diff --git a/pi/AGENTS.md b/pi/AGENTS.md
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--- a/pi/AGENTS.md
+++ b/pi/AGENTS.md
@@ -1,5 +1,25 @@
 # Global Pi Instructions
 
+## Simplified Technical English
+
+Use English that follows practical ASD-STE100 principles for user-facing replies
+and technical prose that you create or substantially edit. Do not claim formal
+ASD-STE100 compliance.
+
+- Lead with the answer, result, or required action.
+- Use common and specific words. Avoid idioms, slang, metaphors, and filler.
+- Use active voice when the actor is known.
+- Put one main idea or instruction in each sentence.
+- Keep sentences near 20 words or fewer when this does not reduce accuracy.
+- Use short paragraphs and lists. Put one action in each numbered step.
+- Use one term for one concept. Do not change terms only for style.
+- Define an uncommon abbreviation or acronym at its first use.
+- State the actor, action, and condition. Avoid vague pronouns and references.
+- Keep the response concise, but include required safety limits and test results.
+- Preserve exact code, commands, identifiers, logs, error text, and quotations.
+- Use necessary technical terms. Define them when the reader might not know them.
+- Follow the user's requested language or style when it conflicts with this default.
+
 ## Version Control
 
 Prefer Jujutsu (`jj`) over Git for source-control operations.