diff --git a/stacks/gemma4-charrp/.env.example b/stacks/gemma4-charrp/.env.example
index 3b3a8ab..d03e982 100644
--- a/stacks/gemma4-charrp/.env.example
+++ b/stacks/gemma4-charrp/.env.example
@@ -37,6 +37,22 @@ GEMMA4_MODEL=/tank/aimodels/gemma4-26b-a4b-it-nvfp4
 # bg-digitalservices and ManniX-ITA both publish repos NAMED "NVFP4A16" whose
 # config.json declares input_activations num_bits 4. Check the field, not the
 # name, before ever substituting a different repo.
+#
+# ⚠⚠ THE A16 BUILD ALSO SHIPS A STALE CHAT TEMPLATE — the control run MUST
+# override it or it moves two axes instead of one:
+#   --chat-template /tank/aimodels/gemma4-26b-a4b-it-nvfp4/chat_template.jinja
+# Verified by hash on 2026-08-24: upstream google/gemma-4-26B-A4B-it is 390
+# lines, the A4 build's is 389 and byte-identical to it once trailing newlines
+# are normalised, and the A16 build's is 266 and is NOT. The thinking machinery
+# is built differently too — upstream and A4 set
+# `enable_thinking | default(false)` at line 186, the A16 template has no such
+# set — and its tokenizer_config response_schema has no `thinking` property.
+# It was quantized from an older revision. Served with its own template the two
+# arms would render DIFFERENT PROMPTS, and a score delta could be the template
+# rather than the activations.
+# Safe to override because the tokenizers agree: vocab identical at 262,144
+# entries, added_tokens identical. Same template over the same vocab renders
+# the same token ids.
 
 GEMMA4_PORT=8016
 GEMMA4_GPU_ID=0