diff --git a/src/cli/index.ts b/src/cli/index.ts
index 940201ab21..aea63f9af2 100755
--- a/src/cli/index.ts
+++ b/src/cli/index.ts
@@ -216,6 +216,17 @@ async function handleStart(options: { block?: boolean } = {}) {
   const requestedPort = parsePortOption();
   const owner = await findProxyOwnerBeforeJournalRecovery();
   if (owner.live) {
+    // Service-wrapper context (opencodex-service.cmd `:loop`): a healthy proxy from
+    // ANY source means the requested port is already served. Exit 0 so the wrapper's
+    // `if %ERRORLEVEL% NEQ 0` retry loop terminates instead of respawning every 5s
+    // against a listener it can never claim (observed as an endless
+    // "Proxy already running" service.log loop).
+    // Only the exact "1" sentinel takes this path — the same check syncCleanup
+    // uses — so an env value like "0" or "false" cannot bypass the conflict error.
+    if (process.env.OCX_SERVICE === "1") {
+      console.log(`Proxy already running (PID ${owner.live.pid ?? owner.pidSnapshot ?? "unknown"}, port ${owner.live.port}); service wrapper staying out of the way.`);
+      process.exit(0);
+    }
     console.error(`⚠️  Proxy already running (PID ${owner.live.pid ?? owner.pidSnapshot ?? "unknown"}, port ${owner.live.port}). Use 'ocx stop' first.`);
     process.exit(1);
   }
diff --git a/src/service.ts b/src/service.ts
index 668f165202..03cc8749ff 100644
--- a/src/service.ts
+++ b/src/service.ts
@@ -24,6 +24,7 @@ import {
   ELEVATION_REQUEST_TIMEOUT_MS,
   OCX_ELEVATED_PROTOCOL_FAILED,
   raceWithTimeout,
+  resolveTrustedWindowsPowerShellExe,
   resolveTrustedWindowsSchtasksExe,
   startElevatedSchtasksCreateAndRun,
   runWindowsElevated,
@@ -2164,6 +2165,50 @@ export function stopWindows(): void {
 }
 function statusWindows(): string { try { return schtasks(["/query", "/tn", TASK]); } catch { return ""; } }
 function statusWindowsXml(): string { try { return schtasks(["/query", "/tn", TASK, "/xml"]); } catch { return ""; } }
+
+/**
+ * Best-effort termination of surviving Windows scheduler launcher/wrapper processes.
+ * `schtasks /end` ends the task instance but often leaves wscript/cmd running the
+ * `:loop` batch, which brings the proxy back during a stop or restart. Same killer
+ * the update job uses, so both teardown paths share the guarantee.
+ *
+ * Matching is scoped to the CANONICAL paths of THIS installation (opencodex-service.cmd
+ * and opencodex-service-launcher.vbs under the current config dir), never a bare
+ * filename: a wrapper from another OpenCodex home — or an unrelated process whose
+ * command line merely contains the filename — must not be force-terminated.
+ * The path must appear as a COMPLETE command-line token (wscript.exe spawns the
+ * .vbs as an argument; cmd.exe /c runs the .cmd), so a substring-only match is
+ * excluded.
+ */
+function killWindowsServiceWrapperProcesses(): void {
+  if (process.platform !== "win32") return;
+  try {
+    const script = windowsServiceScriptPath();
+    const launcher = windowsLauncherVbsPath();
+    // Quote for PowerShell: single-quote the value and double any embedded quote.
+    const quote = (value: string) => `'${value.replace(/'/g, "''")}'`;
+    const ps = [
+      `$pats = @(${quote(script)}, ${quote(launcher)});`,
+      "Get-CimInstance Win32_Process | Where-Object {",
+      "  if ($_.ProcessId -eq $PID) { return $false };",
+      "  $c = $_.CommandLine; if (-not $c) { return $false };",
+      "  foreach ($p in $pats) {",
+      "    $i = $c.IndexOf($p, [System.StringComparison]::OrdinalIgnoreCase);",
+      "    if ($i -lt 0) { continue };",
+      "    $before = if ($i -gt 0) { $c.Substring($i - 1, 1) } else { ' ' };",
+      "    $end = $i + $p.Length;",
+      "    $after = if ($end -lt $c.Length) { $c.Substring($end, 1) } else { ' ' };",
+      "    if ($before -match '[\\s\"'']' -and $after -match '[\\s\"'']') { return $true };",
+      "  };",
+      "  $false",
+      "} | ForEach-Object { Stop-Process -Id $_.ProcessId -Force -ErrorAction SilentlyContinue }",
+    ].join(" ");
+    spawnSync(resolveTrustedWindowsPowerShellExe(), [
+      "-NoProfile", "-NoLogo", "-NonInteractive", "-WindowStyle", "Hidden",
+      "-Command", ps,
+    ], { stdio: "ignore", timeout: 5000, windowsHide: true });
+  } catch { /* best-effort */ }
+}
 function uninstallWindows(): void {
   const probe = probeWindowsSchedulerTask(TASK);
   if (probe.status === "present") {
@@ -2692,6 +2737,10 @@ export function stopServiceIfInstalled(): boolean {
     if (statusWinswRaw() !== "nonexistent") {
       try { stopWinswService(); stopped = true; } catch { /* best-effort */ }
     }
+    // `schtasks /end` ends the task instance but the cmd `:loop` wrapper survives and
+    // respawns its child seconds later (issue #764), resurrecting the proxy during a
+    // stop or a tray restart. Kill the launcher/wrapper processes outright.
+    killWindowsServiceWrapperProcesses();
     if (stopped) return true;
   } else if (process.platform === "linux" && isSystemd() && existsSync(unitPath())) {
     try { stopSystemd(); return true; } catch { return false; }
diff --git a/tests/cli-ready.test.ts b/tests/cli-ready.test.ts
index bb62320c54..9e02e5f6ac 100644
--- a/tests/cli-ready.test.ts
+++ b/tests/cli-ready.test.ts
@@ -835,3 +835,58 @@ describe("runReady production findLiveProxy deadline wiring (source-level)", ()
     expect(readySource).toContain("verifyPidFn: () => null");
   });
 });
+
+// ── handleStart service-wrapper exit guard (source-level) ─────────────────────
+// #764 follow-up: in OCX_SERVICE context a healthy proxy from ANY source must
+// end handleStart with exit 0, so the opencodex-service.cmd `:loop` wrapper
+// (retry on non-zero) does not respawn every 5s against a listener it can never
+// claim. Source-level pin so a future edit cannot drop the guard silently.
+describe("handleStart OCX_SERVICE exit guard (source-level)", () => {
+  const cliSource = readFileSync(join(import.meta.dir, "../src/cli/index.ts"), "utf8");
+
+  test("an already-live proxy exits 0 in OCX_SERVICE context", () => {
+    expect(cliSource).toMatch(/process\.env\.OCX_SERVICE === "1"/);
+    expect(cliSource).toMatch(/process\.exit\(0\)/);
+    const guard = cliSource.match(/if\s*\(process\.env\.OCX_SERVICE === "1"\)\s*\{[\s\S]{0,400}?process\.exit\(0\)/);
+    expect(guard, "OCX_SERVICE guard must exit 0 when the port is already served").not.toBeNull();
+    const nonService = cliSource.match(/Proxy already running[\s\S]{0,200}?process\.exit\(1\)/);
+    expect(nonService, "non-service path keeps the exit 1 conflict error").not.toBeNull();
+  });
+
+  test("service.ts teardown kills surviving wrapper processes on stop", () => {
+    const serviceSource = readFileSync(join(import.meta.dir, "../src/service.ts"), "utf8");
+    expect(serviceSource).toMatch(/killWindowsServiceWrapperProcesses/);
+    const callSite = serviceSource.match(/stopServiceIfInstalled[\s\S]{0,1200}?killWindowsServiceWrapperProcesses\(\)/);
+    expect(callSite, "wrapper kill must run during stopServiceIfInstalled").not.toBeNull();
+  });
+
+  test("wrapper kill matches the canonical paths of THIS installation, not bare filenames", () => {
+    // Review follow-up: matching by bare filename would force-terminate a
+    // wrapper from another OpenCodex home (or any process whose command line
+    // merely contains the name). The kill must target the exact canonical
+    // paths windowsServiceScriptPath()/windowsLauncherVbsPath() produce.
+    const serviceSource = readFileSync(join(import.meta.dir, "../src/service.ts"), "utf8");
+    expect(serviceSource).toMatch(/windowsServiceScriptPath\(\)/);
+    expect(serviceSource).toMatch(/windowsLauncherVbsPath\(\)/);
+    const killBody = serviceSource.match(/function killWindowsServiceWrapperProcesses\(\)[\s\S]*?\n}/);
+    expect(killBody, "killWindowsServiceWrapperProcesses body must exist").not.toBeNull();
+    expect(killBody![0]).toContain("windowsServiceScriptPath()");
+    expect(killBody![0]).toContain("windowsLauncherVbsPath()");
+    // Bare wrapper filenames must NOT be the match target.
+    expect(killBody![0]).not.toMatch(/\$pats = @\('opencodex-service\.cmd'\)/);
+  });
+
+  test("wrapper kill requires the canonical path as a complete command-line token", () => {
+    // Review follow-up: a substring match could force-terminate an unrelated
+    // process whose command line merely contains the canonical path. The
+    // PowerShell filter must check token boundaries (whitespace/quote before
+    // and after the path), not a bare IndexOf.
+    const serviceSource = readFileSync(join(import.meta.dir, "../src/service.ts"), "utf8");
+    const killBody = serviceSource.match(/function killWindowsServiceWrapperProcesses\(\)[\s\S]*?\n}/);
+    expect(killBody, "killWindowsServiceWrapperProcesses body must exist").not.toBeNull();
+    expect(killBody![0]).not.toMatch(/IndexOf\(\$p, \[System\.StringComparison\]::OrdinalIgnoreCase\) -ge 0/);
+    expect(killBody![0]).toMatch(/Substring\(/);
+    expect(killBody![0]).toMatch(/before/);
+    expect(killBody![0]).toMatch(/after/);
+  });
+});