A $5 Coding Agent Memory File Can Cost More

Memory files can make a coding agent feel much smarter. A short file can explain your project structure, test commands, naming rules, and decisions that would otherwise need repeating in every session. On a tiny budget, though, memory is also a recurring input cost. The same instructions may be read again and again, and some relays charge for both cache reads and cache writes.

01 / Start with a $5 budget and one useful memory file

Choose a hard spending limit before you write project instructions. A $5 limit is concrete enough for a beginner to monitor. It also changes the design: your memory file should answer questions the agent frequently asks, rather than document every detail about the repository.

Create one file in the project root, using the filename your coding agent supports. Keep the first version between 300 and 600 words. Include four items:

• ■ The command that installs dependencies.
• ■ The commands for unit tests, formatting, and type checks.
• ■ The main folders and the purpose of each.
• ■ Rules that could cause unwanted changes, such as generated files or migration policies.

Write instructions as commands with a reason. “Run the focused test before changing the API” is more useful than “Be careful with tests.” The goal is to reduce repeated explanation while keeping the file cheap to send.

02 / Separate stable facts from temporary conversation

A memory file should contain facts that remain useful across many sessions. Repository commands, supported runtimes, and review rules belong there. A half-finished debugging theory, a list of yesterday’s failed guesses, or a detailed task plan usually belongs in the conversation instead.

This distinction controls cost. A permanent file is likely to be included in many requests. If it grows by 1,000 tokens and the agent reads it in 20 requests, that is up to 20,000 additional input tokens before counting your code, prompt, and response. The exact bill depends on the provider and route, so treat this as a usage calculation, not a price promise.

03 / Understand cache billing before assuming memory is free

Caching can reduce repeated processing, but it does not automatically mean zero cost. CheapRelay bills per real token, including cache reads and cache writes. That means a large memory file can remain a line item even when the system reuses cached context.

For a small budget, inspect usage after a few sessions. Look for input tokens, output tokens, cache writes, and cache reads. If the memory file is responsible for a large share of input activity, shorten it. Remove duplicated explanations, examples that no longer match the code, and instructions the agent can infer from the repository.

04 / Use a two-layer memory file when the project grows

Once the project needs more documentation, keep a small always-used file and move detailed material into separate files. The small file can point the agent toward architecture notes, release procedures, or database guidance only when those subjects matter.

This gives you a simple cost control: every request carries the compact rules, while specialized context appears on demand. Do not add links or references that the agent cannot access. A pointer to a missing file creates another turn and may cost more than the original documentation.

05 / Test memory with the same task twice

Run one ordinary task without the memory file, then repeat a similar task with it. Record three numbers: total tokens, number of agent turns, and final bill. The memory file is helping if it reduces clarification turns or prevents wrong edits enough to justify its repeated input cost.

If the second run uses more tokens and produces no clearer result, edit the file. Delete broad personality requests, duplicate coding standards, and instructions that apply to only one ticket. Keep the concrete commands and constraints.

06 / Connect a low-cost relay without raising the ceiling

CheapRelay provides pay-as-you-go access through one key, with OpenAI-compatible routes under /v1 and Gemini native routes under /v1beta. It has no monthly fee or subscription, so you can keep a strict spending limit while testing a memory workflow. For a first experiment, use a small model such as Claude Haiku 4.5, review the usage record, and increase context only when the result earns its cost.

If this workflow fits your project, sign up for CheapRelay, set your budget, and begin with one short memory file. Review the receipt after five sessions before adding more instructions.