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+# Agent Instructions — Dolibarr / GoCardless / Shine Reconciliation
+
+## Project Goal
+
+Reconcile invoices and payments across three financial systems:
+- **Dolibarr** — Invoice management (via REST API)
+- **GoCardless** — Direct debit payments (via CSV export)
+- **Shine** — Bank account (via CSV export)
+
+## Design Principles
+
+1. **Manual operation** — CSV-based, no background processes, no API integrations with payment providers
+2. **Standalone** — No coupling to `console.cyanet.fr` or other projects
+3. **Read-only by default** — `--fix` mode is opt-in and only affects invoices flagged `GC_PAID_DOLIBARR_OPEN`
+4. **Audit trail** — CSV exports serve as snapshots; output CSVs written to `tmp/`
+
+## Architecture
+
+```
+bin/reconcile                          # CLI entry point
+lib/
+  boot.rb                              # Dependency loader
+  dolibarr/client.rb                   # HTTP client (HTTParty)
+  reconciliation/
+    dolibarr_fetcher.rb                # Fetch invoices + customer names
+    gocardless_parser.rb               # Parse payments CSV
+    gocardless_payouts_parser.rb       # Parse payouts CSV (fees)
+    shine_parser.rb                    # Parse Shine bank CSV
+    engine.rb                          # 3-pass matching logic
+    reporter.rb                        # Terminal report + CSV export
+    fixer.rb                           # Apply --fix mode
+```
+
+## Data Flow
+
+```
+┌─────────────┐     ┌──────────────┐     ┌─────────────┐
+│  GoCardless │     │   Dolibarr   │     │    Shine    │
+│   payments  │     │   invoices   │     │  transactions│
+│     CSV     │     │     API      │     │     CSV     │
+└──────┬──────┘     └──────┬───────┘     └──────┬──────┘
+       │                   │                    │
+       ▼                   ▼                    ▼
+┌─────────────────────────────────────────────────────────┐
+│                      Engine                             │
+│  Pass 1: GC payments ↔ Dolibarr invoices                │
+│  Pass 2: Open Dolibarr invoice audit                    │
+│  Pass 3: GC payouts ↔ Shine bank credits                │
+└─────────────────────────────────────────────────────────┘
+                           │
+                           ▼
+              ┌────────────────────────┐
+              │  Reporter + Fixer      │
+              │  Terminal report       │
+              │  CSV export to tmp/    │
+              │  Optional --fix        │
+              └────────────────────────┘
+```
+
+## Matching Logic
+
+### Pass 1 — GC ↔ Dolibarr
+
+| Match Type | Criteria |
+|------------|----------|
+| **Strong** | `payment.description == invoice.ref` (case-insensitive) |
+| **Soft**   | Same amount + customer name + date within ±7 days |
+
+### Pass 2 — Open Invoice Audit
+
+All open Dolibarr invoices with no GC match → `DOLIBARR_OPEN_NO_GC`
+
+### Pass 3 — GC Payouts ↔ Shine
+
+| Match Type | Criteria |
+|------------|----------|
+| **Strong** | Payout reference found in Shine `Libellé` |
+| **Fallback** | Exact net amount + date within ±2 days |
+
+## Key Files to Modify
+
+| Task | File |
+|------|------|
+| Add new flag | `lib/reconciliation/engine.rb` (constants + Match struct) |
+| Change matching logic | `lib/reconciliation/engine.rb` (pass1/2/3 methods) |
+| Add parser field | `lib/reconciliation/*_parser.rb` (Payment/Transaction/Invoice struct) |
+| Change report output | `lib/reconciliation/reporter.rb` (print_summary, write_csv) |
+| Add CLI option | `bin/reconcile` (OptionParser + wiring) |
+| Dolibarr API calls | `lib/dolibarr/client.rb`, `lib/reconciliation/dolibarr_fetcher.rb` |
+
+## Coding Conventions
+
+- **Ruby 3.x** — Use `frozen_string_literal: true`
+- **No external dependencies** — Only stdlib + HTTParty (already in Gemfile)
+- **Amounts in cents** — Always use integers to avoid float precision issues
+- **Date tolerance** — Use `DATE_TOLERANCE` / `PAYOUT_DATE_TOLERANCE` constants (configurable via ENV)
+- **Name normalization** — Strip accents, lowercase, sort words for comparison
+
+## Testing Checklist
+
+Before committing changes:
+
+```bash
+# Syntax check
+ruby -c lib/reconciliation/*.rb
+ruby -c bin/reconcile
+
+# Run reconciliation (dry run)
+ruby bin/reconcile --from 2026-01-01 --to 2026-01-31 \
+  --gc gocardless/*.csv --gc-payouts gocardless/*.csv \
+  --shine shine/*/*.csv
+
+# Verify CSV output
+cat tmp/reconciliation_*.csv
+cat tmp/payouts_fees_*.csv
+```
+
+## Common Patterns
+
+### Adding a new flag
+
+```ruby
+# 1. Define constant in Engine
+NEW_FLAG = :new_flag
+
+# 2. Add to Match struct
+Match = Struct.new(
+  :flag, :invoice, :payment, :match_type, :partial, :retry_group,
+  :new_field,  # if needed
+  keyword_init: true
+)
+
+# 3. Set flag in matching logic
+results << Match.new(flag: NEW_FLAG, ...)
+
+# 4. Handle in reporter
+r[:new_flag_matches].each do |m|
+  puts "  #{m.invoice.ref}"
+end
+```
+
+### Adding a new parser field
+
+```ruby
+# 1. Add to struct
+Payment = Struct.new(
+  :id, :charge_date, :amount_cents, :new_field,
+  keyword_init: true
+)
+
+# 2. Parse from CSV
+Payment.new(
+  id: row["id"].to_s.strip,
+  new_field: row["new_column"].to_s.strip,
+  ...
+)
+
+# 3. Use in engine/reporter
+```
+
+## Gotchas
+
+1. **Dolibarr `status=1`** — Returns all non-draft invoices (open + paid + cancelled). Filter by `statut` field in response.
+2. **Shine CSV format** — Semicolon separator, French decimal (`51,10`), Windows CRLF
+3. **GoCardless fees** — Payout net amount < sum of payments (fee deducted). This is normal.
+4. **Credit notes** — Negative `total_ttc` invoices are excluded from reconciliation
+5. **Supplier invoices** — Separate API endpoint (`/supplierinvoices`), not handled
+
+## Environment Variables
+
+| Variable | Default | Purpose |
+|----------|---------|---------|
+| `DOLIBARR_URL` | — | Dolibarr API base URL |
+| `DOLIBARR_API_KEY` | — | API authentication |
+| `DOLIBARR_GC_PAYMENT_ID` | — | Payment method ID for `--fix` |
+| `DOLIBARR_BANK_ACCOUNT_ID` | `1` | Bank account ID for `--fix` |
+| `RECONCILIATION_DATE_TOLERANCE` | `7` | Days for soft date matching |
+| `RECONCILIATION_PAYOUT_TOLERANCE` | `2` | Days for payout date matching |
+
+## Related Files
+
+- `docs/reconciliation_plan.md` — Original design document
+- `docs/dolibarr.json` — Dolibarr API spec
+- `.env.example` — Environment variable template
diff --git a/README.md b/README.md
index 4524fcb..c62e91d 100644
--- a/README.md
+++ b/README.md
@@ -2,6 +2,8 @@
 
 A standalone Ruby script that cross-checks three financial systems and flags discrepancies.
 
+**Manual tool** — Export CSVs from GoCardless and Shine, run the script locally, review the report. No API integrations with payment providers, no background processes, no coupling to other projects.
+
 ## The problem it solves
 
 Payments flow through three separate systems that are not automatically linked: