diff --git a/src/BenchmarkLogger.cpp b/src/BenchmarkLogger.cpp
new file mode 100644
index 0000000..88df9c1
--- /dev/null
+++ b/src/BenchmarkLogger.cpp
@@ -0,0 +1,38 @@
+#include "BenchmarkLogger.h"
+#include "GameEngine.h"
+
+// Global benchmark logger instance
+BenchmarkLogger g_benchmarkLogger;
+
+void BenchmarkLogger::recordFrame(const ProfilingMetrics& metrics) {
+    if (!running) return;
+
+    auto now = std::chrono::high_resolution_clock::now();
+    double timestamp_ms = std::chrono::duration<double, std::milli>(now - start_time).count();
+
+    BenchmarkFrame frame;
+    frame.frame_number = ++frame_counter;
+    frame.timestamp_ms = timestamp_ms;
+    frame.frame_time_ms = metrics.frameTime;
+    frame.fps = metrics.fps;
+
+    frame.work_time_ms = metrics.workTime;
+    frame.grid_render_ms = metrics.gridRenderTime;
+    frame.entity_render_ms = metrics.entityRenderTime;
+    frame.python_time_ms = metrics.pythonScriptTime;
+    frame.animation_time_ms = metrics.animationTime;
+    frame.fov_overlay_ms = metrics.fovOverlayTime;
+
+    frame.draw_calls = metrics.drawCalls;
+    frame.ui_elements = metrics.uiElements;
+    frame.visible_elements = metrics.visibleElements;
+    frame.grid_cells_rendered = metrics.gridCellsRendered;
+    frame.entities_rendered = metrics.entitiesRendered;
+    frame.total_entities = metrics.totalEntities;
+
+    // Move pending logs to this frame
+    frame.logs = std::move(pending_logs);
+    pending_logs.clear();
+
+    frames.push_back(std::move(frame));
+}
diff --git a/src/BenchmarkLogger.h b/src/BenchmarkLogger.h
new file mode 100644
index 0000000..6a0fedb
--- /dev/null
+++ b/src/BenchmarkLogger.h
@@ -0,0 +1,245 @@
+#pragma once
+
+#include <string>
+#include <vector>
+#include <chrono>
+#include <fstream>
+#include <sstream>
+#include <iomanip>
+#include <stdexcept>
+
+#ifdef _WIN32
+#include <process.h>
+#define getpid _getpid
+#else
+#include <unistd.h>
+#endif
+
+// Forward declaration
+struct ProfilingMetrics;
+
+/**
+ * @brief Frame data captured during benchmarking
+ */
+struct BenchmarkFrame {
+    int frame_number;
+    double timestamp_ms;        // Time since benchmark start
+    float frame_time_ms;
+    int fps;
+
+    // Detailed timing breakdown
+    float work_time_ms;       // Actual work time (frame_time - sleep_time)
+    float grid_render_ms;
+    float entity_render_ms;
+    float python_time_ms;
+    float animation_time_ms;
+    float fov_overlay_ms;
+
+    // Counts
+    int draw_calls;
+    int ui_elements;
+    int visible_elements;
+    int grid_cells_rendered;
+    int entities_rendered;
+    int total_entities;
+
+    // User-provided log messages for this frame
+    std::vector<std::string> logs;
+};
+
+/**
+ * @brief Benchmark logging system for capturing performance data to JSON files
+ *
+ * Usage from Python:
+ *   mcrfpy.start_benchmark()      # Start capturing
+ *   mcrfpy.log_benchmark("msg")   # Add comment to current frame
+ *   filename = mcrfpy.end_benchmark()  # Stop and get filename
+ */
+class BenchmarkLogger {
+private:
+    bool running;
+    std::string filename;
+    std::chrono::high_resolution_clock::time_point start_time;
+    std::vector<BenchmarkFrame> frames;
+    std::vector<std::string> pending_logs;  // Logs for current frame (before it's recorded)
+    int frame_counter;
+
+    // Generate filename based on PID and timestamp
+    std::string generateFilename() {
+        auto now = std::chrono::system_clock::now();
+        auto time_t = std::chrono::system_clock::to_time_t(now);
+        std::tm tm = *std::localtime(&time_t);
+
+        std::ostringstream oss;
+        oss << "benchmark_" << getpid() << "_"
+            << std::put_time(&tm, "%Y%m%d_%H%M%S") << ".json";
+        return oss.str();
+    }
+
+    // Get current timestamp as ISO 8601 string
+    std::string getCurrentTimestamp() {
+        auto now = std::chrono::system_clock::now();
+        auto time_t = std::chrono::system_clock::to_time_t(now);
+        std::tm tm = *std::localtime(&time_t);
+
+        std::ostringstream oss;
+        oss << std::put_time(&tm, "%Y-%m-%dT%H:%M:%S");
+        return oss.str();
+    }
+
+    // Escape string for JSON
+    std::string escapeJson(const std::string& str) {
+        std::ostringstream oss;
+        for (char c : str) {
+            switch (c) {
+                case '"':  oss << "\\\""; break;
+                case '\\': oss << "\\\\"; break;
+                case '\b': oss << "\\b"; break;
+                case '\f': oss << "\\f"; break;
+                case '\n': oss << "\\n"; break;
+                case '\r': oss << "\\r"; break;
+                case '\t': oss << "\\t"; break;
+                default:
+                    if ('\x00' <= c && c <= '\x1f') {
+                        oss << "\\u" << std::hex << std::setw(4) << std::setfill('0') << (int)c;
+                    } else {
+                        oss << c;
+                    }
+            }
+        }
+        return oss.str();
+    }
+
+    std::string start_timestamp;
+
+public:
+    BenchmarkLogger() : running(false), frame_counter(0) {}
+
+    /**
+     * @brief Start benchmark logging
+     * @throws std::runtime_error if already running
+     */
+    void start() {
+        if (running) {
+            throw std::runtime_error("Benchmark already running. Call end_benchmark() first.");
+        }
+
+        running = true;
+        filename = generateFilename();
+        start_time = std::chrono::high_resolution_clock::now();
+        start_timestamp = getCurrentTimestamp();
+        frames.clear();
+        pending_logs.clear();
+        frame_counter = 0;
+    }
+
+    /**
+     * @brief Stop benchmark logging and write to file
+     * @return The filename that was written
+     * @throws std::runtime_error if not running
+     */
+    std::string end() {
+        if (!running) {
+            throw std::runtime_error("No benchmark running. Call start_benchmark() first.");
+        }
+
+        running = false;
+
+        // Calculate duration
+        auto end_time = std::chrono::high_resolution_clock::now();
+        double duration_seconds = std::chrono::duration<double>(end_time - start_time).count();
+        std::string end_timestamp = getCurrentTimestamp();
+
+        // Write JSON file
+        std::ofstream file(filename);
+        if (!file.is_open()) {
+            throw std::runtime_error("Failed to open benchmark file for writing: " + filename);
+        }
+
+        file << "{\n";
+        file << "  \"benchmark\": {\n";
+        file << "    \"pid\": " << getpid() << ",\n";
+        file << "    \"start_time\": \"" << start_timestamp << "\",\n";
+        file << "    \"end_time\": \"" << end_timestamp << "\",\n";
+        file << "    \"total_frames\": " << frames.size() << ",\n";
+        file << "    \"duration_seconds\": " << std::fixed << std::setprecision(3) << duration_seconds << "\n";
+        file << "  },\n";
+
+        file << "  \"frames\": [\n";
+        for (size_t i = 0; i < frames.size(); ++i) {
+            const auto& f = frames[i];
+            file << "    {\n";
+            file << "      \"frame_number\": " << f.frame_number << ",\n";
+            file << "      \"timestamp_ms\": " << std::fixed << std::setprecision(3) << f.timestamp_ms << ",\n";
+            file << "      \"frame_time_ms\": " << std::setprecision(3) << f.frame_time_ms << ",\n";
+            file << "      \"fps\": " << f.fps << ",\n";
+            file << "      \"work_time_ms\": " << std::setprecision(3) << f.work_time_ms << ",\n";
+            file << "      \"grid_render_ms\": " << std::setprecision(3) << f.grid_render_ms << ",\n";
+            file << "      \"entity_render_ms\": " << std::setprecision(3) << f.entity_render_ms << ",\n";
+            file << "      \"python_time_ms\": " << std::setprecision(3) << f.python_time_ms << ",\n";
+            file << "      \"animation_time_ms\": " << std::setprecision(3) << f.animation_time_ms << ",\n";
+            file << "      \"fov_overlay_ms\": " << std::setprecision(3) << f.fov_overlay_ms << ",\n";
+            file << "      \"draw_calls\": " << f.draw_calls << ",\n";
+            file << "      \"ui_elements\": " << f.ui_elements << ",\n";
+            file << "      \"visible_elements\": " << f.visible_elements << ",\n";
+            file << "      \"grid_cells_rendered\": " << f.grid_cells_rendered << ",\n";
+            file << "      \"entities_rendered\": " << f.entities_rendered << ",\n";
+            file << "      \"total_entities\": " << f.total_entities << ",\n";
+
+            // Write logs array
+            file << "      \"logs\": [";
+            for (size_t j = 0; j < f.logs.size(); ++j) {
+                file << "\"" << escapeJson(f.logs[j]) << "\"";
+                if (j < f.logs.size() - 1) file << ", ";
+            }
+            file << "]\n";
+
+            file << "    }";
+            if (i < frames.size() - 1) file << ",";
+            file << "\n";
+        }
+        file << "  ]\n";
+        file << "}\n";
+
+        file.close();
+
+        std::string result = filename;
+        filename.clear();
+        frames.clear();
+        pending_logs.clear();
+        frame_counter = 0;
+
+        return result;
+    }
+
+    /**
+     * @brief Add a log message to the current frame
+     * @param message The message to log
+     * @throws std::runtime_error if not running
+     */
+    void log(const std::string& message) {
+        if (!running) {
+            throw std::runtime_error("No benchmark running. Call start_benchmark() first.");
+        }
+        pending_logs.push_back(message);
+    }
+
+    /**
+     * @brief Record frame data (called by game loop at end of each frame)
+     * @param metrics The current frame's profiling metrics
+     */
+    void recordFrame(const ProfilingMetrics& metrics);
+
+    /**
+     * @brief Check if benchmark is currently running
+     */
+    bool isRunning() const { return running; }
+
+    /**
+     * @brief Get current frame count
+     */
+    int getFrameCount() const { return frame_counter; }
+};
+
+// Global benchmark logger instance
+extern BenchmarkLogger g_benchmarkLogger;
diff --git a/src/GameEngine.cpp b/src/GameEngine.cpp
index 75a42eb..7bc9e14 100644
--- a/src/GameEngine.cpp
+++ b/src/GameEngine.cpp
@@ -6,6 +6,7 @@
 #include "Resources.h"
 #include "Animation.h"
 #include "Timer.h"
+#include "BenchmarkLogger.h"
 #include "imgui.h"
 #include "imgui-SFML.h"
 #include <cmath>
@@ -290,6 +291,9 @@ void GameEngine::run()
             ImGui::SFML::Render(*window);
         }
 
+        // Record work time before display (which may block for vsync/framerate limit)
+        metrics.workTime = clock.getElapsedTime().asSeconds() * 1000.0f;
+
         // Display the frame
         if (headless) {
             headless_renderer->display();
@@ -308,7 +312,10 @@ void GameEngine::run()
         
         // Update profiling metrics
         metrics.updateFrameTime(frameTime * 1000.0f); // Convert to milliseconds
-        
+
+        // Record frame data for benchmark logging (if running)
+        g_benchmarkLogger.recordFrame(metrics);
+
         int whole_fps = metrics.fps;
         int tenth_fps = (metrics.fps * 10) % 10;
         
diff --git a/src/GameEngine.h b/src/GameEngine.h
index 884305e..1c984fd 100644
--- a/src/GameEngine.h
+++ b/src/GameEngine.h
@@ -14,6 +14,71 @@
 #include <memory>
 #include <sstream>
 
+/**
+ * @brief Performance profiling metrics structure
+ *
+ * Tracks frame timing, render counts, and detailed timing breakdowns.
+ * Used by GameEngine, ProfilerOverlay (F3), and BenchmarkLogger.
+ */
+struct ProfilingMetrics {
+    float frameTime = 0.0f;          // Current frame time in milliseconds
+    float avgFrameTime = 0.0f;       // Average frame time over last N frames
+    int fps = 0;                     // Frames per second
+    int drawCalls = 0;               // Draw calls per frame
+    int uiElements = 0;              // Number of UI elements rendered
+    int visibleElements = 0;         // Number of visible elements
+
+    // Detailed timing breakdowns (added for profiling system)
+    float gridRenderTime = 0.0f;     // Time spent rendering grids (ms)
+    float entityRenderTime = 0.0f;   // Time spent rendering entities (ms)
+    float fovOverlayTime = 0.0f;     // Time spent rendering FOV overlays (ms)
+    float pythonScriptTime = 0.0f;   // Time spent in Python callbacks (ms)
+    float animationTime = 0.0f;      // Time spent updating animations (ms)
+    float workTime = 0.0f;           // Total work time before display/sleep (ms)
+
+    // Grid-specific metrics
+    int gridCellsRendered = 0;       // Number of grid cells drawn this frame
+    int entitiesRendered = 0;        // Number of entities drawn this frame
+    int totalEntities = 0;           // Total entities in scene
+
+    // Frame time history for averaging
+    static constexpr int HISTORY_SIZE = 60;
+    float frameTimeHistory[HISTORY_SIZE] = {0};
+    int historyIndex = 0;
+
+    void updateFrameTime(float deltaMs) {
+        frameTime = deltaMs;
+        frameTimeHistory[historyIndex] = deltaMs;
+        historyIndex = (historyIndex + 1) % HISTORY_SIZE;
+
+        // Calculate average
+        float sum = 0.0f;
+        for (int i = 0; i < HISTORY_SIZE; ++i) {
+            sum += frameTimeHistory[i];
+        }
+        avgFrameTime = sum / HISTORY_SIZE;
+        fps = avgFrameTime > 0 ? static_cast<int>(1000.0f / avgFrameTime) : 0;
+    }
+
+    void resetPerFrame() {
+        drawCalls = 0;
+        uiElements = 0;
+        visibleElements = 0;
+
+        // Reset per-frame timing metrics
+        gridRenderTime = 0.0f;
+        entityRenderTime = 0.0f;
+        fovOverlayTime = 0.0f;
+        pythonScriptTime = 0.0f;
+        animationTime = 0.0f;
+
+        // Reset per-frame counters
+        gridCellsRendered = 0;
+        entitiesRendered = 0;
+        totalEntities = 0;
+    }
+};
+
 class GameEngine
 {
 public:
@@ -76,64 +141,8 @@ public:
     std::map<std::string, std::shared_ptr<Timer>> timers;
     std::string scene;
     
-    // Profiling metrics
-    struct ProfilingMetrics {
-        float frameTime = 0.0f;          // Current frame time in milliseconds
-        float avgFrameTime = 0.0f;       // Average frame time over last N frames
-        int fps = 0;                     // Frames per second
-        int drawCalls = 0;               // Draw calls per frame
-        int uiElements = 0;              // Number of UI elements rendered
-        int visibleElements = 0;         // Number of visible elements
-
-        // Detailed timing breakdowns (added for profiling system)
-        float gridRenderTime = 0.0f;     // Time spent rendering grids (ms)
-        float entityRenderTime = 0.0f;   // Time spent rendering entities (ms)
-        float fovOverlayTime = 0.0f;     // Time spent rendering FOV overlays (ms)
-        float pythonScriptTime = 0.0f;   // Time spent in Python callbacks (ms)
-        float animationTime = 0.0f;      // Time spent updating animations (ms)
-
-        // Grid-specific metrics
-        int gridCellsRendered = 0;       // Number of grid cells drawn this frame
-        int entitiesRendered = 0;        // Number of entities drawn this frame
-        int totalEntities = 0;           // Total entities in scene
-
-        // Frame time history for averaging
-        static constexpr int HISTORY_SIZE = 60;
-        float frameTimeHistory[HISTORY_SIZE] = {0};
-        int historyIndex = 0;
-
-        void updateFrameTime(float deltaMs) {
-            frameTime = deltaMs;
-            frameTimeHistory[historyIndex] = deltaMs;
-            historyIndex = (historyIndex + 1) % HISTORY_SIZE;
-
-            // Calculate average
-            float sum = 0.0f;
-            for (int i = 0; i < HISTORY_SIZE; ++i) {
-                sum += frameTimeHistory[i];
-            }
-            avgFrameTime = sum / HISTORY_SIZE;
-            fps = avgFrameTime > 0 ? static_cast<int>(1000.0f / avgFrameTime) : 0;
-        }
-
-        void resetPerFrame() {
-            drawCalls = 0;
-            uiElements = 0;
-            visibleElements = 0;
-
-            // Reset per-frame timing metrics
-            gridRenderTime = 0.0f;
-            entityRenderTime = 0.0f;
-            fovOverlayTime = 0.0f;
-            pythonScriptTime = 0.0f;
-            animationTime = 0.0f;
-
-            // Reset per-frame counters
-            gridCellsRendered = 0;
-            entitiesRendered = 0;
-            totalEntities = 0;
-        }
-    } metrics;
+    // Profiling metrics (struct defined above class)
+    ProfilingMetrics metrics;
 
     GameEngine();
     GameEngine(const McRogueFaceConfig& cfg);
diff --git a/src/McRFPy_API.cpp b/src/McRFPy_API.cpp
index 2082c39..c383688 100644
--- a/src/McRFPy_API.cpp
+++ b/src/McRFPy_API.cpp
@@ -10,6 +10,7 @@
 #include "PySceneObject.h"
 #include "GameEngine.h"
 #include "ImGuiConsole.h"
+#include "BenchmarkLogger.h"
 #include "UI.h"
 #include "UILine.h"
 #include "UICircle.h"
@@ -213,6 +214,35 @@ static PyMethodDef mcrfpyMethods[] = {
          MCRF_NOTE("When disabled, the grave/tilde key will not open the console. Use this to ship games without debug features.")
      )},
 
+    {"start_benchmark", McRFPy_API::_startBenchmark, METH_NOARGS,
+     MCRF_FUNCTION(start_benchmark,
+         MCRF_SIG("()", "None"),
+         MCRF_DESC("Start capturing benchmark data to a file."),
+         MCRF_RETURNS("None")
+         MCRF_RAISES("RuntimeError", "If a benchmark is already running")
+         MCRF_NOTE("Benchmark filename is auto-generated from PID and timestamp. Use end_benchmark() to stop and get filename.")
+     )},
+
+    {"end_benchmark", McRFPy_API::_endBenchmark, METH_NOARGS,
+     MCRF_FUNCTION(end_benchmark,
+         MCRF_SIG("()", "str"),
+         MCRF_DESC("Stop benchmark capture and write data to JSON file."),
+         MCRF_RETURNS("str: The filename of the written benchmark data")
+         MCRF_RAISES("RuntimeError", "If no benchmark is currently running")
+         MCRF_NOTE("Returns the auto-generated filename (e.g., 'benchmark_12345_20250528_143022.json')")
+     )},
+
+    {"log_benchmark", McRFPy_API::_logBenchmark, METH_VARARGS,
+     MCRF_FUNCTION(log_benchmark,
+         MCRF_SIG("(message: str)", "None"),
+         MCRF_DESC("Add a log message to the current benchmark frame."),
+         MCRF_ARGS_START
+         MCRF_ARG("message", "Text to associate with the current frame")
+         MCRF_RETURNS("None")
+         MCRF_RAISES("RuntimeError", "If no benchmark is currently running")
+         MCRF_NOTE("Messages appear in the 'logs' array of each frame in the output JSON.")
+     )},
+
     {NULL, NULL, 0, NULL}
 };
 
@@ -1233,17 +1263,29 @@ PyObject* McRFPy_API::_getMetrics(PyObject* self, PyObject* args) {
     // Create a dictionary with metrics
     PyObject* dict = PyDict_New();
     if (!dict) return NULL;
-    
+
     // Add frame time metrics
     PyDict_SetItemString(dict, "frame_time", PyFloat_FromDouble(game->metrics.frameTime));
     PyDict_SetItemString(dict, "avg_frame_time", PyFloat_FromDouble(game->metrics.avgFrameTime));
     PyDict_SetItemString(dict, "fps", PyLong_FromLong(game->metrics.fps));
-    
+
     // Add draw call metrics
     PyDict_SetItemString(dict, "draw_calls", PyLong_FromLong(game->metrics.drawCalls));
     PyDict_SetItemString(dict, "ui_elements", PyLong_FromLong(game->metrics.uiElements));
     PyDict_SetItemString(dict, "visible_elements", PyLong_FromLong(game->metrics.visibleElements));
-    
+
+    // #144 - Add detailed timing breakdown (in milliseconds)
+    PyDict_SetItemString(dict, "grid_render_time", PyFloat_FromDouble(game->metrics.gridRenderTime));
+    PyDict_SetItemString(dict, "entity_render_time", PyFloat_FromDouble(game->metrics.entityRenderTime));
+    PyDict_SetItemString(dict, "fov_overlay_time", PyFloat_FromDouble(game->metrics.fovOverlayTime));
+    PyDict_SetItemString(dict, "python_time", PyFloat_FromDouble(game->metrics.pythonScriptTime));
+    PyDict_SetItemString(dict, "animation_time", PyFloat_FromDouble(game->metrics.animationTime));
+
+    // #144 - Add grid-specific metrics
+    PyDict_SetItemString(dict, "grid_cells_rendered", PyLong_FromLong(game->metrics.gridCellsRendered));
+    PyDict_SetItemString(dict, "entities_rendered", PyLong_FromLong(game->metrics.entitiesRendered));
+    PyDict_SetItemString(dict, "total_entities", PyLong_FromLong(game->metrics.totalEntities));
+
     // Add general metrics
     PyDict_SetItemString(dict, "current_frame", PyLong_FromLong(game->getFrame()));
     PyDict_SetItemString(dict, "runtime", PyFloat_FromDouble(game->runtime.getElapsedTime().asSeconds()));
@@ -1261,6 +1303,42 @@ PyObject* McRFPy_API::_setDevConsole(PyObject* self, PyObject* args) {
     Py_RETURN_NONE;
 }
 
+// Benchmark logging implementation (#104)
+PyObject* McRFPy_API::_startBenchmark(PyObject* self, PyObject* args) {
+    try {
+        g_benchmarkLogger.start();
+        Py_RETURN_NONE;
+    } catch (const std::runtime_error& e) {
+        PyErr_SetString(PyExc_RuntimeError, e.what());
+        return NULL;
+    }
+}
+
+PyObject* McRFPy_API::_endBenchmark(PyObject* self, PyObject* args) {
+    try {
+        std::string filename = g_benchmarkLogger.end();
+        return PyUnicode_FromString(filename.c_str());
+    } catch (const std::runtime_error& e) {
+        PyErr_SetString(PyExc_RuntimeError, e.what());
+        return NULL;
+    }
+}
+
+PyObject* McRFPy_API::_logBenchmark(PyObject* self, PyObject* args) {
+    const char* message;
+    if (!PyArg_ParseTuple(args, "s", &message)) {
+        return NULL;
+    }
+
+    try {
+        g_benchmarkLogger.log(message);
+        Py_RETURN_NONE;
+    } catch (const std::runtime_error& e) {
+        PyErr_SetString(PyExc_RuntimeError, e.what());
+        return NULL;
+    }
+}
+
 // Exception handling implementation
 void McRFPy_API::signalPythonException() {
     // Check if we should exit on exception (consult config via game)
diff --git a/src/McRFPy_API.h b/src/McRFPy_API.h
index aa7c189..55c417d 100644
--- a/src/McRFPy_API.h
+++ b/src/McRFPy_API.h
@@ -82,6 +82,11 @@ public:
     // Profiling/metrics
     static PyObject* _getMetrics(PyObject*, PyObject*);
 
+    // Benchmark logging (#104)
+    static PyObject* _startBenchmark(PyObject*, PyObject*);
+    static PyObject* _endBenchmark(PyObject*, PyObject*);
+    static PyObject* _logBenchmark(PyObject*, PyObject*);
+
     // Developer console
     static PyObject* _setDevConsole(PyObject*, PyObject*);
 
diff --git a/src/UIArc.cpp b/src/UIArc.cpp
index ce8d450..120d59d 100644
--- a/src/UIArc.cpp
+++ b/src/UIArc.cpp
@@ -206,30 +206,36 @@ void UIArc::resize(float w, float h) {
 bool UIArc::setProperty(const std::string& name, float value) {
     if (name == "radius") {
         setRadius(value);
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "start_angle") {
         setStartAngle(value);
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "end_angle") {
         setEndAngle(value);
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "thickness") {
         setThickness(value);
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "x") {
         center.x = value;
         position = center;
         vertices_dirty = true;
+        markDirty();  // #144 - Propagate to parent for texture caching
         return true;
     }
     else if (name == "y") {
         center.y = value;
         position = center;
         vertices_dirty = true;
+        markDirty();  // #144 - Propagate to parent for texture caching
         return true;
     }
     return false;
@@ -238,6 +244,7 @@ bool UIArc::setProperty(const std::string& name, float value) {
 bool UIArc::setProperty(const std::string& name, const sf::Color& value) {
     if (name == "color") {
         setColor(value);
+        markDirty();  // #144 - Content change
         return true;
     }
     return false;
@@ -246,6 +253,7 @@ bool UIArc::setProperty(const std::string& name, const sf::Color& value) {
 bool UIArc::setProperty(const std::string& name, const sf::Vector2f& value) {
     if (name == "center") {
         setCenter(value);
+        markDirty();  // #144 - Propagate to parent for texture caching
         return true;
     }
     return false;
diff --git a/src/UICaption.cpp b/src/UICaption.cpp
index aa3810f..9014ef7 100644
--- a/src/UICaption.cpp
+++ b/src/UICaption.cpp
@@ -471,71 +471,84 @@ bool UICaption::setProperty(const std::string& name, float value) {
     if (name == "x") {
         position.x = value;
         text.setPosition(position);  // Keep text in sync
+        markDirty();  // #144 - Propagate to parent for texture caching
         return true;
     }
     else if (name == "y") {
         position.y = value;
         text.setPosition(position);  // Keep text in sync
+        markDirty();  // #144 - Propagate to parent for texture caching
         return true;
     }
     else if (name == "font_size" || name == "size") { // Support both for backward compatibility
         text.setCharacterSize(static_cast<unsigned int>(value));
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "outline") {
         text.setOutlineThickness(value);
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "fill_color.r") {
         auto color = text.getFillColor();
         color.r = static_cast<sf::Uint8>(std::clamp(value, 0.0f, 255.0f));
         text.setFillColor(color);
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "fill_color.g") {
         auto color = text.getFillColor();
         color.g = static_cast<sf::Uint8>(std::clamp(value, 0.0f, 255.0f));
         text.setFillColor(color);
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "fill_color.b") {
         auto color = text.getFillColor();
         color.b = static_cast<sf::Uint8>(std::clamp(value, 0.0f, 255.0f));
         text.setFillColor(color);
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "fill_color.a") {
         auto color = text.getFillColor();
         color.a = static_cast<sf::Uint8>(std::clamp(value, 0.0f, 255.0f));
         text.setFillColor(color);
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "outline_color.r") {
         auto color = text.getOutlineColor();
         color.r = static_cast<sf::Uint8>(std::clamp(value, 0.0f, 255.0f));
         text.setOutlineColor(color);
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "outline_color.g") {
         auto color = text.getOutlineColor();
         color.g = static_cast<sf::Uint8>(std::clamp(value, 0.0f, 255.0f));
         text.setOutlineColor(color);
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "outline_color.b") {
         auto color = text.getOutlineColor();
         color.b = static_cast<sf::Uint8>(std::clamp(value, 0.0f, 255.0f));
         text.setOutlineColor(color);
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "outline_color.a") {
         auto color = text.getOutlineColor();
         color.a = static_cast<sf::Uint8>(std::clamp(value, 0.0f, 255.0f));
         text.setOutlineColor(color);
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "z_index") {
         z_index = static_cast<int>(value);
+        markDirty();  // #144 - Z-order change affects parent
         return true;
     }
     return false;
@@ -544,10 +557,12 @@ bool UICaption::setProperty(const std::string& name, float value) {
 bool UICaption::setProperty(const std::string& name, const sf::Color& value) {
     if (name == "fill_color") {
         text.setFillColor(value);
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "outline_color") {
         text.setOutlineColor(value);
+        markDirty();  // #144 - Content change
         return true;
     }
     return false;
@@ -556,6 +571,7 @@ bool UICaption::setProperty(const std::string& name, const sf::Color& value) {
 bool UICaption::setProperty(const std::string& name, const std::string& value) {
     if (name == "text") {
         text.setString(value);
+        markDirty();  // #144 - Content change
         return true;
     }
     return false;
diff --git a/src/UICircle.cpp b/src/UICircle.cpp
index 6236e38..d141b95 100644
--- a/src/UICircle.cpp
+++ b/src/UICircle.cpp
@@ -172,15 +172,19 @@ void UICircle::resize(float w, float h) {
 bool UICircle::setProperty(const std::string& name, float value) {
     if (name == "radius") {
         setRadius(value);
+        markDirty();  // #144 - Content change
         return true;
     } else if (name == "outline") {
         setOutline(value);
+        markDirty();  // #144 - Content change
         return true;
     } else if (name == "x") {
         position.x = value;
+        markDirty();  // #144 - Propagate to parent for texture caching
         return true;
     } else if (name == "y") {
         position.y = value;
+        markDirty();  // #144 - Propagate to parent for texture caching
         return true;
     }
     return false;
@@ -189,9 +193,11 @@ bool UICircle::setProperty(const std::string& name, float value) {
 bool UICircle::setProperty(const std::string& name, const sf::Color& value) {
     if (name == "fill_color") {
         setFillColor(value);
+        markDirty();  // #144 - Content change
         return true;
     } else if (name == "outline_color") {
         setOutlineColor(value);
+        markDirty();  // #144 - Content change
         return true;
     }
     return false;
@@ -200,6 +206,7 @@ bool UICircle::setProperty(const std::string& name, const sf::Color& value) {
 bool UICircle::setProperty(const std::string& name, const sf::Vector2f& value) {
     if (name == "center" || name == "position") {
         position = value;
+        markDirty();  // #144 - Propagate to parent for texture caching
         return true;
     }
     return false;
diff --git a/src/UIEntity.cpp b/src/UIEntity.cpp
index 88f1563..bc6eb88 100644
--- a/src/UIEntity.cpp
+++ b/src/UIEntity.cpp
@@ -674,15 +674,18 @@ bool UIEntity::setProperty(const std::string& name, float value) {
     if (name == "x") {
         position.x = value;
         // Don't update sprite position here - UIGrid::render() handles the pixel positioning
+        if (grid) grid->markDirty();  // #144 - Propagate to parent grid for texture caching
         return true;
     }
     else if (name == "y") {
         position.y = value;
         // Don't update sprite position here - UIGrid::render() handles the pixel positioning
+        if (grid) grid->markDirty();  // #144 - Propagate to parent grid for texture caching
         return true;
     }
     else if (name == "sprite_scale") {
         sprite.setScale(sf::Vector2f(value, value));
+        if (grid) grid->markDirty();  // #144 - Content change
         return true;
     }
     return false;
@@ -691,6 +694,7 @@ bool UIEntity::setProperty(const std::string& name, float value) {
 bool UIEntity::setProperty(const std::string& name, int value) {
     if (name == "sprite_index" || name == "sprite_number") {
         sprite.setSpriteIndex(value);
+        if (grid) grid->markDirty();  // #144 - Content change
         return true;
     }
     return false;
diff --git a/src/UIGrid.cpp b/src/UIGrid.cpp
index 3cdbf56..e646178 100644
--- a/src/UIGrid.cpp
+++ b/src/UIGrid.cpp
@@ -2725,54 +2725,66 @@ bool UIGrid::setProperty(const std::string& name, float value) {
         position.x = value;
         box.setPosition(position);
         output.setPosition(position);
+        markDirty();  // #144 - Propagate to parent for texture caching
         return true;
     }
     else if (name == "y") {
         position.y = value;
         box.setPosition(position);
         output.setPosition(position);
+        markDirty();  // #144 - Propagate to parent for texture caching
         return true;
     }
     else if (name == "w" || name == "width") {
         box.setSize(sf::Vector2f(value, box.getSize().y));
         output.setTextureRect(sf::IntRect(0, 0, box.getSize().x, box.getSize().y));
+        markDirty();  // #144 - Size change
         return true;
     }
     else if (name == "h" || name == "height") {
         box.setSize(sf::Vector2f(box.getSize().x, value));
         output.setTextureRect(sf::IntRect(0, 0, box.getSize().x, box.getSize().y));
+        markDirty();  // #144 - Size change
         return true;
     }
     else if (name == "center_x") {
         center_x = value;
+        markDirty();  // #144 - View change affects content
         return true;
     }
     else if (name == "center_y") {
         center_y = value;
+        markDirty();  // #144 - View change affects content
         return true;
     }
     else if (name == "zoom") {
         zoom = value;
+        markDirty();  // #144 - View change affects content
         return true;
     }
     else if (name == "z_index") {
         z_index = static_cast<int>(value);
+        markDirty();  // #144 - Z-order change affects parent
         return true;
     }
     else if (name == "fill_color.r") {
         fill_color.r = static_cast<uint8_t>(std::max(0.0f, std::min(255.0f, value)));
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "fill_color.g") {
         fill_color.g = static_cast<uint8_t>(std::max(0.0f, std::min(255.0f, value)));
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "fill_color.b") {
         fill_color.b = static_cast<uint8_t>(std::max(0.0f, std::min(255.0f, value)));
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "fill_color.a") {
         fill_color.a = static_cast<uint8_t>(std::max(0.0f, std::min(255.0f, value)));
+        markDirty();  // #144 - Content change
         return true;
     }
     return false;
@@ -2783,16 +2795,19 @@ bool UIGrid::setProperty(const std::string& name, const sf::Vector2f& value) {
         position = value;
         box.setPosition(position);
         output.setPosition(position);
+        markDirty();  // #144 - Propagate to parent for texture caching
         return true;
     }
     else if (name == "size") {
         box.setSize(value);
         output.setTextureRect(sf::IntRect(0, 0, box.getSize().x, box.getSize().y));
+        markDirty();  // #144 - Size change
         return true;
     }
     else if (name == "center") {
         center_x = value.x;
         center_y = value.y;
+        markDirty();  // #144 - View change affects content
         return true;
     }
     return false;
diff --git a/src/UILine.cpp b/src/UILine.cpp
index a504c24..f874281 100644
--- a/src/UILine.cpp
+++ b/src/UILine.cpp
@@ -207,36 +207,43 @@ bool UILine::setProperty(const std::string& name, float value) {
     if (name == "thickness") {
         thickness = value;
         vertices_dirty = true;
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "x") {
         float dx = value - position.x;
         move(dx, 0);
+        markDirty();  // #144 - Propagate to parent for texture caching
         return true;
     }
     else if (name == "y") {
         float dy = value - position.y;
         move(0, dy);
+        markDirty();  // #144 - Propagate to parent for texture caching
         return true;
     }
     else if (name == "start_x") {
         start_pos.x = value;
         vertices_dirty = true;
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "start_y") {
         start_pos.y = value;
         vertices_dirty = true;
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "end_x") {
         end_pos.x = value;
         vertices_dirty = true;
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "end_y") {
         end_pos.y = value;
         vertices_dirty = true;
+        markDirty();  // #144 - Content change
         return true;
     }
     return false;
@@ -246,6 +253,7 @@ bool UILine::setProperty(const std::string& name, const sf::Color& value) {
     if (name == "color") {
         color = value;
         vertices_dirty = true;
+        markDirty();  // #144 - Content change
         return true;
     }
     return false;
@@ -255,11 +263,13 @@ bool UILine::setProperty(const std::string& name, const sf::Vector2f& value) {
     if (name == "start") {
         start_pos = value;
         vertices_dirty = true;
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "end") {
         end_pos = value;
         vertices_dirty = true;
+        markDirty();  // #144 - Content change
         return true;
     }
     return false;
diff --git a/src/UISprite.cpp b/src/UISprite.cpp
index a9c0ac5..56bd4de 100644
--- a/src/UISprite.cpp
+++ b/src/UISprite.cpp
@@ -499,27 +499,33 @@ bool UISprite::setProperty(const std::string& name, float value) {
     if (name == "x") {
         position.x = value;
         sprite.setPosition(position);  // Keep sprite in sync
+        markDirty();  // #144 - Propagate to parent for texture caching
         return true;
     }
     else if (name == "y") {
         position.y = value;
         sprite.setPosition(position);  // Keep sprite in sync
+        markDirty();  // #144 - Propagate to parent for texture caching
         return true;
     }
     else if (name == "scale") {
         sprite.setScale(sf::Vector2f(value, value));
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "scale_x") {
         sprite.setScale(sf::Vector2f(value, sprite.getScale().y));
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "scale_y") {
         sprite.setScale(sf::Vector2f(sprite.getScale().x, value));
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "z_index") {
         z_index = static_cast<int>(value);
+        markDirty();  // #144 - Z-order change affects parent
         return true;
     }
     return false;
@@ -528,10 +534,12 @@ bool UISprite::setProperty(const std::string& name, float value) {
 bool UISprite::setProperty(const std::string& name, int value) {
     if (name == "sprite_index" || name == "sprite_number") {
         setSpriteIndex(value);
+        markDirty();  // #144 - Content change
         return true;
     }
     else if (name == "z_index") {
         z_index = value;
+        markDirty();  // #144 - Z-order change affects parent
         return true;
     }
     return false;
diff --git a/tests/benchmarks/benchmark_suite.py b/tests/benchmarks/benchmark_suite.py
new file mode 100644
index 0000000..18806d4
--- /dev/null
+++ b/tests/benchmarks/benchmark_suite.py
@@ -0,0 +1,359 @@
+#!/usr/bin/env python3
+"""Comprehensive Performance Benchmark Suite for McRogueFace (#104, #144)
+
+Runs 6 benchmark scenarios to establish baseline performance metrics:
+1. Empty scene - Pure engine overhead
+2. Static UI - 100 frames, no animation (best case for caching)
+3. Animated UI - 100 frames, all animating (worst case for caching)
+4. Mixed UI - 100 frames, 10 animating (realistic case)
+5. Deep hierarchy - 5 levels of nesting (propagation cost)
+6. Grid stress - Large grid with entities (known bottleneck)
+
+Usage:
+    ./mcrogueface --headless --exec tests/benchmarks/benchmark_suite.py
+
+Results are printed to stdout in a format suitable for tracking over time.
+"""
+
+import mcrfpy
+import sys
+import random
+
+# Benchmark configuration
+WARMUP_FRAMES = 30       # Frames to skip before measuring
+MEASURE_FRAMES = 120     # Frames to measure (2 seconds at 60fps)
+FRAME_BUDGET_MS = 16.67  # Target: 60 FPS
+
+# Storage for results
+results = {}
+current_scenario = None
+frame_count = 0
+metrics_samples = []
+
+
+def collect_metrics(runtime):
+    """Timer callback to collect metrics each frame."""
+    global frame_count, metrics_samples
+
+    frame_count += 1
+
+    # Skip warmup frames
+    if frame_count <= WARMUP_FRAMES:
+        return
+
+    # Collect sample
+    m = mcrfpy.getMetrics()
+    metrics_samples.append({
+        'frame_time': m['frame_time'],
+        'avg_frame_time': m['avg_frame_time'],
+        'fps': m['fps'],
+        'draw_calls': m['draw_calls'],
+        'ui_elements': m['ui_elements'],
+        'visible_elements': m['visible_elements'],
+        'grid_render_time': m['grid_render_time'],
+        'entity_render_time': m['entity_render_time'],
+        'python_time': m['python_time'],
+        'animation_time': m['animation_time'],
+        'grid_cells_rendered': m['grid_cells_rendered'],
+        'entities_rendered': m['entities_rendered'],
+    })
+
+    # Check if we have enough samples
+    if len(metrics_samples) >= MEASURE_FRAMES:
+        finish_scenario()
+
+
+def finish_scenario():
+    """Calculate statistics and store results for current scenario."""
+    global results, current_scenario, metrics_samples
+
+    mcrfpy.delTimer("benchmark_collect")
+
+    if not metrics_samples:
+        print(f"  WARNING: No samples collected for {current_scenario}")
+        return
+
+    # Calculate averages
+    n = len(metrics_samples)
+    avg = lambda key: sum(s[key] for s in metrics_samples) / n
+
+    results[current_scenario] = {
+        'samples': n,
+        'avg_frame_time': avg('frame_time'),
+        'avg_fps': avg('fps'),
+        'avg_draw_calls': avg('draw_calls'),
+        'avg_ui_elements': avg('ui_elements'),
+        'avg_grid_render_time': avg('grid_render_time'),
+        'avg_entity_render_time': avg('entity_render_time'),
+        'avg_python_time': avg('python_time'),
+        'avg_animation_time': avg('animation_time'),
+        'avg_grid_cells': avg('grid_cells_rendered'),
+        'avg_entities': avg('entities_rendered'),
+        'max_frame_time': max(s['frame_time'] for s in metrics_samples),
+        'min_frame_time': min(s['frame_time'] for s in metrics_samples),
+    }
+
+    # Calculate percentage breakdown
+    r = results[current_scenario]
+    total = r['avg_frame_time']
+    if total > 0:
+        r['pct_grid'] = (r['avg_grid_render_time'] / total) * 100
+        r['pct_entity'] = (r['avg_entity_render_time'] / total) * 100
+        r['pct_python'] = (r['avg_python_time'] / total) * 100
+        r['pct_animation'] = (r['avg_animation_time'] / total) * 100
+        r['pct_other'] = 100 - r['pct_grid'] - r['pct_entity'] - r['pct_python'] - r['pct_animation']
+
+    print(f"  Completed: {n} samples, avg {r['avg_frame_time']:.2f}ms ({r['avg_fps']:.0f} FPS)")
+
+    # Run next scenario
+    run_next_scenario()
+
+
+def run_next_scenario():
+    """Run the next benchmark scenario in sequence."""
+    global current_scenario, frame_count, metrics_samples
+
+    scenarios = [
+        ('1_empty', setup_empty_scene),
+        ('2_static_100', setup_static_100),
+        ('3_animated_100', setup_animated_100),
+        ('4_mixed_100', setup_mixed_100),
+        ('5_deep_hierarchy', setup_deep_hierarchy),
+        ('6_grid_stress', setup_grid_stress),
+    ]
+
+    # Find current index
+    current_idx = -1
+    if current_scenario:
+        for i, (name, _) in enumerate(scenarios):
+            if name == current_scenario:
+                current_idx = i
+                break
+
+    # Move to next
+    next_idx = current_idx + 1
+
+    if next_idx >= len(scenarios):
+        # All done
+        print_results()
+        return
+
+    # Setup next scenario
+    current_scenario = scenarios[next_idx][0]
+    frame_count = 0
+    metrics_samples = []
+
+    print(f"\n[{next_idx + 1}/{len(scenarios)}] Running: {current_scenario}")
+
+    # Run setup function
+    scenarios[next_idx][1]()
+
+    # Start collection timer (runs every frame)
+    mcrfpy.setTimer("benchmark_collect", collect_metrics, 1)
+
+
+# ============================================================================
+# Scenario Setup Functions
+# ============================================================================
+
+def setup_empty_scene():
+    """Scenario 1: Empty scene - pure engine overhead."""
+    mcrfpy.createScene("bench_empty")
+    mcrfpy.setScene("bench_empty")
+
+
+def setup_static_100():
+    """Scenario 2: 100 static frames - best case for caching."""
+    mcrfpy.createScene("bench_static")
+    ui = mcrfpy.sceneUI("bench_static")
+
+    # Create 100 frames in a 10x10 grid
+    for i in range(100):
+        x = (i % 10) * 100 + 12
+        y = (i // 10) * 70 + 12
+        frame = mcrfpy.Frame(pos=(x, y), size=(80, 55))
+        frame.fill_color = mcrfpy.Color(50 + i, 100, 150)
+        frame.outline = 2
+        frame.outline_color = mcrfpy.Color(255, 255, 255)
+
+        # Add a caption child
+        cap = mcrfpy.Caption(text=f"F{i}", pos=(5, 5))
+        cap.fill_color = mcrfpy.Color(255, 255, 255)
+        frame.children.append(cap)
+
+        ui.append(frame)
+
+    mcrfpy.setScene("bench_static")
+
+
+def setup_animated_100():
+    """Scenario 3: 100 frames all animating - worst case for caching."""
+    mcrfpy.createScene("bench_animated")
+    ui = mcrfpy.sceneUI("bench_animated")
+
+    frames = []
+    for i in range(100):
+        x = (i % 10) * 100 + 12
+        y = (i // 10) * 70 + 12
+        frame = mcrfpy.Frame(pos=(x, y), size=(80, 55))
+        frame.fill_color = mcrfpy.Color(50 + i, 100, 150)
+        frames.append(frame)
+        ui.append(frame)
+
+    mcrfpy.setScene("bench_animated")
+
+    # Start animations on all frames (color animation = content change)
+    for i, frame in enumerate(frames):
+        # Animate fill color - this dirties the frame
+        target_r = (i * 17) % 256
+        anim = mcrfpy.Animation("fill_color.r", float(target_r), 2.0, "linear")
+        anim.start(frame)
+
+
+def setup_mixed_100():
+    """Scenario 4: 100 frames, only 10 animating - realistic case."""
+    mcrfpy.createScene("bench_mixed")
+    ui = mcrfpy.sceneUI("bench_mixed")
+
+    frames = []
+    for i in range(100):
+        x = (i % 10) * 100 + 12
+        y = (i // 10) * 70 + 12
+        frame = mcrfpy.Frame(pos=(x, y), size=(80, 55))
+        frame.fill_color = mcrfpy.Color(50 + i, 100, 150)
+        frames.append(frame)
+        ui.append(frame)
+
+    mcrfpy.setScene("bench_mixed")
+
+    # Animate only 10 frames (every 10th)
+    for i in range(0, 100, 10):
+        frame = frames[i]
+        anim = mcrfpy.Animation("fill_color.r", 255.0, 2.0, "easeInOut")
+        anim.start(frame)
+
+
+def setup_deep_hierarchy():
+    """Scenario 5: 5 levels of nesting - test dirty flag propagation cost."""
+    mcrfpy.createScene("bench_deep")
+    ui = mcrfpy.sceneUI("bench_deep")
+
+    # Create 10 trees, each with 5 levels of nesting
+    deepest_frames = []
+
+    for tree in range(10):
+        x_offset = tree * 100 + 12
+        current_parent = None
+
+        for level in range(5):
+            frame = mcrfpy.Frame(
+                pos=(10, 10) if level > 0 else (x_offset, 100),
+                size=(80 - level * 10, 500 - level * 80)
+            )
+            frame.fill_color = mcrfpy.Color(50 + level * 40, 100, 200 - level * 30)
+            frame.outline = 1
+
+            if current_parent is None:
+                ui.append(frame)
+            else:
+                current_parent.children.append(frame)
+
+            current_parent = frame
+
+            if level == 4:  # Deepest level
+                deepest_frames.append(frame)
+
+    mcrfpy.setScene("bench_deep")
+
+    # Animate the deepest frames - tests propagation up the hierarchy
+    for frame in deepest_frames:
+        anim = mcrfpy.Animation("fill_color.g", 255.0, 2.0, "linear")
+        anim.start(frame)
+
+
+def setup_grid_stress():
+    """Scenario 6: Large grid with entities - known performance bottleneck."""
+    mcrfpy.createScene("bench_grid")
+    ui = mcrfpy.sceneUI("bench_grid")
+
+    # Create a 50x50 grid (2500 cells)
+    grid = mcrfpy.Grid(grid_size=(50, 50), pos=(50, 50), size=(700, 700))
+    grid.zoom = 0.75
+    grid.center = (400, 400)  # Center view
+    ui.append(grid)
+
+    # Fill with alternating colors
+    for y in range(50):
+        for x in range(50):
+            cell = grid.at(x, y)
+            if (x + y) % 2 == 0:
+                cell.color = mcrfpy.Color(60, 60, 80)
+            else:
+                cell.color = mcrfpy.Color(40, 40, 60)
+
+    # Add 50 entities
+    try:
+        texture = mcrfpy.Texture("assets/kenney_tinydungeon.png", 16, 16)
+
+        for i in range(50):
+            # Entity takes positional args: (position, texture, sprite_index, grid)
+            pos = mcrfpy.Vector(random.randint(5, 45), random.randint(5, 45))
+            entity = mcrfpy.Entity(pos, texture, random.randint(0, 100), grid)
+            grid.entities.append(entity)
+    except Exception as e:
+        print(f"  Note: Could not create entities: {e}")
+
+    mcrfpy.setScene("bench_grid")
+
+
+# ============================================================================
+# Results Output
+# ============================================================================
+
+def print_results():
+    """Print final benchmark results."""
+    print("\n" + "=" * 70)
+    print("BENCHMARK RESULTS")
+    print("=" * 70)
+
+    print(f"\n{'Scenario':<20} {'Avg FPS':>8} {'Avg ms':>8} {'Max ms':>8} {'Draw Calls':>10}")
+    print("-" * 70)
+
+    for name, r in results.items():
+        print(f"{name:<20} {r['avg_fps']:>8.1f} {r['avg_frame_time']:>8.2f} {r['max_frame_time']:>8.2f} {r['avg_draw_calls']:>10.0f}")
+
+    print("\n" + "-" * 70)
+    print("TIMING BREAKDOWN (% of frame time)")
+    print("-" * 70)
+    print(f"{'Scenario':<20} {'Grid':>8} {'Entity':>8} {'Python':>8} {'Anim':>8} {'Other':>8}")
+    print("-" * 70)
+
+    for name, r in results.items():
+        if 'pct_grid' in r:
+            print(f"{name:<20} {r['pct_grid']:>7.1f}% {r['pct_entity']:>7.1f}% {r['pct_python']:>7.1f}% {r['pct_animation']:>7.1f}% {r['pct_other']:>7.1f}%")
+
+    print("\n" + "=" * 70)
+
+    # Performance assessment
+    print("\nPERFORMANCE ASSESSMENT:")
+    for name, r in results.items():
+        status = "PASS" if r['avg_frame_time'] < FRAME_BUDGET_MS else "OVER BUDGET"
+        print(f"  {name}: {status} ({r['avg_frame_time']:.2f}ms vs {FRAME_BUDGET_MS:.2f}ms budget)")
+
+    print("\nBenchmark complete.")
+    sys.exit(0)
+
+
+# ============================================================================
+# Main Entry Point
+# ============================================================================
+
+if __name__ == "__main__":
+    print("=" * 70)
+    print("McRogueFace Performance Benchmark Suite")
+    print("=" * 70)
+    print(f"Configuration: {WARMUP_FRAMES} warmup frames, {MEASURE_FRAMES} measurement frames")
+    print(f"Target: {FRAME_BUDGET_MS:.2f}ms per frame (60 FPS)")
+
+    # Start the benchmark sequence
+    run_next_scenario()
diff --git a/tests/unit/benchmark_logging_test.py b/tests/unit/benchmark_logging_test.py
new file mode 100644
index 0000000..387770c
--- /dev/null
+++ b/tests/unit/benchmark_logging_test.py
@@ -0,0 +1,135 @@
+#!/usr/bin/env python3
+"""Test benchmark logging functionality (Issue #104)"""
+import mcrfpy
+import sys
+import os
+import json
+
+def run_test(runtime):
+    """Timer callback to test benchmark logging"""
+    # Stop the benchmark and get filename
+    try:
+        filename = mcrfpy.end_benchmark()
+        print(f"Benchmark written to: {filename}")
+
+        # Check file exists
+        if not os.path.exists(filename):
+            print(f"FAIL: Benchmark file not found: {filename}")
+            sys.exit(1)
+
+        # Parse and validate JSON
+        with open(filename, 'r') as f:
+            data = json.load(f)
+
+        # Validate structure
+        if 'benchmark' not in data:
+            print("FAIL: Missing 'benchmark' key")
+            sys.exit(1)
+
+        if 'frames' not in data:
+            print("FAIL: Missing 'frames' key")
+            sys.exit(1)
+
+        # Check benchmark metadata
+        bench = data['benchmark']
+        if 'pid' not in bench:
+            print("FAIL: Missing 'pid' in benchmark")
+            sys.exit(1)
+        if 'start_time' not in bench:
+            print("FAIL: Missing 'start_time' in benchmark")
+            sys.exit(1)
+        if 'end_time' not in bench:
+            print("FAIL: Missing 'end_time' in benchmark")
+            sys.exit(1)
+        if 'total_frames' not in bench:
+            print("FAIL: Missing 'total_frames' in benchmark")
+            sys.exit(1)
+
+        print(f"  PID: {bench['pid']}")
+        print(f"  Duration: {bench['duration_seconds']:.3f}s")
+        print(f"  Frames: {bench['total_frames']}")
+
+        # Check we have frames
+        if len(data['frames']) == 0:
+            print("FAIL: No frames recorded")
+            sys.exit(1)
+
+        # Check frame structure
+        frame = data['frames'][0]
+        required_fields = ['frame_number', 'timestamp_ms', 'frame_time_ms', 'fps',
+                          'work_time_ms', 'grid_render_ms', 'entity_render_ms',
+                          'python_time_ms', 'draw_calls', 'ui_elements', 'logs']
+        for field in required_fields:
+            if field not in frame:
+                print(f"FAIL: Missing field '{field}' in frame")
+                sys.exit(1)
+
+        # Check log message was captured
+        found_log = False
+        for frame in data['frames']:
+            if 'Test log message' in frame.get('logs', []):
+                found_log = True
+                break
+
+        if not found_log:
+            print("FAIL: Log message not found in any frame")
+            sys.exit(1)
+
+        # Show timing breakdown
+        f0 = data['frames'][0]
+        print(f"  First frame FPS: {f0['fps']}")
+        print(f"  Frame time: {f0['frame_time_ms']:.3f}ms, Work time: {f0['work_time_ms']:.3f}ms")
+        if f0['frame_time_ms'] > 0:
+            load_pct = (f0['work_time_ms'] / f0['frame_time_ms']) * 100
+            print(f"  Load: {load_pct:.1f}% (sleep time: {f0['frame_time_ms'] - f0['work_time_ms']:.3f}ms)")
+        print(f"  Log messages captured: Yes")
+
+        # Clean up
+        os.remove(filename)
+        print(f"  Cleaned up: {filename}")
+
+        print("PASS")
+        sys.exit(0)
+
+    except Exception as e:
+        print(f"FAIL: {e}")
+        sys.exit(1)
+
+# Test error handling - calling end without start
+try:
+    mcrfpy.end_benchmark()
+    print("FAIL: end_benchmark() should have raised RuntimeError")
+    sys.exit(1)
+except RuntimeError as e:
+    print(f"Correct error on end without start: {e}")
+
+# Test error handling - logging without start
+try:
+    mcrfpy.log_benchmark("test")
+    print("FAIL: log_benchmark() should have raised RuntimeError")
+    sys.exit(1)
+except RuntimeError as e:
+    print(f"Correct error on log without start: {e}")
+
+# Start the benchmark
+mcrfpy.start_benchmark()
+print("Benchmark started")
+
+# Test error handling - double start
+try:
+    mcrfpy.start_benchmark()
+    print("FAIL: double start_benchmark() should have raised RuntimeError")
+    sys.exit(1)
+except RuntimeError as e:
+    print(f"Correct error on double start: {e}")
+
+# Log a test message
+mcrfpy.log_benchmark("Test log message")
+print("Logged test message")
+
+# Set up scene and run for a few frames
+mcrfpy.createScene("test")
+mcrfpy.setScene("test")
+
+# Schedule test completion after ~100ms (to capture some frames)
+mcrfpy.setTimer("test", run_test, 100)