From 1b3a3646d6f1d1e99a28b5004038742319a99227 Mon Sep 17 00:00:00 2001
From: Jared Miller <jared@smell.flowers>
Date: Tue, 10 Feb 2026 15:42:15 -0500
Subject: [PATCH] Pre-consume store byte in op_aread and op_read_char before
 blocking reads

Without this, MUD-level saves during read_line/read_char capture PC pointing
at the store byte, which gets misinterpreted as an opcode on restore.
---
 src/mudlib/embedded_if_session.py |  4 ++--
 src/mudlib/zmachine/zcpu.py       | 15 ++++++++++++---
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/src/mudlib/embedded_if_session.py b/src/mudlib/embedded_if_session.py
index 130c462..c5404d3 100644
--- a/src/mudlib/embedded_if_session.py
+++ b/src/mudlib/embedded_if_session.py
@@ -52,8 +52,8 @@ class EmbeddedIFSession:
           branch data (V3) or store byte (V5+). Process them so execution
           resumes at the next instruction.
         - MUD-level _do_save during sread/aread: PC points past the read
-          instruction. No post-processing needed (phantom output suppressed
-          in start()).
+          instruction (store byte pre-consumed in op_aread/op_read_char).
+          No post-processing needed (phantom output suppressed in start()).
         """
         if not self.save_path.exists():
             return False
diff --git a/src/mudlib/zmachine/zcpu.py b/src/mudlib/zmachine/zcpu.py
index b83ed53..0f76d69 100644
--- a/src/mudlib/zmachine/zcpu.py
+++ b/src/mudlib/zmachine/zcpu.py
@@ -808,7 +808,13 @@ class ZCpu:
         text_buffer_addr = args[0]
         parse_buffer_addr = args[1] if len(args) > 1 else 0
 
-        # Read input from keyboard
+        # Consume store byte BEFORE blocking in read_line(). This ensures
+        # the PC is past the entire instruction when MUD-level saves capture
+        # state during read_line(). Without this, saves point PC at the store
+        # byte, which gets misinterpreted as an opcode on restore.
+        store_addr = self._opdecoder.get_store_address()
+
+        # Read input from keyboard (blocks until player types something)
         text = self._ui.keyboard_input.read_line()
         text = text.lower().strip("\n\r")
 
@@ -840,7 +846,7 @@ class ZCpu:
                 offset = pos + word_len
 
         # Store terminating character (13 = newline)
-        self._write_result(13)
+        self._write_result(13, store_addr=store_addr)
 
     def op_print_char(self, char):
         """Output the given ZSCII character."""
@@ -968,8 +974,11 @@ class ZCpu:
         if time != 0 or input_routine != 0:
             raise ZCpuNotImplemented
 
+        # Consume store byte BEFORE blocking in read_char() — same reason
+        # as op_aread: PC must be past the full instruction for MUD saves.
+        store_addr = self._opdecoder.get_store_address()
         char = self._ui.keyboard_input.read_char()
-        self._write_result(char)
+        self._write_result(char, store_addr=store_addr)
 
     def op_scan_table(self, x, table, length, *args):
         """Search a table for a value, branch if found, store address (V4+).