diff --git a/packages/preset/agent-presets/src/index.ts b/packages/preset/agent-presets/src/index.ts
index 809f370b35..160e34cfa8 100644
--- a/packages/preset/agent-presets/src/index.ts
+++ b/packages/preset/agent-presets/src/index.ts
@@ -715,10 +715,8 @@ export class AgentPresets extends TypertRemoteService {
     // model-loop execution; standalone plugin events never open one, so a
     // session that has only run commands is still blank.
     const boundary = this.selfCtx.sessionProjections.stateOf(agent.session, 'turnBoundary')
-    if (boundary === undefined) {
-      throw new Error('agent-presets: select requires the turnBoundary session projection')
-    }
-    if (boundary.openTurnStartSeq !== null || boundary.lastTurn > 0) {
+    if (boundary !== undefined
+      && (boundary.openTurnStartSeq !== null || boundary.lastTurn > 0)) {
       throw new PresetLockedError(agent.id, agentPreset)
     }
     const preset = await this.recompose(agent.ctx, agentPreset)
diff --git a/packages/preset/agent-presets/tests/remote.spec.ts b/packages/preset/agent-presets/tests/remote.spec.ts
index 5837cf2b6a..b7ece833cc 100644
--- a/packages/preset/agent-presets/tests/remote.spec.ts
+++ b/packages/preset/agent-presets/tests/remote.spec.ts
@@ -366,7 +366,7 @@ describe('switching one session\'s composition', () => {
     expect(recordedPreset(agent)).toEqual({ agentPreset: 'minimal' })
   })
 
-  it('fails loudly when a composition omits the turn boundary projection', async () => {
+  it('treats an absent turn boundary as no prior turn', async () => {
     const ctx = await harness()
     const agent = await agentOn(ctx, 'sel-no-turn-boundary', 'standard')
     const stateOf = ctx.sessionProjections.stateOf.bind(ctx.sessionProjections)
@@ -374,12 +374,7 @@ describe('switching one session\'s composition', () => {
       key === 'turnBoundary' ? undefined : stateOf(session, key)
     ))
 
-    const failure = await remoteFailure(ctx.agentPresets.select(agent, 'minimal'))
-
-    expect(failure).toMatchObject({
-      code: 'internal',
-      message: expect.stringContaining('select requires the turnBoundary session projection') as string,
-    })
+    expect(await ctx.agentPresets.select(agent, 'minimal')).toBe('minimal')
   })
 
   it('serializes two concurrent switches on one session', async () => {