fix: allow in-scope symlinked skill destinations

crates/compass-cli/src/install_commands.rs

@@ -3853,6 +3853,16 @@ fn validate_skill_destination(destination: &Path, default_root: &Path) -> Result
             destination.display()
         ));
     };
+    let canonical_boundary = match fs::canonicalize(&boundary) {
+        Ok(path) => Some(path),
+        Err(error) if error.kind() == std::io::ErrorKind::NotFound => None,
+        Err(error) => {
+            return Err(format!(
+                "error: could not resolve skill destination boundary {}: {error}",
+                boundary.display()
+            ));
+        }
+    };
 
     let mut current = destination.parent();
     while let Some(path) = current {
@@ -3861,11 +3871,23 @@ fn validate_skill_destination(destination: &Path, default_root: &Path) -> Result
         }
         match fs::symlink_metadata(path) {
             Ok(metadata) if metadata.file_type().is_symlink() => {
-                return Err(format!(
-                    "error: skill destination {} traverses symbolic link {}",
-                    destination.display(),
-                    path.display()
-                ));
+                let resolved = fs::canonicalize(path).map_err(|error| {
+                    format!(
+                        "error: could not resolve symbolic link {} while validating skill destination {}: {error}",
+                        path.display(),
+                        destination.display()
+                    )
+                })?;
+                if canonical_boundary
+                    .as_ref()
+                    .is_some_and(|boundary| !resolved.starts_with(boundary))
+                {
+                    return Err(format!(
+                        "error: skill destination {} resolves outside the selected scope through symbolic link {}",
+                        destination.display(),
+                        path.display()
+                    ));
+                }
             }
             Ok(_) => {}
             Err(error) if error.kind() == std::io::ErrorKind::NotFound => {}

crates/compass-cli/tests/install_cli.rs

@@ -156,6 +156,44 @@ fn project_codex_install_creates_native_compass_skill() -> Result<(), Box<dyn Er
     Ok(())
 }
 
+#[cfg(unix)]
+#[test]
+fn project_claude_install_follows_an_in_scope_skills_symlink() -> Result<(), Box<dyn Error>> {
+    let fixture = InstallFixture::new()?;
+    let linked_root = fixture.project.join(".agents/skills");
+    fs::create_dir_all(&linked_root)?;
+    fs::create_dir_all(fixture.project.join(".claude"))?;
+    std::os::unix::fs::symlink("../.agents/skills", fixture.project.join(".claude/skills"))?;
+
+    let output = fixture.run(&["install", "claude"])?;
+    assert_success("Claude install through in-scope skills symlink", &output);
+    assert!(linked_root.join("compass/SKILL.md").is_file());
+    assert!(fixture.project.join(".claude/skills").is_symlink());
+    Ok(())
+}
+
+#[cfg(unix)]
+#[test]
+fn project_claude_install_rejects_an_out_of_scope_skills_symlink() -> Result<(), Box<dyn Error>> {
+    let fixture = InstallFixture::new()?;
+    let outside_root = fixture
+        .project
+        .parent()
+        .ok_or("fixture parent")?
+        .join("external-claude-skills");
+    fs::create_dir_all(&outside_root)?;
+    fs::create_dir_all(fixture.project.join(".claude"))?;
+    fs::write(outside_root.join("sentinel"), "keep")?;
+    std::os::unix::fs::symlink(&outside_root, fixture.project.join(".claude/skills"))?;
+
+    let output = fixture.run(&["install", "claude"])?;
+    assert!(!output.status.success());
+    assert!(String::from_utf8_lossy(&output.stdout).contains("outside the selected scope"));
+    assert!(outside_root.join("sentinel").is_file());
+    assert!(!outside_root.join("compass").exists());
+    Ok(())
+}
+
 #[test]
 fn every_project_platform_installs_native_content() -> Result<(), Box<dyn Error>> {
     for platform in PROJECT_PLATFORMS {