diff --git a/README.md b/README.md
index df30c74..41f4900 100644
--- a/README.md
+++ b/README.md
@@ -68,10 +68,15 @@ launchctl bootstrap gui/$(id -u) ~/Library/LaunchAgents/ai.shre.pulse-bridge.pli
   only (the first `@handle` in a message that matches a workspace agent
   triggers an AI reply). There is no user mention/notification hook, so
   needs-you escalations are the literal text `@nir NEEDS YOU: …`.
-- **Mention trap defence:** all ledger-derived text has `@` neutralised
-  with a zero-width space so an `@ellie` in an item detail can never
-  trigger an AI reply in the feed. Only the bridge's own `@nir` (which
-  matches no agent, hence inert) is emitted raw.
+- **Mention path is broken on this instance (found during smoke):** ANY
+  `@handle` in a message makes `POST …/messages` **500 after the row is
+  inserted** — the mention agent-lookup queries a nonexistent `url_key`
+  column on `agents` (`comms.ts` ~line 226; error in mib007 stderr log).
+  Retrying such a failure duplicates the message. The bridge therefore
+  (a) zwsp-neutralises **every** `@` it emits, including its own
+  `@nir` escalation (renders identically in the UI), and (b) treats an
+  HTTP error on a *comment* as non-retryable (`DROP … comment not
+  retried` in the log) — comments are best-effort; posts still retry.
 - Updates for items that pre-date the bridge and were never seeded
   (closed before first run) are skipped with a log line — there is no
   post to comment on.
diff --git a/bridge.py b/bridge.py
index dc73fb9..1fe9cf4 100644
--- a/bridge.py
+++ b/bridge.py
@@ -115,8 +115,11 @@ def neutralize(text: str) -> str:
     """Insert a zero-width space after '@' in ledger-derived text.
 
     mib007's comms route treats the FIRST '@handle' in a message as an agent
-    mention and fires an AI reply into the thread (e.g. @ellie). Ledger text
-    must never trigger that; only the bridge's own deliberate mention may.
+    mention: a matching agent fires an AI reply into the thread, and on this
+    instance ANY mention 500s after the insert (the agent lookup references a
+    nonexistent url_key column). So no bridge-emitted text may ever contain a
+    bare '@handle' — including the bridge's own needs-you escalation, which is
+    emitted zwsp-neutralised and renders identically in the UI.
     """
     return (text or "").replace("@", "@​")
 
@@ -151,8 +154,8 @@ def update_body(rec: dict) -> str:
     stage = rec.get("stage")
     note = neutralize(rec.get("note", ""))
     if kind == "needs-you":
-        lines.append(f"@{MENTION} NEEDS YOU: this item is now waiting on a human."
-                     + (f" — {note}" if note else ""))
+        lines.append(neutralize(f"@{MENTION}") + " NEEDS YOU: this item is now"
+                     " waiting on a human." + (f" — {note}" if note else ""))
         note = ""  # already included
     elif kind == "failed":
         where = f" at {stage}" if stage else ""
@@ -249,7 +252,14 @@ def comment(state: dict, ledger_id: str, content: str, what: str) -> None:
     if not post_id:
         log(f"SKIP {what} {ledger_id[:8]}: no mapped post (predates bridge)")
         return
-    msg = send_message(ensure_channel(state), content, thread_id=post_id)
+    try:
+        msg = send_message(ensure_channel(state), content, thread_id=post_id)
+    except urllib.error.HTTPError as e:
+        # mib007 comms can 500 AFTER the insert (proven: mention-path crash),
+        # so retrying a failed comment risks duplicates. Comments are
+        # best-effort: log and move on instead of blocking the checkpoint.
+        log(f"DROP {what} {ledger_id[:8]}: HTTP {e.code} (comment not retried)")
+        return
     log(f"{what:6} {ledger_id[:8]} -> comment {msg['id']}")