From 810320d0bfa0b61616109e230ea4a23f0d82d88b Mon Sep 17 00:00:00 2001
From: tcernicovad1 <tcernicovad1@bloomberg.net>
Date: Fri, 16 Oct 2026 10:32:42 +0100
Subject: [PATCH] Ensure `pathsBasePath` is correctly forwarded from the API

---
 .../api/session_createprogram_test.go         | 46 +++++++++++++++++++
 tsc/internal/tsoptions/rawcompileroptions.go  |  2 +
 .../tsoptions/rawcompileroptions_test.go      |  2 +
 3 files changed, 50 insertions(+)

diff --git a/tsc/internal/api/session_createprogram_test.go b/tsc/internal/api/session_createprogram_test.go
index 54709aec92d6a..827ab46eb2961 100644
--- a/tsc/internal/api/session_createprogram_test.go
+++ b/tsc/internal/api/session_createprogram_test.go
@@ -316,3 +316,49 @@ func TestCreateProgramReportsNonCompositeProjectReference(t *testing.T) {
 	}
 	assert.DeepEqual(t, codes, []int32{6306})
 }
+
+func TestCreateSnapshotResolvesPathsRelativeToParsedConfigDirectory(t *testing.T) {
+	t.Parallel()
+
+	const (
+		mainFile = "/project/main.ts"
+		libFile  = "/project/types/lib.d.ts"
+	)
+	init, _ := projecttestutil.GetSessionInitOptions(map[string]any{
+		mainFile: `import { x } from "lib"; export const y: number = x;`,
+		libFile:  `export declare const x: number;`,
+	}, nil, &projecttestutil.TypingsInstallerOptions{})
+	init.Options.CurrentDirectory = "/somewhere-else"
+	session := NewStandaloneSession(init, nil)
+	defer session.Close()
+
+	var parseParams ParseJsonConfigFileContentParams
+	assert.NilError(t, json.Unmarshal([]byte(`{
+		"json": {
+			"compilerOptions": {
+				"module": "esnext",
+				"moduleResolution": "bundler",
+				"noLib": true,
+				"types": [],
+				"paths": { "lib": ["./types/lib.d.ts"] }
+			}
+		},
+		"configDirectory": "/project"
+	}`), &parseParams))
+	parsed, err := session.handleParseJsonConfigFileContent(context.Background(), &parseParams)
+	assert.NilError(t, err)
+
+	// Round-trip the parsed options through JSON as an API client would.
+	encodedOptions, err := json.Marshal(parsed.Options)
+	assert.NilError(t, err)
+	var createParams CreateSnapshotParams
+	assert.NilError(t, json.Unmarshal([]byte(`{"createPrograms":[{"rootFiles":["`+mainFile+`"],"compilerOptions":`+string(encodedOptions)+`}]}`), &createParams))
+
+	response, err := session.handleCreateSnapshot(context.Background(), &createParams)
+	assert.NilError(t, err)
+	snapshot, err := session.getSnapshotData(response.Snapshot)
+	assert.NilError(t, err)
+	program, err := snapshot.getProgram(response.Projects[0].Id)
+	assert.NilError(t, err)
+	assert.Assert(t, program.GetSourceFile(libFile) != nil, "expected 'lib' to resolve via paths relative to /project")
+}
diff --git a/tsc/internal/tsoptions/rawcompileroptions.go b/tsc/internal/tsoptions/rawcompileroptions.go
index d437fa81fb394..1a570da9f19ae 100644
--- a/tsc/internal/tsoptions/rawcompileroptions.go
+++ b/tsc/internal/tsoptions/rawcompileroptions.go
@@ -85,6 +85,8 @@ func (o *RawCompilerOptions) Finalize(basePath tspath.RootedDirectoryPath) (*cor
 			}
 		} else if key == "configFilePath" {
 			pathKind = CommandLineOptionPathKindFile
+		} else if key == "pathsBasePath" {
+			pathKind = CommandLineOptionPathKindDirectory
 		} else if key != "allowNonTsExtensions" && key != "suppressOutputPathCheck" {
 			continue
 		}
diff --git a/tsc/internal/tsoptions/rawcompileroptions_test.go b/tsc/internal/tsoptions/rawcompileroptions_test.go
index f8f8f83e9ecb3..6ccb1c43b323c 100644
--- a/tsc/internal/tsoptions/rawcompileroptions_test.go
+++ b/tsc/internal/tsoptions/rawcompileroptions_test.go
@@ -27,6 +27,7 @@ func TestRawCompilerOptionsFinalizePaths(t *testing.T) {
 		"allowNonTsExtensions": true,
 		"suppressOutputPathCheck": true,
 		"configFilePath": "",
+		"pathsBasePath": "config",
 		"NoImplicitAny": true
 	}`), &raw))
 
@@ -46,5 +47,6 @@ func TestRawCompilerOptionsFinalizePaths(t *testing.T) {
 	assert.Equal(t, options.AllowNonTsExtensions, core.TSTrue)
 	assert.Equal(t, options.SuppressOutputPathCheck, core.TSTrue)
 	assert.Equal(t, options.ConfigFilePath, tspath.RootedFilePath(""))
+	assert.Equal(t, options.PathsBasePath, tspath.RootedDirectoryPath("/project/config"))
 	assert.Equal(t, options.NoImplicitAny, core.TSUnknown)
 }