From 533fb94be6f226e1a0b685219798ead0f3fb29f2 Mon Sep 17 00:00:00 2001
From: HirokiKobayashi-R <hiroki@rhems-japan.co.jp>
Date: Thu, 29 Jan 2026 17:46:16 +0900
Subject: [PATCH] fix(logging): use local timezone for console timestamps

Console log timestamps now respect the TZ environment variable instead
of always using UTC. This only affects pretty-style console output;
compact, JSON, and file logs remain in UTC for tool compatibility.

Closes #3867
---
 src/logging/console.ts   |  6 +++---
 src/logging/subsystem.ts |  3 ++-
 src/logging/time.ts      | 11 +++++++++++
 3 files changed, 16 insertions(+), 4 deletions(-)
 create mode 100644 src/logging/time.ts

diff --git a/src/logging/console.ts b/src/logging/console.ts
index 0a1218494..cca7af327 100644
--- a/src/logging/console.ts
+++ b/src/logging/console.ts
@@ -8,6 +8,7 @@ import { type LogLevel, normalizeLogLevel } from "./levels.js";
 import { getLogger, type LoggerSettings } from "./logger.js";
 import { readLoggingConfig } from "./config.js";
 import { loggingState } from "./state.js";
+import { formatLocalHHMMSS } from "./time.js";
 
 export type ConsoleStyle = "pretty" | "compact" | "json";
 type ConsoleSettings = {
@@ -129,9 +130,8 @@ function isEpipeError(err: unknown): boolean {
 }
 
 function formatConsoleTimestamp(style: ConsoleStyle): string {
-  const now = new Date().toISOString();
-  if (style === "pretty") return now.slice(11, 19);
-  return now;
+  if (style === "pretty") return formatLocalHHMMSS();
+  return new Date().toISOString();
 }
 
 function hasTimestampPrefix(value: string): boolean {
diff --git a/src/logging/subsystem.ts b/src/logging/subsystem.ts
index a156fd8f3..6ed756dc0 100644
--- a/src/logging/subsystem.ts
+++ b/src/logging/subsystem.ts
@@ -8,6 +8,7 @@ import { isVerbose } from "../globals.js";
 import { type LogLevel, levelToMinLevel } from "./levels.js";
 import { getChildLogger } from "./logger.js";
 import { loggingState } from "./state.js";
+import { formatLocalHHMMSS } from "./time.js";
 import { clearActiveProgressLine } from "../terminal/progress-line.js";
 
 type LogObj = { date?: Date } & Record<string, unknown>;
@@ -152,7 +153,7 @@ function formatConsoleLine(opts: {
   const displayMessage = stripRedundantSubsystemPrefixForConsole(opts.message, displaySubsystem);
   const time = (() => {
     if (opts.style === "pretty") {
-      return color.gray(new Date().toISOString().slice(11, 19));
+      return color.gray(formatLocalHHMMSS());
     }
     if (loggingState.consoleTimestampPrefix) {
       return color.gray(new Date().toISOString());
diff --git a/src/logging/time.ts b/src/logging/time.ts
new file mode 100644
index 000000000..6872692fc
--- /dev/null
+++ b/src/logging/time.ts
@@ -0,0 +1,11 @@
+/**
+ * Formats the current local time as HH:MM:SS.
+ * Respects the system TZ environment variable.
+ */
+export function formatLocalHHMMSS(): string {
+  const now = new Date();
+  const hours = String(now.getHours()).padStart(2, "0");
+  const minutes = String(now.getMinutes()).padStart(2, "0");
+  const seconds = String(now.getSeconds()).padStart(2, "0");
+  return `${hours}:${minutes}:${seconds}`;
+}