Agent Config
Forward typed configuration from your UI into the agent's reasoning loop.
/** * Agent factories for the Strands TypeScript showcase backend. * * `buildShowcaseAgent` is the single shared agent that serves the vast * majority of demos (the frontend differentiates each demo via * useFrontendTool / useRenderTool / useHumanInTheLoop / useAgentContext). * It mirrors the Python sibling's `build_showcase_agent` minus A2UI. * * The tool-free specialized agents (voice, byoc-hashbrown, byoc-json-render) * are mounted on dedicated sub-paths by `server.ts`. */import { readFileSync } from "node:fs";import { dirname, join } from "node:path";import { fileURLToPath } from "node:url";import { Agent, tool } from "@strands-agents/sdk";import { z } from "zod";import { StrandsAgent } from "@ag-ui/aws-strands";import type { StrandsAgentConfig } from "@ag-ui/aws-strands";import { A2UI_OPERATIONS_KEY, createSurface, updateComponents, updateDataModel,} from "@ag-ui/a2ui-toolkit";import { createModel } from "./model-factory";import { SHOWCASE_TOOLS } from "./tools";import { buildStatePrompt, salesStateFromArgs, notesStateFromArgs, stepsStateFromArgs, documentStateFromArgs, makeSubagentStateFromResult,} from "./state";import { SYSTEM_PROMPT, VOICE_SYSTEM_PROMPT, BYOC_HASHBROWN_SYSTEM_PROMPT, BYOC_JSON_RENDER_SYSTEM_PROMPT,} from "./prompts";export async function buildShowcaseAgent(): Promise<StrandsAgent> { const config: StrandsAgentConfig = { stateContextBuilder: buildStatePrompt, toolBehaviors: { // Sales pipeline lives in shared state; emit the snapshot from args. manage_sales_todos: { skipMessagesSnapshot: true, stateFromArgs: salesStateFromArgs, }, // Shared State (Read + Write) — notes panel. set_notes: { stateFromArgs: notesStateFromArgs }, // gen-ui-agent — live progress card driven by set_steps transitions. set_steps: { stateFromArgs: stepsStateFromArgs }, // shared-state-streaming — stream the document string into state. write_document: { stateFromArgs: documentStateFromArgs }, // Sub-agents — append a delegation entry carrying the actual output. research_agent: { stateFromResult: makeSubagentStateFromResult("research_agent"), }, writing_agent: { stateFromResult: makeSubagentStateFromResult("writing_agent"), }, critique_agent: { stateFromResult: makeSubagentStateFromResult("critique_agent"), }, }, }; const strandsAgent = new Agent({ model: await createModel(), systemPrompt: SYSTEM_PROMPT, tools: SHOWCASE_TOOLS, }); return new StrandsAgent({ agent: strandsAgent, name: "strands_agent", description: "A polished CopilotKit demo assistant: chat, tools, shared state, HITL, sub-agents.", config, });}/** Tool-free agent for the voice demo (transcription + basic chat). */export async function buildVoiceAgent(): Promise<StrandsAgent> { const strandsAgent = new Agent({ model: await createModel(), systemPrompt: VOICE_SYSTEM_PROMPT, tools: [], }); return new StrandsAgent({ agent: strandsAgent, name: "voice_agent", description: "Simple assistant for the voice demo — no tools.", });}/** Tool-free hashbrown UI-kit envelope generator (declarative-hashbrown). */export async function buildByocHashbrownAgent(): Promise<StrandsAgent> { const strandsAgent = new Agent({ model: await createModel(), systemPrompt: BYOC_HASHBROWN_SYSTEM_PROMPT, tools: [], }); return new StrandsAgent({ agent: strandsAgent, name: "byoc_hashbrown", description: "Hashbrown UI-kit envelope generator for the declarative-hashbrown demo.", });}/** Tool-free json-render flat-spec generator (declarative-json-render). */export async function buildByocJsonRenderAgent(): Promise<StrandsAgent> { const strandsAgent = new Agent({ model: await createModel(), systemPrompt: BYOC_JSON_RENDER_SYSTEM_PROMPT, tools: [], }); return new StrandsAgent({ agent: strandsAgent, name: "byoc_json_render", description: "json-render flat-spec generator for the declarative-json-render demo.", });}// ---------------------------------------------------------------------------// A2UI Fixed Schema (declarative-generative-ui) — dedicated backend tool.// ---------------------------------------------------------------------------//// Unlike the dynamic A2UI demo (which relies on the adapter auto-injecting a// `generate_a2ui` tool to *generate* a surface), the fixed-schema demo wires a// single plain backend tool — `display_flight` — that returns the// `a2ui_operations` envelope (createSurface -> updateComponents ->// updateDataModel). The component tree is fixed and authored ahead of time// (./a2ui_schemas/flight_schema.json); only the *data* changes per call. The// runtime A2UIMiddleware detects the envelope in the tool result and paints.// No sub-agent, no generation, no `generate_a2ui` injection.//// The schema's component names + data paths must match the showcase frontend// catalog at src/app/demos/a2ui-fixed-schema/a2ui/{definitions,renderers,// catalog}.ts — catalog id `copilotkit://flight-fixed-catalog`. This mirrors// the canonical langgraph-python demo (src/agents/a2ui_fixed.py).const _A2UI_DIR = dirname(fileURLToPath(import.meta.url));const A2UI_FIXED_CATALOG_ID = "copilotkit://flight-fixed-catalog";const A2UI_FIXED_SURFACE_ID = "flight-fixed-schema";// Fixed, pre-authored component layout. Loaded from JSON so it can be authored// and reviewed independently of the agent code.const FLIGHT_SCHEMA: Array<Record<string, unknown>> = JSON.parse( readFileSync(join(_A2UI_DIR, "a2ui_schemas", "flight_schema.json"), "utf-8"),);const A2UI_FIXED_SYSTEM_PROMPT = "You help users find flights. When asked about a flight, call " + "`display_flight` exactly ONCE with origin, destination, airline, and " + 'price. Use short airport codes (e.g. "SFO", "JFK") for ' + 'origin/destination and a price string like "$289". The tool\'s return ' + "value is an A2UI surface descriptor — the flight card is already rendered " + "to the user; do NOT call `display_flight` again for the same trip and do " + "NOT repeat the flight details in text. After the tool returns, reply with " + "one short confirmation sentence and stop.";/** * Dedicated agent for the A2UI fixed-schema demo. Returns the envelope as a * plain OBJECT (not a JSON string): the Strands TS SDK wraps an object * tool-return in a `json` content block the adapter reads and re-stringifies * into the TOOL_CALL_RESULT the client A2UIMiddleware scans for * `a2ui_operations`. (A bare string return lands in no content block and the * result comes through empty — unlike the Python SDK, which wraps strings.) */export async function buildA2uiFixedSchemaAgent(): Promise<StrandsAgent> { const displayFlight = tool({ name: "display_flight", description: "Show a flight card for the given trip. Use short airport codes " + '(e.g. "SFO", "JFK") for origin/destination and a price string like ' + '"$289". After this tool returns, the flight card is already rendered ' + "to the user via the A2UI surface — do NOT call it again for the same " + "flight; reply with one short confirmation sentence and stop.", inputSchema: z.object({ origin: z.string().describe('Origin airport code, e.g. "SFO".'), destination: z.string().describe('Destination airport code, e.g. "JFK".'), airline: z.string().describe('Airline name, e.g. "United".'), price: z.string().describe('Price string, e.g. "$289".'), }), callback: ({ origin, destination, airline, price }) => ({ [A2UI_OPERATIONS_KEY]: [ createSurface(A2UI_FIXED_SURFACE_ID, A2UI_FIXED_CATALOG_ID), updateComponents(A2UI_FIXED_SURFACE_ID, FLIGHT_SCHEMA), updateDataModel(A2UI_FIXED_SURFACE_ID, { origin, destination, airline, price, }), ], }), }); const strandsAgent = new Agent({ // Chat Completions API: the Responses adapter buffers tool-call argument // deltas, which would defeat A2UI's progressive surface streaming. model: await createModel({ openaiApi: "chat" }), systemPrompt: A2UI_FIXED_SYSTEM_PROMPT, tools: [displayFlight], }); return new StrandsAgent({ agent: strandsAgent, name: "a2ui_fixed_schema", description: "A2UI surface from a fixed, pre-authored schema (direct backend tool)", });}// ---------------------------------------------------------------------------// A2UI Dynamic Schema (declarative-gen-ui) — adapter auto-injects generate_a2ui.// ---------------------------------------------------------------------------//// Unlike the fixed-schema demo (which wires a `display_flight` tool returning a// pre-authored envelope), the dynamic demo lets the agent *generate* the// surface layout on the fly. The Next.js route// (app/api/copilotkit-declarative-gen-ui/route.ts) sets// `a2ui: { injectA2UITool: true, defaultCatalogId: "declarative-gen-ui-catalog" }`;// the runtime forwards the flag, the Strands adapter auto-injects a// `generate_a2ui` tool and drives a secondary render planner. The// `config.a2ui` block below supplies the catalog id stamped into generated// surfaces and the composition guide that teaches the planner the page's// catalog. Mirrors the ag-ui dynamic-schema reference example.//// The compositionGuide MUST describe the catalog the page registers at// src/app/demos/declarative-gen-ui/a2ui/{definitions,renderers,catalog}.ts// (catalog id `declarative-gen-ui-catalog`): Card / StatusBadge / Metric /// InfoRow / PrimaryButton / PieChart / BarChart / DataTable, composed inside// the basic catalog's Row / Column / Text (`includeBasicCatalog: true`).//// Grounding dataset + composition rules are kept in spirit with the frontend// `sales-context.ts` (SALES_DATASET + COMPOSITION_RULES) the page registers via// `useAgentContext`. The frontend context steers the PRIMARY agent; this// compositionGuide is the channel the adapter feeds to the secondary// `render_a2ui` planner (it gets `guidelines`, not the frontend App Context),// so the planner is self-contained.const A2UI_DYNAMIC_CATALOG_ID = "declarative-gen-ui-catalog";const A2UI_DYNAMIC_SALES_DATASET = `Vantage Threads (fictional B2B apparel company) — Q2 sales data. Ground every visual in these numbers; invent only plausible details consistent with them.- Quarterly revenue: $4.2M (up 12% QoQ). New customers: 186 (up 8%). Win rate: 31% (down 2pts). Avg deal size: $22.6k (up 5%).- Revenue by region: North America $1.9M, EMEA $1.3M, APAC $720k, LATAM $280k.- Monthly revenue: Jan $1.21M, Feb $1.34M, Mar $1.65M, Apr $1.38M, May $1.42M, Jun $1.40M.- Reps (vs quota): Dana Whitfield 124%, Marcus Lee 108%, Priya Sharma 97%, Tom Okafor 88%, Elena Vasquez 71%.- At-risk: total $615k ARR across 3 accounts — Northwind Retail ($340k renewal, no contact 6 weeks; severity high), Cascadia Outfitters ($180k, champion left; severity medium), Atlas Goods ($95k, stalled legal review; severity medium).- Biggest account: Meridian Apparel Group — owner Dana Whitfield, region North America, ARR $612k, renewal Sep 30, last contact 3 days ago, health green, 4 open opportunities worth $210k.- Meridian revenue by product line: Outerwear $260k, Footwear $180k, Accessories $112k, Custom $60k.`;const A2UI_DYNAMIC_COMPOSITION_RULES = `Use ONLY these exact component names (the registered catalog — any other name fails to render): Card, Column, Row, Text, Metric, PieChart, BarChart, DataTable, StatusBadge, InfoRow, PrimaryButton. The single-value KPI tile component is named exactly "Metric" (NOT "MetricTile" or "MetricCard").Pick A2UI components by the shape of the question — never ask which chart the user wants:1. Overall snapshot / "sales dashboard" → a Column (gap 16) whose first child is a Row (gap 16) of 4 Metric components (each with trend + trendValue), followed by a Row with a PieChart (revenue by region) next to a BarChart (monthly revenue, all six months Jan-Jun). Do NOT wrap the dashboard in a surrounding Card — the charts carry their own card chrome. Do NOT use StatusBadge, DataTable, or InfoRow here.2. Rep / team performance → a Column (gap 16) with a Card containing a DataTable (columns: rep, attainment, pipeline) next to or above a BarChart of quota attainment % per rep — no StatusBadge or InfoRow.3. Risk / health checks → a Column (gap 16): first a Row (gap 16) of 3 Metric components (ARR at risk $615k trend down, accounts at risk 3, biggest exposure Northwind $340k), then a Row (gap 16) with one compact Card per at-risk account (title = account name, subtitle = ARR at stake) containing a StatusBadge (error for high severity, warning otherwise) above a one-line Text with the reason and the recommended next action — no DataTable or InfoRow.4. Single account/entity details → a Row (gap 16) with a Card of InfoRow facts (owner, region, ARR, renewal date, last contact) next to a PieChart of that account's revenue by product line — no DataTable or StatusBadge.5. Part-of-whole follow-ups → PieChart; trends or comparisons over time/categories → BarChart.Compose generously — a dashboard should feel like a real analytics product, not a single widget.`;const A2UI_DYNAMIC_COMPOSITION_GUIDE = `${A2UI_DYNAMIC_SALES_DATASET}\n\n${A2UI_DYNAMIC_COMPOSITION_RULES}`;// Mirrors the langgraph-python demo's a2ui_dynamic.py SYSTEM_PROMPT.const A2UI_DYNAMIC_SYSTEM_PROMPT = "You are the embedded sales analyst for Vantage Threads, the fictional " + "B2B apparel company described in your App Context. Answer every " + "business question by calling `generate_a2ui` to draw a rich visual " + "surface, and keep the chat reply to one short sentence.\n\n" + "Ground every number in the sales dataset from App Context — never " + "invent figures that contradict it. Follow the dashboard composition " + "rules from App Context when choosing components: pick the component " + "by the shape of the question (snapshot → composed KPI dashboard with " + "charts; team performance → table; risk → status badges; single " + "account → info rows; part-of-whole → pie; trend/comparison → bar). " + "Never ask the user which chart they want. `generate_a2ui` takes no " + "arguments and handles the rendering automatically. Compose " + "generously — a dashboard should feel like a real analytics product, " + "not a single widget.";/** * Dedicated agent for the A2UI dynamic-schema demo. Wires NO `generate_a2ui` * tool — the runtime's `injectA2UITool: true` makes the adapter auto-inject it * and drive a secondary render planner to GENERATE the surface. */export async function buildA2uiDynamicAgent(): Promise<StrandsAgent> { const strandsAgent = new Agent({ // Chat Completions API: the Responses adapter buffers tool-call argument // deltas, which would defeat A2UI's progressive surface streaming. model: await createModel({ openaiApi: "chat" }), systemPrompt: A2UI_DYNAMIC_SYSTEM_PROMPT, }); const config: StrandsAgentConfig = { a2ui: { defaultCatalogId: A2UI_DYNAMIC_CATALOG_ID, guidelines: { compositionGuide: A2UI_DYNAMIC_COMPOSITION_GUIDE }, }, }; return new StrandsAgent({ agent: strandsAgent, name: "a2ui_dynamic_schema", description: "Dynamic A2UI surfaces generated on the fly (auto-injected tool)", config, });}// ---------------------------------------------------------------------------// A2UI Error Recovery (a2ui-recovery) — adapter auto-injects + runs recovery.// ---------------------------------------------------------------------------//// Same auto-injected dynamic-schema setup as buildA2uiDynamicAgent, but the// aimock fixtures force the inner render_a2ui to emit free-form/sloppy args// (heal pill) or a structurally-invalid surface on every attempt (exhaust// pill). The Strands adapter runs the toolkit validate->retry recovery loop on// its auto-inject path (default 3 attempts) and returns the// a2ui_recovery_exhausted hard-fail envelope when the cap is hit — so this// agent wires NO tool, unlike the langgraph/ADK siblings (which own the tool// explicitly via getA2UITools + injectA2UITool:false). Mirrors the ag-ui dojo// aws-strands recovery example./** * Dedicated agent for the A2UI error-recovery demo. Wires NO `generate_a2ui` * tool — the runtime's `injectA2UITool: true` makes the adapter auto-inject it, * drive the secondary render planner, and run the recovery loop. */export async function buildA2uiRecoveryAgent(): Promise<StrandsAgent> { const strandsAgent = new Agent({ // Chat Completions API: the Responses adapter buffers tool-call argument // deltas, which would defeat A2UI's progressive surface streaming. model: await createModel({ openaiApi: "chat" }), systemPrompt: A2UI_DYNAMIC_SYSTEM_PROMPT, }); const config: StrandsAgentConfig = { a2ui: { defaultCatalogId: A2UI_DYNAMIC_CATALOG_ID, guidelines: { compositionGuide: A2UI_DYNAMIC_COMPOSITION_GUIDE }, }, }; return new StrandsAgent({ agent: strandsAgent, name: "a2ui_recovery", description: "Dynamic A2UI with automatic error recovery (auto-injected tool)", config, });}You have a working agent and want the user to be able to tune how it behaves: tone, expertise level, response length, language, persona. By the end of this guide, your UI will own a typed config object that the agent reads on every run and rebuilds its system prompt from.
When to use this#
Reach for agent config whenever the agent's behaviour depends on user-controllable settings that don't fit naturally as chat input:
- Tone, voice, persona: "playful", "formal", "casual"
- Expertise level: "beginner", "intermediate", "expert"
- Response shape: short / medium / long, structured / prose, language
- Domain switches: which knowledge base to consult, which tool subset to enable
If the values are a channel the user occasionally tunes (a settings panel, a toolbar of selects), agent config is the right shape. If the values are content the agent should write back to (notes, a document, a plan), use Shared State instead.
How agent config flows from the UI into the agent's reasoning loop depends on your runtime architecture. Agents living behind a runtime read it from agent state on every run, while in-process agents receive the same object as forwarded properties on the provider — same UX, slightly different wiring on each side.
How it works#
Agent config is a typed object the frontend owns and publishes to the agent as runtime context. There are two pieces: the UI side, which owns the React state and publishes every change with useAgentContext, and the backend node, which reads that context entry and turns it into a system prompt.
The UI side stays simple. Hold the typed config in React state, then mirror every change into the agent through useAgentContext:
function ConfigContextRelay({ config }: { config: AgentConfig }) {
useAgentContext({
description: "Agent response preferences",
value: {
tone: config.tone,
expertise: config.expertise,
responseLength: config.responseLength,
},
});
return null;
}The backend half is also a single node. Read the latest config context at the top of every run and use it to build the system prompt for that turn:
import json
CONFIG_KEYS = ("tone", "expertise", "responseLength")
def read_config_value(entry):
value = entry.get("value")
if isinstance(value, str):
try:
value = json.loads(value)
except json.JSONDecodeError:
return None
if not isinstance(value, dict):
return None
if any(key in value for key in CONFIG_KEYS):
return value
return None
async def my_agent_node(state: AgentState, config: RunnableConfig):
context_entries = state.get("copilotkit", {}).get("context", [])
cfg = next(
(
value
for entry in reversed(context_entries)
if (value := read_config_value(entry)) is not None
),
{},
)
tone = cfg.get("tone", "professional")
expertise = cfg.get("expertise", "intermediate")
response_length = cfg.get("responseLength", "concise")
system_prompt = build_system_prompt(tone, expertise, response_length)
# ...The agent reads the latest typed config at the start of every turn, rebuilds the system prompt, runs the turn. This is the same shape as the shared-state write-side pattern; agent config is just a specific use of that pattern with a UI-owned typed object on top.