feat: support PlatformIO monitor filters

crates/fbuild-config/src/board/loaders.rs

@@ -76,6 +76,40 @@ fn resolve_max_flash(
     })
 }
 
+fn parse_monitor_filters(value: &str) -> Vec<String> {
+    let trimmed = value.trim();
+    if trimmed.is_empty() || trimmed == "[]" {
+        return Vec::new();
+    }
+
+    trimmed
+        .lines()
+        .flat_map(|line| line.split(','))
+        .map(str::trim)
+        .filter(|filter| !filter.is_empty())
+        .map(ToString::to_string)
+        .collect()
+}
+
+fn resolve_monitor_filters(
+    overrides: &HashMap<String, String>,
+    defaults: &HashMap<String, String>,
+    is_esp32_family: bool,
+) -> Option<Vec<String>> {
+    overrides
+        .get("monitor_filters")
+        .map(|value| parse_monitor_filters(value))
+        .or_else(|| {
+            defaults
+                .get("monitor_filters")
+                .map(|value| parse_monitor_filters(value))
+        })
+        .or_else(|| {
+            is_esp32_family
+                .then(|| vec!["default".to_string(), "esp32_exception_decoder".to_string()])
+        })
+}
+
 impl BoardConfig {
     /// Load board config from a boards.txt file.
     ///
@@ -141,6 +175,7 @@ impl BoardConfig {
             upload_protocol: get("upload.protocol")
                 .or_else(|| props.get("upload.protocol").cloned()),
             upload_speed: get("upload.speed").or_else(|| props.get("upload.speed").cloned()),
+            monitor_filters: resolve_monitor_filters(overrides, &props, is_esp32_family),
             max_flash: resolve_max_flash(overrides, &props),
             max_ram: get("maximum_data_size")
                 .or_else(|| props.get("maximum_data_size").cloned())
@@ -308,6 +343,7 @@ impl BoardConfig {
                 .get("upload.speed")
                 .cloned()
                 .or_else(|| defaults.get("upload.speed").cloned()),
+            monitor_filters: resolve_monitor_filters(overrides, &defaults, is_esp32_family),
             max_flash: resolve_max_flash(overrides, &defaults),
             max_ram: overrides
                 .get("maximum_data_size")

crates/fbuild-config/src/board/methods.rs

@@ -43,6 +43,14 @@ impl BoardConfig {
             && EMULATOR_TOOL_NAMES.contains(&tool_name)
     }
 
+    /// PlatformIO `monitor_filters` value to emit for this board.
+    pub fn monitor_filters_ini_value(&self) -> Option<String> {
+        self.monitor_filters
+            .as_ref()
+            .filter(|filters| !filters.is_empty())
+            .map(|filters| filters.join(", "))
+    }
+
     /// Resolve the effective ESP32 SDK memory profile used for variant headers/libs.
     ///
     /// This keeps the SDK `sdkconfig.h` and memory-profile libraries aligned

crates/fbuild-config/src/board/tests.rs

@@ -283,6 +283,48 @@ fn test_platform_detection() {
     assert_eq!(rpi.platform(), Some(fbuild_core::Platform::RaspberryPi));
 }
 
+#[test]
+fn test_non_esp32_monitor_filters_default_absent() {
+    let config = BoardConfig::from_board_id("uno", &HashMap::new()).unwrap();
+    assert_eq!(config.monitor_filters, None);
+    assert_eq!(config.monitor_filters_ini_value(), None);
+}
+
+#[test]
+fn test_custom_monitor_filters_emit_in_platformio_format() {
+    let mut overrides = HashMap::new();
+    overrides.insert(
+        "monitor_filters".to_string(),
+        "default, time, log2file".to_string(),
+    );
+
+    let config = BoardConfig::from_board_id("uno", &overrides).unwrap();
+
+    assert_eq!(
+        config.monitor_filters,
+        Some(vec![
+            "default".to_string(),
+            "time".to_string(),
+            "log2file".to_string()
+        ])
+    );
+    assert_eq!(
+        config.monitor_filters_ini_value(),
+        Some("default, time, log2file".to_string())
+    );
+}
+
+#[test]
+fn test_empty_monitor_filters_suppresses_emit() {
+    let mut overrides = HashMap::new();
+    overrides.insert("monitor_filters".to_string(), "[]".to_string());
+
+    let config = BoardConfig::from_board_id("esp32dev", &overrides).unwrap();
+
+    assert_eq!(config.monitor_filters, Some(Vec::new()));
+    assert_eq!(config.monitor_filters_ini_value(), None);
+}
+
 #[test]
 fn test_parse_boards_txt_with_comments() {
     let props = parse_boards_txt(

crates/fbuild-config/src/board/tests_enriched_json.rs

@@ -139,6 +139,23 @@ fn test_esp32dev_enriched_fields() {
     assert_eq!(config.upload_speed, Some("460800".to_string()));
 }
 
+#[test]
+fn test_esp32dev_defaults_monitor_filters() {
+    let config = BoardConfig::from_board_id("esp32dev", &HashMap::new()).unwrap();
+
+    assert_eq!(
+        config.monitor_filters,
+        Some(vec![
+            "default".to_string(),
+            "esp32_exception_decoder".to_string()
+        ])
+    );
+    assert_eq!(
+        config.monitor_filters_ini_value(),
+        Some("default, esp32_exception_decoder".to_string())
+    );
+}
+
 #[test]
 fn test_esp32_flash_mode_env_override_honoured() {
     // The user can opt back into QIO via `board_build.flash_mode = qio`

crates/fbuild-config/src/board/types.rs

@@ -60,6 +60,12 @@ pub struct BoardConfig {
     pub upload_protocol: Option<String>,
     /// Upload speed
     pub upload_speed: Option<String>,
+    /// PlatformIO serial monitor filters.
+    ///
+    /// ESP32-family boards default to `default, esp32_exception_decoder` when
+    /// unset. An explicit empty list in project config suppresses that default.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub monitor_filters: Option<Vec<String>>,
     /// Maximum flash size in bytes
     pub max_flash: Option<u64>,
     /// Maximum RAM size in bytes

crates/fbuild-config/src/ini_parser/mod.rs

@@ -348,6 +348,8 @@ impl PlatformIOConfig {
                 overrides.insert(stripped.to_string(), value.clone());
             } else if let Some(stripped) = key.strip_prefix("board_upload.") {
                 overrides.insert(format!("upload.{}", stripped), value.clone());
+            } else if key == "monitor_filters" {
+                overrides.insert(key.clone(), value.clone());
             }
         }
 

crates/fbuild-config/src/ini_parser/tests.rs

@@ -750,6 +750,28 @@ board_upload.flash_size = 4MB
     assert_eq!(overrides.get("upload.flash_size"), Some(&"4MB".to_string()));
 }
 
+#[test]
+fn test_get_board_overrides_preserves_monitor_filters() {
+    let f = write_ini(
+        "\
+[env:esp32dev]
+platform = espressif32
+board = esp32dev
+framework = arduino
+monitor_filters =
+    default
+    esp32_exception_decoder
+",
+    );
+    let config = PlatformIOConfig::from_path(f.path()).unwrap();
+    let overrides = config.get_board_overrides("esp32dev").unwrap();
+
+    assert_eq!(
+        overrides.get("monitor_filters"),
+        Some(&"default\nesp32_exception_decoder".to_string())
+    );
+}
+
 #[test]
 fn test_get_source_filter_prefers_build_src_filter() {
     let f = write_ini(

docs/reference/platformio-ini.md

@@ -30,6 +30,7 @@ board = uno
 framework = arduino
 upload_port = COM3
 monitor_speed = 9600
+monitor_filters = default, esp32_exception_decoder
 build_flags =
     -DDEBUG
     -DLED_PIN=13
@@ -48,6 +49,7 @@ Common keys:
 | `[env:<name>] framework` | Framework, usually `arduino`. |
 | `upload_port` | Preferred deploy port. |
 | `monitor_speed` | Serial monitor baud rate. |
+| `monitor_filters` | Serial monitor filters. ESP32-family boards default to `default, esp32_exception_decoder` when unset; use `monitor_filters = []` to suppress. |
 | `build_flags` | Extra compiler flags. |
 | `lib_deps` | Library dependencies, including GitHub URLs. |
 | `build_type` | Build profile; `debug` preserves unwind metadata. |