diff --git a/packages/loopover-engine/src/discovery-index-contract.ts b/packages/loopover-engine/src/discovery-index-contract.ts
index 6a0b8f06af..c8342ca149 100644
--- a/packages/loopover-engine/src/discovery-index-contract.ts
+++ b/packages/loopover-engine/src/discovery-index-contract.ts
@@ -174,6 +174,15 @@ export function normalizeDiscoveryIndexRequest(raw: unknown): ParsedDiscoveryInd
     warnings.push("DiscoveryIndexRequest must be a mapping; falling back to an empty query.");
   }
   const source = record ?? {};
+  // #9615: surface (never reject) a declared version skew through the existing warnings channel -- the
+  // same push-one-templated-string-and-continue style as clampLimit and the #6774 candidate cap. An
+  // absent or non-number declaration stays silent by the tolerant-parser convention: an older/looser
+  // sender is not an error.
+  if (typeof source.contractVersion === "number" && source.contractVersion !== DISCOVERY_INDEX_CONTRACT_VERSION) {
+    warnings.push(
+      `DiscoveryIndexRequest declared contractVersion ${source.contractVersion}; this build speaks ${DISCOVERY_INDEX_CONTRACT_VERSION}.`,
+    );
+  }
   const query: DiscoveryIndexQuery = {
     repos: normalizeStringList(source.repos, normalizeRepoFullName),
     orgs: normalizeStringList(source.orgs, normalizeOwner),
@@ -239,6 +248,15 @@ export function normalizeDiscoveryIndexResponse(raw: unknown): ParsedDiscoveryIn
   if (!record) {
     warnings.push("DiscoveryIndexResponse must be a mapping; falling back to an empty candidate list.");
   }
+  // #9615: same version-skew warning as the request side -- a server speaking another contract version is
+  // surfaced instead of being silently relabelled as this build's version. Warning only: nothing below is
+  // rejected, dropped, or changed by it.
+  const declaredVersion = record?.contractVersion;
+  if (typeof declaredVersion === "number" && declaredVersion !== DISCOVERY_INDEX_CONTRACT_VERSION) {
+    warnings.push(
+      `DiscoveryIndexResponse declared contractVersion ${declaredVersion}; this build speaks ${DISCOVERY_INDEX_CONTRACT_VERSION}.`,
+    );
+  }
   const rawCandidates = record && Array.isArray(record.candidates) ? record.candidates : [];
   // #6774: the request side clamps page size to MAX_PAGE_LIMIT, but this response comes from the OPTIONAL,
   // only-partially-trusted hosted index (see this module's header). A misbehaving or compromised host could
diff --git a/packages/loopover-engine/test/discovery-index-contract-version.test.ts b/packages/loopover-engine/test/discovery-index-contract-version.test.ts
new file mode 100644
index 0000000000..7931c2e85a
--- /dev/null
+++ b/packages/loopover-engine/test/discovery-index-contract-version.test.ts
@@ -0,0 +1,50 @@
+import assert from "node:assert/strict";
+import { test } from "node:test";
+
+import {
+  DISCOVERY_INDEX_CONTRACT_VERSION,
+  normalizeDiscoveryIndexRequest,
+  normalizeDiscoveryIndexResponse,
+} from "../dist/index.js";
+
+// #9615: a declared contract-version skew is surfaced through the tolerant parser's existing warnings
+// channel on both wire directions, instead of being silently relabelled as this build's version.
+
+test("normalizeDiscoveryIndexRequest surfaces a declared contract-version skew as a warning (#9615)", () => {
+  const parsed = normalizeDiscoveryIndexRequest({ contractVersion: 99, repos: ["a/b"] });
+  assert.ok(
+    parsed.warnings.includes(
+      `DiscoveryIndexRequest declared contractVersion 99; this build speaks ${DISCOVERY_INDEX_CONTRACT_VERSION}.`,
+    ),
+  );
+  assert.equal(parsed.request.contractVersion, DISCOVERY_INDEX_CONTRACT_VERSION);
+  assert.deepEqual(parsed.request.query.repos, ["a/b"]);
+});
+
+test("normalizeDiscoveryIndexResponse surfaces a declared contract-version skew as a warning (#9615)", () => {
+  const parsed = normalizeDiscoveryIndexResponse({ contractVersion: 99, candidates: [] });
+  assert.ok(
+    parsed.warnings.includes(
+      `DiscoveryIndexResponse declared contractVersion 99; this build speaks ${DISCOVERY_INDEX_CONTRACT_VERSION}.`,
+    ),
+  );
+  assert.equal(parsed.response.contractVersion, DISCOVERY_INDEX_CONTRACT_VERSION);
+});
+
+test("version warnings stay silent for absent, non-number, and matching declarations (#9615)", () => {
+  assert.deepEqual(normalizeDiscoveryIndexRequest({ repos: ["a/b"] }).warnings, []);
+  assert.deepEqual(normalizeDiscoveryIndexRequest({ contractVersion: "1", repos: ["a/b"] }).warnings, []);
+  assert.deepEqual(normalizeDiscoveryIndexRequest({ contractVersion: 1, repos: ["a/b"] }).warnings, []);
+  assert.deepEqual(normalizeDiscoveryIndexResponse({ candidates: [] }).warnings, []);
+  assert.deepEqual(normalizeDiscoveryIndexResponse({ contractVersion: "1", candidates: [] }).warnings, []);
+  const matching = normalizeDiscoveryIndexResponse({
+    contractVersion: 1,
+    candidates: [{ repoFullName: "owner/repo", issueNumber: 1, title: "x" }],
+  });
+  assert.deepEqual(matching.warnings, []);
+  assert.equal(matching.response.candidates[0]?.repoFullName, "owner/repo");
+  // A non-mapping response takes the optional-chain's undefined arm and stays version-silent too.
+  assert.deepEqual(normalizeDiscoveryIndexResponse(null).warnings, [
+    "DiscoveryIndexResponse must be a mapping; falling back to an empty candidate list.",
+  ]);
+});
diff --git a/packages/loopover-miner/lib/discovery-index-client.ts b/packages/loopover-miner/lib/discovery-index-client.ts
index 8c0821d3ee..294b7c9e50 100644
--- a/packages/loopover-miner/lib/discovery-index-client.ts
+++ b/packages/loopover-miner/lib/discovery-index-client.ts
@@ -100,7 +100,11 @@ export async function queryDiscoveryIndex(
       {
         method: "POST",
         headers: { "content-type": "application/json", ...authHeaders(env) },
-        body: JSON.stringify(request.query),
+        // #9615: send the whole normalized request -- the contract version WITH the query -- flattened to
+        // one level, because the server parses this body with normalizeDiscoveryIndexRequest, which reads
+        // the query fields (and the declared contractVersion) off the top level. Nesting the query under a
+        // `query` key would make the version travel but the query invisible to the server's parse.
+        body: JSON.stringify({ contractVersion: request.contractVersion, ...request.query }),
       },
       { timeoutMs: options.requestTimeoutMs ?? DEFAULT_REQUEST_TIMEOUT_MS },
     );
diff --git a/test/unit/discovery-index-contract.test.ts b/test/unit/discovery-index-contract.test.ts
index cabf91f61f..883a0ba6c4 100644
--- a/test/unit/discovery-index-contract.test.ts
+++ b/test/unit/discovery-index-contract.test.ts
@@ -219,3 +219,32 @@ describe("repo-segment path safety in candidate normalization (#9610)", () => {
     expect(normalized?.repo).toBe("repo");
   });
 });
+
+describe("contractVersion skew warnings (#9615)", () => {
+  it("warns with the exact request-side message on a mismatched declared version, still emitting version 1", () => {
+    const parsed = normalizeDiscoveryIndexRequest({ contractVersion: 99, repos: ["a/b"] });
+    expect(parsed.warnings).toContain("DiscoveryIndexRequest declared contractVersion 99; this build speaks 1.");
+    expect(parsed.request.contractVersion).toBe(1);
+    expect(parsed.request.query.repos).toEqual(["a/b"]);
+  });
+
+  it("warns with the exact response-side message on a mismatched declared version, still emitting version 1", () => {
+    const parsed = normalizeDiscoveryIndexResponse({ contractVersion: 99, candidates: [] });
+    expect(parsed.warnings).toContain("DiscoveryIndexResponse declared contractVersion 99; this build speaks 1.");
+    expect(parsed.response.contractVersion).toBe(1);
+  });
+
+  it("stays silent when the declared version is absent or not a number (tolerant-parser convention)", () => {
+    expect(normalizeDiscoveryIndexRequest({ repos: ["a/b"] }).warnings).toEqual([]);
+    expect(normalizeDiscoveryIndexRequest({ contractVersion: "1", repos: ["a/b"] }).warnings).toEqual([]);
+    expect(normalizeDiscoveryIndexResponse({ candidates: [] }).warnings).toEqual([]);
+    expect(normalizeDiscoveryIndexResponse({ contractVersion: "1", candidates: [] }).warnings).toEqual([]);
+  });
+
+  it("stays silent on a matching declared version and still returns the candidates", () => {
+    const parsed = normalizeDiscoveryIndexResponse({ contractVersion: 1, candidates: [VALID_CANDIDATE] });
+    expect(parsed.warnings).toEqual([]);
+    expect(parsed.response.candidates.map((candidate) => candidate.repoFullName)).toEqual(["owner/repo"]);
+    expect(normalizeDiscoveryIndexRequest({ contractVersion: 1, repos: ["a/b"] }).warnings).toEqual([]);
+  });
+});
diff --git a/test/unit/miner-discovery-index-client.test.ts b/test/unit/miner-discovery-index-client.test.ts
index a6f218ccc4..730a515e28 100644
--- a/test/unit/miner-discovery-index-client.test.ts
+++ b/test/unit/miner-discovery-index-client.test.ts
@@ -9,6 +9,7 @@ vi.mock("../../packages/loopover-miner/lib/logger.js", () => ({
   getLogger: () => logSpy,
 }));
 
+import { normalizeDiscoveryIndexRequest } from "../../packages/loopover-engine/src/index";
 import {
   DISCOVERY_INDEX_URL_FLAG,
   DISCOVERY_PLANE_FLAG,
@@ -71,7 +72,7 @@ describe("queryDiscoveryIndex (#7168)", () => {
   it("posts the normalized query and returns the normalized response when enabled", async () => {
     const fetchImpl = vi.fn(async (url: string, init: RequestInit) => {
       expect(url).toBe("https://discovery.example.internal/v1/discovery-index/query");
-      expect(JSON.parse(String(init.body))).toMatchObject({ repos: ["a/b"] });
+      expect(JSON.parse(String(init.body))).toMatchObject({ contractVersion: 1, repos: ["a/b"] });
       return Response.json({
         contractVersion: 1,
         candidates: [
@@ -96,6 +97,31 @@ describe("queryDiscoveryIndex (#7168)", () => {
     expect(response.candidates[0]).toMatchObject({ repoFullName: "a/b", issueNumber: 1 });
   });
 
+  it("sends the contract version with the query fields at the top level, in a body the server-side parse round-trips (#9615)", async () => {
+    let sentBody: unknown;
+    const fetchImpl = vi.fn(async (_url: string, init: RequestInit) => {
+      sentBody = JSON.parse(String(init.body));
+      return Response.json({ contractVersion: 1, candidates: [], nextCursor: null });
+    });
+    await queryDiscoveryIndex({ repos: ["a/b"], searchTerms: [" help wanted "] }, { env: ENABLED_ENV, fetchImpl });
+
+    expect(sentBody).toEqual({
+      contractVersion: 1,
+      repos: ["a/b"],
+      orgs: [],
+      searchTerms: ["help wanted"],
+      limit: 50,
+      cursor: null,
+    });
+    // The server parses this exact body with normalizeDiscoveryIndexRequest (top-level fields, #9615):
+    // the widened body round-trips to the same normalized query the client computed, with no warning.
+    const reparsed = normalizeDiscoveryIndexRequest(sentBody);
+    expect(reparsed.warnings).toEqual([]);
+    expect(reparsed.request.query).toEqual(
+      normalizeDiscoveryIndexRequest({ repos: ["a/b"], searchTerms: [" help wanted "] }).request.query,
+    );
+  });
+
   it("fails open (returns empty) on a non-ok response or a thrown error", async () => {
     const notOk = await queryDiscoveryIndex({ repos: ["a/b"] }, { env: ENABLED_ENV, fetchImpl: async () => new Response("err", { status: 500 }) });
     expect(notOk.candidates).toEqual([]);