add usage info to branch summary, compaction and tool result entries (#6671)

* add usage info to branch summary entries

* add usage to compaction entries

* allow custom tools to report llm usage in tool results

* allow observing and patching usage in tool_result hooks

* agent-harness: save usage in entries

for compaction, branch summaries and tool results

packages/coding-agent/src/core/extensions/runner.ts

@@ -883,6 +883,10 @@ export class ExtensionRunner {
 						currentEvent.isError = handlerResult.isError;
 						modified = true;
 					}
+					if (handlerResult.usage !== undefined) {
+						currentEvent.usage = handlerResult.usage;
+						modified = true;
+					}
 				} catch (err) {
 					const message = err instanceof Error ? err.message : String(err);
 					const stack = err instanceof Error ? err.stack : undefined;
@@ -904,6 +908,7 @@ export class ExtensionRunner {
 			content: currentEvent.content,
 			details: currentEvent.details,
 			isError: currentEvent.isError,
+			usage: currentEvent.usage,
 		};
 	}
 

packages/coding-agent/src/core/extensions/types.ts

@@ -30,6 +30,7 @@ import type {
 	SimpleStreamOptions,
 	TextContent,
 	ToolResultMessage,
+	Usage,
 } from "@earendil-works/pi-ai";
 import type {
 	AutocompleteItem,
@@ -905,6 +906,8 @@ interface ToolResultEventBase {
 	input: Record<string, unknown>;
 	content: (TextContent | ImageContent)[];
 	isError: boolean;
+	/** Usage from the tool execution itself, if available. */
+	usage?: Usage;
 }
 
 export interface BashToolResultEvent extends ToolResultEventBase {
@@ -1072,6 +1075,7 @@ export interface ToolResultEventResult {
 	content?: (TextContent | ImageContent)[];
 	details?: unknown;
 	isError?: boolean;
+	usage?: Usage;
 }
 
 export interface MessageEndEventResult {
@@ -1104,6 +1108,7 @@ export interface SessionBeforeTreeResult {
 	summary?: {
 		summary: string;
 		details?: unknown;
+		usage?: Usage;
 	};
 	/** Override custom instructions for summarization */
 	customInstructions?: string;