diff --git a/core/models.py b/core/models.py
index 6914b20..1adae65 100644
--- a/core/models.py
+++ b/core/models.py
@@ -76,8 +76,20 @@ class Session:
             _session_manager._persist_message(self.id, message)
 
     def get_context_messages(self) -> List[Dict[str, Any]]:
-        """Get messages in format for LLM API."""
-        return [msg.to_dict() for msg in self.history]
+        """Get messages in format for LLM API.
+
+        Slash-command / setup replies are persisted to history so they render
+        in the transcript, but they are UI chatter (e.g. ``/setup ...`` and its
+        status lines) the user never meant as conversation. They carry
+        ``metadata.source == "slash"``; exclude them here so they never reach
+        the model. Display/history-load paths use the raw ``history`` and are
+        unaffected.
+        """
+        return [
+            msg.to_dict()
+            for msg in self.history
+            if (msg.metadata or {}).get("source") != "slash"
+        ]
 
     def get(self, key: str, default=None):
         """Dict-like access for compatibility."""
diff --git a/static/js/slashCommands.js b/static/js/slashCommands.js
index 97b3fb3..19bcd7a 100644
--- a/static/js/slashCommands.js
+++ b/static/js/slashCommands.js
@@ -5880,7 +5880,9 @@ async function handleSlashCommand(input) {
   let args = parts.slice(1);
   const ctx = _makeCtx();
   let _userShown = false;
-  function _showUser() { if (!_userShown) { _userShown = true; _addMessage('user', input); _persistMsg('user', input); } }
+  // Tag the echoed command with source:'slash' so it renders in the transcript
+  // but is excluded from LLM context (get_context_messages), like the replies.
+  function _showUser() { if (!_userShown) { _userShown = true; _addMessage('user', input); _persistMsg('user', input, { source: 'slash' }); } }
 
   try {
     // --- Check for --help / -h on any command ---
diff --git a/tests/test_session_context_excludes_slash.py b/tests/test_session_context_excludes_slash.py
new file mode 100644
index 0000000..e9ff152
--- /dev/null
+++ b/tests/test_session_context_excludes_slash.py
@@ -0,0 +1,44 @@
+"""Regression: slash-command / setup messages must not reach LLM context.
+
+Slash replies (and the echoed `/setup ...` command) are persisted to history so
+they render in the transcript, tagged ``metadata.source == "slash"``. They are
+UI chatter the user never meant as conversation, so ``get_context_messages``
+(the LLM-API view) must exclude them while the raw history keeps them for
+display. See issue #2634.
+"""
+
+from core.models import Session, ChatMessage
+
+
+def _session_with_slash():
+    s = Session(id="s1", name="t", endpoint_url="http://x/v1", model="m")
+    s.add_message(ChatMessage("user", "hi, give me a recipe"))
+    s.add_message(ChatMessage("user", "/setup copilot", metadata={"source": "slash"}))
+    s.add_message(ChatMessage("assistant", "Starting GitHub Copilot sign-in...", metadata={"source": "slash"}))
+    s.add_message(ChatMessage("assistant", "Here is a recipe", metadata={"model": "m"}))
+    return s
+
+
+def test_context_excludes_slash_messages():
+    ctx = _session_with_slash().get_context_messages()
+    contents = [m["content"] for m in ctx]
+    assert "hi, give me a recipe" in contents
+    assert "Here is a recipe" in contents
+    # Slash command + its status reply are filtered out of LLM context.
+    assert "/setup copilot" not in contents
+    assert all("sign-in" not in c for c in contents)
+    assert len(ctx) == 2
+
+
+def test_history_still_keeps_slash_messages_for_display():
+    s = _session_with_slash()
+    # Raw history (what the UI renders) is untouched.
+    assert len(s.history) == 4
+    assert any(m.content == "/setup copilot" for m in s.history)
+
+
+def test_no_metadata_messages_are_kept():
+    s = Session(id="s2", name="t", endpoint_url="http://x/v1", model="m")
+    s.add_message(ChatMessage("user", "plain"))
+    s.add_message(ChatMessage("assistant", "reply"))
+    assert [m["content"] for m in s.get_context_messages()] == ["plain", "reply"]