feat: add SSE transport and custom headers support

README.md

@@ -38,6 +38,8 @@ jobs:
 | `command`        | No\*     |              | Server command to run via stdio (e.g., `node dist/index.js`) |
 | `args`           | No       |              | Arguments for the server command (space-separated)        |
 | `url`            | No\*     |              | Server URL for streamable-http transport                  |
+| `sse`            | No       | `false`      | Use SSE transport instead of streamable-http (requires `url`) |
+| `headers`        | No       |              | Custom HTTP headers, one per line as `Key: Value`         |
 | `fail-on`        | No       | `breaking`   | Severity threshold for failure: `safe`, `warning`, `breaking` |
 | `comment-on-pr`  | No       | `true`       | Post diff as a PR comment                                 |
 | `github-token`   | No       | `github.token` | GitHub token for PR comments                            |
@@ -71,3 +73,17 @@ npx mcpdiff snapshot --command node --args server.js -o contracts/baseline.mcpc.
 ```
 
 Commit this file to your repository and reference it in the `baseline` input.
+
+## SSE Transport with Custom Headers
+
+```yaml
+- name: Check MCP contract (SSE)
+  uses: mcp-contracts/github-action@main
+  with:
+    baseline: contracts/baseline.mcpc.json
+    url: https://mcp.example.com/sse
+    sse: "true"
+    headers: |
+      Authorization: Bearer ${{ secrets.MCP_TOKEN }}
+    fail-on: breaking
+```

action.yml

@@ -17,6 +17,13 @@ inputs:
   url:
     description: "Server URL for streamable-http transport"
     required: false
+  sse:
+    description: "Use SSE transport instead of streamable-http (requires url)"
+    required: false
+    default: "false"
+  headers:
+    description: "Custom HTTP headers, one per line as 'Key: Value'"
+    required: false
   fail-on:
     description: "Severity threshold for failure: safe | warning | breaking"
     required: false

biome.json

@@ -0,0 +1,38 @@
+{
+	"$schema": "https://biomejs.dev/schemas/2.4.6/schema.json",
+	"linter": {
+		"enabled": true,
+		"rules": {
+			"recommended": true,
+			"complexity": {
+				"noExcessiveCognitiveComplexity": {
+					"level": "warn",
+					"options": { "maxAllowedComplexity": 20 }
+				},
+				"useLiteralKeys": "off"
+			},
+			"style": {
+				"noDefaultExport": "error",
+				"useNodejsImportProtocol": "error"
+			},
+			"suspicious": {
+				"noExplicitAny": "error"
+			}
+		}
+	},
+	"formatter": {
+		"enabled": true,
+		"indentStyle": "tab",
+		"lineWidth": 100
+	},
+	"javascript": {
+		"formatter": {
+			"quoteStyle": "double",
+			"semicolons": "always",
+			"trailingCommas": "all"
+		}
+	},
+	"files": {
+		"includes": ["**", "!**/dist"]
+	}
+}