fix(runner): refuse to reopen a session whose run failed its turn-end restart

open_session did not check the saved turn-end restart failure, so
session.open or a same-run run.attach reopened the provider and later
turns ran. Refuse there while the marker names the current run.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/paperclip-runner/runner/crates/runner-core/src/acpx_provider_backend.rs

@@ -1788,6 +1788,17 @@ impl AcpxCommandExecutor {
                 "ACPX provider lifetime cleanup is not yet proven",
             ));
         }
+        // No path (session.open, a same-run run.attach) reopens a session whose
+        // run failed closed at its turn-end provider restart.
+        if self.session.is_none()
+            && self.state.as_ref().is_some_and(|state| {
+                state.turn_end_restart_failed_run.as_deref() == Some(self.context.run_id.as_str())
+            })
+        {
+            return Err(DurableRunnerError::invalid(
+                "ACPX session failed closed after this run's turn-end provider restart failed",
+            ));
+        }
         if self.session.is_none() {
             let recovering = self
                 .state

packages/paperclip-runner/runner/crates/runner-core/tests/support/acpx_turn_end_restart.rs

@@ -441,11 +441,30 @@ fn a_runner_restart_in_the_same_run_keeps_the_failed_turn_end_restart_closed() {
         .to_string();
     assert_eq!(failed, "ACPX session is not open");
     assert_eq!(harness.fixture.process_starts().len(), starts);
+    // Neither session.open nor a same-run attach reopens it.
+    let reopened = harness
+        .executor
+        .execute(&command(91, "session.open", json!({})))
+        .unwrap_err()
+        .to_string();
+    assert!(reopened.contains("failed closed"), "{reopened}");
+    let same_run_attach = json!({"provider": harness.descriptor.clone()});
+    let attach_error = harness
+        .executor
+        .execute(&command(92, "run.attach", same_run_attach))
+        .unwrap_err()
+        .to_string();
+    assert!(attach_error.contains("failed closed"), "{attach_error}");
+    assert_eq!(harness.fixture.process_starts().len(), starts);
+    assert_eq!(
+        harness.fixture.state()["turnEndRestartFailedRun"],
+        harness.config.run_id
+    );
     assert_eq!(live_providers(&harness), Vec::<Value>::new());
     assert_eq!(harness.fixture.state()["lifecycle"], "suspended");
     // The next run still resumes the conversation and clears the restriction.
     harness.executor.shutdown().unwrap();
-    harness.sequence = 90;
+    harness.sequence = 92;
     harness.config.run_id = "run-2".to_owned();
     harness.executor =
         NativeProviderCommandExecutor::with_runner_config(&harness.fixture.0, &harness.config);