diff --git a/packages/agent/src/harness/experimental/session/memory.ts b/packages/agent/src/harness/experimental/session/memory.ts
index a79085145..2c212dc0a 100644
--- a/packages/agent/src/harness/experimental/session/memory.ts
+++ b/packages/agent/src/harness/experimental/session/memory.ts
@@ -49,7 +49,6 @@ export class InMemorySessionStorage implements SessionStorage {
 	private readonly usedIds = new Set<string>();
 	private readonly entries: Entry[] = [];
 	private readonly entriesById = new Map<string, Entry>();
-	private readonly laneByEntryId = new Map<string, string>();
 	private readonly records: LaneRecord[] = [];
 	private readonly lanes = new Map<string, string | null>([["main", null]]);
 	private readonly log: LogItem[] = [];
@@ -93,21 +92,13 @@ export class InMemorySessionStorage implements SessionStorage {
 		for (const sourceEntry of copiedEntries) {
 			const entry = structuredClone(sourceEntry);
 			entry.seq = storage.nextSequence();
-			const lane = options.scope === "tree" ? this.requireEntryLane(sourceEntry.id) : "main";
 			storage.entries.push(entry);
 			storage.entriesById.set(entry.id, entry);
-			storage.laneByEntryId.set(entry.id, lane);
 			storage.usedIds.add(entry.id);
-			storage.log.push({ kind: "entry", seq: entry.seq, lane, entry });
+			storage.log.push({ kind: "entry", seq: entry.seq, entry });
 		}
 		for (const [lane, leafId] of options.scope === "tree" ? this.lanes : []) {
-			storage.log.push({
-				kind: "lane",
-				seq: storage.nextSequence(),
-				lane,
-				action: lane === "main" ? "move" : "create",
-				leafId,
-			});
+			storage.log.push({ kind: "lane", seq: storage.nextSequence(), lane, leafId });
 		}
 		if (this.name !== undefined) {
 			storage.name = this.name;
@@ -133,14 +124,14 @@ export class InMemorySessionStorage implements SessionStorage {
 		if (this.lanes.has(lane)) throw new SessionError("already_exists", `Lane already exists: ${lane}`);
 		this.validateTarget(at);
 		this.lanes.set(lane, at);
-		this.log.push({ kind: "lane", seq: this.nextSequence(), lane, action: "create", leafId: at });
+		this.log.push({ kind: "lane", seq: this.nextSequence(), lane, leafId: at });
 	}
 
 	async moveLane(lane: string, to: string | null): Promise<void> {
 		this.requireLane(lane);
 		this.validateTarget(to);
 		this.lanes.set(lane, to);
-		this.log.push({ kind: "lane", seq: this.nextSequence(), lane, action: "move", leafId: to });
+		this.log.push({ kind: "lane", seq: this.nextSequence(), lane, leafId: to });
 	}
 
 	async appendEntry<TEntry extends Entry>(newEntry: ProvisionedEntry<TEntry>, lane: string): Promise<TEntry> {
@@ -151,9 +142,8 @@ export class InMemorySessionStorage implements SessionStorage {
 		this.usedIds.add(entry.id);
 		this.entries.push(entry);
 		this.entriesById.set(entry.id, entry);
-		this.laneByEntryId.set(entry.id, lane);
 		this.lanes.set(lane, entry.id);
-		this.log.push({ kind: "entry", seq: entry.seq, lane, entry });
+		this.log.push({ kind: "entry", seq: entry.seq, entry });
 		if (entry.type === "message") this.stats.messageCount += 1;
 		return structuredClone(entry);
 	}
@@ -265,14 +255,6 @@ export class InMemorySessionStorage implements SessionStorage {
 		return leafId;
 	}
 
-	private requireEntryLane(entryId: string): string {
-		const lane = this.laneByEntryId.get(entryId);
-		if (lane === undefined) {
-			throw new SessionError("invalid_entry", `Entry has no originating lane: ${entryId}`);
-		}
-		return lane;
-	}
-
 	private validateTarget(targetId: string | null): void {
 		if (targetId !== null && !this.entriesById.has(targetId)) {
 			throw new SessionError("not_found", `Entry not found: ${targetId}`);
diff --git a/packages/agent/src/harness/experimental/session/testing/conformance.ts b/packages/agent/src/harness/experimental/session/testing/conformance.ts
index 9f1f720ea..62d76627a 100644
--- a/packages/agent/src/harness/experimental/session/testing/conformance.ts
+++ b/packages/agent/src/harness/experimental/session/testing/conformance.ts
@@ -155,9 +155,9 @@ export function createSessionBackendConformance(
 				await session.moveLane("main", null);
 				deepStrictEqual(await session.getLanes(), [{ lane: "main", leafId: null }]);
 				deepStrictEqual(await session.getLog(), [
-					{ kind: "entry", seq: 1, lane: "main", entry: root },
+					{ kind: "entry", seq: 1, entry: root },
 					{ kind: "record", seq: 2, record: finished },
-					{ kind: "lane", seq: 3, lane: "main", action: "move", leafId: null },
+					{ kind: "lane", seq: 3, lane: "main", leafId: null },
 				]);
 
 				await rejectsWithCode(session.moveLane("main", "missing"), "not_found");
@@ -583,7 +583,7 @@ export function createSessionBackendConformance(
 			if (stored?.type !== "message") throw new Error("Expected message entry");
 			strictEqual(stored.terminate, true);
 			deepStrictEqual(await session.findEntries(), [entry]);
-			deepStrictEqual(await session.getLog(), [{ kind: "entry", seq: entry.seq, lane: "main", entry }]);
+			deepStrictEqual(await session.getLog(), [{ kind: "entry", seq: entry.seq, entry }]);
 		}),
 
 		createCase(
@@ -781,8 +781,8 @@ export function createSessionBackendConformance(
 			deepStrictEqual(
 				(await fork.getLog()).filter((item) => item.kind === "lane"),
 				[
-					{ kind: "lane", seq: 4, lane: "main", action: "move", leafId: mainChild },
-					{ kind: "lane", seq: 5, lane: "thread", action: "create", leafId: threadChild },
+					{ kind: "lane", seq: 4, lane: "main", leafId: mainChild },
+					{ kind: "lane", seq: 5, lane: "thread", leafId: threadChild },
 				],
 			);
 		}),
diff --git a/packages/agent/src/harness/experimental/session/types.ts b/packages/agent/src/harness/experimental/session/types.ts
index acba16e06..066e960b0 100644
--- a/packages/agent/src/harness/experimental/session/types.ts
+++ b/packages/agent/src/harness/experimental/session/types.ts
@@ -1,4 +1,5 @@
 import type { StopReason, Usage } from "@earendil-works/pi-ai";
+import "../../messages.ts";
 import type { AgentMessage } from "../../../types.ts";
 import type { Session } from "./session.ts";
 
@@ -263,9 +264,9 @@ export interface LanePointer {
 }
 
 export type LogItem =
-	| { kind: "entry"; seq: number; lane: string; entry: Entry }
+	| { kind: "entry"; seq: number; entry: Entry }
 	| { kind: "record"; seq: number; record: LaneRecord }
-	| { kind: "lane"; seq: number; lane: string; action: "create" | "move"; leafId: string | null }
+	| { kind: "lane"; seq: number; lane: string; leafId: string | null }
 	| { kind: "fact"; seq: number; fact: "name"; name: string }
 	| { kind: "fact"; seq: number; fact: "label"; targetId: string; label: string | undefined };