From f223009b25b40c7afd1cf0930395ae8b49b8247e Mon Sep 17 00:00:00 2001
From: Stefan Obradovic <me@stefano.id.au>
Date: Sun, 1 Mar 2026 23:50:48 +1000
Subject: [PATCH 1/2] fix: use floor_char_boundary for string truncation to
 prevent UTF-8 panics
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Fixes #273 — cortex_chat.rs panics on CJK memory content because
`&result[..200]` can land inside a multi-byte character. Same issue
existed in discord.rs reply content truncation.

Replace bare byte-index slices with `floor_char_boundary(200)` which
rounds down to the nearest char boundary.
---
 src/agent/cortex_chat.rs | 2 +-
 src/messaging/discord.rs | 5 ++++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/agent/cortex_chat.rs b/src/agent/cortex_chat.rs
index ed5ec0033..ad05db162 100644
--- a/src/agent/cortex_chat.rs
+++ b/src/agent/cortex_chat.rs
@@ -89,7 +89,7 @@ impl<M: CompletionModel> PromptHook<M> for CortexChatHook {
         result: &str,
     ) -> HookAction {
         let preview = if result.len() > 200 {
-            format!("{}...", &result[..200])
+            format!("{}...", &result[..result.floor_char_boundary(200)])
         } else {
             result.to_string()
         };
diff --git a/src/messaging/discord.rs b/src/messaging/discord.rs
index 7f2363450..ef692e301 100644
--- a/src/messaging/discord.rs
+++ b/src/messaging/discord.rs
@@ -930,7 +930,10 @@ async fn build_metadata(
         let reply_content = resolve_mentions(&referenced.content, &referenced.mentions);
         // Truncate to avoid bloating context with long quoted messages
         let truncated = if reply_content.len() > 200 {
-            format!("{}...", &reply_content[..200])
+            format!(
+                "{}...",
+                &reply_content[..reply_content.floor_char_boundary(200)]
+            )
         } else {
             reply_content
         };

From 767799e3ebc0c4c8cf419a93c4d6235b5ef87486 Mon Sep 17 00:00:00 2001
From: Stefan Obradovic <me@stefano.id.au>
Date: Sun, 1 Mar 2026 23:54:51 +1000
Subject: [PATCH 2/2] refactor: extract floor_char_boundary to local for
 readability

---
 src/agent/cortex_chat.rs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/agent/cortex_chat.rs b/src/agent/cortex_chat.rs
index ad05db162..ac2ae06e1 100644
--- a/src/agent/cortex_chat.rs
+++ b/src/agent/cortex_chat.rs
@@ -89,7 +89,8 @@ impl<M: CompletionModel> PromptHook<M> for CortexChatHook {
         result: &str,
     ) -> HookAction {
         let preview = if result.len() > 200 {
-            format!("{}...", &result[..result.floor_char_boundary(200)])
+            let end = result.floor_char_boundary(200);
+            format!("{}...", &result[..end])
         } else {
             result.to_string()
         };