Merge pull request 'fix: line-buffer stdout when redirected so progress/readiness lines flush (#18)' (#19) from claude/issue-18 into master

Reviewed-on: #19

implementations/main.cpp

@@ -17,9 +17,33 @@ License along with this library; if not, write to the Free Software
 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
 */
 
+#include <cstdio>
+#if defined(_WIN32)
+    #include <io.h>
+    #ifndef STDOUT_FILENO
+        #define STDOUT_FILENO _fileno(stdout)
+    #endif
+    #define CRAFTER_MAIN_ISATTY _isatty
+#else
+    #include <unistd.h>
+    #define CRAFTER_MAIN_ISATTY isatty
+#endif
+
 import std;
 import Crafter.Build;
 
 int main(int argc, char** argv) {
+    // Line-buffer stdout when it is not a terminal. Must run before any stdout
+    // write. When stdout is a regular file or pipe the C runtime defaults to
+    // full (block) buffering, so the append-only progress lines ("[N/M]") and
+    // the trailing "Built … steps" / "listening on port …" lines would sit in
+    // the buffer and never reach a redirected log — fatal for tooling that
+    // polls the log for a readiness marker, and worst under -r where the
+    // process blocks in its serve loop and never returns to flush. A TTY is
+    // already line-buffered and its in-place redraw path flushes explicitly, so
+    // only adjust when redirected.
+    if (CRAFTER_MAIN_ISATTY(STDOUT_FILENO) == 0) {
+        std::setvbuf(stdout, nullptr, _IOLBF, 0);
+    }
     return Crafter::Run(argc, argv);
 }