diff --git a/src/process/ownedDebuggerSession.ts b/src/process/ownedDebuggerSession.ts
index 55f29531e7..a5e587c8a1 100644
--- a/src/process/ownedDebuggerSession.ts
+++ b/src/process/ownedDebuggerSession.ts
@@ -174,7 +174,11 @@ const finishExitedDebuggerSession = async (
   return { status };
 };
 
-/** Stop only the directly owned debugger process, never its process group or target. */
+/**
+ * Stop only the directly owned debugger process, never its process group or target.
+ * The caller must permanently close command admission before the first attempt;
+ * retries retain completed detach facts while process termination is pending.
+ */
 export const stopOwnedDebuggerProcess = async (
   session: OwnedDebuggerProcess,
   debuggerName: string,
@@ -218,36 +222,42 @@ export const stopOwnedDebuggerProcess = async (
       status: "incomplete",
       reason: `Owned ${debuggerName} process cannot be stopped safely on Windows because job termination can also terminate its inferior processes.`,
     };
-  try {
-    if (session.detachInferior === undefined) {
-      detachOutcomes.set(session, "unconfirmed");
+  // Admission remains closed once cleanup starts. A verified detach is an
+  // owned completion fact, even when terminating the debugger later fails.
+  // Retrying the command transport can no longer improve that fact and may
+  // block termination if shutdown already made the transport unavailable.
+  if (detachOutcomes.get(session) !== "confirmed") {
+    try {
+      if (session.detachInferior === undefined) {
+        detachOutcomes.set(session, "unconfirmed");
+        return {
+          status: "incomplete",
+          reason: `Owned ${debuggerName} inferior detach cannot be verified because the provider has no detach capability.`,
+        };
+      }
+      const detached = await waitForInferiorDetach(
+        session,
+        session.detachInferior,
+      );
+      if (detached === undefined)
+        return {
+          status: "incomplete",
+          reason: `Owned ${debuggerName} inferior detach was not verified within ${String(DETACH_TIMEOUT_MS)} ms. This release has no runtime override.`,
+        };
+      if (!isVerifiedDetachResult(detached)) {
+        detachOutcomes.set(session, "unconfirmed");
+        return {
+          status: "incomplete",
+          reason: `Owned ${debuggerName} provider did not confirm no inferior or detachment with a durable output sink.`,
+        };
+      }
+      detachOutcomes.set(session, "confirmed");
+    } catch (cause: unknown) {
       return {
         status: "incomplete",
-        reason: `Owned ${debuggerName} inferior detach cannot be verified because the provider has no detach capability.`,
+        reason: `Owned ${debuggerName} inferior detach could not be verified: ${cause instanceof Error ? cause.message : String(cause)}`,
       };
     }
-    const detached = await waitForInferiorDetach(
-      session,
-      session.detachInferior,
-    );
-    if (detached === undefined)
-      return {
-        status: "incomplete",
-        reason: `Owned ${debuggerName} inferior detach was not verified within ${String(DETACH_TIMEOUT_MS)} ms. This release has no runtime override.`,
-      };
-    if (!isVerifiedDetachResult(detached)) {
-      detachOutcomes.set(session, "unconfirmed");
-      return {
-        status: "incomplete",
-        reason: `Owned ${debuggerName} provider did not confirm no inferior or detachment with a durable output sink.`,
-      };
-    }
-    detachOutcomes.set(session, "confirmed");
-  } catch (cause: unknown) {
-    return {
-      status: "incomplete",
-      reason: `Owned ${debuggerName} inferior detach could not be verified: ${cause instanceof Error ? cause.message : String(cause)}`,
-    };
   }
   session.launched.process.kill("SIGTERM");
   if (!(await session.supervisor.waitForExit(300))) {
diff --git a/tests/boundary/process/ownedDebuggerSession.test.ts b/tests/boundary/process/ownedDebuggerSession.test.ts
index a03bea48fc..155f7457e1 100644
--- a/tests/boundary/process/ownedDebuggerSession.test.ts
+++ b/tests/boundary/process/ownedDebuggerSession.test.ts
@@ -224,6 +224,17 @@ it("retains process supervision after an incomplete stop and disposes after a re
   let disposals = 0;
   let outputUnrefs = 0;
   const signals: NodeJS.Signals[] = [];
+  const detachInferior = vi
+    .fn<
+      () => Promise<{
+        readonly status: "detached";
+        readonly outputSink: "durable";
+      }>
+    >()
+    .mockResolvedValueOnce({ status: "detached", outputSink: "durable" })
+    .mockRejectedValue(
+      new Error("debugger transport closed during termination"),
+    );
   const session = {
     id: "debugger-session",
     exited: false,
@@ -235,11 +246,7 @@ it("retains process supervision after an incomplete stop and disposes after a re
         },
       },
     },
-    detachInferior: async () =>
-      ({
-        status: "detached",
-        outputSink: "durable",
-      }) as const,
+    detachInferior,
     supervisor: {
       waitForExit: async (): Promise<boolean> => {
         waits += 1;
@@ -273,6 +280,7 @@ it("retains process supervision after an incomplete stop and disposes after a re
   expect(retry).toEqual({ status: "stopped" });
   expect(disposals).toBe(1);
   expect(waits).toBe(3);
+  expect(detachInferior).toHaveBeenCalledOnce();
 });
 
 it("refuses Windows job-backed debugger termination before signaling", async () => {
@@ -694,11 +702,6 @@ it("retains an owned debugger when inferior detach does not settle", async () =>
       },
       detachInferior: () => {
         detachCalls += 1;
-        if (detachCalls > 1)
-          return Promise.resolve({
-            status: "detached",
-            outputSink: "durable",
-          } as const);
         return new Promise<{
           readonly status: "detached";
           readonly outputSink: "durable";
@@ -744,7 +747,7 @@ it("retains an owned debugger when inferior detach does not settle", async () =>
     expect(
       await stopOwnedDebuggerProcess(session, "GDB", { platform: "linux" }),
     ).toEqual({ status: "stopped" });
-    expect(detachCalls).toBe(2);
+    expect(detachCalls).toBe(1);
     expect(signals).toEqual(["SIGTERM"]);
     expect(disposals).toBe(1);
   } finally {