diff --git a/src/lib/actions/sandbox/dcode-activity-probe.test.ts b/src/lib/actions/sandbox/dcode-activity-probe.test.ts
new file mode 100644
index 00000000000..50586788e04
--- /dev/null
+++ b/src/lib/actions/sandbox/dcode-activity-probe.test.ts
@@ -0,0 +1,138 @@
+// SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+import { spawnSync } from "node:child_process";
+import fs from "node:fs";
+import os from "node:os";
+import path from "node:path";
+import { describe, expect, it } from "vitest";
+import {
+  DCODE_BUSY_PROBE_SCRIPT,
+  DCODE_PROBE_PREFIX,
+  DCODE_PROBE_STATE,
+  parseDcodeProbeState,
+} from "./dcode-activity-probe";
+
+/** Run the shell probe with controlled ps and /proc inputs. */
+function runProbeScriptWithProcessSources({
+  processes = "",
+  procCmdlines = [],
+  psExitCode = 0,
+  unreadableProcEntries = 0,
+}: {
+  processes?: string;
+  procCmdlines?: readonly string[];
+  psExitCode?: number;
+  unreadableProcEntries?: number;
+}): { status: number; output: string } {
+  const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), "nemoclaw-dcode-probe-"));
+  const psPath = path.join(tempDir, "ps");
+  const homeDir = path.join(tempDir, "home");
+  const procRoot = path.join(tempDir, "proc's");
+  fs.mkdirSync(homeDir);
+  fs.mkdirSync(procRoot);
+  fs.mkdirSync(path.join(homeDir, ".deepagents"));
+  for (const [index, cmdline] of procCmdlines.entries()) {
+    const processDir = path.join(procRoot, String(index + 100));
+    fs.mkdirSync(processDir);
+    fs.writeFileSync(path.join(processDir, "cmdline"), cmdline);
+  }
+  for (const index of Array.from({ length: unreadableProcEntries }, (_, offset) => offset)) {
+    const processDir = path.join(procRoot, String(index + 200));
+    fs.mkdirSync(processDir);
+    const cmdlinePath = path.join(processDir, "cmdline");
+    fs.writeFileSync(cmdlinePath, "/usr/bin/dcode\0-n\0work\0");
+    fs.chmodSync(cmdlinePath, 0o000);
+  }
+  fs.writeFileSync(psPath, `#!/bin/sh\ncat <<'EOF'\n${processes}\nEOF\nexit ${psExitCode}\n`);
+  fs.chmodSync(psPath, 0o755);
+  const testProbeScript = DCODE_BUSY_PROBE_SCRIPT.replace(
+    "proc_root=/proc",
+    'proc_root="$NEMOCLAW_TEST_DCODE_PROC_ROOT"',
+  );
+  const result = spawnSync("sh", ["-c", testProbeScript], {
+    encoding: "utf-8",
+    env: {
+      ...process.env,
+      HOME: homeDir,
+      PATH: `${tempDir}:/usr/bin:/bin`,
+      NEMOCLAW_DCODE_PROC_ROOT: path.join(tempDir, "sandbox-controlled-proc"),
+      NEMOCLAW_TEST_DCODE_PROC_ROOT: procRoot,
+    },
+  });
+  fs.rmSync(tempDir, { recursive: true, force: true });
+  return { status: result.status ?? 255, output: result.stdout || "" };
+}
+
+/** Assert the probe emitted exactly one observable sentinel. */
+function expectProbeState(
+  result: { status: number; output: string },
+  state: (typeof DCODE_PROBE_STATE)[keyof typeof DCODE_PROBE_STATE],
+): void {
+  expect(result.status).toBe(0);
+  expect(result.output.trim()).toBe(`${DCODE_PROBE_PREFIX}${state}`);
+}
+
+describe("dcode activity probe", () => {
+  it("does not let sandbox environment redirect the production proc scan (#6180)", () => {
+    expect(DCODE_BUSY_PROBE_SCRIPT).toContain("proc_root=/proc");
+    expect(DCODE_BUSY_PROBE_SCRIPT).not.toContain("NEMOCLAW_DCODE_PROC_ROOT");
+  });
+
+  it("falls back to proc cmdline scanning when ps cannot list processes (#6180)", () => {
+    expectProbeState(
+      runProbeScriptWithProcessSources({
+        procCmdlines: ["/bin/sh\0-c\0sleep 30\0", "/usr/bin/python3\0-m\0not_deepagents_code\0"],
+        psExitCode: 1,
+      }),
+      DCODE_PROBE_STATE.idleDcodeRuntime,
+    );
+    expectProbeState(
+      runProbeScriptWithProcessSources({
+        procCmdlines: ["/opt/venv/bin/python3\0-I\0-m\0deepagents_code\0-n\0work\0"],
+        psExitCode: 1,
+      }),
+      DCODE_PROBE_STATE.active,
+    );
+  });
+
+  it("fails closed when ps and proc cannot verify a marked dcode runtime (#6180)", () => {
+    expectProbeState(
+      runProbeScriptWithProcessSources({ psExitCode: 1 }),
+      DCODE_PROBE_STATE.unverifiableDcodeRuntime,
+    );
+  });
+
+  it("fails closed when proc fallback visibility is incomplete (#6180)", () => {
+    expectProbeState(
+      runProbeScriptWithProcessSources({
+        procCmdlines: ["", "/bin/sh\0-c\0sleep 30\0"],
+        psExitCode: 1,
+      }),
+      DCODE_PROBE_STATE.unverifiableDcodeRuntime,
+    );
+    expectProbeState(
+      runProbeScriptWithProcessSources({
+        procCmdlines: ["/bin/sh\0-c\0sleep 30\0"],
+        psExitCode: 1,
+        unreadableProcEntries: 1,
+      }),
+      DCODE_PROBE_STATE.unverifiableDcodeRuntime,
+    );
+  });
+
+  it("parses every declared probe state", () => {
+    for (const state of Object.values(DCODE_PROBE_STATE)) {
+      expect(parseDcodeProbeState(`${DCODE_PROBE_PREFIX}${state}\n`)).toBe(state);
+    }
+  });
+
+  it("parses exactly one probe sentinel from sandbox exec output", () => {
+    expect(parseDcodeProbeState(`${DCODE_PROBE_PREFIX}idle\n`)).toBe(
+      DCODE_PROBE_STATE.idleDcodeRuntime,
+    );
+    expect(parseDcodeProbeState(`${DCODE_PROBE_PREFIX}idle\n${DCODE_PROBE_PREFIX}active\n`)).toBe(
+      null,
+    );
+  });
+});
diff --git a/src/lib/actions/sandbox/dcode-activity-probe.ts b/src/lib/actions/sandbox/dcode-activity-probe.ts
new file mode 100644
index 00000000000..bef57cb1cb3
--- /dev/null
+++ b/src/lib/actions/sandbox/dcode-activity-probe.ts
@@ -0,0 +1,97 @@
+// SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+export const DCODE_AGENT_NAME = "langchain-deepagents-code";
+export const DCODE_PROBE_PREFIX = "NEMOCLAW_DCODE_PROBE=";
+export const DCODE_PROBE_STATE = {
+  active: "active",
+  idleDcodeRuntime: "idle",
+  unverifiableDcodeRuntime: "unverifiable",
+  noDcodeRuntime: "no-runtime",
+} as const;
+export type DcodeProbeState = (typeof DCODE_PROBE_STATE)[keyof typeof DCODE_PROBE_STATE];
+
+export const DCODE_BUSY_PROBE_SCRIPT = String.raw`emit_dcode_probe_state() {
+  printf 'NEMOCLAW_DCODE_PROBE=%s\n' "$1"
+  exit 0
+}
+has_dcode_runtime=0
+dc_bin="$(printf 'd%s' code)"
+da_bin="$(printf 'deepagents-%s' code)"
+home_dir="$HOME"
+[ -n "$home_dir" ] || home_dir=/sandbox
+[ -d /sandbox/.deepagents ] && has_dcode_runtime=1
+[ -d "$home_dir/.deepagents" ] && has_dcode_runtime=1
+command -v "$dc_bin" >/dev/null 2>&1 && has_dcode_runtime=1
+command -v "$da_bin" >/dev/null 2>&1 && has_dcode_runtime=1
+detect_dcode_processes() {
+  awk '
+/^[[:space:]]*[0-9]+[[:space:]]+([^[:space:]]*\/)?python[0-9.]*[[:space:]]+(-I[[:space:]]+)?-m[[:space:]]+deepagents[_]code([[:space:]]|$)/ {
+  found = 1
+}
+/^[[:space:]]*[0-9]+[[:space:]]+([^[:space:]]*\/)?[d]code([[:space:]]|$)/ {
+  found = 1
+}
+/^[[:space:]]*[0-9]+[[:space:]]+([^[:space:]]*\/)?deepagents[-_]code([[:space:]]|$)/ {
+  found = 1
+}
+END { exit found ? 0 : 1 }
+'
+}
+proc_root=/proc
+processes="$(ps -eo pid=,args= 2>/dev/null)" || {
+  processes=""
+  saw_proc_process=0
+  proc_scan_incomplete=0
+  for cmdline in "$proc_root"/[0-9]*/cmdline; do
+    [ -e "$cmdline" ] || continue
+    [ -r "$cmdline" ] || {
+      proc_scan_incomplete=1
+      continue
+    }
+    pid="$(basename "$(dirname "$cmdline")")"
+    command_line="$(tr '\000\n\r' '   ' < "$cmdline" 2>/dev/null)" || {
+      proc_scan_incomplete=1
+      continue
+    }
+    [ -n "$command_line" ] || {
+      proc_scan_incomplete=1
+      continue
+    }
+    saw_proc_process=1
+    processes="$processes$pid $command_line
+"
+  done
+  [ "$proc_scan_incomplete" -eq 0 ] || {
+    [ "$has_dcode_runtime" -eq 1 ] && emit_dcode_probe_state unverifiable
+    emit_dcode_probe_state no-runtime
+  }
+  [ "$saw_proc_process" -eq 1 ] || {
+    [ "$has_dcode_runtime" -eq 1 ] && emit_dcode_probe_state unverifiable
+    emit_dcode_probe_state no-runtime
+  }
+}
+printf '%s\n' "$processes" | detect_dcode_processes
+matched=$?
+[ "$matched" -eq 0 ] && emit_dcode_probe_state active
+[ "$matched" -ne 1 ] && {
+  [ "$has_dcode_runtime" -eq 1 ] && emit_dcode_probe_state unverifiable
+  emit_dcode_probe_state no-runtime
+}
+[ "$has_dcode_runtime" -eq 1 ] && emit_dcode_probe_state idle
+emit_dcode_probe_state no-runtime
+`;
+
+/** Escape a probe literal before embedding it in a generated regular expression. */
+function escapeRegexLiteral(value: string): string {
+  return value.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
+}
+
+/** Parse a single dcode probe sentinel from sandbox command output. */
+export function parseDcodeProbeState(output: string): DcodeProbeState | null {
+  const escapedPrefix = escapeRegexLiteral(DCODE_PROBE_PREFIX);
+  const stateAlternation = Object.values(DCODE_PROBE_STATE).map(escapeRegexLiteral).join("|");
+  const matches = [...output.matchAll(new RegExp(`^${escapedPrefix}(${stateAlternation})$`, "gm"))];
+  if (matches.length !== 1) return null;
+  return (matches[0][1] as DcodeProbeState | undefined) ?? null;
+}
diff --git a/src/lib/actions/sandbox/snapshot.test.ts b/src/lib/actions/sandbox/snapshot.test.ts
index 738d0a4dd8b..903eadee680 100644
--- a/src/lib/actions/sandbox/snapshot.test.ts
+++ b/src/lib/actions/sandbox/snapshot.test.ts
@@ -309,7 +309,10 @@ describe("runSandboxSnapshot", () => {
   function runProbeScriptWithProcesses(
     script: string,
     processes: string,
-  ): { status: number; output: string } {
+  ): {
+    status: number;
+    output: string;
+  } {
     const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), "nemoclaw-dcode-probe-"));
     const psPath = path.join(tempDir, "ps");
     const homeDir = path.join(tempDir, "home");
diff --git a/src/lib/actions/sandbox/snapshot.ts b/src/lib/actions/sandbox/snapshot.ts
index dadd4f95daf..a2a48301591 100644
--- a/src/lib/actions/sandbox/snapshot.ts
+++ b/src/lib/actions/sandbox/snapshot.ts
@@ -42,6 +42,12 @@ import * as registry from "../../state/registry";
 import { getSandboxEntryInference } from "../../state/registry-entry-view";
 import * as sandboxState from "../../state/sandbox";
 import { cleanupShieldsDestroyArtifacts, removeSandboxRegistryEntry } from "./destroy";
+import {
+  DCODE_AGENT_NAME,
+  DCODE_BUSY_PROBE_SCRIPT,
+  DCODE_PROBE_STATE,
+  parseDcodeProbeState,
+} from "./dcode-activity-probe";
 import {
   buildSandboxExecMarkedCommand,
   createSandboxExecMarker,
@@ -60,54 +66,6 @@ const G = useColor ? (trueColor ? "\x1b[38;2;118;185;0m" : "\x1b[38;5;148m") : "
 const B = useColor ? "\x1b[1m" : "";
 const D = useColor ? "\x1b[2m" : "";
 const R = useColor ? "\x1b[0m" : "";
-const DCODE_AGENT_NAME = "langchain-deepagents-code";
-const DCODE_PROBE_PREFIX = "NEMOCLAW_DCODE_PROBE=";
-const DCODE_PROBE_STATE = {
-  active: "active",
-  idleDcodeRuntime: "idle",
-  unverifiableDcodeRuntime: "unverifiable",
-  noDcodeRuntime: "no-runtime",
-} as const;
-type DcodeProbeState = (typeof DCODE_PROBE_STATE)[keyof typeof DCODE_PROBE_STATE];
-
-const DCODE_BUSY_PROBE_SCRIPT = String.raw`emit_dcode_probe_state() {
-  printf 'NEMOCLAW_DCODE_PROBE=%s\n' "$1"
-  exit 0
-}
-has_dcode_runtime=0
-dc_bin="$(printf 'd%s' code)"
-da_bin="$(printf 'deepagents-%s' code)"
-home_dir="$HOME"
-[ -n "$home_dir" ] || home_dir=/sandbox
-[ -d /sandbox/.deepagents ] && has_dcode_runtime=1
-[ -d "$home_dir/.deepagents" ] && has_dcode_runtime=1
-command -v "$dc_bin" >/dev/null 2>&1 && has_dcode_runtime=1
-command -v "$da_bin" >/dev/null 2>&1 && has_dcode_runtime=1
-processes="$(ps -eo pid=,args= 2>/dev/null)" || {
-  [ "$has_dcode_runtime" -eq 1 ] && emit_dcode_probe_state unverifiable
-  emit_dcode_probe_state no-runtime
-}
-printf '%s\n' "$processes" | awk '
-/^[[:space:]]*[0-9]+[[:space:]]+([^[:space:]]*\/)?python[0-9.]*[[:space:]]+(-I[[:space:]]+)?-m[[:space:]]+deepagents[_]code([[:space:]]|$)/ {
-  found = 1
-}
-/^[[:space:]]*[0-9]+[[:space:]]+([^[:space:]]*\/)?[d]code([[:space:]]|$)/ {
-  found = 1
-}
-/^[[:space:]]*[0-9]+[[:space:]]+([^[:space:]]*\/)?deepagents[-_]code([[:space:]]|$)/ {
-  found = 1
-}
-END { exit found ? 0 : 1 }
-'
-matched=$?
-[ "$matched" -eq 0 ] && emit_dcode_probe_state active
-[ "$matched" -ne 1 ] && {
-  [ "$has_dcode_runtime" -eq 1 ] && emit_dcode_probe_state unverifiable
-  emit_dcode_probe_state no-runtime
-}
-[ "$has_dcode_runtime" -eq 1 ] && emit_dcode_probe_state idle
-emit_dcode_probe_state no-runtime
-`;
 
 export type SnapshotRequest =
   | { kind: "help" }
@@ -428,15 +386,6 @@ function isSnapshotCreationAllowedByShields(sandboxName: string): boolean {
   return isShieldsDown(sandboxName);
 }
 
-function parseDcodeProbeState(output: string): DcodeProbeState | null {
-  const escapedPrefix = DCODE_PROBE_PREFIX.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
-  const matches = [
-    ...output.matchAll(new RegExp(`^${escapedPrefix}(active|idle|unverifiable|no-runtime)$`, "gm")),
-  ];
-  if (matches.length !== 1) return null;
-  return (matches[0][1] as DcodeProbeState | undefined) ?? null;
-}
-
 function shouldCheckDcodeActivity(sandboxName: string): boolean {
   const entry = registry.getSandbox(sandboxName);
   // Preserve the existing snapshot path for registered non-dcode sandboxes while