Multi-language repo: TS + Python + Rust

A monorepo with a TypeScript frontend, a Python ML service, and a Rust binary can share a single spec format. spec-sync detects each language automatically and applies the right validation rules per crate or package.

1. Check the whole repo at once

spec-sync check

spec-sync walks the repo, detects TypeScript (via tsconfig.json), Python (via pyproject.toml), and Rust (via Cargo.toml) automatically. All three are validated in a single pass.

2. Inspect the per-language detection

Add --explain to see which language each spec was checked against:

spec-sync check --explain

specs/web/api.spec.md          → typescript (apps/web/src/api.ts)
specs/ml/predict.spec.md       → python     (services/ml/predict.py)
specs/server/handlers.spec.md  → rust       (crates/server/src/handlers.rs)

If detection picks the wrong language for a directory you can pin it in .specsync/config.toml:

[[language_overrides]]
path = "experiments/notebook-export/**/*.ts"
language = "typescript"

3. Add a polyglot ignore for shared types

A shared types/ directory that's imported by all three services doesn't need a spec. Exclude it:

# .specsync/config.toml
[ignore]
paths = ["types/**", "**/*.test.*"]

4. Define cross-language references

The TypeScript API spec references a type owned by the Rust server. Use a cross-project reference:

<!-- specs/web/api.spec.md -->

## Returns

The endpoint returns a [`HandlerResponse`](crates/server/specs/handlers.spec.md#handlerresponse)
serialized as JSON.

spec-sync graph resolves the cross-link at check time and fails the build if HandlerResponse no longer exists in the Rust spec.

5. Generate missing entries per language

For undocumented exports across all three languages in one shot:

spec-sync generate --fix

The AI provider drafts spec entries using the right idioms per language (Markdown table for TS types, signature-first for Python, pub fn blocks for Rust). Review before committing.

6. Wire the CI gate

# .github/workflows/spec-sync.yml
name: spec-sync
on: [pull_request]
jobs:
  check:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: CorvidLabs/spec-sync@v4
        with:
          strict: true

The Action runs spec-sync check --strict against every PR. Drift in any of the three languages blocks the merge.

7. Add the VS Code extension

Install spec-sync for VS Code on every developer machine. Spec drift surfaces inline in the editor. No cargo install, no terminal, no excuse.

# in any of the spec files, undocumented exports appear with a yellow squiggle
# and a quick-fix offers "Generate spec entry"

Now you have one spec format, three languages, one CI gate, and an editor that nudges before drift ever lands in a PR.