From 895acb9f4e7bdc0cd4994b6efa70a26b5f845e22 Mon Sep 17 00:00:00 2001
From: Kevin Lin <klin5061@gmail.com>
Date: Tue, 24 Feb 2026 14:56:56 -0800
Subject: [PATCH] feat(core): add gpt-5.3-codex model support (#9628)
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* feat(core): add gpt-5.3-codex model support

Add OpenAI gpt-5.3-codex model: context window overrides, model pricing
and capabilities, none-reasoning-effort support, and test config.

🐾 Generated with [Letta Code](https://letta.com)

Co-Authored-By: Letta <noreply@letta.com>

* just stage-api && just publish-api

---------

Co-authored-by: Letta <noreply@letta.com>
---
 fern/openapi.json                             | 12 ++++-----
 letta/constants.py                            |  2 ++
 letta/llm_api/openai_client.py                |  2 +-
 .../model_prices_and_context_window.json      | 26 +++++++++++++++++++
 .../openai-gpt-5.3-codex.json                 |  8 ++++++
 5 files changed, 43 insertions(+), 7 deletions(-)
 create mode 100644 tests/configs/llm_model_configs/openai-gpt-5.3-codex.json

diff --git a/fern/openapi.json b/fern/openapi.json
index e51cc200..90182718 100644
--- a/fern/openapi.json
+++ b/fern/openapi.json
@@ -29104,7 +29104,7 @@
             "type": "integer",
             "title": "Limit",
             "description": "Character limit of the block.",
-            "default": 20000
+            "default": 100000
           },
           "project_id": {
             "anyOf": [
@@ -29317,7 +29317,7 @@
             "type": "integer",
             "title": "Limit",
             "description": "Character limit of the block.",
-            "default": 20000
+            "default": 100000
           },
           "project_id": {
             "anyOf": [
@@ -29535,7 +29535,7 @@
             "type": "integer",
             "title": "Limit",
             "description": "Character limit of the block.",
-            "default": 20000
+            "default": 100000
           },
           "project_id": {
             "anyOf": [
@@ -33178,7 +33178,7 @@
             "type": "integer",
             "title": "Limit",
             "description": "Character limit of the block.",
-            "default": 20000
+            "default": 100000
           },
           "project_id": {
             "anyOf": [
@@ -34592,7 +34592,7 @@
             "type": "integer",
             "title": "Limit",
             "description": "Character limit of the block.",
-            "default": 20000
+            "default": 100000
           },
           "project_id": {
             "anyOf": [
@@ -37733,7 +37733,7 @@
             "type": "integer",
             "title": "Limit",
             "description": "Character limit of the block.",
-            "default": 20000
+            "default": 100000
           },
           "project_id": {
             "anyOf": [
diff --git a/letta/constants.py b/letta/constants.py
index 0abe94a8..0276ea1a 100644
--- a/letta/constants.py
+++ b/letta/constants.py
@@ -278,6 +278,8 @@ LLM_MAX_CONTEXT_WINDOW = {
     "gpt-5.2-pro": 272000,
     "gpt-5.2-pro-2025-12-11": 272000,
     "gpt-5.2-codex": 272000,
+    # gpt-5.3
+    "gpt-5.3-codex": 272000,
     # reasoners
     "o1": 200000,
     # "o1-pro": 200000,  # responses API only
diff --git a/letta/llm_api/openai_client.py b/letta/llm_api/openai_client.py
index 0367072f..8eabfa27 100644
--- a/letta/llm_api/openai_client.py
+++ b/letta/llm_api/openai_client.py
@@ -88,7 +88,7 @@ def supports_none_reasoning_effort(model: str) -> bool:
 
     Currently, GPT-5.1 and GPT-5.2 models support the 'none' reasoning effort level.
     """
-    return model.startswith("gpt-5.1") or model.startswith("gpt-5.2")
+    return model.startswith("gpt-5.1") or model.startswith("gpt-5.2") or model.startswith("gpt-5.3")
 
 
 def is_openai_5_model(model: str) -> bool:
diff --git a/letta/model_specs/model_prices_and_context_window.json b/letta/model_specs/model_prices_and_context_window.json
index 2ce2e366..e932d734 100644
--- a/letta/model_specs/model_prices_and_context_window.json
+++ b/letta/model_specs/model_prices_and_context_window.json
@@ -17295,6 +17295,32 @@
     "supports_tool_choice": true,
     "supports_vision": true
   },
+  "gpt-5.3-codex": {
+    "cache_read_input_token_cost": 1.75e-7,
+    "cache_read_input_token_cost_priority": 3.5e-7,
+    "input_cost_per_token": 1.75e-6,
+    "input_cost_per_token_priority": 3.5e-6,
+    "litellm_provider": "openai",
+    "max_input_tokens": 272000,
+    "max_output_tokens": 128000,
+    "max_tokens": 128000,
+    "mode": "responses",
+    "output_cost_per_token": 1.4e-5,
+    "output_cost_per_token_priority": 2.8e-5,
+    "supported_endpoints": ["/v1/responses"],
+    "supported_modalities": ["text", "image"],
+    "supported_output_modalities": ["text"],
+    "supports_function_calling": true,
+    "supports_native_streaming": true,
+    "supports_parallel_function_calling": true,
+    "supports_pdf_input": true,
+    "supports_prompt_caching": true,
+    "supports_reasoning": true,
+    "supports_response_schema": true,
+    "supports_system_messages": false,
+    "supports_tool_choice": true,
+    "supports_vision": true
+  },
   "gpt-5-mini": {
     "cache_read_input_token_cost": 2.5e-8,
     "cache_read_input_token_cost_flex": 1.25e-8,
diff --git a/tests/configs/llm_model_configs/openai-gpt-5.3-codex.json b/tests/configs/llm_model_configs/openai-gpt-5.3-codex.json
new file mode 100644
index 00000000..3ade6e2f
--- /dev/null
+++ b/tests/configs/llm_model_configs/openai-gpt-5.3-codex.json
@@ -0,0 +1,8 @@
+{
+  "context_window": 32000,
+  "model": "gpt-5.3-codex",
+  "model_endpoint_type": "openai",
+  "model_endpoint": "https://api.openai.com/v1",
+  "model_wrapper": null,
+  "reasoning_effort": "low"
+}