fix(parser): backslash escapes after a quoted segment

crates/bashkit/src/parser/lexer.rs

@@ -1176,6 +1176,26 @@ impl<'a> Lexer<'a> {
                         self.advance();
                     }
                 }
+                Some('\\') => {
+                    // Backslash escape after a quoted segment: `'a'\''b'`.
+                    self.advance();
+                    match self.peek_char() {
+                        // Line continuation.
+                        Some('\n') => {
+                            self.advance();
+                        }
+                        Some(next) => {
+                            let start = content.len();
+                            if next == '$' {
+                                content.push('\x00');
+                            }
+                            content.push(next);
+                            self.advance();
+                            flags.quoted_ranges.push((start, content.len()));
+                        }
+                        None => content.push('\\'),
+                    }
+                }
                 Some(ch) if self.is_word_char(ch) => {
                     if matches!(ch, '*' | '?' | '[') {
                         flags.has_unquoted_glob = true;

crates/bashkit/tests/spec_cases/bash/quote.test.sh

@@ -338,3 +338,36 @@ show "${x}"
 ### expect
 $'a\nb'
 ### end
+
+### quote_backslash_escape_after_quoted_segment
+# `'\''` (close, escaped quote, reopen) and other escapes right after a
+# quoted segment.
+echo 'a'\''b'
+echo 'it'\''s' "x"\'
+echo "a"\$HOME 'a'\$HOME
+echo "a"\ b 'c'\ d
+echo "g"\* 'h'\?
+echo 'p'\"q
+### expect
+a'b
+it's x'
+a$HOME a$HOME
+a b c d
+g* h?
+p"q
+### end
+
+### quote_nested_sh_c_quote_idiom
+sh -c 'sh -c '\''echo deep'\'''
+sh -c 'echo '\''one two'\'''
+### expect
+deep
+one two
+### end
+
+### quote_backslash_newline_after_quoted_segment
+echo 'a'\
+'b'
+### expect
+ab
+### end

knowledge/log.md

@@ -2,6 +2,7 @@
 
 ## 2026-10-07
 
+* **Fix**: A backslash escape right after a quoted segment broke lexing: `'a'\''b'` (the standard way to put a quote inside single quotes, as in `sh -c '...'\''...'\''...'`) failed with "unterminated single quote", and `"a"\$x`, `'a'\ b`, `"g"\*` kept the backslash. The quote-continuation reader now treats `\c` as a quoted `c` and `\<newline>` as a continuation. Still open: single quotes inside an unquoted `${x:-'d'}` operand are not removed.
 * **Fix**: `$SECONDS` counts whole seconds since the `Bash` instance was built (it was always 0), and `SECONDS=N` restarts the count from N; subshells keep their own. The rootfs gained `/proc/sys/kernel/random/uuid`, a fresh v4 UUID per read from the same CSPRNG as `uuidgen`. See [VFS](foundations/vfs.md).
 * **Feature**: Pipelines stream. From the first stage that runs shell code, stages run concurrently on forked shells over 4 KiB pipes, with backpressure and SIGPIPE: `while :; do echo x; done | head -n 2` stops the loop (`PIPESTATUS` `141 0`) instead of running it into the command limit. Single-builtin leading stages keep running in sequence (no fork). The pipe is 4 KiB rather than Linux's 64 KiB because every byte an endless producer runs ahead costs budgeted commands. Nested streaming is capped at 4 levels after a debug-build stack measurement (TM-DOS-124). L-PIPE-001 narrowed. See [Parallel Execution](foundations/parallel-execution.md#pipelines).
 * **Fix**: Pipeline stages are subshells, as in bash: `echo x | read v` leaves `v` unset and `cd /tmp | true` keeps the cwd; `shopt -s lastpipe` keeps the last stage in the shell. Streaming callers no longer see a non-last stage's output (`for ...; done | tac` streamed the loop's lines in input order). Stages still run sequentially (new L-PIPE-001). See [Parallel Execution](foundations/parallel-execution.md#pipelines).