0008. Data-loading orchestration is outside the renderer freeze

• Status: Accepted
• Date: 2026-10-09
• Deciders: tseka
• Amends: ADR 0005

Context

ADR 0005 froze packages/core/src/engine/** to protect rendering. History loading also lives under engine/data/ (chartDataManager.ts, scrollCompensator.ts, incrementalLoadHint.ts). It currently produces a visible defect:

• one 500-bar first page that does not fill the viewport;
• empty slots right-aligned and labelled T-N;
• gap pages loaded one at a time, each with its own flash.

That is loading orchestration, not drawing.

Decision

These may change, with tests:

• engine/data/** loading policy: first-request size, alignment of short data, gap prefetch and batching, load hints.
• data/** (provider, buffer, live).
• The decision of whether the time axis shows placeholder past-slot labels.

These stay frozen:

• engine/renderers/** drawing code
• engine/scale/**
• controllers/**
• foundation/tokens/fonts.ts

Consequences

• Loading fixes ship as normal PRs with unit tests on the orchestration.
• Any change to how bars are drawn still needs its own ADR.