diff --git a/src/process/ProcessOwnership.part2.test.ts b/src/process/ProcessOwnership.part2.test.ts
index 9fed67e43b..af34fde651 100644
--- a/src/process/ProcessOwnership.part2.test.ts
+++ b/src/process/ProcessOwnership.part2.test.ts
@@ -208,7 +208,7 @@ describe("process environment permission diagnostics", () => {
         ),
       ).resolves.toMatchObject({
         cleaned: false,
-        reason: `process ownership token could not be read for 1 live process(es): environment_errno_${code}=1`,
+        reason: `process ownership token could not be read for 1 live process(es): environment_errno_${code}=1; live candidates 900=environment_errno_${code}`,
         failures: [{ pid: 900, reason: "environment-unreadable", diagnostic }],
       });
       expect(signalGroup).not.toHaveBeenCalled();
diff --git a/src/process/ProcessOwnership.test.ts b/src/process/ProcessOwnership.test.ts
index a2a39f89af..1589cce788 100644
--- a/src/process/ProcessOwnership.test.ts
+++ b/src/process/ProcessOwnership.test.ts
@@ -193,6 +193,13 @@ describe("opaque process neighbors during cleanup", () => {
       cleaned: false,
       reason: expect.stringContaining("environment_unavailable=1"),
     });
+    if (result.cleaned)
+      throw new Error("Expected unknown ownership to fail closed");
+    expect(result.reason).toContain(
+      "live candidates 900=environment_unavailable",
+    );
+    expect(result.reason).not.toContain("unowned");
+    expect(result.reason).not.toContain("run-token");
     expect(signalGroup.mock.calls).toEqual([[100, "SIGKILL"]]);
     expect(signalGroup).not.toHaveBeenCalledWith(900, "SIGKILL");
   });
diff --git a/src/process/ProcessOwnership.ts b/src/process/ProcessOwnership.ts
index eff856e6f2..ff883c46ac 100644
--- a/src/process/ProcessOwnership.ts
+++ b/src/process/ProcessOwnership.ts
@@ -566,9 +566,15 @@ const cleanupValidationFailure = (
       .sort(([left], [right]) => left.localeCompare(right))
       .map(([category, count]) => `${category}=${String(count)}`)
       .join(", ");
+    const candidates = unreadable
+      .map(
+        ({ pid, diagnostic }) =>
+          `${String(pid)}=${sanitizedTokenReadFailure(diagnostic)}`,
+      )
+      .sort((left, right) => left.localeCompare(right));
     return {
       cleaned: false,
-      reason: `process ownership token could not be read for ${String(unreadable.length)} live process(es): ${breakdown}`,
+      reason: `process ownership token could not be read for ${String(unreadable.length)} live process(es): ${breakdown}; live candidates ${candidates.join(", ")}`,
       failures,
       ...unverifiedEntry,
     };
diff --git a/src/process/capture/ProcessHarness.test.ts b/src/process/capture/ProcessHarness.test.ts
index 78a3c48ee0..2d4a2832fe 100644
--- a/src/process/capture/ProcessHarness.test.ts
+++ b/src/process/capture/ProcessHarness.test.ts
@@ -304,7 +304,7 @@ it("retains observations and both causes when process cleanup is unverifiable",
     owned_process_group: {
       state: "unverified" as const,
       reason:
-        "process ownership token could not be read for 1 live process(es): environment_unavailable=1",
+        "process ownership token could not be read for 1 live process(es): environment_unavailable=1; live candidates 900=environment_unavailable",
       unverified_processes: [
         { pid: 900, reason: "platform_binary_environment_withheld" },
       ],
diff --git a/tests/boundary/cli/processCli.test.ts b/tests/boundary/cli/processCli.test.ts
index 2b99cd2408..d5c9de51c6 100644
--- a/tests/boundary/cli/processCli.test.ts
+++ b/tests/boundary/cli/processCli.test.ts
@@ -15,6 +15,7 @@ import {
   projectProcessCliError,
 } from "../../../src/application/process/ProcessCli.js";
 import { createEvidence } from "../../../src/domain/evidence.js";
+import { ProcessCaptureError } from "../../../src/process/capture/ProcessCaptureError.js";
 import { PROCESS_PROVIDER } from "../../../src/application/process/ProcessEvidence.js";
 import { INVESTIGATION_EXAMPLES } from "../../../src/contracts/investigationExamples.js";
 
@@ -229,6 +230,30 @@ describe("process CLI environment key diagnostics", () => {
 });
 
 describe("process CLI evidence validation", () => {
+  it("preserves sanitized unknown-process IDs and reasons through CLI projection", () => {
+    const reason =
+      "process ownership token could not be read for 1 live process(es): environment_unavailable=1; live candidates 900=environment_unavailable";
+    const projected = projectProcessCliError(
+      new ProcessCaptureError("cleanup incomplete", {
+        reason: "cleanup_incomplete",
+        cleanupResources: ["owned_process_group"],
+        cleanupReport: {
+          owned_process_group: { state: "unverified", reason },
+          terminal_renderer: { state: "cleaned", reason: null },
+          temporary_root: { state: "cleaned", reason: null },
+        },
+      }),
+    );
+    expect(projected).toMatchObject({
+      code: "cleanup_incomplete",
+      details: {
+        cleanup_report: {
+          owned_process_group: { reason },
+        },
+      },
+    });
+  });
+
   it("captures the minimal executable-and-arguments scenario", async () => {
     const root = await fixture();
     const scenario = join(root, "scenario.json");
diff --git a/tests/boundary/process/processCaptureLifecycle.test.ts b/tests/boundary/process/processCaptureLifecycle.test.ts
index 566c00597e..fdd1bba400 100644
--- a/tests/boundary/process/processCaptureLifecycle.test.ts
+++ b/tests/boundary/process/processCaptureLifecycle.test.ts
@@ -46,12 +46,14 @@ const captureObservations = (
   const partial = result.error.partialObservation;
   expect(result.error.reason).toBe("cleanup_incomplete");
   expect(report?.owned_process_group.state).toBe("unverified");
-  const [summary, breakdown] = (report?.owned_process_group.reason ?? "").split(
-    ": ",
-  );
+  const [summary, diagnostics] = (
+    report?.owned_process_group.reason ?? ""
+  ).split(": ");
   expect(summary).toMatch(
     /^process ownership token could not be read for [1-9][0-9]* live process\(es\)$/u,
   );
+  const [breakdown, liveCandidates] =
+    diagnostics?.split("; live candidates ") ?? [];
   const categories = breakdown?.split(", ") ?? [];
   expect(categories.length).toBeGreaterThan(0);
   const expectedCategory =
@@ -59,6 +61,9 @@ const captureObservations = (
       ? /^environment_errno_(?:EACCES|EPERM)=[1-9][0-9]*$/u
       : /^environment_unavailable=[1-9][0-9]*$/u;
   for (const category of categories) expect(category).toMatch(expectedCategory);
+  expect(liveCandidates).toMatch(
+    /^(?:[1-9][0-9]*=(?:environment_unavailable|environment_errno_(?:EACCES|EPERM)))(?:, [1-9][0-9]*=(?:environment_unavailable|environment_errno_(?:EACCES|EPERM)))*$/u,
+  );
   expect(report?.terminal_renderer.state).toBe("cleaned");
   expect(report?.temporary_root.state).toBe("cleaned");
   if (partial === undefined || !("capture" in partial))