| # CROSS1: API Contract Reconciliation |
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|
| ## Goal |
| The Python client library must correctly communicate with the Go HTTP server. |
| Discrepancies exist between the API spec, the server implementation, and the client. |
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|
| ## Requirements |
| 1. The Go server is the source of truth — fix the Python client to match server behavior |
| 2. Update `api_spec.yaml` to document the actual contract (matching the server) |
| 3. All integration tests must pass: `pytest tests/` |
| 4. The Go server must still compile: `go build ./...` (do not change Go source) |
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|
| ## Supporting Documents |
| - `service/main.go`, `service/handlers.go` — Go server (source of truth) |
| - `client/api.py`, `client/models.py` — Python client (has 3 bugs) |
| - `api_spec.yaml` — API spec (wrong in 3 places) |
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|
| ## The 3 Discrepancies (find them yourself) |
| The spec documents one version of the contract; the server implements another. |
| Read both and reconcile in favor of the server's actual behavior. |
|
|
| ## Important |
| Do NOT modify any Go source files. Only fix: |
| - `client/api.py` — client request/response handling |
| - `client/models.py` — client data models |
| - `client/exceptions.py` — client exception handling |
| - `api_spec.yaml` — update to match actual server behavior |
|
|
| ## Real-World Context |
| API contract mismatches between polyglot services are a leading cause of production |
| incidents. These three discrepancy patterns appear repeatedly in real migrations: |
| - **Field naming (camelCase vs snake_case)**: The Twitter v1 → v2 migration renamed |
| hundreds of fields (e.g., `user.followers_count` → `public_metrics.followers_count`), |
| silently breaking every consumer that referenced old names. |
| - **Pagination key rename** (`data`/`next` → `results`/`cursor`): Stripe's 2022 |
| changelog removed `invoice` from `Charge` objects and renamed pagination fields, |
| breaking dashboard tools and analytics pipelines overnight. |
| - **Error format change** (HTTP 422 + `errors[]` → HTTP 400 + `error` string): The |
| GitHub REST API v3 → v4 transition changed error envelopes, causing silent failures |
| in CI/CD integrations that checked `response.errors[0]`. |
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