From 6e3bacb1824463c30879516b10b5e6fd3017953a Mon Sep 17 00:00:00 2001
From: Kent Overstreet <kent.overstreet@linux.dev>
Date: Fri, 22 May 2026 12:26:05 -0400
Subject: [PATCH] channel-tmux: resolve pane ids by label, don't persist them
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tmux pane ids (%6 etc.) are ephemeral — recycled across pane and
tmux-server restarts. The daemon persisted the id in tmux.json5 and
kept reusing it, so after a restart a channel would attach to whatever
unrelated pane had since inherited that id. (Live: ktest's stored %6
had become a claude pane; the real ktest pane was %10.)

Persist only the label — the pane title / window name, which is
stable. pipe_pane_reader() is now a connect-retry loop: each attempt,
connect_and_stream() resolves the live id with find_pane_by_name(); the
loop retries until the pane exists and pipe-pane succeeds, and
reconnects the same way if the pipe later drops. send() resolves the id
at send time; open() just registers the label and lets the reader find
it.

Co-Authored-By: Proof of Concept <poc@bcachefs.org>
---
 channels/tmux/src/main.rs | 182 ++++++++++++++++++++++----------------
 1 file changed, 104 insertions(+), 78 deletions(-)

diff --git a/channels/tmux/src/main.rs b/channels/tmux/src/main.rs
index f49bdc1..aecb3bd 100644
--- a/channels/tmux/src/main.rs
+++ b/channels/tmux/src/main.rs
@@ -26,10 +26,12 @@ use consciousness::thalamus::channel_log::ChannelLog;
 
 #[derive(Clone, serde::Serialize, serde::Deserialize)]
 struct PaneConfig {
-    /// Human-readable label, becomes the channel name "tmux.<label>"
+    /// Human-readable label: becomes the channel name "tmux.<label>",
+    /// and the tmux pane title / window name the live pane id is
+    /// resolved from. The pane id is deliberately not stored — it is
+    /// ephemeral (recycled across pane and tmux-server restarts), so it
+    /// is looked up fresh on every connect attempt.
     label: String,
-    /// Tmux pane ID, e.g. "%5"
-    pane_id: String,
 }
 
 #[derive(Clone, serde::Serialize, serde::Deserialize)]
@@ -86,11 +88,9 @@ impl State {
         }
     }
 
-    /// Get pane_id for a label
-    fn get_pane(&self, label: &str) -> Option<&str> {
-        self.config.panes.iter()
-            .find(|p| p.label == label)
-            .map(|p| p.pane_id.as_str())
+    /// Whether a pane with this label is registered.
+    fn has_pane(&self, label: &str) -> bool {
+        self.config.panes.iter().any(|p| p.label == label)
     }
 
     /// Check if a pane is connected
@@ -103,98 +103,124 @@ impl State {
         self.connected.insert(label.to_string(), connected);
     }
 
-    /// Add a pane and persist
-    fn add_pane(&mut self, label: String, pane_id: String) {
+    /// Register a pane and persist.
+    fn add_pane(&mut self, label: String) {
         if !self.config.panes.iter().any(|p| p.label == label) {
-            self.config.panes.push(PaneConfig { label, pane_id });
+            self.config.panes.push(PaneConfig { label });
             save_config(&self.config);
         }
     }
 
-    /// Remove a pane and persist
-    fn remove_pane(&mut self, label: &str) -> Option<String> {
+    /// Unregister a pane and persist. Returns whether it was registered.
+    fn remove_pane(&mut self, label: &str) -> bool {
         if let Some(idx) = self.config.panes.iter().position(|p| p.label == label) {
-            let pane = self.config.panes.remove(idx);
+            self.config.panes.remove(idx);
             self.connected.remove(label);
             save_config(&self.config);
-            Some(pane.pane_id)
+            true
         } else {
-            None
+            false
         }
     }
 }
 
 // ── Pipe-Pane Reader ──────────────────────────────────────────
 
-/// Set up pipe-pane for a single pane, reading output into the channel log.
-async fn pipe_pane_reader(state: SharedState, pane: PaneConfig) {
+/// Wait between connect attempts for a pane that is not yet reachable.
+const RETRY_INTERVAL: std::time::Duration = std::time::Duration::from_secs(2);
+
+/// Keep a pane streamed into its channel log for as long as it stays
+/// registered. The pane id is resolved fresh by label on every connect
+/// attempt — tmux pane ids are ephemeral, so the label (pane title /
+/// window name) is the durable identity. Retries until the pane exists
+/// and pipe-pane succeeds, and reconnects the same way if the pipe
+/// later drops. Returns once close() unregisters the pane.
+async fn pipe_pane_reader(state: SharedState, label: String) {
     let pipe_dir = dirs::home_dir()
         .unwrap_or_default()
         .join(".consciousness/channels/tmux-pipes");
     std::fs::create_dir_all(&pipe_dir).ok();
+    let pipe_path = pipe_dir.join(format!("{}.pipe", label));
+    let channel_key = format!("tmux.{}", label);
 
-    let pipe_path = pipe_dir.join(format!("{}.pipe", pane.label));
-    let _ = std::fs::remove_file(&pipe_path);
+    loop {
+        if !state.borrow().has_pane(&label) {
+            return;
+        }
 
-    // Create a named pipe (FIFO)
+        connect_and_stream(&state, &label, &pipe_path, &channel_key).await;
+        state.borrow_mut().set_connected(&label, false);
+
+        if !state.borrow().has_pane(&label) {
+            return;
+        }
+        tokio::time::sleep(RETRY_INTERVAL).await;
+    }
+}
+
+/// One connect attempt: resolve the pane's live id by label, point its
+/// output at the FIFO with pipe-pane, and stream lines into the channel
+/// log. Returns on the first failure, or when the stream ends.
+async fn connect_and_stream(
+    state: &SharedState,
+    label: &str,
+    pipe_path: &std::path::Path,
+    channel_key: &str,
+) {
+    let pane_id = match find_pane_by_name(label) {
+        Some(id) => id,
+        None => return,
+    };
+
+    // Fresh FIFO for this attempt.
+    let _ = std::fs::remove_file(pipe_path);
     unsafe {
         let c_path = std::ffi::CString::new(pipe_path.to_str().unwrap()).unwrap();
         libc::mkfifo(c_path.as_ptr(), 0o644);
     }
 
-    // Tell tmux to pipe this pane's output to our FIFO
-    let pipe_path_str = pipe_path.to_string_lossy().to_string();
-    let result = std::process::Command::new("tmux")
-        .args(["pipe-pane", "-t", &pane.pane_id, &format!("cat >> {}", pipe_path_str)])
-        .output();
-
-    match result {
-        Ok(output) if output.status.success() => {
-            info!("pipe-pane set up for {} ({})", pane.label, pane.pane_id);
-        }
-        Ok(output) => {
-            error!("pipe-pane failed for {}: {}", pane.label,
-                   String::from_utf8_lossy(&output.stderr));
-            state.borrow_mut().set_connected(&pane.label, false);
+    // Point the pane's output at our FIFO.
+    let pipe_cmd = format!("cat >> {}", pipe_path.to_string_lossy());
+    match std::process::Command::new("tmux")
+        .args(["pipe-pane", "-t", &pane_id, &pipe_cmd])
+        .output()
+    {
+        Ok(o) if o.status.success() => {}
+        Ok(o) => {
+            warn!("pipe-pane failed for {} ({}): {}", label, pane_id,
+                  String::from_utf8_lossy(&o.stderr));
             return;
         }
         Err(e) => {
-            error!("failed to run tmux pipe-pane for {}: {}", pane.label, e);
-            state.borrow_mut().set_connected(&pane.label, false);
+            error!("running tmux pipe-pane for {}: {}", label, e);
             return;
         }
     }
 
-    // Open the FIFO and read lines
-    let file = match tokio::fs::File::open(&pipe_path).await {
+    let file = match tokio::fs::File::open(pipe_path).await {
         Ok(f) => f,
         Err(e) => {
-            error!("failed to open pipe for {}: {}", pane.label, e);
-            state.borrow_mut().set_connected(&pane.label, false);
+            warn!("opening pipe for {}: {}", label, e);
             return;
         }
     };
 
-    // Mark as connected once pipe is open
-    state.borrow_mut().set_connected(&pane.label, true);
-
-    let reader = tokio::io::BufReader::new(file);
-    let mut lines = reader.lines();
-    let channel_key = format!("tmux.{}", pane.label);
+    info!("connected channel tmux.{} (pane {})", label, pane_id);
+    state.borrow_mut().set_connected(label, true);
 
+    let mut lines = tokio::io::BufReader::new(file).lines();
     while let Ok(Some(line)) = lines.next_line().await {
         if line.trim().is_empty() {
             continue;
         }
         let mut s = state.borrow_mut();
-        let log = s.channel_logs
-            .entry(channel_key.clone())
-            .or_insert_with(ChannelLog::new);
-        log.push(line);
+        s.channel_logs
+            .entry(channel_key.to_string())
+            .or_insert_with(ChannelLog::new)
+            .push(line);
     }
 
-    warn!("pipe-pane reader ended for {}", pane.label);
-    state.borrow_mut().set_connected(&pane.label, false);
+    warn!("pipe-pane stream ended for {}", label);
 }
 
 // ── ChannelServer Implementation ───────────────────────────────
@@ -244,10 +270,10 @@ impl channel_server::Server for ChannelServerImpl {
         let channel = pry!(pry!(params.get_channel()).to_str()).to_string();
         let message = pry!(pry!(params.get_message()).to_str()).to_string();
 
-        // Send to tmux pane via send-keys
+        // Send to tmux pane via send-keys — resolve the live pane id by
+        // label (it is not stored).
         let label = channel.strip_prefix("tmux.").unwrap_or(&channel);
-        let pane_id = self.state.borrow().get_pane(label).map(String::from);
-        if let Some(pane_id) = pane_id {
+        if let Some(pane_id) = find_pane_by_name(label) {
             let _ = std::process::Command::new("tmux")
                 .args(["send-keys", "-t", &pane_id, &message, "Enter"])
                 .output();
@@ -302,28 +328,22 @@ impl channel_server::Server for ChannelServerImpl {
         let params = pry!(params.get());
         let label = pry!(pry!(params.get_label()).to_str()).to_string();
 
-        // Check if already open
-        if self.state.borrow().get_pane(&label).is_some() {
+        // Already registered — nothing to do.
+        if self.state.borrow().has_pane(&label) {
             return std::future::ready(Ok(()));
         }
 
-        // Find the tmux pane by name (window or pane title)
-        let pane_id = match find_pane_by_name(&label) {
-            Some(id) => id,
-            None => return std::future::ready(Err(capnp::Error::failed(
-                format!("no tmux pane named '{}'", label)))),
-        };
+        info!("opening channel tmux.{}", label);
 
-        info!("opening channel tmux.{} (pane {})", label, pane_id);
+        // Register the label and persist. The pane id is not stored —
+        // the reader resolves it by label on every connect attempt, so
+        // this succeeds even if the pane does not exist yet; the reader
+        // connects once it appears.
+        self.state.borrow_mut().add_pane(label.clone());
 
-        // Register in state and persist
-        self.state.borrow_mut().add_pane(label.clone(), pane_id.clone());
-
-        // Start pipe-pane reader
-        let pane = PaneConfig { label, pane_id };
         let reader_state = self.state.clone();
         tokio::task::spawn_local(async move {
-            pipe_pane_reader(reader_state, pane).await;
+            pipe_pane_reader(reader_state, label).await;
         });
 
         std::future::ready(Ok(()))
@@ -339,14 +359,18 @@ impl channel_server::Server for ChannelServerImpl {
         let label = channel.strip_prefix("tmux.").unwrap_or(&channel).to_string();
 
         let mut s = self.state.borrow_mut();
-        if let Some(pane_id) = s.remove_pane(&label) {
+        if s.remove_pane(&label) {
             info!("closing channel tmux.{}", label);
             s.channel_logs.remove(&format!("tmux.{}", label));
 
-            // Disconnect pipe-pane
-            let _ = std::process::Command::new("tmux")
-                .args(["pipe-pane", "-t", &pane_id])
-                .output();
+            // Stop piping if the pane is still around (if it is gone the
+            // pipe is already dead). The reader then sees the pane
+            // unregistered and exits.
+            if let Some(pane_id) = find_pane_by_name(&label) {
+                let _ = std::process::Command::new("tmux")
+                    .args(["pipe-pane", "-t", &pane_id])
+                    .output();
+            }
         }
 
         std::future::ready(Ok(()))
@@ -397,11 +421,13 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
 
     tokio::task::LocalSet::new()
         .run_until(async move {
-            // Start a pipe-pane reader for each configured pane
+            // Start a pipe-pane reader for each configured pane; each
+            // resolves its live pane id by label and retries until
+            // connected.
             for pane in state.borrow().config.panes.clone() {
                 let reader_state = state.clone();
                 tokio::task::spawn_local(async move {
-                    pipe_pane_reader(reader_state, pane).await;
+                    pipe_pane_reader(reader_state, pane.label).await;
                 });
             }