docs(layout): restore columns_have_prose rustdoc displaced by hoisted const

The hoisted LINE_FILL_THRESHOLD landed between the gate's rustdoc block
and the items that followed, absorbing the function's documentation onto
the constant. The docs return to the function, extended to cover the
sustained-run acceptance path.

src/detector.rs

@@ -403,8 +403,15 @@ pub(crate) fn detect_from_document(
                     && !(analysis.has_decodable_text_fonts && analysis.text_operator_count >= 10);
                 let looks_like_scan =
                     analysis.image_count <= 1 && analysis.text_operator_count < 50 && alphanum_low;
+                // A template-image page below the `pages_with_text` floor is
+                // a scan with incidental chrome (masthead, stamp, date line)
+                // even when that chrome is diverse, decodable text — keep
+                // this in sync with `page_ocr_signals`.
+                let sparse_text_over_scan = analysis.has_template_image
+                    && analysis.text_operator_count < config.min_text_ops_per_page.max(10);
                 if (analysis.has_template_image && looks_like_scan)
                     || analysis.has_vector_text
+                    || sparse_text_over_scan
                     || (analysis.text_operator_count < config.min_text_ops_per_page
                         && analysis.has_images)
                 {
@@ -1795,17 +1802,24 @@ pub(crate) fn analyze_page_images(doc: &Document, page_id: ObjectId) -> (bool, u
 ///    low alphanumeric diversity in raw string operands (unless decodable
 ///    CID/ToUnicode fonts explain that away) — the gate used for
 ///    `pages_with_template_images` and Mixed-type per-page routing.
-/// 2. Insufficient real text volume, using `DetectionConfig::default()`'s
-///    `min_text_ops_per_page` (3) — the same threshold Mixed-type per-page
-///    routing applies via `text_operator_count < config.min_text_ops_per_page
-///    && has_images` (simplified here since a template image implies
-///    `has_images`). Deliberately *not* the higher `effective_min_ops`
-///    floor (`min_text_ops_per_page.max(10)`) that whole-document
-///    `PdfType::ImageBased`/`Scanned` classification uses for
-///    `pages_with_text` — that's a cross-page aggregate decision this
-///    per-page function has no way to replicate exactly, and the lower
-///    per-page threshold is the one a single page's own signals can
-///    actually agree with.
+/// 2. Insufficient real text volume, using the same `effective_min_ops`
+///    floor (`min_text_ops_per_page.max(10)`) that `pages_with_text`
+///    applies to image-bearing pages. That floor is a per-page judgment,
+///    not part of the cross-page aggregate: classification counts a
+///    template-image page with fewer ops as textless and routes it to OCR,
+///    so this function must agree. The lower bare threshold (3) let a
+///    full-page scan carrying a small native masthead — a newspaper
+///    header, stamp, or date line of ~4 diverse, decodable text ops —
+///    extract as "a text page" here while whole-document classification
+///    called the same page scanned, silently dropping the page body from
+///    OCR routing. `alphanum_low` can't catch that case: masthead chrome
+///    is real text, so its byte diversity is high.
+///
+/// This function always evaluates against `DetectionConfig::default()` —
+/// it has no config parameter, and the per-page extraction path that calls
+/// it never carries one. A caller passing a custom `min_text_ops_per_page`
+/// to `detect_from_document` affects whole-document detection only; the
+/// two paths agree under the default configuration.
 ///
 /// `has_vector_text` is true when a page has vector-outlined text (glyphs
 /// drawn as paths rather than shown via text-showing operators) —
@@ -1827,7 +1841,7 @@ pub(crate) fn page_ocr_signals(doc: &Document, page_id: ObjectId) -> (bool, bool
         let looks_like_scan =
             analysis.image_count <= 1 && analysis.text_operator_count < 50 && alphanum_low;
         let insufficient_text =
-            analysis.text_operator_count < DetectionConfig::default().min_text_ops_per_page;
+            analysis.text_operator_count < DetectionConfig::default().min_text_ops_per_page.max(10);
         looks_like_scan || insufficient_text
     };
 
@@ -2995,6 +3009,130 @@ mod tests {
         );
     }
 
+    // ---------- masthead-over-scan tests: template image + sparse chrome ----------
+
+    /// Builds a page whose only image is a full-page scan inside a Form
+    /// XObject, plus `masthead_ops` native text-show ops of diverse,
+    /// decodable chrome (newspaper masthead / date line style).
+    fn masthead_scan_page(masthead_lines: &[&str]) -> (Document, ObjectId) {
+        use lopdf::dictionary;
+        let mut doc = Document::with_version("1.4");
+        let pages_id = doc.new_object_id();
+        let page_id = doc.new_object_id();
+
+        let image_id = doc.add_object(Object::Stream(lopdf::Stream::new(
+            dictionary! {
+                "Type" => "XObject",
+                "Subtype" => Object::Name(b"Image".to_vec()),
+                "Width" => Object::Integer(1500),
+                "Height" => Object::Integer(2383),
+            },
+            Vec::new(),
+        )));
+        let form_id = doc.add_object(Object::Stream(lopdf::Stream::new(
+            dictionary! {
+                "Type" => "XObject",
+                "Subtype" => Object::Name(b"Form".to_vec()),
+                "Resources" => dictionary! {
+                    "XObject" => dictionary! {
+                        "Im0" => Object::Reference(image_id),
+                    },
+                },
+            },
+            b"1500 0 0 2383 0 0 cm /Im0 Do".to_vec(),
+        )));
+        let font_id = doc.add_object(dictionary! {
+            "Type" => "Font",
+            "Subtype" => Object::Name(b"Type1".to_vec()),
+            "BaseFont" => Object::Name(b"Helvetica".to_vec()),
+        });
+
+        let mut content = b"q /Fm0 Do Q BT /F1 12 Tf ".to_vec();
+        for line in masthead_lines {
+            content.extend_from_slice(format!("({line}) Tj ").as_bytes());
+        }
+        content.extend_from_slice(b"ET");
+        let content_id =
+            doc.add_object(Object::Stream(lopdf::Stream::new(dictionary! {}, content)));
+
+        doc.objects.insert(
+            page_id,
+            Object::Dictionary(dictionary! {
+                "Type" => "Page",
+                "Parent" => Object::Reference(pages_id),
+                "MediaBox" => vec![0.into(), 0.into(), 1500.into(), 2383.into()],
+                "Resources" => dictionary! {
+                    "Font" => dictionary! { "F1" => Object::Reference(font_id) },
+                    "XObject" => dictionary! { "Fm0" => Object::Reference(form_id) },
+                },
+                "Contents" => Object::Reference(content_id),
+            }),
+        );
+        doc.objects.insert(
+            pages_id,
+            Object::Dictionary(dictionary! {
+                "Type" => "Pages",
+                "Kids" => vec![Object::Reference(page_id)],
+                "Count" => Object::Integer(1),
+            }),
+        );
+        (doc, page_id)
+    }
+
+    #[test]
+    fn test_masthead_over_form_wrapped_scan_needs_ocr() {
+        // A full-page scan wrapped in a Form XObject with ~4 ops of real,
+        // diverse masthead text. `alphanum_low` can't flag it (the chrome is
+        // genuine text), so the sparse-text floor must: without OCR the page
+        // body is silently lost while classification calls the page scanned.
+        let (doc, page_id) = masthead_scan_page(&[
+            "18",
+            "FINANCIAL EXPRESS",
+            "WWW.FINANCIALEXPRESS.COM",
+            "FRIDAY, DECEMBER 13, 2024",
+        ]);
+        let analysis = analyze_page_content(&doc, page_id);
+        assert!(
+            analysis.has_template_image,
+            "sanity: full-page image inside the form must be found"
+        );
+        assert!(
+            analysis.unique_alphanum_chars >= 10,
+            "sanity: masthead text is diverse, alphanum_low cannot fire"
+        );
+        let (needs_ocr, _) = page_ocr_signals(&doc, page_id);
+        assert!(
+            needs_ocr,
+            "template image + text below the pages_with_text floor is a scan"
+        );
+    }
+
+    #[test]
+    fn test_text_page_over_background_image_stays_native() {
+        // Counterpart: a real text page over a full-page background image
+        // (letterhead/watermark) has enough text ops to clear the
+        // `pages_with_text` floor and must NOT be routed to OCR.
+        let lines: Vec<String> = (0..12)
+            .map(|i| format!("Paragraph line {i} with ordinary body text"))
+            .collect();
+        let refs: Vec<&str> = lines.iter().map(String::as_str).collect();
+        let (doc, page_id) = masthead_scan_page(&refs);
+        let analysis = analyze_page_content(&doc, page_id);
+        assert!(
+            analysis.has_template_image,
+            "sanity: background image found"
+        );
+        assert!(
+            analysis.text_operator_count >= 10,
+            "sanity: body text clears the floor"
+        );
+        let (needs_ocr, _) = page_ocr_signals(&doc, page_id);
+        assert!(
+            !needs_ocr,
+            "a text page with a background image must stay native"
+        );
+    }
+
     // ---------- P2 tests: Form XObject font traversal ----------
 
     #[test]

src/extractor/content_stream.rs

@@ -561,7 +561,11 @@ pub(crate) fn extract_page_text_items(
                                 y,
                                 width,
                                 height: rendered_size,
-                                font: current_font.clone(),
+                                font: crate::extractor::fonts::item_font_name(
+                                    &current_font,
+                                    base_font,
+                                )
+                                .to_string(),
                                 font_size: rendered_size,
                                 page: page_num,
                                 is_bold: is_bold_font(base_font) || desc_bold,
@@ -745,7 +749,11 @@ pub(crate) fn extract_page_text_items(
                                     y,
                                     width,
                                     height: rendered_size,
-                                    font: current_font.clone(),
+                                    font: crate::extractor::fonts::item_font_name(
+                                        &current_font,
+                                        base_font,
+                                    )
+                                    .to_string(),
                                     font_size: rendered_size,
                                     page: page_num,
                                     is_bold: is_bold_font(base_font) || desc_bold,
@@ -852,7 +860,11 @@ pub(crate) fn extract_page_text_items(
                                 y,
                                 width,
                                 height: rendered_size,
-                                font: current_font.clone(),
+                                font: crate::extractor::fonts::item_font_name(
+                                    &current_font,
+                                    base_font,
+                                )
+                                .to_string(),
                                 font_size: rendered_size,
                                 page: page_num,
                                 is_bold: is_bold_font(base_font) || desc_bold,
@@ -1005,7 +1017,11 @@ pub(crate) fn extract_page_text_items(
                                     y,
                                     width,
                                     height: rendered_size,
-                                    font: current_font.clone(),
+                                    font: crate::extractor::fonts::item_font_name(
+                                        &current_font,
+                                        base_font,
+                                    )
+                                    .to_string(),
                                     font_size: rendered_size,
                                     page: page_num,
                                     is_bold: is_bold_font(base_font) || desc_bold,

src/extractor/fonts.rs

@@ -225,6 +225,26 @@ pub(crate) fn build_type3_scales(
     scales
 }
 
+/// The name a `TextItem` carries for its font: the `/BaseFont` family name
+/// ("ABCDEF+CMMI10"), which identifies the actual face, rather than the
+/// arbitrary per-page resource tag ("F2").
+///
+/// Exception: resource names using Distiller's CID convention (`C2_0`,
+/// `C0_1`) are kept as-is — `text_utils::is_cid_font` keys on that prefix
+/// for micro-gap joining, and the family name carries no CID marker to
+/// replace it. This is a known, deliberate wart: `TextItem::font` is the
+/// face name except for this one producer convention. The clean fix is an
+/// explicit CID flag on `TextItem`, which touches its ~29 construction
+/// sites; do that migration when `TextItem` next changes shape, and delete
+/// this carve-out with it.
+pub(crate) fn item_font_name<'a>(resource_name: &'a str, base_font: &'a str) -> &'a str {
+    if crate::text_utils::is_cid_font(resource_name) {
+        resource_name
+    } else {
+        base_font
+    }
+}
+
 /// Parse font widths from a font dictionary, dispatching by Subtype
 pub(crate) fn parse_font_widths(
     doc: &Document,
@@ -1664,6 +1684,17 @@ fn score_text(text: &str) -> i32 {
 #[cfg(test)]
 mod tests {
 
+    #[test]
+    fn item_font_name_prefers_family_over_resource_tag() {
+        use super::item_font_name;
+        assert_eq!(item_font_name("F2", "ABCDEF+CMMI10"), "ABCDEF+CMMI10");
+        assert_eq!(item_font_name("T22", "Times-Roman"), "Times-Roman");
+        // Distiller CID-convention resources keep the resource name:
+        // is_cid_font keys on the C2_/C0_ prefix for micro-gap joining.
+        assert_eq!(item_font_name("C2_0", "ABCDEE+SimSun"), "C2_0");
+        assert_eq!(item_font_name("C0_1", "ABCDEE+MSMincho"), "C0_1");
+    }
+
     #[test]
     fn type3_scale_resolves_indirect_matrix_and_bbox_numbers() {
         use lopdf::{dictionary, Document, Object};

src/extractor/layout.rs

@@ -462,19 +462,95 @@ fn try_xy_cut_split(
     ])
 }
 
+/// A prose line must span at least this fraction of its column's width to
+/// count as "full" — shared by the gate's ratio and run measurements.
+const LINE_FILL_THRESHOLD: f32 = 0.45;
+
+/// Per-column line measurements backing the prose-evidence predicates in
+/// [`columns_have_prose`]: how many grouped lines exist, how many are
+/// "full" (span most of the column), the longest *vertically contiguous*
+/// run of full lines, and the item count per line.
+#[derive(Default)]
+struct ProseLineStats {
+    full_lines: usize,
+    total_lines: usize,
+    total_items: usize,
+    current_run: usize,
+    best_run: usize,
+    previous_line_y: Option<f32>,
+    previous_line_height: f32,
+}
+
+impl ProseLineStats {
+    /// A run only counts as a paragraph block while lines follow at normal
+    /// leading; a full line resuming after a figure-sized vertical gap
+    /// starts a new run rather than extending the previous one.
+    const MAX_LEADING_FACTOR: f32 = 2.5;
+
+    fn flush_line(&mut self, line_items: &[&TextItem], col: &ColumnRegion, col_width: f32) {
+        if line_items.is_empty() {
+            return;
+        }
+        self.total_lines += 1;
+        self.total_items += line_items.len();
+
+        let line_y = line_items[0].y;
+        let line_height = line_items
+            .iter()
+            .map(|i| i.height)
+            .fold(0.0_f32, f32::max)
+            .max(1.0);
+        if let Some(previous_y) = self.previous_line_y {
+            let leading = (previous_y - line_y).abs();
+            if leading > self.previous_line_height.max(line_height) * Self::MAX_LEADING_FACTOR {
+                self.current_run = 0;
+            }
+        }
+        self.previous_line_y = Some(line_y);
+        self.previous_line_height = line_height;
+
+        // Compute the span of text on this line within the column
+        let left = line_items
+            .iter()
+            .map(|i| i.x.max(col.x_min))
+            .fold(f32::INFINITY, f32::min);
+        let right = line_items
+            .iter()
+            .map(|i| (i.x + effective_width(i)).min(col.x_max))
+            .fold(f32::NEG_INFINITY, f32::max);
+        let span = (right - left).max(0.0);
+        if span >= col_width * LINE_FILL_THRESHOLD {
+            self.full_lines += 1;
+            self.current_run += 1;
+            self.best_run = self.best_run.max(self.current_run);
+        } else {
+            self.current_run = 0;
+        }
+    }
+}
+
 /// Check whether each proposed column contains paragraph-like content.
 ///
 /// Groups items per column into rough lines by Y-proximity, then measures
 /// what fraction of those lines span a significant portion of the column
 /// width. Two-column prose (justified or ragged-right) produces lines that
 /// fill most of the column width. Tables, forms, and checklists produce
-/// short scattered items that don't.
+/// short scattered items that don't. A column whose global ratio is diluted
+/// by a figure still qualifies through a sustained run of consecutive
+/// full-width lines at normal leading — a paragraph block scattered
+/// layouts cannot produce.
 ///
-/// Returns true only when *every* column passes a minimum prose density.
+/// Returns true only when *every* column passes the prose evidence.
 fn columns_have_prose(columns: &[ColumnRegion], items: &[&TextItem]) -> bool {
     const Y_TOL: f32 = 3.0; // y-proximity to group items into the same line
-    const LINE_FILL_THRESHOLD: f32 = 0.45; // line must span ≥45% of column width
-    const MIN_PROSE_RATIO: f32 = 0.40; // ≥40% of lines must be "full"
+    const MIN_PROSE_RATIO: f32 = 0.40; // ≥40% of lines must be "full"...
+                                       // ...or the column contains a sustained paragraph block: this many
+                                       // CONSECUTIVE full lines. A prose column hosting a figure + caption can
+                                       // fall under the global ratio (the fragments dilute it), but the
+                                       // scattered layouts this gate exists to reject — tables, TOCs,
+                                       // checklists, forms — cannot produce an unbroken block of full-width
+                                       // lines.
+    const MIN_PROSE_RUN: usize = 6;
     const MIN_LINES: usize = 8; // need enough lines to judge
     const MIN_COL_WIDTH: f32 = 120.0; // columns must be ≥120pt (not narrow sidebars/fragments)
     const MAX_AVG_ITEMS_PER_LINE: f32 = 3.5; // prose has 1-3 items/line; tables/forms have 4+
@@ -504,36 +580,10 @@ fn columns_have_prose(columns: &[ColumnRegion], items: &[&TextItem]) -> bool {
         sorted.sort_by(|a, b| b.y.total_cmp(&a.y));
 
         // Group into lines by Y-proximity and measure fill + item count
-        let mut full_lines = 0usize;
-        let mut total_lines = 0usize;
-        let mut total_items_in_lines = 0usize;
+        let mut stats = ProseLineStats::default();
         let mut line_items: Vec<&TextItem> = Vec::new();
         let mut line_y = f32::NAN;
 
-        let flush_line = |line_items: &[&TextItem],
-                          full: &mut usize,
-                          total: &mut usize,
-                          total_items: &mut usize| {
-            if line_items.is_empty() {
-                return;
-            }
-            *total += 1;
-            *total_items += line_items.len();
-            // Compute the span of text on this line within the column
-            let left = line_items
-                .iter()
-                .map(|i| i.x.max(col.x_min))
-                .fold(f32::INFINITY, f32::min);
-            let right = line_items
-                .iter()
-                .map(|i| (i.x + effective_width(i)).min(col.x_max))
-                .fold(f32::NEG_INFINITY, f32::max);
-            let span = (right - left).max(0.0);
-            if span >= col_width * LINE_FILL_THRESHOLD {
-                *full += 1;
-            }
-        };
-
         for item in &sorted {
             if line_items.is_empty() || (line_y - item.y).abs() < Y_TOL {
                 if line_items.is_empty() {
@@ -541,35 +591,29 @@ fn columns_have_prose(columns: &[ColumnRegion], items: &[&TextItem]) -> bool {
                 }
                 line_items.push(item);
             } else {
-                flush_line(
-                    &line_items,
-                    &mut full_lines,
-                    &mut total_lines,
-                    &mut total_items_in_lines,
-                );
+                stats.flush_line(&line_items, col, col_width);
                 line_items.clear();
                 line_y = item.y;
                 line_items.push(item);
             }
         }
-        flush_line(
-            &line_items,
-            &mut full_lines,
-            &mut total_lines,
-            &mut total_items_in_lines,
-        );
+        stats.flush_line(&line_items, col, col_width);
 
-        if total_lines < MIN_LINES {
+        if stats.total_lines < MIN_LINES {
             return false;
         }
 
+        let full_lines = stats.full_lines;
+        let total_lines = stats.total_lines;
+        let best_run = stats.best_run;
+        let total_items_in_lines = stats.total_items;
         let ratio = full_lines as f32 / total_lines as f32;
         let avg_items = total_items_in_lines as f32 / total_lines as f32;
         debug!(
-            "columns_have_prose: col [{:.0}..{:.0}] lines={} full={} ratio={:.2} avg_items={:.1}",
-            col.x_min, col.x_max, total_lines, full_lines, ratio, avg_items
+            "columns_have_prose: col [{:.0}..{:.0}] lines={} full={} ratio={:.2} run={} avg_items={:.1}",
+            col.x_min, col.x_max, total_lines, full_lines, ratio, best_run, avg_items
         );
-        if ratio < MIN_PROSE_RATIO {
+        if ratio < MIN_PROSE_RATIO && best_run < MIN_PROSE_RUN {
             return false;
         }
         // Tables and forms tend to have many small items per line (one per cell),
@@ -2567,6 +2611,85 @@ mod tests {
         }
     }
 
+    #[test]
+    fn prose_gate_accepts_figure_diluted_column_via_run() {
+        // A prose column hosting a figure: 9 consecutive full-width lines
+        // (a paragraph block) followed by many short caption/figure
+        // fragments. The global full-line ratio falls under 40%, but the
+        // sustained run proves flowing prose.
+        let mut items: Vec<TextItem> = Vec::new();
+        for line in 0..9 {
+            // full-width prose line, ~230pt wide in a 250pt column
+            items.push(make_item(
+                1,
+                10.0,
+                700.0 - line as f32 * 14.0,
+                &"m".repeat(38),
+            ));
+        }
+        for line in 0..16 {
+            // short figure/caption fragments
+            items.push(make_item(1, 60.0, 560.0 - line as f32 * 14.0, "cap"));
+        }
+        let column = ColumnRegion {
+            x_min: 0.0,
+            x_max: 250.0,
+        };
+        let refs: Vec<&TextItem> = items.iter().collect();
+        assert!(columns_have_prose(&[column], &refs));
+    }
+
+    #[test]
+    fn prose_gate_run_requires_vertical_continuity() {
+        // Full-width lines separated by figure-sized vertical gaps are not
+        // a paragraph block: the run must reset across large leading, so a
+        // column of scattered wide labels stays rejected.
+        let mut items: Vec<TextItem> = Vec::new();
+        for line in 0..6 {
+            // Wide labels, sequence-consecutive but 90pt apart — far beyond
+            // normal leading. Without the continuity rule they would count
+            // as a 6-line paragraph block.
+            items.push(make_item(
+                1,
+                10.0,
+                720.0 - line as f32 * 90.0,
+                &"m".repeat(38),
+            ));
+        }
+        for line in 0..12 {
+            // Short fragments below, keeping total lines high and the
+            // global full-line ratio (6/18) under the 40% bar.
+            items.push(make_item(1, 60.0, 150.0 - line as f32 * 12.0, "box"));
+        }
+        let column = ColumnRegion {
+            x_min: 0.0,
+            x_max: 250.0,
+        };
+        let refs: Vec<&TextItem> = items.iter().collect();
+        assert!(!columns_have_prose(&[column], &refs));
+    }
+
+    #[test]
+    fn prose_gate_rejects_scattered_short_lines() {
+        // Checklist/form-like column: no sustained block of full lines and
+        // a low global ratio must still be rejected.
+        let mut items: Vec<TextItem> = Vec::new();
+        for line in 0..24 {
+            let text = if line % 4 == 0 {
+                "m".repeat(38)
+            } else {
+                "box".to_string()
+            };
+            items.push(make_item(1, 10.0, 700.0 - line as f32 * 14.0, &text));
+        }
+        let column = ColumnRegion {
+            x_min: 0.0,
+            x_max: 250.0,
+        };
+        let refs: Vec<&TextItem> = items.iter().collect();
+        assert!(!columns_have_prose(&[column], &refs));
+    }
+
     /// Generate dense items in a horizontal zone across many Y positions.
     /// Items are placed with overlapping coverage so no intra-zone valleys appear.
     fn fill_zone(page: u32, x_start: f32, x_end: f32, y_start: f32, y_end: f32) -> Vec<TextItem> {

src/extractor/xobjects.rs

@@ -620,7 +620,11 @@ fn extract_form_xobject_text_inner(
                                 y,
                                 width,
                                 height: rendered_size,
-                                font: current_font.clone(),
+                                font: crate::extractor::fonts::item_font_name(
+                                    &current_font,
+                                    base_font,
+                                )
+                                .to_string(),
                                 font_size: rendered_size,
                                 page: page_num,
                                 is_bold: is_bold_font(base_font) || desc_bold,
@@ -775,7 +779,11 @@ fn extract_form_xobject_text_inner(
                                     y,
                                     width,
                                     height: rendered_size,
-                                    font: current_font.clone(),
+                                    font: crate::extractor::fonts::item_font_name(
+                                        &current_font,
+                                        base_font,
+                                    )
+                                    .to_string(),
                                     font_size: rendered_size,
                                     page: page_num,
                                     is_bold: is_bold_font(base_font) || desc_bold,

src/markdown/classify.rs

@@ -203,9 +203,42 @@ pub(crate) fn is_code_like(text: &str) -> bool {
     false
 }
 
+/// True when a line's text is essentially all monospace (≥90% by character
+/// count). Code lines are wholly monospace; anything less is prose carrying
+/// mono-styled fragments — a URL sidebar, or a sentence quoting an inline
+/// code literal — and fencing it would split paragraphs mid-sentence.
+/// Any-item matching was safe only while items carried opaque font resource
+/// names that never matched the monospace patterns; items now carry real
+/// family names.
+pub(crate) fn line_is_monospace(line: &crate::types::TextLine) -> bool {
+    let mut monospace_chars = 0usize;
+    let mut total_chars = 0usize;
+    for item in &line.items {
+        let text = item.text.trim();
+        let chars = text.chars().count();
+        total_chars += chars;
+        // Hyperlinks and underlined text set in a mono face are link
+        // styling, not code — a URL sidebar must not fence lyric lines.
+        let looks_like_link = item.is_underline
+            || matches!(item.item_type, crate::types::ItemType::Link(_))
+            || text.contains("://")
+            || text.starts_with("www.");
+        if is_monospace_font(&item.font) && !looks_like_link {
+            monospace_chars += chars;
+        }
+    }
+    total_chars > 0 && monospace_chars * 10 >= total_chars * 9
+}
+
 /// Check if font name indicates monospace
 pub(crate) fn is_monospace_font(font_name: &str) -> bool {
     let lower = font_name.to_lowercase();
+    // "Monotype" is a foundry prefix on proportional faces (Monotype
+    // Corsiva, Monotype Garamond) — it must not satisfy the generic "mono"
+    // token below.
+    if lower.contains("monotype") {
+        return false;
+    }
     let patterns = [
         "courier",
         "consolas",
@@ -230,6 +263,17 @@ pub(crate) fn is_monospace_font(font_name: &str) -> bool {
 mod tests {
     use super::*;
 
+    #[test]
+    fn monotype_foundry_faces_are_not_monospace() {
+        // "Monotype" is a foundry prefix on proportional faces; the generic
+        // "mono" token must not classify them as code fonts.
+        assert!(!is_monospace_font("MonotypeCorsiva"));
+        assert!(!is_monospace_font("ABCDEF+Monotype-Garamond"));
+        assert!(is_monospace_font("RobotoMono-Regular"));
+        assert!(is_monospace_font("PTMono"));
+        assert!(is_monospace_font("Courier"));
+    }
+
     #[test]
     fn format_list_item_plain_bullet() {
         assert_eq!(format_list_item("● Item"), "- Item");

src/markdown/convert.rs

@@ -11,9 +11,7 @@ use super::analysis::{
     detect_header_level, font_size_rarity, has_dot_leaders, is_heading_fragment, is_toc_entry_line,
     is_toc_marker_heading,
 };
-use super::classify::{
-    format_list_item, is_caption_line, is_list_item, is_monospace_font, starts_with_bullet_marker,
-};
+use super::classify::{format_list_item, is_caption_line, is_list_item, starts_with_bullet_marker};
 use super::heading::classify_heading_sequences;
 use super::postprocess::clean_markdown;
 use super::preprocess::{merge_drop_caps, merge_heading_lines};
@@ -771,7 +769,27 @@ pub(super) fn to_markdown_from_lines_with_tables_and_images(
     let mut in_list = false;
     let mut in_paragraph = false;
     let mut last_list_x: Option<f32> = None;
+    // Code lines accumulate here and the fence is emitted only when the
+    // block flushes with content — an empty ``` ``` pair can never appear.
+    fn flush_code_block(output: &mut String, pending_code: &mut String) {
+        let trimmed = pending_code.trim();
+        // A fragment too short to be code — a lone ® or stray glyph set in
+        // a mono face — reads better as plain text than as a fenced block.
+        if trimmed.chars().count() < 3 {
+            if !trimmed.is_empty() {
+                output.push_str(trimmed);
+                output.push_str("\n\n");
+            }
+        } else {
+            output.push_str("```\n");
+            output.push_str(pending_code);
+            output.push_str("```\n");
+        }
+        pending_code.clear();
+    }
+
     let mut in_code_block = false;
+    let mut pending_code = String::new();
     let mut prev_had_dot_leaders = false;
     let mut paragraph_in_wrapped_bold_run = false;
     let mut toc_suppress_page: Option<u32> = None;
@@ -805,7 +823,7 @@ pub(super) fn to_markdown_from_lines_with_tables_and_images(
             // Flush current page's remaining tables and images
             if current_page > 0 {
                 if in_code_block {
-                    output.push_str("```\n");
+                    flush_code_block(&mut output, &mut pending_code);
                     in_code_block = false;
                 }
                 flush_page_tables_and_images(
@@ -867,6 +885,14 @@ pub(super) fn to_markdown_from_lines_with_tables_and_images(
                     PositionedBlockKind::Image => inserted_images.contains(&(current_page, idx)),
                 };
                 if positioned_block_precedes_line(block, line) && !already_inserted {
+                    // Code lines buffer until their block closes; flush them
+                    // first so this block cannot jump ahead of code that
+                    // precedes it in reading order. A code line after the
+                    // block reopens a new fence naturally.
+                    if in_code_block {
+                        flush_code_block(&mut output, &mut pending_code);
+                        in_code_block = false;
+                    }
                     if in_paragraph {
                         output.push_str("\n\n");
                         in_paragraph = false;
@@ -937,15 +963,22 @@ pub(super) fn to_markdown_from_lines_with_tables_and_images(
         // These should be on their own line followed by a paragraph break
         let struct_role = struct_roles.and_then(|roles| resolve_line_struct_role(line, roles));
 
-        // Determine if this line is code (struct-tree or font-based) for block accumulation
+        // Determine if this line is code (struct-tree or font-based) for
+        // block accumulation. Font-based detection only opens a block at a
+        // paragraph boundary: a mono-set line that continues an open prose
+        // paragraph is the producer smearing an inline code literal's style
+        // across a wrapped line (HTML-to-PDF exports do this), and fencing
+        // it would cut the sentence in three.
         let is_code_line = struct_role
             .as_ref()
             .is_some_and(|r| matches!(r, StructRole::Code))
-            || (options.detect_code && line.items.iter().any(|i| is_monospace_font(&i.font)));
+            || (options.detect_code
+                && (in_code_block || !in_paragraph)
+                && super::classify::line_is_monospace(line));
 
         // Close code block when transitioning to non-code
         if in_code_block && !is_code_line {
-            output.push_str("```\n");
+            flush_code_block(&mut output, &mut pending_code);
             in_code_block = false;
         }
 
@@ -1179,12 +1212,9 @@ pub(super) fn to_markdown_from_lines_with_tables_and_images(
                 in_paragraph = false;
                 paragraph_in_wrapped_bold_run = false;
             }
-            if !in_code_block {
-                output.push_str("```\n");
-                in_code_block = true;
-            }
-            output.push_str(plain_trimmed);
-            output.push('\n');
+            in_code_block = true;
+            pending_code.push_str(plain_trimmed);
+            pending_code.push('\n');
             continue;
         }
 
@@ -1209,7 +1239,7 @@ pub(super) fn to_markdown_from_lines_with_tables_and_images(
 
     // Close any trailing code block
     if in_code_block {
-        output.push_str("```\n");
+        flush_code_block(&mut output, &mut pending_code);
     }
 
     // Flush current page and any remaining pages with tables/images
@@ -1370,7 +1400,7 @@ pub fn to_markdown_from_lines(lines: Vec<TextLine>, options: MarkdownOptions) ->
             && !is_toc_entry_line(plain_trimmed)
             && !is_heading_fragment(plain_trimmed)
             && toc_suppress_page != Some(line.page)
-            && !(options.detect_code && line.items.iter().any(|i| is_monospace_font(&i.font)))
+            && !(options.detect_code && super::classify::line_is_monospace(line))
         {
             let line_font_size = line.items.first().map(|i| i.font_size).unwrap_or(base_size);
             if let Some(header_level) = detect_header_level(
@@ -1471,19 +1501,13 @@ pub fn to_markdown_from_lines(lines: Vec<TextLine>, options: MarkdownOptions) ->
             }
         }
 
-        // Detect code blocks by font
-        if options.detect_code {
-            let is_mono = line.items.iter().any(|i| is_monospace_font(&i.font));
-            if is_mono {
-                if in_paragraph {
-                    output.push_str("\n\n");
-                    in_paragraph = false;
-                    paragraph_in_wrapped_bold_run = false;
-                }
-                // Use plain text for code blocks
-                output.push_str(&format!("```\n{}\n```\n", plain_trimmed));
-                continue;
-            }
+        // Detect code blocks by font. Only at a paragraph boundary — a
+        // mono-set line continuing an open prose paragraph is an inline
+        // code literal's style smeared across a wrapped line, not code.
+        if options.detect_code && !in_paragraph && super::classify::line_is_monospace(line) {
+            // Use plain text for code blocks
+            output.push_str(&format!("```\n{}\n```\n", plain_trimmed));
+            continue;
         }
 
         // Regular text - join lines within same paragraph with space

src/vision/contracts.rs

@@ -237,6 +237,13 @@ pub trait OcrEngine: Send + Sync {
         pages: &[RenderedPage],
         options: &OcrOptions,
     ) -> Result<Vec<OcrPage>, Self::Error>;
+
+    /// Number of pages this engine can process concurrently in one
+    /// `recognize` call. The pipeline sizes its page batches from this so a
+    /// parallel engine is not starved by small chunks; `1` means sequential.
+    fn preferred_page_concurrency(&self) -> usize {
+        1
+    }
 }
 
 #[cfg(test)]

src/vision/oar.rs

@@ -1,11 +1,14 @@
 //! PP-OCRv6 Small implementation backed by OAR and ONNX Runtime.
 
 use std::path::PathBuf;
+use std::sync::Arc;
 use std::time::Instant;
 
 use image::RgbImage;
 use oar_ocr::core::config::onnx::OrtSessionConfig;
-use oar_ocr::oarocr::{OAROCRBuilder, OAROCR};
+use oar_ocr::domain::tasks::TextDetectionConfig;
+use oar_ocr::oarocr::{EdgeProcessor, TextCroppingProcessor};
+use oar_ocr::predictors::{TextDetectionPredictor, TextRecognitionPredictor};
 use oar_ocr::processors::BoundingBox;
 use thiserror::Error;
 
@@ -70,17 +73,170 @@ pub enum OarOcrError {
     Backend(#[from] oar_ocr::core::OCRError),
 }
 
-/// CPU PP-OCRv6 Small engine using OAR's detection and recognition pipeline.
+/// Standard detection input cap. PP-OCR detection resizes each page so its
+/// longest side fits this before inference; it is the PaddleOCR default and
+/// is sufficient for ordinary body text at 150 DPI.
+const DETECTION_LIMIT_STANDARD: u32 = 960;
+
+/// Escalated detection input cap for dense fine-print pages. Beyond this the
+/// measured recall plateaus while inference cost keeps growing.
+const DETECTION_LIMIT_ESCALATED: u32 = 2560;
+
+/// Hard ceiling protecting detection from out-of-memory on giant renders.
+const DETECTION_MAXIMUM_SIDE: u32 = 4000;
+
+/// Escalate only for pages dense with small text: at least this many detected
+/// regions in the standard pass...
+const ESCALATION_MINIMUM_REGIONS: usize = 80;
+
+/// ...whose median height, at detection scale, is below this. Calibrated at
+/// `unclip_ratio` 2.0 (the expansion inflates measured heights, so this
+/// constant is coupled to [`detection_config`]): dense fine-print pages that
+/// gain from escalation measure 12.0–14.2 px with 144+ regions; the nearest
+/// non-gaining page above the region gate (an engineering drawing) measures
+/// 15.7 px, and prose/typewriter pages measure 14.5 px+ with too few
+/// regions to qualify at all.
+const ESCALATION_MAXIMUM_MEDIAN_HEIGHT: f32 = 15.0;
+
+/// One worker's model sessions: a standard-limit detector plus a recognizer,
+/// and that worker's own lazily built escalated-limit detector.
+/// Staged (detect, crop, recognize as separate calls) rather than OAROCR's
+/// combined `predict` so an escalated page replaces only its detection pass —
+/// recognition runs exactly once, on the final region set.
+struct OcrWorker {
+    detector: TextDetectionPredictor,
+    recognizer: TextRecognitionPredictor,
+    /// Built on this worker's first dense fine-print page. `None` inside the
+    /// cell records a failed build so it is not retried per page.
+    escalated: std::sync::OnceLock<Option<TextDetectionPredictor>>,
+}
+
+/// CPU PP-OCRv6 Small engine using OAR's detection and recognition components.
 ///
 /// Construction accepts only [`ModelPaths`] that have already passed
 /// pdf-inspector's manifest size and SHA-256 verification. OAR's independent
 /// model auto-download feature is deliberately not enabled.
-#[derive(Debug)]
 pub struct OarOcrEngine {
-    pipeline: OAROCR,
+    workers: Vec<OcrWorker>,
+    detection_path: PathBuf,
+    intra_threads: usize,
+    /// Present only when more than one worker exists; sized to match.
+    pool: Option<rayon::ThreadPool>,
     model: ModelIdentity,
 }
 
+impl std::fmt::Debug for OarOcrEngine {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("OarOcrEngine")
+            .field("workers", &self.workers.len())
+            .field("parallel", &self.pool.is_some())
+            .field("model", &self.model)
+            .finish()
+    }
+}
+
+/// Pages processed concurrently: one OAROCR pipeline (and its ONNX sessions)
+/// per worker, because oar-ocr serializes each session behind a mutex.
+/// Measured on CPU: workers beyond 3 stop scaling (memory-bandwidth bound)
+/// and each worker is fastest with 2 intra-op threads.
+fn pipeline_concurrency() -> usize {
+    let cores = std::thread::available_parallelism()
+        .map(std::num::NonZeroUsize::get)
+        .unwrap_or(1);
+    (cores / 4).clamp(1, 3)
+}
+
+fn intra_threads_per_pipeline(concurrency: usize) -> usize {
+    let cores = std::thread::available_parallelism()
+        .map(std::num::NonZeroUsize::get)
+        .unwrap_or(1);
+    if concurrency > 1 {
+        2
+    } else {
+        cores.min(4)
+    }
+}
+
+/// True when a standard-limit detection pass over a downscaled page shows
+/// dense, small text: the page deserves a second pass at the escalated limit.
+fn should_escalate_detection(
+    median_detection_height: f32,
+    region_count: usize,
+    downscale: f32,
+) -> bool {
+    downscale < 1.0
+        && region_count >= ESCALATION_MINIMUM_REGIONS
+        && median_detection_height < ESCALATION_MAXIMUM_MEDIAN_HEIGHT
+}
+
+/// Median detected-region height in detection-input pixels: original-image
+/// heights multiplied by the downscale detection applied.
+fn median_detection_height(heights: &mut [f32], downscale: f32) -> f32 {
+    if heights.is_empty() {
+        return f32::MAX;
+    }
+    heights.sort_by(|a, b| a.partial_cmp(b).unwrap_or(std::cmp::Ordering::Equal));
+    let middle = heights.len() / 2;
+    let median = if heights.len().is_multiple_of(2) {
+        (heights[middle - 1] + heights[middle]) / 2.0
+    } else {
+        heights[middle]
+    };
+    median * downscale
+}
+
+/// Detection preprocessing config at a given input cap.
+///
+/// Supplying an explicit config suppresses OAROCR's "general" text-type
+/// overrides, so every field the override would have set must be pinned
+/// here to match what the combined pipeline ran with before the staged
+/// split: score 0.3 and box 0.6 (equal to [`TextDetectionConfig`]'s
+/// defaults) and unclip 2.0 (the default is 1.5 — leaving it would
+/// silently shrink detection-box expansion and risk clipping edge glyphs).
+fn detection_config(detection_limit: u32) -> TextDetectionConfig {
+    TextDetectionConfig {
+        limit_side_len: Some(detection_limit),
+        limit_type: Some(oar_ocr::processors::LimitType::Max),
+        max_side_len: Some(DETECTION_MAXIMUM_SIDE),
+        unclip_ratio: 2.0,
+        ..Default::default()
+    }
+}
+
+fn build_detector(
+    detection: &std::path::Path,
+    detection_limit: u32,
+    intra_threads: usize,
+) -> Result<TextDetectionPredictor, OarOcrError> {
+    Ok(TextDetectionPredictor::builder()
+        .with_config(detection_config(detection_limit))
+        .with_ort_config(ocr_session_config(intra_threads))
+        .build(detection)?)
+}
+
+fn build_workers(
+    detection: &std::path::Path,
+    recognition: &std::path::Path,
+    dictionary: &std::path::Path,
+    count: usize,
+    intra_threads: usize,
+) -> Result<Vec<OcrWorker>, OarOcrError> {
+    let mut workers = Vec::with_capacity(count);
+    for _ in 0..count {
+        let detector = build_detector(detection, DETECTION_LIMIT_STANDARD, intra_threads)?;
+        let recognizer = TextRecognitionPredictor::builder()
+            .dict_path(dictionary)
+            .with_ort_config(ocr_session_config(intra_threads))
+            .build(recognition)?;
+        workers.push(OcrWorker {
+            detector,
+            recognizer,
+            escalated: std::sync::OnceLock::new(),
+        });
+    }
+    Ok(workers)
+}
+
 impl OarOcrEngine {
     /// Loads PP-OCRv6 Small from a resolved, verified model set.
     pub fn from_models(models: &ModelPaths) -> Result<Self, OarOcrError> {
@@ -89,36 +245,169 @@ impl OarOcrEngine {
         let recognition = required_model(models, ModelArtifactKind::TextRecognition)?;
         let dictionary = required_model(models, ModelArtifactKind::CharacterDictionary)?;
 
-        let pipeline = OAROCRBuilder::new(detection, recognition, dictionary)
-            .ort_session(ocr_session_config())
-            // Document line crops often have very different widths. Keeping
-            // CPU recognition batches at one avoids padding every crop to the
-            // widest line, reducing both inference work and peak memory.
-            .region_batch_size(1)
-            .build()?;
+        let concurrency = pipeline_concurrency();
+        let intra_threads = intra_threads_per_pipeline(concurrency);
+        let workers = build_workers(
+            detection,
+            recognition,
+            dictionary,
+            concurrency,
+            intra_threads,
+        )?;
+        let pool = if concurrency > 1 {
+            rayon::ThreadPoolBuilder::new()
+                .num_threads(concurrency)
+                .build()
+                .ok()
+        } else {
+            None
+        };
         let model = ModelIdentity::new(models.manifest_id(), models.revision());
-        Ok(Self { pipeline, model })
+        Ok(Self {
+            workers,
+            detection_path: detection.to_path_buf(),
+            intra_threads,
+            pool,
+            model,
+        })
+    }
+
+    /// This worker's escalated-limit detector, built on first use.
+    fn escalated_detector<'w>(&self, worker: &'w OcrWorker) -> Option<&'w TextDetectionPredictor> {
+        worker
+            .escalated
+            .get_or_init(|| {
+                match build_detector(
+                    &self.detection_path,
+                    DETECTION_LIMIT_ESCALATED,
+                    self.intra_threads,
+                ) {
+                    Ok(detector) => Some(detector),
+                    Err(error) => {
+                        log::warn!(
+                            "escalated OCR detection unavailable, keeping standard pass: {error}"
+                        );
+                        None
+                    }
+                }
+            })
+            .as_ref()
+    }
+
+    /// Detects text regions for one page: a standard-limit pass first, then —
+    /// for pages the standard limit demonstrably under-resolves — a second
+    /// pass at the escalated limit whose boxes replace the first. Pages whose
+    /// render dwarfs even the escalated limit skip the standard pass outright.
+    fn detect_boxes(
+        &self,
+        page: &RenderedPage,
+        image: &Arc<RgbImage>,
+        worker: &OcrWorker,
+    ) -> Result<Vec<BoundingBox>, OarOcrError> {
+        let longest_side = page.width().max(page.height()) as f32;
+
+        // A page more than twice the standard limit loses over half its
+        // resolution before detection even runs; go straight to the escalated
+        // detector instead of paying a doomed standard pass.
+        if longest_side > (DETECTION_LIMIT_STANDARD * 2) as f32 {
+            if let Some(escalated) = self.escalated_detector(worker) {
+                log::debug!(
+                    "page {}: direct escalated detection (render {longest_side}px)",
+                    page.page(),
+                );
+                match detect_with(escalated, image, page.page()) {
+                    Ok(boxes) => return Ok(boxes),
+                    Err(error) => {
+                        // Same degradation as the adaptive branch below: a
+                        // failing escalated pass falls back to standard
+                        // detection instead of failing the page outright.
+                        // Return the standard boxes directly — the adaptive
+                        // trigger would only re-invoke the detector that
+                        // just failed (repeating an OOM on a dense page).
+                        log::warn!(
+                            "page {}: direct escalated detection failed, using standard pass: {error}",
+                            page.page()
+                        );
+                        return detect_with(&worker.detector, image, page.page());
+                    }
+                }
+            }
+        }
+
+        let detections = detect_with(&worker.detector, image, page.page())?;
+
+        // Dense fine-print pages (broadsheets, pricing sheets) lose most of
+        // their text when detection downscales them to the standard limit.
+        // When the standard pass shows many regions of tiny detection-scale
+        // height, rerun detection at the escalated limit.
+        let downscale = (DETECTION_LIMIT_STANDARD as f32 / longest_side).min(1.0);
+        let mut heights: Vec<f32> = detections.iter().map(polygon_height).collect();
+        let median = median_detection_height(&mut heights, downscale);
+        log::trace!(
+            "page {}: standard pass {} regions, median height {:.1}px at detection scale",
+            page.page(),
+            detections.len(),
+            median
+        );
+        if should_escalate_detection(median, detections.len(), downscale) {
+            log::debug!(
+                "page {}: escalating detection ({} regions, median height {:.1}px at detection scale)",
+                page.page(),
+                detections.len(),
+                median
+            );
+            if let Some(escalated) = self.escalated_detector(worker) {
+                match detect_with(escalated, image, page.page()) {
+                    Ok(escalated_boxes) => return Ok(escalated_boxes),
+                    Err(error) => {
+                        log::warn!(
+                            "page {}: escalated detection failed, keeping standard pass: {error}",
+                            page.page()
+                        );
+                    }
+                }
+            }
+        }
+        Ok(detections)
     }
 
     fn recognize_page(
         &self,
         page: &RenderedPage,
         options: &OcrOptions,
+        worker: usize,
     ) -> Result<OcrPage, OarOcrError> {
         let started = Instant::now();
-        let image = rendered_page_to_rgb(page)?;
-        let result = self
-            .pipeline
-            .predict(vec![image])?
-            .into_iter()
-            .next()
-            .ok_or(OarOcrError::MissingPageResult { page: page.page() })?;
+        let worker = &self.workers[worker % self.workers.len()];
+        let image = Arc::new(rendered_page_to_rgb(page)?);
+        let boxes = self.detect_boxes(page, &image, worker)?;
+        // Reading order, matching what the combined pipeline produced.
+        let boxes = oar_ocr::processors::sort_quad_boxes(&boxes);
 
-        let mut spans = Vec::with_capacity(result.text_regions.len());
+        // Same rotation-aware cropping the combined pipeline uses.
+        let crops =
+            TextCroppingProcessor::new(true).process((Arc::clone(&image), boxes.clone()))?;
+        drop(image);
+
+        let recognizer = &worker.recognizer;
+        let mut spans = Vec::with_capacity(boxes.len());
         let mut invalid_geometry = 0usize;
         let mut missing_recognition = 0usize;
-        for region in result.text_regions {
-            let (Some(text), Some(confidence)) = (region.text, region.confidence) else {
+        for (bounding_box, crop) in boxes.iter().zip(crops) {
+            let Some(crop) = crop else {
+                invalid_geometry += 1;
+                continue;
+            };
+            // One crop per call: document line crops often have very
+            // different widths, and batching pads every crop to the widest
+            // line. Measured on CPU, batched recognition (even width-sorted)
+            // is 2–3× slower than per-crop calls.
+            let crop = Arc::try_unwrap(crop).unwrap_or_else(|shared| (*shared).clone());
+            let recognized = recognizer.predict(vec![crop])?;
+            let (Some(text), Some(confidence)) = (
+                recognized.texts.into_iter().next(),
+                recognized.scores.into_iter().next(),
+            ) else {
                 missing_recognition += 1;
                 continue;
             };
@@ -131,16 +420,21 @@ impl OarOcrEngine {
                 continue;
             }
 
-            let polygon = region.dt_poly.as_ref().unwrap_or(&region.bounding_box);
-            let Some(polygon) = bounding_box_to_quad(polygon, page.width(), page.height()) else {
+            let Some(polygon) = bounding_box_to_quad(bounding_box, page.width(), page.height())
+            else {
                 invalid_geometry += 1;
                 continue;
             };
             spans.push(OcrSpan {
-                text: text.to_string(),
+                text,
                 polygon,
                 confidence,
-                orientation_degrees: region.orientation_angle,
+                // The combined pipeline's orientation_angle came from the
+                // text-line-orientation classifier, a model this engine has
+                // never loaded — it was structurally None before the staged
+                // split too (the staged/combined A/B was byte-identical).
+                // Region rotation is still carried by the polygon itself.
+                orientation_degrees: None,
             });
         }
 
@@ -174,12 +468,42 @@ impl OarOcrEngine {
     }
 }
 
-fn ocr_session_config() -> OrtSessionConfig {
-    let available = std::thread::available_parallelism()
-        .map(std::num::NonZeroUsize::get)
-        .unwrap_or(1);
+/// Runs one detector over one page image and returns its region polygons.
+fn detect_with(
+    detector: &TextDetectionPredictor,
+    image: &Arc<RgbImage>,
+    page_number: u32,
+) -> Result<Vec<BoundingBox>, OarOcrError> {
+    let mut result = detector.predict(vec![(**image).clone()])?;
+    if result.detections.is_empty() {
+        return Err(OarOcrError::MissingPageResult { page: page_number });
+    }
+    Ok(result
+        .detections
+        .swap_remove(0)
+        .into_iter()
+        .map(|detection| detection.bbox)
+        .collect())
+}
+
+/// Vertical extent of a detection polygon in original-image pixels.
+fn polygon_height(polygon: &BoundingBox) -> f32 {
+    let mut min_y = f32::MAX;
+    let mut max_y = f32::MIN;
+    for point in &polygon.points {
+        min_y = min_y.min(point.y);
+        max_y = max_y.max(point.y);
+    }
+    if max_y > min_y {
+        max_y - min_y
+    } else {
+        0.0
+    }
+}
+
+fn ocr_session_config(intra_threads: usize) -> OrtSessionConfig {
     OrtSessionConfig::new()
-        .with_intra_threads(available.min(4))
+        .with_intra_threads(intra_threads.max(1))
         .with_inter_threads(1)
         .with_parallel_execution(false)
 }
@@ -226,10 +550,33 @@ impl OcrEngine for OarOcrEngine {
     ) -> Result<Vec<OcrPage>, Self::Error> {
         validate_options(options)?;
 
-        pages
-            .iter()
-            .map(|page| self.recognize_page(page, options))
-            .collect()
+        let Some(pool) = self.pool.as_ref().filter(|_| pages.len() > 1) else {
+            return pages
+                .iter()
+                .map(|page| self.recognize_page(page, options, 0))
+                .collect();
+        };
+        pool.install(|| {
+            use rayon::prelude::*;
+            pages
+                .par_iter()
+                .map(|page| {
+                    let worker = rayon::current_thread_index().unwrap_or(0);
+                    self.recognize_page(page, options, worker)
+                })
+                .collect()
+        })
+    }
+
+    fn preferred_page_concurrency(&self) -> usize {
+        // Without a pool, recognition runs sequentially regardless of worker
+        // count — report that honestly so the pipeline doesn't render
+        // oversized page batches for parallelism that isn't there.
+        if self.pool.is_some() {
+            self.workers.len()
+        } else {
+            1
+        }
     }
 }
 
@@ -376,10 +723,13 @@ mod tests {
 
     #[test]
     fn cpu_session_budget_is_bounded_for_small_ocr_models() {
-        let config = ocr_session_config();
+        let concurrency = pipeline_concurrency();
+        let config = ocr_session_config(intra_threads_per_pipeline(concurrency));
         assert!((1..=4).contains(&config.intra_threads.unwrap()));
         assert_eq!(config.inter_threads, Some(1));
         assert_eq!(config.parallel_execution, Some(false));
+        // Zero requests are clamped so a session always has a thread.
+        assert_eq!(ocr_session_config(0).intra_threads, Some(1));
     }
 
     fn page(format: RenderPixelFormat, stride: usize, pixels: Vec<u8>) -> RenderedPage {
@@ -493,4 +843,47 @@ mod tests {
         )
         .is_ok());
     }
+
+    #[test]
+    fn escalation_fires_for_dense_fine_print_pages() {
+        // Measured cases (at unclip 2.0) that gain from escalation: dense
+        // tiled ad pages (12.3–14.2px, 158–286 regions) and a dense pricing
+        // sheet (12.0px, 144 regions), all downscaled by the standard limit.
+        assert!(should_escalate_detection(14.2, 186, 0.55));
+        assert!(should_escalate_detection(13.1, 286, 0.55));
+        assert!(should_escalate_detection(12.3, 158, 0.55));
+        assert!(should_escalate_detection(12.0, 144, 0.55));
+    }
+
+    #[test]
+    fn escalation_skips_ordinary_pages() {
+        // Academic prose: too few regions (and tall enough at unclip 2.0).
+        assert!(!should_escalate_detection(14.5, 47, 0.58));
+        // Engineering drawing: many regions but tall enough text.
+        assert!(!should_escalate_detection(15.7, 205, 0.58));
+        // Typewriter scan: tall text, few regions.
+        assert!(!should_escalate_detection(17.5, 77, 0.55));
+        // Page not downscaled at all: escalation cannot add pixels.
+        assert!(!should_escalate_detection(9.0, 300, 1.0));
+    }
+
+    #[test]
+    fn median_detection_height_scales_and_handles_empty() {
+        let mut heights = vec![30.0, 10.0, 20.0];
+        assert_eq!(median_detection_height(&mut heights, 0.5), 10.0);
+        // Even counts average the two middle values instead of picking the
+        // upper one, so borderline pages don't skew away from escalation.
+        let mut even = vec![10.0, 12.0, 14.0, 30.0];
+        assert_eq!(median_detection_height(&mut even, 1.0), 13.0);
+        let mut empty: Vec<f32> = Vec::new();
+        assert_eq!(median_detection_height(&mut empty, 0.5), f32::MAX);
+    }
+
+    #[test]
+    fn concurrency_derivations_stay_in_bounds() {
+        let concurrency = pipeline_concurrency();
+        assert!((1..=3).contains(&concurrency));
+        assert!(intra_threads_per_pipeline(2) == 2);
+        assert!((1..=4).contains(&intra_threads_per_pipeline(1)));
+    }
 }

src/vision/pipeline.rs

@@ -31,6 +31,17 @@ use super::{
 /// Bounds live rendered-page memory while preserving small OCR batches.
 const OCR_PAGE_CHUNK_SIZE: usize = 4;
 
+/// Pages rendered and held in memory per OCR batch. A parallel engine gets
+/// three waves of work per batch so its workers are not starved at chunk
+/// barriers; a sequential engine keeps the small memory-bounding default.
+/// Engine-reported concurrency is a trait hook, so it is clamped before
+/// sizing anything from it — this helper exists to bound rendered-page
+/// memory and must not let an engine inflate it arbitrarily.
+fn ocr_page_chunk_size(engine_concurrency: usize) -> usize {
+    const MAX_ENGINE_CONCURRENCY: usize = 8;
+    (engine_concurrency.clamp(1, MAX_ENGINE_CONCURRENCY) * 3).max(OCR_PAGE_CHUNK_SIZE)
+}
+
 #[derive(Debug, Clone, PartialEq, Eq)]
 struct OcrEngineCacheKey {
     model_root: PathBuf,
@@ -443,7 +454,7 @@ where
     let mut render_time_ms = 0u64;
     let mut ocr_time_ms = 0u64;
 
-    for chunk in routed_pages.chunks(OCR_PAGE_CHUNK_SIZE) {
+    for chunk in routed_pages.chunks(ocr_page_chunk_size(engine.preferred_page_concurrency())) {
         let native_chunk = chunk
             .iter()
             .map(|page_number| {
@@ -927,6 +938,19 @@ pub enum OcrPipelineError {
 mod tests {
     use super::*;
 
+    #[test]
+    fn chunk_size_scales_with_engine_concurrency() {
+        // Sequential engines keep the memory-bounding default.
+        assert_eq!(ocr_page_chunk_size(1), OCR_PAGE_CHUNK_SIZE);
+        // Parallel engines get three waves of work per batch.
+        assert_eq!(ocr_page_chunk_size(3), 9);
+        assert_eq!(ocr_page_chunk_size(2), 6);
+        // Engine-reported concurrency is untrusted: clamp before sizing so a
+        // misbehaving engine cannot inflate rendered-page memory or overflow.
+        assert_eq!(ocr_page_chunk_size(0), OCR_PAGE_CHUNK_SIZE);
+        assert_eq!(ocr_page_chunk_size(usize::MAX), 24);
+    }
+
     struct TrackingRenderer {
         batches: Mutex<Vec<Vec<u32>>>,
     }