feed: verb-aware smart dedupe — reactions collapse cross-actor, posts stay per-actor + 9 tests

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

lib/feed/conformance.sh

@@ -13,7 +13,7 @@ if [ ! -x "$SX_SERVER" ]; then
   exit 1
 fi
 
-SUITES=(basic fanout rank integration content notify home)
+SUITES=(basic fanout rank integration content notify home dedupe)
 
 OUT_JSON="lib/feed/scoreboard.json"
 OUT_MD="lib/feed/scoreboard.md"

lib/feed/dedupe.sx

@@ -46,11 +46,31 @@
       ((a (get ev :activity)))
       (list (get ev :to) (get a :actor) (get a :verb) (get a :object)))))
 
+; verbs whose duplicates collapse across actors (reactions, not authorship).
+; rebindable: callers can (set! feed/collapse-verbs ...) to tune the policy.
+(define
+  feed/collapse-verbs
+  (list "like" "favourite" "follow" "boost" "repost"))
+
+; per-verb key: collapse-verbs fold on (verb object); the rest key on
+; (actor verb object).
+(define
+  feed/smart-key
+  (fn
+    (a)
+    (if
+      (feed/-elem? (get a :verb) feed/collapse-verbs)
+      (feed/collapse-key a)
+      (feed/activity-key a))))
+
 ; --- ready-made dedupers ----------------------------------------------------
 
 (define feed/dedupe-activities (fn (s) (feed/dedupe s feed/activity-key)))
 
 (define feed/dedupe-collapse (fn (s) (feed/dedupe s feed/collapse-key)))
 
+; verb-aware: reactions collapse cross-actor, posts stay distinct per actor
+(define feed/dedupe-smart (fn (s) (feed/dedupe s feed/smart-key)))
+
 ; dedupe an inbox: at most one event per receiver per (actor verb object)
 (define feed/dedupe-inbox (fn (inbox) (feed/dedupe inbox feed/event-key)))

lib/feed/scoreboard.json

@@ -6,9 +6,10 @@
     "integration": {"pass": 22, "fail": 0},
     "content": {"pass": 15, "fail": 0},
     "notify": {"pass": 8, "fail": 0},
-    "home": {"pass": 6, "fail": 0}
+    "home": {"pass": 6, "fail": 0},
+    "dedupe": {"pass": 9, "fail": 0}
   },
-  "total_pass": 134,
+  "total_pass": 143,
   "total_fail": 0,
-  "total": 134
+  "total": 143
 }

lib/feed/scoreboard.md

@@ -11,4 +11,5 @@ _Generated by `lib/feed/conformance.sh`_
 | content | 15 | 0 | 15 |
 | notify | 8 | 0 | 8 |
 | home | 6 | 0 | 6 |
-| **Total** | **134** | **0** | **134** |
+| dedupe | 9 | 0 | 9 |
+| **Total** | **143** | **0** | **143** |

lib/feed/tests/dedupe.sx

@@ -0,0 +1,56 @@
+; Follow-up — verb-aware (smart) dedupe. (feed-test name got expected)
+
+; reactions (like/follow) collapse cross-actor; posts stay distinct per actor
+(define
+  M
+  (feed/stream
+    (list
+      (feed/activity "alice" "like" "X" 1 (list))
+      (feed/activity "bob" "like" "X" 2 (list))
+      (feed/activity "alice" "post" "P" 3 (list))
+      (feed/activity "bob" "post" "P" 4 (list))
+      (feed/activity "alice" "follow" "C" 5 (list))
+      (feed/activity "bob" "follow" "C" 6 (list))))) ; collapses
+
+(feed-test
+  "smart dedupe total"
+  (feed/count (feed/dedupe-smart M))
+  4)
+(feed-test
+  "smart keeps both posts"
+  (feed/count (feed/by-verb (feed/dedupe-smart M) "post"))
+  2)
+(feed-test
+  "smart collapses likes to one"
+  (feed/count (feed/by-verb (feed/dedupe-smart M) "like"))
+  1)
+(feed-test
+  "smart collapses follows to one"
+  (feed/count (feed/by-verb (feed/dedupe-smart M) "follow"))
+  1)
+(feed-test
+  "collapsed like keeps first actor"
+  (map feed/actor (feed/items (feed/by-verb (feed/dedupe-smart M) "like")))
+  (list "alice"))
+
+; contrast: plain activity dedupe keeps cross-actor likes distinct
+(feed-test
+  "activity dedupe keeps both likes"
+  (feed/count (feed/by-verb (feed/dedupe-activities M) "like"))
+  2)
+
+; contrast: blanket collapse folds the two posts (same verb+object) too
+(feed-test
+  "collapse dedupe folds posts"
+  (feed/count (feed/by-verb (feed/dedupe-collapse M) "post"))
+  1)
+
+; smart-key dispatch
+(feed-test
+  "smart-key reaction -> (verb object)"
+  (feed/smart-key (feed/activity "alice" "like" "X" 0 (list)))
+  (list "like" "X"))
+(feed-test
+  "smart-key post -> (actor verb object)"
+  (feed/smart-key (feed/activity "alice" "post" "P" 0 (list)))
+  (list "alice" "post" "P"))

plans/feed-on-sx.md

@@ -14,7 +14,7 @@ APL, ACL visibility filtering via `lib/acl/`, federation via fed-sx.
 
 ## Status (rolling)
 
-`bash lib/feed/conformance.sh` → **134/134** (Phases 1–4 + TF-IDF + notifications + home)
+`bash lib/feed/conformance.sh` → **143/143** (Phases 1–4 + TF-IDF + notifications + home + smart-dedupe)
 
 ## Ground rules
 
@@ -147,6 +147,10 @@ are function parameters. Real acl-sx / fed-sx wire in at the call site unchanged
 - [x] **Capstone** `feed/home` — the whole pipeline as one line: fanout ∘ inbox ∘
   dedupe ∘ ACL ∘ rank ∘ take (`home.sx`); 6 tests incl. per-viewer ACL + cross-post
   dedupe. (134/134 total.)
+- [x] Per-verb dedupe rules (briefing gotcha #3) — `feed/dedupe-smart` /
+  `feed/smart-key`: reactions (like/follow/boost/...) collapse cross-actor on
+  (verb,object); posts stay distinct per actor. `feed/collapse-verbs` is
+  rebindable policy; 9 tests. (143/143 total.)
 
 (none)