# gRPC advanced capability support matrix

Every capability in `:grpc-advanced:*`, its grade, and what it would take to raise it.
`GrpcAdvancedSupportMatrix` is the machine-readable form; `GrpcAdvancedCapability.defaultGrade`
carries the same values.

All capabilities are off by default. Flags are `ca-skeleton.grpc.advanced.<capability>.enabled`.

## Grades

| Grade | May start | Production needs a separate approval |
| --- | --- | --- |
| `ADVANCED_STABLE` | Yes | No |
| `EXPERIMENTAL` | Yes | Yes |
| `WATCH` | No | — |
| `DISABLED` | No | — |

## Capabilities

| Capability | Flag | Grade | Real infrastructure its evidence needs |
| --- | --- | --- | --- |
| Protobuf Edition 2024 | `edition-2024` | `ADVANCED_STABLE` | — |
| Protobuf Edition 2026 | `edition-2026` | `WATCH` | — |
| Client streaming | `client-streaming` | `ADVANCED_STABLE` | — |
| Bidirectional streaming | `bidi-streaming` | `ADVANCED_STABLE` | — |
| Manual flow control | `manual-flow-control` | `ADVANCED_STABLE` | — |
| Read-only unary hedging | `hedging` | `EXPERIMENTAL` | — |
| Custom name resolver | `custom-resolver` | `ADVANCED_STABLE` | — |
| Custom load balancer | `custom-load-balancer` | `EXPERIMENTAL` | — |
| Proxyless xDS | `xds` | `EXPERIMENTAL` | xDS control plane |
| gRPC-Web | `grpc-web` | `ADVANCED_STABLE` | gRPC-Web proxy |
| Servlet HTTP/2 | `servlet-compat` | `ADVANCED_STABLE` | Servlet container |
| Spring Integration bridge | `integration-bridge` | `ADVANCED_STABLE` | — |
| Reactor adapter | `reactor` | `ADVANCED_STABLE` | — |
| Kotlin coroutine / Flow | `kotlin` | `ADVANCED_STABLE` | Kotlin toolchain |
| Channelz / CSDS diagnostics | `channel-diagnostics` | `ADVANCED_STABLE` | — |

## What the grades mean here, concretely

**Grade is a statement about the contract, not about a deployment.** Every capability's contract is
implemented and tested in this repository. What no capability has is evidence from a real deployment:
`GrpcAdvancedPromotionEvidence` for each one is empty, and no promotion has been granted.

**Four capabilities cannot produce meaningful evidence here at all**, because the infrastructure they
need is absent. `GrpcAdvancedInfrastructureTestkit.missingInfrastructure` names them, and a suite that
runs without its infrastructure passes and establishes nothing.

**Kotlin is the sharpest case.** This repository has no Kotlin toolchain, so
`GrpcKotlinCompatibilityGate.supportableHere()` returns false and always will until one exists. The
four contract requirements — one schema source shared with Java, coroutine cancellation propagated,
Flow backpressure inside the Stable buffer bounds, platform evidence types preserved — are checkable
without a toolchain and are checked. The compile lane is not.

## Promotion thresholds

| To | Soak | Also required |
| --- | --- | --- |
| `ADVANCED_STABLE` | 7 days | compatibility evidence, security review, fault evidence, performance evidence, ADR, runbook, real-environment test |
| Stable default | 30 days | all of the above, plus a dependency, security and operational-cost review |

`WATCH` becomes `EXPERIMENTAL` before anything else. Promotions are independent: promoting one
capability changes no other's grade.