Port a C server to Rust with one prompt and a test loop
Claude Code's creator handed Sonnet 5.5 a whole C server and the tests, then let it loop: do the job, run the tests, fix, run again. The same port with the top model took 12 hours and about twice the cost.
Source
@razeden0 on X · 2026-09-30
Written in our own words. Credit to the original author. Link checked 2026-10-22.
What they did
Claude Code's creator handed Sonnet 5.5 a whole C server and the tests, then let it loop: do the job, run the tests, fix, run again. The same port with the top model took 12 hours and about twice the cost.
Result (as claimed)
Sonnet finished in 9.5 hours for about half the cost, and both versions passed nearly all tests.
Tools they used
Cost: Claude Code: from $17/mo; Claude Sonnet 5.5: from $2 in / $10 out per 1M tokens.
Set it up
Pick a contained repo or task
Start on a branch or side project where mistakes are cheap.
Install and configure
Set up Claude Code, Claude Sonnet 5.5, Rust. Read what it can run on your machine and limit permissions where possible.
Run it on a real task
Give it a well-scoped issue and let it work. Review the diff like any pull request.
Add guardrails
Keep tests and CI in the loop, and never let an agent push to main or touch production secrets unattended.
Copy the full setup prompt
Paste into your agent and it will walk you through the setup, asking before anything that sends, posts or spends.
You are helping me set up this AI use case end to end in Claude Code. Goal: Port a C server to Rust with one prompt and a test loop What the original author did: Claude Code's creator handed Sonnet 5.5 a whole C server and the tests, then let it loop: do the job, run the tests, fix, run again. The same port with the top model took 12 hours and about twice the cost. Reported result (as claimed by the author): Sonnet finished in 9.5 hours for about half the cost, and both versions passed nearly all tests. Source: https://x.com/razeden0/status/2105271250595492168 Tools they used: Claude Code, Claude Sonnet 5.5, Rust Category: Dev & ops Please: 1. Ask me 3 short questions about my situation (accounts I have, budget, what I want the output to look like). 2. Propose a step-by-step plan using these tools or cheaper alternatives, with the time and cost of each step. Use official pricing pages; say "check pricing" if unsure. 3. Then do the setup with me one step at a time, waiting for my OK before anything that sends messages, posts publicly, spends money or deletes data. 4. Finish with a checklist to run it again next time.
You are helping me set up this AI use case end to end in Codex. Goal: Port a C server to Rust with one prompt and a test loop What the original author did: Claude Code's creator handed Sonnet 5.5 a whole C server and the tests, then let it loop: do the job, run the tests, fix, run again. The same port with the top model took 12 hours and about twice the cost. Reported result (as claimed by the author): Sonnet finished in 9.5 hours for about half the cost, and both versions passed nearly all tests. Source: https://x.com/razeden0/status/2105271250595492168 Tools they used: Claude Code, Claude Sonnet 5.5, Rust Category: Dev & ops Please: 1. Ask me 3 short questions about my situation (accounts I have, budget, what I want the output to look like). 2. Propose a step-by-step plan using these tools or cheaper alternatives, with the time and cost of each step. Use official pricing pages; say "check pricing" if unsure. 3. Then do the setup with me one step at a time, waiting for my OK before anything that sends messages, posts publicly, spends money or deletes data. 4. Finish with a checklist to run it again next time.
You are helping me set up this AI use case end to end in Grok Bot. Goal: Port a C server to Rust with one prompt and a test loop What the original author did: Claude Code's creator handed Sonnet 5.5 a whole C server and the tests, then let it loop: do the job, run the tests, fix, run again. The same port with the top model took 12 hours and about twice the cost. Reported result (as claimed by the author): Sonnet finished in 9.5 hours for about half the cost, and both versions passed nearly all tests. Source: https://x.com/razeden0/status/2105271250595492168 Tools they used: Claude Code, Claude Sonnet 5.5, Rust Category: Dev & ops Please: 1. Ask me 3 short questions about my situation (accounts I have, budget, what I want the output to look like). 2. Propose a step-by-step plan using these tools or cheaper alternatives, with the time and cost of each step. Use official pricing pages; say "check pricing" if unsure. 3. Then do the setup with me one step at a time, waiting for my OK before anything that sends messages, posts publicly, spends money or deletes data. 4. Finish with a checklist to run it again next time.
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Guides for this use case
How to vibe code an app with Claude Code · How to port code to another language with AI · How to compare AI models on the same prompt
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