Reduce MCP review latency via shared changed-file resolution + bounded auto-detection

code_review_graph/tools/_common.py

@@ -2,6 +2,10 @@
 
 from __future__ import annotations
 
+import os
+import subprocess
+import threading
+import time
 from pathlib import Path
 from typing import Any
 
@@ -58,6 +62,123 @@ def _error_response(
 }
 
 
+_CHANGED_FILES_CACHE_LOCK = threading.Lock()
+_CHANGED_FILES_CACHE: dict[tuple[str, str], dict[str, Any]] = {}
+_CHANGED_FILES_CACHE_TTL = float(os.environ.get("CRG_CHANGED_FILES_CACHE_TTL", "3.0"))
+_FAST_DIFF_TIMEOUT = float(os.environ.get("CRG_FAST_DIFF_TIMEOUT", "5.0"))
+
+
+def _run_git(root: Path, args: list[str], timeout_s: float) -> subprocess.CompletedProcess:
+    return subprocess.run(
+        ["git", *args],
+        capture_output=True,
+        text=True,
+        encoding="utf-8",
+        errors="replace",
+        cwd=str(root),
+        timeout=timeout_s,
+        stdin=subprocess.DEVNULL,
+        check=False,
+    )
+
+
+def _normalize_changed_files(files: list[str]) -> list[str]:
+    seen: set[str] = set()
+    out: list[str] = []
+    for f in files:
+        rel = f.strip().replace("\\", "/")
+        if not rel or rel in seen:
+            continue
+        seen.add(rel)
+        out.append(rel)
+    return out
+
+
+def _parse_porcelain_paths(stdout: str) -> list[str]:
+    files: list[str] = []
+    for line in stdout.splitlines():
+        if not line.strip() or len(line) < 4:
+            continue
+        path_part = line[3:].strip()
+        # Handle rename lines: "old/path -> new/path"
+        if " -> " in path_part:
+            path_part = path_part.split(" -> ", 1)[1].strip()
+        files.append(path_part)
+    return files
+
+
+def resolve_changed_files(
+    root: Path,
+    changed_files: list[str] | None,
+    base: str,
+) -> tuple[list[str], dict[str, Any]]:
+    """Resolve changed files with fast auto-detect and short-lived cache.
+
+    Returns:
+        (files, meta)
+        meta includes:
+          - source: explicit | cache | auto
+          - auto_detect_timed_out: bool
+          - timeout_seconds: float
+          - cache_hit: bool
+    """
+    if changed_files is not None:
+        return _normalize_changed_files(changed_files), {
+            "source": "explicit",
+            "auto_detect_timed_out": False,
+            "timeout_seconds": _FAST_DIFF_TIMEOUT,
+            "cache_hit": False,
+        }
+
+    cache_key = (str(root.resolve()), base)
+    now = time.monotonic()
+    with _CHANGED_FILES_CACHE_LOCK:
+        cached = _CHANGED_FILES_CACHE.get(cache_key)
+        if cached and (now - float(cached["ts"])) <= _CHANGED_FILES_CACHE_TTL:
+            return list(cached["files"]), {
+                "source": "cache",
+                "auto_detect_timed_out": False,
+                "timeout_seconds": _FAST_DIFF_TIMEOUT,
+                "cache_hit": True,
+            }
+
+    timed_out = False
+    files: list[str] = []
+    try:
+        diff = _run_git(root, ["diff", "--name-only", base, "--"], _FAST_DIFF_TIMEOUT)
+        if diff.returncode == 0:
+            files.extend(diff.stdout.splitlines())
+        else:
+            cached_only = _run_git(
+                root,
+                ["diff", "--name-only", "--cached"],
+                _FAST_DIFF_TIMEOUT,
+            )
+            if cached_only.returncode == 0:
+                files.extend(cached_only.stdout.splitlines())
+
+        status = _run_git(
+            root,
+            ["status", "--porcelain", "--untracked-files=no"],
+            _FAST_DIFF_TIMEOUT,
+        )
+        if status.returncode == 0:
+            files.extend(_parse_porcelain_paths(status.stdout))
+    except (FileNotFoundError, subprocess.TimeoutExpired):
+        timed_out = True
+
+    normalized = _normalize_changed_files(files)
+    with _CHANGED_FILES_CACHE_LOCK:
+        _CHANGED_FILES_CACHE[cache_key] = {"ts": now, "files": normalized}
+
+    return normalized, {
+        "source": "auto",
+        "auto_detect_timed_out": timed_out,
+        "timeout_seconds": _FAST_DIFF_TIMEOUT,
+        "cache_hit": False,
+    }
+
+
 def _validate_repo_root(path: "Path | str") -> Path:
     """Validate that a path is a plausible project root.
 

code_review_graph/tools/context.py

@@ -4,36 +4,13 @@
 
 import logging
 import sqlite3
-import subprocess
-from pathlib import Path
 from typing import Any
 
-from ._common import _get_store, compact_response
+from ._common import _get_store, compact_response, resolve_changed_files
 
 logger = logging.getLogger(__name__)
 
 
-def _has_git_changes(root: Path, base: str) -> bool:
-    """Quick check for uncommitted or diffed changes."""
-    try:
-        result = subprocess.run(
-            ["git", "diff", "--name-only", base, "--"],
-            capture_output=True, stdin=subprocess.DEVNULL, text=True,
-            cwd=str(root), timeout=10,
-        )
-        if result.returncode == 0 and result.stdout.strip():
-            return True
-        # Also check staged/unstaged
-        result2 = subprocess.run(
-            ["git", "status", "--porcelain"],
-            capture_output=True, stdin=subprocess.DEVNULL, text=True,
-            cwd=str(root), timeout=10,
-        )
-        return bool(result2.stdout.strip())
-    except (FileNotFoundError, subprocess.TimeoutExpired):
-        return False
-
-
 def get_minimal_context(
     task: str = "",
     changed_files: list[str] | None = None,
@@ -62,33 +39,29 @@ def get_minimal_context(
         risk_score = 0.0
         top_affected: list[str] = []
         test_gap_count = 0
-        if changed_files or _has_git_changes(root, base):
+        files, detect_meta = resolve_changed_files(root, changed_files, base)
+        if files:
             try:
                 from ..changes import analyze_changes
-                from ..incremental import get_changed_files as _get_changed
 
-                files = changed_files
-                if not files:
-                    files = _get_changed(root, base)
-                if files:
-                    abs_files = [str(root / f) for f in files]
-                    analysis = analyze_changes(
-                        store, abs_files, repo_root=str(root), base=base,
-                    )
-                    risk_score = analysis.get("risk_score", 0.0)
-                    risk = (
-                        "high" if risk_score > 0.7
-                        else "medium" if risk_score > 0.4
-                        else "low"
-                    )
-                    top_affected = [
-                        f.get("name", "")
-                        for f in analysis.get("changed_functions", [])[:5]
-                    ]
-                    test_gap_count = len(analysis.get("test_gaps", []))
+                abs_files = [str(root / f) for f in files]
+                analysis = analyze_changes(
+                    store, abs_files, repo_root=str(root), base=base,
+                )
+                risk_score = analysis.get("risk_score", 0.0)
+                risk = (
+                    "high" if risk_score > 0.7
+                    else "medium" if risk_score > 0.4
+                    else "low"
+                )
+                top_affected = [
+                    f.get("name", "")
+                    for f in analysis.get("changed_functions", [])[:5]
+                ]
+                test_gap_count = len(analysis.get("test_gaps", []))
             except (
                 ImportError, OSError, ValueError,
-                sqlite3.Error, subprocess.SubprocessError,
+                sqlite3.Error,
             ):
                 logger.debug("Risk analysis failed in get_minimal_context", exc_info=True)
 
@@ -137,6 +110,11 @@ def get_minimal_context(
         ]
         if risk != "unknown":
             summary_parts.append(f"Risk: {risk} ({risk_score:.2f}).")
+        if detect_meta.get("auto_detect_timed_out"):
+            summary_parts.append(
+                "Changed-file auto-detection timed out. "
+                "Pass changed_files for faster review tools."
+            )
         if test_gap_count:
             summary_parts.append(f"{test_gap_count} test gaps.")
 

code_review_graph/tools/query.py

@@ -9,9 +9,9 @@
 from ..embeddings import EmbeddingStore
 from ..graph import _sanitize_name, edge_to_dict, node_to_dict
 from ..hints import generate_hints, get_session
-from ..incremental import get_changed_files, get_db_path, get_staged_and_unstaged
+from ..incremental import get_db_path
 from ..search import hybrid_search
-from ._common import _BUILTIN_CALL_NAMES, _get_store
+from ._common import _BUILTIN_CALL_NAMES, _get_store, resolve_changed_files
 
 logger = logging.getLogger(__name__)
 
@@ -56,12 +56,25 @@ def get_impact_radius(
     """
     store, root = _get_store(repo_root)
     try:
-        if changed_files is None:
-            changed_files = get_changed_files(root, base)
-            if not changed_files:
-                changed_files = get_staged_and_unstaged(root)
+        changed_files, detect_meta = resolve_changed_files(root, changed_files, base)
 
         if not changed_files:
+            if detect_meta.get("auto_detect_timed_out"):
+                timeout_s = detect_meta.get("timeout_seconds", 0)
+                return {
+                    "status": "ok",
+                    "summary": (
+                        "Auto-detection of changed files timed out "
+                        f"after {timeout_s:.1f}s. Pass changed_files explicitly "
+                        "to compute impact radius quickly."
+                    ),
+                    "changed_nodes": [],
+                    "impacted_nodes": [],
+                    "impacted_files": [],
+                    "truncated": False,
+                    "total_impacted": 0,
+                    "requires_changed_files": True,
+                }
             return {
                 "status": "ok",
                 "summary": "No changed files detected.",

code_review_graph/tools/review.py

@@ -10,8 +10,7 @@
 from ..flows import get_affected_flows as _get_affected_flows
 from ..graph import edge_to_dict, node_to_dict
 from ..hints import generate_hints, get_session
-from ..incremental import get_changed_files, get_staged_and_unstaged
-from ._common import _get_store
+from ._common import _get_store, resolve_changed_files
 
 logger = logging.getLogger(__name__)
 
@@ -53,12 +52,21 @@ def get_review_context(
     store, root = _get_store(repo_root)
     try:
         # Get impact radius first
-        if changed_files is None:
-            changed_files = get_changed_files(root, base)
-            if not changed_files:
-                changed_files = get_staged_and_unstaged(root)
+        changed_files, detect_meta = resolve_changed_files(root, changed_files, base)
 
         if not changed_files:
+            if detect_meta.get("auto_detect_timed_out"):
+                timeout_s = detect_meta.get("timeout_seconds", 0)
+                return {
+                    "status": "ok",
+                    "summary": (
+                        "Auto-detection of changed files timed out "
+                        f"after {timeout_s:.1f}s. Pass changed_files explicitly "
+                        "for a fast and reliable review context."
+                    ),
+                    "context": {},
+                    "requires_changed_files": True,
+                }
             return {
                 "status": "ok",
                 "summary": "No changes detected. Nothing to review.",
@@ -304,12 +312,22 @@ def get_affected_flows_func(
     """
     store, root = _get_store(repo_root)
     try:
-        if changed_files is None:
-            changed_files = get_changed_files(root, base)
-            if not changed_files:
-                changed_files = get_staged_and_unstaged(root)
+        changed_files, detect_meta = resolve_changed_files(root, changed_files, base)
 
         if not changed_files:
+            if detect_meta.get("auto_detect_timed_out"):
+                timeout_s = detect_meta.get("timeout_seconds", 0)
+                return {
+                    "status": "ok",
+                    "summary": (
+                        "Auto-detection of changed files timed out "
+                        f"after {timeout_s:.1f}s. Pass changed_files explicitly "
+                        "to compute affected flows quickly."
+                    ),
+                    "affected_flows": [],
+                    "total": 0,
+                    "requires_changed_files": True,
+                }
             return {
                 "status": "ok",
                 "summary": "No changed files detected.",
@@ -381,12 +399,25 @@ def detect_changes_func(
     store, root = _get_store(repo_root)
     try:
         # Detect changed files if not provided.
-        if changed_files is None:
-            changed_files = get_changed_files(root, base)
-            if not changed_files:
-                changed_files = get_staged_and_unstaged(root)
+        changed_files, detect_meta = resolve_changed_files(root, changed_files, base)
 
         if not changed_files:
+            if detect_meta.get("auto_detect_timed_out"):
+                timeout_s = detect_meta.get("timeout_seconds", 0)
+                return {
+                    "status": "ok",
+                    "summary": (
+                        "Auto-detection of changed files timed out "
+                        f"after {timeout_s:.1f}s. Pass changed_files explicitly "
+                        "to run detect_changes without delay."
+                    ),
+                    "risk_score": 0.0,
+                    "changed_functions": [],
+                    "affected_flows": [],
+                    "test_gaps": [],
+                    "review_priorities": [],
+                    "requires_changed_files": True,
+                }
             return {
                 "status": "ok",
                 "summary": "No changed files detected.",