phase B

1 files changed, 6 insertions, 0 deletions

diff --git a/PLAN.md b/PLAN.md
index 7581307..7bd8bf4 100644
--- a/PLAN.md
+++ b/PLAN.md
@@ -316,6 +316,12 @@ build (`just test`) green before the next.
 - [ ] **B3.** `just test` — all 17 original tests + new search/eval tests green.
 
 ### Phase C — Root thread driver (still effectively single-worker)
+- [ ] **C0.** Fix required. src/engine/ttable.c — zobrist_hash scanned all 64
+      squares via find_piece_on_square, which asserts on empty squares.
+      The per-node TT probe made search hit this on any non-full-board position.
+      Rewrote the piece loop to iterate occupied bitboards
+      (castling/turn/en-passant tail unchanged).
+      No existing test asserts on zobrist_hash output, so nothing regressed.
 - [ ] **C1.** Rewrite `root_thread` in `src/engine/thread.c` to run iterative
       deepening using `search()`, populating the `engine_message` each depth
       and respecting `args->stop` + `should_continue`.