feat(cursor): add mcp input to configure MCP servers for Cursor (coder#314)

matifali · blink-so[bot] · web-flow · commit 61554aaa8c56 · 2025-08-12T11:18:31.000-05:00
This adds a new optional input `mcp` to the cursor module.

- Accepts a JSON-encoded string with MCP server configuration
- When provided, a `coder_script` writes it to `~/.cursor/mcp.json` on
start
- Keeps existing behavior unchanged if `mcp` is empty
- Adds tests verifying the `mcp.json` is written
- Updates README with `mcp` usage example
- Fixes Prettier and `terraform fmt` formatting issues flagged by CI

CI should now pass after the latest commits.

---------

Co-authored-by: blink-so[bot] &lt;211532188+blink-so[bot]@users.noreply.github.com&gt;
diff --git a/registry/coder/modules/cursor/README.md b/registry/coder/modules/cursor/README.md
@@ -16,7 +16,7 @@ Uses the [Coder Remote VS Code Extension](https://github.com/coder/vscode-coder)
 module "cursor" {
   count    = data.coder_workspace.me.start_count
   source   = "registry.coder.com/coder/cursor/coder"
-  version  = "1.2.1"
+  version  = "1.3.0"
   agent_id = coder_agent.example.id
 }
 ```
@@ -29,8 +29,33 @@ module "cursor" {
 module "cursor" {
   count    = data.coder_workspace.me.start_count
   source   = "registry.coder.com/coder/cursor/coder"
-  version  = "1.2.1"
+  version  = "1.3.0"
   agent_id = coder_agent.example.id
   folder   = "/home/coder/project"
 }
 ```
+
+### Configure MCP servers for Cursor
+
+Provide a JSON-encoded string via the `mcp` input. When set, the module writes the value to `~/.cursor/mcp.json` using a `coder_script` on workspace start.
+
+```tf
+module "cursor" {
+  count    = data.coder_workspace.me.start_count
+  source   = "registry.coder.com/coder/cursor/coder"
+  version  = "1.3.0"
+  agent_id = coder_agent.example.id
+  mcp = jsonencode({
+    mcpServers = {
+      coder = {
+        command = "coder"
+        args    = ["exp", "mcp", "server"]
+        env = {
+          CODER_MCP_APP_STATUS_SLUG = "cursor"
+          CODER_MCP_AI_AGENTAPI_URL = "http://localhost:3284"
+        }
+      }
+    }
+  })
+}
+```
diff --git a/registry/coder/modules/cursor/main.test.ts b/registry/coder/modules/cursor/main.test.ts
@@ -1,8 +1,13 @@
-import { describe, expect, it } from "bun:test";
+import { describe, it, expect } from "bun:test";
 import {
   runTerraformApply,
   runTerraformInit,
   testRequiredVariables,
+  runContainer,
+  execContainer,
+  removeContainer,
+  findResourceInstance,
+  readFileContainer,
 } from "~test";
 
 describe("cursor", async () => {
@@ -85,4 +90,26 @@ describe("cursor", async () => {
     expect(coder_app?.instances.length).toBe(1);
     expect(coder_app?.instances[0].attributes.order).toBe(22);
   });
+
+  it("writes ~/.cursor/mcp.json when mcp provided", async () => {
+    const id = await runContainer("alpine");
+    try {
+      const mcp = JSON.stringify({ servers: { demo: { url: "http://localhost:1234" } } });
+      const state = await runTerraformApply(import.meta.dir, {
+        agent_id: "foo",
+        mcp,
+      });
+      const script = findResourceInstance(state, "coder_script", "cursor_mcp").script;
+      const resp = await execContainer(id, ["sh", "-c", script]);
+      if (resp.exitCode !== 0) {
+        console.log(resp.stdout);
+        console.log(resp.stderr);
+      }
+      expect(resp.exitCode).toBe(0);
+      const content = await readFileContainer(id, "/root/.cursor/mcp.json");
+      expect(content).toBe(mcp);
+    } finally {
+      await removeContainer(id);
+    }
+  });
 });
diff --git a/registry/coder/modules/cursor/main.tf b/registry/coder/modules/cursor/main.tf
@@ -50,9 +50,20 @@ variable "display_name" {
   default     = "Cursor Desktop"
 }
 
+variable "mcp" {
+  type        = string
+  description = "JSON-encoded string to configure MCP servers for Cursor. When set, writes ~/.cursor/mcp.json."
+  default     = ""
+}
+
 data "coder_workspace" "me" {}
+
 data "coder_workspace_owner" "me" {}
 
+locals {
+  mcp_b64 = var.mcp != "" ? base64encode(var.mcp) : ""
+}
+
 resource "coder_app" "cursor" {
   agent_id     = var.agent_id
   external     = true
@@ -75,6 +86,21 @@ resource "coder_app" "cursor" {
   ])
 }
 
+resource "coder_script" "cursor_mcp" {
+  count              = var.mcp != "" ? 1 : 0
+  agent_id           = var.agent_id
+  display_name       = "Cursor MCP"
+  icon               = "/icon/cursor.svg"
+  run_on_start       = true
+  start_blocks_login = false
+  script             = <<-EOT
+    #!/bin/sh
+    set -eu
+    mkdir -p "$HOME/.cursor"
+    echo -n "${local.mcp_b64}" | base64 -d > "$HOME/.cursor/mcp.json"
+  EOT
+}
+
 output "cursor_url" {
   value       = coder_app.cursor.url
   description = "Cursor IDE Desktop URL."
