diff --git a/dap/thread.go b/dap/thread.go
index 52e6bd6a6..5643b08d6 100644
--- a/dap/thread.go
+++ b/dap/thread.go
@@ -2,6 +2,7 @@ package dap
 
 import (
 	"context"
+	"path"
 	"path/filepath"
 	"sync"
 
@@ -106,7 +107,14 @@ func (t *thread) init(ctx Context, c gateway.Client, ref gateway.Reference, meta
 	t.c = c
 	t.ref = ref
 	t.meta = meta
-	t.sourcePath = inputs.ContextPath
+
+	// Combine the dockerfile directory with the context path to find the
+	// real base path. The frontend will report the base path as the filename.
+	dir := path.Dir(inputs.DockerfilePath)
+	if !path.IsAbs(dir) {
+		dir = path.Join(inputs.ContextPath, dir)
+	}
+	t.sourcePath = dir
 
 	if err := t.getLLBState(ctx); err != nil {
 		return err
diff --git a/dap/variables.go b/dap/variables.go
index b5bdb90aa..288209c81 100644
--- a/dap/variables.go
+++ b/dap/variables.go
@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"io/fs"
+	"path"
 	"path/filepath"
 	"strconv"
 	"strings"
@@ -44,6 +45,7 @@ func (f *frame) fillLocation(def *llb.Definition, loc *pb.Locations, ws string)
 
 			info := def.Source.Infos[l.SourceIndex]
 			f.Source = &dap.Source{
+				Name: path.Base(info.Filename),
 				Path: filepath.Join(ws, info.Filename),
 			}
 			return