feat: govslack compatibility

README.md

@@ -141,6 +141,7 @@ Fetches a CSV directory of all users in the workspace.
 | `SLACK_MCP_USERS_CACHE`           | No        | `~/Library/Caches/slack-mcp-server/users_cache.json` (macOS)<br>`~/.cache/slack-mcp-server/users_cache.json` (Linux)<br>`%LocalAppData%/slack-mcp-server/users_cache.json` (Windows) | Path to the users cache file. Used to cache Slack user information to avoid repeated API calls on startup. |
 | `SLACK_MCP_CHANNELS_CACHE`        | No        | `~/Library/Caches/slack-mcp-server/channels_cache_v2.json` (macOS)<br>`~/.cache/slack-mcp-server/channels_cache_v2.json` (Linux)<br>`%LocalAppData%/slack-mcp-server/channels_cache_v2.json` (Windows) | Path to the channels cache file. Used to cache Slack channel information to avoid repeated API calls on startup. |
 | `SLACK_MCP_LOG_LEVEL`             | No        | `info`                    | Log-level for stdout or stderr. Valid values are: `debug`, `info`, `warn`, `error`, `panic` and `fatal`                                                                                                                                                                                   |
+| `SLACK_MCP_GOVSLACK`              | No        | `nil`                     | Set to `true` to enable [GovSlack](https://slack.com/solutions/govslack) mode. Routes API calls to `slack-gov.com` endpoints instead of `slack.com` for FedRAMP-compliant government workspaces.                                                                                          |
 
 *You need one of: `xoxp` (user), `xoxb` (bot), or both `xoxc`/`xoxd` tokens for authentication.
 

pkg/provider/api.go

@@ -123,9 +123,11 @@ type ApiProvider struct {
 func NewMCPSlackClient(authProvider auth.Provider, logger *zap.Logger) (*MCPSlackClient, error) {
 	httpClient := transport.ProvideHTTPClient(authProvider.Cookies(), logger)
 
-	slackClient := slack.New(authProvider.SlackToken(),
-		slack.OptionHTTPClient(httpClient),
-	)
+	slackOpts := []slack.Option{slack.OptionHTTPClient(httpClient)}
+	if os.Getenv("SLACK_MCP_GOVSLACK") == "true" {
+		slackOpts = append(slackOpts, slack.OptionAPIURL("https://slack-gov.com/api/"))
+	}
+	slackClient := slack.New(authProvider.SlackToken(), slackOpts...)
 
 	authResp, err := slackClient.AuthTest()
 	if err != nil {

pkg/provider/edge/edge.go

@@ -64,6 +64,15 @@ var (
 	ErrNoToken  = errors.New("token is empty")
 )
 
+// getSlackBaseDomain returns the base domain for Slack API endpoints.
+// Returns "slack-gov.com" if SLACK_MCP_GOVSLACK=true, otherwise "slack.com".
+func getSlackBaseDomain() string {
+	if os.Getenv("SLACK_MCP_GOVSLACK") == "true" {
+		return "slack-gov.com"
+	}
+	return "slack.com"
+}
+
 func NewWithClient(workspaceName string, teamID string, token string, cl *http.Client, opt ...Option) (*Client, error) {
 	if teamID == "" {
 		return nil, ErrNoTeamID
@@ -79,8 +88,8 @@ func NewWithClient(workspaceName string, teamID string, token string, cl *http.C
 		cl:           cl,
 		token:        token,
 		teamID:       teamID,
-		webclientAPI: fmt.Sprintf("https://%s.slack.com/api/", workspaceName),
-		edgeAPI:      fmt.Sprintf("https://edgeapi.slack.com/cache/%s/", teamID),
+		webclientAPI: fmt.Sprintf("https://%s.%s/api/", workspaceName, getSlackBaseDomain()),
+		edgeAPI:      fmt.Sprintf("https://edgeapi.%s/cache/%s/", getSlackBaseDomain(), teamID),
 		tape:         tape,
 	}, nil
 }
@@ -118,7 +127,7 @@ func NewWithInfo(info *slack.AuthTestResponse, prov auth.Provider, opt ...Option
 		token:        prov.SlackToken(),
 		teamID:       info.TeamID,
 		webclientAPI: info.URL + "api/",
-		edgeAPI:      fmt.Sprintf("https://edgeapi.slack.com/cache/%s/", info.TeamID),
+		edgeAPI:      fmt.Sprintf("https://edgeapi.%s/cache/%s/", getSlackBaseDomain(), info.TeamID),
 		tape:         nopTape{},
 	}