完成阶段 4

openspec/specs/kcp-transport/spec.md

@@ -1,4 +1,4 @@
-# kcp-transport Specification
+# kcp-transport Specification
 
 ## Purpose
 TBD - created by archiving change introduce-kcp-transport. Update Purpose after archive.
@@ -46,4 +46,18 @@ The transport SHALL continue driving KCP timers for every active session while i
 - **WHEN** the application calls `Stop()` on a running transport
 - **THEN** the transport stops receiving new UDP datagrams
 - **THEN** the transport clears its active KCP session state before shutdown completes
+### Requirement: KCP is the sole reliable transport implementation
+The project SHALL expose `KcpTransport` as the only reliable `ITransport` implementation used by runtime networking paths. Reliable business messages, including login, heartbeat, player input, and player state synchronization, MUST continue to flow through KCP-backed sessions rather than any legacy reliable UDP compatibility class.
 
+#### Scenario: Runtime networking uses KCP for reliable delivery
+- **WHEN** the application constructs the transport used by `MessageManager` for its normal runtime networking path
+- **THEN** that transport instance is `KcpTransport`
+- **THEN** reliable business payloads are sent and received through KCP session state
+
+### Requirement: Legacy reliable UDP entry points are retired
+The codebase SHALL NOT keep a directly instantiable `ReliableUdpTransport` entry point that implies a second reliable delivery mechanism. If a non-reliable UDP transport is needed in the future, it MUST use a distinct name and MUST NOT claim reliable semantics.
+
+#### Scenario: Legacy reliable transport is not available to callers
+- **WHEN** developers inspect the transport implementations available to runtime code
+- **THEN** they do not find a usable `ReliableUdpTransport` class representing reliable delivery
+- **THEN** the remaining transport naming makes the reliable-versus-unreliable boundary explicit