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Large Language ModelsAI Coding AssistantsOpen-Source AIZenn AI/MLPublished: Nov 16, 2026, 04:00 JST

opencodex 2.100.2 passes Qwen2.5-32B API translation test

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3 Key Points

  1. What happened

    A Zenn writer tested opencodex 2.100.2, a local gateway that translates between Anthropic Messages, OpenAI Chat Completions, and OpenAI Responses APIs, against Qwen2.5-32B on Ollama. All three formats returned 200, streaming arrived as proper SSE events, and tool calls converted both ways.

  2. Why it matters

    The result suggests a single local gateway can let coding agents built for different API formats talk to the same self-hosted model without rework, and overhead latency was not measurable against the model's own ~6 tok/s generation speed.

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Context & Analysis

The test focused on a practical pain point for developers who use coding agents: each agent tends to expect a specific API format, while local models served through Ollama speak OpenAI-compatible endpoints. opencodex addresses this by translating requests on the fly, and the writer confirmed that translation works not just for plain text but for streaming responses and the tool-call round trips that coding agents rely on. The absence of measurable proxy latency matters because the model itself generated at only about 6 tok/s on the test hardware, leaving little room for conversion overhead to hide.

The writer also highlighted operational caveats. The official README warns that some providers, notably Anthropic, may suspend or restrict accounts that route traffic through third-party proxies, so the test used curl instead of subscription logins. The tool's startup also launches a proxy that intercepts traffic to api.anthropic.com and includes code that writes to Claude Code settings files, which is why the writer isolated the home directory during testing. A separate bug surfaced in the Anthropic-format response: the model field was replaced with "the requested model" because the validation regex rejects the colon in Ollama model names, though the response content and tool calls were unaffected.

FAQ
What is opencodex and what does it do?
opencodex is a local gateway that sits between coding agents such as OpenAI Codex and Claude Code and model providers such as Claude, Gemini, Grok, DeepSeek, or local Ollama. It converts between Anthropic Messages API, OpenAI Chat Completions API, and OpenAI Responses API formats.
Did the proxy add latency?
No. The writer measured direct Ollama requests against requests through opencodex three times each and found the difference within normal variance. The 32B model's own generation speed of about 6 tok/s made the conversion cost negligible.
What quirk was found with Anthropic-format responses?
The model field in Anthropic-format responses was replaced with the string "the requested model" because opencodex validates model names with a regex that does not allow colons, and Ollama model names use the name:tag format. Using a colon-free alias like qwen32b returned the model name as expected.
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