confident-ai/deepeval

Feat request: optional user-defined prompt builder for synthesizer

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#2,396 opened on Dec 26, 2025

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enhancementhelp wanted

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Description

It could be useful to give users flexibility over the user prompt used to generate the goldens in the synthesizer.

generate_goldens_from_contexts and a_generate_goldens_from_contexts may be overridden when inheriting from the Synthesizer class and rely on predefined prompt templates composed from specific arguments context, max_goldens_per_context, scenario, task, input_format

https://github.com/confident-ai/deepeval/blob/a740ca31d6c32d130e93fc1fe0c90d4795a93dc0/deepeval/synthesizer/synthesizer.py#L661-L667

which are passed into the synthetic inputs. Does it make sense to add an optional prompt builder argument and allow the user to construct the prompt for golden generation?

prompt_builder: Optional[Callable[..., str | Prompt]]

Contributor guide

Research direction
Inspect the existing generate goldens from contexts method and the associated template to add an optional prompt builder parameter that allows custom prompt construction.
Tech stack
python
Domain
backendai
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
PythonGit
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
75