Add sim-auto: automatic model routing for the agent block (hosted)

- 'Auto' model option (Sim wordmark icon, hosted-only, new-block default;
  runtime fallback for unset models stays claude-sonnet-5)
- Resolver (lib/model-router): classifies each execution via mothership's
  /api/model-router and routes over two ladders — text: fireworks/glm-5.2 ->
  fireworks/kimi-k3 (new static hosted Fireworks catalog entries on the
  platform FIREWORKS_API_KEY); attachments: claude-haiku-4-5 -> gpt-5.5
  (Fireworks OSS endpoints reject images). Trivial tasks skip the router;
  5-min decision cache; 2s timeout; never fails the workflow
- Hidden identity preamble on every auto run (English by default, don't
  volunteer the underlying model)
- Fireworks executor: wire-name map for catalog ids (glm-5.2 -> glm-5p2),
  pricing keyed on the full catalog id
- Billing: routing cost applied to non-streaming output cost only when
  mothership marks the call billable (bill-model-router flag, default off)
- sim-auto special-cases: API-key condition, serialization tool lookup,
  edit-workflow validation (hosted), VFS model options projection

Author: Sg312

apps/sim/blocks/blocks/agent.ts

@@ -1,5 +1,6 @@
 import { createLogger } from '@sim/logger'
 import { AgentIcon } from '@/components/icons'
+import { isHosted } from '@/lib/core/config/env-flags'
 import type { BlockConfig } from '@/blocks/types'
 import { AuthMode, IntegrationType } from '@/blocks/types'
 import {
@@ -20,6 +21,8 @@ import {
   getReasoningEffortValuesForModel,
   getThinkingLevelsForModel,
   getVerbosityValuesForModel,
+  isAutoModel,
+  SIM_AUTO_MODEL_ID,
   supportsTemperature,
 } from '@/providers/models'
 import { useWorkflowRegistry } from '@/stores/workflows/registry/store'
@@ -132,7 +135,9 @@ Return ONLY the JSON array.`,
       type: 'combobox',
       placeholder: 'Type or select a model...',
       required: true,
-      defaultValue: 'claude-sonnet-5',
+      // Hosted Sim defaults new agent blocks to the automatic model; the
+      // runtime fallback for blocks with no model set stays AGENT.DEFAULT_MODEL.
+      defaultValue: isHosted ? SIM_AUTO_MODEL_ID : 'claude-sonnet-5',
       options: getModelOptions,
       commandSearchable: true,
     },
@@ -522,6 +527,11 @@ Return ONLY the JSON array.`,
         if (!model) {
           throw new Error('No model selected')
         }
+        // sim-auto resolves to a concrete model at execution time; this
+        // serialization-time lookup only needs a stable provider tool id.
+        if (isAutoModel(model)) {
+          return 'anthropic_chat'
+        }
         const tool = getBaseModelProviders()[model]
         if (!tool) {
           throw new Error(`Invalid model selected: ${model}`)

apps/sim/blocks/utils.test.ts

@@ -40,6 +40,8 @@ vi.mock('@/providers/models', () => ({
   getProviderModels: mockGetProviderModels,
   getProviderIcon: mockGetProviderIcon,
   getBaseModelProviders: mockGetBaseModelProviders,
+  SIM_AUTO_MODEL_ID: 'sim-auto',
+  isAutoModel: (model: string) => model.trim().toLowerCase() === 'sim-auto',
 }))
 
 vi.mock('@/providers/utils', () => ({

apps/sim/blocks/utils.ts

@@ -1,4 +1,5 @@
 import { toError } from '@sim/utils/errors'
+import { SimAutoIcon } from '@/components/icons'
 import {
   isAzureConfigured,
   isCohereConfigured,
@@ -14,7 +15,9 @@ import {
   getModelSunsetStatus,
   getProviderIcon,
   getProviderModels,
+  isAutoModel,
   orderModelIdsByReleaseDate,
+  SIM_AUTO_MODEL_ID,
 } from '@/providers/models'
 import { isPiSupportedModel } from '@/providers/pi-providers'
 import { getProviderFromModel } from '@/providers/utils'
@@ -75,12 +78,18 @@ export function getModelOptions() {
     ])
   )
 
-  return allModels
+  const options = allModels
     .filter((model) => getModelSunsetStatus(model) !== 'deprecated')
     .map((model) => {
       const icon = getProviderIcon(model)
       return { label: model, id: model, ...(icon && { icon }) }
     })
+
+  if (isHosted) {
+    options.unshift({ label: 'Auto', id: SIM_AUTO_MODEL_ID, icon: SimAutoIcon })
+  }
+
+  return options
 }
 
 /**
@@ -183,6 +192,9 @@ function shouldRequireApiKeyForModel(model: string): boolean {
   const normalizedModel = model.trim().toLowerCase()
   if (!normalizedModel) return false
 
+  // The auto pseudo-model resolves server-side to a hosted pool model.
+  if (isAutoModel(normalizedModel)) return false
+
   if (isHosted) {
     const hostedModels = getHostedModels()
     if (hostedModels.some((m) => m.toLowerCase() === normalizedModel)) return false

apps/sim/components/icons.tsx

@@ -7558,6 +7558,31 @@ export function SixtyfourIcon(props: SVGProps<SVGSVGElement>) {
   )
 }
 
+/**
+ * The "sim" brand wordmark (v1.0 brand guide simLogotype paths — the same mark
+ * the navbar/login header renders), inked with the theme-adaptive
+ * `--text-body`. Used as the icon for the Auto model option; the wide viewBox
+ * letterboxes itself inside square icon slots.
+ */
+export function SimAutoIcon(props: SVGProps<SVGSVGElement>) {
+  return (
+    <svg
+      {...props}
+      viewBox='0 0 441 212'
+      fill='none'
+      xmlns='http://www.w3.org/2000/svg'
+      aria-hidden='true'
+    >
+      <g fill='var(--text-body)'>
+        <path d='M0 160.9H29.51C29.51 169.08 32.46 175.61 38.37 180.48C44.27 185.12 52.25 187.44 62.31 187.44C73.24 187.44 81.65 185.34 87.56 181.14C93.46 176.71 96.41 170.85 96.41 163.55C96.41 158.24 94.77 153.82 91.49 150.28C88.43 146.74 82.75 143.86 74.44 141.65L46.24 135.01C32.03 131.47 21.42 126.05 14.43 118.75C7.65 111.45 4.26 101.83 4.26 89.88C4.26 79.93 6.78 71.3 11.81 64C17.05 56.7 24.16 51.06 33.12 47.08C42.3 43.09 52.8 41.1 64.6 41.1C76.41 41.1 86.57 43.2 95.1 47.41C103.84 51.61 110.62 57.47 115.43 64.99C120.46 72.52 123.08 81.48 123.3 91.87H93.79C93.57 83.47 90.84 76.94 85.59 72.3C80.34 67.65 73.02 65.33 63.62 65.33C54 65.33 46.57 67.43 41.32 71.63C36.07 75.83 33.45 81.59 33.45 88.89C33.45 99.73 41.32 107.14 57.06 111.12L85.26 118.09C98.81 121.19 108.98 126.28 115.76 133.35C122.53 140.21 125.92 149.61 125.92 161.56C125.92 171.74 123.19 180.7 117.73 188.44C112.26 195.96 104.72 201.82 95.1 206.03C85.7 210.01 74.55 212 61.65 212C42.85 212 27.87 207.35 16.72 198.06C5.57 188.77 0 176.38 0 160.9Z' />
+        <path d='M232.8 212H202.13L202.13 49.76H229.54V77.39C232.8 68.34 239.11 60.66 247.81 54.7C256.73 48.52 267.5 45.43 280.12 45.43C294.26 45.43 306.01 49.29 315.36 57.02C324.72 64.75 330.81 75.01 333.64 87.82H328.09C330.27 75.01 336.25 64.75 346.04 57.02C355.83 49.29 367.9 45.43 382.26 45.43C400.54 45.43 414.89 50.84 425.34 61.66C435.78 72.47 441 87.26 441 106.03V212H410.98V113.65C410.98 100.84 407.71 91.02 401.19 84.17C394.88 77.11 386.29 73.58 375.41 73.58C367.79 73.58 361.05 75.34 355.17 78.88C349.52 82.19 345.06 87.04 341.8 93.45C338.53 99.85 336.9 107.36 336.9 115.97V212H306.55V113.32C306.55 100.51 303.4 90.8 297.09 84.17C290.78 77.33 282.19 73.91 271.31 73.91C263.69 73.91 256.95 75.67 251.08 79.21C245.42 82.52 240.96 87.38 237.7 93.78C234.43 99.96 232.8 107.36 232.8 115.97V212Z' />
+        <path d='M184.83 20.55C184.83 31.9 175.64 41.1 164.29 41.1C152.95 41.1 143.76 31.9 143.76 20.55C143.76 9.2 152.95 0 164.29 0C175.64 0 184.83 9.2 184.83 20.55Z' />
+        <path d='M179.43 212H149.16V49.76C153.76 51.91 158.88 53.12 164.29 53.12C169.7 53.12 174.83 51.91 179.43 49.76V212Z' />
+      </g>
+    </svg>
+  )
+}
+
 export function SimTriggerIcon(props: SVGProps<SVGSVGElement>) {
   return (
     <svg

apps/sim/executor/handlers/agent/agent-handler.ts

@@ -7,6 +7,12 @@ import { truncate } from '@sim/utils/string'
 import { and, eq, inArray, isNull } from 'drizzle-orm'
 import { normalizeStringRecord, normalizeWorkflowVariables } from '@/lib/core/utils/records'
 import { createMcpToolId } from '@/lib/mcp/utils'
+import {
+  type AutoRoutingResult,
+  type AutoRoutingSignals,
+  resolveAutoModel,
+  SIM_AUTO_SYSTEM_PREAMBLE,
+} from '@/lib/model-router/resolve'
 import { processFilesToUserFiles, type RawFileInput } from '@/lib/uploads/utils/file-utils'
 import { hydrateUserFilesWithBase64 } from '@/lib/uploads/utils/user-file-base64.server'
 import { resolveCustomBlockToolBinding } from '@/lib/workflows/custom-blocks/operations'
@@ -46,6 +52,7 @@ import {
   shouldUseLargeFilePath,
   supportsFileAttachments,
 } from '@/providers/attachments'
+import { isAutoModel } from '@/providers/models'
 import { getProviderFromModel, transformBlockTool } from '@/providers/utils'
 import type { SerializedBlock } from '@/serializer/types'
 import { filterSchemaForLLM, type ToolSchema } from '@/tools/params'
@@ -77,7 +84,32 @@ export class AgentBlockHandler implements BlockHandler {
     await this.validateToolPermissions(ctx, filteredInputs.tools || [])
 
     const responseFormat = parseResponseFormat(filteredInputs.responseFormat)
-    const model = filteredInputs.model || AGENT.DEFAULT_MODEL
+    const configuredModel = filteredInputs.model || AGENT.DEFAULT_MODEL
+
+    let model = configuredModel
+    let autoRouting: AutoRoutingResult | null = null
+    if (isAutoModel(configuredModel)) {
+      autoRouting = await resolveAutoModel({
+        ctx,
+        blockId: block.id,
+        signals: this.buildAutoRoutingSignals(filteredInputs, responseFormat),
+        fallbackModel: AGENT.DEFAULT_MODEL,
+      })
+      model = autoRouting.model
+      logger.info('Resolved sim-auto model', {
+        blockId: block.id,
+        model,
+        tier: autoRouting.tier,
+        decidedBy: autoRouting.decidedBy,
+      })
+      // Hidden identity preamble for every auto execution (fallback included):
+      // keeps pool models in English by default and off the topic of which
+      // underlying model they are. Applied after signal building so the
+      // preamble never influences classification.
+      filteredInputs.systemPrompt = [SIM_AUTO_SYSTEM_PREAMBLE, filteredInputs.systemPrompt]
+        .filter(Boolean)
+        .join('\n\n')
+    }
 
     await validateModelProvider(ctx.userId, ctx.workspaceId, model, ctx)
 
@@ -126,6 +158,14 @@ export class AgentBlockHandler implements BlockHandler {
 
     const result = await this.executeProviderRequest(ctx, providerRequest, block, responseFormat)
 
+    // Routing cost lands on non-streaming outputs only for now; streaming
+    // outputs assemble cost at stream end where there is no hook yet. The
+    // charge is gated server-side by mothership's bill-model-router flag
+    // (default off), so this asymmetry currently bills nobody.
+    if (autoRouting && autoRouting.billableRoutingCost > 0 && !this.isStreamingExecution(result)) {
+      this.applyRoutingCost(result as BlockOutput, autoRouting.billableRoutingCost)
+    }
+
     if (this.isStreamingExecution(result)) {
       if (filteredInputs.memoryType && filteredInputs.memoryType !== 'none') {
         return this.wrapStreamForMemoryPersistence(
@@ -144,6 +184,52 @@ export class AgentBlockHandler implements BlockHandler {
     return result
   }
 
+  /**
+   * Derives the compact routing signals for sim-auto resolution from the
+   * block's resolved inputs. Excerpts only — the resolver truncates further
+   * and mothership re-clamps server-side.
+   */
+  private buildAutoRoutingSignals(inputs: AgentInputs, responseFormat: any): AutoRoutingSignals {
+    const lastMessage =
+      typeof inputs.userPrompt === 'string'
+        ? inputs.userPrompt
+        : inputs.userPrompt != null
+          ? stringifyJSON(inputs.userPrompt)
+          : (inputs.messages?.at(-1)?.content ?? '')
+    const systemPrompt = inputs.systemPrompt ?? ''
+    const normalizedFiles = normalizeFileInput(inputs.files)
+    const approxChars =
+      systemPrompt.length +
+      lastMessage.length +
+      (inputs.messages ? stringifyJSON(inputs.messages).length : 0)
+
+    return {
+      systemPrompt,
+      lastMessage,
+      messageCount: (inputs.messages?.length ?? 0) + (inputs.userPrompt ? 1 : 0),
+      toolNames: (inputs.tools ?? []).map((t) => t.title || t.type || 'tool'),
+      hasAttachments: Array.isArray(normalizedFiles)
+        ? normalizedFiles.length > 0
+        : Boolean(normalizedFiles),
+      hasResponseFormat: Boolean(responseFormat),
+      approxInputTokens: Math.ceil(approxChars / 4),
+    }
+  }
+
+  /**
+   * Adds the billable sim-auto routing charge to a non-streaming output's
+   * cost breakdown as a distinct `routing` component.
+   */
+  private applyRoutingCost(output: BlockOutput, routingCost: number): void {
+    const target = output as { cost?: Record<string, number> }
+    if (target.cost && typeof target.cost.total === 'number') {
+      target.cost.routing = routingCost
+      target.cost.total += routingCost
+    } else {
+      target.cost = { input: 0, output: 0, routing: routingCost, total: routingCost }
+    }
+  }
+
   private async validateToolPermissions(ctx: ExecutionContext, tools: ToolInput[]): Promise<void> {
     if (!Array.isArray(tools) || tools.length === 0) return
 

apps/sim/lib/copilot/tools/server/workflow/edit-workflow/validation.ts

@@ -2,6 +2,7 @@ import { createLogger } from '@sim/logger'
 import { toError } from '@sim/utils/errors'
 import { omit } from '@sim/utils/object'
 import { validateSelectorIds } from '@/lib/copilot/validation/selector-validator'
+import { isHosted as isHostedDeployment } from '@/lib/core/config/env-flags'
 import { isBlockTypeAccessControlExempt } from '@/lib/permission-groups/block-access'
 import type { PermissionGroupConfig } from '@/lib/permission-groups/types'
 import { getCustomToolById } from '@/lib/workflows/custom-tools/operations'
@@ -16,7 +17,7 @@ import { getBlock } from '@/blocks/registry'
 import type { SubBlockConfig } from '@/blocks/types'
 import { getModelOptions } from '@/blocks/utils'
 import { BlockType, EDGE, normalizeName } from '@/executor/constants'
-import { isKnownModelId, suggestModelIdsForUnknownModel } from '@/providers/models'
+import { isAutoModel, isKnownModelId, suggestModelIdsForUnknownModel } from '@/providers/models'
 import { isPiByokOnlyMode } from '@/providers/pi-providers'
 import { getTool } from '@/tools/utils'
 import { TRIGGER_RUNTIME_SUBBLOCK_IDS, TRIGGER_WEBHOOK_URL_FIELD } from '@/triggers/constants'
@@ -557,6 +558,12 @@ export function validateValueForSubBlockType(
       if (usesProviderCatalog) {
         const stringValue = typeof value === 'string' ? value : String(value)
         const trimmed = stringValue.trim()
+        // sim-auto is a valid model value on hosted Sim only (mirrors the
+        // options array the agent reads: it is absent from self-hosted
+        // snapshots, so writes of it there are rejected as unknown).
+        if (trimmed !== '' && isAutoModel(trimmed) && isHostedDeployment) {
+          return { valid: true, value: trimmed.toLowerCase() }
+        }
         if (trimmed !== '' && !isKnownModelId(trimmed)) {
           const suggestions = suggestModelIdsForUnknownModel(trimmed)
           const suggestionText =

apps/sim/lib/copilot/vfs/serializers.ts

@@ -12,7 +12,11 @@ import { getBlock } from '@/blocks'
 import { isCustomBlockType } from '@/blocks/custom/build-config'
 import type { BlockConfig, SubBlockConfig } from '@/blocks/types'
 import { isHiddenUnder } from '@/blocks/visibility/context'
-import { DYNAMIC_MODEL_PROVIDERS, PROVIDER_DEFINITIONS } from '@/providers/models'
+import {
+  DYNAMIC_MODEL_PROVIDERS,
+  PROVIDER_DEFINITIONS,
+  SIM_AUTO_MODEL_ID,
+} from '@/providers/models'
 import type { ToolConfig, ToolHostingCondition } from '@/tools/types'
 
 /** The service-account alternative to OAuth for a service, when it offers one. */
@@ -500,6 +504,18 @@ function getStaticModelOptionsForVFS(): StaticModelOption[] {
 
   const models: StaticModelOption[] = []
 
+  // Hosted-only automatic model: presence in this options array is what
+  // licenses the build agent to write it (its prompt guidance is conditioned
+  // on presence), so self-hosted snapshots never carry it.
+  if (isHosted) {
+    models.push({
+      id: SIM_AUTO_MODEL_ID,
+      provider: 'sim',
+      hosted: true,
+      recommended: true,
+    })
+  }
+
   for (const [providerId, def] of Object.entries(PROVIDER_DEFINITIONS)) {
     if (dynamicProviders.has(providerId)) continue
     for (const model of def.models) {