diff --git a/src/main/git/command-runner/git-command-resolution.ts b/src/main/git/command-runner/git-command-resolution.ts
index 1e8adf317a1..337e22d1bf3 100644
--- a/src/main/git/command-runner/git-command-resolution.ts
+++ b/src/main/git/command-runner/git-command-resolution.ts
@@ -1,6 +1,7 @@
+import { wslDistroForCommand } from '../../../shared/wsl-paths'
+export { wslDistroForCommand } from '../../../shared/wsl-paths'
 import { waitForPromiseWithSignal } from '../../../shared/abort-signal-reason'
 import { withTimeout } from '../../../shared/promise-timeout-fallback'
-import { parseWslPath } from '../../wsl'
 import { isWslDirectGitReadCommand } from '../wsl-direct-git-read-commands'
 import {
   disableWslGitReadEnvironment,
@@ -20,14 +21,6 @@ function wslGitArgs(args: string[], options: GitExecOptions): string[] {
   return withWslWindowsCheckoutGitConfig(args, options.cwd, options.wslDistro)
 }
 
-/** The WSL distro a Git command with this cwd runs in, or null when it runs on the host. */
-export function wslDistroForCommand(cwd: string | undefined, override?: string): string | null {
-  if (process.platform !== 'win32') {
-    return null
-  }
-  return (cwd ? parseWslPath(cwd)?.distro : undefined) ?? override ?? null
-}
-
 export function resolveGitCommand(
   args: string[],
   options: GitExecOptions,
diff --git a/src/main/git/command-runner/wsl-aware-spawn.ts b/src/main/git/command-runner/wsl-aware-spawn.ts
index 5567dc941ba..e0fce9a4de7 100644
--- a/src/main/git/command-runner/wsl-aware-spawn.ts
+++ b/src/main/git/command-runner/wsl-aware-spawn.ts
@@ -1,6 +1,11 @@
 import { spawn, type ChildProcess, type SpawnOptions } from 'node:child_process'
 import { recordSubprocessSpawn } from '../../diagnostics/main-thread-churn-probe'
-import { resolveCommand } from './wsl-command-resolution'
+import {
+  commandLineLength,
+  MAX_COMMAND_LINE_CHARS,
+  WindowsCommandLineBudgetError
+} from '../../../shared/windows-command-line-budget'
+import { resolveCommand, withWslPreparation } from './wsl-command-resolution'
 
 export function wslAwareSpawn(
   command: string,
@@ -11,15 +16,28 @@ export function wslAwareSpawn(
     useWslLoginShell?: boolean
     wslShellCommand?: string
     cwdFailureExitCode?: number
+    preparation?: { script: string; args: string[] }
   }
 ): ChildProcess {
-  const { wslDistro, useWslLoginShell, wslShellCommand, cwdFailureExitCode, ...spawnOptions } =
-    options
-  const resolved = resolveCommand(command, args, options.cwd, wslDistro, {
+  const {
+    wslDistro,
+    useWslLoginShell,
+    wslShellCommand,
+    cwdFailureExitCode,
+    preparation,
+    ...spawnOptions
+  } = options
+  let resolved = resolveCommand(command, args, options.cwd, wslDistro, {
     useWslLoginShell,
     wslShellCommand,
     ...(cwdFailureExitCode === undefined ? {} : { cwdFailureExitCode })
   })
+  if (preparation && resolved.wsl) {
+    resolved = withWslPreparation(resolved, preparation)
+    if (commandLineLength([resolved.binary, ...resolved.args]) > MAX_COMMAND_LINE_CHARS) {
+      throw new WindowsCommandLineBudgetError()
+    }
+  }
   const spawnStartedAt = performance.now()
   const child = spawn(resolved.binary, resolved.args, {
     ...spawnOptions,
diff --git a/src/main/git/command-runner/wsl-command-resolution.ts b/src/main/git/command-runner/wsl-command-resolution.ts
index d1149790508..d34b5317802 100644
--- a/src/main/git/command-runner/wsl-command-resolution.ts
+++ b/src/main/git/command-runner/wsl-command-resolution.ts
@@ -208,3 +208,23 @@ function withWslProcessGroupTermination(
     termination
   }
 }
+
+/** Prefix only the opt-in preparation; retain the resolver's original guest argv intact. */
+export function withWslPreparation(
+  command: ResolvedCommand,
+  preparation: { script: string; args: string[] }
+): ResolvedCommand {
+  const execIndex = command.args.indexOf('--exec')
+  return {
+    ...command,
+    args: [
+      ...command.args.slice(0, execIndex + 1),
+      '/bin/sh',
+      '-c',
+      preparation.script,
+      'orca-generation',
+      ...preparation.args,
+      ...command.args.slice(execIndex + 1)
+    ]
+  }
+}
diff --git a/src/main/ssh/ssh-posix-command-wrapper.test.ts b/src/main/ssh/ssh-posix-command-wrapper.test.ts
index 4ac663e77ed..e6c8497c655 100644
--- a/src/main/ssh/ssh-posix-command-wrapper.test.ts
+++ b/src/main/ssh/ssh-posix-command-wrapper.test.ts
@@ -1,3 +1,4 @@
+import { encodePosixPrintfRecords } from '../../shared/posix-printf-encoding'
 import { spawnSync } from 'node:child_process'
 import { createHash } from 'node:crypto'
 import { describe, expect, it } from 'vitest'
@@ -20,6 +21,21 @@ function shimDir(tools: Record<string, string>): string {
   return bin
 }
 
+it.skipIf(process.platform === 'win32')(
+  'keeps incremental printf records byte-bounded and lossless at escape/codepoint boundaries',
+  () => {
+    const controls = Array.from({ length: 128 }, (_, index) => String.fromCharCode(index)).join('')
+    const text = `${'x'.repeat(1023)}🌊${controls}\\c\\012\uFEFF'!%$\`\ud800`.repeat(4)
+    const chunks = [...encodePosixPrintfRecords(text)]
+    expect(chunks.every((chunk) => Buffer.byteLength(chunk) <= 1024)).toBe(true)
+    expect(chunks.every((chunk) => !chunk.includes('\n') && !chunk.includes('\0'))).toBe(true)
+    const result = spawnSync('/bin/sh', ['-c', 'printf "%b" "$@"', 'fixture', ...chunks])
+    expect(result.status).toBe(0)
+    expect(result.stdout).toEqual(Buffer.from(text))
+    expect([...encodePosixPrintfRecords('')]).toEqual([''])
+  }
+)
+
 describe('wrapRemoteCommandForPosixShell', () => {
   it('emits one physical line without requiring a remote decoder binary', () => {
     const wrapped = wrapRemoteCommandForPosixShell("printf 'a\\n'\nprintf 'b\\n'")
diff --git a/src/main/ssh/ssh-posix-command-wrapper.ts b/src/main/ssh/ssh-posix-command-wrapper.ts
index ac921a7930b..acf68f60d47 100644
--- a/src/main/ssh/ssh-posix-command-wrapper.ts
+++ b/src/main/ssh/ssh-posix-command-wrapper.ts
@@ -1,34 +1,8 @@
+import { encodePosixPrintfRecords } from '../../shared/posix-printf-encoding'
 import { gzipSync } from 'node:zlib'
 import { quotePosixShell } from '../../shared/shell-argument-quoting'
 
-const REMOTE_COMMAND_CHUNK_MAX_BYTES = 1_024
 const REMOTE_COMMAND_COMPRESSION_THRESHOLD_BYTES = 8_000
-const REMOTE_COMMAND_PRINTF_ESCAPED_BYTES = new Set([0x21, 0x27, 0x5c])
-
-function encodeRemoteCommandForPrintf(command: string): string[] {
-  const chunks: string[] = []
-  let chunk = ''
-  let chunkBytes = 0
-  for (const character of command) {
-    const codePoint = character.codePointAt(0)!
-    const isSafePrintableAscii =
-      codePoint >= 0x20 && codePoint <= 0x7e && !REMOTE_COMMAND_PRINTF_ESCAPED_BYTES.has(codePoint)
-    const encodedCharacter =
-      codePoint > 0x7f || isSafePrintableAscii
-        ? character
-        : `\\0${codePoint.toString(8).padStart(3, '0')}`
-    const encodedBytes = codePoint > 0x7f ? Buffer.byteLength(character) : encodedCharacter.length
-    if (chunkBytes + encodedBytes > REMOTE_COMMAND_CHUNK_MAX_BYTES) {
-      chunks.push(chunk)
-      chunk = ''
-      chunkBytes = 0
-    }
-    chunk += encodedCharacter
-    chunkBytes += encodedBytes
-  }
-  chunks.push(chunk)
-  return chunks
-}
 
 /** The compressed wrapper's exit when the host has no base64 or gzip; nothing ran. */
 export const REMOTE_COMMAND_DECODER_UNAVAILABLE_EXIT = 125
@@ -39,7 +13,7 @@ export function wrapRemoteCommandForPosixShell(
   options: { compress?: boolean } = {}
 ): string {
   // csh/tcsh split multiline exec strings; rebuild bounded printf chunks without consuming relay stdin.
-  const encodedChunks = encodeRemoteCommandForPrintf(command)
+  const encodedChunks = [...encodePosixPrintfRecords(command)]
   const runDecoded = 'decoded=${decoded%_}; exec /bin/sh -c "$decoded"'
   const decodeAndRun = `decoded=$(printf %b "$@" && printf _) || exit $?; ${runDecoded}`
   const chunkArguments = encodedChunks.map(quotePosixShell).join(' ')
@@ -53,7 +27,7 @@ export function wrapRemoteCommandForPosixShell(
 
   // Compress long scripts before gateways can truncate the exec request.
   const compressed = gzipSync(Buffer.from(command), { level: 9 }).toString('base64')
-  const compressedArguments = encodeRemoteCommandForPrintf(compressed)
+  const compressedArguments = [...encodePosixPrintfRecords(compressed)]
     .map(quotePosixShell)
     .join(' ')
   // Preserve payload stdin and execute only after gzip validation. Missing decoders consume nothing, permitting plain retry; macOS before 13 needs base64 -D.
diff --git a/src/main/text-generation/source-control-agent-launch.ts b/src/main/text-generation/source-control-agent-launch.ts
index 5d98fa6753b..bd2de32de07 100644
--- a/src/main/text-generation/source-control-agent-launch.ts
+++ b/src/main/text-generation/source-control-agent-launch.ts
@@ -1,9 +1,10 @@
+import { wslDistroForCommand } from '../../shared/wsl-paths'
 import { spawnProcess } from '@orca/process-host'
 import { withCliRuntimeOnPath } from '../../shared/node-cli-command-resolution'
 import { resolveCliCommand } from '../codex-cli/command'
 import { createProviderSpawnSpec } from '../provider-process/provider-process-supervisor'
 import { guardSupervisedProviderGroup } from '../provider-process/provider-group-orphan-guard'
-import { SOURCE_CONTROL_KILL_SITE } from './source-control-local-process'
+import { SOURCE_CONTROL_KILL_SITE } from './source-control-agent-termination'
 import { wslAwareSpawn } from '../git/runner'
 import { guestNativeSpawnEnv } from '../ipc/wsl-guest-windows-drive-path'
 import type {
@@ -41,8 +42,11 @@ function buildWslLauncherEnv(explicitEnv: NodeJS.ProcessEnv | undefined): NodeJS
 }
 
 export const spawnSourceControlAgent: SpawnSourceControlAgent = (input) => {
+  const wslDistro = input.preparation
+    ? wslDistroForCommand(input.cwd, input.wslDistro)
+    : input.wslDistro
   const spawnEnv = input.env ?? process.env
-  if (process.platform === 'win32' && input.wslDistro) {
+  if (process.platform === 'win32' && wslDistro) {
     // Apply command assignments after guest login-shell setup, never to the Windows launcher.
     const assignments = Object.entries(input.commandEnv ?? {}).map(
       ([key, value]) => `${key}=${value}`
@@ -56,8 +60,9 @@ export const spawnSourceControlAgent: SpawnSourceControlAgent = (input) => {
         env: buildWslLauncherEnv(input.env),
         stdio: [input.stdinMode, 'pipe', 'pipe'],
         windowsHide: true,
-        wslDistro: input.wslDistro,
-        useWslLoginShell: true
+        wslDistro,
+        useWslLoginShell: true,
+        ...(input.preparation ? { preparation: input.preparation } : {})
       }
     ) as SpawnedSourceControlAgentProcess
   }
diff --git a/src/main/text-generation/source-control-agent-termination.ts b/src/main/text-generation/source-control-agent-termination.ts
new file mode 100644
index 00000000000..0b4f60ebe19
--- /dev/null
+++ b/src/main/text-generation/source-control-agent-termination.ts
@@ -0,0 +1,27 @@
+import { stopSupervisedChildProcess } from '../provider-process/supervised-child-process-stop'
+import { terminateWindowsProcessTree } from '../windows-process-tree-kill'
+import type { SpawnedSourceControlAgentProcess } from './source-control-text-generation-types'
+
+export const SOURCE_CONTROL_KILL_SITE = 'source-control-text-generation'
+
+export async function killSourceControlAgentProcess(
+  child: SpawnedSourceControlAgentProcess
+): Promise<void> {
+  const pid = child.pid
+  if (!pid) {
+    return
+  }
+  if (child.supervised) {
+    await stopSupervisedChildProcess(child, { site: SOURCE_CONTROL_KILL_SITE })
+    return
+  }
+  if (process.platform === 'win32') {
+    // Tree-walk refusal must not release the home lock having killed nothing; root handle kill cannot hit a recycled PID.
+    await terminateWindowsProcessTree(pid, { site: SOURCE_CONTROL_KILL_SITE })
+  }
+  try {
+    child.kill('SIGKILL')
+  } catch {
+    // The process may exit between the PID check and kill.
+  }
+}
diff --git a/src/main/text-generation/source-control-command-line-budget.ts b/src/main/text-generation/source-control-command-line-budget.ts
new file mode 100644
index 00000000000..c9c37bf4f12
--- /dev/null
+++ b/src/main/text-generation/source-control-command-line-budget.ts
@@ -0,0 +1,26 @@
+import type { CommitMessagePlan } from '../../shared/commit-message-plan'
+import { commandLineLength, MAX_COMMAND_LINE_CHARS } from '../../shared/windows-command-line-budget'
+
+// Linux caps each argv entry in bytes (128KiB on 4KiB pages), before total argv capacity; reserve headroom for single-prompt arguments.
+const LINUX_SINGLE_ARGUMENT_BYTE_BUDGET = 120 * 1024
+/** Whether the plan's argv plus reserve fits this host's limit: UTF-16 units on Windows, bytes per argument on Linux. */
+export function fitsLocalCommandLine(plan: CommitMessagePlan, reserve = 0): boolean {
+  if (process.platform === 'win32') {
+    return commandLineLength([plan.binary, ...plan.args]) + reserve <= MAX_COMMAND_LINE_CHARS
+  }
+  if (process.platform === 'linux') {
+    return plan.args.every(
+      (arg) => Buffer.byteLength(arg, 'utf8') + reserve <= LINUX_SINGLE_ARGUMENT_BYTE_BUDGET
+    )
+  }
+  return true
+}
+
+export function argumentBudgetFailure(plan: CommitMessagePlan): string | null {
+  if (fitsLocalCommandLine(plan)) {
+    return null
+  }
+  return process.platform === 'win32'
+    ? `${plan.label} prompt is too large for the Windows command line. Stage fewer changes and try again.`
+    : `${plan.label} prompt is too large to pass as a single command-line argument. Stage fewer changes and try again.`
+}
diff --git a/src/main/text-generation/source-control-local-generation.ts b/src/main/text-generation/source-control-local-generation.ts
index 0005cabfd61..c5c01c4f4a5 100644
--- a/src/main/text-generation/source-control-local-generation.ts
+++ b/src/main/text-generation/source-control-local-generation.ts
@@ -1,3 +1,4 @@
+import { wslDistroForCommand } from '../../shared/wsl-paths'
 import { mergeCommandEnvironment } from '../../shared/command-environment'
 import type { CommitMessagePlan } from '../../shared/commit-message-plan'
 import {
@@ -27,12 +28,16 @@ export function runLocalPlanForAgent(input: {
   spawnAgent: SpawnSourceControlAgent
   shouldExecute?: () => boolean
 }): Promise<InternalTextGenerationResult> {
+  const wslDistro = input.plan.promptFile
+    ? (wslDistroForCommand(input.target.cwd, input.target.wslDistro) ?? undefined)
+    : input.target.wslDistro
   const target = {
     ...input.target,
+    wslDistro,
     env: mergeCommandEnvironment(
       input.target.env,
       input.plan.env,
-      input.target.wslDistro ? 'linux' : process.platform
+      wslDistro ? 'linux' : process.platform
     )
   }
   const start = (): LocalProcessExecution<InternalTextGenerationResult> => {
@@ -45,10 +50,10 @@ export function runLocalPlanForAgent(input: {
     return runLocalSourceControlPlan({
       plan: input.plan,
       cwd: input.target.cwd,
-      env: input.target.wslDistro ? input.target.env : target.env,
+      env: wslDistro ? input.target.env : target.env,
       emptyResultName: input.emptyResultName,
       operation: input.operation,
-      wslDistro: input.target.wslDistro,
+      wslDistro,
       spawnAgent: input.spawnAgent
     })
   }
diff --git a/src/main/text-generation/source-control-local-process.ts b/src/main/text-generation/source-control-local-process.ts
index 2063ce58091..aa2caa4bab1 100644
--- a/src/main/text-generation/source-control-local-process.ts
+++ b/src/main/text-generation/source-control-local-process.ts
@@ -1,9 +1,13 @@
+import { killSourceControlAgentProcess } from './source-control-agent-termination'
+import { wslDistroForCommand } from '../../shared/wsl-paths'
+import { prepareWslPrompt, stageLocalPromptFiles } from './source-control-prompt-files'
+import { producePromptRecords } from './source-control-prompt-producer'
+import { argumentBudgetFailure } from './source-control-command-line-budget'
+export { fitsLocalCommandLine } from './source-control-command-line-budget'
+import { removeTree } from '../../shared/windows-transient-lock-removal'
 import { WindowsCmdLineBreakError } from '@orca/process-host'
-import type { CommitMessagePlan } from '../../shared/commit-message-plan'
-import { commandLineLength, MAX_COMMAND_LINE_CHARS } from '../../shared/windows-command-line-budget'
+import { WindowsCommandLineBudgetError } from '../../shared/windows-command-line-budget'
 import { supervisedProviderSpawnFailure } from '../provider-process/provider-spawn-failure-report'
-import { stopSupervisedChildProcess } from '../provider-process/supervised-child-process-stop'
-import { terminateWindowsProcessTree } from '../windows-process-tree-kill'
 import {
   finalizeFromAgentOutput,
   userFacingUnsafeWindowsBatchArgs
@@ -21,77 +25,43 @@ import type {
   InternalTextGenerationResult,
   LocalProcessExecution,
   SpawnedSourceControlAgentProcess,
-  SpawnSourceControlAgent,
-  TextGenerationOperation
+  LocalSourceControlPlanInput
 } from './source-control-text-generation-types'
 
-export const SOURCE_CONTROL_KILL_SITE = 'source-control-text-generation'
+export * from './source-control-agent-termination'
 
-export async function killSourceControlAgentProcess(
-  child: SpawnedSourceControlAgentProcess
-): Promise<void> {
-  const pid = child.pid
-  if (!pid) {
-    return
-  }
-  if (child.supervised) {
-    await stopSupervisedChildProcess(child, { site: SOURCE_CONTROL_KILL_SITE })
-    return
-  }
-  if (process.platform === 'win32') {
-    // Tree-walk refusal must not release the home lock having killed nothing; root handle kill cannot hit a recycled PID.
-    await terminateWindowsProcessTree(pid, { site: SOURCE_CONTROL_KILL_SITE })
-  }
-  try {
-    child.kill('SIGKILL')
-  } catch {
-    // The process may exit between the PID check and kill.
-  }
-}
-
-// Linux caps each argv entry in bytes (128KiB on 4KiB pages), before total argv capacity; reserve headroom for single-prompt arguments.
-const LINUX_SINGLE_ARGUMENT_BYTE_BUDGET = 120 * 1024
-
-/** Whether the plan's argv plus reserve fits this host's limit: UTF-16 units on Windows, bytes per argument on Linux. */
-export function fitsLocalCommandLine(plan: CommitMessagePlan, reserve = 0): boolean {
-  if (process.platform === 'win32') {
-    return commandLineLength([plan.binary, ...plan.args]) + reserve <= MAX_COMMAND_LINE_CHARS
-  }
-  if (process.platform === 'linux') {
-    return plan.args.every(
-      (arg) => Buffer.byteLength(arg, 'utf8') + reserve <= LINUX_SINGLE_ARGUMENT_BYTE_BUDGET
-    )
-  }
-  return true
-}
-
-function argumentBudgetFailure(plan: CommitMessagePlan): string | null {
-  if (fitsLocalCommandLine(plan)) {
-    return null
-  }
-  return process.platform === 'win32'
-    ? `${plan.label} prompt is too large for the Windows command line. Stage fewer changes and try again.`
-    : `${plan.label} prompt is too large to pass as a single command-line argument. Stage fewer changes and try again.`
-}
-
-export function runLocalSourceControlPlan(input: {
-  plan: CommitMessagePlan
-  cwd: string
-  env: NodeJS.ProcessEnv | undefined
-  emptyResultName: string
-  operation: TextGenerationOperation
-  wslDistro?: string
-  spawnAgent: SpawnSourceControlAgent
-}): LocalProcessExecution<InternalTextGenerationResult> {
-  const { plan, cwd, operation } = input
+export function runLocalSourceControlPlan(
+  input: LocalSourceControlPlanInput
+): LocalProcessExecution<InternalTextGenerationResult> {
+  let { plan } = input
+  const { cwd, operation } = input
+  const distro = plan.promptFile ? wslDistroForCommand(cwd, input.wslDistro) : null
+  const guest = distro ? prepareWslPrompt(plan, distro) : undefined
+  let closed = false
+  let promptDirectory: string | undefined
   let markProcessClosed!: () => void
   const processClosed = new Promise<void>((resolve) => {
-    markProcessClosed = resolve
+    markProcessClosed = () => {
+      closed = true
+      if (promptDirectory) {
+        const directory = promptDirectory
+        promptDirectory = undefined
+        void removeTree(directory).catch((error: unknown) => {
+          console.error('[commit-message] Failed to remove generation prompt:', error)
+        })
+      }
+      resolve()
+    }
   })
   const couldNotStart = `${plan.label} could not be started. Check the agent command in Settings and try again.`
   const result = new Promise<InternalTextGenerationResult>((resolve) => {
     let child: SpawnedSourceControlAgentProcess
     try {
+      plan =
+        guest?.plan ??
+        stageLocalPromptFiles(plan, (directory) => {
+          promptDirectory = directory
+        })
       // Reject oversized argv before opaque E2BIG spawn failure so users can act on the prompt-size limit.
       const budgetFailure = argumentBudgetFailure(plan)
       if (budgetFailure) {
@@ -105,12 +75,20 @@ export function runLocalSourceControlPlan(input: {
         cwd,
         env: input.env,
         commandEnv: plan.env,
-        wslDistro: input.wslDistro,
+        wslDistro: distro ?? input.wslDistro,
+        ...(guest ? { preparation: guest.preparation } : {}),
         stdinMode: 'pipe',
         useCwdForNative: true
       })
     } catch (error) {
       markProcessClosed()
+      if (error instanceof WindowsCommandLineBudgetError) {
+        resolve({
+          success: false,
+          error: `${plan.label} prompt is too large for the Windows command line. Stage fewer changes and try again.`
+        })
+        return
+      }
       if (error instanceof WindowsCmdLineBreakError) {
         resolve({
           success: false,
@@ -123,6 +101,8 @@ export function runLocalSourceControlPlan(input: {
       return
     }
 
+    const stop = new AbortController()
+    const deadline = Date.now() + SOURCE_CONTROL_GENERATION_TIMEOUT_MS
     let stdout = ''
     let stderr = ''
     let stdoutBytes = 0
@@ -135,7 +115,10 @@ export function runLocalSourceControlPlan(input: {
     let terminal = false
     let terminationComplete: Promise<void> | null = null
     let detachChildListeners = (): void => {}
+    const active = (): boolean =>
+      !settled && !terminal && !stop.signal.aborted && Date.now() < deadline
     const startTermination = (): void => {
+      stop.abort()
       terminationComplete ??= killSourceControlAgentProcess(child).catch((error: unknown) => {
         console.error('[commit-message] Local generator termination failed:', error)
       })
@@ -150,6 +133,7 @@ export function runLocalSourceControlPlan(input: {
         return
       }
       settled = true
+      stop.abort()
       if (timer) {
         clearTimeout(timer)
         timer = null
@@ -187,6 +171,9 @@ export function runLocalSourceControlPlan(input: {
       stdout += chunk.toString('utf-8')
     }
     const onStderrData = (chunk: Buffer): void => {
+      if (settled) {
+        return
+      }
       stderrBytes += chunk.byteLength
       if (stderrBytes > MAX_SOURCE_CONTROL_AGENT_OUTPUT_BYTES) {
         outputLimitExceeded = true
@@ -216,6 +203,7 @@ export function runLocalSourceControlPlan(input: {
     }
     const onClose = (code: number | null): void => {
       terminal = true
+      stop.abort()
       child.off?.('close', onClose)
       markClosedAfterTermination()
       if (canceledByUser) {
@@ -255,12 +243,47 @@ export function runLocalSourceControlPlan(input: {
         })
       )
     }
+    child.stdin?.on?.('error', (error: Error) => {
+      if (active()) {
+        startTermination()
+        onError(error)
+      }
+    })
+    child.stdin?.on?.('close', () => {
+      if (guest && active() && !child.stdin?.writableEnded) {
+        startTermination()
+        onError(new Error('Generation input closed.'))
+      }
+    })
     child.stdout?.on('data', onStdoutData)
-    child.stderr?.on('data', onStderrData)
+    if (guest) {
+      child.stderr?.on('data', (chunk: Buffer) => {
+        const proved = guest.observe(chunk, onStderrData)
+        if (proved) {
+          promptDirectory = guest.cleanupPath
+          if (closed) {
+            markProcessClosed()
+          }
+          if (active() && child.stdin) {
+            void producePromptRecords(child.stdin, guest.records(), stop.signal, active).catch(
+              (error: unknown) => {
+                if (active()) {
+                  startTermination()
+                  onError(error instanceof Error ? error : new Error(String(error)))
+                }
+              }
+            )
+          }
+        }
+      })
+    } else {
+      child.stderr?.on('data', onStderrData)
+    }
     child.on('error', onError)
     child.on('close', onClose)
     child.on('exit', () => {
       terminal = true
+      stop.abort()
       markClosedAfterTermination()
     })
     detachChildListeners = () => {
@@ -268,7 +291,11 @@ export function runLocalSourceControlPlan(input: {
       child.stderr?.off?.('data', onStderrData)
     }
     try {
-      child.stdin?.end(plan.stdinPayload ?? undefined)
+      if (!guest) {
+        child.stdin?.end(plan.stdinPayload ?? undefined)
+      } else if (!child.stdin) {
+        throw new Error('Generation input is unavailable.')
+      }
     } catch (error) {
       startTermination()
       onError(error instanceof Error ? error : new Error(String(error)))
diff --git a/src/main/text-generation/source-control-omp-prompt-file.test.ts b/src/main/text-generation/source-control-omp-prompt-file.test.ts
new file mode 100644
index 00000000000..e81dfdad725
--- /dev/null
+++ b/src/main/text-generation/source-control-omp-prompt-file.test.ts
@@ -0,0 +1,440 @@
+import { spawnProcess } from '@orca/process-host'
+import * as agentSpecs from '../../shared/commit-message-agent-spec'
+import type { ResolvedSourceControlAiGenerationParams } from '../../shared/source-control-ai'
+import type { SpawnSourceControlAgent } from './source-control-text-generation-types'
+import {
+  generateCommitMessage,
+  generatePullRequestFields,
+  generateBranchName
+} from './source-control-text-generation-requests'
+import { generateConversationName } from './conversation-name-generation-request'
+import { generateJiraIssueSummaryFromContext } from './jira-issue-summary-text-generation'
+
+import { existsSync, mkdtempSync, readFileSync } from 'node:fs'
+import { rm } from 'node:fs/promises'
+import type * as FsPromises from 'node:fs/promises'
+import { tmpdir } from 'node:os'
+import { dirname, join } from 'node:path'
+import { afterEach, expect, it, vi } from 'vitest'
+import { planCommitMessageGeneration } from '../../shared/commit-message-plan'
+import { cancelLocalGeneration } from './source-control-generation-lanes'
+import { SOURCE_CONTROL_GENERATION_TIMEOUT_MS } from './source-control-generation-limits'
+import { runLocalSourceControlPlan } from './source-control-local-process'
+import {
+  createMockDiscoveryChild,
+  withPlatform
+} from './commit-message-text-generation-test-harness'
+
+vi.mock('../windows-process-tree-kill', () => ({
+  terminateWindowsProcessTree: vi.fn(async () => true)
+}))
+
+vi.mock('node:fs/promises', async (importOriginal) => {
+  const actual = await importOriginal<typeof FsPromises>()
+  return { ...actual, rm: vi.fn(actual.rm) }
+})
+
+const actualFs = await vi.importActual<typeof FsPromises>('node:fs/promises')
+
+afterEach(() => vi.useRealTimers())
+
+// OMP 17.0.5 recorded stdin-only execution: exit 0, empty stdout/stderr, no submitted prompt.
+const recordedPrompt = `Name this chat from the user's first request.
+Write a short, specific title of at most 48 characters.
+Output only the title, with no heading, quotes, or explanation.
+
+First request:
+Trace a lost lighthouse signal.
+
+Additional instructions:
+Return Lighthouse Signal Trace.
+`
+
+it.each(['success', 'failure', 'cancel', 'timeout', 'spawn failure'] as const)(
+  'delivers the recorded OMP prompt without stdin and removes the owned file after %s',
+  async (outcome) => {
+    vi.useFakeTimers()
+    const prompt = recordedPrompt + 'x'.repeat(200_000)
+    const planned = planCommitMessageGeneration({ agentId: 'omp', model: 'default' }, prompt)
+    if (!planned.ok) {
+      throw new Error(planned.error)
+    }
+    const child = createMockDiscoveryChild()
+    let promptPath = ''
+    const execution = withPlatform('win32', () =>
+      runLocalSourceControlPlan({
+        plan: planned.plan,
+        cwd: '/omp-file-test',
+        env: undefined,
+        operation: 'conversation-name',
+        emptyResultName: 'chat name',
+        spawnAgent: ({ args }) => {
+          promptPath = args[planned.plan.promptFile?.argIndex ?? -1]?.slice(1) ?? ''
+          expect(new TextDecoder().decode(readFileSync(promptPath))).toBe(prompt)
+          expect(args.join(' ').length).toBeLessThan(1000)
+          if (outcome === 'spawn failure') {
+            throw new Error('recorded spawn failure')
+          }
+          return child
+        }
+      })
+    )
+    if (outcome === 'success') {
+      // Like the recorded binary, this child never reads stdin; only the explicit file submits input.
+      child.stdout.emit('data', Buffer.from('Lighthouse Signal Trace'))
+    } else if (outcome === 'cancel') {
+      cancelLocalGeneration('conversation-name', '/omp-file-test')
+    } else if (outcome === 'timeout') {
+      await vi.advanceTimersByTimeAsync(SOURCE_CONTROL_GENERATION_TIMEOUT_MS)
+    }
+    if (outcome !== 'spawn failure') {
+      expect(child.stdin.end).toHaveBeenCalledWith(undefined)
+      expect(existsSync(promptPath)).toBe(true)
+      child.emit('close', outcome === 'failure' ? 1 : 0)
+    }
+    const result = await execution.result
+    await execution.processClosed
+    expect(result.success).toBe(outcome === 'success')
+    await vi.waitFor(() => expect(existsSync(dirname(promptPath))).toBe(false))
+  }
+)
+
+// Pinned OMP17 cli/file-processor.ts:16,49-54,119-122: per-file cap, ordered text decoding.
+const attachmentReader = String.raw`
+const fs = require('node:fs');
+const args = process.argv.slice(1);
+const paths = args.filter(arg => arg.startsWith('@')).map(arg => arg.slice(1));
+const chunks = paths.map(path => fs.readFileSync(path));
+const isImage = bytes => ['GIF87a', 'GIF89a'].includes(bytes.subarray(0, 6).toString()) ||
+  (bytes.subarray(0, 4).toString() === 'RIFF' && bytes.subarray(8, 12).toString() === 'WEBP');
+const fragments = chunks.map(bytes => bytes.length > 5 * 1024 * 1024
+  ? '(skipped: too large)' : isImage(bytes) ? '(image instead of text)' : new TextDecoder().decode(bytes));
+let stdin = '';
+process.stdin.setEncoding('utf8');
+process.stdin.on('data', chunk => { stdin += chunk; });
+process.stdin.on('end', () => {
+  fs.writeFileSync(process.env.OMP_RECEIPT, JSON.stringify({
+    paths, sizes: chunks.map(bytes => bytes.length), content: paths.length ? fragments.join('') : stdin, stdin,
+    message: fragments.map((text, index) => '<file name="' + paths[index] + '">\n' + text + '\n</file>\n').join('') + args.at(-1)
+  }));
+  process.stdout.write(process.env.OMP_OUTPUT);
+  if (process.env.OMP_EXIT === '7') process.stderr.write('Fixture provider unavailable');
+  process.exitCode = Number(process.env.OMP_EXIT);
+});
+`
+
+const contractParams = {
+  agentId: 'omp',
+  model: 'generated/model',
+  thinkingLevel: 'low',
+  agentCommandOverride: 'OMP_RECIPE_ENV=kept node /configured/prefix/omp.js --model prefix/model',
+  agentArgs: '--model recipe/model --thinking high -- recipe-message',
+  commandInputTemplate: 'Saved recipe instruction\n{basePrompt}'
+} as const
+const contractTarget = { kind: 'local', cwd: tmpdir() } as const
+const commitContext = {
+  branch: 'feature',
+  stagedSummary: 'signal.ts | 1 +',
+  stagedPatch: '+ Trace lighthouse signal'
+}
+
+type Consumer = {
+  label: string
+  run(
+    params: ResolvedSourceControlAiGenerationParams,
+    spawnAgent: SpawnSourceControlAgent
+  ): Promise<unknown>
+  output: string
+  expected: object
+}
+const consumers: Consumer[] = [
+  {
+    label: 'commit',
+    run: (params, spawnAgent) =>
+      generateCommitMessage({ context: commitContext, params, target: contractTarget, spawnAgent }),
+    output: 'Trace lighthouse signal.\n\nPreserve request bytes\n',
+    expected: { message: 'Trace lighthouse signal\n\nPreserve request bytes' }
+  },
+  {
+    label: 'PR fields',
+    run: (params, spawnAgent) =>
+      generatePullRequestFields({
+        context: {
+          branch: 'feature',
+          base: 'main',
+          branchChangedByPreparation: true,
+          currentTitle: '',
+          currentBody: '',
+          currentDraft: false,
+          commitSummary: 'Trace lighthouse signal',
+          changeSummary: 'signal.ts',
+          patch: '+ Trace lighthouse signal'
+        },
+        params,
+        target: contractTarget,
+        spawnAgent
+      }),
+    output: JSON.stringify({
+      base: 'main',
+      title: 'Trace lighthouse signal.',
+      body: 'Preserve request bytes\n',
+      draft: true
+    }),
+    expected: {
+      fields: {
+        base: 'main',
+        title: 'Trace lighthouse signal',
+        body: 'Preserve request bytes',
+        draft: true
+      },
+      branchChangedByPreparation: true
+    }
+  },
+  {
+    label: 'branch slug / folder title',
+    run: (params, spawnAgent) =>
+      generateBranchName({
+        context: { firstPrompt: 'Trace lighthouse signal' },
+        params,
+        target: contractTarget,
+        spawnAgent
+      }),
+    output: 'Trace Lighthouse Signal!',
+    expected: { slug: 'trace-lighthouse-signal' }
+  },
+  {
+    label: 'conversation name',
+    run: (params, spawnAgent) =>
+      generateConversationName({
+        context: { firstPrompt: 'Trace lighthouse signal' },
+        params,
+        target: contractTarget,
+        spawnAgent
+      }),
+    output: '# Title: "Trace lighthouse signal"\nextra commentary',
+    expected: { name: 'Trace lighthouse signal' }
+  },
+  {
+    label: 'Jira summary',
+    run: (params, spawnAgent) =>
+      generateJiraIssueSummaryFromContext(
+        { description: 'Trace lighthouse signal' },
+        params,
+        contractTarget,
+        spawnAgent
+      ),
+    output: '"Trace lighthouse signal"\nextra commentary',
+    expected: { summary: 'Trace lighthouse signal' }
+  }
+]
+
+type Receipt = { paths: string[]; sizes: number[]; content: string; stdin: string; message: string }
+async function withReader<T>(
+  output: string,
+  fail: boolean,
+  run: (spawnAgent: SpawnSourceControlAgent) => Promise<T>
+) {
+  const directory = mkdtempSync(join(tmpdir(), 'orca-omp-contract-'))
+  const receiptPath = join(directory, 'receipt.json')
+  try {
+    const result = await run((input) => {
+      expect(input.binary).toBe('node')
+      expect(input.args.slice(0, 1)).toEqual(['/configured/prefix/omp.js'])
+      expect(input.args).toContain('recipe/model')
+      expect(input.args).not.toContain('prefix/model')
+      expect(input.args).not.toContain('generated/model')
+      expect(input.args).toContain('high')
+      expect(input.args).not.toContain('low')
+      expect(input.args.slice(-2)).toEqual(['--', 'recipe-message'])
+      expect(input.commandEnv).toEqual({ OMP_RECIPE_ENV: 'kept' })
+      return spawnProcess({
+        program: process.execPath,
+        args: ['-e', attachmentReader, '--', ...input.args],
+        cwd: input.cwd,
+        env: {
+          ...process.env,
+          OMP_RECEIPT: receiptPath,
+          OMP_OUTPUT: output,
+          OMP_EXIT: fail ? '7' : '0'
+        },
+        stdio: 'pipe'
+      })
+    })
+    const receipt: Receipt = JSON.parse(readFileSync(receiptPath, 'utf8'))
+    await vi.waitFor(() => {
+      for (const path of receipt.paths) {
+        expect(existsSync(dirname(path))).toBe(false)
+      }
+    })
+    return { result, receipt }
+  } finally {
+    await rm(directory, { recursive: true, force: true })
+  }
+}
+
+it.each(consumers)(
+  'preserves $label output and failure classification across stdin/file transport',
+  async (consumer) => {
+    const spec = agentSpecs.getCommitMessageAgentSpec('omp')
+    if (!spec) {
+      throw new Error('Missing OMP spec')
+    }
+    for (const fail of [false, true]) {
+      const delivered = await withReader(consumer.output, fail, (spawn) =>
+        consumer.run(contractParams, spawn)
+      )
+      expect(delivered.receipt.paths).toHaveLength(1)
+      expect(delivered.receipt.stdin).toBe('')
+      expect(delivered.receipt.message.endsWith('recipe-message')).toBe(true)
+      expect(delivered.receipt.content).toContain('Trace lighthouse signal')
+      expect(delivered.receipt.content.includes('Saved recipe instruction')).toBe(
+        consumer.label !== 'Jira summary'
+      )
+      if (fail) {
+        expect(delivered.result).toMatchObject({
+          success: false,
+          error: expect.stringContaining('OMP CLI command failed with code 7')
+        })
+      } else {
+        expect(delivered.result).toMatchObject({
+          success: true,
+          agentLabel: 'OMP',
+          ...consumer.expected
+        })
+      }
+      const legacy = vi.spyOn(agentSpecs, 'getCommitMessageAgentSpec').mockReturnValue({
+        ...spec,
+        promptDelivery: 'stdin',
+        buildArgs: (params) => spec.buildArgs(params).slice(0, -1)
+      })
+      try {
+        const previous = await withReader(consumer.output, fail, (spawn) =>
+          consumer.run(contractParams, spawn)
+        )
+        expect(previous.receipt.paths).toHaveLength(0)
+        expect(previous.receipt.content).toBe(delivered.receipt.content)
+        expect(previous.result).toEqual(delivered.result)
+      } finally {
+        legacy.mockRestore()
+      }
+    }
+  }
+)
+
+it.each(['below', 'at', 'above', 'multibyte', 'BOM run', 'GIF', 'RIFF', 'internal magic'] as const)(
+  'delivers complete text recipe content: %s',
+  async (boundary) => {
+    const cap = 5 * 1024 * 1024
+    const payloadCap = cap - 3
+    const patches = {
+      below: () => 'x'.repeat(payloadCap - 1),
+      at: () => 'x'.repeat(payloadCap),
+      above: () => 'x'.repeat(cap + 1),
+      multibyte: () =>
+        `${'x'.repeat(payloadCap - 1)}🌊界é${'界'.repeat(Math.ceil(cap / 3))}\uFEFFEND`,
+      'BOM run': () => `${'\uFEFF'.repeat(Math.ceil(cap / 3))}Preserve every BOM`,
+      GIF: () => 'GIF89a is the header this change handles. Preserve this as text.',
+      RIFF: () => 'RIFFxxxxWEBP is the signature this change handles. Preserve this as text.',
+      'internal magic': () => `${'x'.repeat(payloadCap)}GIF89a preserve this boundary as text.`
+    }
+    const patch = patches[boundary]()
+    const { result, receipt } = await withReader(
+      'Preserve the complete request',
+      false,
+      (spawnAgent) =>
+        generateCommitMessage({
+          context: { ...commitContext, stagedPatch: patch },
+          params: { ...contractParams, commandInputTemplate: '{stagedPatch}' },
+          target: contractTarget,
+          spawnAgent
+        })
+    )
+    expect(result).toMatchObject({ success: true, message: 'Preserve the complete request' })
+    expect(receipt.content).toBe(patch)
+    expect(receipt.sizes.every((size) => size <= cap)).toBe(true)
+    expect(receipt.paths).toHaveLength(
+      boundary === 'multibyte'
+        ? 3
+        : ['above', 'BOM run', 'internal magic'].includes(boundary)
+          ? 2
+          : 1
+    )
+    if (boundary === 'at') {
+      expect(receipt.sizes).toEqual([cap])
+    }
+  }
+)
+
+it.each(['success', 'spawn failure', 'permanent failure'] as const)(
+  'settles independently of bounded async cleanup after %s',
+  async (outcome) => {
+    const originalPlatform = process.platform
+    const rmMock = vi.mocked(rm)
+    const errors = vi.spyOn(console, 'error').mockImplementation(() => {})
+    const locked = Object.assign(new Error('EPERM: prompt handle held'), { code: 'EPERM' })
+    let directory = ''
+    Object.defineProperty(process, 'platform', { configurable: true, value: 'win32' })
+    rmMock.mockClear()
+    rmMock.mockImplementationOnce(async () => {
+      throw locked
+    })
+    if (outcome === 'permanent failure') {
+      rmMock.mockRejectedValue(locked)
+    }
+    try {
+      const planned = planCommitMessageGeneration(
+        { agentId: 'omp', model: 'default' },
+        recordedPrompt
+      )
+      if (!planned.ok) {
+        throw new Error(planned.error)
+      }
+      const child = createMockDiscoveryChild()
+      const execution = runLocalSourceControlPlan({
+        plan: planned.plan,
+        cwd: '/omp-cleanup',
+        env: undefined,
+        operation: 'conversation-name',
+        emptyResultName: 'chat name',
+        spawnAgent: ({ args }) => {
+          directory = dirname(args[planned.plan.promptFile?.argIndex ?? -1].slice(1))
+          if (outcome === 'spawn failure') {
+            throw new Error('Fixture spawn failure')
+          }
+          return child
+        }
+      })
+      if (outcome !== 'spawn failure') {
+        child.stdout.emit('data', Buffer.from('Lighthouse Signal Trace'))
+        child.emit('close', 0)
+      }
+      expect((await execution.result).success).toBe(outcome !== 'spawn failure')
+      await execution.processClosed
+      expect(rmMock).toHaveBeenCalledTimes(1)
+      expect(existsSync(directory)).toBe(true)
+      if (outcome === 'permanent failure') {
+        await vi.waitFor(
+          () =>
+            expect(errors).toHaveBeenCalledWith(
+              '[commit-message] Failed to remove generation prompt:',
+              locked
+            ),
+          { timeout: 5000 }
+        )
+        expect(rmMock).toHaveBeenCalledTimes(5)
+        expect(errors).toHaveBeenCalledTimes(1)
+        expect(existsSync(directory)).toBe(true)
+      } else {
+        await vi.waitFor(() => expect(existsSync(directory)).toBe(false), { timeout: 2000 })
+        expect(rmMock).toHaveBeenCalledTimes(2)
+      }
+    } finally {
+      Object.defineProperty(process, 'platform', { configurable: true, value: originalPlatform })
+      rmMock.mockImplementation(actualFs.rm)
+      if (directory) {
+        await actualFs.rm(directory, { recursive: true, force: true })
+      }
+      errors.mockRestore()
+    }
+  }
+)
diff --git a/src/main/text-generation/source-control-prompt-files.ts b/src/main/text-generation/source-control-prompt-files.ts
new file mode 100644
index 00000000000..eb3f9e4677c
--- /dev/null
+++ b/src/main/text-generation/source-control-prompt-files.ts
@@ -0,0 +1,140 @@
+import { randomUUID } from 'node:crypto'
+import { mkdtempSync, writeFileSync } from 'node:fs'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+import { getUtf8ChunkEndIndex } from '../../shared/utf8-byte-limits'
+import { encodePosixPrintfRecords } from '../../shared/posix-printf-encoding'
+import { toWindowsWslUncPath } from '../../shared/wsl-paths'
+import type { CommitMessagePlan } from '../../shared/commit-message-plan'
+
+// Reserve the transport signature under the native text attachment cap.
+const PAYLOAD_BYTES = 5 * 1024 * 1024 - 3
+
+export function* promptFileContents(content: string): Generator<string> {
+  for (let start = 0; start < content.length;) {
+    const end = getUtf8ChunkEndIndex(content, start, PAYLOAD_BYTES)
+    yield `\uFEFF${content.slice(start, end)}`
+    start = end
+  }
+}
+
+export function stageLocalPromptFiles(
+  plan: CommitMessagePlan,
+  own: (directory: string) => void
+): CommitMessagePlan {
+  if (!plan.promptFile) {
+    return plan
+  }
+  const directory = mkdtempSync(join(tmpdir(), 'orca-generation-'))
+  own(directory)
+  const attachments: string[] = []
+  for (const content of promptFileContents(plan.promptFile.content)) {
+    const path = join(directory, `prompt-${attachments.length + 1}.txt`)
+    writeFileSync(path, content, { mode: 0o600 })
+    attachments.push(`@${path}`)
+  }
+  const args = [...plan.args]
+  args.splice(plan.promptFile.argIndex, 1, ...attachments)
+  return { ...plan, args }
+}
+
+// Preparation precedes profiles; only a proved empty allocation may roll back before ACK.
+export const WSL_PROMPT_PREPARATION = `
+nonce=$1; count=$2; shift 2
+dir=/tmp/orca-generation-$nonce
+old_umask=$(umask)
+umask 077
+mkdir "$dir" || exit 1
+trap 'rmdir "$dir" 2>/dev/null' EXIT
+printf '\\nORCA_GENERATION_READY:%s\\n' "$nonce" >&2 || exit 1
+IFS= read -r record && [ "$record" = "A$nonce" ] || exit 1
+trap - EXIT
+index=1
+while [ "$index" -le "$count" ]; do
+  file=$dir/prompt-$index.txt
+  : > "$file" || exit 1
+  while :; do
+    IFS= read -r record || exit 1
+    case "$record" in
+      D*) printf '%b' "\${record#D}" >> "$file" || exit 1 ;;
+      *) [ "$record" = "F$nonce:$index" ] || exit 1; break ;;
+    esac
+  done
+  index=$((index + 1))
+done
+IFS= read -r record && [ "$record" = "X$nonce" ] || exit 1
+umask "$old_umask"
+exec "$@" </dev/null
+`
+
+export function prepareWslPrompt(plan: CommitMessagePlan, distro: string) {
+  const nonce = randomUUID()
+  const directory = `/tmp/orca-generation-${nonce}`
+  const attachments: string[] = []
+  for (const _content of promptFileContents(plan.promptFile?.content ?? '')) {
+    attachments.push(`@${directory}/prompt-${attachments.length + 1}.txt`)
+  }
+  const args = [...plan.args]
+  args.splice(plan.promptFile?.argIndex ?? 0, 1, ...attachments)
+  const proof = `ORCA_GENERATION_READY:${nonce}`
+  let partial = ''
+  let oversized = false
+  let proved = false
+  return {
+    plan: { ...plan, args },
+    preparation: { script: WSL_PROMPT_PREPARATION, args: [nonce, String(attachments.length)] },
+    cleanupPath: toWindowsWslUncPath(directory, distro),
+    observe(chunk: Buffer, diagnostic?: (bytes: Buffer) => void): boolean {
+      let firstProof = false
+      let passthrough = 0
+      for (let index = 0; index < chunk.length; index++) {
+        const byte = chunk[index]
+        if (oversized) {
+          const end = chunk.indexOf(10, index)
+          if (end === -1) {
+            diagnostic?.(chunk.subarray(passthrough))
+            return firstProof
+          }
+          diagnostic?.(chunk.subarray(passthrough, end + 1))
+          index = end
+          oversized = false
+        } else if (byte === 10) {
+          if (partial === proof) {
+            if (!proved) {
+              proved = true
+              firstProof = true
+            }
+          } else {
+            diagnostic?.(Buffer.from(`${partial}\n`, 'latin1'))
+          }
+          partial = ''
+        } else if (partial.length < proof.length && byte === proof.charCodeAt(partial.length)) {
+          partial += String.fromCharCode(byte)
+        } else {
+          if (partial) {
+            diagnostic?.(Buffer.from(partial, 'latin1'))
+          }
+          partial = ''
+          oversized = true
+          passthrough = index
+          index--
+        }
+        if (!oversized) {
+          passthrough = index + 1
+        }
+      }
+      return firstProof
+    },
+    *records(): Generator<string> {
+      yield `A${nonce}\n`
+      let index = 0
+      for (const content of promptFileContents(plan.promptFile?.content ?? '')) {
+        for (const encoded of encodePosixPrintfRecords(content)) {
+          yield `D${encoded}\n`
+        }
+        yield `F${nonce}:${++index}\n`
+      }
+      yield `X${nonce}\n`
+    }
+  }
+}
diff --git a/src/main/text-generation/source-control-prompt-producer.ts b/src/main/text-generation/source-control-prompt-producer.ts
new file mode 100644
index 00000000000..26a8a637061
--- /dev/null
+++ b/src/main/text-generation/source-control-prompt-producer.ts
@@ -0,0 +1,48 @@
+import { setImmediate as yieldToEvents } from 'node:timers/promises'
+import type { Writable } from 'node:stream'
+
+/** One bounded record at a time; a stopped attempt also releases an outstanding drain wait. */
+export async function producePromptRecords(
+  stdin: Writable,
+  records: Iterable<string>,
+  signal: AbortSignal,
+  active: () => boolean
+): Promise<void> {
+  let batch = 0
+  for (const record of records) {
+    if (!active()) {
+      return
+    }
+    if (!stdin.write(record)) {
+      await new Promise<void>((resolve) => {
+        const done = (): void => {
+          stdin.off('drain', done)
+          stdin.off('error', done)
+          stdin.off('close', done)
+          signal.removeEventListener('abort', done)
+          resolve()
+        }
+        stdin.once('drain', done)
+        stdin.once('error', done)
+        stdin.once('close', done)
+        signal.addEventListener('abort', done, { once: true })
+        if (!active() || stdin.destroyed || stdin.writableEnded) {
+          done()
+        }
+      })
+      if (!active() || stdin.destroyed || stdin.writableEnded) {
+        return
+      }
+    }
+    if (++batch === 16) {
+      batch = 0
+      await yieldToEvents()
+      if (!active()) {
+        return
+      }
+    }
+  }
+  if (active()) {
+    stdin.end()
+  }
+}
diff --git a/src/main/text-generation/source-control-text-generation-types.ts b/src/main/text-generation/source-control-text-generation-types.ts
index 6c93c15f901..4608bcd2ff0 100644
--- a/src/main/text-generation/source-control-text-generation-types.ts
+++ b/src/main/text-generation/source-control-text-generation-types.ts
@@ -108,6 +108,7 @@ export type SourceControlAgentSpawnInput = {
   wslDistro?: string
   // WSL applies these in the guest; native callers already merge them into env.
   commandEnv?: Record<string, string>
+  preparation?: { script: string; args: string[] }
   stdinMode: 'ignore' | 'pipe'
   useCwdForNative: boolean
 }
@@ -115,3 +116,13 @@ export type SourceControlAgentSpawnInput = {
 export type SpawnSourceControlAgent = (
   input: SourceControlAgentSpawnInput
 ) => SpawnedSourceControlAgentProcess
+
+export type LocalSourceControlPlanInput = {
+  plan: CommitMessagePlan
+  cwd: string
+  env: NodeJS.ProcessEnv | undefined
+  emptyResultName: string
+  operation: TextGenerationOperation
+  wslDistro?: string
+  spawnAgent: SpawnSourceControlAgent
+}
diff --git a/src/main/text-generation/source-control-wsl-launch.test.ts b/src/main/text-generation/source-control-wsl-launch.test.ts
new file mode 100644
index 00000000000..4e999c9b6f2
--- /dev/null
+++ b/src/main/text-generation/source-control-wsl-launch.test.ts
@@ -0,0 +1,302 @@
+import { spawnProcess } from '@orca/process-host'
+import type * as ChildProcess from 'node:child_process'
+import { mkdtempSync, mkdirSync, writeFileSync, readFileSync, realpathSync } from 'node:fs'
+import { rm } from 'node:fs/promises'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+import { expect, it, vi, afterEach } from 'vitest'
+import { quotePosixShell } from '../../shared/shell-argument-quoting'
+import { commandLineLength, MAX_COMMAND_LINE_CHARS } from '../../shared/windows-command-line-budget'
+import { prepareWslPrompt } from './source-control-prompt-files'
+import { producePromptRecords } from './source-control-prompt-producer'
+import { planCommitMessageGeneration } from '../../shared/commit-message-plan'
+import {
+  withPlatform,
+  createMockDiscoveryChild
+} from './commit-message-text-generation-test-harness'
+import { spawnSourceControlAgent } from './source-control-agent-launch'
+import { runLocalPlanForAgent } from './source-control-local-generation'
+import { resolveCommand } from '../git/command-runner/wsl-command-resolution'
+
+const { spawnMock } = vi.hoisted(() => ({ spawnMock: vi.fn() }))
+vi.mock('node:child_process', async (original) => {
+  const actual = await original<typeof ChildProcess>()
+  spawnMock.mockImplementation(actual.spawn)
+  return { ...actual, spawn: spawnMock }
+})
+vi.mock('../wsl-background-distro-gate', () => ({ noteWslDistroLaunched: vi.fn() }))
+const nativeSpawn = (await vi.importActual<typeof ChildProcess>('node:child_process')).spawn
+afterEach(() => {
+  spawnMock.mockReset().mockImplementation(nativeSpawn)
+})
+const repo = '\\\\wsl.localhost\\Actual\\home\\dev\\repo'
+function planned(agentId: 'omp' | 'codex' = 'omp') {
+  const result = planCommitMessageGeneration(
+    {
+      agentId,
+      model: 'default',
+      agentCommandOverride: 'lower=recipe LOWER=UPPER omp --model prefix/model',
+      agentArgs: '--thinking high --mode text @user.txt -- recipe-message'
+    },
+    'request'
+  )
+  if (!result.ok) {
+    throw new Error(result.error)
+  }
+  return result.plan
+}
+
+it.each([undefined, 'Wrong', 'Actual'])(
+  'routes UNC before hint %s with Linux assignments retained for OMP only',
+  async (hint) => {
+    const request = planned()
+    const child = createMockDiscoveryChild()
+    let guestPath = ''
+    const result = withPlatform('win32', () =>
+      runLocalPlanForAgent({
+        agentId: 'omp',
+        plan: request,
+        target: {
+          kind: 'local',
+          cwd: repo,
+          wslDistro: hint,
+          env: { lower: 'base', LOWER: 'BASE' }
+        },
+        operation: 'conversation-name',
+        emptyResultName: 'name',
+        spawnAgent: (input) => {
+          expect(input.wslDistro).toBe('Actual')
+          expect(input.env).toEqual({ lower: 'base', LOWER: 'BASE' })
+          expect(input.commandEnv).toEqual({ lower: 'recipe', LOWER: 'UPPER' })
+          expect(input.preparation).toBeDefined()
+          guestPath = input.args.find((arg) => arg.startsWith('@/tmp/')) ?? ''
+          queueMicrotask(() => {
+            child.stdout.emit('data', Buffer.from('Useful name'))
+            child.emit('close', 0)
+          })
+          return child
+        }
+      })
+    )
+    expect(await result).toMatchObject({ success: true })
+    expect(guestPath).toContain('@/tmp/orca-generation-')
+  }
+)
+
+it('preserves ordinary hinted WSL and unrelated provider no-hint native routing', async () => {
+  for (const agentId of ['omp', 'codex'] as const) {
+    const request = planned(agentId)
+    const child = createMockDiscoveryChild()
+    const result = withPlatform('win32', () =>
+      runLocalPlanForAgent({
+        agentId: 'custom',
+        plan: request,
+        target: {
+          kind: 'local',
+          cwd: agentId === 'omp' ? 'C:\\repo' : repo,
+          ...(agentId === 'omp' ? { wslDistro: 'Hint' } : {})
+        },
+        operation: 'conversation-name',
+        emptyResultName: 'name',
+        spawnAgent: (input) => {
+          expect(input.wslDistro).toBe(agentId === 'omp' ? 'Hint' : undefined)
+          expect(!!input.preparation).toBe(agentId === 'omp')
+          queueMicrotask(() => {
+            child.stdout.emit('data', Buffer.from('Useful name'))
+            child.emit('close', 0)
+          })
+          return child
+        }
+      })
+    )
+    expect(await result).toMatchObject({ success: true })
+  }
+})
+
+it('launches the original resolved wrapper once, preserving prefix, recipe, translation and assignment timing', () => {
+  const request = prepareWslPrompt(planned(), 'Actual')
+  spawnMock.mockReturnValueOnce(createMockDiscoveryChild())
+  withPlatform('win32', () => {
+    const assignments = ['lower=recipe', 'LOWER=UPPER']
+    const original = resolveCommand(
+      '/usr/bin/env',
+      [...assignments, planned().binary, ...request.plan.args],
+      repo,
+      'Wrong',
+      { useWslLoginShell: true }
+    )
+    spawnSourceControlAgent({
+      binary: planned().binary,
+      args: request.plan.args,
+      cwd: repo,
+      commandEnv: planned().env,
+      wslDistro: 'Actual',
+      preparation: request.preparation,
+      stdinMode: 'pipe',
+      useCwdForNative: true
+    })
+    const [binary, args] = spawnMock.mock.calls.at(-1)!
+    expect(binary).toBe('wsl.exe')
+    expect(args.slice(0, 3)).toEqual(['-d', 'Actual', '--exec'])
+    expect(args.slice(3, 7)).toEqual([
+      '/bin/sh',
+      '-c',
+      request.preparation.script,
+      'orca-generation'
+    ])
+    expect(args.slice(9)).toEqual(original.args.slice(3))
+    expect(original.args.at(-1)).toContain('/home/dev/repo')
+    expect(original.args.at(-1)).toContain('lower=recipe')
+    expect(args.join(' ')).toContain('@user.txt')
+  })
+})
+
+it('checks the exact composed Windows argv at the inclusive boundary before spawning', () => {
+  const request = prepareWslPrompt(planned(), 'Actual')
+  const launch = (padding: number) =>
+    withPlatform('win32', () =>
+      spawnSourceControlAgent({
+        binary: 'omp',
+        args: [...request.plan.args, 'x'.repeat(padding)],
+        cwd: repo,
+        wslDistro: 'Actual',
+        preparation: request.preparation,
+        stdinMode: 'pipe',
+        useCwdForNative: true
+      })
+    )
+  spawnMock.mockReturnValue(createMockDiscoveryChild())
+  launch(0)
+  const [binary, args] = spawnMock.mock.calls.at(-1)!
+  const slack = MAX_COMMAND_LINE_CHARS - commandLineLength([binary, ...args])
+  const padding = Math.floor(slack / 3)
+  launch(padding)
+  const [atBinary, atArgs] = spawnMock.mock.calls.at(-1)!
+  expect(commandLineLength([atBinary, ...atArgs])).toBeLessThanOrEqual(MAX_COMMAND_LINE_CHARS)
+  expect(commandLineLength([atBinary, ...atArgs])).toBeGreaterThan(MAX_COMMAND_LINE_CHARS - 3)
+  const count = spawnMock.mock.calls.length
+  expect(() => launch(padding + 1)).toThrow()
+  expect(spawnMock).toHaveBeenCalledTimes(count)
+})
+
+it.each([false, true])(
+  'prepares before hostile profiles and preserves login invocation/cwd/env (assigned=%s)',
+  async (assigned) => {
+    const directory = realpathSync(mkdtempSync(join(tmpdir(), 'orca-c3-profiles-')))
+    const repoPath = join(directory, 'repo')
+    const startup = join(directory, 'startup')
+    const changed = join(directory, 'profile-cwd')
+    const reportPath = join(directory, 'report.json')
+    if (!assigned) {
+      mkdirSync(repoPath)
+    }
+    mkdirSync(startup)
+    mkdirSync(changed)
+    const shell = join(directory, 'bash')
+    const profile = join(directory, 'rc')
+    writeFileSync(
+      shell,
+      `#!/bin/sh\nexec /bin/bash --noprofile --rcfile ${quotePosixShell(profile)} -ic "$2"\n`,
+      { mode: 0o700 }
+    )
+    writeFileSync(
+      join(directory, 'getent'),
+      `#!/bin/sh\nprintf '%s\\n' ${quotePosixShell(`user:x:1:1:User:${directory}:${shell}`)}\n`,
+      { mode: 0o700 }
+    )
+    writeFileSync(
+      join(directory, '.profile'),
+      `export PATH=${quotePosixShell(directory)}:"$PATH"\n`
+    )
+    writeFileSync(
+      profile,
+      `
+export STARTUP_CWD="$PWD"
+export PROFILE_LOWER="$lower"
+if IFS= read -r stolen; then export STOLEN=yes; else export STOLEN=no; fi
+alias mkdir='mkdir -pv'
+alias printf='printf CORRUPTED'
+set -C
+command mkdir -p ${quotePosixShell(repoPath)}
+cd ${quotePosixShell(changed)}
+omp() { ${quotePosixShell(process.execPath)} ${quotePosixShell(join(directory, 'reader.cjs'))} "$@"; }
+`
+    )
+    writeFileSync(
+      join(directory, 'reader.cjs'),
+      String.raw`
+const fs=require('node:fs'); const path=process.argv.find(arg=>arg.startsWith('@/tmp/')).slice(1);
+fs.writeFileSync(process.env.REPORT, JSON.stringify({startup:process.env.STARTUP_CWD,cwd:process.cwd(),stolen:process.env.STOLEN,profileLower:process.env.PROFILE_LOWER,lower:process.env.lower,content:new TextDecoder().decode(fs.readFileSync(path)),stdin:fs.readFileSync(0).length,mask:process.umask()}));
+`
+    )
+    const request = prepareWslPrompt(planned(), 'Actual')
+    // Use the actual resolved native cwd and original wrapper, without starting a guest on this Mac.
+    const original = withPlatform('win32', () =>
+      resolveCommand(
+        assigned ? '/usr/bin/env' : 'omp',
+        assigned
+          ? [
+              'lower=recipe',
+              'LOWER=UPPER',
+              process.execPath,
+              join(directory, 'reader.cjs'),
+              ...request.plan.args
+            ]
+          : request.plan.args,
+        `\\\\wsl.localhost\\Actual${repoPath.replaceAll('/', '\\')}`,
+        undefined,
+        { useWslLoginShell: true }
+      )
+    )
+    const child = spawnProcess({
+      program: '/bin/sh',
+      args: [
+        '-c',
+        request.preparation.script,
+        'fixture',
+        ...request.preparation.args,
+        ...original.args.slice(3)
+      ],
+      cwd: startup,
+      env: { ...process.env, HOME: directory, SHELL: shell, REPORT: reportPath, lower: 'base' },
+      stdio: 'pipe'
+    })
+    child.stdin.on('error', () => {})
+    const stop = new AbortController()
+    const closed = new Promise<number | null>((resolve, reject) => {
+      child.on('close', resolve)
+      child.on('error', reject)
+    })
+    child.stderr.on('data', (chunk) => {
+      if (request.observe(chunk)) {
+        void producePromptRecords(
+          child.stdin,
+          request.records(),
+          stop.signal,
+          () => !stop.signal.aborted
+        )
+      }
+    })
+    try {
+      expect(await closed).toBe(0)
+      const receipt = JSON.parse(readFileSync(reportPath, 'utf8'))
+      expect(receipt).toMatchObject({
+        startup,
+        cwd: repoPath,
+        stolen: 'no',
+        profileLower: 'base',
+        lower: assigned ? 'recipe' : 'base',
+        content: 'request',
+        stdin: 0
+      })
+      expect(receipt.mask).toBe(process.umask())
+    } finally {
+      stop.abort()
+      await rm(`/tmp/orca-generation-${request.preparation.args[0]}`, {
+        recursive: true,
+        force: true
+      })
+      await rm(directory, { recursive: true, force: true })
+    }
+  }
+)
diff --git a/src/main/text-generation/source-control-wsl-prompt.test.ts b/src/main/text-generation/source-control-wsl-prompt.test.ts
new file mode 100644
index 00000000000..cef0f83ca79
--- /dev/null
+++ b/src/main/text-generation/source-control-wsl-prompt.test.ts
@@ -0,0 +1,532 @@
+import { spawnProcess } from '@orca/process-host'
+import { existsSync, mkdirSync, readFileSync, writeFileSync } from 'node:fs'
+import { rm } from 'node:fs/promises'
+import { join } from 'node:path'
+import { Writable } from 'node:stream'
+import { afterEach, expect, it, vi } from 'vitest'
+import { planCommitMessageGeneration } from '../../shared/commit-message-plan'
+import { prepareWslPrompt } from './source-control-prompt-files'
+import { producePromptRecords } from './source-control-prompt-producer'
+import { runLocalSourceControlPlan } from './source-control-local-process'
+import { cancelLocalGeneration } from './source-control-generation-lanes'
+import {
+  MAX_SOURCE_CONTROL_AGENT_OUTPUT_BYTES,
+  SOURCE_CONTROL_GENERATION_TIMEOUT_MS
+} from './source-control-generation-limits'
+import {
+  withPlatform,
+  createMockDiscoveryChild
+} from './commit-message-text-generation-test-harness'
+import type { SourceControlAgentSpawnInput } from './source-control-text-generation-types'
+import type * as Removal from '../../shared/windows-transient-lock-removal'
+
+const { removeTreeMock } = vi.hoisted(() => ({ removeTreeMock: vi.fn(async () => {}) }))
+vi.mock('../../shared/windows-transient-lock-removal', async (original) => ({
+  ...(await original<typeof Removal>()),
+  removeTree: removeTreeMock
+}))
+vi.mock('../windows-process-tree-kill', () => ({
+  terminateWindowsProcessTree: vi.fn(async () => true)
+}))
+vi.mock('../wsl-background-distro-gate', () => ({ noteWslDistroLaunched: vi.fn() }))
+
+afterEach(() => {
+  vi.useRealTimers()
+  removeTreeMock.mockReset()
+  removeTreeMock.mockResolvedValue(undefined)
+})
+
+const cwd = '\\\\wsl.localhost\\Actual\\home\\dev\\repo'
+function plan(content = 'sensitive request') {
+  const planned = planCommitMessageGeneration({ agentId: 'omp', model: 'default' }, content)
+  if (!planned.ok) {
+    throw new Error(planned.error)
+  }
+  return planned.plan
+}
+function start(child = createMockDiscoveryChild(), content?: string) {
+  let launch: SourceControlAgentSpawnInput | undefined
+  const execution = withPlatform('win32', () =>
+    runLocalSourceControlPlan({
+      plan: plan(content),
+      cwd,
+      wslDistro: 'Wrong',
+      env: undefined,
+      operation: 'conversation-name',
+      emptyResultName: 'name',
+      spawnAgent: (input) => {
+        launch = input
+        return child
+      }
+    })
+  )
+  const nonce = launch?.preparation?.args[0]
+  if (!nonce) {
+    throw new Error('Expected preparation')
+  }
+  return { child, launch, nonce, execution, proof: `ORCA_GENERATION_READY:${nonce}\n` }
+}
+function close(child: ReturnType<typeof createMockDiscoveryChild>, code = 0) {
+  child.stdout.emit('data', Buffer.from('Lighthouse Signal Trace'))
+  child.emit('exit', code)
+  child.emit('close', code)
+}
+
+it('waits for fragmented exact proof, streams once and cleans only the actual guest after terminal', async () => {
+  const { child, launch, nonce, execution, proof } = start()
+  const writes: string[] = []
+  child.stdin.on('data', (chunk) => writes.push(chunk.toString()))
+  expect(launch?.wslDistro).toBe('Actual')
+  expect(launch?.args).toContain(`@/tmp/orca-generation-${nonce}/prompt-1.txt`)
+  expect(child.stdin.end).not.toHaveBeenCalled()
+  child.stderr.emit('data', Buffer.from(`${proof.trim()}WRONG\n${'x'.repeat(100_000)}\n`))
+  child.stderr.emit('data', Buffer.from(proof.slice(0, 17)))
+  expect(writes).toEqual([])
+  child.stderr.emit('data', Buffer.from(proof.slice(17)))
+  child.stderr.emit('data', Buffer.from(proof))
+  expect(writes.join('')).toBe(`A${nonce}\nDsensitive request\nF${nonce}:1\nX${nonce}\n`)
+  expect(removeTreeMock).not.toHaveBeenCalled()
+  close(child)
+  expect(await execution.result).toMatchObject({ success: true })
+  await execution.processClosed
+  expect(removeTreeMock).toHaveBeenCalledExactlyOnceWith(
+    `\\\\wsl.localhost\\Actual\\tmp\\orca-generation-${nonce}`
+  )
+  child.stderr.emit('data', Buffer.from(proof))
+  expect(removeTreeMock).toHaveBeenCalledTimes(1)
+})
+
+it.each(['cancel', 'deadline', 'exit', 'overflow', 'stdin-error', 'stdin-close'] as const)(
+  'stops pending input on %s, and late proof only cleans without reopening result',
+  async (route) => {
+    vi.useFakeTimers()
+    const { child, execution, proof } = start()
+    const writes = vi.spyOn(child.stdin, 'write')
+    if (route === 'cancel') {
+      cancelLocalGeneration('conversation-name', cwd)
+    }
+    if (route === 'deadline') {
+      await vi.advanceTimersByTimeAsync(SOURCE_CONTROL_GENERATION_TIMEOUT_MS)
+    }
+    if (route === 'exit') {
+      close(child)
+    }
+    if (route === 'overflow') {
+      child.stdout.emit('data', Buffer.alloc(MAX_SOURCE_CONTROL_AGENT_OUTPUT_BYTES + 1))
+    }
+    if (route === 'stdin-error') {
+      child.stdin.emit('error', new Error('EPIPE'))
+    }
+    if (route === 'stdin-close') {
+      child.stdin.emit('close')
+    }
+    child.stderr.emit('data', Buffer.from(proof))
+    expect(writes).not.toHaveBeenCalled()
+    close(child)
+    await execution.result
+    await execution.processClosed
+    expect(removeTreeMock).toHaveBeenCalledTimes(1)
+    child.stdin.emit('error', new Error('late EPIPE'))
+  }
+)
+
+it.each(['cancel', 'deadline', 'exit', 'error', 'close', 'overflow'] as const)(
+  'releases a never-draining producer on %s without final authorization',
+  async (route) => {
+    vi.useFakeTimers()
+    const { child, execution, proof, nonce } = start(undefined, 'x'.repeat(50_000))
+    const write = vi.spyOn(child.stdin, 'write').mockReturnValue(false)
+    child.stderr.emit('data', Buffer.from(proof))
+    expect(write).toHaveBeenCalledExactlyOnceWith(`A${nonce}\n`)
+    if (route === 'cancel') {
+      cancelLocalGeneration('conversation-name', cwd)
+    }
+    if (route === 'deadline') {
+      await vi.advanceTimersByTimeAsync(SOURCE_CONTROL_GENERATION_TIMEOUT_MS)
+    }
+    if (route === 'exit') {
+      child.emit('exit', 1)
+    }
+    if (route === 'error') {
+      child.stdin.emit('error', new Error('EPIPE'))
+    }
+    if (route === 'close') {
+      child.stdin.emit('close')
+    }
+    if (route === 'overflow') {
+      child.stderr.emit('data', Buffer.alloc(MAX_SOURCE_CONTROL_AGENT_OUTPUT_BYTES + 1))
+    }
+    await Promise.resolve()
+    child.stdin.emit('drain')
+    close(child, 1)
+    await execution.result
+    await execution.processClosed
+    expect(write).toHaveBeenCalledTimes(1)
+    expect(child.stdin.listenerCount('drain')).toBe(0)
+    expect(removeTreeMock).toHaveBeenCalledTimes(1)
+  }
+)
+
+it.each(['missing-proof', 'spawn', 'no-pid', 'missing-stdin'] as const)(
+  'settles %s without invented ownership',
+  async (route) => {
+    vi.useFakeTimers()
+    const child = createMockDiscoveryChild()
+    if (route === 'missing-stdin') {
+      Object.defineProperty(child, 'stdin', { value: null })
+    }
+    if (route === 'no-pid') {
+      Object.defineProperty(child, 'pid', { value: undefined })
+    }
+    const execution = withPlatform('win32', () =>
+      runLocalSourceControlPlan({
+        plan: plan(),
+        cwd,
+        env: undefined,
+        operation: 'conversation-name',
+        emptyResultName: 'name',
+        spawnAgent: () => {
+          if (route === 'spawn') {
+            throw new Error('spawn denied')
+          }
+          return child
+        }
+      })
+    )
+    if (route === 'no-pid') {
+      child.emit('error', Object.assign(new Error('not found'), { code: 'ENOENT' }))
+    }
+    if (route === 'missing-proof') {
+      await vi.advanceTimersByTimeAsync(SOURCE_CONTROL_GENERATION_TIMEOUT_MS)
+    }
+    if (route !== 'spawn' && route !== 'no-pid') {
+      close(child, 1)
+    }
+    expect(await execution.result).toMatchObject({ success: false })
+    await execution.processClosed
+    expect(removeTreeMock).not.toHaveBeenCalled()
+  }
+)
+
+it.each(['pending', 'rejected'] as const)(
+  'never gates either promise on %s cleanup, even proof after processClosed',
+  async (outcome) => {
+    removeTreeMock.mockImplementation(() =>
+      outcome === 'pending' ? new Promise(() => {}) : Promise.reject(new Error('share unavailable'))
+    )
+    const log = vi.spyOn(console, 'error').mockImplementation(() => {})
+    try {
+      const { child, execution, proof } = start()
+      close(child)
+      expect(await execution.result).toMatchObject({ success: true })
+      await execution.processClosed
+      child.stderr.emit('data', Buffer.from(proof))
+      child.stderr.emit('data', Buffer.from(proof))
+      expect(removeTreeMock).toHaveBeenCalledTimes(1)
+      expect(child.stdin.end).not.toHaveBeenCalled()
+      await Promise.resolve()
+    } finally {
+      log.mockRestore()
+    }
+  }
+)
+
+const tricky = `${Array.from({ length: 128 }, (_, i) => String.fromCharCode(i)).join('')}\\c\\012\r\n'!%$\`🌊界\ud800`
+
+async function shellFixture(
+  content: string,
+  controls?: (records: string[], nonce: string) => string[],
+  setup?: (directory: string) => void,
+  onProof?: (directory: string) => void
+) {
+  const guest = prepareWslPrompt(plan(content), 'Actual')
+  const [nonce] = guest.preparation.args
+  const directory = `/tmp/orca-generation-${nonce}`
+  setup?.(directory)
+  const child = spawnProcess({
+    program: '/bin/sh',
+    args: [
+      '-c',
+      guest.preparation.script,
+      'fixture',
+      ...guest.preparation.args,
+      process.execPath,
+      '-e',
+      String.raw`
+const fs = require('node:fs');
+const paths = process.argv.slice(1).map(arg => arg.slice(1));
+const files = paths.map(path => fs.readFileSync(path));
+process.stdout.write(JSON.stringify({ content: Buffer.concat(files.map(file => Buffer.from(new TextDecoder().decode(file)))).toString('base64'),
+ sizes: files.map(file => file.length), modes: paths.map(path => fs.statSync(path).mode & 511), directory: fs.statSync(process.env.FIXTURE_DIRECTORY).mode & 511,
+ eof: require('node:fs').readFileSync(0).length }));
+`,
+      '--',
+      ...guest.plan.args.filter((arg) => arg.startsWith('@'))
+    ],
+    stdio: 'pipe',
+    env: { ...process.env, FIXTURE_DIRECTORY: directory }
+  })
+  let stdout = ''
+  let stderr = ''
+  child.stdout.on('data', (bytes) => {
+    stdout += bytes
+  })
+  const finished = new Promise<number | null>((resolve, reject) => {
+    child.once('close', resolve)
+    child.once('error', reject)
+  })
+  child.stdin.on('error', () => {})
+  child.stderr.on('data', (chunk) => {
+    stderr += chunk
+    if (guest.observe(chunk)) {
+      onProof?.(directory)
+      const records = [...guest.records()]
+      child.stdin.end((controls ? controls(records, nonce) : records).join(''))
+    }
+  })
+  try {
+    const code = await finished
+    return {
+      code,
+      stdout,
+      stderr,
+      directory,
+      existed: existsSync(directory),
+      sentinel: existsSync(join(directory, 'sentinel'))
+        ? readFileSync(join(directory, 'sentinel'), 'utf8')
+        : null
+    }
+  } finally {
+    await rm(directory, { recursive: true, force: true })
+  }
+}
+
+it.each(['', tricky.repeat(12), `${'x'.repeat(5 * 1024 * 1024 - 4)}🌊GIF89a${tricky}`])(
+  'materializes exact native text with private modes across encoding and file boundaries',
+  async (content) => {
+    const result = await shellFixture(content)
+    expect(result.code).toBe(0)
+    const receipt = JSON.parse(result.stdout)
+    expect(Buffer.from(receipt.content, 'base64').toString()).toBe(Buffer.from(content).toString())
+    expect(receipt.modes.every((mode: number) => mode === 0o600)).toBe(true)
+    expect(receipt.directory).toBe(0o700)
+    expect(receipt.eof).toBe(0)
+    expect(receipt.sizes.every((size: number) => size <= 5 * 1024 * 1024)).toBe(true)
+    expect(result.existed).toBe(true)
+  }
+)
+
+it.each([
+  'collision',
+  'partial-data',
+  'wrong-end',
+  'missing-end',
+  'partial-execute',
+  'extra-data',
+  'wrong-ack'
+] as const)('does not execute on %s, and never adopts/deletes a collision', async (route) => {
+  const result = await shellFixture(
+    'private data',
+    (records, nonce) => {
+      if (route === 'partial-data') {
+        return [`A${nonce}\nDpartial`]
+      }
+      if (route === 'wrong-end') {
+        return records.map((record) => (record.startsWith('F') ? `F${nonce}:2\n` : record))
+      }
+      if (route === 'missing-end') {
+        return records.filter((record) => !record.startsWith('F'))
+      }
+      if (route === 'partial-execute') {
+        return records.map((record) => (record.startsWith('X') ? record.trim() : record))
+      }
+      if (route === 'extra-data') {
+        return [...records.slice(0, -1), 'Dextra\n', ...records.slice(-1)]
+      }
+      if (route === 'wrong-ack') {
+        return ['Ano\n']
+      }
+      return records
+    },
+    (directory) => {
+      if (route === 'collision') {
+        mkdirSync(directory)
+        writeFileSync(join(directory, 'sentinel'), 'untouched')
+      }
+    }
+  )
+  expect(result.code).not.toBe(0)
+  expect(result.stdout).toBe('')
+  if (route === 'collision') {
+    expect(result.stderr).not.toContain('ORCA_GENERATION_READY:')
+    expect(result.sentinel).toBe('untouched')
+  }
+  if (route === 'wrong-ack') {
+    expect(result.existed).toBe(false)
+  }
+})
+
+it.each([false, true])(
+  'bounds real producer work at N and 10N (backpressure=%s)',
+  async (backpressure) => {
+    const results: number[] = []
+    for (const size of [20_000, 200_000]) {
+      const guest = prepareWslPrompt(
+        plan(tricky.repeat(Math.ceil(size / tricky.length)).slice(0, size)),
+        'Actual'
+      )
+      let writes = 0
+      let maxRecord = 0
+      let pending = 0
+      let maxPending = 0
+      let maxQueued = 0
+      const stream = new Writable({
+        highWaterMark: 2048,
+        write(chunk, _encoding, callback) {
+          writes++
+          maxRecord = Math.max(maxRecord, chunk.length)
+          maxPending = Math.max(maxPending, ++pending)
+          const complete = () => {
+            maxQueued = Math.max(maxQueued, stream.writableLength)
+            pending--
+            callback()
+          }
+          if (backpressure) {
+            setImmediate(complete)
+          } else {
+            complete()
+          }
+        }
+      })
+      let yieldedAt = 0
+      setImmediate(() => {
+        yieldedAt = writes
+      })
+      const finished = new Promise<void>((resolve) => stream.once('finish', resolve))
+      await producePromptRecords(stream, guest.records(), new AbortController().signal, () => true)
+      await finished
+      expect(maxQueued).toBeLessThanOrEqual(2048 + 1026)
+      expect(yieldedAt).toBeGreaterThan(0)
+      expect(yieldedAt).toBeLessThan(writes)
+      expect(maxRecord).toBeLessThanOrEqual(1026)
+      expect(maxPending).toBe(1)
+      results.push(writes)
+    }
+    expect(results[1]).toBeLessThanOrEqual(results[0] * 10 + 10)
+    expect(results[1]).toBeGreaterThan(results[0] * 8)
+  }
+)
+
+it('fails a real post-proof storage redirect without running a partial request', async () => {
+  const result = await shellFixture('private data', undefined, undefined, (directory) =>
+    mkdirSync(join(directory, 'prompt-1.txt'))
+  )
+  expect(result.code).not.toBe(0)
+  expect(result.stdout).toBe('')
+  expect(result.existed).toBe(true)
+})
+
+it.each([
+  { boundary: 'data', stopping: 'cancel' },
+  { boundary: 'final', stopping: 'cancel' },
+  { boundary: 'data', stopping: 'deadline' },
+  { boundary: 'final', stopping: 'deadline' }
+] as const)(
+  'does not authorize after $stopping at $boundary write continuation',
+  async ({ boundary, stopping }) => {
+    vi.useFakeTimers()
+    const { child, execution, proof, nonce } = start()
+    const writes: string[] = []
+    vi.spyOn(child.stdin, 'write').mockImplementation((chunk) => {
+      const record = String(chunk)
+      writes.push(record)
+      if (record.startsWith(boundary === 'data' ? 'D' : 'F')) {
+        if (stopping === 'cancel') {
+          cancelLocalGeneration('conversation-name', cwd)
+        } else {
+          vi.advanceTimersByTime(SOURCE_CONTROL_GENERATION_TIMEOUT_MS)
+        }
+      }
+      return true
+    })
+    child.stderr.emit('data', Buffer.from(proof))
+    close(child)
+    expect(await execution.result).toMatchObject(
+      stopping === 'cancel'
+        ? { success: false, canceled: true }
+        : { success: false, error: 'Generation timed out after 60s.' }
+    )
+    await execution.processClosed
+    expect(writes).not.toContain(`X${nonce}\n`)
+  }
+)
+
+it.each(['success', 'nonzero', 'empty', 'storage', 'pipe-close'] as const)(
+  'runs the production attempt through real private shell preparation and %s',
+  async (outcome) => {
+    let directory = ''
+    let actualPipeError = false
+    const execution = withPlatform('win32', () =>
+      runLocalSourceControlPlan({
+        plan: plan(tricky.repeat(40)),
+        cwd,
+        env: undefined,
+        operation: 'conversation-name',
+        emptyResultName: 'name',
+        spawnAgent: (input) => {
+          const preparation = input.preparation
+          if (!preparation) {
+            throw new Error('Missing preparation')
+          }
+          directory = `/tmp/orca-generation-${preparation.args[0]}`
+          const argv =
+            outcome === 'pipe-close'
+              ? [
+                  '-c',
+                  `exec 0<&-; printf 'ORCA_GENERATION_READY:%s\\n' "$1" >&2; sleep 0.1`,
+                  'fixture',
+                  preparation.args[0]
+                ]
+              : [
+                  '-c',
+                  preparation.script,
+                  'fixture',
+                  ...preparation.args,
+                  '/bin/sh',
+                  '-c',
+                  outcome === 'empty'
+                    ? ':'
+                    : `printf '%s' 'Useful name'; exit ${outcome === 'nonzero' ? 7 : 0}`
+                ]
+          const child = withPlatform('darwin', () =>
+            spawnProcess({ program: '/bin/sh', args: argv, stdio: 'pipe' })
+          )
+          child.stdin.on('error', (error) => {
+            actualPipeError ||= 'code' in error && error.code === 'EPIPE'
+          })
+          if (outcome === 'storage') {
+            child.stderr.once('data', () => mkdirSync(join(directory, 'prompt-1.txt')))
+          }
+          return child
+        }
+      })
+    )
+    try {
+      const result = await execution.result
+      await execution.processClosed
+      expect(result.success).toBe(outcome === 'success')
+      expect(removeTreeMock).toHaveBeenCalledTimes(1)
+      if (outcome === 'pipe-close') {
+        expect(actualPipeError).toBe(true)
+      }
+      if (outcome === 'success') {
+        const file = readFileSync(join(directory, 'prompt-1.txt'))
+        expect(new TextDecoder().decode(file)).toBe(Buffer.from(tricky.repeat(40)).toString())
+      }
+    } finally {
+      if (directory) {
+        await rm(directory, { recursive: true, force: true })
+      }
+    }
+  }
+)
diff --git a/src/renderer/src/lib/source-control-generation-plan.test.ts b/src/renderer/src/lib/source-control-generation-plan.test.ts
index 99f5c86ea02..49cb5aae7dc 100644
--- a/src/renderer/src/lib/source-control-generation-plan.test.ts
+++ b/src/renderer/src/lib/source-control-generation-plan.test.ts
@@ -15,6 +15,16 @@ describe('planSourceControlCommitMessageGeneration', () => {
     ).toEqual({ ok: false, error: 'Command input is empty.' })
   })
 
+  it('describes OMP file delivery in dry-run plans', () => {
+    const result = planSourceControlCommitMessageGeneration({
+      agentId: 'omp',
+      model: 'gpt-5.5',
+      thinkingLevel: 'low'
+    })
+
+    expect(result.ok && result.delivery).toContain('temporary file attachment')
+  })
+
   it('expands linkedIssue when validating commit and pull-request recipes', () => {
     for (const actionId of ['commitMessage', 'pullRequest'] as const) {
       // Why: `{prompt}` puts the rendered template in argv, so commandLabel shows it.
diff --git a/src/renderer/src/lib/source-control-generation-plan.ts b/src/renderer/src/lib/source-control-generation-plan.ts
index ce65a25fcad..d487bf26a08 100644
--- a/src/renderer/src/lib/source-control-generation-plan.ts
+++ b/src/renderer/src/lib/source-control-generation-plan.ts
@@ -75,8 +75,9 @@ export function planSourceControlTextGeneration(
   if (!planned.ok) {
     return { ok: false, error: planned.error }
   }
-  const delivery =
-    planned.plan.stdinPayload === null
+  const delivery = planned.plan.promptFile
+    ? 'Prompt is delivered as a temporary file attachment.'
+    : planned.plan.stdinPayload === null
       ? 'Prompt is delivered as command arguments.'
       : 'Prompt is piped to the agent over stdin.'
   return {
diff --git a/src/shared/commit-message-agent-spec.ts b/src/shared/commit-message-agent-spec.ts
index e9f3031f4df..51b16d598ac 100644
--- a/src/shared/commit-message-agent-spec.ts
+++ b/src/shared/commit-message-agent-spec.ts
@@ -44,8 +44,8 @@ export type CommitMessageAgentSpec = {
   id: TuiAgent
   label: string
   binary: string
-  /** Where the prompt is delivered. Large diffs go via stdin to avoid argv limits. */
-  promptDelivery: 'argv' | 'stdin'
+  /** Transport for the prompt; stdin and file delivery avoid argv limits. */
+  promptDelivery: 'argv' | 'stdin' | 'file'
   buildArgs: (params: {
     prompt: string
     model: string
@@ -94,8 +94,8 @@ export const COMMIT_MESSAGE_AGENT_SPECS: Partial<Record<TuiAgent, CommitMessageA
     id: 'omp',
     label: 'OMP',
     binary: 'omp',
-    promptDelivery: 'stdin',
-    buildArgs: ({ model, thinkingLevel }) => [
+    promptDelivery: 'file',
+    buildArgs: ({ prompt, model, thinkingLevel }) => [
       '--print',
       '--no-session',
       '--no-tools',
@@ -105,7 +105,8 @@ export const COMMIT_MESSAGE_AGENT_SPECS: Partial<Record<TuiAgent, CommitMessageA
       '--mode',
       'text',
       ...(model && model !== 'default' ? ['--model', model] : []),
-      ...(thinkingLevel ? ['--thinking', thinkingLevel] : [])
+      ...(thinkingLevel ? ['--thinking', thinkingLevel] : []),
+      prompt
     ],
     singletonOptions: [['--model'], ['--thinking']],
     modelSource: 'dynamic',
diff --git a/src/shared/commit-message-omp.spec.ts b/src/shared/commit-message-omp.spec.ts
index 479a4566b1d..7ea90d0c0f6 100644
--- a/src/shared/commit-message-omp.spec.ts
+++ b/src/shared/commit-message-omp.spec.ts
@@ -18,13 +18,13 @@ describe('OMP Source Control AI', () => {
       })
     }
   )
-  it('plans stdin delivery with tools and extensions disabled', () => {
+  it('plans file delivery with tools and extensions disabled', () => {
     const spec = getCommitMessageAgentSpec('omp')
-    expect(spec?.promptDelivery).toBe('stdin')
+    expect(spec?.promptDelivery).toBe('file')
     if (!spec) {
       throw new Error('Missing OMP spec')
     }
-    const args = spec.buildArgs({ prompt: 'large diff', model: 'default' })
+    const args = spec.buildArgs({ prompt: '@{prompt-file}', model: 'default' })
     expect(args).toEqual([
       '--print',
       '--no-session',
@@ -33,11 +33,23 @@ describe('OMP Source Control AI', () => {
       '--no-skills',
       '--no-rules',
       '--mode',
-      'text'
+      'text',
+      '@{prompt-file}'
     ])
     expect(
-      spec?.buildArgs({ prompt: '', model: 'provider/exact-model', thinkingLevel: 'low' })
-    ).toEqual([...args, '--model', 'provider/exact-model', '--thinking', 'low'])
+      spec?.buildArgs({
+        prompt: '@{prompt-file}',
+        model: 'provider/exact-model',
+        thinkingLevel: 'low'
+      })
+    ).toEqual([
+      ...args.slice(0, -1),
+      '--model',
+      'provider/exact-model',
+      '--thinking',
+      'low',
+      '@{prompt-file}'
+    ])
   })
   it('discovers provider-qualified models through the existing OMP JSON parser', () => {
     const discovery = getCommitMessageAgentSpec('omp')?.modelDiscovery
@@ -58,8 +70,10 @@ describe('OMP Source Control AI', () => {
         {
           agentId: 'omp',
           model: 'provider/model',
+          thinkingLevel: 'medium',
           backslash,
-          agentArgs: '--model provider/override'
+          agentCommandOverride: 'OMP_ENV=value omp --model provider/prefix --thinking high',
+          agentArgs: '--model provider/override --thinking low --verbose --'
         },
         prompt
       )
@@ -67,7 +81,16 @@ describe('OMP Source Control AI', () => {
       if (!result.ok) {
         throw new Error(result.error)
       }
-      expect(result.plan.stdinPayload).toBe(prompt)
+      expect(result.plan.stdinPayload).toBeNull()
+      expect(result.plan.promptFile).toEqual({
+        content: prompt,
+        argIndex: result.plan.args.indexOf('@{prompt-file}')
+      })
+      expect(result.plan.env).toEqual({ OMP_ENV: 'value' })
+      expect(result.plan.args.slice(-3)).toEqual(['@{prompt-file}', '--verbose', '--'])
+      expect(result.plan.args.filter((arg) => arg === '--thinking')).toHaveLength(1)
+      expect(result.plan.args).toContain('low')
+      expect(result.plan.args).not.toContain('high')
       expect(result.plan.args).not.toContain(prompt)
       expect(result.plan.args.filter((arg) => arg === '--model')).toHaveLength(1)
       expect(result.plan.args).toContain('provider/override')
diff --git a/src/shared/commit-message-plan.ts b/src/shared/commit-message-plan.ts
index ce7ec29e6a8..3bf6ac2f6d1 100644
--- a/src/shared/commit-message-plan.ts
+++ b/src/shared/commit-message-plan.ts
@@ -36,6 +36,8 @@ export type CommitMessagePlan = {
   args: string[]
   /** Non-null when the prompt should be piped via stdin. */
   stdinPayload: string | null
+  /** Execution-host-owned prompt attachment, materialized only when starting the process. */
+  promptFile?: { content: string; argIndex: number }
   /** Human-readable label used in error prefixes (e.g. "Claude failed: ..."). */
   label: string
   /** Leading command assignments, applied on the execution host. */
@@ -137,7 +139,7 @@ function applySingletonOptionOverrides(args: {
 function insertAdditionalAgentArgs(args: {
   baseArgs: string[]
   agentArgs: string[]
-  promptDelivery: 'argv' | 'stdin'
+  promptDelivery: 'argv' | 'stdin' | 'file'
   prompt: string
 }): string[] {
   if (!args.agentArgs.length) {
@@ -221,7 +223,8 @@ export function planCommitMessageGeneration(
     }
   }
 
-  const argvPrompt = spec.promptDelivery === 'argv' ? prompt : ''
+  const argvPrompt =
+    spec.promptDelivery === 'file' ? '@{prompt-file}' : spec.promptDelivery === 'argv' ? prompt : ''
   const agentArgs = planAdditionalAgentArgs(input.agentArgs, input.backslash)
   if (!agentArgs.ok) {
     return agentArgs
@@ -287,6 +290,14 @@ export function planCommitMessageGeneration(
           : spec.promptDelivery === 'stdin'
             ? prompt
             : null,
+      ...(spec.promptDelivery === 'file'
+        ? {
+            promptFile: {
+              content: prompt,
+              argIndex: merged.prefixArgs.length + merged.generatedArgs.length - 1
+            }
+          }
+        : {}),
       label: spec.label,
       ...(formatOption?.value === 'json' ? { outputFormat: 'opencode-json' as const } : {}),
       ...(kimiFormatOption?.value === 'stream-json'
diff --git a/src/shared/omp-source-control-discovery.spec.ts b/src/shared/omp-source-control-discovery.spec.ts
index 432810914fc..1a6d54c9a40 100644
--- a/src/shared/omp-source-control-discovery.spec.ts
+++ b/src/shared/omp-source-control-discovery.spec.ts
@@ -64,7 +64,11 @@ for (const hostKey of ['local', 'ssh:omp-host']) {
           expect(resolved.value.params.model).toBe(selectedModel ?? 'default')
           const args = spec.buildArgs({ prompt: '', model: resolved.value.params.model })
           if (selectedModel === 'provider/exact-model') {
-            expect(args.slice(-2)).toEqual(['--model', 'provider/exact-model'])
+            const modelIndex = args.indexOf('--model')
+            expect(args.slice(modelIndex, modelIndex + 2)).toEqual([
+              '--model',
+              'provider/exact-model'
+            ])
           } else {
             expect(args).not.toContain('--model')
           }
diff --git a/src/shared/posix-printf-encoding.ts b/src/shared/posix-printf-encoding.ts
new file mode 100644
index 00000000000..ad1599aabde
--- /dev/null
+++ b/src/shared/posix-printf-encoding.ts
@@ -0,0 +1,25 @@
+export const POSIX_PRINTF_RECORD_MAX_BYTES = 1_024
+const PRINTF_ESCAPED_BYTES = new Set([0x21, 0x27, 0x5c])
+
+export function* encodePosixPrintfRecords(command: string): Generator<string> {
+  let chunk = ''
+  let chunkBytes = 0
+  for (const character of command) {
+    const codePoint = character.codePointAt(0)!
+    const isSafePrintableAscii =
+      codePoint >= 0x20 && codePoint <= 0x7e && !PRINTF_ESCAPED_BYTES.has(codePoint)
+    const encodedCharacter =
+      codePoint > 0x7f || isSafePrintableAscii
+        ? character
+        : `\\0${codePoint.toString(8).padStart(3, '0')}`
+    const encodedBytes = codePoint > 0x7f ? Buffer.byteLength(character) : encodedCharacter.length
+    if (chunkBytes + encodedBytes > POSIX_PRINTF_RECORD_MAX_BYTES) {
+      yield chunk
+      chunk = ''
+      chunkBytes = 0
+    }
+    chunk += encodedCharacter
+    chunkBytes += encodedBytes
+  }
+  yield chunk
+}
diff --git a/src/shared/windows-command-line-budget.ts b/src/shared/windows-command-line-budget.ts
index cac913e9260..c5d7a35e2af 100644
--- a/src/shared/windows-command-line-budget.ts
+++ b/src/shared/windows-command-line-budget.ts
@@ -46,3 +46,5 @@ function countEscapes(arg: string): number {
   }
   return count
 }
+
+export class WindowsCommandLineBudgetError extends Error {}
diff --git a/src/shared/wsl-paths.ts b/src/shared/wsl-paths.ts
index 4385d231233..c4dac7cc6a5 100644
--- a/src/shared/wsl-paths.ts
+++ b/src/shared/wsl-paths.ts
@@ -162,3 +162,11 @@ export function uncRouteKey(cwd: string): string | null {
   const server = cwd.slice(2).split(/[\\/]/, 1)[0]
   return `unc:${server.toLowerCase()}`
 }
+
+/** Match command routing: a native UNC cwd takes precedence over a distro hint. */
+export function wslDistroForCommand(cwd: string | undefined, override?: string): string | null {
+  if (process.platform !== 'win32') {
+    return null
+  }
+  return (cwd ? parseWslUncPath(cwd)?.distro : undefined) ?? override ?? null
+}