Add stepfun/step-3.5-flash:free (#2342)

Author: chrarnoldus

apps/web/src/lib/models.ts

@@ -20,6 +20,7 @@ import { KIMI_CURRENT_MODEL_ID } from '@/lib/providers/moonshotai';
 import { morph_warp_grep_free_model } from '@/lib/providers/morph';
 import { gpt_oss_20b_free_model } from '@/lib/providers/openai';
 import { qwen36_plus_model } from '@/lib/providers/qwen';
+import { stepfun_35_flash_free_model } from '@/lib/providers/stepfun';
 import { grok_code_fast_1_optimized_free_model } from '@/lib/providers/xai';
 
 export const PRIMARY_DEFAULT_MODEL = CLAUDE_SONNET_CURRENT_MODEL_ID;
@@ -69,6 +70,7 @@ export const kiloExclusiveModels = [
   qwen36_plus_model,
   trinity_large_thinking_free_model,
   claude_sonnet_clawsetup_model,
+  stepfun_35_flash_free_model,
 ] as KiloExclusiveModel[];
 
 export function isKiloStealthModel(model: string): boolean {

apps/web/src/lib/providers/index.ts

@@ -42,6 +42,7 @@ import {
   addCacheBreakpoints,
   injectReasoningIntoContent,
 } from '@/lib/providers/openrouter/request-helpers';
+import { isStepFunModel } from '@/lib/providers/stepfun';
 
 function inferSupportedChatApis(
   aiSdkProvider: CustomLlmProvider | undefined,
@@ -257,6 +258,9 @@ function getPreferredProviderOrder(requestedModel: string): string[] {
   if (isMoonshotModel(requestedModel)) {
     return [OpenRouterInferenceProviderIdSchema.enum.moonshotai];
   }
+  if (isStepFunModel(requestedModel)) {
+    return [OpenRouterInferenceProviderIdSchema.enum.stepfun];
+  }
   if (isZaiModel(requestedModel)) {
     return [OpenRouterInferenceProviderIdSchema.enum['z-ai']];
   }

apps/web/src/lib/providers/openrouter/inference-provider-id.ts

@@ -17,6 +17,7 @@ export const OpenRouterInferenceProviderIdSchema = z.enum([
   'mistral',
   'novita',
   'seed',
+  'stepfun',
   'streamlake',
   'stealth',
   'z-ai',

apps/web/src/lib/providers/stepfun.ts

@@ -0,0 +1,20 @@
+import type { KiloExclusiveModel } from '@/lib/providers/kilo-exclusive-model';
+
+export function isStepFunModel(requestedModel: string) {
+  return requestedModel.startsWith('stepfun/');
+}
+
+export const stepfun_35_flash_free_model: KiloExclusiveModel = {
+  public_id: 'stepfun/step-3.5-flash:free',
+  display_name: 'StepFun: Step 3.5 Flash (free)',
+  description:
+    "Step 3.5 Flash is StepFun's most capable open-source foundation model. Built on a sparse Mixture of Experts (MoE) architecture, it selectively activates only 11B of its 196B parameters per token. It is a reasoning model that is incredibly speed efficient even at long contexts.",
+  context_length: 262_144,
+  max_completion_tokens: 262_144,
+  status: 'public',
+  flags: ['reasoning'],
+  gateway: 'openrouter',
+  internal_id: 'stepfun/step-3.5-flash',
+  inference_provider: null,
+  pricing: null,
+};

apps/web/src/tests/openrouter-models-sorting.approved.json

@@ -702,6 +702,51 @@
       "isFree": true,
       "opencode": {}
     },
+    {
+      "id": "stepfun/step-3.5-flash:free",
+      "canonical_slug": "stepfun/step-3.5-flash:free",
+      "hugging_face_id": "",
+      "name": "StepFun: Step 3.5 Flash (free)",
+      "created": 1756238927,
+      "description": "Step 3.5 Flash is StepFun's most capable open-source foundation model. Built on a sparse Mixture of Experts (MoE) architecture, it selectively activates only 11B of its 196B parameters per token. It is a reasoning model that is incredibly speed efficient even at long contexts.",
+      "context_length": 262144,
+      "architecture": {
+        "modality": "text->text",
+        "input_modalities": [
+          "text"
+        ],
+        "output_modalities": [
+          "text"
+        ],
+        "tokenizer": "Other",
+        "instruct_type": null
+      },
+      "pricing": {
+        "prompt": "0.000000000000",
+        "completion": "0.000000000000",
+        "request": "0",
+        "image": "0",
+        "web_search": "0",
+        "internal_reasoning": "0",
+        "input_cache_read": "0.000000000000"
+      },
+      "top_provider": {
+        "context_length": 262144,
+        "max_completion_tokens": 262144,
+        "is_moderated": false
+      },
+      "per_request_limits": null,
+      "supported_parameters": [
+        "max_tokens",
+        "temperature",
+        "tools",
+        "reasoning",
+        "include_reasoning"
+      ],
+      "default_parameters": {},
+      "isFree": true,
+      "opencode": {}
+    },
     {
       "id": "kilo-auto/small",
       "name": "Kilo Auto Small",