diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0aa4623d..668f7577 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -35,6 +35,16 @@
 
 ### Fixed
 
+- **A `partition_owned` worker no longer crashes dropping the partitions
+  a failed session took from it.** The drop ran inside whatever transaction
+  the pipeline's connection had open, begun by an idle tick's progress
+  write before the drop took its locks. Its snapshot could predate a window
+  pass that had since deleted closed buckets' rows on the manager's
+  connection and committed, and DuckDB refused the drop's delete with
+  "Conflict on tuple deletion"; the pipeline stopped over it, and in a
+  two-worker stack a network blip crashed one worker while the other
+  stalled (#436). The drop now ends that transaction first, so it begins one
+  whose snapshot is after every pass its lock excludes. (#437)
 - **A windowed worker that loses its group session no longer stops closing
   windows after it rejoins.** A lost partition stayed in the worker's
   watermark minimum until it was assigned back; when the rejoin gave it to
diff --git a/internal/core/partitiondrop_test.go b/internal/core/partitiondrop_test.go
index f7936501..4a0a2c6d 100644
--- a/internal/core/partitiondrop_test.go
+++ b/internal/core/partitiondrop_test.go
@@ -4,8 +4,12 @@ import (
 	"context"
 	"testing"
 
+	"time"
+
+	"github.com/apache/arrow-adbc/go/adbc"
 	"github.com/apache/arrow-go/v18/arrow/array"
 	"github.com/turbolytics/sql-flow/internal/coverage"
+	"github.com/turbolytics/sql-flow/internal/duckdb"
 	"github.com/zeebo/assert"
 )
 
@@ -83,3 +87,71 @@ func TestDuckDBPartitionDropper_DropAllEmptiesEveryOwnedTable(t *testing.T) {
 	assert.Equal(t, int64(0), rdr.Record().Column(0).(*array.Int64).Value(0))
 	assert.Equal(t, int64(1), rdr.Record().Column(1).(*array.Int64).Value(0))
 }
+
+// The drop runs on the pipeline's connection, whose transaction may have
+// been open since before the manager's pass deleted the same rows on its
+// own connection and committed. DuckDB then refuses the drop's delete with
+// "Conflict on tuple deletion", and the pipeline stopped over it (#437).
+// The drop must succeed whatever the pipeline's transaction has seen.
+//
+//	pipeline conn (autocommit off)    manager conn
+//	----------------------------------------------------------
+//	INSERT ... ; COMMIT
+//	UPDATE progress (opens the next tx)
+//	                                  DELETE closed rows; COMMIT
+//	lose partitions -> drop  <-- conflict, unless the tx ends first
+func TestTurbine_PartitionDropSucceedsAfterAPassDeletedTheRows(t *testing.T) {
+	coverage.Covers(t, "source.kafka")
+	ctx := context.Background()
+	db, err := duckdb.OpenPath(ctx, "")
+	assert.NoError(t, err)
+	t.Cleanup(func() { db.Close() })
+	pipeline, err := db.Connect(ctx)
+	assert.NoError(t, err)
+	t.Cleanup(func() { pipeline.Close() })
+	manager, err := db.Connect(ctx)
+	assert.NoError(t, err)
+	t.Cleanup(func() { manager.Close() })
+
+	exec(t, pipeline, `CREATE TABLE w (minute TIMESTAMPTZ, kafka_partition INTEGER, n INTEGER)`)
+	exec(t, pipeline, `CREATE TABLE progress (seen TIMESTAMPTZ)`)
+	exec(t, pipeline, `INSERT INTO progress VALUES (now())`)
+	assert.NoError(t, pipeline.(adbc.PostInitOptions).SetOption(adbc.OptionKeyAutoCommit, adbc.OptionValueDisabled))
+	tx := pipeline.(stateTx)
+
+	// A batch: rows for partitions 3 and 4, committed.
+	exec(t, pipeline, `INSERT INTO w VALUES (TIMESTAMPTZ '2026-10-04 19:33:00+00', 3, 1), (TIMESTAMPTZ '2026-10-04 19:33:00+00', 4, 1)`)
+	assert.NoError(t, tx.Commit(ctx))
+	// An idle tick's progress write: opens the pipeline's next transaction.
+	exec(t, pipeline, `UPDATE progress SET seen = now()`)
+	// The manager's pass closes the minute: deletes its rows, commits.
+	exec(t, manager, `DELETE FROM w WHERE minute = TIMESTAMPTZ '2026-10-04 19:33:00+00'`)
+
+	// The session is lost: the turbine drops the partitions.
+	src := newOwnerSource()
+	w := NewWatermarks([]WindowSpec{ownedSpec}, nil)
+	tb := newWindowedTurbine(src, &fakeHandler{}, &fakeSink{}, 100, w,
+		WithPartitionDropper(NewDuckDBPartitionDropper(pipeline, []string{"w"})),
+		WithStateStore(&nopSaver{}, tx))
+	loopCtx, cancel := context.WithCancel(ctx)
+	done := make(chan error, 1)
+	go func() { _, err := tb.ConsumeLoop(loopCtx, 0); done <- err }()
+	// The loop must be gone before the cleanups close its connection and
+	// database: a close under a running loop is a use after free in the
+	// ADBC driver, which segfaulted on CI.
+	defer func() {
+		cancel()
+		<-done
+	}()
+	src.assigned(map[string][]int32{"t": {3, 4, 5}})
+	src.lost(map[string][]int32{"t": {3, 4, 5}}) // blocks until dropped
+	select {
+	case err := <-done:
+		t.Fatalf("the run stopped: %v", err)
+	case <-time.After(200 * time.Millisecond):
+	}
+}
+
+type nopSaver struct{}
+
+func (nopSaver) Save(context.Context, *Marks) error { return nil }
diff --git a/internal/core/turbine.go b/internal/core/turbine.go
index 3dc161a8..70ef9ac8 100644
--- a/internal/core/turbine.go
+++ b/internal/core/turbine.go
@@ -916,6 +916,20 @@ func (t *Turbine) dropPartitions(ctx context.Context, parts map[string][]int32)
 
 	t.lock.Lock()
 	defer t.lock.Unlock()
+	// The drop runs between batches, so the connection's open transaction,
+	// if any, holds only an idle tick's progress write, begun before this
+	// lock was taken. Its snapshot can predate a window pass that has since
+	// deleted closed buckets' rows on the manager's connection and committed;
+	// DuckDB then refuses the drop's delete of those rows as a conflict on
+	// tuple deletion, and the pipeline stopped over it (#437). Committed
+	// here, so the drop begins a transaction whose snapshot is after every
+	// pass this lock excludes. The progress write is rewritten every commit,
+	// so committing it early loses nothing.
+	if t.dropper != nil && t.stateTx != nil {
+		if err := t.stateTx.Commit(ctx); err != nil {
+			return errs.Wrap(errs.CodeStateCommitFailed, err, "ending the transaction before a partition drop")
+		}
+	}
 	fail := func(err error) error {
 		if t.stateTx != nil {
 			if rbErr := t.stateTx.Rollback(context.WithoutCancel(ctx)); rbErr != nil {