ARCADIA-Studio/harness/experiments/label-cue-20261001/change-summary.md

Label association cue candidate B: source handoff

Implemented only in the isolated codex/label-cue-experiment-01a0d717-20261001 worktree from 6ea7518e. No compilation, GUI operation, Gitea mutation, commit, or production acceptance is claimed. Intent was recorded before source edits in label-cue-experiment-intent.md.

Changes

• New private diagram/label_cues.rs derives an edge-ID-to-cue map. For nonempty ordinary labels, it clamps the anchor to the label rectangle to obtain the nearest boundary point. Gap must be strictly greater than 12 world units. Anchor inside/on the box and normal six-unit gaps produce no cue.
• A cue is omitted if its anchor is within 7 world units of any distinct edge's segment, if its closed segment intersects any distinct route, any visible card rectangle, or another ordinary/association-end label rectangle. Touching is rejected. This includes container rectangles: conservative omission is intended.
• Two production Scene constructors cache cues with their already-routed scene, using the preview Project where appropriate. Existing cache reuse handles ordinary selection, hover, zoom and pan without recomputation. Route/placement previews and revisions that build new scenes recompute the map.
• Canvas draws one-world-unit neutral dotted lines (2 on / 3 off) behind the owning label's backing. SVG computes the same geometry once per export and uses matching color, width and dash spacing, with pointer-events="none". There is no marker, arrowhead, endpoint dot, semantic hit region or stored metadata. Existing SVG content is retained; the cue is the only intended export addition.
• One existing attachment-test Scene literal received an empty cue map; that test exercises attachment handles, not label decoration. No unrelated refactor.

Four focused tests are prepared (not run by this agent):

1. Complete representative model admits without errors, retains twelve edges, derives conversation boundary (1180,274.5) to anchor (1162,274.5), emits an arrowless SVG cue, and preserves Project and complete routed geometry.
2. A long normal-offset label with only six units of boundary clearance is skipped; exact 12-unit gap is skipped and 12.25 admitted; a genuinely authored label centered on its anchor is skipped and stays exact.
3. Shared and six-unit-near landings, intersecting foreign route, card and label controls suppress the cue. Additional nonintersecting segments six and exactly seven units LEFT of the anchor are rejected; eight units left is admitted, isolating the clearance guard from the crossing guard.
4. Actual Scene cache identity and cue map remain identical after selection, pointer, zoom and pan changes. A changed Project with an authored label centered on its anchor plus incremented context revision creates a new Scene and removes the obsolete cue, independently checking invalidation as well as cache reuse.

Parent reproduction selector:

cargo test --locked -p oa-desktop diagram::label_cues -- --test-threads=1

Parent should format, compile, run appropriate affected diagram/SVG gates and independently review before native comparison. All changes remain uncommitted.

Limits and explicit tradeoffs

The cue does not fix the foreign Allocation stroke already running through the conversation label. It may be too weak at Fit; this is the central native falsifier. No claim of improved unselected reading follows from source/geometry tests. Closed rectangle and segment guards use projected geometry, not exact text glyph or port-symbol contours. Authored label locations are never moved; a blocked cue is simply omitted. The tests use the established representative scene, not the user's exact source. There are no camera-dependent admission thresholds, so zoom does not introduce cue admission flicker; physical dot size still scales normally.

Rebuild cost scans scene routes/cards/labels for each eligible label. No global optimizer, new index, arbitrary cutoff, or per-hover scan was introduced. Dense rebuild and route-preview latency remain parent performance gates. Individual cue guards do not perform cue-to-cue avoidance; multiple eligible leaders can intersect each other in other scenes. This is an explicit experimental limitation to inspect before widening scope or making a general rendering claim.

The intended native comparison preserves the complete model, paths, labels and camera: baseline versus B, plus the saved manual-label control. Fresh reading must precede Inspector answers, and distinguish correct first association from mere selectability. Revisit or reject B if wrong association persists, added marks are mistaken for relationships, other reading worsens, or rendering/preview cost regresses. Selection disambiguation and automatic-placement A remain separate.