diff --git a/codex-rs/worktree/src/manager.rs b/codex-rs/worktree/src/manager.rs
index e0b20248e9..1492b4ed51 100644
--- a/codex-rs/worktree/src/manager.rs
+++ b/codex-rs/worktree/src/manager.rs
@@ -25,7 +25,7 @@ pub fn ensure_worktree(req: WorktreeRequest) -> Result<WorktreeResolution> {
     let branch = req.branch.clone();
     let slug = paths::slugify_name(&branch)?;
     ensure_safe_branch_name(&repo.root, &branch)?;
-    let worktree_git_root = paths::sibling_worktree_git_root(&repo.root, &branch)?;
+    let worktree_git_root = paths::sibling_worktree_git_root(&repo.primary_root, &branch)?;
     let workspace_cwd = worktree_git_root.join(&repo.relative_cwd);
 
     if worktree_git_root.exists() {
@@ -445,6 +445,7 @@ fn display_branch_or_name(info: &WorktreeInfo) -> &str {
 
 struct SourceRepo {
     root: PathBuf,
+    primary_root: PathBuf,
     relative_cwd: PathBuf,
     common_git_dir: PathBuf,
     repo_name: String,
@@ -462,9 +463,13 @@ impl SourceRepo {
         let common_git_dir = absolutize(&source_cwd, Path::new(&common_git_dir_raw))
             .canonicalize()
             .unwrap_or_else(|_| absolutize(&source_cwd, Path::new(&common_git_dir_raw)));
+        let primary_root = primary_worktree_root(&root)
+            .unwrap_or_else(|_| root.clone())
+            .canonicalize()
+            .unwrap_or_else(|_| root.clone());
         let origin = git::stdout(&root, &["remote", "get-url", "origin"]).ok();
         let id = paths::repo_fingerprint(&common_git_dir, origin.as_deref());
-        let repo_name = root
+        let repo_name = primary_root
             .file_name()
             .context("repository root has no directory name")?
             .to_string_lossy()
@@ -475,6 +480,7 @@ impl SourceRepo {
             .to_path_buf();
         Ok(Self {
             root,
+            primary_root,
             relative_cwd,
             common_git_dir,
             repo_name,
diff --git a/codex-rs/worktree/tests/git_backend.rs b/codex-rs/worktree/tests/git_backend.rs
index 6f9bbc4cdc..473108c487 100644
--- a/codex-rs/worktree/tests/git_backend.rs
+++ b/codex-rs/worktree/tests/git_backend.rs
@@ -94,6 +94,36 @@ fn creates_reuses_lists_and_removes_managed_worktree() -> anyhow::Result<()> {
     Ok(())
 }
 
+#[test]
+fn creates_sibling_from_sibling_using_primary_repo_name() -> anyhow::Result<()> {
+    let fixture = GitFixture::new()?;
+    let first = codex_worktree::ensure_worktree(WorktreeRequest {
+        codex_home: fixture.codex_home.path().to_path_buf(),
+        source_cwd: fixture.repo.path().to_path_buf(),
+        branch: "fcoury/worktrees".to_string(),
+        base_ref: None,
+        dirty_policy: DirtyPolicy::Fail,
+    })?;
+
+    let second = codex_worktree::ensure_worktree(WorktreeRequest {
+        codex_home: fixture.codex_home.path().to_path_buf(),
+        source_cwd: first.info.workspace_cwd,
+        branch: "fcoury/test".to_string(),
+        base_ref: None,
+        dirty_policy: DirtyPolicy::Fail,
+    })?;
+
+    let canonical_repo = fixture.repo.path().canonicalize()?;
+    assert_eq!(
+        second.info.worktree_git_root,
+        canonical_repo.with_file_name(format!(
+            "{}.fcoury-test",
+            canonical_repo.file_name().unwrap().to_string_lossy()
+        ))
+    );
+    Ok(())
+}
+
 #[test]
 fn copy_tracked_preserves_staged_and_unstaged_diffs() -> anyhow::Result<()> {
     let fixture = GitFixture::new()?;