feat(langgraph): expose all channels under @langchain/langgraph/channels (#1613)

.changeset/shiny-banks-bet.md

@@ -0,0 +1,5 @@
+---
+"@langchain/langgraph": patch
+---
+
+Channels are now part of the public API, allowing users to customise behaviour of checkpointing per channel (#976)

libs/langgraph/package.json

@@ -113,6 +113,17 @@
       },
       "input": "./src/web.ts"
     },
+    "./channels": {
+      "import": {
+        "types": "./dist/channels/index.d.ts",
+        "default": "./dist/channels/index.js"
+      },
+      "require": {
+        "types": "./dist/channels/index.d.cts",
+        "default": "./dist/channels/index.cjs"
+      },
+      "input": "./src/channels/index.ts"
+    },
     "./pregel": {
       "import": {
         "types": "./dist/pregel/index.d.ts",

libs/langgraph/src/channels/any_value.ts

@@ -6,8 +6,6 @@ import { BaseChannel } from "./base.js";
  *
  * Note: Unlike 'LastValue' if multiple nodes write to this channel in a single step, the values
  * will be continuously overwritten.
- *
- * @internal
  */
 export class AnyValue<Value> extends BaseChannel<Value, Value, Value> {
   lc_graph_name = "AnyValue";

libs/langgraph/src/channels/dynamic_barrier_value.ts

@@ -20,7 +20,6 @@ function isWaitForNames<Value>(
  * - in the "waiting" state it collects named values until all are received.
  *     - once all named values are received, it can be read once, and it switches
  *       back to the "priming" state.
- * @internal
  */
 export class DynamicBarrierValue<Value> extends BaseChannel<
   void,

libs/langgraph/src/channels/ephemeral_value.ts

@@ -1,9 +1,8 @@
 import { EmptyChannelError, InvalidUpdateError } from "../errors.js";
-import { BaseChannel } from "./index.js";
+import { BaseChannel } from "./base.js";
 
 /**
  * Stores the value received in the step immediately preceding, clears after.
- * @internal
  */
 export class EphemeralValue<Value> extends BaseChannel<Value, Value, Value> {
   lc_graph_name = "EphemeralValue";

libs/langgraph/src/channels/index.ts

@@ -3,12 +3,17 @@ export {
   createCheckpoint,
   emptyChannels as empty,
 } from "./base.js";
-export { type BinaryOperator, BinaryOperatorAggregate } from "./binop.js";
-export type { AnyValue } from "./any_value.js";
-export type {
-  WaitForNames,
+export type { BinaryOperator } from "./binop.js";
+export { AnyValue } from "./any_value.js";
+export { LastValue, LastValueAfterFinish } from "./last_value.js";
+export {
+  type WaitForNames,
   DynamicBarrierValue,
 } from "./dynamic_barrier_value.js";
-export type { LastValue } from "./last_value.js";
-export type { NamedBarrierValue } from "./named_barrier_value.js";
-export type { Topic } from "./topic.js";
+export { BinaryOperatorAggregate } from "./binop.js";
+export { EphemeralValue } from "./ephemeral_value.js";
+export {
+  NamedBarrierValue,
+  NamedBarrierValueAfterFinish,
+} from "./named_barrier_value.js";
+export { Topic } from "./topic.js";

libs/langgraph/src/channels/last_value.ts

@@ -62,7 +62,6 @@ export class LastValue<Value> extends BaseChannel<Value, Value, Value> {
 /**
  * Stores the last value received, but only made available after finish().
  * Once made available, clears the value.
- * @internal
  */
 export class LastValueAfterFinish<Value> extends BaseChannel<
   Value,

libs/langgraph/src/channels/named_barrier_value.ts

@@ -9,7 +9,6 @@ export const areSetsEqual = <T>(a: Set<T>, b: Set<T>) =>
  *
  * This ensures that if node N and node M both write to channel C, the value of C will not be updated
  * until N and M have completed updating.
- * @internal
  */
 export class NamedBarrierValue<Value> extends BaseChannel<
   void,

libs/langgraph/src/channels/topic.ts

@@ -2,7 +2,7 @@ import { EmptyChannelError } from "../errors.js";
 import { BaseChannel } from "./base.js";
 
 /**
- * @internal
+ * A configurable PubSub Topic.
  */
 export class Topic<Value> extends BaseChannel<
   Array<Value>,
@@ -19,7 +19,16 @@ export class Topic<Value> extends BaseChannel<
 
   values: Value[];
 
-  constructor(fields?: { unique?: boolean; accumulate?: boolean }) {
+  constructor(fields?: {
+    /**
+     * Whether to only add unique values to the topic. If `true`, only unique values (using reference equality) will be added to the topic.
+     */
+    unique?: boolean;
+    /**
+     * Whether to accumulate values across steps. If `false`, the channel will be emptied after each step.
+     */
+    accumulate?: boolean;
+  }) {
     super();
 
     this.unique = fields?.unique ?? this.unique;