diff --git a/src/main/runtime/repo-worktree-row-resolution.test.ts b/src/main/runtime/repo-worktree-row-resolution.test.ts
index 828bf0a355e..6ad7d2014d6 100644
--- a/src/main/runtime/repo-worktree-row-resolution.test.ts
+++ b/src/main/runtime/repo-worktree-row-resolution.test.ts
@@ -1,4 +1,7 @@
-import { joinResolvedWorktreeScans } from './workspaces/resolved-worktree-scan-join'
+import {
+  joinResolvedWorktreeScans,
+  projectResolvedWorktreeScans
+} from './workspaces/resolved-worktree-scan-join'
 import { getRepoHostIdentityForParts } from '../../shared/repo-host-identity'
 import { WorkspaceGitIdentity } from './sidebar-inputs/workspace-git-identity'
 import { describe, expect, it, vi } from 'vitest'
@@ -455,7 +458,7 @@ it('stamps the scan/sidebar join while cached catalog projection stays pure acro
   const scans = new Map([
     [key, { ok: true as const, worktrees: [gitWorktree('/repo/work')], gitRun: {} }]
   ])
-  joinResolvedWorktreeScans(deps.store, () => deps, scans, true)
+  projectResolvedWorktreeScans(deps.store, () => deps, scans)
   expect(writes).not.toHaveBeenCalled()
   const first = joinResolvedWorktreeScans(deps.store, () => deps, scans)
   expect(writes).toHaveBeenCalledOnce()
@@ -471,6 +474,6 @@ it('stamps the scan/sidebar join while cached catalog projection stays pure acro
   identity.observeScan(rows(detached), detached.scannedRepoKeys)
   expect(identity.title(detached.worktrees[0]!)).toBe(first.worktrees[0]!.displayName)
   expect(writes).toHaveBeenCalledOnce()
-  joinResolvedWorktreeScans(deps.store, () => deps, scans, true)
+  projectResolvedWorktreeScans(deps.store, () => deps, scans)
   expect(writes).toHaveBeenCalledOnce()
 })
diff --git a/src/main/runtime/runtime-resolved-worktree-cache.ts b/src/main/runtime/runtime-resolved-worktree-cache.ts
index ee4dfe3d8ae..a4193cd3c2b 100644
--- a/src/main/runtime/runtime-resolved-worktree-cache.ts
+++ b/src/main/runtime/runtime-resolved-worktree-cache.ts
@@ -1,4 +1,7 @@
 import type { ResolvedWorktree } from './runtime-worktree-path-identity'
+import type { RuntimeStore } from './runtime-store-contract'
+import type { ResolvedWorktreeRowsJoin } from './workspaces/resolved-worktree-scan-join'
+import { WORKTREE_METADATA_DOMAINS } from '../persistence/loading-store/worktree-identity-metadata'
 
 export type ResolvedWorktreeSnapshot = {
   worktrees: ResolvedWorktree[]
@@ -6,6 +9,8 @@ export type ResolvedWorktreeSnapshot = {
 }
 
 type ResolvedCache = ResolvedWorktreeSnapshot & { expiresAt: number; inventoryRevision: number }
+type CachedScanProjection = { inputs: readonly unknown[]; rows: ResolvedWorktreeRowsJoin }
+type StoreWrites = { store: RuntimeStore; revision: number }
 type ResolvedInFlight = {
   generation: number
   inventoryRevision: number
@@ -15,6 +20,8 @@ export class RuntimeResolvedWorktreeCache {
   private resolved: ResolvedCache | null = null
   private resolvedInFlight: ResolvedInFlight | null = null
   private resolvedGeneration = 0
+  private projection: CachedScanProjection | null = null
+  private storeWrites: StoreWrites | null = null
 
   get generation(): number {
     return this.resolvedGeneration
@@ -64,8 +71,54 @@ export class RuntimeResolvedWorktreeCache {
     }
   }
 
+  /** Rows projected from cached scans, reused until a store write, an invalidation, or a changed scan entry; stores that cannot report writes recompute every read. */
+  projectCachedScans(
+    store: RuntimeStore | null,
+    scanEntries: readonly unknown[],
+    project: () => ResolvedWorktreeRowsJoin
+  ): ResolvedWorktreeRowsJoin {
+    const revision = this.storeWriteRevision(store)
+    if (revision === null) {
+      return project()
+    }
+    // Captured before projecting: a metadata migration the read itself saves must miss next time.
+    const inputs = [revision, ...scanEntries]
+    const held = this.projection
+    if (
+      held &&
+      held.inputs.length === inputs.length &&
+      held.inputs.every((input, index) => input === inputs[index])
+    ) {
+      return held.rows
+    }
+    const generation = this.resolvedGeneration
+    const rows = project()
+    if (generation === this.resolvedGeneration) {
+      this.projection = { inputs, rows }
+    }
+    return rows
+  }
+
+  private storeWriteRevision(store: RuntimeStore | null): number | null {
+    if (!store?.onStateWritten) {
+      return null
+    }
+    if (this.storeWrites?.store !== store) {
+      const writes: StoreWrites = { store, revision: 0 }
+      this.storeWrites = writes
+      // Rows read metadata plus repos, lineage and folder workspaces, whose saves name no domain.
+      store.onStateWritten((domains) => {
+        if (!domains || WORKTREE_METADATA_DOMAINS.some((domain) => domains.includes(domain))) {
+          writes.revision += 1
+        }
+      })
+    }
+    return this.storeWrites.revision
+  }
+
   invalidateResolved(): void {
     this.resolvedGeneration += 1
     this.resolved = null
+    this.projection = null
   }
 }
diff --git a/src/main/runtime/session-tabs/structured-session-catalog-workspace.test.ts b/src/main/runtime/session-tabs/structured-session-catalog-workspace.test.ts
index cf77a9358d9..5153dbada73 100644
--- a/src/main/runtime/session-tabs/structured-session-catalog-workspace.test.ts
+++ b/src/main/runtime/session-tabs/structured-session-catalog-workspace.test.ts
@@ -41,14 +41,14 @@ import type { AgentModelCatalogReadParams } from '../../native-chat/agent-model-
 import type { RuntimeWorktreeScanCache, RuntimeWorktreeScanInFlight } from '../orca-runtime-core'
 import type { RuntimeWorktreeScanResult } from '../repo-worktree-resolution-scan'
 import type { ResolvedWorktree } from '../runtime-worktree-path-identity'
-import type { ResolvedWorktreeScanJoin } from '../workspaces/resolved-worktree-scan-join'
+import type { ResolvedWorktreeRowsJoin } from '../workspaces/resolved-worktree-scan-join'
 import type { OrcaRuntimeWithWorktreePsDependencies } from '../workspaces/workspace-process-listing-dependencies'
 
 type ScopeFixture = {
   store: RuntimeStore
   structuredAgentModelCatalog: OrcaRuntimeWithWorktreePsDependencies['structuredAgentModelCatalog']
   resolvedWorktrees: RuntimeResolvedWorktreeCache
-  projectCachedWorktrees: () => ResolvedWorktreeScanJoin
+  projectCachedWorktrees: () => ResolvedWorktreeRowsJoin
   worktreeScanCache: Map<string, RuntimeWorktreeScanCache>
   worktreeScanGenerations: Map<string, number>
   worktreeScanInFlight: Map<string, RuntimeWorktreeScanInFlight>
@@ -131,6 +131,8 @@ function rig(agent = 'opencode') {
     getWorktreeMeta: (id: string) => metadata[id],
     getAllWorktreeLineage: () => ({}),
     getAllWorkspaceLineage: () => ({}),
+    // Production stores report writes; this fixture's in-place edits are followed by invalidation.
+    onStateWritten: () => () => {},
     removeWorktreeLineage: vi.fn(),
     setWorktreeMeta: writes
   }
diff --git a/src/main/runtime/workspaces/resolved-worktree-scan-join.ts b/src/main/runtime/workspaces/resolved-worktree-scan-join.ts
index e0669e3ea54..d08e9ef57ee 100644
--- a/src/main/runtime/workspaces/resolved-worktree-scan-join.ts
+++ b/src/main/runtime/workspaces/resolved-worktree-scan-join.ts
@@ -29,7 +29,7 @@ export type ResolvedWorktreeRepoScans = Map<
   RepoWorktreeRowsScan & { gitRun: object | null }
 >
 
-export type ResolvedWorktreeScanJoin = ResolvedWorktreeSnapshot & {
+export type ResolvedWorktreeRowsJoin = Pick<ResolvedWorktreeSnapshot, 'worktrees'> & {
   /** Git repos the scans predate, which list no rows until scanned. */
   unscannedRepoKeys: ReadonlySet<HostScopedRepoKey>
   /** Rows a scan that reached a verdict listed, by their git run; stalled scans remain degraded. */
@@ -38,6 +38,8 @@ export type ResolvedWorktreeScanJoin = ResolvedWorktreeSnapshot & {
   scannedRepoKeys: ReadonlySet<HostScopedRepoKey>
 }
 
+export type ResolvedWorktreeScanJoin = ResolvedWorktreeSnapshot & ResolvedWorktreeRowsJoin
+
 function resolvedWorktreeRepoScanKey(repo: Repo): HostScopedRepoKey {
   return getRepoHostIdentityForParts(repo.id, getRepoExecutionHostId(repo))
 }
@@ -82,40 +84,50 @@ export async function scanResolvedWorktreeRepos(
 export function joinResolvedWorktreeScans(
   store: RuntimeStore | null,
   rowDeps: () => RepoWorktreeRowDeps,
-  scans: ResolvedWorktreeRepoScans,
-  projectOnly = false
+  scans: ResolvedWorktreeRepoScans
 ): ResolvedWorktreeScanJoin {
+  const repos = store?.getRepos() ?? []
+  const platformByRepoId = store
+    ? platformsByRepoId(repos, resolveLocalProjectRuntimesForRepos(store, repos))
+    : new Map<string, NodeJS.Platform>()
+  return { ...joinRows(store, rowDeps, scans, joinRepoWorktreeRows), platformByRepoId }
+}
+
+/** The same rows from memory only: no identity stamping and no launch platforms. */
+export function projectResolvedWorktreeScans(
+  store: RuntimeStore | null,
+  rowDeps: () => RepoWorktreeRowDeps,
+  scans: ResolvedWorktreeRepoScans
+): ResolvedWorktreeRowsJoin {
+  return joinRows(store, rowDeps, scans, projectRepoWorktreeRows)
+}
+
+function joinRows(
+  store: RuntimeStore | null,
+  rowDeps: () => RepoWorktreeRowDeps,
+  scans: ResolvedWorktreeRepoScans,
+  rowsForRepo: typeof joinRepoWorktreeRows
+): ResolvedWorktreeRowsJoin {
   if (!store) {
     return {
       worktrees: [],
-      platformByRepoId: new Map(),
       unscannedRepoKeys: new Set(),
       gitRunById: new Map(),
       scannedRepoKeys: new Set()
     }
   }
   const metaById = store.getAllWorktreeMeta() ?? {}
-  const repos = store.getRepos()
-  const platformByRepoId = platformsByRepoId(
-    repos,
-    resolveLocalProjectRuntimesForRepos(store, repos)
-  )
   const deps = rowDeps()
   const unscannedRepoKeys = new Set<HostScopedRepoKey>()
   const gitRunById = new Map<HostScopedWorktreeKey, object | null>()
   const scannedRepoKeys = new Set<HostScopedRepoKey>()
-  const perRepoWorktrees = repos.map((repo) => {
+  const perRepoWorktrees = store.getRepos().map((repo) => {
     const key = resolvedWorktreeRepoScanKey(repo)
     const scan = scans.get(key) ?? null
     if (!scan && !isFolderRepo(repo)) {
       unscannedRepoKeys.add(key)
     }
-    const rows = (projectOnly ? projectRepoWorktreeRows : joinRepoWorktreeRows)(
-      deps,
-      repo,
-      scan,
-      metaById
-    )
+    const rows = rowsForRepo(deps, repo, scan, metaById)
     if (scan?.ok) {
       scannedRepoKeys.add(key)
       for (const row of rows) {
@@ -128,5 +140,5 @@ export function joinResolvedWorktreeScans(
     perRepoWorktrees.flat(),
     store.getAllWorktreeLineage?.() ?? {}
   )
-  return { worktrees, platformByRepoId, unscannedRepoKeys, gitRunById, scannedRepoKeys }
+  return { worktrees, unscannedRepoKeys, gitRunById, scannedRepoKeys }
 }
diff --git a/src/main/runtime/workspaces/workspace-catalog.ts b/src/main/runtime/workspaces/workspace-catalog.ts
index da9321080f2..8d571f148c4 100644
--- a/src/main/runtime/workspaces/workspace-catalog.ts
+++ b/src/main/runtime/workspaces/workspace-catalog.ts
@@ -15,8 +15,10 @@ import {
 import {
   joinResolvedWorktreeScans,
   platformsByRepoId,
+  projectResolvedWorktreeScans,
   scanResolvedWorktreeRepos,
   type ResolvedWorktreeRepoScans,
+  type ResolvedWorktreeRowsJoin,
   type ResolvedWorktreeScanJoin
 } from './resolved-worktree-scan-join'
 import { projectResolvedWorktreeLineage } from '../../../shared/resolved-worktree-lineage'
@@ -33,7 +35,7 @@ import { withUnregisteredRemovalCheckouts } from '../../workspaces/removal/workt
 import { withoutInFlightWorktreeCreates } from '../../workspaces/creation/worktree-create-in-flight'
 import { preserveFolderUpgradeWorktreePath } from '../../workspaces/catalog/folder-upgrade-worktree-path'
 import type { RuntimeWorktreeScanCache } from '../orca-runtime-core'
-import { getRepoHostIdentityForParts } from '../../../shared/repo-host-identity'
+import { getRepoHostIdentity } from '../../../shared/repo-host-identity'
 import {
   resolveWorktreeScanCacheTtlMs,
   resolveWorktreeScanRuntime
@@ -158,26 +160,35 @@ export abstract class RuntimeWorkspaceCatalog extends OrcaRuntimeWithReadKittyFi
     )
   }
 
-  protected projectCachedWorktrees(): ResolvedWorktreeScanJoin {
-    const scans: ResolvedWorktreeRepoScans = new Map()
-    for (const repo of this.store?.getRepos() ?? []) {
-      const cached = this.worktreeScanCache.get(`${repo.id}\0${getRepoExecutionHostId(repo)}`)
-      if (cached) {
-        scans.set(getRepoHostIdentityForParts(repo.id, getRepoExecutionHostId(repo)), {
-          ...(cached.listing ?? cached.result),
-          gitRun: cached
-        })
-      }
-    }
-    return joinResolvedWorktreeScans(
+  /** The fleet from cached scans for synchronous selector matching, reprojected only when its inputs change. */
+  protected projectCachedWorktrees(): ResolvedWorktreeRowsJoin {
+    const cachedScans = (this.store?.getRepos() ?? []).map((repo) => {
+      const entry = this.worktreeScanCache.get(`${repo.id}\0${getRepoExecutionHostId(repo)}`)
+      return { repo, entry, scan: entry && (entry.listing ?? entry.result) }
+    })
+    return this.resolvedWorktrees.projectCachedScans(
       this.store,
-      () => ({
-        ...this.repoWorktreeRowDeps(),
-        listFolderWorkspaces: (repo, count) =>
-          projectRuntimeFolderWorkspaces(this.requireStore(), repo, count)
-      }),
-      scans,
-      true
+      cachedScans.flatMap(({ repo, entry, scan }) => [getRepoHostIdentity(repo), entry, scan]),
+      () => {
+        const scans: ResolvedWorktreeRepoScans = new Map()
+        for (const { repo, entry, scan } of cachedScans) {
+          if (entry && scan) {
+            scans.set(getRepoHostIdentity(repo), {
+              ...scan,
+              gitRun: entry
+            })
+          }
+        }
+        return projectResolvedWorktreeScans(
+          this.store,
+          () => ({
+            ...this.repoWorktreeRowDeps(),
+            listFolderWorkspaces: (repo, count) =>
+              projectRuntimeFolderWorkspaces(this.requireStore(), repo, count)
+          }),
+          scans
+        )
+      }
     )
   }