diff --git a/toolchain/builder/zeta-makepkg b/toolchain/builder/zeta-makepkg
index 690f588..8277c61 100755
--- a/toolchain/builder/zeta-makepkg
+++ b/toolchain/builder/zeta-makepkg
@@ -75,6 +75,8 @@ Flags:
   -w, --workers <N> Number of parallel package builds for --all (default: 1)
   --no-index         Don't update packages/index.lua after building
   --keep-work        Don't remove the build work directory
+  --follow          Build all dependencies first (bottom-up), then the package.
+                     Incompatible with --all.
   --force            Overwrite existing package tarball
   --help             Show this help
 
@@ -101,6 +103,7 @@ local function parse_cli(args)
     force     = false,
     index     = false,
     all       = nil,
+    follow    = false,
     help      = false,
     recipe    = nil,
     jobs      = nil,  -- nil = auto-detect (nproc)
@@ -142,6 +145,8 @@ local function parse_cli(args)
       opts.keep_work = true
     elseif a == "--force" then
       opts.force = true
+    elseif a == "--follow" then
+      opts.follow = true
     elseif a == "--jobs" then
       i = i + 1
       if i > #args then
@@ -217,6 +222,11 @@ if opts.help then
   os.exit(0)
 end
 
+if opts.follow and opts.all then
+  io.stderr:write("error: --follow and --all are incompatible\n")
+  os.exit(1)
+end
+
 if opts.index then
   indexer.generate(path.join(opts.output, "packages"))
 elseif opts.all then
diff --git a/toolchain/examples/custom-demo/build.sh b/toolchain/examples/custom-demo/build.sh
new file mode 100644
index 0000000..4f0a02a
--- /dev/null
+++ b/toolchain/examples/custom-demo/build.sh
@@ -0,0 +1,29 @@
+#!/bin/sh
+# build.sh — example custom build script for zeta-makepkg.
+#
+# Invoked from the extracted source directory.  The tool sets:
+#   $DESTDIR  → staging tree root (e.g. /tmp/zeta-makepkg/mytool-.../stage)
+#
+# This script must compile/assemble the software and install every output
+# file under $DESTDIR with standard FHS paths (usr/bin/, usr/lib/, etc.).
+#
+# For a real project you would replace the example below with:
+#   - Go:      go build -o "$DESTDIR/usr/bin/mytool" .
+#   - Rust:    cargo build --release && install -D target/release/mytool "$DESTDIR/usr/bin/mytool"
+#   - Zig:     zig build -Doptimize=ReleaseSafe --prefix /usr -Ddestdir="$DESTDIR"
+#   - Shell:   install -D mytool.sh "$DESTDIR/usr/bin/mytool"
+#   - Python:  install -D mytool.py "$DESTDIR/usr/bin/mytool"
+#   - Anything you can script.
+
+set -eu
+
+echo "==> Building mytool (custom)"
+
+# Standalone Go binary: init module, build, install
+go mod init mytool
+go build -o mytool .
+
+# Install into the staging tree
+install -Dm755 mytool "$DESTDIR/usr/bin/mytool"
+
+echo "==> Install complete"
diff --git a/toolchain/examples/custom-demo/custom.recipe b/toolchain/examples/custom-demo/custom.recipe
new file mode 100644
index 0000000..6608322
--- /dev/null
+++ b/toolchain/examples/custom-demo/custom.recipe
@@ -0,0 +1,23 @@
+-- custom.recipe — demonstrates build_system = "custom" with a build.sh script.
+--
+-- The custom build system runs `build_script` from inside the extracted
+-- source directory. The script receives $DESTDIR pointing at the staging
+-- tree where installed files must be placed.
+--
+-- To try this:
+--   1. Unpack the source tarball:  tar -xzf mytool-1.0.tar.gz
+--   2. Run the script manually:     cd mytool-1.0 && DESTDIR=/tmp/stage sh build.sh
+--   3. Inspect the staged output:   find /tmp/stage
+--   4. Build with makepkg:          zeta-makepkg custom.recipe
+
+return {
+  name         = "mytool",
+  version      = "1.0",
+  summary      = "Example custom-build package (static Go binary)",
+  url          = "mytool-1.0.tar.gz",
+  sha256       = nil,
+  deps         = {},
+  build_system = "custom",
+  build_script = "build.sh",
+  test         = "test -x ${DESTDIR}/usr/bin/mytool",
+}
diff --git a/toolchain/lib/build.lua b/toolchain/lib/build.lua
index e402f40..df0da16 100644
--- a/toolchain/lib/build.lua
+++ b/toolchain/lib/build.lua
@@ -12,11 +12,86 @@ local builder  = require("builder")
 local packager = require("packager")
 local indexer  = require("indexer")
 
+---------------------------------------------------------------------------
+-- Dependency resolution (--follow)
+---------------------------------------------------------------------------
+
+-- Given a recipe directory and a dep spec (e.g. "ncurses" or "libfoo>=2.0"),
+-- return the path to <dep>.recipe if it exists, or nil.
+local function find_dep_recipe(recipe_dir, dep_spec)
+  local name = dep_spec:match("^([%w%._+%-]+)")
+  if not name then return nil end
+  local p = path.join(recipe_dir, name .. ".recipe")
+  if path.exists(p) then return p end
+  return nil
+end
+
+-- Recursively collect all dependency recipe paths, bottom-up (deps first).
+-- Returns an ordered list (no duplicates) and an in-progress set for cycle
+-- detection. Recipes for deps that don't have a .recipe file are silently
+-- skipped (assumed already installed).
+local function collect_deps(recipe_path, seen, order, in_progress)
+  if seen[recipe_path] then return end
+  if in_progress[recipe_path] then
+    error(("dependency cycle involving %s"):format(path.basename(recipe_path)), 0)
+  end
+
+  in_progress[recipe_path] = true
+
+  local r, err = recipe.load(recipe_path)
+  if not r then
+    in_progress[recipe_path] = nil
+    log.warn(("skipping %s: %s"):format(path.basename(recipe_path), tostring(err)))
+    return
+  end
+
+  local dir = path.dirname(recipe_path)
+  for _, dep in ipairs(r.deps) do
+    local dep_recipe = find_dep_recipe(dir, dep)
+    if dep_recipe then
+      collect_deps(dep_recipe, seen, order, in_progress)
+    end
+  end
+
+  in_progress[recipe_path] = nil
+  seen[recipe_path] = true
+  order[#order + 1] = recipe_path
+end
+
+-- Return an ordered list of recipe paths to build: all dependencies
+-- (bottom-up), then the target recipe itself.
+local function resolve_deps(recipe_path)
+  local seen = {}
+  local order = {}
+  local in_progress = {}
+  collect_deps(recipe_path, seen, order, in_progress)
+  return order
+end
+
 ---------------------------------------------------------------------------
 -- Single recipe pipeline
 ---------------------------------------------------------------------------
 
 function build.single(recipe_path, opts)
+  -- If --follow, build dependencies first (bottom-up order, already sorted).
+  if opts.follow then
+    log.step("resolving dependencies")
+    local ordered = resolve_deps(recipe_path)
+    local dep_count = #ordered - 1  -- last is the target itself
+    if dep_count > 0 then
+      log.info(("found %d dependenc%s"):format(dep_count, dep_count == 1 and "y" or "ies"))
+      for i = 1, dep_count do
+        io.write("\n" .. string.rep("─", 36) .. "\n")
+        log.step(("building dependency %s (%d/%d)"):format(
+          path.basename(ordered[i]), i, dep_count))
+        build.single(ordered[i], opts)
+      end
+      io.write("\n" .. string.rep("─", 36) .. "\n")
+    else
+      log.info("no unresolved dependencies")
+    end
+  end
+
   local r, err = recipe.load(recipe_path)
   if not r then error(("recipe error: %s"):format(tostring(err)), 0) end
 
@@ -37,7 +112,8 @@ function build.single(recipe_path, opts)
   log.info(("work directory: %s"):format(work_dir))
 
   local cache_dir = path.join(os.getenv("HOME") or "/tmp", ".cache", "zeta-makepkg", "sources")
-  local cache_file = builder.fetch_source(r, cache_dir)
+  local recipe_dir = path.dirname(recipe_path)
+  local cache_file = builder.fetch_source(r, cache_dir, recipe_dir)
   local source_dir = builder.extract_source(r, cache_file, work_dir)
 
   builder.run_build(r, source_dir, stage_dir, { jobs = opts.jobs })
diff --git a/toolchain/lib/builder.lua b/toolchain/lib/builder.lua
index 9dadb02..55c5d4d 100644
--- a/toolchain/lib/builder.lua
+++ b/toolchain/lib/builder.lua
@@ -104,7 +104,7 @@ end
 
 -- Fetch source into the cache directory. Returns the cached file path,
 -- or nil if the URL is a git repository (signals "use git clone").
-function builder.fetch_source(recipe, cache_dir)
+function builder.fetch_source(recipe, cache_dir, local_dir)
   local url = recipe.url
 
   -- Git repos are cloned, not cached as files.
@@ -141,7 +141,16 @@ function builder.fetch_source(recipe, cache_dir)
         error(("failed to copy %s"):format(url), 0)
       end
     else
-      error(("unrecognised url scheme: %s"):format(url), 0)
+      -- Bare filename: resolve relative to the recipe's directory.
+      if local_dir then
+        local src = path.join(local_dir, url)
+        log.step("copying " .. src)
+        if not path.run("cp " .. path.quote(src) .. " " .. path.quote(cache_file)) then
+          error(("failed to copy %s"):format(src), 0)
+        end
+      else
+        error(("unrecognised url scheme: %s"):format(url), 0)
+      end
     end
   else
     log.info("using cached source: " .. path.basename(cache_file))