diff --git a/vendor/clawdforge/src/lib.rs b/vendor/clawdforge/src/lib.rs
index 59d8313..bf3c207 100644
--- a/vendor/clawdforge/src/lib.rs
+++ b/vendor/clawdforge/src/lib.rs
@@ -54,5 +54,5 @@ pub use error::Error;
 pub use session::{Session, SessionList, SessionOptions, SessionState, TurnEvent, TurnResult};
 pub use types::{
     AppToken, AppTokenInfo, FileToken, Healthz, RunFailure, RunRequest, RunResult,
-    TokenCreateRequest, TokenList,
+    SystemMode, TokenCreateRequest, TokenList,
 };
diff --git a/vendor/clawdforge/src/types.rs b/vendor/clawdforge/src/types.rs
index 1774539..6f62b9d 100644
--- a/vendor/clawdforge/src/types.rs
+++ b/vendor/clawdforge/src/types.rs
@@ -9,6 +9,23 @@ use serde::{de::DeserializeOwned, Deserialize, Serialize};
 
 use crate::error::Error;
 
+/// How `system` is passed to `claude -p`. See [`RunRequest::system_mode`].
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "lowercase")]
+pub enum SystemMode {
+    /// `--append-system-prompt` — additive on top of Claude's defaults.
+    Append,
+    /// `--system-prompt` — REPLACES Claude's default base prompt
+    /// entirely. Right for personas.
+    Replace,
+}
+
+impl Default for SystemMode {
+    fn default() -> Self {
+        Self::Append
+    }
+}
+
 /// `GET /healthz` response body.
 #[derive(Debug, Clone, Deserialize, Serialize)]
 pub struct Healthz {
@@ -43,10 +60,26 @@ pub struct RunRequest {
     #[serde(skip_serializing_if = "Option::is_none")]
     pub model: Option<String>,
 
-    /// System prompt appended via `claude -p --append-system-prompt`.
+    /// System prompt. How it's passed to `claude -p` depends on
+    /// [`Self::system_mode`].
     #[serde(skip_serializing_if = "Option::is_none")]
     pub system: Option<String>,
 
+    /// How `system` is passed to `claude -p`:
+    ///
+    /// - [`SystemMode::Append`] (default) → `--append-system-prompt`.
+    ///   Claude's default base prompt stays + `system` is added.
+    ///   Right for tool-using assistants where Claude's helpful-
+    ///   honest defaults are useful substrate.
+    /// - [`SystemMode::Replace`] → `--system-prompt`. Replaces the
+    ///   base prompt entirely. Right for personas (fiction authors,
+    ///   chat bots, in-world characters) where Claude's defaults
+    ///   would bleed through as friction.
+    ///
+    /// `None` = server default (currently `append`).
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub system_mode: Option<SystemMode>,
+
     /// File tokens previously returned from [`Client::upload_file`].
     ///
     /// [`Client::upload_file`]: crate::Client::upload_file