diff --git a/scripts/kpi-gate.mjs b/scripts/kpi-gate.mjs
index 12363af16..2ce57ef36 100644
--- a/scripts/kpi-gate.mjs
+++ b/scripts/kpi-gate.mjs
@@ -7,7 +7,9 @@ import { join } from "node:path";
 import { spawnSync } from "node:child_process";
 import { hasUnsafeSourceId } from "./lib/source-id.mjs";
 import { createKpiChildEnvironment } from "./lib/kpi-child-environment.mjs";
+import { hasDuplicateJsonObjectKeys } from "./normalize-commercial-readiness-evidence.mjs";
 
+const fatalUtf8Decoder = new TextDecoder("utf-8", { fatal: true });
 const parsedArgs = parseArgs(process.argv.slice(2));
 const logPath = parsedArgs.positionals[0] ?? process.env.NOEMA_KPI_LOG_PATH ?? "exchange-30d.ndjson";
 const failThreshold = parsedArgs.positionals[1] ?? process.env.NOEMA_KPI_FAILURE_THRESHOLD ?? "0.02";
@@ -233,9 +235,25 @@ async function loadProductionProvenance(path, expectedLogPath) {
     };
   }
 
+  let provenanceText;
+  try {
+    provenanceText = fatalUtf8Decoder.decode(await readFile(path));
+  } catch {
+    return {
+      pass: false,
+      reason: `KPI provenance file is not valid UTF-8: ${path}.`,
+    };
+  }
+
   let parsed;
   try {
-    parsed = JSON.parse(await readFile(path, "utf8"));
+    if (hasDuplicateJsonObjectKeys(provenanceText)) {
+      return {
+        pass: false,
+        reason: `KPI provenance file contains duplicate decoded JSON object keys: ${path}.`,
+      };
+    }
+    parsed = JSON.parse(provenanceText);
   } catch {
     return {
       pass: false,
@@ -461,4 +479,4 @@ function parseArgs(args) {
     result.positionals.push(arg);
   }
   return result;
-}
+}
\ No newline at end of file
diff --git a/test/kpi-provenance-json-integrity.test.ts b/test/kpi-provenance-json-integrity.test.ts
new file mode 100644
index 000000000..c8a072efd
--- /dev/null
+++ b/test/kpi-provenance-json-integrity.test.ts
@@ -0,0 +1,109 @@
+import { createHash } from "node:crypto";
+import { mkdtempSync, readFileSync, rmSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { spawnSync } from "node:child_process";
+import { describe, expect, it } from "vitest";
+
+function writeThirtyDayExchangeLog(path: string) {
+  const records = [
+    {
+      event: "http_request",
+      route: "/exchange",
+      status_code: 200,
+      latency_ms: 120,
+      timestamp: "2026-06-01T00:00:00.000Z",
+    },
+    {
+      event: "http_request",
+      route: "/exchange",
+      status_code: 200,
+      latency_ms: 150,
+      timestamp: "2026-07-01T03:00:00.000Z",
+    },
+  ];
+  writeFileSync(path, `${records.map((record) => JSON.stringify(record)).join("\n")}\n`);
+}
+
+function logIdentity(path: string) {
+  const bytes = readFileSync(path);
+  return {
+    logSha256: createHash("sha256").update(bytes).digest("hex"),
+    logBytes: bytes.byteLength,
+  };
+}
+
+function runStrictGate(logPath: string, provenancePath: string, evidencePath: string) {
+  return spawnSync(process.execPath, ["scripts/kpi-gate.mjs", logPath], {
+    cwd: process.cwd(),
+    encoding: "utf8",
+    env: {
+      ...process.env,
+      NOEMA_KPI_STRICT: "1",
+      NOEMA_KPI_REQUIRE_WINDOW_DAYS: "30",
+      NOEMA_KPI_PROVENANCE_PATH: provenancePath,
+      NOEMA_KPI_EVIDENCE_PATH: evidencePath,
+    },
+  });
+}
+
+function validProvenanceJson(logPath: string) {
+  const identity = logIdentity(logPath);
+  return JSON.stringify({
+    sourceKind: "production",
+    sourceId: "cloudflare-logpush:noema-production",
+    sourceMethod: "log-url",
+    logPath,
+    records: 2,
+    collectedAt: "2026-07-02T00:00:00.000Z",
+    ...identity,
+  });
+}
+
+describe("strict KPI provenance JSON integrity", () => {
+  it("rejects duplicate decoded provenance keys before last-key-wins parsing", () => {
+    const dir = mkdtempSync(join(tmpdir(), "noema-kpi-provenance-integrity-"));
+    try {
+      const logPath = join(dir, "exchange-30d.ndjson");
+      const provenancePath = join(dir, "exchange-30d.ndjson.provenance.json");
+      const evidencePath = join(dir, "evidence.json");
+      writeThirtyDayExchangeLog(logPath);
+      const { logSha256, logBytes } = logIdentity(logPath);
+      writeFileSync(
+        provenancePath,
+        `{"sourceKind":"staging","sourceK\\u0069nd":"production","sourceId":"cloudflare-logpush:noema-production","sourceMethod":"log-url","logPath":${JSON.stringify(logPath)},"records":2,"collectedAt":"2026-07-02T00:00:00.000Z","logSha256":"${logSha256}","logBytes":${logBytes}}`,
+      );
+
+      const result = runStrictGate(logPath, provenancePath, evidencePath);
+
+      expect(result.status).toBe(1);
+      expect(result.stdout).toContain("KPI provenance file");
+    } finally {
+      rmSync(dir, { recursive: true, force: true });
+    }
+  });
+
+  it("rejects malformed UTF-8 provenance bytes instead of replacement-decoding them", () => {
+    const dir = mkdtempSync(join(tmpdir(), "noema-kpi-provenance-integrity-"));
+    try {
+      const logPath = join(dir, "exchange-30d.ndjson");
+      const provenancePath = join(dir, "exchange-30d.ndjson.provenance.json");
+      const evidencePath = join(dir, "evidence.json");
+      writeThirtyDayExchangeLog(logPath);
+      const text = validProvenanceJson(logPath);
+      const bytes = Buffer.from(text, "utf8");
+      const marker = Buffer.from("log-url", "utf8");
+      const markerOffset = bytes.indexOf(marker);
+      expect(markerOffset).toBeGreaterThanOrEqual(0);
+      bytes[markerOffset] = 0x80;
+      writeFileSync(provenancePath, bytes);
+
+      const result = runStrictGate(logPath, provenancePath, evidencePath);
+
+      expect(result.status).toBe(1);
+      expect(result.stdout).toContain("KPI provenance file");
+    } finally {
+      rmSync(dir, { recursive: true, force: true });
+    }
+  });
+});