Every chart in a generated PDF follows the same rules for axis labelling, units, legends, and colour meaning. Reviewers should never have to ask “what does the green bar mean here?” The contract is centralised in src/lib/biosync/pdf-charts.ts — this page documents it.
yLabel ─┐ ← top-left, horizontal
£ per year
┃ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ← gridlines (hair, dashed)
┃ ┃ ┃ ┃
┃ ┃ ┃ +£24k ┃ ← inline value labels (fmtCurrency)
┃ ▓▓ ▓▓ ▓▓
┃ ▓▓ ▓▓ ▓▓
└────┴───────────┴───────────┴───
Stormwater Thermal Carbon
PES stream ← xLabel (centred under axis)
▇ Stream contribution ▇ Engine total ← legend strip, bottom-leftreact-pdf renders).fmtNumber, applied everywhere.Every axis tick, legend value, and inline label routes through fmtNumber (or its currency-aware companion fmtCurrency). Domain-specific formatters — years, NDVI, °C — are the only allowed overrides.
| Rule | Renders as |
|---|---|
| |v| ≥ 1B | 1.2B |
| |v| ≥ 1M | 1.2M |
| |v| ≥ 10k | 27k |
| |v| ≥ 1k | 1.2k |
| |v| ≥ 1 | 1,234 (en-US separator) |
| |v| < 1 | 0.42 (2 dp, trimmed) |
| Currency | £412k via fmtCurrency(cur, v) |
| NaN / Infinity | — (em dash) |
A reader should never need a legend to know the difference between a contribution and a total, or an upside and a downside. The palette below is the only one allowed inside a chart plot area.
| Token | Role |
|---|---|
| brand · Pulse green #22c55e | Primary series, positive deltas, contribution bars, projected trajectories. The 'good news' colour. |
| negative · Red #ef4444 | Downside bound in tornadoes, negative deltas, risk-flagged findings. Never used for primary series. |
| ink · Slate-900 #0f172a | Totals, engine outputs, KPI numerals. Signals 'this is the headline value, not a contribution'. |
| muted · Slate-500 #64748b | Axis tick labels, legend captions, secondary text. Never used for data marks. |
| subtle · Slate-400 #94a3b8 | Axis frame lines. Lighter than muted to recede behind the data. |
| hair · Slate-200 #e2e8f0 | Gridlines (always dashed, 0.3pt). Sets the rhythm without competing with marks. |
| surface · Slate-50 #f8fafc | Optional plot background. Used inside KPI tiles, never inside the plot area of a data chart. |
If you're adding a chart to a report section, copy the matching row. If a chart you're building doesn't fit any of these, surface it for review before shipping — divergence is the bug.
Single-category magnitude comparison (e.g. AAL avoided per peril, social value by MAC theme).
Decomposing a total into additive streams (e.g. PES avoided cost: Stormwater + Thermal + Social + Carbon → Total).
Two-sided sensitivity (NPV swing per driver, downside vs upside).
Time-series trajectories (NDVI 8-yr projection, AAL reduction across horizons).
Share-of-total composition (rare — prefer Waterfall for additive splits).
Multi-dimension scoring (Nature Value Scorecard — 1–5 across 5 dimensions).
Distribution of a single quantity (Monte Carlo NPV bins).
Two-variable relationship (cost vs benefit per intervention).
Two-bar pre/post comparison (stormwater runoff before vs after, UTCI before vs after).
Composition of a single total (cashable vs non-cashable value).
Two-axis density (peril × horizon, intervention × month).
src/lib/biosync/pdf-charts.ts — chart primitives + fmtNumber / fmtCurrency. Change a default here and every chart in every dossier updates.src/lib/biosync/pdf.ts — per-section bindings (which data drives which chart). Domain-specific formatters live alongside their chart call.CI gate: bun scripts/render-canonical.ts renders the canonical fixture end-to-end and fails if any optional section silently drops. Run it after touching either file.