Order getContext sections stable to volatile so provider prompt caching can take effect

src/loop.metta

@@ -7,11 +7,13 @@
 (= (wakeupInterval) (empty))
 (= (memoryDirectory) (empty))
 (= (spamShield) (empty)) ; TODO: this parameter is considered deprecated
+(= (stableContextOrder) (empty)) ; order prompt sections stable->volatile so providers can reuse the cached prefix
 
 (= (initLoop)
    (progn (configure maxNewInputLoops 50) ;20
           (configure maxWakeLoops 1)
           (configure spamShield False)
+          (configure stableContextOrder False)
           (configure sleepInterval 1) ;10
           (configure provider Anthropic)
           (configure maxOutputToken 6000)
@@ -40,10 +42,29 @@
                          " toolName4 arg4" (newline)
                          " toolName5 arg5" (newline)
                          " SAVE_PERMANENT_FILES_DIR: " (memoryDirectory)
-                         " LAST_SKILL_USE_RESULTS: " (last_chars (get-state &lastresults) (maxFeedback))
-                         " HISTORY: " (getHistory) 
+                         (contextVolatileTail)
                          " TIME: " (get_time_as_string)))))
 
+; LAST_SKILL_USE_RESULTS changes every cycle and is one of the largest sections,
+; so keeping it before HISTORY ends the provider's reusable cache prefix right after
+; the static head. With stableContextOrder on, HISTORY (which shifts far less between
+; consecutive calls) comes first and the volatile results section goes last, so more of
+; the prefix stays byte-identical and can be served from cache. Default is off, in which
+; case the tail is byte-for-byte identical to the original layout.
+(= (contextVolatileTail)
+   (py-str (orderedContextSections (stableContextOrder)
+                                   (last_chars (get-state &lastresults) (maxFeedback))
+                                   (getHistory))))
+
+; Section ordering, kept separate from the state reads and the py-str call so it
+; can be checked on its own. Returns the sections as a plain tuple. Flag off keeps
+; the results section ahead of HISTORY (the original layout); flag on puts HISTORY
+; first so the stable part sits in the reusable cache prefix.
+(= (orderedContextSections $stable $results $history)
+   (if $stable
+       (" HISTORY: " $history " LAST_SKILL_USE_RESULTS: " $results)
+       (" LAST_SKILL_USE_RESULTS: " $results " HISTORY: " $history)))
+
 (= (addTelegramPromptExtension)
    (if (== (commchannel) telegram)
        (let $path (joinPath ((memoryDirectory) "tg_prompt.txt"))

tests/src_loop.metta

@@ -0,0 +1,17 @@
+!(import! &self ./tests/lib/utils)
+!(import! &self ../src/helper.py)
+!(import! &self ./src/utils)
+!(import! &self ./src/loop)
+
+; orderedContextSections is a pure function of the two section strings and returns
+; the sections as a plain tuple, so the ordering can be checked directly without
+; loop state, the global flag, or building the final string.
+
+; Flag off (default): the volatile results section stays ahead of HISTORY, which
+; keeps the assembled prompt byte-for-byte identical to the original layout.
+!(test (orderedContextSections False "RESULT" "HIST")
+       (" LAST_SKILL_USE_RESULTS: " "RESULT" " HISTORY: " "HIST"))
+
+; Flag on: HISTORY moves ahead of the volatile results section.
+!(test (orderedContextSections True "RESULT" "HIST")
+       (" HISTORY: " "HIST" " LAST_SKILL_USE_RESULTS: " "RESULT"))