diff --git a/src/lib/global-cli-actions.ts b/src/lib/global-cli-actions.ts
index 49334c3adbe..8b09589634d 100644
--- a/src/lib/global-cli-actions.ts
+++ b/src/lib/global-cli-actions.ts
@@ -39,7 +39,10 @@ export function runBackupAllAction(): void {
 }
 
 export async function runUpgradeSandboxesAction(args: string[] = []): Promise<void> {
-  await getNemoClawRuntimeBridge().upgradeSandboxes(args);
+  const { upgradeSandboxes } = require("./upgrade-sandboxes-action") as {
+    upgradeSandboxes: (args?: string[]) => Promise<void>;
+  };
+  await upgradeSandboxes(args);
 }
 
 export async function runGarbageCollectImagesAction(args: string[] = []): Promise<void> {
diff --git a/src/lib/nemoclaw-runtime-bridge.ts b/src/lib/nemoclaw-runtime-bridge.ts
index 5811dfee5a3..a762ea197cd 100644
--- a/src/lib/nemoclaw-runtime-bridge.ts
+++ b/src/lib/nemoclaw-runtime-bridge.ts
@@ -3,9 +3,7 @@
 
 /* v8 ignore start -- transitional bridge until command actions are extracted from src/nemoclaw.ts. */
 
-export interface NemoClawRuntimeBridge {
-  upgradeSandboxes: (args?: string[]) => Promise<void>;
-}
+export interface NemoClawRuntimeBridge {}
 
 let runtimeFactory = (): NemoClawRuntimeBridge => {
   const runtimeModule = require("../nemoclaw") as {
diff --git a/src/lib/sandbox-runtime-actions.ts b/src/lib/sandbox-runtime-actions.ts
index 6a8d06b1da4..81171c171e6 100644
--- a/src/lib/sandbox-runtime-actions.ts
+++ b/src/lib/sandbox-runtime-actions.ts
@@ -5,7 +5,6 @@
 
 import type { SandboxConnectOptions } from "./sandbox-connect-action";
 import type { SandboxLogsOptions } from "./sandbox-logs-options";
-import { getNemoClawRuntimeBridge } from "./nemoclaw-runtime-bridge";
 
 export async function connectSandbox(
   sandboxName: string,
diff --git a/src/lib/upgrade-sandboxes-action.ts b/src/lib/upgrade-sandboxes-action.ts
new file mode 100644
index 00000000000..281487bd940
--- /dev/null
+++ b/src/lib/upgrade-sandboxes-action.ts
@@ -0,0 +1,125 @@
+// SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+/* v8 ignore start -- exercised through CLI subprocess upgrade tests. */
+
+import { CLI_NAME } from "./branding";
+import { prompt as askPrompt } from "./credentials";
+import { captureOpenshell } from "./openshell-runtime";
+import * as registry from "./registry";
+import { parseLiveSandboxNames } from "./runtime-recovery";
+import { rebuildSandbox } from "./sandbox-rebuild-action";
+import * as sandboxVersion from "./sandbox-version";
+import { B, D, G, R, YW } from "./terminal-style";
+
+// ── Upgrade sandboxes (#1904) ────────────────────────────────────
+// Detect sandboxes running stale agent versions and offer to rebuild them.
+
+export async function upgradeSandboxes(args: string[] = []): Promise<void> {
+  const checkOnly = args.includes("--check");
+  const auto = args.includes("--auto");
+  const skipConfirm = auto || args.includes("--yes");
+
+  const sandboxes = registry.listSandboxes().sandboxes;
+  if (sandboxes.length === 0) {
+    console.log("  No sandboxes found in the registry.");
+    return;
+  }
+
+  // Query live sandboxes so we can tell the user which are running
+  const liveResult = captureOpenshell(["sandbox", "list"], { ignoreError: true });
+  if (liveResult.status !== 0) {
+    console.error("  Failed to query running sandboxes from OpenShell.");
+    console.error("  Ensure OpenShell is running: openshell status");
+    process.exit(liveResult.status || 1);
+  }
+  const liveNames = parseLiveSandboxNames(liveResult.output || "");
+
+  // Classify sandboxes as stale, unknown, or current
+  const stale = [];
+  const unknown = [];
+  for (const sb of sandboxes) {
+    const versionCheck = sandboxVersion.checkAgentVersion(sb.name);
+    if (versionCheck.isStale) {
+      stale.push({
+        name: sb.name,
+        current: versionCheck.sandboxVersion,
+        expected: versionCheck.expectedVersion,
+        running: liveNames.has(sb.name),
+      });
+    } else if (versionCheck.detectionMethod === "unavailable") {
+      unknown.push({
+        name: sb.name,
+        expected: versionCheck.expectedVersion,
+        running: liveNames.has(sb.name),
+      });
+    }
+  }
+
+  if (stale.length === 0 && unknown.length === 0) {
+    console.log("  All sandboxes are up to date.");
+    return;
+  }
+
+  if (stale.length > 0) {
+    console.log(`\n  ${B}Stale sandboxes:${R}`);
+    for (const s of stale) {
+      const status = s.running ? `${G}running${R}` : `${D}stopped${R}`;
+      console.log(`    ${s.name}  v${s.current || "?"} → v${s.expected}  (${status})`);
+    }
+  }
+  if (unknown.length > 0) {
+    console.log(`\n  ${YW}Unknown version:${R}`);
+    for (const s of unknown) {
+      const status = s.running ? `${G}running${R}` : `${D}stopped${R}`;
+      console.log(`    ${s.name}  v? → v${s.expected}  (${status})`);
+    }
+  }
+  console.log("");
+
+  if (checkOnly) {
+    if (stale.length > 0) console.log(`  ${stale.length} sandbox(es) need upgrading.`);
+    if (unknown.length > 0) {
+      console.log(
+        `  ${unknown.length} sandbox(es) could not be version-checked; start them and rerun, or rebuild manually.`,
+      );
+    }
+    console.log(`  Run \`${CLI_NAME} upgrade-sandboxes\` to rebuild them.`);
+    return;
+  }
+
+  const rebuildable = stale.filter((s: { running: boolean }) => s.running);
+  const stopped = stale.filter((s: { running: boolean }) => !s.running);
+  if (stopped.length > 0) {
+    console.log(`  ${D}Skipping ${stopped.length} stopped sandbox(es) — start them first.${R}`);
+  }
+  if (rebuildable.length === 0) {
+    console.log("  No running stale sandboxes to rebuild.");
+    return;
+  }
+
+  let rebuilt = 0;
+  let failed = 0;
+  for (const s of rebuildable) {
+    if (!skipConfirm) {
+      const answer = await askPrompt(`  Rebuild '${s.name}'? [y/N]: `);
+      if (answer.trim().toLowerCase() !== "y" && answer.trim().toLowerCase() !== "yes") {
+        console.log(`  Skipped '${s.name}'.`);
+        continue;
+      }
+    }
+    try {
+      await rebuildSandbox(s.name, ["--yes"], { throwOnError: true });
+      rebuilt++;
+    } catch (err) {
+      const errorMessage = err instanceof Error ? err.message : String(err);
+      console.error(`  ${YW}⚠${R} Failed to rebuild '${s.name}': ${errorMessage}`);
+      failed++;
+    }
+  }
+
+  console.log("");
+  if (rebuilt > 0) console.log(`  ${G}✓${R} ${rebuilt} sandbox(es) rebuilt.`);
+  if (failed > 0) console.log(`  ${YW}⚠${R} ${failed} sandbox(es) failed — see errors above.`);
+  if (failed > 0) process.exit(1);
+}
diff --git a/src/nemoclaw.ts b/src/nemoclaw.ts
index 1e5c6a9461e..3984e225af3 100644
--- a/src/nemoclaw.ts
+++ b/src/nemoclaw.ts
@@ -36,7 +36,6 @@ const {
 } = require("./lib/docker");
 const { resolveOpenshell } = require("./lib/resolve-openshell");
 const { hydrateCredentialEnv, isNonInteractive } = require("./lib/onboard");
-const { prompt: askPrompt } = require("./lib/credentials");
 const registry = require("./lib/registry");
 import type { SandboxEntry } from "./lib/registry";
 const nim = require("./lib/nim");
@@ -48,10 +47,8 @@ const { buildStatusCommandDeps } = require("./lib/status-command-deps");
 const { help, version } = require("./lib/root-help-action");
 const onboardSession = require("./lib/onboard-session");
 import type { Session } from "./lib/onboard-session";
-const { parseLiveSandboxNames } = require("./lib/runtime-recovery");
 const { stripAnsi } = require("./lib/openshell");
 const {
-  captureOpenshell,
   getInstalledOpenshellVersionOrNull,
   runOpenshell,
 } = require("./lib/openshell-runtime");
@@ -70,11 +67,9 @@ const {
 const {
   getSandboxDeleteOutcome,
 } = require("./lib/sandbox-destroy-action");
-const { rebuildSandbox: sandboxRebuild } = require("./lib/sandbox-rebuild-action");
 const { runRegisteredOclifCommand } = require("./lib/oclif-runner");
 const { isErrnoException }: typeof import("./lib/errno") = require("./lib/errno");
 const agentRuntime = require("../bin/lib/agent-runtime");
-const sandboxVersion = require("./lib/sandbox-version");
 const sandboxState = require("./lib/sandbox-state");
 const { parseRestoreArgs } = sandboxState;
 const {
@@ -119,9 +114,6 @@ const DASHBOARD_FORWARD_PORT = String(DASHBOARD_PORT);
 const DEFAULT_LOGS_PROBE_TIMEOUT_MS = 5000;
 const LOGS_PROBE_TIMEOUT_ENV = "NEMOCLAW_LOGS_PROBE_TIMEOUT_MS";
 
-exports.runtimeBridge = {
-  upgradeSandboxes,
-};
 /** Print user-facing guidance when OpenShell is too old to support `openshell logs`. */
 function printOldLogsCompatibilityGuidance(installedVersion = null) {
   const versionText = installedVersion ? ` (${installedVersion})` : "";
@@ -150,117 +142,6 @@ function printSandboxActionUsage(action: string): void {
   console.log(`  Usage: ${CLI_NAME} <name> ${action}`);
 }
 
-// ── Rebuild ──────────────────────────────────────────────────────
-
-async function upgradeSandboxes(args: string[] = []): Promise<void> {
-  const checkOnly = args.includes("--check");
-  const auto = args.includes("--auto");
-  const skipConfirm = auto || args.includes("--yes");
-
-  const sandboxes = registry.listSandboxes().sandboxes;
-  if (sandboxes.length === 0) {
-    console.log("  No sandboxes found in the registry.");
-    return;
-  }
-
-  // Query live sandboxes so we can tell the user which are running
-  const liveResult = captureOpenshell(["sandbox", "list"], { ignoreError: true });
-  if (liveResult.status !== 0) {
-    console.error("  Failed to query running sandboxes from OpenShell.");
-    console.error("  Ensure OpenShell is running: openshell status");
-    process.exit(liveResult.status || 1);
-  }
-  const liveNames = parseLiveSandboxNames(liveResult.output || "");
-
-  // Classify sandboxes as stale, unknown, or current
-  const stale = [];
-  const unknown = [];
-  for (const sb of sandboxes) {
-    const versionCheck = sandboxVersion.checkAgentVersion(sb.name);
-    if (versionCheck.isStale) {
-      stale.push({
-        name: sb.name,
-        current: versionCheck.sandboxVersion,
-        expected: versionCheck.expectedVersion,
-        running: liveNames.has(sb.name),
-      });
-    } else if (versionCheck.detectionMethod === "unavailable") {
-      unknown.push({
-        name: sb.name,
-        expected: versionCheck.expectedVersion,
-        running: liveNames.has(sb.name),
-      });
-    }
-  }
-
-  if (stale.length === 0 && unknown.length === 0) {
-    console.log("  All sandboxes are up to date.");
-    return;
-  }
-
-  if (stale.length > 0) {
-    console.log(`\n  ${B}Stale sandboxes:${R}`);
-    for (const s of stale) {
-      const status = s.running ? `${G}running${R}` : `${D}stopped${R}`;
-      console.log(`    ${s.name}  v${s.current || "?"} → v${s.expected}  (${status})`);
-    }
-  }
-  if (unknown.length > 0) {
-    console.log(`\n  ${YW}Unknown version:${R}`);
-    for (const s of unknown) {
-      const status = s.running ? `${G}running${R}` : `${D}stopped${R}`;
-      console.log(`    ${s.name}  v? → v${s.expected}  (${status})`);
-    }
-  }
-  console.log("");
-
-  if (checkOnly) {
-    if (stale.length > 0) console.log(`  ${stale.length} sandbox(es) need upgrading.`);
-    if (unknown.length > 0) {
-      console.log(
-        `  ${unknown.length} sandbox(es) could not be version-checked; start them and rerun, or rebuild manually.`,
-      );
-    }
-    console.log(`  Run \`${CLI_NAME} upgrade-sandboxes\` to rebuild them.`);
-    return;
-  }
-
-  const rebuildable = stale.filter((s: { running: boolean }) => s.running);
-  const stopped = stale.filter((s: { running: boolean }) => !s.running);
-  if (stopped.length > 0) {
-    console.log(`  ${D}Skipping ${stopped.length} stopped sandbox(es) — start them first.${R}`);
-  }
-  if (rebuildable.length === 0) {
-    console.log("  No running stale sandboxes to rebuild.");
-    return;
-  }
-
-  let rebuilt = 0;
-  let failed = 0;
-  for (const s of rebuildable) {
-    if (!skipConfirm) {
-      const answer = await askPrompt(`  Rebuild '${s.name}'? [y/N]: `);
-      if (answer.trim().toLowerCase() !== "y" && answer.trim().toLowerCase() !== "yes") {
-        console.log(`  Skipped '${s.name}'.`);
-        continue;
-      }
-    }
-    try {
-      await sandboxRebuild(s.name, ["--yes"], { throwOnError: true });
-      rebuilt++;
-    } catch (err) {
-      const errorMessage = err instanceof Error ? err.message : String(err);
-      console.error(`  ${YW}\u26a0${R} Failed to rebuild '${s.name}': ${errorMessage}`);
-      failed++;
-    }
-  }
-
-  console.log("");
-  if (rebuilt > 0) console.log(`  ${G}\u2713${R} ${rebuilt} sandbox(es) rebuilt.`);
-  if (failed > 0) console.log(`  ${YW}\u26a0${R} ${failed} sandbox(es) failed — see errors above.`);
-  if (failed > 0) process.exit(1);
-}
-
 // ── Pre-upgrade backup ───────────────────────────────────────────
 
 // ── Snapshot ─────────────────────────────────────────────────────