diff --git a/changelog.d/features/7879-numeric-helpers-foundation.md b/changelog.d/features/7879-numeric-helpers-foundation.md
new file mode 100644
index 0000000000..c49b2f4453
--- /dev/null
+++ b/changelog.d/features/7879-numeric-helpers-foundation.md
@@ -0,0 +1 @@
+- **feat(shared):** Add canonical numeric coercion helpers (`toNumber`, `toNumberOrNull`, `toNumberArray`) in `src/shared/utils/numeric.ts` with table-driven tests and a lint rule barring new local `toNumber` definitions, then migrate the report/analytics tier (usage analytics route, provider metrics route, usage stats, usage history helpers, call-log formatting, cost-analysis A2A skill) off their local duplicates ([#7879](https://github.com/diegosouzapw/OmniRoute/issues/7879))
diff --git a/config/quality/eslint-suppressions.json b/config/quality/eslint-suppressions.json
index 789ad579cc..0e1a9eccf3 100644
--- a/config/quality/eslint-suppressions.json
+++ b/config/quality/eslint-suppressions.json
@@ -74,11 +74,26 @@
       "count": 1
     }
   },
+  "open-sse/handlers/responseSanitizer.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
+  "open-sse/handlers/responseTranslator.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
   "open-sse/handlers/search.ts": {
     "@typescript-eslint/no-explicit-any": {
       "count": 34
     }
   },
+  "open-sse/handlers/sseParser.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
   "open-sse/handlers/videoGeneration.ts": {
     "@typescript-eslint/no-explicit-any": {
       "count": 1
@@ -104,9 +119,22 @@
       "count": 2
     }
   },
+  "open-sse/mcp-server/audit.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
   "open-sse/mcp-server/server.ts": {
     "@typescript-eslint/no-explicit-any": {
       "count": 3
+    },
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
+  "open-sse/mcp-server/tools/advancedTools.ts": {
+    "no-restricted-syntax": {
+      "count": 1
     }
   },
   "open-sse/mcp-server/tools/gamificationTools.ts": {
@@ -114,14 +142,32 @@
       "count": 2
     }
   },
+  "open-sse/mcp-server/tools/pickFastestModel.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
   "open-sse/mcp-server/tools/pluginTools.ts": {
     "@typescript-eslint/no-explicit-any": {
       "count": 1
     }
   },
+  "open-sse/services/agentrouterQuotaFetcher.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
+  "open-sse/services/bailianQuotaFetcher.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
   "open-sse/services/batchProcessor.ts": {
     "@typescript-eslint/no-explicit-any": {
       "count": 17
+    },
+    "no-restricted-syntax": {
+      "count": 1
     }
   },
   "open-sse/services/claudeWebAutoRefresh.ts": {
@@ -129,6 +175,16 @@
       "count": 3
     }
   },
+  "open-sse/services/codexQuotaFetcher.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
+  "open-sse/services/codexUsageQuotas.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
   "open-sse/services/compression/engines/headroom/gcf/decode_generic.ts": {
     "@typescript-eslint/no-explicit-any": {
       "count": 22
@@ -149,11 +205,41 @@
       "count": 1
     }
   },
+  "open-sse/services/crofUsageFetcher.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
+  "open-sse/services/deepseekQuotaFetcher.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
+  "open-sse/services/genericQuotaFetcher.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
   "open-sse/services/inAppLoginService.ts": {
     "@typescript-eslint/no-explicit-any": {
       "count": 2
     }
   },
+  "open-sse/services/opencodeOllamaUsage.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
+  "open-sse/services/opencodeQuotaFetcher.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
+  "open-sse/services/rateLimitManager.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
   "open-sse/services/taskAwareRouter.ts": {
     "@typescript-eslint/no-explicit-any": {
       "count": 4
@@ -169,11 +255,26 @@
       "count": 2
     }
   },
+  "open-sse/services/usage/scalars.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
+  "open-sse/services/v0QuotaFetcher.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
   "open-sse/utils/setupPolyfill.ts": {
     "@typescript-eslint/no-explicit-any": {
       "count": 5
     }
   },
+  "open-sse/utils/streamPayloadCollector.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
   "src/app/(dashboard)/dashboard/HomePageClient.tsx": {
     "react-hooks/exhaustive-deps": {
       "count": 1
@@ -234,11 +335,96 @@
       "count": 1
     }
   },
+  "src/domain/costRules.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
   "src/hooks/useLiveDashboard.ts": {
     "react-hooks/exhaustive-deps": {
       "count": 2
     }
   },
+  "src/lib/a2a/skills/healthReport.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
+  "src/lib/combos/controlCenter.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
+  "src/lib/db/comboForecast.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
+  "src/lib/db/domainState.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
+  "src/lib/db/prompts.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
+  "src/lib/db/providers/lazyConnectionView.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
+  "src/lib/db/tokenLimits.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
+  "src/lib/monitoring/providerHealthAutopilot.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
+  "src/lib/monitoring/providerHealthMatrix.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
+  "src/lib/semanticCache.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
+  "src/lib/usage/apiKeySelfService.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
+  "src/lib/usage/apiKeyUsageLimits.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
+  "src/lib/usage/costCalculator.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
+  "src/lib/usage/internalUsageCommand.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
+  "src/lib/usage/providerWindowCosts.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
+  "src/lib/usage/routeExplain.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
   "src/shared/components/CursorAuthModal.tsx": {
     "react-hooks/exhaustive-deps": {
       "count": 1
@@ -269,6 +455,16 @@
       "count": 1
     }
   },
+  "src/shared/contracts/quota.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
+  "src/sse/services/auth.ts": {
+    "no-restricted-syntax": {
+      "count": 1
+    }
+  },
   "tests/e2e/api.spec.ts": {
     "@typescript-eslint/no-explicit-any": {
       "count": 3
diff --git a/eslint.config.mjs b/eslint.config.mjs
index 10af3f1154..7dcca1e2b8 100644
--- a/eslint.config.mjs
+++ b/eslint.config.mjs
@@ -1,6 +1,18 @@
 import nextVitals from "eslint-config-next/core-web-vitals";
 import tseslint from "typescript-eslint";
 
+// #7879: bar NEW local `toNumber` definitions outside the canonical helper.
+// Pre-existing definitions (~51 across the codebase) are frozen via
+// config/quality/eslint-suppressions.json and migrated tier-by-tier; only a
+// genuinely NEW `function toNumber`/`const toNumber = ...` should fail.
+const TO_NUMBER_RESTRICTION = {
+  selector: "FunctionDeclaration[id.name='toNumber'], VariableDeclarator[id.name='toNumber']",
+  message:
+    "New local `toNumber` definitions are barred — import `toNumber` from " +
+    "`@/shared/utils/numeric` instead (#7879). See that module's JSDoc for the " +
+    "canonical coercion shape and the `toNumberOrNull`/`toNumberArray` variants.",
+};
+
 /** @type {import("eslint").Linter.Config[]} */
 const eslintConfig = [
   ...nextVitals,
@@ -56,9 +68,28 @@ const eslintConfig = [
           message:
             "Türkçe-güvenli arama için matchesSearch() kullan (@/shared/utils/turkishText). Ham toLowerCase().includes() İ/ı karakterlerini bozar.",
         },
+        TO_NUMBER_RESTRICTION,
       ],
     },
   },
+  // #7879: same toNumber restriction for the rest of src/ and open-sse/ — kept
+  // as a separate block (via `ignores`) so it does not clobber the
+  // app/components-scoped rule array above (flat config replaces a rule's
+  // options entirely per matching file, it does not merge arrays).
+  {
+    files: ["src/**/*.ts", "open-sse/**/*.ts"],
+    ignores: ["src/app/**", "src/components/**"],
+    rules: {
+      "no-restricted-syntax": ["error", TO_NUMBER_RESTRICTION],
+    },
+  },
+  // Canonical helper module itself is exempt from its own restriction.
+  {
+    files: ["src/shared/utils/numeric.ts"],
+    rules: {
+      "no-restricted-syntax": "off",
+    },
+  },
   // Relaxed rules for open-sse and tests (incremental adoption)
   {
     files: ["open-sse/**/*.ts", "tests/**/*.mjs", "tests/**/*.ts"],
diff --git a/src/app/api/provider-metrics/route.ts b/src/app/api/provider-metrics/route.ts
index d849cb9a9e..3b6e16a0a7 100644
--- a/src/app/api/provider-metrics/route.ts
+++ b/src/app/api/provider-metrics/route.ts
@@ -4,18 +4,10 @@ import pino from "pino";
 import { buildErrorBody } from "@omniroute/open-sse/utils/error.ts";
 
 import { getProviderMetrics } from "@/lib/db/callLogStats";
+import { toNumber } from "@/shared/utils/numeric";
 
 const logger = pino({ name: "provider-metrics-api" });
 
-function toNumber(value: unknown): number {
-  if (typeof value === "number" && Number.isFinite(value)) return value;
-  if (typeof value === "string" && value.trim().length > 0) {
-    const parsed = Number(value);
-    return Number.isFinite(parsed) ? parsed : 0;
-  }
-  return 0;
-}
-
 /**
  * GET /api/provider-metrics — Aggregate per-provider stats from call_logs
  * Returns aggregate metrics plus topology recency/error hints for dashboard visualization.
diff --git a/src/app/api/usage/analytics/route.ts b/src/app/api/usage/analytics/route.ts
index 648b3fdbac..ae2c2e9d96 100644
--- a/src/app/api/usage/analytics/route.ts
+++ b/src/app/api/usage/analytics/route.ts
@@ -23,6 +23,7 @@ import {
 } from "@/lib/db/usageAnalytics";
 import { getFallbackStats } from "@/lib/db/callLogStats";
 import { buildByProviderRows } from "@/lib/usage/providerDisplayNames";
+import { toNumber } from "@/shared/utils/numeric";
 
 function getRangeStartIso(range: string): string | null {
   const end = new Date();
@@ -74,15 +75,6 @@ type GetCodexFastCostMultiplier = (
   serviceTier: string | null | undefined
 ) => number;
 
-function toNumber(value: unknown): number {
-  if (typeof value === "number" && Number.isFinite(value)) return value;
-  if (typeof value === "string" && value.trim().length > 0) {
-    const parsed = Number(value);
-    return Number.isFinite(parsed) ? parsed : 0;
-  }
-  return 0;
-}
-
 function toStringValue(value: unknown, fallback = ""): string {
   return typeof value === "string" && value.trim().length > 0 ? value : fallback;
 }
diff --git a/src/lib/a2a/skills/costAnalysis.ts b/src/lib/a2a/skills/costAnalysis.ts
index 300579ef34..7a0cebdc7d 100644
--- a/src/lib/a2a/skills/costAnalysis.ts
+++ b/src/lib/a2a/skills/costAnalysis.ts
@@ -7,6 +7,7 @@
 import type { A2ATask, TaskArtifact } from "../taskManager";
 import { resolveOmniRouteBaseUrl } from "@/shared/utils/resolveOmniRouteBaseUrl";
 import { formatCost } from "@/shared/utils/formatting";
+import { toNumber } from "@/shared/utils/numeric";
 
 type AnalyticsRecord = Record<string, unknown>;
 
@@ -45,14 +46,6 @@ async function costFetch(path: string): Promise<AnalyticsRecord> {
   return response.json();
 }
 
-function toNumber(value: unknown): number {
-  if (typeof value === "number" && Number.isFinite(value)) return value;
-  if (typeof value === "string" && value.trim()) {
-    const parsed = Number(value);
-    return Number.isFinite(parsed) ? parsed : 0;
-  }
-  return 0;
-}
 
 function toCostEntries(value: unknown): CostEntry[] {
   if (!value || typeof value !== "object" || Array.isArray(value)) return [];
diff --git a/src/lib/usage/callLogs/format.ts b/src/lib/usage/callLogs/format.ts
index 12788b371f..4582527482 100644
--- a/src/lib/usage/callLogs/format.ts
+++ b/src/lib/usage/callLogs/format.ts
@@ -2,6 +2,9 @@ import type { RequestPipelinePayloads } from "@omniroute/open-sse/utils/requestL
 import { sanitizePII } from "../../piiSanitizer";
 import { protectPayloadForLog } from "../../logPayloads";
 import type { CallLogDetailState } from "../callLogArtifacts";
+// #7879: re-export the canonical helper so existing consumers of this module
+// keep importing `toNumber` from here unchanged.
+export { toNumber } from "@/shared/utils/numeric";
 
 type JsonRecord = Record<string, unknown>;
 
@@ -9,15 +12,6 @@ export function asRecord(value: unknown): JsonRecord {
   return value && typeof value === "object" && !Array.isArray(value) ? (value as JsonRecord) : {};
 }
 
-export function toNumber(value: unknown): number {
-  if (typeof value === "number" && Number.isFinite(value)) return value;
-  if (typeof value === "string" && value.trim().length > 0) {
-    const parsed = Number(value);
-    return Number.isFinite(parsed) ? parsed : 0;
-  }
-  return 0;
-}
-
 export function toStringOrNull(value: unknown): string | null {
   return typeof value === "string" && value.trim().length > 0 ? value : null;
 }
diff --git a/src/lib/usage/usageHistory/helpers.ts b/src/lib/usage/usageHistory/helpers.ts
index cb18ea3b88..38e8579528 100644
--- a/src/lib/usage/usageHistory/helpers.ts
+++ b/src/lib/usage/usageHistory/helpers.ts
@@ -3,6 +3,10 @@
  * No DB access, no module-level state — safe to import anywhere.
  */
 
+// #7879: re-export the canonical helper so existing consumers of this module
+// keep importing `toNumber` from here unchanged.
+export { toNumber } from "@/shared/utils/numeric";
+
 type JsonRecord = Record<string, unknown>;
 
 export function asRecord(value: unknown): JsonRecord {
@@ -20,15 +24,6 @@ export function normalizeServiceTier(value: unknown): string {
   return "standard";
 }
 
-export function toNumber(value: unknown): number {
-  if (typeof value === "number" && Number.isFinite(value)) return value;
-  if (typeof value === "string" && value.trim().length > 0) {
-    const parsed = Number(value);
-    return Number.isFinite(parsed) ? parsed : 0;
-  }
-  return 0;
-}
-
 export function percentile(sortedValues: number[], p: number): number {
   if (sortedValues.length === 0) return 0;
   if (sortedValues.length === 1) return sortedValues[0];
diff --git a/src/lib/usage/usageStats.ts b/src/lib/usage/usageStats.ts
index 778b843110..b4be4d1967 100644
--- a/src/lib/usage/usageStats.ts
+++ b/src/lib/usage/usageStats.ts
@@ -13,6 +13,7 @@ import { getPendingRequests } from "./usageHistory";
 import { getAccountDisplayName } from "@/lib/display/names";
 import { calculateCost } from "./costCalculator";
 import { getRawDataCutoffDate, isAggregationEnabled } from "./aggregateHistory";
+import { toNumber } from "@/shared/utils/numeric";
 
 type JsonRecord = Record<string, unknown>;
 type UsageBucket = {
@@ -44,15 +45,6 @@ function asRecord(value: unknown): JsonRecord {
   return value && typeof value === "object" && !Array.isArray(value) ? (value as JsonRecord) : {};
 }
 
-function toNumber(value: unknown): number {
-  if (typeof value === "number" && Number.isFinite(value)) return value;
-  if (typeof value === "string" && value.trim().length > 0) {
-    const parsed = Number(value);
-    return Number.isFinite(parsed) ? parsed : 0;
-  }
-  return 0;
-}
-
 function toStringOrEmpty(value: unknown): string {
   return typeof value === "string" ? value : "";
 }
diff --git a/src/shared/utils/numeric.ts b/src/shared/utils/numeric.ts
new file mode 100644
index 0000000000..cb3f04135d
--- /dev/null
+++ b/src/shared/utils/numeric.ts
@@ -0,0 +1,70 @@
+/**
+ * Canonical numeric coercion helpers — DRY extraction from ~51 near-identical
+ * local `toNumber` definitions scattered across `src/` and `open-sse/` (#7879).
+ *
+ * All three variants share the SAME strict coercion shape as the dominant
+ * pre-existing pattern found across the codebase:
+ *   - `number` inputs pass through only when `Number.isFinite`.
+ *   - `string` inputs are `trim()`-med first; empty/whitespace-only strings
+ *     are treated as absent. The trimmed string is coerced with `Number(...)`
+ *     and accepted only when the result is finite (rejects `"12abc"`,
+ *     `"Infinity"`, `"NaN"`, etc).
+ *   - Every other type (`null`, `undefined`, `boolean`, `object`, `array`, ...)
+ *     is treated as absent.
+ *
+ * This is intentionally the STRICT variant — it does NOT use `parseFloat`
+ * (which would accept `"12abc"` -> `12`). A small number of call sites in the
+ * codebase intentionally keep `parseFloat` (leniency is a documented,
+ * deliberate behavior choice there, not a bug) — see
+ * `open-sse/services/crofUsageFetcher.ts` for the annotated exception.
+ *
+ * Migration is happening tier-by-tier (report/analytics first, then
+ * quota/billing, then hot-path auth/costRules/combo) to avoid silently
+ * changing fallback semantics anywhere cost or quota math depends on it.
+ * See the issue for the full plan.
+ */
+
+/**
+ * Coerce an unknown value to a finite number, or return `fallback` (default
+ * `0`) when the value cannot be strictly coerced.
+ *
+ * @param v - the value to coerce.
+ * @param fallback - value returned when coercion fails (default `0`).
+ */
+export function toNumber(v: unknown, fallback = 0): number {
+  if (typeof v === "number" && Number.isFinite(v)) return v;
+  if (typeof v === "string" && v.trim().length > 0) {
+    const parsed = Number(v.trim());
+    return Number.isFinite(parsed) ? parsed : fallback;
+  }
+  return fallback;
+}
+
+/**
+ * Coerce an unknown value to a finite number, or `null` when the value
+ * cannot be strictly coerced. Same coercion shape as {@link toNumber}, but
+ * with a `null` fallback instead of `0` — useful where "absent" must stay
+ * distinguishable from "zero" downstream (e.g. optional metrics).
+ */
+export function toNumberOrNull(v: unknown): number | null {
+  if (typeof v === "number" && Number.isFinite(v)) return v;
+  if (typeof v === "string" && v.trim().length > 0) {
+    const parsed = Number(v.trim());
+    return Number.isFinite(parsed) ? parsed : null;
+  }
+  return null;
+}
+
+/**
+ * Coerce an unknown value to an array of finite numbers.
+ *
+ * - Non-array inputs return `fallback` (default `[]`) unchanged.
+ * - Each array element is coerced independently via {@link toNumber}; an
+ *   element that fails to coerce becomes `0` (NOT the array-level
+ *   `fallback` — the two fallbacks are intentionally independent so a
+ *   caller can distinguish "no array at all" from "one bad element").
+ */
+export function toNumberArray(v: unknown, fallback: number[] = []): number[] {
+  if (!Array.isArray(v)) return fallback;
+  return v.map((item) => toNumber(item, 0));
+}
diff --git a/tests/unit/a2a-cost-analysis-numeric-fallback.test.ts b/tests/unit/a2a-cost-analysis-numeric-fallback.test.ts
new file mode 100644
index 0000000000..734ca47437
--- /dev/null
+++ b/tests/unit/a2a-cost-analysis-numeric-fallback.test.ts
@@ -0,0 +1,80 @@
+import assert from "node:assert/strict";
+import { test } from "node:test";
+
+import { executeCostAnalysis } from "../../src/lib/a2a/skills/costAnalysis.ts";
+import type { A2ATask } from "../../src/lib/a2a/taskManager.ts";
+
+// #7879: the cost-analysis A2A skill migrated its local `toNumber` to the
+// canonical `@/shared/utils/numeric` helper. This test proves the 0-fallback
+// semantics for missing/non-numeric analytics fields still hold after the
+// migration (the whole point of the tier-1 move).
+
+function buildTask(): A2ATask {
+  const now = new Date().toISOString();
+  return {
+    id: "test-task",
+    skill: "cost-analysis",
+    state: "working",
+    input: { skill: "cost-analysis", messages: [{ role: "user", content: "cost report" }] },
+    artifacts: [],
+    events: [],
+    metadata: {},
+    createdAt: now,
+    updatedAt: now,
+    expiresAt: now,
+  };
+}
+
+test("executeCostAnalysis: missing/non-numeric summary fields fall back to 0", async (t) => {
+  const originalFetch = globalThis.fetch;
+  t.after(() => {
+    globalThis.fetch = originalFetch;
+  });
+
+  globalThis.fetch = (async () =>
+    new Response(
+      JSON.stringify({
+        summary: {
+          totalCost: "abc", // non-numeric -> 0
+          // totalRequests missing entirely -> 0
+          fallbackRatePct: null, // -> 0
+        },
+        byProvider: {},
+        byModel: {},
+      }),
+      { status: 200, headers: { "Content-Type": "application/json" } }
+    )) as typeof fetch;
+
+  const result = await executeCostAnalysis(buildTask());
+
+  assert.equal(result.metadata.totalCost, 0);
+  assert.equal(result.metadata.totalRequests, 0);
+  assert.equal(result.metadata.providerCosts.length, 0);
+  assert.equal(result.metadata.modelCosts.length, 0);
+});
+
+test("executeCostAnalysis: numeric-string summary fields coerce correctly", async (t) => {
+  const originalFetch = globalThis.fetch;
+  t.after(() => {
+    globalThis.fetch = originalFetch;
+  });
+
+  globalThis.fetch = (async () =>
+    new Response(
+      JSON.stringify({
+        summary: { totalCost: "12.5", totalRequests: "42", fallbackRatePct: "3.2" },
+        byProvider: {
+          openai: { cost: "1.5", requests: "3", tokens: "100" },
+        },
+        byModel: {},
+      }),
+      { status: 200, headers: { "Content-Type": "application/json" } }
+    )) as typeof fetch;
+
+  const result = await executeCostAnalysis(buildTask());
+
+  assert.equal(result.metadata.totalCost, 12.5);
+  assert.equal(result.metadata.totalRequests, 42);
+  assert.equal(result.metadata.providerCosts[0]?.cost, 1.5);
+  assert.equal(result.metadata.providerCosts[0]?.requests, 3);
+});
diff --git a/tests/unit/numeric-helpers.test.ts b/tests/unit/numeric-helpers.test.ts
new file mode 100644
index 0000000000..4002f0e55c
--- /dev/null
+++ b/tests/unit/numeric-helpers.test.ts
@@ -0,0 +1,89 @@
+import assert from "node:assert/strict";
+import { test } from "node:test";
+
+import {
+  toNumber,
+  toNumberOrNull,
+  toNumberArray,
+} from "../../src/shared/utils/numeric.ts";
+
+// Shared input matrix covering the coercion edge cases that motivated
+// consolidating ~51 near-duplicate `toNumber` definitions (#7879).
+const CASES: Array<{ label: string; input: unknown; finite: number | null }> = [
+  { label: "null", input: null, finite: null },
+  { label: "undefined", input: undefined, finite: null },
+  { label: "empty string", input: "", finite: null },
+  { label: "whitespace string", input: "  ", finite: null },
+  { label: "numeric string", input: "12", finite: 12 },
+  { label: "decimal string", input: "12.5", finite: 12.5 },
+  { label: "negative string", input: "-3", finite: -3 },
+  { label: "zero string", input: "0", finite: 0 },
+  { label: "non-numeric string", input: "abc", finite: null },
+  { label: "partially-numeric string", input: "12abc", finite: null },
+  { label: "NaN", input: NaN, finite: null },
+  { label: "Infinity", input: Infinity, finite: null },
+  { label: "-Infinity", input: -Infinity, finite: null },
+  { label: "plain object", input: {}, finite: null },
+  { label: "empty array", input: [], finite: null },
+  { label: "exponential string", input: "1e3", finite: 1000 },
+  { label: "boolean true", input: true, finite: null },
+];
+
+test("toNumber: matrix with default fallback (0)", () => {
+  for (const { label, input, finite } of CASES) {
+    const expected = finite ?? 0;
+    assert.equal(toNumber(input), expected, `toNumber(${label}) should be ${expected}`);
+  }
+});
+
+test("toNumber: matrix with custom fallback", () => {
+  for (const { label, input, finite } of CASES) {
+    const expected = finite ?? -1;
+    assert.equal(
+      toNumber(input, -1),
+      expected,
+      `toNumber(${label}, -1) should be ${expected}`
+    );
+  }
+});
+
+test("toNumber: numbers pass through untouched", () => {
+  assert.equal(toNumber(42), 42);
+  assert.equal(toNumber(-7.5), -7.5);
+  assert.equal(toNumber(0), 0);
+});
+
+test("toNumberOrNull: matrix returns null instead of 0 fallback", () => {
+  for (const { label, input, finite } of CASES) {
+    assert.equal(
+      toNumberOrNull(input),
+      finite,
+      `toNumberOrNull(${label}) should be ${finite}`
+    );
+  }
+});
+
+test("toNumberOrNull: numbers pass through untouched", () => {
+  assert.equal(toNumberOrNull(42), 42);
+  assert.equal(toNumberOrNull(0), 0);
+});
+
+test("toNumberArray: non-array input returns the fallback unchanged", () => {
+  assert.deepEqual(toNumberArray(null), []);
+  assert.deepEqual(toNumberArray(undefined), []);
+  assert.deepEqual(toNumberArray("not an array"), []);
+  assert.deepEqual(toNumberArray({}), []);
+  assert.deepEqual(toNumberArray(null, [1, 2]), [1, 2]);
+});
+
+test("toNumberArray: maps each element through toNumber, bad elements become 0", () => {
+  assert.deepEqual(toNumberArray(["12", "12.5", "abc", null, 3]), [12, 12.5, 0, 0, 3]);
+  assert.deepEqual(toNumberArray([]), []);
+});
+
+test("toNumberArray: element-level fallback (0) is independent of the array-level fallback", () => {
+  // Array itself IS present (so array-level fallback does not apply), but one
+  // element fails to coerce and must fall back to 0, not to the caller's
+  // array-level fallback value.
+  assert.deepEqual(toNumberArray(["abc"], [99]), [0]);
+});