diff --git a/app/(chat)/api/chat/_lib/stream.ts b/app/(chat)/api/chat/_lib/stream.ts
new file mode 100644
index 000000000..02fe5c313
--- /dev/null
+++ b/app/(chat)/api/chat/_lib/stream.ts
@@ -0,0 +1,416 @@
+import { JsonToSseTransformStream } from "ai";
+import { extractImageUrlsFromText } from "@/lib/image-url";
+import type {
+  ResolvedChatMediaInput,
+  ResolvedImageRef,
+  ResolvedTargetAssets,
+} from "@/lib/ai/context-memory/types";
+import { generateUUID } from "@/lib/utils";
+
+export type StreamWriter = {
+  write: (chunk: any) => void;
+};
+
+export function safeWriteStreamChunk(
+  writer: StreamWriter,
+  chunk: any,
+  label: string
+): boolean {
+  try {
+    writer.write(chunk);
+    return true;
+  } catch (error) {
+    console.warn(`[Chat API] Stream write skipped (${label})`, error);
+    return false;
+  }
+}
+
+export function writeAssistantTextChunk(
+  writer: StreamWriter,
+  text: string,
+  label: string,
+  messageId = generateUUID()
+) {
+  safeWriteStreamChunk(
+    writer,
+    {
+      type: "data-appendMessage",
+      data: JSON.stringify({
+        id: messageId,
+        role: "assistant",
+        parts: [{ type: "text", text }],
+      }),
+    },
+    label
+  );
+  return messageId;
+}
+
+export function writeStructuredDataChunk(
+  writer: StreamWriter,
+  type: string,
+  data: unknown,
+  label: string
+) {
+  safeWriteStreamChunk(
+    writer,
+    {
+      type,
+      data: JSON.stringify(data),
+    },
+    label
+  );
+}
+
+export function writeProtocolDebugChunk(
+  writer: StreamWriter,
+  enabled: boolean,
+  data: unknown,
+  label: string
+) {
+  if (!enabled) return;
+  writeStructuredDataChunk(writer, "data-protocolDebug", data, label);
+}
+
+function normalizeImageLoadingProviderType(providerType?: string | null): string {
+  const normalized = String(providerType || "").trim().toLowerCase();
+  if (normalized === "gemini-image" || normalized === "huanke-gemini") {
+    return "gemini";
+  }
+  if (
+    normalized === "alibaba-image" ||
+    normalized === "bfl-image" ||
+    normalized === "ruxa-image" ||
+    normalized === "fal-image" ||
+    normalized === "openai-image" ||
+    normalized === "stepfun-image" ||
+    normalized === "midjourney" ||
+    normalized === "runway" ||
+    normalized === "krea" ||
+    normalized === "volcano-vision" ||
+    normalized === "gemini"
+  ) {
+    return normalized;
+  }
+  return "alibaba-image";
+}
+
+export function writeImageGenerationStatusChunk(
+  writer: StreamWriter,
+  params: {
+    phase: "queued" | "processing" | "finalizing" | "failed" | "completed";
+    providerType?: string | null;
+    modelName?: string | null;
+    imageCount?: number | null;
+    queuePosition?: number | null;
+    sameModelRunningCount?: number | null;
+    concurrencyLimit?: number | null;
+    estimatedWaitMs?: number | null;
+  },
+  label: string
+) {
+  writeStructuredDataChunk(
+    writer,
+    "data-imageGenerationStatus",
+    {
+      phase: params.phase,
+      providerType: normalizeImageLoadingProviderType(params.providerType),
+      modelName: String(params.modelName || "").trim() || undefined,
+      imageCount:
+        Number.isFinite(Number(params.imageCount)) && Number(params.imageCount) > 0
+          ? Number(params.imageCount)
+          : undefined,
+      queuePosition:
+        Number.isFinite(Number(params.queuePosition)) &&
+        Number(params.queuePosition) >= 0
+          ? Number(params.queuePosition)
+          : undefined,
+      sameModelRunningCount:
+        Number.isFinite(Number(params.sameModelRunningCount)) &&
+        Number(params.sameModelRunningCount) >= 0
+          ? Number(params.sameModelRunningCount)
+          : undefined,
+      concurrencyLimit:
+        Number.isFinite(Number(params.concurrencyLimit)) &&
+        Number(params.concurrencyLimit) > 0
+          ? Number(params.concurrencyLimit)
+          : undefined,
+      estimatedWaitMs:
+        Number.isFinite(Number(params.estimatedWaitMs)) &&
+        Number(params.estimatedWaitMs) >= 0
+          ? Number(params.estimatedWaitMs)
+          : undefined,
+    },
+    label
+  );
+}
+
+export type AgentProgressStreamPayload = {
+  stage: "planning" | "clarify" | "executing" | "completed" | "failed";
+  currentStep:
+    | "lock_target"
+    | "analyze"
+    | "select_tool"
+    | "execute"
+    | "finalize";
+  title?: string;
+  message?: string;
+  toolName?: string;
+  capability?: string;
+};
+
+export function writeAgentProgressChunk(
+  writer: StreamWriter,
+  payload: AgentProgressStreamPayload,
+  label: string
+) {
+  writeStructuredDataChunk(
+    writer,
+    "data-agentProgress",
+    {
+      stage: payload.stage,
+      currentStep: payload.currentStep,
+      title: String(payload.title || "").trim() || undefined,
+      message: String(payload.message || "").trim() || undefined,
+      toolName: String(payload.toolName || "").trim() || undefined,
+      capability: String(payload.capability || "").trim() || undefined,
+    },
+    label
+  );
+}
+
+export function writeCanvasMediaChunk(
+  writer: StreamWriter,
+  params: {
+    messageId: string;
+    text?: string;
+    imageUrls?: string[];
+    videoUrls?: string[];
+    prompt?: string | null;
+    sourceImageUrls?: string[] | null;
+    agentPresetId?: string | null;
+    agentPresetName?: string | null;
+    agentCategoryId?: string | null;
+    agentCategoryName?: string | null;
+    agentExecutionSnapshotId?: string | null;
+  },
+  label: string
+) {
+  const imageUrls = Array.isArray(params.imageUrls)
+    ? params.imageUrls
+    : extractImageUrlsFromText(String(params.text || ""));
+  const videoUrls = Array.isArray(params.videoUrls) ? params.videoUrls : [];
+  const normalizedImageUrls = Array.from(
+    new Set(
+      imageUrls
+        .map((url) => String(url || "").trim())
+        .filter((url) => /^https?:\/\//i.test(url))
+    )
+  );
+  const normalizedVideoUrls = Array.from(
+    new Set(
+      videoUrls
+        .map((url) => String(url || "").trim())
+        .filter((url) => /^https?:\/\//i.test(url))
+    )
+  );
+
+  if (normalizedImageUrls.length === 0 && normalizedVideoUrls.length === 0) {
+    return;
+  }
+
+  writeStructuredDataChunk(
+    writer,
+    "data-canvasMedia",
+    {
+      messageId: params.messageId,
+      imageUrls: normalizedImageUrls,
+      videoUrls: normalizedVideoUrls,
+      prompt: String(params.prompt || "").trim() || undefined,
+      sourceImageUrls: Array.isArray(params.sourceImageUrls)
+        ? params.sourceImageUrls
+            .map((url) => String(url || "").trim())
+            .filter((url) => /^https?:\/\//i.test(url))
+        : [],
+      agentPresetId: String(params.agentPresetId || "").trim() || undefined,
+      agentPresetName: String(params.agentPresetName || "").trim() || undefined,
+      agentCategoryId: String(params.agentCategoryId || "").trim() || undefined,
+      agentCategoryName: String(params.agentCategoryName || "").trim() || undefined,
+      agentExecutionSnapshotId:
+        String(params.agentExecutionSnapshotId || "").trim() || undefined,
+    },
+    label
+  );
+}
+
+type AgentTargetLockRefPreview = {
+  url: string;
+  title?: string;
+  nodeId?: string;
+  assetId?: string;
+  source: ResolvedImageRef["source"];
+  role: ResolvedImageRef["role"];
+  isSelected?: boolean;
+  positionLabel?: string;
+};
+
+export type AgentTargetLockStreamPayload = {
+  stage: "locked" | "clarify" | "unresolved";
+  resolutionMode: ResolvedTargetAssets["resolutionMode"];
+  confidence: number;
+  reason: string;
+  needsClarification: boolean;
+  clarificationMessage?: string;
+  targetCount: number;
+  candidateCount: number;
+  targets: AgentTargetLockRefPreview[];
+  candidates: AgentTargetLockRefPreview[];
+};
+
+function sortTargetLockRefsForCanvasOrdering(refs: ResolvedImageRef[]) {
+  return [...refs].sort((left, right) => {
+    const leftY = Number(left.y ?? 0);
+    const rightY = Number(right.y ?? 0);
+    if (Math.abs(leftY - rightY) > 12) {
+      return leftY - rightY;
+    }
+    return Number(left.x ?? 0) - Number(right.x ?? 0);
+  });
+}
+
+function getTargetLockPositionLabel(
+  ref: ResolvedImageRef,
+  refs: ResolvedImageRef[]
+): string {
+  if (refs.length <= 1) return "中间";
+  const xs = refs.map((item) => Number(item.x ?? 0));
+  const ys = refs.map((item) => Number(item.y ?? 0));
+  const minX = Math.min(...xs);
+  const maxX = Math.max(...xs);
+  const minY = Math.min(...ys);
+  const maxY = Math.max(...ys);
+  const spanX = Math.max(1, maxX - minX);
+  const spanY = Math.max(1, maxY - minY);
+  const relX = (Number(ref.x ?? 0) - minX) / spanX;
+  const relY = (Number(ref.y ?? 0) - minY) / spanY;
+
+  const horizontal = relX <= 0.33 ? "左" : relX >= 0.66 ? "右" : "中";
+  const vertical = relY <= 0.33 ? "上" : relY >= 0.66 ? "下" : "中";
+
+  if (horizontal === "中" && vertical === "中") return "中间";
+  return `${vertical}${horizontal}`;
+}
+
+function serializeAgentTargetLockRefs(refs: ResolvedImageRef[]) {
+  const orderedRefs = sortTargetLockRefsForCanvasOrdering(refs).slice(0, 4);
+  return orderedRefs.map((ref) => ({
+    url: ref.url,
+    title: String(ref.title || "").trim() || undefined,
+    nodeId: ref.nodeId,
+    assetId: ref.assetId,
+    source: ref.source,
+    role: ref.role,
+    isSelected: ref.isSelected === true,
+    positionLabel: getTargetLockPositionLabel(ref, orderedRefs),
+  })) satisfies AgentTargetLockRefPreview[];
+}
+
+export function buildAgentTargetLockPayload(params: {
+  requestTargetResolution: ResolvedTargetAssets;
+  requestResolvedMediaInput: ResolvedChatMediaInput;
+  needsClarification: boolean;
+  clarificationMessage?: string;
+}): AgentTargetLockStreamPayload {
+  const stage = params.needsClarification
+    ? "clarify"
+    : params.requestTargetResolution.targetRefs.length > 0
+      ? "locked"
+      : "unresolved";
+
+  return {
+    stage,
+    resolutionMode: params.requestTargetResolution.resolutionMode,
+    confidence: Number(params.requestTargetResolution.confidence || 0),
+    reason: params.requestTargetResolution.reason,
+    needsClarification: params.needsClarification,
+    clarificationMessage: params.clarificationMessage?.trim() || undefined,
+    targetCount: params.requestTargetResolution.targetRefs.length,
+    candidateCount: params.requestTargetResolution.candidateRefs.length,
+    targets: serializeAgentTargetLockRefs(params.requestTargetResolution.targetRefs),
+    candidates: serializeAgentTargetLockRefs(
+      params.requestTargetResolution.candidateRefs.length > 0
+        ? params.requestTargetResolution.candidateRefs
+        : params.requestResolvedMediaInput.imageRefs
+    ),
+  };
+}
+
+export function writeAgentTargetLockChunk(
+  writer: StreamWriter,
+  payload: AgentTargetLockStreamPayload,
+  label: string
+) {
+  writeStructuredDataChunk(writer, "data-agentTargetLock", payload, label);
+}
+
+export function createSseResponse(stream: ReadableStream) {
+  return new Response(stream.pipeThrough(new JsonToSseTransformStream()), {
+    headers: {
+      "Content-Type": "text/event-stream; charset=utf-8",
+      "Cache-Control": "no-cache, no-transform",
+      Connection: "keep-alive",
+      "X-Accel-Buffering": "no",
+    },
+  });
+}
+
+export function startStreamKeepalive(
+  writer: StreamWriter,
+  label: string,
+  intervalMs = 15_000
+) {
+  const timer = setInterval(() => {
+    safeWriteStreamChunk(
+      writer,
+      {
+        type: "data-keepalive",
+        data: JSON.stringify({ ts: Date.now(), label }),
+      },
+      `${label}:keepalive`
+    );
+  }, intervalMs);
+
+  return () => clearInterval(timer);
+}
+
+export async function runBoundedParallel<T>(
+  items: T[],
+  workerCount: number,
+  worker: (item: T, index: number) => Promise<void>
+) {
+  const maxWorkers = Math.max(1, Math.min(workerCount, items.length));
+  let cursor = 0;
+  let firstError: unknown = null;
+
+  const workers = Array.from({ length: maxWorkers }, async () => {
+    while (cursor < items.length) {
+      const index = cursor;
+      cursor += 1;
+      if (firstError) {
+        return;
+      }
+
+      try {
+        await worker(items[index]!, index);
+      } catch (error) {
+        firstError = firstError || error;
+      }
+    }
+  });
+
+  await Promise.all(workers);
+
+  if (firstError) {
+    throw firstError;
+  }
+}
diff --git a/app/(chat)/api/chat/route.ts b/app/(chat)/api/chat/route.ts
index 69fb07ea3..69e2397e9 100644
--- a/app/(chat)/api/chat/route.ts
+++ b/app/(chat)/api/chat/route.ts
@@ -3,7 +3,6 @@ import {
   convertToModelMessages,
   createUIMessageStream,
   generateText,
-  JsonToSseTransformStream,
   smoothStream,
   stepCountIs,
   streamText,
@@ -120,7 +119,6 @@ import { resolveChatMediaInput } from "@/lib/ai/context-memory/media-input";
 import { resolveTargetAssets } from "@/lib/ai/context-memory/target-resolution";
 import type {
   ResolvedChatMediaInput,
-  ResolvedImageRef,
   ResolvedTargetAssets,
 } from "@/lib/ai/context-memory/types";
 import { ChatSDKError } from "@/lib/errors";
@@ -249,6 +247,20 @@ import type {
 import { generateTitleFromUserMessage } from "../../actions";
 import { type PostRequestBody, postRequestBodySchema } from "./schema";
 import { isAiModelMultimodal } from "@/lib/db/ai-model-flags";
+import {
+  buildAgentTargetLockPayload,
+  createSseResponse,
+  runBoundedParallel,
+  safeWriteStreamChunk,
+  startStreamKeepalive,
+  type StreamWriter,
+  writeAgentProgressChunk,
+  writeAgentTargetLockChunk,
+  writeAssistantTextChunk,
+  writeCanvasMediaChunk,
+  writeImageGenerationStatusChunk,
+  writeProtocolDebugChunk,
+} from "./_lib/stream";
 
 const AGENT_REPLACEMENT_PARALLEL_WORKER_COUNT = Math.max(
   1,
@@ -412,402 +424,6 @@ function injectOptimizedPromptSection(params: {
   return `${message.trim()}\n\n${optimizedPromptSection}`;
 }
 
-type StreamWriter = {
-  write: (chunk: any) => void;
-};
-
-function safeWriteStreamChunk(writer: StreamWriter, chunk: any, label: string): boolean {
-  try {
-    writer.write(chunk);
-    return true;
-  } catch (error) {
-    console.warn(`[Chat API] Stream write skipped (${label})`, error);
-    return false;
-  }
-}
-
-function writeAssistantTextChunk(
-  writer: StreamWriter,
-  text: string,
-  label: string,
-  messageId = generateUUID(),
-) {
-  safeWriteStreamChunk(
-    writer,
-    {
-      type: "data-appendMessage",
-      data: JSON.stringify({
-        id: messageId,
-        role: "assistant",
-        parts: [{ type: "text", text }],
-      }),
-    },
-    label,
-  );
-  return messageId;
-}
-
-function writeStructuredDataChunk(
-  writer: StreamWriter,
-  type: string,
-  data: unknown,
-  label: string,
-) {
-  safeWriteStreamChunk(
-    writer,
-    {
-      type,
-      data: JSON.stringify(data),
-    },
-    label,
-  );
-}
-
-function writeProtocolDebugChunk(
-  writer: StreamWriter,
-  enabled: boolean,
-  data: unknown,
-  label: string,
-) {
-  if (!enabled) return;
-  writeStructuredDataChunk(writer, "data-protocolDebug", data, label);
-}
-
-function normalizeImageLoadingProviderType(providerType?: string | null): string {
-  const normalized = String(providerType || "").trim().toLowerCase();
-  if (normalized === "gemini-image" || normalized === "huanke-gemini") {
-    return "gemini";
-  }
-  if (
-    normalized === "alibaba-image" ||
-    normalized === "bfl-image" ||
-    normalized === "ruxa-image" ||
-    normalized === "fal-image" ||
-    normalized === "openai-image" ||
-    normalized === "stepfun-image" ||
-    normalized === "midjourney" ||
-    normalized === "runway" ||
-    normalized === "krea" ||
-    normalized === "volcano-vision" ||
-    normalized === "gemini"
-  ) {
-    return normalized;
-  }
-  return "alibaba-image";
-}
-
-function writeImageGenerationStatusChunk(
-  writer: StreamWriter,
-  params: {
-    phase: "queued" | "processing" | "finalizing" | "failed" | "completed";
-    providerType?: string | null;
-    modelName?: string | null;
-    imageCount?: number | null;
-    queuePosition?: number | null;
-    sameModelRunningCount?: number | null;
-    concurrencyLimit?: number | null;
-    estimatedWaitMs?: number | null;
-  },
-  label: string,
-) {
-  writeStructuredDataChunk(
-    writer,
-    "data-imageGenerationStatus",
-    {
-      phase: params.phase,
-      providerType: normalizeImageLoadingProviderType(params.providerType),
-      modelName: String(params.modelName || "").trim() || undefined,
-      imageCount:
-        Number.isFinite(Number(params.imageCount)) && Number(params.imageCount) > 0
-          ? Number(params.imageCount)
-          : undefined,
-      queuePosition:
-        Number.isFinite(Number(params.queuePosition)) && Number(params.queuePosition) >= 0
-          ? Number(params.queuePosition)
-          : undefined,
-      sameModelRunningCount:
-        Number.isFinite(Number(params.sameModelRunningCount)) &&
-        Number(params.sameModelRunningCount) >= 0
-          ? Number(params.sameModelRunningCount)
-          : undefined,
-      concurrencyLimit:
-        Number.isFinite(Number(params.concurrencyLimit)) &&
-        Number(params.concurrencyLimit) > 0
-          ? Number(params.concurrencyLimit)
-          : undefined,
-      estimatedWaitMs:
-        Number.isFinite(Number(params.estimatedWaitMs)) && Number(params.estimatedWaitMs) >= 0
-          ? Number(params.estimatedWaitMs)
-          : undefined,
-    },
-    label,
-  );
-}
-
-type AgentProgressStreamPayload = {
-  stage: "planning" | "clarify" | "executing" | "completed" | "failed";
-  currentStep:
-    | "lock_target"
-    | "analyze"
-    | "select_tool"
-    | "execute"
-    | "finalize";
-  title?: string;
-  message?: string;
-  toolName?: string;
-  capability?: string;
-};
-
-function writeAgentProgressChunk(
-  writer: StreamWriter,
-  payload: AgentProgressStreamPayload,
-  label: string,
-) {
-  writeStructuredDataChunk(
-    writer,
-    "data-agentProgress",
-    {
-      stage: payload.stage,
-      currentStep: payload.currentStep,
-      title: String(payload.title || "").trim() || undefined,
-      message: String(payload.message || "").trim() || undefined,
-      toolName: String(payload.toolName || "").trim() || undefined,
-      capability: String(payload.capability || "").trim() || undefined,
-    },
-    label,
-  );
-}
-
-function writeCanvasMediaChunk(
-  writer: StreamWriter,
-  params: {
-    messageId: string;
-    text?: string;
-    imageUrls?: string[];
-    videoUrls?: string[];
-    prompt?: string | null;
-    sourceImageUrls?: string[] | null;
-    agentPresetId?: string | null;
-    agentPresetName?: string | null;
-    agentCategoryId?: string | null;
-    agentCategoryName?: string | null;
-    agentExecutionSnapshotId?: string | null;
-  },
-  label: string,
-) {
-  const imageUrls = Array.isArray(params.imageUrls)
-    ? params.imageUrls
-    : extractImageUrlsFromText(String(params.text || ""));
-  const videoUrls = Array.isArray(params.videoUrls) ? params.videoUrls : [];
-  const normalizedImageUrls = Array.from(
-    new Set(
-      imageUrls
-        .map((url) => String(url || "").trim())
-        .filter((url) => /^https?:\/\//i.test(url)),
-    ),
-  );
-  const normalizedVideoUrls = Array.from(
-    new Set(
-      videoUrls
-        .map((url) => String(url || "").trim())
-        .filter((url) => /^https?:\/\//i.test(url)),
-    ),
-  );
-
-  if (normalizedImageUrls.length === 0 && normalizedVideoUrls.length === 0) {
-    return;
-  }
-
-  writeStructuredDataChunk(
-    writer,
-    "data-canvasMedia",
-    {
-      messageId: params.messageId,
-      imageUrls: normalizedImageUrls,
-      videoUrls: normalizedVideoUrls,
-      prompt: String(params.prompt || "").trim() || undefined,
-      sourceImageUrls: Array.isArray(params.sourceImageUrls)
-        ? params.sourceImageUrls
-            .map((url) => String(url || "").trim())
-            .filter((url) => /^https?:\/\//i.test(url))
-        : [],
-      agentPresetId: String(params.agentPresetId || "").trim() || undefined,
-      agentPresetName: String(params.agentPresetName || "").trim() || undefined,
-      agentCategoryId: String(params.agentCategoryId || "").trim() || undefined,
-      agentCategoryName: String(params.agentCategoryName || "").trim() || undefined,
-      agentExecutionSnapshotId:
-        String(params.agentExecutionSnapshotId || "").trim() || undefined,
-    },
-    label,
-  );
-}
-
-type AgentTargetLockRefPreview = {
-  url: string;
-  title?: string;
-  nodeId?: string;
-  assetId?: string;
-  source: ResolvedImageRef["source"];
-  role: ResolvedImageRef["role"];
-  isSelected?: boolean;
-  positionLabel?: string;
-};
-
-type AgentTargetLockStreamPayload = {
-  stage: "locked" | "clarify" | "unresolved";
-  resolutionMode: ResolvedTargetAssets["resolutionMode"];
-  confidence: number;
-  reason: string;
-  needsClarification: boolean;
-  clarificationMessage?: string;
-  targetCount: number;
-  candidateCount: number;
-  targets: AgentTargetLockRefPreview[];
-  candidates: AgentTargetLockRefPreview[];
-};
-
-function sortTargetLockRefsForCanvasOrdering(refs: ResolvedImageRef[]) {
-  return [...refs].sort((left, right) => {
-    const leftY = Number(left.y ?? 0);
-    const rightY = Number(right.y ?? 0);
-    if (Math.abs(leftY - rightY) > 12) {
-      return leftY - rightY;
-    }
-    return Number(left.x ?? 0) - Number(right.x ?? 0);
-  });
-}
-
-function getTargetLockPositionLabel(ref: ResolvedImageRef, refs: ResolvedImageRef[]): string {
-  if (refs.length <= 1) return "中间";
-  const xs = refs.map((item) => Number(item.x ?? 0));
-  const ys = refs.map((item) => Number(item.y ?? 0));
-  const minX = Math.min(...xs);
-  const maxX = Math.max(...xs);
-  const minY = Math.min(...ys);
-  const maxY = Math.max(...ys);
-  const spanX = Math.max(1, maxX - minX);
-  const spanY = Math.max(1, maxY - minY);
-  const relX = (Number(ref.x ?? 0) - minX) / spanX;
-  const relY = (Number(ref.y ?? 0) - minY) / spanY;
-
-  const horizontal = relX <= 0.33 ? "左" : relX >= 0.66 ? "右" : "中";
-  const vertical = relY <= 0.33 ? "上" : relY >= 0.66 ? "下" : "中";
-
-  if (horizontal === "中" && vertical === "中") return "中间";
-  return `${vertical}${horizontal}`;
-}
-
-function serializeAgentTargetLockRefs(refs: ResolvedImageRef[]) {
-  const orderedRefs = sortTargetLockRefsForCanvasOrdering(refs).slice(0, 4);
-  return orderedRefs.map((ref) => ({
-    url: ref.url,
-    title: String(ref.title || "").trim() || undefined,
-    nodeId: ref.nodeId,
-    assetId: ref.assetId,
-    source: ref.source,
-    role: ref.role,
-    isSelected: ref.isSelected === true,
-    positionLabel: getTargetLockPositionLabel(ref, orderedRefs),
-  })) satisfies AgentTargetLockRefPreview[];
-}
-
-function buildAgentTargetLockPayload(params: {
-  requestTargetResolution: ResolvedTargetAssets;
-  requestResolvedMediaInput: ResolvedChatMediaInput;
-  needsClarification: boolean;
-  clarificationMessage?: string;
-}): AgentTargetLockStreamPayload {
-  const stage =
-    params.needsClarification
-      ? "clarify"
-      : params.requestTargetResolution.targetRefs.length > 0
-        ? "locked"
-        : "unresolved";
-
-  return {
-    stage,
-    resolutionMode: params.requestTargetResolution.resolutionMode,
-    confidence: Number(params.requestTargetResolution.confidence || 0),
-    reason: params.requestTargetResolution.reason,
-    needsClarification: params.needsClarification,
-    clarificationMessage: params.clarificationMessage?.trim() || undefined,
-    targetCount: params.requestTargetResolution.targetRefs.length,
-    candidateCount: params.requestTargetResolution.candidateRefs.length,
-    targets: serializeAgentTargetLockRefs(params.requestTargetResolution.targetRefs),
-    candidates: serializeAgentTargetLockRefs(
-      params.requestTargetResolution.candidateRefs.length > 0
-        ? params.requestTargetResolution.candidateRefs
-        : params.requestResolvedMediaInput.imageRefs,
-    ),
-  };
-}
-
-function writeAgentTargetLockChunk(
-  writer: StreamWriter,
-  payload: AgentTargetLockStreamPayload,
-  label: string,
-) {
-  writeStructuredDataChunk(writer, "data-agentTargetLock", payload, label);
-}
-
-function createSseResponse(stream: ReadableStream) {
-  return new Response(stream.pipeThrough(new JsonToSseTransformStream()), {
-    headers: {
-      "Content-Type": "text/event-stream; charset=utf-8",
-      "Cache-Control": "no-cache, no-transform",
-      Connection: "keep-alive",
-      "X-Accel-Buffering": "no",
-    },
-  });
-}
-
-function startStreamKeepalive(writer: StreamWriter, label: string, intervalMs = 15000) {
-  const timer = setInterval(() => {
-    safeWriteStreamChunk(
-      writer,
-      {
-        type: "data-keepalive",
-        data: JSON.stringify({ ts: Date.now(), label }),
-      },
-      `${label}:keepalive`,
-    );
-  }, intervalMs);
-
-  return () => clearInterval(timer);
-}
-
-async function runBoundedParallel<T>(
-  items: T[],
-  workerCount: number,
-  worker: (item: T, index: number) => Promise<void>
-) {
-  const maxWorkers = Math.max(1, Math.min(workerCount, items.length));
-  let cursor = 0;
-  let firstError: unknown = null;
-
-  const workers = Array.from({ length: maxWorkers }, async () => {
-    while (cursor < items.length) {
-      const index = cursor;
-      cursor += 1;
-      if (firstError) {
-        return;
-      }
-
-      try {
-        await worker(items[index]!, index);
-      } catch (error) {
-        firstError = firstError || error;
-      }
-    }
-  });
-
-  await Promise.all(workers);
-
-  if (firstError) {
-    throw firstError;
-  }
-}
-
 type VideoModeType = "text-to-video" | "first-frame" | "first-last-frame" | "reference-images";
 
 function isVideoProviderType(