diff --git a/packages/ai/src/protocols/mistral-chat.ts b/packages/ai/src/protocols/mistral-chat.ts
index b1b1720f204c..99f20487341a 100644
--- a/packages/ai/src/protocols/mistral-chat.ts
+++ b/packages/ai/src/protocols/mistral-chat.ts
@@ -426,6 +426,7 @@ interface ActiveContent {
   readonly type: "text" | "reasoning"
   readonly id: string
   readonly thinking?: MistralThinkingContent
+  readonly thinkingUnits?: MistralThinkingUnit[]
 }
 
 export interface ParserState {
@@ -502,8 +503,8 @@ const closeActive = (state: ParserState, events: LLMEvent[]) => {
           state.lifecycle,
           events,
           state.active.id,
-          thinkingMetadata(state.active.thinking ?? { type: "thinking", thinking: [] }),
-          thinkingText(state.active.thinking?.thinking ?? []),
+          thinkingMetadata({ ...state.active.thinking, type: "thinking", thinking: state.active.thinkingUnits ?? [] }),
+          thinkingText(state.active.thinkingUnits ?? []),
         )
   return { ...state, lifecycle, active: undefined }
 }
@@ -524,20 +525,23 @@ const appendThinking = (state: ParserState, events: LLMEvent[], part: MistralOut
   const current = state.active?.type === "reasoning" ? state : closeActive(state, events)
   const units = thinkingUnits(part.thinking)
   const active = current.active ?? { type: "reasoning" as const, id: `reasoning-${current.nextContent}` }
+  // Keep native units out of streamed events until the block is complete.
+  const accumulated = active.thinkingUnits ?? []
+  accumulated.push(...units)
   const thinking = {
     ...active.thinking,
     ...part,
     type: "thinking" as const,
-    thinking: [...(active.thinking?.thinking ?? []), ...units],
+    thinking: [],
   }
   const text = thinkingText(units)
   return {
     ...current,
     lifecycle:
       text.length > 0
-        ? Lifecycle.reasoningDelta(current.lifecycle, events, active.id, text, thinkingMetadata(thinking))
-        : Lifecycle.reasoningStart(current.lifecycle, events, active.id, thinkingMetadata(thinking)),
-    active: { ...active, thinking },
+        ? Lifecycle.reasoningDelta(current.lifecycle, events, active.id, text)
+        : Lifecycle.reasoningStart(current.lifecycle, events, active.id),
+    active: { ...active, thinking, thinkingUnits: accumulated },
     nextContent: current.active ? current.nextContent : current.nextContent + 1,
   }
 }
diff --git a/packages/ai/test/provider/mistral-chat.test.ts b/packages/ai/test/provider/mistral-chat.test.ts
index c8e51d3cff69..fddfee4a9f58 100644
--- a/packages/ai/test/provider/mistral-chat.test.ts
+++ b/packages/ai/test/provider/mistral-chat.test.ts
@@ -303,7 +303,8 @@ describe("Mistral Chat", () => {
           fixedResponse(
             sseEvents(
               chunk({ content: [{ type: "thinking", thinking: [], marker: "empty" }] }),
-              chunk({ content: [{ type: "thinking", thinking: [{ type: "text", text: "Consider" }] }] }),
+              chunk({ content: [{ type: "thinking", thinking: [{ type: "text", text: "Con" }] }] }),
+              chunk({ content: [{ type: "thinking", thinking: [{ type: "text", text: "sider" }], closed: true }] }),
               chunk({ content: [{ type: "text", text: "Answer" }] }),
               chunk({}, "stop"),
             ),
@@ -313,6 +314,11 @@ describe("Mistral Chat", () => {
 
       expect(response.reasoning).toBe("Consider")
       expect(response.text).toBe("Answer")
+      expect(response.events.find(LLMEvent.is.reasoningStart)?.providerMetadata).toBeUndefined()
+      expect(response.events.filter(LLMEvent.is.reasoningDelta).map((event) => [event.text, event.providerMetadata])).toEqual([
+        ["Con", undefined],
+        ["sider", undefined],
+      ])
       expect(response.message.content).toEqual([
         {
           type: "reasoning",
@@ -321,8 +327,12 @@ describe("Mistral Chat", () => {
             mistral: {
               thinking: {
                 type: "thinking",
-                thinking: [{ type: "text", text: "Consider" }],
+                thinking: [
+                  { type: "text", text: "Con" },
+                  { type: "text", text: "sider" },
+                ],
                 marker: "empty",
+                closed: true,
               },
             },
           },
@@ -337,8 +347,12 @@ describe("Mistral Chat", () => {
           content: [
             {
               type: "thinking",
-              thinking: [{ type: "text", text: "Consider" }],
+              thinking: [
+                { type: "text", text: "Con" },
+                { type: "text", text: "sider" },
+              ],
               marker: "empty",
+              closed: true,
             },
             { type: "text", text: "Answer" },
           ],
@@ -357,6 +371,8 @@ describe("Mistral Chat", () => {
           ),
         ),
       )
+      expect(response.events.find(LLMEvent.is.reasoningStart)?.providerMetadata).toBeUndefined()
+      expect(response.events.filter(LLMEvent.is.reasoningDelta)).toEqual([])
       expect(response.message.content).toEqual([
         {
           type: "reasoning",