Security Architecture — Restoration Decision

Historical decision; superseded by the worked example at docs/helix/02-design/security-architecture.md.

security-architecture is restored as the canonical design-activity artifact for trust boundaries, controls, and design-level security decisions.

Decision

This artifact is restored rather than retired. Security requirements and the threat model define the problem, but they do not replace the architectural control surface that shapes implementation and testing.

Why It Exists

Security requirements say what must be protected.
The threat model identifies what can go wrong.
Security architecture decides how the system will prevent, detect, and recover from those threats.

Canonical Inputs

docs/helix/01-frame/security-requirements.md
docs/helix/01-frame/threat-model.md
docs/helix/02-design/architecture.md

Minimum Prompt Bar

Start from security requirements and the threat model.
Define trust boundaries and control points.
Map threats to controls and controls to tests.
Make identity, access, data protection, logging, and monitoring decisions explicit.
Stay at the design level and do not drift into implementation code.

Minimum Template Bar

scope and decision summary
trust boundaries
control mapping
identity and access
data protection
logging and monitoring
residual risk
test hooks or verification notes

Canonical Replacement Status

security-architecture is not replaced by architecture or threat-model. Those artifacts are upstream inputs. The security architecture remains the place where the design-level security decisions are made concrete.

The deleted data-protection artifact stays retired as a standalone design document. Its intent is already covered more cleanly by:

docs/helix/02-design/security-architecture.md for design-level data protection controls, trust boundaries, encryption decisions, and monitoring
docs/helix/01-frame/compliance-requirements.md for privacy, retention, and regulatory obligations
docs/helix/02-design/data-design.md for schema, lifecycle, and storage consequences

Reintroducing data-protection as its own artifact would recreate the thin stub that duplicated these responsibilities without a distinct review bar.