Requirement
Every product in the portfolio speaks with one shared voice character — the DX voice: plain, second person, active, kind. Products differ only in weight, not in system. Copy on a product's surface carries that product's calibrated register; it must not adopt another product's register (celebratory warmth on a sensitive casework screen, or casework reserve on an encouraging moment). This is the verbal twin of COL-1's per-product colour rule.
Per-product tone register
Each product declares its tone register in its own DESIGN.md: the register and how it
calibrates the shared voice. For example:
| Surface | Register | Calibration |
|---|---|---|
| A daily-use workspace | Calm daily command centre | Neutral, steady, quietly confident |
| A sensitive casework product | Higher gravity | More reserved, restrained celebration, privacy-forward |
| An encouragement product | Lighter, encouraging | Warmer accents, more celebratory moments |
A product may declare surfaces it hosts that carry its register with no nuance of their own.
Rationale
Voice is identity. People recognise a product partly by how it talks to them; a page that switches register reads as if a different team wrote it, and on a sensitive casework screen a bubbly register is not just off-brand but tonally wrong. The shared character keeps the portfolio coherent; the calibrated weight keeps each product itself. This is not CNT-2/CNT-3 (plain-language naming, lead-with-purpose) — those are the voice mechanics, the same everywhere; this is the per-product weighting of that one voice.
How to verify
Judgment. The evaluator reads the surface's copy against the register the product
declares in its DESIGN.md. Does it hold the shared character at that product's weight,
or has it switched systems? The failure is a switched register, not a shared voice —
flag encouragement-style celebration on a sensitive casework surface, casework-style
reserve on an encouraging moment, or product nuance on a hosted surface the host declares
as carrying its own voice.
Evaluator guidance
Flag: copy that adopts another product's register (a switched voice system); a declared hosted surface carrying its own nuance instead of the host's voice.
Do not flag: a product using the shared voice character (that is correct, not a
finding); calibrated weight within the shared system; a deliberate, reasoned deviation
carrying an inline dx-waive IDN-3 reason="…" (L2).
Deconfliction. COL-1 is the per-product colour register; this is the per-product tone register — orthogonal (a surface can pass one and fail the other). CNT-2/CNT-3 are portfolio-wide voice mechanics this control depends on, not restates. IDN-4 hardens the sensitivity of casework surfaces into a concrete prohibition on gamified/celebratory elements (not just copy) — this control covers the words, IDN-4 covers the interface treatment.