From 9b56a337f8db2c3f63e33e06468cb8de2b93fbf1 Mon Sep 17 00:00:00 2001
From: Codex-ytr83r <Codex-ytr83r@example.com>
Date: Sat, 12 Sep 2026 18:35:52 -0700
Subject: [PATCH] Prepare measured scenario labels and clear corridor
 evaluators

---
 .../oa-desktop/src/behavior/scenario_label.rs | 429 +++++++++++++++
 .../src/behavior/scenario_label/corridor.rs   | 189 +++++++
 .../src/behavior/scenario_label/tests.rs      | 487 ++++++++++++++++++
 .../.gitattributes                            |   3 +
 .../README.md                                 | 147 ++++++
 .../attempt1/manifest.json                    |  17 +
 .../attempt1/scenario_label.rs                | 206 ++++++++
 .../attempt1/tests.rs                         | 120 +++++
 .../attempt2/README.md                        |  87 ++++
 .../attempt2/manifest.json                    |  22 +
 .../attempt2/scenario_label.rs                | 271 ++++++++++
 .../attempt2/tests.rs                         | 200 +++++++
 .../attempt3/corridor.rs                      | 154 ++++++
 .../attempt3/manifest.json                    |  17 +
 .../attempt3/scenario_label.rs                | 281 ++++++++++
 .../attempt3/tests.rs                         | 271 ++++++++++
 .../run-font-version-test.ps1                 |  50 ++
 .../standalone.rs                             |   5 +
 18 files changed, 2956 insertions(+)
 create mode 100644 crates/oa-desktop/src/behavior/scenario_label.rs
 create mode 100644 crates/oa-desktop/src/behavior/scenario_label/corridor.rs
 create mode 100644 crates/oa-desktop/src/behavior/scenario_label/tests.rs
 create mode 100644 harness/experiments/scenario-label-measurement-20260913/.gitattributes
 create mode 100644 harness/experiments/scenario-label-measurement-20260913/README.md
 create mode 100644 harness/experiments/scenario-label-measurement-20260913/attempt1/manifest.json
 create mode 100644 harness/experiments/scenario-label-measurement-20260913/attempt1/scenario_label.rs
 create mode 100644 harness/experiments/scenario-label-measurement-20260913/attempt1/tests.rs
 create mode 100644 harness/experiments/scenario-label-measurement-20260913/attempt2/README.md
 create mode 100644 harness/experiments/scenario-label-measurement-20260913/attempt2/manifest.json
 create mode 100644 harness/experiments/scenario-label-measurement-20260913/attempt2/scenario_label.rs
 create mode 100644 harness/experiments/scenario-label-measurement-20260913/attempt2/tests.rs
 create mode 100644 harness/experiments/scenario-label-measurement-20260913/attempt3/corridor.rs
 create mode 100644 harness/experiments/scenario-label-measurement-20260913/attempt3/manifest.json
 create mode 100644 harness/experiments/scenario-label-measurement-20260913/attempt3/scenario_label.rs
 create mode 100644 harness/experiments/scenario-label-measurement-20260913/attempt3/tests.rs
 create mode 100644 harness/experiments/scenario-label-measurement-20260913/run-font-version-test.ps1
 create mode 100644 harness/experiments/scenario-label-measurement-20260913/standalone.rs

diff --git a/crates/oa-desktop/src/behavior/scenario_label.rs b/crates/oa-desktop/src/behavior/scenario_label.rs
new file mode 100644
index 00000000..5e7fe6a3
--- /dev/null
+++ b/crates/oa-desktop/src/behavior/scenario_label.rs
@@ -0,0 +1,429 @@
+//! Unwired single-line scenario label experiment. No renderer or schema is changed.
+//!
+//! Iced 0.14.0 WGPU `geometry::Frame::fill_text` shapes positive uniform-scale
+//! canvas text at `size * zoom`; its `text::prepare` uses graphics text::Cache.
+//! This adapter uses that same allocator/font system/attributes, not a character
+//! width estimate. Canvas Text::max_width is wrapping, so it stays infinite.
+//! Experimental parity requires settled fonts and a fresh renderer/cache after
+//! font loading. Iced's WGPU text cache key omits FontSystem::Version, so merely
+//! remeasuring here cannot repair its cached glyph buffers after dynamic loading.
+//! A RenderSession is caller attestation of that lifecycle, not its enforcement.
+//! No fonts may be loaded between measurement, guarded access and actual draw.
+//!
+//! Integration seam: after lifecycle/activation endpoint alignment, a caller
+//! supplies a usable text width in world units and retains one cache per live
+//! labelled occurrence across Scene rebuilds. Paint, hit testing, navigation and extents
+//! consume the returned Label. Position/color do not invalidate measurement.
+//! This does NOT choose a self-call, reversed-arrow or obstacle corridor policy.
+//! It measures layout advances, not raster ink; overhang/clip/activation-border
+//! acceptance still requires the real WGPU evaluator. The old 32-grapheme/225px
+//! renderer is deliberately untouched for a later baseline comparison.
+use iced::advanced::{
+    graphics::text as graphics_text,
+    text::{Alignment, LineHeight, Shaping},
+};
+use iced::{Color, Font, Pixels, Point, Rectangle, Size, widget::canvas::Text};
+use std::{collections::VecDeque, ops::Range, sync::Arc};
+use unicode_segmentation::UnicodeSegmentation;
+
+const MAX_SOURCE_BYTES: usize = 64 * 1024;
+const MAX_GRAPHEMES: usize = 4096;
+const MAX_ENTRIES: usize = 2;
+
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub(super) struct Style {
+    pub font: Font,
+    pub size: Pixels,
+    pub line_height: LineHeight,
+    pub shaping: Shaping,
+}
+
+impl Default for Style {
+    fn default() -> Self {
+        let text = Text::default();
+        Self {
+            font: text.font,
+            size: Pixels(12.),
+            line_height: text.line_height,
+            shaping: text.shaping,
+        }
+    }
+}
+
+impl Style {
+    fn scaled(self, zoom: f32) -> (f32, f32) {
+        let size = Pixels(self.size.0 * zoom);
+        let line_height = match self.line_height {
+            LineHeight::Absolute(value) => LineHeight::Absolute(Pixels(value.0 * zoom)),
+            LineHeight::Relative(value) => LineHeight::Relative(value),
+        };
+        (size.0, line_height.to_absolute(size).0)
+    }
+}
+
+/// Explicit experimental contract: the caller finishes loading fonts and starts
+/// a fresh renderer/cache BEFORE capturing this session, then keeps fonts fixed.
+/// This module cannot inspect or reset the actual renderer's text cache.
+#[derive(Clone, Debug)]
+pub(super) struct RenderSession {
+    version: graphics_text::Version,
+    identity: Arc<()>,
+}
+
+impl RenderSession {
+    pub fn after_fonts_settled_and_renderer_reset() -> Result<Self, Error> {
+        let fonts = graphics_text::font_system()
+            .read()
+            .map_err(|_| Error::FontSystemUnavailable)?;
+        Ok(Self {
+            version: fonts.version(),
+            identity: Arc::new(()),
+        })
+    }
+}
+
+#[derive(Clone, Debug)]
+pub(super) struct Label {
+    source: String,
+    displayed: String,
+    /// Original-label bytes represented before any added ellipsis. Includes
+    /// collapsed whitespace, but `retains_any` never counts whitespace as text.
+    retained_source: Range<usize>,
+    /// World-space layout advances, at origin; not glyph-ink containment.
+    bounds: Rectangle,
+    style: Style,
+    measured_session: RenderSession,
+    measured_zoom: f32,
+}
+
+impl Label {
+    fn check(&self, session: &RenderSession, zoom: f32) -> Result<(), Error> {
+        if !Arc::ptr_eq(&self.measured_session.identity, &session.identity) {
+            return Err(Error::StaleRenderSession);
+        }
+        if !zoom.is_finite() || zoom != self.measured_zoom {
+            return Err(Error::StaleZoom);
+        }
+        let fonts = graphics_text::font_system()
+            .read()
+            .map_err(|_| Error::FontSystemUnavailable)?;
+        if fonts.version() != self.measured_session.version || fonts.version() != session.version {
+            return Err(Error::FontSetChanged);
+        }
+        Ok(())
+    }
+
+    pub fn displayed(&self, session: &RenderSession, zoom: f32) -> Result<&str, Error> {
+        self.check(session, zoom)?;
+        Ok(&self.displayed)
+    }
+
+    pub fn retained_source(
+        &self,
+        session: &RenderSession,
+        zoom: f32,
+    ) -> Result<Range<usize>, Error> {
+        self.check(session, zoom)?;
+        Ok(self.retained_source.clone())
+    }
+
+    pub fn retains_any(
+        &self,
+        session: &RenderSession,
+        zoom: f32,
+        field: Range<usize>,
+    ) -> Result<bool, Error> {
+        self.check(session, zoom)?;
+        if field.start > field.end || self.source.get(field.clone()).is_none() {
+            return Ok(false);
+        }
+        let end = field.end.min(self.retained_source.end);
+        Ok(field.start < end
+            && self
+                .source
+                .get(field.start..end)
+                .is_some_and(|text| text.chars().any(|c| !c.is_whitespace())))
+    }
+
+    /// Validate finite world position and rectangle endpoints only. Camera
+    /// transforms and raster bounds remain a separate integration contract.
+    pub fn bounds_at(
+        &self,
+        session: &RenderSession,
+        zoom: f32,
+        position: Point,
+    ) -> Result<Rectangle, Error> {
+        self.check(session, zoom)?;
+        translated_bounds(position, self.bounds.size())
+    }
+
+    /// Paint under the same positive uniform zoom used for `Cache::resolve`.
+    /// No per-label wrapping or implicit text maximum is introduced.
+    /// The returned Text must be consumed immediately in this session/zoom;
+    /// retaining raw Text past another font load/zoom change bypasses the guard.
+    pub fn canvas_text(
+        &self,
+        session: &RenderSession,
+        zoom: f32,
+        position: Point,
+        color: Color,
+    ) -> Result<Text, Error> {
+        self.bounds_at(session, zoom, position)?;
+        Ok(Text {
+            content: self.displayed.clone(),
+            position,
+            color,
+            size: self.style.size,
+            line_height: self.style.line_height,
+            font: self.style.font,
+            shaping: self.style.shaping,
+            max_width: f32::INFINITY,
+            ..Text::default()
+        })
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub(super) enum Error {
+    InvalidMetrics,
+    SourceBudget,
+    GraphemeBudget,
+    FontSystemUnavailable,
+    InvalidMeasurement,
+    InvalidPosition,
+    StaleZoom,
+    StaleRenderSession,
+    FontSetChanged,
+}
+
+struct Entry {
+    source: String,
+    style: Style,
+    zoom: f32,
+    width: f32,
+    label: Arc<Label>,
+}
+
+#[derive(Default)]
+/// Two recent resolutions for ONE live labelled occurrence. A global small LRU
+/// would thrash when a larger Scene is rebuilt in order. The integration owner
+/// must retain these by occurrence identity and prune on removal/document change.
+pub(super) struct Cache {
+    version: Option<graphics_text::Version>,
+    session: Option<Arc<()>>,
+    entries: VecDeque<Entry>,
+    #[cfg(test)]
+    allocations: usize,
+}
+
+impl Cache {
+    /// `width` excludes any caller-chosen backplate padding. Zero is valid.
+    /// Cache ownership must survive redraws; constructing one per Scene defeats
+    /// reuse. Changed fonts invalidate the SESSION: the caller must establish
+    /// a fresh renderer and a new settled session, not just remeasure this cache.
+    /// Error handling/fallback for these explicit experiment budgets is an
+    /// integration decision; never silently paint the old truncated contract.
+    pub fn resolve(
+        &mut self,
+        session: &RenderSession,
+        source: &str,
+        width: f32,
+        zoom: f32,
+        style: Style,
+    ) -> Result<Arc<Label>, Error> {
+        let (size, line_height) = style.scaled(zoom);
+        if !width.is_finite()
+            || width < 0.
+            || !zoom.is_finite()
+            || zoom <= 0.
+            || !size.is_finite()
+            || size <= 0.
+            || !line_height.is_finite()
+            || line_height <= 0.
+            || !(width * zoom).is_finite()
+            || !(size / zoom).is_finite()
+            || !(line_height / zoom).is_finite()
+        {
+            return Err(Error::InvalidMetrics);
+        }
+        if source.len() > MAX_SOURCE_BYTES {
+            return Err(Error::SourceBudget);
+        }
+        let mut fonts = graphics_text::font_system()
+            .write()
+            .map_err(|_| Error::FontSystemUnavailable)?;
+        if session.version != fonts.version() {
+            return Err(Error::FontSetChanged);
+        }
+        if self.version != Some(fonts.version())
+            || self
+                .session
+                .as_ref()
+                .is_none_or(|identity| !Arc::ptr_eq(identity, &session.identity))
+        {
+            self.entries.clear();
+            self.version = Some(fonts.version());
+            self.session = Some(session.identity.clone());
+        }
+        if let Some(index) = self.entries.iter().position(|entry| {
+            entry.source == source
+                && entry.style == style
+                && entry.zoom == zoom
+                && entry.width == width
+        }) {
+            let entry = self.entries.remove(index).unwrap();
+            let label = entry.label.clone();
+            self.entries.push_back(entry);
+            return Ok(label);
+        }
+        let normalized = Normalized::new(source);
+        let cuts: Vec<usize> = normalized
+            .text
+            .grapheme_indices(true)
+            .map(|(i, _)| i)
+            .chain(std::iter::once(normalized.text.len()))
+            .collect();
+        if cuts.len().saturating_sub(1) > MAX_GRAPHEMES {
+            return Err(Error::GraphemeBudget);
+        }
+        // Candidate buffers are temporary. Only the resolved strings/metrics
+        // survive, bounded by MAX_ENTRIES; renderer caching remains independent.
+        let mut shapes = graphics_text::Cache::new();
+        let mut measure = |content: &str| -> Result<Size, Error> {
+            if content.is_empty() {
+                return Ok(Size::ZERO);
+            }
+            #[cfg(test)]
+            {
+                self.allocations += 1;
+            }
+            let (_, entry) = shapes.allocate(
+                fonts.raw(),
+                graphics_text::cache::Key {
+                    content,
+                    size,
+                    line_height,
+                    font: style.font,
+                    bounds: Size::INFINITE,
+                    shaping: style.shaping,
+                    align_x: Alignment::Default,
+                },
+            );
+            if entry.buffer.layout_runs().count() != 1
+                || !entry.min_bounds.width.is_finite()
+                || !entry.min_bounds.height.is_finite()
+            {
+                return Err(Error::InvalidMeasurement);
+            }
+            world_size(entry.min_bounds, zoom)
+        };
+        let full = measure(&normalized.text)?;
+        let (displayed, retained, measured) = if full.width <= width {
+            (normalized.text.clone(), normalized.text.len(), full)
+        } else {
+            let ellipsis = measure("…")?;
+            if ellipsis.width > width {
+                (String::new(), 0, Size::ZERO)
+            } else {
+                // Every accepted candidate is actually shaped and fits. Search
+                // is bounded/logarithmic; contextual shaping is not universally
+                // monotone, so this does NOT promise the globally longest prefix.
+                // Full content is always checked first and never needlessly cut.
+                let mut best = ("…".to_owned(), 0, ellipsis);
+                let (mut low, mut high) = (1, cuts.len().saturating_sub(1));
+                while low < high {
+                    let middle = low + (high - low) / 2;
+                    let candidate = format!("{}…", &normalized.text[..cuts[middle]]);
+                    let measured = measure(&candidate)?;
+                    if measured.width <= width {
+                        best = (candidate, cuts[middle], measured);
+                        low = middle + 1;
+                    } else {
+                        high = middle;
+                    }
+                }
+                best
+            }
+        };
+        let label = Arc::new(Label {
+            source: source.into(),
+            displayed,
+            retained_source: 0..normalized.source_end(retained),
+            bounds: Rectangle::with_size(measured),
+            style,
+            measured_session: session.clone(),
+            measured_zoom: zoom,
+        });
+        if self.entries.len() == MAX_ENTRIES {
+            self.entries.pop_front();
+        }
+        self.entries.push_back(Entry {
+            source: source.into(),
+            style,
+            zoom,
+            width,
+            label: label.clone(),
+        });
+        Ok(label)
+    }
+}
+
+fn world_size(scaled: Size, zoom: f32) -> Result<Size, Error> {
+    let world = Size::new(scaled.width / zoom, scaled.height / zoom);
+    if !world.width.is_finite()
+        || !world.height.is_finite()
+        || world.width < 0.
+        || world.height < 0.
+    {
+        return Err(Error::InvalidMeasurement);
+    }
+    Ok(world)
+}
+
+fn translated_bounds(position: Point, size: Size) -> Result<Rectangle, Error> {
+    if !position.x.is_finite()
+        || !position.y.is_finite()
+        || !(position.x + size.width).is_finite()
+        || !(position.y + size.height).is_finite()
+    {
+        return Err(Error::InvalidPosition);
+    }
+    Ok(Rectangle::new(position, size))
+}
+
+struct Normalized {
+    text: String,
+    ends: Vec<(usize, usize)>,
+}
+impl Normalized {
+    fn new(source: &str) -> Self {
+        let mut result = Self {
+            text: String::new(),
+            ends: vec![(0, 0)],
+        };
+        let mut separator = false;
+        for (start, c) in source.char_indices() {
+            if c.is_whitespace() {
+                separator = !result.text.is_empty();
+                continue;
+            }
+            if separator {
+                result.text.push(' ');
+                result.ends.push((result.text.len(), start));
+                separator = false;
+            }
+            result.text.push(c);
+            result.ends.push((result.text.len(), start + c.len_utf8()));
+        }
+        result
+    }
+    fn source_end(&self, normalized_end: usize) -> usize {
+        self.ends
+            .binary_search_by_key(&normalized_end, |(end, _)| *end)
+            .map(|index| self.ends[index].1)
+            .expect("grapheme cuts are character boundaries")
+    }
+}
+
+#[cfg(test)]
+mod tests;
diff --git a/crates/oa-desktop/src/behavior/scenario_label/corridor.rs b/crates/oa-desktop/src/behavior/scenario_label/corridor.rs
new file mode 100644
index 00000000..5ad0aac2
--- /dev/null
+++ b/crates/oa-desktop/src/behavior/scenario_label/corridor.rs
@@ -0,0 +1,189 @@
+//! Unwired corridor-policy candidate for the measured scenario-label experiment.
+//!
+//! The caller supplies a finite structural label band AFTER endpoint/activation
+//! alignment, with padding already removed from its edges. Blockers include
+//! padded activation/card/header bounds over the complete text band, including
+//! stroke/ink clearance. This function does not infer a self-message corridor,
+//! alter scene extents, change zoom, or establish raster-ink containment.
+use iced::Rectangle;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub(super) struct InvalidGeometry;
+
+fn edges(rect: Rectangle) -> Result<(f32, f32, f32, f32), InvalidGeometry> {
+    let right = rect.x + rect.width;
+    let bottom = rect.y + rect.height;
+    if [rect.x, rect.y, rect.width, rect.height, right, bottom]
+        .into_iter()
+        .any(|value| !value.is_finite())
+        || rect.width < 0.
+        || rect.height < 0.
+    {
+        return Err(InvalidGeometry);
+    }
+    Ok((rect.x, right, rect.y, bottom))
+}
+
+/// Select one connected clear interval; never assemble text across blockers.
+/// Prefer greater width, then proximity to the previous label anchor, then the
+/// leftmost interval. Input order has no influence. A zero-area band has no
+/// corridor. Touching the padded vertical band is conservatively obstructing;
+/// a zero-area blocker has no area and must receive stroke padding upstream.
+pub(super) fn widest_clear(
+    band: Rectangle,
+    blockers: &[Rectangle],
+    preferred_anchor: f32,
+) -> Result<Option<Rectangle>, InvalidGeometry> {
+    let (left, right, top, bottom) = edges(band)?;
+    if !preferred_anchor.is_finite() {
+        return Err(InvalidGeometry);
+    }
+    let mut blocked = Vec::new();
+    for &blocker in blockers {
+        let (x0, x1, y0, y1) = edges(blocker)?;
+        if blocker.width > 0. && blocker.height > 0. && y1 >= top && y0 <= bottom {
+            let interval = (x0.max(left), x1.min(right));
+            if interval.0 < interval.1 {
+                blocked.push(interval);
+            }
+        }
+    }
+    if band.width == 0. || band.height == 0. {
+        return Ok(None);
+    }
+    blocked.sort_by(|a, b| a.0.total_cmp(&b.0).then(a.1.total_cmp(&b.1)));
+    let mut best: Option<Rectangle> = None;
+    let mut consider = |start: f32, end: f32| {
+        if start >= end {
+            return;
+        }
+        let candidate = Rectangle {
+            x: start,
+            width: end - start,
+            ..band
+        };
+        // Use f64 only for comparison distance: subtracting two admitted f32
+        // world coordinates can overflow even though each rectangle is finite.
+        let distance = |x: f32| (f64::from(x) - f64::from(preferred_anchor)).abs();
+        if best.is_none_or(|old| {
+            candidate.width > old.width
+                || (candidate.width == old.width
+                    && (distance(candidate.x) < distance(old.x)
+                        || (distance(candidate.x) == distance(old.x) && candidate.x < old.x)))
+        }) {
+            best = Some(candidate);
+        }
+    };
+    let mut cursor = left;
+    for (start, end) in blocked {
+        consider(cursor, start);
+        cursor = cursor.max(end);
+    }
+    consider(cursor, right);
+    Ok(best)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn rect(x: f32, y: f32, width: f32, height: f32) -> Rectangle {
+        Rectangle {
+            x,
+            y,
+            width,
+            height,
+        }
+    }
+
+    #[test]
+    fn long_message_does_not_cross_an_intermediate_execution() {
+        let band = rect(20., 100., 700., 22.);
+        let blockers = [rect(250., 80., 16., 80.), rect(490., 90., 28., 140.)];
+        let result = widest_clear(band, &blockers, band.x).unwrap().unwrap();
+        assert_eq!(result, rect(20., 100., 230., 22.));
+        for blocker in blockers {
+            assert!(result.x + result.width <= blocker.x || result.x >= blocker.x + blocker.width);
+        }
+        assert_eq!(widest_clear(band, &[], band.x).unwrap(), Some(band));
+    }
+
+    #[test]
+    fn overlapping_unsorted_blockers_merge_and_widest_gap_wins() {
+        let band = rect(-100., 10., 600., 20.);
+        let blockers = [
+            rect(50., 0., 80., 60.),
+            rect(0., 5., 70., 30.),
+            rect(450., 0., 100., 60.),
+        ];
+        let expected = Some(rect(130., 10., 320., 20.));
+        assert_eq!(widest_clear(band, &blockers, -100.).unwrap(), expected);
+        let mut reversed = blockers;
+        reversed.reverse();
+        assert_eq!(widest_clear(band, &reversed, -100.).unwrap(), expected);
+    }
+
+    #[test]
+    fn complete_padded_band_and_touching_boundaries_are_obstructed() {
+        let band = rect(0., 100., 200., 20.);
+        // The first blocker ends at the band top: checking only a baseline
+        // would miss it. The second starts at the band bottom.
+        let blockers = [rect(0., 70., 60., 30.), rect(150., 120., 50., 30.)];
+        assert_eq!(
+            widest_clear(band, &blockers, 0.).unwrap(),
+            Some(rect(60., 100., 90., 20.))
+        );
+        let outside = [rect(0., 70., 200., 29.), rect(0., 121., 200., 30.)];
+        assert_eq!(widest_clear(band, &outside, 0.).unwrap(), Some(band));
+    }
+
+    #[test]
+    fn ties_keep_the_nearest_anchor_then_choose_leftmost() {
+        let band = rect(0., 0., 300., 20.);
+        let blockers = [rect(100., 0., 100., 20.)];
+        assert_eq!(
+            widest_clear(band, &blockers, 190.).unwrap(),
+            Some(rect(200., 0., 100., 20.))
+        );
+        assert_eq!(
+            widest_clear(band, &blockers, 100.).unwrap(),
+            Some(rect(0., 0., 100., 20.))
+        );
+    }
+
+    #[test]
+    fn caller_defined_self_and_reversed_corridors_keep_their_geometry() {
+        // Direction and self-loop policy are explicit caller inputs. Neither
+        // a zero endpoint gap nor screen width can silently supply a corridor.
+        for band in [rect(420., 40., 180., 22.), rect(-400., 90., 350., 22.)] {
+            assert_eq!(widest_clear(band, &[], band.x).unwrap(), Some(band));
+        }
+        assert_eq!(
+            widest_clear(rect(420., 40., 0., 22.), &[], 420.).unwrap(),
+            None
+        );
+        assert_eq!(
+            widest_clear(rect(420., 40., 180., 0.), &[], 420.).unwrap(),
+            None
+        );
+        assert_eq!(
+            widest_clear(rect(0., 0., 100., 20.), &[rect(-10., -10., 200., 50.)], 0.).unwrap(),
+            None
+        );
+    }
+
+    #[test]
+    fn invalid_or_overflowing_geometry_never_enters_a_corridor() {
+        let band = rect(0., 0., 100., 20.);
+        for invalid in [
+            rect(f32::NAN, 0., 10., 20.),
+            rect(0., 0., -1., 20.),
+            rect(f32::MAX, 0., f32::MAX, 20.),
+            rect(0., f32::MAX, 10., f32::MAX),
+        ] {
+            assert_eq!(widest_clear(invalid, &[], 0.), Err(InvalidGeometry));
+            assert_eq!(widest_clear(band, &[invalid], 0.), Err(InvalidGeometry));
+        }
+        assert_eq!(widest_clear(band, &[], f32::INFINITY), Err(InvalidGeometry));
+    }
+}
diff --git a/crates/oa-desktop/src/behavior/scenario_label/tests.rs b/crates/oa-desktop/src/behavior/scenario_label/tests.rs
new file mode 100644
index 00000000..461ac400
--- /dev/null
+++ b/crates/oa-desktop/src/behavior/scenario_label/tests.rs
@@ -0,0 +1,487 @@
+//! Unexecuted evaluator candidates; the module is intentionally not wired yet.
+use super::*;
+use iced::advanced::{
+    graphics::text::Paragraph,
+    text::{Paragraph as _, Text as ParagraphText, Wrapping},
+};
+
+// Independent paragraph construction: no candidate cache, normalization, search,
+// or character-width estimate is used by this measurement oracle.
+fn paragraph_size(content: &str, zoom: f32, style: Style) -> Size {
+    let size = Pixels(style.size.0 * zoom);
+    let line_height = match style.line_height {
+        LineHeight::Relative(factor) => LineHeight::Relative(factor),
+        LineHeight::Absolute(pixels) => LineHeight::Absolute(Pixels(pixels.0 * zoom)),
+    };
+    let paragraph = Paragraph::with_text(ParagraphText {
+        content,
+        bounds: Size::INFINITE,
+        size,
+        line_height,
+        font: style.font,
+        align_x: Alignment::Default,
+        align_y: iced::alignment::Vertical::Top,
+        shaping: style.shaping,
+        wrapping: Wrapping::default(),
+    });
+    assert_eq!(paragraph.buffer().layout_runs().count(), 1);
+    Size::new(paragraph.min_width() / zoom, paragraph.min_height() / zoom)
+}
+
+#[test]
+fn adequate_corridor_reveals_full_realistic_names_and_distinguishing_suffixes() {
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    let style = Style::default();
+    for text in [
+        "1. call · Request valve repair · Technician service conversation",
+        "2. reply · Return pressure after repair · Technician service conversation",
+        "1. call · Request redundant hydraulic pressure calibration channel A",
+        "1. call · Request redundant hydraulic pressure calibration channel B",
+    ] {
+        let wide = cache.resolve(&session, text, 1600., 1., style).unwrap();
+        assert_eq!(wide.displayed(&session, 1.).unwrap(), text);
+        assert_eq!(wide.retained_source(&session, 1.).unwrap(), 0..text.len());
+        assert_eq!(wide.bounds.size(), paragraph_size(text, 1., style));
+        let narrow = cache.resolve(&session, text, 80., 1., style).unwrap();
+        assert_ne!(narrow.displayed, text);
+        assert!(narrow.bounds.width <= 80.);
+        assert_eq!(
+            narrow.bounds.size(),
+            paragraph_size(&narrow.displayed, 1., style)
+        );
+    }
+}
+
+#[test]
+fn normalized_visible_prefix_maps_to_original_bytes_without_claiming_hidden_operation() {
+    let raw = " \t1.  call · Pump\r\n  · Operation: Need\u{301}le  ";
+    let expected = "1. call · Pump · Operation: Need\u{301}le";
+    let n = Normalized::new(raw);
+    assert_eq!(n.text, expected);
+    let prefix = "1. call · Pump ";
+    assert_eq!(n.source_end(prefix.len()), raw.find("· Operation").unwrap());
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    let wide = cache
+        .resolve(&session, raw, 1600., 1., Style::default())
+        .unwrap();
+    assert_eq!(wide.displayed, expected);
+    assert_eq!(wide.retained_source.end, raw.trim_end().len());
+    let field = raw.find("Need").unwrap()..raw.trim_end().len();
+    assert!(wide.retains_any(&session, 1., field.clone()).unwrap());
+    assert!(
+        !wide.retains_any(&session, 1., 0..2).unwrap(),
+        "normalized whitespace is not a visible field"
+    );
+    let small = cache
+        .resolve(&session, raw, 70., 1., Style::default())
+        .unwrap();
+    assert!(!small.retains_any(&session, 1., field).unwrap());
+    assert!(small.retained_source.end < raw.find("Operation").unwrap());
+}
+
+#[test]
+fn grapheme_prefixes_and_zoom_match_actual_paragraph_layout() {
+    let text = "call · 戻り値 圧力 e\u{301} 👩‍🔬 safety valve verification";
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    for zoom in [0.66, 1., 1.75] {
+        let label = cache
+            .resolve(&session, text, 105., zoom, Style::default())
+            .unwrap();
+        assert!(label.bounds.width <= 105.);
+        assert_eq!(
+            label.bounds.size(),
+            paragraph_size(&label.displayed, zoom, Style::default())
+        );
+        assert!(
+            text.grapheme_indices(true)
+                .any(|(i, _)| i == label.retained_source.end)
+                || label.retained_source.end == text.len()
+        );
+        let painted = label
+            .canvas_text(&session, zoom, Point::new(400., 90.), Color::BLACK)
+            .unwrap();
+        assert_eq!(painted.content, label.displayed);
+        assert!(painted.max_width.is_infinite());
+        assert_eq!(
+            label
+                .bounds_at(&session, zoom, painted.position)
+                .unwrap()
+                .size(),
+            label.bounds.size()
+        );
+    }
+}
+
+#[test]
+fn empty_and_too_narrow_labels_never_claim_source_visibility() {
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    for text in ["", " \t\n", "Operation: Pump"] {
+        let label = cache
+            .resolve(&session, text, 0., 1., Style::default())
+            .unwrap();
+        assert_eq!(label.displayed, "");
+        assert_eq!(label.retained_source, 0..0);
+        assert_eq!(label.bounds.size(), Size::ZERO);
+        assert!(!label.retains_any(&session, 1., 0..text.len()).unwrap());
+    }
+}
+
+#[test]
+fn redraws_reuse_resolution_but_width_zoom_and_style_are_dependencies() {
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    let text = "call · Pressure verification with a descriptive operation label";
+    let style = Style::default();
+    let a = cache.resolve(&session, text, 100., 1., style).unwrap();
+    let measured = cache.allocations;
+    let b = cache.resolve(&session, text, 100., 1., style).unwrap();
+    assert!(Arc::ptr_eq(&a, &b));
+    assert_eq!(cache.allocations, measured);
+    for (width, zoom, style) in [
+        (120., 1., style),
+        (100., 0.66, style),
+        (
+            100.,
+            1.,
+            Style {
+                size: Pixels(14.),
+                ..style
+            },
+        ),
+    ] {
+        let other = cache.resolve(&session, text, width, zoom, style).unwrap();
+        assert!(!Arc::ptr_eq(&a, &other));
+    }
+}
+
+#[test]
+fn resident_entry_is_remeasured_for_a_fresh_settled_render_session() {
+    let mut cache = Cache::default();
+    let old_session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    let text = "call · Pressure verification";
+    let a = cache
+        .resolve(&old_session, text, 100., 1., Style::default())
+        .unwrap();
+    assert_eq!(cache.entries.len(), 1);
+    assert!(Arc::ptr_eq(&cache.entries.front().unwrap().label, &a));
+    let measured = cache.allocations;
+    assert!(measured > 0);
+    assert!(Arc::ptr_eq(
+        &a,
+        &cache
+            .resolve(&old_session, text, 100., 1., Style::default())
+            .unwrap()
+    ));
+    assert_eq!(cache.allocations, measured);
+    // A fresh renderer session invalidates a still-resident entry. This does
+    // not mutate global fonts or purport to test dynamic WGPU font loading.
+    let new_session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    let refreshed = cache
+        .resolve(&new_session, text, 100., 1., Style::default())
+        .unwrap();
+    assert!(!Arc::ptr_eq(&a, &refreshed));
+    assert!(cache.allocations > measured);
+    assert_eq!(cache.entries.len(), 1);
+    assert!(Arc::ptr_eq(
+        &cache.entries.front().unwrap().label,
+        &refreshed
+    ));
+}
+
+#[test]
+fn resident_entry_remeasures_after_local_font_epoch_invalidation() {
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    let text = "call · Resident pressure label";
+    let a = cache
+        .resolve(&session, text, 100., 1., Style::default())
+        .unwrap();
+    assert_eq!(cache.entries.len(), 1);
+    assert!(Arc::ptr_eq(&cache.entries.front().unwrap().label, &a));
+    let measured = cache.allocations;
+    assert!(measured > 0);
+    // Exercise the local memo epoch branch while a is still resident. No
+    // intervening width/zoom/style resolution can cause incidental eviction.
+    // This is not an actual font-load or renderer-cache acceptance test.
+    cache.version = None;
+    let refreshed = cache
+        .resolve(&session, text, 100., 1., Style::default())
+        .unwrap();
+    assert!(!Arc::ptr_eq(&a, &refreshed));
+    assert!(cache.allocations > measured);
+    assert_eq!(cache.entries.len(), 1);
+    assert!(Arc::ptr_eq(
+        &cache.entries.front().unwrap().label,
+        &refreshed
+    ));
+}
+
+#[test]
+fn retained_artifact_rejects_other_zoom_and_render_session_for_every_consumer() {
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    let label = cache
+        .resolve(&session, "Operation: Pressure", 200., 1., Style::default())
+        .unwrap();
+    let other = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    for (context, zoom, expected) in [
+        (&session, 0.66, Error::StaleZoom),
+        (&other, 1., Error::StaleRenderSession),
+    ] {
+        assert_eq!(label.displayed(context, zoom).unwrap_err(), expected);
+        assert_eq!(label.retained_source(context, zoom).unwrap_err(), expected);
+        assert_eq!(
+            label.retains_any(context, zoom, 0..9).unwrap_err(),
+            expected
+        );
+        assert_eq!(
+            label.bounds_at(context, zoom, Point::ORIGIN).unwrap_err(),
+            expected
+        );
+        assert_eq!(
+            label
+                .canvas_text(context, zoom, Point::ORIGIN, Color::BLACK)
+                .unwrap_err(),
+            expected
+        );
+    }
+    assert!(
+        label
+            .canvas_text(&session, 1., Point::ORIGIN, Color::BLACK)
+            .is_ok()
+    );
+}
+
+#[test]
+fn finite_scaled_metrics_cannot_escape_as_infinite_world_dimensions() {
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    let style = Style {
+        size: Pixels(2.),
+        line_height: LineHeight::Relative(f32::MAX),
+        ..Style::default()
+    };
+    // At zoom 0.5 the scaled size=1 and line height=MAX are finite. The
+    // required world line height is not; reject before passing it to shaping.
+    let scaled = style.scaled(0.5);
+    assert!(scaled.0.is_finite() && scaled.1.is_finite());
+    assert_eq!(
+        cache
+            .resolve(&session, "call", 100., 0.5, style)
+            .unwrap_err(),
+        Error::InvalidMetrics
+    );
+    assert_eq!(cache.allocations, 0);
+    assert!(cache.entries.is_empty());
+    // Independently exercise validation after division for actual measured
+    // dimensions: finite scaled width/height do not imply finite world values.
+    assert_eq!(
+        world_size(Size::new(f32::MAX, 1.), 0.5),
+        Err(Error::InvalidMeasurement)
+    );
+    assert_eq!(
+        world_size(Size::new(1., f32::MAX), 0.5),
+        Err(Error::InvalidMeasurement)
+    );
+    assert_eq!(
+        world_size(Size::new(20., 8.), 0.5).unwrap(),
+        Size::new(40., 16.)
+    );
+}
+
+#[test]
+fn malformed_metrics_and_explicit_experiment_budgets_fail_without_a_cached_candidate() {
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    for (width, zoom) in [(f32::NAN, 1.), (-1., 1.), (100., 0.), (100., f32::INFINITY)] {
+        assert_eq!(
+            cache
+                .resolve(&session, "call", width, zoom, Style::default())
+                .unwrap_err(),
+            Error::InvalidMetrics
+        );
+    }
+    assert_eq!(
+        cache
+            .resolve(
+                &session,
+                &"x".repeat(MAX_SOURCE_BYTES + 1),
+                100.,
+                1.,
+                Style::default()
+            )
+            .unwrap_err(),
+        Error::SourceBudget
+    );
+    assert_eq!(
+        cache
+            .resolve(
+                &session,
+                &"x".repeat(MAX_GRAPHEMES + 1),
+                100.,
+                1.,
+                Style::default()
+            )
+            .unwrap_err(),
+        Error::GraphemeBudget
+    );
+    assert!(cache.entries.is_empty());
+}
+
+#[test]
+fn bounds_translation_rejects_nonfinite_world_positions_and_endpoints() {
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    let label = cache
+        .resolve(&session, "call", 100., 1., Style::default())
+        .unwrap();
+    for position in [Point::new(f32::NAN, 0.), Point::new(0., f32::INFINITY)] {
+        assert_eq!(
+            label.bounds_at(&session, 1., position).unwrap_err(),
+            Error::InvalidPosition
+        );
+        assert_eq!(
+            label
+                .canvas_text(&session, 1., position, Color::BLACK)
+                .unwrap_err(),
+            Error::InvalidPosition
+        );
+    }
+    assert_eq!(
+        translated_bounds(Point::new(f32::MAX, 0.), Size::new(f32::MAX, 1.)),
+        Err(Error::InvalidPosition)
+    );
+    assert_eq!(
+        translated_bounds(Point::new(0., f32::MAX), Size::new(1., f32::MAX)),
+        Err(Error::InvalidPosition)
+    );
+    assert_eq!(
+        label
+            .bounds_at(&session, 1., Point::new(-20., -10.))
+            .unwrap()
+            .position(),
+        Point::new(-20., -10.)
+    );
+}
+
+/// Must run as the ONLY selected test in a dedicated, fresh test process.
+/// The ignored marker keeps this global-font mutation out of normal parallel
+/// desktop tests. See the evidence directory's exact executable runner.
+#[test]
+#[ignore = "mutates the global font database; run only this exact test in a fresh process"]
+fn actual_font_load_rejects_retained_label_and_old_session() {
+    use graphics_text::cosmic_text::fontdb;
+    use std::borrow::Cow;
+
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    let source = "Operation: Pressure";
+    let label = cache
+        .resolve(&session, source, 200., 1., Style::default())
+        .unwrap();
+    assert_eq!(label.displayed(&session, 1.).unwrap(), source);
+    assert!(
+        label
+            .canvas_text(&session, 1., Point::ORIGIN, Color::BLACK)
+            .is_ok()
+    );
+    let measured = cache.allocations;
+    assert!(measured > 0);
+    assert!(Arc::ptr_eq(&cache.entries.front().unwrap().label, &label));
+
+    let (version_before, version_after, faces_before, faces_after) = {
+        let mut fonts = graphics_text::font_system().write().unwrap();
+        let face = fonts
+            .raw()
+            .db()
+            .faces()
+            .find(|face| {
+                face.families
+                    .iter()
+                    .any(|(family, _)| family == "Iced-Icons")
+            })
+            .expect("Iced 0.14 embeds and loads its known Iced-Icons.ttf face")
+            .id;
+        let bytes = fonts
+            .raw()
+            .db()
+            .with_face_data(face, |data, _| data.to_vec())
+            .expect("the built-in binary font has accessible bytes");
+        assert!(!bytes.is_empty());
+        // load_font increments Version even for invalid bytes. Independently
+        // establish actual face admission so this cannot pass with invalid data.
+        let mut probe = fontdb::Database::new();
+        probe.load_font_data(bytes.clone());
+        let admitted = probe
+            .faces()
+            .filter(|face| {
+                face.families
+                    .iter()
+                    .any(|(family, _)| family == "Iced-Icons")
+            })
+            .count();
+        assert!(
+            admitted > 0,
+            "the extracted bytes parse as the expected real font"
+        );
+        let before = fonts.version();
+        assert_eq!(before, session.version);
+        let count = fonts.raw().db().faces().count();
+        // Owned bytes intentionally bypass Borrowed-address deduplication.
+        // This is an actual valid duplicate-face load, not a claim the chosen
+        // face or rendered metrics change; the stale-epoch rule is the oracle.
+        fonts.load_font(Cow::Owned(bytes));
+        (
+            before,
+            fonts.version(),
+            count,
+            fonts.raw().db().faces().count(),
+        )
+    };
+    assert_ne!(version_before, version_after);
+    assert!(
+        faces_after > faces_before,
+        "actual font admission must accompany the version increment"
+    );
+    assert_eq!(
+        label.displayed(&session, 1.).unwrap_err(),
+        Error::FontSetChanged
+    );
+    assert_eq!(
+        label.retained_source(&session, 1.).unwrap_err(),
+        Error::FontSetChanged
+    );
+    assert_eq!(
+        label.retains_any(&session, 1., 0..9).unwrap_err(),
+        Error::FontSetChanged
+    );
+    assert_eq!(
+        label.bounds_at(&session, 1., Point::ORIGIN).unwrap_err(),
+        Error::FontSetChanged
+    );
+    assert_eq!(
+        label
+            .canvas_text(&session, 1., Point::ORIGIN, Color::BLACK)
+            .unwrap_err(),
+        Error::FontSetChanged
+    );
+    assert_eq!(
+        cache
+            .resolve(&session, source, 200., 1., Style::default())
+            .unwrap_err(),
+        Error::FontSetChanged
+    );
+    assert_eq!(
+        cache.allocations, measured,
+        "an invalid session must not remeasure and imply renderer repair"
+    );
+    println!(
+        "Valid Iced-Icons load: faces {faces_before}->{faces_after}, font Version {version_before:?}->{version_after:?}; old label and session rejected"
+    );
+    // Do not create a fresh session or claim dynamic WGPU cache recovery here.
+    // Process exit is the isolation boundary; no other test may run afterward.
+}
diff --git a/harness/experiments/scenario-label-measurement-20260913/.gitattributes b/harness/experiments/scenario-label-measurement-20260913/.gitattributes
new file mode 100644
index 00000000..a3f24269
--- /dev/null
+++ b/harness/experiments/scenario-label-measurement-20260913/.gitattributes
@@ -0,0 +1,3 @@
+attempt1/* -text whitespace=cr-at-eol
+attempt2/* -text whitespace=cr-at-eol
+attempt3/* -text whitespace=cr-at-eol
diff --git a/harness/experiments/scenario-label-measurement-20260913/README.md b/harness/experiments/scenario-label-measurement-20260913/README.md
new file mode 100644
index 00000000..aa8730ef
--- /dev/null
+++ b/harness/experiments/scenario-label-measurement-20260913/README.md
@@ -0,0 +1,147 @@
+# Scenario label measurement: preserved candidate and source correction
+
+This is an **unwired, uncompiled experiment**, not an accepted renderer policy.
+Source base: `208268c8aa7f6bc3c2bab6a3c0657358f3f7dc23`.
+Parent's docs-only worktree HEAD: `75cb09dade2cf4b9a176b5e6159f43e2345d196e`.
+Only the two new `crates/oa-desktop/src/behavior/scenario_label` module/test
+paths and this evidence directory belong to this correction.
+
+## Preserved attempt 1
+
+`attempt1/scenario_label.rs` and `attempt1/tests.rs` are the exact raw files
+reviewed before correction. Both SHA256 values were checked before copying and
+again after copying; [manifest](attempt1/manifest.json) records source paths and
+hashes. They remain historical evidence, not alternate compiler inputs.
+
+Independent static review identified:
+
+1. A retained Label Arc lacked its font epoch and zoom. Cached dimensions could
+   be reused by painting/hit/navigation after their measurement context changed.
+2. Iced's WGPU text cache omits font Version; remeasuring only this module cannot
+   establish dynamic-font parity with an already-populated renderer cache.
+3. The font-epoch test had already evicted its original entry with three variants
+   in a capacity-two cache. Different Arc identity did not prove invalidation.
+4. Finite scaled metrics could overflow when converted back to world units.
+   Concrete example: size 2, Relative(MAX) line height, zoom 0.5.
+
+These were source findings. Neither the old candidate nor the correction was
+compiled or executed by this worker; no failure/pass count is inferred.
+
+## Preserved attempt 2 and missing font-version branch
+
+`attempt2/` preserves both corrected raw source files and this note before the
+follow-up, with exact SHA256 checks before and after copying. The root reviewer
+found that local cache epoch invalidation and a fresh session identity did not
+exercise an actual global font Version change. That specific branch was still
+untested; the historical ten tests were not evidence for it.
+
+## Corrected experimental seam
+
+`RenderSession::after_fonts_settled_and_renderer_reset()` explicitly records a
+caller-established settled-font rendering lifetime. It does not reset or inspect
+the renderer. The caller must finish font loading and create a fresh renderer
+cache, then prohibit font changes between resolution, guarded consumption and
+draw. A changed global font Version rejects the old session; a new local cache
+alone is not a repair for WGPU's old glyph buffers.
+
+Labels record that session identity/font Version and measured zoom. Displayed
+text, retained-source bytes, bounds, field retention and canvas Text construction
+use checked accessors. Another session, another zoom or a detected font change
+rejects a retained artifact. Returned raw Text/bounds must be consumed in that
+checked context: holding those values across context changes bypasses the guard.
+This is an explicit limited contract, not atomic protection against a concurrent
+font load or an incorrect renderer transform supplied by the caller.
+
+Finite world line metrics are checked before shaping. Actual measured dimensions
+are checked again after division by zoom. The existing 64KiB source and 4096
+grapheme budgets remain explicit experiment errors, not adopted product limits.
+
+Eleven ordinary test candidates now include separate resident-entry font-epoch invalidation,
+fresh-session invalidation, stale artifact rejection for every consumer, and
+the overflow counterexample, plus finite world-position/rectangle-endpoint
+validation for bounds_at and canvas_text. This last check does not establish
+validity under arbitrary camera transforms or contain raster ink.
+The invalidation assertions require a still-resident
+entry, positive prior measurement count and an increased count afterward.
+These ordinary tests do not mutate the global font database or claim dynamic-font rendering
+acceptance. The existing actual Paragraph comparisons remain layout-metric
+oracles, not raster-ink/Scene collision evidence.
+
+One additional **ignored** test, `actual_font_load_rejects_retained_label_and_old_session`,
+must run alone in a fresh process. It resolves a label, extracts the actual
+Iced-Icons font bytes that pinned Iced embeds in its global fontdb, independently
+parses them into a fresh fontdb and confirms the expected family, then loads owned
+valid bytes through actual FontSystem::load_font. Both a new face and a changed
+Version must be observed. The old Label's five consumer accessors and old-session
+Cache::resolve must return FontSetChanged; no new measurements may occur.
+
+This is a valid duplicate-face load, not invalid input used merely to increment
+a version. It does not claim the selected face or visual metrics change, create
+a WGPU renderer, or test renderer recovery after dynamic loading. No font asset,
+system-specific font path, download, or new dependency is needed. Version mutation
+is not undone; dedicated process exit is the isolation boundary.
+
+## Pinned primary APIs and remaining evaluator
+
+Cargo.lock pins iced_graphics/iced_wgpu 0.14.0 and iced_widget 0.14.2. Relevant
+local registry sources: `iced_wgpu-0.14.0/src/geometry.rs` (`fill_text`, scaled
+font metrics), `iced_wgpu-0.14.0/src/text.rs` (`Text::Cached` allocation),
+`iced_graphics-0.14.0/src/text/cache.rs` (Key/hash lacks Version), and
+`iced_graphics-0.14.0/src/text.rs` (FontSystem::load_font/version).
+Independent reviewer confirmed `geometry.rs:306-360`, WGPU `text.rs:443-500`
+and its retained BufferCache at line 304 (trim at 435 only evicts unused
+entries), graphics `text/cache.rs:109-146`, and graphics `compositor.rs:69`.
+The compositor's font-load path changes the global FontSystem, not the WGPU
+buffer cache. A check immediately before canvas_text is therefore not atomic
+with the later WGPU prepare; fonts must remain unchanged for the entire session.
+
+The module remains undeclared in behavior.rs. Parent may separately add test-only
+`#[cfg(test)] mod scenario_label;` and run:
+
+```
+cargo test -p oa-desktop --locked --offline behavior::scenario_label::tests:: -- --test-threads=1
+```
+
+The normal filter selects twelve tests: eleven ordinary tests and one ignored
+global-font test. This is an expected selection, not a claim they pass. Do not run
+the whole desktop suite with `--include-ignored` to exercise the font test.
+
+After the parent compiles and records a matching test executable, use the exact
+isolation runner (no Cargo invocation inside the runner):
+
+```powershell
+& ./harness/experiments/scenario-label-measurement-20260913/run-font-version-test.ps1 `
+    -TestExecutable $desktopTestExe -ExpectedSha256 $expectedTestHash `
+    -RunDirectory $freshEvidenceDir
+```
+
+It verifies the supplied binary hash, lists exactly one ignored test, then starts
+a separate fresh executable process with:
+
+```
+--ignored --exact behavior::scenario_label::tests::actual_font_load_rejects_retained_label_and_old_session --nocapture --test-threads=1
+```
+
+The runner refuses an existing result directory and requires exactly one passing
+test, preserving selection/output/receipt. Parent must provide the matching DLL
+environment and source-to-binary provenance. Runner and tests are unexecuted.
+It also accepts `-TestName scenario_label::tests::actual_font_load_rejects_retained_label_and_old_session`
+for a parent-built standalone test wrapper importing the exact module at crate
+root. That result must be reported as standalone Iced/module evidence, not desktop
+or native integration. Wrapper, dependency artifacts and source hashes must be
+bound separately by the compiler owner.
+
+Corridors remain
+external; ordinary/reversed and self-message positioning is not selected here.
+The bounded prefix search guarantees measured fit, not a globally maximal prefix
+for all contextual shaping. No wrapping, row-height change, public schema or
+production gesture is introduced. Real WGPU label ink, activation shoulders,
+clipping, viewport transforms, and actual navigation integration remain required
+before adopting the seam. Original fixed 32-grapheme/225-unit rendering is still
+unchanged for baseline comparison.
+
+## Parent corridor candidate and isolated evaluator
+
+The parent added `scenario_label/corridor.rs`: a bounded geometric candidate that subtracts padded blockers intersecting the full label band and selects the widest connected interval, with deterministic anchor/leftmost tie-breaking. It takes an explicit finite caller-supplied band; self/reversed corridor construction, actual Scene integration, font/ink clearance and release gesture policy remain unimplemented. Six unexecuted tests cover intermediate activations, unsorted overlapping blockers, complete-band intersections, ties, explicit self/reversed bands and invalid/overflow coordinates. This is an evaluation candidate, not an adopted paint policy.
+
+`attempt3` preserves both corrected raw label modules and the first raw corridor before scoped rustfmt. `standalone.rs` imports the actual three current source files without copying their implementation or wiring the desktop. Its expected listing is 18 tests: 17 ordinary and one ignored global-font mutation. Compiling/running that wrapper against explicitly identified pinned Iced/unicode dependencies is a standalone evaluator only; it does not establish desktop integration or WGPU/native acceptance. Use the font runner with the standalone exact test name documented above, in a separate process. No execution result is claimed by this prepared note; subsequent gate evidence will record actual results.
diff --git a/harness/experiments/scenario-label-measurement-20260913/attempt1/manifest.json b/harness/experiments/scenario-label-measurement-20260913/attempt1/manifest.json
new file mode 100644
index 00000000..9ed7f841
--- /dev/null
+++ b/harness/experiments/scenario-label-measurement-20260913/attempt1/manifest.json
@@ -0,0 +1,17 @@
+{
+  "base": "208268c8aa7f6bc3c2bab6a3c0657358f3f7dc23",
+  "status": "Original uncompiled, unwired candidate; static review found stale reuse, vacuous epoch test and post-division overflow gaps",
+  "files": [
+    {
+      "path": "crates/oa-desktop/src/behavior/scenario_label.rs",
+      "hash": "1CACEDE2BCB0E3E86C0D0B691D6E65FDADEA75F93FC74BBAF94E8E2082D6E877",
+      "name": "scenario_label.rs"
+    },
+    {
+      "path": "crates/oa-desktop/src/behavior/scenario_label/tests.rs",
+      "hash": "9AC3A0D091E3A319D7822C76B34DCEA56B8D400DBB7F55B3711659E84B6F2BDB",
+      "name": "tests.rs"
+    }
+  ],
+  "docsOnlyHead": "75cb09dade2cf4b9a176b5e6159f43e2345d196e"
+}
diff --git a/harness/experiments/scenario-label-measurement-20260913/attempt1/scenario_label.rs b/harness/experiments/scenario-label-measurement-20260913/attempt1/scenario_label.rs
new file mode 100644
index 00000000..e5fef669
--- /dev/null
+++ b/harness/experiments/scenario-label-measurement-20260913/attempt1/scenario_label.rs
@@ -0,0 +1,206 @@
+//! Unwired single-line scenario label experiment. No renderer or schema is changed.
+//!
+//! Iced 0.14.0 WGPU `geometry::Frame::fill_text` shapes positive uniform-scale
+//! canvas text at `size * zoom`; its `text::prepare` uses graphics text::Cache.
+//! This adapter uses that same allocator/font system/attributes, not a character
+//! width estimate. Canvas Text::max_width is wrapping, so it stays infinite.
+//!
+//! Integration seam: after lifecycle/activation endpoint alignment, a caller
+//! supplies a usable text width in world units and retains one cache per live
+//! labelled occurrence across Scene rebuilds. Paint, hit testing, navigation and extents
+//! consume the returned Label. Position/color do not invalidate measurement.
+//! This does NOT choose a self-call, reversed-arrow or obstacle corridor policy.
+//! It measures layout advances, not raster ink; overhang/clip/activation-border
+//! acceptance still requires the real WGPU evaluator. The old 32-grapheme/225px
+//! renderer is deliberately untouched for a later baseline comparison.
+use iced::advanced::{graphics::text as graphics_text, text::{Alignment, LineHeight, Shaping}};
+use iced::{Color, Font, Pixels, Point, Rectangle, Size, widget::canvas::Text};
+use std::{collections::VecDeque, ops::Range, sync::Arc};
+use unicode_segmentation::UnicodeSegmentation;
+
+const MAX_SOURCE_BYTES: usize = 64 * 1024;
+const MAX_GRAPHEMES: usize = 4096;
+const MAX_ENTRIES: usize = 2;
+
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub(super) struct Style {
+    pub font: Font,
+    pub size: Pixels,
+    pub line_height: LineHeight,
+    pub shaping: Shaping,
+}
+
+impl Default for Style {
+    fn default() -> Self {
+        let text = Text::default();
+        Self { font: text.font, size: Pixels(12.), line_height: text.line_height, shaping: text.shaping }
+    }
+}
+
+impl Style {
+    fn scaled(self, zoom: f32) -> (f32, f32) {
+        let size = Pixels(self.size.0 * zoom);
+        let line_height = match self.line_height {
+            LineHeight::Absolute(value) => LineHeight::Absolute(Pixels(value.0 * zoom)),
+            LineHeight::Relative(value) => LineHeight::Relative(value),
+        };
+        (size.0, line_height.to_absolute(size).0)
+    }
+}
+
+#[derive(Clone, Debug)]
+pub(super) struct Label {
+    source: String,
+    pub displayed: String,
+    /// Original-label bytes represented before any added ellipsis. Includes
+    /// collapsed whitespace, but `retains_any` never counts whitespace as text.
+    pub retained_source: Range<usize>,
+    /// World-space layout advances, at origin; not glyph-ink containment.
+    pub bounds: Rectangle,
+    style: Style,
+}
+
+impl Label {
+    pub fn retains_any(&self, field: Range<usize>) -> bool {
+        if field.start > field.end || self.source.get(field.clone()).is_none() {
+            return false;
+        }
+        let end = field.end.min(self.retained_source.end);
+        field.start < end && self.source.get(field.start..end)
+            .is_some_and(|text| text.chars().any(|c| !c.is_whitespace()))
+    }
+
+    pub fn bounds_at(&self, position: Point) -> Rectangle {
+        Rectangle::new(position, self.bounds.size())
+    }
+
+    /// Paint under the same positive uniform zoom used for `Cache::resolve`.
+    /// No per-label wrapping or implicit text maximum is introduced.
+    pub fn canvas_text(&self, position: Point, color: Color) -> Text {
+        Text { content: self.displayed.clone(), position, color,
+            size: self.style.size, line_height: self.style.line_height,
+            font: self.style.font, shaping: self.style.shaping,
+            max_width: f32::INFINITY, ..Text::default() }
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub(super) enum Error { InvalidMetrics, SourceBudget, GraphemeBudget, FontSystemUnavailable, InvalidMeasurement }
+
+struct Entry { source: String, style: Style, zoom: f32, width: f32, label: Arc<Label> }
+
+#[derive(Default)]
+/// Two recent resolutions for ONE live labelled occurrence. A global small LRU
+/// would thrash when a larger Scene is rebuilt in order. The integration owner
+/// must retain these by occurrence identity and prune on removal/document change.
+pub(super) struct Cache {
+    version: Option<graphics_text::Version>,
+    entries: VecDeque<Entry>,
+    #[cfg(test)]
+    allocations: usize,
+}
+
+impl Cache {
+    /// `width` excludes any caller-chosen backplate padding. Zero is valid.
+    /// Cache ownership must survive redraws; constructing one per Scene defeats
+    /// reuse. Fonts loaded through Iced invalidate all entries by Version.
+    /// Error handling/fallback for these explicit experiment budgets is an
+    /// integration decision; never silently paint the old truncated contract.
+    pub fn resolve(&mut self, source: &str, width: f32, zoom: f32, style: Style) -> Result<Arc<Label>, Error> {
+        let (size, line_height) = style.scaled(zoom);
+        if !width.is_finite() || width < 0. || !zoom.is_finite() || zoom <= 0.
+            || !size.is_finite() || size <= 0. || !line_height.is_finite() || line_height <= 0.
+            || !(width * zoom).is_finite() {
+            return Err(Error::InvalidMetrics);
+        }
+        if source.len() > MAX_SOURCE_BYTES { return Err(Error::SourceBudget); }
+        let mut fonts = graphics_text::font_system().write().map_err(|_| Error::FontSystemUnavailable)?;
+        if self.version != Some(fonts.version()) {
+            self.entries.clear();
+            self.version = Some(fonts.version());
+        }
+        if let Some(index) = self.entries.iter().position(|entry|
+            entry.source == source && entry.style == style && entry.zoom == zoom && entry.width == width) {
+            let entry = self.entries.remove(index).unwrap();
+            let label = entry.label.clone();
+            self.entries.push_back(entry);
+            return Ok(label);
+        }
+        let normalized = Normalized::new(source);
+        let cuts: Vec<usize> = normalized.text.grapheme_indices(true).map(|(i, _)| i)
+            .chain(std::iter::once(normalized.text.len())).collect();
+        if cuts.len().saturating_sub(1) > MAX_GRAPHEMES { return Err(Error::GraphemeBudget); }
+        // Candidate buffers are temporary. Only the resolved strings/metrics
+        // survive, bounded by MAX_ENTRIES; renderer caching remains independent.
+        let mut shapes = graphics_text::Cache::new();
+        let mut measure = |content: &str| -> Result<Size, Error> {
+            if content.is_empty() { return Ok(Size::ZERO); }
+            #[cfg(test)] { self.allocations += 1; }
+            let (_, entry) = shapes.allocate(fonts.raw(), graphics_text::cache::Key {
+                content, size, line_height, font: style.font, bounds: Size::INFINITE,
+                shaping: style.shaping, align_x: Alignment::Default,
+            });
+            if entry.buffer.layout_runs().count() != 1 || !entry.min_bounds.width.is_finite()
+                || !entry.min_bounds.height.is_finite() { return Err(Error::InvalidMeasurement); }
+            Ok(Size::new(entry.min_bounds.width / zoom, entry.min_bounds.height / zoom))
+        };
+        let full = measure(&normalized.text)?;
+        let (displayed, retained, measured) = if full.width <= width {
+            (normalized.text.clone(), normalized.text.len(), full)
+        } else {
+            let ellipsis = measure("…")?;
+            if ellipsis.width > width {
+                (String::new(), 0, Size::ZERO)
+            } else {
+                // Every accepted candidate is actually shaped and fits. Search
+                // is bounded/logarithmic; contextual shaping is not universally
+                // monotone, so this does NOT promise the globally longest prefix.
+                // Full content is always checked first and never needlessly cut.
+                let mut best = ("…".to_owned(), 0, ellipsis);
+                let (mut low, mut high) = (1, cuts.len().saturating_sub(1));
+                while low < high {
+                    let middle = low + (high - low) / 2;
+                    let candidate = format!("{}…", &normalized.text[..cuts[middle]]);
+                    let measured = measure(&candidate)?;
+                    if measured.width <= width {
+                        best = (candidate, cuts[middle], measured);
+                        low = middle + 1;
+                    } else { high = middle; }
+                }
+                best
+            }
+        };
+        let label = Arc::new(Label { source: source.into(), displayed,
+            retained_source: 0..normalized.source_end(retained),
+            bounds: Rectangle::with_size(measured), style });
+        if self.entries.len() == MAX_ENTRIES { self.entries.pop_front(); }
+        self.entries.push_back(Entry { source: source.into(), style, zoom, width, label: label.clone() });
+        Ok(label)
+    }
+}
+
+struct Normalized { text: String, ends: Vec<(usize, usize)> }
+impl Normalized {
+    fn new(source: &str) -> Self {
+        let mut result = Self { text: String::new(), ends: vec![(0, 0)] };
+        let mut separator = false;
+        for (start, c) in source.char_indices() {
+            if c.is_whitespace() { separator = !result.text.is_empty(); continue; }
+            if separator {
+                result.text.push(' ');
+                result.ends.push((result.text.len(), start));
+                separator = false;
+            }
+            result.text.push(c);
+            result.ends.push((result.text.len(), start + c.len_utf8()));
+        }
+        result
+    }
+    fn source_end(&self, normalized_end: usize) -> usize {
+        self.ends.binary_search_by_key(&normalized_end, |(end, _)| *end)
+            .map(|index| self.ends[index].1).expect("grapheme cuts are character boundaries")
+    }
+}
+
+#[cfg(test)]
+mod tests;
diff --git a/harness/experiments/scenario-label-measurement-20260913/attempt1/tests.rs b/harness/experiments/scenario-label-measurement-20260913/attempt1/tests.rs
new file mode 100644
index 00000000..9f50d7d8
--- /dev/null
+++ b/harness/experiments/scenario-label-measurement-20260913/attempt1/tests.rs
@@ -0,0 +1,120 @@
+//! Unexecuted evaluator candidates; the module is intentionally not wired yet.
+use super::*;
+use iced::advanced::{graphics::text::Paragraph, text::{Paragraph as _, Text as ParagraphText, Wrapping}};
+
+// Independent paragraph construction: no candidate cache, normalization, search,
+// or character-width estimate is used by this measurement oracle.
+fn paragraph_size(content: &str, zoom: f32, style: Style) -> Size {
+    let size = Pixels(style.size.0 * zoom);
+    let line_height = match style.line_height {
+        LineHeight::Relative(factor) => LineHeight::Relative(factor),
+        LineHeight::Absolute(pixels) => LineHeight::Absolute(Pixels(pixels.0 * zoom)),
+    };
+    let paragraph = Paragraph::with_text(ParagraphText { content, bounds: Size::INFINITE,
+        size, line_height, font: style.font, align_x: Alignment::Default,
+        align_y: iced::alignment::Vertical::Top, shaping: style.shaping, wrapping: Wrapping::default() });
+    assert_eq!(paragraph.buffer().layout_runs().count(), 1);
+    Size::new(paragraph.min_width() / zoom, paragraph.min_height() / zoom)
+}
+
+#[test]
+fn adequate_corridor_reveals_full_realistic_names_and_distinguishing_suffixes() {
+    let mut cache = Cache::default();
+    let style = Style::default();
+    for text in [
+        "1. call · Request valve repair · Technician service conversation",
+        "2. reply · Return pressure after repair · Technician service conversation",
+        "1. call · Request redundant hydraulic pressure calibration channel A",
+        "1. call · Request redundant hydraulic pressure calibration channel B",
+    ] {
+        let wide = cache.resolve(text, 1600., 1., style).unwrap();
+        assert_eq!(wide.displayed, text);
+        assert_eq!(wide.retained_source, 0..text.len());
+        assert_eq!(wide.bounds.size(), paragraph_size(text, 1., style));
+        let narrow = cache.resolve(text, 80., 1., style).unwrap();
+        assert_ne!(narrow.displayed, text);
+        assert!(narrow.bounds.width <= 80.);
+        assert_eq!(narrow.bounds.size(), paragraph_size(&narrow.displayed, 1., style));
+    }
+}
+
+#[test]
+fn normalized_visible_prefix_maps_to_original_bytes_without_claiming_hidden_operation() {
+    let raw = " \t1.  call · Pump\r\n  · Operation: Need\u{301}le  ";
+    let expected = "1. call · Pump · Operation: Need\u{301}le";
+    let n = Normalized::new(raw);
+    assert_eq!(n.text, expected);
+    let prefix = "1. call · Pump ";
+    assert_eq!(n.source_end(prefix.len()), raw.find("· Operation").unwrap());
+    let mut cache = Cache::default();
+    let wide = cache.resolve(raw, 1600., 1., Style::default()).unwrap();
+    assert_eq!(wide.displayed, expected);
+    assert_eq!(wide.retained_source.end, raw.trim_end().len());
+    let field = raw.find("Need").unwrap()..raw.trim_end().len();
+    assert!(wide.retains_any(field.clone()));
+    assert!(!wide.retains_any(0..2), "normalized whitespace is not a visible field");
+    let small = cache.resolve(raw, 70., 1., Style::default()).unwrap();
+    assert!(!small.retains_any(field));
+    assert!(small.retained_source.end < raw.find("Operation").unwrap());
+}
+
+#[test]
+fn grapheme_prefixes_and_zoom_match_actual_paragraph_layout() {
+    let text = "call · 戻り値 圧力 e\u{301} 👩‍🔬 safety valve verification";
+    let mut cache = Cache::default();
+    for zoom in [0.66, 1., 1.75] {
+        let label = cache.resolve(text, 105., zoom, Style::default()).unwrap();
+        assert!(label.bounds.width <= 105.);
+        assert_eq!(label.bounds.size(), paragraph_size(&label.displayed, zoom, Style::default()));
+        assert!(text.grapheme_indices(true).any(|(i, _)| i == label.retained_source.end)
+            || label.retained_source.end == text.len());
+        let painted = label.canvas_text(Point::new(400., 90.), Color::BLACK);
+        assert_eq!(painted.content, label.displayed);
+        assert!(painted.max_width.is_infinite());
+        assert_eq!(label.bounds_at(painted.position).size(), label.bounds.size());
+    }
+}
+
+#[test]
+fn empty_and_too_narrow_labels_never_claim_source_visibility() {
+    let mut cache = Cache::default();
+    for text in ["", " \t\n", "Operation: Pump"] {
+        let label = cache.resolve(text, 0., 1., Style::default()).unwrap();
+        assert_eq!(label.displayed, "");
+        assert_eq!(label.retained_source, 0..0);
+        assert_eq!(label.bounds.size(), Size::ZERO);
+        assert!(!label.retains_any(0..text.len()));
+    }
+}
+
+#[test]
+fn redraws_reuse_resolution_but_width_zoom_style_and_font_epoch_are_dependencies() {
+    let mut cache = Cache::default();
+    let text = "call · Pressure verification with a descriptive operation label";
+    let style = Style::default();
+    let a = cache.resolve(text, 100., 1., style).unwrap();
+    let measured = cache.allocations;
+    let b = cache.resolve(text, 100., 1., style).unwrap();
+    assert!(Arc::ptr_eq(&a, &b));
+    assert_eq!(cache.allocations, measured);
+    for (width, zoom, style) in [(120., 1., style), (100., 0.66, style),
+        (100., 1., Style { size: Pixels(14.), ..style })] {
+        let other = cache.resolve(text, width, zoom, style).unwrap();
+        assert!(!Arc::ptr_eq(&a, &other));
+    }
+    // Simulate an invalidated local epoch without mutating the shared font DB.
+    cache.version = None;
+    let refreshed = cache.resolve(text, 100., 1., style).unwrap();
+    assert!(!Arc::ptr_eq(&a, &refreshed));
+}
+
+#[test]
+fn malformed_metrics_and_explicit_experiment_budgets_fail_without_a_cached_candidate() {
+    let mut cache = Cache::default();
+    for (width, zoom) in [(f32::NAN, 1.), (-1., 1.), (100., 0.), (100., f32::INFINITY)] {
+        assert_eq!(cache.resolve("call", width, zoom, Style::default()).unwrap_err(), Error::InvalidMetrics);
+    }
+    assert_eq!(cache.resolve(&"x".repeat(MAX_SOURCE_BYTES + 1), 100., 1., Style::default()).unwrap_err(), Error::SourceBudget);
+    assert_eq!(cache.resolve(&"x".repeat(MAX_GRAPHEMES + 1), 100., 1., Style::default()).unwrap_err(), Error::GraphemeBudget);
+    assert!(cache.entries.is_empty());
+}
diff --git a/harness/experiments/scenario-label-measurement-20260913/attempt2/README.md b/harness/experiments/scenario-label-measurement-20260913/attempt2/README.md
new file mode 100644
index 00000000..4da5686c
--- /dev/null
+++ b/harness/experiments/scenario-label-measurement-20260913/attempt2/README.md
@@ -0,0 +1,87 @@
+# Scenario label measurement: preserved candidate and source correction
+
+This is an **unwired, uncompiled experiment**, not an accepted renderer policy.
+Source base: `208268c8aa7f6bc3c2bab6a3c0657358f3f7dc23`.
+Parent's docs-only worktree HEAD: `75cb09dade2cf4b9a176b5e6159f43e2345d196e`.
+Only the two new `crates/oa-desktop/src/behavior/scenario_label` module/test
+paths and this evidence directory belong to this correction.
+
+## Preserved attempt 1
+
+`attempt1/scenario_label.rs` and `attempt1/tests.rs` are the exact raw files
+reviewed before correction. Both SHA256 values were checked before copying and
+again after copying; [manifest](attempt1/manifest.json) records source paths and
+hashes. They remain historical evidence, not alternate compiler inputs.
+
+Independent static review identified:
+
+1. A retained Label Arc lacked its font epoch and zoom. Cached dimensions could
+   be reused by painting/hit/navigation after their measurement context changed.
+2. Iced's WGPU text cache omits font Version; remeasuring only this module cannot
+   establish dynamic-font parity with an already-populated renderer cache.
+3. The font-epoch test had already evicted its original entry with three variants
+   in a capacity-two cache. Different Arc identity did not prove invalidation.
+4. Finite scaled metrics could overflow when converted back to world units.
+   Concrete example: size 2, Relative(MAX) line height, zoom 0.5.
+
+These were source findings. Neither the old candidate nor the correction was
+compiled or executed by this worker; no failure/pass count is inferred.
+
+## Corrected experimental seam
+
+`RenderSession::after_fonts_settled_and_renderer_reset()` explicitly records a
+caller-established settled-font rendering lifetime. It does not reset or inspect
+the renderer. The caller must finish font loading and create a fresh renderer
+cache, then prohibit font changes between resolution, guarded consumption and
+draw. A changed global font Version rejects the old session; a new local cache
+alone is not a repair for WGPU's old glyph buffers.
+
+Labels record that session identity/font Version and measured zoom. Displayed
+text, retained-source bytes, bounds, field retention and canvas Text construction
+use checked accessors. Another session, another zoom or a detected font change
+rejects a retained artifact. Returned raw Text/bounds must be consumed in that
+checked context: holding those values across context changes bypasses the guard.
+This is an explicit limited contract, not atomic protection against a concurrent
+font load or an incorrect renderer transform supplied by the caller.
+
+Finite world line metrics are checked before shaping. Actual measured dimensions
+are checked again after division by zoom. The existing 64KiB source and 4096
+grapheme budgets remain explicit experiment errors, not adopted product limits.
+
+Ten test candidates now include separate resident-entry font-epoch invalidation,
+fresh-session invalidation, stale artifact rejection for every consumer, and
+the overflow counterexample. The invalidation assertions require a still-resident
+entry, positive prior measurement count and an increased count afterward.
+These tests do not mutate the global font database or claim dynamic-font rendering
+acceptance. The existing actual Paragraph comparisons remain layout-metric
+oracles, not raster-ink/Scene collision evidence.
+
+## Pinned primary APIs and remaining evaluator
+
+Cargo.lock pins iced_graphics/iced_wgpu 0.14.0 and iced_widget 0.14.2. Relevant
+local registry sources: `iced_wgpu-0.14.0/src/geometry.rs` (`fill_text`, scaled
+font metrics), `iced_wgpu-0.14.0/src/text.rs` (`Text::Cached` allocation),
+`iced_graphics-0.14.0/src/text/cache.rs` (Key/hash lacks Version), and
+`iced_graphics-0.14.0/src/text.rs` (FontSystem::load_font/version).
+Independent reviewer confirmed `geometry.rs:306-360`, WGPU `text.rs:443-500`
+and its retained BufferCache at line 304 (trim at 435 only evicts unused
+entries), graphics `text/cache.rs:109-146`, and graphics `compositor.rs:69`.
+The compositor's font-load path changes the global FontSystem, not the WGPU
+buffer cache. A check immediately before canvas_text is therefore not atomic
+with the later WGPU prepare; fonts must remain unchanged for the entire session.
+
+The module remains undeclared in behavior.rs. Parent may separately add test-only
+`#[cfg(test)] mod scenario_label;` and run:
+
+```
+cargo test -p oa-desktop --locked --offline behavior::scenario_label::tests:: -- --test-threads=1
+```
+
+Expected selection is exactly ten tests, not a claim they pass. Corridors remain
+external; ordinary/reversed and self-message positioning is not selected here.
+The bounded prefix search guarantees measured fit, not a globally maximal prefix
+for all contextual shaping. No wrapping, row-height change, public schema or
+production gesture is introduced. Real WGPU label ink, activation shoulders,
+clipping, viewport transforms, and actual navigation integration remain required
+before adopting the seam. Original fixed 32-grapheme/225-unit rendering is still
+unchanged for baseline comparison.
diff --git a/harness/experiments/scenario-label-measurement-20260913/attempt2/manifest.json b/harness/experiments/scenario-label-measurement-20260913/attempt2/manifest.json
new file mode 100644
index 00000000..916f9f49
--- /dev/null
+++ b/harness/experiments/scenario-label-measurement-20260913/attempt2/manifest.json
@@ -0,0 +1,22 @@
+{
+  "sourceBase": "208268c8aa7f6bc3c2bab6a3c0657358f3f7dc23",
+  "docsOnlyHead": "75cb09dade2cf4b9a176b5e6159f43e2345d196e",
+  "files": [
+    {
+      "name": "scenario_label.rs",
+      "hash": "82789CF6C9D0C3F0B027671D13E286F869A359DF1F163D8B47EA1B1E442CAAF4",
+      "path": "crates/oa-desktop/src/behavior/scenario_label.rs"
+    },
+    {
+      "name": "tests.rs",
+      "hash": "0C7A0CE80570B8DA347B5147AD00DB9AF26AE4E3FDE0F445683D1958348972AF",
+      "path": "crates/oa-desktop/src/behavior/scenario_label/tests.rs"
+    },
+    {
+      "name": "README.md",
+      "hash": "D49F5A48B6C943C4FBA3DB86BFC5C916719DB01A9D962FAB381D976B96E5D993",
+      "path": "harness/experiments/scenario-label-measurement-20260913/README.md"
+    }
+  ],
+  "status": "Uncompiled corrected candidate before actual font-load coverage"
+}
diff --git a/harness/experiments/scenario-label-measurement-20260913/attempt2/scenario_label.rs b/harness/experiments/scenario-label-measurement-20260913/attempt2/scenario_label.rs
new file mode 100644
index 00000000..c81eb10b
--- /dev/null
+++ b/harness/experiments/scenario-label-measurement-20260913/attempt2/scenario_label.rs
@@ -0,0 +1,271 @@
+//! Unwired single-line scenario label experiment. No renderer or schema is changed.
+//!
+//! Iced 0.14.0 WGPU `geometry::Frame::fill_text` shapes positive uniform-scale
+//! canvas text at `size * zoom`; its `text::prepare` uses graphics text::Cache.
+//! This adapter uses that same allocator/font system/attributes, not a character
+//! width estimate. Canvas Text::max_width is wrapping, so it stays infinite.
+//! Experimental parity requires settled fonts and a fresh renderer/cache after
+//! font loading. Iced's WGPU text cache key omits FontSystem::Version, so merely
+//! remeasuring here cannot repair its cached glyph buffers after dynamic loading.
+//! A RenderSession is caller attestation of that lifecycle, not its enforcement.
+//! No fonts may be loaded between measurement, guarded access and actual draw.
+//!
+//! Integration seam: after lifecycle/activation endpoint alignment, a caller
+//! supplies a usable text width in world units and retains one cache per live
+//! labelled occurrence across Scene rebuilds. Paint, hit testing, navigation and extents
+//! consume the returned Label. Position/color do not invalidate measurement.
+//! This does NOT choose a self-call, reversed-arrow or obstacle corridor policy.
+//! It measures layout advances, not raster ink; overhang/clip/activation-border
+//! acceptance still requires the real WGPU evaluator. The old 32-grapheme/225px
+//! renderer is deliberately untouched for a later baseline comparison.
+use iced::advanced::{graphics::text as graphics_text, text::{Alignment, LineHeight, Shaping}};
+use iced::{Color, Font, Pixels, Point, Rectangle, Size, widget::canvas::Text};
+use std::{collections::VecDeque, ops::Range, sync::Arc};
+use unicode_segmentation::UnicodeSegmentation;
+
+const MAX_SOURCE_BYTES: usize = 64 * 1024;
+const MAX_GRAPHEMES: usize = 4096;
+const MAX_ENTRIES: usize = 2;
+
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub(super) struct Style {
+    pub font: Font,
+    pub size: Pixels,
+    pub line_height: LineHeight,
+    pub shaping: Shaping,
+}
+
+impl Default for Style {
+    fn default() -> Self {
+        let text = Text::default();
+        Self { font: text.font, size: Pixels(12.), line_height: text.line_height, shaping: text.shaping }
+    }
+}
+
+impl Style {
+    fn scaled(self, zoom: f32) -> (f32, f32) {
+        let size = Pixels(self.size.0 * zoom);
+        let line_height = match self.line_height {
+            LineHeight::Absolute(value) => LineHeight::Absolute(Pixels(value.0 * zoom)),
+            LineHeight::Relative(value) => LineHeight::Relative(value),
+        };
+        (size.0, line_height.to_absolute(size).0)
+    }
+}
+
+/// Explicit experimental contract: the caller finishes loading fonts and starts
+/// a fresh renderer/cache BEFORE capturing this session, then keeps fonts fixed.
+/// This module cannot inspect or reset the actual renderer's text cache.
+#[derive(Clone, Debug)]
+pub(super) struct RenderSession {
+    version: graphics_text::Version,
+    identity: Arc<()>,
+}
+
+impl RenderSession {
+    pub fn after_fonts_settled_and_renderer_reset() -> Result<Self, Error> {
+        let fonts = graphics_text::font_system().read().map_err(|_| Error::FontSystemUnavailable)?;
+        Ok(Self { version: fonts.version(), identity: Arc::new(()) })
+    }
+}
+
+#[derive(Clone, Debug)]
+pub(super) struct Label {
+    source: String,
+    displayed: String,
+    /// Original-label bytes represented before any added ellipsis. Includes
+    /// collapsed whitespace, but `retains_any` never counts whitespace as text.
+    retained_source: Range<usize>,
+    /// World-space layout advances, at origin; not glyph-ink containment.
+    bounds: Rectangle,
+    style: Style,
+    measured_session: RenderSession,
+    measured_zoom: f32,
+}
+
+impl Label {
+    fn check(&self, session: &RenderSession, zoom: f32) -> Result<(), Error> {
+        if !Arc::ptr_eq(&self.measured_session.identity, &session.identity) {
+            return Err(Error::StaleRenderSession);
+        }
+        if !zoom.is_finite() || zoom != self.measured_zoom { return Err(Error::StaleZoom); }
+        let fonts = graphics_text::font_system().read().map_err(|_| Error::FontSystemUnavailable)?;
+        if fonts.version() != self.measured_session.version || fonts.version() != session.version {
+            return Err(Error::FontSetChanged);
+        }
+        Ok(())
+    }
+
+    pub fn displayed(&self, session: &RenderSession, zoom: f32) -> Result<&str, Error> {
+        self.check(session, zoom)?;
+        Ok(&self.displayed)
+    }
+
+    pub fn retained_source(&self, session: &RenderSession, zoom: f32) -> Result<Range<usize>, Error> {
+        self.check(session, zoom)?;
+        Ok(self.retained_source.clone())
+    }
+
+    pub fn retains_any(&self, session: &RenderSession, zoom: f32, field: Range<usize>) -> Result<bool, Error> {
+        self.check(session, zoom)?;
+        if field.start > field.end || self.source.get(field.clone()).is_none() {
+            return Ok(false);
+        }
+        let end = field.end.min(self.retained_source.end);
+        Ok(field.start < end && self.source.get(field.start..end)
+            .is_some_and(|text| text.chars().any(|c| !c.is_whitespace())))
+    }
+
+    pub fn bounds_at(&self, session: &RenderSession, zoom: f32, position: Point) -> Result<Rectangle, Error> {
+        self.check(session, zoom)?;
+        Ok(Rectangle::new(position, self.bounds.size()))
+    }
+
+    /// Paint under the same positive uniform zoom used for `Cache::resolve`.
+    /// No per-label wrapping or implicit text maximum is introduced.
+    /// The returned Text must be consumed immediately in this session/zoom;
+    /// retaining raw Text past another font load/zoom change bypasses the guard.
+    pub fn canvas_text(&self, session: &RenderSession, zoom: f32, position: Point, color: Color) -> Result<Text, Error> {
+        self.check(session, zoom)?;
+        Ok(Text { content: self.displayed.clone(), position, color,
+            size: self.style.size, line_height: self.style.line_height,
+            font: self.style.font, shaping: self.style.shaping,
+            max_width: f32::INFINITY, ..Text::default() })
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub(super) enum Error { InvalidMetrics, SourceBudget, GraphemeBudget, FontSystemUnavailable, InvalidMeasurement, StaleZoom, StaleRenderSession, FontSetChanged }
+
+struct Entry { source: String, style: Style, zoom: f32, width: f32, label: Arc<Label> }
+
+#[derive(Default)]
+/// Two recent resolutions for ONE live labelled occurrence. A global small LRU
+/// would thrash when a larger Scene is rebuilt in order. The integration owner
+/// must retain these by occurrence identity and prune on removal/document change.
+pub(super) struct Cache {
+    version: Option<graphics_text::Version>,
+    session: Option<Arc<()>>,
+    entries: VecDeque<Entry>,
+    #[cfg(test)]
+    allocations: usize,
+}
+
+impl Cache {
+    /// `width` excludes any caller-chosen backplate padding. Zero is valid.
+    /// Cache ownership must survive redraws; constructing one per Scene defeats
+    /// reuse. Changed fonts invalidate the SESSION: the caller must establish
+    /// a fresh renderer and a new settled session, not just remeasure this cache.
+    /// Error handling/fallback for these explicit experiment budgets is an
+    /// integration decision; never silently paint the old truncated contract.
+    pub fn resolve(&mut self, session: &RenderSession, source: &str, width: f32, zoom: f32, style: Style) -> Result<Arc<Label>, Error> {
+        let (size, line_height) = style.scaled(zoom);
+        if !width.is_finite() || width < 0. || !zoom.is_finite() || zoom <= 0.
+            || !size.is_finite() || size <= 0. || !line_height.is_finite() || line_height <= 0.
+            || !(width * zoom).is_finite() || !(size / zoom).is_finite()
+            || !(line_height / zoom).is_finite() {
+            return Err(Error::InvalidMetrics);
+        }
+        if source.len() > MAX_SOURCE_BYTES { return Err(Error::SourceBudget); }
+        let mut fonts = graphics_text::font_system().write().map_err(|_| Error::FontSystemUnavailable)?;
+        if session.version != fonts.version() { return Err(Error::FontSetChanged); }
+        if self.version != Some(fonts.version())
+            || self.session.as_ref().is_none_or(|identity| !Arc::ptr_eq(identity, &session.identity)) {
+            self.entries.clear();
+            self.version = Some(fonts.version());
+            self.session = Some(session.identity.clone());
+        }
+        if let Some(index) = self.entries.iter().position(|entry|
+            entry.source == source && entry.style == style && entry.zoom == zoom && entry.width == width) {
+            let entry = self.entries.remove(index).unwrap();
+            let label = entry.label.clone();
+            self.entries.push_back(entry);
+            return Ok(label);
+        }
+        let normalized = Normalized::new(source);
+        let cuts: Vec<usize> = normalized.text.grapheme_indices(true).map(|(i, _)| i)
+            .chain(std::iter::once(normalized.text.len())).collect();
+        if cuts.len().saturating_sub(1) > MAX_GRAPHEMES { return Err(Error::GraphemeBudget); }
+        // Candidate buffers are temporary. Only the resolved strings/metrics
+        // survive, bounded by MAX_ENTRIES; renderer caching remains independent.
+        let mut shapes = graphics_text::Cache::new();
+        let mut measure = |content: &str| -> Result<Size, Error> {
+            if content.is_empty() { return Ok(Size::ZERO); }
+            #[cfg(test)] { self.allocations += 1; }
+            let (_, entry) = shapes.allocate(fonts.raw(), graphics_text::cache::Key {
+                content, size, line_height, font: style.font, bounds: Size::INFINITE,
+                shaping: style.shaping, align_x: Alignment::Default,
+            });
+            if entry.buffer.layout_runs().count() != 1 || !entry.min_bounds.width.is_finite()
+                || !entry.min_bounds.height.is_finite() { return Err(Error::InvalidMeasurement); }
+            world_size(entry.min_bounds, zoom)
+        };
+        let full = measure(&normalized.text)?;
+        let (displayed, retained, measured) = if full.width <= width {
+            (normalized.text.clone(), normalized.text.len(), full)
+        } else {
+            let ellipsis = measure("…")?;
+            if ellipsis.width > width {
+                (String::new(), 0, Size::ZERO)
+            } else {
+                // Every accepted candidate is actually shaped and fits. Search
+                // is bounded/logarithmic; contextual shaping is not universally
+                // monotone, so this does NOT promise the globally longest prefix.
+                // Full content is always checked first and never needlessly cut.
+                let mut best = ("…".to_owned(), 0, ellipsis);
+                let (mut low, mut high) = (1, cuts.len().saturating_sub(1));
+                while low < high {
+                    let middle = low + (high - low) / 2;
+                    let candidate = format!("{}…", &normalized.text[..cuts[middle]]);
+                    let measured = measure(&candidate)?;
+                    if measured.width <= width {
+                        best = (candidate, cuts[middle], measured);
+                        low = middle + 1;
+                    } else { high = middle; }
+                }
+                best
+            }
+        };
+        let label = Arc::new(Label { source: source.into(), displayed,
+            retained_source: 0..normalized.source_end(retained),
+            bounds: Rectangle::with_size(measured), style,
+            measured_session: session.clone(), measured_zoom: zoom });
+        if self.entries.len() == MAX_ENTRIES { self.entries.pop_front(); }
+        self.entries.push_back(Entry { source: source.into(), style, zoom, width, label: label.clone() });
+        Ok(label)
+    }
+}
+
+fn world_size(scaled: Size, zoom: f32) -> Result<Size, Error> {
+    let world = Size::new(scaled.width / zoom, scaled.height / zoom);
+    if !world.width.is_finite() || !world.height.is_finite() || world.width < 0. || world.height < 0. {
+        return Err(Error::InvalidMeasurement);
+    }
+    Ok(world)
+}
+
+struct Normalized { text: String, ends: Vec<(usize, usize)> }
+impl Normalized {
+    fn new(source: &str) -> Self {
+        let mut result = Self { text: String::new(), ends: vec![(0, 0)] };
+        let mut separator = false;
+        for (start, c) in source.char_indices() {
+            if c.is_whitespace() { separator = !result.text.is_empty(); continue; }
+            if separator {
+                result.text.push(' ');
+                result.ends.push((result.text.len(), start));
+                separator = false;
+            }
+            result.text.push(c);
+            result.ends.push((result.text.len(), start + c.len_utf8()));
+        }
+        result
+    }
+    fn source_end(&self, normalized_end: usize) -> usize {
+        self.ends.binary_search_by_key(&normalized_end, |(end, _)| *end)
+            .map(|index| self.ends[index].1).expect("grapheme cuts are character boundaries")
+    }
+}
+
+#[cfg(test)]
+mod tests;
diff --git a/harness/experiments/scenario-label-measurement-20260913/attempt2/tests.rs b/harness/experiments/scenario-label-measurement-20260913/attempt2/tests.rs
new file mode 100644
index 00000000..3212a553
--- /dev/null
+++ b/harness/experiments/scenario-label-measurement-20260913/attempt2/tests.rs
@@ -0,0 +1,200 @@
+//! Unexecuted evaluator candidates; the module is intentionally not wired yet.
+use super::*;
+use iced::advanced::{graphics::text::Paragraph, text::{Paragraph as _, Text as ParagraphText, Wrapping}};
+
+// Independent paragraph construction: no candidate cache, normalization, search,
+// or character-width estimate is used by this measurement oracle.
+fn paragraph_size(content: &str, zoom: f32, style: Style) -> Size {
+    let size = Pixels(style.size.0 * zoom);
+    let line_height = match style.line_height {
+        LineHeight::Relative(factor) => LineHeight::Relative(factor),
+        LineHeight::Absolute(pixels) => LineHeight::Absolute(Pixels(pixels.0 * zoom)),
+    };
+    let paragraph = Paragraph::with_text(ParagraphText { content, bounds: Size::INFINITE,
+        size, line_height, font: style.font, align_x: Alignment::Default,
+        align_y: iced::alignment::Vertical::Top, shaping: style.shaping, wrapping: Wrapping::default() });
+    assert_eq!(paragraph.buffer().layout_runs().count(), 1);
+    Size::new(paragraph.min_width() / zoom, paragraph.min_height() / zoom)
+}
+
+#[test]
+fn adequate_corridor_reveals_full_realistic_names_and_distinguishing_suffixes() {
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    let style = Style::default();
+    for text in [
+        "1. call · Request valve repair · Technician service conversation",
+        "2. reply · Return pressure after repair · Technician service conversation",
+        "1. call · Request redundant hydraulic pressure calibration channel A",
+        "1. call · Request redundant hydraulic pressure calibration channel B",
+    ] {
+        let wide = cache.resolve(&session, text, 1600., 1., style).unwrap();
+        assert_eq!(wide.displayed(&session, 1.).unwrap(), text);
+        assert_eq!(wide.retained_source(&session, 1.).unwrap(), 0..text.len());
+        assert_eq!(wide.bounds.size(), paragraph_size(text, 1., style));
+        let narrow = cache.resolve(&session, text, 80., 1., style).unwrap();
+        assert_ne!(narrow.displayed, text);
+        assert!(narrow.bounds.width <= 80.);
+        assert_eq!(narrow.bounds.size(), paragraph_size(&narrow.displayed, 1., style));
+    }
+}
+
+#[test]
+fn normalized_visible_prefix_maps_to_original_bytes_without_claiming_hidden_operation() {
+    let raw = " \t1.  call · Pump\r\n  · Operation: Need\u{301}le  ";
+    let expected = "1. call · Pump · Operation: Need\u{301}le";
+    let n = Normalized::new(raw);
+    assert_eq!(n.text, expected);
+    let prefix = "1. call · Pump ";
+    assert_eq!(n.source_end(prefix.len()), raw.find("· Operation").unwrap());
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    let wide = cache.resolve(&session, raw, 1600., 1., Style::default()).unwrap();
+    assert_eq!(wide.displayed, expected);
+    assert_eq!(wide.retained_source.end, raw.trim_end().len());
+    let field = raw.find("Need").unwrap()..raw.trim_end().len();
+    assert!(wide.retains_any(&session, 1., field.clone()).unwrap());
+    assert!(!wide.retains_any(&session, 1., 0..2).unwrap(), "normalized whitespace is not a visible field");
+    let small = cache.resolve(&session, raw, 70., 1., Style::default()).unwrap();
+    assert!(!small.retains_any(&session, 1., field).unwrap());
+    assert!(small.retained_source.end < raw.find("Operation").unwrap());
+}
+
+#[test]
+fn grapheme_prefixes_and_zoom_match_actual_paragraph_layout() {
+    let text = "call · 戻り値 圧力 e\u{301} 👩‍🔬 safety valve verification";
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    for zoom in [0.66, 1., 1.75] {
+        let label = cache.resolve(&session, text, 105., zoom, Style::default()).unwrap();
+        assert!(label.bounds.width <= 105.);
+        assert_eq!(label.bounds.size(), paragraph_size(&label.displayed, zoom, Style::default()));
+        assert!(text.grapheme_indices(true).any(|(i, _)| i == label.retained_source.end)
+            || label.retained_source.end == text.len());
+        let painted = label.canvas_text(&session, zoom, Point::new(400., 90.), Color::BLACK).unwrap();
+        assert_eq!(painted.content, label.displayed);
+        assert!(painted.max_width.is_infinite());
+        assert_eq!(label.bounds_at(&session, zoom, painted.position).unwrap().size(), label.bounds.size());
+    }
+}
+
+#[test]
+fn empty_and_too_narrow_labels_never_claim_source_visibility() {
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    for text in ["", " \t\n", "Operation: Pump"] {
+        let label = cache.resolve(&session, text, 0., 1., Style::default()).unwrap();
+        assert_eq!(label.displayed, "");
+        assert_eq!(label.retained_source, 0..0);
+        assert_eq!(label.bounds.size(), Size::ZERO);
+        assert!(!label.retains_any(&session, 1., 0..text.len()).unwrap());
+    }
+}
+
+#[test]
+fn redraws_reuse_resolution_but_width_zoom_and_style_are_dependencies() {
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    let text = "call · Pressure verification with a descriptive operation label";
+    let style = Style::default();
+    let a = cache.resolve(&session, text, 100., 1., style).unwrap();
+    let measured = cache.allocations;
+    let b = cache.resolve(&session, text, 100., 1., style).unwrap();
+    assert!(Arc::ptr_eq(&a, &b));
+    assert_eq!(cache.allocations, measured);
+    for (width, zoom, style) in [(120., 1., style), (100., 0.66, style),
+        (100., 1., Style { size: Pixels(14.), ..style })] {
+        let other = cache.resolve(&session, text, width, zoom, style).unwrap();
+        assert!(!Arc::ptr_eq(&a, &other));
+    }
+}
+
+#[test]
+fn resident_entry_is_remeasured_for_a_fresh_settled_render_session() {
+    let mut cache = Cache::default();
+    let old_session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    let text = "call · Pressure verification";
+    let a = cache.resolve(&old_session, text, 100., 1., Style::default()).unwrap();
+    assert_eq!(cache.entries.len(), 1);
+    assert!(Arc::ptr_eq(&cache.entries.front().unwrap().label, &a));
+    let measured = cache.allocations;
+    assert!(measured > 0);
+    assert!(Arc::ptr_eq(&a, &cache.resolve(&old_session, text, 100., 1., Style::default()).unwrap()));
+    assert_eq!(cache.allocations, measured);
+    // A fresh renderer session invalidates a still-resident entry. This does
+    // not mutate global fonts or purport to test dynamic WGPU font loading.
+    let new_session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    let refreshed = cache.resolve(&new_session, text, 100., 1., Style::default()).unwrap();
+    assert!(!Arc::ptr_eq(&a, &refreshed));
+    assert!(cache.allocations > measured);
+    assert_eq!(cache.entries.len(), 1);
+    assert!(Arc::ptr_eq(&cache.entries.front().unwrap().label, &refreshed));
+}
+
+#[test]
+fn resident_entry_remeasures_after_local_font_epoch_invalidation() {
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    let text = "call · Resident pressure label";
+    let a = cache.resolve(&session, text, 100., 1., Style::default()).unwrap();
+    assert_eq!(cache.entries.len(), 1);
+    assert!(Arc::ptr_eq(&cache.entries.front().unwrap().label, &a));
+    let measured = cache.allocations;
+    assert!(measured > 0);
+    // Exercise the local memo epoch branch while a is still resident. No
+    // intervening width/zoom/style resolution can cause incidental eviction.
+    // This is not an actual font-load or renderer-cache acceptance test.
+    cache.version = None;
+    let refreshed = cache.resolve(&session, text, 100., 1., Style::default()).unwrap();
+    assert!(!Arc::ptr_eq(&a, &refreshed));
+    assert!(cache.allocations > measured);
+    assert_eq!(cache.entries.len(), 1);
+    assert!(Arc::ptr_eq(&cache.entries.front().unwrap().label, &refreshed));
+}
+
+#[test]
+fn retained_artifact_rejects_other_zoom_and_render_session_for_every_consumer() {
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    let label = cache.resolve(&session, "Operation: Pressure", 200., 1., Style::default()).unwrap();
+    let other = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    for (context, zoom, expected) in [(&session, 0.66, Error::StaleZoom), (&other, 1., Error::StaleRenderSession)] {
+        assert_eq!(label.displayed(context, zoom).unwrap_err(), expected);
+        assert_eq!(label.retained_source(context, zoom).unwrap_err(), expected);
+        assert_eq!(label.retains_any(context, zoom, 0..9).unwrap_err(), expected);
+        assert_eq!(label.bounds_at(context, zoom, Point::ORIGIN).unwrap_err(), expected);
+        assert_eq!(label.canvas_text(context, zoom, Point::ORIGIN, Color::BLACK).unwrap_err(), expected);
+    }
+    assert!(label.canvas_text(&session, 1., Point::ORIGIN, Color::BLACK).is_ok());
+}
+
+#[test]
+fn finite_scaled_metrics_cannot_escape_as_infinite_world_dimensions() {
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    let style = Style { size: Pixels(2.), line_height: LineHeight::Relative(f32::MAX), ..Style::default() };
+    // At zoom 0.5 the scaled size=1 and line height=MAX are finite. The
+    // required world line height is not; reject before passing it to shaping.
+    let scaled = style.scaled(0.5);
+    assert!(scaled.0.is_finite() && scaled.1.is_finite());
+    assert_eq!(cache.resolve(&session, "call", 100., 0.5, style).unwrap_err(), Error::InvalidMetrics);
+    assert_eq!(cache.allocations, 0);
+    assert!(cache.entries.is_empty());
+    // Independently exercise validation after division for actual measured
+    // dimensions: finite scaled width/height do not imply finite world values.
+    assert_eq!(world_size(Size::new(f32::MAX, 1.), 0.5), Err(Error::InvalidMeasurement));
+    assert_eq!(world_size(Size::new(1., f32::MAX), 0.5), Err(Error::InvalidMeasurement));
+    assert_eq!(world_size(Size::new(20., 8.), 0.5).unwrap(), Size::new(40., 16.));
+}
+
+#[test]
+fn malformed_metrics_and_explicit_experiment_budgets_fail_without_a_cached_candidate() {
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    for (width, zoom) in [(f32::NAN, 1.), (-1., 1.), (100., 0.), (100., f32::INFINITY)] {
+        assert_eq!(cache.resolve(&session, "call", width, zoom, Style::default()).unwrap_err(), Error::InvalidMetrics);
+    }
+    assert_eq!(cache.resolve(&session, &"x".repeat(MAX_SOURCE_BYTES + 1), 100., 1., Style::default()).unwrap_err(), Error::SourceBudget);
+    assert_eq!(cache.resolve(&session, &"x".repeat(MAX_GRAPHEMES + 1), 100., 1., Style::default()).unwrap_err(), Error::GraphemeBudget);
+    assert!(cache.entries.is_empty());
+}
diff --git a/harness/experiments/scenario-label-measurement-20260913/attempt3/corridor.rs b/harness/experiments/scenario-label-measurement-20260913/attempt3/corridor.rs
new file mode 100644
index 00000000..8434cdd8
--- /dev/null
+++ b/harness/experiments/scenario-label-measurement-20260913/attempt3/corridor.rs
@@ -0,0 +1,154 @@
+//! Unwired corridor-policy candidate for the measured scenario-label experiment.
+//!
+//! The caller supplies a finite structural label band AFTER endpoint/activation
+//! alignment, with padding already removed from its edges. Blockers include
+//! padded activation/card/header bounds over the complete text band, including
+//! stroke/ink clearance. This function does not infer a self-message corridor,
+//! alter scene extents, change zoom, or establish raster-ink containment.
+use iced::Rectangle;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub(super) struct InvalidGeometry;
+
+fn edges(rect: Rectangle) -> Result<(f32, f32, f32, f32), InvalidGeometry> {
+    let right = rect.x + rect.width;
+    let bottom = rect.y + rect.height;
+    if [rect.x, rect.y, rect.width, rect.height, right, bottom]
+        .into_iter()
+        .any(|value| !value.is_finite())
+        || rect.width < 0.
+        || rect.height < 0.
+    {
+        return Err(InvalidGeometry);
+    }
+    Ok((rect.x, right, rect.y, bottom))
+}
+
+/// Select one connected clear interval; never assemble text across blockers.
+/// Prefer greater width, then proximity to the previous label anchor, then the
+/// leftmost interval. Input order has no influence. A zero-area band has no
+/// corridor. Touching the padded vertical band is conservatively obstructing;
+/// a zero-area blocker has no area and must receive stroke padding upstream.
+pub(super) fn widest_clear(
+    band: Rectangle,
+    blockers: &[Rectangle],
+    preferred_anchor: f32,
+) -> Result<Option<Rectangle>, InvalidGeometry> {
+    let (left, right, top, bottom) = edges(band)?;
+    if !preferred_anchor.is_finite() {
+        return Err(InvalidGeometry);
+    }
+    let mut blocked = Vec::new();
+    for &blocker in blockers {
+        let (x0, x1, y0, y1) = edges(blocker)?;
+        if blocker.width > 0. && blocker.height > 0. && y1 >= top && y0 <= bottom {
+            let interval = (x0.max(left), x1.min(right));
+            if interval.0 < interval.1 {
+                blocked.push(interval);
+            }
+        }
+    }
+    if band.width == 0. || band.height == 0. {
+        return Ok(None);
+    }
+    blocked.sort_by(|a, b| a.0.total_cmp(&b.0).then(a.1.total_cmp(&b.1)));
+    let mut best: Option<Rectangle> = None;
+    let mut consider = |start: f32, end: f32| {
+        if start >= end {
+            return;
+        }
+        let candidate = Rectangle { x: start, width: end - start, ..band };
+        // Use f64 only for comparison distance: subtracting two admitted f32
+        // world coordinates can overflow even though each rectangle is finite.
+        let distance = |x: f32| (f64::from(x) - f64::from(preferred_anchor)).abs();
+        if best.is_none_or(|old| {
+            candidate.width > old.width
+                || (candidate.width == old.width
+                    && (distance(candidate.x) < distance(old.x)
+                        || (distance(candidate.x) == distance(old.x) && candidate.x < old.x)))
+        }) {
+            best = Some(candidate);
+        }
+    };
+    let mut cursor = left;
+    for (start, end) in blocked {
+        consider(cursor, start);
+        cursor = cursor.max(end);
+    }
+    consider(cursor, right);
+    Ok(best)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn rect(x: f32, y: f32, width: f32, height: f32) -> Rectangle {
+        Rectangle { x, y, width, height }
+    }
+
+    #[test]
+    fn long_message_does_not_cross_an_intermediate_execution() {
+        let band = rect(20., 100., 700., 22.);
+        let blockers = [rect(250., 80., 16., 80.), rect(490., 90., 28., 140.)];
+        let result = widest_clear(band, &blockers, band.x).unwrap().unwrap();
+        assert_eq!(result, rect(20., 100., 230., 22.));
+        for blocker in blockers {
+            assert!(result.x + result.width <= blocker.x || result.x >= blocker.x + blocker.width);
+        }
+        assert_eq!(widest_clear(band, &[], band.x).unwrap(), Some(band));
+    }
+
+    #[test]
+    fn overlapping_unsorted_blockers_merge_and_widest_gap_wins() {
+        let band = rect(-100., 10., 600., 20.);
+        let blockers = [rect(50., 0., 80., 60.), rect(0., 5., 70., 30.), rect(450., 0., 100., 60.)];
+        let expected = Some(rect(130., 10., 320., 20.));
+        assert_eq!(widest_clear(band, &blockers, -100.).unwrap(), expected);
+        let mut reversed = blockers;
+        reversed.reverse();
+        assert_eq!(widest_clear(band, &reversed, -100.).unwrap(), expected);
+    }
+
+    #[test]
+    fn complete_padded_band_and_touching_boundaries_are_obstructed() {
+        let band = rect(0., 100., 200., 20.);
+        // The first blocker ends at the band top: checking only a baseline
+        // would miss it. The second starts at the band bottom.
+        let blockers = [rect(0., 70., 60., 30.), rect(150., 120., 50., 30.)];
+        assert_eq!(widest_clear(band, &blockers, 0.).unwrap(), Some(rect(60., 100., 90., 20.)));
+        let outside = [rect(0., 70., 200., 29.), rect(0., 121., 200., 30.)];
+        assert_eq!(widest_clear(band, &outside, 0.).unwrap(), Some(band));
+    }
+
+    #[test]
+    fn ties_keep_the_nearest_anchor_then_choose_leftmost() {
+        let band = rect(0., 0., 300., 20.);
+        let blockers = [rect(100., 0., 100., 20.)];
+        assert_eq!(widest_clear(band, &blockers, 190.).unwrap(), Some(rect(200., 0., 100., 20.)));
+        assert_eq!(widest_clear(band, &blockers, 100.).unwrap(), Some(rect(0., 0., 100., 20.)));
+    }
+
+    #[test]
+    fn caller_defined_self_and_reversed_corridors_keep_their_geometry() {
+        // Direction and self-loop policy are explicit caller inputs. Neither
+        // a zero endpoint gap nor screen width can silently supply a corridor.
+        for band in [rect(420., 40., 180., 22.), rect(-400., 90., 350., 22.)] {
+            assert_eq!(widest_clear(band, &[], band.x).unwrap(), Some(band));
+        }
+        assert_eq!(widest_clear(rect(420., 40., 0., 22.), &[], 420.).unwrap(), None);
+        assert_eq!(widest_clear(rect(420., 40., 180., 0.), &[], 420.).unwrap(), None);
+        assert_eq!(widest_clear(rect(0., 0., 100., 20.), &[rect(-10., -10., 200., 50.)], 0.).unwrap(), None);
+    }
+
+    #[test]
+    fn invalid_or_overflowing_geometry_never_enters_a_corridor() {
+        let band = rect(0., 0., 100., 20.);
+        for invalid in [rect(f32::NAN, 0., 10., 20.), rect(0., 0., -1., 20.),
+            rect(f32::MAX, 0., f32::MAX, 20.), rect(0., f32::MAX, 10., f32::MAX)] {
+            assert_eq!(widest_clear(invalid, &[], 0.), Err(InvalidGeometry));
+            assert_eq!(widest_clear(band, &[invalid], 0.), Err(InvalidGeometry));
+        }
+        assert_eq!(widest_clear(band, &[], f32::INFINITY), Err(InvalidGeometry));
+    }
+}
diff --git a/harness/experiments/scenario-label-measurement-20260913/attempt3/manifest.json b/harness/experiments/scenario-label-measurement-20260913/attempt3/manifest.json
new file mode 100644
index 00000000..8b8a7a70
--- /dev/null
+++ b/harness/experiments/scenario-label-measurement-20260913/attempt3/manifest.json
@@ -0,0 +1,17 @@
+[
+  {
+    "name": "scenario_label.rs",
+    "bytes": 13548,
+    "sha256": "b452249c45b1225760d1b9bd8f2d9241c4d599e8a68d7328641d61381c28cbbd"
+  },
+  {
+    "name": "tests.rs",
+    "bytes": 15683,
+    "sha256": "1af0115850ae826f3af211499006c26bd290c17cc186d08b41be0ee40981a83b"
+  },
+  {
+    "name": "corridor.rs",
+    "bytes": 6657,
+    "sha256": "94747ab1b161564c8901f3d0702034e43f14f263decd8e7b823c801fbcb80dd7"
+  }
+]
diff --git a/harness/experiments/scenario-label-measurement-20260913/attempt3/scenario_label.rs b/harness/experiments/scenario-label-measurement-20260913/attempt3/scenario_label.rs
new file mode 100644
index 00000000..1a7c94ee
--- /dev/null
+++ b/harness/experiments/scenario-label-measurement-20260913/attempt3/scenario_label.rs
@@ -0,0 +1,281 @@
+//! Unwired single-line scenario label experiment. No renderer or schema is changed.
+//!
+//! Iced 0.14.0 WGPU `geometry::Frame::fill_text` shapes positive uniform-scale
+//! canvas text at `size * zoom`; its `text::prepare` uses graphics text::Cache.
+//! This adapter uses that same allocator/font system/attributes, not a character
+//! width estimate. Canvas Text::max_width is wrapping, so it stays infinite.
+//! Experimental parity requires settled fonts and a fresh renderer/cache after
+//! font loading. Iced's WGPU text cache key omits FontSystem::Version, so merely
+//! remeasuring here cannot repair its cached glyph buffers after dynamic loading.
+//! A RenderSession is caller attestation of that lifecycle, not its enforcement.
+//! No fonts may be loaded between measurement, guarded access and actual draw.
+//!
+//! Integration seam: after lifecycle/activation endpoint alignment, a caller
+//! supplies a usable text width in world units and retains one cache per live
+//! labelled occurrence across Scene rebuilds. Paint, hit testing, navigation and extents
+//! consume the returned Label. Position/color do not invalidate measurement.
+//! This does NOT choose a self-call, reversed-arrow or obstacle corridor policy.
+//! It measures layout advances, not raster ink; overhang/clip/activation-border
+//! acceptance still requires the real WGPU evaluator. The old 32-grapheme/225px
+//! renderer is deliberately untouched for a later baseline comparison.
+use iced::advanced::{graphics::text as graphics_text, text::{Alignment, LineHeight, Shaping}};
+use iced::{Color, Font, Pixels, Point, Rectangle, Size, widget::canvas::Text};
+use std::{collections::VecDeque, ops::Range, sync::Arc};
+use unicode_segmentation::UnicodeSegmentation;
+
+const MAX_SOURCE_BYTES: usize = 64 * 1024;
+const MAX_GRAPHEMES: usize = 4096;
+const MAX_ENTRIES: usize = 2;
+
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub(super) struct Style {
+    pub font: Font,
+    pub size: Pixels,
+    pub line_height: LineHeight,
+    pub shaping: Shaping,
+}
+
+impl Default for Style {
+    fn default() -> Self {
+        let text = Text::default();
+        Self { font: text.font, size: Pixels(12.), line_height: text.line_height, shaping: text.shaping }
+    }
+}
+
+impl Style {
+    fn scaled(self, zoom: f32) -> (f32, f32) {
+        let size = Pixels(self.size.0 * zoom);
+        let line_height = match self.line_height {
+            LineHeight::Absolute(value) => LineHeight::Absolute(Pixels(value.0 * zoom)),
+            LineHeight::Relative(value) => LineHeight::Relative(value),
+        };
+        (size.0, line_height.to_absolute(size).0)
+    }
+}
+
+/// Explicit experimental contract: the caller finishes loading fonts and starts
+/// a fresh renderer/cache BEFORE capturing this session, then keeps fonts fixed.
+/// This module cannot inspect or reset the actual renderer's text cache.
+#[derive(Clone, Debug)]
+pub(super) struct RenderSession {
+    version: graphics_text::Version,
+    identity: Arc<()>,
+}
+
+impl RenderSession {
+    pub fn after_fonts_settled_and_renderer_reset() -> Result<Self, Error> {
+        let fonts = graphics_text::font_system().read().map_err(|_| Error::FontSystemUnavailable)?;
+        Ok(Self { version: fonts.version(), identity: Arc::new(()) })
+    }
+}
+
+#[derive(Clone, Debug)]
+pub(super) struct Label {
+    source: String,
+    displayed: String,
+    /// Original-label bytes represented before any added ellipsis. Includes
+    /// collapsed whitespace, but `retains_any` never counts whitespace as text.
+    retained_source: Range<usize>,
+    /// World-space layout advances, at origin; not glyph-ink containment.
+    bounds: Rectangle,
+    style: Style,
+    measured_session: RenderSession,
+    measured_zoom: f32,
+}
+
+impl Label {
+    fn check(&self, session: &RenderSession, zoom: f32) -> Result<(), Error> {
+        if !Arc::ptr_eq(&self.measured_session.identity, &session.identity) {
+            return Err(Error::StaleRenderSession);
+        }
+        if !zoom.is_finite() || zoom != self.measured_zoom { return Err(Error::StaleZoom); }
+        let fonts = graphics_text::font_system().read().map_err(|_| Error::FontSystemUnavailable)?;
+        if fonts.version() != self.measured_session.version || fonts.version() != session.version {
+            return Err(Error::FontSetChanged);
+        }
+        Ok(())
+    }
+
+    pub fn displayed(&self, session: &RenderSession, zoom: f32) -> Result<&str, Error> {
+        self.check(session, zoom)?;
+        Ok(&self.displayed)
+    }
+
+    pub fn retained_source(&self, session: &RenderSession, zoom: f32) -> Result<Range<usize>, Error> {
+        self.check(session, zoom)?;
+        Ok(self.retained_source.clone())
+    }
+
+    pub fn retains_any(&self, session: &RenderSession, zoom: f32, field: Range<usize>) -> Result<bool, Error> {
+        self.check(session, zoom)?;
+        if field.start > field.end || self.source.get(field.clone()).is_none() {
+            return Ok(false);
+        }
+        let end = field.end.min(self.retained_source.end);
+        Ok(field.start < end && self.source.get(field.start..end)
+            .is_some_and(|text| text.chars().any(|c| !c.is_whitespace())))
+    }
+
+    /// Validate finite world position and rectangle endpoints only. Camera
+    /// transforms and raster bounds remain a separate integration contract.
+    pub fn bounds_at(&self, session: &RenderSession, zoom: f32, position: Point) -> Result<Rectangle, Error> {
+        self.check(session, zoom)?;
+        translated_bounds(position, self.bounds.size())
+    }
+
+    /// Paint under the same positive uniform zoom used for `Cache::resolve`.
+    /// No per-label wrapping or implicit text maximum is introduced.
+    /// The returned Text must be consumed immediately in this session/zoom;
+    /// retaining raw Text past another font load/zoom change bypasses the guard.
+    pub fn canvas_text(&self, session: &RenderSession, zoom: f32, position: Point, color: Color) -> Result<Text, Error> {
+        self.bounds_at(session, zoom, position)?;
+        Ok(Text { content: self.displayed.clone(), position, color,
+            size: self.style.size, line_height: self.style.line_height,
+            font: self.style.font, shaping: self.style.shaping,
+            max_width: f32::INFINITY, ..Text::default() })
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub(super) enum Error { InvalidMetrics, SourceBudget, GraphemeBudget, FontSystemUnavailable, InvalidMeasurement, InvalidPosition, StaleZoom, StaleRenderSession, FontSetChanged }
+
+struct Entry { source: String, style: Style, zoom: f32, width: f32, label: Arc<Label> }
+
+#[derive(Default)]
+/// Two recent resolutions for ONE live labelled occurrence. A global small LRU
+/// would thrash when a larger Scene is rebuilt in order. The integration owner
+/// must retain these by occurrence identity and prune on removal/document change.
+pub(super) struct Cache {
+    version: Option<graphics_text::Version>,
+    session: Option<Arc<()>>,
+    entries: VecDeque<Entry>,
+    #[cfg(test)]
+    allocations: usize,
+}
+
+impl Cache {
+    /// `width` excludes any caller-chosen backplate padding. Zero is valid.
+    /// Cache ownership must survive redraws; constructing one per Scene defeats
+    /// reuse. Changed fonts invalidate the SESSION: the caller must establish
+    /// a fresh renderer and a new settled session, not just remeasure this cache.
+    /// Error handling/fallback for these explicit experiment budgets is an
+    /// integration decision; never silently paint the old truncated contract.
+    pub fn resolve(&mut self, session: &RenderSession, source: &str, width: f32, zoom: f32, style: Style) -> Result<Arc<Label>, Error> {
+        let (size, line_height) = style.scaled(zoom);
+        if !width.is_finite() || width < 0. || !zoom.is_finite() || zoom <= 0.
+            || !size.is_finite() || size <= 0. || !line_height.is_finite() || line_height <= 0.
+            || !(width * zoom).is_finite() || !(size / zoom).is_finite()
+            || !(line_height / zoom).is_finite() {
+            return Err(Error::InvalidMetrics);
+        }
+        if source.len() > MAX_SOURCE_BYTES { return Err(Error::SourceBudget); }
+        let mut fonts = graphics_text::font_system().write().map_err(|_| Error::FontSystemUnavailable)?;
+        if session.version != fonts.version() { return Err(Error::FontSetChanged); }
+        if self.version != Some(fonts.version())
+            || self.session.as_ref().is_none_or(|identity| !Arc::ptr_eq(identity, &session.identity)) {
+            self.entries.clear();
+            self.version = Some(fonts.version());
+            self.session = Some(session.identity.clone());
+        }
+        if let Some(index) = self.entries.iter().position(|entry|
+            entry.source == source && entry.style == style && entry.zoom == zoom && entry.width == width) {
+            let entry = self.entries.remove(index).unwrap();
+            let label = entry.label.clone();
+            self.entries.push_back(entry);
+            return Ok(label);
+        }
+        let normalized = Normalized::new(source);
+        let cuts: Vec<usize> = normalized.text.grapheme_indices(true).map(|(i, _)| i)
+            .chain(std::iter::once(normalized.text.len())).collect();
+        if cuts.len().saturating_sub(1) > MAX_GRAPHEMES { return Err(Error::GraphemeBudget); }
+        // Candidate buffers are temporary. Only the resolved strings/metrics
+        // survive, bounded by MAX_ENTRIES; renderer caching remains independent.
+        let mut shapes = graphics_text::Cache::new();
+        let mut measure = |content: &str| -> Result<Size, Error> {
+            if content.is_empty() { return Ok(Size::ZERO); }
+            #[cfg(test)] { self.allocations += 1; }
+            let (_, entry) = shapes.allocate(fonts.raw(), graphics_text::cache::Key {
+                content, size, line_height, font: style.font, bounds: Size::INFINITE,
+                shaping: style.shaping, align_x: Alignment::Default,
+            });
+            if entry.buffer.layout_runs().count() != 1 || !entry.min_bounds.width.is_finite()
+                || !entry.min_bounds.height.is_finite() { return Err(Error::InvalidMeasurement); }
+            world_size(entry.min_bounds, zoom)
+        };
+        let full = measure(&normalized.text)?;
+        let (displayed, retained, measured) = if full.width <= width {
+            (normalized.text.clone(), normalized.text.len(), full)
+        } else {
+            let ellipsis = measure("…")?;
+            if ellipsis.width > width {
+                (String::new(), 0, Size::ZERO)
+            } else {
+                // Every accepted candidate is actually shaped and fits. Search
+                // is bounded/logarithmic; contextual shaping is not universally
+                // monotone, so this does NOT promise the globally longest prefix.
+                // Full content is always checked first and never needlessly cut.
+                let mut best = ("…".to_owned(), 0, ellipsis);
+                let (mut low, mut high) = (1, cuts.len().saturating_sub(1));
+                while low < high {
+                    let middle = low + (high - low) / 2;
+                    let candidate = format!("{}…", &normalized.text[..cuts[middle]]);
+                    let measured = measure(&candidate)?;
+                    if measured.width <= width {
+                        best = (candidate, cuts[middle], measured);
+                        low = middle + 1;
+                    } else { high = middle; }
+                }
+                best
+            }
+        };
+        let label = Arc::new(Label { source: source.into(), displayed,
+            retained_source: 0..normalized.source_end(retained),
+            bounds: Rectangle::with_size(measured), style,
+            measured_session: session.clone(), measured_zoom: zoom });
+        if self.entries.len() == MAX_ENTRIES { self.entries.pop_front(); }
+        self.entries.push_back(Entry { source: source.into(), style, zoom, width, label: label.clone() });
+        Ok(label)
+    }
+}
+
+fn world_size(scaled: Size, zoom: f32) -> Result<Size, Error> {
+    let world = Size::new(scaled.width / zoom, scaled.height / zoom);
+    if !world.width.is_finite() || !world.height.is_finite() || world.width < 0. || world.height < 0. {
+        return Err(Error::InvalidMeasurement);
+    }
+    Ok(world)
+}
+
+fn translated_bounds(position: Point, size: Size) -> Result<Rectangle, Error> {
+    if !position.x.is_finite() || !position.y.is_finite()
+        || !(position.x + size.width).is_finite() || !(position.y + size.height).is_finite() {
+        return Err(Error::InvalidPosition);
+    }
+    Ok(Rectangle::new(position, size))
+}
+
+struct Normalized { text: String, ends: Vec<(usize, usize)> }
+impl Normalized {
+    fn new(source: &str) -> Self {
+        let mut result = Self { text: String::new(), ends: vec![(0, 0)] };
+        let mut separator = false;
+        for (start, c) in source.char_indices() {
+            if c.is_whitespace() { separator = !result.text.is_empty(); continue; }
+            if separator {
+                result.text.push(' ');
+                result.ends.push((result.text.len(), start));
+                separator = false;
+            }
+            result.text.push(c);
+            result.ends.push((result.text.len(), start + c.len_utf8()));
+        }
+        result
+    }
+    fn source_end(&self, normalized_end: usize) -> usize {
+        self.ends.binary_search_by_key(&normalized_end, |(end, _)| *end)
+            .map(|index| self.ends[index].1).expect("grapheme cuts are character boundaries")
+    }
+}
+
+#[cfg(test)]
+mod tests;
diff --git a/harness/experiments/scenario-label-measurement-20260913/attempt3/tests.rs b/harness/experiments/scenario-label-measurement-20260913/attempt3/tests.rs
new file mode 100644
index 00000000..1bec0dab
--- /dev/null
+++ b/harness/experiments/scenario-label-measurement-20260913/attempt3/tests.rs
@@ -0,0 +1,271 @@
+//! Unexecuted evaluator candidates; the module is intentionally not wired yet.
+use super::*;
+use iced::advanced::{graphics::text::Paragraph, text::{Paragraph as _, Text as ParagraphText, Wrapping}};
+
+// Independent paragraph construction: no candidate cache, normalization, search,
+// or character-width estimate is used by this measurement oracle.
+fn paragraph_size(content: &str, zoom: f32, style: Style) -> Size {
+    let size = Pixels(style.size.0 * zoom);
+    let line_height = match style.line_height {
+        LineHeight::Relative(factor) => LineHeight::Relative(factor),
+        LineHeight::Absolute(pixels) => LineHeight::Absolute(Pixels(pixels.0 * zoom)),
+    };
+    let paragraph = Paragraph::with_text(ParagraphText { content, bounds: Size::INFINITE,
+        size, line_height, font: style.font, align_x: Alignment::Default,
+        align_y: iced::alignment::Vertical::Top, shaping: style.shaping, wrapping: Wrapping::default() });
+    assert_eq!(paragraph.buffer().layout_runs().count(), 1);
+    Size::new(paragraph.min_width() / zoom, paragraph.min_height() / zoom)
+}
+
+#[test]
+fn adequate_corridor_reveals_full_realistic_names_and_distinguishing_suffixes() {
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    let style = Style::default();
+    for text in [
+        "1. call · Request valve repair · Technician service conversation",
+        "2. reply · Return pressure after repair · Technician service conversation",
+        "1. call · Request redundant hydraulic pressure calibration channel A",
+        "1. call · Request redundant hydraulic pressure calibration channel B",
+    ] {
+        let wide = cache.resolve(&session, text, 1600., 1., style).unwrap();
+        assert_eq!(wide.displayed(&session, 1.).unwrap(), text);
+        assert_eq!(wide.retained_source(&session, 1.).unwrap(), 0..text.len());
+        assert_eq!(wide.bounds.size(), paragraph_size(text, 1., style));
+        let narrow = cache.resolve(&session, text, 80., 1., style).unwrap();
+        assert_ne!(narrow.displayed, text);
+        assert!(narrow.bounds.width <= 80.);
+        assert_eq!(narrow.bounds.size(), paragraph_size(&narrow.displayed, 1., style));
+    }
+}
+
+#[test]
+fn normalized_visible_prefix_maps_to_original_bytes_without_claiming_hidden_operation() {
+    let raw = " \t1.  call · Pump\r\n  · Operation: Need\u{301}le  ";
+    let expected = "1. call · Pump · Operation: Need\u{301}le";
+    let n = Normalized::new(raw);
+    assert_eq!(n.text, expected);
+    let prefix = "1. call · Pump ";
+    assert_eq!(n.source_end(prefix.len()), raw.find("· Operation").unwrap());
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    let wide = cache.resolve(&session, raw, 1600., 1., Style::default()).unwrap();
+    assert_eq!(wide.displayed, expected);
+    assert_eq!(wide.retained_source.end, raw.trim_end().len());
+    let field = raw.find("Need").unwrap()..raw.trim_end().len();
+    assert!(wide.retains_any(&session, 1., field.clone()).unwrap());
+    assert!(!wide.retains_any(&session, 1., 0..2).unwrap(), "normalized whitespace is not a visible field");
+    let small = cache.resolve(&session, raw, 70., 1., Style::default()).unwrap();
+    assert!(!small.retains_any(&session, 1., field).unwrap());
+    assert!(small.retained_source.end < raw.find("Operation").unwrap());
+}
+
+#[test]
+fn grapheme_prefixes_and_zoom_match_actual_paragraph_layout() {
+    let text = "call · 戻り値 圧力 e\u{301} 👩‍🔬 safety valve verification";
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    for zoom in [0.66, 1., 1.75] {
+        let label = cache.resolve(&session, text, 105., zoom, Style::default()).unwrap();
+        assert!(label.bounds.width <= 105.);
+        assert_eq!(label.bounds.size(), paragraph_size(&label.displayed, zoom, Style::default()));
+        assert!(text.grapheme_indices(true).any(|(i, _)| i == label.retained_source.end)
+            || label.retained_source.end == text.len());
+        let painted = label.canvas_text(&session, zoom, Point::new(400., 90.), Color::BLACK).unwrap();
+        assert_eq!(painted.content, label.displayed);
+        assert!(painted.max_width.is_infinite());
+        assert_eq!(label.bounds_at(&session, zoom, painted.position).unwrap().size(), label.bounds.size());
+    }
+}
+
+#[test]
+fn empty_and_too_narrow_labels_never_claim_source_visibility() {
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    for text in ["", " \t\n", "Operation: Pump"] {
+        let label = cache.resolve(&session, text, 0., 1., Style::default()).unwrap();
+        assert_eq!(label.displayed, "");
+        assert_eq!(label.retained_source, 0..0);
+        assert_eq!(label.bounds.size(), Size::ZERO);
+        assert!(!label.retains_any(&session, 1., 0..text.len()).unwrap());
+    }
+}
+
+#[test]
+fn redraws_reuse_resolution_but_width_zoom_and_style_are_dependencies() {
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    let text = "call · Pressure verification with a descriptive operation label";
+    let style = Style::default();
+    let a = cache.resolve(&session, text, 100., 1., style).unwrap();
+    let measured = cache.allocations;
+    let b = cache.resolve(&session, text, 100., 1., style).unwrap();
+    assert!(Arc::ptr_eq(&a, &b));
+    assert_eq!(cache.allocations, measured);
+    for (width, zoom, style) in [(120., 1., style), (100., 0.66, style),
+        (100., 1., Style { size: Pixels(14.), ..style })] {
+        let other = cache.resolve(&session, text, width, zoom, style).unwrap();
+        assert!(!Arc::ptr_eq(&a, &other));
+    }
+}
+
+#[test]
+fn resident_entry_is_remeasured_for_a_fresh_settled_render_session() {
+    let mut cache = Cache::default();
+    let old_session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    let text = "call · Pressure verification";
+    let a = cache.resolve(&old_session, text, 100., 1., Style::default()).unwrap();
+    assert_eq!(cache.entries.len(), 1);
+    assert!(Arc::ptr_eq(&cache.entries.front().unwrap().label, &a));
+    let measured = cache.allocations;
+    assert!(measured > 0);
+    assert!(Arc::ptr_eq(&a, &cache.resolve(&old_session, text, 100., 1., Style::default()).unwrap()));
+    assert_eq!(cache.allocations, measured);
+    // A fresh renderer session invalidates a still-resident entry. This does
+    // not mutate global fonts or purport to test dynamic WGPU font loading.
+    let new_session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    let refreshed = cache.resolve(&new_session, text, 100., 1., Style::default()).unwrap();
+    assert!(!Arc::ptr_eq(&a, &refreshed));
+    assert!(cache.allocations > measured);
+    assert_eq!(cache.entries.len(), 1);
+    assert!(Arc::ptr_eq(&cache.entries.front().unwrap().label, &refreshed));
+}
+
+#[test]
+fn resident_entry_remeasures_after_local_font_epoch_invalidation() {
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    let text = "call · Resident pressure label";
+    let a = cache.resolve(&session, text, 100., 1., Style::default()).unwrap();
+    assert_eq!(cache.entries.len(), 1);
+    assert!(Arc::ptr_eq(&cache.entries.front().unwrap().label, &a));
+    let measured = cache.allocations;
+    assert!(measured > 0);
+    // Exercise the local memo epoch branch while a is still resident. No
+    // intervening width/zoom/style resolution can cause incidental eviction.
+    // This is not an actual font-load or renderer-cache acceptance test.
+    cache.version = None;
+    let refreshed = cache.resolve(&session, text, 100., 1., Style::default()).unwrap();
+    assert!(!Arc::ptr_eq(&a, &refreshed));
+    assert!(cache.allocations > measured);
+    assert_eq!(cache.entries.len(), 1);
+    assert!(Arc::ptr_eq(&cache.entries.front().unwrap().label, &refreshed));
+}
+
+#[test]
+fn retained_artifact_rejects_other_zoom_and_render_session_for_every_consumer() {
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    let label = cache.resolve(&session, "Operation: Pressure", 200., 1., Style::default()).unwrap();
+    let other = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    for (context, zoom, expected) in [(&session, 0.66, Error::StaleZoom), (&other, 1., Error::StaleRenderSession)] {
+        assert_eq!(label.displayed(context, zoom).unwrap_err(), expected);
+        assert_eq!(label.retained_source(context, zoom).unwrap_err(), expected);
+        assert_eq!(label.retains_any(context, zoom, 0..9).unwrap_err(), expected);
+        assert_eq!(label.bounds_at(context, zoom, Point::ORIGIN).unwrap_err(), expected);
+        assert_eq!(label.canvas_text(context, zoom, Point::ORIGIN, Color::BLACK).unwrap_err(), expected);
+    }
+    assert!(label.canvas_text(&session, 1., Point::ORIGIN, Color::BLACK).is_ok());
+}
+
+#[test]
+fn finite_scaled_metrics_cannot_escape_as_infinite_world_dimensions() {
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    let style = Style { size: Pixels(2.), line_height: LineHeight::Relative(f32::MAX), ..Style::default() };
+    // At zoom 0.5 the scaled size=1 and line height=MAX are finite. The
+    // required world line height is not; reject before passing it to shaping.
+    let scaled = style.scaled(0.5);
+    assert!(scaled.0.is_finite() && scaled.1.is_finite());
+    assert_eq!(cache.resolve(&session, "call", 100., 0.5, style).unwrap_err(), Error::InvalidMetrics);
+    assert_eq!(cache.allocations, 0);
+    assert!(cache.entries.is_empty());
+    // Independently exercise validation after division for actual measured
+    // dimensions: finite scaled width/height do not imply finite world values.
+    assert_eq!(world_size(Size::new(f32::MAX, 1.), 0.5), Err(Error::InvalidMeasurement));
+    assert_eq!(world_size(Size::new(1., f32::MAX), 0.5), Err(Error::InvalidMeasurement));
+    assert_eq!(world_size(Size::new(20., 8.), 0.5).unwrap(), Size::new(40., 16.));
+}
+
+#[test]
+fn malformed_metrics_and_explicit_experiment_budgets_fail_without_a_cached_candidate() {
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    for (width, zoom) in [(f32::NAN, 1.), (-1., 1.), (100., 0.), (100., f32::INFINITY)] {
+        assert_eq!(cache.resolve(&session, "call", width, zoom, Style::default()).unwrap_err(), Error::InvalidMetrics);
+    }
+    assert_eq!(cache.resolve(&session, &"x".repeat(MAX_SOURCE_BYTES + 1), 100., 1., Style::default()).unwrap_err(), Error::SourceBudget);
+    assert_eq!(cache.resolve(&session, &"x".repeat(MAX_GRAPHEMES + 1), 100., 1., Style::default()).unwrap_err(), Error::GraphemeBudget);
+    assert!(cache.entries.is_empty());
+}
+
+#[test]
+fn bounds_translation_rejects_nonfinite_world_positions_and_endpoints() {
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    let label = cache.resolve(&session, "call", 100., 1., Style::default()).unwrap();
+    for position in [Point::new(f32::NAN, 0.), Point::new(0., f32::INFINITY)] {
+        assert_eq!(label.bounds_at(&session, 1., position).unwrap_err(), Error::InvalidPosition);
+        assert_eq!(label.canvas_text(&session, 1., position, Color::BLACK).unwrap_err(), Error::InvalidPosition);
+    }
+    assert_eq!(translated_bounds(Point::new(f32::MAX, 0.), Size::new(f32::MAX, 1.)), Err(Error::InvalidPosition));
+    assert_eq!(translated_bounds(Point::new(0., f32::MAX), Size::new(1., f32::MAX)), Err(Error::InvalidPosition));
+    assert_eq!(label.bounds_at(&session, 1., Point::new(-20., -10.)).unwrap().position(), Point::new(-20., -10.));
+}
+
+/// Must run as the ONLY selected test in a dedicated, fresh test process.
+/// The ignored marker keeps this global-font mutation out of normal parallel
+/// desktop tests. See the evidence directory's exact executable runner.
+#[test]
+#[ignore = "mutates the global font database; run only this exact test in a fresh process"]
+fn actual_font_load_rejects_retained_label_and_old_session() {
+    use std::borrow::Cow;
+    use graphics_text::cosmic_text::fontdb;
+
+    let mut cache = Cache::default();
+    let session = RenderSession::after_fonts_settled_and_renderer_reset().unwrap();
+    let source = "Operation: Pressure";
+    let label = cache.resolve(&session, source, 200., 1., Style::default()).unwrap();
+    assert_eq!(label.displayed(&session, 1.).unwrap(), source);
+    assert!(label.canvas_text(&session, 1., Point::ORIGIN, Color::BLACK).is_ok());
+    let measured = cache.allocations;
+    assert!(measured > 0);
+    assert!(Arc::ptr_eq(&cache.entries.front().unwrap().label, &label));
+
+    let (version_before, version_after, faces_before, faces_after) = {
+        let mut fonts = graphics_text::font_system().write().unwrap();
+        let face = fonts.raw().db().faces()
+            .find(|face| face.families.iter().any(|(family, _)| family == "Iced-Icons"))
+            .expect("Iced 0.14 embeds and loads its known Iced-Icons.ttf face").id;
+        let bytes = fonts.raw().db().with_face_data(face, |data, _| data.to_vec())
+            .expect("the built-in binary font has accessible bytes");
+        assert!(!bytes.is_empty());
+        // load_font increments Version even for invalid bytes. Independently
+        // establish actual face admission so this cannot pass with invalid data.
+        let mut probe = fontdb::Database::new();
+        probe.load_font_data(bytes.clone());
+        let admitted = probe.faces().filter(|face|
+            face.families.iter().any(|(family, _)| family == "Iced-Icons")).count();
+        assert!(admitted > 0, "the extracted bytes parse as the expected real font");
+        let before = fonts.version();
+        assert_eq!(before, session.version);
+        let count = fonts.raw().db().faces().count();
+        // Owned bytes intentionally bypass Borrowed-address deduplication.
+        // This is an actual valid duplicate-face load, not a claim the chosen
+        // face or rendered metrics change; the stale-epoch rule is the oracle.
+        fonts.load_font(Cow::Owned(bytes));
+        (before, fonts.version(), count, fonts.raw().db().faces().count())
+    };
+    assert_ne!(version_before, version_after);
+    assert!(faces_after > faces_before, "actual font admission must accompany the version increment");
+    assert_eq!(label.displayed(&session, 1.).unwrap_err(), Error::FontSetChanged);
+    assert_eq!(label.retained_source(&session, 1.).unwrap_err(), Error::FontSetChanged);
+    assert_eq!(label.retains_any(&session, 1., 0..9).unwrap_err(), Error::FontSetChanged);
+    assert_eq!(label.bounds_at(&session, 1., Point::ORIGIN).unwrap_err(), Error::FontSetChanged);
+    assert_eq!(label.canvas_text(&session, 1., Point::ORIGIN, Color::BLACK).unwrap_err(), Error::FontSetChanged);
+    assert_eq!(cache.resolve(&session, source, 200., 1., Style::default()).unwrap_err(), Error::FontSetChanged);
+    assert_eq!(cache.allocations, measured, "an invalid session must not remeasure and imply renderer repair");
+    println!("Valid Iced-Icons load: faces {faces_before}->{faces_after}, font Version {version_before:?}->{version_after:?}; old label and session rejected");
+    // Do not create a fresh session or claim dynamic WGPU cache recovery here.
+    // Process exit is the isolation boundary; no other test may run afterward.
+}
diff --git a/harness/experiments/scenario-label-measurement-20260913/run-font-version-test.ps1 b/harness/experiments/scenario-label-measurement-20260913/run-font-version-test.ps1
new file mode 100644
index 00000000..ac007fb3
--- /dev/null
+++ b/harness/experiments/scenario-label-measurement-20260913/run-font-version-test.ps1
@@ -0,0 +1,50 @@
+# Runs an ALREADY BUILT desktop test executable. This script never invokes Cargo.
+# Supply the matching runtime DLL environment prepared by the compiler owner.
+[CmdletBinding()]
+param(
+    [Parameter(Mandatory=$true)][string]$TestExecutable,
+    [Parameter(Mandatory=$true)][ValidatePattern('^[0-9a-fA-F]{64}$')][string]$ExpectedSha256,
+    [Parameter(Mandatory=$true)][string]$RunDirectory,
+    [ValidateSet('behavior::scenario_label::tests::actual_font_load_rejects_retained_label_and_old_session', 'scenario_label::tests::actual_font_load_rejects_retained_label_and_old_session')]
+    [string]$TestName = 'behavior::scenario_label::tests::actual_font_load_rejects_retained_label_and_old_session'
+)
+$ErrorActionPreference = 'Stop'
+$fontTestName = $TestName
+$fontTestExe = (Resolve-Path -LiteralPath $TestExecutable).Path
+$fontTestHash = (Get-FileHash -LiteralPath $fontTestExe -Algorithm SHA256).Hash
+if ($fontTestHash -ne $ExpectedSha256) { throw 'Test executable SHA256 differs from the supplied compiler receipt' }
+if (Test-Path -LiteralPath $RunDirectory) { throw 'Use a fresh evidence directory; refusing to overwrite a previous run' }
+$fontTestOutput = (New-Item -ItemType Directory -Path $RunDirectory).FullName
+
+# Listing is a separate process and runs no test. Refuse zero/multiple matches
+# before launching the one process that will mutate global font state.
+$fontTestList = & $fontTestExe --list --ignored --exact $fontTestName 2>&1
+$fontTestListExit = $LASTEXITCODE
+$fontTestListText = $fontTestList | Out-String
+$fontTestListText | Set-Content -LiteralPath (Join-Path $fontTestOutput 'selection.log') -Encoding utf8
+$fontTestSelected = $fontTestListExit -eq 0 -and
+    $fontTestListText -match ('(?m)^' + [regex]::Escape($fontTestName) + ': test\s*$') -and
+    $fontTestListText -match '(?m)^1 test, 0 benchmarks\s*$'
+if (-not $fontTestSelected) { throw 'The exact ignored-test selection did not list exactly one test; inspect selection.log' }
+
+# Fresh dedicated executable invocation; no normal/other ignored test is chosen.
+$fontTestStarted = (Get-Date).ToUniversalTime().ToString('o')
+$fontTestRun = & $fontTestExe --ignored --exact $fontTestName --nocapture --test-threads=1 2>&1
+$fontTestExit = $LASTEXITCODE
+$fontTestRunText = $fontTestRun | Out-String
+$fontTestRunText | Set-Content -LiteralPath (Join-Path $fontTestOutput 'test.log') -Encoding utf8
+$fontTestPassed = $fontTestExit -eq 0 -and
+    $fontTestRunText -match 'test result: ok\. 1 passed; 0 failed; 0 ignored;'
+@{
+    test = $fontTestName
+    executable = $fontTestExe
+    sha256 = $fontTestHash
+    exactSelection = $fontTestSelected
+    startedUtc = $fontTestStarted
+    finishedUtc = (Get-Date).ToUniversalTime().ToString('o')
+    exitCode = $fontTestExit
+    passedExactlyOne = $fontTestPassed
+    scope = 'Actual global font Version invalidation and artifact rejection; no WGPU dynamic cache recovery claim'
+} | ConvertTo-Json | Set-Content -LiteralPath (Join-Path $fontTestOutput 'receipt.json') -Encoding utf8
+Write-Output $fontTestRunText
+if (-not $fontTestPassed) { throw 'Isolated font-version test did not pass exactly one test; inspect test.log and receipt.json' }
diff --git a/harness/experiments/scenario-label-measurement-20260913/standalone.rs b/harness/experiments/scenario-label-measurement-20260913/standalone.rs
new file mode 100644
index 00000000..e85f123d
--- /dev/null
+++ b/harness/experiments/scenario-label-measurement-20260913/standalone.rs
@@ -0,0 +1,5 @@
+//! Isolated evaluator only: does not wire the desktop renderer.
+#[path = "../../../crates/oa-desktop/src/behavior/scenario_label.rs"]
+mod scenario_label;
+#[path = "../../../crates/oa-desktop/src/behavior/scenario_label/corridor.rs"]
+mod scenario_label_corridor;