[eric] browser: a learned skill no longer disarms the fast write path on sends

backend/apps/agents/browser/browser_agent.py

@@ -1148,21 +1148,23 @@ async def run_browser_agent(
     # Removal tasks never replay a skill (see the record gate): a delete is a destructive one-shot,
     # not a replayable nav prefix, so a stale delete-"skill" of scrolls must not hijack it.
     p_task_is_removal = is_removal_task(skill_key_task)
+    # Computed here (pure, task-only) so the skill gate, prestage, and every dispatch tier below
+    # share one verdict. `task` here is prompt + an aux-written routing brief (compose_task), and
+    # the brief's prose can read informational and wrongly disarm a real send (facebook: the brief
+    # tripped the info-ask gate while the user's own "start a post" is plainly an action). The
+    # user's words are authoritative, so a send stands if EITHER the composed task OR the raw
+    # prompt says action.
+    task_is_send = not (deliverable_is_informational("", task)
+                        and deliverable_is_informational("", user_prompt or task))
     p_early_host = browser_skills.host_of(initial_url or current_url or next(iter(re.findall(r"https?://\S+", task)), ""))
-    p_skip_prestage_for_skill = bool(p_early_host and not p_task_is_removal
-                                     and browser_skills.find_skill(p_early_host, skill_key_task))
+    p_skip_prestage_for_skill = browser_skills.replay_owns_nav(
+        p_early_host, bool(browser_skills.find_skill(p_early_host, skill_key_task)),
+        p_task_is_removal, task_is_send)
     if p_skip_prestage_for_skill:
         logger.info(f"[browser-skills] skill exists for {p_early_host}; skipping prestage (replay owns the nav)")
 
     from backend.apps.agents.browser import browser_prestage
     from backend.apps.agents.browser import browser_plan_dispatch
-    # Computed here (pure, task-only) so prestage + every dispatch tier below shares one verdict.
-    # `task` here is prompt + an aux-written routing brief (compose_task), and the brief's prose
-    # can read informational and wrongly disarm a real send (facebook: the brief tripped the
-    # info-ask gate while the user's own "start a post" is plainly an action). The user's words
-    # are authoritative, so a send stands if EITHER the composed task OR the raw prompt says action.
-    task_is_send = not (deliverable_is_informational("", task)
-                        and deliverable_is_informational("", user_prompt or task))
     if (browser_prestage.prestage_enabled() and not app_mode and not cancel_event.is_set()
             and not p_skip_prestage_for_skill):
         try:

backend/apps/agents/browser/browser_skills.py

@@ -798,6 +798,23 @@ def hint_step_adopted(step_key: tuple, action_log: list[dict]) -> bool:
     return False
 
 
+def replay_owns_nav(host: str, has_skill: bool, task_is_removal: bool, task_is_send: bool) -> bool:
+    """Should a learned skill's replay take over navigation, letting the caller skip prestage?
+
+    Yes for a READ: the replayed prefix does the same navigation prestage would aux-drive, faster.
+
+    No for a SEND, and this is the part that was wrong. Prestage is also what hands the send-script
+    its composer perception; skip it and the entire fill/click/receipt tail is unreachable, so the
+    model falls back to burning 4-5 turns. Measured live on x.com with a learned skill present:
+    5/5 writes went the slow way at 41-146s (median ~57s) with the receipt never speaking, against
+    19.4s with the script armed. Prestage on an already-loaded page costs ~2-5s.
+
+    No for a removal either: a delete is a destructive one-shot, not a replayable nav prefix, so a
+    stale delete-"skill" made of scrolls must never hijack it.
+    """
+    return bool(host and has_skill and not task_is_removal and not task_is_send)
+
+
 def mark_replay_succeeded(host: str, task: str) -> None:
     """A replay ran end to end. Count it and, if the skill was still on
     probation, PROMOTE it to trusted (the verify gate just passed)."""

backend/tests/test_skill_replay_vs_send_script.py

@@ -0,0 +1,67 @@
+"""A learned skill must not disarm the fast write path.
+
+Measured live on x.com 2026-07-28. A skill had been learned for the host, so every write took the
+"skill exists ... skipping prestage (replay owns the nav)" branch. Prestage is also what hands the
+send-script its composer perception, so with it skipped the whole fill/click/receipt tail was
+unreachable and the model fell back to 4-5 turns:
+
+    with a skill (replay owns nav)   5/5 writes, 41-146s, median ~57s, receipt never spoke
+    with the send-script armed       19.4s, receipt correct
+
+The skip was a real optimisation for READS, where the replayed prefix genuinely replaces prestage's
+navigation. It just was never true for sends. Prestage on an already-loaded page measured 1.9-5.0s,
+so a send trades a few seconds to save tens.
+
+This is the second time this exact interaction bit: the removal case was already carved out because
+a stale delete-"skill" of scrolls could hijack a destructive one-shot. Same shape, so it is worth a
+pure predicate with a test rather than a condition buried in a 2000-line function.
+"""
+from backend.apps.agents.browser import browser_skills as bs
+
+
+def test_a_read_with_a_learned_skill_lets_replay_own_the_nav():
+    """The optimisation this branch exists for must survive."""
+    assert bs.replay_owns_nav("x.com", has_skill=True, task_is_removal=False, task_is_send=False)
+
+
+def test_a_send_keeps_its_prestage_even_when_a_skill_exists():
+    """The regression: skipping here costs the send-script its composer perception."""
+    assert not bs.replay_owns_nav("x.com", has_skill=True, task_is_removal=False, task_is_send=True)
+
+
+def test_a_removal_never_replays_a_skill():
+    """A delete is a destructive one-shot, not a replayable nav prefix."""
+    assert not bs.replay_owns_nav("x.com", has_skill=True, task_is_removal=True, task_is_send=False)
+
+
+def test_no_skill_means_nothing_to_replay():
+    assert not bs.replay_owns_nav("x.com", has_skill=False, task_is_removal=False, task_is_send=False)
+
+
+def test_no_host_means_nothing_to_replay():
+    """host_of returns "" for a task with no resolvable URL; that must not read as a skill hit."""
+    assert not bs.replay_owns_nav("", has_skill=True, task_is_removal=False, task_is_send=False)
+
+
+def test_a_send_that_is_also_a_removal_still_stands_down():
+    """is_removal_task and task_is_send both fire on "delete the post that says X" (the classifier
+    keys on the verb). Either one alone must be enough to keep replay out."""
+    assert not bs.replay_owns_nav("x.com", has_skill=True, task_is_removal=True, task_is_send=True)
+
+
+def test_the_predicate_returns_a_real_bool():
+    """It feeds an `if`; a truthy string or None would still work by accident and then stop working
+    the moment someone logs or serialises it."""
+    for send in (True, False):
+        got = bs.replay_owns_nav("x.com", True, False, send)
+        assert got is True or got is False
+
+
+def test_the_agent_uses_the_predicate_rather_than_reinventing_the_condition():
+    """The whole point of extracting it. If someone re-inlines the check, these tests would keep
+    passing while the live path regressed, which is exactly how this bug survived the first time."""
+    src = (bs.__file__).replace("browser_skills.py", "browser_agent.py")
+    with open(src) as f:
+        text = f.read()
+    assert "browser_skills.replay_owns_nav(" in text
+    assert "p_skip_prestage_for_skill = bool(" not in text, "the condition was re-inlined"