From cbc6f54e1cdf62b3fca443434829f19d5937b0f8 Mon Sep 17 00:00:00 2001
From: OrcaWin <alpha-eng@stably.ai>
Date: Fri, 9 Oct 2026 11:40:51 -0700
Subject: [PATCH] refactor(runtime-core): clean up Phase 3-3.8 code (#26894)

* refactor(runtime-core): clean up Phase 3-3.8 code

- worktree.ps: summary lookup is a closure, not a 4-arg callback
- relay: shared RelayStreamAckWindow for fs and git response streams
- relay: terminal-frame slots live on RelayStreamRegistry
- one isBinaryBuffer/BINARY_PROBE_BYTES in shared/binary-buffer
- one automation owner fence on the controller, no casts
- drop unchecked Store cast in remote repo registration
- speech download reuses the shared abort-aware delay, no casts
- RelayRuntimeServices: drop leftover handler list and param casts
- use shared errorMessage() in audited files

Co-Authored-By: Claude <noreply@anthropic.com>

* test(cross-version-wire): pass worktree ps summary lookup in both builds' shapes

---------

Co-authored-by: m4air <m4air@Mac.localdomain>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: m4air <m4air@m4airs-MacBook-Air.local>
---
 src/main/automations/precheck-runner.ts       |  7 +-
 .../filesystem-file-content-inspection.ts     | 13 +--
 src/main/memory/hydrate-local-pty-registry.ts | 10 +-
 src/main/providers/ssh-pty-errors.ts          |  6 +-
 .../providers/ssh-sftp-filesystem-provider.ts |  8 +-
 .../service/service-inactive-accounts.ts      |  7 +-
 src/main/rate-limits/service/service-types.ts | 17 ----
 .../orca-runtime-automation-operations.ts     | 55 +++++------
 .../runtime/orca-runtime-get-worktree-ps.ts   | 33 ++-----
 .../orca-runtime-preserved-branch-cleanup.ts  |  3 +-
 ...runtime-stop-explicitly-closed-tab-ptys.ts |  6 +-
 ...runtime-write-orchestration-pointer-pty.ts | 37 +------
 .../runtime/runtime-automation-controller.ts  | 32 +++---
 src/main/runtime/runtime-file-command-host.ts | 10 --
 ...ile-commands-read-file-explorer-preview.ts |  2 +-
 ...ntime-file-commands-terminal-file-paths.ts |  2 +-
 ...e-commands-write-terminal-artifact-file.ts |  3 +-
 .../runtime-rpc/runtime-rpc-lifecycle.ts      |  3 +-
 ...ime-worktree-agent-rows-structured.test.ts |  4 +-
 ...untime-worktree-agent-rows-verdict.test.ts |  8 +-
 .../runtime/runtime-worktree-agent-rows.ts    | 18 +---
 .../runtime/runtime-worktree-ps-activity.ts   | 43 ++------
 ...worktree-ps-unverifiable-terminals.test.ts |  8 +-
 ...time-worktree-ps-unverifiable-terminals.ts | 15 +--
 ...ree-structured-agent-rows-liveness.test.ts |  7 +-
 .../runtime/runtime-worktree-summary-paths.ts | 35 +++++++
 .../speech/speech-model-download-response.ts  | 18 ----
 .../speech/speech-model-download-transport.ts | 17 ++--
 src/main/terminal-scrollback-snapshots.ts     |  9 +-
 src/relay/agent-exec-handler.ts               |  3 +-
 src/relay/ai-vault-transcript-stream.ts       |  2 +-
 src/relay/fs-handler-file-read.ts             | 13 +--
 src/relay/fs-handler-terminal-artifact.ts     |  2 +-
 src/relay/fs-handler-utils.ts                 | 14 +--
 src/relay/fs-stream-registry.ts               | 97 ++++++++-----------
 src/relay/fs-stream-terminal-frame-slots.ts   | 51 ----------
 src/relay/git-response-stream.ts              | 86 ++++------------
 src/relay/relay-daemon.ts                     |  9 +-
 src/relay/relay-grace-lifecycle.ts            |  5 +-
 src/relay/relay-runtime-services.ts           | 61 ++++--------
 src/relay/relay-stream-ack-window.ts          | 51 ++++++++++
 src/relay/relay-watcher-setup-wait.ts         |  3 +-
 src/shared/abort-aware-delay.ts               | 16 +++
 src/shared/binary-buffer.ts                   |  4 +-
 .../cross-version-stopping.unit.test.ts       |  7 +-
 ...s-version-worktree-ps-verdict.unit.test.ts |  7 +-
 46 files changed, 317 insertions(+), 550 deletions(-)
 delete mode 100644 src/relay/fs-stream-terminal-frame-slots.ts
 create mode 100644 src/relay/relay-stream-ack-window.ts
 create mode 100644 src/shared/abort-aware-delay.ts

diff --git a/src/main/automations/precheck-runner.ts b/src/main/automations/precheck-runner.ts
index d4ab63b4d75..bf777d02af1 100644
--- a/src/main/automations/precheck-runner.ts
+++ b/src/main/automations/precheck-runner.ts
@@ -5,6 +5,7 @@ import { MAX_AUTOMATION_PRECHECK_OUTPUT_CHARS } from '../../shared/automation-pr
 import { getSshConnectionManager } from '../ssh/ssh-target-registry'
 import { shellEscape } from '../ssh/ssh-connection-utils'
 import { admitSelfInitiatedTreeKill } from '../own-chromium-tree-kill-guard'
+import { errorMessage } from '../../shared/error-message'
 
 type AutomationPrecheckExecutionTarget =
   | {
@@ -266,11 +267,7 @@ async function runSshPrecheck(
     const channel = await connection.exec(remoteCommand)
     return await runSshChannelPrecheck({ precheck, channel, startedAt })
   } catch (error) {
-    return failedPrecheckResult(
-      precheck,
-      startedAt,
-      error instanceof Error ? error.message : String(error)
-    )
+    return failedPrecheckResult(precheck, startedAt, errorMessage(error))
   }
 }
 
diff --git a/src/main/ipc/filesystem/filesystem-file-content-inspection.ts b/src/main/ipc/filesystem/filesystem-file-content-inspection.ts
index 6bd7fc754ed..4d386093e15 100644
--- a/src/main/ipc/filesystem/filesystem-file-content-inspection.ts
+++ b/src/main/ipc/filesystem/filesystem-file-content-inspection.ts
@@ -1,5 +1,6 @@
 import { extname } from 'node:path'
 import { localLogFileIdentity } from '../../ai-vault/local-log-tail-reader'
+import { BINARY_PROBE_BYTES, isBinaryBuffer } from '../../../shared/binary-buffer'
 import {
   fileTooLargeError,
   openLocalRegularFile,
@@ -9,7 +10,6 @@ import {
 
 // Why: Monaco degrades features on large files like VS Code, so a 5MB block would needlessly lock out ordinary JSON/log files.
 export const MAX_TEXT_FILE_SIZE = 50 * 1024 * 1024 // 50MB
-export const BINARY_PROBE_BYTES = 8192
 // Why: previewable binaries are base64 blobs (not parsed as text), and local IPC has no frame limit (unlike the relay's 10MB), so 50MB is safe.
 export const MAX_PREVIEWABLE_BINARY_SIZE = 50 * 1024 * 1024 // 50MB
 export const PREVIEWABLE_BINARY_MIME_TYPES: Record<string, string> = {
@@ -90,17 +90,6 @@ export async function readLocalLogSnapshot(filePath: string): Promise<LocalFileC
   }
 }
 
-/** Check if a buffer appears to be binary (contains null bytes in first 8KB). */
-export function isBinaryBuffer(buffer: Buffer): boolean {
-  const len = Math.min(buffer.length, BINARY_PROBE_BYTES)
-  for (let i = 0; i < len; i++) {
-    if (buffer[i] === 0) {
-      return true
-    }
-  }
-  return false
-}
-
 export function isDirectoryEntry(entry: {
   isDirectory(): boolean
   isSymbolicLink(): boolean
diff --git a/src/main/memory/hydrate-local-pty-registry.ts b/src/main/memory/hydrate-local-pty-registry.ts
index 43a11a89e4e..fa1c176728a 100644
--- a/src/main/memory/hydrate-local-pty-registry.ts
+++ b/src/main/memory/hydrate-local-pty-registry.ts
@@ -15,6 +15,7 @@ import { getLocalProjectWorktreeGitOptions } from '../project-runtime-git-option
 import { listLocalRepoWorktreesStrict } from '../repo-worktrees'
 import { listRegisteredPtys, registerPty } from './pty-registry'
 import { getVerifiedLocalFolderWorkspaceKeys } from './verified-local-folder-workspaces'
+import { errorMessage } from '../../shared/error-message'
 
 type HydrationStore = Store
 
@@ -58,10 +59,7 @@ export function hydrateLocalPtyRegistryAtBoot(store: HydrationStore): Promise<vo
       }
     })
     .catch((error) => {
-      console.warn(
-        '[memory] Boot-time pty-registry hydration failed:',
-        error instanceof Error ? error.message : String(error)
-      )
+      console.warn('[memory] Boot-time pty-registry hydration failed:', errorMessage(error))
     })
     .finally(() => {
       clearTimeout(deadline)
@@ -139,7 +137,7 @@ async function hydrateLocalPtyRegistry(
         complete = false
         console.warn(
           '[memory] Worktree enumeration failed during pty-registry hydration:',
-          result.reason instanceof Error ? result.reason.message : String(result.reason)
+          errorMessage(result.reason)
         )
         continue
       }
@@ -260,7 +258,7 @@ async function collectSessionInfos(
         throwIfSignalAborted(signal)
         console.warn(
           '[memory] listSessions failed for one adapter during hydration:',
-          error instanceof Error ? error.message : String(error)
+          errorMessage(error)
         )
         return { complete: false, sessions: [] }
       }
diff --git a/src/main/providers/ssh-pty-errors.ts b/src/main/providers/ssh-pty-errors.ts
index 24f0467263e..bd25bff4f5c 100644
--- a/src/main/providers/ssh-pty-errors.ts
+++ b/src/main/providers/ssh-pty-errors.ts
@@ -1,3 +1,5 @@
+import { errorMessage } from '../../shared/error-message'
+
 export const SSH_SESSION_EXPIRED_ERROR = 'SSH_SESSION_EXPIRED'
 export const SSH_PTY_IDENTITY_MISMATCH_ERROR = 'SSH_PTY_IDENTITY_MISMATCH'
 /**
@@ -13,12 +15,12 @@ export const SSH_PTY_SOURCE_RESTORE_REQUIRED_ERROR = 'SSH_PTY_SOURCE_RESTORE_REQ
 export const SSH_PTY_HELD_BY_PREVIOUS_RELAY_ERROR = 'SSH_PTY_HELD_BY_PREVIOUS_RELAY'
 
 export function isSshPtyNotFoundError(error: unknown): boolean {
-  const message = error instanceof Error ? error.message : String(error)
+  const message = errorMessage(error)
   return /PTY ".+" not found/i.test(message)
 }
 
 export function isSshPtyIdentityMismatchError(error: unknown): boolean {
-  const message = error instanceof Error ? error.message : String(error)
+  const message = errorMessage(error)
   return message.includes(SSH_PTY_IDENTITY_MISMATCH_ERROR) || /identity mismatch/i.test(message)
 }
 
diff --git a/src/main/providers/ssh-sftp-filesystem-provider.ts b/src/main/providers/ssh-sftp-filesystem-provider.ts
index 016be885e57..ddbcabe951f 100644
--- a/src/main/providers/ssh-sftp-filesystem-provider.ts
+++ b/src/main/providers/ssh-sftp-filesystem-provider.ts
@@ -9,6 +9,7 @@ export { readSftpDirectory } from './ssh-sftp-directory-listing'
 import { extname } from 'node:path'
 import type { SFTPWrapper, Stats } from 'ssh2'
 import { IMAGE_FILE_MIME_TYPES } from '../../shared/image-file-extensions'
+import { isBinaryBuffer } from '../../shared/binary-buffer'
 import { capturePathExistence, type PathExistenceResult } from '../../shared/path-existence-batch'
 import type { SearchResult } from '../../shared/code-search-types'
 import type { DirEntry } from '../../shared/filesystem-entry-types'
@@ -23,10 +24,9 @@ import {
 import { fileStatFromSftpStats, lstatViaSftp, statViaSftp } from './ssh-filesystem-provider-sftp'
 import type { FileReadLimits, FileReadResult, FileStat, IFilesystemProvider } from './types'
 
-// Why: same caps and probe window as the relay's fs.readFile so previews behave identically.
+// Why: same caps as the relay's fs.readFile so previews behave identically.
 const MAX_TEXT_FILE_SIZE = 10 * 1024 * 1024
 const MAX_PREVIEWABLE_BINARY_SIZE = 50 * 1024 * 1024
-const BINARY_PROBE_BYTES = 8192
 const SFTP_NO_SUCH_FILE = 2
 const PREVIEW_MIME_TYPES: Record<string, string> = {
   ...IMAGE_FILE_MIME_TYPES,
@@ -55,10 +55,6 @@ function normalizeSftpError(error: unknown): Error {
   return err
 }
 
-function isBinaryBuffer(buffer: Buffer): boolean {
-  return buffer.subarray(0, BINARY_PROBE_BYTES).includes(0)
-}
-
 export class SshSftpFilesystemProvider implements IFilesystemProvider {
   private readonly channel: SftpFilesystemChannel
 
diff --git a/src/main/rate-limits/service/service-inactive-accounts.ts b/src/main/rate-limits/service/service-inactive-accounts.ts
index e59d1eeb3a9..e0d388639c8 100644
--- a/src/main/rate-limits/service/service-inactive-accounts.ts
+++ b/src/main/rate-limits/service/service-inactive-accounts.ts
@@ -1,11 +1,8 @@
 import { fetchManagedAccountUsage } from '../claude-fetcher'
 import { fetchCodexRateLimits } from '../codex-fetcher'
 import { RateLimitServicePolling } from './service-polling'
-import {
-  INACTIVE_CODEX_PROBE_STAGGER_MS,
-  INACTIVE_FETCH_DEBOUNCE_MS,
-  delayUnlessAborted
-} from './service-types'
+import { INACTIVE_CODEX_PROBE_STAGGER_MS, INACTIVE_FETCH_DEBOUNCE_MS } from './service-types'
+import { delayUnlessAborted } from '../../../shared/abort-aware-delay'
 
 export abstract class RateLimitServiceInactiveAccounts extends RateLimitServicePolling {
   async fetchInactiveClaudeAccountsOnOpen(): Promise<void> {
diff --git a/src/main/rate-limits/service/service-types.ts b/src/main/rate-limits/service/service-types.ts
index 5bae83b1449..eec4ffd50cb 100644
--- a/src/main/rate-limits/service/service-types.ts
+++ b/src/main/rate-limits/service/service-types.ts
@@ -162,23 +162,6 @@ export function normalizeClaudeConfigDir(dir: string | null | undefined): string
   return trimmed || null
 }
 
-export function delayUnlessAborted(ms: number, signal: AbortSignal): Promise<void> {
-  if (signal.aborted) {
-    return Promise.resolve()
-  }
-  return new Promise((resolve) => {
-    const onAbort = (): void => {
-      clearTimeout(timer)
-      resolve()
-    }
-    const timer = setTimeout(() => {
-      signal.removeEventListener('abort', onAbort)
-      resolve()
-    }, ms)
-    signal.addEventListener('abort', onAbort, { once: true })
-  })
-}
-
 export function isSameUsageWindow(
   a: ProviderRateLimits['session'],
   b: ProviderRateLimits['session']
diff --git a/src/main/runtime/orca-runtime-automation-operations.ts b/src/main/runtime/orca-runtime-automation-operations.ts
index 32d47c59951..294d540c0ca 100644
--- a/src/main/runtime/orca-runtime-automation-operations.ts
+++ b/src/main/runtime/orca-runtime-automation-operations.ts
@@ -1,7 +1,6 @@
 // @ts-nocheck -- mechanically split from OrcaRuntimeService; behavior is covered by AST equivalence and characterization tests.
 import { OrcaRuntimeWithPtyForegroundProcessReads } from './orca-runtime-pty-foreground-process-reads'
 import type {
-  AutomationOwnerFenceOperation,
   AutomationOwnerPrecondition,
   AutomationDestination
 } from '../../shared/automation-owner-precondition'
@@ -25,33 +24,29 @@ import { makePaneKey } from '../../shared/stable-pane-id'
 import { runtimeWorktreeIdsEqual } from './runtime-worktree-path-identity'
 
 export class OrcaRuntimeWithAutomationOperations extends OrcaRuntimeWithPtyForegroundProcessReads {
-  protected fenceAutomationOwner(
-    id: string,
+  private readAutomationRuns<T>(
+    automationId: string | undefined,
     expectedOwner: AutomationOwnerPrecondition | undefined,
-    operation: AutomationOwnerFenceOperation
-  ): void {
-    if (!this.store?.assertAutomationOwnerFence) {
-      if (expectedOwner) {
-        throw new Error('runtime_unavailable')
-      }
-      return
+    read: () => T
+  ): T {
+    if (expectedOwner && !automationId) {
+      throw new Error('An expected owner requires an automation id.')
     }
-    this.store.assertAutomationOwnerFence({ id, expectedOwner, operation })
+    return this.automation.withExternalProbePriority(() => {
+      if (automationId) {
+        this.automation.assertOwner(automationId, expectedOwner, 'read')
+      }
+      return read()
+    })
   }
 
   listAutomationRuns(
     automationId?: string,
     expectedOwner?: AutomationOwnerPrecondition
   ): AutomationRun[] {
-    if (expectedOwner && !automationId) {
-      throw new Error('An expected owner requires an automation id.')
-    }
-    return this.automation.withExternalProbePriority(() => {
-      if (automationId) {
-        this.fenceAutomationOwner(automationId, expectedOwner, 'read')
-      }
-      return this.automation.listRuns(automationId)
-    })
+    return this.readAutomationRuns(automationId, expectedOwner, () =>
+      this.automation.listRuns(automationId)
+    )
   }
 
   listAutomationRunsPage(
@@ -60,20 +55,14 @@ export class OrcaRuntimeWithAutomationOperations extends OrcaRuntimeWithPtyForeg
     limit?: number,
     cursor?: string
   ) {
-    if (expectedOwner && !automationId) {
-      throw new Error('An expected owner requires an automation id.')
-    }
-    return this.automation.withExternalProbePriority(() => {
-      if (automationId) {
-        this.fenceAutomationOwner(automationId, expectedOwner, 'read')
-      }
-      return this.automation.listRunsPage(automationId, limit, cursor)
-    })
+    return this.readAutomationRuns(automationId, expectedOwner, () =>
+      this.automation.listRunsPage(automationId, limit, cursor)
+    )
   }
 
   showAutomation(id: string, expectedOwner?: AutomationOwnerPrecondition): Automation {
     const automation = this.automation.show(id)
-    this.fenceAutomationOwner(id, expectedOwner, 'read')
+    this.automation.assertOwner(id, expectedOwner, 'read')
     return automation
   }
 
@@ -107,11 +96,11 @@ export class OrcaRuntimeWithAutomationOperations extends OrcaRuntimeWithPtyForeg
   updateAutomation(
     id: string,
     updates: RuntimeAutomationUpdateInput,
-    options?: unknown
+    options?: { expectedOwner?: AutomationOwnerPrecondition; destination?: AutomationDestination }
   ): Promise<Automation> {
     return this.automation.withExternalProbePriority(() => {
       const source = this.automationChangeSelector(id)
-      return this.automation.update(id, updates, options as never).then((automation) => {
+      return this.automation.update(id, updates, options).then((automation) => {
         this.publishAutomationDefinitionChange(source, this.automationChangeSelector(automation.id))
         return automation
       })
@@ -136,7 +125,7 @@ export class OrcaRuntimeWithAutomationOperations extends OrcaRuntimeWithPtyForeg
     expectedOwner?: AutomationOwnerPrecondition
   ): Promise<AutomationRun> {
     return this.automation.withExternalProbePriority(() =>
-      this.automation.runNow(id, expectedOwner as never)
+      this.automation.runNow(id, expectedOwner)
     )
   }
 
diff --git a/src/main/runtime/orca-runtime-get-worktree-ps.ts b/src/main/runtime/orca-runtime-get-worktree-ps.ts
index 1698676a3cb..2fe58e13de3 100644
--- a/src/main/runtime/orca-runtime-get-worktree-ps.ts
+++ b/src/main/runtime/orca-runtime-get-worktree-ps.ts
@@ -5,7 +5,10 @@ import { OrcaRuntimeWithStartTuiIdleVisibleReadProbe } from './orca-runtime-star
 import { DEFAULT_WORKTREE_PS_LIMIT } from './orca-runtime-postlude'
 import type { RuntimeWorktreePsResult } from '../../shared/runtime-types'
 import { buildRuntimeWorktreePsSummaries } from './runtime-worktree-ps-summaries'
-import { buildRuntimeWorktreeSummaryPathIndex } from './runtime-worktree-summary-paths'
+import {
+  buildRuntimeWorktreeSummaryPathIndex,
+  createRuntimeWorktreePsSummaryLookup
+} from './runtime-worktree-summary-paths'
 import {
   applyRuntimeWorktreePsSessionActivity,
   applyRuntimeWorktreePsTerminalActivity
@@ -85,18 +88,13 @@ export class OrcaRuntimeWithGetWorktreePs extends OrcaRuntimeWithStartTuiIdleVis
       platformByRepoId
     })
 
-    const runtimeWorktreeSummaryPathIndex = buildRuntimeWorktreeSummaryPathIndex(
+    const getSummary = createRuntimeWorktreePsSummaryLookup(
       summaries,
-      resolvedWorktrees,
-      platformByRepoId
+      buildRuntimeWorktreeSummaryPathIndex(summaries, resolvedWorktrees, platformByRepoId)
     )
-    const missingRuntimeWorktreeIds = new Set<string>()
     const session = this.store?.getWorkspaceSession?.()
     const countedPtyIds = new Set<string>()
     const workingTerminalEvidenceByWorktreeId = applyRuntimeWorktreePsTerminalActivity({
-      summaries,
-      pathIndex: runtimeWorktreeSummaryPathIndex,
-      missingIds: missingRuntimeWorktreeIds,
       freshPtyLiveness,
       countedPtyIds,
       leaves: this.leaves.values(),
@@ -105,37 +103,27 @@ export class OrcaRuntimeWithGetWorktreePs extends OrcaRuntimeWithStartTuiIdleVis
       session,
       getPaneKey: (leaf) => this.makeRuntimePaneKey(leaf),
       getTitleDisplayClear: (ptyId) => this.getPtyTitleDisplayClear(ptyId),
-      getSummary: (summaryMap, pathIndex, missingIds, worktreeId) =>
-        this.getSummaryForRuntimeWorktreeId(summaryMap, pathIndex, missingIds, worktreeId)
+      getSummary
     })
     applyRuntimeWorktreePsUnverifiableTerminals({
-      summaries,
-      pathIndex: runtimeWorktreeSummaryPathIndex,
-      missingIds: missingRuntimeWorktreeIds,
       countedPtyIds,
       leaves: this.leaves.values(),
       ptysById: this.ptysById,
       getLivenessVerdict: (ptyId) => this.getPtyLivenessVerdict(ptyId),
-      getSummary: (summaryMap, pathIndex, missingIds, worktreeId) =>
-        this.getSummaryForRuntimeWorktreeId(summaryMap, pathIndex, missingIds, worktreeId)
+      getSummary
     })
     const { mirroredWorktreeIdByTabId, connectedPtyEvidence } =
       applyRuntimeWorktreePsSessionActivity({
         store: this.store,
         summaries,
         repoById,
-        pathIndex: runtimeWorktreeSummaryPathIndex,
-        missingIds: missingRuntimeWorktreeIds,
         ptysById: this.ptysById,
         tabs: this.tabs,
         getTerminalHandlesForPty: (ptyId) => this.getExistingTerminalHandlesForPtyId(ptyId),
-        getSummary: (summaryMap, pathIndex, missingIds, worktreeId) =>
-          this.getSummaryForRuntimeWorktreeId(summaryMap, pathIndex, missingIds, worktreeId)
+        getSummary
       })
     attachRuntimeWorktreeAgentRows({
       summaries,
-      pathIndex: runtimeWorktreeSummaryPathIndex,
-      missingWorktreeIds: missingRuntimeWorktreeIds,
       workingTerminalEvidenceByWorktreeId,
       rowSources: collectRuntimeWorktreeAgentSources({
         mirroredWorktreeIdByTabId,
@@ -144,8 +132,7 @@ export class OrcaRuntimeWithGetWorktreePs extends OrcaRuntimeWithStartTuiIdleVis
         hookSnapshots: this.getAgentStatusSnapshotFn?.() ?? []
       }),
       orchestrationByPaneKey: this.agentOrchestrationProjection.buildByPaneKey(),
-      getSummary: (summaryMap, pathIndex, missingIds, worktreeId) =>
-        this.getSummaryForRuntimeWorktreeId(summaryMap, pathIndex, missingIds, worktreeId)
+      getSummary
     })
 
     const sorted = [...summaries.values()].sort(compareWorktreePs)
diff --git a/src/main/runtime/orca-runtime-preserved-branch-cleanup.ts b/src/main/runtime/orca-runtime-preserved-branch-cleanup.ts
index 992b371daf2..be727819a06 100644
--- a/src/main/runtime/orca-runtime-preserved-branch-cleanup.ts
+++ b/src/main/runtime/orca-runtime-preserved-branch-cleanup.ts
@@ -32,7 +32,6 @@ import { RuntimeMobileSpeechCatalog } from './runtime-mobile-speech-catalog'
 import { RuntimeMobileDictationController } from './runtime-mobile-dictation-controller'
 import { RuntimeProjectHostSetupController } from './runtime-project-host-setup-controller'
 import { addRemoteRepoFromPath } from '../ipc/repos/remote-repo-registration'
-import type { Store } from '../persistence'
 import { RuntimeProjectGroupController } from './runtime-project-group-controller'
 import { RuntimeNestedRepoImport } from './runtime-nested-repo-import'
 import { RuntimeRepositoryRegistrationController } from './runtime-repository-registration-controller'
@@ -253,7 +252,7 @@ export class OrcaRuntimeWithPreservedBranchCleanup extends OrcaRuntimeWithTermin
       (this as RuntimeCommandSurfaceHost<this>).addRepo(path, kind, hostId),
     addRemoteRepo: async (remote) => {
       // The same registration the desktop IPC handler uses, so both surfaces agree on SSH hosts.
-      const result = await addRemoteRepoFromPath(this.requireStore() as unknown as Store, remote)
+      const result = await addRemoteRepoFromPath(this.requireStore(), remote)
       if ('error' in result) {
         throw new Error(result.error)
       }
diff --git a/src/main/runtime/orca-runtime-stop-explicitly-closed-tab-ptys.ts b/src/main/runtime/orca-runtime-stop-explicitly-closed-tab-ptys.ts
index ea954fbce8b..e87a6fd996d 100644
--- a/src/main/runtime/orca-runtime-stop-explicitly-closed-tab-ptys.ts
+++ b/src/main/runtime/orca-runtime-stop-explicitly-closed-tab-ptys.ts
@@ -5,6 +5,7 @@ import { SSH_PROVIDER_UNREGISTERED_REASON } from '../../shared/pty-liveness-verd
 import type { RuntimeTerminalClose } from '../../shared/runtime-types'
 import type { RuntimePtyTabCloseAuthority } from './runtime-terminal-state-records'
 import { parsePaneKey } from '../../shared/stable-pane-id'
+import { errorMessage } from '../../shared/error-message'
 
 /** How an explicit close's stop of its addressed PTY ended. */
 type ExplicitCloseStop = { stopped: boolean; pendingKillRecorded: boolean }
@@ -27,10 +28,7 @@ export class OrcaRuntimeWithStopExplicitlyClosedTabPtys extends OrcaRuntimeWithF
         try {
           stopped = await this.ptyController.stopAndWait(ptyId, { deadlineMs })
         } catch (error) {
-          this.markPtyLivenessUnverifiable(
-            ptyId,
-            error instanceof Error ? error.message : String(error)
-          )
+          this.markPtyLivenessUnverifiable(ptyId, errorMessage(error))
         }
         // Preserve an observed exit when a broader inventory check could not finish.
         if (
diff --git a/src/main/runtime/orca-runtime-write-orchestration-pointer-pty.ts b/src/main/runtime/orca-runtime-write-orchestration-pointer-pty.ts
index 2d95f3bf3e5..244b88f52fd 100644
--- a/src/main/runtime/orca-runtime-write-orchestration-pointer-pty.ts
+++ b/src/main/runtime/orca-runtime-write-orchestration-pointer-pty.ts
@@ -10,10 +10,7 @@ import type { TerminalAgent } from '../../shared/terminal-agent'
 import { selectRuntimeHookAgentRowForPane } from './runtime-mobile-agent-status-projection'
 import { isTuiAgent } from '../../shared/tui-agent-config'
 import { resolvePublishedPaneAgentIdentity } from '../../shared/published-pane-agent-identity'
-import type { RuntimeTerminalSummary, RuntimeWorktreePsSummary } from '../../shared/runtime-types'
-import type { RuntimeWorktreeSummaryPathIndex } from './runtime-worktree-summary-paths'
-import { parseRuntimeWorktreeId } from './runtime-worktree-path-identity'
-import { findRuntimeWorktreeSummaryByPath } from './runtime-worktree-summary-paths'
+import type { RuntimeTerminalSummary } from '../../shared/runtime-types'
 import type { ResolvedWorktree } from './runtime-worktree-path-identity'
 import { getLatestLeafTitle } from './runtime-worktree-status-projection'
 import { parseAppSshPtyId } from '../../shared/ssh-pty-id'
@@ -108,38 +105,6 @@ export class OrcaRuntimeWithWriteOrchestrationPointerPty extends OrcaRuntimeWith
     return agentIdentity ? { agentIdentity } : {}
   }
 
-  protected getSummaryForRuntimeWorktreeId(
-    summaries: Map<string, RuntimeWorktreePsSummary>,
-    runtimeWorktreeSummaryPathIndex: RuntimeWorktreeSummaryPathIndex,
-    missingRuntimeWorktreeIds: Set<string>,
-    runtimeWorktreeId: string
-  ): RuntimeWorktreePsSummary | null {
-    const exact = summaries.get(runtimeWorktreeId)
-    if (exact) {
-      return exact
-    }
-    if (missingRuntimeWorktreeIds.has(runtimeWorktreeId)) {
-      return null
-    }
-    const parsed = parseRuntimeWorktreeId(runtimeWorktreeId)
-    if (!parsed) {
-      return null
-    }
-    const comparisonPlatform =
-      runtimeWorktreeSummaryPathIndex.platformByRepoId.get(parsed.repoId) ?? process.platform
-    const indexed = findRuntimeWorktreeSummaryByPath(
-      runtimeWorktreeSummaryPathIndex,
-      parsed.repoId,
-      parsed.worktreePath,
-      comparisonPlatform
-    )
-    if (indexed) {
-      return indexed
-    }
-    missingRuntimeWorktreeIds.add(runtimeWorktreeId)
-    return null
-  }
-
   protected buildTerminalSummary(
     leaf: RuntimeLeafRecord,
     worktreesById: Map<string, ResolvedWorktree>,
diff --git a/src/main/runtime/runtime-automation-controller.ts b/src/main/runtime/runtime-automation-controller.ts
index 173a6580964..2c6b95dfb95 100644
--- a/src/main/runtime/runtime-automation-controller.ts
+++ b/src/main/runtime/runtime-automation-controller.ts
@@ -11,6 +11,7 @@ import type { Worktree } from '../../shared/worktree/types'
 import type { RuntimeStore } from './runtime-store-contract'
 import type { AutomationListParams, AutomationListResult } from '../../shared/automation-list-scope'
 import type {
+  AutomationOwnerFenceOperation,
   AutomationOwnerPrecondition,
   AutomationDestination
 } from '../../shared/automation-owner-precondition'
@@ -209,26 +210,27 @@ export class RuntimeAutomationController {
     if (!this.service) {
       throw new Error('runtime_unavailable')
     }
-    const service = this.service
     return await runAutomationNowFenced({
       automationId: id,
-      service,
-      fence: () => {
-        if (!this.store?.assertAutomationOwnerFence) {
-          if (expectedOwner) {
-            throw new Error('runtime_unavailable')
-          }
-          return
-        }
-        this.store.assertAutomationOwnerFence({
-          id,
-          expectedOwner,
-          operation: 'execute'
-        })
-      }
+      service: this.service,
+      fence: () => this.assertOwner(id, expectedOwner, 'execute')
     })
   }
 
+  assertOwner(
+    id: string,
+    expectedOwner: AutomationOwnerPrecondition | undefined,
+    operation: AutomationOwnerFenceOperation
+  ): void {
+    if (!this.store?.assertAutomationOwnerFence) {
+      if (expectedOwner) {
+        throw new Error('runtime_unavailable')
+      }
+      return
+    }
+    this.store.assertAutomationOwnerFence({ id, expectedOwner, operation })
+  }
+
   private copyPatchValues(
     updates: RuntimeAutomationUpdateInput,
     patch: AutomationUpdateInput
diff --git a/src/main/runtime/runtime-file-command-host.ts b/src/main/runtime/runtime-file-command-host.ts
index 3fb74c71632..0f9d684e3a1 100644
--- a/src/main/runtime/runtime-file-command-host.ts
+++ b/src/main/runtime/runtime-file-command-host.ts
@@ -187,13 +187,3 @@ export function isRuntimeDirectoryEntry(entry: {
   }
   return false
 }
-
-export function isBinaryBuffer(buffer: Buffer): boolean {
-  const len = Math.min(buffer.length, 8192)
-  for (let i = 0; i < len; i += 1) {
-    if (buffer[i] === 0) {
-      return true
-    }
-  }
-  return false
-}
diff --git a/src/main/runtime/runtime-file-commands-read-file-explorer-preview.ts b/src/main/runtime/runtime-file-commands-read-file-explorer-preview.ts
index 25f7069e213..fc0a5a21917 100644
--- a/src/main/runtime/runtime-file-commands-read-file-explorer-preview.ts
+++ b/src/main/runtime/runtime-file-commands-read-file-explorer-preview.ts
@@ -20,7 +20,7 @@ import {
   NodeFileReadTooLargeError,
   readNodeFileWithinLimit
 } from '../../shared/node-bounded-file-reader'
-import { isBinaryBuffer } from './runtime-file-command-host'
+import { isBinaryBuffer } from '../../shared/binary-buffer'
 import type {
   DocPreviewFileAccessRequest,
   DocPreviewFileAccessResult
diff --git a/src/main/runtime/runtime-file-commands-terminal-file-paths.ts b/src/main/runtime/runtime-file-commands-terminal-file-paths.ts
index dca41999ad8..03ee354dcba 100644
--- a/src/main/runtime/runtime-file-commands-terminal-file-paths.ts
+++ b/src/main/runtime/runtime-file-commands-terminal-file-paths.ts
@@ -20,7 +20,7 @@ import {
   localTerminalArtifactRoots,
   readFileHandleBufferBounded
 } from './runtime-file-commands-terminal-artifact-access'
-import { isBinaryBuffer } from './runtime-file-command-host'
+import { isBinaryBuffer } from '../../shared/binary-buffer'
 import type { RuntimeFilePreviewResult } from '../../shared/runtime-types'
 import {
   isPathInsideOrEqual,
diff --git a/src/main/runtime/runtime-file-commands-write-terminal-artifact-file.ts b/src/main/runtime/runtime-file-commands-write-terminal-artifact-file.ts
index 26c41e66b5f..15a1a47a951 100644
--- a/src/main/runtime/runtime-file-commands-write-terminal-artifact-file.ts
+++ b/src/main/runtime/runtime-file-commands-write-terminal-artifact-file.ts
@@ -6,7 +6,8 @@ import {
   MOBILE_FILE_READ_MAX_BYTES,
   previewableBinaryByteLimit
 } from './runtime-file-commands-mobile-file-list-limit'
-import { isBinaryBuffer, isMobileBinaryPath } from './runtime-file-command-host'
+import { isBinaryBuffer } from '../../shared/binary-buffer'
+import { isMobileBinaryPath } from './runtime-file-command-host'
 import {
   assertTerminalArtifactContentUnchanged,
   assertTerminalFileGrantFresh,
diff --git a/src/main/runtime/runtime-rpc/runtime-rpc-lifecycle.ts b/src/main/runtime/runtime-rpc/runtime-rpc-lifecycle.ts
index efa05957f40..3a9ec672e3c 100644
--- a/src/main/runtime/runtime-rpc/runtime-rpc-lifecycle.ts
+++ b/src/main/runtime/runtime-rpc/runtime-rpc-lifecycle.ts
@@ -19,6 +19,7 @@ import {
   createRuntimeTransportMetadata,
   sweepOrphanedRuntimeSockets
 } from './runtime-rpc-socket-metadata'
+import { errorMessage } from '../../../shared/error-message'
 
 export class RuntimeRpcLifecycle extends RuntimeRpcWebSocketDispatch {
   async start(): Promise<void> {
@@ -51,7 +52,7 @@ export class RuntimeRpcLifecycle extends RuntimeRpcWebSocketDispatch {
           reply(JSON.stringify(response))
         })
         .catch((error) => {
-          const message = error instanceof Error ? error.message : String(error)
+          const message = errorMessage(error)
           // Why: best-effort id recovery so the client can correlate the error frame to its pending request.
           let id = 'unknown'
           try {
diff --git a/src/main/runtime/runtime-worktree-agent-rows-structured.test.ts b/src/main/runtime/runtime-worktree-agent-rows-structured.test.ts
index 3b30f932a1e..7d6f94207be 100644
--- a/src/main/runtime/runtime-worktree-agent-rows-structured.test.ts
+++ b/src/main/runtime/runtime-worktree-agent-rows-structured.test.ts
@@ -59,8 +59,6 @@ function attach(summaries: AgentSessionStatusSummary[]): RuntimeWorktreePsSummar
   const summariesById = new Map<string, RuntimeWorktreePsSummary>([[WORKTREE_ID, row]])
   attachRuntimeWorktreeAgentRows({
     summaries: summariesById,
-    pathIndex: { byPath: new Map(), byRealPath: new Map() } as never,
-    missingWorktreeIds: new Set(),
     workingTerminalEvidenceByWorktreeId: new Map(),
     rowSources: collectRuntimeWorktreeAgentSources({
       mirroredWorktreeIdByTabId: new Map(),
@@ -72,7 +70,7 @@ function attach(summaries: AgentSessionStatusSummary[]): RuntimeWorktreePsSummar
       hookSnapshots: store.getStatusSnapshot()
     }),
     orchestrationByPaneKey: null,
-    getSummary: (map, _p, _m, id) => map.get(id) ?? null
+    getSummary: (id) => summariesById.get(id) ?? null
   })
   return row
 }
diff --git a/src/main/runtime/runtime-worktree-agent-rows-verdict.test.ts b/src/main/runtime/runtime-worktree-agent-rows-verdict.test.ts
index ff82a61406e..ca955e241c0 100644
--- a/src/main/runtime/runtime-worktree-agent-rows-verdict.test.ts
+++ b/src/main/runtime/runtime-worktree-agent-rows-verdict.test.ts
@@ -109,11 +109,9 @@ function ingest(summary: AgentSessionStatusSummary, children: AgentChildWorkEvid
     hasHostSidebarActivity: false,
     agents: []
   } as unknown as RuntimeWorktreePsSummary
+  const summaries = new Map([[WORKSPACE_ID, row]])
   attachRuntimeWorktreeAgentRows({
-    summaries: new Map([[WORKSPACE_ID, row]]),
-    // oxlint-disable-next-line typescript/consistent-type-assertions -- SAFETY: `getSummary` below resolves every row by id, so the path index is never read.
-    pathIndex: { byPath: new Map(), byRealPath: new Map() } as never,
-    missingWorktreeIds: new Set(),
+    summaries,
     workingTerminalEvidenceByWorktreeId: new Map(),
     rowSources: collectRuntimeWorktreeAgentSources({
       mirroredWorktreeIdByTabId: new Map(),
@@ -125,7 +123,7 @@ function ingest(summary: AgentSessionStatusSummary, children: AgentChildWorkEvid
       hookSnapshots
     }),
     orchestrationByPaneKey: null,
-    getSummary: (map, _p, _m, id) => map.get(id) ?? null
+    getSummary: (id) => summaries.get(id) ?? null
   })
   return { status: hookSnapshots[0], ps: row.agents[0] }
 }
diff --git a/src/main/runtime/runtime-worktree-agent-rows.ts b/src/main/runtime/runtime-worktree-agent-rows.ts
index 310b0f6bc52..3bad0943a10 100644
--- a/src/main/runtime/runtime-worktree-agent-rows.ts
+++ b/src/main/runtime/runtime-worktree-agent-rows.ts
@@ -1,7 +1,7 @@
 import { isFreshNonDoneAgentStatus } from '../../shared/agent-status-types'
 import type { RuntimeWorktreeAgentRow, RuntimeWorktreePsSummary } from '../../shared/runtime-types'
 import { mergeWorktreeSummaryStatus } from './runtime-worktree-status-projection'
-import type { RuntimeWorktreeSummaryPathIndex } from './runtime-worktree-summary-paths'
+import type { RuntimeWorktreePsSummaryLookup } from './runtime-worktree-summary-paths'
 import type { RuntimeWorkingTerminalEvidence } from './runtime-worktree-ps-activity'
 import type { RuntimeWorktreeAgentSource } from './runtime-worktree-agent-source'
 export type { RuntimeAgentRowSnapshot } from './runtime-hook-agent-row-selection'
@@ -14,20 +14,13 @@ type OrchestrationDisplay = {
 
 export function attachRuntimeWorktreeAgentRows(args: {
   summaries: Map<string, RuntimeWorktreePsSummary>
-  pathIndex: RuntimeWorktreeSummaryPathIndex
-  missingWorktreeIds: Set<string>
   rowSources: ReadonlyMap<string, RuntimeWorktreeAgentSource>
   workingTerminalEvidenceByWorktreeId: ReadonlyMap<
     string,
     readonly RuntimeWorkingTerminalEvidence[]
   >
   orchestrationByPaneKey: Record<string, OrchestrationDisplay> | null | undefined
-  getSummary: (
-    summaries: Map<string, RuntimeWorktreePsSummary>,
-    pathIndex: RuntimeWorktreeSummaryPathIndex,
-    missingWorktreeIds: Set<string>,
-    worktreeId: string
-  ) => RuntimeWorktreePsSummary | null
+  getSummary: RuntimeWorktreePsSummaryLookup
 }): void {
   const { rowSources } = args
   const now = Date.now()
@@ -37,12 +30,7 @@ export function attachRuntimeWorktreeAgentRows(args: {
     if (!worktreeId) {
       continue
     }
-    const summary = args.getSummary(
-      args.summaries,
-      args.pathIndex,
-      args.missingWorktreeIds,
-      worktreeId
-    )
+    const summary = args.getSummary(worktreeId)
     if (!summary) {
       continue
     }
diff --git a/src/main/runtime/runtime-worktree-ps-activity.ts b/src/main/runtime/runtime-worktree-ps-activity.ts
index 496acb46def..1b347c9080c 100644
--- a/src/main/runtime/runtime-worktree-ps-activity.ts
+++ b/src/main/runtime/runtime-worktree-ps-activity.ts
@@ -5,7 +5,7 @@ import { getRepoExecutionHostId, type ExecutionHostId } from '../../shared/execu
 import { parsePaneKey } from '../../shared/stable-pane-id'
 import type { RuntimeStore } from './runtime-store-contract'
 import type { RuntimeLeafRecord, RuntimePtyWorktreeRecord } from './runtime-terminal-state-records'
-import type { RuntimeWorktreeSummaryPathIndex } from './runtime-worktree-summary-paths'
+import type { RuntimeWorktreePsSummaryLookup } from './runtime-worktree-summary-paths'
 import {
   getLatestPtyTitle,
   getLeafDisplayRecord,
@@ -18,13 +18,6 @@ import {
 } from './runtime-worktree-status-projection'
 import { runtimeWorktreeIdsEqual } from './runtime-worktree-path-identity'
 
-type SummaryLookup = (
-  summaries: Map<string, RuntimeWorktreePsSummary>,
-  pathIndex: RuntimeWorktreeSummaryPathIndex,
-  missingIds: Set<string>,
-  worktreeId: string
-) => RuntimeWorktreePsSummary | null
-
 export type RuntimeWorkingTerminalEvidence = {
   paneKey: string | null
   ptyId: string | null
@@ -32,9 +25,6 @@ export type RuntimeWorkingTerminalEvidence = {
 }
 
 export function applyRuntimeWorktreePsTerminalActivity(args: {
-  summaries: Map<string, RuntimeWorktreePsSummary>
-  pathIndex: RuntimeWorktreeSummaryPathIndex
-  missingIds: Set<string>
   freshPtyLiveness: ReadonlySet<string> | null
   /** Filled with every PTY this pass counts as live. */
   countedPtyIds: Set<string>
@@ -44,7 +34,7 @@ export function applyRuntimeWorktreePsTerminalActivity(args: {
   session: WorkspaceSessionState | null | undefined
   getPaneKey: (leaf: RuntimeLeafRecord) => string
   getTitleDisplayClear: (ptyId: string) => TitleDisplayClear | null
-  getSummary: SummaryLookup
+  getSummary: RuntimeWorktreePsSummaryLookup
 }): Map<string, RuntimeWorkingTerminalEvidence[]> {
   const workingEvidence = new Map<string, RuntimeWorkingTerminalEvidence[]>()
   const savedTabOwnerById = new Map<string, { worktreeId: string; title: string }>()
@@ -78,12 +68,7 @@ export function applyRuntimeWorktreePsTerminalActivity(args: {
     ) {
       continue
     }
-    const summary = args.getSummary(
-      args.summaries,
-      args.pathIndex,
-      args.missingIds,
-      leaf.worktreeId
-    )
+    const summary = args.getSummary(leaf.worktreeId)
     if (!summary) {
       continue
     }
@@ -146,12 +131,7 @@ export function applyRuntimeWorktreePsTerminalActivity(args: {
     if (!owner) {
       continue
     }
-    const summary = args.getSummary(
-      args.summaries,
-      args.pathIndex,
-      args.missingIds,
-      owner.worktreeId
-    )
+    const summary = args.getSummary(owner.worktreeId)
     if (!summary) {
       continue
     }
@@ -197,13 +177,11 @@ export function applyRuntimeWorktreePsSessionActivity(args: {
   store: RuntimeStore | null
   summaries: Map<string, RuntimeWorktreePsSummary>
   repoById: ReadonlyMap<string, Repo>
-  pathIndex: RuntimeWorktreeSummaryPathIndex
-  missingIds: Set<string>
   ptysById: ReadonlyMap<string, RuntimePtyWorktreeRecord>
   tabs: ReadonlyMap<string, RuntimeSyncedTab>
   /** Non-minting: a listing must not issue handles, only recognise the ones already bound. */
   getTerminalHandlesForPty: (ptyId: string) => readonly string[]
-  getSummary: SummaryLookup
+  getSummary: RuntimeWorktreePsSummaryLookup
 }): {
   mirroredWorktreeIdByTabId: Map<string, string>
   connectedPtyEvidence: {
@@ -229,7 +207,7 @@ export function applyRuntimeWorktreePsSessionActivity(args: {
       if (tabs.length === 0) {
         continue
       }
-      const summary = args.getSummary(args.summaries, args.pathIndex, args.missingIds, worktreeId)
+      const summary = args.getSummary(worktreeId)
       if (summary && tabs.some((tab) => tab.ptyId && args.ptysById.get(tab.ptyId)?.connected)) {
         summary.hasHostSidebarActivity = true
       }
@@ -238,18 +216,13 @@ export function applyRuntimeWorktreePsSessionActivity(args: {
       if (tabs.length === 0) {
         continue
       }
-      const summary = args.getSummary(args.summaries, args.pathIndex, args.missingIds, worktreeId)
+      const summary = args.getSummary(worktreeId)
       if (summary) {
         summary.hasHostSidebarActivity = true
       }
     }
     if (session.activeWorktreeId) {
-      const summary = args.getSummary(
-        args.summaries,
-        args.pathIndex,
-        args.missingIds,
-        session.activeWorktreeId
-      )
+      const summary = args.getSummary(session.activeWorktreeId)
       if (summary) {
         summary.isActive = true
       }
diff --git a/src/main/runtime/runtime-worktree-ps-unverifiable-terminals.test.ts b/src/main/runtime/runtime-worktree-ps-unverifiable-terminals.test.ts
index 8696b75ceba..b6c24cf3bba 100644
--- a/src/main/runtime/runtime-worktree-ps-unverifiable-terminals.test.ts
+++ b/src/main/runtime/runtime-worktree-ps-unverifiable-terminals.test.ts
@@ -9,18 +9,14 @@ describe('unverifiable terminal attribution', () => {
       ['wt-new', {}]
     ])
     applyRuntimeWorktreePsUnverifiableTerminals({
-      // oxlint-disable-next-line typescript/consistent-type-assertions -- SAFETY: only the counters this pass writes are read back.
-      summaries: summaries as Map<string, RuntimeWorktreePsSummary>,
-      // oxlint-disable-next-line typescript/consistent-type-assertions -- SAFETY: getSummary below ignores the index.
-      pathIndex: {} as never,
-      missingIds: new Set(),
       countedPtyIds: new Set(),
       // oxlint-disable-next-line typescript/consistent-type-assertions -- SAFETY: the pass reads only ptyId and worktreeId.
       leaves: [{ ptyId: 'pty-1', worktreeId: 'wt-old' } as never],
       // oxlint-disable-next-line typescript/consistent-type-assertions -- SAFETY: the pass reads only ptyId and worktreeId.
       ptysById: new Map([['pty-1', { ptyId: 'pty-1', worktreeId: 'wt-new' } as never]]),
       getLivenessVerdict: () => ({ status: 'unverifiable', reason: 'lost contact' }),
-      getSummary: (all, _index, _missing, worktreeId) => all.get(worktreeId) ?? null
+      // oxlint-disable-next-line typescript/consistent-type-assertions -- SAFETY: only the counters this pass writes are read back.
+      getSummary: (id) => (summaries.get(id) as RuntimeWorktreePsSummary | undefined) ?? null
     })
     expect(summaries.get('wt-new')?.unverifiableTerminalCount).toBe(1)
     expect(summaries.get('wt-old')?.unverifiableTerminalCount).toBeUndefined()
diff --git a/src/main/runtime/runtime-worktree-ps-unverifiable-terminals.ts b/src/main/runtime/runtime-worktree-ps-unverifiable-terminals.ts
index 23ee5dcab07..ec3f9f93d89 100644
--- a/src/main/runtime/runtime-worktree-ps-unverifiable-terminals.ts
+++ b/src/main/runtime/runtime-worktree-ps-unverifiable-terminals.ts
@@ -1,7 +1,6 @@
-import type { RuntimeWorktreePsSummary } from '../../shared/runtime-types'
 import type { PtyLivenessVerdict } from '../../shared/pty-liveness-verdict'
 import type { RuntimeLeafRecord, RuntimePtyWorktreeRecord } from './runtime-terminal-state-records'
-import type { RuntimeWorktreeSummaryPathIndex } from './runtime-worktree-summary-paths'
+import type { RuntimeWorktreePsSummaryLookup } from './runtime-worktree-summary-paths'
 
 /**
  * Counts each terminal that was not counted live but whose host only lost contact.
@@ -9,19 +8,11 @@ import type { RuntimeWorktreeSummaryPathIndex } from './runtime-worktree-summary
  * the row read as no terminals at all (docs/reference/ssh-execution-boundary.md).
  */
 export function applyRuntimeWorktreePsUnverifiableTerminals(args: {
-  summaries: Map<string, RuntimeWorktreePsSummary>
-  pathIndex: RuntimeWorktreeSummaryPathIndex
-  missingIds: Set<string>
   countedPtyIds: ReadonlySet<string>
   leaves: Iterable<RuntimeLeafRecord>
   ptysById: ReadonlyMap<string, RuntimePtyWorktreeRecord>
   getLivenessVerdict: (ptyId: string) => PtyLivenessVerdict | null
-  getSummary: (
-    summaries: Map<string, RuntimeWorktreePsSummary>,
-    pathIndex: RuntimeWorktreeSummaryPathIndex,
-    missingIds: Set<string>,
-    worktreeId: string
-  ) => RuntimeWorktreePsSummary | null
+  getSummary: RuntimeWorktreePsSummaryLookup
 }): void {
   // Like the live pass, the host's PTY record owns the worktree; a pane only fills in a PTY with no record.
   const ownerByPtyId = new Map<string, string>()
@@ -40,7 +31,7 @@ export function applyRuntimeWorktreePsUnverifiableTerminals(args: {
     ) {
       continue
     }
-    const summary = args.getSummary(args.summaries, args.pathIndex, args.missingIds, worktreeId)
+    const summary = args.getSummary(worktreeId)
     if (summary) {
       summary.unverifiableTerminalCount = (summary.unverifiableTerminalCount ?? 0) + 1
       summary.hasHostSidebarActivity = true
diff --git a/src/main/runtime/runtime-worktree-structured-agent-rows-liveness.test.ts b/src/main/runtime/runtime-worktree-structured-agent-rows-liveness.test.ts
index 5f6020e8d0f..b37091cf17b 100644
--- a/src/main/runtime/runtime-worktree-structured-agent-rows-liveness.test.ts
+++ b/src/main/runtime/runtime-worktree-structured-agent-rows-liveness.test.ts
@@ -130,10 +130,9 @@ function worktreeFor(store: AgentHookServer): RuntimeWorktreePsSummary {
     status: 'inactive',
     agents: []
   } as unknown as RuntimeWorktreePsSummary
+  const summaries = new Map([[WORKTREE_ID, row]])
   attachRuntimeWorktreeAgentRows({
-    summaries: new Map([[WORKTREE_ID, row]]),
-    pathIndex: { byPath: new Map(), byRealPath: new Map() } as never,
-    missingWorktreeIds: new Set(),
+    summaries,
     workingTerminalEvidenceByWorktreeId: new Map(),
     rowSources: collectRuntimeWorktreeAgentSources({
       mirroredWorktreeIdByTabId: new Map(),
@@ -145,7 +144,7 @@ function worktreeFor(store: AgentHookServer): RuntimeWorktreePsSummary {
       hookSnapshots: store.getStatusSnapshot()
     }),
     orchestrationByPaneKey: null,
-    getSummary: (map, _paths, _missing, id) => map.get(id) ?? null
+    getSummary: (id) => summaries.get(id) ?? null
   })
   return row
 }
diff --git a/src/main/runtime/runtime-worktree-summary-paths.ts b/src/main/runtime/runtime-worktree-summary-paths.ts
index 77ecae27e5c..99a304f6789 100644
--- a/src/main/runtime/runtime-worktree-summary-paths.ts
+++ b/src/main/runtime/runtime-worktree-summary-paths.ts
@@ -1,6 +1,7 @@
 import type { RuntimeWorktreePsSummary } from '../../shared/runtime-types'
 import { isWindowsAbsolutePathLike } from '../../shared/cross-platform-path'
 import { worktreePathComparisonKey } from '../ipc/worktree-path-comparison'
+import { parseRuntimeWorktreeId } from './runtime-worktree-path-identity'
 
 type ResolvedWorktreePath = { id: string; repoId: string; path: string }
 type RuntimeWorktreeSummaryPathCandidate = { summary: RuntimeWorktreePsSummary; order: number }
@@ -55,6 +56,40 @@ export function buildRuntimeWorktreeSummaryPathIndex(
   return index
 }
 
+export type RuntimeWorktreePsSummaryLookup = (worktreeId: string) => RuntimeWorktreePsSummary | null
+
+export function createRuntimeWorktreePsSummaryLookup(
+  summaries: ReadonlyMap<string, RuntimeWorktreePsSummary>,
+  pathIndex: RuntimeWorktreeSummaryPathIndex
+): RuntimeWorktreePsSummaryLookup {
+  const missingIds = new Set<string>()
+  return (worktreeId) => {
+    const exact = summaries.get(worktreeId)
+    if (exact) {
+      return exact
+    }
+    if (missingIds.has(worktreeId)) {
+      return null
+    }
+    const parsed = parseRuntimeWorktreeId(worktreeId)
+    if (!parsed) {
+      return null
+    }
+    const platform = pathIndex.platformByRepoId.get(parsed.repoId) ?? process.platform
+    const indexed = findRuntimeWorktreeSummaryByPath(
+      pathIndex,
+      parsed.repoId,
+      parsed.worktreePath,
+      platform
+    )
+    if (indexed) {
+      return indexed
+    }
+    missingIds.add(worktreeId)
+    return null
+  }
+}
+
 export function findRuntimeWorktreeSummaryByPath(
   index: RuntimeWorktreeSummaryPathIndex,
   repoId: string,
diff --git a/src/main/speech/speech-model-download-response.ts b/src/main/speech/speech-model-download-response.ts
index 226f0053b2c..64275b586e6 100644
--- a/src/main/speech/speech-model-download-response.ts
+++ b/src/main/speech/speech-model-download-response.ts
@@ -73,21 +73,3 @@ export function describeInterruptedDownload(
     `Model download interrupted at ${received} after ${attempts} attempts: ${causeMessage}`
   )
 }
-
-export function sleepUnlessAborted(ms: number, signal: AbortSignal): Promise<void> {
-  return new Promise((resolve) => {
-    if (signal.aborted) {
-      resolve()
-      return
-    }
-    const onAbort = (): void => {
-      clearTimeout(timer)
-      resolve()
-    }
-    const timer = setTimeout(() => {
-      signal.removeEventListener('abort', onAbort)
-      resolve()
-    }, ms)
-    signal.addEventListener('abort', onAbort, { once: true })
-  })
-}
diff --git a/src/main/speech/speech-model-download-transport.ts b/src/main/speech/speech-model-download-transport.ts
index 929158a8ba6..1d887a1295e 100644
--- a/src/main/speech/speech-model-download-transport.ts
+++ b/src/main/speech/speech-model-download-transport.ts
@@ -6,11 +6,11 @@ import {
   MAX_RETRY_AFTER_MS,
   MAX_TOTAL_DOWNLOAD_REQUESTS,
   describeInterruptedDownload,
-  sleepUnlessAborted,
   type DownloadTotals
 } from './speech-model-download-response'
 import { isRetryableDownloadError, type HttpStatusError } from '../network/transient-download-error'
 import { SpeechModelHttpDownload } from './speech-model-http-download'
+import { delayUnlessAborted } from '../../shared/abort-aware-delay'
 
 export abstract class SpeechModelDownloadTransport extends SpeechModelHttpDownload {
   protected getPartialDownloadBytes(filePath: string): number {
@@ -72,7 +72,7 @@ export abstract class SpeechModelDownloadTransport extends SpeechModelHttpDownlo
             `Model download exceeded its expected size (${receivedBytes} of ${totals.totalBytes} bytes)`
           )
         }
-        const incompleteResponse = new Error(
+        const incompleteResponse: HttpStatusError = new Error(
           `Model download response ended at ${receivedBytes} of ${totals.totalBytes} bytes`
         )
         if (receivedBytes > offset) {
@@ -80,9 +80,8 @@ export abstract class SpeechModelDownloadTransport extends SpeechModelHttpDownlo
           noProgressStreak = 0
           continue
         }
-        const retryableIncompleteResponse = incompleteResponse as HttpStatusError
-        retryableIncompleteResponse.retryable = true
-        throw retryableIncompleteResponse
+        incompleteResponse.retryable = true
+        throw incompleteResponse
       } catch (err) {
         if (isAborted() || signal.aborted) {
           throw err
@@ -99,11 +98,11 @@ export abstract class SpeechModelDownloadTransport extends SpeechModelHttpDownlo
         if (noProgressStreak >= MAX_NO_PROGRESS_ATTEMPTS) {
           throw describeInterruptedDownload(err, receivedBytes, totals.totalBytes, requestCount)
         }
-        const retryAfterMs = (err as HttpStatusError).retryAfterMs
+        const statusError: HttpStatusError | undefined = err instanceof Error ? err : undefined
+        const retryAfterMs = statusError?.retryAfterMs
         if (retryAfterMs !== undefined && retryAfterMs > MAX_RETRY_AFTER_MS) {
-          const statusCode = (err as HttpStatusError).httpStatusCode
           throw new Error(
-            `HTTP ${statusCode}; server requested retry after ${Math.ceil(retryAfterMs / 1_000)} seconds`
+            `HTTP ${statusError?.httpStatusCode}; server requested retry after ${Math.ceil(retryAfterMs / 1_000)} seconds`
           )
         }
         console.warn(
@@ -111,7 +110,7 @@ export abstract class SpeechModelDownloadTransport extends SpeechModelHttpDownlo
           modelId,
           err
         )
-        await sleepUnlessAborted(
+        await delayUnlessAborted(
           retryAfterMs ??
             DOWNLOAD_RETRY_DELAYS_MS[
               Math.min(Math.max(0, noProgressStreak - 1), DOWNLOAD_RETRY_DELAYS_MS.length - 1)
diff --git a/src/main/terminal-scrollback-snapshots.ts b/src/main/terminal-scrollback-snapshots.ts
index 352edb5ebb4..e7d1561f61b 100644
--- a/src/main/terminal-scrollback-snapshots.ts
+++ b/src/main/terminal-scrollback-snapshots.ts
@@ -18,6 +18,7 @@ import {
   TERMINAL_SCROLLBACK_REPLAY_BYTE_LIMIT,
   TERMINAL_SCROLLBACK_STORE_BYTE_LIMIT
 } from '../shared/terminal-scrollback-limits'
+import { errorMessage } from '../shared/error-message'
 
 const SNAPSHOT_DIR_NAME = 'terminal-scrollback'
 const REF_PREFIX = 'v1'
@@ -156,9 +157,7 @@ export function writeTerminalScrollbackSnapshotSync(args: {
     }
     return ref
   } catch (err) {
-    console.warn(
-      `[terminal-scrollback] Failed to write snapshot: ${err instanceof Error ? err.message : String(err)}`
-    )
+    console.warn(`[terminal-scrollback] Failed to write snapshot: ${errorMessage(err)}`)
     return null
   }
 }
@@ -188,9 +187,7 @@ export async function writeTerminalScrollbackSnapshot(args: {
     renamed = true
     return ref
   } catch (err) {
-    console.warn(
-      `[terminal-scrollback] Failed to write snapshot: ${err instanceof Error ? err.message : String(err)}`
-    )
+    console.warn(`[terminal-scrollback] Failed to write snapshot: ${errorMessage(err)}`)
     return null
   } finally {
     if (!renamed) {
diff --git a/src/relay/agent-exec-handler.ts b/src/relay/agent-exec-handler.ts
index f35302f7c31..d54c2098be1 100644
--- a/src/relay/agent-exec-handler.ts
+++ b/src/relay/agent-exec-handler.ts
@@ -9,6 +9,7 @@ import { mergeGitConfigEnvProtocol } from '../shared/git-credential-prompt-env'
 import { terminateRelaySubprocessTree } from './subprocess-tree-termination'
 import { RelayAgentProcessLifetime } from './relay-agent-process-lifetime'
 import { resolveLoginShellEnvironment } from '../main/startup/login-shell-environment'
+import { errorMessage } from '../shared/error-message'
 
 const DEFAULT_TIMEOUT_MS = 60_000
 const MAX_TIMEOUT_MS = 5 * 60 * 1000
@@ -234,7 +235,7 @@ export class AgentExecHandler {
           stderr: '',
           exitCode: null,
           timedOut: false,
-          spawnError: error instanceof Error ? error.message : String(error)
+          spawnError: errorMessage(error)
         })
         return
       }
diff --git a/src/relay/ai-vault-transcript-stream.ts b/src/relay/ai-vault-transcript-stream.ts
index 42e24733551..7f88a6e4dbe 100644
--- a/src/relay/ai-vault-transcript-stream.ts
+++ b/src/relay/ai-vault-transcript-stream.ts
@@ -1,7 +1,7 @@
 import { open } from 'node:fs/promises'
 import { throwIfAiVaultScanCancelled } from '../main/ai-vault/ai-vault-scan-cancellation'
 import { BinarySessionTranscriptError } from '../main/ai-vault/remote-session-content-lines'
-import { BINARY_PROBE_BYTES, isBinaryBuffer } from './fs-handler-utils'
+import { BINARY_PROBE_BYTES, isBinaryBuffer } from '../shared/binary-buffer'
 import { readNodeFileWithinLimit } from '../shared/node-bounded-file-reader'
 
 /** The same open handle supplies the probe and stream, including across renames. */
diff --git a/src/relay/fs-handler-file-read.ts b/src/relay/fs-handler-file-read.ts
index c07c897fc8b..e0f7fa590a9 100644
--- a/src/relay/fs-handler-file-read.ts
+++ b/src/relay/fs-handler-file-read.ts
@@ -4,15 +4,14 @@ import { extname } from 'node:path'
 import type { RelayDispatcher, RequestContext } from './dispatcher'
 import { STREAM_ACK_WINDOW_CHUNKS, STREAM_CHUNK_SIZE } from './protocol'
 import type { RelayStreamRegistry } from './fs-stream-registry'
-import { reserveTerminalFrameSlot } from './fs-stream-terminal-frame-slots'
+import { BINARY_PROBE_BYTES, isBinaryBuffer } from '../shared/binary-buffer'
 import {
-  BINARY_PROBE_BYTES,
   IMAGE_MIME_TYPES,
   MAX_PREVIEWABLE_BINARY_SIZE,
   MAX_TEXT_FILE_SIZE,
-  isBinaryBuffer,
   isBinaryFilePrefix
 } from './fs-handler-utils'
+import { errorMessage as describeError } from '../shared/error-message'
 
 export async function readRelayFileContent(filePath: string) {
   const stats = await stat(filePath)
@@ -124,7 +123,7 @@ async function prepareRelayFileStream(
 
   // Why: reserved before the fd opens so a refusal costs nothing, and released only
   // once the terminal frame settles — see reserveTerminalFrameSlot.
-  const releaseTerminalFrameSlot = reserveTerminalFrameSlot(registry, context.clientId)
+  const releaseTerminalFrameSlot = registry.reserveTerminalFrameSlot(context.clientId)
   let handle: FileHandle | undefined
   let streamId: number
   try {
@@ -267,7 +266,7 @@ async function pumpChunks(
       } else {
         endReason = 'error'
         errorCode = code ?? 'ESTREAMREAD'
-        errorMessage = err instanceof Error ? err.message : String(err)
+        errorMessage = describeError(err)
       }
     }
 
@@ -310,9 +309,7 @@ async function pumpChunks(
         process.stderr.write(`[relay] stream stale id=${streamId}\n`)
       }
     } catch (err) {
-      process.stderr.write(
-        `[relay] stream notify failed id=${streamId}: ${err instanceof Error ? err.message : String(err)}\n`
-      )
+      process.stderr.write(`[relay] stream notify failed id=${streamId}: ${describeError(err)}\n`)
     }
   } finally {
     // Why: the fd goes back first — a terminal frame that can never be delivered must not
diff --git a/src/relay/fs-handler-terminal-artifact.ts b/src/relay/fs-handler-terminal-artifact.ts
index 02af753f134..91f17d3174c 100644
--- a/src/relay/fs-handler-terminal-artifact.ts
+++ b/src/relay/fs-handler-terminal-artifact.ts
@@ -4,9 +4,9 @@ import { chmod, open, realpath, rename, rm, writeFile } from 'node:fs/promises'
 import type { FileHandle } from 'node:fs/promises'
 import { basename, dirname, extname, join } from 'node:path'
 import { randomUUID } from 'node:crypto'
+import { isBinaryBuffer } from '../shared/binary-buffer'
 import {
   IMAGE_MIME_TYPES,
-  isBinaryBuffer,
   MAX_PREVIEWABLE_BINARY_SIZE,
   MAX_TEXT_FILE_SIZE
 } from './fs-handler-utils'
diff --git a/src/relay/fs-handler-utils.ts b/src/relay/fs-handler-utils.ts
index 4a951eac9f0..2af88784b9a 100644
--- a/src/relay/fs-handler-utils.ts
+++ b/src/relay/fs-handler-utils.ts
@@ -18,6 +18,7 @@ import {
   SEARCH_TIMEOUT_MS as SHARED_SEARCH_TIMEOUT_MS
 } from '../shared/text-search'
 import { IMAGE_FILE_MIME_TYPES } from '../shared/image-file-extensions'
+import { BINARY_PROBE_BYTES, isBinaryBuffer } from '../shared/binary-buffer'
 import type { SearchResult as SharedSearchResult } from '../shared/code-search-types'
 import {
   absorbPendingRipgrepSpawnError,
@@ -44,7 +45,6 @@ export const MAX_TEXT_FILE_SIZE = 10 * 1024 * 1024
 // Reads above the legacy 16MB single-frame budget go through fs.readFileStream,
 // which chunks at STREAM_CHUNK_SIZE; see docs/relay-file-stream-design.md.
 export const MAX_PREVIEWABLE_BINARY_SIZE = 50 * 1024 * 1024
-export const BINARY_PROBE_BYTES = 8192
 export const SEARCH_TIMEOUT_MS = SHARED_SEARCH_TIMEOUT_MS
 export const DEFAULT_MAX_RESULTS = 2000
 
@@ -53,18 +53,6 @@ export const IMAGE_MIME_TYPES: Record<string, string> = {
   '.pdf': 'application/pdf'
 }
 
-// ─── Binary detection ────────────────────────────────────────────────
-
-export function isBinaryBuffer(buffer: Buffer): boolean {
-  const len = Math.min(buffer.length, 8192)
-  for (let i = 0; i < len; i++) {
-    if (buffer[i] === 0) {
-      return true
-    }
-  }
-  return false
-}
-
 export async function isBinaryFilePrefix(
   filePath: string,
   releaseHandle: (handle: Awaited<ReturnType<typeof open>>) => Promise<void> = (handle) =>
diff --git a/src/relay/fs-stream-registry.ts b/src/relay/fs-stream-registry.ts
index 59c0ad19032..e0cc395df2d 100644
--- a/src/relay/fs-stream-registry.ts
+++ b/src/relay/fs-stream-registry.ts
@@ -1,16 +1,9 @@
 import type { FileHandle } from 'node:fs/promises'
 import { settlesWithin } from './settles-within'
-import { MAX_CONCURRENT_STREAMS, RelayErrorCode, STREAM_ACK_STALL_RECHECK_MS } from './protocol'
+import { MAX_CONCURRENT_STREAMS, RelayErrorCode } from './protocol'
+import { RelayStreamAckWindow } from './relay-stream-ack-window'
 
-type StreamEntry = {
-  handle: FileHandle
-  aborted: boolean
-  /** Highest chunk seq the client acknowledged (in-order; -1 = none yet). */
-  ackedThroughSeq: number
-  /** Pumps parked on the ack credit window. Woken by acks, abort, release,
-   * and a periodic stall recheck so a vanished client cannot strand a pump. */
-  ackWaiters: Set<() => void>
-}
+type StreamEntry = { handle: FileHandle; ack: RelayStreamAckWindow }
 
 // Why: a stalled but connected client can hold a terminal-frame slot open indefinitely.
 const OPERATION_SETTLE_DEADLINE_MS = 10_000
@@ -29,6 +22,11 @@ export class RelayStreamRegistry {
   private closing = new Map<number, Promise<void>>()
   private closeFailures = new Map<number, unknown>()
   private operations = new Set<Promise<void>>()
+  // Why: terminal frames ride the non-dropping control lane, which destroys the link at 256 frames / 1 MB.
+  // Holding a per-client slot until the frame settles caps queued terminal frames at
+  // MAX_CONCURRENT_STREAMS per client (the control queue is per client); each slot is a
+  // registry operation, so shutdown waits for undelivered terminal frames too.
+  private pendingTerminalFramesByClient = new Map<number, number>()
 
   constructor(private readonly operationDeadlineMs = OPERATION_SETTLE_DEADLINE_MS) {}
 
@@ -49,6 +47,31 @@ export class RelayStreamRegistry {
     }
   }
 
+  /** Holds a per-client slot until a stream's terminal frame settles; see comment. */
+  reserveTerminalFrameSlot(clientId: number): () => void {
+    const pending = this.pendingTerminalFramesByClient.get(clientId) ?? 0
+    if (pending >= MAX_CONCURRENT_STREAMS) {
+      throw new TooManyStreamsError()
+    }
+    const finish = this.beginOperation()
+    this.pendingTerminalFramesByClient.set(clientId, pending + 1)
+    let released = false
+    return () => {
+      if (released) {
+        return
+      }
+      released = true
+      finish()
+      const remaining = (this.pendingTerminalFramesByClient.get(clientId) ?? 1) - 1
+      // Drop the entry at zero so a long-lived registry cannot accumulate one per detached client.
+      if (remaining <= 0) {
+        this.pendingTerminalFramesByClient.delete(clientId)
+        return
+      }
+      this.pendingTerminalFramesByClient.set(clientId, remaining)
+    }
+  }
+
   register(handle: FileHandle): number {
     if (this.disposed) {
       throw new Error('relay_file_stream_shutdown_fenced')
@@ -66,25 +89,16 @@ export class RelayStreamRegistry {
 
   private retainHandle(handle: FileHandle): number {
     const streamId = this.nextId++
-    this.streams.set(streamId, {
-      handle,
-      aborted: false,
-      ackedThroughSeq: -1,
-      ackWaiters: new Set()
-    })
+    this.streams.set(streamId, { handle, ack: new RelayStreamAckWindow() })
     return streamId
   }
 
   abort(streamId: number): void {
-    const entry = this.streams.get(streamId)
-    if (entry) {
-      entry.aborted = true
-      this.wakeAckWaiters(entry)
-    }
+    this.streams.get(streamId)?.ack.abort()
   }
 
   isAborted(streamId: number): boolean {
-    return this.streams.get(streamId)?.aborted ?? true
+    return this.streams.get(streamId)?.ack.aborted ?? true
   }
 
   get(streamId: number): StreamEntry | undefined {
@@ -92,55 +106,24 @@ export class RelayStreamRegistry {
   }
 
   recordAck(streamId: number, seq: number): void {
-    const entry = this.streams.get(streamId)
-    if (!entry || typeof seq !== 'number' || !Number.isFinite(seq)) {
-      return
-    }
-    if (seq > entry.ackedThroughSeq) {
-      entry.ackedThroughSeq = seq
-    }
-    this.wakeAckWaiters(entry)
+    this.streams.get(streamId)?.ack.recordAck(seq)
   }
 
   ackedThroughSeq(streamId: number): number {
-    return this.streams.get(streamId)?.ackedThroughSeq ?? Number.MAX_SAFE_INTEGER
+    return this.streams.get(streamId)?.ack.ackedThroughSeq ?? Number.MAX_SAFE_INTEGER
   }
 
   /** Resolves on the next ack/abort/release for this stream, or after the
    * stall-recheck interval so callers can re-evaluate staleness. */
   waitForAck(streamId: number): Promise<void> {
-    const entry = this.streams.get(streamId)
-    if (!entry || entry.aborted) {
-      return Promise.resolve()
-    }
-    return new Promise<void>((resolve) => {
-      let settled = false
-      const timer = setTimeout(() => finish(), STREAM_ACK_STALL_RECHECK_MS)
-      timer.unref?.()
-      const finish = (): void => {
-        if (settled) {
-          return
-        }
-        settled = true
-        clearTimeout(timer)
-        entry.ackWaiters.delete(finish)
-        resolve()
-      }
-      entry.ackWaiters.add(finish)
-    })
+    return this.streams.get(streamId)?.ack.wait() ?? Promise.resolve()
   }
 
   /** Wake every parked pump (all streams) so it re-checks staleness — used
    * when a client detaches and its acks will never arrive. */
   wakeAllAckWaiters(): void {
     for (const entry of this.streams.values()) {
-      this.wakeAckWaiters(entry)
-    }
-  }
-
-  private wakeAckWaiters(entry: StreamEntry): void {
-    for (const waiter of Array.from(entry.ackWaiters)) {
-      waiter()
+      entry.ack.wake()
     }
   }
 
diff --git a/src/relay/fs-stream-terminal-frame-slots.ts b/src/relay/fs-stream-terminal-frame-slots.ts
deleted file mode 100644
index 5ede13b5d79..00000000000
--- a/src/relay/fs-stream-terminal-frame-slots.ts
+++ /dev/null
@@ -1,51 +0,0 @@
-import { MAX_CONCURRENT_STREAMS } from './protocol'
-import { TooManyStreamsError, type RelayStreamRegistry } from './fs-stream-registry'
-
-/**
- * Terminal frames (fs.streamEnd/fs.streamError) ride the control lane, which does not
- * drop on overflow — it destroys the link at 256 queued frames / 1 MB. A stream's
- * registry slot is gone the moment its last chunk is read, so on a socket that is not
- * draining, back-to-back reads could stack one undelivered terminal frame each until
- * that budget blew. Holding the slot until the frame settles keeps the number of queued
- * terminal frames at MAX_CONCURRENT_STREAMS, far below the killing threshold; the
- * overflow now costs one refused read (TooManyStreams, which clients already handle)
- * instead of the whole connection.
- *
- * Counted per client, because the control queue this protects is per client: one peer whose
- * socket stopped draining must not refuse reads for every other peer on the same relay.
- * Counted independently of released file descriptors, and each slot is a registry operation
- * so shutdown waits for undelivered terminal frames too.
- */
-const pendingTerminalFramesByClient = new WeakMap<RelayStreamRegistry, Map<number, number>>()
-
-export function reserveTerminalFrameSlot(
-  registry: RelayStreamRegistry,
-  clientId: number
-): () => void {
-  let byClient = pendingTerminalFramesByClient.get(registry)
-  if (!byClient) {
-    byClient = new Map()
-    pendingTerminalFramesByClient.set(registry, byClient)
-  }
-  const pending = byClient.get(clientId) ?? 0
-  if (pending >= MAX_CONCURRENT_STREAMS) {
-    throw new TooManyStreamsError()
-  }
-  const finish = registry.beginOperation()
-  byClient.set(clientId, pending + 1)
-  let released = false
-  return () => {
-    if (released) {
-      return
-    }
-    released = true
-    finish()
-    const remaining = (byClient.get(clientId) ?? 1) - 1
-    // Drop the entry at zero so a long-lived registry cannot accumulate one per detached client.
-    if (remaining <= 0) {
-      byClient.delete(clientId)
-      return
-    }
-    byClient.set(clientId, remaining)
-  }
-}
diff --git a/src/relay/git-response-stream.ts b/src/relay/git-response-stream.ts
index 7097b3b2d8d..254c140478a 100644
--- a/src/relay/git-response-stream.ts
+++ b/src/relay/git-response-stream.ts
@@ -1,7 +1,7 @@
 // Streams large RPC responses onto the bulk lane in chunks instead of one
 // JSON-RPC frame, so a big reply cannot head-of-line-block interactive pty.data
-// echo on the shared SSH channel. Mirrors the fs read-stream credit-window
-// pattern (see fs-handler-file-read.ts) but the payload is an in-memory
+// echo on the shared SSH channel. Shares RelayStreamAckWindow with the fs
+// read stream (see fs-handler-file-read.ts) but the payload is an in-memory
 // serialized string rather than a file handle.
 //
 // ONE REGISTRY PER RELAY. The `git.*` method names below are the shipped wire
@@ -18,18 +18,13 @@ import {
   GIT_RESPONSE_CHUNK_SIZE,
   GIT_RESPONSE_STREAM_THRESHOLD,
   STREAM_ACK_WINDOW_CHUNKS,
-  STREAM_ACK_STALL_RECHECK_MS,
   type GitResponseStreamMarker
 } from './protocol'
 import { settlesWithin } from './settles-within'
+import { RelayStreamAckWindow } from './relay-stream-ack-window'
+import { errorMessage } from '../shared/error-message'
 
-type GitResponseStreamEntry = {
-  ownerClientId: number
-  aborted: boolean
-  /** Highest chunk seq the client acknowledged (in-order; -1 = none yet). */
-  ackedThroughSeq: number
-  ackWaiters: Set<() => void>
-}
+type GitResponseStreamEntry = { ownerClientId: number; ack: RelayStreamAckWindow }
 
 /** Serialized git responses are chunked as base64 so multi-byte UTF-8
  * sequences never split across a chunk boundary (the client concatenates the
@@ -58,36 +53,22 @@ export class GitResponseStreamRegistry {
       throw new Error('relay_response_stream_shutdown_fenced')
     }
     const streamId = this.nextId++
-    this.streams.set(streamId, {
-      ownerClientId,
-      aborted: false,
-      ackedThroughSeq: -1,
-      ackWaiters: new Set()
-    })
+    this.streams.set(streamId, { ownerClientId, ack: new RelayStreamAckWindow() })
     return streamId
   }
 
   recordAck(streamId: number, seq: number, clientId: number): void {
     const entry = this.streams.get(streamId)
-    if (
-      !entry ||
-      entry.ownerClientId !== clientId ||
-      typeof seq !== 'number' ||
-      !Number.isFinite(seq)
-    ) {
+    if (!entry || entry.ownerClientId !== clientId) {
       return
     }
-    if (seq > entry.ackedThroughSeq) {
-      entry.ackedThroughSeq = seq
-    }
-    this.wake(entry)
+    entry.ack.recordAck(seq)
   }
 
   abort(streamId: number, clientId: number): void {
     const entry = this.streams.get(streamId)
     if (entry?.ownerClientId === clientId) {
-      entry.aborted = true
-      this.wake(entry)
+      entry.ack.abort()
     }
   }
 
@@ -95,38 +76,10 @@ export class GitResponseStreamRegistry {
    * detaches and its acks will never arrive. */
   wakeAll(): void {
     for (const entry of this.streams.values()) {
-      this.wake(entry)
+      entry.ack.wake()
     }
   }
 
-  private wake(entry: GitResponseStreamEntry): void {
-    for (const waiter of Array.from(entry.ackWaiters)) {
-      waiter()
-    }
-  }
-
-  private waitForAck(streamId: number): Promise<void> {
-    const entry = this.streams.get(streamId)
-    if (!entry || entry.aborted) {
-      return Promise.resolve()
-    }
-    return new Promise<void>((resolve) => {
-      let settled = false
-      const finish = (): void => {
-        if (settled) {
-          return
-        }
-        settled = true
-        clearTimeout(timer)
-        entry.ackWaiters.delete(finish)
-        resolve()
-      }
-      const timer = setTimeout(finish, STREAM_ACK_STALL_RECHECK_MS)
-      timer.unref?.()
-      entry.ackWaiters.add(finish)
-    })
-  }
-
   /**
    * Register a stream for `payload`, kick off the bulk-lane pump on a later
    * task (so the sentinel response reaches the client first), and return the
@@ -188,24 +141,24 @@ export class GitResponseStreamRegistry {
           endReason = 'stale'
           break
         }
-        if (entry.aborted) {
+        if (entry.ack.aborted) {
           endReason = 'aborted'
           break
         }
         // Why: credit window — the client acks each chunk, bounding how many
         // bulk bytes a keystroke echo can queue behind on the shared channel.
         while (
-          seq - entry.ackedThroughSeq > STREAM_ACK_WINDOW_CHUNKS &&
+          seq - entry.ack.ackedThroughSeq > STREAM_ACK_WINDOW_CHUNKS &&
           !context.isStale() &&
-          !entry.aborted
+          !entry.ack.aborted
         ) {
-          await this.waitForAck(streamId)
+          await entry.ack.wait()
         }
         if (context.isStale()) {
           endReason = 'stale'
           break
         }
-        if (entry.aborted) {
+        if (entry.ack.aborted) {
           endReason = 'aborted'
           break
         }
@@ -222,17 +175,17 @@ export class GitResponseStreamRegistry {
         chunks[seq] = ''
       }
       // Why: disposal may abort while the final chunk write is in flight.
-      if (endReason === 'end' && !entry.aborted && !context.isStale()) {
+      if (endReason === 'end' && !entry.ack.aborted && !context.isStale()) {
         await dispatcher.notifyBulk('git.responseEnd', { streamId }, { clientId })
       }
     } catch (err) {
-      if (!context.isStale() && !entry.aborted) {
+      if (!context.isStale() && !entry.ack.aborted) {
         try {
           await dispatcher.notifyBulk(
             'git.responseError',
             {
               streamId,
-              message: err instanceof Error ? err.message : String(err)
+              message: errorMessage(err)
             },
             { clientId }
           )
@@ -250,8 +203,7 @@ export class GitResponseStreamRegistry {
   disposeAll(): void {
     this.disposed = true
     for (const entry of this.streams.values()) {
-      entry.aborted = true
-      this.wake(entry)
+      entry.ack.abort()
     }
     this.streams.clear()
   }
diff --git a/src/relay/relay-daemon.ts b/src/relay/relay-daemon.ts
index daca737a3df..31eb57b9f98 100644
--- a/src/relay/relay-daemon.ts
+++ b/src/relay/relay-daemon.ts
@@ -15,6 +15,7 @@ import {
 } from './relay-endpoint-credential-publication'
 import { SKILL_RELAY_CAPABILITIES } from './skill-install-handler'
 import { publishRelayPid } from './relay-pid-publication'
+import { errorMessage } from '../shared/error-message'
 
 export async function runRelayDaemon(options: RelayLaunchOptions): Promise<void> {
   if (options.detached && options.logFile) {
@@ -30,9 +31,7 @@ export async function runRelayDaemon(options: RelayLaunchOptions): Promise<void>
     } catch (reapError) {
       // Why log rather than swallow: exit must still win, but this line is the only
       // forensic trace a crashed remote daemon leaves behind for an orphaned shell.
-      relayLogLine(
-        `[relay] Fatal PTY reap failed: ${reapError instanceof Error ? reapError.message : String(reapError)}`
-      )
+      relayLogLine(`[relay] Fatal PTY reap failed: ${errorMessage(reapError)}`)
     }
     socketOwnership.cleanup()
     process.exit(1)
@@ -112,9 +111,7 @@ export async function runRelayDaemon(options: RelayLaunchOptions): Promise<void>
     reconnectListener.setEndpointCredential(publishRelayEndpointCredential(options.credentialFile))
     agentHooks.publishEndpointFile()
   } catch (error) {
-    relayLogLine(
-      `[relay] Startup failed: ${error instanceof Error ? error.message : String(error)}`
-    )
+    relayLogLine(`[relay] Startup failed: ${errorMessage(error)}`)
     process.exit(1)
     return
   }
diff --git a/src/relay/relay-grace-lifecycle.ts b/src/relay/relay-grace-lifecycle.ts
index 653e2a44eaa..8415b71793c 100644
--- a/src/relay/relay-grace-lifecycle.ts
+++ b/src/relay/relay-grace-lifecycle.ts
@@ -7,6 +7,7 @@ import {
 import { relayLogLine } from './relay-diagnostic-log'
 import { SSH_RELAY_CONFIGURE_GRACE_TIME_METHOD } from '../shared/ssh-types'
 import type { RelayDispatcher } from './dispatcher'
+import { errorMessage } from '../shared/error-message'
 
 type RelayGraceLifecycleOptions = {
   dispatcher: RelayDispatcher
@@ -139,9 +140,7 @@ export class RelayGraceLifecycle {
       .catch((error) => {
         this.shutdownInFlight = false
         this.options.reopenOwnedProcesses()
-        relayLogLine(
-          `[relay] Shutdown deferred: ${error instanceof Error ? error.message : String(error)}`
-        )
+        relayLogLine(`[relay] Shutdown deferred: ${errorMessage(error)}`)
         if (this.options.readSocketClientCount() === 0) {
           this.start('shutdown deferred', { retryDeferredShutdown: true })
         }
diff --git a/src/relay/relay-runtime-services.ts b/src/relay/relay-runtime-services.ts
index 1325e792d07..e19e2e20973 100644
--- a/src/relay/relay-runtime-services.ts
+++ b/src/relay/relay-runtime-services.ts
@@ -24,6 +24,7 @@ import { RelayPtySourcePublication } from './relay-pty-source-publication'
 import { SkillInstallHandler } from './skill-install-handler'
 import { relayLogLine } from './relay-diagnostic-log'
 import { remoteCliRequestTimeoutMs } from './remote-cli-timeout'
+import { errorMessage } from '../shared/error-message'
 
 export class RelayRuntimeServices {
   readonly ptyHandler: PtyHandler
@@ -36,7 +37,6 @@ export class RelayRuntimeServices {
   private readonly responseStreams: GitResponseStreamRegistry
   private readonly aiVaultService: ReturnType<typeof createRelayAiVaultService> | null
   private readonly sessionSearch: { dispose(): void } | null
-  private readonly registeredHandlers: readonly unknown[]
 
   constructor(
     readonly dispatcher: RelayDispatcher,
@@ -76,12 +76,12 @@ export class RelayRuntimeServices {
       this.ptyHandler.shutdownForWorktreePath(rootPath)
     )
     this.gitHandler = new GitHandler(dispatcher, context, watchRegistry, responseStreams)
-    const preflightHandler = new PreflightHandler(dispatcher)
+    new PreflightHandler(dispatcher)
     this.skillInstallHandler = new SkillInstallHandler(dispatcher)
-    const externalAutomationsHandler = new ExternalAutomationsHandler(dispatcher)
-    const portScanHandler = new PortScanHandler(dispatcher)
+    new ExternalAutomationsHandler(dispatcher)
+    new PortScanHandler(dispatcher)
     this.agentExecHandler = new AgentExecHandler(dispatcher)
-    const workspaceSessionHandler = new WorkspaceSessionHandler(dispatcher)
+    new WorkspaceSessionHandler(dispatcher)
     const relayPlatform = parseUnameToRelayPlatform(process.platform, process.arch)
     const hostPlatform = relayPlatform ? getRemoteHostPlatform(relayPlatform) : undefined
     this.aiVaultService = hostPlatform ? createRelayAiVaultService(homedir(), hostPlatform) : null
@@ -96,23 +96,9 @@ export class RelayRuntimeServices {
       dataRoot: join(homedir(), RELAY_REMOTE_DIR),
       roots: { executionHostId: LOCAL_EXECUTION_HOST_ID },
       settings: DEFAULT_AI_VAULT_SEARCH_SETTINGS,
-      onError: (error) =>
-        relayLogLine(
-          `[relay] session search: ${error instanceof Error ? error.message : String(error)}`
-        )
+      onError: (error) => relayLogLine(`[relay] session search: ${errorMessage(error)}`)
     })
-    this.registeredHandlers = [
-      preflightHandler,
-      this.skillInstallHandler,
-      externalAutomationsHandler,
-      portScanHandler,
-      this.agentExecHandler,
-      workspaceSessionHandler,
-      new AiVaultHandler(dispatcher, {
-        hostPlatform,
-        service: this.aiVaultService ?? undefined
-      })
-    ]
+    new AiVaultHandler(dispatcher, { hostPlatform, service: this.aiVaultService ?? undefined })
 
     registerRelayPluginHostCallHandlers(
       dispatcher,
@@ -146,14 +132,10 @@ export class RelayRuntimeServices {
    */
   async disposeExitOnlyServices(): Promise<void> {
     await this.skillInstallHandler.dispose().catch((error) => {
-      relayLogLine(
-        `[relay] Skill upload cleanup failed: ${error instanceof Error ? error.message : String(error)}`
-      )
+      relayLogLine(`[relay] Skill upload cleanup failed: ${errorMessage(error)}`)
     })
     await this.aiVaultService?.dispose().catch((error) => {
-      relayLogLine(
-        `[relay] AI Vault sidecar shutdown failed: ${error instanceof Error ? error.message : String(error)}`
-      )
+      relayLogLine(`[relay] AI Vault sidecar shutdown failed: ${errorMessage(error)}`)
     })
   }
 
@@ -167,26 +149,25 @@ export class RelayRuntimeServices {
     this.sessionSearch?.dispose()
     this.fsHandler.dispose()
     this.gitHandler.dispose()
-    void this.registeredHandlers
   }
 
   private registerSessionHandlers(context: RelayContext): void {
-    this.dispatcher.onNotification('session.registerRoot', (params) => {
-      const rootPath = params.rootPath as string
-      if (rootPath) {
-        context.registerRoot(rootPath)
+    const registerRoot = (params: Record<string, unknown>): void => {
+      if (typeof params.rootPath === 'string' && params.rootPath) {
+        context.registerRoot(params.rootPath)
       }
-    })
+    }
+    this.dispatcher.onNotification('session.registerRoot', (params) => registerRoot(params))
     this.dispatcher.onRequest('session.registerRoot', async (params) => {
-      const rootPath = params.rootPath as string
-      if (rootPath) {
-        context.registerRoot(rootPath)
-      }
+      registerRoot(params)
       return { ok: true }
     })
-    this.dispatcher.onRequest('session.resolveHome', async (params) => ({
-      resolvedPath: expandTilde(params.path as string)
-    }))
+    this.dispatcher.onRequest('session.resolveHome', async (params) => {
+      if (typeof params.path !== 'string') {
+        throw new Error('session.resolveHome: path must be a string')
+      }
+      return { resolvedPath: expandTilde(params.path) }
+    })
   }
 
   private registerRemoteCliRoutes(): void {
diff --git a/src/relay/relay-stream-ack-window.ts b/src/relay/relay-stream-ack-window.ts
new file mode 100644
index 00000000000..de4b1aecda4
--- /dev/null
+++ b/src/relay/relay-stream-ack-window.ts
@@ -0,0 +1,51 @@
+import { STREAM_ACK_STALL_RECHECK_MS } from './protocol'
+
+/** Waiters wake on ack, abort, or a stall recheck so a vanished client cannot strand a pump. */
+export class RelayStreamAckWindow {
+  aborted = false
+  /** Highest chunk seq the client acknowledged (in-order; -1 = none yet). */
+  ackedThroughSeq = -1
+  private readonly waiters = new Set<() => void>()
+
+  recordAck(seq: number): void {
+    if (typeof seq !== 'number' || !Number.isFinite(seq)) {
+      return
+    }
+    if (seq > this.ackedThroughSeq) {
+      this.ackedThroughSeq = seq
+    }
+    this.wake()
+  }
+
+  abort(): void {
+    this.aborted = true
+    this.wake()
+  }
+
+  wake(): void {
+    for (const waiter of Array.from(this.waiters)) {
+      waiter()
+    }
+  }
+
+  wait(): Promise<void> {
+    if (this.aborted) {
+      return Promise.resolve()
+    }
+    return new Promise<void>((resolve) => {
+      let settled = false
+      const finish = (): void => {
+        if (settled) {
+          return
+        }
+        settled = true
+        clearTimeout(timer)
+        this.waiters.delete(finish)
+        resolve()
+      }
+      const timer = setTimeout(finish, STREAM_ACK_STALL_RECHECK_MS)
+      timer.unref?.()
+      this.waiters.add(finish)
+    })
+  }
+}
diff --git a/src/relay/relay-watcher-setup-wait.ts b/src/relay/relay-watcher-setup-wait.ts
index f09dfb7470b..8502b228cbe 100644
--- a/src/relay/relay-watcher-setup-wait.ts
+++ b/src/relay/relay-watcher-setup-wait.ts
@@ -2,6 +2,7 @@ import { isWatcherProcessFailure } from '../main/ipc/parcel-watcher-process-fail
 import type { PromiseSettlementWaiters } from '../shared/promise-settlement-waiters'
 import type { RequestContext } from './dispatcher'
 import type { RelayWatcherTeardownState } from './relay-watcher-teardown-tracker'
+import { errorMessage } from '../shared/error-message'
 
 export async function startInitialRelayWatch(
   state: RelayWatcherTeardownState,
@@ -42,7 +43,7 @@ export async function awaitRelayWatcherSetupForClient(
     if (expectedAbort) {
       return
     }
-    const message = error instanceof Error ? error.message : String(error)
+    const message = errorMessage(error)
     process.stderr.write(`[relay] File watcher not available for ${state.rootPath}: ${message}\n`)
     throw error
   }
diff --git a/src/shared/abort-aware-delay.ts b/src/shared/abort-aware-delay.ts
new file mode 100644
index 00000000000..8bf55d597e3
--- /dev/null
+++ b/src/shared/abort-aware-delay.ts
@@ -0,0 +1,16 @@
+export function delayUnlessAborted(ms: number, signal: AbortSignal): Promise<void> {
+  if (signal.aborted) {
+    return Promise.resolve()
+  }
+  return new Promise((resolve) => {
+    const onAbort = (): void => {
+      clearTimeout(timer)
+      resolve()
+    }
+    const timer = setTimeout(() => {
+      signal.removeEventListener('abort', onAbort)
+      resolve()
+    }, ms)
+    signal.addEventListener('abort', onAbort, { once: true })
+  })
+}
diff --git a/src/shared/binary-buffer.ts b/src/shared/binary-buffer.ts
index f294d260367..efd410df3b4 100644
--- a/src/shared/binary-buffer.ts
+++ b/src/shared/binary-buffer.ts
@@ -1,8 +1,8 @@
 // A NUL byte in the first chunk is git's own heuristic for "this is binary".
-const BINARY_SNIFF_BYTES = 8192
+export const BINARY_PROBE_BYTES = 8192
 
 export function isBinaryBuffer(buffer: Buffer): boolean {
-  const len = Math.min(buffer.length, BINARY_SNIFF_BYTES)
+  const len = Math.min(buffer.length, BINARY_PROBE_BYTES)
   for (let i = 0; i < len; i += 1) {
     if (buffer[i] === 0) {
       return true
diff --git a/tests/e2e/cross-version-wire/cross-version-stopping.unit.test.ts b/tests/e2e/cross-version-wire/cross-version-stopping.unit.test.ts
index 8fdfd9033de..855aa880695 100644
--- a/tests/e2e/cross-version-wire/cross-version-stopping.unit.test.ts
+++ b/tests/e2e/cross-version-wire/cross-version-stopping.unit.test.ts
@@ -79,8 +79,9 @@ function publishRow(host: HostRowModules, mainAgent: Record<string, unknown>): R
     stateStartedAt: NOW - 60_000,
     mainAgent
   }
+  const summaries = new Map([[WORKTREE_ID, summary]])
   host.attachRuntimeWorktreeAgentRows({
-    summaries: new Map([[WORKTREE_ID, summary]]),
+    summaries,
     pathIndex: { byPath: new Map(), byRealPath: new Map() },
     missingWorktreeIds: new Set(),
     workingTerminalEvidenceByWorktreeId: new Map(),
@@ -94,8 +95,8 @@ function publishRow(host: HostRowModules, mainAgent: Record<string, unknown>): R
       }
     }),
     orchestrationByPaneKey: null,
-    getSummary: (map: Map<string, unknown>, _paths: unknown, _missing: unknown, id: string) =>
-      map.get(id) ?? null
+    // Old builds pass (summaries, pathIndex, missingIds, id); newer ones pass (id). The id is last in both.
+    getSummary: (...args: unknown[]) => summaries.get(String(args.at(-1))) ?? null
   })
   // oxlint-disable-next-line typescript/consistent-type-assertions -- SAFETY: JSON.parse of the rows the host just attached, which are plain objects.
   const [row] = JSON.parse(JSON.stringify(summary.agents)) as Row[]
diff --git a/tests/e2e/cross-version-wire/cross-version-worktree-ps-verdict.unit.test.ts b/tests/e2e/cross-version-wire/cross-version-worktree-ps-verdict.unit.test.ts
index ac53bc112b9..54f54051673 100644
--- a/tests/e2e/cross-version-wire/cross-version-worktree-ps-verdict.unit.test.ts
+++ b/tests/e2e/cross-version-wire/cross-version-worktree-ps-verdict.unit.test.ts
@@ -97,8 +97,9 @@ function publishRows(host: HostRowModules): Record<string, AgentRow> {
     hasHostSidebarActivity: false,
     agents: []
   }
+  const summaries = new Map([[WORKTREE_ID, summary]])
   host.attachRuntimeWorktreeAgentRows({
-    summaries: new Map([[WORKTREE_ID, summary]]),
+    summaries,
     pathIndex: { byPath: new Map(), byRealPath: new Map() },
     missingWorktreeIds: new Set(),
     workingTerminalEvidenceByWorktreeId: new Map(),
@@ -112,8 +113,8 @@ function publishRows(host: HostRowModules): Record<string, AgentRow> {
       }
     }),
     orchestrationByPaneKey: null,
-    getSummary: (map: Map<string, unknown>, _paths: unknown, _missing: unknown, id: string) =>
-      map.get(id) ?? null
+    // Old builds pass (summaries, pathIndex, missingIds, id); newer ones pass (id). The id is last in both.
+    getSummary: (...args: unknown[]) => summaries.get(String(args.at(-1))) ?? null
   })
   // oxlint-disable-next-line typescript/consistent-type-assertions -- SAFETY: JSON.parse of the rows the host just attached, which are plain objects keyed by paneKey.
   const rows = JSON.parse(JSON.stringify(summary.agents)) as AgentRow[]