diff --git a/packages/loopover-mcp/bin/loopover-mcp.js b/packages/loopover-mcp/bin/loopover-mcp.js
index 2f8e61d3e8..0ea9b9b5ac 100755
--- a/packages/loopover-mcp/bin/loopover-mcp.js
+++ b/packages/loopover-mcp/bin/loopover-mcp.js
@@ -10,6 +10,7 @@ import { buildFeasibilityVerdict, buildPrTextLint } from "@loopover/engine";
 // registering them locally is just importing the same engine builders the remote server uses.
 import {
   buildApplyLabelsSpec,
+  buildClosePrSpec,
   buildCreateBranchSpec,
   buildDeleteBranchSpec,
   buildFileIssueSpec,
@@ -362,6 +363,11 @@ const applyLabelsShape = {
   number: z.number().int().positive(),
   labels: z.array(z.string().min(1).max(100)).min(1).max(20),
 };
+const closePrShape = {
+  repoFullName: writeToolRepoFullName,
+  number: z.number().int().positive(),
+  comment: z.string().max(WRITE_TOOL_BODY_MAX).optional(),
+};
 const postEligibilityCommentShape = {
   repoFullName: writeToolRepoFullName,
   number: z.number().int().positive(),
@@ -1094,6 +1100,12 @@ const STDIO_TOOL_DESCRIPTORS = [
     description:
       "Build a LOCAL-execution spec to file a follow-up issue for a review finding a maintainer wants TRACKED rather than blocked on this PR. Composes a bounded, public-safe title/body from the finding (run it with your own gh creds; loopover never performs the write).",
   },
+  {
+    name: "loopover_close_pr",
+    category: "agent",
+    description:
+      "Build a LOCAL-execution spec to close a pull request, optionally with a comment (run it with your own gh creds; loopover never performs the write).",
+  },
 ];
 
 // #6301 — coarse tool categories for grouping `loopover-mcp tools` output. Ordered
@@ -2165,6 +2177,15 @@ registerStdioTool(
   (input) => localWriteSpecResult(buildFollowUpIssueSpec(input)),
 );
 
+registerStdioTool(
+  "loopover_close_pr",
+  {
+    description: stdioToolDescription("loopover_close_pr"),
+    inputSchema: closePrShape,
+  },
+  (input) => localWriteSpecResult(buildClosePrSpec(input)),
+);
+
 // ── Resources: decision-pack, doctor, compatibility, changelog (#292) ─────────
 
 server.registerResource(
diff --git a/src/mcp/server.ts b/src/mcp/server.ts
index 2367d87aa3..127f2c23ba 100644
--- a/src/mcp/server.ts
+++ b/src/mcp/server.ts
@@ -146,6 +146,7 @@ import { computeLocalScorerTokens } from "../signals/local-scorer";
 import { buildPullRequestReviewability, type PullRequestReviewability } from "../signals/reward-risk";
 import {
   buildApplyLabelsSpec,
+  buildClosePrSpec,
   buildCreateBranchSpec,
   buildDeleteBranchSpec,
   buildFileIssueSpec,
@@ -422,6 +423,11 @@ const applyLabelsShape = {
   number: z.number().int().positive(),
   labels: z.array(z.string().min(1).max(100)).min(1).max(20),
 };
+const closePrShape = {
+  repoFullName: z.string().min(3).max(SCENARIO_MAX_REPO_FULL_NAME_CHARS),
+  number: z.number().int().positive(),
+  comment: z.string().max(WRITE_TOOL_BODY_MAX).optional(),
+};
 const postEligibilityCommentShape = {
   repoFullName: z.string().min(3).max(SCENARIO_MAX_REPO_FULL_NAME_CHARS),
   number: z.number().int().positive(),
@@ -1772,6 +1778,7 @@ export const MCP_TOOL_CATEGORIES: Record<string, McpToolCategory> = {
   loopover_delete_branch: "agent",
   loopover_generate_tests: "agent",
   loopover_file_follow_up_issue: "agent",
+  loopover_close_pr: "agent",
   loopover_build_plan: "agent",
   loopover_plan_status: "agent",
   loopover_record_step_result: "agent",
@@ -2429,6 +2436,11 @@ export class LoopoverMcp {
       },
       async (input) => this.toolResult(this.localWriteSpec(buildFollowUpIssueSpec(input))),
     );
+    register(
+      "loopover_close_pr",
+      { description: "Build a LOCAL-execution spec to close a pull request, optionally with a comment (run it with your own gh creds; loopover never performs the write).", inputSchema: closePrShape, outputSchema: localWriteActionOutputSchema },
+      async (input) => this.toolResult(this.localWriteSpec(buildClosePrSpec(input))),
+    );
 
     // #783 multi-step plan DAG — stateless: pass the plan back each call.
     register(
diff --git a/test/unit/mcp-cli-write-tools.test.ts b/test/unit/mcp-cli-write-tools.test.ts
index 0de741ec63..a152b5b942 100644
--- a/test/unit/mcp-cli-write-tools.test.ts
+++ b/test/unit/mcp-cli-write-tools.test.ts
@@ -40,6 +40,7 @@ const WRITE_TOOLS = [
   "loopover_delete_branch",
   "loopover_generate_tests",
   "loopover_file_follow_up_issue",
+  "loopover_close_pr",
 ];
 
 function spec(result: unknown): { action: string; command: string; boundary: string } {
@@ -47,7 +48,7 @@ function spec(result: unknown): { action: string; command: string; boundary: str
 }
 
 describe("loopover-mcp write-tools (#6149)", () => {
-  it("registers all 8 write-tools on the local stdio server", async () => {
+  it("registers all 9 write-tools on the local stdio server", async () => {
     const names = new Set((await client.listTools()).tools.map((t) => t.name));
     for (const name of WRITE_TOOLS) expect(names, `missing ${name}`).toContain(name);
   });
@@ -86,6 +87,25 @@ describe("loopover-mcp write-tools (#6149)", () => {
     expect(spec(result).command).toContain("--add-label");
   });
 
+  it("loopover_close_pr composes a gh pr close spec, optionally with a follow-up comment", async () => {
+    const noComment = await client.callTool({
+      name: "loopover_close_pr",
+      arguments: { repoFullName: "acme/widgets", number: 7 },
+    });
+    expect(noComment.isError).toBeFalsy();
+    expect(spec(noComment).action).toBe("close_pr");
+    expect(spec(noComment).command).toBe("gh pr close 7 --repo 'acme/widgets'");
+
+    const withComment = await client.callTool({
+      name: "loopover_close_pr",
+      arguments: { repoFullName: "acme/widgets", number: 7, comment: "superseded by a fresh PR" },
+    });
+    expect(withComment.isError).toBeFalsy();
+    expect(spec(withComment).command).toBe(
+      "gh pr close 7 --repo 'acme/widgets' && gh pr comment 7 --repo 'acme/widgets' --body 'superseded by a fresh PR'",
+    );
+  });
+
   it("loopover_post_eligibility_comment composes a gh issue comment spec", async () => {
     const result = await client.callTool({
       name: "loopover_post_eligibility_comment",
diff --git a/test/unit/mcp-tool-rename-aliases.test.ts b/test/unit/mcp-tool-rename-aliases.test.ts
index fa1194db8f..7c71330c8b 100644
--- a/test/unit/mcp-tool-rename-aliases.test.ts
+++ b/test/unit/mcp-tool-rename-aliases.test.ts
@@ -7,6 +7,7 @@
 // (#6150 registered the local-scorer and plan-DAG/predict-gate tools, taking the count from 55 to 60.)
 // (#6619 registered the pr-ai-review-findings CLI mirror, taking the count from 60 to 61.)
 // (#6621 registered the loopover_get_eligibility_plan REST/CLI mirror, taking the count from 61 to 62.)
+// (#6615 registered the loopover_close_pr write-tool — 9th of the 9 buildXSpec builders — taking the count from 62 to 63.)
 import { Client } from "@modelcontextprotocol/sdk/client/index.js";
 import { StdioClientTransport } from "@modelcontextprotocol/sdk/client/stdio.js";
 import { mkdtempSync, rmSync } from "node:fs";
@@ -50,14 +51,14 @@ describe("MCP legacy alias retirement (#4777) — discovery invariants", () => {
   });
   afterEach(disconnect);
 
-  it("lists exactly 62 loopover_ tools and zero gittensory_-prefixed aliases", async () => {
+  it("lists exactly 63 loopover_ tools and zero gittensory_-prefixed aliases", async () => {
     const { tools } = await client.listTools();
     const names = tools.map((t) => t.name);
     const primary = names.filter((n) => n.startsWith("loopover_"));
     const legacy = names.filter((n) => n.startsWith("gittensory_"));
-    expect(primary.length).toBe(62);
+    expect(primary.length).toBe(63);
     expect(legacy.length).toBe(0);
-    expect(names.length).toBe(62);
+    expect(names.length).toBe(63);
   });
 
   it("no loopover_ tool's description carries a stale deprecation notice", async () => {
@@ -67,11 +68,11 @@ describe("MCP legacy alias retirement (#4777) — discovery invariants", () => {
     }
   });
 
-  it("`loopover-mcp tools --json` reports the same 62-tool count the live server registers", async () => {
+  it("`loopover-mcp tools --json` reports the same 63-tool count the live server registers", async () => {
     const { tools } = await client.listTools();
     const payload = JSON.parse(run(["tools", "--json"])) as { count: number; tools: Array<{ name: string }> };
     expect(payload.count).toBe(tools.length);
-    expect(payload.count).toBe(62);
+    expect(payload.count).toBe(63);
     expect([...payload.tools.map((t) => t.name)].sort()).toEqual([...tools.map((t) => t.name)].sort());
   });
 });
diff --git a/test/unit/mcp-write-tools.test.ts b/test/unit/mcp-write-tools.test.ts
index 0cbb28bf03..60c4809252 100644
--- a/test/unit/mcp-write-tools.test.ts
+++ b/test/unit/mcp-write-tools.test.ts
@@ -38,6 +38,12 @@ describe("MCP miner write-tools (#780)", () => {
       { name: "loopover_post_eligibility_comment", args: { repoFullName: "o/r", number: 7, body: "hi" }, expect: "gh issue comment 7 --repo 'o/r' --body 'hi'" },
       { name: "loopover_create_branch", args: { branch: "feat/x", base: "main" }, expect: "git switch -c 'feat/x' 'main'" },
       { name: "loopover_delete_branch", args: { branch: "feat/x", remote: true }, expect: "git branch -D 'feat/x' && git push origin --delete 'feat/x'" },
+      { name: "loopover_close_pr", args: { repoFullName: "o/r", number: 7 }, expect: "gh pr close 7 --repo 'o/r'" },
+      {
+        name: "loopover_close_pr",
+        args: { repoFullName: "o/r", number: 7, comment: "dup" },
+        expect: "gh pr close 7 --repo 'o/r' && gh pr comment 7 --repo 'o/r' --body 'dup'",
+      },
     ];
     for (const testCase of cases) {
       const result = await client.callTool({ name: testCase.name, arguments: testCase.args });