diff --git a/memwalk/__init__.py b/memwalk/__init__.py
index 2e572c9..47d5c16 100644
--- a/memwalk/__init__.py
+++ b/memwalk/__init__.py
@@ -1,3 +1,3 @@
 """memwalk — ask AI about any codebase via cached SSM state."""
 
-__version__ = "0.4.0"
+__version__ = "0.4.1"
diff --git a/memwalk/cli.py b/memwalk/cli.py
index 647fd0f..e40cc92 100644
--- a/memwalk/cli.py
+++ b/memwalk/cli.py
@@ -181,24 +181,34 @@ def list_caches() -> None:
 @cli.command("list-subdirs")
 def list_subdirs(
     path: str = typer.Argument(..., help="Codebase root to inspect"),
+    n_ctx: int = typer.Option(None, "--n-ctx", help="Budget n_ctx for size check"),
 ) -> None:
-    """Show immediate subdirectories with sizes and cache status."""
+    """Show subdirectories with sizes and cache status (recursive split view)."""
+    from .gpu import auto_n_ctx
     source = Path(path).expanduser().resolve()
-    subdirs = corpus.discover_subdirs(source)
+    chosen = auto_n_ctx(n_ctx if n_ctx else None)
+    max_chars = chosen * 3
+    subdirs = corpus.discover_subdirs(source, max_chars=max_chars)
     if not subdirs:
         console.print(f"[dim]No digestable subdirectories under {source}[/dim]")
         return
-    table = Table(title=f"Subdirectories of {source.name}", show_lines=False)
+    table = Table(
+        title=f"Subdirectories of {source.name} (budget {max_chars:,} chars, n_ctx={chosen:,})",
+        show_lines=False,
+    )
     table.add_column("Directory", style="cyan")
     table.add_column("Files", justify="right")
     table.add_column("Chars", justify="right")
+    table.add_column("Depth", justify="right")
     table.add_column("Cache", justify="center")
     for d in subdirs:
+        prefix = "  " * d.depth
         cache_status = f"[green]cached[/green] (n_ctx={d.cache_n_ctx:,})" if d.is_cached else "[dim]none[/dim]"
         table.add_row(
-            d.rel_path,
+            prefix + d.rel_path,
             f"{d.n_files}",
             f"{d.n_chars:,}",
+            f"{d.depth}",
             cache_status,
         )
     console.print(table)
diff --git a/memwalk/corpus.py b/memwalk/corpus.py
index d27f170..ad4bf36 100644
--- a/memwalk/corpus.py
+++ b/memwalk/corpus.py
@@ -58,18 +58,92 @@ class CorpusFile:
 
 @dataclass(slots=True)
 class SubDirInfo:
-    """Metadata about an immediate subdirectory for split-digest decisions."""
     rel_path: str
     abs_path: Path
     n_files: int
     n_chars: int
     is_cached: bool
+    depth: int = 0
     cache_n_ctx: int = 0
 
 
+def _scan_dir(
+    entry: Path,
+    root: Path,
+    *,
+    max_chars: int,
+    include_suffixes: frozenset[str],
+    exclude_dirs: frozenset[str],
+    exclude_patterns: tuple[str, ...],
+    max_file_bytes: int,
+    depth: int = 0,
+) -> list[SubDirInfo]:
+    from . import cache as _cache
+
+    files = collect_files(
+        entry,
+        include_suffixes=include_suffixes,
+        exclude_dirs=exclude_dirs,
+        exclude_patterns=exclude_patterns,
+        max_file_bytes=max_file_bytes,
+    )
+    n_chars = sum(len(f.text) for f in files)
+
+    meta = _cache.load_meta(entry)
+    is_cached = False
+    cache_n_ctx = 0
+    if meta is not None:
+        mh = manifest_hash(files)
+        if _cache.is_fresh(meta, mh):
+            is_cached = True
+            cache_n_ctx = meta.n_ctx
+
+    rel = entry.relative_to(root).as_posix()
+
+    if n_chars <= max_chars or is_cached:
+        return [SubDirInfo(
+            rel_path=rel,
+            abs_path=entry,
+            n_files=len(files),
+            n_chars=n_chars,
+            is_cached=is_cached,
+            depth=depth,
+            cache_n_ctx=cache_n_ctx,
+        )]
+
+    children: list[SubDirInfo] = []
+    for child in sorted(entry.iterdir()):
+        if not child.is_dir():
+            continue
+        if child.name in exclude_dirs:
+            continue
+        children.extend(_scan_dir(
+            child, root,
+            max_chars=max_chars,
+            include_suffixes=include_suffixes,
+            exclude_dirs=exclude_dirs,
+            exclude_patterns=exclude_patterns,
+            max_file_bytes=max_file_bytes,
+            depth=depth + 1,
+        ))
+
+    if not children:
+        return [SubDirInfo(
+            rel_path=rel,
+            abs_path=entry,
+            n_files=len(files),
+            n_chars=n_chars,
+            is_cached=False,
+            depth=depth,
+        )]
+
+    return children
+
+
 def discover_subdirs(
     root: Path,
     *,
+    max_chars: int = 200_000,
     include_suffixes: frozenset[str] = DEFAULT_INCLUDE_SUFFIXES,
     exclude_dirs: frozenset[str] = DEFAULT_EXCLUDE_DIRS,
     exclude_patterns: tuple[str, ...] = DEFAULT_EXCLUDE_PATTERNS,
@@ -87,31 +161,13 @@ def discover_subdirs(
         if entry.name in exclude_dirs:
             continue
 
-        files = collect_files(
-            entry,
+        results.extend(_scan_dir(
+            entry, root,
+            max_chars=max_chars,
             include_suffixes=include_suffixes,
             exclude_dirs=exclude_dirs,
             exclude_patterns=exclude_patterns,
             max_file_bytes=max_file_bytes,
-        )
-        n_chars = sum(len(f.text) for f in files)
-
-        meta = _cache.load_meta(entry)
-        is_cached = False
-        cache_n_ctx = 0
-        if meta is not None:
-            mh = manifest_hash(files)
-            if _cache.is_fresh(meta, mh):
-                is_cached = True
-                cache_n_ctx = meta.n_ctx
-
-        results.append(SubDirInfo(
-            rel_path=entry.name,
-            abs_path=entry,
-            n_files=len(files),
-            n_chars=n_chars,
-            is_cached=is_cached,
-            cache_n_ctx=cache_n_ctx,
         ))
 
     results.sort(key=lambda d: d.n_chars, reverse=True)
diff --git a/memwalk/engine.py b/memwalk/engine.py
index 7e3c513..96dfb05 100644
--- a/memwalk/engine.py
+++ b/memwalk/engine.py
@@ -167,13 +167,21 @@ def digest_subdirs(
     force: bool = False,
     verbose: bool = False,
 ) -> list[SubDirDigestResult]:
-    """Discover immediate subdirectories and digest each independently."""
-    subdirs = corpus.discover_subdirs(source_path)
+    n_ctx = auto_n_ctx(n_ctx if n_ctx else None)
+    max_chars = n_ctx * 3
+    subdirs = corpus.discover_subdirs(source_path, max_chars=max_chars)
     if not subdirs:
         return []
 
     results: list[SubDirDigestResult] = []
     for sub in subdirs:
+        if sub.n_chars > max_chars and not sub.is_cached:
+            results.append(SubDirDigestResult(
+                rel_path=sub.rel_path,
+                result=None,
+                error=f"Too large ({sub.n_chars:,} chars > {max_chars:,} budget)",
+            ))
+            continue
         try:
             result = digest(cfg, sub.abs_path, n_ctx=n_ctx, force=force,
                             verbose=verbose)
@@ -187,4 +195,6 @@ def digest_subdirs(
                 result=None,
                 error=str(e),
             ))
+        import gc
+        gc.collect()
     return results
diff --git a/memwalk/gpu.py b/memwalk/gpu.py
index 88ba559..0e1d874 100644
--- a/memwalk/gpu.py
+++ b/memwalk/gpu.py
@@ -7,12 +7,12 @@ import subprocess
 
 _NEMOTRON_PROFILE: list[tuple[int, float]] = [
     (8192,  4.5),
-    (16384, 5.0),
-    (32768, 5.5),
-    (65536, 6.5),
-    (131072, 8.5),
-    (262144, 12.0),
-    (524288, 18.0),
+    (16384, 5.5),
+    (32768, 7.0),
+    (65536, 9.5),
+    (131072, 14.0),
+    (262144, 22.0),
+    (524288, 36.0),
 ]
 
 
diff --git a/pyproject.toml b/pyproject.toml
index 35ba8f3..0a4ef9b 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name        = "memwalk"
-version     = "0.4.0"
+version     = "0.4.1"
 description = "Ask AI about any codebase — local, cached, SSM-state-backed exploration via memba + Nemotron"
 readme      = "README.md"
 license     = { text = "MIT" }