diff --git a/apps/desktop/src/app/chat/sidebar/projects/workspace-groups.test.ts b/apps/desktop/src/app/chat/sidebar/projects/workspace-groups.test.ts
index 6548d4a3b6..931a4dad5c 100644
--- a/apps/desktop/src/app/chat/sidebar/projects/workspace-groups.test.ts
+++ b/apps/desktop/src/app/chat/sidebar/projects/workspace-groups.test.ts
@@ -901,6 +901,39 @@ describe('overlayLiveLanes', () => {
 
     expect(overlayLiveLanes(home, [makeSession('/www/app', { id: 'fresh' })])).toBe(home)
   })
+
+  it('evicts a session from the main lane when the live overlay places it into a worktree lane', () => {
+    // Session was in main when the backend tree was captured, but the live
+    // $sessions cache now has it under a worktree cwd. The overlay must place
+    // it ONLY in the worktree lane — not both.
+    const session = makeSession('/www/app/.worktrees/feature', { id: 'moved', git_branch: 'feature' })
+
+    const project = projectNode({
+      id: '/www/app',
+      repos: [
+        {
+          id: '/www/app',
+          label: 'app',
+          path: '/www/app',
+          sessionCount: 1,
+          groups: [
+            lane({ id: '/www/app::branch::main', label: 'main', isMain: true, path: '/www/app', sessions: [session] }),
+            lane({ id: '/www/app/.worktrees/feature', label: 'feature', path: '/www/app/.worktrees/feature', sessions: [] })
+          ]
+        }
+      ]
+    })
+
+    const overlaid = overlayLiveLanes(project, [session])
+    const mainLane = overlaid.repos[0].groups.find(g => g.isMain)
+    const featureLane = overlaid.repos[0].groups.find(g => g.path === '/www/app/.worktrees/feature')
+
+    // Session must NOT appear in the main lane
+    expect(mainLane?.sessions ?? []).toHaveLength(0)
+    // Session must appear only in the worktree lane
+    expect(featureLane?.sessions.map(s => s.id)).toEqual(['moved'])
+    expect(overlaid.sessionCount).toBe(1)
+  })
 })
 
 describe('overlayLivePreviews', () => {
diff --git a/apps/desktop/src/app/chat/sidebar/projects/workspace-groups.ts b/apps/desktop/src/app/chat/sidebar/projects/workspace-groups.ts
index 756600d495..52370653ba 100644
--- a/apps/desktop/src/app/chat/sidebar/projects/workspace-groups.ts
+++ b/apps/desktop/src/app/chat/sidebar/projects/workspace-groups.ts
@@ -586,6 +586,22 @@ export function overlayRepoLanes(
       }
     }
 
+    // Evict the session from any OTHER lane the backend snapshot may have
+    // placed it in (e.g. a turn that moved the session's cwd from main to a
+    // new worktree — the overlay places it into the worktree lane, but without
+    // this eviction the stale main-lane entry persists and the session appears
+    // under both groups until the next backend tree refresh).
+    for (const g of lanes) {
+      if (g !== lane) {
+        const idx = g.sessions.findIndex(s => s.id === session.id)
+
+        if (idx >= 0) {
+          g.sessions = [...g.sessions.slice(0, idx), ...g.sessions.slice(idx + 1)]
+          changed = true
+        }
+      }
+    }
+
     lane.sessions = upsertSession(lane.sessions, session)
     changed = true
   }