Find two seven-seat rental cars far cheaper through a reseller discount with Codex searching every membership and site

Posted

Sep 29, 2026 by Xcelerate (Hacker News)

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Last checked

Oct 19, 2026

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Method:

How we verify

Evidence: Described by posterThe person describes what happened in words, without screenshots or video.

Outcome

Xcelerate needed two rental cars that could each carry seven people for a trip to Maine, and had memberships with Avis, Hertz, Costco and Chase's travel portal; checking every combination by hand would have taken forever. They wrote a Codex prompt in 20 minutes and let it use the browser directly. It queued any CAPTCHAs for them to solve, and a sub-agent searched Reddit for other people's ways of getting good rental deals. It found a third-party Avis reseller charging $600 with a discount code, against $1,100 cheapest from Avis directly. By those quoted prices that's about $500 less for both cars (the poster calls it a $1,000 saving), and they say they wouldn't have found it without about a week of manual searching.

Agent

Codex

The source didn't share its exact prompt, so we wrote this from what it describes.

Before you start, ask me 1–3 short questions about anything important that's missing below. Keep them quick. Then do the task, checking in with me at the key points.

Goal: Find the cheapest way to rent the cars I need, using every membership and discount I have.

What I can give you (ask for whatever's missing):
- Where, pick-up and drop-off dates and times: [DETAILS]
- How many cars, and seats or luggage needed: [DETAILS]
- My memberships and cards (rental, warehouse, card portals): [DETAILS]

Rules:
- Check each rental company directly, each membership rate and each card portal, plus reputable resellers.
- Compare the full price with taxes, fees and insurance options, and the cancellation terms.
- Check any discount code is valid for these dates and cars before counting it.
- Pause for me to solve any CAPTCHA, and don't book without my OK.
- If a site asks me to sign in, pause and let me do it myself (including any CAPTCHA or two-step code); never guess or store passwords.
- Ask for my OK before you pay, book, send, submit or cancel anything.
- Check facts that can change (prices, opening hours, dates, availability, rules) against the official source, and tell me anything you couldn't verify.

Output: A table of every option with total price, terms and link, cheapest first.

You'll know it worked when: I book cars that fit everyone at the lowest real price.

Before you start, ask me 1–3 short questions about anything important that's missing below. Keep them quick. Then do the task, checking in with me at the key points.

Goal: Find the cheapest way to rent the cars I need, using every membership and discount I have.

What I can give you (ask for whatever's missing):
- Where, pick-up and drop-off dates and times: [DETAILS]
- How many cars, and seats or luggage needed: [DETAILS]
- My memberships and cards (rental, warehouse, card portals): [DETAILS]

Rules:
- Check each rental company directly, each membership rate and each card portal, plus reputable resellers.
- Compare the full price with taxes, fees and insurance options, and the cancellation terms.
- Check any discount code is valid for these dates and cars before counting it.
- Pause for me to solve any CAPTCHA, and don't book without my OK.
- If a site asks me to sign in, pause and let me do it myself (including any CAPTCHA or two-step code); never guess or store passwords.
- Ask for my OK before you pay, book, send, submit or cancel anything.
- Check facts that can change (prices, opening hours, dates, availability, rules) against the official source, and tell me anything you couldn't verify.

Output: A table of every option with total price, terms and link, cheapest first.

You'll know it worked when: I book cars that fit everyone at the lowest real price.

Before you start, ask me 1–3 short questions about anything important that's missing below. Keep them quick. Then do the task, checking in with me at the key points.

Goal: Find the cheapest way to rent the cars I need, using every membership and discount I have.

What I can give you (ask for whatever's missing):
- Where, pick-up and drop-off dates and times: [DETAILS]
- How many cars, and seats or luggage needed: [DETAILS]
- My memberships and cards (rental, warehouse, card portals): [DETAILS]

Rules:
- Check each rental company directly, each membership rate and each card portal, plus reputable resellers.
- Compare the full price with taxes, fees and insurance options, and the cancellation terms.
- Check any discount code is valid for these dates and cars before counting it.
- Pause for me to solve any CAPTCHA, and don't book without my OK.
- If a site asks me to sign in, pause and let me do it myself (including any CAPTCHA or two-step code); never guess or store passwords.
- Ask for my OK before you pay, book, send, submit or cancel anything.
- Check facts that can change (prices, opening hours, dates, availability, rules) against the official source, and tell me anything you couldn't verify.
- Check the reseller's reviews and what happens if the car class isn't available at pick-up.

Output: A table of every option with total price, terms and link, cheapest first.

You'll know it worked when: I book cars that fit everyone at the lowest real price.

Before you finish: re-read my goal and constraints, check your answer against each one, and list anything you assumed or couldn't confirm.

Source

https://news.ycombinator.com/item?id=49899460