diff --git a/src/extensions/score_mounts/__init__.py b/src/extensions/score_mounts/__init__.py
index 55157f475..03c537815 100644
--- a/src/extensions/score_mounts/__init__.py
+++ b/src/extensions/score_mounts/__init__.py
@@ -123,6 +123,16 @@ def _canonical_mount_dir(walk_dir: Path, spec: MountSpec) -> Path:
       generated files below it can resolve to the action execroot spelling,
       for example
       ``~/.cache/bazel/.../execroot/_main/bazel-out/.../docs/generated/index.rst``.
+    - for in-tree (same-workspace) source bundles, the mount root directory
+      exists in the sandbox but the individual source files are symlinks back
+      to the original workspace, for example
+      ``.../sandbox/.../execroot/_main/score/socom/docs/index.rst``
+      ``→ /home/user/workspace/score/socom/docs/index.rst``.
+
+    This applies to all bundle types: external repositories, generated data
+    bundles, and in-tree (same-workspace) source bundles.  Resolve one mounted
+    source file first and walk back by its bundle-relative suffix to get the
+    canonical root.
 
     Resolving only ``walk_dir`` therefore keeps the sandbox spelling, while
     resolving a referenced image/include from Sphinx follows the file symlink.
@@ -143,19 +153,6 @@ def _canonical_mount_dir(walk_dir: Path, spec: MountSpec) -> Path:
     the canonical mount root. For ``subdir/page.rst`` we walk back two
     components, yielding the same canonical root.
     """
-    if not spec.external and not spec.data:
-        return walk_dir.resolve()
-
-    # Bazel materializes the mount directory structure in the sandbox but may
-    # symlink the individual files either to the external repository cache or to
-    # the action execroot's bazel-out tree. A mounted documentation source gives
-    # us the same canonical spelling that Sphinx will later see for dependency
-    # files. Walking back by the source file's path relative to the mount
-    # reconstructs the canonical mount root:
-    #
-    #   source_file = walk_dir / "subdir/page.rst"
-    #   relative_path.parts = ("subdir", "page.rst")
-    #   source_file.resolve().parents[1] == canonical walk_dir
     for source_file in walk_dir.rglob("*"):
         if not source_file.is_file() or source_file.suffix not in {".md", ".rst"}:
             continue
diff --git a/src/extensions/score_mounts/tests/test_data_mounts.py b/src/extensions/score_mounts/tests/test_data_mounts.py
index 87e2d5c5f..a8144e343 100644
--- a/src/extensions/score_mounts/tests/test_data_mounts.py
+++ b/src/extensions/score_mounts/tests/test_data_mounts.py
@@ -85,6 +85,46 @@ def test_mount_entry_uses_canonical_directory_for_symlinked_bundle(
     assert entry["dir"] == str(canonical_dir)
 
 
+def test_canonical_mount_dir_in_tree_sandbox_bundle(tmp_path: Path) -> None:
+    """In-tree bundles with symlinked files must resolve to the workspace root."""
+    workspace_docs = tmp_path / "workspace" / "module" / "docs"
+    workspace_docs.mkdir(parents=True)
+    (workspace_docs / "index.rst").write_text("Index", encoding="utf-8")
+    (workspace_docs / "guide").mkdir()
+    (workspace_docs / "guide" / "overview.rst").write_text("Overview", encoding="utf-8")
+
+    sandbox_docs = tmp_path / "sandbox" / "module" / "docs"
+    sandbox_docs.mkdir(parents=True)
+    sandbox_docs.joinpath("index.rst").symlink_to(workspace_docs / "index.rst")
+    (sandbox_docs / "guide").mkdir()
+    sandbox_docs.joinpath("guide", "overview.rst").symlink_to(
+        workspace_docs / "guide" / "overview.rst"
+    )
+
+    spec = MountSpec(
+        src_root="module/docs", runtime_path="module/docs", mount_at="module"
+    )
+
+    entry = _make_mount_entry(sandbox_docs, spec)
+
+    assert entry["dir"] == str(workspace_docs)
+
+
+def test_canonical_mount_dir_empty_bundle_fallback(tmp_path: Path) -> None:
+    """A bundle with no .rst/.md files falls back to walk_dir.resolve()."""
+    bundle_dir = tmp_path / "bundle"
+    bundle_dir.mkdir()
+    (bundle_dir / "diagram.puml").write_text("@startuml\n@enduml", encoding="utf-8")
+
+    spec = MountSpec(
+        src_root="module/docs", runtime_path="module/docs", mount_at="module"
+    )
+
+    entry = _make_mount_entry(bundle_dir, spec)
+
+    assert entry["dir"] == str(bundle_dir.resolve())
+
+
 def test_mount_entry_uses_canonical_directory_for_generated_data_bundle(
     tmp_path: Path,
 ) -> None: