Architecture Decision Records

Every significant design decision, with context and rationale. Read these to understand why things are the way they are.

#	Decision	Status	Summary
001	Sidecar, not central gateway	Accepted	Enforcement at the agent, not a chokepoint. Complements APIM.
002	SPIFFE/SPIRE, not custom mTLS	Accepted	Open standard, auto-rotating certs, multi-cloud portable.
003	Join token attestation	Accepted (workaround)	azure_msi incompatible with Container Apps. Production needs upstream fix.
004	Transparent proxy, not SDK	Accepted	Zero code changes to agents. Works with any language.
005	SPIRE, not Istio	Accepted	Container Apps can't run Istio. Both speak SPIFFE — they interoperate.
006	Budget Backend scenario	Accepted	Business-relevant naming for the authorization demo.
007	Container Apps, not AKS	Accepted	Matches actual agent hosting. Proves the hard case (no K8s, no IMDS).
008	OPA complementary, not core	Accepted	OPA is cluster hardening. SPIRE + Dunloe is runtime east-west.
009	Remove Azure AI Foundry	Accepted	Zero enforcement value. All security layers work through SPIFFE + Entra. -597 lines.
010	Conditional Access as admin governance	Accepted	Fourth enforcement layer. Admin-defined policy via CA supersedes developer-defined RBAC. Regulatory non-negotiable.

How to Add a New ADR

1. Create docs/decisions/NNN-short-descriptive-name.md
2. Use the template: Status, Date, Deciders, Context, Decision, Rationale, Consequences, Alternatives Considered, Related
3. Add to this index
4. Reference from CLAUDE.md root if it affects always-on context