feat(cli): add file path autocomplete in the input prompt (#1545)

When typing a path-like token (./  ../  ~/  /  or containing /),
the CLI now shows filesystem completions in the dropdown menu.
Directories show a trailing slash and 'dir' label; files show
their size. Completions are case-insensitive and capped at 30
entries.

Triggered by tokens like:
  edit ./src/ma     → shows ./src/main.py, ./src/manifest.json, ...
  check ~/doc       → shows ~/docs/, ~/documents/, ...
  read /etc/hos     → shows /etc/hosts, /etc/hostname, ...
  open tools/reg    → shows tools/registry.py

Slash command autocomplete (/help, /model, etc.) is unaffected —
it still triggers when the input starts with /.

Inspired by OpenCode PR #145 (file path completion menu).

Implementation:
- hermes_cli/commands.py: _extract_path_word() detects path-like
  tokens, _path_completions() yields filesystem Completions with
  size labels, get_completions() routes to paths vs slash commands
- tests/hermes_cli/test_path_completion.py: 26 tests covering
  path extraction, prefix filtering, directory markers, home
  expansion, case-insensitivity, integration with slash commands

hermes_cli/commands.py

@@ -7,7 +7,9 @@ interactive CLI.
 
 from __future__ import annotations
 
+import os
 from collections.abc import Callable, Mapping
+from pathlib import Path
 from typing import Any
 
 from prompt_toolkit.completion import Completer, Completion
@@ -92,9 +94,88 @@ class SlashCommandCompleter(Completer):
         """
         return f"{cmd_name} " if cmd_name == word else cmd_name
 
+    @staticmethod
+    def _extract_path_word(text: str) -> str | None:
+        """Extract the current word if it looks like a file path.
+
+        Returns the path-like token under the cursor, or None if the
+        current word doesn't look like a path.  A word is path-like when
+        it starts with ``./``, ``../``, ``~/``, ``/``, or contains a
+        ``/`` separator (e.g. ``src/main.py``).
+        """
+        if not text:
+            return None
+        # Walk backwards to find the start of the current "word".
+        # Words are delimited by spaces, but paths can contain almost anything.
+        i = len(text) - 1
+        while i >= 0 and text[i] != " ":
+            i -= 1
+        word = text[i + 1:]
+        if not word:
+            return None
+        # Only trigger path completion for path-like tokens
+        if word.startswith(("./", "../", "~/", "/")) or "/" in word:
+            return word
+        return None
+
+    @staticmethod
+    def _path_completions(word: str, limit: int = 30):
+        """Yield Completion objects for file paths matching *word*."""
+        expanded = os.path.expanduser(word)
+        # Split into directory part and prefix to match inside it
+        if expanded.endswith("/"):
+            search_dir = expanded
+            prefix = ""
+        else:
+            search_dir = os.path.dirname(expanded) or "."
+            prefix = os.path.basename(expanded)
+
+        try:
+            entries = os.listdir(search_dir)
+        except OSError:
+            return
+
+        count = 0
+        prefix_lower = prefix.lower()
+        for entry in sorted(entries):
+            if prefix and not entry.lower().startswith(prefix_lower):
+                continue
+            if count >= limit:
+                break
+
+            full_path = os.path.join(search_dir, entry)
+            is_dir = os.path.isdir(full_path)
+
+            # Build the completion text (what replaces the typed word)
+            if word.startswith("~"):
+                display_path = "~/" + os.path.relpath(full_path, os.path.expanduser("~"))
+            elif os.path.isabs(word):
+                display_path = full_path
+            else:
+                # Keep relative
+                display_path = os.path.relpath(full_path)
+
+            if is_dir:
+                display_path += "/"
+
+            suffix = "/" if is_dir else ""
+            meta = "dir" if is_dir else _file_size_label(full_path)
+
+            yield Completion(
+                display_path,
+                start_position=-len(word),
+                display=entry + suffix,
+                display_meta=meta,
+            )
+            count += 1
+
     def get_completions(self, document, complete_event):
         text = document.text_before_cursor
         if not text.startswith("/"):
+            # Try file path completion for non-slash input
+            path_word = self._extract_path_word(text)
+            if path_word is not None:
+                yield from self._path_completions(path_word)
             return
 
         word = text[1:]
@@ -120,3 +201,18 @@ class SlashCommandCompleter(Completer):
                     display=cmd,
                     display_meta=f"⚡ {short_desc}",
                 )
+
+
+def _file_size_label(path: str) -> str:
+    """Return a compact human-readable file size, or '' on error."""
+    try:
+        size = os.path.getsize(path)
+    except OSError:
+        return ""
+    if size < 1024:
+        return f"{size}B"
+    if size < 1024 * 1024:
+        return f"{size / 1024:.0f}K"
+    if size < 1024 * 1024 * 1024:
+        return f"{size / (1024 * 1024):.1f}M"
+    return f"{size / (1024 * 1024 * 1024):.1f}G"

tests/hermes_cli/test_path_completion.py

@@ -0,0 +1,184 @@
+"""Tests for file path autocomplete in the CLI completer."""
+
+import os
+from unittest.mock import MagicMock
+
+import pytest
+from prompt_toolkit.document import Document
+from prompt_toolkit.formatted_text import to_plain_text
+
+from hermes_cli.commands import SlashCommandCompleter, _file_size_label
+
+
+def _display_names(completions):
+    """Extract plain-text display names from a list of Completion objects."""
+    return [to_plain_text(c.display) for c in completions]
+
+
+def _display_metas(completions):
+    """Extract plain-text display_meta from a list of Completion objects."""
+    return [to_plain_text(c.display_meta) if c.display_meta else "" for c in completions]
+
+
+@pytest.fixture
+def completer():
+    return SlashCommandCompleter()
+
+
+class TestExtractPathWord:
+    def test_relative_path(self):
+        assert SlashCommandCompleter._extract_path_word("look at ./src/main.py") == "./src/main.py"
+
+    def test_home_path(self):
+        assert SlashCommandCompleter._extract_path_word("edit ~/docs/") == "~/docs/"
+
+    def test_absolute_path(self):
+        assert SlashCommandCompleter._extract_path_word("read /etc/hosts") == "/etc/hosts"
+
+    def test_parent_path(self):
+        assert SlashCommandCompleter._extract_path_word("check ../config.yaml") == "../config.yaml"
+
+    def test_path_with_slash_in_middle(self):
+        assert SlashCommandCompleter._extract_path_word("open src/utils/helpers.py") == "src/utils/helpers.py"
+
+    def test_plain_word_not_path(self):
+        assert SlashCommandCompleter._extract_path_word("hello world") is None
+
+    def test_empty_string(self):
+        assert SlashCommandCompleter._extract_path_word("") is None
+
+    def test_single_word_no_slash(self):
+        assert SlashCommandCompleter._extract_path_word("README.md") is None
+
+    def test_word_after_space(self):
+        assert SlashCommandCompleter._extract_path_word("fix the bug in ./tools/") == "./tools/"
+
+    def test_just_dot_slash(self):
+        assert SlashCommandCompleter._extract_path_word("./") == "./"
+
+    def test_just_tilde_slash(self):
+        assert SlashCommandCompleter._extract_path_word("~/") == "~/"
+
+
+class TestPathCompletions:
+    def test_lists_current_directory(self, tmp_path):
+        (tmp_path / "file_a.py").touch()
+        (tmp_path / "file_b.txt").touch()
+        (tmp_path / "subdir").mkdir()
+
+        old_cwd = os.getcwd()
+        os.chdir(tmp_path)
+        try:
+            completions = list(SlashCommandCompleter._path_completions("./"))
+            names = _display_names(completions)
+            assert "file_a.py" in names
+            assert "file_b.txt" in names
+            assert "subdir/" in names
+        finally:
+            os.chdir(old_cwd)
+
+    def test_filters_by_prefix(self, tmp_path):
+        (tmp_path / "alpha.py").touch()
+        (tmp_path / "beta.py").touch()
+        (tmp_path / "alpha_test.py").touch()
+
+        completions = list(SlashCommandCompleter._path_completions(f"{tmp_path}/alpha"))
+        names = _display_names(completions)
+        assert "alpha.py" in names
+        assert "alpha_test.py" in names
+        assert "beta.py" not in names
+
+    def test_directories_have_trailing_slash(self, tmp_path):
+        (tmp_path / "mydir").mkdir()
+        (tmp_path / "myfile.txt").touch()
+
+        completions = list(SlashCommandCompleter._path_completions(f"{tmp_path}/"))
+        names = _display_names(completions)
+        metas = _display_metas(completions)
+        assert "mydir/" in names
+        idx = names.index("mydir/")
+        assert metas[idx] == "dir"
+
+    def test_home_expansion(self, tmp_path, monkeypatch):
+        monkeypatch.setenv("HOME", str(tmp_path))
+        (tmp_path / "testfile.md").touch()
+
+        completions = list(SlashCommandCompleter._path_completions("~/test"))
+        names = _display_names(completions)
+        assert "testfile.md" in names
+
+    def test_nonexistent_dir_returns_empty(self):
+        completions = list(SlashCommandCompleter._path_completions("/nonexistent_dir_xyz/"))
+        assert completions == []
+
+    def test_respects_limit(self, tmp_path):
+        for i in range(50):
+            (tmp_path / f"file_{i:03d}.txt").touch()
+
+        completions = list(SlashCommandCompleter._path_completions(f"{tmp_path}/", limit=10))
+        assert len(completions) == 10
+
+    def test_case_insensitive_prefix(self, tmp_path):
+        (tmp_path / "README.md").touch()
+
+        completions = list(SlashCommandCompleter._path_completions(f"{tmp_path}/read"))
+        names = _display_names(completions)
+        assert "README.md" in names
+
+
+class TestIntegration:
+    """Test the completer produces path completions via the prompt_toolkit API."""
+
+    def test_slash_commands_still_work(self, completer):
+        doc = Document("/hel", cursor_position=4)
+        event = MagicMock()
+        completions = list(completer.get_completions(doc, event))
+        names = _display_names(completions)
+        assert "/help" in names
+
+    def test_path_completion_triggers_on_dot_slash(self, completer, tmp_path):
+        (tmp_path / "test.py").touch()
+        old_cwd = os.getcwd()
+        os.chdir(tmp_path)
+        try:
+            doc = Document("edit ./te", cursor_position=9)
+            event = MagicMock()
+            completions = list(completer.get_completions(doc, event))
+            names = _display_names(completions)
+            assert "test.py" in names
+        finally:
+            os.chdir(old_cwd)
+
+    def test_no_completion_for_plain_words(self, completer):
+        doc = Document("hello world", cursor_position=11)
+        event = MagicMock()
+        completions = list(completer.get_completions(doc, event))
+        assert completions == []
+
+    def test_absolute_path_triggers_completion(self, completer):
+        doc = Document("check /etc/hos", cursor_position=14)
+        event = MagicMock()
+        completions = list(completer.get_completions(doc, event))
+        names = _display_names(completions)
+        # /etc/hosts should exist on Linux
+        assert any("host" in n.lower() for n in names)
+
+
+class TestFileSizeLabel:
+    def test_bytes(self, tmp_path):
+        f = tmp_path / "small.txt"
+        f.write_text("hi")
+        assert _file_size_label(str(f)) == "2B"
+
+    def test_kilobytes(self, tmp_path):
+        f = tmp_path / "medium.txt"
+        f.write_bytes(b"x" * 2048)
+        assert _file_size_label(str(f)) == "2K"
+
+    def test_megabytes(self, tmp_path):
+        f = tmp_path / "large.bin"
+        f.write_bytes(b"x" * (2 * 1024 * 1024))
+        assert _file_size_label(str(f)) == "2.0M"
+
+    def test_nonexistent(self):
+        assert _file_size_label("/nonexistent_xyz") == ""