diff --git a/deploy/install.sh b/deploy/install.sh
index db48f38..76bfede 100755
--- a/deploy/install.sh
+++ b/deploy/install.sh
@@ -33,16 +33,24 @@
 # ── 1. prerequisites ────────────────────────────────────────────────
 say "Checking prerequisites"
 
-if ! command -v python3 >/dev/null; then
-    err "python3 not found — install Python 3.11+ first"; exit 1
-fi
-PYOK=$(python3 - <<'EOF'
-import sys
-print(0 if sys.version_info >= (3, 11) else 1)
-EOF
-)
-if [ "$PYOK" != "0" ]; then
-    err "python3 is older than 3.11 — upgrade and re-run"; exit 1
+# Pick the first interpreter >= 3.11. Ubuntu 22.04's system python3 is 3.10
+# (and must NOT be replaced — apt depends on it); a newer Python installed
+# alongside (deadsnakes PPA) lives under its own name, e.g. python3.12.
+PYBIN=""
+for cand in python3.13 python3.12 python3.11 python3; do
+    command -v "$cand" >/dev/null 2>&1 || continue
+    if "$cand" -c 'import sys; sys.exit(0 if sys.version_info >= (3, 11) else 1)'; then
+        PYBIN="$cand"
+        break
+    fi
+done
+if [ -z "$PYBIN" ]; then
+    err "no python >= 3.11 found (system python3 is too old)."
+    err "Ubuntu 22.04: sudo add-apt-repository ppa:deadsnakes/ppa && sudo apt update"
+    err "             sudo apt install python3.12 python3.12-venv"
+    err "Ubuntu 24.04 already ships 3.12 as python3."
+    err "Do NOT replace the system python3 — install alongside and re-run."
+    exit 1
 fi
 
 if ! command -v docker >/dev/null; then
@@ -51,7 +59,7 @@
 if ! $SUDO docker compose version >/dev/null 2>&1; then
     err "docker compose (v2 plugin) not available"; exit 1
 fi
-echo "OK: python3 $(python3 --version | cut -d' ' -f2), docker + compose"
+echo "OK: $PYBIN ($($PYBIN --version 2>&1)), docker + compose"
 
 # ── 2. .env ────────────────────────────────────────────────────────
 say "Provisioning .env"
@@ -91,7 +99,7 @@
 # ── 4. venv + install ───────────────────────────────────────────────
 say "Building venv and installing navi"
 if [ ! -d .venv ]; then
-    python3 -m venv .venv
+    "$PYBIN" -m venv .venv
 fi
 ./.venv/bin/pip install --upgrade pip -q
 ./.venv/bin/pip install -e .