arena: implement v39 mutation-diff action feedback (Agent-E) -- all four Tier-1 ingestions now flag-gated and ready to pilot

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WsbS5x2rYsMDxP2kW3qqmQ

e2e/browser-v3/arena/llm_policy.py

@@ -190,6 +190,10 @@ class LlmPolicy:
     notes: list[str] = field(default_factory=list)
     # v38: table->markdown rendering of table/grid subtrees (perception.tables_markdown).
     table_md: bool = False
+    # v39: mutation-diff action feedback -- run.py appends the page-text delta after each action
+    # (Agent-E's MutationObserver, approximated text-side). Autocomplete popups, error banners,
+    # and new rows become explicit feedback instead of something the model must notice unaided.
+    mutation_diff: bool = False
 
     def notes_gated(self, goal: str) -> bool:
         return self.note_pad and bool(re.search(
@@ -995,6 +999,15 @@ def build(name: str, model: str = "", endpoint: str = "", **_: Any) -> Any:
                                   scripted_drag=True, auto_complete=True, som=False,
                                   native_pickers=True, verify_terminal=True, post_mouse_vision=True,
                                   multi_cap=6, fill_verify=True, **v17)
+    if name == "osw-llm-v39":  # v35 + mutation-diff action feedback (Agent-E observer, text-side)
+        v39 = dict(v7, system=OSW_SYSTEM_V8 + OSW_SYSTEM_V9_WIDGETS + OSW_SYSTEM_V16 + OSW_SYSTEM_V30,
+                   max_tokens=800)
+        return OpenSwarmLlmPolicy(name=name, multi=True, vision="progressive", fastpath=True,
+                                  scripted_drag=True, auto_complete=True, som=False,
+                                  native_pickers=True, verify_terminal=True, post_mouse_vision=True,
+                                  multi_cap=6, fill_verify=True, dispatch=True, offscreen=True,
+                                  local_ctx=True, blocker_probe=True, suppress_wrappers=True,
+                                  force_unblock=True, native_js_fallback=True, mutation_diff=True, **v39)
     if name == "osw-llm-v38":  # v35 + table->markdown page rendering (AgentOccam action_reformat_table)
         v38 = dict(v7, system=OSW_SYSTEM_V8 + OSW_SYSTEM_V9_WIDGETS + OSW_SYSTEM_V16 + OSW_SYSTEM_V30,
                    max_tokens=800)

e2e/browser-v3/arena/run.py

@@ -236,9 +236,28 @@ def run_episode(arm: str, task: str, seed: int, rec: Recorder, args: argparse.Na
                 break
             if ep.first_action_s == 0.0:
                 ep.first_action_s = time.time() - t0
+            # v39 (gated, ingested from Agent-E's mutation observer): snapshot the page text
+            # before the action so the delta after it can ride into history as feedback.
+            pre_text = ""
+            if getattr(policy, "mutation_diff", False):
+                try:
+                    pre_text = perception.page_text(obs, limit=2000)
+                except Exception:
+                    pass
             t_act = time.time()
             obs, reward, terminated, truncated, _ = with_deadline(
                 lambda: env.step(decision.action), args.step_timeout)
+            if getattr(policy, "mutation_diff", False) and hasattr(policy, "history"):
+                try:
+                    post_text = perception.page_text(obs, limit=2000)
+                    pre_lines = set(pre_text.split("\n"))
+                    fresh = [l.strip() for l in post_text.split("\n")
+                             if l.strip() and l not in pre_lines][:4]
+                    if fresh:
+                        policy.history.append(
+                            "(page reacted: new text appeared -> " + " | ".join(fresh)[:220] + ")")
+                except Exception:
+                    pass
             rec_step.action_ms = (time.time() - t_act) * 1000
             rec_step.reward = float(reward or 0)
             err = str(obs.get("last_action_error") or "")