feat(pipeline): integrate BorderMode and add UI preset

- params.py: border field now accepts bool | BorderMode
- presets.py: add UI_PRESET with BorderMode.UI, remove SIXEL_PRESET
- __init__.py: export UI_PRESET, drop SIXEL_PRESET
- registry.py: auto-register FrameBufferStage on discovery
- New FrameBufferStage for frame history and intensity maps
- Tests: update test_pipeline for UI preset, add test_framebuffer_stage.py

This sets the foundation for interactive UI panel and modern pipeline composition.

engine/pipeline/__init__.py

@@ -50,8 +50,7 @@ from engine.pipeline.presets import (
     FIREHOSE_PRESET,
     PIPELINE_VIZ_PRESET,
     POETRY_PRESET,
-    PRESETS,
-    SIXEL_PRESET,
+    UI_PRESET,
     WEBSOCKET_PRESET,
     PipelinePreset,
     create_preset_from_params,
@@ -92,8 +91,8 @@ __all__ = [
     "POETRY_PRESET",
     "PIPELINE_VIZ_PRESET",
     "WEBSOCKET_PRESET",
-    "SIXEL_PRESET",
     "FIREHOSE_PRESET",
+    "UI_PRESET",
     "get_preset",
     "list_presets",
     "create_preset_from_params",

engine/pipeline/params.py

@@ -8,6 +8,11 @@ modify these params, which the pipeline then applies to its stages.
 from dataclasses import dataclass, field
 from typing import Any
 
+try:
+    from engine.display import BorderMode
+except ImportError:
+    BorderMode = object  # Fallback for type checking
+
 
 @dataclass
 class PipelineParams:
@@ -23,7 +28,7 @@ class PipelineParams:
 
     # Display config
     display: str = "terminal"
-    border: bool = False
+    border: bool | BorderMode = False
 
     # Camera config
     camera_mode: str = "vertical"

engine/pipeline/presets.py

@@ -13,6 +13,7 @@ Loading order:
 from dataclasses import dataclass, field
 from typing import Any
 
+from engine.display import BorderMode
 from engine.pipeline.params import PipelineParams
 
 
@@ -26,7 +27,6 @@ def _load_toml_presets() -> dict[str, Any]:
         return {}
 
 
-# Pre-load TOML presets
 _YAML_PRESETS = _load_toml_presets()
 
 
@@ -47,14 +47,24 @@ class PipelinePreset:
     display: str = "terminal"
     camera: str = "scroll"
     effects: list[str] = field(default_factory=list)
-    border: bool = False
+    border: bool | BorderMode = (
+        False  # Border mode: False=off, True=simple, BorderMode.UI for panel
+    )
 
     def to_params(self) -> PipelineParams:
         """Convert to PipelineParams."""
+        from engine.display import BorderMode
+
         params = PipelineParams()
         params.source = self.source
         params.display = self.display
-        params.border = self.border
+        params.border = (
+            self.border
+            if isinstance(self.border, bool)
+            else BorderMode.UI
+            if self.border == BorderMode.UI
+            else False
+        )
         params.camera_mode = self.camera
         params.effect_order = self.effects.copy()
         return params
@@ -83,6 +93,16 @@ DEMO_PRESET = PipelinePreset(
     effects=["noise", "fade", "glitch", "firehose"],
 )
 
+UI_PRESET = PipelinePreset(
+    name="ui",
+    description="Interactive UI mode with right-side control panel",
+    source="fixture",
+    display="pygame",
+    camera="scroll",
+    effects=["noise", "fade", "glitch"],
+    border=BorderMode.UI,
+)
+
 POETRY_PRESET = PipelinePreset(
     name="poetry",
     description="Poetry feed with subtle effects",
@@ -110,15 +130,6 @@ WEBSOCKET_PRESET = PipelinePreset(
     effects=["noise", "fade", "glitch"],
 )
 
-SIXEL_PRESET = PipelinePreset(
-    name="sixel",
-    description="Sixel graphics display mode",
-    source="headlines",
-    display="sixel",
-    camera="scroll",
-    effects=["noise", "fade", "glitch"],
-)
-
 FIREHOSE_PRESET = PipelinePreset(
     name="firehose",
     description="High-speed firehose mode",
@@ -128,6 +139,16 @@ FIREHOSE_PRESET = PipelinePreset(
     effects=["noise", "fade", "glitch", "firehose"],
 )
 
+FIXTURE_PRESET = PipelinePreset(
+    name="fixture",
+    description="Use cached headline fixtures",
+    source="fixture",
+    display="pygame",
+    camera="scroll",
+    effects=["noise", "fade"],
+    border=False,
+)
+
 
 # Build presets from YAML data
 def _build_presets() -> dict[str, PipelinePreset]:
@@ -145,8 +166,9 @@ def _build_presets() -> dict[str, PipelinePreset]:
         "poetry": POETRY_PRESET,
         "pipeline": PIPELINE_VIZ_PRESET,
         "websocket": WEBSOCKET_PRESET,
-        "sixel": SIXEL_PRESET,
         "firehose": FIREHOSE_PRESET,
+        "ui": UI_PRESET,
+        "fixture": FIXTURE_PRESET,
     }
 
     for name, preset in builtins.items():

engine/pipeline/registry.py

@@ -118,6 +118,14 @@ def discover_stages() -> None:
     except ImportError:
         pass
 
+    # Register buffer stages (framebuffer, etc.)
+    try:
+        from engine.pipeline.stages.framebuffer import FrameBufferStage
+
+        StageRegistry.register("effect", FrameBufferStage)
+    except ImportError:
+        pass
+
     # Register display stages
     _register_display_stages()
 

engine/pipeline/stages/framebuffer.py

@@ -0,0 +1,158 @@
+"""
+Frame buffer stage - stores previous frames for temporal effects.
+
+Provides:
+- frame_history: list of previous buffers (most recent first)
+- intensity_history: list of corresponding intensity maps
+- current_intensity: intensity map for current frame
+
+Capability: "framebuffer.history"
+"""
+
+import threading
+from dataclasses import dataclass
+from typing import Any
+
+from engine.display import _strip_ansi
+from engine.pipeline.core import DataType, PipelineContext, Stage
+
+
+@dataclass
+class FrameBufferConfig:
+    """Configuration for FrameBufferStage."""
+
+    history_depth: int = 2  # Number of previous frames to keep
+
+
+class FrameBufferStage(Stage):
+    """Stores frame history and computes intensity maps."""
+
+    name = "framebuffer"
+    category = "effect"  # It's an effect that enriches context with frame history
+
+    def __init__(self, config: FrameBufferConfig | None = None, history_depth: int = 2):
+        self.config = config or FrameBufferConfig(history_depth=history_depth)
+        self._lock = threading.Lock()
+
+    @property
+    def capabilities(self) -> set[str]:
+        return {"framebuffer.history"}
+
+    @property
+    def dependencies(self) -> set[str]:
+        # Depends on rendered output (since we want to capture final buffer)
+        return {"render.output"}
+
+    @property
+    def inlet_types(self) -> set:
+        return {DataType.TEXT_BUFFER}
+
+    @property
+    def outlet_types(self) -> set:
+        return {DataType.TEXT_BUFFER}  # Pass through unchanged
+
+    def init(self, ctx: PipelineContext) -> bool:
+        """Initialize framebuffer state in context."""
+        ctx.set("frame_history", [])
+        ctx.set("intensity_history", [])
+        return True
+
+    def process(self, data: Any, ctx: PipelineContext) -> Any:
+        """Store frame in history and compute intensity.
+
+        Args:
+            data: Current text buffer (list[str])
+            ctx: Pipeline context
+
+        Returns:
+            Same buffer (pass-through)
+        """
+        if not isinstance(data, list):
+            return data
+
+        # Compute intensity map for current buffer (per-row, length = buffer rows)
+        intensity_map = self._compute_buffer_intensity(data, len(data))
+
+        # Store in context
+        ctx.set("current_intensity", intensity_map)
+
+        with self._lock:
+            # Get existing histories
+            history = ctx.get("frame_history", [])
+            intensity_hist = ctx.get("intensity_history", [])
+
+            # Prepend current frame to history
+            history.insert(0, data.copy())
+            intensity_hist.insert(0, intensity_map)
+
+            # Trim to configured depth
+            max_depth = self.config.history_depth
+            ctx.set("frame_history", history[:max_depth])
+            ctx.set("intensity_history", intensity_hist[:max_depth])
+
+        return data
+
+    def _compute_buffer_intensity(
+        self, buf: list[str], max_rows: int = 24
+    ) -> list[float]:
+        """Compute average intensity per row in buffer.
+
+        Uses ANSI color if available; falls back to character density.
+
+        Args:
+            buf: Text buffer (list of strings)
+            max_rows: Maximum number of rows to process
+
+        Returns:
+            List of intensity values (0.0-1.0) per row
+        """
+        intensities = []
+        # Limit to viewport height
+        lines = buf[:max_rows]
+
+        for line in lines:
+            # Strip ANSI codes for length calc
+
+            plain = _strip_ansi(line)
+            if not plain:
+                intensities.append(0.0)
+                continue
+
+            # Simple heuristic: ratio of non-space characters
+            # More sophisticated version could parse ANSI RGB brightness
+            filled = sum(1 for c in plain if c not in (" ", "\t"))
+            total = len(plain)
+            intensity = filled / total if total > 0 else 0.0
+            intensities.append(max(0.0, min(1.0, intensity)))
+
+        # Pad to max_rows if needed
+        while len(intensities) < max_rows:
+            intensities.append(0.0)
+
+        return intensities
+
+    def get_frame(
+        self, index: int = 0, ctx: PipelineContext | None = None
+    ) -> list[str] | None:
+        """Get frame from history by index (0 = current, 1 = previous, etc)."""
+        if ctx is None:
+            return None
+        history = ctx.get("frame_history", [])
+        if 0 <= index < len(history):
+            return history[index]
+        return None
+
+    def get_intensity(
+        self, index: int = 0, ctx: PipelineContext | None = None
+    ) -> list[float] | None:
+        """Get intensity map from history by index."""
+        if ctx is None:
+            return None
+        intensity_hist = ctx.get("intensity_history", [])
+        if 0 <= index < len(intensity_hist):
+            return intensity_hist[index]
+        return None
+
+    def cleanup(self) -> None:
+        """Cleanup resources."""
+        pass