feat(coding-agent): show compaction usage notices

packages/coding-agent/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Added
+
+- Added transcript usage notices for compaction and branch summaries when cache miss notices are enabled.
+
 ### Fixed
 
 - Fixed the subagent example repeatedly prompting before running project-local agents in trusted repositories ([#8261](https://github.com/earendil-works/pi/issues/8261)).

packages/coding-agent/docs/settings.md

@@ -31,7 +31,7 @@ Use `/trust` in interactive mode to save a project trust decision for future ses
 | `defaultModel` | string | - | Default model ID |
 | `defaultThinkingLevel` | string | - | `"off"`, `"minimal"`, `"low"`, `"medium"`, `"high"`, `"xhigh"`, `"max"` |
 | `hideThinkingBlock` | boolean | `false` | Hide thinking blocks in output |
-| `showCacheMissNotices` | boolean | `false` | Show transcript notices for significant prompt-cache misses |
+| `showCacheMissNotices` | boolean | `false` | Show transcript notices for significant prompt-cache misses and compaction or branch-summary usage |
 | `thinkingBudgets` | object | - | Custom token budgets per thinking level |
 
 #### thinkingBudgets

packages/coding-agent/src/core/settings-manager.ts

@@ -100,7 +100,7 @@ export interface Settings {
 	branchSummary?: BranchSummarySettings;
 	retry?: RetrySettings;
 	hideThinkingBlock?: boolean;
-	showCacheMissNotices?: boolean; // default: false - show transcript notices for significant prompt-cache misses
+	showCacheMissNotices?: boolean; // default: false - show prompt-cache miss and compaction cost notices
 	externalEditor?: string; // Command for Ctrl+G external editor; takes precedence over VISUAL/EDITOR
 	shellPath?: string; // Custom shell path (e.g., for Cygwin users on Windows); supports leading ~ expansion
 	quietStartup?: boolean;

packages/coding-agent/src/modes/interactive/components/settings-selector.ts

@@ -549,7 +549,7 @@ export class SettingsSelectorComponent extends Container {
 			{
 				id: "cache-miss-notices",
 				label: "Cache miss notices",
-				description: "Show transcript notices for significant prompt-cache misses",
+				description: "Show transcript notices for significant prompt-cache misses and compaction costs",
 				currentValue: config.showCacheMissNotices ? "true" : "false",
 				values: ["true", "false"],
 			},

packages/coding-agent/src/modes/interactive/interactive-mode.ts

@@ -9,7 +9,7 @@ import * as os from "node:os";
 import * as path from "node:path";
 import type { AgentMessage } from "@earendil-works/pi-agent-core";
 import type { AuthEvent, AuthPrompt } from "@earendil-works/pi-ai";
-import type { AssistantMessage, ImageContent, Message, Model } from "@earendil-works/pi-ai/compat";
+import type { AssistantMessage, ImageContent, Message, Model, Usage } from "@earendil-works/pi-ai/compat";
 import type {
 	AutocompleteItem,
 	AutocompleteProvider,
@@ -204,12 +204,22 @@ type CompactionQueuedMessage = {
 	mode: "steer" | "followUp";
 };
 
-type RenderSessionItem = AgentMessage | Extract<SessionEntry, { type: "custom" }>;
+type CompactionCostNotice = {
+	type: "compaction_cost";
+	kind: "compaction" | "branch_summary";
+	usage: Usage;
+};
+
+type RenderSessionItem = AgentMessage | Extract<SessionEntry, { type: "custom" }> | CompactionCostNotice;
 
 function isCustomSessionEntry(item: RenderSessionItem): item is Extract<SessionEntry, { type: "custom" }> {
 	return "type" in item && item.type === "custom";
 }
 
+function isCompactionCostNotice(item: RenderSessionItem): item is CompactionCostNotice {
+	return "type" in item && item.type === "compaction_cost";
+}
+
 const DEAD_TERMINAL_ERROR_CODES = new Set(["EIO", "EPIPE", "ENOTCONN"]);
 
 function isDeadTerminalError(error: unknown): boolean {
@@ -3349,8 +3359,13 @@ export class InteractiveMode {
 						this.showStatus("Auto-compaction cancelled");
 					}
 				} else if (event.result) {
+					const entries = this.sessionManager.buildContextEntries();
+					if (entries[0]?.type !== "compaction") {
+						throw new Error("Completed compaction is missing from the session context");
+					}
 					this.chatContainer.clear();
-					this.rebuildChatFromMessages();
+					// The latest compaction is prepended for model context; append it below at its chronological position.
+					this.renderSessionEntries(entries.slice(1));
 					this.addMessageToChat(
 						createCompactionSummaryMessage(
 							event.result.summary,
@@ -3358,6 +3373,13 @@ export class InteractiveMode {
 							new Date().toISOString(),
 						),
 					);
+					if (event.result.usage) {
+						this.addCompactionCostNotice({
+							type: "compaction_cost",
+							kind: "compaction",
+							usage: event.result.usage,
+						});
+					}
 					this.footer.invalidate();
 				} else if (event.errorMessage) {
 					if (event.reason === "manual") {
@@ -3629,6 +3651,10 @@ export class InteractiveMode {
 				this.addCustomEntryToChat(item);
 				continue;
 			}
+			if (isCompactionCostNotice(item)) {
+				this.addCompactionCostNotice(item);
+				continue;
+			}
 
 			const message = item;
 			// Assistant messages need special handling for tool calls
@@ -3706,11 +3732,32 @@ export class InteractiveMode {
 			if (entry.type === "custom") {
 				return [entry];
 			}
-			return sessionEntryToContextMessages(entry);
+			const messages = sessionEntryToContextMessages(entry);
+			if ((entry.type === "compaction" || entry.type === "branch_summary") && entry.usage && messages.length > 0) {
+				return [...messages, { type: "compaction_cost", kind: entry.type, usage: entry.usage }];
+			}
+			return messages;
 		});
 		this.renderSessionItems(items, options);
 	}
 
+	/**
+	 * Render billing usage for a compaction or branch summary. The notice is derived
+	 * from persisted summary usage and is not stored as a separate session entry.
+	 */
+	private addCompactionCostNotice(notice: CompactionCostNotice): void {
+		if (!this.settingsManager.getShowCacheMissNotices()) return;
+
+		const { usage } = notice;
+		const tokens = usage.input + usage.output + usage.cacheRead + usage.cacheWrite;
+		const cost = usage.cost.total >= 0.01 ? ` (~$${usage.cost.total.toFixed(2)})` : "";
+		const label = notice.kind === "compaction" ? "Compaction" : "Branch summary";
+		this.chatContainer.addChild(new Spacer(1));
+		this.chatContainer.addChild(
+			new Text(theme.fg("warning", `${label}: ${formatTokens(tokens)} tokens billed${cost}`), 1, 0),
+		);
+	}
+
 	/**
 	 * Show a transcript notice when a completed assistant message paid for a
 	 * significant cache miss. Only states observable facts: the miss itself,

packages/coding-agent/test/interactive-mode-compaction.test.ts

@@ -1,8 +1,140 @@
+import type { Usage } from "@earendil-works/pi-ai";
+import { Container } from "@earendil-works/pi-tui";
 import { describe, expect, test, vi } from "vitest";
+import type { SessionEntry } from "../src/core/session-manager.ts";
 import { InteractiveMode } from "../src/modes/interactive/interactive-mode.ts";
+import { initTheme } from "../src/modes/interactive/theme/theme.ts";
+import { stripAnsi } from "../src/utils/ansi.ts";
 
 describe("InteractiveMode compaction events", () => {
-	test("rebuilds chat and appends a synthetic compaction summary at the bottom", async () => {
+	test("uses the cache miss notice setting for compaction and branch summary costs", () => {
+		const usage: Usage = {
+			input: 10,
+			output: 20,
+			cacheRead: 30,
+			cacheWrite: 40,
+			totalTokens: 100,
+			cost: { input: 0.01, output: 0.02, cacheRead: 0.03, cacheWrite: 0.065, total: 0.125 },
+		};
+		const addCompactionCostNotice = Reflect.get(InteractiveMode.prototype, "addCompactionCostNotice") as (
+			this: { chatContainer: Container; settingsManager: { getShowCacheMissNotices(): boolean } },
+			notice: {
+				type: "compaction_cost";
+				kind: "compaction" | "branch_summary";
+				usage: Usage;
+			},
+		) => void;
+
+		initTheme("dark");
+		const enabled = {
+			chatContainer: new Container(),
+			settingsManager: { getShowCacheMissNotices: () => true },
+		};
+		addCompactionCostNotice.call(enabled, { type: "compaction_cost", kind: "compaction", usage });
+		addCompactionCostNotice.call(enabled, {
+			type: "compaction_cost",
+			kind: "branch_summary",
+			usage,
+		});
+		const output = stripAnsi(enabled.chatContainer.render(120).join("\n"));
+		expect(output).toContain("Compaction: 100 tokens billed (~$0.13)");
+		expect(output).toContain("Branch summary: 100 tokens billed (~$0.13)");
+
+		const disabled = {
+			chatContainer: new Container(),
+			settingsManager: { getShowCacheMissNotices: () => false },
+		};
+		addCompactionCostNotice.call(disabled, { type: "compaction_cost", kind: "compaction", usage });
+		expect(disabled.chatContainer.children).toHaveLength(0);
+	});
+
+	test("renders each compaction cost after its summary", () => {
+		const currentUsage: Usage = {
+			input: 10,
+			output: 20,
+			cacheRead: 30,
+			cacheWrite: 40,
+			totalTokens: 100,
+			cost: { input: 0.01, output: 0.02, cacheRead: 0.03, cacheWrite: 0.04, total: 0.1 },
+		};
+		const previousUsage: Usage = {
+			input: 1,
+			output: 2,
+			cacheRead: 3,
+			cacheWrite: 4,
+			totalTokens: 10,
+			cost: { input: 0.001, output: 0.002, cacheRead: 0.003, cacheWrite: 0.004, total: 0.01 },
+		};
+		const entries: SessionEntry[] = [
+			{
+				type: "compaction",
+				id: "current",
+				parentId: "previous",
+				timestamp: "2025-01-02T00:00:00Z",
+				summary: "current summary",
+				firstKeptEntryId: "kept",
+				tokensBefore: 200,
+				usage: currentUsage,
+			},
+			{
+				type: "compaction",
+				id: "previous",
+				parentId: null,
+				timestamp: "2025-01-01T00:00:00Z",
+				summary: "previous summary",
+				firstKeptEntryId: "kept",
+				tokensBefore: 100,
+				usage: previousUsage,
+			},
+		];
+		const fakeThis = { renderSessionItems: vi.fn() };
+		const renderSessionEntries = Reflect.get(InteractiveMode.prototype, "renderSessionEntries") as (
+			this: typeof fakeThis,
+			entries: SessionEntry[],
+		) => void;
+
+		renderSessionEntries.call(fakeThis, entries);
+
+		expect(fakeThis.renderSessionItems).toHaveBeenCalledWith(
+			[
+				expect.objectContaining({ role: "compactionSummary", summary: "current summary" }),
+				{ type: "compaction_cost", kind: "compaction", usage: currentUsage },
+				expect.objectContaining({ role: "compactionSummary", summary: "previous summary" }),
+				{ type: "compaction_cost", kind: "compaction", usage: previousUsage },
+			],
+			{},
+		);
+	});
+
+	test("renders retained entries and appends the latest summary cost at the bottom", async () => {
+		const usage: Usage = {
+			input: 10,
+			output: 20,
+			cacheRead: 30,
+			cacheWrite: 40,
+			totalTokens: 100,
+			cost: { input: 0.01, output: 0.02, cacheRead: 0.03, cacheWrite: 0.065, total: 0.125 },
+		};
+		const latestCompaction: SessionEntry = {
+			type: "compaction",
+			id: "latest",
+			parentId: "previous",
+			timestamp: "2025-01-02T00:00:00Z",
+			summary: "summary",
+			firstKeptEntryId: "kept",
+			tokensBefore: 123,
+			usage,
+		};
+		const previousCompaction: SessionEntry = {
+			type: "compaction",
+			id: "previous",
+			parentId: null,
+			timestamp: "2025-01-01T00:00:00Z",
+			summary: "previous summary",
+			firstKeptEntryId: "kept",
+			tokensBefore: 100,
+			usage,
+		};
 		const fakeThis = {
 			isInitialized: true,
 			footer: { invalidate: vi.fn() },
@@ -11,8 +143,10 @@ describe("InteractiveMode compaction events", () => {
 			defaultEditor: {},
 			statusContainer: { clear: vi.fn() },
 			chatContainer: { clear: vi.fn() },
-			rebuildChatFromMessages: vi.fn(),
+			sessionManager: { buildContextEntries: vi.fn().mockReturnValue([latestCompaction, previousCompaction]) },
+			renderSessionEntries: vi.fn(),
 			addMessageToChat: vi.fn(),
+			addCompactionCostNotice: vi.fn(),
 			showError: vi.fn(),
 			showStatus: vi.fn(),
 			clearStatusIndicator: vi.fn(),
@@ -26,7 +160,7 @@ describe("InteractiveMode compaction events", () => {
 			event: {
 				type: "compaction_end";
 				reason: "manual" | "threshold" | "overflow";
-				result: { tokensBefore: number; summary: string } | undefined;
+				result: { tokensBefore: number; summary: string; usage?: Usage } | undefined;
 				aborted: boolean;
 				willRetry: boolean;
 				errorMessage?: string;
@@ -39,13 +173,14 @@ describe("InteractiveMode compaction events", () => {
 			result: {
 				tokensBefore: 123,
 				summary: "summary",
+				usage,
 			},
 			aborted: false,
 			willRetry: false,
 		});
 
 		expect(fakeThis.chatContainer.clear).toHaveBeenCalledTimes(1);
-		expect(fakeThis.rebuildChatFromMessages).toHaveBeenCalledTimes(1);
+		expect(fakeThis.renderSessionEntries).toHaveBeenCalledWith([previousCompaction]);
 		expect(fakeThis.addMessageToChat).toHaveBeenCalledTimes(1);
 		expect(fakeThis.addMessageToChat).toHaveBeenCalledWith(
 			expect.objectContaining({
@@ -54,6 +189,11 @@ describe("InteractiveMode compaction events", () => {
 				summary: "summary",
 			}),
 		);
+		expect(fakeThis.addCompactionCostNotice).toHaveBeenCalledWith({
+			type: "compaction_cost",
+			kind: "compaction",
+			usage,
+		});
 		expect(fakeThis.flushCompactionQueue).toHaveBeenCalledWith({ willRetry: false });
 	});