show token usage on per-agent web ui after each turn

hive-ag3nt/src/events.rs

@@ -156,6 +156,23 @@ impl EventStore {
     }
 }
 
+/// Token usage emitted by claude in the final `result` stream-json event.
+/// All counts are in tokens. `None` fields mean the server didn't report them.
+#[derive(Debug, Clone, Copy, Default, Serialize, Deserialize, PartialEq, Eq)]
+pub struct TokenUsage {
+    pub input_tokens: u64,
+    pub output_tokens: u64,
+    pub cache_read_input_tokens: u64,
+    pub cache_creation_input_tokens: u64,
+}
+
+impl TokenUsage {
+    /// Total context consumed this turn (input + cache reads + cache writes).
+    pub fn context_tokens(&self) -> u64 {
+        self.input_tokens + self.cache_read_input_tokens + self.cache_creation_input_tokens
+    }
+}
+
 /// Authoritative turn-loop state. The harness owns it; the web UI
 /// reads via `/api/state` and renders. Lives alongside the bus
 /// because everyone who has a `Bus` already has the right handle to
@@ -191,6 +208,12 @@ pub struct Bus {
     /// Model name passed to `claude --model`. Default `haiku`; the
     /// operator can override at runtime via `POST /api/model`.
     model: Arc<Mutex<String>>,
+    /// Last token usage reported by claude (from the `result` stream-json
+    /// event). `None` until the first turn with usage data completes.
+    /// Updated on every turn; survives across turns within one harness
+    /// process lifetime (resets on container restart, which is fine —
+    /// it's a live indicator, not a cumulative counter).
+    last_usage: Arc<Mutex<Option<TokenUsage>>>,
     /// One-shot: next `run_claude` call drops `--continue`, starting
     /// a fresh claude session. Set by `POST /api/new-session` from
     /// the per-agent web UI; consumed (cleared back to false) by the
@@ -220,6 +243,7 @@ impl Bus {
             store,
             state: Arc::new(Mutex::new((TurnState::Idle, now_unix()))),
             model: Arc::new(Mutex::new(initial_model)),
+            last_usage: Arc::new(Mutex::new(None)),
             skip_continue_once: Arc::new(AtomicBool::new(false)),
         }
     }
@@ -258,6 +282,17 @@ impl Bus {
         }
     }
 
+    /// Record the latest token usage from a completed turn.
+    pub fn record_usage(&self, usage: TokenUsage) {
+        *self.last_usage.lock().unwrap() = Some(usage);
+    }
+
+    /// Last known token usage, or `None` if no turn has completed yet.
+    #[must_use]
+    pub fn last_usage(&self) -> Option<TokenUsage> {
+        *self.last_usage.lock().unwrap()
+    }
+
     /// Update the harness's authoritative turn-loop state. Records
     /// the transition time so `state_snapshot` can return a since-age.
     pub fn set_state(&self, next: TurnState) {