diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..0bee5ef
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,61 @@
+# Driver Makefile — nulsl-libc
+#
+# This is the HAND-WRITTEN top-level makefile (committed to git). It never
+# runs the autotools machinery in-tree; instead it drives two out-of-tree
+# builds, one per bin/ directory, exactly as the Null Linux guidelines want:
+#
+#   make release   -> ./configure CFLAGS='-O2'   into bin/release/
+#   make debug     -> ./configure CFLAGS='-O0 -g' into bin/debug/
+#
+# Run `./autogen.sh` once after cloning (or just run `make release` — it
+# regenerates the configure script itself when needed).
+#
+# Never run `./configure` at the repository root: configure.ac refuses it.
+
+.PHONY: all release debug bench check clean distclean compile_commands
+
+all: release
+
+# --- bootstrapping ---------------------------------------------------------
+
+# Regenerates configure (and friends) when autogen.sh is newer.
+configure: autogen.sh
+	./autogen.sh
+
+# --- builds ----------------------------------------------------------------
+
+# Release is ALWAYS -O2 (project guideline #4).
+bin/release/Makefile: configure
+	@mkdir -p bin/release
+	@cd bin/release && ../../configure CFLAGS='-O2'
+
+bin/debug/Makefile: configure
+	@mkdir -p bin/debug
+	@cd bin/debug && ../../configure CFLAGS='-O0 -g'
+
+release: bin/release/Makefile
+	$(MAKE) -C bin/release
+
+debug: bin/debug/Makefile
+	$(MAKE) -C bin/debug
+
+# --- developer conveniences -------------------------------------------------
+
+bench: release
+	$(MAKE) -C bin/release bench
+
+check: release
+	$(MAKE) -C bin/release check
+
+# LSP support: compile_commands.json for clangd (requires `bear`).
+compile_commands: release
+	@command -v bear >/dev/null 2>&1 || { \
+	    echo "error: 'bear' is not installed (sudo pacman -S bear, apt install bear, ...)"; exit 1; }
+	@cd bin/release && bear --output ../../compile_commands.json -- $(MAKE) clean all
+
+clean:
+	@test ! -f bin/release/Makefile || $(MAKE) -C bin/release clean
+	@test ! -f bin/debug/Makefile || $(MAKE) -C bin/debug clean
+
+distclean: clean
+	rm -rf bin/release bin/debug
diff --git a/Makefile.am b/Makefile.am
new file mode 100644
index 0000000..3b9cb6c
--- /dev/null
+++ b/Makefile.am
@@ -0,0 +1,66 @@
+# Makefile.am — nulsl-libc
+#
+# This is the AUTOTOOLS makefile. It is only ever instantiated by a configure
+# run inside bin/release/ or bin/debug/ (never at the repository root).
+#
+# Everything is a static library. No libtool, no shared objects, no dynamic
+# linker. See docs/architecture.md.
+#
+# Benchmarks and tests live in one Makefile on purpose: automake orders
+# targets by dependency, so libc.a (and crt0.o) are guaranteed to exist
+# before any -nostdlib binary links against them. With SUBDIRS, recursion
+# builds the subdirectories first and linking breaks.
+
+AUTOMAKE_OPTIONS = foreign
+
+AM_CPPFLAGS = -I$(top_srcdir)/include
+AM_CFLAGS = -std=c17 -ffreestanding -fno-builtin -fno-stack-protector \
+            -Wall -Wextra -Wshadow -Wpointer-arith
+
+lib_LIBRARIES = libc.a
+
+libc_a_SOURCES = \
+    src/errno.c \
+    src/stdio.c \
+    src/stdlib.c \
+    src/string.c \
+    src/syscall.c \
+    src/unistd.c
+
+# The C runtime entry point is deliberately NOT a member of libc.a: nothing
+# references _start, so the linker would never extract it from an archive.
+# It is built as a standalone object and linked explicitly by everything
+# that wants a runnable binary.
+noinst_DATA = crt0.o
+crt0.o: $(top_srcdir)/src/crt/crt0.S
+	$(CC) $(AM_CPPFLAGS) $(CFLAGS) -c -o $@ $<
+CLEANFILES = crt0.o
+
+EXTRA_DIST = autogen.sh
+
+# --- benchmarks ------------------------------------------------------------
+# Fully static, -nostdlib: the numbers reflect exactly what ships.
+
+noinst_PROGRAMS = benchmarks/bench_strlen benchmarks/bench_syscall
+
+benchmarks_bench_strlen_SOURCES = benchmarks/bench_strlen.c
+benchmarks_bench_strlen_LDADD = crt0.o libc.a -lgcc
+benchmarks_bench_strlen_LDFLAGS = -nostdlib -static -no-pie -Wno-unused-command-line-argument
+
+benchmarks_bench_syscall_SOURCES = benchmarks/bench_syscall.c
+benchmarks_bench_syscall_LDADD = crt0.o libc.a -lgcc
+benchmarks_bench_syscall_LDFLAGS = -nostdlib -static -no-pie -Wno-unused-command-line-argument
+
+.PHONY: bench
+bench: all
+	./benchmarks/bench_strlen
+	./benchmarks/bench_syscall
+
+# --- tests ------------------------------------------------------------------
+
+check_PROGRAMS = tests/smoke
+TESTS = tests/smoke
+
+tests_smoke_SOURCES = tests/smoke.c
+tests_smoke_LDADD = crt0.o libc.a -lgcc
+tests_smoke_LDFLAGS = -nostdlib -static -no-pie -Wno-unused-command-line-argument
diff --git a/autogen.sh b/autogen.sh
new file mode 100755
index 0000000..7efa2bb
--- /dev/null
+++ b/autogen.sh
@@ -0,0 +1,19 @@
+#!/bin/sh
+# autogen.sh — regenerate all autotools machinery.
+#
+# Usage: ./autogen.sh        (then: make release / make debug / make bench)
+#
+# Never run ./configure at the repository root — use the driver Makefile
+# targets instead, which configure out-of-tree into bin/{release,debug}.
+
+set -e
+cd "$(dirname "$0")"
+
+autoreconf -i -f -v
+
+echo
+echo "autotools machinery regenerated."
+echo "next: make release   (bin/release/, CFLAGS='-O2')"
+echo "      make debug     (bin/debug/,   CFLAGS='-O0 -g')"
+echo "      make bench     (benchmarks against the release build)"
+echo "      make check     (smoke tests)"
diff --git a/configure.ac b/configure.ac
new file mode 100644
index 0000000..4ca1243
--- /dev/null
+++ b/configure.ac
@@ -0,0 +1,50 @@
+dnl configure.ac — nulsl-libc, a very lightweight C17 libc for Linux.
+dnl
+dnl Static-only on purpose: the dynamic linker is a memory tax we refuse to
+dnl pay (see docs/architecture.md). libc.a is a plain archive, so no libtool.
+dnl
+dnl IMPORTANT: never run ./configure at the repository root. The root holds a
+dnl hand-written driver Makefile that builds into bin/{release,debug}; the
+dnl guard below refuses to overwrite it.
+
+AC_PREREQ([2.71])
+AC_INIT([nulsl-libc], [0.1.0], [], [nulsl-libc],
+        [https://git.spectoria.dev/The-Null-Linux-Project/nulsl-libc])
+AC_CONFIG_SRCDIR([include/stdio.h])
+AC_CONFIG_AUX_DIR([build-aux])
+AC_CANONICAL_HOST
+
+AM_INIT_AUTOMAKE([foreign subdir-objects])
+
+dnl C17, and only C17 (project guideline #1). Modern autoconf ships no
+dnl AC_PROG_CC_C17 macro, so prove it with a compile test instead.
+AC_PROG_CC
+saved_CFLAGS="$CFLAGS"
+CFLAGS="$CFLAGS -std=c17"
+AC_COMPILE_IFELSE([AC_LANG_PROGRAM([#if __STDC_VERSION__ < 201710L
+#error "not C17"
+#endif
+], [])],
+    [],
+    [AC_MSG_ERROR([nulsl-libc requires a C17 compiler (GCC >= 8 or Clang >= 6); -std=c17 was rejected])])
+CFLAGS="$saved_CFLAGS"
+
+dnl Target validation: Linux on x86_64, for now.
+AS_CASE([$host_os],
+        [linux*], [],
+        [AC_MSG_ERROR([nulsl-libc currently targets Linux only (configured for $host_os)])])
+AS_CASE([$host_cpu],
+        [x86_64], [],
+        [AC_MSG_ERROR([nulsl-libc currently targets x86_64 only (configured for $host_cpu); src/arch/ is where new ports go])])
+
+dnl Plain archives need ar/ranlib; no libtool, no shared objects.
+AC_CHECK_TOOL([AR], [ar])
+AC_PROG_RANLIB
+
+dnl Refuse in-tree configuration: it would clobber the committed driver
+dnl Makefile that dispatches into bin/{release,debug}.
+AS_IF([test "x$srcdir" = "x." && test -f Makefile],
+      [AC_MSG_ERROR([in-tree builds are disabled — run 'make release' or 'make debug' from the repository root instead])])
+
+AC_CONFIG_FILES([Makefile])
+AC_OUTPUT