transformContextText

SUPPORT · function · Runtime value

Apply a text transform to a fragment value, including strings nested inside objects.

Structured values are walked through a JSON round trip, which is what the budget measurement serializes later; values that JSON cannot represent are therefore not preserved.

Import

TypeScript

import { transformContextText } from '@jangts/agent-core/support';

JavaScript

import { transformContextText } from '@jangts/agent-core/support';

Other public entry points:@jangts/agent-core, @jangts/agent-core/types, @jangts/agent-core/support, @jangts/agent-core/support/context.

Definition

Call

transformContextText(fragment: ContextFragment, transform: (text: string) => string): ContextFragment

Apply a text transform to a fragment value, including strings nested inside objects.

Structured values are walked through a JSON round trip, which is what the budget measurement serializes later; values that JSON cannot represent are therefore not preserved.

Parameter	Type	Passing	Description
fragment	ContextFragment	Required	—
transform	(text: string) => string	Required	—

Fields of fragment

Field	Type	Required	Description
id	string	Required	Unique, stable id matching ^[a-z][a-zA-Z0-9:._-]*$; duplicates are rejected.
sourceId	string	Required	Owning source (module or registration) used to explain where the content came from.
trust	ContextTrust	Required	Producer trust level. user and tool content cannot become a system message.
lifetime	ContextLifetime	Required	Declared validity window of this content.
maxChars	number	Required	Hard upper bound in JSON characters; must be a positive safe integer.
role	"system" | "user"	Required	Message slot the fragment occupies when assembled.
value	string | Record<string, unknown>	Required	Rendered content. A system message accepts a string only, never a record.

Returns: ContextFragment.

Return value structure

Field	Type	Required	Description
id	string	Required	Unique, stable id matching ^[a-z][a-zA-Z0-9:._-]*$; duplicates are rejected.
sourceId	string	Required	Owning source (module or registration) used to explain where the content came from.
trust	ContextTrust	Required	Producer trust level. user and tool content cannot become a system message.
lifetime	ContextLifetime	Required	Declared validity window of this content.
maxChars	number	Required	Hard upper bound in JSON characters; must be a positive safe integer.
role	"system" | "user"	Required	Message slot the fragment occupies when assembled.
value	string | Record<string, unknown>	Required	Rendered content. A system message accepts a string only, never a record.

Examples

• Context assembly: configure stable metadata once: Support binds fragment metadata, formatting, and order in advance, and requests supply only the changing business input.

Configure once, then supply only question and history

Beginner · Node.js

TypeScript

import { Support } from '@jangts/agent-core';
type Input = { question: string; history: readonly { role: string; content: string }[] };
const builder = Support.defineContextFragments<Input>([
  { id: 'question', sourceId: 'request', trust: 'user', lifetime: 'turn', maxChars: 1000,
    role: 'user', format: input => input.question },
  { id: 'history', sourceId: 'conversation', trust: 'user', lifetime: 'turn', maxChars: 10000,
    role: 'user', format: input => ({ messages: input.history }) },
], { maxInputChars: 1200 });
const context = builder.build({ input: { question: '服务状态？', history: [] } });
console.log(context.messages);

JavaScript

import { Support } from '@jangts/agent-core';
const builder = Support.defineContextFragments([
    { id: 'question', sourceId: 'request', trust: 'user', lifetime: 'turn', maxChars: 1000,
        role: 'user', format: input => input.question },
    { id: 'history', sourceId: 'conversation', trust: 'user', lifetime: 'turn', maxChars: 10000,
        role: 'user', format: input => ({ messages: input.history }) },
], { maxInputChars: 1200 });
const context = builder.build({ input: { question: '服务状态？', history: [] } });
console.log(context.messages);

The same builder produces a plan in advance

Configuration · Node.js

TypeScript

import { Support } from '@jangts/agent-core';
type Input = { question: string; history: readonly { role: string; content: string }[] };
const builder = Support.defineContextFragments<Input>([
  { id: 'question', sourceId: 'request', trust: 'user', lifetime: 'turn', maxChars: 1000,
    role: 'user', format: input => input.question },
  { id: 'history', sourceId: 'conversation', trust: 'user', lifetime: 'turn', maxChars: 10000,
    role: 'user', format: input => ({ messages: input.history }) },
], { maxInputChars: 1200 });
const input = { question: '服务状态？', history: [] };
const plan = builder.plan({ input });
const expanded = builder.fragments(input);
console.log(plan.maxInputChars, expanded.map(fragment => fragment.id));
const largerRequest = builder.build({ input, maxInputChars: 2000 });
console.log(largerRequest.maxInputChars);

JavaScript

import { Support } from '@jangts/agent-core';
const builder = Support.defineContextFragments([
    { id: 'question', sourceId: 'request', trust: 'user', lifetime: 'turn', maxChars: 1000,
        role: 'user', format: input => input.question },
    { id: 'history', sourceId: 'conversation', trust: 'user', lifetime: 'turn', maxChars: 10000,
        role: 'user', format: input => ({ messages: input.history }) },
], { maxInputChars: 1200 });
const input = { question: '服务状态？', history: [] };
const plan = builder.plan({ input });
const expanded = builder.fragments(input);
console.log(plan.maxInputChars, expanded.map(fragment => fragment.id));
const largerRequest = builder.build({ input, maxInputChars: 2000 });
console.log(largerRequest.maxInputChars);

Reuse a metadata catalog and request contribution slots

Extension · Node.js

TypeScript

import { Support } from '@jangts/agent-core';
import type { ContextFragment } from '@jangts/agent-core/types';
type Input = { question: string; evidence: string };
const builder = Support.defineContextAssembly<Input, 'question', 'evidence'>([
  { kind: 'fragment', id: 'question', format: input => input.question },
  { kind: 'contributions', placement: 'evidence' },
], {
  maxInputChars: 2000,
  fragment(id, value): ContextFragment { return { id, sourceId: 'request', trust: 'user', lifetime: 'turn', role: 'user', maxChars: 1000, value }; },
  contributions: { evidence(input) { return [{ id: 'evidence', sourceId: 'service', trust: 'server', lifetime: 'turn', role: 'user', maxChars: 1000, value: input.evidence }]; } },
});
console.log(builder.build({ input: { question: '状态？', evidence: '最近检查：正常' } }).messages);

JavaScript

import { Support } from '@jangts/agent-core';
const builder = Support.defineContextAssembly([
    { kind: 'fragment', id: 'question', format: input => input.question },
    { kind: 'contributions', placement: 'evidence' },
], {
    maxInputChars: 2000,
    fragment(id, value) { return { id, sourceId: 'request', trust: 'user', lifetime: 'turn', role: 'user', maxChars: 1000, value }; },
    contributions: { evidence(input) { return [{ id: 'evidence', sourceId: 'service', trust: 'server', lifetime: 'turn', role: 'user', maxChars: 1000, value: input.evidence }]; } },
});
console.log(builder.build({ input: { question: '状态？', evidence: '最近检查：正常' } }).messages);

Related policy source

• Assembly order, dependency snapshots, and request budget overrides

Related definitions

• ContextFragment