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fix(agents): dedupe ReAct draft text per-round while preserving live streaming (#421) #446

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fix(agents): dedupe ReAct draft text per-round while preserving live streaming (#421) #446

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255 changes: 225 additions & 30 deletions apps/dev-playground/client/src/routes/agent.route.tsx
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Original file line number Diff line number Diff line change
@@ -1,5 +1,11 @@
import { getPluginClientConfig } from "@databricks/appkit-ui/js";
import { Button } from "@databricks/appkit-ui/react";
import type { AgentTurnItem } from "@databricks/appkit-ui/react";
import {
Button,
Collapsible,
CollapsibleContent,
CollapsibleTrigger,
} from "@databricks/appkit-ui/react";
import { createFileRoute } from "@tanstack/react-router";
import { useCallback, useEffect, useRef, useState } from "react";

Expand Down Expand Up @@ -39,7 +45,113 @@ interface SSEEvent {
interface ChatMessage {
id: number;
role: "user" | "assistant";
/** User text, or — for assistant turns — the terminal answer text. */
content: string;
/**
* For assistant turns: the ordered per-round trace (intermediate draft
* messages, tool calls, tool results, and the final answer). Rendered as a
* collapsible "Steps" section above the answer. Undefined for user turns.
*/
items?: AgentTurnItem[];
}

/** Parse a wire JSON string, falling back to the raw value. */
function parseMaybeJson(value: string | undefined): unknown {
if (value === undefined || value === "") return value;
try {
return JSON.parse(value);
} catch {
return value;
}
}

/** Text of the last `message` item — the terminal answer. */
function lastMessageText(items: AgentTurnItem[]): string {
for (let i = items.length - 1; i >= 0; i--) {
const it = items[i];
if (it.kind === "message") return it.text;
}
return "";
}

function summarizeArgs(args: unknown): string {
if (args === undefined || args === "") return "";
const s = typeof args === "string" ? args : JSON.stringify(args);
return s.length > 80 ? `${s.slice(0, 80)}…` : s;
}

function summarizeOutput(output: unknown): string {
const s = typeof output === "string" ? output : JSON.stringify(output);
return s.length > 200 ? `${s.slice(0, 200)}…` : s;
}

/**
* Renders an assistant turn: collapsible intermediate steps (every item before
* the last `message`) plus the terminal answer streamed live below.
*/
function AssistantTurn({ items }: { items: AgentTurnItem[] }) {
const lastMessageIdx = (() => {
for (let i = items.length - 1; i >= 0; i--) {
if (items[i].kind === "message") return i;
}
return -1;
})();
const steps = lastMessageIdx >= 0 ? items.slice(0, lastMessageIdx) : items;
const answer = lastMessageIdx >= 0 ? lastMessageText(items) : "";

return (
<div className="max-w-[85%] space-y-2">
{steps.length > 0 && (
<Collapsible>
<CollapsibleTrigger className="text-xs text-muted-foreground underline-offset-2 hover:underline">
Steps ({steps.length})
</CollapsibleTrigger>
<CollapsibleContent className="mt-1 space-y-1 border-l-2 border-muted pl-3">
{steps.map((it) => {
if (it.kind === "message") {
return (
<p
key={it.id}
className="whitespace-pre-wrap text-xs text-muted-foreground/80"
>
{it.text}
</p>
);
}
if (it.kind === "tool_call") {
return (
<div
key={it.id}
className="inline-flex max-w-full items-center gap-1 rounded bg-muted px-2 py-0.5 text-xs font-mono"
>
<span className="font-semibold">{it.name}</span>
<span className="opacity-60 truncate">
({summarizeArgs(it.args)})
</span>
</div>
);
}
return (
<div
key={it.id}
className={`rounded px-2 py-0.5 text-xs font-mono ${
it.error
? "bg-red-500/10 text-red-600"
: "bg-muted text-muted-foreground"
}`}
>
{it.error ? `error: ${it.error}` : summarizeOutput(it.output)}
</div>
);
})}
</CollapsibleContent>
</Collapsible>
)}
<div className="rounded-lg bg-muted px-4 py-2">
<p className="whitespace-pre-wrap text-sm">{answer}</p>
</div>
</div>
);
}

interface PendingApproval {
Expand Down Expand Up @@ -138,7 +250,7 @@ function useAutocomplete(enabled: boolean) {

function AgentRoute() {
const [messages, setMessages] = useState<ChatMessage[]>([]);
const [events, setEvents] = useState<AgentEvent[]>([]);
const [events, setEvents] = useState<SSEEvent[]>([]);
const [input, setInput] = useState("");
const [isLoading, setIsLoading] = useState(false);
const [threadId, setThreadId] = useState<string | null>(null);
Expand Down Expand Up @@ -232,9 +344,31 @@ function AgentRoute() {
if (!reader) return;

const decoder = new TextDecoder();
let assistantContent = "";
// Per-round trace items for this assistant turn, keyed by wire item id.
const turnItems: AgentTurnItem[] = [];
const assistantId = ++msgIdCounter.current;
let buffer = "";

const flushAssistant = () => {
const snapshot = turnItems.map((x) => ({ ...x }));
setMessages((prev) => {
const updated = [...prev];
const last = updated[updated.length - 1];
const next: ChatMessage = {
id: assistantId,
role: "assistant",
content: lastMessageText(snapshot),
items: snapshot,
};
if (last?.role === "assistant" && last.id === assistantId) {
updated[updated.length - 1] = next;
} else {
updated.push(next);
}
return updated;
});
};

while (true) {
const { done, value } = await reader.read();
if (done) break;
Expand Down Expand Up @@ -273,26 +407,81 @@ function AgentRoute() {
setThreadId(event.data.threadId as string);
}

if (event.type === "response.output_text.delta" && event.delta) {
assistantContent += event.delta;
setMessages((prev) => {
const updated = [...prev];
const last = updated[updated.length - 1];
if (last?.role === "assistant") {
updated[updated.length - 1] = {
...last,
content: assistantContent,
};
} else {
updated.push({
id: ++msgIdCounter.current,
role: "assistant",
content: assistantContent,
});
// Build the ordered per-round item list. The translator emits
// items in output_index order, so appending on `added` keeps it
// ordered. Each ReAct round's draft is its own message item, so the
// duplicated drafts surface as collapsible steps, not the answer.
let changed = false;
const it = event.item;
if (event.type === "response.output_item.added") {
if (it?.type === "message" && it.id) {
turnItems.push({
kind: "message",
id: it.id,
text: "",
status: "in_progress",
});
changed = true;
} else if (it?.type === "function_call") {
turnItems.push({
kind: "tool_call",
id: it.id ?? it.call_id ?? `fc_${turnItems.length}`,
callId: it.call_id ?? "",
name: it.name ?? "",
args: parseMaybeJson(it.arguments),
status: "in_progress",
});
changed = true;
} else if (it?.type === "function_call_output") {
turnItems.push({
kind: "tool_result",
id: it.id ?? `fc_output_${turnItems.length}`,
callId: it.call_id ?? "",
output: parseMaybeJson(it.output),
});
changed = true;
}
} else if (event.type === "response.output_item.done") {
if (it?.type === "function_call") {
for (let i = turnItems.length - 1; i >= 0; i--) {
const t = turnItems[i];
if (
t.kind === "tool_call" &&
(t.callId === it.call_id || t.id === it.id)
) {
t.status = "completed";
if (it.arguments !== undefined) {
t.args = parseMaybeJson(it.arguments);
}
changed = true;
break;
}
}
return updated;
});
} else if (it?.type === "message" && it.id) {
for (let i = turnItems.length - 1; i >= 0; i--) {
const t = turnItems[i];
if (t.kind === "message" && t.id === it.id) {
t.status = "completed";
changed = true;
break;
}
}
}
} else if (
event.type === "response.output_text.delta" &&
event.delta
) {
for (let i = turnItems.length - 1; i >= 0; i--) {
const t = turnItems[i];
if (t.kind === "message" && t.id === event.item_id) {
t.text += event.delta;
changed = true;
break;
}
}
}

if (changed) flushAssistant();
} catch {
// skip malformed events
}
Expand Down Expand Up @@ -368,15 +557,21 @@ function AgentRoute() {
key={msg.id}
className={`flex ${msg.role === "user" ? "justify-end" : "justify-start"}`}
>
<div
className={`max-w-[85%] rounded-lg px-4 py-2 ${
msg.role === "user"
? "bg-primary text-primary-foreground"
: "bg-muted"
}`}
>
<p className="whitespace-pre-wrap text-sm">{msg.content}</p>
</div>
{msg.role === "assistant" && msg.items ? (
<AssistantTurn items={msg.items} />
) : (
<div
className={`max-w-[85%] rounded-lg px-4 py-2 ${
msg.role === "user"
? "bg-primary text-primary-foreground"
: "bg-muted"
}`}
>
<p className="whitespace-pre-wrap text-sm">
{msg.content}
</p>
</div>
)}
</div>
))}

Expand Down
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