From ae1c9418b52eb0366118ccb564cf5b753bd1089b Mon Sep 17 00:00:00 2001
From: Mason Daugherty <mason@langchain.dev>
Date: Wed, 17 Jun 2026 16:29:08 -0400
Subject: [PATCH] fix(langchain): detect provider strategy for dated
 `gpt-5.2`/`gpt-5.4` snapshots (#38222)
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Closes #38220

---

Users calling `create_agent(..., response_format=<schema>)` with an
OpenAI model pinned to a dated snapshot (e.g. `gpt-5.4-2026-03-05`) were
silently downgraded from native structured output (`ProviderStrategy`)
to tool-calling (`ToolStrategy`). This changes runtime behavior: extra
tool-call traces, different token usage, and no provider-side schema
enforcement.

The cause is in `_supports_provider_strategy`'s fallback patterns: the
`gpt-5.2` and `gpt-5.4` base patterns terminated with `($|[/:])`, which
— unlike their sibling families — rejected a trailing `-`, so OpenAI's
`-YYYY-MM-DD` dated-snapshot suffix matched none of the patterns. The
base patterns were deliberately strict to keep
`gpt-5.2-pro`/`gpt-5.4-pro` blocked, so rather than allowing any
trailing `-` (which would re-admit those `-pro` variants) this change
adds an optional dated-snapshot group `(-\d{4}-\d{2}-\d{2})?`. Dated
snapshots now resolve to `ProviderStrategy` while `-pro` variants stay
blocked.

Made by [Open
SWE](https://openswe.vercel.app/agents/c5ebcb29-8ce5-dda0-73f6-198e49f0c36c)

Co-authored-by: open-swe[bot] <open-swe@users.noreply.github.com>
---
 libs/langchain_v1/langchain/agents/factory.py             | 4 ++--
 .../tests/unit_tests/agents/test_response_format.py       | 2 ++
 libs/langchain_v1/uv.lock                                 | 8 ++++----
 3 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/libs/langchain_v1/langchain/agents/factory.py b/libs/langchain_v1/langchain/agents/factory.py
index 795dad15a30..be891cfafd4 100644
--- a/libs/langchain_v1/langchain/agents/factory.py
+++ b/libs/langchain_v1/langchain/agents/factory.py
@@ -158,10 +158,10 @@ FALLBACK_MODELS_WITH_STRUCTURED_OUTPUT = [
     r"(^|[/:.])gpt-4o($|[-/:])",
     r"(^|[/:.])gpt-5($|[-/:])",
     r"(^|[/:.])gpt-5\.1($|[-/:])",
-    r"(^|[/:.])gpt-5\.2($|[/:])",
+    r"(^|[/:.])gpt-5\.2(-\d{4}-\d{2}-\d{2})?($|[/:])",
     r"(^|[/:.])gpt-5\.2-(chat|codex)($|[-/:])",
     r"(^|[/:.])gpt-5\.3($|[-/:])",
-    r"(^|[/:.])gpt-5\.4($|[/:])",
+    r"(^|[/:.])gpt-5\.4(-\d{4}-\d{2}-\d{2})?($|[/:])",
     r"(^|[/:.])gpt-5\.4-(mini|nano)($|[-/:])",
     r"(^|[/:.])gpt-5\.5($|[-/:])",
     r"(^|[/:.])claude-(fable|mythos)-5(?:-\d{8})?(?:-v\d(?::\d)?)?($|[/:])",
diff --git a/libs/langchain_v1/tests/unit_tests/agents/test_response_format.py b/libs/langchain_v1/tests/unit_tests/agents/test_response_format.py
index f2c237f0cf6..05358887887 100644
--- a/libs/langchain_v1/tests/unit_tests/agents/test_response_format.py
+++ b/libs/langchain_v1/tests/unit_tests/agents/test_response_format.py
@@ -953,11 +953,13 @@ class TestSupportsProviderStrategy:
             "gpt-5.1",
             "gpt-5.1-codex",
             "gpt-5.2",
+            "gpt-5.2-2025-12-01",
             "gpt-5.2-chat-latest",
             "gpt-5.2-codex",
             "gpt-5.3",
             "gpt-5.3-codex-spark",
             "gpt-5.4",
+            "gpt-5.4-2026-03-05",
             "gpt-5.4-mini",
             "gpt-5.4-nano",
             "gpt-5.5-pro",
diff --git a/libs/langchain_v1/uv.lock b/libs/langchain_v1/uv.lock
index 6a657f1ef6c..10a2c2b992e 100644
--- a/libs/langchain_v1/uv.lock
+++ b/libs/langchain_v1/uv.lock
@@ -2276,7 +2276,7 @@ dependencies = [
 [package.metadata]
 requires-dist = [
     { name = "jsonpatch", specifier = ">=1.33.0,<2.0.0" },
-    { name = "langchain-protocol", specifier = ">=0.0.14" },
+    { name = "langchain-protocol", specifier = ">=0.0.17" },
     { name = "langsmith", specifier = ">=0.3.45,<1.0.0" },
     { name = "packaging", specifier = ">=23.2.0" },
     { name = "pydantic", specifier = ">=2.7.4,<3.0.0" },
@@ -2505,14 +2505,14 @@ wheels = [
 
 [[package]]
 name = "langchain-protocol"
-version = "0.0.15"
+version = "0.0.17"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
     { name = "typing-extensions" },
 ]
-sdist = { url = "https://files.pythonhosted.org/packages/4f/24/9777489d6fbbee64af0c8f96d4f840239c408cf694f3394672807dafc490/langchain_protocol-0.0.15.tar.gz", hash = "sha256:9ab2d11ee73944754f10e037e717098d3a6796f0e58afa9cadda6154e7655ade", size = 5862, upload-time = "2026-05-01T22:30:04.748Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/44/b3/4e2429876c7a35585618caa2b9f9089f7162a6b50562b614ad82ac11c17e/langchain_protocol-0.0.17.tar.gz", hash = "sha256:e7cbe58c205df4b4fd87dc6d5bb23f10e13b236d0e2e1b0b9d05bc2b648f3eea", size = 6026, upload-time = "2026-06-12T18:39:51.923Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/1d/7a/9c97a7b9cbe4c5dc6a44cdb1545450c28f0c8ce89b9c1f0ee7fbad896263/langchain_protocol-0.0.15-py3-none-any.whl", hash = "sha256:461eb794358f83d5e42635a5797799ffec7b4702314e34edf73ac21e75d3ef79", size = 6982, upload-time = "2026-05-01T22:30:03.877Z" },
+    { url = "https://files.pythonhosted.org/packages/13/0a/a1bfe72c6ec856e99773bbd96c8086421e554b3693d0142b9ea009c6ac92/langchain_protocol-0.0.17-py3-none-any.whl", hash = "sha256:982a08fe152586ed10d4ff3d538c2e0b5766e5f307cdea325e10be3f2c17cae6", size = 7096, upload-time = "2026-06-12T18:39:50.973Z" },
 ]
 
 [[package]]