refactor: deduplicate toPosixPath, ZERO_USAGE, and shortenPath utilities

- toPosixPath: remove private copies in skills.ts and package-manager.ts,
  import from canonical utils/path-display.ts
- ZERO_USAGE: export from agent-loop.ts, replace inline zero-usage
  objects in agent.ts and proxy.ts
- shortenPath: extract to shared modes/interactive/utils/shorten-path.ts,
  import in tool-execution.ts and session-selector.ts

packages/pi-agent-core/src/agent-loop.ts

@@ -22,7 +22,7 @@ import type {
 	StreamFn,
 } from "./types.js";
 
-const ZERO_USAGE = {
+export const ZERO_USAGE = {
 	input: 0,
 	output: 0,
 	cacheRead: 0,
@@ -199,14 +199,7 @@ async function runLoop(
 					api: config.model.api,
 					provider: config.model.provider,
 					model: config.model.id,
-					usage: {
-						input: 0,
-						output: 0,
-						cacheRead: 0,
-						cacheWrite: 0,
-						totalTokens: 0,
-						cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
-					},
+					usage: ZERO_USAGE,
 					stopReason: signal?.aborted ? "aborted" : "error",
 					errorMessage: errorText,
 					timestamp: Date.now(),

packages/pi-agent-core/src/agent.ts

@@ -14,7 +14,7 @@ import {
 	type ThinkingBudgets,
 	type Transport,
 } from "@gsd/pi-ai";
-import { agentLoop, agentLoopContinue } from "./agent-loop.js";
+import { agentLoop, agentLoopContinue, ZERO_USAGE } from "./agent-loop.js";
 import type {
 	AgentContext,
 	AgentEvent,
@@ -557,14 +557,7 @@ export class Agent {
 				api: model.api,
 				provider: model.provider,
 				model: model.id,
-				usage: {
-					input: 0,
-					output: 0,
-					cacheRead: 0,
-					cacheWrite: 0,
-					totalTokens: 0,
-					cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
-				},
+				usage: ZERO_USAGE,
 				stopReason: this.abortController?.signal.aborted ? "aborted" : "error",
 				errorMessage: err?.message || String(err),
 				timestamp: Date.now(),

packages/pi-agent-core/src/proxy.ts

@@ -15,6 +15,7 @@ import {
 	type StopReason,
 	type ToolCall,
 } from "@gsd/pi-ai";
+import { ZERO_USAGE } from "./agent-loop.js";
 
 // Create stream class matching ProxyMessageEventStream
 class ProxyMessageEventStream extends EventStream<AssistantMessageEvent, AssistantMessage> {
@@ -94,14 +95,7 @@ export function streamProxy(model: Model<any>, context: Context, options: ProxyS
 			api: model.api,
 			provider: model.provider,
 			model: model.id,
-			usage: {
-				input: 0,
-				output: 0,
-				cacheRead: 0,
-				cacheWrite: 0,
-				totalTokens: 0,
-				cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
-			},
+			usage: { ...ZERO_USAGE, cost: { ...ZERO_USAGE.cost } },
 			timestamp: Date.now(),
 		};
 

packages/pi-coding-agent/src/core/package-manager.ts

@@ -7,6 +7,7 @@ import ignore from "ignore";
 import { minimatch } from "minimatch";
 import { CONFIG_DIR_NAME } from "../config.js";
 import { type GitSource, parseGitUrl } from "../utils/git.js";
+import { toPosixPath } from "../utils/path-display.js";
 import type { PackageSource, SettingsManager } from "./settings-manager.js";
 
 const NETWORK_TIMEOUT_MS = 10000;
@@ -121,10 +122,6 @@ const IGNORE_FILE_NAMES = [".gitignore", ".ignore", ".fdignore"];
 
 type IgnoreMatcher = ReturnType<typeof ignore>;
 
-function toPosixPath(p: string): string {
-	return p.split(sep).join("/");
-}
-
 function prefixIgnorePattern(line: string, prefix: string): string | null {
 	const trimmed = line.trim();
 	if (!trimmed) return null;

packages/pi-coding-agent/src/core/skills.ts

@@ -4,6 +4,7 @@ import { homedir } from "os";
 import { basename, dirname, isAbsolute, join, relative, resolve, sep } from "path";
 import { CONFIG_DIR_NAME, getAgentDir } from "../config.js";
 import { parseFrontmatter } from "../utils/frontmatter.js";
+import { toPosixPath } from "../utils/path-display.js";
 import type { ResourceDiagnostic } from "./diagnostics.js";
 
 /** Max name length per spec */
@@ -16,10 +17,6 @@ const IGNORE_FILE_NAMES = [".gitignore", ".ignore", ".fdignore"];
 
 type IgnoreMatcher = ReturnType<typeof ignore>;
 
-function toPosixPath(p: string): string {
-	return p.split(sep).join("/");
-}
-
 function prefixIgnorePattern(line: string, prefix: string): string | null {
 	const trimmed = line.trim();
 	if (!trimmed) return null;

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

@@ -1,7 +1,6 @@
 import { spawnSync } from "node:child_process";
 import { existsSync } from "node:fs";
 import { unlink } from "node:fs/promises";
-import * as os from "node:os";
 import {
 	type Component,
 	Container,
@@ -17,21 +16,13 @@ import {
 import { KeybindingsManager } from "../../../core/keybindings.js";
 import type { SessionInfo, SessionListProgress } from "../../../core/session-manager.js";
 import { theme } from "../theme/theme.js";
+import { shortenPath } from "../utils/shorten-path.js";
 import { DynamicBorder } from "./dynamic-border.js";
 import { appKey, appKeyHint, keyHint } from "./keybinding-hints.js";
 import { filterAndSortSessions, hasSessionName, type NameFilter, type SortMode } from "./session-selector-search.js";
 
 type SessionScope = "current" | "all";
 
-function shortenPath(path: string): string {
-	const home = os.homedir();
-	if (!path) return path;
-	if (path.startsWith(home)) {
-		return `~${path.slice(home.length)}`;
-	}
-	return path;
-}
-
 function formatSessionDate(date: Date): string {
 	const now = new Date();
 	const diffMs = now.getTime() - date.getTime();

packages/pi-coding-agent/src/modes/interactive/components/tool-execution.ts

@@ -1,4 +1,3 @@
-import * as os from "node:os";
 import {
 	Box,
 	Container,
@@ -18,6 +17,7 @@ import { DEFAULT_MAX_BYTES, DEFAULT_MAX_LINES, formatSize } from "../../../core/
 import { convertToPng } from "../../../utils/image-convert.js";
 import { sanitizeBinaryOutput } from "../../../utils/shell.js";
 import { getLanguageFromPath, highlightCode, theme } from "../theme/theme.js";
+import { shortenPath } from "../utils/shorten-path.js";
 import { renderDiff } from "./diff.js";
 import { keyHint } from "./keybinding-hints.js";
 import { truncateToVisualLines } from "./visual-truncate.js";
@@ -28,18 +28,6 @@ const BASH_PREVIEW_LINES = 5;
 // to keep multiline tokenization mostly correct without re-highlighting the full file.
 const WRITE_PARTIAL_FULL_HIGHLIGHT_LINES = 50;
 
-/**
- * Convert absolute path to tilde notation if it's in home directory
- */
-function shortenPath(path: unknown): string {
-	if (typeof path !== "string") return "";
-	const home = os.homedir();
-	if (path.startsWith(home)) {
-		return `~${path.slice(home.length)}`;
-	}
-	return path;
-}
-
 /**
  * Replace tabs with spaces for consistent rendering
  */

packages/pi-coding-agent/src/modes/interactive/utils/shorten-path.ts

@@ -0,0 +1,14 @@
+import * as os from "node:os";
+
+/**
+ * Convert absolute path to tilde notation if it's in home directory.
+ * Returns empty string for non-string or empty inputs.
+ */
+export function shortenPath(path: unknown): string {
+	if (typeof path !== "string" || !path) return "";
+	const home = os.homedir();
+	if (path.startsWith(home)) {
+		return `~${path.slice(home.length)}`;
+	}
+	return path;
+}