上下文处理是普通 Workflow 节点
通过正常节点与路由接入选择、裁切、压缩，Core 统一记录并调度它们。
Support 提供完整处理节点，以及可独立配置的选择／单步缩减节点；最终模型调用沿用同一 PreparedModelCall，测量和发送共用一次准备的传输。
createContextProcessingNode 负责选定策略并完成装配；createContextSelectionNode 只返回允许的 stepIds，不自动执行缩减；createContextReductionNode 只执行已登记的一个 stepId。它们都是 WorkflowNode，不是另一种执行框架，App 用正常 routes 决定何时进入。
节点具有本次 signal、期限和同一模型端口。选择与压缩使用的模型调用同样消耗祖先额度，不创建新的免费请求；超限、保护片段变化、未知步骤和迟到结果仍拒绝。自定义节点可以实现同一 WorkflowNode 合同，不受 Support 算法限制。
由简到繁的同业务示例
只验证与装配，先不增加压缩
入门 · Node.js
ts
import { AgentCoreEngine, defineWorkflow, route } from '@jangts/agent-core/engine';
import { Support } from '@jangts/agent-core';
import type { BuiltContext, PreparedModelCall } from '@jangts/agent-core/types';
type State = { question: string; input?: BuiltContext; prepared?: PreparedModelCall; answer?: string };
const builder = Support.defineContextFragments<State>([
{ id: 'question', sourceId: 'request', trust: 'user', lifetime: 'turn', role: 'user', maxChars: 1000, format: state => state.question },
], { maxInputChars: 2000 });
const prepare = Support.createContextProcessingNode<State, string>({
id: 'prepare', description: '装配并校验输入', startsRound: true,
plan: state => builder.plan({ input: state }),
update: result => ({ input: result.input, prepared: result.prepared }),
routes: [route.to('reply')],
});
const workflow = defineWorkflow<State, string>({ id: 'chat', nodes: [prepare, {
id: 'reply', description: '使用同次准备回答', requires: ['input', 'prepared'],
async run(state, { model }) { const { value } = await model.invoke({ input: state.input!, prepared: state.prepared! }); return { answer: String(value) }; },
routes: [route.deliver('answer')],
}] });
const agent = new AgentCoreEngine({ workflow, model: { provider: { async *stream() { yield '服务正常'; } } } });
console.log(await agent.run({ question: '状态？' }));js
import { AgentCoreEngine, defineWorkflow, route } from '@jangts/agent-core/engine';
import { Support } from '@jangts/agent-core';
const builder = Support.defineContextFragments([
{ id: 'question', sourceId: 'request', trust: 'user', lifetime: 'turn', role: 'user', maxChars: 1000, format: state => state.question },
], { maxInputChars: 2000 });
const prepare = Support.createContextProcessingNode({
id: 'prepare', description: '装配并校验输入', startsRound: true,
plan: state => builder.plan({ input: state }),
update: result => ({ input: result.input, prepared: result.prepared }),
routes: [route.to('reply')],
});
const workflow = defineWorkflow({ id: 'chat', nodes: [prepare, {
id: 'reply', description: '使用同次准备回答', requires: ['input', 'prepared'],
async run(state, { model }) { const { value } = await model.invoke({ input: state.input, prepared: state.prepared }); return { answer: String(value) }; },
routes: [route.deliver('answer')],
}] });
const agent = new AgentCoreEngine({ workflow, model: { provider: { async *stream() { yield '服务正常'; } } } });
console.log(await agent.run({ question: '状态？' }));同一节点合同增加历史裁切策略
配置 · Node.js
将该节点放回前例相同 Workflow；每次 run 的 State 增加 history 即可，模型 reply 节点不换接口。完整流程里的 reply 目标必须存在。
ts
import { Support } from '@jangts/agent-core';
import { route } from '@jangts/agent-core/engine';
import type { BuiltContext, PreparedModelCall } from '@jangts/agent-core/types';
type State = { question: string; history: { role: string; content: string }[]; input?: BuiltContext; prepared?: PreparedModelCall };
const builder = Support.defineContextFragments<State>([
{ id: 'question', sourceId: 'request', trust: 'user', lifetime: 'turn', role: 'user', maxChars: 1000, format: state => state.question },
{ id: 'history', sourceId: 'conversation', trust: 'user', lifetime: 'turn', role: 'user', maxChars: 10000, format: state => ({ messages: state.history }) },
], { maxInputChars: 1200 });
const prepare = Support.createContextProcessingNode<State, string>({
id: 'prepare', description: '按需要裁切旧历史', startsRound: true,
plan: state => builder.plan({ input: state }),
policy: { mode: 'reduce', steps: [{ id: 'recent', kind: 'trim', fragmentId: 'history', field: 'messages',
targetChars: 700, grouping: { kind: 'user-turn' }, keepGroups: 1 }] },
update: result => ({ input: result.input, prepared: result.prepared }),
routes: [route.to('reply')],
});
console.log(prepare.id);js
import { Support } from '@jangts/agent-core';
import { route } from '@jangts/agent-core/engine';
const builder = Support.defineContextFragments([
{ id: 'question', sourceId: 'request', trust: 'user', lifetime: 'turn', role: 'user', maxChars: 1000, format: state => state.question },
{ id: 'history', sourceId: 'conversation', trust: 'user', lifetime: 'turn', role: 'user', maxChars: 10000, format: state => ({ messages: state.history }) },
], { maxInputChars: 1200 });
const prepare = Support.createContextProcessingNode({
id: 'prepare', description: '按需要裁切旧历史', startsRound: true,
plan: state => builder.plan({ input: state }),
policy: { mode: 'reduce', steps: [{ id: 'recent', kind: 'trim', fragmentId: 'history', field: 'messages',
targetChars: 700, grouping: { kind: 'user-turn' }, keepGroups: 1 }] },
update: result => ({ input: result.input, prepared: result.prepared }),
routes: [route.to('reply')],
});
console.log(prepare.id);