From 2f522cc78572d2eea29442093e14d8a1a0dcd849 Mon Sep 17 00:00:00 2001
From: fan wu <336798967+FanWu-ai@users.noreply.github.com>
Date: Sun, 11 Oct 2026 14:44:44 -0700
Subject: [PATCH] Route nested completion after any whitespace

Recognize whitespace consistently with the existing splitter and trimmer,
so tabs and Unicode separators enter the nested completion branch.

AI assistance: OpenAI Codex.
---
 src/prompt_toolkit/completion/nested.py |  6 +--
 tests/test_completion.py                | 49 +++++++++++++++++++++++++
 2 files changed, 52 insertions(+), 3 deletions(-)

diff --git a/src/prompt_toolkit/completion/nested.py b/src/prompt_toolkit/completion/nested.py
index 5c18114ef..8487cbd6c 100644
--- a/src/prompt_toolkit/completion/nested.py
+++ b/src/prompt_toolkit/completion/nested.py
@@ -84,9 +84,9 @@ def get_completions(
         text = document.text_before_cursor.lstrip()
         stripped_len = len(document.text_before_cursor) - len(text)
 
-        # If there is a space, check for the first term, and use a
+        # If there is whitespace, check for the first term, and use a
         # subcompleter.
-        if " " in text:
+        if any(c.isspace() for c in text):
             first_term = text.split()[0]
             completer = self.options.get(first_term)
 
@@ -102,7 +102,7 @@ def get_completions(
 
                 yield from completer.get_completions(new_document, complete_event)
 
-        # No space in the input: behave exactly like `WordCompleter`.
+        # No whitespace in the input: behave exactly like `WordCompleter`.
         else:
             completer = WordCompleter(
                 list(self.options.keys()), ignore_case=self.ignore_case
diff --git a/tests/test_completion.py b/tests/test_completion.py
index 8b3541af0..3c8871d8a 100644
--- a/tests/test_completion.py
+++ b/tests/test_completion.py
@@ -6,6 +6,8 @@
 import tempfile
 from contextlib import contextmanager
 
+import pytest
+
 from prompt_toolkit.completion import (
     CompleteEvent,
     FuzzyWordCompleter,
@@ -444,6 +446,53 @@ def test_nested_completer():
     assert {c.text for c in completions} == {"brief"}
 
 
+@pytest.mark.parametrize(
+    "separator", [" ", "\t", "\n", "\r", "\v", "\f", "\u00a0", "\u2003"]
+)
+@pytest.mark.parametrize("word", ["", "ve"])
+def test_nested_completer_whitespace_separators(separator, word):
+    completer = NestedCompleter.from_nested_dict({"show": {"version": None}})
+    before_cursor = " \tshow" + separator + word
+    document = Document(before_cursor + " suffix", cursor_position=len(before_cursor))
+
+    completions = completer.get_completions(document, CompleteEvent())
+
+    assert [(c.text, c.start_position) for c in completions] == [
+        ("version", -len(word))
+    ]
+
+
+@pytest.mark.parametrize("command", ["exit", "unknown"])
+@pytest.mark.parametrize("separator", [" ", "\t", "\n", "\u2003"])
+def test_nested_completer_whitespace_terminal_and_unknown(command, separator):
+    completer = NestedCompleter.from_nested_dict(
+        {"show": {"version": None}, "exit": None}
+    )
+
+    completions = completer.get_completions(
+        Document(command + separator), CompleteEvent()
+    )
+
+    assert list(completions) == []
+
+
+def test_nested_completer_mixed_whitespace_multiple_levels():
+    completer = NestedCompleter.from_nested_dict({"show": {"ip": {"route": None}}})
+
+    completions = completer.get_completions(Document("show\tip\nro"), CompleteEvent())
+
+    assert [(c.text, c.start_position) for c in completions] == [("route", -2)]
+
+
+@pytest.mark.parametrize("text", ["", " \t\n", "sh", "\tsh"])
+def test_nested_completer_whitespace_root_controls(text):
+    completer = NestedCompleter.from_nested_dict({"show": {"version": None}})
+
+    completions = completer.get_completions(Document(text), CompleteEvent())
+
+    assert [c.text for c in completions] == ["show"]
+
+
 def test_deduplicate_completer():
     def create_completer(deduplicate: bool):
         return merge_completers(