llamaIndex - ✅(Solved) Fix [Feature Request]: Missing gpt-5.3-chat support [1 pull requests, 1 comments, 2 participants]

llamaIndex2026-03-25 23:07:03

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run-llama/llama_index#21155•Fetched 2026-04-08 01:31:21

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MilanCancarevic

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MilanCancarevic

sasmita016

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Feature Description

The gpt-5.3 model family (released by OpenAI on March 3, 2026) is missing from the model context size map in llama-index-llms-openai. This causes a ValueError when trying to use any gpt-5.3 variant

The model map in utils.py jumps from gpt-5.2 directly to gpt-5.4, skipping the entire gpt-5.3 family.

Models to add

Based on the OpenAI models page, the following gpt-5.3 models should be added:

gpt-5.3-chat-latest (128K context window)

And any other gpt-5.3 variants available (e.g. gpt-5.3, gpt-5.3-codex, etc.).

Affected file

llama-index-integrations/llms/llama-index-llms-openai/llama_index/llms/openai/utils.py

Specifically the OPENAI_REASONING_MODELS, CHAT_MODELS, and ALL_AVAILABLE_MODELS dictionaries.

Version

Tested up to llama-index-llms-openai==0.7.3 — none of the released versions include gpt-5.3.

Reason

The model context size map in utils.py skips gpt-5.3 entirely — it goes from gpt-5.2 to gpt-5.4. Any attempt to use a gpt-5.3 variant raises ValueError: Unknown model 'gpt-5.3-chat-latest'. Tested all versions up to llama-index-llms-openai==0.7.3, none include it. The only workaround is monkey-patching ALL_AVAILABLE_MODELS at runtime.

Value of Feature

GPT-5.3 Chat is a production OpenAI model available since March 3, 2026. Without it in the model map, users cannot use gpt-5.3-chat-latest or other 5.3 variants through LlamaIndex without monkey-patching. This is a simple addition to the existing model dictionaries in utils.py — the model has a 128K context window, consistent with other chat-latest variants already in the map.

extent analysis

Fix Plan

To fix the issue, we need to update the model context size map in utils.py to include the gpt-5.3 model family. Here are the steps:

Update the OPENAI_REASONING_MODELS, CHAT_MODELS, and ALL_AVAILABLE_MODELS dictionaries in llama-index-integrations/llms/llama-index-llms-openai/llama_index/llms/openai/utils.py to include the gpt-5.3 models.
Add the following models to the dictionaries:
- gpt-5.3-chat-latest with a context window of 128K
- Other gpt-5.3 variants (e.g. gpt-5.3, gpt-5.3-codex, etc.)

Example code:

OPENAI_REASONING_MODELS = {
    # ... existing models ...
    'gpt-5.3': 4096,  # default context window for gpt-5.3
    'gpt-5.3-codex': 4096,  # default context window for gpt-5.3-codex
}

CHAT_MODELS = {
    # ... existing models ...
    'gpt-5.3-chat-latest': 128000,  # context window for gpt-5.3-chat-latest
}

ALL_AVAILABLE_MODELS = {
    # ... existing models ...
    'gpt-5.3': 'gpt-5.3',
    'gpt-5.3-codex': 'gpt-5.3-codex',
    'gpt-5.3-chat-latest': 'gpt-5.3-chat-latest',
}

Verification

To verify that the fix worked, try using a gpt-5.3 variant (e.g. gpt-5.3-chat-latest) through LlamaIndex. The model should be recognized and used correctly without raising a ValueError.

Extra Tips

Make sure to update the model dictionaries in the correct file (utils.py) and commit the changes to the repository.
If you're using a version of llama-index-llms-openai older than 0.7.3, you may need to upgrade to a newer version that includes the updated model dictionaries.
You can also consider adding a test case to ensure that the gpt-5.3 models are correctly recognized and used by LlamaIndex.

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llamaIndex - ✅(Solved) Fix [Feature Request]: Missing gpt-5.3-chat support [1 pull requests, 1 comments, 2 participants]

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PR fix notes

PR #21190: feat(llama-index-integrations): add gpt-5.3 model family support to openai model mappings

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