lang-core: accept triple-quoted strings

.changeset/lang-core-triple-quotes.md

@@ -0,0 +1,5 @@
+---
+"@openuidev/lang-core": patch
+---
+
+Accept Python-style triple-quoted strings (`"""…"""` / `'''…'''`) for multi-line values such as code snippets, including while streaming. Quotes inside `//` and `#` comments no longer throw off string detection.

packages/lang-core/src/parser/__tests__/parser.test.ts

@@ -370,3 +370,30 @@ a = Title("y")`;
     expect(titleText(sp.push(`")\n`))).toBe("y");
   });
 });
+
+describe("triple-quoted strings", () => {
+  const text = (input: string) => {
+    const root = parse(input, schema).root as unknown as {
+      props: { children: { props: { text: string } }[] };
+    };
+    return root.props.children[0].props.text;
+  };
+
+  it("keeps newlines, quotes and # lines in the body", () => {
+    const src = `root = Stack([a])\na = Title(code)\ncode = """\nimport os  # list\nprint("hi", 'x')\n"""`;
+    expect(text(src)).toBe(`import os  # list\nprint("hi", 'x')`);
+  });
+
+  it("supports ''' delimiters", () => {
+    expect(text(`root = Stack([Title('''a\nb''')])`)).toBe("a\nb");
+  });
+
+  it("streams an unclosed body without the partial closing quotes", () => {
+    const sp = createStreamParser(schema);
+    sp.push(`root = Stack([a])\na = Title(code)\ncode = """\nline 1\n`);
+    const root = sp.push(`line 2""`).root as unknown as {
+      props: { children: { props: { text: string } }[] };
+    };
+    expect(root.props.children[0].props.text).toBe("line 1\nline 2");
+  });
+});

packages/lang-core/src/parser/merge.ts

@@ -6,7 +6,7 @@ import type { ASTNode } from "./ast";
 import { walkAST } from "./ast";
 import { parseExpression } from "./expressions";
 import { tokenize } from "./lexer";
-import { stripFences } from "./parser";
+import { normalizeTripleQuotes, stripFences } from "./parser";
 import { split } from "./statements";
 
 interface ParsedStatement {
@@ -57,7 +57,7 @@ function splitStatementSource(input: string): string[] {
 }
 
 function parseStatements(input: string): ParsedStatement[] {
-  const trimmed = input.trim();
+  const trimmed = normalizeTripleQuotes(input.trim());
   if (!trimmed) return [];
 
   const result: ParsedStatement[] = [];

packages/lang-core/src/parser/parser.ts

@@ -443,9 +443,72 @@ function stripComments(input: string): string {
     .join("\n");
 }
 
-/** Clean LLM response: strip fences, comments, whitespace. */
+/**
+ * Rewrite Python-style triple-quoted strings ("""…""" or '''…''') as JSON
+ * string literals, so the rest of the pipeline only sees ordinary strings.
+ * LLMs reach for them for multi-line code (`code = """…"""`); without this the
+ * lexer reads `"""` as an empty string followed by an open quote.
+ *
+ * The body is kept raw (backslashes are literal, newlines preserved). One
+ * newline right after the opening quotes and a whitespace-only last line before
+ * the closing quotes are dropped. An unclosed body (streaming) becomes an
+ * unclosed string, with any trailing quotes held back since they may be the
+ * start of the closing delimiter.
+ */
+export function normalizeTripleQuotes(input: string): string {
+  if (!input.includes('"""') && !input.includes("'''")) return input;
+  let out = "";
+  let i = 0;
+  let inStr: false | '"' | "'" = false;
+  while (i < input.length) {
+    const c = input[i];
+    if (inStr) {
+      out += c;
+      if (c === "\\" && i + 1 < input.length) {
+        out += input[i + 1];
+        i += 2;
+        continue;
+      }
+      if (c === inStr) inStr = false;
+      i++;
+      continue;
+    }
+    if ((c === '"' || c === "'") && input.startsWith(c.repeat(3), i)) {
+      const delim = c.repeat(3);
+      const bodyStart = i + 3;
+      const close = input.indexOf(delim, bodyStart);
+      let body = input.slice(bodyStart, close === -1 ? input.length : close);
+      if (body.startsWith("\r\n")) body = body.slice(2);
+      else if (body.startsWith("\n")) body = body.slice(1);
+      if (close === -1) {
+        body = body.replace(new RegExp(`${c}{1,2}$`), "");
+        out += JSON.stringify(body).slice(0, -1);
+        break;
+      }
+      body = body.replace(/\r?\n[ \t]*$/, "");
+      out += JSON.stringify(body);
+      i = close + 3;
+      continue;
+    }
+    // Copy // and # comments through untouched, so an apostrophe in one
+    // can't open a string (stripComments removes them later).
+    if (c === "#" || (c === "/" && input[i + 1] === "/")) {
+      const eol = input.indexOf("\n", i);
+      const end = eol === -1 ? input.length : eol;
+      out += input.slice(i, end);
+      i = end;
+      continue;
+    }
+    if (c === '"' || c === "'") inStr = c;
+    out += c;
+    i++;
+  }
+  return out;
+}
+
+/** Clean LLM response: strip fences, triple quotes, comments, whitespace. */
 function preprocess(input: string): string {
-  return stripComments(stripFences(input.trim())).trim();
+  return stripComments(normalizeTripleQuotes(stripFences(input.trim()))).trim();
 }
 
 /**