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Codex Astra Comparison
A practical, step-by-step conversation that helps builders make a sound technical choice.
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A practical, step-by-step conversation that helps builders make a sound technical choice.
Codex Astra Extra High vs Ultra
In Codex with GPT-6 Astra, Extra High and Ultra use the same underlying Astra model. The difference is how aggressively Codex lets Astra work.
Astra Extra High****Astra UltraReasoningxhighMaximum reasoningMulti-agent behaviorNormal Codex workflowCan use additional agents for parallel workSpeedUsually faster and more predictableCan take longer or do substantially more workCredit usageHighPotentially much higherBest forMost serious codingExceptionally difficult, broad tasksOverthinking riskLowerHigher on straightforward tasks
Astra itself supports reasoning levels through xhigh and max. In Codex, Ultra is more than simply "think slightly harder". OpenAI says Ultra uses maximum reasoning and may run additional agents, effectively giving Codex more compute and parallel workstreams. OpenAI Developers+1
This also explains the credit difference. The per-token Astra rate doesn't change just because you choose Extra High versus Ultra, but Ultra can generate substantially more reasoning/tool/agent activity. So the task can consume more credits overall. OpenAI Help Center+1
For practical use, I'd think of them this way:
Extra High = "one very smart senior engineer working carefully."
Ultra = "give the senior engineer maximum thinking time and let them assemble a small engineering team if useful."
For the kind of work you've been doing recently, I'd use:
HTML/UI mockup from scratch: High or Extra High
Reimagine an app while preserving a business concept: Extra High
Build a complete production feature across many files: Extra High
Major architectural decision involving auth, DB, billing, agents, security: Ultra
Large unfamiliar repo where Codex must investigate before touching anything: Ultra
Extremely nasty bug with no obvious cause: Ultra
Simple layout fixes, CSS, copy, component changes: Medium or High
Repeated iterations after Astra already understands the repo: usually High
And Astra itself is already a major capability jump. OpenAI reports substantially stronger software-engineering and long-context performance than GPT-5.6 Sol, so Astra Extra High is already extremely strong. OpenAI
For your Salesrefer HTML mockup/reimagination, I would choose Astra Extra High, not Ultra. You're intentionally leaving out the backend and giving Astra room to interpret the product. Ultra probably spends computation solving a problem that isn't complicated enough to benefit from multi-agent orchestration.
I'd reserve Ultra for the later stage when you tell Codex something like: "Take this mockup and turn it into the complete production Salesrefer application, inspect the existing PartnerBird patterns where useful, implement auth/database/agents/billing, test everything, and resolve architectural decisions yourself." That's where Ultra starts earning its keep.
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