feat: implement Agent V2 node with enhanced file handling and direct implementation

[Nov1c444]

Summary

This PR introduces Agent V2, a new implementation of agent functionality in Dify workflows with significant improvements over V1.

close #18812

Key Features

1. Enhanced File Handling

• Multi-modal Support: Files can now be transferred between tools and models
• Flexible File Input: Files can be passed via vision field (for vision-enabled models) or via prompt (for model/tool processing)
• Tool-Model File Exchange: Enables complex workflows where tools generate files that can be consumed by models and vice versa

2. Plugin-free Architecture

• Direct Implementation: Removes the plugin system dependency from V1
• Better Performance: Eliminates plugin overhead and communication layers
• Simplified Deployment: No need to manage external plugin processes
• Improved Reliability: Fewer moving parts mean fewer potential failure points

3. Unified Architecture

• Shared Agent Patterns: Leverages a common module used by both Agent nodes and Agent applications
• Consistent Behavior: Ensures same execution logic across different agent implementations
• Code Reuse: Reduces duplication between Agent APP and workflow agents

Technical Implementation

• Agent Patterns Module (api/core/agent/patterns/): Core execution strategies

  • base.py: Abstract interface for all strategies
  • function_call.py: Native tool calling implementation
  • react.py: ReAct prompting implementation
  • strategy_factory.py: Strategy selection based on model features

• Agent V2 Node (api/core/workflow/nodes/agent/v2/): Workflow integration

  • Full LLM node compatibility (prompt templates, memory, vision, context)
  • Support for all tool types (builtin, API, MCP, workflow, plugin)
  • Standard workflow error handling and retry mechanisms

Screenshots

Before	After
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Checklist

• [ ] This change requires a documentation update, included: Dify Document
• [x] I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• [x] I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• [x] I've updated the documentation accordingly.
• [x] I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods

[fdb02983rhy]

Noice!