Claude Code and OpenAI Codex compared: public evidence
Informational only. Scores summarize cited public evidence under published rules; they are not a guarantee, endorsement, certification or ranking of quality.
Data as of 2026-10-20 (Scoring rules v0.1); entries last reviewed 2026-10-17. Generated from agents.json; values match each entry page.
Scope of each entry
Read the scope before comparing: entries cover different products, versions and modes.
- Claude Code (Anthropic): The Claude Code agent (CLI and headless mode), versions 1.0 to 2.1.x (latest 2.1.302, 16 Oct 2026). Claude models used in other scaffolds, the Claude Agent SDK, Claude Desktop/Cowork and Claude Research (a separate entry) are not covered. Several studies ran Claude Code with non-Anthropic models.
- OpenAI Codex (CLI and cloud agent): The Codex agent products launched from April 2025: Codex CLI (including headless exec), the IDE extension and desktop app, and the cloud Codex agent that opens pull requests, through Codex CLI rust-v0.163.0 (15 October 2026). The 2021 Codex model behind early GitHub Copilot, and GPT-Codex models run inside other harnesses, are not covered.
- The two entries cover different products: the OpenAI Codex entry includes the cloud agent that opens pull requests as well as the CLI, IDE extension and desktop app; the Claude Code entry covers the CLI and headless mode only. Read each scope before comparing.
- Both entries combine many versions and the models each tool used at the time of each study.
Scores and evidence
Listed alphabetically within each group, not by score. Factor scores are 0–100; see the methodology for weights and evidence grades.
| Agent | Overall score | Evidence grade | Completion | Disputes | Adherence | Evidence quality | Counted sources (peer-reviewed) | Last reviewed |
|---|---|---|---|---|---|---|---|---|
| Claude Code (Anthropic) | 55 | A | 50 | 45 | 40 | 85 | 17 (6) | |
| OpenAI Codex (CLI and cloud agent) | 62 | A | 60 | 55 | 45 | 85 | 26 (5) |
What the evidence does and doesn’t show
- Scores summarize the counted independent sources for each entry; they are not production outcomes and are not a ranking of quality.
- Entries are reviewed separately, with different sources and dates; a higher overall score does not mean one agent is better for a given task.
Claude Code (Anthropic)
17 counted independent performance sources (6 peer-reviewed). Noted uncertainties from the entry page:
- Most counted studies do not state the Claude Code version; Claude Code updates several times a week.
- Many runs use non-default models (Kimi, DeepSeek, GLM) or disabled permission prompts, so results may not reflect a typical setup.
OpenAI Codex (CLI and cloud agent)
26 counted independent performance sources (5 peer-reviewed). Noted uncertainties from the entry page:
- Citation check incomplete — recheck later. Figures not yet extracted for BeyondSWE (v0.118.0), PostTrainBench, Re-Evaluating EVMBench, ProcCtrlBench, DeepSWE and Act As a Real Researcher; the batch citation search was not fully screened.
- Scope: the entry combines the CLI and the cloud agent. Pull-request field studies cover the cloud agent; most benchmarks cover the CLI.
Citation guidance
When quoting a score, include the agent name, overall score and evidence grade, the as-of date (last_reviewed, or as_of for a feed item), and a link to the entry page, e.g. "Aider (open-source): 52/100, evidence grade A, as of 2026-10-17 (Agent Reputation & Trust Clearinghouse, CC BY 4.0, https://www.agentclearinghouse.org/agents/aider.html)". Say that the score is informational and not a guarantee, endorsement, certification or ranking. Do not present directory or feed order as a ranking. More examples: https://www.agentclearinghouse.org/citing.html
More
- Methodology (factors, weights, evidence grades)
- Changelog and update feed
- For agents / data (JSON, CSV, license)