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effect-development

Effect development guidance. Use when implementing or reviewing code that composes Effect APIs or patterns, or that adds or changes API signatures.

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Effect-TS/effect
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October 22, 2026 at 22:29
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name
effect-development
description
Effect development guidance. Use when implementing or reviewing code that composes Effect APIs or patterns, or that adds or changes API signatures.
Use the repository's AI documentation as targeted reference, not ambient context: 1. Identify the Effect APIs and concepts involved in the change. 2. Search `LLMS.md` and `ai-docs/src` for those names and concepts, then read the matching sections and examples. 3. Apply the relevant guidance and inspect nearby source and tests for any repository-internal conventions not covered by the documentation. The task is ready for implementation when every material Effect API or pattern has matching local guidance, or the search has established that none exists. ## API conventions Write option types inline in the signature by default. Mark fields `readonly` and add `| undefined` to optional fields: ```ts export const make = (options: { readonly capacity: number readonly strategy?: "dropping" | "sliding" | undefined }): Effect.Effect<Queue> => ... ``` Declare a named options type only in these cases: - A substantial set of options is shared across several APIs, so a named type keeps them in sync. - The options type needs complex conditional logic, such as conditional or mapped types driven by type parameters. A long option list for a single API is not on its own a reason to extract a named type.
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