refactor: dedupe finite number coercion helper

src/agents/usage.ts

@@ -1,3 +1,5 @@
+import { asFiniteNumber } from "../shared/number-coercion.js";
+
 export type UsageLike = {
   input?: number;
   output?: number;
@@ -68,16 +70,6 @@ export function makeZeroUsageSnapshot(): AssistantUsageSnapshot {
   };
 }
 
-const asFiniteNumber = (value: unknown): number | undefined => {
-  if (typeof value !== "number") {
-    return undefined;
-  }
-  if (!Number.isFinite(value)) {
-    return undefined;
-  }
-  return value;
-};
-
 export function hasNonzeroUsage(usage?: NormalizedUsage | null): usage is NormalizedUsage {
   if (!usage) {
     return false;

src/infra/retry.ts

@@ -1,3 +1,4 @@
+import { asFiniteNumber } from "../shared/number-coercion.js";
 import { sleep } from "../utils.js";
 import { generateSecureFraction } from "./secure-random.js";
 
@@ -30,9 +31,6 @@ const DEFAULT_RETRY_CONFIG = {
   jitter: 0,
 };
 
-const asFiniteNumber = (value: unknown): number | undefined =>
-  typeof value === "number" && Number.isFinite(value) ? value : undefined;
-
 const clampNumber = (value: unknown, fallback: number, min?: number, max?: number) => {
   const next = asFiniteNumber(value);
   if (next === undefined) {

src/infra/session-cost-usage.ts

@@ -18,6 +18,7 @@ import {
 } from "../config/sessions/paths.js";
 import type { SessionEntry } from "../config/sessions/types.js";
 import { stripEnvelope, stripMessageIdHints } from "../shared/chat-envelope.js";
+import { asFiniteNumber } from "../shared/number-coercion.js";
 import { countToolResults, extractToolCallNames } from "../utils/transcript-tools.js";
 import { estimateUsageCost, resolveModelCostConfig } from "../utils/usage-format.js";
 import type {
@@ -74,16 +75,6 @@ const emptyTotals = (): CostUsageTotals => ({
   missingCostEntries: 0,
 });
 
-const toFiniteNumber = (value: unknown): number | undefined => {
-  if (typeof value !== "number") {
-    return undefined;
-  }
-  if (!Number.isFinite(value)) {
-    return undefined;
-  }
-  return value;
-};
-
 const extractCostBreakdown = (usageRaw?: UsageLike | null): CostBreakdown | undefined => {
   if (!usageRaw || typeof usageRaw !== "object") {
     return undefined;
@@ -94,17 +85,17 @@ const extractCostBreakdown = (usageRaw?: UsageLike | null): CostBreakdown | unde
     return undefined;
   }
 
-  const total = toFiniteNumber(cost.total);
+  const total = asFiniteNumber(cost.total);
   if (total === undefined || total < 0) {
     return undefined;
   }
 
   return {
     total,
-    input: toFiniteNumber(cost.input),
-    output: toFiniteNumber(cost.output),
-    cacheRead: toFiniteNumber(cost.cacheRead),
-    cacheWrite: toFiniteNumber(cost.cacheWrite),
+    input: asFiniteNumber(cost.input),
+    output: asFiniteNumber(cost.output),
+    cacheRead: asFiniteNumber(cost.cacheRead),
+    cacheWrite: asFiniteNumber(cost.cacheWrite),
   };
 };
 
@@ -117,7 +108,7 @@ const parseTimestamp = (entry: Record<string, unknown>): Date | undefined => {
     }
   }
   const message = entry.message as Record<string, unknown> | undefined;
-  const messageTimestamp = toFiniteNumber(message?.timestamp);
+  const messageTimestamp = asFiniteNumber(message?.timestamp);
   if (messageTimestamp !== undefined) {
     const parsed = new Date(messageTimestamp);
     if (!Number.isNaN(parsed.valueOf())) {
@@ -152,7 +143,7 @@ const parseTranscriptEntry = (entry: Record<string, unknown>): ParsedTranscriptE
 
   const costBreakdown = extractCostBreakdown(usageRaw);
   const stopReason = typeof message.stopReason === "string" ? message.stopReason : undefined;
-  const durationMs = toFiniteNumber(message.durationMs ?? entry.durationMs);
+  const durationMs = asFiniteNumber(message.durationMs ?? entry.durationMs);
 
   return {
     message,

src/shared/number-coercion.ts

@@ -0,0 +1,3 @@
+export function asFiniteNumber(value: unknown): number | undefined {
+  return typeof value === "number" && Number.isFinite(value) ? value : undefined;
+}

src/tts/provider-error-utils.ts

@@ -1,3 +1,5 @@
+export { asFiniteNumber } from "../shared/number-coercion.js";
+
 export function trimToUndefined(value: unknown): string | undefined {
   return typeof value === "string" && value.trim().length > 0 ? value.trim() : undefined;
 }
@@ -6,10 +8,6 @@ export function asBoolean(value: unknown): boolean | undefined {
   return typeof value === "boolean" ? value : undefined;
 }
 
-export function asFiniteNumber(value: unknown): number | undefined {
-  return typeof value === "number" && Number.isFinite(value) ? value : undefined;
-}
-
 export function asObject(value: unknown): Record<string, unknown> | undefined {
   return typeof value === "object" && value !== null && !Array.isArray(value)
     ? (value as Record<string, unknown>)