fix(config): consume INI shell-quoting layer in parse_flags

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

@@ -578,6 +578,36 @@ fn test_parse_flags() {
     );
 }
 
+/// FastLED/fbuild#947: the INI shell-quoting layer must be consumed here,
+/// exactly once, so string-valued defines reach the compiler as a single
+/// direct-exec argv element like `-DPROJECT_NAME="Demo"`.
+#[test]
+fn test_parse_flags_dequotes_shell_layer() {
+    // Outer-quoted escaped form (NightDriverStrip demo env).
+    assert_eq!(
+        parse_flags(r#"-DPROJECT_NAME="\"Demo\"" -DMATRIX_WIDTH=144"#),
+        vec![r#"-DPROJECT_NAME="Demo""#, "-DMATRIX_WIDTH=144"]
+    );
+    // Bare escaped form (no outer quotes) — common in other projects.
+    assert_eq!(parse_flags(r#"-DFOO=\"Bar\""#), vec![r#"-DFOO="Bar""#]);
+    // Quoted values with spaces group into one token.
+    assert_eq!(
+        parse_flags(r#"-DGREETING="\"Hello World\"""#),
+        vec![r#"-DGREETING="Hello World""#]
+    );
+    // Quote delimiters around paths are consumed; backslashes that are
+    // not escaping a double quote stay literal (Windows paths).
+    assert_eq!(
+        parse_flags(r#"-I"C:\Program Files\SDK" -Ifoo"#),
+        vec![r"-IC:\Program Files\SDK", "-Ifoo"]
+    );
+    // Single-quoted regions are fully literal.
+    assert_eq!(
+        parse_flags(r#"-DMSG='\"x\"' -DY=1"#),
+        vec![r#"-DMSG=\"x\""#, "-DY=1"]
+    );
+}
+
 #[test]
 fn test_parse_lib_deps() {
     assert_eq!(

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

@@ -22,6 +22,13 @@ pub(super) fn strip_inline_comment(s: &str) -> String {
 /// - Multi-line: one flag per line
 /// - `-D FLAG` → `-DFLAG` normalization
 /// - Preserves arguments for `-include`, `-I`, `-L`, etc.
+/// - Consumes the INI shell-quoting layer (FastLED/fbuild#947): quote
+///   delimiters group and are stripped, and `\"` (outside single quotes)
+///   is an escaped literal `"`. PlatformIO feeds `build_flags` through
+///   Python `shlex`, so `-DNAME="\"Demo\""` must emerge here as the
+///   single direct-exec argv element `-DNAME="Demo"`. Backslashes not
+///   escaping a double quote stay literal (Windows paths) — the one
+///   deliberate divergence from POSIX shlex.
 pub(super) fn parse_flags(flags_str: &str) -> Vec<String> {
     let mut result = Vec::new();
 
@@ -31,21 +38,23 @@ pub(super) fn parse_flags(flags_str: &str) -> Vec<String> {
             continue;
         }
 
-        let chars = trimmed.chars();
+        let mut chars = trimmed.chars().peekable();
         let mut current = String::new();
         let mut in_quotes = false;
         let mut quote_char = ' ';
 
-        for c in chars {
+        while let Some(c) = chars.next() {
             match c {
+                '\\' if chars.peek() == Some(&'"') && !(in_quotes && quote_char == '\'') => {
+                    chars.next();
+                    current.push('"');
+                }
                 '"' | '\'' if !in_quotes => {
                     in_quotes = true;
                     quote_char = c;
-                    current.push(c);
                 }
                 c if in_quotes && c == quote_char => {
                     in_quotes = false;
-                    current.push(c);
                 }
                 ' ' | '\t' if !in_quotes => {
                     if !current.is_empty() {