human behavior: classifier gate, pacing, splitting, quiet hours, stable prompt prefix

specs/SPEC-001-responder-envelope.md

@@ -66,13 +66,23 @@ link syntax from the model reads as noise.
 When the envelope `channel` is null/none/empty, the response channel
 is the channel the message came from.
 
-### ENV-10 — System prompt template substitution (coverage: test)
+### ENV-10 — Dynamic context reaches the system prompt (coverage: test)
 
-`message()` substitutes `{date}` (YYYY-MM-DD), `{time}`, `{memory}`
-(the assembled memory block — legacy memory string while the
-structured memory is inactive, see MEM-10) in the system prompt;
-`{news}` is replaced with the news file content when the configured
-file exists and stays literal when it does not.
+The system message carries the current date, time, news (when the
+configured file exists) and the memory block (legacy string while
+structured memory is inactive, see MEM-10). Since FDB-008 these live
+in a context suffix, not inline — see ENV-20; legacy `{date}`,
+`{time}`, `{news}`, `{memory}` placeholders in operator templates are
+stripped.
+
+### ENV-20 — Persona prefix is byte-stable (coverage: test)
+
+`message()` renders the system message as: static persona text
+(config template with all dynamic placeholders removed) followed by a
+`## Context` suffix holding date, time, news and memory. Two calls in
+the same channel produce byte-identical persona prefixes — the prompt
+cache can actually hit (the old inline `{date}`/`{time}` substitution
+invalidated it every minute).
 
 ### ENV-11 — Per-channel history shrink prefers busy channels (coverage: test)