transport: split into client/ and server/ subdirectories

Move client-only and server-only transport files into dedicated
subdirectories to make navigability clearer for people finding
their way around the codebase. Split types.ts into shared (root),
client/types.ts, and server/types.ts. Mirror the same structure
in test/core/transport/.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: lawrence-forooghian

.claude/rules/ABSTRACTIONS.md

@@ -6,7 +6,9 @@
 src/
 ├── core/               # Core SDK — no model/agent library/framework -specific dependencies
 │   ├── codec/          # Core codec definitions
-│   └── transport/      # Core transport definitions
+│   └── transport/      # Shared transport types and headers
+│       ├── client/     # Client transport, conversation tree, stream router, history
+│       └── server/     # Server transport, turn manager, pipe stream
 ├── react/              # React bindings
 │   ├── hooks/          # React hooks - one file per hook
 │   │   └── internal/   # Shared hook helpers (not exported)

README.md

@@ -410,7 +410,9 @@ npm run precommit         # format:check + lint + typecheck
 src/
 ├── core/               # Generic transport and codec (no framework deps)
 │   ├── codec/          # Codec interfaces and core encoder/decoder
-│   └── transport/      # ClientTransport, ServerTransport, ConversationTree
+│   └── transport/      # Shared types and headers
+│       ├── client/     # ClientTransport, ConversationTree, StreamRouter, decodeHistory
+│       └── server/     # ServerTransport, TurnManager, pipeStream
 ├── react/              # React hooks for any codec
 ├── vercel/             # Vercel AI SDK codec and transport adapters
 │   ├── codec/          # UIMessageCodec

docs/internals/client-transport.md

@@ -1,6 +1,6 @@
 # Client transport
 
-The client transport (`src/core/transport/client-transport.ts`) manages the full client-side conversation lifecycle over a single Ably channel. It composes a [stream router](transport-components.md#streamrouter), [conversation tree](conversation-tree.md), and codec [decoder](decoder.md)/[accumulator](codec-interface.md#accumulator) to handle sending messages, receiving streamed responses, managing conversation state, and supporting branching operations (edit, regenerate).
+The client transport (`src/core/transport/client/client-transport.ts`) manages the full client-side conversation lifecycle over a single Ably channel. It composes a [stream router](transport-components.md#streamrouter), [conversation tree](conversation-tree.md), and codec [decoder](decoder.md)/[accumulator](codec-interface.md#accumulator) to handle sending messages, receiving streamed responses, managing conversation state, and supporting branching operations (edit, regenerate).
 
 The client never publishes domain messages directly to the channel. Instead, it sends them to the server via HTTP POST. The server publishes user messages and [turn lifecycle events](wire-protocol.md#lifecycle-events) on behalf of the client. The channel subscription is the sole source of truth for conversation state.
 

docs/internals/conversation-tree.md

@@ -1,6 +1,6 @@
 # Conversation tree
 
-The conversation tree (`src/core/transport/conversation-tree.ts`) materializes a branching conversation from a flat stream of Ably messages. It handles message ordering, sibling grouping for edit/regenerate forks, and branch selection - producing a linear message list via `flatten()` that represents the currently selected conversation path.
+The conversation tree (`src/core/transport/client/conversation-tree.ts`) materializes a branching conversation from a flat stream of Ably messages. It handles message ordering, sibling grouping for edit/regenerate forks, and branch selection - producing a linear message list via `flatten()` that represents the currently selected conversation path.
 
 The tree is the single source of truth for conversation state. The transport's `getMessages()` delegates directly to `tree.flatten()`.
 

docs/internals/glossary.md

@@ -45,7 +45,7 @@ Every Ably message has an `extras` field that can carry metadata. The AI Transpo
 
 The SDK has two layers with a strict boundary:
 
-- **Transport layer** - generic machinery shared by all codecs. Handles turn lifecycle, stream routing, optimistic reconciliation, cancel signals, and conversation tree management. Uses `x-ably-*` headers. Lives in `src/core/transport/`.
+- **Transport layer** - generic machinery shared by all codecs. Handles turn lifecycle, stream routing, optimistic reconciliation, cancel signals, and conversation tree management. Uses `x-ably-*` headers. Lives in `src/core/transport/` (with client-side components in `src/core/transport/client/` and server-side components in `src/core/transport/server/`).
 - **Domain layer** - framework-specific encoding/decoding. Maps between domain events (e.g. Vercel's `UIMessageChunk`) and Ably messages. Uses `x-domain-*` headers. Lives in codec implementations (e.g. `src/vercel/codec/`).
 
 The [codec interface](codec-interface.md) is the boundary between these layers.

docs/internals/history.md

@@ -1,6 +1,6 @@
 # History hydration
 
-`decodeHistory` (`src/core/transport/decode-history.ts`) loads conversation history from an Ably channel's history API and returns decoded domain messages. It handles the mismatch between Ably's newest-first history pagination and the decoder's requirement for chronological input.
+`decodeHistory` (`src/core/transport/client/decode-history.ts`) loads conversation history from an Ably channel's history API and returns decoded domain messages. It handles the mismatch between Ably's newest-first history pagination and the decoder's requirement for chronological input.
 
 ## The problem
 

docs/internals/server-transport.md

@@ -1,6 +1,6 @@
 # Server transport
 
-The server transport (`src/core/transport/server-transport.ts`) handles the server-side turn lifecycle over an Ably channel. It composes a [TurnManager](transport-components.md#turnmanager) for turn state and lifecycle event publishing, and delegates stream piping to [pipeStream](transport-components.md#pipestream).
+The server transport (`src/core/transport/server/server-transport.ts`) handles the server-side turn lifecycle over an Ably channel. It composes a [TurnManager](transport-components.md#turnmanager) for turn state and lifecycle event publishing, and delegates stream piping to [pipeStream](transport-components.md#pipestream).
 
 The transport exposes a single factory method - `newTurn()` - which returns a `Turn` object with explicit lifecycle methods: `start()`, `addMessages()`, `streamResponse()`, and `end()`.
 

docs/internals/transport-components.md

@@ -4,7 +4,7 @@ The client and server transports are composed from several focused sub-component
 
 ## StreamRouter
 
-`src/core/transport/stream-router.ts` - client-side only.
+`src/core/transport/client/stream-router.ts` - client-side only.
 
 The stream router maps decoded events to per-turn `ReadableStream` instances for [own turns](glossary.md#own-turn-vs-observer-turn) - turns this client initiated via `send()`, `regenerate()`, or `edit()`. When the client starts a turn, the router creates a new stream. As decoded events arrive from the channel subscription, the transport routes them through the router to the correct stream.
 
@@ -31,7 +31,7 @@ The router accepts an [`isTerminal`](codec-interface.md#the-codec-interface) pre
 
 ## TurnManager
 
-`src/core/transport/turn-manager.ts` - server-side only.
+`src/core/transport/server/turn-manager.ts` - server-side only.
 
 The turn manager tracks active turns and publishes [turn lifecycle events](wire-protocol.md#lifecycle-events) (`x-ably-turn-start`, `x-ably-turn-end`) on the Ably channel.
 
@@ -55,7 +55,7 @@ The turn manager publishes `x-ably-turn-end` **before** deleting local state. If
 
 ## pipeStream
 
-`src/core/transport/pipe-stream.ts` - server-side only.
+`src/core/transport/server/pipe-stream.ts` - server-side only.
 
 A pure function that reads events from a `ReadableStream`, writes them through a [streaming encoder](codec-interface.md#encoder-architecture), and handles abort/error. No dependencies on turn state or transport internals.
 
@@ -90,7 +90,7 @@ Returns `{ reason }` where reason is `'complete'`, `'cancelled'`, or `'error'`.
 
 ## Cancel routing (server transport)
 
-Cancel routing lives in the server transport (`src/core/transport/server-transport.ts`), not in a separate component.
+Cancel routing lives in the server transport (`src/core/transport/server/server-transport.ts`), not in a separate component.
 
 The server transport subscribes to [`x-ably-cancel`](wire-protocol.md#lifecycle-events) events on channel construction. When a cancel message arrives, it:
 

src/core/transport/client-transport.ts …ore/transport/client/client-transport.tssrc/core/transport/client-transport.ts renamed to src/core/transport/client/client-transport.ts src/core/transport/client-transport.ts renamed to src/core/transport/client/client-transport.ts

@@ -26,31 +26,28 @@ import {
   HEADER_TURN_CLIENT_ID,
   HEADER_TURN_ID,
   HEADER_TURN_REASON,
-} from '../../constants.js';
-import { ErrorCode } from '../../errors.js';
-import { EventEmitter } from '../../event-emitter.js';
-import type { Logger } from '../../logger.js';
-import { LogLevel, makeLogger } from '../../logger.js';
-import { getHeaders } from '../../utils.js';
-import type { DecoderOutput, MessageAccumulator, StreamDecoder } from '../codec/types.js';
+} from '../../../constants.js';
+import { ErrorCode } from '../../../errors.js';
+import { EventEmitter } from '../../../event-emitter.js';
+import type { Logger } from '../../../logger.js';
+import { LogLevel, makeLogger } from '../../../logger.js';
+import { getHeaders } from '../../../utils.js';
+import type { DecoderOutput, MessageAccumulator, StreamDecoder } from '../../codec/types.js';
+import { buildTransportHeaders } from '../headers.js';
+import type { CancelFilter, MessageWithHeaders, TurnEndReason, TurnLifecycleEvent } from '../types.js';
 import { createConversationTree } from './conversation-tree.js';
 import { decodeHistory } from './decode-history.js';
-import { buildTransportHeaders } from './headers.js';
 import type { StreamRouter } from './stream-router.js';
 import { createStreamRouter } from './stream-router.js';
 import type {
   ActiveTurn,
-  CancelFilter,
   ClientTransport,
   ClientTransportOptions,
   CloseOptions,
   ConversationTree,
   LoadHistoryOptions,
-  MessageWithHeaders,
   PaginatedMessages,
   SendOptions,
-  TurnEndReason,
-  TurnLifecycleEvent,
 } from './types.js';
 
 /**

src/core/transport/conversation-tree.ts …re/transport/client/conversation-tree.tssrc/core/transport/conversation-tree.ts renamed to src/core/transport/client/conversation-tree.ts src/core/transport/conversation-tree.ts renamed to src/core/transport/client/conversation-tree.ts

@@ -16,8 +16,8 @@
  * `getMessages()` delegates to.
  */
 
-import { HEADER_FORK_OF, HEADER_PARENT } from '../../constants.js';
-import type { Logger } from '../../logger.js';
+import { HEADER_FORK_OF, HEADER_PARENT } from '../../../constants.js';
+import type { Logger } from '../../../logger.js';
 import type { ConversationNode, ConversationTree } from './types.js';
 
 // ---------------------------------------------------------------------------