From aa3d6f708d50a310f60bca8f3e0ee310e4dce61c Mon Sep 17 00:00:00 2001
From: Shreyas Goenka <shreyas.goenka@databricks.com>
Date: Wed, 14 Jan 2026 16:30:39 +0100
Subject: [PATCH] Use workspace FUSE for reading and writing files on
 serverless

---
 bundle/config/mutator/configure_wsfs.go      |  5 +++++
 bundle/config/mutator/configure_wsfs_test.go | 11 +++++++++++
 libs/dbr/context.go                          | 11 ++++++++++-
 libs/dbr/context_test.go                     |  7 +++++++
 4 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/bundle/config/mutator/configure_wsfs.go b/bundle/config/mutator/configure_wsfs.go
index 110e1a3819..4ef7d553c5 100644
--- a/bundle/config/mutator/configure_wsfs.go
+++ b/bundle/config/mutator/configure_wsfs.go
@@ -34,6 +34,11 @@ func (m *configureWSFS) Apply(ctx context.Context, b *bundle.Bundle) diag.Diagno
 		return nil
 	}
 
+	// If running on serverless, use OS file functions directly.
+	if dbr.RunsOnServerless(ctx) {
+		return nil
+	}
+
 	// If so, swap out vfs.Path instance of the sync root with one that
 	// makes all Workspace File System interactions extension aware.
 	p, err := vfs.NewFilerPath(ctx, root, func(path string) (filer.Filer, error) {
diff --git a/bundle/config/mutator/configure_wsfs_test.go b/bundle/config/mutator/configure_wsfs_test.go
index 6762a446b4..ea1bf8cbce 100644
--- a/bundle/config/mutator/configure_wsfs_test.go
+++ b/bundle/config/mutator/configure_wsfs_test.go
@@ -63,3 +63,14 @@ func TestConfigureWSFS_SwapSyncRoot(t *testing.T) {
 	assert.Empty(t, diags)
 	assert.NotEqual(t, originalSyncRoot, b.SyncRoot)
 }
+
+func TestConfigureWSFS_SkipsIfRunningOnServerless(t *testing.T) {
+	b := mockBundleForConfigureWSFS(t, "/Workspace/foo")
+	originalSyncRoot := b.SyncRoot
+
+	ctx := context.Background()
+	ctx = dbr.MockRuntime(ctx, dbr.Environment{IsDbr: true, Version: "client.1.13"})
+	diags := bundle.Apply(ctx, b, mutator.ConfigureWSFS())
+	assert.Empty(t, diags)
+	assert.Equal(t, originalSyncRoot, b.SyncRoot)
+}
diff --git a/libs/dbr/context.go b/libs/dbr/context.go
index 303e911fba..06d5f00c62 100644
--- a/libs/dbr/context.go
+++ b/libs/dbr/context.go
@@ -1,6 +1,9 @@
 package dbr
 
-import "context"
+import (
+	"context"
+	"strings"
+)
 
 // key is a package-local type to use for context keys.
 //
@@ -61,3 +64,9 @@ func RuntimeVersion(ctx context.Context) string {
 
 	return v.(Environment).Version
 }
+
+// RunsOnServerless returns true if running on serverless compute.
+// Serverless runtime versions are prefixed with "client.".
+func RunsOnServerless(ctx context.Context) bool {
+	return strings.HasPrefix(RuntimeVersion(ctx), "client.")
+}
diff --git a/libs/dbr/context_test.go b/libs/dbr/context_test.go
index 94e155ab59..f73c204e62 100644
--- a/libs/dbr/context_test.go
+++ b/libs/dbr/context_test.go
@@ -84,3 +84,10 @@ func TestContext_RuntimeVersionWithMock(t *testing.T) {
 	assert.Equal(t, "15.4", RuntimeVersion(MockRuntime(ctx, Environment{IsDbr: true, Version: "15.4"})))
 	assert.Empty(t, RuntimeVersion(MockRuntime(ctx, Environment{})))
 }
+
+func TestContext_RunsOnServerless(t *testing.T) {
+	ctx := context.Background()
+	assert.True(t, RunsOnServerless(MockRuntime(ctx, Environment{IsDbr: true, Version: "client.1.13"})))
+	assert.False(t, RunsOnServerless(MockRuntime(ctx, Environment{IsDbr: true, Version: "15.4"})))
+	assert.False(t, RunsOnServerless(MockRuntime(ctx, Environment{})))
+}