diff --git a/.github/workflows/pr.yml b/.github/workflows/pr.yml
index bc05e1d2a7e..19d420e3ff2 100644
--- a/.github/workflows/pr.yml
+++ b/.github/workflows/pr.yml
@@ -219,6 +219,17 @@ jobs:
           if [ "$PREFLIGHT_PHASE_SELECTED" != true ] || [ "$PREFLIGHT_PRIOR_SUCCESS" != true ]; then exit 0; fi
           bun --bun run check:process-host-imports
 
+      - name: Check main-process sync launches
+        if: '!cancelled()'
+        id: main-sync-spawn-ratchet
+        background: true
+        env:
+          PREFLIGHT_PHASE_SELECTED: ${{ needs.code_paths.outputs.static_analysis == 'true' }}
+          PREFLIGHT_PRIOR_SUCCESS: ${{ job.status == 'success' }}
+        run: |
+          if [ "$PREFLIGHT_PHASE_SELECTED" != true ] || [ "$PREFLIGHT_PRIOR_SUCCESS" != true ]; then exit 0; fi
+          bun --bun run check:main-sync-spawn-ratchet
+
       # Keep each check in its own log while sharing this runner.
       - name: Lint
         if: '!cancelled()'
@@ -472,6 +483,8 @@ jobs:
 
       - wait: process-host-imports
 
+      - wait: main-sync-spawn-ratchet
+
       - wait: unit-plan
 
       - uses: actions/upload-artifact@v7
diff --git a/config/main-sync-spawn-baseline.txt b/config/main-sync-spawn-baseline.txt
new file mode 100644
index 00000000000..14a347ff772
--- /dev/null
+++ b/config/main-sync-spawn-baseline.txt
@@ -0,0 +1,86 @@
+# Synchronous child-process launches in production src/main and src/shared, per file: uses of
+# execFileSync/spawnSync/execSync, runProcessSync and the repo sync wrappers listed in
+# config/scripts/check-main-sync-spawn-ratchet.mjs (secure writers run icacls on Windows).
+# Some entries run in the daemon or orcad process, or are test harnesses outside the test-path
+# conventions. This is a RATCHET: counts may only go DOWN.
+# Prune after removing launches: pnpm check:main-sync-spawn-ratchet --prune
+1 src/main/agent-hooks/installer-utils.ts
+1 src/main/artifacts/artifact-create-intent-store.ts
+5 src/main/artifacts/artifact-share-record-store.ts
+2 src/main/browser/browser-cookie-key.ts
+1 src/main/browser/browser-route-egress-electron-launch.ts
+1 src/main/browser/browser-route-partition-binding-store.ts
+1 src/main/browser/browser-route-persisted-worker-electron-process.ts
+1 src/main/claude-accounts/runtime-auth-service.ts
+3 src/main/codex-accounts/fs-utils.ts
+2 src/main/codex-accounts/legacy-wsl-runtime-auth-drain-recovery-script-harness.ts
+2 src/main/codex-accounts/legacy-wsl-runtime-auth-drain-script-harness.ts
+1 src/main/codex-accounts/runtime-home-service-home-routing.ts
+1 src/main/codex-accounts/runtime-home-service-wsl.ts
+2 src/main/codex-accounts/service.ts
+1 src/main/computer/macos-computer-use-permissions.ts
+2 src/main/credentials/encrypted-api-key-file-store.ts
+2 src/main/daemon/daemon-cgroup-scope.ts
+1 src/main/daemon/daemon-process-identity-query.ts
+1 src/main/daemon/daemon-process-start-time.ts
+1 src/main/daemon/daemon-user-manager-lifetime.ts
+1 src/main/daemon/pty-subprocess/shell-launch-plan.ts
+1 src/main/emulator/serve-sim-runtime-materializer.ts
+1 src/main/git/command-runner/git-exec-file.ts
+1 src/main/git/repo-detection-command.ts
+1 src/main/git/runner.ts
+1 src/main/ipc/worktree-logic.ts
+2 src/main/macos-press-and-hold-default.ts
+2 src/main/managed-data-accounts/credential-capture.ts
+1 src/main/managed-data-accounts/profile-removal.ts
+1 src/main/managed-data-accounts/service.ts
+2 src/main/minimax/minimax-cookie-store.ts
+1 src/main/network/macos-tailscale-dns-diagnostic.ts
+1 src/main/opencode/legacy-plugin-acl-retry.ts
+2 src/main/orca-profiles/profile-artifact-cloud-cleanup.ts
+1 src/main/orca-profiles/profile-cloud-session-mutation.ts
+2 src/main/orca-profiles/profile-cloud-session-store.ts
+2 src/main/orcad/node-pty-precondition.ts
+1 src/main/orcad/orcad-completed-stop-receipt.ts
+1 src/main/orcad/orcad-data-root-privacy.ts
+1 src/main/orcad/orcad-idle-stop-record.ts
+1 src/main/orcad/orcad-managed-stop-completion.ts
+1 src/main/orcad/orcad-managed-stop-decision.ts
+2 src/main/persistence/profile-state/profile-state-access-identity.ts
+1 src/main/persistence/profile-state/profile-state-recovery-copy.ts
+1 src/main/plugins/plugin-private-marketplace-ssh-shim.cjs
+2 src/main/plugins/plugin-secrets-store.ts
+2 src/main/plugins/plugin-storage-store.ts
+1 src/main/providers/working-directory-validation.ts
+1 src/main/pty/posix-pty-foreground-group.ts
+1 src/main/pty/posix-pty-process-groups.ts
+1 src/main/pwsh.ts
+3 src/main/runtime/device-registry.ts
+1 src/main/runtime/e2ee-keypair.ts
+1 src/main/runtime/mobile-notification-dismissal-store.ts
+1 src/main/runtime/push/push-unregister-outbox.ts
+1 src/main/runtime/relay/relay-region-preference.ts
+1 src/main/runtime/relay/relay-revoke-outbox.ts
+1 src/main/runtime/runtime-metadata.ts
+1 src/main/runtime/runtime-skill-install-authority.ts
+1 src/main/runtime/tls-certificate.ts
+1 src/main/skills/skill-discovery-target.ts
+1 src/main/ssh/orcad-held-fence-tokens.ts
+1 src/main/ssh/orcad-migration-cutover-journal.ts
+2 src/main/startup/cli-launch-redirect.ts
+1 src/main/startup/linux-secret-service-probe.ts
+2 src/main/win32-utils.ts
+1 src/main/worktree-runner-script.ts
+2 src/main/wsl-availability.ts
+5 src/main/wsl.ts
+3 src/main/zcode/zcode-plan-api-key-store.ts
+2 src/main/zsh-startup-hook-pty-harness.ts
+1 src/shared/bounded-secure-json-file.ts
+1 src/shared/ephemeral-vm-runtime-feature-store.ts
+2 src/shared/ephemeral-vm-runtime-store.ts
+1 src/shared/fish-binary-requirement.ts
+1 src/shared/openssh-default-shell.ts
+1 src/shared/runtime-environment-sidecar.ts
+1 src/shared/runtime-environment-store-file.ts
+3 src/shared/secure-file.ts
+3 src/shared/secure-path-windows-acl.ts
diff --git a/config/scripts/check-main-sync-spawn-ratchet.mjs b/config/scripts/check-main-sync-spawn-ratchet.mjs
new file mode 100644
index 00000000000..b5e2be3a49f
--- /dev/null
+++ b/config/scripts/check-main-sync-spawn-ratchet.mjs
@@ -0,0 +1,436 @@
+import { globSync, readFileSync, writeFileSync } from 'node:fs'
+import path from 'node:path'
+import { pathToFileURL } from 'node:url'
+import ts from 'typescript-api'
+import {
+  diffCounts,
+  formatBaseline,
+  parseBaseline,
+  parseBaselineNotes
+} from './check-focus-read-ratchet.mjs'
+import { literalString, propertyName, unwrap } from './static-module-specifiers.mjs'
+import { isTestOnlySourcePath } from './test-only-source-path.mjs'
+
+// Ratchet for synchronous child-process launches in Electron main and shared code: each one
+// freezes every window until the child exits, and on Windows antivirus makes every launch slow.
+// Per file it counts uses of the launch APIs and of the repo's synchronous wrappers around them.
+
+const ROOT = path.resolve(import.meta.dirname, '..', '..')
+const BASELINE_PATH = 'config/main-sync-spawn-baseline.txt'
+const SCAN_DIRECTORIES = ['src/main', 'src/shared']
+const PROCESS_ADVICE = 'use runProcess or spawnProcess from @orca/process-host'
+const SECURE_ADVICE = `no async secure writer exists yet; keep the synchronous one and raise this file's count in ${BASELINE_PATH} (or add a row), never a plain write (it loses the Windows ACL hardening)`
+const SECURE_WRITERS = [
+  'writeSecureFile',
+  'writeSecureJsonFile',
+  'writeDurableSecureJsonFile',
+  'writeSecureJsonFileWithinLimit'
+]
+// Gated modules (package names, or repo-relative paths without extension, re-exporters included)
+// and the advice for each gated function they export.
+const GATED_FAMILIES = [
+  {
+    modules: ['child_process', 'node:child_process'],
+    advice: { execFileSync: PROCESS_ADVICE, spawnSync: PROCESS_ADVICE, execSync: PROCESS_ADVICE }
+  },
+  { modules: ['@orca/process-host'], advice: { runProcessSync: PROCESS_ADVICE } },
+  {
+    modules: ['src/shared/secure-file', 'src/shared/bounded-secure-json-file'],
+    advice: Object.fromEntries(
+      [...SECURE_WRITERS, 'hardenSecurePath'].map((name) => [name, SECURE_ADVICE])
+    )
+  },
+  {
+    modules: ['src/shared/secure-path-windows-acl'],
+    advice: { restrictWindowsPathSync: SECURE_ADVICE }
+  },
+  {
+    modules: ['src/main/git/command-runner/git-exec-file', 'src/main/git/runner'],
+    advice: { gitExecFileSync: 'use gitExecFileAsync' }
+  },
+  {
+    modules: ['src/main/wsl'],
+    advice: {
+      getWslHome: 'use getWslHomeAsync',
+      listWslDistros: 'use listWslDistrosAsync',
+      wslUncDirectoryExists: 'use wslUncDirectoryExistsAsync'
+    }
+  },
+  {
+    modules: ['src/main/wsl-availability', 'src/main/wsl'],
+    advice: { isWslAvailable: 'use isWslAvailableAsync' }
+  },
+  { modules: ['src/main/pwsh'], advice: { isPwshAvailable: 'use isPwshAvailableAsync' } },
+  { modules: ['src/main/win32-utils'], advice: { grantDirAcl: 'use grantDirAclAsync' } }
+]
+const ADVICE = new Map(GATED_FAMILIES.flatMap((family) => Object.entries(family.advice)))
+// Only spread-free calls with no options or a literal with absent/false `sync` are exempt.
+const SYNC_FLAG_SYMBOLS = new Set(['hardenSecurePath'])
+const FALLBACK_OPERATORS = new Set([ts.SyntaxKind.QuestionQuestionToken, ts.SyntaxKind.BarBarToken])
+const BASELINE_HEADER = [
+  '# Synchronous child-process launches in production src/main and src/shared, per file: uses of',
+  '# execFileSync/spawnSync/execSync, runProcessSync and the repo sync wrappers listed in',
+  '# config/scripts/check-main-sync-spawn-ratchet.mjs (secure writers run icacls on Windows).',
+  '# Some entries run in the daemon or orcad process, or are test harnesses outside the test-path',
+  '# conventions. This is a RATCHET: counts may only go DOWN.',
+  '# Prune after removing launches: pnpm check:main-sync-spawn-ratchet --prune'
+]
+
+function normalized(file) {
+  return file.replaceAll('\\', '/')
+}
+
+function moduleKey(file) {
+  return normalized(file).replace(/\.[cm]?[jt]sx?$/, '')
+}
+
+function symbolsOf(key) {
+  const names = GATED_FAMILIES.filter((family) => family.modules.includes(key)).flatMap((family) =>
+    Object.keys(family.advice)
+  )
+  return names.length > 0 ? new Set(names) : null
+}
+
+/** Gated functions a module specifier exports, or null when the module is not gated. */
+export function gatedSymbolsFor(file, specifier) {
+  const normalizedSpecifier = normalized(specifier)
+  if (!normalizedSpecifier.startsWith('.')) {
+    return symbolsOf(normalizedSpecifier)
+  }
+  return symbolsOf(
+    moduleKey(
+      path.posix.normalize(
+        path.posix.join(path.posix.dirname(normalized(file)), normalizedSpecifier)
+      )
+    )
+  )
+}
+
+function isAsyncOnlyCall(callee) {
+  const call = callee.parent
+  if (
+    !ts.isCallExpression(call) ||
+    call.expression !== callee ||
+    call.arguments.some(ts.isSpreadElement)
+  ) {
+    return false
+  }
+  const options = unwrap(call.arguments[1])
+  return (
+    !options ||
+    (ts.isObjectLiteralExpression(options) &&
+      options.properties.every((property) => {
+        if (ts.isSpreadAssignment(property)) {
+          return false
+        }
+        const name = ts.isIdentifier(property.name)
+          ? property.name.text
+          : literalString(property.name)
+        return (
+          name !== null &&
+          (name !== 'sync' ||
+            (ts.isPropertyAssignment(property) &&
+              unwrap(property.initializer).kind === ts.SyntaxKind.FalseKeyword))
+        )
+      }))
+  )
+}
+
+function isValueReference(node) {
+  const parent = node.parent
+  if (
+    ts.isImportSpecifier(parent) ||
+    ts.isImportClause(parent) ||
+    ts.isNamespaceImport(parent) ||
+    ts.isImportEqualsDeclaration(parent)
+  ) {
+    return false
+  }
+  if (ts.isExportSpecifier(parent)) {
+    return !parent.parent.parent.moduleSpecifier && node === (parent.propertyName ?? parent.name)
+  }
+  if (ts.isBindingElement(parent)) {
+    return node === parent.initializer
+  }
+  return (
+    ts.isShorthandPropertyAssignment(parent) ||
+    (parent.name !== node && parent.propertyName !== node && parent.label !== node)
+  )
+}
+
+/**
+ * Every value reference to a gated function counts (call, hand-off, alias initializer, each alias
+ * use), plus each re-export and a gated module's own references; imports alone count nothing.
+ * File-wide, not scope-aware; computed specifiers and member names are not resolved.
+ * Counted by reference only: not traced through non-const holders or the file's own wrappers.
+ */
+export function collectSyncLaunchUses(file, contents) {
+  const source = ts.createSourceFile(file, contents, ts.ScriptTarget.Latest, true)
+  if (source.parseDiagnostics.length > 0) {
+    throw new Error(`Cannot parse ${file}; the sync-spawn ratchet must not skip it.`)
+  }
+  const used = new Set()
+  let count = 0
+  const namespaces = new Map()
+  // Local name -> gated function it refers to.
+  const functions = new Map([...(symbolsOf(moduleKey(file)) ?? [])].map((name) => [name, name]))
+  const aliases = []
+  const members = []
+  const identifiers = []
+  const destructures = []
+
+  function moduleSymbols(node) {
+    node = unwrap(node)
+    if (!node) {
+      return null
+    }
+    if (ts.isIdentifier(node)) {
+      return namespaces.get(node.text) ?? null
+    }
+    const loads =
+      ts.isCallExpression(node) &&
+      (node.expression.kind === ts.SyntaxKind.ImportKeyword ||
+        (ts.isIdentifier(node.expression) && node.expression.text === 'require'))
+    const specifier = loads ? literalString(node.arguments[0]) : null
+    return specifier === null ? null : gatedSymbolsFor(file, specifier)
+  }
+  function gatedFunction(node) {
+    node = unwrap(node)
+    if (!node) {
+      return null
+    }
+    if (ts.isIdentifier(node)) {
+      return functions.get(node.text) ?? null
+    }
+    if (ts.isPropertyAccessExpression(node) || ts.isElementAccessExpression(node)) {
+      const name = propertyName(node)
+      return moduleSymbols(node.expression)?.has(name) ? name : null
+    }
+    if (ts.isConditionalExpression(node)) {
+      return gatedFunction(node.whenTrue) ?? gatedFunction(node.whenFalse)
+    }
+    if (ts.isBinaryExpression(node) && FALLBACK_OPERATORS.has(node.operatorToken.kind)) {
+      return gatedFunction(node.left) ?? gatedFunction(node.right)
+    }
+    return null
+  }
+  function recordUse(name, node) {
+    if (SYNC_FLAG_SYMBOLS.has(name) && isAsyncOnlyCall(node)) {
+      return
+    }
+    used.add(name)
+    count += 1
+  }
+  function visitImport(node) {
+    const symbols = gatedSymbolsFor(file, node.moduleSpecifier.text)
+    const clause = node.importClause
+    if (!symbols || !clause || clause.isTypeOnly) {
+      return
+    }
+    if (clause.name) {
+      namespaces.set(clause.name.text, symbols)
+    }
+    const named = clause.namedBindings
+    if (named && ts.isNamespaceImport(named)) {
+      namespaces.set(named.name.text, symbols)
+    }
+    for (const element of named && ts.isNamedImports(named) ? named.elements : []) {
+      const imported = (element.propertyName ?? element.name).text
+      if (!element.isTypeOnly && symbols.has(imported)) {
+        functions.set(element.name.text, imported)
+      }
+    }
+  }
+  function visitExport(node) {
+    const symbols =
+      node.moduleSpecifier && ts.isStringLiteral(node.moduleSpecifier) && !node.isTypeOnly
+        ? gatedSymbolsFor(file, node.moduleSpecifier.text)
+        : null
+    if (!symbols) {
+      return
+    }
+    const names =
+      !node.exportClause || ts.isNamespaceExport(node.exportClause)
+        ? [...symbols]
+        : node.exportClause.elements
+            .filter((element) => !element.isTypeOnly)
+            .map((element) => (element.propertyName ?? element.name).text)
+    for (const name of names.filter((name) => symbols.has(name))) {
+      used.add(name)
+      count += 1
+    }
+  }
+  function visit(node) {
+    if (ts.isTypeNode(node) && !ts.isExpressionWithTypeArguments(node)) {
+      return
+    }
+    if (ts.isImportDeclaration(node) && ts.isStringLiteral(node.moduleSpecifier)) {
+      visitImport(node)
+    } else if (
+      ts.isImportEqualsDeclaration(node) &&
+      !node.isTypeOnly &&
+      ts.isExternalModuleReference(node.moduleReference) &&
+      ts.isStringLiteral(node.moduleReference.expression)
+    ) {
+      const symbols = gatedSymbolsFor(file, node.moduleReference.expression.text)
+      if (symbols) {
+        namespaces.set(node.name.text, symbols)
+      }
+    } else if (ts.isExportDeclaration(node)) {
+      visitExport(node)
+    } else if (ts.isPropertyAccessExpression(node) || ts.isElementAccessExpression(node)) {
+      members.push(node)
+    } else if (ts.isIdentifier(node) && isValueReference(node)) {
+      identifiers.push(node)
+    } else if (ts.isVariableDeclaration(node) && node.initializer) {
+      if (ts.isIdentifier(node.name)) {
+        aliases.push({ name: node.name.text, initializer: node.initializer })
+      } else if (ts.isObjectBindingPattern(node.name)) {
+        destructures.push(node)
+      }
+    }
+    ts.forEachChild(node, visit)
+  }
+  visit(source)
+
+  // Aliases can chain (`const cp = require('child_process'); const run = cp.execFileSync`).
+  for (let changed = true; changed;) {
+    changed = false
+    for (const { name, initializer } of aliases) {
+      const symbols = moduleSymbols(initializer)
+      const gated = symbols ? null : gatedFunction(initializer)
+      if (symbols && !namespaces.has(name)) {
+        namespaces.set(name, symbols)
+        changed = true
+      } else if (gated && !functions.has(name)) {
+        functions.set(name, gated)
+        changed = true
+      }
+    }
+    for (const node of destructures) {
+      const symbols = moduleSymbols(node.initializer)
+      for (const element of symbols ? node.name.elements : []) {
+        const key = element.propertyName ?? element.name
+        const name = ts.isIdentifier(key) ? key.text : literalString(key)
+        if (
+          symbols.has(name) &&
+          ts.isIdentifier(element.name) &&
+          !functions.has(element.name.text)
+        ) {
+          functions.set(element.name.text, name)
+          changed = true
+        }
+      }
+    }
+  }
+  for (const node of members) {
+    const name = propertyName(node)
+    if (moduleSymbols(node.expression)?.has(name)) {
+      recordUse(name, node)
+    }
+  }
+  for (const node of identifiers) {
+    const name = functions.get(node.text)
+    if (name) {
+      recordUse(name, node)
+    }
+  }
+  return { count, symbols: [...used].sort() }
+}
+
+export function isRatchetedSourcePath(file) {
+  return (
+    SCAN_DIRECTORIES.some((directory) => file.startsWith(`${directory}/`)) &&
+    !file.endsWith('.d.ts') &&
+    !isTestOnlySourcePath(file)
+  )
+}
+
+/** Per-file use counts and the gated functions each file uses. */
+export function countSyncSpawnUses(sources) {
+  const counts = new Map()
+  const symbols = new Map()
+  for (const [file, contents] of sources) {
+    if (!isRatchetedSourcePath(file)) {
+      continue
+    }
+    const uses = collectSyncLaunchUses(file, contents)
+    if (uses.count > 0) {
+      counts.set(file, uses.count)
+      symbols.set(file, uses.symbols)
+    }
+  }
+  return { counts, symbols }
+}
+
+export function adviceFor(symbols) {
+  const groups = new Map()
+  for (const symbol of symbols) {
+    groups.set(ADVICE.get(symbol), [...(groups.get(ADVICE.get(symbol)) ?? []), symbol])
+  }
+  return [...groups].map(([advice, names]) => `${names.join(', ')}: ${advice}.`).join(' ')
+}
+
+export function collectSyncSpawnSources(root = ROOT) {
+  return new Map(
+    globSync(
+      SCAN_DIRECTORIES.map((directory) => `${directory}/**/*.{ts,tsx,mts,cts,js,mjs,cjs}`),
+      { cwd: root, exclude: ['**/node_modules/**'] }
+    )
+      .map(normalized)
+      .filter(isRatchetedSourcePath)
+      .sort()
+      .map((file) => [file, readFileSync(path.join(root, file), 'utf8')])
+  )
+}
+
+function total(counts) {
+  return [...counts.values()].reduce((sum, count) => sum + count, 0)
+}
+
+export function main(root = ROOT) {
+  const { counts, symbols } = countSyncSpawnUses(collectSyncSpawnSources(root))
+  const { grown, shrunk } = diffCounts(
+    counts,
+    parseBaseline(readFileSync(path.join(root, BASELINE_PATH), 'utf8'))
+  )
+  for (const { file, now, allowed } of grown) {
+    console.error(
+      `::error file=${file}::${now} synchronous launch use(s), baseline allows ${allowed}. They block the main thread. ${adviceFor(symbols.get(file))}`
+    )
+  }
+  for (const { file, now, allowed } of shrunk) {
+    console.error(
+      `::error file=${file}::${now} synchronous launch use(s), baseline still allows ${allowed}. Run: pnpm check:main-sync-spawn-ratchet --prune`
+    )
+  }
+  if (grown.length + shrunk.length > 0) {
+    return 1
+  }
+  console.log(
+    `Main sync-spawn ratchet OK — ${total(counts)} use(s) in ${counts.size} legacy file(s).`
+  )
+  return 0
+}
+
+export function prune(root = ROOT) {
+  const baselineFile = path.join(root, BASELINE_PATH)
+  const text = readFileSync(baselineFile, 'utf8')
+  const { counts } = countSyncSpawnUses(collectSyncSpawnSources(root))
+  // Lowers entries only; growth still has to be fixed in the code.
+  const pruned = new Map(
+    [...parseBaseline(text)].map(([file, allowed]) => [
+      file,
+      Math.min(allowed, counts.get(file) ?? 0)
+    ])
+  )
+  writeFileSync(baselineFile, formatBaseline(pruned, BASELINE_HEADER, parseBaselineNotes(text)))
+  console.log(`Pruned ${BASELINE_PATH} to ${total(pruned)} use(s).`)
+}
+
+if (process.argv[1] && import.meta.url === pathToFileURL(path.resolve(process.argv[1])).href) {
+  if (process.argv[2] === '--prune') {
+    prune()
+  }
+  process.exitCode = main()
+}
diff --git a/config/scripts/check-main-sync-spawn-ratchet.test.mjs b/config/scripts/check-main-sync-spawn-ratchet.test.mjs
new file mode 100644
index 00000000000..b622cc99d7b
--- /dev/null
+++ b/config/scripts/check-main-sync-spawn-ratchet.test.mjs
@@ -0,0 +1,310 @@
+import { afterEach, describe, expect, it, vi } from 'vitest'
+import { mkdirSync, mkdtempSync, readFileSync, rmSync, writeFileSync } from 'node:fs'
+import { tmpdir } from 'node:os'
+import path from 'node:path'
+import {
+  adviceFor,
+  collectSyncLaunchUses,
+  countSyncSpawnUses,
+  gatedSymbolsFor,
+  main,
+  prune
+} from './check-main-sync-spawn-ratchet.mjs'
+
+const roots = []
+const BASELINE = 'config/main-sync-spawn-baseline.txt'
+
+afterEach(() => {
+  vi.restoreAllMocks()
+  for (const root of roots.splice(0)) {
+    rmSync(root, { recursive: true, force: true })
+  }
+})
+
+function uses(source, file = 'src/main/consumer.ts') {
+  return collectSyncLaunchUses(file, source)
+}
+
+function tree(files) {
+  const root = mkdtempSync(path.join(tmpdir(), 'orca-main-sync-spawn-'))
+  roots.push(root)
+  for (const [file, source] of Object.entries(files)) {
+    mkdirSync(path.dirname(path.join(root, file)), { recursive: true })
+    writeFileSync(path.join(root, file), source)
+  }
+  return root
+}
+
+function captureErrors() {
+  vi.spyOn(console, 'log').mockImplementation(() => {})
+  return vi.spyOn(console, 'error').mockImplementation(() => {})
+}
+
+describe('main sync-spawn ratchet', () => {
+  it.each([
+    ["import { execFileSync } from 'node:child_process'\nexecFileSync('git')", 1, ['execFileSync']],
+    [
+      "import { execFileSync as run } from 'child_process'\nrun('git')\nrun('gh')",
+      2,
+      ['execFileSync']
+    ],
+    ["import * as cp from 'node:child_process'\ncp.spawnSync('git')", 1, ['spawnSync']],
+    ["import cp from 'child_process'\ncp['execSync']('git')", 1, ['execSync']],
+    ["import cp = require('child_process')\ncp.execFileSync('git')", 1, ['execFileSync']],
+    ["require('node:child_process').execSync('git')", 1, ['execSync']],
+    [
+      "const cp = require('child_process')\nconst alias = cp\nalias.spawnSync('git')",
+      1,
+      ['spawnSync']
+    ],
+    ["const { spawnSync: run } = require('node:child_process')\nrun('git')", 1, ['spawnSync']],
+    ["const { execSync } = await import('node:child_process')\nexecSync('git')", 1, ['execSync']],
+    ["(await import('child_process')).execFileSync('git')", 1, ['execFileSync']],
+    ["export { spawnSync } from 'node:child_process'", 1, ['spawnSync']],
+    ["import { execSync } from 'child_process'\nexport { execSync }", 1, ['execSync']],
+    [
+      "import { execSync } from 'child_process'\nqueue.push(execSync, { execSync })",
+      2,
+      ['execSync']
+    ],
+    [
+      "import { runProcessSync } from '@orca/process-host'\nconst run = options.run ?? runProcessSync\nrun(a)\nrun(b)",
+      3,
+      ['runProcessSync']
+    ],
+    [
+      "import { writeDurableSecureJsonFile, writeSecureJsonFile } from '../shared/secure-file.ts'\nconst write = durable ? writeDurableSecureJsonFile : writeSecureJsonFile\nwrite(p, v)",
+      3,
+      ['writeDurableSecureJsonFile', 'writeSecureJsonFile']
+    ],
+    [
+      "import * as store from '..\\\\shared\\\\bounded-secure-json-file'\nstore.writeSecureJsonFileWithinLimit(p, v, 1)",
+      1,
+      ['writeSecureJsonFileWithinLimit']
+    ],
+    [
+      "const { execSync } = require('child_process')\nconst run = execSync\nrun('a')",
+      2,
+      ['execSync']
+    ],
+    [
+      "function f() { const run = cp.execSync; run('a') }\nconst cp = require('child_process')",
+      2,
+      ['execSync']
+    ],
+    [
+      "import { execFileSync } from 'child_process'\nclass A extends mixin(execFileSync) {}",
+      1,
+      ['execFileSync']
+    ],
+    [
+      "import { runProcessSync } from '@orca/process-host'\nconst run = runProcessSync<string>",
+      1,
+      ['runProcessSync']
+    ]
+  ])('counts %s', (source, count, symbols) => {
+    expect(uses(source)).toEqual({ count, symbols })
+  })
+
+  it.each([
+    "import { execFileSync } from 'node:child_process'",
+    "import { spawn, execFile } from 'node:child_process'\nspawn('git')",
+    "import type { execFileSync } from 'node:child_process'\nexecFileSync('x')",
+    "import { type spawnSync } from 'child_process'\nspawnSync('x')",
+    "import * as cp from 'child_process'\ntype Run = typeof cp.execFileSync",
+    "import { runProcessSync } from '@orca/process-host'\ntype O = { run?: typeof runProcessSync }",
+    "import { runProcess } from '@orca/process-host'\nrunProcess(spec)",
+    "import { runProcessSync } from '@orca/process-host/process-spec'\nrunProcessSync(spec)",
+    "import { writeSecureFile } from './secure-file'\nwriteSecureFile(p, v)",
+    "import { execFileSync } from 'child_process'\nconst o = { execFileSync: 1 }\no.execFileSync",
+    'const other = { spawnSync() {} }\nother.spawnSync()',
+    "// execFileSync('git')\nconst script = \"require('child_process').execSync('ls')\"",
+    "import * as cp from 'child_process'\ncp.spawn('git')",
+    "import { gitExecFileAsync } from './git/runner'\ngitExecFileAsync(['status'])"
+  ])('ignores %s', (source) => {
+    expect(uses(source)).toEqual({ count: 0, symbols: [] })
+  })
+
+  it.each([
+    [
+      "import { gitExecFileSync } from './git/runner'\ngitExecFileSync(['status'])",
+      'gitExecFileSync'
+    ],
+    [
+      "import { gitExecFileSync as git } from './git/command-runner/git-exec-file.js'\ngit([])",
+      'gitExecFileSync'
+    ],
+    [
+      "import { restrictWindowsPathSync } from '../shared/secure-path-windows-acl'\nrestrictWindowsPathSync(p, true)",
+      'restrictWindowsPathSync'
+    ],
+    ["import { grantDirAcl } from './win32-utils'\ngrantDirAcl(dir)", 'grantDirAcl'],
+    ["import { getWslHome } from './wsl'\ngetWslHome(distro)", 'getWslHome'],
+    ["import { listWslDistros } from './wsl'\nlistWslDistros()", 'listWslDistros'],
+    [
+      "import { wslUncDirectoryExists } from './wsl'\nwslUncDirectoryExists(p)",
+      'wslUncDirectoryExists'
+    ],
+    ["import { isWslAvailable } from './wsl'\nisWslAvailable()", 'isWslAvailable'],
+    ["import { isWslAvailable } from './wsl-availability'\nisWslAvailable()", 'isWslAvailable'],
+    ["import { isPwshAvailable } from './pwsh'\nisPwshAvailable()", 'isPwshAvailable']
+  ])('gates the repo sync wrapper in %s', (source, symbol) => {
+    expect(uses(source)).toEqual({ count: 1, symbols: [symbol] })
+  })
+
+  it('counts hardenSecurePath unless the call is visibly async', () => {
+    const imported = "import { hardenSecurePath } from '../shared/secure-file'\n"
+    const count = (call) => uses(`${imported}${call}`).count
+    expect(count('hardenSecurePath(p, { isDirectory: true, sync: true })')).toBe(1)
+    expect(count("hardenSecurePath(p, { isDirectory: true, 'sync': true })")).toBe(1)
+    expect(count('hardenSecurePath(p, options)')).toBe(1)
+    expect(count('hardenSecurePath(p, { ...base, isDirectory: true })')).toBe(1)
+    expect(count('hardenSecurePath(p, { isDirectory: true, sync })')).toBe(1)
+    expect(count('hardenSecurePath(p, { sync: true } as const)')).toBe(1)
+    expect(count('tasks.map(hardenSecurePath)')).toBe(1)
+    expect(count('hardenSecurePath(p, { isDirectory: true })')).toBe(0)
+    expect(count('hardenSecurePath(p, { isDirectory: true, sync: false })')).toBe(0)
+    expect(count('hardenSecurePath(p)')).toBe(0)
+    expect(
+      uses("import * as sf from '../shared/secure-file'\nsf.hardenSecurePath(p, { sync: true })")
+    ).toEqual({ count: 1, symbols: ['hardenSecurePath'] })
+  })
+
+  it.each([
+    'const args = [p, { isDirectory: false, platform: "win32", sync: true }] as const\nhardenSecurePath(...args)',
+    'const options = [{ isDirectory: false, platform: "win32", sync: true }] as const\nhardenSecurePath(p, ...options)',
+    'hardenSecurePath(...paths, { isDirectory: true, sync: false })'
+  ])('counts hardenSecurePath with spread call arguments: %s', (source) => {
+    expect(uses(`import { hardenSecurePath } from '../shared/secure-file'\n${source}`)).toEqual({
+      count: 1,
+      symbols: ['hardenSecurePath']
+    })
+  })
+
+  it('counts re-exports in the re-exporting module and internal calls in the defining one', () => {
+    expect(
+      uses(
+        "export { gitExecFileAsync, gitExecFileSync } from './command-runner/git-exec-file'",
+        'src/main/git/runner.ts'
+      )
+    ).toEqual({ count: 1, symbols: ['gitExecFileSync'] })
+    expect(
+      uses(
+        'export function listWslDistros() { return [] }\nexport function first() { return listWslDistros()[0] }',
+        'src/main/wsl.ts'
+      )
+    ).toEqual({ count: 1, symbols: ['listWslDistros'] })
+  })
+
+  it('resolves writer imports by the module they point at, not by name', () => {
+    expect(
+      uses(
+        "import { writeSecureFile } from './secure-file'\nwriteSecureFile(p, v)",
+        'src/shared/store.ts'
+      )
+    ).toEqual({
+      count: 1,
+      symbols: ['writeSecureFile']
+    })
+  })
+
+  it('resolves backslash paths in both the importing file and the specifier', () => {
+    expect([...(gatedSymbolsFor('src\\main\\foo\\x.ts', '..\\wsl') ?? [])]).toContain('getWslHome')
+  })
+
+  it('fails closed on source it cannot parse', () => {
+    expect(() => uses('import {')).toThrow('Cannot parse src/main/consumer.ts')
+  })
+
+  it('counts only production main and shared source', () => {
+    const sync = "import { execSync } from 'node:child_process'\nexecSync('a')\nexecSync('b')"
+    const { counts } = countSyncSpawnUses(
+      new Map(
+        Object.entries({
+          'src/main/legacy.ts': sync,
+          'src/shared/new.ts':
+            "import { runProcessSync } from '@orca/process-host'\nrunProcessSync(s)",
+          'src/main/clean.ts': "import { spawn } from 'node:child_process'\nspawn('a')",
+          'src/main/consumer.test.ts': sync,
+          'src/main/fixtures/script.ts': sync,
+          'src/main/types.d.ts': sync,
+          'src/cli/handlers/core.ts': sync,
+          'src/relay/host.ts': sync
+        })
+      )
+    )
+    expect([...counts]).toEqual([
+      ['src/main/legacy.ts', 2],
+      ['src/shared/new.ts', 1]
+    ])
+  })
+
+  it('gives each gated family its own advice', () => {
+    expect(adviceFor(['execFileSync', 'runProcessSync'])).toBe(
+      'execFileSync, runProcessSync: use runProcess or spawnProcess from @orca/process-host.'
+    )
+    expect(adviceFor(['writeSecureFile'])).toContain(
+      "no async secure writer exists yet; keep the synchronous one and raise this file's count in config/main-sync-spawn-baseline.txt"
+    )
+    expect(adviceFor(['restrictWindowsPathSync'])).toContain('never a plain write')
+    expect(adviceFor(['gitExecFileSync', 'grantDirAcl'])).toBe(
+      'gitExecFileSync: use gitExecFileAsync. grantDirAcl: use grantDirAclAsync.'
+    )
+  })
+
+  it('fails a new file and a rising count, and passes at the baseline count', () => {
+    const one = "import { spawnSync } from 'node:child_process'\nspawnSync('a')"
+    const root = tree({
+      'src/main/launch.ts': one,
+      'src/main/launch.test.ts': `${one}\nspawnSync('b')`,
+      'src/renderer/src/view.ts': one,
+      [BASELINE]: '# debt\n'
+    })
+    const error = captureErrors()
+    expect(main(root)).toBe(1)
+    expect(error.mock.calls.map(([line]) => line)).toEqual([
+      '::error file=src/main/launch.ts::1 synchronous launch use(s), baseline allows 0. They block the main thread. spawnSync: use runProcess or spawnProcess from @orca/process-host.'
+    ])
+    writeFileSync(path.join(root, BASELINE), '1 src/main/launch.ts\n')
+    expect(main(root)).toBe(0)
+    writeFileSync(path.join(root, 'src/main/launch.ts'), `${one}\nspawnSync('b')`)
+    error.mockClear()
+    expect(main(root)).toBe(1)
+    expect(error.mock.calls[0][0]).toContain('2 synchronous launch use(s), baseline allows 1.')
+  })
+
+  it('fails a lowered or stale count until it is pruned, and prune never raises', () => {
+    const write = "import { writeSecureFile } from '../shared/secure-file'\nwriteSecureFile(a, b)\n"
+    const root = tree({
+      'src/main/store.ts': write,
+      'src/main/clean.ts': 'export const done = true\n',
+      'src/main/new.ts': write,
+      'src/main/grown.ts': `${write}writeSecureFile(c, d)\n`,
+      [BASELINE]:
+        '# old header\n3 src/main/store.ts # tracked in #26754\n1 src/main/clean.ts\n1 src/main/grown.ts\n'
+    })
+    const error = captureErrors()
+    expect(main(root)).toBe(1)
+    const lines = error.mock.calls.map(([line]) => line)
+    expect(lines[0]).toContain('src/main/grown.ts::2 synchronous launch use(s), baseline allows 1.')
+    expect(lines[1]).toContain('src/main/new.ts::1 synchronous launch use(s), baseline allows 0.')
+    expect(lines[1]).toContain('writeSecureFile: no async secure writer exists yet')
+    expect(lines.slice(2)).toEqual([
+      '::error file=src/main/clean.ts::0 synchronous launch use(s), baseline still allows 1. Run: pnpm check:main-sync-spawn-ratchet --prune',
+      '::error file=src/main/store.ts::1 synchronous launch use(s), baseline still allows 3. Run: pnpm check:main-sync-spawn-ratchet --prune'
+    ])
+    prune(root)
+    const pruned = readFileSync(path.join(root, BASELINE), 'utf8')
+    expect(pruned).toContain('counts may only go DOWN')
+    expect(pruned.split('\n').filter((line) => line && !line.startsWith('#'))).toEqual([
+      '1 src/main/grown.ts',
+      '1 src/main/store.ts # tracked in #26754'
+    ])
+    error.mockClear()
+    expect(main(root)).toBe(1)
+    expect(error.mock.calls.map(([line]) => line.split('::')[1])).toEqual([
+      'error file=src/main/grown.ts',
+      'error file=src/main/new.ts'
+    ])
+  })
+})
diff --git a/config/scripts/pr-preflight-gates.test.mjs b/config/scripts/pr-preflight-gates.test.mjs
index cbf0581bc01..367ed18294f 100644
--- a/config/scripts/pr-preflight-gates.test.mjs
+++ b/config/scripts/pr-preflight-gates.test.mjs
@@ -244,6 +244,7 @@ it('pins every foreground and background step to its selected phase', () => {
       .map((step) => [step.id, step.env.PREFLIGHT_PHASE_SELECTED])
   ).toEqual([
     ['process-host-imports', `\${{ ${staticPhase} }}`],
+    ['main-sync-spawn-ratchet', `\${{ ${staticPhase} }}`],
     ['root-lint', `\${{ ${staticPhase} }}`],
     ['native-code-quality', `\${{ ${staticPhase} }}`],
     ['changed-code-quality', `\${{ ${staticPhase} }}`],
diff --git a/config/scripts/static-module-specifiers.mjs b/config/scripts/static-module-specifiers.mjs
index 01d284bc853..c79b7900a29 100644
--- a/config/scripts/static-module-specifiers.mjs
+++ b/config/scripts/static-module-specifiers.mjs
@@ -3,7 +3,7 @@ import ts from 'typescript-api'
 const MODULE_BUILTINS = new Set(['module', 'node:module'])
 const PROCESS_BUILTINS = new Set(['process', 'node:process'])
 
-function unwrap(node) {
+export function unwrap(node) {
   while (
     node &&
     (ts.isParenthesizedExpression(node) ||
@@ -22,14 +22,14 @@ function isNamed(node, name) {
   return ts.isIdentifier(node) && node.text === name
 }
 
-function literalString(node) {
+export function literalString(node) {
   node = unwrap(node)
   return node && (ts.isStringLiteral(node) || ts.isNoSubstitutionTemplateLiteral(node))
     ? node.text
     : null
 }
 
-function propertyName(node) {
+export function propertyName(node) {
   if (ts.isPropertyAccessExpression(node)) {
     return node.name.text
   }
diff --git a/package.json b/package.json
index 4e3e2a62d0d..c742c4a8433 100644
--- a/package.json
+++ b/package.json
@@ -14,7 +14,7 @@
     "audit:perf": "oxlint --config config/oxlint-performance-audit.json --format json src",
     "test:perf:contracts": "vitest run --config config/vitest.performance.config.ts",
     "format": "oxfmt --write .",
-    "lint": "oxlint && pnpm run audit:anti-slop && pnpm run audit:code-quality:native && pnpm run audit:code-quality:type-aware && pnpm run check:reliability-gates && pnpm run check:dead-classes && pnpm run check:max-lines-ratchet && pnpm run check:ts-nocheck-ratchet && pnpm run check:runtime-electron-ratchet && pnpm run check:focus-read-ratchet && pnpm run check:layout-writer-ratchets && pnpm run check:readme-local-links && pnpm run check:node-runtime-pin && pnpm run verify:rpc-params-catalog && pnpm run verify:acp-protocol && pnpm run verify:bundled-skill-guides && pnpm run verify:skill-bundle-manifest && pnpm run verify:localization-catalogs && pnpm run verify:localization-extraction && pnpm run verify:localization-coverage && pnpm run check:process-host-imports && pnpm run check:compat-boundary-imports",
+    "lint": "oxlint && pnpm run audit:anti-slop && pnpm run audit:code-quality:native && pnpm run audit:code-quality:type-aware && pnpm run check:reliability-gates && pnpm run check:dead-classes && pnpm run check:max-lines-ratchet && pnpm run check:ts-nocheck-ratchet && pnpm run check:runtime-electron-ratchet && pnpm run check:focus-read-ratchet && pnpm run check:layout-writer-ratchets && pnpm run check:readme-local-links && pnpm run check:node-runtime-pin && pnpm run verify:rpc-params-catalog && pnpm run verify:acp-protocol && pnpm run verify:bundled-skill-guides && pnpm run verify:skill-bundle-manifest && pnpm run verify:localization-catalogs && pnpm run verify:localization-extraction && pnpm run verify:localization-coverage && pnpm run check:process-host-imports && pnpm run check:main-sync-spawn-ratchet && pnpm run check:compat-boundary-imports",
     "audit:code-quality": "pnpm run audit:code-quality:native && pnpm run audit:code-quality:type-aware && pnpm run audit:react-doctor",
     "audit:code-quality:native": "oxlint --config config/oxlint-code-quality-native-plugins.json src config tests mobile --deny-warnings",
     "audit:code-quality:type-aware": "oxlint --type-aware --config config/oxlint-code-quality-type-aware.json src config tests --deny-warnings",
@@ -178,6 +178,7 @@
     "sync:anti-slop-plugin": "node config/scripts/sync-anti-slop-plugin.mjs",
     "build:packages": "pnpm --filter @orca/process-host build",
     "check:process-host-imports": "node config/scripts/check-process-host-imports.mjs",
+    "check:main-sync-spawn-ratchet": "node config/scripts/check-main-sync-spawn-ratchet.mjs",
     "check:compat-boundary-imports": "node config/scripts/check-compat-boundary-imports.mjs"
   },
   "dependencies": {
diff --git a/src/main/diagnostics/main-thread-churn-probe.ts b/src/main/diagnostics/main-thread-churn-probe.ts
index af6877e408e..7b68fd384c1 100644
--- a/src/main/diagnostics/main-thread-churn-probe.ts
+++ b/src/main/diagnostics/main-thread-churn-probe.ts
@@ -76,8 +76,8 @@ export function classifySubprocessCommand(command: string, args: readonly string
 
 export type SubprocessSpawnStats = {
   count: number
-  // Cumulative and worst synchronous cost of initiating the spawn (the
-  // uv_spawn → posix_spawn call runs on the main thread before returning).
+  // Cumulative and worst main-thread block: the spawn initiation (uv_spawn →
+  // posix_spawn) for async launches, the whole run for runProcessSync.
   blockMsTotal: number
   blockMsMax: number
 }
@@ -86,7 +86,7 @@ const spawnStatsByCommand = new Map<string, SubprocessSpawnStats>()
 
 /**
  * Record one subprocess spawn from the main process. `blockMs` is how long
- * the synchronous spawn/execFile initiation call held the main thread.
+ * the spawn call held the main thread (until exit for synchronous launches).
  * No-op unless ORCA_MAIN_THREAD_DIAGNOSTICS=1.
  */
 export function recordSubprocessSpawn(
diff --git a/src/packages/process-host/src/run-process.ts b/src/packages/process-host/src/run-process.ts
index 7cf50c12c0d..a5d5c2d2e37 100644
--- a/src/packages/process-host/src/run-process.ts
+++ b/src/packages/process-host/src/run-process.ts
@@ -3,7 +3,7 @@ import {
   spawnSync as nodeSpawnSync,
   type ChildProcess
 } from 'node:child_process'
-import { resolveSpawn } from './spawn-resolution'
+import { resolveSpawn, type ResolvedSpawn } from './spawn-resolution'
 import { forceTerminateProcessTree, signalProcessTree } from './process-tree-termination'
 
 import { hasSpawnObserver, notifySpawnObserver } from './spawn-observer'
@@ -339,6 +339,19 @@ function terminate(child: ChildProcess, signal?: NodeJS.Signals): void {
  */
 export function runProcessSync(spec: ProcessSpec): ProcessResult {
   const resolved = resolveSpawn(spec, process.platform)
+  // Diagnostics only: spawnSync holds the calling thread until the child exits,
+  // so the whole call is the block, reported even when it throws.
+  const spawnStartedAt = hasSpawnObserver() ? performance.now() : null
+  try {
+    return runResolvedProcessSync(spec, resolved)
+  } finally {
+    if (spawnStartedAt !== null) {
+      notifySpawnObserver(resolved.file, resolved.args, performance.now() - spawnStartedAt)
+    }
+  }
+}
+
+function runResolvedProcessSync(spec: ProcessSpec, resolved: ResolvedSpawn): ProcessResult {
   const result = nodeSpawnSync(resolved.file, [...resolved.args], {
     ...resolved.options,
     input: spec.input,
diff --git a/src/packages/process-host/src/spawn-observer.test.ts b/src/packages/process-host/src/spawn-observer.test.ts
index 6700fb1b351..bd21ffa4f53 100644
--- a/src/packages/process-host/src/spawn-observer.test.ts
+++ b/src/packages/process-host/src/spawn-observer.test.ts
@@ -1,6 +1,8 @@
 import { afterEach, describe, expect, it } from 'vitest'
+import { tmpdir } from 'node:os'
+import path from 'node:path'
 import { setSpawnObserver } from './spawn-observer'
-import { runProcess, spawnProcess } from './run-process'
+import { runProcess, runProcessSync, spawnProcess } from './run-process'
 
 afterEach(() => {
   setSpawnObserver(null)
@@ -27,6 +29,33 @@ describe('spawn observer', () => {
     expect(calls).toBe(1)
   })
 
+  it('reports the whole blocking run of runProcessSync', () => {
+    const seen: { command: string; blockMs: number }[] = []
+    setSpawnObserver((command, _args, blockMs) => seen.push({ command, blockMs }))
+    const result = runProcessSync({
+      program: process.execPath,
+      args: ['-e', 'setTimeout(() => process.exit(3), 50)']
+    })
+    expect(result.code).toBe(3)
+    expect(seen).toHaveLength(1)
+    expect(seen[0].command).toBe(process.execPath)
+    expect(seen[0].blockMs).toBeGreaterThanOrEqual(40)
+  })
+
+  it('reports a runProcessSync launch that throws or times out', () => {
+    const seen: string[] = []
+    setSpawnObserver((command) => seen.push(command))
+    const missing = path.join(tmpdir(), 'orca-spawn-observer-missing-program')
+    expect(() => runProcessSync({ program: missing, args: [] })).toThrow()
+    const timedOut = runProcessSync({
+      program: process.execPath,
+      args: ['-e', 'setTimeout(() => {}, 10_000)'],
+      timeoutMs: 50
+    })
+    expect(timedOut.timedOut).toBe(true)
+    expect(seen).toEqual([missing, process.execPath])
+  })
+
   it('stays silent with no observer registered', async () => {
     let calls = 0
     setSpawnObserver(null)
diff --git a/tests/e2e/main-thread-git-cost.spec.ts b/tests/e2e/main-thread-git-cost.spec.ts
index 53784cfe779..b7e977229e4 100644
--- a/tests/e2e/main-thread-git-cost.spec.ts
+++ b/tests/e2e/main-thread-git-cost.spec.ts
@@ -7,7 +7,7 @@
  * paint and git. This one runs git churn alone against a hidden window and
  * takes a V8 CPU profile OF THE MAIN PROCESS for each phase, which is the only
  * way to split spawn initiation from stdout drain from porcelain parsing — the
- * churn probe reports spawn initiation only.
+ * churn probe reports spawn initiation only (the whole run for synchronous launches).
  *
  * Run: ORCA_GIT_COST_BENCH=1 ORCA_BACKGROUND_LAUNCH=1 \
  *   npx playwright test tests/e2e/main-thread-git-cost.spec.ts \
diff --git a/tests/tools/benchmarks/main-thread-jank-bench.mjs b/tests/tools/benchmarks/main-thread-jank-bench.mjs
index a64eecaf985..12284e176fb 100644
--- a/tests/tools/benchmarks/main-thread-jank-bench.mjs
+++ b/tests/tools/benchmarks/main-thread-jank-bench.mjs
@@ -8,8 +8,9 @@
  * `[main-thread] {json}` stderr line every 5s containing:
  *   - worst event-loop stall in the window (maxGapMs) and stall counts
  *   - subprocess spawns since the last report, keyed by command
- *     ("git status", "gh api", …) with the synchronous spawn-initiation cost
- *     that held the main thread (blockMsTotal/blockMsMax)
+ *     ("git status", "gh api", …) with how long each launch held the main
+ *     thread (blockMsTotal/blockMsMax): spawn initiation for async launches,
+ *     the whole run for synchronous ones
  * On macOS the bench also tails the unified log for the exact
  * "Performance Diagnostics" warnings from the issue and records which process
  * emitted them, so spawn churn and OS warnings can be correlated by timestamp.