[eric] browser: make a read wait until the page stops growing, not just until it looks long enough

backend/tests/test_browser_read_script.py

@@ -14,8 +14,14 @@ class Resp:
 
 
 class Aux:
-    def __init__(self, text): self.txt = text; self.messages = self; self.calls = 0
-    async def create(self, **kw): self.calls += 1; return Resp(self.txt)
+    def __init__(self, text):
+        self.txt = text; self.messages = self; self.calls = 0; self.last_page = ""
+
+    async def create(self, **kw):
+        self.calls += 1
+        # Keep what the aux was actually shown: which page reached it IS the hydration contract.
+        self.last_page = str(kw.get("messages", [{}])[0].get("content", ""))
+        return Resp(self.txt)
 
 
 def tool_returning(text):
@@ -28,6 +34,65 @@ def tool_returning(text):
 PAGE = "Tyler Chen\nHe/Him · 1st\nSomething Here\nIrvine, California\nEntrepreneurs First\n" + ("filler " * 200)
 
 
+def tool_returning_sequence(pages):
+    """A page that changes between reads, like an SPA finishing its render."""
+    seen = []
+
+    async def run_tool(name, params, browser_id, tab_id):
+        assert name == "BrowserGetText"
+        seen.append(len(seen))
+        return {"text": pages[min(len(seen) - 1, len(pages) - 1)]}
+    run_tool.seen = seen
+    return run_tool
+
+
+# Chrome that clears the 500-char floor while the actual content is still missing. This is the
+# shape that made the bug invisible: it is long enough to look like a real page.
+CHROME_ONLY = ("Home Feed My Network Jobs Messaging Notifications Me Work "
+               "Skip to main content Keyboard shortcuts Close jump menu " * 12)
+HYDRATED = CHROME_ONLY + "\nTyler Chen\nSomething Here\nEntrepreneurs First\n" + ("filler " * 200)
+
+
+def test_waits_for_the_page_to_stop_growing(monkeypatch):
+    """The false-clean: a hydrating SPA crosses the char floor on nav and footer chrome long before
+    the content lands. Answering from that first passing read produces a CONFIDENT WRONG answer,
+    because the aux reports what it can see and nothing declines, so the INSUFFICIENT retry never
+    fires. Two reads have to agree the page stopped growing before the aux sees anything."""
+    monkeypatch.setattr(rs, "P_THIN_SETTLE_S", 0)
+    monkeypatch.setattr(rs, "P_STABLE_SETTLE_S", 0)
+    aux = Aux("His title is \"Something Here\".")
+    tool = tool_returning_sequence([CHROME_ONLY, HYDRATED, HYDRATED])
+    out = asyncio.run(rs.run_read_script(aux, "m", "find tyler chen's title", "b1", "t1", tool))
+
+    assert out == "His title is \"Something Here\"."
+    assert len(tool.seen) >= 3, "must re-read until two reads agree, not answer off the first"
+    sent = aux.last_page
+    assert "Tyler Chen" in sent, "the aux must be handed the HYDRATED page, not the chrome-only one"
+
+
+def test_a_settled_page_still_answers_without_extra_waiting(monkeypatch):
+    """The guard must not turn every read into a slow read: a page that is already done answers as
+    soon as two reads agree, which is immediately."""
+    monkeypatch.setattr(rs, "P_THIN_SETTLE_S", 0)
+    monkeypatch.setattr(rs, "P_STABLE_SETTLE_S", 0)
+    aux = Aux("answer")
+    tool = tool_returning_sequence([HYDRATED, HYDRATED])
+    assert asyncio.run(rs.run_read_script(aux, "m", "q", "b1", "t1", tool)) == "answer"
+    assert len(tool.seen) == 2, "a settled page costs exactly one confirming re-read"
+
+
+def test_a_page_that_never_settles_still_answers_from_the_last_read(monkeypatch):
+    """Something that keeps streaming forever (a live feed) must not fail closed to the loop just
+    for being busy; after the read budget we use the fullest page we got."""
+    monkeypatch.setattr(rs, "P_THIN_SETTLE_S", 0)
+    monkeypatch.setattr(rs, "P_STABLE_SETTLE_S", 0)
+    grows = [HYDRATED + ("more " * 200 * i) for i in range(1, 8)]
+    aux = Aux("answer")
+    tool = tool_returning_sequence(grows)
+    assert asyncio.run(rs.run_read_script(aux, "m", "q", "b1", "t1", tool)) == "answer"
+    assert len(tool.seen) == rs.MAX_READS
+
+
 def test_flag_gate(monkeypatch):
     monkeypatch.delenv("OSW_READ_SCRIPT", raising=False)
     assert rs.read_script_enabled() is False