API proxy: first-class AI-credit accounting for Copilot auto dynamic selector

containers/api-proxy/guards/ai-credits-guard.js

@@ -27,6 +27,26 @@ const BUILTIN_FALLBACK_PRICING = Object.freeze({
   output: 15.00,
 });
 
+// Conservative fallback pricing for recognized dynamic selectors whose concrete
+// runtime model is unknown at accounting time.
+const DYNAMIC_SELECTOR_FALLBACK_PRICING = Object.freeze({
+  input: 3.00,
+  cachedInput: 0.30,
+  cacheWrite: 3.75,
+  output: 15.00,
+});
+
+function getDynamicSelectorDescriptor(model, provider = undefined) {
+  if (typeof model !== 'string') return null;
+  if (provider !== PROVIDER_COPILOT) return null;
+  if (model.toLowerCase() !== 'auto') return null;
+  return { name: 'copilot:auto' };
+}
+
+function isRecognizedDynamicSelector(model, provider = undefined) {
+  return !!getDynamicSelectorDescriptor(model, provider);
+}
+
 function roundCredits(value) {
   return Math.round((value + Number.EPSILON) * 1_000_000) / 1_000_000;
 }
@@ -102,7 +122,7 @@ function resolveModelPricing(model, state = aiCreditsState, provider = undefined
     .every(field => Object.hasOwn(runtime.pricing, field))) {
     return runtime;
   }
-  const fallback = resolveLowerPriorityPricing(model, state, options);
+  const fallback = resolveLowerPriorityPricing(model, state, { ...options, provider });
   if (!runtime) return fallback;
   const mergedPricing = {};
   for (const field of ['input', 'cachedInput', 'cacheWrite', 'output']) {
@@ -147,6 +167,18 @@ function resolveLowerPriorityPricing(model, state, options = {}) {
     return { pricing: catalogModel.pricing, source: 'models.dev', tier: 'default' };
   }
 
+  const dynamicSelector = getDynamicSelectorDescriptor(model, options.provider);
+  if (dynamicSelector) {
+    return {
+      pricing: DYNAMIC_SELECTOR_FALLBACK_PRICING,
+      source: 'dynamic_selector_fallback',
+      tier: 'conservative',
+      accountingPolicy: 'dynamic_selector_fallback',
+      dynamicSelector: dynamicSelector.name,
+      usedFallbackPricing: true,
+    };
+  }
+
   // Speculative callers (e.g. filtering a fallback candidate pool) pass quiet:true
   // so that probing a model neither emits an operator-facing warning nor marks the
   // model as already-warned — which would suppress the warning if it is genuinely
@@ -249,6 +281,7 @@ function calculateAiCredits(normalizedUsage, model, state = aiCreditsState, prov
   const pricingResolution = resolveModelPricing(model, state, provider, totalInputForTier);
   if (!pricingResolution) return null;
   const { pricing } = pricingResolution;
+  const dynamicSelector = getDynamicSelectorDescriptor(model, provider);
 
   // input_tokens semantics differ by provider:
   //  - Anthropic and Copilot's precise copilot_usage report input_tokens as the
@@ -283,6 +316,13 @@ function calculateAiCredits(normalizedUsage, model, state = aiCreditsState, prov
     pricingObservedAt: pricingResolution.observedAt,
     pricingApiVersion: pricingResolution.apiVersion,
     pricingDiscountPercent: pricingResolution.discountPercent,
+    accountingPolicy: pricingResolution.accountingPolicy ||
+      (dynamicSelector ? 'dynamic_selector_runtime' : model === 'unknown' ? 'unknown_model_fallback' : 'concrete_model'),
+    usedFallbackPricing: pricingResolution.usedFallbackPricing === true ||
+      pricingResolution.source === 'configured_default' ||
+      pricingResolution.source === 'builtin_fallback' ||
+      pricingResolution.source === 'dynamic_selector_fallback',
+    dynamicSelector: pricingResolution.dynamicSelector || dynamicSelector?.name || null,
   };
 }
 
@@ -301,6 +341,9 @@ function applyAiCreditsUsage(normalizedUsage, model, provider = undefined) {
       totalCredits: 0,
       pricingSource: calc.pricingSource,
       pricingTier: calc.pricingTier,
+      accountingPolicy: calc.accountingPolicy,
+      fallbackPricingUsed: calc.usedFallbackPricing,
+      dynamicSelector: calc.dynamicSelector,
     };
   }
 
@@ -312,6 +355,9 @@ function applyAiCreditsUsage(normalizedUsage, model, provider = undefined) {
   modelBucket.totalCredits += calc.totalCredits;
   modelBucket.pricingSource = calc.pricingSource;
   modelBucket.pricingTier = calc.pricingTier;
+  modelBucket.accountingPolicy = calc.accountingPolicy;
+  modelBucket.fallbackPricingUsed = calc.usedFallbackPricing;
+  modelBucket.dynamicSelector = calc.dynamicSelector;
   aiCreditsState.totalAiCredits += calc.totalCredits;
 
   process.env.AWF_AI_CREDITS_USED = String(roundCredits(aiCreditsState.totalAiCredits));
@@ -325,6 +371,9 @@ function applyAiCreditsUsage(normalizedUsage, model, provider = undefined) {
     totalAiCredits: roundCredits(aiCreditsState.totalAiCredits),
     pricingSource: calc.pricingSource,
     pricingTier: calc.pricingTier,
+    accountingPolicy: calc.accountingPolicy,
+    fallbackPricingUsed: calc.usedFallbackPricing,
+    dynamicSelector: calc.dynamicSelector,
     ...(calc.pricingObservedAt ? { pricingObservedAt: calc.pricingObservedAt } : {}),
     ...(calc.pricingApiVersion ? { pricingApiVersion: calc.pricingApiVersion } : {}),
     ...(calc.pricingDiscountPercent !== undefined
@@ -344,6 +393,9 @@ function getAiCreditsReflectState() {
       total: roundCredits(usage.totalCredits),
       pricing_source: usage.pricingSource,
       pricing_tier: usage.pricingTier,
+      accounting_policy: usage.accountingPolicy || null,
+      fallback_pricing_used: usage.fallbackPricingUsed === true,
+      dynamic_selector: usage.dynamicSelector || null,
     };
   }
   return {
@@ -404,6 +456,7 @@ module.exports = {
   getAiCreditsBlockState,
   buildAiCreditsLimitError,
   checkUnknownModelRejection,
+  isRecognizedDynamicSelector,
   isModelPriceable,
   canonicalizeModel,
   resetAiCreditsGuardForTests,

containers/api-proxy/guards/ai-credits-guard.test.js

@@ -5,6 +5,7 @@ const {
   getAiCreditsBlockState,
   buildAiCreditsLimitError,
   checkUnknownModelRejection,
+  isRecognizedDynamicSelector,
   isModelPriceable,
   canonicalizeModel,
   resetAiCreditsGuardForTests,
@@ -77,6 +78,9 @@ describe('ai-credits-guard', () => {
           total: 0.12275,
           pricing_source: 'curated',
           pricing_tier: 'default',
+          accounting_policy: 'concrete_model',
+          fallback_pricing_used: false,
+          dynamic_selector: null,
         },
       },
     });
@@ -665,15 +669,53 @@ describe('ai-credits-guard', () => {
       expect(sonnet5).toBeNull();
     });
 
-    it('rejects the auto selector when runtime pricing cannot be proven', () => {
+    it('allows the Copilot auto selector and rejects unknown-provider auto selectors', () => {
       process.env.AWF_MAX_AI_CREDITS = '10';
       resetAiCreditsGuardForTests();
 
-      expect(checkUnknownModelRejection('auto', PROVIDER_COPILOT)).not.toBeNull();
+      expect(checkUnknownModelRejection('auto', PROVIDER_COPILOT)).toBeNull();
       expect(checkUnknownModelRejection('auto', PROVIDER_OPENAI)).not.toBeNull();
     });
   });
 
+  it('uses conservative dynamic-selector fallback pricing for Copilot auto', () => {
+    process.env.AWF_MAX_AI_CREDITS = '10';
+    resetAiCreditsGuardForTests();
+
+    const usage = applyAiCreditsUsage({
+      input_tokens: 1000,
+      output_tokens: 500,
+    }, 'auto', PROVIDER_COPILOT);
+
+    expect(usage).toMatchObject({
+      aiCreditsThisResponse: 1.05,
+      pricingSource: 'dynamic_selector_fallback',
+      pricingTier: 'conservative',
+      accountingPolicy: 'dynamic_selector_fallback',
+      fallbackPricingUsed: true,
+      dynamicSelector: 'copilot:auto',
+    });
+    expect(isRecognizedDynamicSelector('auto', PROVIDER_COPILOT)).toBe(true);
+    expect(isRecognizedDynamicSelector('auto', PROVIDER_OPENAI)).toBe(false);
+    expect(getAiCreditsReflectState()).toEqual({
+      total: 1.05,
+      by_model: {
+        auto: {
+          input_credits: 0.3,
+          cached_input_credits: 0,
+          cache_write_credits: 0,
+          output_credits: 0.75,
+          total: 1.05,
+          pricing_source: 'dynamic_selector_fallback',
+          pricing_tier: 'conservative',
+          accounting_policy: 'dynamic_selector_fallback',
+          fallback_pricing_used: true,
+          dynamic_selector: 'copilot:auto',
+        },
+      },
+    });
+  });
+
   describe('isModelPriceable (side-effect-free)', () => {
     it('reports priced and unpriced models correctly', () => {
       expect(isModelPriceable('gpt-4-turbo', PROVIDER_OPENAI)).toBe(true);

containers/api-proxy/guards/common-guard-checks.js

@@ -131,7 +131,7 @@ function buildCommonGuardChecks(deps, model, provider = null) {
     // Model-specific guards — only active when a model was identified in the request.
     ...(model ? [
       {
-        block: getModelMultiplierCapBlockState(model),
+        block: getModelMultiplierCapBlockState(model, provider),
         isBlocked: block => !!block,
         statusCode: 400,
         eventName: 'model_multiplier_cap_exceeded',

containers/api-proxy/guards/max-model-multiplier-guard.js

@@ -2,6 +2,7 @@
 
 const { sanitizeForLog } = require('../logging');
 const { parseModelMultipliers, parsePositiveNumber } = require('./guard-utils');
+const { isRecognizedDynamicSelector } = require('./ai-credits-guard');
 
 const maxModelMultiplierConfigCache = {
   rawCap: undefined,
@@ -65,11 +66,11 @@ function resolveMultiplierForModel(model, config) {
  * @param {string|null} model - The model name from the request body (may be null)
  * @returns {{ model: string, multiplier: number, maxModelMultiplier: number } | null}
  */
-function getModelMultiplierCapBlockState(model) {
+function getModelMultiplierCapBlockState(model, provider = undefined) {
   const config = getMaxModelMultiplierConfig();
   if (!config.cap || !model) return null;
 
-  if (model.toLowerCase() === 'auto' && !Object.hasOwn(config.multipliers, model)) {
+  if (isRecognizedDynamicSelector(model, provider) && !Object.hasOwn(config.multipliers, model)) {
     return {
       model: sanitizeForLog(model),
       multiplier: null,
@@ -99,7 +100,7 @@ function buildModelMultiplierCapError(state) {
     return {
       error: {
         type: 'model_multiplier_cap_unverifiable',
-        message: 'Model "auto" selects a concrete model at runtime, so its multiplier cannot be proven to be within the configured cap. Configure an explicit multiplier for "auto" to opt in.',
+        message: `Model "${state.model}" selects a concrete model at runtime, so its multiplier cannot be proven to be within the configured cap. Configure an explicit multiplier for "${state.model}" to opt in.`,
         model: state.model,
         model_multiplier: null,
         max_model_multiplier: state.maxModelMultiplier,

containers/api-proxy/guards/max-model-multiplier-guard.test.js

@@ -5,6 +5,7 @@ const {
   buildModelMultiplierCapError,
   resetMaxModelMultiplierGuardForTests,
 } = require('./max-model-multiplier-guard');
+const { PROVIDER_COPILOT, PROVIDER_OPENAI } = require('../provider-names');
 
 describe('max-model-multiplier-guard', () => {
   beforeEach(() => {
@@ -85,10 +86,10 @@ describe('max-model-multiplier-guard', () => {
       expect(getModelMultiplierCapBlockState('unknown-model')).toBeNull();
     });
 
-    it('fails closed for auto unless an explicit multiplier is configured', () => {
+    it('fails closed for Copilot auto unless an explicit multiplier is configured', () => {
       process.env.AWF_MAX_MODEL_MULTIPLIER = '5';
 
-      const state = getModelMultiplierCapBlockState('auto');
+      const state = getModelMultiplierCapBlockState('auto', PROVIDER_COPILOT);
       expect(state).toMatchObject({
         model: 'auto',
         multiplier: null,
@@ -102,7 +103,13 @@ describe('max-model-multiplier-guard', () => {
       process.env.AWF_MAX_MODEL_MULTIPLIER = '5';
       process.env.AWF_EFFECTIVE_TOKEN_MODEL_MULTIPLIERS = JSON.stringify({ auto: 5 });
 
-      expect(getModelMultiplierCapBlockState('auto')).toBeNull();
+      expect(getModelMultiplierCapBlockState('auto', PROVIDER_COPILOT)).toBeNull();
+    });
+
+    it('treats non-Copilot auto as a normal model name', () => {
+      process.env.AWF_MAX_MODEL_MULTIPLIER = '5';
+
+      expect(getModelMultiplierCapBlockState('auto', PROVIDER_OPENAI)).toBeNull();
     });
 
     it('blocks when configured default multiplier for unknown model exceeds cap', () => {

containers/api-proxy/server.token-guards.test.js

@@ -341,7 +341,7 @@ describe('proxyRequest max-ai-credits guard', () => {
     expect(payload.error.total_ai_credits).toBeGreaterThanOrEqual(0.1);
   });
 
-  it('rejects Copilot auto when its concrete runtime price cannot be proven', async () => {
+  it('allows Copilot auto and defers accounting to runtime usage tracking', async () => {
     const upstreamRequest = makeProxyReq();
     const httpsRequestSpy = jest.spyOn(https, 'request').mockImplementation(() => upstreamRequest);
 
@@ -351,11 +351,8 @@ describe('proxyRequest max-ai-credits guard', () => {
     req.emit('end');
     await flushPromises();
 
-    expect(httpsRequestSpy).not.toHaveBeenCalled();
-    expect(res.writeHead).toHaveBeenCalledWith(400, expect.objectContaining({
-      'Content-Type': 'application/json',
-    }));
-    expect(JSON.parse(res.end.mock.calls[0][0]).type).toBe('unknown_model_ai_credits');
+    expect(httpsRequestSpy).toHaveBeenCalledTimes(1);
+    expect(res.writeHead).not.toHaveBeenCalledWith(400, expect.anything());
   });
 });
 

containers/api-proxy/token-budget-log.js

@@ -30,6 +30,9 @@ function computeTokenBudgetUsage({ logRequest, requestId, provider }, normalized
       ai_credits_total: aiCreditsUsage.totalAiCredits,
       pricing_source: aiCreditsUsage.pricingSource,
       pricing_tier: aiCreditsUsage.pricingTier,
+      accounting_policy: aiCreditsUsage.accountingPolicy,
+      fallback_pricing_used: aiCreditsUsage.fallbackPricingUsed,
+      dynamic_selector: aiCreditsUsage.dynamicSelector,
     });
   }
   const budgetFields = {};
@@ -43,6 +46,9 @@ function computeTokenBudgetUsage({ logRequest, requestId, provider }, normalized
     budgetFields.ai_credits_total = aiCreditsUsage.totalAiCredits;
     budgetFields.ai_credits_pricing_source = aiCreditsUsage.pricingSource;
     budgetFields.ai_credits_pricing_tier = aiCreditsUsage.pricingTier;
+    budgetFields.ai_credits_accounting_policy = aiCreditsUsage.accountingPolicy;
+    budgetFields.ai_credits_fallback_pricing_used = aiCreditsUsage.fallbackPricingUsed;
+    budgetFields.ai_credits_dynamic_selector = aiCreditsUsage.dynamicSelector;
     if (aiCreditsUsage.pricingObservedAt) {
       budgetFields.ai_credits_pricing_observed_at = aiCreditsUsage.pricingObservedAt;
     }

containers/api-proxy/token-budget-log.test.js

@@ -112,4 +112,30 @@ describe('computeTokenBudgetUsage', () => {
     });
     expect(logRequest).toHaveBeenCalledTimes(1);
   });
+
+  it('reports dynamic selector accounting policy in token diagnostics', () => {
+    process.env.AWF_MAX_AI_CREDITS = '100';
+    const result = computeTokenBudgetUsage(
+      { logRequest, requestId: 'req-dynamic', provider: 'copilot' },
+      { input_tokens: 1000, output_tokens: 500 },
+      'auto',
+    );
+
+    expect(result).toMatchObject({
+      ai_credits_pricing_source: 'dynamic_selector_fallback',
+      ai_credits_pricing_tier: 'conservative',
+      ai_credits_accounting_policy: 'dynamic_selector_fallback',
+      ai_credits_fallback_pricing_used: true,
+      ai_credits_dynamic_selector: 'copilot:auto',
+    });
+    expect(logRequest).toHaveBeenCalledWith('info', 'token_budget_usage', expect.objectContaining({
+      request_id: 'req-dynamic',
+      provider: 'copilot',
+      model: 'auto',
+      pricing_source: 'dynamic_selector_fallback',
+      accounting_policy: 'dynamic_selector_fallback',
+      fallback_pricing_used: true,
+      dynamic_selector: 'copilot:auto',
+    }));
+  });
 });

containers/api-proxy/token-tracker-shared.js

@@ -45,6 +45,9 @@ function mergeBudgetFields(record, budgetResult) {
   for (const field of [
     'ai_credits_pricing_source',
     'ai_credits_pricing_tier',
+    'ai_credits_accounting_policy',
+    'ai_credits_fallback_pricing_used',
+    'ai_credits_dynamic_selector',
     'ai_credits_pricing_observed_at',
     'ai_credits_pricing_api_version',
     'ai_credits_pricing_discount_percent',