fix(amp): fallback missing model pricing to zero-cost in codex/amp (#858)

* fix: fallback missing model pricing to zero-cost in codex/amp

* refactor(codex,amp): use `as const satisfies` for zero-cost pricing constants

Replace explicit type annotations with `as const satisfies ModelPricing`
for FREE_MODEL_PRICING (codex) and ZERO_MODEL_PRICING (amp) to get
narrower literal types while maintaining type safety.

---------

Co-authored-by: ryoppippi <1560508+ryoppippi@users.noreply.github.com>

Author: gulivan

apps/amp/src/pricing.ts

@@ -7,6 +7,12 @@ import { prefetchAmpPricing } from './_macro.ts' with { type: 'macro' };
 import { logger } from './logger.ts';
 
 const AMP_PROVIDER_PREFIXES = ['anthropic/'];
+const ZERO_MODEL_PRICING = {
+	inputCostPerMToken: 0,
+	cachedInputCostPerMToken: 0,
+	cacheCreationCostPerMToken: 0,
+	outputCostPerMToken: 0,
+} as const satisfies ModelPricing;
 
 function toPerMillion(value: number | undefined, fallback?: number): number {
 	const perToken = value ?? fallback ?? 0;
@@ -44,7 +50,8 @@ export class AmpPricingSource implements PricingSource, Disposable {
 
 		const pricing = directLookup.value;
 		if (pricing == null) {
-			throw new Error(`Pricing not found for model ${model}`);
+			logger.warn(`Pricing not found for model ${model}; defaulting to zero-cost pricing.`);
+			return ZERO_MODEL_PRICING;
 		}
 
 		return {
@@ -134,5 +141,15 @@ if (import.meta.vitest != null) {
 			const expected = 1000 * 1e-6 + 500 * 5e-6 + 200 * 1e-7 + 100 * 1.25e-6;
 			expect(cost).toBeCloseTo(expected);
 		});
+
+		it('falls back to zero pricing for unknown models', async () => {
+			using source = new AmpPricingSource({
+				offline: true,
+				offlineLoader: async () => ({}),
+			});
+
+			const pricing = await source.getPricing('anthropic/unknown');
+			expect(pricing).toEqual(ZERO_MODEL_PRICING);
+		});
 	});
 }

apps/codex/src/pricing.ts

@@ -11,6 +11,20 @@ const CODEX_MODEL_ALIASES_MAP = new Map<string, string>([
 	['gpt-5-codex', 'gpt-5'],
 	['gpt-5.3-codex', 'gpt-5.2-codex'],
 ]);
+const FREE_MODEL_PRICING = {
+	inputCostPerMToken: 0,
+	cachedInputCostPerMToken: 0,
+	outputCostPerMToken: 0,
+} as const satisfies ModelPricing;
+
+function isOpenRouterFreeModel(model: string): boolean {
+	const normalized = model.trim().toLowerCase();
+	if (normalized === 'openrouter/free') {
+		return true;
+	}
+
+	return normalized.startsWith('openrouter/') && normalized.endsWith(':free');
+}
 
 function hasNonZeroTokenPricing(pricing: LiteLLMModelPricing): boolean {
 	return (
@@ -49,6 +63,10 @@ export class CodexPricingSource implements PricingSource, Disposable {
 	}
 
 	async getPricing(model: string): Promise<ModelPricing> {
+		if (isOpenRouterFreeModel(model)) {
+			return FREE_MODEL_PRICING;
+		}
+
 		const directLookup = await this.fetcher.getModelPricing(model);
 		if (Result.isFailure(directLookup)) {
 			throw directLookup.error;
@@ -67,7 +85,8 @@ export class CodexPricingSource implements PricingSource, Disposable {
 		}
 
 		if (pricing == null) {
-			throw new Error(`Pricing not found for model ${model}`);
+			logger.warn(`Pricing not found for model ${model}; defaulting to zero-cost pricing.`);
+			return FREE_MODEL_PRICING;
 		}
 
 		return {
@@ -101,6 +120,29 @@ if (import.meta.vitest != null) {
 			expect(pricing.cachedInputCostPerMToken).toBeCloseTo(0.125);
 		});
 
+		it('returns zero pricing for OpenRouter free routes', async () => {
+			using source = new CodexPricingSource({
+				offline: true,
+				offlineLoader: async () => ({}),
+			});
+
+			const directFree = await source.getPricing('openrouter/free');
+			expect(directFree).toEqual(FREE_MODEL_PRICING);
+
+			const modelFree = await source.getPricing('openrouter/openai/gpt-5:free');
+			expect(modelFree).toEqual(FREE_MODEL_PRICING);
+		});
+
+		it('falls back to zero pricing for unknown non-free models', async () => {
+			using source = new CodexPricingSource({
+				offline: true,
+				offlineLoader: async () => ({}),
+			});
+
+			const pricing = await source.getPricing('openrouter/unknown');
+			expect(pricing).toEqual(FREE_MODEL_PRICING);
+		});
+
 		it('falls back to alias pricing when direct model pricing is all zeros', async () => {
 			using source = new CodexPricingSource({
 				offline: true,