Multi-Repository Setup: Separate Specs Repo with FE and BE as Independent Repos

[sbale-cci]

Hi everyone,

I’m exploring a multi-repository architecture and would appreciate guidance on the recommended way to structure this using Spec Kit.

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Current Setup

I have three separate repositories:

1. projectX-specs

   • Contains constitution, specs, OpenAPI, domain models, ADRs
   • Intended to be the single source of truth
   • All /speckit.constitution, /speckit.specify, and /speckit.plan are run here

2. projectX-be

   • FastAPI backend
   • Needs to consume specs and potentially run /speckit.implement

3. projectX-fe

   • Next.js frontend
   • Needs to consume OpenAPI and shared contracts

The goal is:

• Keep specs authoritative and isolated in their own repository
• Avoid duplicating spec files in FE or BE
• Allow BE and FE to consume the same versioned specs
• Prevent spec drift

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Core Question

What is the recommended way to use Spec Kit in this multi-repo setup?

More specifically:

• Is Spec Kit designed to work across repositories?
• Is there a supported way to configure a spec root that lives outside the current repo?
• Should specs be shared via Git submodules?
• Or is the expected pattern to publish generated artifacts (for example OpenAPI, TypeScript types, Pydantic models) as versioned packages?

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Additional Context

I want to avoid:

• Accidental regeneration of specs inside implementation repos
• Duplicate spec directories
• Spec drift between FE and BE

The ideal workflow would be:

1. Specs repo evolves and versions contracts
2. FE and BE depend on a specific spec version
3. /speckit.implement runs only against the canonical spec

Would appreciate any guidance or examples of how others are handling multi-repo setups with Spec Kit.

Thanks!

[mnriem]

Use Spec Kit at the top-level and create the specs there

[sbale-cci]

Hi @mnriem ,

I’m planning to keep the specs in a separate repository and then reference or use those specs within each FE and BE repository. The goal is to avoid a monorepo setup while still allowing both repositories to consume the same specification source.

[mnriem]

So, the constitution applies to both? I would expect some overlap, but if you are keeping them in separate repositories you are doing that for a reason?

[vmourac-vtex]

@mnriem
Could you elaborate on your suggestion of using a top-level repo?

In many cases the sub repos would be sufficiently different to require their own constitution files. Should we create separate constitutions on both sub repos or one at the top level repo? In any case, will spec kit know how effectively read each one depending on the context of the task?

Thanks for reaching out and helping with this scenario!

[mnriem]

If they are different then no you would not want to share constitution and treat them as separate projects altogether

[gaeviola]

Hi,

Have you made any progress with this? Have you come across any additional information?
I have the same questions and would be interested in hearing your thoughts if you've been able to take this further.

[specularis-org]

@sbale-cci @vmourac-vtex I've been working on solving this problem (amongst others). It comes down to the core question what's the single source of truth for specs and how to keep them in sync across repos in a multi-human-agent team even before they get committed (because writings specs should happen before implementation...). Specularis tries to solve this by adding spec layer on top of your project, allowing you to govern all the markdown from one place (canonical + human-in-the-loop), auto-sync and manage conflict resolutions so all agents/repos can see the same canonical specs at any time. Still early days but happy if it helps. https://specularis.org

[mnriem]

We are aware of the problem and will be addressing this issue soon!