Fix relative path bypass in write validator and add Codex flag probes in bitlesson selector

Write validator had the same relative-path fallback issue as the read
validator: when realpath is unavailable, relative FILE_PATH bypassed
the absolute prefix guard during methodology analysis.

Bitlesson selector unconditionally passed --disable codex_hooks,
--skip-git-repo-check, and --ephemeral to codex exec without checking
if the CLI supports them. Added capability probes matching the pattern
already used in loop-codex-stop-hook.sh.

Author: SihaoLiu

hooks/loop-write-validator.sh

@@ -121,8 +121,21 @@ if [[ -n "$_MA_LOOP_DIR" ]] && [[ -f "$_MA_LOOP_DIR/methodology-analysis-state.m
     fi
     _ma_real_loop=$(realpath "$_MA_LOOP_DIR" 2>/dev/null || echo "")
     # Fallback to raw paths when realpath is unavailable (older macOS/BSD)
-    [[ -z "$_ma_real_path" ]] && _ma_real_path="$FILE_PATH"
-    [[ -z "$_ma_real_loop" ]] && _ma_real_loop="$_MA_LOOP_DIR"
+    # Ensure paths are absolute so prefix guards cannot be bypassed
+    if [[ -z "$_ma_real_path" ]]; then
+        if [[ "$FILE_PATH" == /* ]]; then
+            _ma_real_path="$FILE_PATH"
+        else
+            _ma_real_path="$PROJECT_ROOT/$FILE_PATH"
+        fi
+    fi
+    if [[ -z "$_ma_real_loop" ]]; then
+        if [[ "$_MA_LOOP_DIR" == /* ]]; then
+            _ma_real_loop="$_MA_LOOP_DIR"
+        else
+            _ma_real_loop="$PROJECT_ROOT/$_MA_LOOP_DIR"
+        fi
+    fi
     if [[ "$_ma_real_path" == "$_ma_real_loop/"* ]]; then
         _ma_basename=$(basename "$_ma_real_path")
         case "$_ma_basename" in

scripts/bitlesson-select.sh

@@ -185,10 +185,19 @@ run_selector() {
     local model="$2"
 
     if [[ "$provider" == "codex" ]]; then
-        local codex_exec_args=(
-            "--disable" "codex_hooks"
-            "--skip-git-repo-check"
-            "--ephemeral"
+        local codex_exec_args=()
+        # Probe whether the installed Codex CLI supports --disable flag
+        if codex --help 2>&1 | grep -q -- '--disable'; then
+            codex_exec_args+=("--disable" "codex_hooks")
+        fi
+        # Probe for --skip-git-repo-check and --ephemeral support
+        if codex exec --help 2>&1 | grep -q -- '--skip-git-repo-check'; then
+            codex_exec_args+=("--skip-git-repo-check")
+        fi
+        if codex exec --help 2>&1 | grep -q -- '--ephemeral'; then
+            codex_exec_args+=("--ephemeral")
+        fi
+        codex_exec_args+=(
             "-s" "read-only"
             "-m" "$model"
             "-c" "model_reasoning_effort=low"

tests/test-bitlesson-select-routing.sh

@@ -448,6 +448,15 @@ CAPTURE_BIN="$TEST_DIR/capture-bin"
 mkdir -p "$CAPTURE_BIN"
 cat > "$CAPTURE_BIN/codex" <<'EOF'
 #!/usr/bin/env bash
+# Respond to help probes with supported flags
+for arg in "$@"; do
+    if [[ "$arg" == "--help" ]]; then
+        echo "  --disable <feature>   Disable a feature"
+        echo "  --skip-git-repo-check Skip git repo check"
+        echo "  --ephemeral           Ephemeral mode"
+        exit 0
+    fi
+done
 printf '%s\n' "$@" > "${TEST_CAPTURE_ARGS:?}"
 cat > /dev/null
 cat <<'OUT'