chore(telemetry): implement state-based loop governor, 180s tool timeout, visual-qa path fix, and fs_write diff-guard

vibn-frontend/app/api/mcp/route.ts

@@ -4657,7 +4657,7 @@ async function toolRequestVisualQA(
     );
   }
 
-  const absPath = normalizeFsPath(targetPath);
+  const absPath = normalizeFsPath(targetPath, project.slug);
   if (absPath instanceof NextResponse) return absPath;
 
   const r = await runFsCmd(
@@ -4969,20 +4969,50 @@ async function toolFsWrite(principal: Principal, params: Record<string, any>) {
   const path = normalizeFsPath(String(params.path ?? ""), project.slug);
   if (path instanceof NextResponse) return path;
   const content = typeof params.content === "string" ? params.content : "";
+  const force = Boolean(params.force);
 
-  // Stream content via base64 to avoid shell-quoting headaches with
-  // arbitrary binary / multibyte input.
   const b64 = Buffer.from(content, "utf8").toString("base64");
-  const cmd =
-    `mkdir -p ${shq(path.replace(/\/[^/]+$/, "") || FS_ROOT)} && ` +
-    `printf %s ${shq(b64)} | base64 -d > ${shq(path)}`;
+
+  const py = `import sys, os, difflib, base64
+path = sys.argv[1]
+new_b64 = sys.argv[2]
+force_overwrite = sys.argv[3] == 'true'
+
+new_content = base64.b64decode(new_b64).decode('utf-8')
+
+if os.path.exists(path) and not force_overwrite:
+  try:
+    with open(path, 'r', encoding='utf-8', errors='ignore') as f:
+      old_content = f.read()
+    old_lines = old_content.splitlines()
+    new_lines = new_content.splitlines()
+    if len(old_lines) > 5:
+      diff = list(difflib.unified_diff(old_lines, new_lines))
+      add_rem = len([l for l in diff if l.startswith('+') or l.startswith('-')]) - 2
+      change_pct = add_rem / max(1, len(old_lines))
+      if change_pct > 0.60:
+        sys.stderr.write(f"REWRITE_GUARD_TRIGGERED: Your fs_write would overwrite {int(change_pct*100)}% of this {len(old_lines)}-line file. To replace large blocks or the entire file, please use surgical 'fs_edit' anchors instead, or pass 'force: true' on fs_write if you genuinely need a full rewrite.\\n")
+        sys.exit(4)
+  except Exception as e:
+    pass
+
+os.makedirs(os.path.dirname(path), exist_ok=True)
+with open(path, 'w', encoding='utf-8') as f:
+  f.write(new_content)
+`;
+
+  const pyB64 = Buffer.from(py, "utf8").toString("base64");
+  const cmd = `python3 -c "$(printf %s ${shq(pyB64)} | base64 -d)" ${shq(path)} ${shq(b64)} ${shq(String(force))} && sha256sum ${shq(path)} | cut -d' ' -f1 && wc -c < ${shq(path)}`;
+
   const r = await runFsCmd(principal, project, cmd);
   if (r.code !== 0) {
+    const status = r.code === 4 ? 409 : 500;
     return NextResponse.json(
       { error: `fs.write failed: ${r.stderr.trim() || "unknown error"}` },
-      { status: 500 },
+      { status },
     );
   }
+  const stdoutParts = r.stdout.split("\n").filter(Boolean);
   const { createHash } = require("crypto");
   const bytes = Buffer.byteLength(content, "utf8");
   const sha256 = createHash("sha256").update(content, "utf8").digest("hex");