diff --git a/src/lib/onboard/machine/flow-phases/agent-policy-finalization.test.ts b/src/lib/onboard/machine/flow-phases/agent-policy-finalization.test.ts
index 6a858175469..5f848695f23 100644
--- a/src/lib/onboard/machine/flow-phases/agent-policy-finalization.test.ts
+++ b/src/lib/onboard/machine/flow-phases/agent-policy-finalization.test.ts
@@ -3,14 +3,6 @@
 
 import { describe, expect, it } from "vitest";
 
-import {
-  createSession,
-  filterSafeUpdates,
-  MACHINE_SNAPSHOT_VERSION,
-  normalizeSession,
-  type Session,
-  type SessionUpdates,
-} from "../../../state/onboard-session";
 import type { OnboardFlowContext } from "../flow-context";
 import { advanceTo, completeOnboardMachine } from "../result";
 import { OnboardRuntime, type OnboardRuntimeDeps } from "../runtime";
@@ -22,6 +14,18 @@ import {
   createPoliciesPhase,
   createPostVerifyPhase,
 } from "./agent-policy-finalization";
+import {
+  MACHINE_SNAPSHOT_VERSION,
+  type Session,
+  type SessionUpdates,
+  cloneSession,
+  createSession,
+  createTestRuntime,
+} from "../../../../../test/helpers/onboard-machine-runtime-fixture";
+
+function createRuntime(initialSession: Session = createSession()) {
+  return createTestRuntime(initialSession, { now: () => "2026-05-29T00:00:00.000Z" });
+}
 
 function context(): OnboardFlowContext<null, null, null> {
   return {
@@ -52,51 +56,6 @@ function context(): OnboardFlowContext<null, null, null> {
   };
 }
 
-function cloneSession(session: Session): Session {
-  return normalizeSession(JSON.parse(JSON.stringify(session))) ?? session;
-}
-
-function createRuntime(initialSession: Session = createSession()) {
-  let session = cloneSession(initialSession);
-  const updateSession = (mutator: (value: Session) => Session | void): Session => {
-    session = cloneSession(mutator(cloneSession(session)) ?? session);
-    return cloneSession(session);
-  };
-  const deps: OnboardRuntimeDeps = {
-    loadSession: () => cloneSession(session),
-    createSession,
-    saveSession: (next) => {
-      session = cloneSession(next);
-      return cloneSession(session);
-    },
-    updateSession,
-    markStepStarted: () => cloneSession(session),
-    markStepComplete: (_stepName, updates: SessionUpdates = {}) =>
-      updateSession((current) => {
-        Object.assign(current, filterSafeUpdates(updates));
-        return current;
-      }),
-    markStepSkipped: () => cloneSession(session),
-    markStepFailed: (stepName, message) =>
-      updateSession((current) => {
-        current.steps[stepName].status = "failed";
-        current.steps[stepName].error = message ?? null;
-        return current;
-      }),
-    completeSession: (updates: SessionUpdates = {}) =>
-      updateSession((current) => {
-        Object.assign(current, filterSafeUpdates(updates));
-        current.status = "complete";
-        current.resumable = false;
-        return current;
-      }),
-    filterSafeUpdates,
-    emitEvent: () => undefined,
-    now: () => "2026-05-29T00:00:00.000Z",
-  };
-  return new OnboardRuntime(deps);
-}
-
 describe("agent/policy/finalization phases", () => {
   it("creates branch-specific setup phases", async () => {
     const agentPhase = createAgentSetupPhase(async () => ({ result: advanceTo("policies") }));
diff --git a/src/lib/onboard/machine/flow-sequence.test.ts b/src/lib/onboard/machine/flow-sequence.test.ts
index a0e8d6c763e..1fe51188963 100644
--- a/src/lib/onboard/machine/flow-sequence.test.ts
+++ b/src/lib/onboard/machine/flow-sequence.test.ts
@@ -3,20 +3,24 @@
 
 import { describe, expect, it } from "vitest";
 
-import {
-  createSession,
-  filterSafeUpdates,
-  MACHINE_SNAPSHOT_VERSION,
-  normalizeSession,
-  type Session,
-  type SessionUpdates,
-} from "../../state/onboard-session";
 import type { OnboardFlowContext, OnboardFlowPhaseResult } from "./flow-context";
 import { onboardFlowPhaseResult } from "./flow-context";
 import { buildOnboardFlowPhaseSequence } from "./flow-sequence";
 import { advanceTo, branchTo, completeOnboardMachine } from "./result";
 import { OnboardRuntime, type OnboardRuntimeDeps } from "./runtime";
 import { runOnboardSequenceWithRunner } from "./sequence-runner";
+import {
+  MACHINE_SNAPSHOT_VERSION,
+  type Session,
+  type SessionUpdates,
+  cloneSession,
+  createSession,
+  createTestRuntime,
+} from "../../../../test/helpers/onboard-machine-runtime-fixture";
+
+function createRuntime(initialSession: Session = createSession()) {
+  return createTestRuntime(initialSession, { now: () => "2026-05-29T00:00:00.000Z" });
+}
 
 type Context = OnboardFlowContext<null, { type: string }, { mode: string }>;
 
@@ -57,51 +61,6 @@ function result(
   return onboardFlowPhaseResult(ctx, advanceTo(next));
 }
 
-function cloneSession(session: Session): Session {
-  return normalizeSession(JSON.parse(JSON.stringify(session))) ?? session;
-}
-
-function createRuntime(initialSession: Session = createSession()) {
-  let session = cloneSession(initialSession);
-  const updateSession = (mutator: (value: Session) => Session | void): Session => {
-    session = cloneSession(mutator(cloneSession(session)) ?? session);
-    return cloneSession(session);
-  };
-  const deps: OnboardRuntimeDeps = {
-    loadSession: () => cloneSession(session),
-    createSession,
-    saveSession: (next) => {
-      session = cloneSession(next);
-      return cloneSession(session);
-    },
-    updateSession,
-    markStepStarted: () => cloneSession(session),
-    markStepComplete: (_stepName, updates: SessionUpdates = {}) =>
-      updateSession((current) => {
-        Object.assign(current, filterSafeUpdates(updates));
-        return current;
-      }),
-    markStepSkipped: () => cloneSession(session),
-    markStepFailed: (stepName, message) =>
-      updateSession((current) => {
-        current.steps[stepName].status = "failed";
-        current.steps[stepName].error = message ?? null;
-        return current;
-      }),
-    completeSession: (updates: SessionUpdates = {}) =>
-      updateSession((current) => {
-        Object.assign(current, filterSafeUpdates(updates));
-        current.status = "complete";
-        current.resumable = false;
-        return current;
-      }),
-    filterSafeUpdates,
-    emitEvent: () => undefined,
-    now: () => "2026-05-29T00:00:00.000Z",
-  };
-  return new OnboardRuntime(deps);
-}
-
 describe("onboard flow phase sequence", () => {
   it("assembles phases in machine order", () => {
     const phases = buildOnboardFlowPhaseSequence<Context>({
diff --git a/src/lib/onboard/machine/flow-slices.test.ts b/src/lib/onboard/machine/flow-slices.test.ts
index b4b4cafb55a..f76d6f41d9f 100644
--- a/src/lib/onboard/machine/flow-slices.test.ts
+++ b/src/lib/onboard/machine/flow-slices.test.ts
@@ -3,14 +3,6 @@
 
 import { describe, expect, it } from "vitest";
 
-import {
-  createSession,
-  filterSafeUpdates,
-  MACHINE_SNAPSHOT_VERSION,
-  normalizeSession,
-  type Session,
-  type SessionUpdates,
-} from "../../state/onboard-session";
 import type { OnboardFlowContext } from "./flow-context";
 import {
   coreOnboardFlowPhases,
@@ -23,10 +15,14 @@ import {
 import { advanceTo, branchTo, completeOnboardMachine } from "./result";
 import { OnboardRuntime, type OnboardRuntimeDeps } from "./runtime";
 import type { OnboardSequencePhase } from "./sequence-runner";
-
-function cloneSession(session: Session): Session {
-  return normalizeSession(JSON.parse(JSON.stringify(session))) ?? session;
-}
+import {
+  MACHINE_SNAPSHOT_VERSION,
+  type Session,
+  type SessionUpdates,
+  cloneSession,
+  createSession,
+  filterSafeUpdates,
+} from "../../../../test/helpers/onboard-machine-runtime-fixture";
 
 function runtime(initialSession: Session = createSession()) {
   let session = cloneSession(initialSession);
diff --git a/src/lib/onboard/machine/runner-sequence.test.ts b/src/lib/onboard/machine/runner-sequence.test.ts
index 97837bbed3b..8a13f838e36 100644
--- a/src/lib/onboard/machine/runner-sequence.test.ts
+++ b/src/lib/onboard/machine/runner-sequence.test.ts
@@ -3,14 +3,6 @@
 
 import { describe, expect, it, vi } from "vitest";
 
-import {
-  createSession,
-  filterSafeUpdates,
-  MACHINE_SNAPSHOT_VERSION,
-  normalizeSession,
-  type Session,
-  type SessionUpdates,
-} from "../../state/onboard-session";
 import { advanceTo, branchTo, completeOnboardMachine, failOnboardMachine, retryTo } from "./result";
 import {
   EmptyOnboardStateHandlerResultError,
@@ -21,58 +13,20 @@ import {
   runOnboardMachine,
 } from "./runner";
 import { OnboardRuntime, type OnboardRuntimeDeps } from "./runtime";
+import {
+  MACHINE_SNAPSHOT_VERSION,
+  type Session,
+  type SessionUpdates,
+  cloneSession,
+  createSession,
+  createTestRuntime as createRuntime,
+} from "../../../../test/helpers/onboard-machine-runtime-fixture";
 
 interface RunnerContext {
   attempts: number;
   visited: string[];
 }
 
-function cloneSession(session: Session): Session {
-  return normalizeSession(JSON.parse(JSON.stringify(session))) ?? session;
-}
-
-function createRuntime(initialSession: Session = createSession()) {
-  let session = cloneSession(initialSession);
-  const updateSession = (mutator: (value: Session) => Session | void): Session => {
-    const next = mutator(cloneSession(session)) ?? session;
-    session = cloneSession(next);
-    return cloneSession(session);
-  };
-  const deps: OnboardRuntimeDeps = {
-    loadSession: () => cloneSession(session),
-    createSession,
-    saveSession: (next) => {
-      session = cloneSession(next);
-      return cloneSession(session);
-    },
-    updateSession,
-    markStepStarted: () => cloneSession(session),
-    markStepComplete: (_stepName, updates: SessionUpdates = {}) =>
-      updateSession((current) => {
-        Object.assign(current, filterSafeUpdates(updates));
-        return current;
-      }),
-    markStepSkipped: () => cloneSession(session),
-    markStepFailed: (stepName, message) =>
-      updateSession((current) => {
-        current.steps[stepName].status = "failed";
-        current.steps[stepName].error = message ?? null;
-        return current;
-      }),
-    completeSession: (updates: SessionUpdates = {}) =>
-      updateSession((current) => {
-        Object.assign(current, filterSafeUpdates(updates));
-        current.status = "complete";
-        current.resumable = false;
-        return current;
-      }),
-    filterSafeUpdates,
-    emitEvent: () => undefined,
-    now: () => "2026-05-28T00:00:00.000Z",
-  };
-  return new OnboardRuntime(deps);
-}
-
 describe("runOnboardMachine result sequences", () => {
   it("runs handlers until completion while applying multiple results in order", async () => {
     const runtime = createRuntime();
diff --git a/src/lib/onboard/machine/runner.test.ts b/src/lib/onboard/machine/runner.test.ts
index f520f480b59..5d5bca43c8a 100644
--- a/src/lib/onboard/machine/runner.test.ts
+++ b/src/lib/onboard/machine/runner.test.ts
@@ -3,14 +3,6 @@
 
 import { describe, expect, it, vi } from "vitest";
 
-import {
-  createSession,
-  filterSafeUpdates,
-  MACHINE_SNAPSHOT_VERSION,
-  normalizeSession,
-  type Session,
-  type SessionUpdates,
-} from "../../state/onboard-session";
 import {
   advanceTo,
   branchTo,
@@ -26,58 +18,20 @@ import {
   runOnboardMachine,
 } from "./runner";
 import { OnboardRuntime, type OnboardRuntimeDeps } from "./runtime";
+import {
+  MACHINE_SNAPSHOT_VERSION,
+  type Session,
+  type SessionUpdates,
+  cloneSession,
+  createSession,
+  createTestRuntime as createRuntime,
+} from "../../../../test/helpers/onboard-machine-runtime-fixture";
 
 interface RunnerContext {
   attempts: number;
   visited: string[];
 }
 
-function cloneSession(session: Session): Session {
-  return normalizeSession(JSON.parse(JSON.stringify(session))) ?? session;
-}
-
-function createRuntime(initialSession: Session = createSession()) {
-  let session = cloneSession(initialSession);
-  const updateSession = (mutator: (value: Session) => Session | void): Session => {
-    const next = mutator(cloneSession(session)) ?? session;
-    session = cloneSession(next);
-    return cloneSession(session);
-  };
-  const deps: OnboardRuntimeDeps = {
-    loadSession: () => cloneSession(session),
-    createSession,
-    saveSession: (next) => {
-      session = cloneSession(next);
-      return cloneSession(session);
-    },
-    updateSession,
-    markStepStarted: () => cloneSession(session),
-    markStepComplete: (_stepName, updates: SessionUpdates = {}) =>
-      updateSession((current) => {
-        Object.assign(current, filterSafeUpdates(updates));
-        return current;
-      }),
-    markStepSkipped: () => cloneSession(session),
-    markStepFailed: (stepName, message) =>
-      updateSession((current) => {
-        current.steps[stepName].status = "failed";
-        current.steps[stepName].error = message ?? null;
-        return current;
-      }),
-    completeSession: (updates: SessionUpdates = {}) =>
-      updateSession((current) => {
-        Object.assign(current, filterSafeUpdates(updates));
-        current.status = "complete";
-        current.resumable = false;
-        return current;
-      }),
-    filterSafeUpdates,
-    emitEvent: () => undefined,
-    now: () => "2026-05-28T00:00:00.000Z",
-  };
-  return new OnboardRuntime(deps);
-}
-
 describe("runOnboardMachine", () => {
   it("runs handlers until completion while applying retry and branch transitions", async () => {
     const runtime = createRuntime();
diff --git a/src/lib/onboard/machine/runtime.test.ts b/src/lib/onboard/machine/runtime.test.ts
index 84d3add6852..d76820af90a 100644
--- a/src/lib/onboard/machine/runtime.test.ts
+++ b/src/lib/onboard/machine/runtime.test.ts
@@ -3,13 +3,6 @@
 
 import { describe, expect, it } from "vitest";
 
-import {
-  createSession,
-  filterSafeUpdates,
-  normalizeSession,
-  type Session,
-  type SessionUpdates,
-} from "../../state/onboard-session";
 import type { OnboardMachineEvent } from "./events";
 import {
   advanceTo,
@@ -21,10 +14,13 @@ import {
 } from "./result";
 import { OnboardRuntime, type OnboardRuntimeDeps } from "./runtime";
 import { InvalidOnboardMachineTransitionError } from "./transitions";
-
-function cloneSession(session: Session): Session {
-  return normalizeSession(JSON.parse(JSON.stringify(session))) ?? session;
-}
+import {
+  type Session,
+  type SessionUpdates,
+  cloneSession,
+  createSession,
+  filterSafeUpdates,
+} from "../../../../test/helpers/onboard-machine-runtime-fixture";
 
 function createHarness(initialSession: Session | null = createSession()) {
   let session = initialSession ? cloneSession(initialSession) : null;
diff --git a/src/lib/onboard/machine/sequence-runner.test.ts b/src/lib/onboard/machine/sequence-runner.test.ts
index 579b2158943..ed8c3026baf 100644
--- a/src/lib/onboard/machine/sequence-runner.test.ts
+++ b/src/lib/onboard/machine/sequence-runner.test.ts
@@ -3,13 +3,6 @@
 
 import { describe, expect, it } from "vitest";
 
-import {
-  createSession,
-  filterSafeUpdates,
-  normalizeSession,
-  type Session,
-  type SessionUpdates,
-} from "../../state/onboard-session";
 import { advanceTo, branchTo, completeOnboardMachine, retryTo } from "./result";
 import { OnboardRuntime, type OnboardRuntimeDeps } from "./runtime";
 import {
@@ -18,57 +11,23 @@ import {
   type OnboardSequencePhase,
   runOnboardSequenceWithRunner,
 } from "./sequence-runner";
+import {
+  type Session,
+  type SessionUpdates,
+  cloneSession,
+  createSession,
+  createTestRuntime,
+} from "../../../../test/helpers/onboard-machine-runtime-fixture";
+
+function createRuntime(initialSession: Session = createSession()) {
+  return createTestRuntime(initialSession, { now: () => "2026-05-29T00:00:00.000Z" });
+}
 
 interface SequenceContext {
   attempt: number;
   log: string[];
 }
 
-function cloneSession(session: Session): Session {
-  return normalizeSession(JSON.parse(JSON.stringify(session))) ?? session;
-}
-
-function createRuntime(initialSession: Session = createSession()) {
-  let session = cloneSession(initialSession);
-  const updateSession = (mutator: (value: Session) => Session | void): Session => {
-    session = cloneSession(mutator(cloneSession(session)) ?? session);
-    return cloneSession(session);
-  };
-  const deps: OnboardRuntimeDeps = {
-    loadSession: () => cloneSession(session),
-    createSession,
-    saveSession: (next) => {
-      session = cloneSession(next);
-      return cloneSession(session);
-    },
-    updateSession,
-    markStepStarted: () => cloneSession(session),
-    markStepComplete: (_stepName, updates: SessionUpdates = {}) =>
-      updateSession((current) => {
-        Object.assign(current, filterSafeUpdates(updates));
-        return current;
-      }),
-    markStepSkipped: () => cloneSession(session),
-    markStepFailed: (stepName, message) =>
-      updateSession((current) => {
-        current.steps[stepName].status = "failed";
-        current.steps[stepName].error = message ?? null;
-        return current;
-      }),
-    completeSession: (updates: SessionUpdates = {}) =>
-      updateSession((current) => {
-        Object.assign(current, filterSafeUpdates(updates));
-        current.status = "complete";
-        current.resumable = false;
-        return current;
-      }),
-    filterSafeUpdates,
-    emitEvent: () => undefined,
-    now: () => "2026-05-29T00:00:00.000Z",
-  };
-  return new OnboardRuntime(deps);
-}
-
 function phase(
   state: OnboardSequencePhase<SequenceContext>["state"],
   run: OnboardSequencePhase<SequenceContext>["run"],
diff --git a/src/lib/onboard/machine/transition-traces.test.ts b/src/lib/onboard/machine/transition-traces.test.ts
index a21951cc017..9e28ad929fe 100644
--- a/src/lib/onboard/machine/transition-traces.test.ts
+++ b/src/lib/onboard/machine/transition-traces.test.ts
@@ -14,16 +14,6 @@
 
 import { describe, expect, it, vi } from "vitest";
 
-import {
-  createSession,
-  filterSafeUpdates,
-  MACHINE_SNAPSHOT_VERSION,
-  normalizeSession,
-  type OnboardMachineSnapshot,
-  type Session,
-  type SessionUpdates,
-  type StepState,
-} from "../../state/onboard-session";
 import type { OnboardMachineEvent } from "./events";
 import { handleSandboxState } from "./handlers/sandbox";
 import { baseOptions, bindJournaledRecreate, createDeps } from "./handlers/sandbox-test-fixtures";
@@ -31,13 +21,18 @@ import { advanceTo, branchTo, completeOnboardMachine, failOnboardMachine } from
 import { type OnboardStateHandlers, runOnboardMachine } from "./runner";
 import { OnboardRuntime, type OnboardRuntimeDeps } from "./runtime";
 import type { OnboardMachineState } from "./types";
+import type { OnboardMachineSnapshot, StepState } from "../../state/onboard-session";
+import {
+  MACHINE_SNAPSHOT_VERSION,
+  type Session,
+  type SessionUpdates,
+  cloneSession,
+  createSession,
+  filterSafeUpdates,
+} from "../../../../test/helpers/onboard-machine-runtime-fixture";
 
 const NOW = "2026-07-04T00:00:00.000Z";
 
-function cloneSession(session: Session): Session {
-  return normalizeSession(JSON.parse(JSON.stringify(session))) ?? session;
-}
-
 function machineAt(state: OnboardMachineState, revision = 0): OnboardMachineSnapshot {
   return { version: MACHINE_SNAPSHOT_VERSION, state, stateEnteredAt: NOW, revision };
 }
diff --git a/test/helpers/onboard-machine-runtime-fixture.ts b/test/helpers/onboard-machine-runtime-fixture.ts
new file mode 100644
index 00000000000..58b88d01a95
--- /dev/null
+++ b/test/helpers/onboard-machine-runtime-fixture.ts
@@ -0,0 +1,87 @@
+// SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+import {
+  createSession,
+  filterSafeUpdates,
+  normalizeSession,
+  type Session,
+  type SessionUpdates,
+} from "../../src/lib/state/onboard-session";
+import { OnboardRuntime, type OnboardRuntimeDeps } from "../../src/lib/onboard/machine/runtime";
+
+export {
+  createSession,
+  filterSafeUpdates,
+  MACHINE_SNAPSHOT_VERSION,
+} from "../../src/lib/state/onboard-session";
+export type { Session, SessionUpdates } from "../../src/lib/state/onboard-session";
+
+/**
+ * In-memory onboarding-machine runtime for the machine test suites. The
+ * fixture owns the session store mechanics the suites previously each
+ * declared inline; scenario sessions, timestamps that assertions depend on,
+ * and behavior expectations stay in each test. Every call returns fresh
+ * state, and nothing outside the returned runtime is touched.
+ */
+
+/** A deep session copy that survives independent mutation. */
+export function cloneSession(session: Session): Session {
+  return normalizeSession(JSON.parse(JSON.stringify(session))) ?? session;
+}
+
+/** Behavior options for createTestRuntime. */
+export interface TestRuntimeOptions {
+  /** The deterministic clock the runtime stamps sessions with. */
+  now?: () => string;
+}
+
+/**
+ * An OnboardRuntime over an in-memory session store. Step transitions
+ * mutate the stored session the way the suites' inline copies did; the
+ * clock defaults to a fixed timestamp and is overridable where assertions
+ * depend on a specific value.
+ */
+export function createTestRuntime(
+  initialSession: Session = createSession(),
+  options?: TestRuntimeOptions,
+): OnboardRuntime {
+  let session = cloneSession(initialSession);
+  const updateSession = (mutator: (value: Session) => Session | void): Session => {
+    session = cloneSession(mutator(cloneSession(session)) ?? session);
+    return cloneSession(session);
+  };
+  const deps: OnboardRuntimeDeps = {
+    loadSession: () => cloneSession(session),
+    createSession,
+    saveSession: (next) => {
+      session = cloneSession(next);
+      return cloneSession(session);
+    },
+    updateSession,
+    markStepStarted: () => cloneSession(session),
+    markStepComplete: (_stepName, updates: SessionUpdates = {}) =>
+      updateSession((current) => {
+        Object.assign(current, filterSafeUpdates(updates));
+        return current;
+      }),
+    markStepSkipped: () => cloneSession(session),
+    markStepFailed: (stepName, message) =>
+      updateSession((current) => {
+        current.steps[stepName].status = "failed";
+        current.steps[stepName].error = message ?? null;
+        return current;
+      }),
+    completeSession: (updates: SessionUpdates = {}) =>
+      updateSession((current) => {
+        Object.assign(current, filterSafeUpdates(updates));
+        current.status = "complete";
+        current.resumable = false;
+        return current;
+      }),
+    filterSafeUpdates,
+    emitEvent: () => undefined,
+    now: options?.now ?? (() => "2026-05-28T00:00:00.000Z"),
+  };
+  return new OnboardRuntime(deps);
+}