Agent identified fixes 2

README.md

@@ -112,8 +112,9 @@ with EPUB styles, punctuation, and repeated invented names:
 
 The output directory must be empty unless `--overwrite` is supplied. Copy the
 resulting `Example Book` directory into `/books` on the card. A
-section may be up to 1.5 MiB. The converter writes `CONVERSION_REPORT.txt` in
-the book directory. It records any unsupported non-ASCII characters left after
+section and its `.rsvp` sidecar may each be up to 1 MiB. The converter writes
+`CONVERSION_REPORT.txt` in the book directory. It records any unsupported
+non-ASCII characters left after
 normalizing common punctuation, ligatures, accents, whitespace, fractions, and
 ornamental breaks. Review that report before copying the book: transliterate or
 replace reported characters deliberately, or defer the book until a
@@ -123,8 +124,10 @@ printable ASCII.
 The converter also writes a compact `<section>.rsvp` file alongside every
 section. Its versioned, delta-encoded records preserve italic and bold EPUB
 markup—including semantic tags, CSS classes, and inline CSS—and reading-timing
-metadata. During conversion, the desktop-only English dictionary marks each
-word not in that dictionary. The first ten appearances of each marked word in
+metadata. The fingerprint covers the source `.txt` bytes, before the device
+applies display-only punctuation normalization. During conversion, the
+desktop-only English dictionary marks each word not in that dictionary. The
+first ten appearances of each marked word in
 the book, plus its first appearance in every section, use a 3× delay. Later
 appearances use a 2× delay. The reader uses the strongest applicable delay, so
 sentence and paragraph pauses are never compounded with unfamiliar-word
@@ -228,6 +231,10 @@ pressing the touch-edge Home button begins at the saved paragraph. It validates
 the saved section against its `TOC.txt` before opening it, then falls back to
 the first available book if the card has changed.
 
+When continuous reading reaches the end of a section, it opens the next
+section's title card and pauses. Press the touch-edge Home button to begin that
+section.
+
 The physical power switch only disconnects the battery. USB power is sufficient
 for development and flashing. The reader intentionally has no Wi-Fi, Bluetooth,
 cloud account, or synchronization feature.
@@ -248,7 +255,7 @@ cloud account, or synchronization feature.
 
 ## Limits of the first MVP
 
-- It reads sections up to 1.5 MiB from `/books/<book>/<section>.txt`, in the
+- It reads sections up to 1 MiB from `/books/<book>/<section>.txt`, in the
   order declared by that book's `TOC.txt`.
 - The built-in display font is best for printable ASCII text. UTF-8 text files
   are accepted, but accented/non-Latin characters need a Unicode font addition

TODO.md

@@ -16,13 +16,32 @@ profile that preserves the current cadence.
 
 Add a `--check` mode that reports section and sidecar sizes, filename issues,
 and unsupported characters without writing output. Offer optional splitting at
-paragraph boundaries for sections that exceed the device's 1.5 MiB file limit.
+paragraph boundaries for sections that exceed the device's 1 MiB file limit.
 
 ## Memory-limit hardware validation
 
-Stress-test the advertised maximum section and sidecar sizes on real hardware,
-record PSRAM headroom, and lower the supported limit if token indexing or
-sidecar metadata leaves insufficient memory for reliable reading.
+Stress-test the 1 MiB section and sidecar limits on real hardware, record PSRAM
+headroom, and lower the supported limit if token indexing or sidecar metadata
+leaves insufficient memory for reliable reading. Include adversarial short-word
+and dense-sidecar inputs, not just ordinary prose.
+
+## Reading continuity preference
+
+Keep the current default of pausing on every chapter title, but add an optional
+auto-continue mode for readers who want uninterrupted reading across sections.
+
+## RSVP orientation point
+
+Offer an optional focal-letter/orientation-point treatment that subtly marks a
+consistent letter within each displayed word. Keep the current centered plain
+word rendering as the default and make the feature work with italic and bold
+fonts.
+
+## Library diagnostics and import validation
+
+Add a device diagnostics screen for SD-card, TOC, missing-section, sidecar,
+and memory-limit errors. Extend converter preflight to report the same issues,
+including oversized tokens, before a book is copied to the card.
 
 ## Add anti-aliased reader fonts
 

epub_to_chapters.py

@@ -122,7 +122,8 @@ SIDECAR_HEADER = struct.Struct("<4sBBQI")
 CSS_RULE = re.compile(r"([^{}]+)\{([^{}]*)\}")
 CSS_CLASS = re.compile(r"\.([A-Za-z_-][A-Za-z0-9_-]*)")
 WORD_LOOKUP_KEY = re.compile(r"^[^A-Za-z]*([A-Za-z]+(?:['-][A-Za-z]+)*)[^A-Za-z]*$")
-MAX_SECTION_BYTES = 1500 * 1024
+MAX_SECTION_BYTES = 1024 * 1024
+MAX_TOKEN_BYTES = 256 * 1024
 MAX_SECTION_NAME_BYTES = 200
 
 TIMING_NONE = 0
@@ -333,6 +334,16 @@ def lookup_word_key(token):
     return match.group(1).lower() if match else None
 
 
+def validate_token_lengths(text):
+    """Reject a malformed section containing an impractically long token."""
+
+    for word_number, match in enumerate(re.finditer(r"\S+", text), start=1):
+        if len(match.group().encode("utf-8")) > MAX_TOKEN_BYTES:
+            raise ValueError(
+                f"token {word_number} exceeds the {MAX_TOKEN_BYTES} byte limit"
+            )
+
+
 def load_english_dictionary():
     """Load the desktop-only English dictionary required for timing analysis."""
 
@@ -1404,6 +1415,11 @@ def convert_epub(epub_path, output_dir, overwrite=False):
 
     for title, chapter in prepared_sections:
         text_bytes = chapter["text"].encode("utf-8")
+        try:
+            validate_token_lengths(chapter["text"])
+        except ValueError as exc:
+            print(f"Error: {title!r} contains an invalid token: {exc}")
+            sys.exit(1)
         sidecar_bytes = style_sidecar_bytes(
             chapter["text"], chapter["style_records"]
         )

include/Config.h

@@ -22,7 +22,11 @@ constexpr uint8_t kButtonPrevious = 12;
 constexpr uint8_t kButtonNext = 16;
 
 constexpr char kBooksDirectory[] = "/books";
-constexpr size_t kMaxBookBytes = 1500 * 1024;
+// Source sections and their optional RSVP sidecars are loaded into memory.
+constexpr size_t kMaxSectionBytes = 1024 * 1024;
+// A single token can be a long URL or identifier, but should never consume a
+// material fraction of the reader's working memory.
+constexpr uint32_t kMaxTokenBytes = 256 * 1024;
 
 constexpr uint16_t kDefaultWpm = 300;
 constexpr uint16_t kMinimumWpm = 100;

include/Reader.h

@@ -5,7 +5,7 @@
 
 struct Token {
   uint32_t offset;
-  uint16_t length;
+  uint32_t length;
   uint32_t paragraph;
   uint8_t trailingLineBreaks;
 };
@@ -39,6 +39,7 @@ class Reader {
   uint32_t index_ = 0;
   size_t nextStyleToken_ = 0;
   bool sidecarValid_ = false;
+  uint64_t sourceFingerprint_ = 0;
 
   bool loadSidecar(const std::vector<uint8_t>& sidecar);
   void seekStyleToken();

src/Library.cpp

@@ -44,7 +44,7 @@ bool Library::loadSidecar(const String& chapterPath,
   sidecarPath += ".rsvp";
   File file = SD.open(sidecarPath, FILE_READ);
   if (!file || file.isDirectory() || file.size() == 0 ||
-      static_cast<size_t>(file.size()) > config::kMaxBookBytes) {
+      static_cast<size_t>(file.size()) > config::kMaxSectionBytes) {
     file.close();
     return false;
   }
@@ -227,7 +227,7 @@ String Library::chapterName(const String& chapterPath) const {
 bool Library::loadFile(const String& path, String& contents) const {
   File file = SD.open(path, FILE_READ);
   if (!file || file.isDirectory() || file.size() == 0 ||
-      static_cast<size_t>(file.size()) > config::kMaxBookBytes) {
+      static_cast<size_t>(file.size()) > config::kMaxSectionBytes) {
     return false;
   }
   contents = file.readString();

src/Reader.cpp

@@ -4,6 +4,8 @@
 #include <ctype.h>
 #include <limits.h>
 
+#include "Config.h"
+
 namespace {
 
 constexpr uint8_t kStyleItalic = 0x01;
@@ -120,6 +122,9 @@ String normalizePunctuation(const String& text) {
 }  // namespace
 
 bool Reader::load(const String& book, const std::vector<uint8_t>& sidecar) {
+  // The sidecar describes the exact bytes on the card. Keep its fingerprint
+  // separate from the display normalization applied for tokenization.
+  sourceFingerprint_ = sourceFingerprint(book);
   book_ = normalizePunctuation(book);
   tokens_.clear();
   styleTokens_.clear();
@@ -148,7 +153,13 @@ bool Reader::load(const String& book, const std::vector<uint8_t>& sidecar) {
       lineBreaks = 0;
     }
     if (whitespace && inWord) {
-      tokens_.push_back({wordStart, static_cast<uint16_t>(i - wordStart),
+      const uint32_t wordLength = i - wordStart;
+      if (wordLength > config::kMaxTokenBytes) {
+        tokens_.clear();
+        paragraphStarts_.clear();
+        return false;
+      }
+      tokens_.push_back({wordStart, wordLength,
                          static_cast<uint32_t>(paragraphStarts_.size() - 1), 0});
       inWord = false;
     }
@@ -167,7 +178,7 @@ bool Reader::loadSidecar(const std::vector<uint8_t>& sidecar) {
       sidecar[2] != 'V' || sidecar[3] != 'P' ||
       (sidecar[4] != kSidecarVersion1 && sidecar[4] != kSidecarVersion2) ||
       sidecar[5] != 0 ||
-      readUint64Le(sidecar, 6) != sourceFingerprint(book_)) {
+      readUint64Le(sidecar, 6) != sourceFingerprint_) {
     return false;
   }
   const uint8_t sidecarVersion = sidecar[4];

src/main.cpp

@@ -23,8 +23,6 @@ bool displayIsOff = false;
 bool displayIsDimmed = false;
 uint32_t lastInteractionMs = 0;
 uint32_t nextWordMs = 0;
-uint32_t lastPersistMs = 0;
-bool stateDirty = false;
 TouchDrvCSTXXX touch;
 bool touchAvailable = false;
 bool touchPlayPauseRequested = false;
@@ -87,21 +85,9 @@ bool released(Button& button) {
   return wasPressed && button.stable == HIGH;
 }
 
-void markStateDirty() { stateDirty = true; }
-
-void persist(bool force = false) {
-  const uint32_t currentWord = reader.currentIndex();
-  if (state.wordIndex != currentWord) {
-    state.wordIndex = currentWord;
-    stateDirty = true;
-  }
-  constexpr uint32_t kProgressCheckpointMs = 30UL * 1000UL;
-  if (!stateDirty || (!force && millis() - lastPersistMs < kProgressCheckpointMs)) {
-    return;
-  }
+void persistState() {
+  state.wordIndex = reader.currentIndex();
   settings.save(state);
-  stateDirty = false;
-  lastPersistMs = millis();
 }
 
 void setReadingContext(uint8_t progressPercent) {
@@ -144,7 +130,6 @@ bool loadChapter(const String& path) {
   state.bookPath = path;
   state.wordIndex = 0;
   reader.restoreAtParagraphStart(0);
-  markStateDirty();
   readerView = ReaderView::kChapterTitle;
   playing = false;
   return true;
@@ -187,6 +172,8 @@ void drawPicker() {
 }
 
 void openMenu() {
+  // Opening the menu stops playback, so it is a manual pause checkpoint.
+  if (playing) persistState();
   playing = false;
   menuSelection = 0;
   screen = Screen::kMenu;
@@ -246,8 +233,7 @@ void applyPicker() {
   } else {
     loadChapter(pendingChapterPath);
   }
-  markStateDirty();
-  persist(true);
+  persistState();
   returnToReader();
 }
 
@@ -263,7 +249,9 @@ void togglePlayback() {
   } else {
     playing = !playing;
   }
-  persist(true);
+  // Playing progress is intentionally not checkpointed. Resume is paragraph
+  // based, so writing at each pause avoids needless NVS wear.
+  if (!playing) persistState();
   if (playing) nextWordMs = millis() + reader.delayMs(state.wpm);
 }
 
@@ -388,7 +376,7 @@ void wakeDisplay() {
 }
 
 void enterDeepSleep() {
-  persist(true);
+  persistState();
   board.displayOff();
   // GPIO12 is RTC-capable on ESP32-S3. A press (active low) wakes the reader.
   esp_sleep_enable_ext0_wakeup(static_cast<gpio_num_t>(config::kButtonPrevious), 0);
@@ -421,12 +409,10 @@ void handleInput() {
       state.wpm = state.wpm > config::kMinimumWpm + config::kWpmStep
                       ? state.wpm - config::kWpmStep
                       : config::kMinimumWpm;
-      markStateDirty();
       showCurrentWord();
     } else {
       navigatePreviousPaused();
     }
-    persist(true);
   }
   if (released(next)) {
     wakeDisplay();
@@ -443,12 +429,10 @@ void handleInput() {
       state.wpm = state.wpm + config::kWpmStep < config::kMaximumWpm
                       ? state.wpm + config::kWpmStep
                       : config::kMaximumWpm;
-      markStateDirty();
       showCurrentWord();
     } else {
       navigateNextPaused();
     }
-    persist(true);
   }
 }
 }  // namespace
@@ -509,8 +493,7 @@ void setup() {
   const uint32_t savedWord = state.wordIndex;
   reader.restoreAtParagraphStart(savedWord);
   state.wordIndex = reader.currentIndex();
-  stateDirty = sanitizedSettings || state.wordIndex != savedWord;
-  persist(true);
+  if (sanitizedSettings || state.wordIndex != savedWord) persistState();
   readerView = ReaderView::kChapterTitle;
   showReaderScreen();
   lastInteractionMs = millis();
@@ -531,11 +514,12 @@ void loop() {
         playing = false;
         showReaderScreen();
       }
-      persist();
+      // Reaching a chapter boundary pauses automatically; save that new
+      // chapter before waiting for the reader to continue.
+      persistState();
       lastInteractionMs = millis();
     } else {
       showCurrentWord();
-      persist();
       nextWordMs = millis() + reader.delayMs(state.wpm);
     }
   }

tests/test_epub_to_chapters.py

@@ -12,6 +12,7 @@ from epub_to_chapters import (
     STYLE_ITALIC,
     TIMING_DOUBLE,
     TIMING_TRIPLE,
+    MAX_TOKEN_BYTES,
     add_unfamiliar_word_timing,
     decode_styled_text,
     document_root,
@@ -24,6 +25,7 @@ from epub_to_chapters import (
     parse_document,
     source_fingerprint,
     stylesheet_class_styles,
+    validate_token_lengths,
     write_style_sidecar,
     write_conversion_report,
 )
@@ -66,6 +68,15 @@ class DisplayTextNormalizationTests(unittest.TestCase):
         self.assertLessEqual(len(name.encode("utf-8")), 200)
 
 
+class TokenValidationTests(unittest.TestCase):
+    def test_allows_a_token_at_the_configured_byte_limit(self):
+        validate_token_lengths("a" * MAX_TOKEN_BYTES)
+
+    def test_rejects_a_token_larger_than_the_configured_byte_limit(self):
+        with self.assertRaises(ValueError):
+            validate_token_lengths("a" * (MAX_TOKEN_BYTES + 1))
+
+
 class ConversionReportTests(unittest.TestCase):
     def test_reports_remaining_non_ascii_characters_by_generated_file(self):
         with tempfile.TemporaryDirectory() as temporary_directory: