fix(acp): preserve file attachments in custom-agent history

src-tauri/src/acp/connection.rs

@@ -8439,7 +8439,12 @@ fn normalize_grok_image_blocks(blocks: Vec<PromptInputBlock>) -> Vec<PromptInput
         .collect()
 }
 
-fn map_prompt_blocks(blocks: Vec<PromptInputBlock>) -> Vec<ContentBlock> {
+/// `pub(crate)` for one reader beyond this module: the ACP-native history
+/// parser's parity test, which needs the EXACT wire bytes `record_prompt`
+/// writes in order to assert its projection equals the live one
+/// ([`crate::acp::types::user_blocks_from_prompt`]). Rebuilding those bytes by
+/// hand in the test would let the two drift without failing anything.
+pub(crate) fn map_prompt_blocks(blocks: Vec<PromptInputBlock>) -> Vec<ContentBlock> {
     blocks
         .into_iter()
         .map(|block| match block {

src-tauri/src/acp/manager.rs

@@ -250,10 +250,15 @@ fn user_prompt_text_preview(blocks: &[PromptInputBlock]) -> Option<String> {
 /// delegating prompt's text blocks (the sub-agent's task). Uses the parser's own
 /// `title_from_user_text` (folds reference links, caps at 100 chars) so the value
 /// matches what `refresh_auto_title` would later compute from that same first
-/// turn — the conditional UPDATE then sees no change and doesn't churn. Returns
-/// `None` for a textless prompt, leaving the title unset to be backfilled on
-/// first detail load as before. Kept unlocked by the caller so an AI-generated
-/// title can still replace it later.
+/// turn — the conditional UPDATE then sees no change and doesn't churn. Kept
+/// unlocked by the caller so an AI-generated title can still replace it later.
+///
+/// A prompt with no prose at all — one dropped-in file and nothing else — is
+/// named after what it carries instead. That row would otherwise read
+/// "Untitled" forever: for an agent with no store parser, ACP has no title
+/// channel and the history parse honestly reports no title. This value only
+/// ever reaches `seed_auto_title_if_empty` / a fresh row's `title`, never
+/// `refresh_auto_title`, so it cannot displace a name the agent published.
 fn delegation_child_title_seed(blocks: &[PromptInputBlock]) -> Option<String> {
     let joined = blocks
         .iter()
@@ -267,11 +272,11 @@ fn delegation_child_title_seed(blocks: &[PromptInputBlock]) -> Option<String> {
         .collect::<Vec<_>>()
         .join(" ");
     let trimmed = joined.trim();
-    if trimmed.is_empty() {
-        None
-    } else {
-        Some(crate::parsers::title_from_user_text(trimmed))
+    if !trimmed.is_empty() {
+        return Some(crate::parsers::title_from_user_text(trimmed));
     }
+    crate::acp::types::attachment_names_from_prompt(blocks)
+        .map(|names| crate::parsers::title_from_user_text(&names))
 }
 
 /// Composite key identifying a logical agent session for spawn-time dedup.
@@ -6082,6 +6087,48 @@ mod tests {
         assert!(delegation_child_title_seed(&img).is_none());
     }
 
+    /// A message that is one dropped-in file and no prose. The row would read
+    /// "Untitled" forever otherwise — for an agent with no store parser, ACP
+    /// has no title channel and the history parse honestly reports none. The
+    /// value is a SEED: it reaches `seed_auto_title_if_empty` / a fresh row's
+    /// `title`, never `refresh_auto_title`, so a name the agent publishes over
+    /// `session_info_update` still wins.
+    #[test]
+    fn delegation_child_title_seed_names_an_attachment_only_prompt() {
+        let blocks = vec![
+            PromptInputBlock::ResourceLink {
+                uri: "file:///tmp/report.pdf".into(),
+                name: "report.pdf".into(),
+                mime_type: None,
+                description: None,
+            },
+            PromptInputBlock::Resource {
+                uri: "clipboard://my%20notes.txt-9f2".into(),
+                mime_type: Some("text/plain".into()),
+                text: Some("body".into()),
+                blob: None,
+            },
+        ];
+        assert_eq!(
+            delegation_child_title_seed(&blocks).as_deref(),
+            Some("report.pdf, my notes.txt-9f2")
+        );
+
+        // Prose still wins outright, attachments and all — and matches what
+        // `refresh_auto_title` will later compute, so the row doesn't churn.
+        let mut with_prose = blocks.clone();
+        with_prose.insert(
+            0,
+            PromptInputBlock::Text {
+                text: "Review these".into(),
+            },
+        );
+        assert_eq!(
+            delegation_child_title_seed(&with_prose),
+            Some(crate::parsers::title_from_user_text("Review these"))
+        );
+    }
+
     #[test]
     fn delegation_child_title_seed_caps_long_task_text() {
         // Mirrors the parser cap (100 chars) so an over-long task doesn't store a