diff --git a/src/gdb/GdbSessionManager.ts b/src/gdb/GdbSessionManager.ts
index 49e4207751..5695044ba2 100644
--- a/src/gdb/GdbSessionManager.ts
+++ b/src/gdb/GdbSessionManager.ts
@@ -464,22 +464,6 @@ export class GdbSessionManager {
           },
         ]),
       );
-    if (this.#closing || signal?.aborted)
-      return err(
-        signal?.aborted
-          ? cancelledWithCallerReason("start_gdb_session", signal)
-          : cancelledBy("start_gdb_session", OwnerCancellation.ownerClosed),
-      );
-    if (!persistentDebuggerHostSupported(this.#platform))
-      return err(
-        new AnalysisCapabilityUnavailableError(
-          "gdb",
-          "start_gdb_session",
-          this.#platform === "win32"
-            ? "Persistent Windows GDB sessions are unavailable because owned Job Object cleanup can terminate debugger inferiors."
-            : "Persistent GDB sessions are available only on Linux because REA verifies live inferior output descriptors through /proc.",
-        ),
-      );
     return this.#sessions.start("start_gdb_session", signal, (started) =>
       this.#startWithReservation(started, options),
     );
@@ -495,6 +479,16 @@ export class GdbSessionManager {
     >
   > {
     if (signal?.aborted) return err(cancelledBy("start_gdb_session", signal));
+    if (!persistentDebuggerHostSupported(this.#platform))
+      return err(
+        new AnalysisCapabilityUnavailableError(
+          "gdb",
+          "start_gdb_session",
+          this.#platform === "win32"
+            ? "Persistent Windows GDB sessions are unavailable because owned Job Object cleanup can terminate debugger inferiors."
+            : "Persistent GDB sessions are available only on Linux because REA verifies live inferior output descriptors through /proc.",
+        ),
+      );
     const occupied = this.#sessions.occupied();
     if (occupied >= this.#maxSessions.value)
       return err(
@@ -1360,7 +1354,7 @@ export class GdbSessionManager {
   }
 
   async #drainStartsAndCloseSessions(): Promise<void> {
-    await this.#sessions.abortStarts();
+    await this.#sessions.closeStarts();
     await Promise.all(
       [...this.#sessions.values()].map((session) => session.commandTail),
     );
diff --git a/src/process/OwnedDebuggerSessionRegistry.ts b/src/process/OwnedDebuggerSessionRegistry.ts
index 5907b00f9e..98e770a2e9 100644
--- a/src/process/OwnedDebuggerSessionRegistry.ts
+++ b/src/process/OwnedDebuggerSessionRegistry.ts
@@ -65,6 +65,8 @@ export class OwnedDebuggerSessionRegistry<
   #reservations = 0;
   /** In-flight starts; closing aborts each as owner-closed and awaits it. */
   readonly #starts = new Map<AbortController, Promise<unknown>>();
+  /** Set once closing begins; later starts are refused as owner-closed. */
+  #closed = false;
 
   constructor(options: OwnedDebuggerSessionRegistryOptions<Session>) {
     this.#options = options;
@@ -110,15 +112,25 @@ export class OwnedDebuggerSessionRegistry<
   }
 
   /**
-   * Run one session start that closing aborts as owner-closed. The caller's
-   * abort is relayed; when it came first, a cancellation reports the
-   * caller's reason. Register before awaiting, so a close cannot miss it.
+   * Run one session start that closing aborts as owner-closed. A start made
+   * after closing began is refused the same way, and a caller that already
+   * aborted gets its own reason. The caller's abort is relayed; when it came
+   * first, a cancellation reports the caller's reason. Register before
+   * awaiting, so a close cannot miss it.
    */
   start<Value>(
     operation: string,
     callerSignal: AbortSignal | undefined,
     run: (signal: AbortSignal) => Promise<Result<Value, AnalysisError>>,
   ): Promise<Result<Value, AnalysisError>> {
+    if (callerSignal?.aborted)
+      return Promise.resolve(
+        err(cancelledWithCallerReason(operation, callerSignal)),
+      );
+    if (this.#closed)
+      return Promise.resolve(
+        err(cancelledBy(operation, OwnerCancellation.ownerClosed)),
+      );
     const controller = new AbortController();
     let callerAbortWon = false;
     const relayAbort = (): void => {
@@ -127,7 +139,6 @@ export class OwnedDebuggerSessionRegistry<
       controller.abort(callerSignal?.reason);
     };
     callerSignal?.addEventListener("abort", relayAbort, { once: true });
-    if (callerSignal?.aborted) relayAbort();
     const started = Promise.resolve()
       .then(() => run(controller.signal))
       .finally(() => {
@@ -145,8 +156,12 @@ export class OwnedDebuggerSessionRegistry<
     );
   }
 
-  /** Abort every in-flight start as owner-closed and wait for each to settle. */
-  async abortStarts(): Promise<void> {
+  /**
+   * Refuse new starts, abort every in-flight start as owner-closed and wait
+   * for each to settle.
+   */
+  async closeStarts(): Promise<void> {
+    this.#closed = true;
     const active = [...this.#starts.entries()];
     for (const [controller] of active)
       controller.abort(OwnerCancellation.ownerClosed);
@@ -241,7 +256,7 @@ export class OwnedDebuggerSessionRegistry<
 
   /**
    * Stop every session; sessions whose stop is incomplete stay registered for
-   * retry. Callers block new starts and abort in-flight ones first.
+   * retry. Callers close starts first.
    */
   closeAll(): Promise<void> {
     return closeOwnedDebuggerSessions(
diff --git a/src/rizin/RizinDebugSessionManager.ts b/src/rizin/RizinDebugSessionManager.ts
index e6fc9bbd4a..364194f875 100644
--- a/src/rizin/RizinDebugSessionManager.ts
+++ b/src/rizin/RizinDebugSessionManager.ts
@@ -371,17 +371,28 @@ export class RizinDebugSessionManager {
       AnalysisError
     >
   > {
-    if (this.#closingAll)
-      return err(
-        new AnalysisInputError("start_rizin_debug_session", undefined, [
-          {
-            path: ["inferior_tty"],
-            reason: "missing_argument",
-            message:
-              "Select a persistent readable and writable Linux terminal for inferior input and output.",
-          },
-        ]),
-      );
+    return this.#sessions.start(
+      "start_rizin_debug_session",
+      signal,
+      (started) => this.#startWithReservation(input, started),
+    );
+  }
+
+  async #startWithReservation(
+    input: {
+      readonly path: string;
+      readonly inferior_tty: string;
+      readonly backend?: string;
+    },
+    signal: AbortSignal,
+  ): Promise<
+    Result<
+      { readonly session_id: string; readonly backend: string | null },
+      AnalysisError
+    >
+  > {
+    if (signal.aborted)
+      return err(cancelledBy("start_rizin_debug_session", signal));
     const occupied = this.#sessions.occupied();
     if (occupied >= this.#maxSessions.value)
       return err(
@@ -398,11 +409,11 @@ export class RizinDebugSessionManager {
         ),
       );
     const releaseReservation = this.#sessions.reserve();
-    return this.#sessions
-      .start("start_rizin_debug_session", signal, (started) =>
-        this.#start(input, started, releaseReservation),
-      )
-      .finally(releaseReservation);
+    try {
+      return await this.#start(input, signal, releaseReservation);
+    } finally {
+      releaseReservation();
+    }
   }
 
   async #start(
@@ -411,7 +422,7 @@ export class RizinDebugSessionManager {
       readonly inferior_tty: string;
       readonly backend?: string;
     },
-    signal: AbortSignal | undefined,
+    signal: AbortSignal,
     releaseReservation: () => void,
   ): Promise<
     Result<
@@ -419,8 +430,6 @@ export class RizinDebugSessionManager {
       AnalysisError
     >
   > {
-    if (signal?.aborted)
-      return err(cancelledBy("start_rizin_debug_session", signal));
     if (!persistentDebuggerHostSupported(this.#platform))
       return err(
         new AnalysisCapabilityUnavailableError(
@@ -1184,7 +1193,7 @@ export class RizinDebugSessionManager {
 
   async closeAll(): Promise<void> {
     this.#closingAll = true;
-    await this.#sessions.abortStarts();
+    await this.#sessions.closeStarts();
     const outcomes = await Promise.allSettled([
       this.#sessions.closeAll(),
       this.#ttyResources.close(),
diff --git a/tests/boundary/providers/RizinDebugSessionReviewRegressions.test.ts b/tests/boundary/providers/RizinDebugSessionReviewRegressions.test.ts
index 72ecd1a6f6..cc663d6dca 100644
--- a/tests/boundary/providers/RizinDebugSessionReviewRegressions.test.ts
+++ b/tests/boundary/providers/RizinDebugSessionReviewRegressions.test.ts
@@ -184,6 +184,32 @@ it.skipIf(process.platform === "win32")(
   },
 );
 
+it("refuses a Rizin start made after closeAll began as owner-closed, keeping a caller's own abort reason", async () => {
+  const manager = new RizinDebugSessionManager(process.env, {
+    platform: "linux",
+    spawnProcess: () => {
+      throw new Error("a refused start must not spawn Rizin");
+    },
+  });
+  managers.push(manager);
+  await manager.closeAll();
+  const input = { path: "/tmp/fixture.bin", inferior_tty: "/dev/null" };
+  await expect(manager.start(input)).resolves.toMatchObject({
+    ok: false,
+    error: {
+      _tag: "AnalysisCancelledError",
+      cause: OwnerCancellation.ownerClosed,
+    },
+  });
+  const caller = new AbortController();
+  const reason = new Error("caller stopped waiting");
+  caller.abort(reason);
+  await expect(manager.start(input, caller.signal)).resolves.toMatchObject({
+    ok: false,
+    error: { _tag: "AnalysisCancelledError", cause: reason },
+  });
+});
+
 it("keeps persistent Rizin sessions unavailable on Windows", async () => {
   const rizin = await createRizinTestManager(
     { REA_RIZIN_COMMAND: "/missing/rizin" },