--- title: Can ChatGPT, Copilot & Claude Beat an Expert Developer? description: A developer tests OpenAI's Codex coding agent (using the newly released GPT-5.3 model) against a real C#/Avalonia desktop application, giving it the same basic... canonical: https://daily.dev/posts/can-chatgpt-copilot-claude-beat-an-expert-developer--jsmsnq2xb twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Can ChatGPT, Copilot & Claude Beat an Expert Developer? | daily.dev og:description: A developer tests OpenAI's Codex coding agent (using the newly released GPT-5.3 model) against a real C#/Avalonia desktop application, giving it the same basic... og:url: https://daily.dev/posts/can-chatgpt-copilot-claude-beat-an-expert-developer--jsmsnq2xb og:image: https://api.daily.dev/og/posts/jsMsNq2XB.png og:image:alt: Can ChatGPT, Copilot & Claude Beat an Expert Developer? og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Can ChatGPT, Copilot & Claude Beat an Expert Developer? **[AngelSix](https://daily.dev/sources/angelsix)** · 29 min read · 0 upvotes · 0 comments ## Summary A developer tests OpenAI's Codex coding agent (using the newly released GPT-5.3 model) against a real C#/Avalonia desktop application, giving it the same basic feature-implementation tasks previously given to Cursor and other AI tools. The agent struggles repeatedly with build failures tied to sandboxed network access (Avalonia telemetry blocked by Codex's sandbox), wasting several minutes per task. Code quality is mixed: functional but riddled with duplicated logic, unnecessary double-checks, missing case-insensitive file handling, and no exception handling. The reviewer scores individual features between 6 and 9 out of 10, concludes Codex and Cursor are currently the best of the AI tools tested so far, but maintains that none produce code a competent developer would commit as-is, with Claude still to be evaluated next. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### Does OpenAI Codex use the GPT-5.3 model now? Yes, Codex received a major update shortly before this testing that switched it to a new GPT-5.3 model, alongside efforts to make the Codex app build and respond faster than relying on the VS Code extension alone. _Developers tracking which model powers their coding agent can follow updates like this on daily.dev._ ### Why does OpenAI Codex keep failing to build an Avalonia desktop app project? Builds repeatedly hang and fail because the Codex sandbox blocks outbound network access needed for NuGet package restore and Avalonia telemetry calls, causing multi-minute delays on every single task before the agent gives up or retries with reduced functionality. _Anyone debugging sandboxed AI agent build failures can compare notes on daily.dev._ ### What are the subscription prices for OpenAI Codex? Codex is priced with a Plus tier at 20 dollars a month and a Pro tier at 200 dollars a month; heavy real-world daily use was reported to exhaust the Plus tier's allowance quickly, while the Pro tier held up better but still came close to its limit under daily professional use. _Developers weighing AI coding tool costs against usage limits can track pricing comparisons on daily.dev._ ## Similar posts on daily.dev - [Codex is now the recommended agent in JetBrains IDEs](https://daily.dev/posts/codex-is-now-the-recommended-agent-in-jetbrains-ides-q3gxvk24g) · JetBrains · 1 upvotes · 0 comments --- Tags: [#ai-coding](https://daily.dev/tags/ai-coding), [#vscode](https://daily.dev/tags/vscode), [#code-review](https://daily.dev/tags/code-review), [#openai-codex](https://daily.dev/tags/openai-codex), [#avalonia](https://daily.dev/tags/avalonia) [View this post on daily.dev](https://daily.dev/posts/can-chatgpt-copilot-claude-beat-an-expert-developer--jsmsnq2xb) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Can ChatGPT, Copilot & Claude Beat an Expert Developer?","url":"https://daily.dev/posts/can-chatgpt-copilot-claude-beat-an-expert-developer--jsmsnq2xb","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/can-chatgpt-copilot-claude-beat-an-expert-developer--jsmsnq2xb"},"datePublished":"2026-10-04T13:04:28.452Z","dateModified":"2026-10-04T13:06:28.813Z","description":"A developer tests OpenAI's Codex coding agent (using the newly released GPT-5.3 model) against a real C#/Avalonia desktop application, giving it the same basic...","image":"https://i.ytimg.com/vi/DK7ZmFronxo/sddefault.jpg","thumbnailUrl":"https://i.ytimg.com/vi/DK7ZmFronxo/sddefault.jpg","isAccessibleForFree":true,"articleSection":"AngelSix","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"AngelSix","logo":"https://media.daily.dev/image/upload/s--h1ikmN_u--/f_auto,q_auto/v1791119063/logos/angelsix?_a=BAMAMicg0","url":"https://daily.dev/sources/angelsix"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/can-chatgpt-copilot-claude-beat-an-expert-developer--jsmsnq2xb","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"ai-coding,vscode,code-review,openai-codex,avalonia","timeRequired":"PT29M","video":{"@type":"VideoObject","name":"Can ChatGPT, Copilot & Claude Beat an Expert Developer?","description":"A developer tests OpenAI's Codex coding agent (using the newly released GPT-5.3 model) against a real C#/Avalonia desktop application, giving it the same basic...","thumbnailUrl":"https://i.ytimg.com/vi/DK7ZmFronxo/sddefault.jpg","uploadDate":"2026-10-04T13:04:28.452Z","duration":"PT29M","url":"https://api.daily.dev/r/jsMsNq2XB","embedUrl":"https://www.youtube.com/embed/DK7ZmFronxo"}} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"AngelSix","item":"https://daily.dev/sources/angelsix"},{"@type":"ListItem","position":3,"name":"Can ChatGPT, Copilot & Claude Beat an Expert Developer?"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/can-chatgpt-copilot-claude-beat-an-expert-developer--jsmsnq2xb#faq","mainEntity":[{"@type":"Question","name":"Does OpenAI Codex use the GPT-5.3 model now?","acceptedAnswer":{"@type":"Answer","text":"Yes, Codex received a major update shortly before this testing that switched it to a new GPT-5.3 model, alongside efforts to make the Codex app build and respond faster than relying on the VS Code extension alone. 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