🔖 Release 0.4.0

README.md

@@ -26,6 +26,7 @@ BitLogger 是一个使用 MoonBit 编写的结构化日志库
 - 🧷 可绑定上下文: 支持 `bind(...)` 与 `fields(...)`, 便于复用上下文字段.
 - 📮 显式队列: 支持 `queued_sink(...)` / `with_queue(...)`, 支持有界积压和溢出策略.
 - 🧾 可配置文本格式: 支持 `text_formatter(...)`, `format_text(...)`, `text_console_sink(...)`, `formatted_callback_sink(...)` 和模板化 `template` 输出.
+- 🎨 轻量样式标签: 支持 `color_mode`, inline markup, `TextStyle`, `StyleTagRegistry`, 自定义标签与内置标签覆盖.
 - 💾 Native 文件输出: 支持 `file_sink(...)`, 基础 size rotation / backup retention, 显式 `reopen()` / `reopen_with_current_policy()` / `reopen_append()` / `reopen_truncate()` 与失败计数, 仅在 `native/llvm` backend 可用.
 - 📦 MoonBit 适配: API 和工程结构与 MoonBit 的 package / visibility / toolchain 模型保持一致.
 
@@ -168,6 +169,7 @@ let formatter = text_formatter(
   show_timestamp=false,
   field_separator=",",
   template="[{level}] {target} {message} :: {fields}",
+  color_mode=ColorMode::Always,
 )
 let logger = Logger::new(text_console_sink(formatter), target="pretty")
 
@@ -176,11 +178,44 @@ logger.info("hello", fields=[field("mode", "pretty")])
 
 </details>
 
+<details><summary>inline style tag 示例</summary>
+
+```moonbit
+let formatter = text_formatter(
+  show_timestamp=false,
+  color_mode=ColorMode::Always,
+).with_style_tags(
+  default_style_tag_registry()
+    .set_tag("accent", fg=Some("#4cc9f0"), bold=true)
+    .define_alias("danger", "red"),
+)
+
+let logger = Logger::new(text_console_sink(formatter), target="styled")
+
+logger.info("<accent>styled</> output and <danger>alert</>")
+```
+
+</details>
+
+<details><summary>关闭 style markup 解析示例</summary>
+
+```moonbit
+let formatter = text_formatter(
+  color_mode=ColorMode::Always,
+).without_style_markup()
+
+let logger = Logger::new(text_console_sink(formatter), target="raw")
+
+logger.info("<red>kept as raw text</>")
+```
+
+</details>
+
 <details><summary>JSON 配置加载示例</summary>
 
 ```moonbit
 let config = parse_logger_config_text(
-  "{\"min_level\":\"debug\",\"target\":\"config.demo\",\"timestamp\":true,\"sink\":{\"kind\":\"text_console\",\"text_formatter\":{\"show_timestamp\":false,\"field_separator\":\",\",\"template\":\"[{level}] {target} {message} :: {fields}\"}},\"queue\":{\"max_pending\":2,\"overflow\":\"DropOldest\"}}",
+  "{\"min_level\":\"debug\",\"target\":\"config.demo\",\"timestamp\":true,\"sink\":{\"kind\":\"text_console\",\"text_formatter\":{\"show_timestamp\":false,\"field_separator\":\",\",\"template\":\"[{level}] {target} {message} :: {fields}\",\"color_mode\":\"always\"}},\"queue\":{\"max_pending\":2,\"overflow\":\"DropOldest\"}}",
 )
 
 let logger = build_logger(config)
@@ -191,6 +226,34 @@ ignore(logger.flush())
 
 </details>
 
+<details><summary>JSON style_tags 示例</summary>
+
+```moonbit
+let config = parse_logger_config_text(
+  "{\"sink\":{\"kind\":\"text_console\",\"text_formatter\":{\"show_timestamp\":false,\"color_mode\":\"always\",\"style_tags\":{\"accent\":{\"fg\":\"#4cc9f0\",\"bold\":true}}}}}",
+)
+
+let logger = build_logger(config)
+
+logger.info("<accent>styled from json</>")
+```
+
+</details>
+
+<details><summary>JSON style_markup 模式示例</summary>
+
+```moonbit
+let config = parse_logger_config_text(
+  "{\"sink\":{\"kind\":\"text_console\",\"text_formatter\":{\"color_mode\":\"always\",\"style_markup\":\"disabled\"}}}",
+)
+
+let logger = build_logger(config)
+
+logger.info("<red>still raw</>")
+```
+
+</details>
+
 <details><summary>native 文件 sink 示例</summary>
 
 ```moonbit
@@ -241,6 +304,17 @@ match logger.file_runtime_state() {
 - 提供 JSON 配置层: `parse_logger_config_text(...)`, `stringify_logger_config(...)`, `build_logger(...)`
 - `QueueConfig`, `TextFormatterConfig`, `SinkConfig` 可分别通过 `queue_config_to_json(...)` / `stringify_queue_config(...)`, `text_formatter_config_to_json(...)` / `stringify_text_formatter_config(...)`, `sink_config_to_json(...)` / `stringify_sink_config(...)` 单独导出 JSON
 - 支持字段: `min_level`, `target`, `timestamp`, `sink.kind`, `sink.path`, `sink.append`, `sink.auto_flush`, `sink.rotation`, `sink.text_formatter`, `queue`
+- `TextFormatter` / `TextFormatterConfig` 提供 `color_mode = Never | Auto | Always`, 可控制 ANSI 文本着色
+- `TextFormatter` / `TextFormatterConfig` 提供 `color_support = basic | truecolor`, 可控制 hex / RGB 样式是否降级到基础 ANSI 色
+- `TextFormatter` / `TextFormatterConfig` 提供 `style_markup = disabled | builtin | full`, 可决定是否解析 style markup 以及是否启用 custom style tag
+- `target_style_markup` 与 `fields_style_markup` 可独立控制 `target` 和 `fields` 是否解析 style markup
+- `message` 支持轻量 inline style tag: `<red>...</>`, `<b>...</>`, `<#ff0000>...</>`, `<bg:#202020>...</>`
+- 闭合同时支持简写 `</>` 与具名闭合 `</red>`, `</danger>`, `</b>`
+- 内置语义标签包括: `<accent>`, `<info>`, `<success>`, `<warning>`, `<danger>`, `<muted>`
+- 运行期样式标签 API: `TextStyle`, `StyleTagRegistry`, `style_tag_registry()`, `default_style_tag_registry()`, `set_tag(...)`, `define_alias(...)`
+- 样式标签优先级: formatter 局部 `style_tags` > 全局 style tag registry > 内置标签
+- `sink.text_formatter.style_tags` 现支持最小对象映射配置, 可声明 `fg`, `bg`, `bold`, `dim`, `italic`, `underline`
+- `define_alias(...)` 仍为运行期 API, 当前不在 JSON schema 中
 - `sink.rotation` 支持 `max_bytes` 与 `max_backups`, 用于基础 size-based rotation 和 backup retention
 - `file_sink(...)` 提供 `reopen()`, `reopen_with_current_policy()`, `reopen_append()`, `reopen_truncate()`, `open_failures()`, `write_failures()`, `flush_failures()`, `rotation_failures()`, 用于基础可观测性
 - `file_sink(...)` 提供 `append_mode()`. 显式传入 `reopen(append=...)` 时, 会更新后续 reopen 使用的 append 策略. `reopen_with_current_policy()` 使用当前保存的策略重开文件, `reopen_append()` / `reopen_truncate()` 提供常见的 append 和 truncate 模式
@@ -264,6 +338,12 @@ match logger.file_runtime_state() {
 - `file_sink_policy_to_json(...)`, `stringify_file_sink_policy(...)` 可将独立 file policy 直接导出为 JSON, 便于策略快照, 配置对比或诊断上报
 - `file_sink_state_to_json(...)`, `stringify_file_sink_state(...)`, `runtime_file_state_to_json(...)`, `stringify_runtime_file_state(...)` 可直接把 file / queued-file 快照导出为 JSON, 便于排障或上报
 - `sink.text_formatter.template` 支持固定 token: `{timestamp}`, `{timestamp_ms}`, `{level}`, `{target}`, `{message}`, `{fields}`
+- `sink.text_formatter.color_mode` 支持 `never`, `auto`, `always`
+- `sink.text_formatter.color_support` 支持 `basic`, `truecolor`
+- `sink.text_formatter.style_markup` 支持 `disabled`, `builtin`, `full`
+- `sink.text_formatter.target_style_markup` 与 `sink.text_formatter.fields_style_markup` 支持 `disabled`, `builtin`, `full`
+- `sink.text_formatter.style_tags.<name>` 支持 `fg`, `bg`, `bold`, `dim`, `italic`, `underline`
+- `fields_style_markup` 当前只解析 field value, 不解析 field key
 - 可由配置直接组装的 sink 类型: `console`, `json_console`, `text_console`, `file`
 - `queue` 作为显式包装层附着在最终 sink 外侧. 这仍然是同步 drain 模型, 不是 async runtime
 

bitlogger/BitLogger_test.mbt

@@ -50,7 +50,7 @@ test "logger config parser reads core options" {
 
 test "logger config parser reads formatter and queue options" {
   let config = parse_logger_config_text(
-    "{\"sink\":{\"kind\":\"text_console\",\"text_formatter\":{\"separator\":\" | \",\"show_timestamp\":false,\"template\":\"[{level}] {message}\"}},\"queue\":{\"max_pending\":32,\"overflow\":\"DropOldest\"}}",
+    "{\"sink\":{\"kind\":\"text_console\",\"text_formatter\":{\"separator\":\" | \",\"show_timestamp\":false,\"template\":\"[{level}] {message}\",\"color_mode\":\"always\"}},\"queue\":{\"max_pending\":32,\"overflow\":\"DropOldest\"}}",
   )
   inspect(match config.sink.kind {
     SinkKind::TextConsole => "TextConsole"
@@ -59,6 +59,7 @@ test "logger config parser reads formatter and queue options" {
   inspect(config.sink.text_formatter.separator, content=" | ")
   inspect(config.sink.text_formatter.show_timestamp, content="false")
   inspect(config.sink.text_formatter.template, content="[{level}] {message}")
+  inspect(color_mode_label(config.sink.text_formatter.color_mode), content="always")
   match config.queue {
     Some(queue) => {
       inspect(queue.max_pending, content="32")
@@ -71,6 +72,32 @@ test "logger config parser reads formatter and queue options" {
   }
 }
 
+test "logger config parser reads formatter style tags" {
+  let config = parse_logger_config_text(
+    "{\"sink\":{\"kind\":\"text_console\",\"text_formatter\":{\"color_mode\":\"always\",\"color_support\":\"basic\",\"style_markup\":\"builtin\",\"target_style_markup\":\"builtin\",\"fields_style_markup\":\"disabled\",\"style_tags\":{\"accent\":{\"fg\":\"#4cc9f0\",\"bold\":true},\"panel\":{\"bg\":\"#202020\",\"underline\":true}}}}}",
+  )
+  inspect(style_markup_mode_label(config.sink.text_formatter.style_markup), content="builtin")
+  inspect(color_support_label(config.sink.text_formatter.color_support), content="basic")
+  inspect(style_markup_mode_label(config.sink.text_formatter.target_style_markup), content="builtin")
+  inspect(style_markup_mode_label(config.sink.text_formatter.fields_style_markup), content="disabled")
+  inspect(config.sink.text_formatter.style_tags.length(), content="2")
+  match config.sink.text_formatter.style_tags.get("accent") {
+    Some(style) => {
+      inspect(style.fg.unwrap(), content="#4cc9f0")
+      inspect(style.bold, content="true")
+      inspect(style.bg is None, content="true")
+    }
+    None => inspect(false, content="true")
+  }
+  match config.sink.text_formatter.style_tags.get("panel") {
+    Some(style) => {
+      inspect(style.bg.unwrap(), content="#202020")
+      inspect(style.underline, content="true")
+    }
+    None => inspect(false, content="true")
+  }
+}
+
 test "logger config parser reads file rotation options" {
   let config = parse_logger_config_text(
     "{\"sink\":{\"kind\":\"file\",\"path\":\"bitlogger.log\",\"rotation\":{\"max_bytes\":128,\"max_backups\":3}}}",
@@ -118,6 +145,38 @@ test "logger config stringify roundtrips stable fields" {
   inspect(config.sink.text_formatter.template, content="[{level}] {target} {message}")
 }
 
+test "logger config stringify roundtrips formatter style tags" {
+  let text = stringify_logger_config(
+    LoggerConfig::new(
+      sink=SinkConfig::new(
+        kind=SinkKind::TextConsole,
+        text_formatter=TextFormatterConfig::new(
+          color_mode=ColorMode::Always,
+          color_support=ColorSupport::Basic,
+          style_markup=StyleMarkupMode::Builtin,
+          target_style_markup=StyleMarkupMode::Builtin,
+          fields_style_markup=StyleMarkupMode::Disabled,
+          style_tags={
+            "accent": text_style(fg=Some("#4cc9f0"), bold=true),
+            "panel": text_style(bg=Some("#202020"), dim=true),
+          },
+        ),
+      ),
+    ),
+  )
+  let config = parse_logger_config_text(text)
+  inspect(color_mode_label(config.sink.text_formatter.color_mode), content="always")
+  inspect(color_support_label(config.sink.text_formatter.color_support), content="basic")
+  inspect(style_markup_mode_label(config.sink.text_formatter.style_markup), content="builtin")
+  inspect(style_markup_mode_label(config.sink.text_formatter.target_style_markup), content="builtin")
+  inspect(style_markup_mode_label(config.sink.text_formatter.fields_style_markup), content="disabled")
+  inspect(config.sink.text_formatter.style_tags.length(), content="2")
+  inspect(config.sink.text_formatter.style_tags.get("accent").unwrap().fg.unwrap(), content="#4cc9f0")
+  inspect(config.sink.text_formatter.style_tags.get("accent").unwrap().bold, content="true")
+  inspect(config.sink.text_formatter.style_tags.get("panel").unwrap().bg.unwrap(), content="#202020")
+  inspect(config.sink.text_formatter.style_tags.get("panel").unwrap().dim, content="true")
+}
+
 test "logger config stringify roundtrips file rotation fields" {
   let text = stringify_logger_config(
     LoggerConfig::new(
@@ -156,9 +215,17 @@ test "config subtype json helpers stringify stable shapes" {
         separator=" | ",
         field_separator=",",
         template="[{level}] {message} :: {fields}",
+        color_mode=ColorMode::Always,
+        color_support=ColorSupport::Basic,
+        style_markup=StyleMarkupMode::Builtin,
+        target_style_markup=StyleMarkupMode::Builtin,
+        fields_style_markup=StyleMarkupMode::Disabled,
+        style_tags={
+          "accent": text_style(fg=Some("#4cc9f0"), bold=true),
+        },
       ),
     ),
-    content="{\"show_timestamp\":false,\"show_level\":true,\"show_target\":false,\"show_fields\":true,\"separator\":\" | \",\"field_separator\":\",\",\"template\":\"[{level}] {message} :: {fields}\"}",
+    content="{\"show_timestamp\":false,\"show_level\":true,\"show_target\":false,\"show_fields\":true,\"separator\":\" | \",\"field_separator\":\",\",\"template\":\"[{level}] {message} :: {fields}\",\"color_mode\":\"always\",\"color_support\":\"basic\",\"style_markup\":\"builtin\",\"target_style_markup\":\"builtin\",\"fields_style_markup\":\"disabled\",\"style_tags\":{\"accent\":{\"bold\":true,\"dim\":false,\"italic\":false,\"underline\":false,\"fg\":\"#4cc9f0\"}}}",
   )
   inspect(
     stringify_sink_config(
@@ -168,10 +235,97 @@ test "config subtype json helpers stringify stable shapes" {
         append=false,
         auto_flush=false,
         rotation=Some(file_rotation(128, max_backups=2)),
-        text_formatter=TextFormatterConfig::new(show_timestamp=false),
+        text_formatter=TextFormatterConfig::new(show_timestamp=false, color_mode=ColorMode::Auto),
       ),
     ),
-    content="{\"kind\":\"file\",\"path\":\"demo.log\",\"append\":false,\"auto_flush\":false,\"text_formatter\":{\"show_timestamp\":false,\"show_level\":true,\"show_target\":true,\"show_fields\":true,\"separator\":\" \",\"field_separator\":\" \",\"template\":\"\"},\"rotation\":{\"max_bytes\":128,\"max_backups\":2}}",
+    content="{\"kind\":\"file\",\"path\":\"demo.log\",\"append\":false,\"auto_flush\":false,\"text_formatter\":{\"show_timestamp\":false,\"show_level\":true,\"show_target\":true,\"show_fields\":true,\"separator\":\" \",\"field_separator\":\" \",\"template\":\"\",\"color_mode\":\"auto\",\"color_support\":\"truecolor\",\"style_markup\":\"full\",\"target_style_markup\":\"disabled\",\"fields_style_markup\":\"disabled\"},\"rotation\":{\"max_bytes\":128,\"max_backups\":2}}",
+  )
+}
+
+test "config basic color support downgrades hex colors" {
+  let formatter = TextFormatterConfig::new(
+    show_level=false,
+    show_target=false,
+    color_mode=ColorMode::Always,
+    color_support=ColorSupport::Basic,
+  )
+  let rendered = format_text(
+    Record::new(Level::Info, "<#ff0000>hot</> <bg:#010203>bg</>"),
+    formatter=formatter.to_formatter(),
+  )
+  inspect(rendered, content="\u{001b}[31mhot\u{001b}[0m \u{001b}[100mbg\u{001b}[0m")
+}
+
+test "config formatter style tags render in built logger" {
+  let formatter = TextFormatterConfig::new(
+    show_timestamp=false,
+    show_target=false,
+    color_mode=ColorMode::Always,
+    style_tags={
+      "accent": text_style(fg=Some("#4cc9f0"), bold=true),
+    },
+  )
+  let rendered = format_text(
+    Record::new(Level::Info, "<accent>tag</>"),
+    formatter=formatter.to_formatter(),
+  )
+  inspect(rendered, content="[\u{001b}[32mINFO\u{001b}[0m] \u{001b}[38;2;76;201;240;1mtag\u{001b}[0m")
+}
+
+test "config builtin style markup ignores custom tags" {
+  let formatter = TextFormatterConfig::new(
+    show_level=false,
+    show_target=false,
+    color_mode=ColorMode::Always,
+    style_markup=StyleMarkupMode::Builtin,
+    style_tags={
+      "brand": text_style(fg=Some("#4cc9f0"), bold=true),
+    },
+  )
+  let rendered = format_text(
+    Record::new(Level::Info, "<brand>custom</> <red>builtin</>"),
+    formatter=formatter.to_formatter(),
+  )
+  inspect(rendered, content="<brand>custom</> \u{001b}[31mbuiltin\u{001b}[0m")
+}
+
+test "config disabled style markup keeps raw tags" {
+  let formatter = TextFormatterConfig::new(
+    show_level=false,
+    show_target=false,
+    color_mode=ColorMode::Always,
+    style_markup=StyleMarkupMode::Disabled,
+    style_tags={
+      "accent": text_style(fg=Some("#4cc9f0"), bold=true),
+    },
+  )
+  let rendered = format_text(
+    Record::new(Level::Info, "<accent>raw</> <red>tag</>"),
+    formatter=formatter.to_formatter(),
+  )
+  inspect(rendered, content="<accent>raw</> <red>tag</>")
+}
+
+test "config target and fields markup modes render separately" {
+  let formatter = TextFormatterConfig::new(
+    show_level=false,
+    color_mode=ColorMode::Always,
+    style_markup=StyleMarkupMode::Disabled,
+    target_style_markup=StyleMarkupMode::Builtin,
+    fields_style_markup=StyleMarkupMode::Builtin,
+  )
+  let rendered = format_text(
+    Record::new(
+      Level::Info,
+      "<danger>message stays raw</>",
+      target="<danger>svc</>",
+      fields=[field("status", "<success>ok</>")],
+    ),
+    formatter=formatter.to_formatter(),
+  )
+  inspect(
+    rendered,
+    content="[\u{001b}[34m\u{001b}[31;1msvc\u{001b}[0m\u{001b}[0m] <danger>message stays raw</> \u{001b}[35mstatus=\u{001b}[32;1mok\u{001b}[0m\u{001b}[0m",
   )
 }
 

bitlogger/BitLogger_wbtest.mbt

@@ -60,6 +60,286 @@ test "text formatter supports template rendering" {
   )
 }
 
+test "text formatter can render ansi level colors" {
+  let rec = record(Level::Error, "boom", target="svc")
+  let formatter = text_formatter(color_mode=ColorMode::Always)
+  inspect(
+    format_text(rec, formatter=formatter),
+    content="[\u{001b}[31;1mERROR\u{001b}[0m] [\u{001b}[34msvc\u{001b}[0m] boom",
+  )
+}
+
+test "text formatter auto color respects NO_COLOR" {
+  let rec = record(Level::Warn, "boom", target="svc")
+  let previous = @env.get_env_var("NO_COLOR")
+  @env.set_env_var("NO_COLOR", "1")
+  inspect(
+    format_text(rec, formatter=text_formatter(color_mode=ColorMode::Auto)),
+    content="[WARN] [svc] boom",
+  )
+  match previous {
+    Some(value) => @env.set_env_var("NO_COLOR", value)
+    None => @env.unset_env_var("NO_COLOR")
+  }
+}
+
+test "text formatter renders named inline color tags in ansi mode" {
+  let rec = record(Level::Info, "<red>boom</>", target="svc")
+  inspect(
+    format_text(rec, formatter=text_formatter(color_mode=ColorMode::Always)),
+    content="[\u{001b}[32mINFO\u{001b}[0m] [\u{001b}[34msvc\u{001b}[0m] \u{001b}[31mboom\u{001b}[0m",
+  )
+}
+
+test "text formatter strips inline tags in plain mode" {
+  let rec = record(Level::Info, "<red>boom</> <b>bold</>", target="svc")
+  inspect(
+    format_text(rec, formatter=text_formatter(color_mode=ColorMode::Never)),
+    content="[INFO] [svc] boom bold",
+  )
+}
+
+test "text formatter supports nested inline tags" {
+  let rec = record(Level::Info, "<red><b>fatal</></>")
+  inspect(
+    format_text(rec, formatter=text_formatter(show_level=false, show_target=false, color_mode=ColorMode::Always)),
+    content="\u{001b}[31;1mfatal\u{001b}[0m",
+  )
+}
+
+test "text formatter supports named closing tags" {
+  let rec = record(Level::Info, "<red>boom</red>")
+  inspect(
+    format_text(rec, formatter=text_formatter(show_level=false, show_target=false, color_mode=ColorMode::Always)),
+    content="\u{001b}[31mboom\u{001b}[0m",
+  )
+}
+
+test "text formatter supports mixed short and named closing tags" {
+  let rec = record(Level::Info, "<red><b>fatal</b></red>")
+  inspect(
+    format_text(rec, formatter=text_formatter(show_level=false, show_target=false, color_mode=ColorMode::Always)),
+    content="\u{001b}[31;1mfatal\u{001b}[0m",
+  )
+}
+
+test "text formatter keeps unmatched named closing tags as plain text" {
+  let rec = record(Level::Info, "boom</red>")
+  inspect(
+    format_text(rec, formatter=text_formatter(show_level=false, show_target=false)),
+    content="boom</red>",
+  )
+}
+
+test "text formatter supports hex inline colors" {
+  let rec = record(Level::Info, "<#ff0000>hot</> <bg:#010203>bg</>")
+  inspect(
+    format_text(rec, formatter=text_formatter(show_level=false, show_target=false, color_mode=ColorMode::Always)),
+    content="\u{001b}[38;2;255;0;0mhot\u{001b}[0m \u{001b}[48;2;1;2;3mbg\u{001b}[0m",
+  )
+}
+
+test "text formatter can downgrade hex colors to basic ansi" {
+  let rec = record(Level::Info, "<#ff0000>hot</> <bg:#010203>bg</>")
+  inspect(
+    format_text(
+      rec,
+      formatter=text_formatter(
+        show_level=false,
+        show_target=false,
+        color_mode=ColorMode::Always,
+        color_support=ColorSupport::Basic,
+      ),
+    ),
+    content="\u{001b}[31mhot\u{001b}[0m \u{001b}[100mbg\u{001b}[0m",
+  )
+}
+
+test "text formatter keeps unknown inline tags as plain text" {
+  let rec = record(Level::Info, "<unknown>boom</>")
+  inspect(
+    format_text(rec, formatter=text_formatter(show_level=false, show_target=false)),
+    content="<unknown>boom</>",
+  )
+}
+
+test "text formatter can disable style markup parsing" {
+  let rec = record(Level::Info, "<red>boom</> <b>bold</>", target="svc")
+  inspect(
+    format_text(
+      rec,
+      formatter=text_formatter(color_mode=ColorMode::Always).without_style_markup(),
+    ),
+    content="[\u{001b}[32mINFO\u{001b}[0m] [\u{001b}[34msvc\u{001b}[0m] <red>boom</> <b>bold</>",
+  )
+}
+
+test "text formatter builtin style markup mode ignores custom tags" {
+  let formatter = text_formatter(
+    show_level=false,
+    show_target=false,
+    color_mode=ColorMode::Always,
+    style_markup=StyleMarkupMode::Builtin,
+  ).with_style_tags(
+    style_tag_registry().set_tag("brand", fg=Some("#4cc9f0"), bold=true),
+  )
+  let rec = record(Level::Info, "<brand>custom</> <red>builtin</>")
+  inspect(
+    format_text(rec, formatter=formatter),
+    content="<brand>custom</> \u{001b}[31mbuiltin\u{001b}[0m",
+  )
+}
+
+test "style markup mode label is stable" {
+  inspect(style_markup_mode_label(StyleMarkupMode::Disabled), content="disabled")
+  inspect(style_markup_mode_label(StyleMarkupMode::Builtin), content="builtin")
+  inspect(style_markup_mode_label(StyleMarkupMode::Full), content="full")
+}
+
+test "text formatter supports custom style tags" {
+  let formatter = text_formatter(
+    show_level=false,
+    show_target=false,
+    color_mode=ColorMode::Always,
+  ).with_style_tags(
+    style_tag_registry().set_tag("accent", fg=Some("#4cc9f0"), bold=true),
+  )
+  let rec = record(Level::Info, "<accent>api</>")
+  inspect(
+    format_text(rec, formatter=formatter),
+    content="\u{001b}[38;2;76;201;240;1mapi\u{001b}[0m",
+  )
+}
+
+test "text formatter can override builtin style tags" {
+  let formatter = text_formatter(
+    show_level=false,
+    show_target=false,
+    color_mode=ColorMode::Always,
+  ).with_style_tags(
+    default_style_tag_registry().set_tag("red", fg=Some("#ff5a5f"), underline=true),
+  )
+  let rec = record(Level::Info, "<red>alert</>")
+  inspect(
+    format_text(rec, formatter=formatter),
+    content="\u{001b}[38;2;255;90;95;4malert\u{001b}[0m",
+  )
+}
+
+test "formatter style tags take priority over global style tags" {
+  let previous = global_style_tag_registry()
+  set_global_style_tag_registry(style_tag_registry().set_tag("accent", fg=Some("#123456")))
+  let formatter = text_formatter(
+    show_level=false,
+    show_target=false,
+    color_mode=ColorMode::Always,
+  ).with_style_tags(
+    style_tag_registry().set_tag("accent", fg=Some("#abcdef")),
+  )
+  let rec = record(Level::Info, "<accent>tag</>")
+  inspect(
+    format_text(rec, formatter=formatter),
+    content="\u{001b}[38;2;171;205;239mtag\u{001b}[0m",
+  )
+  set_global_style_tag_registry(previous)
+}
+
+test "global style tags apply when formatter has no local registry" {
+  let previous = global_style_tag_registry()
+  set_global_style_tag_registry(style_tag_registry().set_tag("accent", fg=Some("#102030"), dim=true))
+  let rec = record(Level::Info, "<accent>tag</>")
+  inspect(
+    format_text(rec, formatter=text_formatter(show_level=false, show_target=false, color_mode=ColorMode::Always)),
+    content="\u{001b}[38;2;16;32;48;2mtag\u{001b}[0m",
+  )
+  set_global_style_tag_registry(previous)
+}
+
+test "style tag alias can reuse builtin tags" {
+  let formatter = text_formatter(
+    show_level=false,
+    show_target=false,
+    color_mode=ColorMode::Always,
+  ).with_style_tags(
+    style_tag_registry().define_alias("danger", "red"),
+  )
+  let rec = record(Level::Info, "<danger>boom</>")
+  inspect(
+    format_text(rec, formatter=formatter),
+    content="\u{001b}[31mboom\u{001b}[0m",
+  )
+}
+
+test "builtin semantic style tags are available" {
+  let formatter = text_formatter(
+    show_level=false,
+    show_target=false,
+    color_mode=ColorMode::Always,
+    style_markup=StyleMarkupMode::Builtin,
+  )
+  let rec = record(Level::Info, "<success>ok</> <warning>careful</> <danger>boom</> <muted>quiet</>")
+  inspect(
+    format_text(rec, formatter=formatter),
+    content="\u{001b}[32;1mok\u{001b}[0m \u{001b}[33;1mcareful\u{001b}[0m \u{001b}[31;1mboom\u{001b}[0m \u{001b}[90;2mquiet\u{001b}[0m",
+  )
+}
+
+test "builtin semantic style tags can still be overridden" {
+  let formatter = text_formatter(
+    show_level=false,
+    show_target=false,
+    color_mode=ColorMode::Always,
+  ).with_style_tags(
+    default_style_tag_registry().set_tag("success", fg=Some("#00ffaa"), underline=true),
+  )
+  let rec = record(Level::Info, "<success>ok</>")
+  inspect(
+    format_text(rec, formatter=formatter),
+    content="\u{001b}[38;2;0;255;170;4mok\u{001b}[0m",
+  )
+}
+
+test "text formatter can enable markup for target separately" {
+  let formatter = text_formatter(
+    show_level=false,
+    color_mode=ColorMode::Always,
+    target_style_markup=StyleMarkupMode::Builtin,
+  )
+  let rec = record(Level::Info, "hello", target="<danger>svc</>")
+  inspect(
+    format_text(rec, formatter=formatter),
+    content="[\u{001b}[34m\u{001b}[31;1msvc\u{001b}[0m\u{001b}[0m] hello",
+  )
+}
+
+test "text formatter can enable markup for field values separately" {
+  let formatter = text_formatter(
+    show_level=false,
+    show_target=false,
+    color_mode=ColorMode::Always,
+    fields_style_markup=StyleMarkupMode::Builtin,
+  )
+  let rec = record(Level::Info, "hello", fields=[field("status", "<success>ok</>")])
+  inspect(
+    format_text(rec, formatter=formatter),
+    content="hello \u{001b}[35mstatus=\u{001b}[32;1mok\u{001b}[0m\u{001b}[0m",
+  )
+}
+
+test "text formatter leaves field keys raw when field markup is enabled" {
+  let formatter = text_formatter(
+    show_level=false,
+    show_target=false,
+    color_mode=ColorMode::Always,
+    fields_style_markup=StyleMarkupMode::Builtin,
+  )
+  let rec = record(Level::Info, "hello", fields=[field("<danger>status</>", "ok")])
+  inspect(
+    format_text(rec, formatter=formatter),
+    content="hello \u{001b}[35m<danger>status</>=ok\u{001b}[0m",
+  )
+}
+
 test "text formatter template respects disabled fields" {
   let rec = record(Level::Warn, "just message", target="svc")
   let formatter = text_formatter(

bitlogger/README.mbt.md

@@ -42,8 +42,12 @@ BitLogger 是一个使用 MoonBit 编写的结构化日志库.
 - 支持 `queued_sink(...)`, `with_queue(...)`, 有界积压与溢出策略
 - configurable text formatting via `text_formatter(...)`, `format_text(...)`, `text_console_sink(...)`, and template-driven `template` output
 - 支持 `text_formatter(...)`, `format_text(...)`, `text_console_sink(...)` 以及模板化 `template` 文本输出
+- lightweight style tags via `color_mode`, inline markup, `TextStyle`, `StyleTagRegistry`, custom tags, and builtin-tag overrides
+- 支持 `color_mode`, inline markup, `TextStyle`, `StyleTagRegistry`, 自定义标签与内置标签覆盖
 - JSON config parsing via `parse_logger_config_text(...)` and `stringify_logger_config(...)`
 - 支持 `parse_logger_config_text(...)`, `stringify_logger_config(...)` 进行最小 JSON 配置读写
+- `TextFormatter` / `TextFormatterConfig` now support `color_mode = Never | Auto | Always`
+- `TextFormatter` / `TextFormatterConfig` 现支持 `color_mode = Never | Auto | Always`
 - `QueueConfig` / `TextFormatterConfig` / `SinkConfig` can also be exported independently through dedicated JSON helpers
 - `QueueConfig` / `TextFormatterConfig` / `SinkConfig` 也可分别通过专用 JSON helper 单独导出
 - config-driven logger assembly via `build_logger(...)`
@@ -180,16 +184,42 @@ test {
     show_timestamp=false,
     field_separator=",",
     template="[{level}] {target} {message} :: {fields}",
+    color_mode=ColorMode::Always,
   )
   let logger = Logger::new(text_console_sink(formatter), target="pretty")
   logger.info("hello", fields=[field("mode", "pretty")])
 }
 ```
 
+```mbt check
+test {
+  let formatter = text_formatter(
+    show_timestamp=false,
+    color_mode=ColorMode::Always,
+  ).with_style_tags(
+    default_style_tag_registry()
+      .set_tag("accent", fg=Some("#4cc9f0"), bold=true)
+      .define_alias("danger", "red"),
+  )
+  let logger = Logger::new(text_console_sink(formatter), target="styled")
+  logger.info("<accent>styled</> output and <danger>alert</>")
+}
+```
+
+```mbt check
+test {
+  let formatter = text_formatter(
+    color_mode=ColorMode::Always,
+  ).without_style_markup()
+  let logger = Logger::new(text_console_sink(formatter), target="raw")
+  logger.info("<red>kept as raw text</>")
+}
+```
+
 ```mbt check
 test {
   let config = parse_logger_config_text(
-    "{\"min_level\":\"debug\",\"target\":\"config.demo\",\"timestamp\":true,\"sink\":{\"kind\":\"text_console\",\"text_formatter\":{\"show_timestamp\":false,\"field_separator\":\",\",\"template\":\"[{level}] {target} {message} :: {fields}\"}},\"queue\":{\"max_pending\":2,\"overflow\":\"DropOldest\"}}",
+    "{\"min_level\":\"debug\",\"target\":\"config.demo\",\"timestamp\":true,\"sink\":{\"kind\":\"text_console\",\"text_formatter\":{\"show_timestamp\":false,\"field_separator\":\",\",\"template\":\"[{level}] {target} {message} :: {fields}\",\"color_mode\":\"always\"}},\"queue\":{\"max_pending\":2,\"overflow\":\"DropOldest\"}}",
   )
   let logger = build_logger(config)
   logger.info("configured from json")
@@ -197,9 +227,41 @@ test {
 }
 ```
 
+```mbt check
+test {
+  let config = parse_logger_config_text(
+    "{\"sink\":{\"kind\":\"text_console\",\"text_formatter\":{\"show_timestamp\":false,\"color_mode\":\"always\",\"style_tags\":{\"accent\":{\"fg\":\"#4cc9f0\",\"bold\":true}}}}}",
+  )
+  let logger = build_logger(config)
+  logger.info("<accent>styled from json</>")
+}
+```
+
+```mbt check
+test {
+  let config = parse_logger_config_text(
+    "{\"sink\":{\"kind\":\"text_console\",\"text_formatter\":{\"color_mode\":\"always\",\"style_markup\":\"disabled\"}}}",
+  )
+  let logger = build_logger(config)
+  logger.info("<red>still raw</>")
+}
+```
+
 ## Formatter Template / 模板格式
 
 - supported tokens / 支持的 token: `{timestamp}`, `{timestamp_ms}`, `{level}`, `{target}`, `{message}`, `{fields}`
+- `color_mode` / `color_mode`: `never`, `auto`, `always`
+- `color_support` / `color_support`: `basic`, `truecolor`
+- `style_markup` / `style_markup`: `disabled`, `builtin`, `full`
+- `target_style_markup` / `target_style_markup`, `fields_style_markup` / `fields_style_markup`: `disabled`, `builtin`, `full`
+- inline style tags / inline 样式标签: `<red>...</>`, `<b>...</>`, `<#ff0000>...</>`, `<bg:#202020>...</>`
+- closing tags / 闭合标签: `</>` 以及具名闭合 `</red>`, `</danger>`, `</b>`
+- builtin semantic tags / 内置语义标签: `<accent>`, `<info>`, `<success>`, `<warning>`, `<danger>`, `<muted>`
+- runtime style tags / 运行期样式标签: `TextStyle`, `StyleTagRegistry`, `style_tag_registry()`, `default_style_tag_registry()`, `set_tag(...)`, `define_alias(...)`
+- style tag priority / 标签优先级: formatter local `style_tags` > global style tag registry > builtin tags
+- `sink.text_formatter.style_tags` / `sink.text_formatter.style_tags` 现支持最小对象映射: `fg`, `bg`, `bold`, `dim`, `italic`, `underline`
+- `fields_style_markup` currently affects values only / `fields_style_markup` 当前仅影响 field value, 不影响 field key
+- `define_alias(...)` is still runtime-only / `define_alias(...)` 目前仍为运行期 API
 - disabled or missing parts render as empty text / 被关闭或缺失的部分会渲染为空字符串
 - `template` is intentionally a simple token replacement layer, not a full DSL / `template` 使用轻量 token 替换方式, 不是完整 DSL
 

bitlogger/config.mbt

@@ -17,6 +17,12 @@ pub struct TextFormatterConfig {
   separator : String
   field_separator : String
   template : String
+  color_mode : ColorMode
+  color_support : ColorSupport
+  style_markup : StyleMarkupMode
+  target_style_markup : StyleMarkupMode
+  fields_style_markup : StyleMarkupMode
+  style_tags : Map[String, TextStyle]
 }
 
 pub fn TextFormatterConfig::new(
@@ -27,6 +33,12 @@ pub fn TextFormatterConfig::new(
   separator~ : String = " ",
   field_separator~ : String = " ",
   template~ : String = "",
+  color_mode~ : ColorMode = ColorMode::Never,
+  color_support~ : ColorSupport = ColorSupport::TrueColor,
+  style_markup~ : StyleMarkupMode = StyleMarkupMode::Full,
+  target_style_markup~ : StyleMarkupMode = StyleMarkupMode::Disabled,
+  fields_style_markup~ : StyleMarkupMode = StyleMarkupMode::Disabled,
+  style_tags~ : Map[String, TextStyle] = {},
 ) -> TextFormatterConfig {
   {
     show_timestamp,
@@ -36,9 +48,23 @@ pub fn TextFormatterConfig::new(
     separator,
     field_separator,
     template,
+    color_mode,
+    color_support,
+    style_markup,
+    target_style_markup,
+    fields_style_markup,
+    style_tags,
   }
 }
 
+fn style_tag_registry_from_config(style_tags : Map[String, TextStyle]) -> StyleTagRegistry {
+  let registry = style_tag_registry()
+  for name, style in style_tags {
+    ignore(registry.set_tag(name, style=style))
+  }
+  registry
+}
+
 pub fn TextFormatterConfig::to_formatter(self : TextFormatterConfig) -> TextFormatter {
   text_formatter(
     show_timestamp=self.show_timestamp,
@@ -48,6 +74,16 @@ pub fn TextFormatterConfig::to_formatter(self : TextFormatterConfig) -> TextForm
     separator=self.separator,
     field_separator=self.field_separator,
     template=self.template,
+    color_mode=self.color_mode,
+    color_support=self.color_support,
+    style_markup=self.style_markup,
+    target_style_markup=self.target_style_markup,
+    fields_style_markup=self.fields_style_markup,
+    style_tags=if self.style_tags.length() == 0 {
+      None
+    } else {
+      Some(style_tag_registry_from_config(self.style_tags))
+    },
   )
 }
 
@@ -755,6 +791,19 @@ fn get_string(
   }
 }
 
+fn get_optional_string(
+  obj : Map[String, @json_parser.JsonValue],
+  key : String,
+) -> String? raise ConfigError {
+  match obj.get(key) {
+    None => None
+    Some(value) => match value.as_string() {
+      Some(text) => Some(text)
+      None => raise ConfigError::InvalidConfig("Expected string at key " + key)
+    }
+  }
+}
+
 fn get_bool(
   obj : Map[String, @json_parser.JsonValue],
   key : String,
@@ -815,6 +864,32 @@ fn parse_sink_kind(name : String) -> SinkKind raise ConfigError {
   }
 }
 
+fn parse_color_mode(name : String) -> ColorMode raise ConfigError {
+  match name.to_upper() {
+    "NEVER" => ColorMode::Never
+    "AUTO" => ColorMode::Auto
+    "ALWAYS" => ColorMode::Always
+    _ => raise ConfigError::InvalidConfig("Unsupported color mode: " + name)
+  }
+}
+
+fn parse_color_support(name : String) -> ColorSupport raise ConfigError {
+  match name.to_upper() {
+    "BASIC" => ColorSupport::Basic
+    "TRUECOLOR" => ColorSupport::TrueColor
+    _ => raise ConfigError::InvalidConfig("Unsupported color support: " + name)
+  }
+}
+
+fn parse_style_markup_mode(name : String) -> StyleMarkupMode raise ConfigError {
+  match name.to_upper() {
+    "DISABLED" => StyleMarkupMode::Disabled
+    "BUILTIN" => StyleMarkupMode::Builtin
+    "FULL" => StyleMarkupMode::Full
+    _ => raise ConfigError::InvalidConfig("Unsupported style markup mode: " + name)
+  }
+}
+
 fn sink_kind_label(kind : SinkKind) -> String {
   match kind {
     SinkKind::Console => "console"
@@ -834,9 +909,42 @@ fn parse_text_formatter_config(value : @json_parser.JsonValue) -> TextFormatterC
     separator=get_string(obj, "separator", default=" "),
     field_separator=get_string(obj, "field_separator", default=" "),
     template=get_string(obj, "template", default=""),
+    color_mode=parse_color_mode(get_string(obj, "color_mode", default="never")),
+    color_support=parse_color_support(get_string(obj, "color_support", default="truecolor")),
+    style_markup=parse_style_markup_mode(get_string(obj, "style_markup", default="full")),
+    target_style_markup=parse_style_markup_mode(get_string(obj, "target_style_markup", default="disabled")),
+    fields_style_markup=parse_style_markup_mode(get_string(obj, "fields_style_markup", default="disabled")),
+    style_tags=match obj.get("style_tags") {
+      None => {}
+      Some(inner) => parse_style_tags_config(inner)
+    },
   )
 }
 
+fn parse_text_style_config(
+  value : @json_parser.JsonValue,
+  context : String,
+) -> TextStyle raise ConfigError {
+  let obj = expect_object(value, context)
+  text_style(
+    fg=get_optional_string(obj, "fg"),
+    bg=get_optional_string(obj, "bg"),
+    bold=get_bool(obj, "bold", default=false),
+    dim=get_bool(obj, "dim", default=false),
+    italic=get_bool(obj, "italic", default=false),
+    underline=get_bool(obj, "underline", default=false),
+  )
+}
+
+fn parse_style_tags_config(value : @json_parser.JsonValue) -> Map[String, TextStyle] raise ConfigError {
+  let obj = expect_object(value, "text_formatter.style_tags")
+  let style_tags : Map[String, TextStyle] = {}
+  for name, item in obj {
+    style_tags[name] = parse_text_style_config(item, "text_formatter.style_tags." + name)
+  }
+  style_tags
+}
+
 fn parse_queue_config(value : @json_parser.JsonValue) -> QueueConfig raise ConfigError {
   let obj = expect_object(value, "queue")
   QueueConfig::new(
@@ -920,7 +1028,7 @@ pub fn stringify_queue_config(queue : QueueConfig, pretty~ : Bool = false) -> St
 }
 
 pub fn text_formatter_config_to_json(config : TextFormatterConfig) -> @json_parser.JsonValue {
-  @json_parser.JsonValue::Object({
+  let obj : Map[String, @json_parser.JsonValue] = {
     "show_timestamp": @json_parser.JsonValue::Bool(config.show_timestamp),
     "show_level": @json_parser.JsonValue::Bool(config.show_level),
     "show_target": @json_parser.JsonValue::Bool(config.show_target),
@@ -928,7 +1036,42 @@ pub fn text_formatter_config_to_json(config : TextFormatterConfig) -> @json_pars
     "separator": @json_parser.JsonValue::String(config.separator),
     "field_separator": @json_parser.JsonValue::String(config.field_separator),
     "template": @json_parser.JsonValue::String(config.template),
-  })
+    "color_mode": @json_parser.JsonValue::String(color_mode_label(config.color_mode)),
+    "color_support": @json_parser.JsonValue::String(color_support_label(config.color_support)),
+    "style_markup": @json_parser.JsonValue::String(style_markup_mode_label(config.style_markup)),
+    "target_style_markup": @json_parser.JsonValue::String(style_markup_mode_label(config.target_style_markup)),
+    "fields_style_markup": @json_parser.JsonValue::String(style_markup_mode_label(config.fields_style_markup)),
+  }
+  if config.style_tags.length() != 0 {
+    obj["style_tags"] = style_tags_config_to_json(config.style_tags)
+  }
+  @json_parser.JsonValue::Object(obj)
+}
+
+fn text_style_config_to_json(style : TextStyle) -> @json_parser.JsonValue {
+  let obj : Map[String, @json_parser.JsonValue] = {
+    "bold": @json_parser.JsonValue::Bool(style.bold),
+    "dim": @json_parser.JsonValue::Bool(style.dim),
+    "italic": @json_parser.JsonValue::Bool(style.italic),
+    "underline": @json_parser.JsonValue::Bool(style.underline),
+  }
+  match style.fg {
+    Some(value) => obj["fg"] = @json_parser.JsonValue::String(value)
+    None => ()
+  }
+  match style.bg {
+    Some(value) => obj["bg"] = @json_parser.JsonValue::String(value)
+    None => ()
+  }
+  @json_parser.JsonValue::Object(obj)
+}
+
+fn style_tags_config_to_json(style_tags : Map[String, TextStyle]) -> @json_parser.JsonValue {
+  let obj : Map[String, @json_parser.JsonValue] = {}
+  for name, style in style_tags {
+    obj[name] = text_style_config_to_json(style)
+  }
+  @json_parser.JsonValue::Object(obj)
 }
 
 pub fn stringify_text_formatter_config(

bitlogger/formatter.mbt

@@ -1,5 +1,185 @@
 pub type RecordFormatter = (Record) -> String
 
+pub(all) enum ColorMode {
+  Never
+  Auto
+  Always
+}
+
+pub(all) enum ColorSupport {
+  Basic
+  TrueColor
+}
+
+pub(all) enum StyleMarkupMode {
+  Disabled
+  Builtin
+  Full
+}
+
+pub struct TextStyle {
+  fg : String?
+  bg : String?
+  bold : Bool
+  dim : Bool
+  italic : Bool
+  underline : Bool
+}
+
+pub fn text_style(
+  fg~ : String? = None,
+  bg~ : String? = None,
+  bold~ : Bool = false,
+  dim~ : Bool = false,
+  italic~ : Bool = false,
+  underline~ : Bool = false,
+) -> TextStyle {
+  { fg, bg, bold, dim, italic, underline }
+}
+
+pub struct StyleTagRegistry {
+  entries : Map[String, TextStyle]
+}
+
+fn normalize_style_tag_name(name : String) -> String {
+  name.trim().to_lower().to_owned()
+}
+
+pub fn style_tag_registry() -> StyleTagRegistry {
+  { entries: {} }
+}
+
+fn merge_text_style(base : TextStyle, overlay : TextStyle) -> TextStyle {
+  {
+    fg: match overlay.fg {
+      Some(_) => overlay.fg
+      None => base.fg
+    },
+    bg: match overlay.bg {
+      Some(_) => overlay.bg
+      None => base.bg
+    },
+    bold: base.bold || overlay.bold,
+    dim: base.dim || overlay.dim,
+    italic: base.italic || overlay.italic,
+    underline: base.underline || overlay.underline,
+  }
+}
+
+pub fn StyleTagRegistry::set_tag(
+  self : StyleTagRegistry,
+  name : String,
+  style~ : TextStyle = text_style(),
+  fg~ : String? = None,
+  bg~ : String? = None,
+  bold~ : Bool = false,
+  dim~ : Bool = false,
+  italic~ : Bool = false,
+  underline~ : Bool = false,
+) -> StyleTagRegistry {
+  let overlay = text_style(fg=fg, bg=bg, bold=bold, dim=dim, italic=italic, underline=underline)
+  self.entries[normalize_style_tag_name(name)] = merge_text_style(style, overlay)
+  self
+}
+
+pub fn StyleTagRegistry::get(self : StyleTagRegistry, name : String) -> TextStyle? {
+  self.entries.get(normalize_style_tag_name(name))
+}
+
+pub fn StyleTagRegistry::contains(self : StyleTagRegistry, name : String) -> Bool {
+  self.entries.contains(normalize_style_tag_name(name))
+}
+
+pub fn StyleTagRegistry::define_alias(
+  self : StyleTagRegistry,
+  name : String,
+  target : String,
+) -> StyleTagRegistry {
+  match self.get(target) {
+    Some(style) => self.set_tag(name, style=style)
+    None => match global_style_tag_registry().get(target) {
+      Some(style) => self.set_tag(name, style=style)
+      None => match builtin_text_style_for_tag(normalize_style_tag_name(target)) {
+        Some(style) => self.set_tag(name, style=style)
+        None => self
+      }
+    }
+  }
+}
+
+pub fn default_style_tag_registry() -> StyleTagRegistry {
+  style_tag_registry()
+    .set_tag("black", fg=Some("black"))
+    .set_tag("red", fg=Some("red"))
+    .set_tag("green", fg=Some("green"))
+    .set_tag("yellow", fg=Some("yellow"))
+    .set_tag("blue", fg=Some("blue"))
+    .set_tag("magenta", fg=Some("magenta"))
+    .set_tag("cyan", fg=Some("cyan"))
+    .set_tag("white", fg=Some("white"))
+    .set_tag("bright_black", fg=Some("bright_black"))
+    .set_tag("bright_red", fg=Some("bright_red"))
+    .set_tag("bright_green", fg=Some("bright_green"))
+    .set_tag("bright_yellow", fg=Some("bright_yellow"))
+    .set_tag("bright_blue", fg=Some("bright_blue"))
+    .set_tag("bright_magenta", fg=Some("bright_magenta"))
+    .set_tag("bright_cyan", fg=Some("bright_cyan"))
+    .set_tag("bright_white", fg=Some("bright_white"))
+    .set_tag("accent", fg=Some("bright_cyan"), bold=true)
+    .set_tag("info", fg=Some("cyan"))
+    .set_tag("success", fg=Some("green"), bold=true)
+    .set_tag("warning", fg=Some("yellow"), bold=true)
+    .set_tag("danger", fg=Some("red"), bold=true)
+    .set_tag("muted", fg=Some("bright_black"), dim=true)
+    .set_tag("b", bold=true)
+    .set_tag("dim", dim=true)
+    .set_tag("i", italic=true)
+    .set_tag("u", underline=true)
+}
+
+let global_style_tag_registry_ref : Ref[StyleTagRegistry] = Ref::new(style_tag_registry())
+
+pub fn global_style_tag_registry() -> StyleTagRegistry {
+  global_style_tag_registry_ref.val
+}
+
+pub fn set_global_style_tag_registry(registry : StyleTagRegistry) -> Unit {
+  global_style_tag_registry_ref.val = registry
+}
+
+pub fn reset_global_style_tag_registry() -> Unit {
+  global_style_tag_registry_ref.val = style_tag_registry()
+}
+
+priv struct InlineStyle {
+  fg_code : String?
+  bg_code : String?
+  fg_basic_name : String?
+  bg_basic_name : String?
+  bold : Bool
+  dim : Bool
+  italic : Bool
+  underline : Bool
+}
+
+priv struct StyledSegment {
+  text : String
+  style : InlineStyle
+}
+
+priv struct StyleFrame {
+  tag : String
+  style : InlineStyle
+}
+
+fn code_unit(ch : Char) -> Int {
+  ch.to_int()
+}
+
+fn code_unit16(ch : UInt16) -> Int {
+  ch.to_int()
+}
+
 pub struct TextFormatter {
   show_timestamp : Bool
   show_level : Bool
@@ -8,6 +188,12 @@ pub struct TextFormatter {
   separator : String
   field_separator : String
   template : String
+  color_mode : ColorMode
+  color_support : ColorSupport
+  style_markup : StyleMarkupMode
+  target_style_markup : StyleMarkupMode
+  fields_style_markup : StyleMarkupMode
+  style_tags : StyleTagRegistry?
 }
 
 pub fn text_formatter(
@@ -18,6 +204,12 @@ pub fn text_formatter(
   separator~ : String = " ",
   field_separator~ : String = " ",
   template~ : String = "",
+  color_mode~ : ColorMode = ColorMode::Never,
+  color_support~ : ColorSupport = ColorSupport::TrueColor,
+  style_markup~ : StyleMarkupMode = StyleMarkupMode::Full,
+  target_style_markup~ : StyleMarkupMode = StyleMarkupMode::Disabled,
+  fields_style_markup~ : StyleMarkupMode = StyleMarkupMode::Disabled,
+  style_tags~ : StyleTagRegistry? = None,
 ) -> TextFormatter {
   {
     show_timestamp,
@@ -27,6 +219,588 @@ pub fn text_formatter(
     separator,
     field_separator,
     template,
+    color_mode,
+    color_support,
+    style_markup,
+    target_style_markup,
+    fields_style_markup,
+    style_tags,
+  }
+}
+
+pub fn color_support_label(support : ColorSupport) -> String {
+  match support {
+    ColorSupport::Basic => "basic"
+    ColorSupport::TrueColor => "truecolor"
+  }
+}
+
+pub fn TextFormatter::with_color_support(self : TextFormatter, color_support : ColorSupport) -> TextFormatter {
+  { ..self, color_support }
+}
+
+pub fn style_markup_mode_label(mode : StyleMarkupMode) -> String {
+  match mode {
+    StyleMarkupMode::Disabled => "disabled"
+    StyleMarkupMode::Builtin => "builtin"
+    StyleMarkupMode::Full => "full"
+  }
+}
+
+pub fn TextFormatter::with_style_markup(self : TextFormatter, style_markup : StyleMarkupMode) -> TextFormatter {
+  { ..self, style_markup }
+}
+
+pub fn TextFormatter::without_style_markup(self : TextFormatter) -> TextFormatter {
+  { ..self, style_markup: StyleMarkupMode::Disabled }
+}
+
+pub fn TextFormatter::with_target_style_markup(
+  self : TextFormatter,
+  style_markup : StyleMarkupMode,
+) -> TextFormatter {
+  { ..self, target_style_markup: style_markup }
+}
+
+pub fn TextFormatter::with_fields_style_markup(
+  self : TextFormatter,
+  style_markup : StyleMarkupMode,
+) -> TextFormatter {
+  { ..self, fields_style_markup: style_markup }
+}
+
+pub fn TextFormatter::with_style_tags(self : TextFormatter, style_tags : StyleTagRegistry) -> TextFormatter {
+  { ..self, style_tags: Some(style_tags) }
+}
+
+pub fn color_mode_label(mode : ColorMode) -> String {
+  match mode {
+    ColorMode::Never => "never"
+    ColorMode::Auto => "auto"
+    ColorMode::Always => "always"
+  }
+}
+
+fn use_ansi_color(mode : ColorMode) -> Bool {
+  match mode {
+    ColorMode::Never => false
+    ColorMode::Always => true
+    ColorMode::Auto => match @env.get_env_var("NO_COLOR") {
+      Some(_) => false
+      None => true
+    }
+  }
+}
+
+fn ansi_wrap(text : String, code : String, enabled : Bool) -> String {
+  if !enabled || text == "" {
+    text
+  } else {
+    "\u{001b}[\{code}m\{text}\u{001b}[0m"
+  }
+}
+
+fn ansi_wrap_with_style(text : String, style : InlineStyle, enabled : Bool) -> String {
+  if !enabled || text == "" {
+    text
+  } else {
+    let codes : Array[String] = []
+    match style.fg_code {
+      Some(code) => codes.push(code)
+      None => ()
+    }
+    match style.bg_code {
+      Some(code) => codes.push(code)
+      None => ()
+    }
+    if style.bold {
+      codes.push("1")
+    }
+    if style.dim {
+      codes.push("2")
+    }
+    if style.italic {
+      codes.push("3")
+    }
+    if style.underline {
+      codes.push("4")
+    }
+    if codes.length() == 0 {
+      text
+    } else {
+      let joined = codes.join(";")
+      "\u{001b}[\{joined}m\{text}\u{001b}[0m"
+    }
+  }
+}
+
+fn default_inline_style() -> InlineStyle {
+  {
+    fg_code: None,
+    bg_code: None,
+    fg_basic_name: None,
+    bg_basic_name: None,
+    bold: false,
+    dim: false,
+    italic: false,
+    underline: false,
+  }
+}
+
+fn named_color_code(tag : String) -> String? {
+  match tag {
+    "black" => Some("30")
+    "red" => Some("31")
+    "green" => Some("32")
+    "yellow" => Some("33")
+    "blue" => Some("34")
+    "magenta" => Some("35")
+    "cyan" => Some("36")
+    "white" => Some("37")
+    "bright_black" => Some("90")
+    "bright_red" => Some("91")
+    "bright_green" => Some("92")
+    "bright_yellow" => Some("93")
+    "bright_blue" => Some("94")
+    "bright_magenta" => Some("95")
+    "bright_cyan" => Some("96")
+    "bright_white" => Some("97")
+    _ => None
+  }
+}
+
+fn named_bg_color_code(tag : String) -> String? {
+  match tag {
+    "black" => Some("40")
+    "red" => Some("41")
+    "green" => Some("42")
+    "yellow" => Some("43")
+    "blue" => Some("44")
+    "magenta" => Some("45")
+    "cyan" => Some("46")
+    "white" => Some("47")
+    "bright_black" => Some("100")
+    "bright_red" => Some("101")
+    "bright_green" => Some("102")
+    "bright_yellow" => Some("103")
+    "bright_blue" => Some("104")
+    "bright_magenta" => Some("105")
+    "bright_cyan" => Some("106")
+    "bright_white" => Some("107")
+    _ => None
+  }
+}
+
+fn basic_name_from_hex(value : String) -> String {
+  let r = hex_pair_to_int(value.unsafe_get(1), value.unsafe_get(2))
+  let g = hex_pair_to_int(value.unsafe_get(3), value.unsafe_get(4))
+  let b = hex_pair_to_int(value.unsafe_get(5), value.unsafe_get(6))
+  let max_value = if r >= g && r >= b { r } else if g >= b { g } else { b }
+  if max_value < 48 {
+    "bright_black"
+  } else {
+    let min_value = if r <= g && r <= b { r } else if g <= b { g } else { b }
+    let spread = max_value - min_value
+    if spread < 24 {
+      if max_value > 170 {
+        "white"
+      } else if max_value > 96 {
+        "bright_black"
+      } else {
+        "black"
+      }
+    } else if r >= g && r >= b {
+      if g > 96 && b < 96 {
+        "yellow"
+      } else if b > 96 && g < 96 {
+        "magenta"
+      } else {
+        "red"
+      }
+    } else if g >= r && g >= b {
+      if r > 96 && b < 96 {
+        "yellow"
+      } else if b > 96 && r < 96 {
+        "cyan"
+      } else {
+        "green"
+      }
+    } else {
+      if r > 96 && g < 96 {
+        "magenta"
+      } else if g > 96 && r < 96 {
+        "cyan"
+      } else {
+        "blue"
+      }
+    }
+  }
+}
+
+fn resolve_inline_color_code(
+  formatter : TextFormatter,
+  basic_name : String?,
+  truecolor_code : String,
+) -> String {
+  match formatter.color_support {
+    ColorSupport::TrueColor => truecolor_code
+    ColorSupport::Basic => match basic_name {
+      Some(name) => named_code_from_basic_name(name).unwrap_or(truecolor_code)
+      None => truecolor_code
+    }
+  }
+}
+
+fn named_code_from_basic_name(name : String) -> String? {
+  named_color_code(name)
+}
+
+fn named_bg_code_from_basic_name(name : String) -> String? {
+  named_bg_color_code(name)
+}
+
+fn resolve_inline_bg_code(
+  formatter : TextFormatter,
+  basic_name : String?,
+  truecolor_code : String,
+) -> String {
+  match formatter.color_support {
+    ColorSupport::TrueColor => truecolor_code
+    ColorSupport::Basic => match basic_name {
+      Some(name) => named_bg_code_from_basic_name(name).unwrap_or(truecolor_code)
+      None => truecolor_code
+    }
+  }
+}
+
+fn is_hex_color(value : String) -> Bool {
+  if value.length() != 7 {
+    return false
+  }
+  if value.unsafe_get(0) != '#' {
+    return false
+  }
+  for i = 1; i < value.length(); i = i + 1 {
+    let ch = value.unsafe_get(i)
+    let is_digit = ch >= '0' && ch <= '9'
+    let is_lower = ch >= 'a' && ch <= 'f'
+    let is_upper = ch >= 'A' && ch <= 'F'
+    if !(is_digit || is_lower || is_upper) {
+      return false
+    }
+  }
+  true
+}
+
+fn hex_to_int(ch : UInt16) -> Int {
+  let code = code_unit16(ch)
+  if code >= code_unit('0') && code <= code_unit('9') {
+    code_unit16(ch) - code_unit('0')
+  } else if code >= code_unit('a') && code <= code_unit('f') {
+    code_unit16(ch) - code_unit('a') + 10
+  } else {
+    code_unit16(ch) - code_unit('A') + 10
+  }
+}
+
+fn hex_pair_to_int(high : UInt16, low : UInt16) -> Int {
+  hex_to_int(high) * 16 + hex_to_int(low)
+}
+
+fn rgb_fg_code(value : String) -> String {
+  let r = hex_pair_to_int(value.unsafe_get(1), value.unsafe_get(2))
+  let g = hex_pair_to_int(value.unsafe_get(3), value.unsafe_get(4))
+  let b = hex_pair_to_int(value.unsafe_get(5), value.unsafe_get(6))
+  "38;2;\{r};\{g};\{b}"
+}
+
+fn rgb_bg_code(value : String) -> String {
+  let r = hex_pair_to_int(value.unsafe_get(4), value.unsafe_get(5))
+  let g = hex_pair_to_int(value.unsafe_get(6), value.unsafe_get(7))
+  let b = hex_pair_to_int(value.unsafe_get(8), value.unsafe_get(9))
+  "48;2;\{r};\{g};\{b}"
+}
+
+fn rgb_bg_code_from_hex(value : String) -> String {
+  let r = hex_pair_to_int(value.unsafe_get(1), value.unsafe_get(2))
+  let g = hex_pair_to_int(value.unsafe_get(3), value.unsafe_get(4))
+  let b = hex_pair_to_int(value.unsafe_get(5), value.unsafe_get(6))
+  "48;2;\{r};\{g};\{b}"
+}
+
+fn inline_style_from_text_style(
+  base : InlineStyle,
+  style : TextStyle,
+  formatter : TextFormatter,
+) -> InlineStyle? {
+  let fg = match style.fg {
+    None => Some((base.fg_code, base.fg_basic_name))
+    Some(value) => {
+      let normalized = normalize_style_tag_name(value)
+      match named_color_code(normalized) {
+        Some(code) => Some((Some(code), Some(normalized)))
+        None => if is_hex_color(value) {
+          let basic_name = basic_name_from_hex(value)
+          Some((
+            Some(resolve_inline_color_code(formatter, Some(basic_name), rgb_fg_code(value))),
+            Some(basic_name),
+          ))
+        } else {
+          None
+        }
+      }
+    }
+  }
+  let bg = match style.bg {
+    None => Some((base.bg_code, base.bg_basic_name))
+    Some(value) => {
+      let normalized = normalize_style_tag_name(value)
+      match named_bg_color_code(normalized) {
+        Some(code) => {
+          let bg_name = if normalized.has_prefix("bright_") {
+            normalized
+          } else {
+            normalized
+          }
+          Some((Some(code), Some(bg_name)))
+        }
+        None => if is_hex_color(value) {
+          let basic_name = basic_name_from_hex(value)
+          Some((
+    Some(resolve_inline_bg_code(formatter, Some(basic_name), rgb_bg_code_from_hex(value))),
+            Some(basic_name),
+          ))
+        } else {
+          None
+        }
+      }
+    }
+  }
+  match fg {
+    Some((next_fg_code, next_fg_name)) => match bg {
+      Some((next_bg_code, next_bg_name)) => Some({
+        fg_code: next_fg_code,
+        bg_code: next_bg_code,
+        fg_basic_name: next_fg_name,
+        bg_basic_name: next_bg_name,
+        bold: base.bold || style.bold,
+        dim: base.dim || style.dim,
+        italic: base.italic || style.italic,
+        underline: base.underline || style.underline,
+      })
+      None => None
+    }
+    None => None
+  }
+}
+
+fn builtin_text_style_for_tag(tag : String) -> TextStyle? {
+  match normalize_style_tag_name(tag) {
+    "black" => Some(text_style(fg=Some("black")))
+    "red" => Some(text_style(fg=Some("red")))
+    "green" => Some(text_style(fg=Some("green")))
+    "yellow" => Some(text_style(fg=Some("yellow")))
+    "blue" => Some(text_style(fg=Some("blue")))
+    "magenta" => Some(text_style(fg=Some("magenta")))
+    "cyan" => Some(text_style(fg=Some("cyan")))
+    "white" => Some(text_style(fg=Some("white")))
+    "bright_black" => Some(text_style(fg=Some("bright_black")))
+    "bright_red" => Some(text_style(fg=Some("bright_red")))
+    "bright_green" => Some(text_style(fg=Some("bright_green")))
+    "bright_yellow" => Some(text_style(fg=Some("bright_yellow")))
+    "bright_blue" => Some(text_style(fg=Some("bright_blue")))
+    "bright_magenta" => Some(text_style(fg=Some("bright_magenta")))
+    "bright_cyan" => Some(text_style(fg=Some("bright_cyan")))
+    "bright_white" => Some(text_style(fg=Some("bright_white")))
+    "accent" => Some(text_style(fg=Some("bright_cyan"), bold=true))
+    "info" => Some(text_style(fg=Some("cyan")))
+    "success" => Some(text_style(fg=Some("green"), bold=true))
+    "warning" => Some(text_style(fg=Some("yellow"), bold=true))
+    "danger" => Some(text_style(fg=Some("red"), bold=true))
+    "muted" => Some(text_style(fg=Some("bright_black"), dim=true))
+    "b" => Some(text_style(bold=true))
+    "dim" => Some(text_style(dim=true))
+    "i" => Some(text_style(italic=true))
+    "u" => Some(text_style(underline=true))
+    _ => None
+  }
+}
+
+fn resolve_registered_text_style(tag : String, formatter : TextFormatter) -> TextStyle? {
+  let normalized = normalize_style_tag_name(tag)
+  match formatter.style_markup {
+    StyleMarkupMode::Builtin => return builtin_text_style_for_tag(normalized)
+    _ => ()
+  }
+  match formatter.style_tags {
+    Some(registry) => match registry.get(normalized) {
+      Some(style) => Some(style)
+      None => match global_style_tag_registry().get(normalized) {
+        Some(style) => Some(style)
+        None => builtin_text_style_for_tag(normalized)
+      }
+    }
+    None => match global_style_tag_registry().get(normalized) {
+      Some(style) => Some(style)
+      None => builtin_text_style_for_tag(normalized)
+    }
+  }
+}
+
+fn apply_inline_tag(style : InlineStyle, tag : String, formatter : TextFormatter) -> InlineStyle? {
+  let normalized = normalize_style_tag_name(tag)
+  if is_hex_color(tag) {
+    let basic_name = basic_name_from_hex(tag)
+    Some({
+      ..style,
+      fg_code: Some(resolve_inline_color_code(formatter, Some(basic_name), rgb_fg_code(tag))),
+      fg_basic_name: Some(basic_name),
+    })
+  } else if normalized.length() == 10 && normalized.has_prefix("bg:") && is_hex_color(normalized[3:].to_owned()) {
+    let basic_name = basic_name_from_hex(normalized[3:].to_owned())
+    Some({
+      ..style,
+      bg_code: Some(resolve_inline_bg_code(formatter, Some(basic_name), rgb_bg_code(normalized))),
+      bg_basic_name: Some(basic_name),
+    })
+  } else {
+    match resolve_registered_text_style(normalized, formatter) {
+      Some(spec) => inline_style_from_text_style(style, spec, formatter)
+      None => None
+    }
+  }
+}
+
+fn push_plain_segment(
+  segments : Array[StyledSegment],
+  buffer : StringBuilder,
+  style : InlineStyle,
+) -> Unit {
+  let text = buffer.to_string()
+  if text != "" {
+    segments.push({ text, style })
+    buffer.reset()
+  }
+}
+
+fn pop_named_style_frame(stack : Array[StyleFrame], tag : String) -> Bool {
+  let normalized = normalize_style_tag_name(tag)
+  if stack.length() <= 1 {
+    return false
+  }
+  for i = stack.length() - 1; i > 0; i = i - 1 {
+    if stack[i].tag == normalized {
+      while stack.length() - 1 >= i {
+        ignore(stack.pop())
+      }
+      return true
+    }
+  }
+  false
+}
+
+fn has_named_style_frame(stack : Array[StyleFrame], tag : String) -> Bool {
+  let normalized = normalize_style_tag_name(tag)
+  if stack.length() <= 1 {
+    return false
+  }
+  for i = stack.length() - 1; i > 0; i = i - 1 {
+    if stack[i].tag == normalized {
+      return true
+    }
+  }
+  false
+}
+
+fn parse_inline_markup(input : String, formatter : TextFormatter) -> Array[StyledSegment] {
+  let segments : Array[StyledSegment] = []
+  let buffer = StringBuilder::new()
+  let stack : Array[StyleFrame] = [{ tag: "", style: default_inline_style() }]
+  let chars = input.to_array()
+  let current_style = fn() { stack[stack.length() - 1].style }
+  let flush = fn() { push_plain_segment(segments, buffer, current_style()) }
+  let append_raw = fn(start : Int, finish : Int) {
+    for i = start; i < finish; i = i + 1 {
+      buffer.write_char(chars.unsafe_get(i))
+    }
+  }
+  let find_tag_end = fn(start : Int) -> Int {
+    for i = start; i < chars.length(); i = i + 1 {
+      if chars.unsafe_get(i) == '>' {
+        return i
+      }
+    }
+    -1
+  }
+  for i = 0; i < chars.length(); {
+    if chars.unsafe_get(i) != '<' {
+      buffer.write_char(chars.unsafe_get(i))
+      continue i + 1
+    }
+    let end = find_tag_end(i + 1)
+    if end == -1 {
+      buffer.write_char(chars[i])
+      continue i + 1
+    }
+    let tag = input[i + 1:end].to_owned()
+    if tag == "/" {
+      if stack.length() > 1 {
+        flush()
+        ignore(stack.pop())
+      } else {
+        append_raw(i, end + 1)
+      }
+      continue end + 1
+    }
+    if tag.has_prefix("/") {
+      let close_tag = tag[1:].to_owned()
+      if close_tag != "" && has_named_style_frame(stack, close_tag) {
+        flush()
+        ignore(pop_named_style_frame(stack, close_tag))
+      } else {
+        append_raw(i, end + 1)
+      }
+      continue end + 1
+    }
+    match apply_inline_tag(current_style(), tag, formatter) {
+      Some(next_style) => {
+        flush()
+        stack.push({ tag: normalize_style_tag_name(tag), style: next_style })
+      }
+      None => append_raw(i, end + 1)
+    }
+    continue end + 1
+  }
+  flush()
+  segments
+}
+
+fn render_styled_text(text : String, formatter : TextFormatter, mode : StyleMarkupMode) -> String {
+  match mode {
+    StyleMarkupMode::Disabled => return text
+    _ => ()
+  }
+  let enabled = use_ansi_color(formatter.color_mode)
+  let scoped = { ..formatter, style_markup: mode }
+  let segments = parse_inline_markup(text, scoped)
+  let out = StringBuilder::new()
+  for segment in segments {
+    out.write_string(ansi_wrap_with_style(segment.text, segment.style, enabled))
+  }
+  out.to_string()
+}
+
+fn render_inline_markup(message : String, formatter : TextFormatter) -> String {
+  render_styled_text(message, formatter, formatter.style_markup)
+}
+
+fn level_ansi_code(level : Level) -> String {
+  match level {
+    Level::Trace => "90"
+    Level::Debug => "36"
+    Level::Info => "32"
+    Level::Warn => "33"
+    Level::Error => "31;1"
   }
 }
 
@@ -38,13 +812,9 @@ fn fields_to_json(fields : Array[Field]) -> Json {
   Json::object(obj)
 }
 
-fn format_fields(fields : Array[Field], separator : String) -> String {
-  fields.map(fn(f) { "\{f.key}=\{f.value}" }).join(separator)
-}
-
 fn timestamp_text(rec : Record, formatter : TextFormatter) -> String {
   if formatter.show_timestamp && rec.timestamp_ms != 0UL {
-    rec.timestamp_ms.to_string()
+    ansi_wrap(rec.timestamp_ms.to_string(), "90", use_ansi_color(formatter.color_mode))
   } else {
     ""
   }
@@ -52,7 +822,7 @@ fn timestamp_text(rec : Record, formatter : TextFormatter) -> String {
 
 fn level_text(rec : Record, formatter : TextFormatter) -> String {
   if formatter.show_level {
-    rec.level.label()
+    ansi_wrap(rec.level.label(), level_ansi_code(rec.level), use_ansi_color(formatter.color_mode))
   } else {
     ""
   }
@@ -60,15 +830,22 @@ fn level_text(rec : Record, formatter : TextFormatter) -> String {
 
 fn target_text(rec : Record, formatter : TextFormatter) -> String {
   if formatter.show_target && rec.target != "" {
-    rec.target
+    let rendered = render_styled_text(rec.target, formatter, formatter.target_style_markup)
+    ansi_wrap(rendered, "34", use_ansi_color(formatter.color_mode))
   } else {
     ""
   }
 }
 
+fn format_field_text(field : Field, formatter : TextFormatter) -> String {
+  let value = render_styled_text(field.value, formatter, formatter.fields_style_markup)
+  "\{field.key}=\{value}"
+}
+
 fn fields_text(rec : Record, formatter : TextFormatter) -> String {
   if formatter.show_fields && rec.fields.length() != 0 {
-    format_fields(rec.fields, formatter.field_separator)
+    let content = rec.fields.map(fn(field) { format_field_text(field, formatter) }).join(formatter.field_separator)
+    ansi_wrap(content, "35", use_ansi_color(formatter.color_mode))
   } else {
     ""
   }
@@ -80,7 +857,7 @@ fn render_template(rec : Record, formatter : TextFormatter) -> String {
     .replace_all(old="{timestamp_ms}", new=timestamp_text(rec, formatter))
     .replace_all(old="{level}", new=level_text(rec, formatter))
     .replace_all(old="{target}", new=target_text(rec, formatter))
-    .replace_all(old="{message}", new=rec.message)
+    .replace_all(old="{message}", new=render_inline_markup(rec.message, formatter))
     .replace_all(old="{fields}", new=fields_text(rec, formatter))
     .trim()
     .to_owned()
@@ -92,20 +869,20 @@ pub fn format_text(rec : Record, formatter~ : TextFormatter = text_formatter())
   }
   let parts : Array[String] = []
   if formatter.show_timestamp && rec.timestamp_ms != 0UL {
-    parts.push("[\{rec.timestamp_ms.to_string()}]")
+    parts.push("[\{timestamp_text(rec, formatter)}]")
   }
   if formatter.show_level {
-    parts.push("[\{rec.level.label()}]")
+    parts.push("[\{level_text(rec, formatter)}]")
   }
   if formatter.show_target && rec.target != "" {
-    parts.push("[\{rec.target}]")
+    parts.push("[\{target_text(rec, formatter)}]")
   }
-  parts.push(rec.message)
+  parts.push(render_inline_markup(rec.message, formatter))
   let base = parts.join(formatter.separator)
   if !formatter.show_fields || rec.fields.length() == 0 {
     base
   } else {
-    let details = format_fields(rec.fields, formatter.field_separator)
+    let details = fields_text(rec, formatter)
     "\{base}\{formatter.separator}\{details}"
   }
 }

docs/README-en.md

@@ -25,6 +25,7 @@ BitLogger currently provides:
 - explicit queued delivery via `queued_sink(...)` and `with_queue(...)`
 - bounded backlog with `QueueOverflowPolicy::DropNewest` and `QueueOverflowPolicy::DropOldest`
 - configurable text formatting via `text_formatter(...)`, `format_text(...)`, `text_console_sink(...)`, and template-driven `template` output
+- lightweight style tags via `color_mode`, inline markup, `TextStyle`, `StyleTagRegistry`, custom tags, and builtin-tag overrides
 - formatter-based callback integration via `formatted_callback_sink(...)`
 - native-only file output via `file_sink(...)`, with basic size rotation, backup retention, explicit `reopen()` / `reopen_with_current_policy()` / `reopen_append()` / `reopen_truncate()`, and failure counters
 - `native_files_supported()` for backend capability detection
@@ -158,17 +159,47 @@ let formatter = text_formatter(
   show_timestamp=false,
   field_separator=",",
   template="[{level}] {target} {message} :: {fields}",
+  color_mode=ColorMode::Always,
 )
 let logger = Logger::new(text_console_sink(formatter), target="pretty")
 
 logger.info("hello", fields=[field("mode", "pretty")])
 ```
 
+Inline style tags:
+
+```moonbit
+let formatter = text_formatter(
+  show_timestamp=false,
+  color_mode=ColorMode::Always,
+).with_style_tags(
+  default_style_tag_registry()
+    .set_tag("accent", fg=Some("#4cc9f0"), bold=true)
+    .define_alias("danger", "red"),
+)
+
+let logger = Logger::new(text_console_sink(formatter), target="styled")
+
+logger.info("<accent>styled</> output and <danger>alert</>")
+```
+
+Disable style markup parsing:
+
+```moonbit
+let formatter = text_formatter(
+  color_mode=ColorMode::Always,
+).without_style_markup()
+
+let logger = Logger::new(text_console_sink(formatter), target="raw")
+
+logger.info("<red>kept as raw text</>")
+```
+
 JSON config loading:
 
 ```moonbit
 let config = parse_logger_config_text(
-  "{\"min_level\":\"debug\",\"target\":\"config.demo\",\"timestamp\":true,\"sink\":{\"kind\":\"text_console\",\"text_formatter\":{\"show_timestamp\":false,\"field_separator\":\",\",\"template\":\"[{level}] {target} {message} :: {fields}\"}},\"queue\":{\"max_pending\":2,\"overflow\":\"DropOldest\"}}",
+  "{\"min_level\":\"debug\",\"target\":\"config.demo\",\"timestamp\":true,\"sink\":{\"kind\":\"text_console\",\"text_formatter\":{\"show_timestamp\":false,\"field_separator\":\",\",\"template\":\"[{level}] {target} {message} :: {fields}\",\"color_mode\":\"always\"}},\"queue\":{\"max_pending\":2,\"overflow\":\"DropOldest\"}}",
 )
 
 let logger = build_logger(config)
@@ -177,6 +208,30 @@ logger.info("configured from json")
 ignore(logger.flush())
 ```
 
+JSON `style_tags`:
+
+```moonbit
+let config = parse_logger_config_text(
+  "{\"sink\":{\"kind\":\"text_console\",\"text_formatter\":{\"show_timestamp\":false,\"color_mode\":\"always\",\"style_tags\":{\"accent\":{\"fg\":\"#4cc9f0\",\"bold\":true}}}}}",
+)
+
+let logger = build_logger(config)
+
+logger.info("<accent>styled from json</>")
+```
+
+JSON `style_markup` mode:
+
+```moonbit
+let config = parse_logger_config_text(
+  "{\"sink\":{\"kind\":\"text_console\",\"text_formatter\":{\"color_mode\":\"always\",\"style_markup\":\"disabled\"}}}",
+)
+
+let logger = build_logger(config)
+
+logger.info("<red>still raw</>")
+```
+
 Native file sink:
 
 ```moonbit
@@ -225,6 +280,17 @@ match logger.file_runtime_state() {
 - BitLogger now includes a JSON config layer via `parse_logger_config_text(...)`, `stringify_logger_config(...)`, and `build_logger(...)`.
 - `QueueConfig`, `TextFormatterConfig`, and `SinkConfig` can also be exported independently through `queue_config_to_json(...)` / `stringify_queue_config(...)`, `text_formatter_config_to_json(...)` / `stringify_text_formatter_config(...)`, and `sink_config_to_json(...)` / `stringify_sink_config(...)`.
 - Supported keys include `min_level`, `target`, `timestamp`, `sink.kind`, `sink.path`, `sink.append`, `sink.auto_flush`, `sink.rotation`, `sink.text_formatter`, and `queue`.
+- `TextFormatter` and `TextFormatterConfig` now include `color_mode = Never | Auto | Always` for ANSI text coloring control.
+- `TextFormatter` and `TextFormatterConfig` also include `color_support = basic | truecolor` so hex / RGB styling can be forced to downgrade to basic ANSI colors.
+- `TextFormatter` and `TextFormatterConfig` also include `style_markup = disabled | builtin | full` so callers can choose whether style markup is parsed and whether custom tags are active.
+- `target_style_markup` and `fields_style_markup` independently control whether `target` and `fields` are parsed for style markup.
+- `message` also supports lightweight inline style tags such as `<red>...</>`, `<b>...</>`, `<#ff0000>...</>`, and `<bg:#202020>...</>`.
+- Closing tags now support both the short form `</>` and named closing tags such as `</red>`, `</danger>`, and `</b>`.
+- Builtin semantic tags now include `<accent>`, `<info>`, `<success>`, `<warning>`, `<danger>`, and `<muted>`.
+- Runtime style-tag APIs now include `TextStyle`, `StyleTagRegistry`, `style_tag_registry()`, `default_style_tag_registry()`, `set_tag(...)`, and `define_alias(...)`.
+- Style-tag lookup priority is formatter-local `style_tags` > global style tag registry > builtin tags.
+- `sink.text_formatter.style_tags` now supports a minimal object mapping with `fg`, `bg`, `bold`, `dim`, `italic`, and `underline`.
+- `define_alias(...)` remains a runtime-only API and is not yet part of the JSON config schema.
 - `sink.rotation` currently supports `max_bytes` and `max_backups` for basic size-based rotation and backup retention.
 - `file_sink(...)` also exposes `reopen()`, `reopen_with_current_policy()`, `reopen_append()`, `reopen_truncate()`, `open_failures()`, `write_failures()`, `flush_failures()`, and `rotation_failures()` for basic observability.
 - `file_sink(...)` also exposes `append_mode()`. Passing `append=...` to `reopen(...)` updates the current append policy used by later reopen calls, `reopen_with_current_policy()` makes that stored-policy reopen path explicit, and `reopen_append()` / `reopen_truncate()` cover the two common policy switches directly.
@@ -248,6 +314,12 @@ match logger.file_runtime_state() {
 - `file_sink_policy_to_json(...)` and `stringify_file_sink_policy(...)` can export standalone file-policy snapshots directly as JSON for policy diffing, diagnostics, or reporting.
 - `file_sink_state_to_json(...)`, `stringify_file_sink_state(...)`, `runtime_file_state_to_json(...)`, and `stringify_runtime_file_state(...)` can export file and queued-file snapshots directly as JSON for diagnostics or reporting.
 - `sink.text_formatter.template` currently supports fixed tokens: `{timestamp}`, `{timestamp_ms}`, `{level}`, `{target}`, `{message}`, and `{fields}`.
+- `sink.text_formatter.color_mode` currently supports `never`, `auto`, and `always`.
+- `sink.text_formatter.color_support` currently supports `basic` and `truecolor`.
+- `sink.text_formatter.style_markup` currently supports `disabled`, `builtin`, and `full`.
+- `sink.text_formatter.target_style_markup` and `sink.text_formatter.fields_style_markup` currently support `disabled`, `builtin`, and `full`.
+- `sink.text_formatter.style_tags.<name>` currently supports `fg`, `bg`, `bold`, `dim`, `italic`, and `underline`.
+- `fields_style_markup` currently applies to field values only, not field keys.
 - Config-driven sink assembly currently supports `console`, `json_console`, `text_console`, and `file`.
 - `queue` remains a synchronous bounded wrapper around the final sink, not an async runtime.
 

docs/changes/0.4.0.md

@@ -0,0 +1,54 @@
+## BitLogger Update Changes
+
+version 0.4.0
+
+### Feature
+
+- feat: add `ColorMode = Never | Auto | Always` for text formatter color control
+- feat: add ANSI level, target, timestamp, and field rendering to `format_text(...)`
+- feat: add `color_mode` to `TextFormatter` and `TextFormatterConfig`
+- feat: support `text_formatter.color_mode` in JSON config parsing and serialization
+- feat: add inline style markup support in message text for ANSI text formatter output
+- feat: support named color tags like `<red>...</>`, style tags like `<b>...</>`, and hex tags like `<#ff0000>...</>` / `<bg:#010203>...</>`
+- feat: keep JSON formatter output unchanged and limit inline style parsing to text message rendering only
+- feat: add `TextStyle`, `StyleTagRegistry`, `style_tag_registry()`, and `default_style_tag_registry()` for reusable inline style tags
+- feat: add formatter-local `style_tags`, global style tag registry helpers, builtin-tag override support, and alias reuse via `define_alias(...)`
+- feat: support minimal `sink.text_formatter.style_tags` JSON config parsing and serialization for custom formatter tag styles
+- feat: add `StyleMarkupMode = Disabled | Builtin | Full` plus formatter helpers so callers can explicitly disable style parsing or allow builtin-only parsing
+- feat: support `sink.text_formatter.style_markup` in JSON config parsing and serialization
+- feat: add builtin semantic style tags such as `accent`, `info`, `success`, `warning`, `danger`, and `muted`
+- feat: add independent `target_style_markup` and `fields_style_markup` controls for `TextFormatter` and `TextFormatterConfig`
+- feat: support named closing tags like `</red>` alongside the existing short close `</>`
+- feat: add `ColorSupport = Basic | TrueColor` and support `sink.text_formatter.color_support` so hex / RGB styles can downgrade to basic ANSI colors
+
+### Test
+
+- test: cover ANSI text formatter rendering in `Always` mode
+- test: cover `Auto` mode fallback behavior when `NO_COLOR` is present
+- test: cover config parsing and serialization for `color_mode`
+- test: cover named inline color tags in ANSI mode
+- test: cover plain mode tag stripping, nested tags, hex tags, and unknown-tag fallback behavior
+- test: cover custom tags, builtin-tag override, formatter-vs-global priority, global registry fallback, and alias reuse
+- test: cover formatter `style_tags` JSON parsing, config roundtrip, JSON helper export, and config-driven styled formatter rendering
+- test: cover disabled markup mode, builtin-only mode, and config-driven `style_markup` behavior
+- test: cover builtin semantic tag rendering and confirm user overrides still take precedence
+- test: cover target and field markup rendering, plus config roundtrip for the new formatter markup scopes
+- test: cover named closing tags, mixed short/named closing, and unmatched named-close fallback behavior
+- test: cover basic color-support downgrade for hex foreground/background rendering in runtime and config paths
+
+### Example
+
+- docs: add `color_mode` usage examples to formatter documentation
+- docs: add runtime and JSON `style_tags` examples, and document current JSON schema scope
+- docs: add runtime and JSON examples for toggling style markup parsing
+
+### Notes
+
+- `Auto` currently uses a conservative rule: if `NO_COLOR` exists, ANSI is disabled; otherwise ANSI is enabled
+- inline style markup supports both short close `</>` and named closing tags like `</red>`
+- unknown or invalid inline tags currently fall back to plain text and do not raise formatter errors
+- formatter-local tag lookup currently takes precedence over global tag lookup, and global lookup takes precedence over builtin tags
+- JSON config currently supports concrete style objects only; alias-style declarations remain runtime-only
+- users can now decide whether custom style parsing is enabled through runtime formatter APIs or `sink.text_formatter.style_markup`
+- `fields_style_markup` currently styles field values only and intentionally leaves field keys raw
+- `basic` color support currently keeps ANSI styling but downgrades hex / RGB colors to the nearest basic ANSI color family

examples/basic/main.mbt

@@ -68,6 +68,21 @@ fn main {
   )
   pretty_logger.info("custom text format", fields=[@lib.field("mode", "pretty")])
 
+  let styled_formatter = @lib.text_formatter(
+    show_timestamp=false,
+    color_mode=@lib.ColorMode::Always,
+  ).with_style_tags(
+    @lib.default_style_tag_registry()
+      .set_tag("accent", fg=Some("#4cc9f0"), bold=true)
+      .define_alias("danger", "red"),
+  )
+  let styled_logger = @lib.Logger::new(
+    @lib.text_console_sink(styled_formatter),
+    min_level=@lib.Level::Info,
+    target="styled",
+  )
+  styled_logger.info("<accent>styled</> output and <danger>alert</>")
+
   if @lib.native_files_supported() {
     let file_logger = @lib.Logger::new(
       @lib.file_sink(

moon.mod.json

@@ -1,6 +1,6 @@
 {
   "name": "Nanaloveyuki/BitLogger",
-  "version": "0.3.0",
+  "version": "0.4.0",
   "deps": {
     "maria/json_parser": "0.1.1",
     "moonbitlang/async": "0.18.1"