feat: Add skill discovery, loading, and invocation (#3444)

Adds a skills system that lets users define reusable LLM instructions as `SKILL.md` files with YAML frontmatter.

3 files changed, 56 insertions, 12 deletions

diff --git a/crates/atuin-ai/src/tui/state.rs b/crates/atuin-ai/src/tui/state.rs
index e008bd3c..71da6ff5 100644
--- a/crates/atuin-ai/src/tui/state.rs
+++ b/crates/atuin-ai/src/tui/state.rs
@@ -37,6 +37,14 @@ pub(crate) enum ConversationEvent {
     /// Context injected for the LLM that is not rendered in the TUI.
     /// Converted to a user message in the API protocol.
     SystemContext { content: String },
+    /// A skill was loaded and its content injected into the conversation.
+    /// Serialized as a full user message for the API but rendered compactly
+    /// in the TUI (just the `/name args` invocation line).
+    SkillInvocation {
+        name: String,
+        arguments: Option<String>,
+        content: String,
+    },
 }
 
 impl ConversationEvent {
@@ -49,6 +57,7 @@ impl ConversationEvent {
             ConversationEvent::ToolResult { .. } => true,
             ConversationEvent::OutOfBandOutput { .. } => false,
             ConversationEvent::SystemContext { .. } => false,
+            ConversationEvent::SkillInvocation { .. } => true,
         }
     }
 
@@ -206,6 +215,21 @@ pub(crate) fn events_to_messages(events: &[ConversationEvent]) -> Vec<serde_json
                 }));
                 i += 1;
             }
+            ConversationEvent::SkillInvocation {
+                name,
+                arguments,
+                content,
+            } => {
+                let header = match arguments {
+                    Some(args) => format!("[Loaded skill: {name}]\n[Arguments: {args}]"),
+                    None => format!("[Loaded skill: {name}]"),
+                };
+                messages.push(serde_json::json!({
+                    "role": "user",
+                    "content": format!("{header}\n\n{content}")
+                }));
+                i += 1;
+            }
         }
     }
 
diff --git a/crates/atuin-ai/src/tui/view/mod.rs b/crates/atuin-ai/src/tui/view/mod.rs
index 2061ec38..96ad5d85 100644
--- a/crates/atuin-ai/src/tui/view/mod.rs
+++ b/crates/atuin-ai/src/tui/view/mod.rs
@@ -73,7 +73,7 @@ pub(crate) fn ai_view(state: &ViewState) -> Elements {
                         user_turn_view(events, index == 0)
                     }
                     turn::UiTurn::Agent { events } => {
-                        agent_turn_view(events, busy && index == last_index)
+                        agent_turn_view(events, busy && index == last_index, state.tools.awaiting_permission().is_some())
                     }
                     turn::UiTurn::OutOfBand { events } => {
                         out_of_band_turn_view(events)
@@ -85,7 +85,7 @@ pub(crate) fn ai_view(state: &ViewState) -> Elements {
                 let needs_pending_banner = busy && !matches!(turns.last(), Some(turn::UiTurn::Agent { .. }));
                 if needs_pending_banner {
                     let empty: &[turn::UiEvent] = &[];
-                    agent_turn_view(empty, true)
+                    agent_turn_view(empty, true, false)
                 } else {
                     element! {}
                 }
@@ -170,6 +170,7 @@ fn tool_call_view(tool_call: &crate::fsm::tools::TrackedTool, in_git_project: bo
         ClientToolCall::Write(tool) => tool.path.display().to_string(),
         ClientToolCall::Shell(tool) => tool.command.clone(),
         ClientToolCall::AtuinHistory(tool) => tool.query.clone(),
+        ClientToolCall::LoadSkill(tool) => format!("skill: {}", tool.name),
     };
 
     let select_options = permission_options_for_tool(&tool_call.tool, in_git_project);
@@ -273,21 +274,16 @@ fn user_turn_view(events: &[turn::UiEvent], first_turn: bool) -> Elements {
     }
 }
 
-fn agent_turn_view(events: &[turn::UiEvent], busy: bool) -> Elements {
+fn agent_turn_view(events: &[turn::UiEvent], busy: bool, showing_ui: bool) -> Elements {
     let label_style = Style::default()
         .fg(Color::Yellow)
         .add_modifier(Modifier::BOLD);
 
     element! {
         View {
-            Spinner(
-                label: " Atuin AI ",
-                label_style: label_style.reversed(),
-                done_label_style: label_style.reversed(),
-                hide_checkmark: true,
-                label_first: true,
-                done: !busy,
-            )
+            Text {
+                Span(text: " Atuin AI ", style: label_style.reversed())
+            }
             #(for (i, event) in events.iter().enumerate() {
                 #(if i > 0 {
                     Text { Span(text: "") }
@@ -325,7 +321,8 @@ fn agent_turn_view(events: &[turn::UiEvent], busy: bool) -> Elements {
                                         tool_status_view(&details.name, &details.status)
                                     },
                                     turn::ToolRenderData::FileRead { .. }
-                                    | turn::ToolRenderData::HistorySearch { .. } => {
+                                    | turn::ToolRenderData::HistorySearch { .. }
+                                    | turn::ToolRenderData::SkillLoad { .. } => {
                                         element!{}
                                     },
                                 })
@@ -350,6 +347,15 @@ fn agent_turn_view(events: &[turn::UiEvent], busy: bool) -> Elements {
                     _ => element!{}
                 })
             })
+
+            #(if busy && !showing_ui {
+                View(key: "agent-working-spinner", padding_left: Cells::from(2), padding_top: Cells::from(1)) {
+                    Spinner(
+                        label: "",
+                        spinner_style: Style::default().fg(Color::Yellow).add_modifier(Modifier::BOLD),
+                    )
+                }
+            })
         }
     }
 }
diff --git a/crates/atuin-ai/src/tui/view/turn.rs b/crates/atuin-ai/src/tui/view/turn.rs
index 98ae5eff..9f4460eb 100644
--- a/crates/atuin-ai/src/tui/view/turn.rs
+++ b/crates/atuin-ai/src/tui/view/turn.rs
@@ -151,6 +151,8 @@ pub(crate) enum ToolRenderData {
         query: String,
         filter_modes: Vec<HistorySearchFilterMode>,
     },
+    /// Skill loading — read-only, auto-approved.
+    SkillLoad { _name: String },
     /// Server-side tool — no client rendering data available.
     Remote,
 }
@@ -257,6 +259,15 @@ impl<'a> TurnBuilder<'a> {
             ConversationEvent::SystemContext { .. } => {
                 // Not rendered in the TUI — only sent to the API
             }
+            ConversationEvent::SkillInvocation {
+                name, arguments, ..
+            } => {
+                let display = match arguments {
+                    Some(args) => format!("/{name} {args}"),
+                    None => format!("/{name}"),
+                };
+                self.add_user_message(&display);
+            }
         }
     }
 
@@ -459,6 +470,9 @@ impl<'a> TurnBuilder<'a> {
                     query: history.query.clone(),
                     filter_modes: history.filter_modes.clone(),
                 },
+                ClientToolCall::LoadSkill(skill) => ToolRenderData::SkillLoad {
+                    _name: skill.name.clone(),
+                },
             }
         } else {
             // Not in tracker → server-side tool