diff --git a/setup/auto.ts b/setup/auto.ts
index 203b0bf..ea5dec3 100644
--- a/setup/auto.ts
+++ b/setup/auto.ts
@@ -115,10 +115,44 @@ async function main(): Promise<void> {
         4,
       ),
     );
-    const res = await runQuietStep('onecli', {
-      running: "Setting up OneCLI, your agent's vault…",
-      done: 'OneCLI vault ready.',
-    });
+
+    // Respect an existing OneCLI install. Re-running the installer would
+    // rebind the listener and knock any other app using that gateway
+    // offline — confirm with the user before doing that.
+    const existing = detectExistingOnecli();
+    let reuse = false;
+    if (existing) {
+      const choice = ensureAnswer(
+        await p.select({
+          message: `Found an existing OneCLI at ${existing.apiHost}. What would you like to do?`,
+          options: [
+            {
+              value: 'reuse',
+              label: 'Use the existing instance',
+              hint: 'recommended — keeps other apps bound to this vault working',
+            },
+            {
+              value: 'fresh',
+              label: 'Install a fresh instance for NanoClaw',
+              hint: 'reinstalls onecli; other apps may need to reconnect',
+            },
+          ],
+        }),
+      ) as 'reuse' | 'fresh';
+      setupLog.userInput('onecli_choice', choice);
+      reuse = choice === 'reuse';
+    }
+
+    const res = await runQuietStep(
+      'onecli',
+      {
+        running: reuse
+          ? 'Hooking up to your existing OneCLI…'
+          : "Setting up OneCLI, your agent's vault…",
+        done: 'OneCLI vault ready.',
+      },
+      reuse ? ['--reuse'] : [],
+    );
     if (!res.ok) {
       const err = res.terminal?.fields.ERROR;
       if (err === 'onecli_not_on_path_after_install') {
@@ -691,6 +725,46 @@ function anthropicSecretExists(): boolean {
   }
 }
 
+/**
+ * Probe the host for a working OneCLI install so we can offer to reuse it
+ * instead of re-running the installer (which rebinds the listener and breaks
+ * any other app already using that gateway).
+ */
+function detectExistingOnecli(): { version: string; apiHost: string } | null {
+  try {
+    const ver = spawnSync('onecli', ['version'], {
+      encoding: 'utf-8',
+      stdio: ['ignore', 'pipe', 'ignore'],
+    });
+    if (ver.status !== 0) return null;
+    const version = (ver.stdout ?? '').trim();
+    if (!version) return null;
+
+    const host = spawnSync('onecli', ['config', 'get', 'api-host'], {
+      encoding: 'utf-8',
+      stdio: ['ignore', 'pipe', 'ignore'],
+    });
+    if (host.status !== 0) return null;
+    const raw = (host.stdout ?? '').trim();
+    if (!raw) return null;
+
+    // onecli 1.3+ emits JSON by default. Older versions would print raw text.
+    try {
+      const parsed = JSON.parse(raw) as { data?: unknown; value?: unknown };
+      const val = parsed.data ?? parsed.value;
+      if (typeof val === 'string' && val.trim()) {
+        return { version, apiHost: val.trim() };
+      }
+    } catch {
+      // not JSON — try to extract a URL directly
+    }
+    const m = raw.match(/https?:\/\/[\w.\-]+(?::\d+)?/);
+    return m ? { version, apiHost: m[0] } : null;
+  } catch {
+    return null;
+  }
+}
+
 function runInheritScript(cmd: string, args: string[]): Promise<number> {
   return new Promise((resolve) => {
     const child = spawn(cmd, args, { stdio: 'inherit' });
diff --git a/setup/onecli.ts b/setup/onecli.ts
index c4ce83f..6be722a 100644
--- a/setup/onecli.ts
+++ b/setup/onecli.ts
@@ -1,13 +1,15 @@
 /**
  * Step: onecli — Install + configure the OneCLI gateway and CLI.
  *
- * Aggregates what the old /setup + /init-onecli skills ran as loose shell
- * commands. Idempotent: skips install if `onecli` already works, and safely
- * re-applies PATH, api-host, and .env updates.
+ * Two modes:
+ *   (default) run the OneCLI installer, configure api-host, write .env.
+ *   --reuse   skip the installer; reuse the onecli instance already running
+ *             on the host. Required for users who have other apps bound to
+ *             an existing gateway, since re-running the installer rebinds
+ *             the listener and breaks those consumers.
  *
- * Emits ONECLI_URL so /new-setup SKILL.md can forward it downstream (e.g. as
- * ${ONECLI_URL} in status messages). Polls /health to give downstream steps
- * (auth, service) a ready gateway.
+ * Emits ONECLI_URL and polls /health so downstream steps (auth, service)
+ * get a ready gateway.
  */
 import { execFileSync, execSync } from 'child_process';
 import fs from 'fs';
@@ -37,6 +39,32 @@ function onecliVersion(): string | null {
   }
 }
 
+/**
+ * Ask the installed onecli CLI for its configured api-host. Returns null if
+ * onecli isn't on PATH, errors, or has no api-host configured.
+ *
+ * Tolerates both JSON output (onecli 1.3+) and older raw-text output.
+ */
+export function getOnecliApiHost(): string | null {
+  try {
+    const out = execFileSync('onecli', ['config', 'get', 'api-host'], {
+      encoding: 'utf-8',
+      env: childEnv(),
+      stdio: ['ignore', 'pipe', 'ignore'],
+    }).trim();
+    try {
+      const parsed = JSON.parse(out) as { data?: unknown; value?: unknown };
+      const val = parsed.data ?? parsed.value;
+      if (typeof val === 'string' && val.trim()) return val.trim();
+    } catch {
+      // not JSON — fall through to URL extraction
+    }
+    return extractUrlFromOutput(out);
+  } catch {
+    return null;
+  }
+}
+
 function extractUrlFromOutput(output: string): string | null {
   const match = output.match(/https?:\/\/[\w.\-]+(?::\d+)?/);
   return match ? match[0] : null;
@@ -106,9 +134,49 @@ async function pollHealth(url: string, timeoutMs: number): Promise<boolean> {
   return false;
 }
 
-export async function run(_args: string[]): Promise<void> {
+export async function run(args: string[]): Promise<void> {
+  const reuse = args.includes('--reuse');
   ensureShellProfilePath();
 
+  if (reuse) {
+    // Reuse-mode: don't touch the running gateway at all. Just verify it
+    // exists, read its api-host, write ONECLI_URL to .env, and move on.
+    const version = onecliVersion();
+    if (!version) {
+      emitStatus('ONECLI', {
+        INSTALLED: false,
+        STATUS: 'failed',
+        ERROR: 'onecli_not_found_for_reuse',
+        HINT: 'onecli not on PATH. Re-run setup and choose "install fresh".',
+        LOG: 'logs/setup.log',
+      });
+      process.exit(1);
+    }
+    const url = getOnecliApiHost();
+    if (!url) {
+      emitStatus('ONECLI', {
+        INSTALLED: true,
+        STATUS: 'failed',
+        ERROR: 'onecli_api_host_not_configured',
+        HINT: 'Existing onecli has no api-host set. Run `onecli config set api-host <url>` or re-run setup with install-fresh.',
+        LOG: 'logs/setup.log',
+      });
+      process.exit(1);
+    }
+    writeEnvOnecliUrl(url);
+    log.info('Reusing existing OneCLI', { url });
+    const healthy = await pollHealth(url, 5000);
+    emitStatus('ONECLI', {
+      INSTALLED: true,
+      REUSED: true,
+      ONECLI_URL: url,
+      HEALTHY: healthy,
+      STATUS: 'success',
+      LOG: 'logs/setup.log',
+    });
+    return;
+  }
+
   log.info('Installing OneCLI gateway and CLI');
   const res = installOnecli();
   if (!res.ok) {