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# Project Analysis & Migration Runbook Report

## 1. Executive Summary

**Does MIGRATION_RUNBOOK.md apply to this project?**
**YES. This is the exact project described in the runbook.**

The codebase is currently in the **Execution Phase** of the migration described in [MIGRATION_RUNBOOK.md](file:///Users/ibrahim/Projects/smsapp/MIGRATION_RUNBOOK.md):
- **Source System**: Laravel Monolith (confirmed).
- **Target System**: Go Messaging Service (confirmed in `services/messaging-service`).
- **Status**: Active migration. Timestamps on migration files indicate work is happening *right now* (Feb 2026).

---

## 2. Detailed Evidence

### A. Repository Structure Matches Runbook Strategy
The runbook describes a "Strangler Pattern" migration where a new Go service sits alongside the Laravel monolith.

| Runbook Component | Found in Codebase | Status |
|-------------------|-------------------|--------|
| **Go Send Service** | `services/messaging-service` | ✅ Implemented |
| **Feature Flags** | `app/Models/FeatureFlag.php` | ✅ Implemented |
| **Internal Client** | `app/Services/MessagingServiceClient.php` | ✅ Implemented |
| **Tracing Columns** | `database/migrations/*_add_tracing_to_sms_logs.php` | ✅ Implemented |

### B. Service Verification (`services/messaging-service`)
The Go service strictly implements the **Canonical Contract** defined in the runbook:
- **Endpoint**: `POST /internal/v1/sms/send-batch` defined in `cmd/server/main.go`.
- **Logic**: 
    - Enforces **Invariant 1** (Single Execution Authority) via `go_sms_logs`.
    - Enforces **Invariant 3** (No writes to legacy `sms_logs`).
    - Implements **Dry Run** mode (returns `accepted` without calling providers), which is critical for the `SHADOW` mode described in the runbook.
    - Uses `internal/handlers` and `internal/models` that mirror the runbook's JSON schemas.

### C. Laravel Monolith Verification
The Laravel codebase has been modified to support the migration steps:
- **Dependencies**: `doctrine/dbal` is present in `composer.json` (Step 1).
- **Database**: 
    - `sms_logs` has been extended with `message_uuid`, `tenant_id`, `source`.
    - `feature_flags` table has been created (Step 6).
- **Code**:
    - `app/Helpers.php` contains the updated `smsLog()` signature to support tracing.
    - `resolveTenantId()` function is verified to exist and be used.
    - `MessagingServiceClient` is configured with a 500ms timeout budget, matching the "Circuit Breaker" requirement.

---

## 3. Recommendations & Next Steps

Since the migration is confirmed to be active and aligned with the runbook:

1.  **Continue Following the Runbook**: The codebase is in a consistent state with the runbook's "Phase B". Do not deviate.
2.  **Verify Feature Flag Status**: Check the `feature_flags` table in the database to see which tenants (or if global) are in `SHADOW` or `ON` mode.
3.  **Monitor `go_sms_logs`**: As traffic shifts, ensure the Go service is correctly populating its internal logs.
4.  **Finish Backfills**: Ensure the `BackfillSmsLogTracing` command (Step 4) has completed 100% before fully switching to `ON` mode for all tenants.

## 4. Services Folder Analysis

The `services` folder currently contains:
- `messaging-service/`: A production-ready Go application.
    - **Architecture**: Standard Go layout (`cmd`, `internal`, `pkg`).
    - **Dependencies**: Uses `gin-gonic` for HTTP, `gorm` for DB, and official SDKs for providers (Twilio, Vonage, Plivo).
    - **Readiness**: High. It has a `loadtest` command, structured logging, and robust invariant checks.

**Conclusion**: The `services` folder is the home for the new microservices architecture emerging from this migration.
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