fix: map claude-sonnet-4-5 alias to full snapshot name claude-sonnet-4-5-20250929

- Add claude-sonnet-4-5-20250929 model definition to anthropic.ts
- Update AnthropicHandler to map the alias to snapshot name for API calls
- Add tests to verify the mapping works correctly
- Fixes issue where custom base URLs that require exact snapshot IDs were failing

Fixes #8545

Author: roomote

packages/types/src/providers/anthropic.ts

@@ -28,6 +28,28 @@ export const anthropicModels = {
 			},
 		],
 	},
+	"claude-sonnet-4-5-20250929": {
+		maxTokens: 64_000, // Overridden to 8k if `enableReasoningEffort` is false.
+		contextWindow: 200_000, // Default 200K, extendable to 1M with beta flag 'context-1m-2025-08-07'
+		supportsImages: true,
+		supportsComputerUse: true,
+		supportsPromptCache: true,
+		inputPrice: 3.0, // $3 per million input tokens (≤200K context)
+		outputPrice: 15.0, // $15 per million output tokens (≤200K context)
+		cacheWritesPrice: 3.75, // $3.75 per million tokens
+		cacheReadsPrice: 0.3, // $0.30 per million tokens
+		supportsReasoningBudget: true,
+		// Tiered pricing for extended context (requires beta flag 'context-1m-2025-08-07')
+		tiers: [
+			{
+				contextWindow: 1_000_000, // 1M tokens with beta flag
+				inputPrice: 6.0, // $6 per million input tokens (>200K context)
+				outputPrice: 22.5, // $22.50 per million output tokens (>200K context)
+				cacheWritesPrice: 7.5, // $7.50 per million tokens (>200K context)
+				cacheReadsPrice: 0.6, // $0.60 per million tokens (>200K context)
+			},
+		],
+	},
 	"claude-sonnet-4-20250514": {
 		maxTokens: 64_000, // Overridden to 8k if `enableReasoningEffort` is false.
 		contextWindow: 200_000, // Default 200K, extendable to 1M with beta flag 'context-1m-2025-08-07'

src/api/providers/__tests__/anthropic.spec.ts

@@ -288,5 +288,55 @@ describe("AnthropicHandler", () => {
 			expect(model.info.inputPrice).toBe(6.0)
 			expect(model.info.outputPrice).toBe(22.5)
 		})
+
+		it("should map claude-sonnet-4-5 to claude-sonnet-4-5-20250929 for API calls", async () => {
+			const handler = new AnthropicHandler({
+				apiKey: "test-api-key",
+				apiModelId: "claude-sonnet-4-5",
+			})
+
+			// Test createMessage
+			const stream = handler.createMessage("Test system", [{ role: "user", content: "Test message" }])
+
+			// Consume the stream to trigger the API call
+			for await (const chunk of stream) {
+				// Just consume the stream
+			}
+
+			// Verify the API was called with the full snapshot name
+			expect(mockCreate).toHaveBeenCalledWith(
+				expect.objectContaining({
+					model: "claude-sonnet-4-5-20250929",
+					stream: true,
+				}),
+				expect.any(Object),
+			)
+
+			// Clear mock for next test
+			mockCreate.mockClear()
+
+			// Test completePrompt
+			await handler.completePrompt("Test prompt")
+
+			// Verify the API was called with the full snapshot name
+			expect(mockCreate).toHaveBeenCalledWith(
+				expect.objectContaining({
+					model: "claude-sonnet-4-5-20250929",
+					stream: false,
+				}),
+			)
+		})
+
+		it("should handle claude-sonnet-4-5-20250929 model directly", () => {
+			const handler = new AnthropicHandler({
+				apiKey: "test-api-key",
+				apiModelId: "claude-sonnet-4-5-20250929",
+			})
+			const model = handler.getModel()
+			expect(model.id).toBe("claude-sonnet-4-5-20250929")
+			expect(model.info.maxTokens).toBe(64000)
+			expect(model.info.contextWindow).toBe(200000)
+			expect(model.info.supportsReasoningBudget).toBe(true)
+		})
 	})
 })

src/api/providers/anthropic.ts

@@ -47,14 +47,20 @@ export class AnthropicHandler extends BaseProvider implements SingleCompletionHa
 
 		// Add 1M context beta flag if enabled for Claude Sonnet 4 and 4.5
 		if (
-			(modelId === "claude-sonnet-4-20250514" || modelId === "claude-sonnet-4-5") &&
+			(modelId === "claude-sonnet-4-20250514" ||
+				modelId === "claude-sonnet-4-5" ||
+				modelId === "claude-sonnet-4-5-20250929") &&
 			this.options.anthropicBeta1MContext
 		) {
 			betas.push("context-1m-2025-08-07")
 		}
 
+		// Map the alias to the full snapshot name for API calls
+		const apiModelId = modelId === "claude-sonnet-4-5" ? "claude-sonnet-4-5-20250929" : modelId
+
 		switch (modelId) {
 			case "claude-sonnet-4-5":
+			case "claude-sonnet-4-5-20250929":
 			case "claude-sonnet-4-20250514":
 			case "claude-opus-4-1-20250805":
 			case "claude-opus-4-20250514":
@@ -83,7 +89,7 @@ export class AnthropicHandler extends BaseProvider implements SingleCompletionHa
 
 				stream = await this.client.messages.create(
 					{
-						model: modelId,
+						model: apiModelId,
 						max_tokens: maxTokens ?? ANTHROPIC_DEFAULT_MAX_TOKENS,
 						temperature,
 						thinking,
@@ -115,6 +121,7 @@ export class AnthropicHandler extends BaseProvider implements SingleCompletionHa
 						// Then check for models that support prompt caching
 						switch (modelId) {
 							case "claude-sonnet-4-5":
+							case "claude-sonnet-4-5-20250929":
 							case "claude-sonnet-4-20250514":
 							case "claude-opus-4-1-20250805":
 							case "claude-opus-4-20250514":
@@ -134,7 +141,7 @@ export class AnthropicHandler extends BaseProvider implements SingleCompletionHa
 			}
 			default: {
 				stream = (await this.client.messages.create({
-					model: modelId,
+					model: apiModelId,
 					max_tokens: maxTokens ?? ANTHROPIC_DEFAULT_MAX_TOKENS,
 					temperature,
 					system: [{ text: systemPrompt, type: "text" }],
@@ -249,7 +256,10 @@ export class AnthropicHandler extends BaseProvider implements SingleCompletionHa
 		let info: ModelInfo = anthropicModels[id]
 
 		// If 1M context beta is enabled for Claude Sonnet 4 or 4.5, update the model info
-		if ((id === "claude-sonnet-4-20250514" || id === "claude-sonnet-4-5") && this.options.anthropicBeta1MContext) {
+		if (
+			(id === "claude-sonnet-4-20250514" || id === "claude-sonnet-4-5" || id === "claude-sonnet-4-5-20250929") &&
+			this.options.anthropicBeta1MContext
+		) {
 			// Use the tier pricing for 1M context
 			const tier = info.tiers?.[0]
 			if (tier) {
@@ -286,8 +296,11 @@ export class AnthropicHandler extends BaseProvider implements SingleCompletionHa
 	async completePrompt(prompt: string) {
 		let { id: model, temperature } = this.getModel()
 
+		// Map the alias to the full snapshot name for API calls
+		const apiModel = model === "claude-sonnet-4-5" ? "claude-sonnet-4-5-20250929" : model
+
 		const message = await this.client.messages.create({
-			model,
+			model: apiModel,
 			max_tokens: ANTHROPIC_DEFAULT_MAX_TOKENS,
 			thinking: undefined,
 			temperature,
@@ -310,8 +323,11 @@ export class AnthropicHandler extends BaseProvider implements SingleCompletionHa
 			// Use the current model
 			const { id: model } = this.getModel()
 
+			// Map the alias to the full snapshot name for API calls
+			const apiModel = model === "claude-sonnet-4-5" ? "claude-sonnet-4-5-20250929" : model
+
 			const response = await this.client.messages.countTokens({
-				model,
+				model: apiModel,
 				messages: [{ role: "user", content: content }],
 			})