diff --git a/tests/boundary/process/processSettlementDeadline.test.ts b/tests/boundary/process/processSettlementDeadline.test.ts
index 83c7483663..eed7975c36 100644
--- a/tests/boundary/process/processSettlementDeadline.test.ts
+++ b/tests/boundary/process/processSettlementDeadline.test.ts
@@ -1,5 +1,10 @@
-import { spawn } from "node:child_process";
 import { describe, expect, it } from "vitest";
+
+import {
+  spawnOwnedProviderProcess,
+  type ProviderProcessHandle,
+} from "../../../src/process/ProviderProcess.js";
+import { cleanupOwnedProcessGroup } from "../../../src/process/ProcessOwnership.js";
 import { observeSettlement } from "../../../src/process/capture/ProcessCaptureLifecycle.js";
 import { observeOwnedProcessGroups } from "../../../src/process/ProcessOwnershipObservation.js";
 
@@ -9,65 +14,121 @@ const ABSENT_GROUP_ID = 4_294_967_295;
 const observeGroup = async (groupId: number) =>
   observeOwnedProcessGroups("settlement-deadline-probe", [groupId]);
 
-describe("settlement deadline classification", () => {
-  it("does not report a single empty observation as alive_at_deadline", async () => {
-    expect(
-      (await observeGroup(ABSENT_GROUP_ID)).get(ABSENT_GROUP_ID)?.state,
-    ).toBe("empty");
-
-    const settlement = await observeSettlement(
-      "settlement-single-empty",
-      [ABSENT_GROUP_ID],
-      0,
-      () => undefined,
-      "linux",
-    );
-    expect(settlement.state).toBe("unverifiable");
+const waitForOwnedExit = (
+  child: ProviderProcessHandle,
+  timeoutMs: number,
+): Promise<boolean> =>
+  new Promise((resolve) => {
+    if (child.exitCode !== null || child.signalCode !== null) {
+      resolve(true);
+      return;
+    }
+    const onExit = (): void => {
+      clearTimeout(timer);
+      resolve(true);
+    };
+    const timer = setTimeout(() => {
+      child.off("exit", onExit);
+      resolve(false);
+    }, timeoutMs);
+    child.once("exit", onExit);
   });
 
-  it("still reports observed liveness as alive_at_deadline", async () => {
-    const runId = "settlement-live-group";
-    // A detached child leads its own process group and carries the run token,
-    // so the group observes as a genuinely owned live member.
-    const child = spawn("sleep", ["30"], {
-      detached: true,
-      stdio: "ignore",
-      env: { ...process.env, REA_PROCESS_RUN_ID: runId },
-    });
-    child.unref();
-    try {
-      // Wait until the child is actually listed before asserting on it.
-      const started = Date.now();
-      while (
-        (await observeOwnedProcessGroups(runId, [child.pid!])).get(child.pid!)
-          ?.state !== "alive"
-      ) {
-        if (Date.now() - started > 5_000)
-          throw new Error("live fixture group never observed as alive");
-        await new Promise((resolve) => setTimeout(resolve, 50));
-      }
+const stopOwnedFixture = async (
+  child: ProviderProcessHandle,
+  ownership: Parameters<typeof cleanupOwnedProcessGroup>[0],
+): Promise<void> => {
+  let cleanupFailure: string | undefined;
+  try {
+    const result = await cleanupOwnedProcessGroup(ownership);
+    if (!result.cleaned) cleanupFailure = result.reason;
+  } catch (cause: unknown) {
+    cleanupFailure = cause instanceof Error ? cause.message : String(cause);
+  }
+
+  if (child.exitCode === null && child.signalCode === null)
+    child.kill("SIGKILL");
+  if (!(await waitForOwnedExit(child, 5_000)))
+    throw new Error("owned settlement fixture did not exit after cleanup");
+  if (cleanupFailure !== undefined)
+    throw new Error(
+      `owned settlement fixture cleanup failed: ${cleanupFailure}`,
+    );
+};
+
+// Windows Job Object ownership has a separate settlement path from POSIX PGIDs.
+describe.skipIf(process.platform === "win32")(
+  "settlement deadline classification",
+  () => {
+    it("does not report a single empty observation as alive_at_deadline", async () => {
+      expect(
+        (await observeGroup(ABSENT_GROUP_ID)).get(ABSENT_GROUP_ID)?.state,
+      ).toBe("empty");
 
       const settlement = await observeSettlement(
-        runId,
-        [child.pid!],
+        "settlement-single-empty",
+        [ABSENT_GROUP_ID],
         0,
         () => undefined,
         "linux",
       );
-      expect(settlement.state).toBe("alive_at_deadline");
-    } finally {
-      child.kill("SIGKILL");
-    }
-  });
+      expect(settlement.state).toBe("unverifiable");
+    });
 
-  it("still reports two consecutive empty observations as quiesced", async () => {
-    const settlement = await observeSettlement(
-      "settlement-two-empty",
-      [ABSENT_GROUP_ID],
-      1_000,
-      () => undefined,
-      "linux",
-    );
-    expect(settlement.state).toBe("quiesced");
-  });
-});
+    it("still reports observed owned liveness as alive_at_deadline", async () => {
+      const runId = "settlement-live-group";
+      const launched = await spawnOwnedProviderProcess({
+        command: process.execPath,
+        arguments: ["-e", "setInterval(() => undefined, 1000)"],
+        runId,
+      });
+      try {
+        const started = Date.now();
+        let observation = (
+          await observeOwnedProcessGroups(runId, [
+            launched.ownership.processGroupId,
+          ])
+        ).get(launched.ownership.processGroupId);
+        while (
+          observation?.state === "empty" &&
+          Date.now() - started <= 5_000
+        ) {
+          await new Promise((resolve) => setTimeout(resolve, 50));
+          observation = (
+            await observeOwnedProcessGroups(runId, [
+              launched.ownership.processGroupId,
+            ])
+          ).get(launched.ownership.processGroupId);
+        }
+        expect(
+          observation?.state,
+          observation?.state === "unverifiable"
+            ? observation.reason
+            : undefined,
+        ).toBe("alive");
+
+        const settlement = await observeSettlement(
+          runId,
+          [launched.ownership.processGroupId],
+          0,
+          () => undefined,
+          process.platform,
+        );
+        expect(settlement.state).toBe("alive_at_deadline");
+      } finally {
+        await stopOwnedFixture(launched.process, launched.ownership);
+      }
+    });
+
+    it("still reports two consecutive empty observations as quiesced", async () => {
+      const settlement = await observeSettlement(
+        "settlement-two-empty",
+        [ABSENT_GROUP_ID],
+        1_000,
+        () => undefined,
+        "linux",
+      );
+      expect(settlement.state).toBe("quiesced");
+    });
+  },
+);