diff --git a/Makefile b/Makefile
index 5cc55ef2d..26e5101c6 100644
--- a/Makefile
+++ b/Makefile
@@ -97,12 +97,7 @@ install-nim:
 	scripts/install_nim.sh $(REQUIRED_NIM_VERSION)
 
 install-nimble: install-nim
-	@nimble_ver=$$(nimble --version 2>/dev/null | head -1 | grep -oE '[0-9]+\.[0-9]+\.[0-9]+' | head -1); \
-	if [ "$$nimble_ver" = "$(REQUIRED_NIMBLE_VERSION)" ]; then \
-	  echo "nimble $(REQUIRED_NIMBLE_VERSION) already installed, skipping."; \
-	else \
-	  cd $$(mktemp -d) && nimble install "nimble@$(REQUIRED_NIMBLE_VERSION)" -y; \
-	fi
+	scripts/install_nimble.sh $(REQUIRED_NIMBLE_VERSION)
 
 build:
 	mkdir -p build
diff --git a/scripts/install_nimble.sh b/scripts/install_nimble.sh
new file mode 100755
index 000000000..e7f575f59
--- /dev/null
+++ b/scripts/install_nimble.sh
@@ -0,0 +1,70 @@
+#!/usr/bin/env bash
+# Installs a specific nimble version without using `nimble install nimble`.
+#
+# `nimble install nimble` is inherently fragile:
+#   - ETXTBSY: overwriting the running nimble binary in pkgs2/
+#   - JSON parse failures with older nimble versions reading packages_official.json
+#
+# Strategy:
+#   1. If the right version is already at ~/.nimble/bin/nimble → done.
+#   2. If a previously-compiled binary exists in pkgs2/ → re-link it.
+#   3. Otherwise: clone the nimble git repo, init submodules, build with nim,
+#      and atomically replace the target (mv avoids ETXTBSY on the old binary).
+
+set -e
+
+NIMBLE_VERSION="${1:-}"
+if [ -z "${NIMBLE_VERSION}" ]; then
+  echo "Usage: $0 <nimble-version>" >&2
+  exit 1
+fi
+
+NIMBLE_BIN="${HOME}/.nimble/bin/nimble"
+
+# 1. Already installed at the right version?
+if [ -x "${NIMBLE_BIN}" ]; then
+  nimble_ver=$("${NIMBLE_BIN}" --version 2>/dev/null \
+    | head -1 | grep -oE '[0-9]+\.[0-9]+\.[0-9]+' | head -1 || true)
+  if [ "${nimble_ver}" = "${NIMBLE_VERSION}" ]; then
+    echo "Nimble ${NIMBLE_VERSION} already installed, skipping."
+    exit 0
+  fi
+fi
+
+# 2. Already compiled into pkgs2/ from a previous (possibly partial) run?
+PKGS2_NIMBLE=$(ls -dt "${HOME}/.nimble/pkgs2/nimble-${NIMBLE_VERSION}-"*/nimble \
+  2>/dev/null | head -1 || true)
+if [ -n "${PKGS2_NIMBLE}" ] && [ -x "${PKGS2_NIMBLE}" ]; then
+  echo "Nimble ${NIMBLE_VERSION} found in pkgs2, re-linking to ${NIMBLE_BIN}."
+  mkdir -p "${HOME}/.nimble/bin"
+  ln -sf "${PKGS2_NIMBLE}" "${NIMBLE_BIN}"
+  exit 0
+fi
+
+# 3. Build from source.
+NIM_BIN="${HOME}/.nimble/bin/nim"
+if [ ! -x "${NIM_BIN}" ]; then
+  NIM_BIN="$(command -v nim)"
+fi
+
+WORK_DIR="$(mktemp -d)"
+trap 'rm -rf "${WORK_DIR}"' EXIT
+
+echo "Cloning nimble v${NIMBLE_VERSION} with submodules..."
+git clone --depth=1 --branch "v${NIMBLE_VERSION}" \
+  --recurse-submodules --shallow-submodules \
+  https://github.com/nim-lang/nimble.git \
+  "${WORK_DIR}/nimble"
+
+echo "Building nimble ${NIMBLE_VERSION} with $("${NIM_BIN}" --version | head -1)..."
+cd "${WORK_DIR}/nimble"
+# nim reads nim.cfg / config.nims in the current dir, which sets vendor paths.
+"${NIM_BIN}" c -d:release --path:src \
+  -o:"${WORK_DIR}/nimble_new" src/nimble.nim
+
+mkdir -p "${HOME}/.nimble/bin"
+# Atomic rename: avoids ETXTBSY when the old binary at NIMBLE_BIN is still running.
+cp "${WORK_DIR}/nimble_new" "${NIMBLE_BIN}.new.$$"
+mv -f "${NIMBLE_BIN}.new.$$" "${NIMBLE_BIN}"
+
+echo "Nimble ${NIMBLE_VERSION} installed to ${NIMBLE_BIN}"