✨ Add ANSI color support fallback modes

README.md

@@ -305,6 +305,7 @@ match logger.file_runtime_state() {
 - `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>...</>`
@@ -338,6 +339,7 @@ match logger.file_runtime_state() {
 - `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`

bitlogger/BitLogger_test.mbt

@@ -74,9 +74,10 @@ 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\",\"style_markup\":\"builtin\",\"target_style_markup\":\"builtin\",\"fields_style_markup\":\"disabled\",\"style_tags\":{\"accent\":{\"fg\":\"#4cc9f0\",\"bold\":true},\"panel\":{\"bg\":\"#202020\",\"underline\":true}}}}}",
+    "{\"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")
@@ -151,6 +152,7 @@ test "logger config stringify roundtrips formatter style tags" {
         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,
@@ -164,6 +166,7 @@ test "logger config stringify roundtrips formatter style tags" {
   )
   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")
@@ -213,6 +216,7 @@ test "config subtype json helpers stringify stable shapes" {
         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,
@@ -221,7 +225,7 @@ test "config subtype json helpers stringify stable shapes" {
         },
       ),
     ),
-    content="{\"show_timestamp\":false,\"show_level\":true,\"show_target\":false,\"show_fields\":true,\"separator\":\" | \",\"field_separator\":\",\",\"template\":\"[{level}] {message} :: {fields}\",\"color_mode\":\"always\",\"style_markup\":\"builtin\",\"target_style_markup\":\"builtin\",\"fields_style_markup\":\"disabled\",\"style_tags\":{\"accent\":{\"bold\":true,\"dim\":false,\"italic\":false,\"underline\":false,\"fg\":\"#4cc9f0\"}}}",
+    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(
@@ -234,10 +238,24 @@ test "config subtype json helpers stringify stable shapes" {
         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\":\"\",\"color_mode\":\"auto\",\"style_markup\":\"full\",\"target_style_markup\":\"disabled\",\"fields_style_markup\":\"disabled\"},\"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,

bitlogger/BitLogger_wbtest.mbt

@@ -139,6 +139,22 @@ test "text formatter supports hex inline colors" {
   )
 }
 
+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(

bitlogger/README.mbt.md

@@ -251,6 +251,7 @@ test {
 
 - 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>...</>`

bitlogger/config.mbt

@@ -18,6 +18,7 @@ pub struct TextFormatterConfig {
   field_separator : String
   template : String
   color_mode : ColorMode
+  color_support : ColorSupport
   style_markup : StyleMarkupMode
   target_style_markup : StyleMarkupMode
   fields_style_markup : StyleMarkupMode
@@ -33,6 +34,7 @@ pub fn TextFormatterConfig::new(
   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,
@@ -47,6 +49,7 @@ pub fn TextFormatterConfig::new(
     field_separator,
     template,
     color_mode,
+    color_support,
     style_markup,
     target_style_markup,
     fields_style_markup,
@@ -72,6 +75,7 @@ pub fn TextFormatterConfig::to_formatter(self : TextFormatterConfig) -> TextForm
     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,
@@ -869,6 +873,14 @@ fn parse_color_mode(name : String) -> ColorMode raise ConfigError {
   }
 }
 
+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
@@ -898,6 +910,7 @@ fn parse_text_formatter_config(value : @json_parser.JsonValue) -> TextFormatterC
     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")),
@@ -1024,6 +1037,7 @@ pub fn text_formatter_config_to_json(config : TextFormatterConfig) -> @json_pars
     "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)),

bitlogger/formatter.mbt

@@ -6,6 +6,11 @@ pub(all) enum ColorMode {
   Always
 }
 
+pub(all) enum ColorSupport {
+  Basic
+  TrueColor
+}
+
 pub(all) enum StyleMarkupMode {
   Disabled
   Builtin
@@ -149,6 +154,8 @@ pub fn reset_global_style_tag_registry() -> Unit {
 priv struct InlineStyle {
   fg_code : String?
   bg_code : String?
+  fg_basic_name : String?
+  bg_basic_name : String?
   bold : Bool
   dim : Bool
   italic : Bool
@@ -182,6 +189,7 @@ pub struct TextFormatter {
   field_separator : String
   template : String
   color_mode : ColorMode
+  color_support : ColorSupport
   style_markup : StyleMarkupMode
   target_style_markup : StyleMarkupMode
   fields_style_markup : StyleMarkupMode
@@ -197,6 +205,7 @@ pub fn text_formatter(
   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,
@@ -211,6 +220,7 @@ pub fn text_formatter(
     field_separator,
     template,
     color_mode,
+    color_support,
     style_markup,
     target_style_markup,
     fields_style_markup,
@@ -218,6 +228,17 @@ pub fn text_formatter(
   }
 }
 
+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"
@@ -314,7 +335,16 @@ fn ansi_wrap_with_style(text : String, style : InlineStyle, enabled : Bool) -> S
 }
 
 fn default_inline_style() -> InlineStyle {
-  { fg_code: None, bg_code: None, bold: false, dim: false, italic: false, underline: false }
+  {
+    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? {
@@ -361,6 +391,88 @@ fn named_bg_color_code(tag : String) -> String? {
   }
 }
 
+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
@@ -416,34 +528,61 @@ fn rgb_bg_code_from_hex(value : String) -> String {
   "48;2;\{r};\{g};\{b}"
 }
 
-fn inline_style_from_text_style(base : InlineStyle, style : TextStyle) -> InlineStyle? {
-  let fg_code = match style.fg {
-    None => Some(base.fg_code)
-    Some(value) => match named_color_code(normalize_style_tag_name(value)) {
-      Some(code) => Some(Some(code))
+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) {
-        Some(Some(rgb_fg_code(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_code = match style.bg {
-    None => Some(base.bg_code)
-    Some(value) => match named_bg_color_code(normalize_style_tag_name(value)) {
-      Some(code) => Some(Some(code))
+  }
+  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) {
-        Some(Some(rgb_bg_code_from_hex(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_code {
-    Some(next_fg) => match bg_code {
-      Some(next_bg) => Some({
-        fg_code: next_fg,
-        bg_code: next_bg,
+  }
+  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,
@@ -511,12 +650,22 @@ fn resolve_registered_text_style(tag : String, formatter : TextFormatter) -> Tex
 fn apply_inline_tag(style : InlineStyle, tag : String, formatter : TextFormatter) -> InlineStyle? {
   let normalized = normalize_style_tag_name(tag)
   if is_hex_color(tag) {
-    Some({ ..style, fg_code: Some(rgb_fg_code(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()) {
-    Some({ ..style, bg_code: Some(rgb_bg_code(normalized)) })
+    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)
+      Some(spec) => inline_style_from_text_style(style, spec, formatter)
       None => None
     }
   }

docs/README-en.md

@@ -281,6 +281,7 @@ match logger.file_runtime_state() {
 - `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>...</>`.
@@ -314,6 +315,7 @@ match logger.file_runtime_state() {
 - `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`.

docs/changes/0.4.0.md

@@ -19,6 +19,7 @@ version 0.4.0
 - 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
 
@@ -33,6 +34,7 @@ version 0.4.0
 - 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
 
@@ -49,3 +51,4 @@ version 0.4.0
 - 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