Aider vs OpenAI Codex
Aider vs OpenAI Codex (Coding Agents (CLI & Cloud)). Agent test scores: Aider 9.3/10, OpenAI Codex 7.4/10. Aider scored 1.9 higher overall in our separate rubric v0.1 tests (editions and tasks can differ — see Edition tested and the notes below). Pricing: Aider — Free open source (Apache 2.0); pay your LLM provider; OpenAI Codex — Included in every ChatGPT plan (Free, Go, Plus, Pro, Business, Enterprise, Edu); usage limits vary by plan. Codex Cloud needs Plus, Pro, Business, Enterprise or Edu. Plus/Pro buyers can add credits. Plan prices on chatgpt.com/pricing.
Every fact on this page comes from our tool records and test logs. Last updated:
- VibeToolRank score
- 9.3/10
- Last tested
- 2026-10-16
- Runs
- 3 runs
- Outcome score
- 9/10
- Edition tested
- Aider 0.86.2 CLI with OpenRouter free model cohere/north-mini-code:free
- Free plan, as measured
- About 1.0K tokens sent and 1.3K received per bugfix run, $0 on a free OpenRouter model
- Free plan
- Yes: free tool, BYO API key or local models
- Price
- Free open source (Apache 2.0); pay your LLM provider
- Pricing checked
- 2026-10-16
- VibeToolRank score
- 7.4/10
- Last tested
- 2026-10-16
- Runs
- 3 runs
- Outcome score
- 8/10
- Edition tested
- Codex CLI 0.163.0 with OpenRouter free model cohere/north-mini-code:free (no ChatGPT login; not OpenAI's models)
- Free plan, as measured
- 33K–262K tokens per bugfix run on a free OpenRouter model, $0
- Free plan
- Yes: Codex CLI, IDE extension and app on ChatGPT Free and Go with plan usage limits (no Codex Cloud)
- Price
- Included in every ChatGPT plan (Free, Go, Plus, Pro, Business, Enterprise, Edu); usage limits vary by plan. Codex Cloud needs Plus, Pro, Business, Enterprise or Edu. Plus/Pro buyers can add credits. Plan prices on chatgpt.com/pricing
- Pricing checked
- 2026-11-02
Side by side
| Field | Aider | OpenAI Codex |
|---|---|---|
| What it is | AiderOpen-source AI pair programming in the terminal. | OpenAI CodexOpenAI's coding agent for CLI, IDE and cloud. |
| Pricing | AiderFree open source (Apache 2.0); pay your LLM provider | OpenAI CodexIncluded in every ChatGPT plan (Free, Go, Plus, Pro, Business, Enterprise, Edu); usage limits vary by plan. Codex Cloud needs Plus, Pro, Business, Enterprise or Edu. Plus/Pro buyers can add credits. Plan prices on chatgpt.com/pricing |
| Free tier | AiderYes: free tool, BYO API key or local models | OpenAI CodexYes: Codex CLI, IDE extension and app on ChatGPT Free and Go with plan usage limits (no Codex Cloud) |
| Pricing verified | Aider2026-10-16 | OpenAI Codex2026-11-02 |
| Edition tested | AiderAider 0.86.2 CLI with OpenRouter free model cohere/north-mini-code:free | OpenAI CodexCodex CLI 0.163.0 with OpenRouter free model cohere/north-mini-code:free (no ChatGPT login; not OpenAI's models) |
| Tested on | Aider2026-10-16 | OpenAI Codex2026-10-16 |
| Outcome score | Aider9 | OpenAI Codex8 |
| Speed score | Aider10 | OpenAI Codex8 |
| Cost score | Aider10 | OpenAI Codex9 |
| Developer experience score | Aider8 | OpenAI Codex6 |
| Reliability score | Aider10 | OpenAI Codex5 |
| Overall score | Aider9.3 | OpenAI Codex7.4 |
What our tests found
Aider
3/3 runs fixed our seeded cart bug (4/4 tests pass) in 9-13s with a free OpenRouter model, without touching the test file. Install needed uv because pip was blocked on the system Python.CLI, free model
- Fixed the seeded bug correctly in 3 of 3 runs, in 9-13 seconds
- Works with free OpenRouter models, so our test cost $0
- Built-in --auto-test loop runs your tests after each edit
- pip install was refused on Debian's system Python; we needed uv
- Unattended runs need several flags (--yes-always, --message, --test-cmd)
- Free model slugs change; one we tried returned 'unavailable for free'
Who it’s for: Terminal-first developers who want an open-source pair programmer that works with any model, including free ones.
OpenAI Codex
Using a custom OpenRouter provider and a small free model, Codex CLI fixed our seeded cart bug in 2 of 3 runs (19-76s). In the failed run the model issued an apply_patch call that Codex rejected. Token use was high (33K-262K). Not tested with OpenAI's own models.CLI, free model
- Runs without a ChatGPT login through any Responses-compatible provider
- Fixed the bug in 2 of 3 runs on a free model at $0
- Sandboxed workspace-write mode for unattended runs
- With a free model, 1 of 3 runs failed on an unsupported apply_patch call
- Used 33K-262K tokens per run, versus about 2K for Aider
- Flags change between versions (--full-auto removed) and the chat wire API is no longer supported
- Our test did not use OpenAI's own models
- Codex cloud (the web agent) needs ChatGPT Plus, Pro or Business; the Go plan redirects to an upgrade (2026-10-16)
Who it’s for: Developers in the OpenAI ecosystem who want a terminal agent; it works best with OpenAI models via a ChatGPT plan or API key.
Verdict
Scores use rubric v0.1 from separate runs. Editions and tasks can differ (see Edition tested and What our tests found); some tests were a single run, which caps reliability scores. Overall: Aider 9.3, OpenAI Codex 7.4. Check the free-tier limits above against your project before choosing.
FAQ
Which is better, Aider or OpenAI Codex?
In our tests Aider scored higher overall (9.3/10 vs 7.4/10). Scores use the same rubric (v0.1) but came from separate runs; editions and tasks may differ (see Edition tested and test summaries), so check the per-dimension scores for what matters to you.
Is Aider free?
Yes: free tool, BYO API key or local models (pricing checked 2026-10-16).
Is OpenAI Codex free?
Yes: Codex CLI, IDE extension and app on ChatGPT Free and Go with plan usage limits (no Codex Cloud) (pricing checked 2026-11-02).
How much does Aider cost compared with OpenAI Codex?
Aider: Free open source (Apache 2.0); pay your LLM provider. OpenAI Codex: Included in every ChatGPT plan (Free, Go, Plus, Pro, Business, Enterprise, Edu); usage limits vary by plan. Codex Cloud needs Plus, Pro, Business, Enterprise or Edu. Plus/Pro buyers can add credits. Plan prices on chatgpt.com/pricing.
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Scores come from our own tests and are never for sale; sponsored placements are always labelled. Some links are affiliate links (currently Railway). Disclosure