fix: honor explicit model provider routing

Author: Sushanth012

src/agent/agent.ts

@@ -36,6 +36,7 @@ const OVERFLOW_KEEP_ROUNDS = 3;
  */
 export class Agent {
   private readonly model: string;
+  private readonly modelProvider?: string;
   private readonly maxIterations: number;
   private readonly tools: StructuredToolInterface[];
   private readonly toolMap: Map<string, StructuredToolInterface>;
@@ -53,6 +54,7 @@ export class Agent {
     concurrencyMap: Map<string, boolean>,
   ) {
     this.model = config.model ?? DEFAULT_MODEL;
+    this.modelProvider = config.modelProvider;
     this.maxIterations = config.maxIterations ?? DEFAULT_MAX_ITERATIONS;
     this.tools = tools;
     this.toolMap = new Map(tools.map(t => [t.name, t]));
@@ -160,7 +162,7 @@ export class Agent {
           }
 
           const totalTime = Date.now() - ctx.startTime;
-          const provider = resolveProvider(this.model).displayName;
+          const provider = resolveProvider(this.model, this.modelProvider).displayName;
           yield {
             type: 'done',
             answer: `Error: ${formatUserFacingError(errorMessage, provider)}`,
@@ -300,6 +302,7 @@ export class Agent {
 
     for await (const chunk of streamLlmWithMessages(messages, {
       model: this.model,
+      modelProvider: this.modelProvider,
       tools: this.tools,
       signal: this.signal,
     })) {
@@ -345,6 +348,7 @@ export class Agent {
   ): Promise<{ response: AIMessage; usage?: TokenUsage }> {
     const result = await callLlmWithMessages(messages, {
       model: this.model,
+      modelProvider: this.modelProvider,
       tools: this.tools,
       signal: this.signal,
     });
@@ -541,7 +545,7 @@ export class Agent {
       : estimateTokens(messageState.messages.map(m =>
           typeof m.content === 'string' ? m.content : JSON.stringify(m.content),
         ).join('\n'));
-    const threshold = getAutoCompactThreshold(this.model);
+    const threshold = getAutoCompactThreshold(this.model, this.modelProvider);
 
     if (estimatedContextTokens <= threshold) {
       return;
@@ -560,6 +564,7 @@ export class Agent {
       yield { type: 'memory_flush', phase: 'start' };
       const flushResult = await runMemoryFlush({
         model: this.model,
+        modelProvider: this.modelProvider,
         systemPrompt: this.systemPrompt,
         query,
         toolResults: fullToolResults,
@@ -583,6 +588,7 @@ export class Agent {
       try {
         const result = await compactContext({
           model: this.model,
+          modelProvider: this.modelProvider,
           systemPrompt: this.systemPrompt,
           query,
           toolResults: fullToolResults,
@@ -611,7 +617,7 @@ export class Agent {
           success: true,
           preCompactTokens: estimatedContextTokens,
           postCompactTokens,
-          compactionModel: resolveProvider(this.model).fastModel ?? this.model,
+          compactionModel: resolveProvider(this.model, this.modelProvider).fastModel ?? this.model,
         };
 
         return;

src/agent/compact.ts

@@ -168,6 +168,8 @@ Continue working toward answering the query without asking the user any further
 export interface CompactContextParams {
   /** Main model name (used to resolve provider and fast model). */
   model: string;
+  /** Explicit provider override from agent settings. */
+  modelProvider?: string;
   /** System prompt for the compaction call. */
   systemPrompt: string;
   /** Original user query. */
@@ -192,10 +194,10 @@ export interface CompactResult {
  * Throws on failure — caller is responsible for fallback to clearing.
  */
 export async function compactContext(params: CompactContextParams): Promise<CompactResult> {
-  const { model, systemPrompt, query, toolResults, signal } = params;
+  const { model, modelProvider, systemPrompt, query, toolResults, signal } = params;
 
   // Resolve fast model for the current provider
-  const provider = resolveProvider(model);
+  const provider = resolveProvider(model, modelProvider);
   const fastModel = provider.fastModel ?? model;
 
   // Build the compaction prompt
@@ -204,6 +206,7 @@ export async function compactContext(params: CompactContextParams): Promise<Comp
   // Call LLM with no tools bound — callLlm returns string in this case
   const result = await callLlm(prompt, {
     model: fastModel,
+    modelProvider: provider.id,
     systemPrompt,
     signal,
   });

src/memory/flush.ts

@@ -38,6 +38,7 @@ export function shouldRunMemoryFlush(params: {
 
 export async function runMemoryFlush(params: {
   model: string;
+  modelProvider?: string;
   systemPrompt: string;
   query: string;
   toolResults: string;
@@ -55,6 +56,7 @@ ${MEMORY_FLUSH_PROMPT}
 
   const result = await callLlm(prompt, {
     model: params.model,
+    modelProvider: params.modelProvider,
     systemPrompt: params.systemPrompt,
     signal: params.signal,
   });

src/model/llm.ts

@@ -143,16 +143,18 @@ const DEFAULT_FACTORY: ModelFactory = (name, opts) =>
 
 export function getChatModel(
   modelName: string = DEFAULT_MODEL,
-  streaming: boolean = false
+  streaming: boolean = false,
+  providerOverride?: string,
 ): BaseChatModel {
   const opts: ModelOpts = { streaming };
-  const provider = resolveProvider(modelName);
+  const provider = resolveProvider(modelName, providerOverride);
   const factory = MODEL_FACTORIES[provider.id] ?? DEFAULT_FACTORY;
   return factory(modelName, opts);
 }
 
 interface CallLlmOptions {
   model?: string;
+  modelProvider?: string;
   systemPrompt?: string;
   outputSchema?: z.ZodType<unknown>;
   tools?: StructuredToolInterface[];
@@ -213,10 +215,10 @@ function buildAnthropicMessages(systemPrompt: string, userPrompt: string) {
 }
 
 export async function callLlm(prompt: string, options: CallLlmOptions = {}): Promise<LlmResult> {
-  const { model = DEFAULT_MODEL, systemPrompt, outputSchema, tools, signal } = options;
+  const { model = DEFAULT_MODEL, modelProvider, systemPrompt, outputSchema, tools, signal } = options;
   const finalSystemPrompt = systemPrompt || DEFAULT_SYSTEM_PROMPT;
 
-  const llm = getChatModel(model, false);
+  const llm = getChatModel(model, false, modelProvider);
 
   // eslint-disable-next-line @typescript-eslint/no-explicit-any
   let runnable: Runnable<any, any> = llm;
@@ -228,7 +230,7 @@ export async function callLlm(prompt: string, options: CallLlmOptions = {}): Pro
   }
 
   const invokeOpts = signal ? { signal } : undefined;
-  const provider = resolveProvider(model);
+  const provider = resolveProvider(model, modelProvider);
   let result;
 
   if (provider.id === 'anthropic') {
@@ -287,6 +289,7 @@ function annotateSystemMessageForCaching(messages: BaseMessage[]): BaseMessage[]
 
 interface CallLlmWithMessagesOptions {
   model?: string;
+  modelProvider?: string;
   tools?: StructuredToolInterface[];
   signal?: AbortSignal;
 }
@@ -306,9 +309,9 @@ export async function callLlmWithMessages(
   messages: BaseMessage[],
   options: CallLlmWithMessagesOptions = {},
 ): Promise<LlmResult> {
-  const { model = DEFAULT_MODEL, tools, signal } = options;
+  const { model = DEFAULT_MODEL, modelProvider, tools, signal } = options;
 
-  const llm = getChatModel(model, false);
+  const llm = getChatModel(model, false, modelProvider);
 
   // eslint-disable-next-line @typescript-eslint/no-explicit-any
   let runnable: Runnable<any, any> = llm;
@@ -318,7 +321,7 @@ export async function callLlmWithMessages(
   }
 
   const invokeOpts = signal ? { signal } : undefined;
-  const provider = resolveProvider(model);
+  const provider = resolveProvider(model, modelProvider);
 
   // For Anthropic: annotate SystemMessage with cache_control for prompt caching
   const finalMessages = provider.id === 'anthropic'
@@ -349,9 +352,9 @@ export async function* streamLlmWithMessages(
   messages: BaseMessage[],
   options: CallLlmWithMessagesOptions = {},
 ): AsyncGenerator<AIMessageChunk, void> {
-  const { model = DEFAULT_MODEL, tools, signal } = options;
+  const { model = DEFAULT_MODEL, modelProvider, tools, signal } = options;
 
-  const llm = getChatModel(model, true);
+  const llm = getChatModel(model, true, modelProvider);
 
   // eslint-disable-next-line @typescript-eslint/no-explicit-any
   let runnable: Runnable<any, any> = llm;
@@ -361,7 +364,7 @@ export async function* streamLlmWithMessages(
   }
 
   const invokeOpts = signal ? { signal } : undefined;
-  const provider = resolveProvider(model);
+  const provider = resolveProvider(model, modelProvider);
 
   const finalMessages = provider.id === 'anthropic'
     ? annotateSystemMessageForCaching(messages)

src/providers.test.ts

@@ -0,0 +1,22 @@
+import { describe, expect, test } from 'bun:test';
+import { resolveProvider } from './providers.js';
+
+describe('resolveProvider', () => {
+  test('uses explicit provider before model prefix routing', () => {
+    const provider = resolveProvider('deepseek-v4-flash', 'openai');
+
+    expect(provider.id).toBe('openai');
+  });
+
+  test('falls back to model prefix routing without override', () => {
+    const provider = resolveProvider('deepseek-v4-flash');
+
+    expect(provider.id).toBe('deepseek');
+  });
+
+  test('ignores unknown provider override', () => {
+    const provider = resolveProvider('claude-sonnet-4-5', 'unknown-provider');
+
+    expect(provider.id).toBe('anthropic');
+  });
+});

src/providers.ts

@@ -86,10 +86,16 @@ export const PROVIDERS: ProviderDef[] = [
 const defaultProvider = PROVIDERS.find((p) => p.id === 'openai')!;
 
 /**
- * Resolve the provider for a given model name based on its prefix.
- * Falls back to OpenAI when no prefix matches.
+ * Resolve the provider for a given model name.
+ * Explicit provider settings take precedence over model-name prefix routing.
+ * Falls back to OpenAI when no prefix matches or an override is unknown.
  */
-export function resolveProvider(modelName: string): ProviderDef {
+export function resolveProvider(modelName: string, providerOverride?: string): ProviderDef {
+  if (providerOverride) {
+    const provider = getProviderById(providerOverride);
+    if (provider) return provider;
+  }
+
   return (
     PROVIDERS.find((p) => p.modelPrefix && modelName.startsWith(p.modelPrefix)) ??
     defaultProvider

src/utils/tokens.ts

@@ -36,8 +36,8 @@ const DEFAULT_CONTEXT_WINDOW = 128_000;
  * Get the effective context window size for a model, accounting for
  * reserved output tokens.
  */
-export function getEffectiveContextWindow(model: string): number {
-  const provider = resolveProvider(model);
+export function getEffectiveContextWindow(model: string, modelProvider?: string): number {
+  const provider = resolveProvider(model, modelProvider);
   const contextWindow = provider.contextWindow ?? DEFAULT_CONTEXT_WINDOW;
   return contextWindow - MAX_OUTPUT_TOKENS_FOR_SUMMARY;
 }
@@ -47,8 +47,8 @@ export function getEffectiveContextWindow(model: string): number {
  * This is the token count at which compaction should trigger.
  * Formula: effectiveWindow - 13K buffer.
  */
-export function getAutoCompactThreshold(model: string): number {
-  return getEffectiveContextWindow(model) - AUTOCOMPACT_BUFFER_TOKENS;
+export function getAutoCompactThreshold(model: string, modelProvider?: string): number {
+  return getEffectiveContextWindow(model, modelProvider) - AUTOCOMPACT_BUFFER_TOKENS;
 }
 
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