[eric] browser: reddit clears its composer without posting, so treat it as a ghost-drop host

backend/apps/agents/browser/browser_delivery_check.py

@@ -21,7 +21,11 @@ from backend.apps.agents.browser import browser_submit_click
 ToolRunner = Callable[[str, dict, str, str], Awaitable[dict]]
 
 # Hosts known to accept-then-silently-drop an automated post. A newly-found one is a one-line add.
-GHOST_DROP_HOSTS = ("youtube.com",)
+# reddit joined 2026-07-31 on live evidence, twice: the r/test submit form clears the composer and
+# the post never appears in r/test/new (markers canary5ef128b9 and canary99b063a2, both audited
+# absent). Without this the cleared composer is trusted as delivery and the user gets told
+# 'Done, I sent "canary..." for you' about a post that does not exist.
+GHOST_DROP_HOSTS = ("youtube.com", "reddit.com")
 
 # What a site says when it REFUSED the write. Only ever consulted inside a live announcement
 # region, never against the whole page, so an unrelated "failed" in an article body can't match.

backend/tests/test_browser_delivery_check.py

@@ -6,18 +6,24 @@ import pytest
 from backend.apps.agents.browser import browser_delivery_check as dc
 
 
-def test_ghost_drop_host_matches_youtube_only():
+def test_ghost_drop_hosts_are_the_ones_that_eat_a_post():
     assert dc.is_ghost_drop_host("https://www.youtube.com/watch?v=abc")
     assert dc.is_ghost_drop_host("https://youtube.com/watch")
     assert dc.is_ghost_drop_host("https://m.youtube.com/watch")
-    # every proven-good write host stays OFF the ghost path (zero added latency there)
+    # reddit joined 2026-07-31 on live evidence, twice: the r/test submit form clears the composer
+    # and the post never lands in r/test/new (markers canary5ef128b9 and canary99b063a2, both
+    # audited absent) while the run announced 'Done, I sent "canary..." for you'. This assertion
+    # used to say the opposite, on the assumption reddit was a proven-good write host.
+    assert dc.is_ghost_drop_host("https://www.reddit.com/r/test/submit")
+    assert dc.is_ghost_drop_host("https://old.reddit.com/r/test")
+    # every still-proven write host stays OFF the ghost path (zero added latency there)
     assert not dc.is_ghost_drop_host("https://x.com/home")
-    assert not dc.is_ghost_drop_host("https://www.reddit.com/r/test")
     assert not dc.is_ghost_drop_host("https://mail.google.com/mail")
     assert not dc.is_ghost_drop_host("https://www.linkedin.com/feed/")
     assert not dc.is_ghost_drop_host("")
     # a lookalike domain must not match the bare-endswith by accident
     assert not dc.is_ghost_drop_host("https://notyoutube.com.evil.test/")
+    assert not dc.is_ghost_drop_host("https://notreddit.com/r/test")
 
 
 def test_probe_expression_escapes_and_truncates():