diff --git a/BTC.sh b/BTC.sh
old mode 100755
new mode 100644
index d382641..a11ba20
--- a/BTC.sh
+++ b/BTC.sh
@@ -541,8 +541,17 @@ function f_exec_log() {
             pv -t -r -b -N "${log_base}" | \
             tee -a "${log_file}" > /dev/null; then
         echo ">> [FAILED] ${log_base} exited non-zero." >&2
-        echo ">> [FAILED] Last 40 lines of ${log_file}:" >&2
-        tail -n 40 "${log_file}" >&2 2>/dev/null || true
+        echo ">> [FAILED] Last 80 lines of ${log_file}:" >&2
+        tail -n 80 "${log_file}" >&2 2>/dev/null || true
+        echo "" >&2
+        echo ">> [FAILED] Lines matching error patterns (case-insensitive):" >&2
+        # Surface lines containing common error markers so the actual root
+        # cause is visible even if it's far from the tail (e.g. a linker
+        # error mid-log that triggered a cascade of later failures).
+        # "exceeds" catches the kernel's UTS_RELEASE length limit;
+        # "Error [0-9]" catches make's "*** [target] Error N" lines.
+        grep -iE 'error:|error [0-9]|cannot find|undefined reference|no such file|not found|failed|fatal|exceeds|too (long|short|large)' \
+            "${log_file}" 2>/dev/null | tail -n 30 >&2 || true
         echo ">> [FAILED] Full log: ${log_file}" >&2
         return 1
     fi
@@ -1352,7 +1361,16 @@ function f_kernel_binary() {
     fi
 
     # Inject Custom Enterprise Swarm Labels & Architecture Parameters
-    sed -i "s/CONFIG_LOCALVERSION=\"\"/CONFIG_LOCALVERSION=\"-dcosnet-${SYS_LABEL}\"/" .config
+    #
+    # NOTE: the LOCALVERSION tag (-dcosnet-${SYS_LABEL}) is passed on the
+    # `make` command line below, NOT written into CONFIG_LOCALVERSION here.
+    # Writing it to .config AND passing it on the make command line would
+    # concatenate the two, producing a version string like
+    #   "7.1.7-dcosnet-DCOSNET-BROADWELL-AVX2-LTO-dcosnet-DCOSNET-BROADWELL-AVX2-LTO"
+    # which exceeds the kernel's 64-byte UTS_RELEASE limit and aborts the
+    # build at utsrelease.h generation with "exceeds 64 characters".
+    # Pick ONE source of truth — the make command line is the LFS convention.
+    sed -i "s|CONFIG_LOCALVERSION=.*|CONFIG_LOCALVERSION=\"\"|" .config || true
 
     # Modern Hardening Optimization Suite Injection
     sed -i "s/# CONFIG_MODULES is not set/CONFIG_MODULES=n/" .config || true
@@ -1360,6 +1378,22 @@ function f_kernel_binary() {
     echo "CONFIG_KALLSYMS=n" >> .config
     echo "CONFIG_DEBUG_FS=n" >> .config
 
+    # Disable objtool (CONFIG_STACK_VALIDATION) and switch to the
+    # frame-pointer unwinder.  objtool is a HOST tool that links against
+    # libelf; if the host lacks libelf-dev (the -dev package that provides
+    # the libelf.so symlink, not just the runtime libelf.so.1), the LINK
+    # step for tools/objtool/objtool fails with "cannot find -lelf" and
+    # the whole kernel build aborts.  Installing libelf-dev on the host
+    # would fix it at the source, but we don't want to impose that
+    # dependency — the frame-pointer unwinder is functionally equivalent
+    # for a toolchain build (slightly larger kernel binary, marginally
+    # slower stack traces in production, but no functional regression).
+    # The olddefconfig step below will clean up any resulting conflicts.
+    echo "CONFIG_STACK_VALIDATION=n" >> .config
+    echo "CONFIG_UNWINDER_ORC=n" >> .config
+    echo "CONFIG_UNWINDER_FRAME_POINTER=y" >> .config
+    echo "CONFIG_OBJTOOL=n" >> .config 2>/dev/null || true
+
     # Cross-compile kernel using the canonical ARCH= name and the
     # Stage 2 cross-compiler (now on PATH after f_gcc_p2()).
     #