3 files changed, 19 insertions, 0 deletions
diff --git a/packages/kernel/src/contracts/events.ts b/packages/kernel/src/contracts/events.ts
index b1385a2..6c9652d 100644
--- a/packages/kernel/src/contracts/events.ts
+++ b/packages/kernel/src/contracts/events.ts
@@ -14,6 +14,7 @@ export type {
 	TurnReasoningDeltaEvent,
 	TurnSealedEvent,
 	TurnStartEvent,
+	TurnSteeringEvent,
 	TurnStepCompleteEvent,
 	TurnTextDeltaEvent,
 	TurnToolCallEvent,
diff --git a/packages/kernel/src/contracts/index.ts b/packages/kernel/src/contracts/index.ts
index ffcbe76..4b1350b 100644
--- a/packages/kernel/src/contracts/index.ts
+++ b/packages/kernel/src/contracts/index.ts
@@ -38,6 +38,7 @@ export type {
 	TurnReasoningDeltaEvent,
 	TurnSealedEvent,
 	TurnStartEvent,
+	TurnSteeringEvent,
 	TurnStepCompleteEvent,
 	TurnTextDeltaEvent,
 	TurnToolCallEvent,
diff --git a/packages/kernel/src/contracts/runtime.ts b/packages/kernel/src/contracts/runtime.ts
index b7fe23c..c449a68 100644
--- a/packages/kernel/src/contracts/runtime.ts
+++ b/packages/kernel/src/contracts/runtime.ts
@@ -100,6 +100,23 @@ export interface RunTurnInput {
 	 * absent) — backward-compatible with callers that don't provide a clock.
 	 */
 	readonly now?: () => number;
+
+	/**
+	 * Optional. Called by the runtime at the tool-result boundary — after a
+	 * step whose tool calls have all executed, before the next step begins —
+	 * to drain messages to inject alongside the tool results. Whatever it
+	 * returns is appended as user-role messages to the next step's input, so
+	 * a caller can inject mid-turn guidance the model sees with the tool
+	 * results. When omitted or returning an empty array, no injection happens
+	 * (the runtime is unchanged).
+	 *
+	 * Injected (not ambient) so the kernel stays pure: it owns no queue and
+	 * names no feature — it just calls the callback and appends what it gets.
+	 * Only invoked when a step PRODUCED tool calls (the tool-result boundary);
+	 * a step that ends without tool calls does not drain (the caller decides
+	 * what to do with any pending messages after the turn ends).
+	 */
+	readonly drainSteering?: () => readonly ChatMessage[];
 }
 
 /**