Union
 
+from ..stability import beta
 from ..types import Message, Role, ToolCall
 from ..usage import UsageStats
 from .base import Provider
 
 
+@beta
 class LocalProvider(Provider):
     """
     Local fallback provider.
diff --git a/src/selectools/sessions.py b/src/selectools/sessions.py
index 0e18e45..0883f94 100644
--- a/src/selectools/sessions.py
+++ b/src/selectools/sessions.py
@@ -15,6 +15,7 @@
 from typing import Any, Dict, List, Optional, Protocol
 
 from .memory import ConversationMemory
+from .stability import beta, stable
 
 
 @dataclass
@@ -34,6 +35,7 @@ class SessionMetadata:
     updated_at: float
 
 
+@stable
 class SessionStore(Protocol):
     """Protocol for persistent session backends."""
 
@@ -74,6 +76,7 @@ def branch(self, source_id: str, new_id: str) -> None:
 # ======================================================================
 
 
+@stable
 class JsonFileSessionStore:
     """File-based session store using one JSON file per session.
 
@@ -215,6 +218,7 @@ def branch(self, source_id: str, new_id: str) -> None:
 # ======================================================================
 
 
+@stable
 class SQLiteSessionStore:
     """SQLite-based session store.
 
@@ -366,6 +370,7 @@ def branch(self, source_id: str, new_id: str) -> None:
 # ======================================================================
 
 
+@beta
 class RedisSessionStore:
     """Redis-backed session store.
 
diff --git a/src/selectools/stability.py b/src/selectools/stability.py
index d234a19..a47dd3b 100644
--- a/src/selectools/stability.py
+++ b/src/selectools/stability.py
@@ -33,18 +33,40 @@ def old_function(): ...
 _C = TypeVar("_C", bound=type)
 
 
+@overload
+def stable(obj: _C) -> _C: ...
+
+
+@overload
+def stable(obj: _F) -> _F: ...
+
+
 def stable(obj: Union[_F, _C]) -> Union[_F, _C]:
     """Set stability marker to 'stable' (API is frozen)."""
     obj.__stability__ = "stable"  # type: ignore[union-attr]
     return obj
 
 
+stable.__stability__ = "stable"  # type: ignore[attr-defined]
+
+
+@overload
+def beta(obj: _C) -> _C: ...
+
+
+@overload
+def beta(obj: _F) -> _F: ...
+
+
 def beta(obj: Union[_F, _C]) -> Union[_F, _C]:
     """Set stability marker to 'beta' (API may change in minor releases)."""
     obj.__stability__ = "beta"  # type: ignore[union-attr]
     return obj
 
 
+beta.__stability__ = "stable"  # type: ignore[attr-defined]
+
+
 def deprecated(
     since: str,
     replacement: Optional[str] = None,
@@ -108,4 +130,6 @@ def _wrapper(*args: Any, **kwargs: Any) -> Any:
     return decorator  # type: ignore[return-value]
 
 
+deprecated.__stability__ = "stable"  # type: ignore[attr-defined]
+
 __all__ = ["stable", "beta", "deprecated"]
diff --git a/src/selectools/token_estimation.py b/src/selectools/token_estimation.py
index c7eff59..13840a4 100644
--- a/src/selectools/token_estimation.py
+++ b/src/selectools/token_estimation.py
@@ -16,7 +16,10 @@
     from .tools.base import Tool
     from .types import Message
 
+from .stability import stable
 
+
+@stable
 @dataclass
 class TokenEstimate:
     """Breakdown of estimated token usage for the first iteration of an agent run.
@@ -64,6 +67,7 @@ def _tiktoken_count(text: str, model: str) -> Optional[int]:
     return len(enc.encode(text))
 
 
+@stable
 def estimate_tokens(text: str, model: str = "gpt-4o") -> int:
     """Estimate the token count for a string.
 
@@ -85,6 +89,7 @@ def estimate_tokens(text: str, model: str = "gpt-4o") -> int:
     return _heuristic_count(text)
 
 
+@stable
 def estimate_run_tokens(
     messages: List[Message],
     tools: List[Tool],
diff --git a/src/selectools/tools/base.py b/src/selectools/tools/base.py
index 55cc237..69ac2ea 100644
--- a/src/selectools/tools/base.py
+++ b/src/selectools/tools/base.py
@@ -16,6 +16,7 @@
 from typing import Any, Callable, Dict, List, Optional, Union
 
 from ..exceptions import ToolExecutionError, ToolValidationError
+from ..stability import stable
 
 JsonSchema = Dict[str, Any]
 
@@ -53,6 +54,7 @@ def _python_type_to_json(param_type: type) -> str:
     return type_map.get(param_type, "string")
 
 
+@stable
 @dataclass
 class ToolParameter:
     """
@@ -110,6 +112,7 @@ def to_schema(self) -> JsonSchema:
         return schema
 
 
+@stable
 class Tool:
     """
     Encapsulates a callable tool with validation and schema generation.
diff --git a/src/selectools/tools/decorators.py b/src/selectools/tools/decorators.py
index 665a60e..c258998 100644
--- a/src/selectools/tools/decorators.py
+++ b/src/selectools/tools/decorators.py
@@ -8,6 +8,7 @@
 import sys
 from typing import Any, Callable, Dict, List, Optional, Union, get_args, get_origin, get_type_hints
 
+from ..stability import stable
 from .base import ParamMetadata, Tool, ToolParameter
 
 
@@ -111,6 +112,7 @@ def _infer_parameters_from_callable(
     return parameters
 
 
+@stable
 def tool(
     *,
     name: Optional[str] = None,
diff --git a/src/selectools/tools/registry.py b/src/selectools/tools/registry.py
index 7896122..eaa888c 100644
--- a/src/selectools/tools/registry.py
+++ b/src/selectools/tools/registry.py
@@ -7,10 +7,12 @@
 import warnings
 from typing import Any, Callable, Dict, List, Optional
 
+from ..stability import stable
 from .base import ParamMetadata, Tool
 from .decorators import tool
 
 
+@stable
 class ToolRegistry:
     """
     Central registry for managing a collection of tools.
diff --git a/src/selectools/trace.py b/src/selectools/trace.py
index 853daf9..4bd4ef4 100644
--- a/src/selectools/trace.py
+++ b/src/selectools/trace.py
@@ -14,7 +14,10 @@
 from enum import Enum
 from typing import Any, Dict, Iterator, List, Optional
 
+from selectools.stability import beta, stable
 
+
+@stable
 class StepType(str, Enum):
     """Enumeration of trace step types.
 
@@ -51,6 +54,7 @@ class StepType(str, Enum):
     GRAPH_LOOP_DETECTED = "graph_loop_detected"
 
 
+@stable
 @dataclass
 class TraceStep:
     """A single step in the agent execution timeline."""
@@ -91,6 +95,7 @@ def _new_run_id() -> str:
     return uuid.uuid4().hex
 
 
+@stable
 @dataclass
 class AgentTrace:
     """Ordered list of trace steps from a single agent run.
@@ -327,6 +332,7 @@ def _span_id() -> str:
 _DEFAULT_COLOR = "#64748b"
 
 
+@beta
 def trace_to_html(trace: "AgentTrace") -> str:
     """Render an AgentTrace as a standalone HTML waterfall timeline.
 
diff --git a/src/selectools/types.py b/src/selectools/types.py
index b5affb3..8427ff0 100644
--- a/src/selectools/types.py
+++ b/src/selectools/types.py
@@ -13,7 +13,10 @@
 from pathlib import Path
 from typing import Any, Dict, List, Optional, Protocol
 
+from selectools.stability import stable
 
+
+@stable
 class Role(str, Enum):
     """
     Enumeration of conversation roles for messages.
@@ -41,6 +44,7 @@ def _encode_image(image_path: str) -> str:
     return base64.b64encode(data).decode("utf-8")
 
 
+@stable
 @dataclass
 class Message:
     """
@@ -153,6 +157,7 @@ def from_dict(cls, data: Dict[str, Any]) -> "Message":
         return msg
 
 
+@stable
 @dataclass
 class ToolCall:
     """
@@ -179,6 +184,7 @@ class ToolCall:
     thought_signature: Optional[str] = None
 
 
+@stable
 @dataclass
 class AgentResult:
     """
diff --git a/src/selectools/usage.py b/src/selectools/usage.py
index 2e75b17..fde454b 100644
--- a/src/selectools/usage.py
+++ b/src/selectools/usage.py
@@ -7,7 +7,10 @@
 from dataclasses import dataclass, field
 from typing import Any, Dict, List, Optional
 
+from .stability import stable
 
+
+@stable
 @dataclass
 class UsageStats:
     """
@@ -39,6 +42,7 @@ def __post_init__(self) -> None:
             self.total_tokens = self.prompt_tokens + self.completion_tokens
 
 
+@stable
 @dataclass
 class AgentUsage:
     """