story-kit: merge 300_story_show_token_cost_badge_on_pipeline_board_work_items

server/src/http/agents.rs

@@ -112,6 +112,24 @@ struct AgentOutputResponse {
     output: String,
 }
 
+/// Per-agent cost breakdown entry for the token cost endpoint.
+#[derive(Object, Serialize)]
+struct AgentCostEntry {
+    agent_name: String,
+    input_tokens: u64,
+    output_tokens: u64,
+    cache_creation_input_tokens: u64,
+    cache_read_input_tokens: u64,
+    total_cost_usd: f64,
+}
+
+/// Response for the work item token cost endpoint.
+#[derive(Object, Serialize)]
+struct TokenCostResponse {
+    total_cost_usd: f64,
+    agents: Vec<AgentCostEntry>,
+}
+
 /// Returns true if the story file exists in `work/5_done/` or `work/6_archived/`.
 ///
 /// Used to exclude agents for already-archived stories from the `list_agents`
@@ -463,6 +481,57 @@ impl AgentsApi {
 
         Ok(Json(true))
     }
+
+    /// Get the total token cost and per-agent breakdown for a work item.
+    ///
+    /// Returns the sum of all recorded token usage for the given story_id.
+    /// If no usage has been recorded, returns zero cost with an empty agents list.
+    #[oai(path = "/work-items/:story_id/token-cost", method = "get")]
+    async fn get_work_item_token_cost(
+        &self,
+        story_id: Path<String>,
+    ) -> OpenApiResult<Json<TokenCostResponse>> {
+        let project_root = self
+            .ctx
+            .agents
+            .get_project_root(&self.ctx.state)
+            .map_err(bad_request)?;
+
+        let all_records = crate::agents::token_usage::read_all(&project_root)
+            .map_err(|e| bad_request(format!("Failed to read token usage: {e}")))?;
+
+        let mut agent_map: std::collections::HashMap<String, AgentCostEntry> =
+            std::collections::HashMap::new();
+
+        let mut total_cost_usd = 0.0_f64;
+
+        for record in all_records.into_iter().filter(|r| r.story_id == story_id.0) {
+            total_cost_usd += record.usage.total_cost_usd;
+            let entry = agent_map
+                .entry(record.agent_name.clone())
+                .or_insert_with(|| AgentCostEntry {
+                    agent_name: record.agent_name.clone(),
+                    input_tokens: 0,
+                    output_tokens: 0,
+                    cache_creation_input_tokens: 0,
+                    cache_read_input_tokens: 0,
+                    total_cost_usd: 0.0,
+                });
+            entry.input_tokens += record.usage.input_tokens;
+            entry.output_tokens += record.usage.output_tokens;
+            entry.cache_creation_input_tokens += record.usage.cache_creation_input_tokens;
+            entry.cache_read_input_tokens += record.usage.cache_read_input_tokens;
+            entry.total_cost_usd += record.usage.total_cost_usd;
+        }
+
+        let mut agents: Vec<AgentCostEntry> = agent_map.into_values().collect();
+        agents.sort_by(|a, b| a.agent_name.cmp(&b.agent_name));
+
+        Ok(Json(TokenCostResponse {
+            total_cost_usd,
+            agents,
+        }))
+    }
 }
 
 #[cfg(test)]