fix(models): derive forced tool support from capability metadata

Author: j15z

apps/sim/providers/models.test.ts

@@ -16,6 +16,7 @@ import {
   PROVIDER_DEFINITIONS,
   supportsForcedToolUse,
   updateFireworksModels,
+  updateOpenRouterModels,
 } from '@/providers/models'
 import { supportsPromptCaching } from '@/providers/utils'
 
@@ -31,11 +32,49 @@ describe('forced tool use capability', () => {
     'claude-fable-5-1',
     'CLAUDE-FABLE-5-1-20260901',
     'azure-anthropic/claude-fable-5-1',
+    'azure-anthropic/claude-fable-5-1-20260901',
+    'bedrock/anthropic.claude-fable-5-1-v1:0',
     'claude-mythos-5-1',
+    'claude-mythos-5-1-20260901',
   ])('disables forced tool use for %s', (model) => {
+    expect(getModelCapabilities(model)).toMatchObject({
+      toolUsageControl: true,
+      forcedToolUse: false,
+    })
     expect(supportsForcedToolUse(model)).toBe(false)
   })
 
+  it('adds only known alias capabilities to provider defaults', () => {
+    expect(getModelCapabilities('claude-mythos-5-1')).toEqual({
+      ...PROVIDER_DEFINITIONS.anthropic.capabilities,
+      forcedToolUse: false,
+    })
+  })
+
+  it('inherits alias capabilities for dynamic models and respects explicit overrides', () => {
+    const originalModels = PROVIDER_DEFINITIONS.openrouter.models
+    const modelId = 'anthropic/claude-fable-5-1'
+    try {
+      updateOpenRouterModels([modelId])
+      expect(getModelCapabilities(modelId)?.forcedToolUse).toBe(false)
+      expect(supportsForcedToolUse(modelId)).toBe(false)
+
+      PROVIDER_DEFINITIONS.openrouter.models[0].capabilities.forcedToolUse = true
+      expect(getModelCapabilities(modelId)?.forcedToolUse).toBe(true)
+      expect(supportsForcedToolUse(modelId)).toBe(true)
+    } finally {
+      PROVIDER_DEFINITIONS.openrouter.models = originalModels
+    }
+  })
+
+  it.each(['claude-fable-5-10', 'claude-mythos-5-10', 'claude-not-fable-5-1'])(
+    'does not apply alias restrictions to unrelated model %s',
+    (model) => {
+      expect(getModelCapabilities(model)).toEqual(PROVIDER_DEFINITIONS.anthropic.capabilities)
+      expect(supportsForcedToolUse(model)).toBe(true)
+    }
+  )
+
   it.each(['claude-sonnet-5', 'claude-fable-5', 'claude-opus-5', 'gpt-5.5'])(
     'inherits provider tool-control support for %s',
     (model) => {
@@ -44,6 +83,7 @@ describe('forced tool use capability', () => {
   )
 
   it('does not enable Force for an unknown model without tool-control capabilities', () => {
+    expect(getModelCapabilities('unknown-model')).toBeNull()
     expect(supportsForcedToolUse('unknown-model')).toBe(false)
   })
 })

apps/sim/providers/models.ts

@@ -164,6 +164,16 @@ export function getProviderFileAttachment(providerId: string): ProviderFileAttac
   return PROVIDER_DEFINITIONS[providerId]?.fileAttachment ?? DEFAULT_FILE_ATTACHMENT
 }
 
+const CLAUDE_5_1_TOOL_CAPABILITIES = { forcedToolUse: false } as const satisfies ModelCapabilities
+
+/** Known capabilities for model aliases; explicit catalog capabilities take precedence. */
+const MODEL_CAPABILITY_FALLBACKS = [
+  {
+    pattern: /(?:^|[/.])claude-(?:fable|mythos)-5-1(?:$|[-:])/,
+    capabilities: CLAUDE_5_1_TOOL_CAPABILITIES,
+  },
+] satisfies { pattern: RegExp; capabilities: ModelCapabilities }[]
+
 export const PROVIDER_DEFINITIONS: Record<string, ProviderDefinition> = {
   fireworks: {
     id: 'fireworks',
@@ -836,7 +846,7 @@ export const PROVIDER_DEFINITIONS: Record<string, ProviderDefinition> = {
           updatedAt: '2026-09-01',
         },
         capabilities: {
-          forcedToolUse: false,
+          ...CLAUDE_5_1_TOOL_CAPABILITIES,
           nativeStructuredOutputs: true,
           maxOutputTokens: 128000,
           promptCaching: { minimumCacheableTokens: 512 },
@@ -4297,25 +4307,36 @@ export function getModelPricing(modelId: string): ModelPricing | null {
 }
 
 export function getModelCapabilities(modelId: string): ModelCapabilities | null {
+  const normalizedModel = modelId.toLowerCase()
+  const fallbackCapabilities = MODEL_CAPABILITY_FALLBACKS.find(({ pattern }) =>
+    pattern.test(normalizedModel)
+  )?.capabilities
+
   for (const provider of Object.values(PROVIDER_DEFINITIONS)) {
-    const model = provider.models.find((m) => m.id.toLowerCase() === modelId.toLowerCase())
+    const model = provider.models.find((m) => m.id.toLowerCase() === normalizedModel)
     if (model) {
-      const capabilities: ModelCapabilities = { ...provider.capabilities, ...model.capabilities }
+      const capabilities: ModelCapabilities = {
+        ...provider.capabilities,
+        ...fallbackCapabilities,
+        ...model.capabilities,
+      }
       return capabilities
     }
   }
 
   for (const provider of Object.values(PROVIDER_DEFINITIONS)) {
     if (provider.modelPatterns) {
       for (const pattern of provider.modelPatterns) {
-        if (pattern.test(modelId.toLowerCase())) {
-          return provider.capabilities || null
+        if (pattern.test(normalizedModel)) {
+          return fallbackCapabilities
+            ? { ...provider.capabilities, ...fallbackCapabilities }
+            : provider.capabilities || null
         }
       }
     }
   }
 
-  return null
+  return fallbackCapabilities || null
 }
 
 export function getModelsWithTemperatureSupport(): string[] {
@@ -4394,18 +4415,10 @@ export function supportsToolUsageControl(providerId: string): boolean {
   return getProvidersWithToolUsageControl().includes(providerId)
 }
 
-/** Whether the model accepts forced tool choice, including uncataloged Claude aliases. */
+/** Whether the model accepts forced tool choice. */
 export function supportsForcedToolUse(modelId: string): boolean {
   const capabilities = getModelCapabilities(modelId)
-  if (capabilities?.forcedToolUse !== undefined) return capabilities.forcedToolUse
-
-  /** Preserve the restriction for date-suffixed and reseller IDs outside the catalog. */
-  const normalizedModel = modelId.toLowerCase()
-  if (normalizedModel.includes('fable-5-1') || normalizedModel.includes('mythos-5-1')) {
-    return false
-  }
-
-  return capabilities?.toolUsageControl ?? false
+  return capabilities?.forcedToolUse ?? capabilities?.toolUsageControl ?? false
 }
 
 export function updateOllamaModels(models: string[]): void {