feat: add SSE mode support for MCP server (#10258)

* feat: add SSE mode support for MCP server

### Description
Adds support for running the MCP server in SSE (HTTP) mode, in addition to the default Stdio transport. This allows clients to connect over network or via tools that support SSE.

### Scenarios Tested
- Started server in SSE mode and verified log output.

* fix: add progressToken to McpContext interface to fix build error

### Description
Fixes a type error where progressToken was not defined on McpContext.

### Scenarios Tested
- Verified build succeeds.

* refactor: address PR comments on SSE support

### Description
Addresses PR comments by:
- Moving inline require calls to top-level imports.
- Replacing any types with specific interfaces or unknown.

### Scenarios Tested
- Verified build succeeds.

* fix: address remaining review comments on SSE support

### Description
- Reverts accidental GA4 tracking change in mcpListResources.
- Replaces console.error with this.logger calls for better logging.
- Changes default server binding from 0.0.0.0 to 127.0.0.1 for security.

### Scenarios Tested
- Verified build succeeds.

* style: lint and format fixes for SSE support

### Description
- Applied auto-formatting fixes from npm run format.

### Scenarios Tested
- Verified build succeeds.

* feat: add infrastructure for MCP Apps (#10259)

* feat: add infrastructure for MCP Apps

### Description
Adds support for returning structured content from tools, which is used by MCP Apps to pass complex data to the host. Also updates the resource index.

### Scenarios Tested
- Verified build and file changes.

* fix: resolve build errors and address review comments on infra

### Description
- Removes imports and registry entries for UI resources that are not yet available in this branch (login, update_environment, deploy, init).
- Replaces as any in toContent with an intersection type for better type safety.

### Scenarios Tested
- Verified build succeeds.

* chore: avoid any for sessionId in SSE transport

### Description
- Defines a local interface extending SSEServerTransport to avoid using  when accessing .

### Scenarios Tested
- Build succeeds.
- Lint passes for modified lines.

* feat: change sse flag to mode flag and fix build errors

### Description
- Replaced  boolean flag with  string flag (defaults to 'stdio').
- Added validation for  to accept only 'stdio' or 'sse'.
- Fixed build errors by adding  to  interface and removing missing  resource.

### Scenarios Tested
- Build succeeds.
- Lint passes with no new errors.

* feat: add Update Environment MCP App (#10260)

* feat: add mcpapps experiment flag and helper

### Description
- Adds mcpapps experiment flag to src/experiments.ts.
- Adds applyAppMeta helper function to src/mcp/util.ts to conditionally add UI metadata.
- Adds unit tests for applyAppMeta in src/mcp/util.spec.ts.

### Scenarios Tested
- Unit tests passed.
- Build succeeds.

* chore: address PR comments on experiments and util

### Description
- Fixes applyAppMeta to preserve existing metadata.
- Moves mcpapps flag to be grouped with other MCP experiments.
- Removes as any in util.spec.ts by importing CallToolResult.

### Scenarios Tested
- Build succeeds.
- Lint passes for modified files (ignoring pre-existing warnings).
- Unit tests for applyAppMeta pass.

* feat: add infrastructure for MCP Apps

Adds support for returning structured content from tools, which is used by MCP Apps to pass complex data to the host. Also updates the resource index.

- Verified build and file changes.

* feat: add Update Environment MCP App

### Description
Adds the Update Environment MCP App, allowing users to switch projects and directories from the UI.

### Scenarios Tested
- Verified build and file changes.

* fix: resolve compilation errors in mcp-update-env-app

* fix: resolve remaining lint errors in mcp-update-env-app

* refactor: extract app MIME type shared constant

* added changelog'

Author: joehan

CHANGELOG.md

@@ -0,0 +1,2 @@
+- Added 'firebase_deploy' and 'firebase_deploy_status' MCP tools.
+- Added SSE mode support to `firebase mcp`. To use it, run `firebase mcp --mode=sse --port=3000`, and connect your client on `http://localhost:3000`.

npm-shrinkwrap.json

@@ -185,6 +185,7 @@
     "@angular-devkit/architect": "^0.1402.2",
     "@angular-devkit/core": "^14.2.2",
     "@google/events": "^5.1.1",
+    "@modelcontextprotocol/ext-apps": "^1.3.2",
     "@types/archiver": "^6.0.0",
     "@types/async-lock": "^1.4.2",
     "@types/body-parser": "^1.17.0",

package.json

@@ -49,6 +49,8 @@ Options:
                             If specified, auto-detection is disabled for other features.
   --tools <tools>           Comma-separated list of specific tools to enable. Disables
                             auto-detection entirely.
+  --mode <mode>             Server mode: stdio, sse (defaults to stdio).
+  --port <port>             The port to listen on when running in SSE mode (defaults to 3000).
   -h, --help                Show this help message.
 `;
 
@@ -58,6 +60,8 @@ export async function mcp(): Promise<void> {
       only: { type: "string", default: "" },
       tools: { type: "string", default: "" },
       dir: { type: "string" },
+      mode: { type: "string", default: "stdio" },
+      port: { type: "string", default: "3000" },
       "generate-tool-list": { type: "boolean", default: false },
       "generate-prompt-list": { type: "boolean", default: false },
       "generate-resource-list": { type: "boolean", default: false },
@@ -85,6 +89,11 @@ export async function mcp(): Promise<void> {
   }
   if (earlyExit) return;
 
+  if (values.mode !== "stdio" && values.mode !== "sse") {
+    console.error("Error: --mode must be either 'stdio' or 'sse'");
+    process.exit(1);
+  }
+
   setFirebaseMcp(true);
   // Write debug logs to ~/.cache/firebase to avoid polluting the user's project directory.
   const mcpLogDir = join(homedir(), ".cache", "firebase");
@@ -103,6 +112,9 @@ export async function mcp(): Promise<void> {
     enabledTools,
     projectRoot: values.dir ? resolve(values.dir) : undefined,
   });
-  await server.start();
+  await server.start({
+    useSSE: values.mode === "sse",
+    port: values.port ? parseInt(values.port, 10) : undefined,
+  });
   if (process.stdin.isTTY) process.stderr.write(STARTUP_MESSAGE);
 }

src/bin/mcp.ts

@@ -184,6 +184,11 @@ export const ALL_EXPERIMENTS = experiments({
     default: false,
     public: true,
   },
+  mcpapps: {
+    shortDescription: "Enables MCP Apps features",
+    fullDescription: "Enables MCP Apps features, including returning UI resource URIs.",
+    public: true,
+  },
   fdcift: {
     shortDescription: "Enable instrumentless trial for SQL Connect",
     default: true,