Pricing, context window, capabilities, and release date — pulled from each provider's public docs. Both are available via the same AIgateway OpenAI-compatible endpoint; flip the model string to switch.
Both models stream in parallel through your own AIgateway key. Tokens, latency, and cost update as they arrive.
| GPT-5.5 openai/gpt-5.5 | Inworld TTS 2 inworld/tts-2 | |
|---|---|---|
| Provider | OpenAI | Inworld |
| Family | GPT-5 | Inworld TTS |
| Modality | text | audio-tts |
| Context window | 1,000,000 tok | — |
| Max output | 16,384 tok | — |
| Released | 2026-04-24 | 2026-05-05 |
| Input price | $5.00 /1M | $0.035 /1K ch |
| Output price | $30.00 /1M | — |
| Cache read | — | — |
| Tools | yes | — |
| Streaming | yes | — |
| Vision | — | — |
| JSON mode | yes | — |
| Reasoning | yes | — |
| Prompt caching | — | — |
GPT-5.5 is OpenAI's flagship model with strong coding, reasoning, and multimodal capabilities.
Inworld's most powerful and expressive text-to-speech model. Builds on TTS 1.5 with rich expressive speech, real-time latency, natural language steering (e.g. [whisper], [say excitedly]), and stronger multilingual support across 15 production languages plus 90+ experimental languages.
# pip install aigateway-py openai
# aigateway-py: sub-accounts, evals, replays, jobs, webhook verify.
# openai SDK: chat/embeddings/images/audio — drop-in compat per our SDK's own guidance.
from openai import OpenAI
client = OpenAI(
base_url="https://api.aigateway.sh/v1",
api_key="sk-aig-...",
)
# Try GPT-5.5
client.chat.completions.create(
model="openai/gpt-5.5",
messages=[{"role":"user","content":"hello"}],
)
# Try Inworld TTS 2 — same client, same key
client.chat.completions.create(
model="inworld/tts-2",
messages=[{"role":"user","content":"hello"}],
)