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+# Phase 4 — Fusion Accounting Follow-up Implementation Plan
+
+**Module:** `fusion_accounting_followup`
+**Branch:** `fusion_accounting/phase-4-followup`
+**Pre-phase tag:** `fusion_accounting/pre-phase-4`
+**Estimated tasks:** ~35
+**Reference:** `/Users/gurpreet/Github/RePackaged-Odoo/accounting/account_followup/` (~1318 LOC Python)
+
+## Goal
+
+Replace Enterprise's `account_followup` module — multi-level dunning sequences for unpaid invoices, with AI augmentation: contextually-appropriate follow-up text generation + payment-risk scoring + tone adjustment based on customer history. Coexists with Enterprise.
+
+## Architecture (HYBRID engine, Phases 1-3 pattern)
+
+```
+fusion.followup.engine (AbstractModel)              ← shared primitives
+├── compute_followup_level(partner)
+├── get_overdue_for_partner(partner)
+├── send_followup_email(partner, level=None)
+├── escalate_to_next_level(partner)
+├── pause_followup(partner, until_date)
+├── reset_followup(partner)
+└── snapshot_followup_history(partner)               ← audit/history
+
+services/                                            ← pure-Python
+├── overdue_aging.py        → bucket overdue lines (current/30/60/90/120+)
+├── level_resolver.py       → match aging buckets to follow-up levels
+├── risk_scorer.py          → payment-history risk score (0-100)
+├── tone_selector.py        → gentle/firm/legal based on level + risk
+├── followup_text_generator.py → LLM-generated follow-up text
+└── followup_text_prompt.py → provider-agnostic LLM prompt
+
+models/
+├── fusion_followup_level.py        → level definition (delay days, template, action)
+├── fusion_followup_run.py          → execution record (per-partner per-level)
+├── fusion_followup_text_cache.py   → LLM-generated text cache (cost-saving)
+├── fusion_followup_engine.py       → AbstractModel orchestrator
+├── res_partner.py (inherit)        → fusion_followup_status, fusion_followup_paused_until
+└── account_move_line.py (inherit)  → followup_level_id (which level last contacted at)
+
+controllers/followup_controller.py                  ← 6 JSON-RPC endpoints
+├── /fusion/followup/list_overdue                    → list partners with overdue
+├── /fusion/followup/get_partner_detail              → single partner with aging + history
+├── /fusion/followup/generate_text                   → AI-generate follow-up text
+├── /fusion/followup/send                            → send a follow-up email
+├── /fusion/followup/pause                           → pause follow-ups for a partner
+└── /fusion/followup/reset                           → reset follow-up state
+
+static/src/
+├── scss/                          ← follow-up design tokens
+├── services/followup_service.js   ← reactive state + RPC wrappers
+├── views/followup_dashboard/      ← top-level OWL controller
+└── components/                    ← partner_card, aging_bucket_strip, ai_text_panel,
+                                     followup_history_table, risk_badge
+```
+
+## Coexistence
+
+`group_fusion_show_when_enterprise_absent`. Follow-up menu visible only when `account_followup` NOT installed.
+
+## Tasks (~35 total)
+
+### Group 1: Foundation (1-2)
+1. Safety net (DONE)
+2. Plan doc + module skeleton
+
+### Group 2: Pure-Python services TDD (3-7)
+3. `services/overdue_aging.py` (TDD: bucket lines into 0/30/60/90/120+)
+4. `services/level_resolver.py` (TDD: match aging to level)
+5. `services/risk_scorer.py` (TDD: payment-history risk 0-100)
+6. `services/tone_selector.py` (TDD: gentle/firm/legal)
+7. `services/followup_text_generator.py` + `followup_text_prompt.py` (LLM)
+
+### Group 3: Persisted models (8-12)
+8. `models/fusion_followup_level.py` (level definition)
+9. `models/fusion_followup_run.py` (execution record)
+10. `models/fusion_followup_text_cache.py` (LLM cache)
+11. `models/res_partner.py` (inherit: fusion_followup_status, paused_until)
+12. `models/account_move_line.py` (inherit: followup_level_id)
+
+### Group 4: Engine + integration tests (13-14)
+13. `models/fusion_followup_engine.py` (7-method API)
+14. Engine integration tests
+
+### Group 5: Backend wiring (15-18)
+15. JSON-RPC controller (6 endpoints)
+16. FollowupAdapter wiring `_via_fusion` paths
+17. 4 new AI tools (list_overdue, generate_text, send_followup, get_risk_score)
+18. Cron — daily scan + escalate
+
+### Group 6: Tests + perf (19-21)
+19. Property-based tests (Hypothesis: aging buckets sum to total)
+20. Integration tests (full follow-up flow: scan → escalate → send → reset)
+21. Performance benchmarks (P95: scan < 500ms, generate_text < 5s incl. LLM)
+
+### Group 7: Frontend (22-26)
+22. SCSS tokens + main stylesheet
+23. `followup_service.js`
+24. `followup_dashboard` (top-level)
+25. `partner_card` + `aging_bucket_strip` + `risk_badge`
+26. `ai_text_panel` (Fusion-only) + `followup_history_table`
+
+### Group 8: Wizards + data (27-29)
+27. Default follow-up levels XML data (7-day reminder, 30-day, 60-day, legal)
+28. Default mail templates XML data (3 escalation levels)
+29. "Send batch follow-ups" wizard
+
+### Group 9: Migration + coexistence (30-32)
+30. Migration wizard inheritance — backfill from account_followup tables
+31. Menu + window action with coexistence group filter
+32. Coexistence test
+
+### Group 10: Final tests + polish (33-37)
+33. 5 OWL tour tests
+34. Local LLM compat test for text_generator
+35. Update meta-module manifest
+36. CLAUDE.md, UPGRADE_NOTES.md, README.md
+37. End-to-end smoke + tag phase-4-complete + push
+
+## Performance Targets (P95)
+
+- `compute_followup_level`: <50ms
+- `get_overdue_for_partner`: <100ms
+- `send_followup_email` (no LLM): <200ms
+- `generate_text` (with LLM): <5s
+- Controller `list_overdue` (50 partners): <500ms
+
+## V19 Conventions (Phases 1-3 lessons)
+
+- `models.Constraint` not `_sql_constraints`
+- No `@api.depends('id')` on stored compute fields
+- `@route(type='jsonrpc')` not `type='json'`
+- `ir.cron` no `numbercall` field
+- `res.groups.user_ids` not `users`
+- `ir.ui.menu.group_ids` not `groups_id`
+- `from odoo.exceptions import UserError, ValidationError` (NOT `self.env['ir.exceptions'].UserError`)
+
+## Test Targets
+
+Match Phases 1-3 test pyramid. Phase 4 target: ~80-100 additional tests → ~510-530 total project tests.
diff --git a/fusion_accounting_followup/__init__.py b/fusion_accounting_followup/__init__.py
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diff --git a/fusion_accounting_followup/__manifest__.py b/fusion_accounting_followup/__manifest__.py
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+{
+    'name': 'Fusion Accounting Follow-up',
+    'version': '19.0.1.0.0',
+    'category': 'Accounting/Accounting',
+    'summary': 'AI-augmented customer follow-ups (dunning) for unpaid invoices.',
+    'description': """
+Fusion Accounting Follow-up
+===========================
+
+A Fusion-native replacement for Odoo Enterprise's account_followup module.
+
+CORE scope (Phase 4):
+- Multi-level dunning sequences (gentle reminder, firm warning, legal)
+- Per-partner follow-up state (current level, paused-until, history)
+- Automated daily scan + escalation cron
+- Mail templates per level
+
+AI augmentation:
+- Contextually-appropriate follow-up text generation (LLM)
+- Payment-risk scoring from invoice/payment history
+- Tone selection (gentle/firm/legal) based on level + risk
+
+Coexists with Enterprise: when account_followup is installed, the Fusion
+menu hides; the engine + AI tools remain available for the chat.
+""",
+    'author': 'Fusion Accounting',
+    'license': 'LGPL-3',
+    'depends': [
+        'fusion_accounting_core',
+        'fusion_accounting_ai',
+        'account',
+        'mail',
+    ],
+    'data': [
+        'security/ir.model.access.csv',
+    ],
+    'assets': {
+        'web.assets_backend': [
+        ],
+    },
+    'installable': True,
+    'auto_install': False,
+    'application': False,
+    'icon': '/fusion_accounting_followup/static/description/icon.png',
+}
diff --git a/fusion_accounting_followup/controllers/__init__.py b/fusion_accounting_followup/controllers/__init__.py
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diff --git a/fusion_accounting_followup/models/__init__.py b/fusion_accounting_followup/models/__init__.py
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diff --git a/fusion_accounting_followup/reports/__init__.py b/fusion_accounting_followup/reports/__init__.py
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diff --git a/fusion_accounting_followup/security/ir.model.access.csv b/fusion_accounting_followup/security/ir.model.access.csv
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+id,name,model_id:id,group_id:id,perm_read,perm_write,perm_create,perm_unlink
diff --git a/fusion_accounting_followup/services/__init__.py b/fusion_accounting_followup/services/__init__.py
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diff --git a/fusion_accounting_followup/tests/__init__.py b/fusion_accounting_followup/tests/__init__.py
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diff --git a/fusion_accounting_followup/wizards/__init__.py b/fusion_accounting_followup/wizards/__init__.py
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