diff --git a/EvoScientist/commands/_completion_engine.py b/EvoScientist/commands/_completion_engine.py
index 2b52b22..ac094e2 100644
--- a/EvoScientist/commands/_completion_engine.py
+++ b/EvoScientist/commands/_completion_engine.py
@@ -58,12 +58,20 @@ def compute_completions(text: str, cursor_pos: int) -> CompletionResult:
         commands = cmd_manager.list_commands()
         matches = [(c, d) for c, d in commands if c.startswith(prefix)]
 
+        # Whether the typed prefix is itself a complete command name. Checked
+        # via membership rather than ``len(matches) == 1`` so a command whose
+        # name is a strict prefix of another (e.g. ``/model`` vs
+        # ``/model-fallback``) still counts as an exact match — otherwise the
+        # popup never hides on the shorter command and Enter completes instead
+        # of submitting it.
+        exact = any(c == prefix for c, _ in matches)
+
         # Exact match with no trailing space → hide
-        if len(matches) == 1 and matches[0][0] == prefix and not has_trailing_space:
+        if exact and not has_trailing_space:
             return CompletionResult(CompletionKind.EMPTY, [])
 
         # Exact match + trailing space + has subcommands → show subcommands
-        if len(matches) == 1 and matches[0][0] == prefix and has_trailing_space:
+        if exact and has_trailing_space:
             if not cmd_manager.get_subcommands(prefix):
                 return CompletionResult(CompletionKind.EMPTY, [])
             sub_items = cmd_manager.list_subcommands(cmd_name)
diff --git a/tests/test_cli_completion.py b/tests/test_cli_completion.py
index a9224d1..606ae22 100644
--- a/tests/test_cli_completion.py
+++ b/tests/test_cli_completion.py
@@ -29,6 +29,20 @@ class TestSlashCommandCompleter:
         completions = list(completer.get_completions(_doc("/help"), None))
         assert completions == []
 
+    def test_exact_command_hides_even_when_prefix_of_another(self):
+        """Regression for #293: ``/model`` must hide on exact match so Enter
+        submits it, even though ``/model-fallback`` shares the prefix. Before
+        the fix the popup stayed visible (two prefix matches) and the TUI's
+        Enter handler completed the text instead of executing the command.
+        """
+        completer = SlashCommandCompleter()
+        # Sanity: both commands share the prefix, so a partial prefix lists both.
+        partial = {c.text for c in completer.get_completions(_doc("/mode"), None)}
+        assert {"/model", "/model-fallback"} <= partial
+        # Exact ``/model`` with no trailing space → hide.
+        completions = list(completer.get_completions(_doc("/model"), None))
+        assert completions == []
+
     def test_non_slash_returns_empty(self):
         completer = SlashCommandCompleter()
         completions = list(completer.get_completions(_doc("hello"), None))