feat(cli): draft F45 tui log buffering

features/F45-tui-performance-optimization/REPORT.md

@@ -0,0 +1,22 @@
+# Execution Report - F45 TUI Performance Optimization
+
+## Summary
+
+Added bounded log rendering for the dashboard log viewer so large persisted outputs do not overwhelm the TUI.
+
+## Changes
+
+- Added `tui_log_buffer_lines` to `AppSettings` with a default of `1000`.
+- Added `truncate_logs()` in `src/aignt_os/cli/rendering.py` to keep only the newest lines and prepend a truncation marker.
+- Updated `LogViewer` in `src/aignt_os/cli/dashboard.py` to optionally watch a log file, reload it when the file size changes, and render the truncated content.
+- Updated `RunDashboard.action_show_logs()` to pass the log file path into the viewer and truncate the initial payload before opening the modal.
+- Added unit coverage for truncation behavior and log viewer refresh handling.
+
+## Validation
+
+- `python -m pytest tests/unit/test_dashboard_log_viewer.py tests/unit/test_tui_rendering.py -q`
+- `./scripts/commit-check.sh --no-sync --skip-branch-validation --skip-docker --skip-security`
+
+## Residual Risk
+
+The viewer currently uses file size changes as the refresh heuristic. This is sufficient for the MVP branch stack, but a future feature could switch to content hashing if operators ever need same-size rewrites to trigger refreshes.

features/F45-tui-performance-optimization/SPEC.md

@@ -0,0 +1,28 @@
+---
+id: F45-tui-performance-optimization
+type: feature
+summary: "Optimize TUI log rendering for large outputs"
+inputs:
+  - Configurable TUI log buffer limit in `AppSettings`
+outputs:
+  - Truncated log rendering in the dashboard log viewer
+  - Responsive log modal even for large persisted outputs
+acceptance_criteria:
+  - "Configuration `tui_log_buffer_lines` exists with default `1000`"
+  - "The dashboard log viewer truncates old lines and keeps the newest lines visible"
+  - "A truncation marker indicates how many lines were omitted"
+  - "The log viewer can refresh from disk without reloading unchanged files"
+  - "Unit tests validate truncation and refresh behavior"
+non_goals:
+  - Implement virtualized infinite scrolling
+  - Change persisted log storage format
+  - Add distributed log streaming
+---
+
+# Context
+
+The AIgnt OS dashboard can open persisted step logs inside a TUI modal. Large logs can degrade responsiveness and force the UI to repaint far more text than the operator needs.
+
+# Objective
+
+Add a bounded log buffer for the dashboard viewer so the TUI remains responsive while still showing the latest output that matters to an operator.

src/aignt_os/cli/dashboard.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+from pathlib import Path
 from typing import Any
 
 from textual.app import App, ComposeResult
@@ -18,6 +19,7 @@
     TabPane,
 )
 
+from aignt_os.cli.rendering import truncate_logs
 from aignt_os.config import AppSettings
 from aignt_os.persistence import ArtifactStore, RunRecord, RunRepository, RunStepRecord
 
@@ -59,10 +61,12 @@ class LogViewer(ModalScreen[None]):
 
     BINDINGS = [("escape", "app.pop_screen", "Close")]
 
-    def __init__(self, title: str, content: str) -> None:
+    def __init__(self, title: str, content: str, path: str | None = None) -> None:
         super().__init__()
         self.dialog_title = title
         self.log_content = content
+        self.log_path = path
+        self._last_size: int | None = None
 
     def compose(self) -> ComposeResult:
         yield Vertical(
@@ -75,6 +79,32 @@ def compose(self) -> ComposeResult:
     def on_mount(self) -> None:
         log_widget = self.query_one("#log_content", RichLog)
         log_widget.write(self.log_content)
+        if self.log_path:
+            self.set_interval(1.0, self.refresh_log)
+
+    def refresh_log(self) -> None:
+        if not self.log_path:
+            return
+
+        try:
+            current_path = Path(self.log_path)
+            if not current_path.exists():
+                return
+
+            current_size = current_path.stat().st_size
+            if current_size == self._last_size:
+                return
+
+            settings = AppSettings()
+            new_content = current_path.read_text(encoding="utf-8", errors="replace")
+            truncated = truncate_logs(new_content, settings.tui_log_buffer_lines)
+
+            log_widget = self.query_one("#log_content", RichLog)
+            log_widget.clear()
+            log_widget.write(truncated)
+            self._last_size = current_size
+        except Exception:
+            pass
 
 
 class RunHeader(Static):
@@ -458,6 +488,7 @@ def action_show_logs(self) -> None:
         if self.step_detail.step:
             step = self.step_detail.step
             log_content = "No logs available."
+            log_path: str | None = None
 
             paths_to_check = []
             if step.clean_output_path:
@@ -467,17 +498,23 @@ def action_show_logs(self) -> None:
 
             for path_str in paths_to_check:
                 try:
-                    from pathlib import Path
-
                     p = Path(path_str)
                     if p.exists():
-                        log_content = p.read_text(encoding="utf-8", errors="replace")
+                        full_content = p.read_text(encoding="utf-8", errors="replace")
+                        log_content = truncate_logs(
+                            full_content, self.settings.tui_log_buffer_lines
+                        )
+                        log_path = path_str
                         break
                 except Exception as e:
                     log_content = f"Error reading log file: {e}"
 
             self.push_screen(
-                LogViewer(f"Logs: Step {step.step_id} ({step.tool_name})", log_content)
+                LogViewer(
+                    f"Logs: Step {step.step_id} ({step.tool_name})",
+                    log_content,
+                    path=log_path,
+                )
             )
         else:
             self.notify("Select a step first.", severity="warning")

src/aignt_os/cli/rendering.py

@@ -21,6 +21,20 @@ class RunArtifactPreview:
     truncated: bool
 
 
+def truncate_logs(text: str | None, max_lines: int) -> str:
+    if not text:
+        return ""
+
+    lines = text.splitlines(keepends=True)
+    if len(lines) <= max_lines:
+        return text
+
+    truncated_count = len(lines) - max_lines
+    kept_lines = lines[-max_lines:]
+    marker = f"\n... {truncated_count} lines truncated ...\n"
+    return marker + "".join(kept_lines)
+
+
 def render_runtime_status(
     state: RuntimeState,
     *,

src/aignt_os/config.py

@@ -30,6 +30,7 @@ class AppSettings(BaseSettings):
 
     execution_timeout_seconds: float = Field(default=300.0, gt=0)
     max_retries: int = Field(default=3, ge=0)
+    tui_log_buffer_lines: int = Field(default=1000, gt=0)
 
     @property
     def runtime_state_dir_resolved(self) -> Path:

tests/unit/test_dashboard_log_viewer.py

@@ -0,0 +1,35 @@
+from unittest.mock import MagicMock
+
+from aignt_os.cli.dashboard import LogViewer
+
+
+def test_log_viewer_refreshes_file_when_size_changes(tmp_path, monkeypatch):
+    log_file = tmp_path / "viewer.log"
+    log_file.write_text("line1\nline2\nline3\n", encoding="utf-8")
+    monkeypatch.setenv("AIGNT_OS_TUI_LOG_BUFFER_LINES", "2")
+
+    viewer = LogViewer("Test Log", "Initial", path=str(log_file))
+    log_widget = MagicMock()
+    viewer.query_one = MagicMock(return_value=log_widget)
+
+    viewer.refresh_log()
+
+    log_widget.clear.assert_called_once()
+    log_widget.write.assert_called_once_with("\n... 1 lines truncated ...\nline2\nline3\n")
+
+    log_widget.reset_mock()
+    viewer.refresh_log()
+
+    log_widget.clear.assert_not_called()
+    log_widget.write.assert_not_called()
+
+
+def test_log_viewer_refresh_ignores_missing_file():
+    viewer = LogViewer("Test Log", "Initial", path="/tmp/does-not-exist.log")
+    log_widget = MagicMock()
+    viewer.query_one = MagicMock(return_value=log_widget)
+
+    viewer.refresh_log()
+
+    log_widget.clear.assert_not_called()
+    log_widget.write.assert_not_called()

tests/unit/test_tui_rendering.py

@@ -0,0 +1,34 @@
+from aignt_os.cli.rendering import truncate_logs
+
+
+def test_truncate_logs_empty():
+    assert truncate_logs("", 10) == ""
+    assert truncate_logs(None, 10) == ""
+
+
+def test_truncate_logs_below_limit():
+    text = "line1\nline2\nline3"
+    assert truncate_logs(text, 10) == text
+
+
+def test_truncate_logs_at_limit():
+    text = "line1\nline2\nline3"
+    assert truncate_logs(text, 3) == text
+
+
+def test_truncate_logs_exceeds_limit():
+    text = "line1\nline2\nline3\nline4\nline5"
+    truncated = truncate_logs(text, 2)
+
+    assert "truncated" in truncated
+    assert "3 lines truncated" in truncated
+    assert truncated.endswith("line4\nline5")
+    assert "line1" not in truncated
+
+
+def test_truncate_logs_single_line_limit():
+    text = "line1\nline2\nline3"
+    truncated = truncate_logs(text, 1)
+
+    assert "truncated" in truncated
+    assert truncated.endswith("line3")