Feature/at agent mention (#8571)

Signed-off-by: Douwe Osinga <douwe@squareup.com>
Co-authored-by: Douwe Osinga <douwe@squareup.com>

crates/goose-server/src/routes/config_management.rs

@@ -136,6 +136,7 @@ pub enum CommandType {
     Builtin,
     Recipe,
     Skill,
+    Agent,
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize, ToSchema)]
@@ -436,6 +437,26 @@ pub async fn get_slash_commands(
         });
     }
 
+    let discover_dir = working_dir
+        .as_deref()
+        .unwrap_or_else(|| std::path::Path::new("."));
+    for source in
+        goose::agents::platform_extensions::summon::discover_filesystem_sources(discover_dir)
+    {
+        use goose::agents::platform_extensions::SourceKind;
+        if matches!(
+            source.kind,
+            SourceKind::Agent | SourceKind::Recipe | SourceKind::Subrecipe
+        ) && !source.content.is_empty()
+        {
+            commands.push(SlashCommand {
+                command: source.name,
+                help: source.description,
+                command_type: CommandType::Agent,
+            });
+        }
+    }
+
     Ok(Json(SlashCommandsResponse { commands }))
 }
 

crates/goose/src/agents/agent.rs

@@ -21,6 +21,7 @@ use crate::agents::extension_manager::{
     get_parameter_names, ExtensionManager, ExtensionManagerCapabilities,
 };
 use crate::agents::final_output_tool::{FINAL_OUTPUT_CONTINUATION_MESSAGE, FINAL_OUTPUT_TOOL_NAME};
+use crate::agents::platform_extensions::summon::discover_filesystem_sources;
 use crate::agents::platform_extensions::MANAGE_EXTENSIONS_TOOL_NAME_COMPLETE;
 use crate::agents::platform_tools::PLATFORM_MANAGE_SCHEDULE_TOOL_NAME;
 use crate::agents::prompt_manager::PromptManager;
@@ -354,10 +355,17 @@ impl Agent {
         }
         let initial_messages = conversation.messages().clone();
 
-        let (tools, toolshim_tools, system_prompt) = self
+        let (tools, toolshim_tools, mut system_prompt) = self
             .prepare_tools_and_prompt(session_id, working_dir)
             .await?;
 
+        if let Some(instructions) = self.resolve_at_mention(&conversation, working_dir) {
+            system_prompt = format!(
+                "{}\n\n# Instructions from active agent:\n\n{}",
+                system_prompt, instructions
+            );
+        }
+
         let goose_mode = *self.current_goose_mode.lock().await;
 
         if goose_mode == GooseMode::SmartApprove {
@@ -391,6 +399,30 @@ impl Agent {
         })
     }
 
+    fn resolve_at_mention(
+        &self,
+        conversation: &Conversation,
+        working_dir: &std::path::Path,
+    ) -> Option<String> {
+        let last_message = conversation.messages().last()?;
+        if last_message.role == rmcp::model::Role::User {
+            let after_at = last_message
+                .as_concat_text()
+                .trim()
+                .strip_prefix('@')?
+                .to_lowercase();
+
+            for source in discover_filesystem_sources(working_dir) {
+                let name = source.name.to_lowercase();
+                let is_match = after_at == name || after_at.starts_with(&format!("{} ", name));
+                if is_match && !source.content.is_empty() {
+                    return Some(source.content.clone());
+                }
+            }
+        }
+        None
+    }
+
     async fn categorize_tools(
         &self,
         response: &Message,

crates/goose/src/agents/platform_extensions/summon.rs

@@ -218,7 +218,7 @@ fn scan_agents_from_dir(
     }
 }
 
-fn discover_filesystem_sources(working_dir: &Path) -> Vec<Source> {
+pub fn discover_filesystem_sources(working_dir: &Path) -> Vec<Source> {
     let mut sources: Vec<Source> = Vec::new();
     let mut seen: std::collections::HashSet<String> = std::collections::HashSet::new();
 
@@ -240,6 +240,7 @@ fn discover_filesystem_sources(working_dir: &Path) -> Vec<Source> {
         })
         .chain(
             [
+                home.as_ref().map(|h| h.join(".goose/recipes")),
                 Some(config.join("recipes")),
                 home.as_ref().map(|h| h.join(".agents/recipes")),
             ]
@@ -255,6 +256,7 @@ fn discover_filesystem_sources(working_dir: &Path) -> Vec<Source> {
     ];
 
     let global_agent_dirs: Vec<PathBuf> = [
+        home.as_ref().map(|h| h.join(".goose/agents")),
         home.as_ref().map(|h| h.join(".agents/agents")),
         Some(config.join("agents")),
         home.as_ref().map(|h| h.join(".claude/agents")),