The gotcha there still described a -EUTF-8 flag the task no longer passes,
and the Rakefile comment explained no decision once the override was gone.

Assisted-by: Claude Opus 5 via Claude Code

diff --git a/AGENTS.md b/AGENTS.md
index 5fecc46..c7a7cbb 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -100,6 +100,8 @@ before regenerating.
   docs/plans/2026-08-20-type-checking.md.
 - An instance variable declaration has to be the first thing in the
   class body. Further down it is reported as an unused annotation.
-- `rake steep` runs the check with `-EUTF-8` because RBS reads source
-  in the default external encoding: under a C locale the em dashes in
-  these comments are invalid bytes and the parse dies on them.
+- `rake steep` needs a UTF-8 locale, which comes from the environment
+  rather than anything in this repo. RBS reads source in the default
+  external encoding, so under a C locale the em dashes in these comments
+  are invalid bytes and the parse dies on them. The same footgun the
+  ASCII-only rule in `config.ru` exists for.
diff --git a/Rakefile b/Rakefile
index 6574d3a..159fbbe 100644
--- a/Rakefile
+++ b/Rakefile
@@ -27,11 +27,6 @@ end
 
 desc "Type check lib against the RBS comments in it"
 task :steep do
-  # RBS reads source with the default external encoding, so this needs a
-  # UTF-8 locale: under a C one every em dash in a comment is an invalid
-  # byte rather than a character and the check dies parsing them. LANG is
-  # set in .ramekin/config.kdl for agents and by the login environment
-  # otherwise. The same footgun the ASCII-only rule in config.ru exists for.
   sh "steep", "check"
 end