diff --git a/docs/DESIGN.md b/docs/DESIGN.md
index 4bf8db1..1268b85 100644
--- a/docs/DESIGN.md
+++ b/docs/DESIGN.md
@@ -481,6 +481,11 @@ above, including:
   doesn't need to fill a rectangle for belts, conveyors and the like. Belts, filters, screw
   conveyors, shafts, pipes, pumps and outlets (`lineOnly()`) always draw a line, Shift or not, and
   a diagonal belt drag stays sloped. Walls, grates and gates still Shift-fill.
+- **The dev console ships in every build (t66, 2026-10-27).** The owner is happy for players to
+  experiment and play their own way, so the console isn't hidden behind a dev build. Turning it
+  on warns first that the save will be marked, and the mark stays with the world; any future
+  achievements won't unlock in a marked world. Besides money, items and upgrades it may have
+  game speed and other things just for fun.
 
 ## Ideas not built yet
 
diff --git a/docs/agent-log.md b/docs/agent-log.md
index aa9c82c..a98c2ae 100644
--- a/docs/agent-log.md
+++ b/docs/agent-log.md
@@ -4,6 +4,13 @@ What agents have done, newest first. Add an entry for every piece of work: the d
 note or request it was for, what changed, the files touched, the tests run, and anything left
 open or not verified. Keep each entry short; the git history has the details.
 
+## 2026-10-27: t66 dev console in every build (Claude Code)
+
+- Owner decision: the console ships in production too, with a warning when it's turned on that
+  the save gets marked (and future achievements won't unlock). Recorded in `docs/DESIGN.md`;
+  t66 gained subtasks for the warning, the save mark, and game speed and fun controls. No code
+  changed.
+
 ## 2026-10-27: t66 dev console added to Todo (Claude Code)
 
 - Owner request: a dev console to add money, items and upgrades quickly for testing. Subtasks