Fix server compatibility with pre-0.19.27 runners (#3054)

Closes: #3048

Author: un-def

runner/consts/consts.go

@@ -26,10 +26,10 @@ const (
 	// The current user's homedir (as of 2024-12-28, it's always root) should be used
 	// instead of the hardcoded value
 	RunnerHomeDir = "/root"
-	// A repo directory and a default working directory for the job
-	RunnerWorkingDir = "/workflow"
 )
 
+const LegacyRepoDir = "/workflow"
+
 const (
 	RunnerHTTPPort = 10999
 	RunnerSSHPort  = 10022

runner/internal/executor/executor.go

@@ -360,7 +360,10 @@ func (ex *RunExecutor) prepareJobWorkingDir(ctx context.Context) error {
 			return gerrors.Wrap(err)
 		}
 	} else {
-		ex.jobWorkingDir, err = common.ExpandPath(*ex.jobSpec.WorkingDir, "", ex.jobHomeDir)
+		// We still support relative paths, as 0.19.27 server uses relative paths when possible
+		// for compatibility with pre-0.19.27 runners.
+		// Replace consts.LegacyRepoDir with "" eventually.
+		ex.jobWorkingDir, err = common.ExpandPath(*ex.jobSpec.WorkingDir, consts.LegacyRepoDir, ex.jobHomeDir)
 		if err != nil {
 			return gerrors.Wrap(err)
 		}

src/dstack/_internal/server/services/jobs/configurators/base.py

@@ -318,14 +318,23 @@ def _repo_dir(self) -> str:
 
     def _working_dir(self) -> Optional[str]:
         """
-        Returns absolute path or None
+        Returns path or None
+
         None means the default working directory taken from the image
+
+        Currently, for compatibility with pre-0.19.27 runners, the path may be relative.
+        Future versions should return only absolute paths
         """
         working_dir = self.run_spec.configuration.working_dir
-        if working_dir is None or is_absolute_posix_path(working_dir):
+        if working_dir is None:
             return working_dir
-        # Legacy configuration; relative working_dir is deprecated
-        return str(PurePosixPath(LEGACY_REPO_DIR) / working_dir)
+        # Return a relative path if possible
+        if is_absolute_posix_path(working_dir):
+            try:
+                return str(PurePosixPath(working_dir).relative_to(LEGACY_REPO_DIR))
+            except ValueError:
+                pass
+        return working_dir
 
     def _python(self) -> str:
         if self.run_spec.configuration.python is not None: