mod: Ext 2 — weighted/aggregate scoring (:score-at-least), 154/154

Report :signals ({:kind :weight}) project to signal(Id, 'kind', weight) facts;
condition (:score-at-least N) compiles to aggregate_all(sum(W), signal(Id,_,W),T),
T >= N. Low-confidence signals accumulate past a threshold via genuine Prolog
arithmetic aggregation. Default policy untouched — proven via custom rule sets.
+8 extension tests.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/mod/tests/extensions.sx

@@ -1,9 +1,12 @@
 ;; lib/mod/tests/extensions.sx — beyond-roadmap extensions.
 ;;
 ;; Ext 1: negation-as-failure conditions (:not / :attr) + report attributes.
-;; These exercise closed-world reasoning: "hide spam UNLESS the author is
-;; verified". Demonstrated with custom rule sets so the default policy (and its
-;; 132 conformance tests) stays untouched.
+;;        "hide spam UNLESS the author is verified" (closed-world reasoning).
+;; Ext 2: weighted/aggregate evidence scoring (:score-at-least) + report signals.
+;;        Many low-confidence signals accumulate past a threshold via Prolog
+;;        aggregate_all(sum(W), ...).
+;; Demonstrated with custom rule sets so the default policy (and its conformance
+;; tests) stays untouched.
 
 (define mod-ext-count 0)
 (define mod-ext-pass 0)
@@ -25,7 +28,7 @@
             mod-ext-failures
             (str name "\n    expected: " expected "\n    got:      " got)))))))
 
-;; ── report attributes ──
+;; ── Ext 1: report attributes ──
 
 (define mod-ext-r0 (mod/mk-report "r1" "a" "b" "this is spam"))
 (mod-ext-test!
@@ -50,7 +53,7 @@
       (mod/attach-evidence mod-ext-rv (mod/mk-evidence "x" "y"))))
   1)
 
-;; ── negation-as-failure: spam hidden unless author verified ──
+;; ── Ext 1: negation-as-failure: spam hidden unless author verified ──
 
 (define
   mod-ext-rules
@@ -93,7 +96,7 @@
     :action)
   "keep")
 
-;; ── negation appears in the goal text + proof ──
+;; ── Ext 1: negation appears in the goal text + proof ──
 
 (define
   mod-ext-dec
@@ -117,7 +120,7 @@
   (get (nth mod-ext-goals 1) :solved)
   true)
 
-;; ── cond->goal compiles :attr and :not directly ──
+;; ── Ext 1: cond->goal compiles :attr and :not directly ──
 
 (mod-ext-test!
   "cond->goal :attr"
@@ -128,7 +131,7 @@
   (mod/cond->goal (list :not (list :classification "spam")) "Id")
   "not(classification(Id, spam))")
 
-;; ── positive :attr condition (allowlist-style) ──
+;; ── Ext 1: positive :attr condition (allowlist-style) ──
 
 (define
   mod-ext-allow-rules
@@ -150,4 +153,98 @@
     :action)
   "keep")
 
+;; ── Ext 2: weighted signals + aggregate scoring ──
+
+(define mod-ext-s0 (mod/mk-report "s1" "a" "b" "neutral"))
+(mod-ext-test!
+  "fresh report has no signals"
+  (len (mod/report-signals mod-ext-s0))
+  0)
+(define
+  mod-ext-s1
+  (mod/attach-signal mod-ext-s0 (mod/mk-signal "link" 2)))
+(mod-ext-test!
+  "attach-signal adds one"
+  (len (mod/report-signals mod-ext-s1))
+  1)
+(mod-ext-test!
+  "attach-signal preserves attrs"
+  (len
+    (mod/report-attrs
+      (mod/attach-signal mod-ext-rv (mod/mk-signal "x" 1))))
+  1)
+
+(define
+  mod-ext-score-rules
+  (list
+    (mod/mk-rule
+      "high-score-hide"
+      :hide (list (list :score-at-least 5)))
+    (mod/mk-rule "default-keep" :keep (list))))
+
+;; one weak signal (2) — below threshold
+(define
+  mod-ext-weak
+  (mod/attach-signal
+    (mod/mk-report "w1" "a" "b" "neutral")
+    (mod/mk-signal "link" 2)))
+(mod-ext-test!
+  "single weak signal → keep (below threshold)"
+  (get
+    (mod/decide-report mod-ext-weak (list mod-ext-weak) mod-ext-score-rules)
+    :action)
+  "keep")
+
+;; three signals summing to 6 — over threshold
+(define
+  mod-ext-strong0
+  (mod/attach-signal
+    (mod/mk-report "w2" "a" "b" "neutral")
+    (mod/mk-signal "link" 2)))
+(define
+  mod-ext-strong1
+  (mod/attach-signal mod-ext-strong0 (mod/mk-signal "newaccount" 2)))
+(define
+  mod-ext-strong
+  (mod/attach-signal mod-ext-strong1 (mod/mk-signal "burst" 2)))
+(mod-ext-test!
+  "accumulated signals (2+2+2=6) → hide"
+  (get
+    (mod/decide-report
+      mod-ext-strong
+      (list mod-ext-strong)
+      mod-ext-score-rules)
+    :action)
+  "hide")
+(mod-ext-test!
+  "scoring rule named in decision"
+  (get
+    (mod/decide-report
+      mod-ext-strong
+      (list mod-ext-strong)
+      mod-ext-score-rules)
+    :rule)
+  "high-score-hide")
+
+;; exactly at threshold (5) fires
+(define
+  mod-ext-exact0
+  (mod/attach-signal
+    (mod/mk-report "w3" "a" "b" "neutral")
+    (mod/mk-signal "link" 3)))
+(define
+  mod-ext-exact
+  (mod/attach-signal mod-ext-exact0 (mod/mk-signal "burst" 2)))
+(mod-ext-test!
+  "exactly at threshold (5) → hide"
+  (get
+    (mod/decide-report mod-ext-exact (list mod-ext-exact) mod-ext-score-rules)
+    :action)
+  "hide")
+
+(mod-ext-test!
+  "cond->goal :score-at-least"
+  (mod/cond->goal (list :score-at-least 5) "Id")
+  "aggregate_all(sum(W), signal(Id, _, W), T), T >= 5")
+
 (define mod-extensions-tests-run! (fn () {:failures mod-ext-failures :total mod-ext-count :passed mod-ext-pass :failed mod-ext-fail}))