@@ -12,20 +12,8 @@ import {
1212 ProviderOptions ,
1313} from '../types.js' ;
1414
15- // Define model context window sizes for Anthropic models
16- const ANTHROPIC_MODEL_LIMITS : Record < string , number > = {
17- default : 200000 ,
18- 'claude-3-7-sonnet-20250219' : 200000 ,
19- 'claude-3-7-sonnet-latest' : 200000 ,
20- 'claude-3-5-sonnet-20241022' : 200000 ,
21- 'claude-3-5-sonnet-latest' : 200000 ,
22- 'claude-3-haiku-20240307' : 200000 ,
23- 'claude-3-opus-20240229' : 200000 ,
24- 'claude-3-sonnet-20240229' : 200000 ,
25- 'claude-2.1' : 100000 ,
26- 'claude-2.0' : 100000 ,
27- 'claude-instant-1.2' : 100000 ,
28- } ;
15+ // Cache for model context window sizes
16+ const modelContextWindowCache : Record < string , number > = { } ;
2917
3018/**
3119 * Anthropic-specific options
@@ -96,15 +84,27 @@ function addCacheControlToMessages(
9684 } ) ;
9785}
9886
99- function tokenUsageFromMessage ( message : Anthropic . Message , model : string ) {
87+ function tokenUsageFromMessage (
88+ message : Anthropic . Message ,
89+ model : string ,
90+ contextWindow ?: number ,
91+ ) {
10092 const usage = new TokenUsage ( ) ;
10193 usage . input = message . usage . input_tokens ;
10294 usage . cacheWrites = message . usage . cache_creation_input_tokens ?? 0 ;
10395 usage . cacheReads = message . usage . cache_read_input_tokens ?? 0 ;
10496 usage . output = message . usage . output_tokens ;
10597
10698 const totalTokens = usage . input + usage . output ;
107- const maxTokens = ANTHROPIC_MODEL_LIMITS [ model ] || 100000 ; // Default fallback
99+
100+ // Use provided context window or fallback to cached value
101+ const maxTokens = contextWindow || modelContextWindowCache [ model ] ;
102+
103+ if ( ! maxTokens ) {
104+ throw new Error (
105+ `Context window size not available for model: ${ model } ,
106+ ) ;
107+ }
108108
109109 return {
110110 usage,
@@ -123,6 +123,7 @@ export class AnthropicProvider implements LLMProvider {
123123 private client : Anthropic ;
124124 private apiKey : string ;
125125 private baseUrl ?: string ;
126+ private modelContextWindow ?: number ;
126127
127128 constructor ( model : string , options : AnthropicOptions = { } ) {
128129 this . model = model ;
@@ -138,6 +139,73 @@ export class AnthropicProvider implements LLMProvider {
138139 apiKey : this . apiKey ,
139140 ...( this . baseUrl && { baseURL : this . baseUrl } ) ,
140141 } ) ;
142+
143+ // Initialize model context window detection
144+ // This is async but we don't need to await it here
145+ // If it fails, an error will be thrown when the model is used
146+ this . initializeModelContextWindow ( ) . catch ( ( error ) => {
147+ console . error (
148+ `Failed to initialize model context window: ${ error . message } ,
149+ ) ;
150+ } ) ;
151+ }
152+
153+ /**
154+ * Fetches the model context window size from the Anthropic API
155+ *
156+ * @returns The context window size
157+ * @throws Error if the context window size cannot be determined
158+ */
159+ private async initializeModelContextWindow ( ) : Promise < number > {
160+ try {
161+ const response = await this . client . models . list ( ) ;
162+
163+ if ( ! response ?. data || ! Array . isArray ( response . data ) ) {
164+ throw new Error (
165+ `Invalid response from models.list() for ${ this . model } ,
166+ ) ;
167+ }
168+
169+ // Try to find the exact model
170+ let model = response . data . find ( ( m ) => m . id === this . model ) ;
171+
172+ // If not found, try to find a model that starts with the same name
173+ // This helps with model aliases like 'claude-3-sonnet-latest'
174+ if ( ! model ) {
175+ // Split by '-latest' or '-20' to get the base model name
176+ const parts = this . model . split ( '-latest' ) ;
177+ const modelPrefix =
178+ parts . length > 1 ? parts [ 0 ] : this . model . split ( '-20' ) [ 0 ] ;
179+
180+ if ( modelPrefix ) {
181+ model = response . data . find ( ( m ) => m . id . startsWith ( modelPrefix ) ) ;
182+
183+ if ( model ) {
184+ console . info (
185+ `Model ${ this . model } ${ model . id } ,
186+ ) ;
187+ }
188+ }
189+ }
190+
191+ // Using type assertion to access context_window property
192+ // The Anthropic API returns context_window but it may not be in the TypeScript definitions
193+ if ( model && 'context_window' in model ) {
194+ const contextWindow = ( model as any ) . context_window ;
195+ this . modelContextWindow = contextWindow ;
196+ // Cache the result for future use
197+ modelContextWindowCache [ this . model ] = contextWindow ;
198+ return contextWindow ;
199+ } else {
200+ throw new Error (
201+ `No context window information found for model: ${ this . model } ,
202+ ) ;
203+ }
204+ } catch ( error ) {
205+ throw new Error (
206+ `Failed to determine context window size for model ${ this . model } ${ ( error as Error ) . message } ,
207+ ) ;
208+ }
141209 }
142210
143211 /**
@@ -198,7 +266,11 @@ export class AnthropicProvider implements LLMProvider {
198266 } ;
199267 } ) ;
200268
201- const tokenInfo = tokenUsageFromMessage ( response , this . model ) ;
269+ const tokenInfo = tokenUsageFromMessage (
270+ response ,
271+ this . model ,
272+ this . modelContextWindow ,
273+ ) ;
202274
203275 return {
204276 text : content ,
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