diff --git a/src/mcp/server.ts b/src/mcp/server.ts
index 2d4568338d..e4221f88f9 100644
--- a/src/mcp/server.ts
+++ b/src/mcp/server.ts
@@ -2346,13 +2346,15 @@ export class GittensoryMcp {
     if (!input.contributorLogin) throw new Error("contributorLogin is required for score breakdown.");
     this.requireContributorAccess(input.contributorLogin);
     await this.requireRepoAccess(input.repoFullName);
-    const [repo, snapshot, evidence] = await Promise.all([
+    const [repo, snapshot, evidence, contributorIssues] = await Promise.all([
       getRepository(this.env, input.repoFullName),
       getOrCreateScoringModelSnapshot(this.env),
       getContributorEvidence(this.env, input.contributorLogin),
+      listContributorIssues(this.env, input.contributorLogin),
     ]);
+    const openIssueCount = contributorOpenIssueCount(contributorIssues, input.repoFullName);
     // Time-decay (#703) is an owner-gated global, injected server-side (not caller-controllable).
-    const scoreInput = { ...input, applyTimeDecay: isTimeDecayEnabled(this.env) };
+    const scoreInput = { ...input, openIssueCount, applyTimeDecay: isTimeDecayEnabled(this.env) };
     const preview = buildScorePreview({ input: scoreInput, repo, snapshot, contributorEvidence: evidence });
     const breakdown = explainScoreBreakdown(preview);
     return {
diff --git a/test/unit/mcp-output-schemas.test.ts b/test/unit/mcp-output-schemas.test.ts
index eb67d72a70..9c505bbd84 100644
--- a/test/unit/mcp-output-schemas.test.ts
+++ b/test/unit/mcp-output-schemas.test.ts
@@ -271,6 +271,58 @@ describe("MCP tool calls return schema-valid structured content", () => {
     expect(data.highestLeverageLever).toBeTruthy();
   });
 
+  it("gittensory_explain_score_breakdown applies trusted open-issue counts", async () => {
+    const env = createTestEnv();
+    await upsertRepositoryFromGitHub(env, { name: "demo", full_name: "octo/demo", private: false, owner: { login: "octo" }, default_branch: "main" });
+    for (const number of [1, 2, 3]) {
+      await upsertIssueFromGitHub(env, "octo/demo", {
+        number,
+        title: `Open contributor issue ${number}`,
+        state: "open",
+        user: { login: "alice" },
+        labels: [],
+        body: "Issue body",
+      });
+    }
+    await upsertIssueFromGitHub(env, "octo/other", {
+      number: 99,
+      title: "Other repo issue",
+      state: "open",
+      user: { login: "alice" },
+      labels: [],
+      body: "Issue body",
+    });
+    await upsertIssueFromGitHub(env, "octo/demo", {
+      number: 4,
+      title: "Closed contributor issue",
+      state: "closed",
+      user: { login: "alice" },
+      labels: [],
+      body: "Issue body",
+    });
+
+    const { client } = await connectTestClient(env);
+    const result = await client.callTool({
+      name: "gittensory_explain_score_breakdown",
+      arguments: {
+        repoFullName: "octo/demo",
+        contributorLogin: "alice",
+        sourceTokenScore: 40,
+        totalTokenScore: 60,
+        sourceLines: 80,
+        openPrCount: 0,
+        credibility: 1,
+      },
+    });
+
+    expect(result.isError).toBeFalsy();
+    const data = result.structuredContent as Record<string, unknown>;
+    expect(data.effectiveEstimatedScore).toBe(0);
+    expect(data.gateHighlights).toEqual(
+      expect.arrayContaining([expect.objectContaining({ gate: "open_issue_threshold" })]),
+    );
+  });
+
   it("gittensory_explain_score_breakdown requires contributorLogin", async () => {
     const env = createTestEnv();
     await upsertRepositoryFromGitHub(env, { name: "demo", full_name: "octo/demo", private: false, owner: { login: "octo" }, default_branch: "main" });