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diff --git a/AGENTS.md b/AGENTS.md
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--- a/AGENTS.md
+++ b/AGENTS.md
@@ -30,6 +30,21 @@
 - All balance mutations (`SET balance = balance ± ?`) must happen in a
   transaction.
 
+## Crash
+- The client draws the multiplier from its own clock for display only. A
+  cashout carries a session id and nothing else; the multiplier and payout come
+  from the server's clock at receipt.
+- Never send the crash point to the client before the round ends. A client that
+  knows it can cash out at `crash - epsilon` every round for a guaranteed win.
+- The crash point is `max(1.0, (1 - edge) / (1 - u))`; do not "fix" the 1% of
+  rounds that crash at 1.00x. That is where the house edge is charged on an
+  instant cashout, and it is why no cashout lockout is needed.
+- The crash event is a server-initiated line (`CRASH_BUSTED`), not a reply.
+  Client code must drain the socket on a timer and route pushed lines by
+  prefix instead of assuming the next line answers the last request.
+- `ServerCore::poll` must be idempotent: it settles the round, removes the
+  session, and pushes once. A second poll must produce nothing.
+
 ## Client TUI
 - `render_lines()` and `render()` must agree. If `render()` uses `\r\n`,
   count lines against the same string the cursor will erase.