diff --git a/src/cli/orchestration-mutation-recovery.ts b/src/cli/orchestration-mutation-recovery.ts
index 3777b04755e..d5d80326c49 100644
--- a/src/cli/orchestration-mutation-recovery.ts
+++ b/src/cli/orchestration-mutation-recovery.ts
@@ -1,3 +1,4 @@
+import { quotePosixShellDoubleQuotedApostrophe } from '../shared/shell-argument-quoting'
 import { RuntimeClientError, RuntimeRpcFailureError } from './runtime-client'
 import {
   recoverableOrchestrationArgs,
@@ -208,7 +209,7 @@ function shellQuote(value: string): string {
   if (/^[A-Za-z0-9_./:@%+=,-]+$/.test(value)) {
     return value
   }
-  return `'${value.replaceAll("'", `'"'"'`)}'`
+  return quotePosixShellDoubleQuotedApostrophe(value)
 }
 
 function stripUnsafeRetryAdvice(message: string, requestId: string): string {
diff --git a/src/cli/shell-command-quote.ts b/src/cli/shell-command-quote.ts
index c5dff7f62a3..6ad5e3d73f2 100644
--- a/src/cli/shell-command-quote.ts
+++ b/src/cli/shell-command-quote.ts
@@ -1,3 +1,5 @@
+import { quotePosixShell } from '../shared/shell-argument-quoting'
+
 export function quoteCliCommandArgument(value: string): string {
   if (/^[a-zA-Z0-9._:/@-]+$/.test(value)) {
     return value
@@ -5,5 +7,5 @@ export function quoteCliCommandArgument(value: string): string {
   if (process.platform === 'win32') {
     return `"${value.replace(/"/g, '\\"')}"`
   }
-  return `'${value.replaceAll("'", "'\\''")}'`
+  return quotePosixShell(value)
 }
diff --git a/src/main/agent-hooks/posix-hook-command.ts b/src/main/agent-hooks/posix-hook-command.ts
index 8a9f6dc7bf4..b51cc90632a 100644
--- a/src/main/agent-hooks/posix-hook-command.ts
+++ b/src/main/agent-hooks/posix-hook-command.ts
@@ -1,9 +1,6 @@
+import { quotePosixShell } from '../../shared/shell-argument-quoting'
 import { POSIX_HOOK_STDIN_DRAIN_COMMAND } from './hook-stdin-contract'
 
-export function quotePosixShellString(value: string): string {
-  return `'${value.replaceAll("'", "'\\''")}'`
-}
-
 // Why: guard for a readable executable so a stale entry at a missing script becomes a silent no-op, not an exit-127 failure on every tool call.
 export function wrapPosixHookCommand(
   scriptPath: string,
@@ -12,15 +9,15 @@ export function wrapPosixHookCommand(
   options: { fallbackStdout?: string; requiredEnvVar?: string } = {}
 ): string {
   // Why: single-quote escape so $, `, ", \ in scriptPath stay literal — avoids shell injection from an arbitrary path.
-  const quoted = quotePosixShellString(scriptPath)
+  const quoted = quotePosixShell(scriptPath)
   const envPrefix = Object.entries(env)
-    .map(([key, value]) => `${key}='${value.replaceAll("'", "'\\''")}'`)
+    .map(([key, value]) => `${key}=${quotePosixShell(value)}`)
     .join(' ')
   const invocation = envPrefix ? `${envPrefix} /bin/sh ${quoted}` : `/bin/sh ${quoted}`
   const fallback =
     options.fallbackStdout === undefined
       ? POSIX_HOOK_STDIN_DRAIN_COMMAND
-      : `printf '%s\\n' ${quotePosixShellString(options.fallbackStdout)}; ${POSIX_HOOK_STDIN_DRAIN_COMMAND}`
+      : `printf '%s\\n' ${quotePosixShell(options.fallbackStdout)}; ${POSIX_HOOK_STDIN_DRAIN_COMMAND}`
   // Why: default form avoids Grok rejecting unset vars or splicing values into shell quotes at load
   // time; the child shell checks the current pane env before spawning the managed script.
   const guards = [
diff --git a/src/main/antigravity/antigravity-browser-helper.ts b/src/main/antigravity/antigravity-browser-helper.ts
index 62ae8822b5c..ecf5f6febeb 100644
--- a/src/main/antigravity/antigravity-browser-helper.ts
+++ b/src/main/antigravity/antigravity-browser-helper.ts
@@ -2,6 +2,7 @@
 // one-line program run by its own executable in Node mode, which prints the link on error output
 // instead: the link is captured either way, and no browser opens on the host.
 
+import { quotePosixShellDoubleQuotedApostrophe } from '../../shared/shell-argument-quoting'
 import { runProcess } from '@orca/process-host'
 
 export const ANTIGRAVITY_BROWSER_MARKER = '__ORCA_ANTIGRAVITY_AUTH_URL__'
@@ -13,14 +14,15 @@ const HELPER_SOURCE =
 const PREFLIGHT_URL = 'https://example.invalid/orca-antigravity-browser-preflight'
 
 // Python splits BROWSER with shlex.
-const quote = (value: string): string => `'${value.replaceAll("'", `'"'"'`)}'`
 
 // Node mode is set in the command itself: the provider supervisor strips ELECTRON_RUN_AS_NODE from
 // the server, which keeps it out of the agent's own tools.
 const executable = process.execPath.replaceAll('\\', '\\\\').replaceAll(':', '\\072')
-const shell = `exec /usr/bin/env ELECTRON_RUN_AS_NODE=1 "$(printf %b ${quote(executable)})" -e ${quote(HELPER_SOURCE)} -- "$1"`
+const shell = `exec /usr/bin/env ELECTRON_RUN_AS_NODE=1 "$(printf %b ${quotePosixShellDoubleQuotedApostrophe(executable)})" -e ${quotePosixShellDoubleQuotedApostrophe(HELPER_SOURCE)} -- "$1"`
 const BROWSER_ARGV = ['/bin/sh', '-c', shell, '--', '%s']
-export const ANTIGRAVITY_BROWSER_COMMAND = BROWSER_ARGV.map(quote).join(' ')
+export const ANTIGRAVITY_BROWSER_COMMAND = BROWSER_ARGV.map(
+  quotePosixShellDoubleQuotedApostrophe
+).join(' ')
 const usable = !/[\r\n\0]|%s/.test(process.execPath)
 
 /** The exact template the server's Python browser controller executes. */
diff --git a/src/main/antigravity/hook-service.ts b/src/main/antigravity/hook-service.ts
index 071ca59bf48..846f6bb1e9e 100644
--- a/src/main/antigravity/hook-service.ts
+++ b/src/main/antigravity/hook-service.ts
@@ -27,7 +27,7 @@ import {
   ANTIGRAVITY_PRE_TOOL_USE_DECISION,
   type AntigravityEvent
 } from './hook-events'
-import { quotePosixShellString } from '../agent-hooks/posix-hook-command'
+import { quotePosixShell } from '../../shared/shell-argument-quoting'
 import { getManagedScript, getWindowsWrapperScript } from './hook-script'
 import {
   buildInstalledConfig,
@@ -64,7 +64,7 @@ function getPosixManagedCommand(scriptPath: string, event: AntigravityEvent): st
     event.eventName === 'PreToolUse' ? { fallbackStdout: ANTIGRAVITY_PRE_TOOL_USE_DECISION } : {}
   )
   // ACP hosts tokenize the command into argv; the shell must be the executable, not `if`.
-  return `/bin/sh -c ${quotePosixShellString(command)}`
+  return `/bin/sh -c ${quotePosixShell(command)}`
 }
 
 function getManagedCommand(scriptPath: string, event: AntigravityEvent): string {
diff --git a/src/main/cli/appimage-stable-launcher.ts b/src/main/cli/appimage-stable-launcher.ts
index 9494479abd8..e74797fadfb 100644
--- a/src/main/cli/appimage-stable-launcher.ts
+++ b/src/main/cli/appimage-stable-launcher.ts
@@ -16,7 +16,7 @@ import {
 } from 'node:fs'
 import { dirname, join, resolve } from 'node:path'
 import { LINUX_CLI_COMMAND_NAME } from './bundled-cli-launcher-path'
-import { quoteShell } from './cli-install-path-format'
+import { quotePosixShellDoubleQuotedApostrophe } from '../../shared/shell-argument-quoting'
 
 const LAUNCHER_DIRECTORY_NAME = 'launcher'
 const LIVE_ENDPOINT_NAME = 'live'
@@ -226,7 +226,7 @@ function buildStableLauncherScript(cacheRootPath: string): string {
   return `#!/usr/bin/env bash
 ${LAUNCHER_MARKER}
 shopt -s execfail
-launcher_dir=${quoteShell(launcherDirectory)}
+launcher_dir=${quotePosixShellDoubleQuotedApostrophe(launcherDirectory)}
 deadline=$((SECONDS + ${LAUNCHER_WAIT_SECONDS}))
 while (( SECONDS <= deadline )); do
   launcher="$launcher_dir/${INSTALLED_ENDPOINT_NAME}"
diff --git a/src/main/cli/cli-command-filesystem-transaction.ts b/src/main/cli/cli-command-filesystem-transaction.ts
index 6b7261dfefd..ab89d0bb55e 100644
--- a/src/main/cli/cli-command-filesystem-transaction.ts
+++ b/src/main/cli/cli-command-filesystem-transaction.ts
@@ -4,7 +4,7 @@ import { basename, dirname, join } from 'node:path'
 import type { CliInstallStatus } from '../../shared/cli-install-types'
 import { isPermissionError } from '../win32-utils'
 import { isMissingError } from './cli-install-errors'
-import { quoteShell } from './cli-install-path-format'
+import { quotePosixShellDoubleQuotedApostrophe } from '../../shared/shell-argument-quoting'
 
 export type EntryIdentity = {
   dev: bigint
@@ -171,10 +171,12 @@ export function buildMacPrivilegedSymlinkReadableCommand(args: {
   commandPath: string
   expected: EntryIdentity
 }): string {
-  const commandPath = quoteShell(args.commandPath)
-  const changed = quoteShell(`The command at ${args.commandPath} changed while Orca inspected it.`)
+  const commandPath = quotePosixShellDoubleQuotedApostrophe(args.commandPath)
+  const changed = quotePosixShellDoubleQuotedApostrophe(
+    `The command at ${args.commandPath} changed while Orca inspected it.`
+  )
   return (
-    `if [ -L ${commandPath} ] && [ "$(/usr/bin/stat -f '%d:%i' ${commandPath})" = ${quoteShell(`${args.expected.dev}:${args.expected.ino}`)} ]; ` +
+    `if [ -L ${commandPath} ] && [ "$(/usr/bin/stat -f '%d:%i' ${commandPath})" = ${quotePosixShellDoubleQuotedApostrophe(`${args.expected.dev}:${args.expected.ino}`)} ]; ` +
     `then /bin/chmod -h 755 ${commandPath}; else echo ${changed} >&2; exit 73; fi`
   )
 }
@@ -194,43 +196,45 @@ export function buildMacPrivilegedSymlinkTransaction(
   const heldPath = join(transactionDirectory, basename(args.commandPath))
   const publishDirectory = join(transactionDirectory, 'publish')
   const publishPath = join(publishDirectory, basename(args.commandPath))
-  const recoveryMessage = quoteShell(`The displaced entry is preserved at ${heldPath}.`)
+  const recoveryMessage = quotePosixShellDoubleQuotedApostrophe(
+    `The displaced entry is preserved at ${heldPath}.`
+  )
   const restore =
-    `/bin/ln -P ${quoteShell(heldPath)} ${quoteShell(commandDirectory)} && ` +
-    `/bin/rm ${quoteShell(heldPath)} && /bin/rmdir ${quoteShell(transactionDirectory)}`
+    `/bin/ln -P ${quotePosixShellDoubleQuotedApostrophe(heldPath)} ${quotePosixShellDoubleQuotedApostrophe(commandDirectory)} && ` +
+    `/bin/rm ${quotePosixShellDoubleQuotedApostrophe(heldPath)} && /bin/rmdir ${quotePosixShellDoubleQuotedApostrophe(transactionDirectory)}`
   const restoreOrPreserve = `if ${restore}; then :; else echo ${recoveryMessage} >&2; exit 74; fi`
   const { fileSha256, rawSymlinkTarget, snapshot } = args.inspected
   const fileMismatch = fileSha256
-    ? ` || [ "$(/usr/bin/shasum -a 256 ${quoteShell(heldPath)} | /usr/bin/awk '{print $1}')" != ${quoteShell(fileSha256)} ]`
+    ? ` || [ "$(/usr/bin/shasum -a 256 ${quotePosixShellDoubleQuotedApostrophe(heldPath)} | /usr/bin/awk '{print $1}')" != ${quotePosixShellDoubleQuotedApostrophe(fileSha256)} ]`
     : ''
   const symlinkMismatch = rawSymlinkTarget
-    ? ` || [ "$(/usr/bin/readlink -n ${quoteShell(heldPath)}; /usr/bin/printf x)" != ${quoteShell(`${rawSymlinkTarget}x`)} ]`
+    ? ` || [ "$(/usr/bin/readlink -n ${quotePosixShellDoubleQuotedApostrophe(heldPath)}; /usr/bin/printf x)" != ${quotePosixShellDoubleQuotedApostrophe(`${rawSymlinkTarget}x`)} ]`
     : ''
   const rejectCaptured = snapshot
-    ? `if [ "$captured" -eq 1 ] && { [ "$(/usr/bin/stat -f '%d:%i' ${quoteShell(heldPath)})" != ${quoteShell(`${snapshot.identity.dev}:${snapshot.identity.ino}`)} ]${fileMismatch}${symlinkMismatch}; }; then ${restoreOrPreserve}; exit 73; fi`
+    ? `if [ "$captured" -eq 1 ] && { [ "$(/usr/bin/stat -f '%d:%i' ${quotePosixShellDoubleQuotedApostrophe(heldPath)})" != ${quotePosixShellDoubleQuotedApostrophe(`${snapshot.identity.dev}:${snapshot.identity.ino}`)} ]${fileMismatch}${symlinkMismatch}; }; then ${restoreOrPreserve}; exit 73; fi`
     : `if [ "$captured" -eq 1 ]; then ${restoreOrPreserve}; exit 73; fi`
   // Why: macOS applies the umask to symlinks too, so the script publishes under 022 and only the
   // transaction directories are created private.
   const capture =
-    `umask 022; /bin/mkdir -p ${quoteShell(commandDirectory)} || exit $?; ` +
-    `/bin/mkdir -m 700 ${quoteShell(transactionDirectory)} || exit $?; captured=0; ` +
-    `if [ -e ${quoteShell(args.commandPath)} ] || [ -L ${quoteShell(args.commandPath)} ]; then ` +
-    `/bin/mv ${quoteShell(args.commandPath)} ${quoteShell(heldPath)} && captured=1 || exit $?; fi; ` +
+    `umask 022; /bin/mkdir -p ${quotePosixShellDoubleQuotedApostrophe(commandDirectory)} || exit $?; ` +
+    `/bin/mkdir -m 700 ${quotePosixShellDoubleQuotedApostrophe(transactionDirectory)} || exit $?; captured=0; ` +
+    `if [ -e ${quotePosixShellDoubleQuotedApostrophe(args.commandPath)} ] || [ -L ${quotePosixShellDoubleQuotedApostrophe(args.commandPath)} ]; then ` +
+    `/bin/mv ${quotePosixShellDoubleQuotedApostrophe(args.commandPath)} ${quotePosixShellDoubleQuotedApostrophe(heldPath)} && captured=1 || exit $?; fi; ` +
     `${rejectCaptured}; `
 
   if (args.action === 'remove') {
-    return `${capture}if [ "$captured" -eq 1 ]; then /bin/rm ${quoteShell(heldPath)}; fi; /bin/rmdir ${quoteShell(transactionDirectory)}`
+    return `${capture}if [ "$captured" -eq 1 ]; then /bin/rm ${quotePosixShellDoubleQuotedApostrophe(heldPath)}; fi; /bin/rmdir ${quotePosixShellDoubleQuotedApostrophe(transactionDirectory)}`
   }
 
   const rollback =
-    `/bin/rm -f ${quoteShell(publishPath)}; /bin/rmdir ${quoteShell(publishDirectory)} 2>/dev/null || :; ` +
-    `if [ "$captured" -eq 1 ]; then ${restoreOrPreserve}; else /bin/rmdir ${quoteShell(transactionDirectory)}; fi; exit 73`
+    `/bin/rm -f ${quotePosixShellDoubleQuotedApostrophe(publishPath)}; /bin/rmdir ${quotePosixShellDoubleQuotedApostrophe(publishDirectory)} 2>/dev/null || :; ` +
+    `if [ "$captured" -eq 1 ]; then ${restoreOrPreserve}; else /bin/rmdir ${quotePosixShellDoubleQuotedApostrophe(transactionDirectory)}; fi; exit 73`
   return (
-    `${capture}if /bin/mkdir -m 700 ${quoteShell(publishDirectory)} && ` +
-    `/bin/ln -s ${quoteShell(args.launcherPath)} ${quoteShell(publishPath)} && ` +
-    `/bin/ln -P ${quoteShell(publishPath)} ${quoteShell(commandDirectory)}; then ` +
-    `/bin/rm ${quoteShell(publishPath)}; /bin/rmdir ${quoteShell(publishDirectory)}; ` +
-    `if [ "$captured" -eq 1 ]; then /bin/rm ${quoteShell(heldPath)}; fi; ` +
-    `/bin/rmdir ${quoteShell(transactionDirectory)}; else ${rollback}; fi`
+    `${capture}if /bin/mkdir -m 700 ${quotePosixShellDoubleQuotedApostrophe(publishDirectory)} && ` +
+    `/bin/ln -s ${quotePosixShellDoubleQuotedApostrophe(args.launcherPath)} ${quotePosixShellDoubleQuotedApostrophe(publishPath)} && ` +
+    `/bin/ln -P ${quotePosixShellDoubleQuotedApostrophe(publishPath)} ${quotePosixShellDoubleQuotedApostrophe(commandDirectory)}; then ` +
+    `/bin/rm ${quotePosixShellDoubleQuotedApostrophe(publishPath)}; /bin/rmdir ${quotePosixShellDoubleQuotedApostrophe(publishDirectory)}; ` +
+    `if [ "$captured" -eq 1 ]; then /bin/rm ${quotePosixShellDoubleQuotedApostrophe(heldPath)}; fi; ` +
+    `/bin/rmdir ${quotePosixShellDoubleQuotedApostrophe(transactionDirectory)}; else ${rollback}; fi`
   )
 }
diff --git a/src/main/cli/cli-dev-launcher.ts b/src/main/cli/cli-dev-launcher.ts
index e7b0f75c4b5..839cc8f2eb4 100644
--- a/src/main/cli/cli-dev-launcher.ts
+++ b/src/main/cli/cli-dev-launcher.ts
@@ -2,11 +2,8 @@ import { existsSync } from 'node:fs'
 import { mkdir, writeFile } from 'node:fs/promises'
 import { dirname, isAbsolute, join } from 'node:path'
 import { DEV_COMMAND_NAME, DEV_LAUNCHER_DIR } from './cli-install-constants'
-import {
-  escapeWindowsBatchValue,
-  isAbsoluteForPlatform,
-  quoteShell
-} from './cli-install-path-format'
+import { escapeWindowsBatchValue, isAbsoluteForPlatform } from './cli-install-path-format'
+import { quotePosixShellDoubleQuotedApostrophe } from '../../shared/shell-argument-quoting'
 
 export async function ensureDevLauncher(args: {
   platform: NodeJS.Platform
@@ -58,16 +55,16 @@ export function buildUnixCliLauncher(
   if (runtime === 'node') {
     return `#!/usr/bin/env sh
 set -eu
-export ORCA_USER_DATA_PATH=${quoteShell(userDataPath)}
+export ORCA_USER_DATA_PATH=${quotePosixShellDoubleQuotedApostrophe(userDataPath)}
 unset NODE_OPTIONS NODE_REPL_EXTERNAL_MODULE ELECTRON_RUN_AS_NODE
-exec ${quoteShell(execPathValue)} ${quoteShell(cliEntryPath)} "$@"
+exec ${quotePosixShellDoubleQuotedApostrophe(execPathValue)} ${quotePosixShellDoubleQuotedApostrophe(cliEntryPath)} "$@"
 `
   }
   return `#!/usr/bin/env bash
 set -euo pipefail
-ELECTRON=${quoteShell(execPathValue)}
-CLI=${quoteShell(cliEntryPath)}
-export ORCA_USER_DATA_PATH=${quoteShell(userDataPath)}
+ELECTRON=${quotePosixShellDoubleQuotedApostrophe(execPathValue)}
+CLI=${quotePosixShellDoubleQuotedApostrophe(cliEntryPath)}
+export ORCA_USER_DATA_PATH=${quotePosixShellDoubleQuotedApostrophe(userDataPath)}
 if [ -z "\${ORCA_APP_EXECUTABLE:-}" ]; then
   export ORCA_APP_EXECUTABLE="$ELECTRON"
   export ORCA_APP_EXECUTABLE_NEEDS_APP_ROOT=1
diff --git a/src/main/cli/cli-install-path-format.ts b/src/main/cli/cli-install-path-format.ts
index 1192594c270..6af5ca168d3 100644
--- a/src/main/cli/cli-install-path-format.ts
+++ b/src/main/cli/cli-install-path-format.ts
@@ -73,10 +73,6 @@ export function escapeWindowsBatchValue(value: string): string {
   return value.replaceAll('"', '""')
 }
 
-export function quoteShell(value: string): string {
-  return `'${value.replaceAll("'", `'"'"'`)}'`
-}
-
 export function isAbsoluteForPlatform(platform: NodeJS.Platform, value: string): boolean {
   if (platform === 'win32') {
     return /^[A-Za-z]:[\\/]/.test(value) || value.startsWith('\\\\')
diff --git a/src/main/cli/legacy-appimage-cli-wrapper.ts b/src/main/cli/legacy-appimage-cli-wrapper.ts
index 1e22b2dc577..8af84bc1588 100644
--- a/src/main/cli/legacy-appimage-cli-wrapper.ts
+++ b/src/main/cli/legacy-appimage-cli-wrapper.ts
@@ -1,4 +1,4 @@
-import { quoteShell } from './cli-install-path-format'
+import { quotePosixShellDoubleQuotedApostrophe } from '../../shared/shell-argument-quoting'
 
 const APPIMAGE_CLI_SCRIPT = [
   '(async()=>{',
@@ -25,7 +25,7 @@ export function extractLegacyAppImageCliWrapperTarget(content: string): string |
 export function buildLegacyAppImageCliWrapper(appImagePath: string): string {
   return `#!/usr/bin/env bash
 set -euo pipefail
-APPIMAGE=${quoteShell(appImagePath)}
+APPIMAGE=${quotePosixShellDoubleQuotedApostrophe(appImagePath)}
 if [ ! -f "$APPIMAGE" ]; then
   echo "Orca AppImage not found at $APPIMAGE" >&2
   echo "If you moved the AppImage, re-run CLI registration from Orca Settings." >&2
@@ -36,7 +36,7 @@ export ORCA_NODE_REPL_EXTERNAL_MODULE="\${NODE_REPL_EXTERNAL_MODULE-}"
 unset NODE_OPTIONS
 unset NODE_REPL_EXTERNAL_MODULE
 # Why: AppImage mount paths change on each launch; $APPDIR is the runtime mount.
-ELECTRON_RUN_AS_NODE=1 exec "$APPIMAGE" -e ${quoteShell(APPIMAGE_CLI_SCRIPT)} -- "$@"
+ELECTRON_RUN_AS_NODE=1 exec "$APPIMAGE" -e ${quotePosixShellDoubleQuotedApostrophe(APPIMAGE_CLI_SCRIPT)} -- "$@"
 `
 }
 
@@ -45,5 +45,5 @@ function unquoteShell(value: string): string | null {
     return null
   }
   const decoded = value.slice(1, -1).split(`'"'"'`).join("'")
-  return quoteShell(decoded) === value ? decoded : null
+  return quotePosixShellDoubleQuotedApostrophe(decoded) === value ? decoded : null
 }
diff --git a/src/main/cli/linux-bare-orca-dispatcher.ts b/src/main/cli/linux-bare-orca-dispatcher.ts
index ac23081a2ce..7260d3de100 100644
--- a/src/main/cli/linux-bare-orca-dispatcher.ts
+++ b/src/main/cli/linux-bare-orca-dispatcher.ts
@@ -16,7 +16,7 @@ import { pruneAppImageExtractedRoots } from './appimage-extraction-pruning'
 import { resolveGenerationStableLauncherPath } from './appimage-generation-stable-launcher'
 import { withAppImageRegistrationLock } from './appimage-registration-lock'
 import { getBundledLauncherPath } from './bundled-cli-launcher-path'
-import { quoteShell } from './cli-install-path-format'
+import { quotePosixShellDoubleQuotedApostrophe } from '../../shared/shell-argument-quoting'
 
 // Why: marks a dispatcher this function wrote so repeat serve starts overwrite
 // our own file idempotently but never clobber a user's own ~/.local/bin/orca.
@@ -80,7 +80,7 @@ export async function installLinuxBareOrcaDispatcher(
 
 /** Bare-`orca` script that execs the one Linux CLI launcher. */
 export function buildBareOrcaCliScript(launcherPath: string): string {
-  return `#!/usr/bin/env bash\nexec ${quoteShell(launcherPath)} "$@"\n`
+  return `#!/usr/bin/env bash\nexec ${quotePosixShellDoubleQuotedApostrophe(launcherPath)} "$@"\n`
 }
 
 /**
diff --git a/src/main/cli/linux-terminal-orca-cli-shim.ts b/src/main/cli/linux-terminal-orca-cli-shim.ts
index 7697bac01ac..21874d6a847 100644
--- a/src/main/cli/linux-terminal-orca-cli-shim.ts
+++ b/src/main/cli/linux-terminal-orca-cli-shim.ts
@@ -22,7 +22,7 @@ import {
 } from './appimage-stable-launcher'
 import { getBundledLauncherPath } from './bundled-cli-launcher-path'
 import { buildBareOrcaCliScript } from './linux-bare-orca-dispatcher'
-import { quoteShell } from './cli-install-path-format'
+import { quotePosixShellDoubleQuotedApostrophe } from '../../shared/shell-argument-quoting'
 
 const SHIM_DIR_NAME = 'linux-orca-cli-shim'
 
@@ -175,12 +175,12 @@ function buildAppImageLiveLauncherScript(
   launcherPath: string,
   fence: AppImageRuntimeFence
 ): string {
-  const runtimePid = quoteShell(String(fence.pid))
-  const runtimeStartTime = quoteShell(fence.startTime)
-  const runtimeRoot = quoteShell(fence.runtimeRoot)
-  const expectedRuntimeIdentity = quoteShell(fence.runtimeIdentity)
-  const expectedLauncherIdentity = quoteShell(fence.launcherIdentity)
-  const quotedLauncherPath = quoteShell(launcherPath)
+  const runtimePid = quotePosixShellDoubleQuotedApostrophe(String(fence.pid))
+  const runtimeStartTime = quotePosixShellDoubleQuotedApostrophe(fence.startTime)
+  const runtimeRoot = quotePosixShellDoubleQuotedApostrophe(fence.runtimeRoot)
+  const expectedRuntimeIdentity = quotePosixShellDoubleQuotedApostrophe(fence.runtimeIdentity)
+  const expectedLauncherIdentity = quotePosixShellDoubleQuotedApostrophe(fence.launcherIdentity)
+  const quotedLauncherPath = quotePosixShellDoubleQuotedApostrophe(launcherPath)
   return `#!/usr/bin/env bash
 runtime_pid=${runtimePid}
 runtime_start_time=${runtimeStartTime}
diff --git a/src/main/cli/wsl-cli-installer.ts b/src/main/cli/wsl-cli-installer.ts
index b827542a17a..6345cd3a301 100644
--- a/src/main/cli/wsl-cli-installer.ts
+++ b/src/main/cli/wsl-cli-installer.ts
@@ -11,9 +11,9 @@ import {
   getPosixDirname,
   getWslBridgeMarker,
   getWslLauncherMarker,
-  parseManagedLauncherTarget,
-  quoteShell
+  parseManagedLauncherTarget
 } from './wsl-cli-scripts'
+import { quotePosixShellDoubleQuotedApostrophe } from '../../shared/shell-argument-quoting'
 import { buildWslCliInstallCommand } from './wsl-cli-registration-command'
 import {
   buildWslCliStatus,
@@ -242,7 +242,10 @@ export class WslCliInstaller {
       // startup reconciliation as opt-in proof, silently undoing this removal.
       await this.run(
         this.distro as string,
-        ['set -eu', buildManagedLegacyRemoveCommand(quoteShell(legacyCommandPath))].join('\n')
+        [
+          'set -eu',
+          buildManagedLegacyRemoveCommand(quotePosixShellDoubleQuotedApostrophe(legacyCommandPath))
+        ].join('\n')
       )
       return status
     }
diff --git a/src/main/cli/wsl-cli-registration-command.ts b/src/main/cli/wsl-cli-registration-command.ts
index 53d39eaec86..4158031653b 100644
--- a/src/main/cli/wsl-cli-registration-command.ts
+++ b/src/main/cli/wsl-cli-registration-command.ts
@@ -8,9 +8,9 @@ import {
   getBridgePathFromCommandPath,
   getPosixDirname,
   getWslBridgeMarker,
-  getWslLauncherMarker,
-  quoteShell
+  getWslLauncherMarker
 } from './wsl-cli-scripts'
+import { quotePosixShellDoubleQuotedApostrophe } from '../../shared/shell-argument-quoting'
 
 const MANAGED_MARKER = getWslLauncherMarker()
 const BRIDGE_MANAGED_MARKER = getWslBridgeMarker()
@@ -25,12 +25,13 @@ export function buildWslCliInstallCommand(
     // Why -eu not -euo pipefail: transported via runWslProcess's `sh -s`,
     // and no pipe here needs pipefail -- dash on Ubuntu 20.04 lacks the option.
     'set -eu',
-    `mkdir -p ${quoteShell(status.pathDirectory as string)}`,
-    `mkdir -p ${quoteShell(getPosixDirname(bridgePath))}`,
+    // oxlint-disable-next-line typescript/consistent-type-assertions -- SAFETY: WSL status sets pathDirectory to dirname(commandPath) whenever commandPath is set, and the caller requires commandPath.
+    `mkdir -p ${quotePosixShellDoubleQuotedApostrophe(status.pathDirectory as string)}`,
+    `mkdir -p ${quotePosixShellDoubleQuotedApostrophe(getPosixDirname(bridgePath))}`,
     buildRegistrationLockPrelude(status.commandPath),
-    `command_tmp=${quoteShell(`${status.commandPath}.tmp`)}.$$`,
-    `bridge_path=${quoteShell(bridgePath)}`,
-    `legacy_command_path=${quoteShell(legacyCommandPath)}`,
+    `command_tmp=${quotePosixShellDoubleQuotedApostrophe(`${status.commandPath}.tmp`)}.$$`,
+    `bridge_path=${quotePosixShellDoubleQuotedApostrophe(bridgePath)}`,
+    `legacy_command_path=${quotePosixShellDoubleQuotedApostrophe(legacyCommandPath)}`,
     'bridge_tmp="${bridge_path}.tmp.$$"',
     'bridge_backup="${bridge_tmp}.backup"',
     'bridge_had_original=0',
@@ -40,7 +41,7 @@ export function buildWslCliInstallCommand(
     '  result=$?',
     '  set +e',
     '  if [ "$committed" -ne 1 ]; then',
-    `    if [ "$bridge_had_original" -eq 1 ]; then mv -f "$bridge_backup" ${quoteShell(bridgePath)}; elif [ "$bridge_touched" -eq 1 ]; then rm -f ${quoteShell(bridgePath)}; fi`,
+    `    if [ "$bridge_had_original" -eq 1 ]; then mv -f "$bridge_backup" ${quotePosixShellDoubleQuotedApostrophe(bridgePath)}; elif [ "$bridge_touched" -eq 1 ]; then rm -f ${quotePosixShellDoubleQuotedApostrophe(bridgePath)}; fi`,
     '  fi',
     '  rm -f "$command_tmp" "$bridge_tmp" "$bridge_backup"',
     '  exit "$result"',
@@ -58,10 +59,10 @@ export function buildWslCliInstallCommand(
     'chmod 644 "$bridge_tmp"',
     buildSafeReplaceGuard(status.commandPath, MANAGED_MARKER),
     buildSafeReplaceGuard(bridgePath, BRIDGE_MANAGED_MARKER),
-    `if [ -f ${quoteShell(bridgePath)} ]; then cp -p ${quoteShell(bridgePath)} "$bridge_backup"; bridge_had_original=1; fi`,
-    `mv -f "$bridge_tmp" ${quoteShell(bridgePath)}`,
+    `if [ -f ${quotePosixShellDoubleQuotedApostrophe(bridgePath)} ]; then cp -p ${quotePosixShellDoubleQuotedApostrophe(bridgePath)} "$bridge_backup"; bridge_had_original=1; fi`,
+    `mv -f "$bridge_tmp" ${quotePosixShellDoubleQuotedApostrophe(bridgePath)}`,
     'bridge_touched=1',
-    `mv -f "$command_tmp" ${quoteShell(status.commandPath)}`,
+    `mv -f "$command_tmp" ${quotePosixShellDoubleQuotedApostrophe(status.commandPath)}`,
     'committed=1',
     'rm -f "$bridge_backup"',
     buildManagedLegacyRemoveCommand('"$legacy_command_path"'),
diff --git a/src/main/cli/wsl-cli-scripts.ts b/src/main/cli/wsl-cli-scripts.ts
index 3f4e4156433..44da53fbad9 100644
--- a/src/main/cli/wsl-cli-scripts.ts
+++ b/src/main/cli/wsl-cli-scripts.ts
@@ -1,3 +1,4 @@
+import { quotePosixShellDoubleQuotedApostrophe } from '../../shared/shell-argument-quoting'
 import { quotePowerShellLiteral } from '../../shared/powershell-native-argument'
 
 const MANAGED_MARKER = '# Orca managed WSL CLI launcher'
@@ -16,7 +17,11 @@ export function buildWslLauncher(
   windowsLauncherPath: string,
   bridgePath = '${XDG_DATA_HOME:-$HOME/.local/share}/orca/orca-wsl-bridge.ps1'
 ): string {
-  return buildLauncher(windowsLauncherPath, quoteShell(bridgePath), FIND_INTEROP_POWERSHELL)
+  return buildLauncher(
+    windowsLauncherPath,
+    quotePosixShellDoubleQuotedApostrophe(bridgePath),
+    FIND_INTEROP_POWERSHELL
+  )
 }
 
 /** Launcher that finds its bridge beside itself and PowerShell by Windows path, independent of guest PATH. */
@@ -27,7 +32,7 @@ export function buildColocatedWslLauncher(
   return buildLauncher(
     windowsLauncherPath,
     '"$(dirname -- "$0")/orca-wsl-bridge.ps1"',
-    `ORCA_POWERSHELL=$(wslpath -u ${quoteShell(windowsPowerShellPath)})
+    `ORCA_POWERSHELL=$(wslpath -u ${quotePosixShellDoubleQuotedApostrophe(windowsPowerShellPath)})
 if [ ! -x "$ORCA_POWERSHELL" ]; then
   echo "Orca WSL CLI requires Windows interop and access to $ORCA_POWERSHELL." >&2
   exit 1
@@ -45,7 +50,7 @@ function buildLauncher(
 set -euo pipefail
 ${MANAGED_MARKER}
 # ORCA_WIN_LAUNCHER_B64=${encodedTarget}
-ORCA_WIN_LAUNCHER=${quoteShell(windowsLauncherPath)}
+ORCA_WIN_LAUNCHER=${quotePosixShellDoubleQuotedApostrophe(windowsLauncherPath)}
 ORCA_BRIDGE_PS1=${bridgePathExpression}
 ${resolvePowerShell}
 # Why: a shell can outlive a deleted worktree; keep explicit CLI selectors and
@@ -200,8 +205,8 @@ export function getBridgePathFromCommandPath(commandPath: string): string {
 }
 
 export function buildSafeReplaceGuard(path: string, managedMarker: string): string {
-  const quotedPath = quoteShell(path)
-  const quotedMarker = quoteShell(managedMarker)
+  const quotedPath = quotePosixShellDoubleQuotedApostrophe(path)
+  const quotedMarker = quotePosixShellDoubleQuotedApostrophe(managedMarker)
   return [
     `if [ -L ${quotedPath} ]; then`,
     '  echo "__ORCA_CONFLICT__"',
@@ -218,8 +223,8 @@ export function buildRegistrationLockPrelude(commandPath: string): string {
   // Why: the per-distro queue only serializes one Orca process; flock covers
   // a second install (e.g. stable + nightly) mutating the same distro files.
   return [
-    `if command -v flock >/dev/null 2>&1 && mkdir -p ${quoteShell(lockDir)} 2>/dev/null; then`,
-    `  exec 9>${quoteShell(`${lockDir}/.orca-wsl-cli.lock`)}`,
+    `if command -v flock >/dev/null 2>&1 && mkdir -p ${quotePosixShellDoubleQuotedApostrophe(lockDir)} 2>/dev/null; then`,
+    `  exec 9>${quotePosixShellDoubleQuotedApostrophe(`${lockDir}/.orca-wsl-cli.lock`)}`,
     '  flock -x -w 30 9',
     'fi'
   ].join('\n')
@@ -228,7 +233,7 @@ export function buildRegistrationLockPrelude(commandPath: string): string {
 export function buildManagedLegacyRemoveCommand(quotedLegacyCommandPath: string): string {
   // Why: remove only the Orca-managed pre-rename wrapper; user-owned `orca`
   // commands and symlinks must survive.
-  return `if [ ! -L ${quotedLegacyCommandPath} ] && [ -f ${quotedLegacyCommandPath} ] && grep -Fq ${quoteShell(MANAGED_MARKER)} ${quotedLegacyCommandPath}; then rm -f ${quotedLegacyCommandPath}; fi`
+  return `if [ ! -L ${quotedLegacyCommandPath} ] && [ -f ${quotedLegacyCommandPath} ] && grep -Fq ${quotePosixShellDoubleQuotedApostrophe(MANAGED_MARKER)} ${quotedLegacyCommandPath}; then rm -f ${quotedLegacyCommandPath}; fi`
 }
 
 export function buildSafeRemoveCommand(commandPath: string, legacyCommandPath?: string): string {
@@ -240,10 +245,12 @@ export function buildSafeRemoveCommand(commandPath: string, legacyCommandPath?:
     buildRegistrationLockPrelude(commandPath),
     buildSafeReplaceGuard(commandPath, MANAGED_MARKER),
     buildSafeReplaceGuard(bridgePath, BRIDGE_MANAGED_MARKER),
-    `rm -f ${quoteShell(commandPath)} ${quoteShell(bridgePath)}`,
+    `rm -f ${quotePosixShellDoubleQuotedApostrophe(commandPath)} ${quotePosixShellDoubleQuotedApostrophe(bridgePath)}`,
     // Why: leaving a managed legacy `orca` behind lets startup reconciliation
     // re-adopt it as opt-in proof and silently undo this removal.
-    ...(legacyCommandPath ? [buildManagedLegacyRemoveCommand(quoteShell(legacyCommandPath))] : [])
+    ...(legacyCommandPath
+      ? [buildManagedLegacyRemoveCommand(quotePosixShellDoubleQuotedApostrophe(legacyCommandPath))]
+      : [])
   ].join('\n')
 }
 
@@ -272,7 +279,3 @@ export function getWslLauncherMarker(): string {
 export function getWslBridgeMarker(): string {
   return BRIDGE_MANAGED_MARKER
 }
-
-export function quoteShell(value: string): string {
-  return `'${value.replaceAll("'", `'"'"'`)}'`
-}
diff --git a/src/main/cli/wsl-cli-status.ts b/src/main/cli/wsl-cli-status.ts
index e8e9a0519ca..62f33dbd2ee 100644
--- a/src/main/cli/wsl-cli-status.ts
+++ b/src/main/cli/wsl-cli-status.ts
@@ -1,5 +1,6 @@
 import type { CliInstallStatus } from '../../shared/cli-install-types'
-import { getBridgePathFromCommandPath, getPosixDirname, quoteShell } from './wsl-cli-scripts'
+import { getBridgePathFromCommandPath, getPosixDirname } from './wsl-cli-scripts'
+import { quotePosixShellDoubleQuotedApostrophe } from '../../shared/shell-argument-quoting'
 
 const WSL_COMMAND_NAME = 'orca-ide'
 
@@ -47,14 +48,14 @@ export async function readWslCliCommandFile(
   const output = await run(
     distro,
     [
-      `if [ -L ${quoteShell(commandPath)} ]; then`,
+      `if [ -L ${quotePosixShellDoubleQuotedApostrophe(commandPath)} ]; then`,
       '  printf __ORCA_NOT_FILE__',
-      `elif [ ! -e ${quoteShell(commandPath)} ]; then`,
+      `elif [ ! -e ${quotePosixShellDoubleQuotedApostrophe(commandPath)} ]; then`,
       '  printf __ORCA_MISSING__',
-      `elif [ ! -f ${quoteShell(commandPath)} ]; then`,
+      `elif [ ! -f ${quotePosixShellDoubleQuotedApostrophe(commandPath)} ]; then`,
       '  printf __ORCA_NOT_FILE__',
       'else',
-      `  cat ${quoteShell(commandPath)}`,
+      `  cat ${quotePosixShellDoubleQuotedApostrophe(commandPath)}`,
       'fi'
     ].join('\n'),
     { loginPath: 'none' }
@@ -208,7 +209,7 @@ async function readPathConfigured(
   try {
     const output = await run(
       distro,
-      `case ":$PATH:" in *:${quoteShell(pathDirectory)}:*) printf yes ;; *) printf no ;; esac`,
+      `case ":$PATH:" in *:${quotePosixShellDoubleQuotedApostrophe(pathDirectory)}:*) printf yes ;; *) printf no ;; esac`,
       { loginPath: 'preferred' }
     )
     return output.trim() === 'yes'
diff --git a/src/main/codex/codex-hook-definition.ts b/src/main/codex/codex-hook-definition.ts
index d3ced21c96f..9f44b948b49 100644
--- a/src/main/codex/codex-hook-definition.ts
+++ b/src/main/codex/codex-hook-definition.ts
@@ -1,3 +1,4 @@
+import { quotePosixShell } from '../../shared/shell-argument-quoting'
 import { join } from 'node:path'
 import {
   buildManagedCommandHook,
@@ -138,7 +139,7 @@ export function getCodexManagedHookInstallMaterial(): CodexManagedHookInstallMat
 }
 
 export function wrapReadablePosixHookCommand(scriptPath: string): string {
-  const quoted = `'${scriptPath.replaceAll("'", "'\\''")}'`
+  const quoted = quotePosixShell(scriptPath)
   // Why: WSL hooks are written from Windows over UNC where the exec bit is unreliable; a missing script must still own stdin.
   return `if [ -f ${quoted} ] && [ -r ${quoted} ]; then /bin/sh ${quoted}; else ${POSIX_HOOK_STDIN_DRAIN_COMMAND}; fi`
 }
diff --git a/src/main/external-editor-launch.ts b/src/main/external-editor-launch.ts
index 5b5d41cdd26..c07909a64d4 100644
--- a/src/main/external-editor-launch.ts
+++ b/src/main/external-editor-launch.ts
@@ -1,3 +1,4 @@
+import { quotePosixShellUnlessPlain } from '../shared/shell-argument-quoting'
 import { spawn, type ChildProcess } from 'node:child_process'
 import { spawnProcess } from '@orca/process-host'
 import { existsSync } from 'node:fs'
@@ -43,13 +44,6 @@ export type ExternalEditorLaunchSpec =
   | ExternalEditorExecutableLaunchSpec
   | ExternalEditorShellLaunchSpec
 
-function escapePosixPathForShell(pathValue: string): string {
-  if (/^[a-zA-Z0-9_./@:-]+$/.test(pathValue)) {
-    return pathValue
-  }
-  return `'${pathValue.replace(/'/g, "'\\''")}'`
-}
-
 function escapeWindowsPathForShell(pathValue: string): string {
   return /^[a-zA-Z0-9_./@:\\-]+$/.test(pathValue) ? pathValue : `"${pathValue}"`
 }
@@ -57,7 +51,7 @@ function escapeWindowsPathForShell(pathValue: string): string {
 function escapePathForShell(pathValue: string, platform: NodeJS.Platform): string {
   return platform === 'win32'
     ? escapeWindowsPathForShell(pathValue)
-    : escapePosixPathForShell(pathValue)
+    : quotePosixShellUnlessPlain(pathValue)
 }
 
 function isWindowsExecutablePath(command: string): boolean {
diff --git a/src/main/ipc/preflight-command-exec.ts b/src/main/ipc/preflight-command-exec.ts
index 2197f8e9c4f..d97b3bc49c0 100644
--- a/src/main/ipc/preflight-command-exec.ts
+++ b/src/main/ipc/preflight-command-exec.ts
@@ -1,3 +1,4 @@
+import { quotePosixShell } from '../../shared/shell-argument-quoting'
 import { execFile } from 'node:child_process'
 import path from 'node:path'
 import { homedir } from 'node:os'
@@ -20,10 +21,6 @@ const WSL_COMMAND_PATH_SENTINEL = '__ORCA_PREFLIGHT_COMMAND_PATH__'
 
 export type PreflightCommandResult = { stdout: string; stderr: string }
 
-export function shellQuote(value: string): string {
-  return `'${value.replace(/'/g, "'\\''")}'`
-}
-
 async function withPreflightTimeout<T>(
   command: string,
   commandPromise: Promise<T>,
@@ -226,7 +223,7 @@ export async function isCommandAvailable(
     return (await findRunnableLocalCommand(command)).status === 'available'
   }
   try {
-    await execCommandInWslOrThrow(wslTarget, `${shellQuote(command)} --version`)
+    await execCommandInWslOrThrow(wslTarget, `${quotePosixShell(command)} --version`)
     return true
   } catch {
     return false
diff --git a/src/main/ipc/preflight-provider-command-selection.test.ts b/src/main/ipc/preflight-provider-command-selection.test.ts
index a51ac4a886c..f7b1fcd5376 100644
--- a/src/main/ipc/preflight-provider-command-selection.test.ts
+++ b/src/main/ipc/preflight-provider-command-selection.test.ts
@@ -9,9 +9,9 @@ import { execFileCaptureToTermination } from '../git/command-runner/exec-file-ca
 import { beginLocalCommandSelection, resolveSelectedLocalCommand } from './command-path-resolver'
 import {
   execLocalPreflightCommandOrThrow,
-  findRunnableLocalCommand,
-  shellQuote
+  findRunnableLocalCommand
 } from './preflight-command-exec'
+import { quotePosixShell } from '../../shared/shell-argument-quoting'
 
 vi.mock('../../shared/system-cli-install-dirs', () => ({
   getSystemCliInstallDirectories: (_platform: NodeJS.Platform, home: string) => [
@@ -32,7 +32,7 @@ async function fixtureCli(
   const binary = path.join(dir, cli)
   await writeFile(
     binary,
-    `#!/bin/sh\nprintf '%s\\n' "$*" >> ${shellQuote(`${binary}-calls`)}\n${body}`,
+    `#!/bin/sh\nprintf '%s\\n' "$*" >> ${quotePosixShell(`${binary}-calls`)}\n${body}`,
     { mode: 0o755 }
   )
   return binary
diff --git a/src/main/ipc/preflight-runnable-local-cli.test.ts b/src/main/ipc/preflight-runnable-local-cli.test.ts
index 5f960f0cee7..64ea0d31398 100644
--- a/src/main/ipc/preflight-runnable-local-cli.test.ts
+++ b/src/main/ipc/preflight-runnable-local-cli.test.ts
@@ -7,9 +7,9 @@ import {
   execLocalPreflightCommandOrThrow,
   findRunnableLocalCommand,
   isCommandAvailable,
-  isCommandOnPath,
-  shellQuote
+  isCommandOnPath
 } from './preflight-command-exec'
+import { quotePosixShell } from '../../shared/shell-argument-quoting'
 
 const COMMAND = 'orca-22975-gh'
 const BROKEN_SHIM = 'echo broken-shim >&2\nexit 126\n'
@@ -20,7 +20,7 @@ async function cliInDirectory(label: string, body = 'echo gh-version-fixture\n')
   await mkdir(dir, { recursive: true })
   await writeFile(
     path.join(dir, COMMAND),
-    `#!/bin/sh\nprintf '%s\\n' "$@" >> ${shellQuote(path.join(dir, 'argv.txt'))}\n${body}`,
+    `#!/bin/sh\nprintf '%s\\n' "$@" >> ${quotePosixShell(path.join(dir, 'argv.txt'))}\n${body}`,
     { mode: 0o755 }
   )
   return dir
@@ -188,8 +188,11 @@ describe.skipIf(process.platform === 'win32')(
 
     it('recovers a working copy after a real launcher timeout', async () => {
       const marker = path.join(root, 'descendant-terminated')
-      const childScript = `trap ${shellQuote(`printf terminated > ${shellQuote(marker)}; exit 0`)} TERM\n/bin/sleep 30 &\nwait\n`
-      const hung = await cliInDirectory('hung', `/bin/sh -c ${shellQuote(childScript)} &\nwait\n`)
+      const childScript = `trap ${quotePosixShell(`printf terminated > ${quotePosixShell(marker)}; exit 0`)} TERM\n/bin/sleep 30 &\nwait\n`
+      const hung = await cliInDirectory(
+        'hung',
+        `/bin/sh -c ${quotePosixShell(childScript)} &\nwait\n`
+      )
       const good = await cliInDirectory('good')
       vi.stubEnv('PATH', [hung, good].join(path.delimiter))
 
diff --git a/src/main/ipc/preflight-wsl-agent-detection.ts b/src/main/ipc/preflight-wsl-agent-detection.ts
index a0e843b43b1..214ec0a10e9 100644
--- a/src/main/ipc/preflight-wsl-agent-detection.ts
+++ b/src/main/ipc/preflight-wsl-agent-detection.ts
@@ -1,3 +1,4 @@
+import { quotePosixShell } from '../../shared/shell-argument-quoting'
 import path from 'node:path'
 import { buildPosixFallbackPathPrelude } from '../../shared/posix-version-manager-bin-dirs'
 import { buildPosixCommandPathLookupScript } from '../../shared/posix-command-path-lookup'
@@ -19,7 +20,7 @@ export async function detectWslCommandsOnPath(
     return new Set()
   }
 
-  const commandList = uniqueCommands.map(shellQuote).join(' ')
+  const commandList = uniqueCommands.map(quotePosixShell).join(' ')
   const lookupScript = buildPosixCommandPathLookupScript(
     { kind: 'shell-variable', name: 'cmd' },
     // Skip Windows mounts DURING the walk, not after it: WSL appends the
@@ -65,10 +66,6 @@ export async function detectWslCommandsOnPath(
   }
 }
 
-function shellQuote(value: string): string {
-  return `'${value.replace(/'/g, "'\\''")}'`
-}
-
 function parseWslDetectedCommands(stdout: string): Set<string> {
   const found = new Set<string>()
   for (const rawLine of stdout.split(/\r?\n/)) {
diff --git a/src/main/linux-package-install-command.test.ts b/src/main/linux-package-install-command.test.ts
index c76c062bbce..5cc86cef8cd 100644
--- a/src/main/linux-package-install-command.test.ts
+++ b/src/main/linux-package-install-command.test.ts
@@ -1,4 +1,5 @@
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+import { quotePosixShellDoubleQuotedApostrophe } from '../shared/shell-argument-quoting'
 
 const { statSyncMock } = vi.hoisted(() => ({ statSyncMock: vi.fn() }))
 
@@ -34,38 +35,36 @@ afterEach(() => {
   vi.unstubAllEnvs()
 })
 
-describe('quoteForPosixShell', () => {
-  it('wraps plain values in single quotes', async () => {
-    const { quoteForPosixShell } = await loadCommandModule()
-    expect(quoteForPosixShell('/tmp/orca.deb')).toBe("'/tmp/orca.deb'")
+describe('quotePosixShellDoubleQuotedApostrophe', () => {
+  it('wraps plain values in single quotes', () => {
+    expect(quotePosixShellDoubleQuotedApostrophe('/tmp/orca.deb')).toBe("'/tmp/orca.deb'")
   })
 
-  it('quotes spaces', async () => {
-    const { quoteForPosixShell } = await loadCommandModule()
-    expect(quoteForPosixShell('/tmp/Orca Setup.deb')).toBe("'/tmp/Orca Setup.deb'")
+  it('quotes spaces', () => {
+    expect(quotePosixShellDoubleQuotedApostrophe('/tmp/Orca Setup.deb')).toBe(
+      "'/tmp/Orca Setup.deb'"
+    )
   })
 
-  it('neutralizes expansion, command substitution, separators, and double quotes', async () => {
-    const { quoteForPosixShell } = await loadCommandModule()
-    expect(quoteForPosixShell('/tmp/$HOME.deb')).toBe("'/tmp/$HOME.deb'")
-    expect(quoteForPosixShell('/tmp/`id`.deb')).toBe("'/tmp/`id`.deb'")
-    expect(quoteForPosixShell('/tmp/a;rm -rf ~.deb')).toBe("'/tmp/a;rm -rf ~.deb'")
-    expect(quoteForPosixShell('/tmp/"quoted".deb')).toBe('\'/tmp/"quoted".deb\'')
+  it('neutralizes expansion, command substitution, separators, and double quotes', () => {
+    expect(quotePosixShellDoubleQuotedApostrophe('/tmp/$HOME.deb')).toBe("'/tmp/$HOME.deb'")
+    expect(quotePosixShellDoubleQuotedApostrophe('/tmp/`id`.deb')).toBe("'/tmp/`id`.deb'")
+    expect(quotePosixShellDoubleQuotedApostrophe('/tmp/a;rm -rf ~.deb')).toBe(
+      "'/tmp/a;rm -rf ~.deb'"
+    )
+    expect(quotePosixShellDoubleQuotedApostrophe('/tmp/"quoted".deb')).toBe('\'/tmp/"quoted".deb\'')
   })
 
-  it('closes and reopens the quote around a literal single quote', async () => {
-    const { quoteForPosixShell } = await loadCommandModule()
-    expect(quoteForPosixShell("/tmp/it's.deb")).toBe(`'/tmp/it'"'"'s.deb'`)
+  it('closes and reopens the quote around a literal single quote', () => {
+    expect(quotePosixShellDoubleQuotedApostrophe("/tmp/it's.deb")).toBe(`'/tmp/it'"'"'s.deb'`)
   })
 
-  it('escapes every single quote in a value', async () => {
-    const { quoteForPosixShell } = await loadCommandModule()
-    expect(quoteForPosixShell("'; rm -rf /; '")).toBe(`''"'"'; rm -rf /; '"'"''`)
+  it('escapes every single quote in a value', () => {
+    expect(quotePosixShellDoubleQuotedApostrophe("'; rm -rf /; '")).toBe(`''"'"'; rm -rf /; '"'"''`)
   })
 
-  it('quotes an empty value', async () => {
-    const { quoteForPosixShell } = await loadCommandModule()
-    expect(quoteForPosixShell('')).toBe("''")
+  it('quotes an empty value', () => {
+    expect(quotePosixShellDoubleQuotedApostrophe('')).toBe("''")
   })
 })
 
diff --git a/src/main/linux-package-install-command.ts b/src/main/linux-package-install-command.ts
index 728ffcd1d92..b9c9191b2de 100644
--- a/src/main/linux-package-install-command.ts
+++ b/src/main/linux-package-install-command.ts
@@ -1,3 +1,4 @@
+import { quotePosixShellDoubleQuotedApostrophe } from '../shared/shell-argument-quoting'
 import { statSync } from 'node:fs'
 import path from 'node:path'
 import type { LinuxRootPackageType } from '../shared/update-status-types'
@@ -26,11 +27,6 @@ export type LinuxPackageInstallCommandResult =
   | { ok: true; command: string }
   | { ok: false; reason: 'no-sudo' | 'no-package-manager' | 'invalid-package-path' }
 
-/** POSIX single-quoting: the only metacharacter left is `'`, closed and re-opened around a literal. */
-export function quoteForPosixShell(value: string): string {
-  return `'${value.split("'").join(`'"'"'`)}'`
-}
-
 /**
  * Resolves an executable strictly from the trusted system directories. A symlink inside those
  * directories is fine — its target is what `statSync` checks — but nothing outside them is consulted
@@ -86,7 +82,12 @@ export function buildLinuxPackageInstallCommand(
       continue
     }
     // No -y/--noconfirm: the user must see and confirm the privileged transaction.
-    const tokens = [sudoPath, managerPath, ...candidate.args, quoteForPosixShell(packagePath)]
+    const tokens = [
+      sudoPath,
+      managerPath,
+      ...candidate.args,
+      quotePosixShellDoubleQuotedApostrophe(packagePath)
+    ]
     return { ok: true, command: tokens.join(' ') }
   }
   return { ok: false, reason: 'no-package-manager' }
diff --git a/src/main/preflight/agent-detection.ts b/src/main/preflight/agent-detection.ts
index 56730c6be9e..fc5a27f52f0 100644
--- a/src/main/preflight/agent-detection.ts
+++ b/src/main/preflight/agent-detection.ts
@@ -27,9 +27,9 @@ import {
   execCommandInWslOrThrow,
   execLocalPreflightCommandOrThrow,
   findRunnableLocalCommand,
-  isCommandAvailable,
-  shellQuote
+  isCommandAvailable
 } from '../ipc/preflight-command-exec'
+import { quotePosixShell } from '../../shared/shell-argument-quoting'
 import {
   detectRemoteWindowsTerminalCapabilities,
   type RemoteWindowsTerminalCapabilities
@@ -220,7 +220,7 @@ export async function refreshShellPathAndDetectAgents(
 async function isGhAuthenticated(probe: CommandRuntime): Promise<boolean> {
   try {
     await (probe.wslTarget
-      ? execCommandInWslOrThrow(probe.wslTarget, `${shellQuote('gh')} auth status`)
+      ? execCommandInWslOrThrow(probe.wslTarget, `${quotePosixShell('gh')} auth status`)
       : execLocalPreflightCommandOrThrow(probe.binary ?? 'gh', ['auth', 'status']))
     // Why: for plain-text `gh auth status`, exit 0 means gh did not detect any
     // authentication issues for the checked hosts/accounts.
@@ -241,7 +241,7 @@ async function isGhAuthenticated(probe: CommandRuntime): Promise<boolean> {
 async function isGlabAuthenticated(probe: CommandRuntime): Promise<boolean> {
   try {
     await (probe.wslTarget
-      ? execCommandInWslOrThrow(probe.wslTarget, `${shellQuote('glab')} auth status`)
+      ? execCommandInWslOrThrow(probe.wslTarget, `${quotePosixShell('glab')} auth status`)
       : execLocalPreflightCommandOrThrow(probe.binary ?? 'glab', ['auth', 'status']))
     return true
   } catch (error) {
diff --git a/src/main/rate-limits/codex-fetcher.ts b/src/main/rate-limits/codex-fetcher.ts
index 8892a275cf6..7a5649dbc73 100644
--- a/src/main/rate-limits/codex-fetcher.ts
+++ b/src/main/rate-limits/codex-fetcher.ts
@@ -33,7 +33,7 @@ import {
   getHiddenRateLimitWslCwdSetupCommands,
   resolveHiddenRateLimitPtyCwd
 } from './hidden-rate-limit-pty-cwd'
-import { quoteHiddenRateLimitShellValue } from './hidden-rate-limit-shell'
+import { quotePosixShell } from '../../shared/shell-argument-quoting'
 import { resolveWslInteropSpawnCwd } from '../wsl-interop-spawn-directory'
 
 const RPC_TIMEOUT_MS = 10_000
@@ -53,9 +53,9 @@ function buildWslCodexCommand(
   }
   const setupCommands = [
     ...getHiddenRateLimitWslCwdSetupCommands(),
-    `export CODEX_HOME=${quoteHiddenRateLimitShellValue(wslInfo.linuxPath)}`
+    `export CODEX_HOME=${quotePosixShell(wslInfo.linuxPath)}`
   ].join(' && ')
-  const execSuffix = `${args.map(quoteHiddenRateLimitShellValue).join(' ')} <&3 >&4 3<&- 4>&-`
+  const execSuffix = `${args.map(quotePosixShell).join(' ')} <&3 >&4 3<&- 4>&-`
   const loginShellCommand = buildWslLoginShellCommand(
     [setupCommands, `exec codex ${execSuffix}`].join(' && ')
   )
diff --git a/src/main/rate-limits/hidden-rate-limit-shell.ts b/src/main/rate-limits/hidden-rate-limit-shell.ts
deleted file mode 100644
index 261f4519926..00000000000
--- a/src/main/rate-limits/hidden-rate-limit-shell.ts
+++ /dev/null
@@ -1,3 +0,0 @@
-export function quoteHiddenRateLimitShellValue(value: string): string {
-  return `'${value.replace(/'/g, "'\\''")}'`
-}
diff --git a/src/main/runtime/orchestration/setup-completion-signal.ts b/src/main/runtime/orchestration/setup-completion-signal.ts
index 15c74d2294e..255423dd534 100644
--- a/src/main/runtime/orchestration/setup-completion-signal.ts
+++ b/src/main/runtime/orchestration/setup-completion-signal.ts
@@ -1,3 +1,4 @@
+import { quotePosixShell } from '../../../shared/shell-argument-quoting'
 import {
   resolveSetupRunnerCommand,
   type SetupRunnerCommandPlatform,
@@ -42,7 +43,7 @@ export function buildObservedSetupCommand(
     `printf '\\n${completionPrefix(completionToken)}%s\\n' "$status"`,
     'exit "$status"'
   ].join('; ')
-  return { command: `bash -lc ${quotePosixArg(script)}` }
+  return { command: `bash -lc ${quotePosixShell(script)}` }
 }
 
 export function createSetupCompletionScanner(
@@ -78,7 +79,3 @@ export function createSetupCompletionScanner(
 function completionPrefix(completionToken: string): string {
   return `${SETUP_COMPLETION_PREFIX}${completionToken}:`
 }
-
-function quotePosixArg(value: string): string {
-  return `'${value.replace(/'/g, `'\\''`)}'`
-}
diff --git a/src/main/ssh/ssh-remote-directory-browse.ts b/src/main/ssh/ssh-remote-directory-browse.ts
index ba3748ca8f5..8abc6997334 100644
--- a/src/main/ssh/ssh-remote-directory-browse.ts
+++ b/src/main/ssh/ssh-remote-directory-browse.ts
@@ -1,3 +1,4 @@
+import { quotePosixShell } from '../../shared/shell-argument-quoting'
 import type { SshConnectionManager } from './connection/ssh-connection-manager'
 import type { SshExecOptions } from './connection/ssh-exec-options'
 import { powerShellCommand } from './ssh-remote-powershell'
@@ -266,13 +267,9 @@ function shellEscape(s: string): string {
     return '"$HOME"'
   }
   if (s.startsWith('~/')) {
-    return `"$HOME"/${shellEscapeRaw(s.slice(2))}`
+    return `"$HOME"/${quotePosixShell(s.slice(2))}`
   }
-  return shellEscapeRaw(s)
-}
-
-function shellEscapeRaw(s: string): string {
-  return `'${s.replace(/'/g, "'\\''")}'`
+  return quotePosixShell(s)
 }
 
 function powerShellPathExpression(s: string): string {
diff --git a/src/renderer/src/components/editor/ipynb-kernel-setup-commands.ts b/src/renderer/src/components/editor/ipynb-kernel-setup-commands.ts
index dd15a8586c5..39500c3dcba 100644
--- a/src/renderer/src/components/editor/ipynb-kernel-setup-commands.ts
+++ b/src/renderer/src/components/editor/ipynb-kernel-setup-commands.ts
@@ -1,10 +1,11 @@
+import { quotePosixShell } from '../../../../shared/shell-argument-quoting'
 import { getRendererAppPlatform } from '@/lib/renderer-app-platform'
 import { venvInterpreterSegments } from '../../../../shared/notebook-venv-location'
 import { quotePowerShellLiteral } from '../../../../shared/powershell-native-argument'
 
 /** Quotes a path for a shell; single quotes are literal in POSIX shells and PowerShell. */
 function shellQuote(path: string, windows: boolean): string {
-  return windows ? quotePowerShellLiteral(path) : `'${path.replaceAll("'", "'\\''")}'`
+  return windows ? quotePowerShellLiteral(path) : quotePosixShell(path)
 }
 
 /** PowerShell runs a quoted program path only through `&`. */
diff --git a/src/renderer/src/components/terminal-pane/pane-helpers.ts b/src/renderer/src/components/terminal-pane/pane-helpers.ts
index 0de7278022c..9104b091e59 100644
--- a/src/renderer/src/components/terminal-pane/pane-helpers.ts
+++ b/src/renderer/src/components/terminal-pane/pane-helpers.ts
@@ -1,3 +1,4 @@
+import { quotePosixShellUnlessPlain } from '../../../../shared/shell-argument-quoting'
 import type { PaneManager } from '@/lib/pane-manager/pane-manager'
 import { focusPanePreservingOverlays } from '@/lib/pane-manager/pane-overlay-focus'
 
@@ -75,9 +76,5 @@ export function shellEscapePath(path: string, targetShell: 'posix' | 'windows'):
     return /^[a-zA-Z0-9_./@:\\-]+$/.test(path) ? path : `"${path}"`
   }
 
-  if (/^[a-zA-Z0-9_./@:-]+$/.test(path)) {
-    return path
-  }
-
-  return `'${path.replace(/'/g, "'\\''")}'`
+  return quotePosixShellUnlessPlain(path)
 }
diff --git a/src/shared/ai-vault-resume-command.ts b/src/shared/ai-vault-resume-command.ts
index 2c3dcdf6f26..7a159ef554f 100644
--- a/src/shared/ai-vault-resume-command.ts
+++ b/src/shared/ai-vault-resume-command.ts
@@ -1,6 +1,7 @@
 // Resume-command construction for Agent Session History rows: turns a scanned
 // session into the shell line that re-enters it, quoted for the target platform
 // and (when known) the live tab's shell.
+import { quoteCmdDoubleQuoted } from './shell-argument-quoting'
 import {
   isAntigravityReferenceSession,
   antigravityTranscriptReferencePrompt
@@ -42,7 +43,7 @@ export function buildAiVaultResumeCommand(args: {
       : sessionId
   const sessionArg =
     shell === 'cmd'
-      ? quoteWindowsCmdArg(resumeTarget)
+      ? quoteCmdDoubleQuoted(resumeTarget)
       : shell
         ? quoteStartupArg(resumeTarget, shell)
         : quoteShellArg(resumeTarget, platform)
@@ -118,15 +119,15 @@ export function buildAiVaultResumeShellCommand(args: {
   if (platform === 'win32' && shell === 'cmd') {
     // Why: an interactive cmd splits the doubled quotes required by a nested
     // `cmd /s /c` wrapper, so queued commands must use direct cmd syntax.
-    return `${clearPrefix}${cwd ? `cd /d ${quoteWindowsCmdArg(cwd)} && ${resumeCommand}` : resumeCommand}`
+    return `${clearPrefix}${cwd ? `cd /d ${quoteCmdDoubleQuoted(cwd)} && ${resumeCommand}` : resumeCommand}`
   }
   if (!cwd) {
     return `${clearPrefix}${resumeCommand}`
   }
 
   if (platform === 'win32') {
-    const inner = `${clearPrefix}cd /d ${quoteWindowsCmdArg(cwd)} && ${resumeCommand}`
-    return `cmd /d /s /c ${quoteWindowsCmdArg(inner)}`
+    const inner = `${clearPrefix}cd /d ${quoteCmdDoubleQuoted(cwd)} && ${resumeCommand}`
+    return `cmd /d /s /c ${quoteCmdDoubleQuoted(inner)}`
   }
 
   return `cd ${quoteResumeArg(cwd, platform, shell)} && ${resumeCommand}`
@@ -263,7 +264,7 @@ function codexHomeEnvPrefix(
     return ''
   }
   if (platform === 'win32') {
-    return `set ${quoteWindowsCmdArg(`CODEX_HOME=${codexHome}`)} && `
+    return `set ${quoteCmdDoubleQuoted(`CODEX_HOME=${codexHome}`)} && `
   }
   // fish accepts the `NAME=value cmd` prefix (3.1+), but not sh's quoting.
   return `CODEX_HOME=${quoteResumeArg(codexHome, platform, shell)} `
@@ -284,9 +285,5 @@ function quoteResumeArg(
  *  `quoteStartupArg` keeps one spelling regardless of whether a caller happened
  *  to pass a shell. */
 function quoteShellArg(value: string, platform: NodeJS.Platform): string {
-  return platform === 'win32' ? quoteWindowsCmdArg(value) : quoteStartupArg(value, 'posix')
-}
-
-function quoteWindowsCmdArg(value: string): string {
-  return `"${value.replace(/"/g, '""')}"`
+  return platform === 'win32' ? quoteCmdDoubleQuoted(value) : quoteStartupArg(value, 'posix')
 }
diff --git a/src/shared/ephemeral-vm-recipe-process.ts b/src/shared/ephemeral-vm-recipe-process.ts
index 1557de74ca4..ed84c4d9932 100644
--- a/src/shared/ephemeral-vm-recipe-process.ts
+++ b/src/shared/ephemeral-vm-recipe-process.ts
@@ -1,3 +1,4 @@
+import { quoteCmdDoubleQuoted, quotePosixShell } from './shell-argument-quoting'
 import { spawn, type ChildProcessWithoutNullStreams } from 'node:child_process'
 import { StringDecoder } from 'node:string_decoder'
 import type { EphemeralVmRecipeContext } from './ephemeral-vm-recipe-runner'
@@ -20,9 +21,9 @@ export function quoteShellToken(value: string): string {
     // Inside cmd.exe double quotes, `^` is literal; an embedded `"` is escaped
     // by doubling it. This token is only displayed for manual cleanup, so it
     // must be valid when pasted into cmd.exe.
-    return `"${value.replace(/"/g, '""')}"`
+    return quoteCmdDoubleQuoted(value)
   }
-  return `'${value.replace(/'/g, `'\\''`)}'`
+  return quotePosixShell(value)
 }
 
 export async function runRecipeCommand(args: {
diff --git a/src/shared/posix-command-path-lookup.ts b/src/shared/posix-command-path-lookup.ts
index ea09ca83e2f..5e5c6c598fd 100644
--- a/src/shared/posix-command-path-lookup.ts
+++ b/src/shared/posix-command-path-lookup.ts
@@ -1,3 +1,5 @@
+import { quotePosixShell } from './shell-argument-quoting'
+
 export type PosixCommandPathLookupTarget =
   | { kind: 'literal'; value: string }
   | { kind: 'shell-variable'; name: string }
@@ -100,14 +102,10 @@ export function buildPosixCommandPathLookupScript(
 
 function buildCommandAssignment(target: PosixCommandPathLookupTarget): string {
   if (target.kind === 'literal') {
-    return shellQuote(target.value)
+    return quotePosixShell(target.value)
   }
   if (!SHELL_VARIABLE_NAME_PATTERN.test(target.name)) {
     throw new Error(`Invalid shell variable name: ${target.name}`)
   }
   return `\${${target.name}-}`
 }
-
-function shellQuote(value: string): string {
-  return `'${value.replace(/'/g, "'\\''")}'`
-}
diff --git a/src/shared/setup-agent-sequencing.ts b/src/shared/setup-agent-sequencing.ts
index 31c68e2da76..c5d1a7ba98c 100644
--- a/src/shared/setup-agent-sequencing.ts
+++ b/src/shared/setup-agent-sequencing.ts
@@ -1,3 +1,4 @@
+import { quotePosixShellUnlessPlainNoAt } from './shell-argument-quoting'
 import { encodePowerShellCommand } from './powershell-command-encoding'
 import { getPosixCodexShellLaunchPreflight } from './codex-shell-function'
 import { getPosixClaudeShellFunction } from './claude-shell-function'
@@ -89,9 +90,9 @@ export function createSequencedSetupAgentCommands(args: {
 }
 
 function buildPosixSetupCommand(setupCommand: string, markerPath: string, nonce: string): string {
-  const marker = quotePosixArg(markerPath)
-  const tmp = quotePosixArg(`${markerPath}.tmp`)
-  const nonceValue = quotePosixArg(nonce)
+  const marker = quotePosixShellUnlessPlainNoAt(markerPath)
+  const tmp = quotePosixShellUnlessPlainNoAt(`${markerPath}.tmp`)
+  const nonceValue = quotePosixShellUnlessPlainNoAt(nonce)
 
   const script = [
     `rm -f ${marker} ${tmp} 2>/dev/null`,
@@ -102,7 +103,7 @@ function buildPosixSetupCommand(setupCommand: string, markerPath: string, nonce:
     'exit "$status"'
   ].join('; ')
 
-  return `bash -lc ${quotePosixArg(script)}`
+  return `bash -lc ${quotePosixShellUnlessPlainNoAt(script)}`
 }
 
 function buildPosixStartupScript(
@@ -111,9 +112,9 @@ function buildPosixStartupScript(
   nonce: string,
   waitTimeoutSeconds: number
 ): string {
-  const marker = quotePosixArg(markerPath)
-  const tmp = quotePosixArg(`${markerPath}.tmp`)
-  const nonceValue = quotePosixArg(nonce)
+  const marker = quotePosixShellUnlessPlainNoAt(markerPath)
+  const tmp = quotePosixShellUnlessPlainNoAt(`${markerPath}.tmp`)
+  const nonceValue = quotePosixShellUnlessPlainNoAt(nonce)
   const timeout = Math.max(1, Math.floor(waitTimeoutSeconds))
   const startupSuccessCommand = buildPosixStartupSuccessCommand(startupCommand)
   // Why: the PTY launch path feeds this command through an interactive shell,
@@ -131,7 +132,7 @@ function buildPosixStartupScript(
     // "Waiting for setup..." as the pane's last line forever.
     // Why here and not first: setup may be what puts codex on PATH, and this
     // `bash -lc` never reads Orca's shell wrapper, so it defines the function itself.
-    `if [ "$status" = "0" ]; then echo ${quotePosixArg(SETUP_COMPLETE_MESSAGE)} >&2;\n${getPosixCodexShellLaunchPreflight() + getPosixClaudeShellFunction()}if [ -n "\${${SETUP_AGENT_SEQUENCE_STARTUP_COMMAND_ENV}:-}" ]; then eval "\$${SETUP_AGENT_SEQUENCE_STARTUP_COMMAND_ENV}"; exit "$?"; else ${startupSuccessCommand}; fi; fi;`,
+    `if [ "$status" = "0" ]; then echo ${quotePosixShellUnlessPlainNoAt(SETUP_COMPLETE_MESSAGE)} >&2;\n${getPosixCodexShellLaunchPreflight() + getPosixClaudeShellFunction()}if [ -n "\${${SETUP_AGENT_SEQUENCE_STARTUP_COMMAND_ENV}:-}" ]; then eval "\$${SETUP_AGENT_SEQUENCE_STARTUP_COMMAND_ENV}"; exit "$?"; else ${startupSuccessCommand}; fi; fi;`,
     'echo "Setup failed; skipping agent startup." >&2;',
     'exit "${status:-1}";',
     'fi;',
@@ -152,7 +153,7 @@ function buildPosixStartupSuccessCommand(startupCommand: string): string {
     hasUnquotedPosixCommandSeparator(startupCommand) ||
     hasLeadingPosixEnvAssignment(startupCommand)
   ) {
-    return `eval ${quotePosixArg(startupCommand)}; exit "$?"`
+    return `eval ${quotePosixShellUnlessPlainNoAt(startupCommand)}; exit "$?"`
   }
   return `exec ${startupCommand}`
 }
@@ -297,10 +298,3 @@ function buildWindowsStartupCommand(
 function encodePowerShellInvocation(script: string): string {
   return `powershell.exe -NoProfile -NonInteractive -EncodedCommand ${encodePowerShellCommand(script)}`
 }
-
-function quotePosixArg(value: string): string {
-  if (/^[A-Za-z0-9_./:-]+$/.test(value)) {
-    return value
-  }
-  return `'${value.replace(/'/g, `'\\''`)}'`
-}
diff --git a/src/shared/setup-runner-command.ts b/src/shared/setup-runner-command.ts
index 7b1dee560fd..080b2105754 100644
--- a/src/shared/setup-runner-command.ts
+++ b/src/shared/setup-runner-command.ts
@@ -1,3 +1,4 @@
+import { quoteCmdDoubleQuoted, quotePosixShellUnlessPlainNoAt } from './shell-argument-quoting'
 import { isWindowsAbsolutePathLike } from './cross-platform-path'
 import {
   buildWindowsCmdRunnerDelayedLaunchCommand,
@@ -48,14 +49,14 @@ export function resolveSetupRunnerCommand(
     if (isWslUncPath(runnerScriptPath)) {
       const linuxPath = wslUncToLinuxPath(runnerScriptPath)
       return {
-        command: `bash ${quotePosixArg(linuxPath)}`,
+        command: `bash ${quotePosixShellUnlessPlainNoAt(linuxPath)}`,
         runnerScriptPathForShell: linuxPath,
         shell: 'posix'
       }
     }
     if (runnerScriptPath.startsWith('/') && !isWindowsAbsolutePathLike(runnerScriptPath)) {
       return {
-        command: `bash ${quotePosixArg(runnerScriptPath)}`,
+        command: `bash ${quotePosixShellUnlessPlainNoAt(runnerScriptPath)}`,
         runnerScriptPathForShell: runnerScriptPath,
         shell: 'posix'
       }
@@ -68,7 +69,7 @@ export function resolveSetupRunnerCommand(
       if (isWslExecutable(shell?.executable)) {
         const wslPath = nativeWindowsPathToWslShellPath(runnerScriptPath)
         return {
-          command: `bash ${quotePosixArg(wslPath)}`,
+          command: `bash ${quotePosixShellUnlessPlainNoAt(wslPath)}`,
           runnerScriptPathForShell: wslPath,
           shell: 'posix'
         }
@@ -76,7 +77,7 @@ export function resolveSetupRunnerCommand(
       // Why: queued setup launches can outlive the process that generated them, so convert native paths before handing off to POSIX shells.
       const posixPath = nativeWindowsPathToPosixShellPath(runnerScriptPath)
       return {
-        command: `bash ${quotePosixArg(posixPath)}`,
+        command: `bash ${quotePosixShellUnlessPlainNoAt(posixPath)}`,
         runnerScriptPathForShell: posixPath,
         shell: 'posix'
       }
@@ -90,14 +91,14 @@ export function resolveSetupRunnerCommand(
       command:
         shell?.family === 'posix' || windowsRunnerPathNeedsCmdGuard(runnerScriptPath)
           ? buildWindowsCmdRunnerDelayedLaunchCommand(runnerScriptPath)
-          : `cmd.exe /c ${quoteWindowsArg(runnerScriptPath)}`,
+          : `cmd.exe /c ${quoteCmdDoubleQuoted(runnerScriptPath)}`,
       runnerScriptPathForShell: runnerScriptPath,
       shell: 'windows'
     }
   }
 
   return {
-    command: `bash ${quotePosixArg(runnerScriptPath)}`,
+    command: `bash ${quotePosixShellUnlessPlainNoAt(runnerScriptPath)}`,
     runnerScriptPathForShell: runnerScriptPath,
     shell: 'posix'
   }
@@ -119,18 +120,6 @@ export function wslUncToLinuxPath(windowsPath: string): string {
   return match?.[2] || '/'
 }
 
-function quotePosixArg(value: string): string {
-  if (/^[A-Za-z0-9_./:-]+$/.test(value)) {
-    return value
-  }
-
-  return `'${value.replace(/'/g, `'\\''`)}'`
-}
-
-function quoteWindowsArg(value: string): string {
-  return `"${value.replace(/"/g, '""')}"`
-}
-
 export function nativeWindowsPathToPosixShellPath(value: string): string {
   const driveMatch = value.match(/^([A-Za-z]):[\\/](.*)$/)
   if (driveMatch) {
diff --git a/src/shared/shell-argument-quoting.test.ts b/src/shared/shell-argument-quoting.test.ts
index f23dde4c7c6..44898d0a75b 100644
--- a/src/shared/shell-argument-quoting.test.ts
+++ b/src/shared/shell-argument-quoting.test.ts
@@ -1,7 +1,110 @@
 import { describe, expect, it } from 'vitest'
-import { quotePosixShell } from './shell-argument-quoting'
+import {
+  quoteCmdDoubleQuoted,
+  quotePosixShell,
+  quotePosixShellDoubleQuotedApostrophe,
+  quotePosixShellUnlessPlain,
+  quotePosixShellUnlessPlainNoAt
+} from './shell-argument-quoting'
 
-// ── quotePosixShell ──────────────────────────────────────────────────────
+// Verbatim bodies of the copies this module replaced, keyed by where each one lived. Every
+// former copy must produce byte-identical output to the function that now serves its callers.
+const sq = (value: string): string => `'${value.replace(/'/g, "'\\''")}'`
+const sqAll = (value: string): string => `'${value.replaceAll("'", "'\\''")}'`
+const plainAt = (value: string): string => (/^[a-zA-Z0-9_./@:-]+$/.test(value) ? value : sq(value))
+const plainNoAt = (value: string): string => (/^[A-Za-z0-9_./:-]+$/.test(value) ? value : sq(value))
+const dq = (value: string): string => `'${value.replaceAll("'", `'"'"'`)}'`
+
+const FORMER_COPIES: [string, (value: string) => string, (value: string) => string][] = [
+  ['main/ssh/ssh-connection-utils shellEscape', sq, quotePosixShell],
+  ['shared/wsl-login-shell-command quotePosixShell', sq, quotePosixShell],
+  ['main/agent-hooks/posix-hook-command quotePosixShellString', sqAll, quotePosixShell],
+  ['main/codex/codex-hook-definition inline', sqAll, quotePosixShell],
+  ['main/ipc/preflight-command-exec shellQuote', sq, quotePosixShell],
+  ['main/ipc/preflight-wsl-agent-detection shellQuote', sq, quotePosixShell],
+  ['main/rate-limits/hidden-rate-limit-shell', sq, quotePosixShell],
+  ['main/runtime/orchestration/setup-completion-signal quotePosixArg', sq, quotePosixShell],
+  ['main/ssh/ssh-remote-directory-browse shellEscapeRaw', sq, quotePosixShell],
+  ['shared/posix-command-path-lookup shellQuote', sq, quotePosixShell],
+  ['renderer ipynb-kernel-setup-commands POSIX branch', sqAll, quotePosixShell],
+  ['shared/ephemeral-vm-recipe-process POSIX branch', sq, quotePosixShell],
+  ['cli/shell-command-quote POSIX tail', sqAll, quotePosixShell],
+  ['main/external-editor-launch escapePosixPathForShell', plainAt, quotePosixShellUnlessPlain],
+  ['renderer pane-helpers shellEscapePath POSIX', plainAt, quotePosixShellUnlessPlain],
+  ['shared/setup-agent-sequencing quotePosixArg', plainNoAt, quotePosixShellUnlessPlainNoAt],
+  ['shared/setup-runner-command quotePosixArg', plainNoAt, quotePosixShellUnlessPlainNoAt],
+  ['main/cli/cli-install-path-format quoteShell', dq, quotePosixShellDoubleQuotedApostrophe],
+  ['main/cli/wsl-cli-scripts quoteShell', dq, quotePosixShellDoubleQuotedApostrophe],
+  ['main/antigravity/antigravity-browser-helper quote', dq, quotePosixShellDoubleQuotedApostrophe],
+  [
+    'cli/orchestration-mutation-recovery shellQuote tail',
+    dq,
+    quotePosixShellDoubleQuotedApostrophe
+  ],
+  [
+    'main/linux-package-install-command quoteForPosixShell',
+    (value) => `'${value.split("'").join(`'"'"'`)}'`,
+    quotePosixShellDoubleQuotedApostrophe
+  ],
+  [
+    'shared/ephemeral-vm-recipe-process win32 branch',
+    (value) => `"${value.replace(/"/g, '""')}"`,
+    quoteCmdDoubleQuoted
+  ],
+  [
+    'shared/setup-runner-command quoteWindowsArg',
+    (value) => `"${value.replace(/"/g, '""')}"`,
+    quoteCmdDoubleQuoted
+  ],
+  [
+    'shared/ai-vault-resume-command quoteWindowsCmdArg',
+    (value) => `"${value.replace(/"/g, '""')}"`,
+    quoteCmdDoubleQuoted
+  ]
+]
+
+const HOSTILE_INPUTS = [
+  '',
+  "'",
+  "''",
+  "it's",
+  "'; rm -rf /; '",
+  'plain',
+  'a@b',
+  'user@host:/path',
+  '/tmp/Orca Setup.deb',
+  '$HOME',
+  '${PATH}',
+  '`id`',
+  '$(id)',
+  '"quoted"',
+  '\\',
+  'trailing\\',
+  'C:\\Program Files\\Orca\\orca.exe',
+  '%PATH%',
+  '!x!',
+  '^&|<>()',
+  '~',
+  '~/dir',
+  '-n',
+  '--flag=value',
+  'a b\tc',
+  'line1\nline2',
+  'crlf\r\n',
+  'nul\u0000byte',
+  'é☃😀',
+  '*?[a]{b,c}',
+  '#comment',
+  'a;b&&c||d'
+]
+
+describe('shell-argument-quoting matches every former copy byte for byte', () => {
+  describe.each(FORMER_COPIES)('%s', (_site, former, current) => {
+    it.each(HOSTILE_INPUTS)('%j', (input) => {
+      expect(current(input)).toBe(former(input))
+    })
+  })
+})
 
 describe('quotePosixShell', () => {
   it('wraps string in single quotes', () => {
@@ -20,3 +123,19 @@ describe('quotePosixShell', () => {
     expect(quotePosixShell('foo bar; rm -rf /')).toBe("'foo bar; rm -rf /'")
   })
 })
+
+describe('the spellings stay distinct', () => {
+  it('spells an apostrophe two different ways', () => {
+    expect(quotePosixShell("it's")).toBe(`'it'\\''s'`)
+    expect(quotePosixShellDoubleQuotedApostrophe("it's")).toBe(`'it'"'"'s'`)
+  })
+
+  it('leaves @ bare only in the plain-with-@ variant', () => {
+    expect(quotePosixShellUnlessPlain('a@b')).toBe('a@b')
+    expect(quotePosixShellUnlessPlainNoAt('a@b')).toBe("'a@b'")
+  })
+
+  it('doubles embedded quotes for cmd.exe', () => {
+    expect(quoteCmdDoubleQuoted('say "hi"')).toBe('"say ""hi"""')
+  })
+})
diff --git a/src/shared/shell-argument-quoting.ts b/src/shared/shell-argument-quoting.ts
index 327fa6ef2f5..c34d8c45ff9 100644
--- a/src/shared/shell-argument-quoting.ts
+++ b/src/shared/shell-argument-quoting.ts
@@ -1,4 +1,31 @@
+// One home for shell-argument quoting. Each spelling below is a separate contract: callers embed,
+// compare or parse back these exact bytes, so variants stay separate functions, never flags.
+// PowerShell quoting lives in powershell-native-argument.ts; CommandLineToArgvW in @orca/process-host.
+
 /** POSIX sh single-quoting: each `'` closes the quote, is escaped, and reopens it (`'\''`). */
 export function quotePosixShell(value: string): string {
   return `'${value.replace(/'/g, "'\\''")}'`
 }
+
+/** As `quotePosixShell`, but a non-empty word of only `A-Za-z0-9_./@:-` stays bare. */
+export function quotePosixShellUnlessPlain(value: string): string {
+  return /^[a-zA-Z0-9_./@:-]+$/.test(value) ? value : quotePosixShell(value)
+}
+
+/** As `quotePosixShellUnlessPlain`, except `@` also forces quoting. */
+export function quotePosixShellUnlessPlainNoAt(value: string): string {
+  return /^[A-Za-z0-9_./:-]+$/.test(value) ? value : quotePosixShell(value)
+}
+
+/**
+ * POSIX sh single-quoting that spells each `'` as `'"'"'`. Installed CLI wrappers are read back
+ * in this spelling (legacy-appimage-cli-wrapper.ts, wsl-cli-scripts.ts), so it must not change.
+ */
+export function quotePosixShellDoubleQuotedApostrophe(value: string): string {
+  return `'${value.replaceAll("'", `'"'"'`)}'`
+}
+
+/** cmd.exe double-quoting with `"` doubled. Leaves `%`, `^` and `!` as they are. */
+export function quoteCmdDoubleQuoted(value: string): string {
+  return `"${value.replace(/"/g, '""')}"`
+}