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+<!-- m-wiki: type=concept slug=adr-index topic=adr base-sha=d6708eca4236 generated-at=2026-05-12T12:00:00+00:00 sources=[docs/adr/README.md, docs/adr/0001-single-shared-library-for-all-services.md, docs/adr/0002-branch-name-as-sole-environment-selector.md, docs/adr/0003-policy-exceptions-in-separate-whitelist-repo.md, docs/adr/0004-fresh-whitelist-clone-per-build.md, docs/adr/0005-config-only-change-detection-skip-build.md, docs/adr/0006-ringmaster-mandatory-build-trigger-gate.md, docs/adr/0007-gitops-via-argocd-4-step-sync-sequence.md, docs/adr/0008-canary-mandatory-for-tier1-services-in-prd.md, docs/adr/0009-jvm-heap-auto-derived-from-pod-memory-request.md] -->
+
+> Generated 2026-05-12 at base-sha d6708eca4236. Type: concept. 10 sources.
+
+# Architecture Decision Records — Index
+
+devops-lib's ADRs capture the "why" behind the library's design — the decisions that would otherwise be tribal knowledge. All 9 ADRs were retroactively documented on 2026-05-12 from codebase analysis and developer interviews. All are **Status: Accepted** and assessed as still appropriate.
+
+## Why ADRs matter here
+
+devops-lib has several decisions whose rationale is non-obvious: why does the whitelist get re-cloned on every build (not cached)? Why is the 4-step ArgoCD sequence non-interchangeable? Why must all builds go through Ringmaster? Without ADRs, engineers modifying the library break load-bearing constraints without realising it.
+
+## Decision inventory
+
+| # | Decision | Category | Key insight |
+|---|----------|----------|-------------|
+| [ADR-0001](../../../adr/0001-single-shared-library-for-all-services.md) | Single shared library for all services | PATTERN | Policy enforcement must be uniform; per-team Jenkinsfiles produce drift |
+| [ADR-0002](../../../adr/0002-branch-name-as-sole-environment-selector.md) | Branch name as sole environment selector | PATTERN | Branch IS the environment contract; per-service env config creates misconfiguration risk |
+| [ADR-0003](../../../adr/0003-policy-exceptions-in-separate-whitelist-repo.md) | Policy exceptions in Meesho/whitelists repo | PATTERN | Service teams cannot self-grant bypasses; all exceptions require DevOps review |
+| [ADR-0004](../../../adr/0004-fresh-whitelist-clone-per-build.md) | Fresh whitelist clone per build | PATTERN | Policy changes must take effect on the very next build without a library release |
+| [ADR-0005](../../../adr/0005-config-only-change-detection-skip-build.md) | Config-only change detection — skip build | PATTERN | No source change → no new binary; reuse the latest image tag from GAR |
+| [ADR-0006](../../../adr/0006-ringmaster-mandatory-build-trigger-gate.md) | Ringmaster mandatory trigger gate | PATTERN | Every deployment must be tracked; direct Jenkins triggers bypass Ringmaster's ledger |
+| [ADR-0007](../../../adr/0007-gitops-via-argocd-4-step-sync-sequence.md) | GitOps via 4-step ArgoCD sync sequence | INFRA | Steps 2 and 4 are non-interchangeable; swapping them causes silent sync failures |
+| [ADR-0008](../../../adr/0008-canary-mandatory-for-tier1-services-in-prd.md) | Canary mandatory for Tier-1 (sp0/up0) in prd | RELIABILITY | Incident-driven: non-canary prd deploys for critical services caused outages |
+| [ADR-0009](../../../adr/0009-jvm-heap-auto-derived-from-pod-memory-request.md) | JVM heap auto-derived from pod memory_request | RELIABILITY | OOM incident remediation: auto-calc prevents under-sizing; `jvm_memory_override: true` escapes it |
+
+## Decisions that are load-bearing constraints
+
+These three decisions have "never change without understanding this" consequences:
+
+**ADR-0004 (fresh whitelist clone)** — `getWhitelistedRepos` in `src/com/meesho/utilities/constructParam.groovy:getWhitelistedRepos` re-clones `Meesho/whitelists` on every call by design. Never add a cache — it would prevent immediate policy enforcement.
+
+**ADR-0006 (Ringmaster gate)** — The string `"ringmaster-bot"` at `vars/eksCICD.groovy:call` is the sole routing signal between Ringmaster and Turbo-Turtle callbacks. Never rename it without coordinating with both teams.
+
+**ADR-0007 (4-step ArgoCD sequence)** — Steps 2 (`refresh_app_of_apps`) and 4 (`refresh_and_sync`) in `src/com/meesho/stages/deployArgoCD.groovy:run` are non-interchangeable. For a first-deploy, step 2 must create the Application object before step 4 can sync it.
+
+## When to read which ADR
+
+- **Debugging a build not triggering**: ADR-0006 (Ringmaster gate)
+- **Debugging a deploy that failed on ArgoCD sync**: ADR-0007 (4-step sequence)
+- **Understanding why policy changes take effect immediately**: ADR-0004 (fresh clone)
+- **Service team asking for a sonar bypass**: ADR-0003 (whitelist repo)
+- **Canary enforcement failing for a prd deploy**: ADR-0008
+- **OOM in a Java service pod**: ADR-0009
+
+## Related concepts
+
+- [Whitelist system](../policy/whitelist-system.md) — runtime whitelist enforcement (ADR-0003, ADR-0004)
+- [ArgoCD sync](../deploy/argocd-sync.md) — step-by-step walkthrough (ADR-0007)
+- [Ringmaster integration](../deploy/ringmaster-integration.md) — callback flow (ADR-0006)
+- [Environment mapping](../05-ENVIRONMENT-MAPPING.md) — branch → environment (ADR-0002)
+
+## Notes
+
+<!-- Anything below is human-owned. wiki-init never reads or modifies content under this heading. -->