fix: Resolve prompt completions at the caret position

src/tau_coding/tui/app.py

@@ -4766,8 +4766,27 @@ def on_text_area_changed(self, event: TextArea.Changed) -> None:
             return
         prompt = self.query_one("#prompt", PromptInput)
         prompt.sync_pending_paste()
-        self._sync_prompt_shell_mode(event.text_area.text)
-        self._completion_state = self._build_completion_state(event.text_area.text)
+        # Read text and cursor from the widget so both come from one snapshot.
+        text = prompt.text
+        self._sync_prompt_shell_mode(text)
+        self._completion_state = self._build_completion_state(text, cursor=prompt.cursor_position)
+        self._refresh_completions()
+
+    def on_text_area_selection_changed(self, event: TextArea.SelectionChanged) -> None:
+        """Close prompt autocomplete when the caret leaves the completed token."""
+        if event.text_area.id != "prompt":
+            return
+        # Edits post SelectionChanged before Changed; check after Changed has rebuilt.
+        self.call_later(self._close_completions_if_caret_left_token)
+
+    def _close_completions_if_caret_left_token(self) -> None:
+        if not self._completion_state.items:
+            return
+        item = self._completion_state.items[0]
+        cursor = self.query_one("#prompt", PromptInput).cursor_position
+        if item.start < cursor <= item.end:
+            return
+        self._completion_state = CompletionState()
         self._refresh_completions()
 
     async def action_submit_prompt(self) -> None:
@@ -6193,12 +6212,14 @@ def action_accept_completion(self) -> None:
             self.screen.action_select_cursor()
             return
         prompt = self.query_one("#prompt", PromptInput)
+        item = self._completion_state.selected
         applied = self._apply_selected_completion(prompt.text)
-        if applied is None:
+        if applied is None or item is None:
             return
         prompt.text = applied
-        prompt.move_cursor(_text_end_location(applied))
-        self._completion_state = self._build_completion_state(prompt.text)
+        cursor = item.cursor_after_apply()
+        prompt.cursor_position = cursor
+        self._completion_state = self._build_completion_state(prompt.text, cursor=cursor)
         self._refresh_completions()
 
     def action_completion_next(self) -> None:
@@ -7431,10 +7452,11 @@ def _toggle_sidebar_visibility(self) -> None:
         state = "shown" if self._sidebar_visibility_override else "hidden"
         self._notify(f"Sidebar {state} for this session.")
 
-    def _build_completion_state(self, text: str) -> CompletionState:
+    def _build_completion_state(self, text: str, *, cursor: int | None = None) -> CompletionState:
         registry = _session_command_registry(self.session)
         return build_completion_state(
             text,
+            cursor=cursor,
             command_registry=registry,
             skills=self.session.skills,
             prompt_templates=self.session.prompt_templates,

src/tau_coding/tui/autocomplete.py

@@ -65,6 +65,10 @@ def apply(self, text: str) -> str:
         """Apply this completion to input text."""
         return f"{text[: self.start]}{self.replacement}{text[self.end :]}"
 
+    def cursor_after_apply(self) -> int:
+        """Return the cursor offset just after the applied replacement."""
+        return self.start + len(self.replacement)
+
 
 @dataclass(frozen=True, slots=True)
 class CompletionState:
@@ -102,6 +106,7 @@ def select_previous(self) -> CompletionState:
 def build_completion_state(
     text: str,
     *,
+    cursor: int | None = None,
     command_registry: CommandRegistry,
     skills: Sequence[Skill],
     prompt_templates: Sequence[PromptTemplate],
@@ -114,12 +119,13 @@ def build_completion_state(
     cwd: Path | None = None,
 ) -> CompletionState:
     """Build autocomplete suggestions for the current prompt text."""
+    cursor = len(text) if cursor is None else max(0, min(cursor, len(text)))
     if not text.startswith("/") or text.startswith("//"):
         if cwd is not None:
-            shell_completions = _shell_path_completions(text=text, cwd=cwd)
+            shell_completions = _shell_path_completions(text=text, cursor=cursor, cwd=cwd)
             if shell_completions is not None:
                 return CompletionState(shell_completions)
-            return CompletionState(_file_reference_completions(text=text, cwd=cwd))
+            return CompletionState(_file_reference_completions(text=text, cursor=cursor, cwd=cwd))
         return CompletionState()
 
     token_end = _first_token_end(text)
@@ -129,7 +135,9 @@ def build_completion_state(
         if has_argument_text and _matches_skill_command(token, skills):
             # Skill arguments are prompt text, so @ file references stay available.
             if cwd is not None:
-                return CompletionState(_file_reference_completions(text=text, cwd=cwd))
+                return CompletionState(
+                    _file_reference_completions(text=text, cursor=cursor, cwd=cwd)
+                )
             return CompletionState()
         return CompletionState(_skill_completions(token=token, token_end=token_end, skills=skills))
 
@@ -151,7 +159,7 @@ def build_completion_state(
 
     if has_argument_text and _matches_prompt_template_command(token, prompt_templates):
         if cwd is not None:
-            return CompletionState(_file_reference_completions(text=text, cwd=cwd))
+            return CompletionState(_file_reference_completions(text=text, cursor=cursor, cwd=cwd))
         return CompletionState()
 
     if has_argument_text and _matches_registered_command(token, command_registry):
@@ -167,14 +175,16 @@ def build_completion_state(
     )
 
 
-def _file_reference_completions(*, text: str, cwd: Path) -> tuple[CompletionItem, ...]:
-    token = _active_file_reference_token(text)
+def _file_reference_completions(*, text: str, cursor: int, cwd: Path) -> tuple[CompletionItem, ...]:
+    token = _active_file_reference_token(text, cursor)
     if token is None:
         return ()
     start, end = token
-    prefix = text[start + 1 : end]
+    prefix = text[start + 1 : cursor]
+    existing = text[start:end]
     external_completions = _external_file_reference_completions(
         prefix=prefix,
+        existing=existing,
         start=start,
         end=end,
         cwd=cwd,
@@ -188,6 +198,8 @@ def _file_reference_completions(*, text: str, cwd: Path) -> tuple[CompletionItem
         if prefix.lower() not in relative.lower():
             continue
         display = f"@{relative}{'/' if path.is_dir() else ''}"
+        if display == existing:
+            continue
         suggestions.append(
             CompletionItem(
                 display=display,
@@ -204,13 +216,15 @@ def _file_reference_completions(*, text: str, cwd: Path) -> tuple[CompletionItem
 
 
 def _external_file_reference_completions(
-    *, prefix: str, start: int, end: int, cwd: Path
+    *, prefix: str, existing: str, start: int, end: int, cwd: Path
 ) -> tuple[CompletionItem, ...] | None:
     if prefix == ".." or prefix.endswith("/.."):
         target = cwd / prefix
         if not target.is_dir():
             return ()
         display = f"@{prefix}/"
+        if display == existing:
+            return ()
         return (
             CompletionItem(
                 display=display,
@@ -244,7 +258,7 @@ def _external_file_reference_completions(
         if not child.name.lower().startswith(name_prefix.lower()):
             continue
         display = f"@{parent_text}/{child.name}{'/' if child.is_dir() else ''}"
-        if display == f"@{prefix}":
+        if display == existing:
             continue
         suggestions.append(
             CompletionItem(
@@ -261,13 +275,15 @@ def _external_file_reference_completions(
     return tuple(suggestions)
 
 
-def _active_file_reference_token(text: str) -> tuple[int, int] | None:
-    cursor = len(text)
+def _active_file_reference_token(text: str, cursor: int) -> tuple[int, int] | None:
     token_start = max(text.rfind(" ", 0, cursor), text.rfind("\n", 0, cursor)) + 1
     at_index = text.rfind("@", token_start, cursor)
     if at_index == -1:
         return None
-    return at_index, cursor
+    end = cursor
+    while end < len(text) and not text[end].isspace():
+        end += 1
+    return at_index, end
 
 
 def _iter_file_reference_paths(cwd: Path) -> tuple[Path, ...]:
@@ -298,13 +314,17 @@ def _is_ignored_file_completion_path(path: Path, *, cwd: Path) -> bool:
     return any(part in IGNORED_FILE_COMPLETION_DIRS for part in relative_parts)
 
 
-def _shell_path_completions(*, text: str, cwd: Path) -> tuple[CompletionItem, ...] | None:
+def _shell_path_completions(
+    *, text: str, cursor: int, cwd: Path
+) -> tuple[CompletionItem, ...] | None:
     prefix_span = _shell_command_prefix_span(text)
     if prefix_span is None:
         return None
+    if cursor < prefix_span[1]:
+        return ()
 
-    start, end = _active_shell_path_token(text=text, command_start=prefix_span[1])
-    token = text[start:end]
+    start, end = _active_shell_path_token(text=text, cursor=cursor, command_start=prefix_span[1])
+    token = text[start:cursor]
     if not token:
         return ()
 
@@ -332,7 +352,7 @@ def _shell_path_completions(*, text: str, cwd: Path) -> tuple[CompletionItem, ..
             continue
         relative = child.relative_to(cwd).as_posix()
         replacement = f"{replacement_prefix}{relative}{'/' if child.is_dir() else ''}"
-        if replacement == token:
+        if replacement == text[start:end]:
             continue
         suggestions.append(
             CompletionItem(
@@ -359,8 +379,7 @@ def _shell_command_prefix_span(text: str) -> tuple[int, int] | None:
     return None
 
 
-def _active_shell_path_token(*, text: str, command_start: int) -> tuple[int, int]:
-    cursor = len(text)
+def _active_shell_path_token(*, text: str, cursor: int, command_start: int) -> tuple[int, int]:
     token_start = command_start
     escaped = False
     for index in range(cursor - 1, command_start - 1, -1):
@@ -374,7 +393,20 @@ def _active_shell_path_token(*, text: str, command_start: int) -> tuple[int, int
         if char.isspace():
             token_start = index + 1
             break
-    return token_start, cursor
+    return token_start, _shell_token_end(text, cursor)
+
+
+def _shell_token_end(text: str, cursor: int) -> int:
+    index = cursor
+    while index < len(text):
+        char = text[index]
+        if char == "\\":
+            index += 2
+            continue
+        if char.isspace():
+            return index
+        index += 1
+    return len(text)
 
 
 def _parse_shell_path_token(token: str) -> tuple[str, str, str] | None:

tests/test_tui_app.py

@@ -3056,6 +3056,84 @@ async def test_tui_submit_multiple_large_pastes_sends_all_full_content() -> None
     assert session.prompt_texts == [f"{first}\nthen\n{second}"]
 
 
+@pytest.mark.anyio
+async def test_tui_caret_leaving_mention_closes_completions_but_does_not_open(
+    tmp_path: Path,
+) -> None:
+    (tmp_path / "src").mkdir()
+    (tmp_path / "src" / "app.py").write_text("print('hi')\n", encoding="utf-8")
+    session = FakeSession()
+    session.cwd = tmp_path
+    app = TauTuiApp(session)
+
+    async with app.run_test() as pilot:
+        prompt = app.query_one("#prompt", PromptInput)
+        prompt.text = "look at @a and fix it"
+        prompt.cursor_position = len("look at @a")
+        prompt.insert("p")
+        await pilot.pause()
+        assert [item.display for item in app._completion_state.items] == ["@src/app.py"]
+
+        prompt.cursor_position = len("look at @a")
+        await pilot.pause()
+        assert [item.display for item in app._completion_state.items] == ["@src/app.py"]
+
+        prompt.cursor_position = len("look at @ap and")
+        await pilot.pause()
+        assert app._completion_state.items == ()
+
+        prompt.cursor_position = len("look at @ap")
+        await pilot.pause()
+        assert app._completion_state.items == ()
+
+
+@pytest.mark.anyio
+async def test_tui_enter_submits_with_caret_parked_in_complete_mention(
+    tmp_path: Path,
+) -> None:
+    (tmp_path / "src").mkdir()
+    (tmp_path / "src" / "app.py").write_text("print('hi')\n", encoding="utf-8")
+    session = FakeSession()
+    session.cwd = tmp_path
+    app = TauTuiApp(session)
+
+    async with app.run_test() as pilot:
+        prompt = app.query_one("#prompt", PromptInput)
+        prompt.text = "look at @src/app.py and fix"
+        await pilot.pause()
+        prompt.cursor_position = len("look at @src")
+        await pilot.pause()
+        assert app._completion_state.items == ()
+        await pilot.press("enter")
+        await pilot.pause()
+
+    assert session.prompt_texts == ["look at @src/app.py and fix"]
+
+
+@pytest.mark.anyio
+async def test_tui_accepting_mid_prompt_completion_keeps_cursor_after_mention(
+    tmp_path: Path,
+) -> None:
+    (tmp_path / "src").mkdir()
+    (tmp_path / "src" / "app.py").write_text("print('hi')\n", encoding="utf-8")
+    session = FakeSession()
+    session.cwd = tmp_path
+    app = TauTuiApp(session)
+
+    async with app.run_test() as pilot:
+        prompt = app.query_one("#prompt", PromptInput)
+        prompt.text = "look at @ap and fix it"
+        prompt.cursor_position = len("look at @ap")
+        prompt.insert("p")
+        await pilot.pause()
+        app.action_accept_completion()
+        await pilot.pause()
+
+        assert prompt.text == "look at @src/app.py and fix it"
+        assert prompt.cursor_position == len("look at @src/app.py")
+        assert app._completion_state.items == ()
+
+
 @pytest.mark.anyio
 async def test_tui_app_mounts_sidebar_and_transcript() -> None:
     app = TauTuiApp(FakeSession())