feat: add GPT-5.3-Codex model for GitHub Copilot provider

[emvnuel]

Summary

• Add GPT-5.3-Codex model configuration for the GitHub Copilot provider
• Model is accessible via VS Code through GitHub Copilot

Model Details

Field	Value
Name	GPT-5.3-Codex
Family	gpt-codex
Vendor	OpenAI
Context Window	400,000 tokens
Max Output	128,000 tokens
Max Prompt	272,000 tokens
Tokenizer	o200k_base
Category	Powerful
Preview	No

Capabilities

• Reasoning
• Tool calls (parallel)
• Structured outputs
• Vision (JPEG, PNG, WebP, GIF — max 3MB, 1 image)
• Streaming

Source

{
  "capabilities": {
    "family": "gpt-5.3-codex",
    "limits": {
      "max_context_window_tokens": 400000,
      "max_output_tokens": 128000,
      "max_prompt_tokens": 272000,
      "vision": {
        "max_prompt_image_size": 3145728,
        "max_prompt_images": 1,
        "supported_media_types": [
          "image/jpeg",
          "image/png",
          "image/webp",
          "image/gif"
        ]
      }
    },
    "object": "model_capabilities",
    "supports": {
      "parallel_tool_calls": true,
      "streaming": true,
      "structured_outputs": true,
      "tool_calls": true,
      "vision": true
    },
    "tokenizer": "o200k_base",
    "type": "chat"
  },
  "id": "gpt-5.3-codex",
  "model_picker_category": "powerful",
  "model_picker_enabled": true,
  "name": "GPT-5.3-Codex",
  "object": "model",
  "policy": {
    "state": "enabled",
    "terms": "Enable access to the latest GPT-5.3-Codex model from OpenAI. [Learn more about how GitHub Copilot serves GPT-5.3-Codex](https://gh.io/copilot-openai)."
  },
  "preview": false,
  "supported_endpoints": [
    "/responses"
  ],
  "vendor": "OpenAI",
  "version": "gpt-5.3-codex"
}

[Copilot]

Pull request overview

This PR adds configuration for the new GPT-5.3-Codex model to the GitHub Copilot provider. The model is part of OpenAI's GPT Codex family and is designed for code generation with enhanced capabilities including reasoning, tool calls, structured outputs, and vision support.

Changes:

• Add TOML configuration file for GPT-5.3-Codex model with specifications including 400K token context window, 128K max output, zero-cost pricing, and multi-modal support (text and image inputs)

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💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Missing 'knowledge' field that is present in almost all other GitHub Copilot model configurations. This field specifies the knowledge cutoff date for the model's training data and should be added for consistency. For reference, gpt-5.2-codex has 'knowledge = "2025-08-31"' and gpt-5.1-codex has 'knowledge = "2024-09-30"'. The field should be placed between the 'temperature' and 'tool_call' fields following the established convention.

Suggested change

	temperature = false
	temperature = false
	knowledge = "2026-02-05"

[rekram1-node]

Not yet supported in opencode app (this is the 3rd or 4th pr at this point so if u wanna know why please read one of the closed ones)

[emvnuel]

sry