fix: correct context size for deepseek/deepseek-chat-v3.1:free model

- OpenRouter incorrectly reports 64k context for deepseek-chat-v3.1:free
- Actual context size should be 163.8k tokens as per provider documentation
- Added special handling in parseOpenRouterModel to override the incorrect value
- Added test case to verify the fix

Fixes #7952

Author: roomote

src/api/providers/fetchers/__tests__/openrouter.spec.ts

@@ -337,6 +337,36 @@ describe("OpenRouter API", () => {
 			expect(result.contextWindow).toBe(128000)
 		})
 
+		it("sets deepseek-chat-v3.1:free model to 163.8k context window", () => {
+			const mockModel = {
+				name: "DeepSeek Chat V3.1 Free",
+				description: "DeepSeek Chat V3.1 Free model",
+				context_length: 65536, // OpenRouter incorrectly reports 64k
+				max_completion_tokens: null,
+				pricing: {
+					prompt: "0",
+					completion: "0",
+					input_cache_write: undefined,
+					input_cache_read: undefined,
+				},
+			}
+
+			const result = parseOpenRouterModel({
+				id: "deepseek/deepseek-chat-v3.1:free",
+				model: mockModel,
+				inputModality: ["text"],
+				outputModality: ["text"],
+				maxTokens: null,
+				supportedParameters: ["temperature", "top_p", "max_tokens"],
+			})
+
+			// Should override the incorrect 64k context with 163.8k
+			expect(result.contextWindow).toBe(163840)
+			// maxTokens should be recalculated based on corrected context
+			expect(result.maxTokens).toBe(Math.ceil(163840 * 0.2))
+			expect(result.description).toBe("DeepSeek Chat V3.1 Free model")
+		})
+
 		it("filters out image generation models", () => {
 			const mockImageModel = {
 				name: "Image Model",

src/api/providers/fetchers/openrouter.ts

@@ -263,5 +263,13 @@ export const parseOpenRouterModel = ({
 		modelInfo.maxTokens = 32768
 	}
 
+	// Set deepseek-chat-v3.1:free model to correct context size
+	// OpenRouter reports 64k but the actual context is 163.8k tokens
+	if (id === "deepseek/deepseek-chat-v3.1:free") {
+		modelInfo.contextWindow = 163840 // 163.8k tokens
+		// Recalculate maxTokens based on the corrected context window
+		modelInfo.maxTokens = maxTokens || Math.ceil(163840 * 0.2)
+	}
+
 	return modelInfo
 }