diff --git a/Makefile b/Makefile
index 3738e20..cd676c9 100644
--- a/Makefile
+++ b/Makefile
@@ -9,6 +9,7 @@ LD := lld-link
 BUILD_DIR := build
 KERNEL_ELF := $(BUILD_DIR)/image/kernel.elf
 DEBUG_LOG := $(BUILD_DIR)/debug.log
+SERIAL_LOG := $(BUILD_DIR)/serial.log
 
 ifeq ($(ARCH),x86_64)
 ARCH_MAKEFILE := arch/x86/Makefile
@@ -28,7 +29,7 @@ all: $(BOOT_EFI) $(KERNEL_ELF)
 dirs:
 	mkdir -p $(BUILD_DIR)/arch/boot $(BUILD_DIR)/arch/kernel $(BUILD_DIR)/kernel $(EFI_DIR)
 
-$(BUILD_DIR)/arch/boot/%.obj: $(ARCH_DIR)/boot/%.c $(ARCH_DIR)/include/efi.h $(ARCH_DIR)/include/tianole/early_log.h include/tianole/boot_info.h include/tianole/elf.h | dirs
+$(BUILD_DIR)/arch/boot/%.obj: $(ARCH_DIR)/boot/%.c $(ARCH_DIR)/include/efi.h $(ARCH_DIR)/boot/debug_log.h include/tianole/boot_info.h include/tianole/elf.h | dirs
 	$(CC) $(CFLAGS) -c $< -o $@
 
 $(BOOT_EFI): $(BOOT_OBJS) | dirs
@@ -37,7 +38,10 @@ $(BOOT_EFI): $(BOOT_OBJS) | dirs
 $(BUILD_DIR)/arch/kernel/entry.o: $(ARCH_DIR)/kernel/entry.S | dirs
 	$(CC) $(KERNEL_ASFLAGS) -c $< -o $@
 
-$(BUILD_DIR)/kernel/%.o: kernel/%.c include/tianole/boot_info.h include/tianole/kernel_init.h $(ARCH_DIR)/include/tianole/early_log.h | dirs
+$(BUILD_DIR)/arch/kernel/%.o: $(ARCH_DIR)/kernel/%.c include/tianole/arch.h | dirs
+	$(CC) $(KERNEL_CFLAGS) -c $< -o $@
+
+$(BUILD_DIR)/kernel/%.o: kernel/%.c include/tianole/boot_info.h include/tianole/kernel_init.h include/tianole/arch.h include/tianole/early_log.h | dirs
 	$(CC) $(KERNEL_CFLAGS) -c $< -o $@
 
 $(KERNEL_ELF): $(KERNEL_OBJS) $(ARCH_DIR)/kernel/linker.ld | dirs
@@ -50,10 +54,11 @@ run: $(BOOT_EFI) $(OVMF_VARS)
 	qemu-system-x86_64 \
 		-drive if=pflash,format=raw,readonly=on,file=$(OVMF_CODE) \
 		-drive if=pflash,format=raw,file=$(OVMF_VARS) \
-		-drive format=raw,file=fat:rw:$(BUILD_DIR)/image
+		-drive format=raw,file=fat:rw:$(BUILD_DIR)/image \
+		-serial stdio
 
 run-headless: $(BOOT_EFI) $(OVMF_VARS)
-	rm -f $(DEBUG_LOG)
+	rm -f $(DEBUG_LOG) $(SERIAL_LOG)
 	qemu-system-x86_64 \
 		-display none \
 		-nodefaults \
@@ -62,7 +67,8 @@ run-headless: $(BOOT_EFI) $(OVMF_VARS)
 		-drive if=pflash,format=raw,file=$(OVMF_VARS) \
 		-drive format=raw,file=fat:rw:$(BUILD_DIR)/image \
 		-debugcon file:$(DEBUG_LOG) \
-		-global isa-debugcon.iobase=0xe9
+		-global isa-debugcon.iobase=0xe9 \
+		-serial file:$(SERIAL_LOG)
 
 clean:
 	rm -rf $(BUILD_DIR)
diff --git a/arch/x86/boot/debug_log.h b/arch/x86/boot/debug_log.h
new file mode 100644
index 0000000..e7a7c12
--- /dev/null
+++ b/arch/x86/boot/debug_log.h
@@ -0,0 +1,19 @@
+#ifndef X86_BOOT_DEBUG_LOG_H
+#define X86_BOOT_DEBUG_LOG_H
+
+static inline void boot_debug_log_putc(char ch)
+{
+	__asm__ volatile("outb %0, $0xe9" : : "a"(ch));
+}
+
+static inline void boot_debug_log_puts(const char *text)
+{
+	while (*text != '\0') {
+		if (*text == '\n') {
+			boot_debug_log_putc('\r');
+		}
+		boot_debug_log_putc(*text++);
+	}
+}
+
+#endif
diff --git a/arch/x86/boot/main.c b/arch/x86/boot/main.c
index 18b95f4..cf1cece 100644
--- a/arch/x86/boot/main.c
+++ b/arch/x86/boot/main.c
@@ -1,9 +1,9 @@
+#include "debug_log.h"
 #include "efi.h"
 #include "elf_loader.h"
 #include "file.h"
 #include "memory_map.h"
 #include "tianole/boot_info.h"
-#include "tianole/early_log.h"
 
 static efi_char16_t boot_banner_text[] = u"Tianole x86 bootloader.\r\n";
 static efi_char16_t kernel_path_text[] = u"\\kernel.elf";
@@ -22,7 +22,7 @@ efi_status EFIAPI efi_main(
 
 	system_table->con_out->output_string(
 		system_table->con_out, boot_banner_text);
-	early_log_puts("Tianole x86 bootloader loaded.\n");
+	boot_debug_log_puts("Tianole x86 bootloader loaded.\n");
 
 	status = boot_read_file(image_handle,
 		system_table,
@@ -30,28 +30,28 @@ efi_status EFIAPI efi_main(
 		&kernel_image,
 		&kernel_size);
 	if (status != EFI_SUCCESS) {
-		early_log_puts("failed: read kernel.elf\n");
+		boot_debug_log_puts("failed: read kernel.elf\n");
 		return status;
 	}
 
 	status = boot_load_kernel_elf(
 		system_table, kernel_image, kernel_size, &kernel_entry);
 	if (status != EFI_SUCCESS) {
-		early_log_puts("failed: load kernel image\n");
+		boot_debug_log_puts("failed: load kernel image\n");
 		return status;
 	}
 
 	status = boot_exit_services_with_latest_memory_map(
 		image_handle, system_table, &boot_info);
 	if (status != EFI_SUCCESS) {
-		early_log_puts("failed: exit boot services\n");
+		boot_debug_log_puts("failed: exit boot services\n");
 		return status;
 	}
 
-	early_log_puts("jumping to kernel entry\n");
+	boot_debug_log_puts("jumping to kernel entry\n");
 	kernel_entry(&boot_info);
 
-	early_log_puts("kernel returned unexpectedly\n");
+	boot_debug_log_puts("kernel returned unexpectedly\n");
 	for (;;) {
 		__asm__ volatile("hlt");
 	}
diff --git a/arch/x86/include/tianole/early_log.h b/arch/x86/include/tianole/early_log.h
deleted file mode 100644
index 8038823..0000000
--- a/arch/x86/include/tianole/early_log.h
+++ /dev/null
@@ -1,41 +0,0 @@
-#ifndef X86_EARLY_LOG_H
-#define X86_EARLY_LOG_H
-
-#include <stdint.h>
-
-static inline void early_log_putc(char ch)
-{
-	__asm__ volatile("outb %0, $0xe9" : : "a"(ch));
-}
-
-static inline void early_log_puts(const char *text)
-{
-	while (*text != '\0') {
-		if (*text == '\n') {
-			early_log_putc('\r');
-		}
-		early_log_putc(*text++);
-	}
-}
-
-static inline void early_log_u64_decimal(uint64_t value)
-{
-	char digits[20];
-	uint32_t index = 0;
-
-	if (value == 0) {
-		early_log_putc('0');
-		return;
-	}
-
-	while (value != 0) {
-		digits[index++] = (char)('0' + (value % 10));
-		value /= 10;
-	}
-
-	while (index != 0) {
-		early_log_putc(digits[--index]);
-	}
-}
-
-#endif
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 40f5feb..5f277d5 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -1,2 +1,6 @@
+ARCH_KERNEL_SRCS := \
+	$(ARCH_DIR)/kernel/early_log.c
+
 ARCH_KERNEL_OBJS := \
-	$(BUILD_DIR)/arch/kernel/entry.o
+	$(BUILD_DIR)/arch/kernel/entry.o \
+	$(patsubst $(ARCH_DIR)/kernel/%.c,$(BUILD_DIR)/arch/kernel/%.o,$(ARCH_KERNEL_SRCS))
diff --git a/arch/x86/kernel/early_log.c b/arch/x86/kernel/early_log.c
new file mode 100644
index 0000000..12d92fa
--- /dev/null
+++ b/arch/x86/kernel/early_log.c
@@ -0,0 +1,75 @@
+#include <stdint.h>
+
+#include "tianole/arch.h"
+
+#define X86_QEMU_DEBUG_PORT 0xe9
+
+#define X86_COM1_BASE 0x3f8
+#define X86_COM_DATA 0
+#define X86_COM_INTERRUPT_ENABLE 1
+#define X86_COM_FIFO_CONTROL 2
+#define X86_COM_LINE_CONTROL 3
+#define X86_COM_MODEM_CONTROL 4
+#define X86_COM_LINE_STATUS 5
+
+#define X86_COM_LCR_DLAB 0x80
+#define X86_COM_LCR_8N1 0x03
+#define X86_COM_LSR_THRE 0x20
+
+static inline void outb(uint16_t port, uint8_t value)
+{
+	__asm__ volatile("outb %0, %1" : : "a"(value), "Nd"(port));
+}
+
+static inline uint8_t inb(uint16_t port)
+{
+	uint8_t value;
+
+	__asm__ volatile("inb %1, %0" : "=a"(value) : "Nd"(port));
+	return value;
+}
+
+static void debug_port_putc(char ch)
+{
+	outb(X86_QEMU_DEBUG_PORT, (uint8_t)ch);
+}
+
+static void serial_putc(char ch)
+{
+	uint32_t timeout;
+
+	for (timeout = 0; timeout < 100000; timeout++) {
+		if ((inb(X86_COM1_BASE + X86_COM_LINE_STATUS) &
+			    X86_COM_LSR_THRE) != 0) {
+			break;
+		}
+	}
+
+	outb(X86_COM1_BASE + X86_COM_DATA, (uint8_t)ch);
+}
+
+void arch_early_log_init(void)
+{
+	outb(X86_COM1_BASE + X86_COM_INTERRUPT_ENABLE, 0x00);
+	outb(X86_COM1_BASE + X86_COM_LINE_CONTROL, X86_COM_LCR_DLAB);
+	outb(X86_COM1_BASE + X86_COM_DATA, 0x03);
+	outb(X86_COM1_BASE + X86_COM_INTERRUPT_ENABLE, 0x00);
+	outb(X86_COM1_BASE + X86_COM_LINE_CONTROL, X86_COM_LCR_8N1);
+	outb(X86_COM1_BASE + X86_COM_FIFO_CONTROL, 0xc7);
+	outb(X86_COM1_BASE + X86_COM_MODEM_CONTROL, 0x0b);
+}
+
+void arch_early_log_putc(char ch)
+{
+	debug_port_putc(ch);
+	serial_putc(ch);
+}
+
+void arch_halt_forever(void)
+{
+	__asm__ volatile("cli");
+
+	for (;;) {
+		__asm__ volatile("hlt");
+	}
+}
diff --git a/docs/agents/tasks/01-early-debug.md b/docs/agents/tasks/01-early-debug.md
index a17d4d4..100baeb 100644
--- a/docs/agents/tasks/01-early-debug.md
+++ b/docs/agents/tasks/01-early-debug.md
@@ -37,3 +37,18 @@
 - QEMU 日志中能看到 bootloader 和 kernel 输出。
 - 串口或 debug log 中能看到 `boot services exited`。
 - 人为触发 panic 时能看到 panic 信息并停止。
+
+## 当前状态
+
+已完成：
+
+- kernel early log 已拆成通用前端和 x86 backend。
+- x86 backend 已同时写 QEMU debug port 和 COM1。
+- `panic()` 已接入 early log 和 `arch_halt_forever()`。
+- `scripts/check.sh` 已验证 `build/debug.log` 和 `build/serial.log` 中的关键启动行。
+
+后续进入异常阶段时继续补齐：
+
+- oops 格式。
+- 异常栈输出。
+- 内核符号化输出。
diff --git a/docs/roadmap.md b/docs/roadmap.md
index 1a610e4..a712b24 100644
--- a/docs/roadmap.md
+++ b/docs/roadmap.md
@@ -13,15 +13,16 @@
 - 进入 kernel 前调用 `ExitBootServices`。
 - `memory map` 通过 `boot_info` 传入 kernel。
 - kernel 能统计 memory map 描述符数量和 conventional memory 页数。
-- x86 早期日志接口已集中到 `arch/x86/include/tianole/early_log.h`。
+- kernel early log 已拆成通用前端和 x86 backend。
+- x86 early log backend 同时输出到 QEMU debug port 和 COM1 串口。
+- 最小 `panic()` 已接入 early log 和架构 halt 路径。
 - 构建系统已拆成根 Makefile、`arch/x86/Makefile` 和目录 Makefile。
-- `scripts/check.sh` 和 GitHub Actions 已接入。
+- `scripts/check.sh` 已验证启动日志和串口日志，GitHub Actions 已接入。
 - `.clang-format` 已用于强制当前 C 代码风格。
 
 还没有完成：
 
-- COM1 串口日志。
-- panic/oops 早期错误路径。
+- oops 早期错误路径。
 - GDT/IDT/异常/中断。
 - 物理页分配器、虚拟内存和内核堆。
 - 调度、进程、文件系统、用户态和 shell。
@@ -30,19 +31,14 @@
 
 下一步执行：
 
-- `docs/agents/tasks/01-early-debug.md`
+- `docs/agents/tasks/02-cpu-interrupts.md`
 
 目标：
 
-- 加入 COM1 串口 backend。
-- 保留当前 QEMU debug port backend。
-- 提供统一 early log 前端。
-- 增加最小 `panic()`。
-- 让启动日志可以通过 firmware 之外的路径稳定输出。
-
-这一步完成后进入：
-
-- `docs/agents/tasks/02-cpu-interrupts.md`
+- 建立 x86_64 GDT/TSS/IDT。
+- 建立异常入口和 trap frame。
+- 让未处理异常进入 panic。
+- 为后续 IRQ、timer 和 page fault 做准备。
 
 ## 任务路由
 
diff --git a/include/tianole/arch.h b/include/tianole/arch.h
new file mode 100644
index 0000000..757dad1
--- /dev/null
+++ b/include/tianole/arch.h
@@ -0,0 +1,8 @@
+#ifndef TIANOLE_ARCH_H
+#define TIANOLE_ARCH_H
+
+void arch_early_log_init(void);
+void arch_early_log_putc(char ch);
+void arch_halt_forever(void) __attribute__((noreturn));
+
+#endif
diff --git a/include/tianole/early_log.h b/include/tianole/early_log.h
new file mode 100644
index 0000000..59bc5b2
--- /dev/null
+++ b/include/tianole/early_log.h
@@ -0,0 +1,12 @@
+#ifndef TIANOLE_EARLY_LOG_H
+#define TIANOLE_EARLY_LOG_H
+
+#include <stdint.h>
+
+void early_log_init(void);
+void early_log_putc(char ch);
+void early_log_puts(const char *text);
+void early_log_u64_decimal(uint64_t value);
+void panic(const char *message) __attribute__((noreturn));
+
+#endif
diff --git a/kernel/Makefile b/kernel/Makefile
index 32e6638..a567341 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -1,6 +1,7 @@
 KERNEL_SRCS := \
 	kernel/main.c \
-	kernel/boot_report.c
+	kernel/boot_report.c \
+	kernel/early_log.c
 
 KERNEL_OBJS := \
 	$(ARCH_KERNEL_OBJS) \
diff --git a/kernel/early_log.c b/kernel/early_log.c
new file mode 100644
index 0000000..13d3c32
--- /dev/null
+++ b/kernel/early_log.c
@@ -0,0 +1,68 @@
+#include <stdint.h>
+
+#include "tianole/arch.h"
+#include "tianole/early_log.h"
+
+static int early_log_ready;
+
+void early_log_init(void)
+{
+	if (early_log_ready != 0) {
+		return;
+	}
+
+	arch_early_log_init();
+	early_log_ready = 1;
+}
+
+void early_log_putc(char ch)
+{
+	if (early_log_ready == 0) {
+		early_log_init();
+	}
+
+	arch_early_log_putc(ch);
+}
+
+void early_log_puts(const char *text)
+{
+	if (text == 0) {
+		return;
+	}
+
+	while (*text != '\0') {
+		if (*text == '\n') {
+			early_log_putc('\r');
+		}
+		early_log_putc(*text++);
+	}
+}
+
+void early_log_u64_decimal(uint64_t value)
+{
+	char digits[20];
+	uint32_t index = 0;
+
+	if (value == 0) {
+		early_log_putc('0');
+		return;
+	}
+
+	while (value != 0) {
+		digits[index++] = (char)('0' + (value % 10));
+		value /= 10;
+	}
+
+	while (index != 0) {
+		early_log_putc(digits[--index]);
+	}
+}
+
+void panic(const char *message)
+{
+	early_log_puts("panic: ");
+	early_log_puts(message);
+	early_log_puts("\n");
+
+	arch_halt_forever();
+}
diff --git a/kernel/main.c b/kernel/main.c
index e47dbe7..aeadaea 100644
--- a/kernel/main.c
+++ b/kernel/main.c
@@ -3,6 +3,7 @@
 
 void kernel_main(const boot_info_t *boot_info)
 {
+	early_log_init();
 	early_log_puts("kernel_main entered\n");
 	kernel_report_boot_state(boot_info);
 
diff --git a/scripts/check.sh b/scripts/check.sh
index d56cbb8..e338b92 100755
--- a/scripts/check.sh
+++ b/scripts/check.sh
@@ -23,10 +23,27 @@ required_lines=(
 )
 
 for line in "${required_lines[@]}"; do
-  if ! grep -F "$line" build/debug.log >/dev/null; then
+	if ! grep -F "$line" build/debug.log >/dev/null; then
     echo "missing expected boot log line: $line" >&2
     echo "--- build/debug.log ---" >&2
     cat build/debug.log >&2 || true
+    exit 1
+	fi
+done
+
+serial_required_lines=(
+  "kernel_main entered"
+  "boot_info.version ok"
+  "boot services exited"
+  "memory map descriptors="
+  "conventional memory pages="
+)
+
+for line in "${serial_required_lines[@]}"; do
+  if ! grep -F "$line" build/serial.log >/dev/null; then
+    echo "missing expected serial log line: $line" >&2
+    echo "--- build/serial.log ---" >&2
+    cat build/serial.log >&2 || true
     exit 1
   fi
 done