From 49b4d8e58a85e518018b17ef21e51962fe10ccd8 Mon Sep 17 00:00:00 2001
From: Prathamesh Jadhav <55660103+lollinng@users.noreply.github.com>
Date: Sat, 6 Jun 2026 02:46:49 +0530
Subject: [PATCH 1/2] Emit {0,n} for at_most so the regex compiles on
 outlines-core

QuantifyMaximum (Term.at_most / at_most) compiled to (...){,n}. Python's re
accepts the lower-bound-omitted form, but the default outlines-core backend
(Rust regex-automata) does not, so any structured generation using at_most
raised 'Failed to build DFA' when the Index was built. Emit the equivalent
(...){0,n}. Updates the test that asserted the old output.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---
 outlines/types/dsl.py   | 2 +-
 tests/types/test_dsl.py | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/outlines/types/dsl.py b/outlines/types/dsl.py
index 255b8bd11..cfd9af88c 100644
--- a/outlines/types/dsl.py
+++ b/outlines/types/dsl.py
@@ -955,7 +955,7 @@ def to_regex(term: Term) -> str:
     elif isinstance(term, QuantifyMinimum):
         return f"({to_regex(term.term)}){{{term.min_count},}}"
     elif isinstance(term, QuantifyMaximum):
-        return f"({to_regex(term.term)}){{,{term.max_count}}}"
+        return f"({to_regex(term.term)}){{0,{term.max_count}}}"
     elif isinstance(term, QuantifyBetween):
         return f"({to_regex(term.term)}){{{term.min_count},{term.max_count}}}"
     else:
diff --git a/tests/types/test_dsl.py b/tests/types/test_dsl.py
index 6361b534e..3ca3d2e30 100644
--- a/tests/types/test_dsl.py
+++ b/tests/types/test_dsl.py
@@ -1118,7 +1118,7 @@ def test_to_regex():
     assert to_regex(min_term) == r"(a){2,}"
 
     max_term = QuantifyMaximum(String("a"), 5)
-    assert to_regex(max_term) == r"(a){,5}"
+    assert to_regex(max_term) == r"(a){0,5}"
 
     between_term = QuantifyBetween(String("a"), 1, 3)
     assert to_regex(between_term) == r"(a){1,3}"

From 686b4a913181220daf267be6a461f552e9292bd4 Mon Sep 17 00:00:00 2001
From: Prathamesh Jadhav <pratameshjadhav@gmail.com>
Date: Fri, 19 Jun 2026 17:33:02 +0530
Subject: [PATCH 2/2] Update test_to_regex_simple for {0,n} at_most output

The QuantifyMaximum assertion in test_to_regex.py still expected the
old (a){,2} form; align it with the (a){0,2} output.
---
 tests/types/test_to_regex.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/types/test_to_regex.py b/tests/types/test_to_regex.py
index 6f33fb6e3..8955d6a27 100644
--- a/tests/types/test_to_regex.py
+++ b/tests/types/test_to_regex.py
@@ -73,7 +73,7 @@ def test_to_regex_simple():
     assert a.matches("aaa") is True
 
     a = QuantifyMaximum(String("a"), 2)
-    assert to_regex(a) == "(a){,2}"
+    assert to_regex(a) == "(a){0,2}"
     assert a.matches("aa") is True
     assert a.matches("aaa") is False