fix: resolve split current from caller pane

refs #902

3 files changed, 44 insertions, 12 deletions

diff --git a/docs/next/CHANGELOG.md b/docs/next/CHANGELOG.md
index 1f61ded0..02d8cf5b 100644
--- a/docs/next/CHANGELOG.md
+++ b/docs/next/CHANGELOG.md
@@ -15,6 +15,7 @@
 - Bumped the client/server protocol version to 15 for socket API placement mutation event and response compatibility.
 
 ### Fixed
+- `herdr pane split --current` now resolves to the calling Herdr pane instead of the UI-focused pane when run inside a pane. (#902)
 - Native Windows clients running inside Alacritty now preserve mouse reports and `ctrl+j` input instead of leaking mouse escape sequences into panes. `shift+enter` remains dependent on whether the outer terminal reports it as a distinct modified Enter key. (#792)
 - OMP integration state now recovers after resumed sessions such as `omp -c` and reports Ask/tool approval waits as blocked instead of leaving the pane working or stuck on the previous OMP session. (#879)
 - Remote attach now discovers compatible Homebrew, mise, and Nix profile installs before offering to install a sidecar binary to `~/.local/bin/herdr`. (#840)
diff --git a/docs/next/website/src/content/docs/cli-reference.mdx b/docs/next/website/src/content/docs/cli-reference.mdx
index 4d2980fb..53fe9579 100644
--- a/docs/next/website/src/content/docs/cli-reference.mdx
+++ b/docs/next/website/src/content/docs/cli-reference.mdx
@@ -176,6 +176,11 @@ herdr pane move <pane_id> --new-workspace [--label TEXT] [--tab-label TEXT] [--f
 herdr pane close <pane_id>
 ```
 
+For pane commands that accept `--current`, Herdr uses the calling pane's
+`HERDR_PANE_ID` when the command runs inside a Herdr pane. For `pane split`,
+an explicit pane id or `--pane ID` splits that pane, `--current` splits the
+calling pane, and an omitted target keeps using the UI-focused pane.
+
 Read output:
 
 ```bash
diff --git a/src/cli/pane.rs b/src/cli/pane.rs
index c81e5835..b2579d42 100644
--- a/src/cli/pane.rs
+++ b/src/cli/pane.rs
@@ -529,7 +529,10 @@ fn pane_read(args: &[String]) -> std::io::Result<i32> {
 }
 
 fn pane_split(args: &[String]) -> std::io::Result<i32> {
-    let params = match parse_pane_split_args(args) {
+    let env_pane_id = std::env::var("HERDR_PANE_ID")
+        .ok()
+        .filter(|value| !value.trim().is_empty());
+    let params = match parse_pane_split_args(args, env_pane_id.as_deref()) {
         Ok(params) => params,
         Err(message) => {
             eprintln!("{message}");
@@ -543,7 +546,10 @@ fn pane_split(args: &[String]) -> std::io::Result<i32> {
     })?)
 }
 
-fn parse_pane_split_args(args: &[String]) -> Result<PaneSplitParams, String> {
+fn parse_pane_split_args(
+    args: &[String],
+    env_pane_id: Option<&str>,
+) -> Result<PaneSplitParams, String> {
     let mut env = std::collections::HashMap::new();
     let mut pane_id = None;
     let mut direction = None;
@@ -569,7 +575,7 @@ fn parse_pane_split_args(args: &[String]) -> Result<PaneSplitParams, String> {
                 index += 2;
             }
             "--current" => {
-                pane_id = None;
+                pane_id = env_pane_id.map(super::normalize_pane_id);
                 index += 1;
             }
             "--direction" => {
@@ -1470,13 +1476,10 @@ mod tests {
 
     #[test]
     fn parse_pane_split_args_accepts_ratio() {
-        let params = parse_pane_split_args(&args(&[
-            "issue-1",
-            "--direction",
-            "right",
-            "--ratio",
-            "0.333",
-        ]))
+        let params = parse_pane_split_args(
+            &args(&["issue-1", "--direction", "right", "--ratio", "0.333"]),
+            None,
+        )
         .unwrap();
 
         assert_eq!(params.target_pane_id, Some("issue-1".into()));
@@ -1486,7 +1489,29 @@ mod tests {
 
     #[test]
     fn parse_pane_split_args_accepts_current_target() {
-        let params = parse_pane_split_args(&args(&["--direction", "down", "--current"])).unwrap();
+        let params = parse_pane_split_args(
+            &args(&["--direction", "down", "--current"]),
+            Some("issue-1"),
+        )
+        .unwrap();
+
+        assert_eq!(params.target_pane_id, Some("issue-1".into()));
+        assert_eq!(params.direction, crate::api::schema::SplitDirection::Down);
+    }
+
+    #[test]
+    fn parse_pane_split_args_current_without_env_keeps_focused_fallback() {
+        let params =
+            parse_pane_split_args(&args(&["--direction", "down", "--current"]), None).unwrap();
+
+        assert_eq!(params.target_pane_id, None);
+        assert_eq!(params.direction, crate::api::schema::SplitDirection::Down);
+    }
+
+    #[test]
+    fn parse_pane_split_args_omitted_target_keeps_focused_fallback() {
+        let params =
+            parse_pane_split_args(&args(&["--direction", "down"]), Some("issue-1")).unwrap();
 
         assert_eq!(params.target_pane_id, None);
         assert_eq!(params.direction, crate::api::schema::SplitDirection::Down);
@@ -1495,7 +1520,8 @@ mod tests {
     #[test]
     fn parse_pane_split_args_accepts_pane_option() {
         let params =
-            parse_pane_split_args(&args(&["--pane", "issue-2", "--direction", "right"])).unwrap();
+            parse_pane_split_args(&args(&["--pane", "issue-2", "--direction", "right"]), None)
+                .unwrap();
 
         assert_eq!(params.target_pane_id, Some("issue-2".into()));
         assert_eq!(params.direction, crate::api::schema::SplitDirection::Right);