diff --git a/controller/cleanup_test.go b/controller/cleanup_test.go
new file mode 100644
index 00000000..36c6915a
--- /dev/null
+++ b/controller/cleanup_test.go
@@ -0,0 +1,211 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"log/slog"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/actions/scaleset"
+	"github.com/actions/scaleset/listener"
+	dockerclient "github.com/docker/docker/client"
+)
+
+func TestOverlappingRunnerCleanupPreservesTheListenerBatch(t *testing.T) {
+	const runner = "ci-fleet-example-0123abcd"
+	const other = "ci-fleet-example-89abcdef"
+	removing := make(chan struct{})
+	finishRemoval := make(chan struct{})
+	removed := make(chan struct{})
+	var finish sync.Once
+	var removals, otherRemovals atomic.Int32
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		path := strings.TrimPrefix(r.URL.Path, "/v1.48")
+		switch {
+		case path == "/containers/runner-id/wait":
+			switch r.URL.Query().Get("condition") {
+			case "not-running":
+				json.NewEncoder(w).Encode(map[string]int{"StatusCode": 0})
+			case "removed":
+				// Release the watcher's DELETE only once completion waits for removal.
+				finish.Do(func() { close(finishRemoval) })
+				select {
+				case <-removed:
+					json.NewEncoder(w).Encode(map[string]int{"StatusCode": 0})
+				case <-r.Context().Done():
+				}
+			default:
+				t.Errorf("unexpected wait condition: %s", r.URL)
+				w.WriteHeader(http.StatusBadRequest)
+			}
+		case path == "/containers/runner-id/json":
+			json.NewEncoder(w).Encode(map[string]any{"State": map[string]bool{"Running": false}})
+		case strings.HasSuffix(path, "/logs"):
+			w.WriteHeader(http.StatusOK)
+		case path == "/containers/runner-id" && r.Method == http.MethodDelete:
+			if removals.Add(1) == 1 {
+				if r.URL.Query().Get("force") == "1" {
+					t.Error("exit watcher forced removal")
+				}
+				close(removing)
+				select {
+				case <-finishRemoval:
+					close(removed)
+					w.WriteHeader(http.StatusNoContent)
+				case <-r.Context().Done():
+				}
+			} else {
+				if r.URL.Query().Get("force") != "1" {
+					t.Error("job completion did not force removal")
+				}
+				w.WriteHeader(http.StatusConflict)
+				json.NewEncoder(w).Encode(map[string]string{"message": "removal of container runner-id is already in progress"})
+			}
+		case path == "/containers/other-id" && r.Method == http.MethodDelete:
+			otherRemovals.Add(1)
+			w.WriteHeader(http.StatusNoContent)
+		default:
+			t.Errorf("unexpected Docker request %s %s", r.Method, r.URL)
+			w.WriteHeader(http.StatusNotFound)
+		}
+	}))
+	defer server.Close()
+	defer finish.Do(func() { close(finishRemoval) })
+	docker, err := dockerclient.NewClientWithOpts(dockerclient.WithHost("tcp://"+server.Listener.Addr().String()), dockerclient.WithHTTPClient(server.Client()), dockerclient.WithVersion("1.48"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer docker.Close()
+	scaler := &Scaler{runners: newRunnerState(), dockerClient: docker, logger: slog.New(slog.DiscardHandler),
+		config: Config{MaxRunners: 2, StatusFile: t.TempDir() + "/status.json"}}
+	scaler.runners.addBusy(runner, "runner-id")
+	scaler.runners.addBusy(other, "other-id")
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+	watchDone := make(chan struct{})
+	go func() {
+		scaler.watchRunner(ctx, runner, "runner-id")
+		close(watchDone)
+	}()
+	select {
+	case <-removing:
+	case <-ctx.Done():
+		t.Fatal("watcher did not begin removal")
+	}
+	client := &lifecycleBatchClient{message: &scaleset.RunnerScaleSetMessage{
+		MessageID: 7, Statistics: &scaleset.RunnerScaleSetStatistic{},
+		JobCompletedMessages: []*scaleset.JobCompleted{{RunnerName: runner}, {RunnerName: other}},
+	}}
+	l, err := listener.New(client, listener.Config{ScaleSetID: 42, MaxRunners: 2})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := l.Run(ctx, scaler); !errors.Is(err, context.Canceled) || ctx.Err() != nil {
+		t.Fatalf("overlapping cleanup interrupted the listener batch: %v", err)
+	}
+	select {
+	case <-watchDone:
+	case <-ctx.Done():
+		t.Fatal("exit watcher did not finish")
+	}
+	if !client.acknowledged.Load() || client.polls != 2 || removals.Load() != 2 || otherRemovals.Load() != 1 {
+		t.Fatalf("batch did not finish: acknowledged=%v polls=%d removals=%d other removals=%d", client.acknowledged.Load(), client.polls, removals.Load(), otherRemovals.Load())
+	}
+	if scaler.runners.contains(runner, "runner-id") || scaler.runners.count() != 0 {
+		t.Fatal("completed runners retained lifecycle state or capacity")
+	}
+	select {
+	case <-removed:
+	default:
+		t.Fatal("cleanup succeeded before container removal")
+	}
+}
+
+func TestRunnerRemovalResults(t *testing.T) {
+	const inProgress = "removal of container runner-id is already in progress"
+	for _, test := range []struct {
+		name, message, waitBody, want string
+		removeStatus, waitStatus      int
+		cancelWait                    bool
+	}{
+		{name: "removed", removeStatus: http.StatusNoContent},
+		{name: "already absent", removeStatus: http.StatusNotFound},
+		{name: "daemon error", removeStatus: http.StatusInternalServerError, message: "daemon failure", want: "daemon failure"},
+		{name: "permission denied", removeStatus: http.StatusForbidden, message: "permission denied", want: "permission denied"},
+		{name: "unrelated conflict", removeStatus: http.StatusConflict, message: "container is running", want: "container is running"},
+		{name: "another container", removeStatus: http.StatusConflict, message: "removal of container other-id is already in progress", want: "other-id"},
+		{name: "wrong error class", removeStatus: http.StatusInternalServerError, message: inProgress, want: inProgress},
+		{name: "removed during wait", removeStatus: http.StatusConflict, message: inProgress, waitStatus: http.StatusOK, waitBody: `{"StatusCode":0}`},
+		{name: "absent before wait", removeStatus: http.StatusConflict, message: inProgress, waitStatus: http.StatusNotFound},
+		{name: "wait daemon error", removeStatus: http.StatusConflict, message: inProgress, waitStatus: http.StatusInternalServerError, want: "wait failure"},
+		{name: "wait result error", removeStatus: http.StatusConflict, message: inProgress, waitStatus: http.StatusOK, waitBody: `{"Error":{"Message":"removal failed"}}`, want: "removal failed"},
+		{name: "incomplete wait response", removeStatus: http.StatusConflict, message: inProgress, waitStatus: http.StatusOK, waitBody: `{"StatusCode":`, want: "unexpected EOF"},
+		{name: "deadline", removeStatus: http.StatusConflict, message: inProgress, want: "context deadline exceeded"},
+		{name: "cancellation", removeStatus: http.StatusConflict, message: inProgress, want: "context canceled", cancelWait: true},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			ctx, cancel := context.WithTimeout(context.Background(), 250*time.Millisecond)
+			defer cancel()
+			var waits atomic.Int32
+			server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				w.Header().Set("Content-Type", "application/json")
+				switch {
+				case strings.HasSuffix(r.URL.Path, "/logs"):
+					w.WriteHeader(http.StatusOK)
+				case r.Method == http.MethodDelete:
+					w.WriteHeader(test.removeStatus)
+					if test.removeStatus != http.StatusNoContent {
+						json.NewEncoder(w).Encode(map[string]string{"message": test.message})
+					}
+				case strings.HasSuffix(r.URL.Path, "/wait"):
+					waits.Add(1)
+					if r.URL.Query().Get("condition") != "removed" {
+						t.Error("wait did not require container removal")
+					}
+					if test.waitStatus == 0 {
+						if test.cancelWait {
+							cancel()
+						}
+						<-r.Context().Done()
+						return
+					}
+					w.WriteHeader(test.waitStatus)
+					if test.waitStatus != http.StatusOK {
+						json.NewEncoder(w).Encode(map[string]string{"message": "wait failure"})
+					} else {
+						w.Write([]byte(test.waitBody))
+					}
+				default:
+					t.Errorf("unexpected Docker request %s %s", r.Method, r.URL)
+					w.WriteHeader(http.StatusNotFound)
+				}
+			}))
+			defer server.Close()
+			docker, err := dockerclient.NewClientWithOpts(dockerclient.WithHost("tcp://"+server.Listener.Addr().String()), dockerclient.WithHTTPClient(server.Client()), dockerclient.WithVersion("1.48"))
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer docker.Close()
+			scaler := &Scaler{dockerClient: docker, logger: slog.New(slog.DiscardHandler)}
+			err = scaler.logAndRemove(ctx, "runner", "runner-id", true)
+			if test.want == "" && err != nil || test.want != "" && (err == nil || !strings.Contains(err.Error(), test.want)) {
+				t.Fatalf("cleanup error = %v, want %q", err, test.want)
+			}
+			wantWaits := int32(0)
+			if test.removeStatus == http.StatusConflict && test.message == inProgress {
+				wantWaits = 1
+			}
+			if waits.Load() != wantWaits {
+				t.Fatalf("removal waits = %d, want %d", waits.Load(), wantWaits)
+			}
+		})
+	}
+}
diff --git a/controller/scaler.go b/controller/scaler.go
index f5758895..da1bc612 100644
--- a/controller/scaler.go
+++ b/controller/scaler.go
@@ -290,7 +290,23 @@ func (s *Scaler) logAndRemove(ctx context.Context, name, id string, force bool)
 		s.logger.Warn("could not collect runner logs", "runner", name, "error", err)
 	}
 	if err := s.dockerClient.ContainerRemove(ctx, id, container.RemoveOptions{Force: force, RemoveVolumes: true}); err != nil && !errdefs.IsNotFound(err) {
-		return fmt.Errorf("remove runner %s: %w", name, err)
+		if !errdefs.IsConflict(err) || !strings.Contains(err.Error(), "removal of container "+id+" is already in progress") {
+			return fmt.Errorf("remove runner %s: %w", name, err)
+		}
+		// Completion and exit cleanup can overlap; confirm the other removal finishes.
+		waitCtx, cancel := context.WithTimeout(ctx, 30*time.Second)
+		defer cancel()
+		removed, errors := s.dockerClient.ContainerWait(waitCtx, id, container.WaitConditionRemoved)
+		select {
+		case result := <-removed:
+			if result.Error != nil {
+				return fmt.Errorf("wait for runner %s removal: %s", name, result.Error.Message)
+			}
+		case err := <-errors:
+			if !errdefs.IsNotFound(err) {
+				return fmt.Errorf("wait for runner %s removal: %w", name, err)
+			}
+		}
 	}
 	return nil
 }
diff --git a/docs/ARCHITECTURE.md b/docs/ARCHITECTURE.md
index b296e361..3110a968 100644
--- a/docs/ARCHITECTURE.md
+++ b/docs/ARCHITECTURE.md
@@ -146,6 +146,12 @@ flowchart TD
 
 Host-wide pruning must not run as an uncoordinated per-job operation. Hard cancellation and host failure may bypass project traps, so resources must remain identifiable by run and age.
 
+Job completion and the runner exit watcher can request removal of the same
+container concurrently. If Docker reports that removal is already in progress,
+the controller waits up to 30 seconds for that container's removal. Confirmed
+removal or an already absent container lets processing continue. Other Docker
+errors, cancellation and an expired wait remain cleanup failures.
+
 The existing host cleanup timer also reclaims empty networks at least ten
 minutes old whose allocations
 lie entirely inside rendered Docker default address pools. This includes