diff --git a/codewiki/cli/commands/generate.py b/codewiki/cli/commands/generate.py
index b7caea2d..1c370cb8 100644
--- a/codewiki/cli/commands/generate.py
+++ b/codewiki/cli/commands/generate.py
@@ -49,8 +49,11 @@ def _detect_changed_files(
     Detect files changed since the last documentation generation.
 
     Reads the commit_id from metadata.json and compares with current HEAD
-    using git diff. Returns list of changed file paths, or None if unable
-    to determine (e.g., no metadata, not a git repo).
+    using git diff. When running inside a subdirectory of a monorepo,
+    only files under that subdirectory are returned.
+
+    Returns list of changed file paths relative to repo_path, or None if
+    unable to determine (e.g., no metadata, not a git repo).
     """
     import json
 
@@ -85,6 +88,21 @@ def _detect_changed_files(
             logger.debug(f"HEAD is still at {current_commit[:8]} — no changes.")
         return []
 
+    # Determine subdirectory prefix relative to the git root
+    if repo.working_tree_dir is None:
+        if verbose:
+            logger.debug("Bare git repository — running full generation.")
+        return None
+    git_root = Path(repo.working_tree_dir).resolve()
+    repo_path_resolved = repo_path.resolve()
+    try:
+        subpath_prefix = repo_path_resolved.relative_to(git_root).as_posix()
+    except ValueError:
+        # repo_path is outside git root — shouldn't happen, but fall back to full generation
+        if verbose:
+            logger.debug("Repo path is outside git root — running full generation.")
+        return None
+
     # Get changed files between previous and current commit
     try:
         diff_index = repo.commit(prev_commit).diff(current_commit)
@@ -95,14 +113,27 @@ def _detect_changed_files(
             if diff.b_path and diff.b_path != diff.a_path:
                 changed.append(diff.b_path)
 
+        # Filter to files under the current subdirectory and strip the prefix
+        # so paths align with module_tree.json component paths
+        filtered = []
+        if subpath_prefix == ".":
+            filtered = changed
+        else:
+            prefix = subpath_prefix + "/"
+            for path in changed:
+                if path.startswith(prefix):
+                    filtered.append(path[len(prefix):])
+
         if verbose:
             logger.debug(f"Changes between {prev_commit[:8]} and {current_commit[:8]}:")
-            for f in changed[:10]:
+            if subpath_prefix != ".":
+                logger.debug(f"  Scoped to subdirectory: {subpath_prefix}")
+            for f in filtered[:10]:
                 logger.debug(f"  {f}")
-            if len(changed) > 10:
-                logger.debug(f"  ... and {len(changed) - 10} more")
+            if len(filtered) > 10:
+                logger.debug(f"  ... and {len(filtered) - 10} more")
 
-        return changed
+        return filtered
     except Exception as e:
         if verbose:
             logger.debug(f"Git diff failed: {e} — running full generation.")
diff --git a/codewiki/cli/utils/repo_validator.py b/codewiki/cli/utils/repo_validator.py
index 608e6037..12e9f952 100644
--- a/codewiki/cli/utils/repo_validator.py
+++ b/codewiki/cli/utils/repo_validator.py
@@ -116,36 +116,56 @@ def check_writable_output(output_dir: Path) -> Path:
     return output_dir
 
 
+def _get_git_repo(repo_path: Path):
+    """
+    Find a git repository starting at repo_path and searching parent directories.
+    
+    Args:
+        repo_path: Path to start searching from
+        
+    Returns:
+        git.Repo instance or None if no repository found
+    """
+    try:
+        import git
+        return git.Repo(repo_path, search_parent_directories=True)
+    except Exception:
+        return None
+
+
 def is_git_repository(repo_path: Path) -> bool:
     """
-    Check if path is a git repository.
+    Check if path is inside a git repository.
+    
+    Searches parent directories if .git is not directly at repo_path,
+    supporting monorepo subdirectories.
     
     Args:
         repo_path: Path to check
         
     Returns:
-        True if git repository, False otherwise
+        True if inside a git repository, False otherwise
     """
-    git_dir = repo_path / ".git"
-    return git_dir.exists() and git_dir.is_dir()
+    return _get_git_repo(repo_path) is not None
 
 
 def get_git_commit_hash(repo_path: Path) -> str:
     """
     Get current git commit hash.
     
+    Searches parent directories to support monorepo subdirectories.
+    
     Args:
-        repo_path: Repository path
+        repo_path: Path inside a git repository
         
     Returns:
-        Commit hash or empty string if not a git repo
+        Commit hash or empty string if not in a git repo
     """
-    if not is_git_repository(repo_path):
+    repo = _get_git_repo(repo_path)
+    if repo is None:
         return ""
     
     try:
-        import git
-        repo = git.Repo(repo_path)
         return repo.head.commit.hexsha
     except Exception:
         return ""
@@ -155,18 +175,19 @@ def get_git_branch(repo_path: Path) -> str:
     """
     Get current git branch name.
     
+    Searches parent directories to support monorepo subdirectories.
+    
     Args:
-        repo_path: Repository path
+        repo_path: Path inside a git repository
         
     Returns:
-        Branch name or empty string if not a git repo
+        Branch name or empty string if not in a git repo
     """
-    if not is_git_repository(repo_path):
+    repo = _get_git_repo(repo_path)
+    if repo is None:
         return ""
     
     try:
-        import git
-        repo = git.Repo(repo_path)
         return repo.active_branch.name
     except Exception:
         return ""