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fix: map gpt-5.1 model names to o200k_base #582

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fix: map gpt-5.1 model names to o200k_base #582

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3 changes: 3 additions & 0 deletions tests/test_misc.py
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,9 @@ def test_encoding_for_model():
assert enc.name == "o200k_base"
enc = tiktoken.encoding_for_model("gpt-oss-120b")
assert enc.name == "o200k_harmony"
# gpt-5.1 uses a dotted name and must not require a hyphenated prefix match
assert tiktoken.model.encoding_name_for_model("gpt-5.1") == "o200k_base"
assert tiktoken.model.encoding_name_for_model("gpt-5.1-2025-11-13") == "o200k_base"


def test_optional_blobfile_dependency():
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4 changes: 4 additions & 0 deletions tiktoken/model.py
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Expand Up @@ -9,6 +9,9 @@
"o3-": "o200k_base",
"o4-mini-": "o200k_base",
# chat
# gpt-5.1 / gpt-5.2 style names use a dot, not a hyphen, so they do not
# match the "gpt-5-" prefix used for dated gpt-5-* snapshots.
"gpt-5.": "o200k_base",
"gpt-5-": "o200k_base",
"gpt-4.5-": "o200k_base",
"gpt-4.1-": "o200k_base",
Expand All @@ -33,6 +36,7 @@
"o4-mini": "o200k_base",
# chat
"gpt-5": "o200k_base",
"gpt-5.1": "o200k_base",
"gpt-4.1": "o200k_base",
"gpt-4o": "o200k_base",
"gpt-4": "cl100k_base",
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