Fix bitlesson codex stdin handling

Author: zenus

scripts/bitlesson-select.sh

@@ -175,7 +175,7 @@ if [[ "$BITLESSON_PROVIDER" == "codex" ]]; then
     fi
     CODEX_EXEC_ARGS+=("$CODEX_AUTO_FLAG" "-C" "$CODEX_PROJECT_ROOT")
 
-    RAW_OUTPUT="$(printf '%s' "$PROMPT" | run_with_timeout "$SELECTOR_TIMEOUT" codex exec "${CODEX_EXEC_ARGS[@]}")" || CODEX_EXIT_CODE=$?
+    RAW_OUTPUT="$(printf '%s' "$PROMPT" | run_with_timeout "$SELECTOR_TIMEOUT" codex exec "${CODEX_EXEC_ARGS[@]}" -)" || CODEX_EXIT_CODE=$?
 elif [[ "$BITLESSON_PROVIDER" == "claude" ]]; then
     RAW_OUTPUT="$(printf '%s' "$PROMPT" | run_with_timeout "$SELECTOR_TIMEOUT" claude --print --model "$BITLESSON_MODEL")" || CODEX_EXIT_CODE=$?
 fi

tests/test-bitlesson-select-routing.sh

@@ -32,7 +32,44 @@ create_mock_codex() {
     mkdir -p "$bin_dir"
     cat > "$bin_dir/codex" <<'EOF'
 #!/bin/bash
-# Mock codex that outputs valid bitlesson-selector format
+# Mock codex that only reads prompt content from stdin when invoked with trailing '-'
+if [[ "${*: -1}" != "-" ]]; then
+    echo "mock codex expected trailing '-' to read prompt from stdin" >&2
+    exit 9
+fi
+
+stdin_content=$(cat)
+if [[ -z "$stdin_content" ]]; then
+    echo "mock codex expected non-empty stdin prompt" >&2
+    exit 10
+fi
+
+cat <<'OUT'
+LESSON_IDS: NONE
+RATIONALE: No matching lessons found (mock codex).
+OUT
+EOF
+    chmod +x "$bin_dir/codex"
+}
+
+# Helper: create a mock codex binary that records stdin for assertions
+create_recording_mock_codex() {
+    local bin_dir="$1"
+    local stdin_file="$2"
+    mkdir -p "$bin_dir"
+    cat > "$bin_dir/codex" <<EOF
+#!/bin/bash
+if [[ "\${*: -1}" != "-" ]]; then
+    echo "mock codex expected trailing '-' to read prompt from stdin" >&2
+    exit 9
+fi
+
+cat > "$stdin_file"
+if [[ ! -s "$stdin_file" ]]; then
+    echo "mock codex expected non-empty stdin prompt" >&2
+    exit 10
+fi
+
 cat <<'OUT'
 LESSON_IDS: NONE
 RATIONALE: No matching lessons found (mock codex).
@@ -86,6 +123,41 @@ else
     fail "Codex branch: gpt-* model routes to codex" "LESSON_IDS: in output (exit 0)" "exit=$exit_code, output=$result"
 fi
 
+# ========================================
+# Test 1b: Codex branch passes '-' and consumes stdin prompt
+# ========================================
+echo ""
+echo "--- Test 1b: gpt-* codex path passes stdin prompt via trailing '-' ---"
+echo ""
+
+setup_test_dir
+create_mock_bitlesson "$TEST_DIR"
+BIN_DIR="$TEST_DIR/bin"
+STDIN_FILE="$TEST_DIR/codex-stdin.txt"
+create_recording_mock_codex "$BIN_DIR" "$STDIN_FILE"
+mkdir -p "$TEST_DIR/.humanize"
+printf '{"bitlesson_model": "gpt-4o"}' > "$TEST_DIR/.humanize/config.json"
+
+result=""
+exit_code=0
+result=$(CLAUDE_PROJECT_DIR="$TEST_DIR" XDG_CONFIG_HOME="$TEST_DIR/no-user" \
+    PATH="$BIN_DIR:$PATH" \
+    bash "$BITLESSON_SELECT" \
+    --task "Fix a bug" \
+    --paths "scripts/bitlesson-select.sh" \
+    --bitlesson-file "$TEST_DIR/.humanize/bitlesson.md" 2>/dev/null) || exit_code=$?
+
+if [[ $exit_code -eq 0 ]] \
+    && [[ -s "$STDIN_FILE" ]] \
+    && grep -q "Sub-task description:" "$STDIN_FILE" \
+    && grep -q "Fix a bug" "$STDIN_FILE"; then
+    pass "Codex branch: selector passes trailing '-' and prompt content through stdin"
+else
+    fail "Codex branch: selector passes trailing '-' and prompt content through stdin" \
+        "exit=0 with recorded stdin prompt" \
+        "exit=$exit_code, output=$result, stdin=$(cat "$STDIN_FILE" 2>/dev/null || true)"
+fi
+
 # ========================================
 # Test 2: Claude branch chosen for haiku model
 # ========================================