# Backdiff
> AI tools change through model replacements, revised plan limits, disappearing endpoints and rewritten terms.

## Entries
- [What a Model Version Bump Can Change in a Routine Prompt: A Re-Test Guide](https://backdiff.pages.dev/model-version-bump-routine-prompts/): A model version bump can change instruction following, output structure, tone, factual detail, tool use and the way ambiguous requests are interpreted.
- [Reading an AI Deprecation Notice: Dates, Endpoints and Sunset Terms](https://backdiff.pages.dev/reading-ai-deprecation-notices/): An AI deprecation notice signals that a model, endpoint, feature or service is being phased out, but it does not always mean immediate unavailability.
- [A Free Tier Became a Trial: Documenting a Plan-Page Change Without Guessing](https://backdiff.pages.dev/documenting-free-tier-trial-changes/): When an AI service changes a free tier into a trial, the key task is to document the difference between the previous published offer and the current published.
- [Keeping a Frozen Prompt Set: Spreadsheet and Plain-Text Templates for Repeatable Comparisons](https://backdiff.pages.dev/frozen-prompt-set-templates/): A frozen prompt set is a dated collection of unchanged prompts and their associated instructions, inputs and expected output characteristics.
- [How to Read an AI Feature List: Text Chat, Audio, Short Films and Follow Functions](https://backdiff.pages.dev/reading-ai-feature-lists/): An AI feature list describes the capabilities a provider chooses to advertise, but individual labels can refer to different types of functionality.
- [Output Length Drift: A Method for Checking Whether AI Summaries Get Shorter After Updates](https://backdiff.pages.dev/summary-output-length-drift-method/): Output length drift occurs when summaries become consistently shorter or longer under conditions that were previously comparable.

## About
- [About Backdiff](https://backdiff.pages.dev/about/): what the site covers and how entries are made

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