diff --git a/test/onboard-fsm-live-slices.test.ts b/test/onboard-fsm-live-slices.test.ts
new file mode 100644
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+++ b/test/onboard-fsm-live-slices.test.ts
@@ -0,0 +1,354 @@
+// SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+import assert from "node:assert/strict";
+import { type SpawnSyncReturns, spawnSync } from "node:child_process";
+import fs from "node:fs";
+import os from "node:os";
+import path from "node:path";
+import { beforeAll, describe, it } from "vitest";
+
+const repoRoot = path.join(import.meta.dirname, "..");
+const probeTimeoutMs = 10_000;
+
+type SliceName = "initial" | "core" | "final";
+type ProbeMode = "fresh" | "resume-initial" | "ahead-core";
+
+interface ProbeOptions {
+  slice: SliceName;
+  mode?: ProbeMode;
+}
+
+interface DistArtifact {
+  label: string;
+  sourcePath: string;
+  distPath: string;
+}
+
+const requiredDistArtifacts: readonly DistArtifact[] = [
+  {
+    label: "onboard dispatcher",
+    sourcePath: path.join(repoRoot, "src", "lib", "onboard.ts"),
+    distPath: path.join(repoRoot, "dist", "lib", "onboard.js"),
+  },
+  {
+    label: "flow slices",
+    sourcePath: path.join(repoRoot, "src", "lib", "onboard", "machine", "flow-slices.ts"),
+    distPath: path.join(repoRoot, "dist", "lib", "onboard", "machine", "flow-slices.js"),
+  },
+  {
+    label: "state results",
+    sourcePath: path.join(repoRoot, "src", "lib", "onboard", "machine", "result.ts"),
+    distPath: path.join(repoRoot, "dist", "lib", "onboard", "machine", "result.js"),
+  },
+  {
+    label: "session persistence",
+    sourcePath: path.join(repoRoot, "src", "lib", "state", "onboard-session.ts"),
+    distPath: path.join(repoRoot, "dist", "lib", "state", "onboard-session.js"),
+  },
+  {
+    label: "preflight handler",
+    sourcePath: path.join(repoRoot, "src", "lib", "onboard", "machine", "handlers", "preflight.ts"),
+    distPath: path.join(repoRoot, "dist", "lib", "onboard", "machine", "handlers", "preflight.js"),
+  },
+  {
+    label: "provider inference handler",
+    sourcePath: path.join(
+      repoRoot,
+      "src",
+      "lib",
+      "onboard",
+      "machine",
+      "handlers",
+      "provider-inference.ts",
+    ),
+    distPath: path.join(
+      repoRoot,
+      "dist",
+      "lib",
+      "onboard",
+      "machine",
+      "handlers",
+      "provider-inference.js",
+    ),
+  },
+];
+
+function distArtifactStatus(): { ok: true } | { ok: false; reason: string } {
+  for (const artifact of requiredDistArtifacts) {
+    if (!fs.existsSync(artifact.distPath)) {
+      return {
+        ok: false,
+        reason: `${artifact.label} is missing at ${path.relative(repoRoot, artifact.distPath)}`,
+      };
+    }
+    if (!fs.existsSync(artifact.sourcePath)) continue;
+    const sourceMtime = fs.statSync(artifact.sourcePath).mtimeMs;
+    const distMtime = fs.statSync(artifact.distPath).mtimeMs;
+    if (sourceMtime > distMtime + 1000) {
+      return {
+        ok: false,
+        reason: `${artifact.label} is older than ${path.relative(repoRoot, artifact.sourcePath)}`,
+      };
+    }
+  }
+  return { ok: true };
+}
+
+function assertFreshDistArtifacts(): void {
+  const status = distArtifactStatus();
+  if (status.ok) return;
+  throw new Error(
+    `Live onboard FSM slice boundary tests require fresh compiled CLI artifacts: ${status.reason}. Run npm run build:cli before this test.`,
+  );
+}
+
+function probeEnvironment(tmpDir: string): NodeJS.ProcessEnv {
+  const env: NodeJS.ProcessEnv = {
+    HOME: tmpDir,
+    TMPDIR: tmpDir,
+    PATH: process.env.PATH || "/usr/bin:/bin",
+    NODE_ENV: "test",
+    NEMOCLAW_NON_INTERACTIVE: "1",
+    NEMOCLAW_SANDBOX_NAME: "fsm-sandbox",
+    NEMOCLAW_YES: "1",
+    NO_COLOR: "1",
+  };
+  for (const key of ["ComSpec", "PATHEXT", "SystemRoot", "WINDIR"]) {
+    if (process.env[key]) env[key] = process.env[key];
+  }
+  return env;
+}
+
+function redactProbeOutput(value: string): string {
+  return value
+    .replace(/(authorization:\s*bearer\s+)[^\s]+/gi, "$1<redacted>")
+    .replace(/(bearer\s+)[A-Za-z0-9._~+/=-]+/gi, "$1<redacted>")
+    .replace(/((?:api[_-]?key|token|password|secret)=)[^\s]+/gi, "$1<redacted>")
+    .replace(/(https?:\/\/)[^@\s]+@/gi, "$1<redacted>@")
+    .slice(0, 4000);
+}
+
+function probeFailureMessage(result: SpawnSyncReturns<string>): string {
+  const details = [
+    `slice probe exited with status ${result.status ?? "null"}${result.signal ? ` and signal ${result.signal}` : ""}`,
+    result.error ? `error: ${redactProbeOutput(result.error.message)}` : null,
+    result.stderr ? `stderr:\n${redactProbeOutput(result.stderr)}` : null,
+    result.stdout ? `stdout:\n${redactProbeOutput(result.stdout)}` : null,
+  ].filter(Boolean);
+  return details.join("\n\n");
+}
+
+function runSliceProbe(options: ProbeOptions) {
+  const scenario = { mode: options.mode ?? "fresh", slice: options.slice };
+  const tmpDir = fs.mkdtempSync(
+    path.join(os.tmpdir(), `nemoclaw-onboard-fsm-${scenario.mode}-${scenario.slice}-`),
+  );
+  const scriptPath = path.join(tmpDir, `probe-${scenario.mode}-${scenario.slice}.js`);
+  const onboardPath = JSON.stringify(path.join(repoRoot, "dist", "lib", "onboard.js"));
+  const flowSlicesPath = JSON.stringify(
+    path.join(repoRoot, "dist", "lib", "onboard", "machine", "flow-slices.js"),
+  );
+  const resultPath = JSON.stringify(
+    path.join(repoRoot, "dist", "lib", "onboard", "machine", "result.js"),
+  );
+  const sessionPath = JSON.stringify(
+    path.join(repoRoot, "dist", "lib", "state", "onboard-session.js"),
+  );
+  const preflightHandlerPath = JSON.stringify(
+    path.join(repoRoot, "dist", "lib", "onboard", "machine", "handlers", "preflight.js"),
+  );
+  const providerHandlerPath = JSON.stringify(
+    path.join(repoRoot, "dist", "lib", "onboard", "machine", "handlers", "provider-inference.js"),
+  );
+
+  fs.writeFileSync(
+    scriptPath,
+    `
+const scenario = ${JSON.stringify(scenario)};
+const flowSlices = require(${flowSlicesPath});
+const { advanceTo, branchTo } = require(${resultPath});
+const onboardSession = require(${sessionPath});
+const preflightHandlers = require(${preflightHandlerPath});
+const providerHandlers = require(${providerHandlerPath});
+const called = [];
+const sentinel = new Error("slice-called");
+
+function machine(state, revision = 1) {
+  return { version: 1, state, stateEnteredAt: null, revision };
+}
+
+function seedResumeSession(state) {
+  onboardSession.saveSession(onboardSession.createSession({
+    mode: "non-interactive",
+    sandboxName: "fsm-sandbox",
+    machine: machine(state),
+    metadata: { gatewayName: "nemoclaw", fromDockerfile: null },
+  }));
+}
+
+function baseContext(context, overrides = {}) {
+  return {
+    ...context,
+    session: overrides.session ?? context.session ?? null,
+    sandboxName: overrides.sandboxName ?? context.sandboxName ?? "fsm-sandbox",
+    model: overrides.model ?? context.model ?? "model",
+    provider: overrides.provider ?? context.provider ?? "provider",
+    endpointUrl: overrides.endpointUrl ?? context.endpointUrl ?? null,
+    credentialEnv: overrides.credentialEnv ?? context.credentialEnv ?? null,
+    hermesAuthMethod: overrides.hermesAuthMethod ?? context.hermesAuthMethod ?? null,
+    hermesToolGateways: overrides.hermesToolGateways ?? context.hermesToolGateways ?? [],
+    preferredInferenceApi: overrides.preferredInferenceApi ?? context.preferredInferenceApi ?? null,
+    nimContainer: overrides.nimContainer ?? context.nimContainer ?? null,
+    webSearchConfig: overrides.webSearchConfig ?? context.webSearchConfig ?? null,
+    webSearchSupported: overrides.webSearchSupported ?? context.webSearchSupported ?? false,
+    selectedMessagingChannels: overrides.selectedMessagingChannels ?? context.selectedMessagingChannels ?? [],
+    gpu: overrides.gpu ?? context.gpu ?? null,
+    sandboxGpuConfig: overrides.sandboxGpuConfig ?? context.sandboxGpuConfig ?? { sandboxGpuEnabled: false, mode: "0" },
+    gpuPassthrough: overrides.gpuPassthrough ?? context.gpuPassthrough ?? false,
+    resumeHasResolvedGpuIntent: false,
+    requestedGpuPassthrough: false,
+  };
+}
+
+preflightHandlers.handlePreflightState = async () => {
+  if (scenario.mode !== "resume-initial") {
+    throw new Error("unexpected preflight compatibility handler");
+  }
+  called.push("preflight-compat");
+  throw sentinel;
+};
+
+providerHandlers.handleProviderInferenceState = async () => {
+  if (scenario.mode !== "ahead-core") {
+    throw new Error("unexpected provider compatibility handler");
+  }
+  called.push("provider-compat");
+  throw sentinel;
+};
+
+flowSlices.runInitialOnboardFlowSequence = async ({ context, runtime }) => {
+  called.push("initial");
+  if (scenario.mode === "resume-initial") {
+    throw new Error("strict initial runner should not run on resume");
+  }
+  if (scenario.slice === "initial") throw sentinel;
+  const initialSession = await runtime.session();
+  if (initialSession.machine?.state === "init") {
+    await runtime.applyResult(advanceTo("preflight"));
+  }
+  await runtime.applyResult(advanceTo("gateway", { metadata: { state: "preflight" } }));
+  await runtime.applyResult(advanceTo("provider_selection", { metadata: { state: "gateway" } }));
+  if (scenario.mode === "ahead-core") {
+    await runtime.applyResult(advanceTo("inference", { metadata: { state: "provider_selection" } }));
+  }
+  const session = await runtime.session();
+  return { context: baseContext(context, { session }), session };
+};
+
+flowSlices.runCoreOnboardFlowSequence = async ({ context, runtime }) => {
+  called.push("core");
+  if (scenario.mode === "ahead-core") {
+    throw new Error("strict core runner should not run after an ahead-state handoff");
+  }
+  if (scenario.slice === "core") throw sentinel;
+  await runtime.applyResult(advanceTo("inference", { metadata: { state: "provider_selection" } }));
+  await runtime.applyResult(advanceTo("sandbox", { metadata: { state: "inference" } }));
+  await runtime.applyResult(branchTo("openclaw", { metadata: { state: "sandbox" } }));
+  const session = await runtime.session();
+  return { context: baseContext(context, { session }), session };
+};
+
+flowSlices.runFinalOnboardFlowSequence = async ({ context }) => {
+  called.push("final");
+  if (scenario.slice === "final") throw sentinel;
+  throw new Error("unexpected final slice fallthrough");
+};
+
+if (scenario.mode === "resume-initial") {
+  seedResumeSession("preflight");
+}
+
+const { onboard } = require(${onboardPath});
+
+(async () => {
+  try {
+    await onboard({
+      nonInteractive: true,
+      autoYes: true,
+      acceptThirdPartySoftware: true,
+      noGpu: true,
+      sandboxName: "fsm-sandbox",
+      resume: scenario.mode === "resume-initial",
+    });
+    throw new Error("expected slice sentinel");
+  } catch (error) {
+    if (error === sentinel || error?.message === sentinel.message) {
+      console.log(JSON.stringify({ called }));
+      return;
+    }
+    console.error(error);
+    process.exit(1);
+  }
+})();
+`,
+  );
+
+  const result = spawnSync(process.execPath, [scriptPath], {
+    cwd: repoRoot,
+    encoding: "utf-8",
+    env: probeEnvironment(tmpDir),
+    timeout: probeTimeoutMs,
+  });
+  try {
+    assert.equal(result.status, 0, probeFailureMessage(result));
+    const lines = result.stdout.trim().split(/\r?\n/).filter(Boolean);
+    const payload = JSON.parse(lines.at(-1) || "{}") as { called?: string[] };
+    assert.ok(
+      Array.isArray(payload.called),
+      `slice probe did not return called slices\n${probeFailureMessage(result)}`,
+    );
+    return payload.called as string[];
+  } finally {
+    fs.rmSync(tmpDir, { recursive: true, force: true });
+  }
+}
+
+describe("live onboard FSM slice boundaries", () => {
+  /*
+   * The live dispatcher is still loaded from compiled CommonJS:
+   * src/lib/onboard.ts captures these helpers through require-time bindings,
+   * and a source-level Vitest import cannot replace them without adding a
+   * production-only injection seam. Keep the monkeypatch in a short-lived
+   * child process, with a minimal environment and a timeout, until onboard's
+   * dispatcher exposes an explicit test hook or moves to source-testable ESM.
+   */
+  beforeAll(() => {
+    assertFreshDistArtifacts();
+  });
+
+  it("enters the initial slice on fresh onboard runs", () => {
+    assert.deepEqual(runSliceProbe({ slice: "initial" }), ["initial"]);
+  });
+
+  it("enters the core slice after the initial slice reaches provider selection", () => {
+    assert.deepEqual(runSliceProbe({ slice: "core" }), ["initial", "core"]);
+  });
+
+  it("enters the final slice after the core slice reaches the branch state", () => {
+    assert.deepEqual(runSliceProbe({ slice: "final" }), ["initial", "core", "final"]);
+  });
+
+  it("bypasses the strict initial runner on resume and reaches compatibility phases", () => {
+    assert.deepEqual(runSliceProbe({ slice: "initial", mode: "resume-initial" }), [
+      "preflight-compat",
+    ]);
+  });
+
+  it("bypasses the strict core runner when fresh state is already past the core entry", () => {
+    assert.deepEqual(runSliceProbe({ slice: "core", mode: "ahead-core" }), [
+      "initial",
+      "provider-compat",
+    ]);
+  });
+});