Behavior Changes

server: Remove support for GRPC_GO_EXPERIMENTAL_DISABLE_STRICT_PATH_CHECKING environment varibale. Strict incoming RPC path validation (which has been the default since v1.79.3) can no longer be disabled. (#9112)
transport: Add environment variable to change the default max header list size from 16MB to 8KB. This may be enabled by setting GRPC_GO_EXPERIMENTAL_ENABLE_8KB_DEFAULT_HEADER_LIST_SIZE=true. This will be enabled by default in a subsequent release. (#9019)
balancer: Load Balancing policy registry is now case-sensitive. Set GRPC_GO_EXPERIMENTAL_CASE_SENSITIVE_BALANCER_REGISTRIES=false (and file an issue) to revert to case-insensitive behavior. (#9017)

New Features

experimental/stats: Expose a new API, NewContextWithLabelCallback, to register a callback that is invoked when telemetry labels are added. (#8877)
- Special Thanks: @seth-epps
client: Return a portion of the response body in the error message, when the client receives an unexpected non-gRPC HTTP response, to make debugging easier. (#8929)
- Special Thanks: @chengxilo
server: Add environment variable GRPC_GO_SERVER_GOROUTINE_LABELS that controls setting runtime/pprof.Labels on goroutines spawned by the server. Set GRPC_GO_SERVER_GOROUTINE_LABELS=grpc.method=true to add the grpc.method label on goroutines spawned to handle incoming requests. (#9082)
- Special Thanks: @dfinkel

xds/server: Fix a memory leak of HTTP filter instances occurring when route configurations are updated in-place during a Route Discovery Service (RDS) update. (#9138)
grpc: In the deprecated gzip Compressor (used via the deprecated WithCompressor dial option), enforce the MaxRecvMsgSize limit on the decompressed message buffer, preventing excessive memory allocation from highly compressed payloads. (#9114)
- Special Thanks: @evilgensec
stats/opentelemetry: Record retry attempts, grpc.previous-rpc-attempts, at the call level and not the attempt level. (#8923)
encoding: Ensure Close() is always called on readers returned from Compressor.Decompress if possible. (#9135)
channelz: Fix the LastMessageSentTimestamp and LastMessageReceivedTimestamp fields in SocketMetrics to ensure they contain correct timestamp values. (#9109)