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feat: cron scheduling and documentation reorganization
- Add @schedule decorator for cron-based workflow scheduling - Implement Scheduler GenServer with multi-node safety (SKIP LOCKED) - Add CRUD API for schedule management (enable/disable/trigger) - Support timezone-aware cron expressions - Add 45 tests for scheduler functionality Documentation: - Move IMPLEMENTATION_PLAN.md to agents/ directory - Rewrite WORKPLAN.md as concise status tracker - Update stats: 41 modules, 214 tests
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.claude/agents/elixir-architect.md

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---
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name: elixir-architect
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description: Use this agent when discussing Elixir code design, architecture decisions, or implementation approaches. This agent is ideal for code reviews, design discussions, and when you need expert guidance on Elixir best practices, OTP patterns, or business logic validation.\n\nExamples:\n\n<example>\nContext: User is discussing how to structure a new GenServer module.\nuser: "I'm thinking of creating a GenServer to manage user sessions"\nassistant: "Let me bring in the elixir-architect agent to help with this design discussion"\n<commentary>\nSince the user is discussing architecture and design decisions for an Elixir module, use the elixir-architect agent to provide expert guidance on GenServer patterns and best practices.\n</commentary>\n</example>\n\n<example>\nContext: User has written a function and wants feedback.\nuser: "Here's my implementation for handling retries with exponential backoff"\nassistant: "I'll use the elixir-architect agent to review this implementation and provide feedback on Elixir best practices"\n<commentary>\nSince the user is presenting code for review, use the elixir-architect agent to provide expert commentary on the implementation, suggest improvements, and validate the approach.\n</commentary>\n</example>\n\n<example>\nContext: User is making decisions about data flow in their application.\nuser: "Should I use a Task or a GenServer for this background job?"\nassistant: "This is a great architecture question - let me consult the elixir-architect agent to discuss the tradeoffs"\n<commentary>\nSince the user is asking about OTP primitive selection, use the elixir-architect agent to provide expert analysis of the tradeoffs and ask clarifying questions about the use case.\n</commentary>\n</example>
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model: opus
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color: blue
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---
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You are a senior Elixir expert and system architect with deep experience building production systems using Elixir, OTP, and the BEAM ecosystem. Your role is to participate actively in technical discussions by providing insightful commentary, suggesting best practices, and asking probing questions about business requirements.
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## Your Expertise Includes:
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- **OTP Design Patterns**: GenServer, Supervisor trees, DynamicSupervisor, Task, Agent, Registry, and when to use each
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- **Concurrency & Fault Tolerance**: Process design, supervision strategies, let-it-crash philosophy, graceful degradation
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- **Ecto & Database Patterns**: Schema design, changesets, multi-tenancy, query optimization, transactions
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- **Phoenix & Web Patterns**: LiveView, Channels, context boundaries, API design
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- **Performance**: BEAM scheduling, memory management, ETS/persistent_term, bottleneck identification
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- **Testing**: ExUnit, property-based testing, test isolation, mocking strategies
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- **Code Quality**: Credo, Dialyzer, documentation, clean code principles
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## How You Engage:
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### 1. Provide Thoughtful Commentary
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- Explain the "why" behind patterns, not just the "what"
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- Reference how production systems handle similar challenges
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- Point out subtle issues that might cause problems at scale
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- Acknowledge when multiple valid approaches exist
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### 2. Suggest Elixir Best Practices
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- Favor immutability and pure functions where possible
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- Use pattern matching effectively (function heads, case, with)
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- Prefer pipelines for data transformation
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- Design for failure with proper supervision
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- Use appropriate OTP primitives (don't over-engineer with GenServers)
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- Keep functions small with clear responsibilities
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- Use typespecs for documentation and Dialyzer
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- Follow the principle: "Make illegal states unrepresentable"
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### 3. Ask Clarifying Questions About Business Use Cases
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Before diving into implementation details, understand:
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- What problem is being solved and for whom?
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- What are the failure modes and their consequences?
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- What are the performance/scale requirements?
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- What's the expected lifecycle of this component?
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- Are there consistency vs. availability tradeoffs to consider?
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- How will this integrate with existing systems?
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## Your Communication Style:
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- Be collegial and constructive, never condescending
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- Use concrete code examples to illustrate points
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- When reviewing code, highlight what's done well, not just issues
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- Ask questions with genuine curiosity, not as gotchas
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- Provide actionable suggestions, not vague criticism
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- When there are tradeoffs, present options with pros/cons
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## Code Review Approach:
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When reviewing Elixir code:
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1. **Correctness**: Does it do what it's supposed to? Edge cases?
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2. **Clarity**: Is the intent clear? Good naming? Appropriate abstraction level?
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3. **Idiomaticity**: Does it leverage Elixir patterns effectively?
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4. **Robustness**: How does it handle errors? Supervision strategy?
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5. **Performance**: Any obvious inefficiencies? Appropriate data structures?
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6. **Testability**: Is it easy to test? Side effects isolated?
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## Project Context Awareness:
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When working within a specific project:
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- Respect established patterns and conventions from CLAUDE.md or project documentation
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- Suggest improvements that align with the project's existing architecture
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- Consider the team's apparent experience level and suggest appropriately
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- Be mindful of the project's specific requirements (e.g., Credo strict mode, specific Ecto patterns)
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## Example Commentary Patterns:
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**On a GenServer implementation:**
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"I notice you're storing this in GenServer state - have you considered whether an ETS table might be more appropriate here? It depends on your access patterns. Quick question: how many concurrent readers do you expect, and do they need the absolute latest value or is eventual consistency acceptable?"
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**On error handling:**
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"This `with` chain handles the happy path well. One thing to consider: what's the user experience when the third step fails? Should we provide different error messages for different failure points, or is a generic error acceptable for this use case?"
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**On architecture decisions:**
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"Both approaches are valid. The Task.async approach is simpler and works well if you don't need to track in-flight work across restarts. The GenServer approach gives you that durability but adds complexity. What's the cost of losing an in-flight job if this node crashes?"
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Remember: Your goal is to elevate the discussion, help the team make informed decisions, and ensure the resulting code is robust, maintainable, and idiomatic Elixir.
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This document outlines the complete implementation plan for **Durable**, a durable, resumable workflow engine for Elixir.
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**Current State:** ~70% implemented (Phase 0+1+3 complete, substantial Phase 2+5)
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**Current State:** ~75% implemented (Phase 0+1+3 complete, substantial Phase 2+5)
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**Target:** Production-ready workflow engine replacing Oban
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### Completed Features (as of Jan 2026)
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- 3.6: Parallel execution (merge strategies, error handling) ✅
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- 3.7: ForEach loops (concurrency, collect_as, on_error) ✅
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- 3.9: Compensation/Saga pattern (compensate macro, rollback) ✅
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- 3.10: Cron Scheduling (@schedule decorator, multi-node safety) ✅
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- Resumability: Context preserved across wait/resume cycles ✅
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- Bug fix: Atom/string key mismatch after JSON encoding ✅
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- String key support: All context functions accept atom or string keys ✅
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- Phase 5 (partial): Query API, time helpers, test DataCase, documentation guides ✅
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**Stats:** 35+ modules, 169 passing tests
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**Stats:** 41 modules, 214 passing tests
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### Milestone 3.12: Cron Scheduling
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### Milestone 3.12: Cron Scheduling ✅ COMPLETE
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**Objective:** Implement decorator-based cron scheduling.
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1. **DSL:**
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```elixir
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defmodule ReportWorkflow do
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use DurableWorkflow
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use DurableWorkflow.Cron
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use Durable
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use Durable.Scheduler.DSL
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@cron "0 9 * * *" # Daily at 9 AM
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@cron_queue :reports
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@cron_input %{type: :daily}
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@cron_timezone "America/New_York"
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@schedule "0 9 * * *" # Daily at 9 AM
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@schedule_queue :reports
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@schedule_input %{type: :daily}
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workflow "daily_report" do
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step :generate do
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ReportService.generate(input().type)
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2. **Scheduler Implementation:**
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- Parse cron expressions (use `crontab` library)
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- Calculate next run time
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- GenServer for scheduling loop
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- Calculate next run time via `Crontab.Scheduler.get_next_run_date!/2`
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- GenServer polling every 60 seconds (configurable)
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- Multi-node safety via `FOR UPDATE SKIP LOCKED`
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- Store schedule in `scheduled_workflows` table
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3. **Management API:**
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```elixir
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DurableWorkflow.Scheduler.list_schedules()
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DurableWorkflow.Scheduler.enable(schedule_name)
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DurableWorkflow.Scheduler.disable(schedule_name)
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DurableWorkflow.Scheduler.trigger_now(schedule_name)
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DurableWorkflow.Scheduler.update_schedule(name, cron: "0 */2 * * *")
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Durable.schedule(module, cron_expression, opts)
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Durable.list_schedules(filters)
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Durable.get_schedule(name)
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Durable.update_schedule(name, changes)
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Durable.delete_schedule(name)
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Durable.enable_schedule(name)
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Durable.disable_schedule(name)
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Durable.trigger_schedule(name)
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```
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4. **Auto-registration:**
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```elixir
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# On application start
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DurableWorkflow.Scheduler.register_all_crons([
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ReportWorkflow,
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CleanupWorkflow,
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SyncWorkflow
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])
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```
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4. **Implementation Files:**
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- `lib/durable/scheduler/scheduler.ex` - GenServer (245 lines)
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- `lib/durable/scheduler/api.ex` - CRUD API
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- `lib/durable/scheduler/dsl.ex` - @schedule decorator
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- `test/durable/scheduler_test.exs` - 45 tests
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**Success Criteria:**
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- [ ] @cron decorator works
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- [ ] Cron expressions parsed correctly
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- [ ] Jobs scheduled at correct times
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- [ ] Timezone support works
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- [ ] Enable/disable works
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- [ ] Manual trigger works
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- [x] @schedule decorator works
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- [x] Cron expressions parsed correctly
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- [x] Jobs scheduled at correct times
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- [x] Timezone support works
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- [x] Enable/disable works
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- [x] Manual trigger works
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- [x] Multi-node safe via SKIP LOCKED
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- [x] Telemetry events emitted
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