diff --git a/packages/ai/src/protocols/openai-chat.ts b/packages/ai/src/protocols/openai-chat.ts
index b3ce1d3f66c9..d257581bca23 100644
--- a/packages/ai/src/protocols/openai-chat.ts
+++ b/packages/ai/src/protocols/openai-chat.ts
@@ -858,12 +858,7 @@ const mapFinishReason = Effect.fnUntraced(function* (event: OpenAIChatEvent, rea
     case "tool_calls":
       return "tool-calls" as const
     default:
-      return yield* new AIError({
-        reason: new UnknownProviderError({
-          message: `Provider finish_reason: ${reason}`,
-          body: ProviderShared.encodeJson(event),
-        }),
-      })
+      return "unknown" as const
   }
 })
 
diff --git a/packages/ai/test/provider/openai-chat.test.ts b/packages/ai/test/provider/openai-chat.test.ts
index 43d1ded6c6ac..c0c906e618e6 100644
--- a/packages/ai/test/provider/openai-chat.test.ts
+++ b/packages/ai/test/provider/openai-chat.test.ts
@@ -2072,47 +2072,14 @@ describe("OpenAI Chat route", () => {
     }),
   )
 
-  it.effect("rejects unknown finish reasons without finalizing streamed tool calls", () =>
+  it.effect("maps unknown finish reasons to unknown and keeps the raw value", () =>
     Effect.gen(function* () {
-      const body = sseEvents(
-        deltaChunk({
-          tool_calls: [{ index: 0, id: "call_1", function: { name: "lookup", arguments: '{"query":"weather"' } }],
-        }),
-        deltaChunk({}, "future_reason"),
-      )
-      const events = yield* Ref.make<ReadonlyArray<LLMEvent>>([])
-      const error = yield* LLMClient.stream(
-        LLMRequest.update(request, {
-          tools: [ToolDefinition.make({ name: "lookup", description: "Lookup data", inputSchema: { type: "object" } })],
-        }),
-      ).pipe(
-        Stream.tap((event) => Ref.update(events, (current) => [...current, event])),
-        Stream.runDrain,
-        Effect.provide(fixedResponse(body)),
-        Effect.flip,
+      const response = yield* LLMClient.generate(request).pipe(
+        Effect.provide(fixedResponse(sseEvents(deltaChunk({ content: "Hello" }), deltaChunk({}, "future_reason")))),
       )
 
-      expect(error).toMatchObject({
-        reason: { _tag: "UnknownProvider" },
-        message: "Provider finish_reason: future_reason",
-      })
-      expect(yield* Ref.get(events)).toEqual([
-        { type: "step-start", index: 0 },
-        {
-          type: "tool-input-start",
-          id: "call_1",
-          name: "lookup",
-          providerExecuted: undefined,
-          providerMetadata: undefined,
-        },
-        {
-          type: "tool-input-delta",
-          id: "call_1",
-          name: "lookup",
-          text: '{"query":"weather"',
-          input: { query: "weather" },
-        },
-      ])
+      expect(response.text).toBe("Hello")
+      expect(response.finishReason).toEqual({ normalized: "unknown", raw: "future_reason" })
     }),
   )
 
diff --git a/packages/ai/test/provider/openai-compatible-chat.test.ts b/packages/ai/test/provider/openai-compatible-chat.test.ts
index 2f26ae52af16..368a8d5ed7f4 100644
--- a/packages/ai/test/provider/openai-compatible-chat.test.ts
+++ b/packages/ai/test/provider/openai-compatible-chat.test.ts
@@ -572,16 +572,8 @@ describe("OpenAI-compatible Chat route", () => {
 
       const unknown = yield* LLMClient.generate(request).pipe(
         Effect.provide(fixedResponse(sseEvents(deltaChunk({}, "future_reason")))),
-        Effect.flip,
       )
-      expect(unknown).toMatchObject({
-        reason: { _tag: "UnknownProvider" },
-        message: "Provider finish_reason: future_reason",
-      })
-      expect(decodeJson(unknown.reason.body ?? "")).toMatchObject({
-        id: "chatcmpl_fixture",
-        choices: [{ finish_reason: "future_reason" }],
-      })
+      expect(unknown.finishReason).toEqual({ normalized: "unknown", raw: "future_reason" })
     }),
   )