diff --git a/server/src/agents/pty/runner.rs b/server/src/agents/pty/runner.rs
index b36b3c3b..cd94625c 100644
--- a/server/src/agents/pty/runner.rs
+++ b/server/src/agents/pty/runner.rs
@@ -112,13 +112,14 @@ fn run_agent_pty_blocking(
     // Launch mode: resume an existing session or start fresh.
     if let Some(sid) = session_id_to_resume {
         // Resume: --resume <session_id> restores previous conversation context.
-        // Only the failure context (prompt) is sent as a new message via -p.
+        // The failure context (or empty string) is sent as a new message via -p.
+        // Always pass -p so --include-partial-messages (added below) works:
+        // claude CLI requires --print/-p to be set when --include-partial-messages
+        // is used, regardless of whether the prompt is empty.
         cmd.arg("--resume");
         cmd.arg(sid);
-        if !prompt.is_empty() {
-            cmd.arg("-p");
-            cmd.arg(prompt);
-        }
+        cmd.arg("-p");
+        cmd.arg(prompt);
     } else {
         // Fresh session: deliver the full rendered prompt via -p.
         cmd.arg("-p");