diff --git a/src/api.rs b/src/api.rs
index efaa19d..9570e68 100644
--- a/src/api.rs
+++ b/src/api.rs
@@ -74,7 +74,8 @@ impl MisskeyClient {
         if let Some(ref base) = self.base_url {
             return format!("{base}/api/{endpoint}");
         }
-        format!("https://{host}/api/{endpoint}")
+        let scheme = crate::insecure::http_scheme(host);
+        format!("{scheme}://{host}/api/{endpoint}")
     }
 
     /// Read the response body with a streaming size limit to prevent DoS.
@@ -2126,7 +2127,8 @@ impl MisskeyClient {
     /// Fetch nodeinfo via .well-known/nodeinfo.
     /// Returns the parsed nodeinfo JSON.
     pub async fn fetch_nodeinfo(&self, host: &str) -> Result<Value, NoteDeckError> {
-        let well_known_url = format!("https://{host}/.well-known/nodeinfo");
+        let scheme = crate::insecure::http_scheme(host);
+        let well_known_url = format!("{scheme}://{host}/.well-known/nodeinfo");
         let res = self
             .client
             .get(&well_known_url)
@@ -2162,7 +2164,7 @@ impl MisskeyClient {
             })?;
 
         // Validate URL to prevent SSRF: must be https://{host}/...
-        let expected_prefix = format!("https://{host}/");
+        let expected_prefix = format!("{scheme}://{host}/");
         if !nodeinfo_url.starts_with(&expected_prefix) {
             return Err(NoteDeckError::Api {
                 endpoint: ".well-known/nodeinfo".to_string(),
diff --git a/src/commands/auth.rs b/src/commands/auth.rs
index 0c95952..bf9a766 100644
--- a/src/commands/auth.rs
+++ b/src/commands/auth.rs
@@ -88,8 +88,9 @@ pub async fn run_login(
         "write:votes",
     ];
     let permission_str = permissions.join(",");
+    let scheme = crate::insecure::http_scheme(host);
     let auth_url = format!(
-        "https://{host}/miauth/{session_id}?name=notecli&permission={permission_str}"
+        "{scheme}://{host}/miauth/{session_id}?name=notecli&permission={permission_str}"
     );
 
     match fmt {
diff --git a/src/insecure.rs b/src/insecure.rs
new file mode 100644
index 0000000..60f90f5
--- /dev/null
+++ b/src/insecure.rs
@@ -0,0 +1,59 @@
+//! E2E テスト用の insecure host 判定 (notedeck #702)。
+//!
+//! 環境変数 `NOTECLI_INSECURE_HOSTS` (カンマ区切り・完全一致) に列挙された
+//! ホストへは https/wss の代わりに http/ws で接続する。ローカルのモック
+//! Misskey サーバー (`127.0.0.1:PORT`) に接続するための仕組みで、
+//! デバッグビルド限定 (リリースビルドでは常に secure)。
+
+pub(crate) fn is_insecure_host(host: &str) -> bool {
+    #[cfg(debug_assertions)]
+    {
+        std::env::var("NOTECLI_INSECURE_HOSTS")
+            .map(|v| v.split(',').any(|h| h.trim().eq_ignore_ascii_case(host)))
+            .unwrap_or(false)
+    }
+    #[cfg(not(debug_assertions))]
+    {
+        let _ = host;
+        false
+    }
+}
+
+pub(crate) fn http_scheme(host: &str) -> &'static str {
+    if is_insecure_host(host) {
+        "http"
+    } else {
+        "https"
+    }
+}
+
+pub(crate) fn ws_scheme(host: &str) -> &'static str {
+    if is_insecure_host(host) {
+        "ws"
+    } else {
+        "wss"
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn insecure_only_for_exact_listed_host() {
+        // 他テストと衝突しない値を使う (env はプロセス全体で共有されるため)
+        unsafe { std::env::set_var("NOTECLI_INSECURE_HOSTS", "127.0.0.1:39821, mock.test:8080") };
+        assert_eq!(http_scheme("127.0.0.1:39821"), "http");
+        assert_eq!(ws_scheme("mock.test:8080"), "ws");
+        // 完全一致のみ — 列挙外・部分一致は secure のまま
+        assert_eq!(http_scheme("127.0.0.1:39999"), "https");
+        assert_eq!(ws_scheme("127.0.0.1"), "wss");
+        unsafe { std::env::remove_var("NOTECLI_INSECURE_HOSTS") };
+    }
+
+    #[test]
+    fn secure_by_default() {
+        assert_eq!(http_scheme("misskey.io"), "https");
+        assert_eq!(ws_scheme("misskey.io"), "wss");
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 2ec1e11..bf70e4c 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -6,6 +6,7 @@ pub mod error;
 pub mod event_bus;
 pub mod format;
 pub mod http_server;
+pub(crate) mod insecure;
 pub mod keychain;
 pub mod models;
 pub mod streaming;
diff --git a/src/streaming.rs b/src/streaming.rs
index f41a3c7..ab13dc6 100644
--- a/src/streaming.rs
+++ b/src/streaming.rs
@@ -314,7 +314,8 @@ impl StreamingManager {
             return Ok(());
         }
 
-        let url = format!("wss://{host}/streaming?i={token}");
+        let scheme = crate::insecure::ws_scheme(&host);
+        let url = format!("{scheme}://{host}/streaming?i={token}");
 
         // Attempt the initial connection (with timeout to prevent hang DoS).
         // 失敗しても Err を返さず connection_task の再接続ループに委ねる: