chore(deps-dev): bump @biomejs/biome from 2.4.12 to 2.5.6

package.json

@@ -40,7 +40,7 @@
     }
   },
   "devDependencies": {
-    "@biomejs/biome": "2.4.12",
+    "@biomejs/biome": "2.5.6",
     "@changesets/cli": "^2.31.0",
     "@types/node": "^25.9.3",
     "tsx": "^4.21.1",

packages/cea/package.json

@@ -59,7 +59,7 @@
   "devDependencies": {
     "@ai-sdk/provider": "^4.0.0",
     "@ai-sdk/provider-utils": "^4.0.23",
-    "@biomejs/biome": "2.4.12",
+    "@biomejs/biome": "2.5.6",
     "@types/node": "^25.9.3",
     "tsx": "^4.21.1",
     "typescript": "^6.0.3",

packages/cea/src/entrypoints/main.ts

@@ -209,8 +209,7 @@ const collectReadCallPathMap = (
     for (const part of content) {
       const record = toRecord(part);
       if (
-        !record ||
-        record.type !== "tool-call" ||
+        record?.type !== "tool-call" ||
         record.toolName !== "read_file" ||
         typeof record.toolCallId !== "string"
       ) {
@@ -233,7 +232,7 @@ const trackReadResultPart = (
   readCallPaths: Map<string, string>
 ): void => {
   const record = toRecord(part);
-  if (!record || record.type !== "tool-result") {
+  if (record?.type !== "tool-result") {
     return;
   }
 

packages/cea/src/middleware/index.ts

@@ -1,18 +1,24 @@
-import type { LanguageModelV3Middleware } from "@ai-sdk/provider";
+import type { LanguageModelV4Middleware } from "@ai-sdk/provider";
 import {
   hermesToolMiddleware,
   morphXmlToolMiddleware,
   qwen3CoderToolMiddleware,
 } from "@ai-sdk-tool/parser";
+import type { LanguageModelMiddleware } from "ai";
 import type { ToolFallbackMode } from "../tool-fallback-mode";
 import { trimLeadingNewlinesMiddleware as trimMiddleware } from "./trim-leading-newlines";
 
 export interface MiddlewareOptions {
   toolFallbackMode: ToolFallbackMode;
 }
 
+/**
+ * Parser/tool middlewares are LanguageModelV4Middleware; ai@6 wrapLanguageModel
+ * still types its parameter as LanguageModelV3Middleware. Runtime only uses the
+ * hook functions, so we cast at the boundary.
+ */
 const TOOL_FALLBACK_MIDDLEWARES: Readonly<
-  Record<Exclude<ToolFallbackMode, "disable">, LanguageModelV3Middleware>
+  Record<Exclude<ToolFallbackMode, "disable">, LanguageModelV4Middleware>
 > = {
   morphxml: morphXmlToolMiddleware,
   hermes: hermesToolMiddleware,
@@ -21,12 +27,12 @@ const TOOL_FALLBACK_MIDDLEWARES: Readonly<
 
 export function buildMiddlewares(
   options: MiddlewareOptions
-): LanguageModelV3Middleware[] {
-  const middlewares: LanguageModelV3Middleware[] = [trimMiddleware];
+): LanguageModelMiddleware[] {
+  const middlewares: LanguageModelV4Middleware[] = [trimMiddleware];
 
   if (options.toolFallbackMode !== "disable") {
     middlewares.push(TOOL_FALLBACK_MIDDLEWARES[options.toolFallbackMode]);
   }
 
-  return middlewares;
+  return middlewares as unknown as LanguageModelMiddleware[];
 }

packages/cea/src/middleware/trim-leading-newlines.ts

@@ -1,14 +1,14 @@
 import type {
-  LanguageModelV3Content,
-  LanguageModelV3Middleware,
-  LanguageModelV3StreamPart,
+  LanguageModelV4Content,
+  LanguageModelV4Middleware,
+  LanguageModelV4StreamPart,
 } from "@ai-sdk/provider";
 
 const LEADING_NEWLINES = /^\n+/;
 
 function trimContentLeadingNewlines(
-  content: LanguageModelV3Content[]
-): LanguageModelV3Content[] {
+  content: LanguageModelV4Content[]
+): LanguageModelV4Content[] {
   if (content.length === 0) {
     return content;
   }
@@ -24,8 +24,8 @@ function trimContentLeadingNewlines(
   return content;
 }
 
-export const trimLeadingNewlinesMiddleware: LanguageModelV3Middleware = {
-  specificationVersion: "v3",
+export const trimLeadingNewlinesMiddleware: LanguageModelV4Middleware = {
+  specificationVersion: "v4",
   wrapGenerate: async ({ doGenerate }) => {
     const result = await doGenerate();
     return {
@@ -40,8 +40,8 @@ export const trimLeadingNewlinesMiddleware: LanguageModelV3Middleware = {
     let hasTrimmed = false;
 
     const transformStream = new TransformStream<
-      LanguageModelV3StreamPart,
-      LanguageModelV3StreamPart
+      LanguageModelV4StreamPart,
+      LanguageModelV4StreamPart
     >({
       transform(chunk, controller) {
         if (chunk.type === "text-delta" && !hasTrimmed) {

packages/harness/src/checkpoint-history.ts

@@ -1472,8 +1472,7 @@ export class CheckpointHistory {
     message: CheckpointMessage | undefined
   ): boolean {
     if (
-      !message ||
-      message.message.role !== "assistant" ||
+      message?.message.role !== "assistant" ||
       typeof message.message.content !== "string"
     ) {
       return false;
@@ -2594,7 +2593,7 @@ export class CheckpointHistory {
       if (current && hasToolCalls(current.message)) {
         const nextIndex = index + 1;
         const next = messages[nextIndex];
-        if (!next || next.message.role !== "tool") {
+        if (next?.message.role !== "tool") {
           messages.splice(index, 1);
           continue;
         }

packages/harness/src/tool-pruning.test.ts

@@ -374,8 +374,11 @@ describe("pruneToolOutputs", () => {
         const nextMessage = result.messages[i + 1]?.message;
         expect(nextMessage?.role).toBe("tool");
         expect(Array.isArray(nextMessage?.content)).toBe(true);
+        if (!(nextMessage && Array.isArray(nextMessage.content))) {
+          continue;
+        }
 
-        const matchingResult = (nextMessage?.content as any[]).find(
+        const matchingResult = (nextMessage.content as any[]).find(
           (part) =>
             part.type === "tool-result" &&
             part.toolCallId === toolCall.toolCallId

packages/minimal-agent/index.ts

@@ -179,7 +179,7 @@ try {
       },
       preprocessCommand: async (input, hooks) => {
         const parsed = parseCommand(input);
-        if (!parsed || parsed.name !== "reasoning" || parsed.args.length > 0) {
+        if (parsed?.name !== "reasoning" || parsed.args.length > 0) {
           return input;
         }
         const selected = await showReasoningSelector(hooks);

packages/tui/src/stream-handlers.test.ts

@@ -421,14 +421,13 @@ const FLAGS_ALL_OFF: PiTuiRenderFlags = {
 describe("isVisibleStreamPart — reasoning parts must never trigger first-visible", () => {
   // Regression: if reasoning parts become visible, clearStreamingLoader fires
   // on reasoning-start and the "Thinking..." spinner label is lost.
-  it.each([
-    "reasoning-start",
-    "reasoning-delta",
-    "reasoning-end",
-  ] as const)("%s is invisible regardless of flags", (type) => {
-    expect(isVisibleStreamPart({ type } as never, FLAGS_ALL_ON)).toBe(false);
-    expect(isVisibleStreamPart({ type } as never, FLAGS_ALL_OFF)).toBe(false);
-  });
+  it.each(["reasoning-start", "reasoning-delta", "reasoning-end"] as const)(
+    "%s is invisible regardless of flags",
+    (type) => {
+      expect(isVisibleStreamPart({ type } as never, FLAGS_ALL_ON)).toBe(false);
+      expect(isVisibleStreamPart({ type } as never, FLAGS_ALL_OFF)).toBe(false);
+    }
+  );
 
   it("tool-input-end is always invisible", () => {
     expect(