feat(runtime): close deploy integration contract gaps

CHANGELOG.md

@@ -7,6 +7,30 @@ the GitHub Release body, so a release with no entry here fails.
 
 Versioning follows [docs/versioning.md](docs/versioning.md).
 
+## [0.4.0] - 2026-09-03
+
+### Added
+
+- `ToolResult` now carries optional structured failure, recovery, and repeated-
+  invocation metadata. `ToolExecutionHooks.result_metadata` lets products
+  populate those fields without moving product-specific classifiers or stores
+  into AgentCore. Timeouts and exceptions receive stable core-owned
+  `error_kind` values.
+- Loop observers can inspect the exact pre-provider LLM input, correlate calls
+  and retries through stable identifiers, and receive pre/post snapshots for
+  rollback, overflow recovery, and policy-driven context compaction.
+- Products can dynamically constrain the tools available to an individual turn,
+  supply callable per-call addenda as system or user messages, customize tool
+  history rendering, and preserve host-owned recovery metadata.
+- Deterministic and LLM-backed compaction now retain the original task,
+  tool-call/result pairing, recoverability references, and recovery-index order.
+
+### Fixed
+
+- Context-discard notifications now fire when overflow recovery replaces a
+  message without changing history length and when a custom compactor mutates
+  the history list in place.
+
 ## [0.3.0] - 2026-09-03
 
 First published release. AgentCore is now open source under Apache-2.0 and

agent_core/loop_types.py

@@ -183,8 +183,9 @@ class LoopConfig:
     summary_prompt: str = ""
 
     # Per-call reminder added to a copy of history, never persisted.
-    system_addendum_per_call: str = ""
+    system_addendum_per_call: str | Callable[[], str] = ""
     system_addendum_min_turn: int = 0
+    system_addendum_per_call_role: str = "system"
 
 
 @dataclass
@@ -306,6 +307,30 @@ class ToolResult:
     is_error: bool
     # Interrupted results remain in history to preserve tool-call pairing.
     interrupted: bool = False
+    # Stable machine-readable failure category supplied by the execution
+    # engine or a host classifier. Empty for successful legacy tools.
+    error_kind: str = ""
+    # Opaque host-owned handle for a result body shed from model context.
+    result_id: str = ""
+    # Host-provided repeated-invocation metadata. Execution is never skipped.
+    repeat_count: int = 1
+    repeat_recovery_id: str = ""
+
+
+@dataclass
+class ContextCompactionContext:
+    """Pre/post snapshot for any loop operation that discards history."""
+
+    turn: int
+    task_id: str
+    role_id: str
+    reason: str
+    compactor: str
+    policy: str
+    messages_before: list[Message]
+    messages_after: list[Message]
+    tokens_before: int
+    metadata: dict[str, Any]
 
 
 @dataclass
@@ -472,6 +497,9 @@ async def on_compaction(self, event: CompactionEvent) -> None:
         """History was rewritten. Passive: compaction has already happened by
         the time this runs, so there is no intervention to return."""
 
+    async def on_context_compacted(self, ctx: ContextCompactionContext) -> None:
+        """History was discarded while its pre-change form was still reachable."""
+
     async def on_loop_end(self, result: AgentLoopResult) -> None:
         pass
 
@@ -689,6 +717,7 @@ async def notify_tool_result(
     "CancellationObserver",
     "CompactionEvent",
     "CompactionObserver",
+    "ContextCompactionContext",
     "Intervention",
     "LLMAttemptContext",
     "LLMDeltaContext",