feat: add inline diff previews for write actions

agent/display.py

@@ -10,13 +10,32 @@
 import sys
 import threading
 import time
+from dataclasses import dataclass, field
+from difflib import unified_diff
+from pathlib import Path
 
 # ANSI escape codes for coloring tool failure indicators
 _RED = "\033[31m"
 _RESET = "\033[0m"
 
 logger = logging.getLogger(__name__)
 
+_ANSI_RESET = "\033[0m"
+_ANSI_DIM = "\033[38;2;150;150;150m"
+_ANSI_FILE = "\033[38;2;180;160;255m"
+_ANSI_HUNK = "\033[38;2;120;120;140m"
+_ANSI_MINUS = "\033[38;2;255;255;255;48;2;120;20;20m"
+_ANSI_PLUS = "\033[38;2;255;255;255;48;2;20;90;20m"
+_MAX_INLINE_DIFF_FILES = 6
+_MAX_INLINE_DIFF_LINES = 80
+
+
+@dataclass
+class LocalEditSnapshot:
+    """Pre-tool filesystem snapshot used to render diffs locally after writes."""
+    paths: list[Path] = field(default_factory=list)
+    before: dict[str, str | None] = field(default_factory=dict)
+
 # =========================================================================
 # Configurable tool preview length (0 = no limit)
 # Set once at startup by CLI or gateway from display.tool_preview_length config.
@@ -218,6 +237,300 @@ def build_tool_preview(tool_name: str, args: dict, max_len: int | None = None) -
     return preview
 
 
+# =========================================================================
+# Inline diff previews for write actions
+# =========================================================================
+
+def _resolved_path(path: str) -> Path:
+    """Resolve a possibly-relative filesystem path against the current cwd."""
+    candidate = Path(os.path.expanduser(path))
+    if candidate.is_absolute():
+        return candidate
+    return Path.cwd() / candidate
+
+
+def _snapshot_text(path: Path) -> str | None:
+    """Return UTF-8 file content, or None for missing/unreadable files."""
+    try:
+        return path.read_text(encoding="utf-8")
+    except (FileNotFoundError, IsADirectoryError, UnicodeDecodeError, OSError):
+        return None
+
+
+def _display_diff_path(path: Path) -> str:
+    """Prefer cwd-relative paths in diffs when available."""
+    try:
+        return str(path.resolve().relative_to(Path.cwd().resolve()))
+    except Exception:
+        return str(path)
+
+
+def _resolve_skill_manage_paths(args: dict) -> list[Path]:
+    """Resolve skill_manage write targets to filesystem paths."""
+    action = args.get("action")
+    name = args.get("name")
+    if not action or not name:
+        return []
+
+    from tools.skill_manager_tool import _find_skill, _resolve_skill_dir
+
+    if action == "create":
+        skill_dir = _resolve_skill_dir(name, args.get("category"))
+        return [skill_dir / "SKILL.md"]
+
+    existing = _find_skill(name)
+    if not existing:
+        return []
+
+    skill_dir = Path(existing["path"])
+    if action in {"edit", "patch"}:
+        file_path = args.get("file_path")
+        return [skill_dir / file_path] if file_path else [skill_dir / "SKILL.md"]
+    if action in {"write_file", "remove_file"}:
+        file_path = args.get("file_path")
+        return [skill_dir / file_path] if file_path else []
+    if action == "delete":
+        files = [path for path in sorted(skill_dir.rglob("*")) if path.is_file()]
+        return files
+    return []
+
+
+def _resolve_local_edit_paths(tool_name: str, function_args: dict | None) -> list[Path]:
+    """Resolve local filesystem targets for write-capable tools."""
+    if not isinstance(function_args, dict):
+        return []
+
+    if tool_name == "write_file":
+        path = function_args.get("path")
+        return [_resolved_path(path)] if path else []
+
+    if tool_name == "patch":
+        path = function_args.get("path")
+        return [_resolved_path(path)] if path else []
+
+    if tool_name == "skill_manage":
+        return _resolve_skill_manage_paths(function_args)
+
+    return []
+
+
+def capture_local_edit_snapshot(tool_name: str, function_args: dict | None) -> LocalEditSnapshot | None:
+    """Capture before-state for local write previews."""
+    paths = _resolve_local_edit_paths(tool_name, function_args)
+    if not paths:
+        return None
+
+    snapshot = LocalEditSnapshot(paths=paths)
+    for path in paths:
+        snapshot.before[str(path)] = _snapshot_text(path)
+    return snapshot
+
+
+def _result_succeeded(result: str | None) -> bool:
+    """Conservatively detect whether a tool result represents success."""
+    if not result:
+        return False
+    try:
+        data = json.loads(result)
+    except (json.JSONDecodeError, TypeError):
+        return False
+    if not isinstance(data, dict):
+        return False
+    if data.get("error"):
+        return False
+    if "success" in data:
+        return bool(data.get("success"))
+    return True
+
+
+def _diff_from_snapshot(snapshot: LocalEditSnapshot | None) -> str | None:
+    """Generate unified diff text from a stored before-state and current files."""
+    if not snapshot:
+        return None
+
+    chunks: list[str] = []
+    for path in snapshot.paths:
+        before = snapshot.before.get(str(path))
+        after = _snapshot_text(path)
+        if before == after:
+            continue
+
+        display_path = _display_diff_path(path)
+        diff = "".join(
+            unified_diff(
+                [] if before is None else before.splitlines(keepends=True),
+                [] if after is None else after.splitlines(keepends=True),
+                fromfile=f"a/{display_path}",
+                tofile=f"b/{display_path}",
+            )
+        )
+        if diff:
+            chunks.append(diff)
+
+    if not chunks:
+        return None
+    return "".join(chunk if chunk.endswith("\n") else chunk + "\n" for chunk in chunks)
+
+
+def extract_edit_diff(
+    tool_name: str,
+    result: str | None,
+    *,
+    function_args: dict | None = None,
+    snapshot: LocalEditSnapshot | None = None,
+) -> str | None:
+    """Extract a unified diff from a file-edit tool result."""
+    if tool_name == "patch" and result:
+        try:
+            data = json.loads(result)
+        except (json.JSONDecodeError, TypeError):
+            data = None
+        if isinstance(data, dict):
+            diff = data.get("diff")
+            if isinstance(diff, str) and diff.strip():
+                return diff
+
+    if tool_name not in {"write_file", "patch", "skill_manage"}:
+        return None
+    if not _result_succeeded(result):
+        return None
+    return _diff_from_snapshot(snapshot)
+
+
+def _emit_inline_diff(diff_text: str, print_fn) -> bool:
+    """Emit rendered diff text through the CLI's prompt_toolkit-safe printer."""
+    if print_fn is None or not diff_text:
+        return False
+    try:
+        print_fn("  ┊ review diff")
+        for line in diff_text.rstrip("\n").splitlines():
+            print_fn(line)
+        return True
+    except Exception:
+        return False
+
+
+def _render_inline_unified_diff(diff: str) -> list[str]:
+    """Render unified diff lines in Hermes' inline transcript style."""
+    rendered: list[str] = []
+    from_file = None
+    to_file = None
+
+    for raw_line in diff.splitlines():
+        if raw_line.startswith("--- "):
+            from_file = raw_line[4:].strip()
+            continue
+        if raw_line.startswith("+++ "):
+            to_file = raw_line[4:].strip()
+            if from_file or to_file:
+                rendered.append(f"{_ANSI_FILE}{from_file or 'a/?'} → {to_file or 'b/?'}{_ANSI_RESET}")
+            continue
+        if raw_line.startswith("@@"):
+            rendered.append(f"{_ANSI_HUNK}{raw_line}{_ANSI_RESET}")
+            continue
+        if raw_line.startswith("-"):
+            rendered.append(f"{_ANSI_MINUS}{raw_line}{_ANSI_RESET}")
+            continue
+        if raw_line.startswith("+"):
+            rendered.append(f"{_ANSI_PLUS}{raw_line}{_ANSI_RESET}")
+            continue
+        if raw_line.startswith(" "):
+            rendered.append(f"{_ANSI_DIM}{raw_line}{_ANSI_RESET}")
+            continue
+        if raw_line:
+            rendered.append(raw_line)
+
+    return rendered
+
+
+def _split_unified_diff_sections(diff: str) -> list[str]:
+    """Split a unified diff into per-file sections."""
+    sections: list[list[str]] = []
+    current: list[str] = []
+
+    for line in diff.splitlines():
+        if line.startswith("--- ") and current:
+            sections.append(current)
+            current = [line]
+            continue
+        current.append(line)
+
+    if current:
+        sections.append(current)
+
+    return ["\n".join(section) for section in sections if section]
+
+
+def _summarize_rendered_diff_sections(
+    diff: str,
+    *,
+    max_files: int = _MAX_INLINE_DIFF_FILES,
+    max_lines: int = _MAX_INLINE_DIFF_LINES,
+) -> list[str]:
+    """Render diff sections while capping file count and total line count."""
+    sections = _split_unified_diff_sections(diff)
+    rendered: list[str] = []
+    omitted_files = 0
+    omitted_lines = 0
+
+    for idx, section in enumerate(sections):
+        if idx >= max_files:
+            omitted_files += 1
+            omitted_lines += len(_render_inline_unified_diff(section))
+            continue
+
+        section_lines = _render_inline_unified_diff(section)
+        remaining_budget = max_lines - len(rendered)
+        if remaining_budget <= 0:
+            omitted_lines += len(section_lines)
+            omitted_files += 1
+            continue
+
+        if len(section_lines) <= remaining_budget:
+            rendered.extend(section_lines)
+            continue
+
+        rendered.extend(section_lines[:remaining_budget])
+        omitted_lines += len(section_lines) - remaining_budget
+        omitted_files += 1 + max(0, len(sections) - idx - 1)
+        for leftover in sections[idx + 1:]:
+            omitted_lines += len(_render_inline_unified_diff(leftover))
+        break
+
+    if omitted_files or omitted_lines:
+        summary = f"… omitted {omitted_lines} diff line(s)"
+        if omitted_files:
+            summary += f" across {omitted_files} additional file(s)/section(s)"
+        rendered.append(f"{_ANSI_HUNK}{summary}{_ANSI_RESET}")
+
+    return rendered
+
+
+def render_edit_diff_with_delta(
+    tool_name: str,
+    result: str | None,
+    *,
+    function_args: dict | None = None,
+    snapshot: LocalEditSnapshot | None = None,
+    print_fn=None,
+) -> bool:
+    """Render an edit diff inline without taking over the terminal UI."""
+    diff = extract_edit_diff(
+        tool_name,
+        result,
+        function_args=function_args,
+        snapshot=snapshot,
+    )
+    if not diff:
+        return False
+    try:
+        rendered_lines = _summarize_rendered_diff_sections(diff)
+    except Exception as exc:
+        logger.debug("Could not render inline diff: %s", exc)
+        return False
+    return _emit_inline_diff("\n".join(rendered_lines), print_fn)
+
+
 # =========================================================================
 # KawaiiSpinner
 # =========================================================================

cli.py

@@ -1077,12 +1077,16 @@ def __init__(
         # streaming: stream tokens to the terminal as they arrive (display.streaming in config.yaml)
         self.streaming_enabled = CLI_CONFIG["display"].get("streaming", False)
 
+        # Inline diff previews for write actions (display.inline_diffs in config.yaml)
+        self._inline_diffs_enabled = CLI_CONFIG["display"].get("inline_diffs", True)
+
         # Streaming display state
         self._stream_buf = ""        # Partial line buffer for line-buffered rendering
         self._stream_started = False  # True once first delta arrives
         self._stream_box_opened = False  # True once the response box header is printed
         self._reasoning_stream_started = False  # True once live reasoning starts streaming
         self._reasoning_preview_buf = ""  # Coalesce tiny reasoning chunks for [thinking] output
+        self._pending_edit_snapshots = {}
 
         # Configuration - priority: CLI args > env vars > config file
         # Model comes from: CLI arg or config.yaml (single source of truth).
@@ -2132,6 +2136,8 @@ def _init_agent(self, *, model_override: str = None, runtime_override: dict = No
                 checkpoint_max_snapshots=self.checkpoint_max_snapshots,
                 pass_session_id=self.pass_session_id,
                 tool_progress_callback=self._on_tool_progress,
+                tool_start_callback=self._on_tool_start if self._inline_diffs_enabled else None,
+                tool_complete_callback=self._on_tool_complete if self._inline_diffs_enabled else None,
                 stream_delta_callback=self._stream_delta if self.streaming_enabled else None,
                 tool_gen_callback=self._on_tool_gen_start if self.streaming_enabled else None,
             )
@@ -5034,6 +5040,33 @@ def _on_tool_progress(self, function_name: str, preview: str, function_args: dic
         except Exception:
             pass
 
+    def _on_tool_start(self, tool_call_id: str, function_name: str, function_args: dict):
+        """Capture local before-state for write-capable tools."""
+        try:
+            from agent.display import capture_local_edit_snapshot
+
+            snapshot = capture_local_edit_snapshot(function_name, function_args)
+            if snapshot is not None:
+                self._pending_edit_snapshots[tool_call_id] = snapshot
+        except Exception:
+            logger.debug("Edit snapshot capture failed for %s", function_name, exc_info=True)
+
+    def _on_tool_complete(self, tool_call_id: str, function_name: str, function_args: dict, function_result: str):
+        """Render file edits with inline diff after write-capable tools complete."""
+        snapshot = self._pending_edit_snapshots.pop(tool_call_id, None)
+        try:
+            from agent.display import render_edit_diff_with_delta
+
+            render_edit_diff_with_delta(
+                function_name,
+                function_result,
+                function_args=function_args,
+                snapshot=snapshot,
+                print_fn=_cprint,
+            )
+        except Exception:
+            logger.debug("Edit diff preview failed for %s", function_name, exc_info=True)
+
     # ====================================================================
     # Voice mode methods
     # ====================================================================