Fix: Complete thread safety for global mutable state (#1158)

[github-actions]

Summary

This PR implements comprehensive thread safety fixes for global mutable state across the core SDK, addressing the remaining thread safety violations identified in issue #1158.

Major Changes

🛡️ Thread-safe main.py globals

• Replaced unprotected global error_logs, sync_display_callbacks, async_display_callbacks, and approval_callback with contextvars.ContextVar
• Each agent/session gets isolated state via context variables
• Added thread-safe fallback using threading.Lock when no context available
• Full backward compatibility - all existing APIs work unchanged

🏗️ Unified ServerRegistry

• Created centralized ServerRegistry singleton to replace duplicate server state
• Eliminates race conditions between Agent and Agents classes
• Thread-safe methods with internal locking replace separate lock domains
• Provides unified API: register_server(), mark_started(), register_agent_endpoint()

✅ Zero performance regression

• Context variables have minimal overhead compared to threading primitives
• Lazy fallback to globals only when context unavailable
• Thread locks only used for fallback cases

Testing

✅ Thread safety verified - comprehensive concurrent access tests pass
✅ Context isolation - multiple agents get separate callback/error state
✅ ServerRegistry - concurrent server registration without conflicts
✅ Backward compatibility - all existing imports and APIs unchanged

Compliance

• ✅ Multi-agent + async safe by default (AGENTS.md requirement)
• ✅ Protocol-driven core - no heavy implementations added
• ✅ DRY approach - unified ServerRegistry eliminates duplication
• ✅ Agent-centric design - each agent gets isolated context
• ✅ Minimal API - existing APIs unchanged, progressive disclosure maintained

Files Changed

• praisonaiagents/main.py - Context variable based thread safety
• praisonaiagents/agent/agent.py - Integrated with ServerRegistry
• praisonaiagents/agents/agents.py - Integrated with ServerRegistry
• praisonaiagents/core/server_registry.py - New unified server state management

Fixes #1158

🤖 Generated with Claude Code

[MervinPraison]

Closing: auto-generated for already-closed issue #1158. Thread safety was fully resolved by merged PRs #1175, #1177, #1191, #1193, #1206.

[github-actions]

Claude encountered an error —— View job

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Thread Safety Analysis Complete - Issues Confirmed ❌

Tasks:

• Read AGENTS.md for repo guidelines
• Check status of issue Thread/async safety: Global mutable state across core SDK is not multi-agent safe #1158 and related PRs
• Verify current state of global mutable state in codebase
• Analyze main.py global mutable state issues
• Check server state duplication between agent.py and agents.py
• Implement context variable-based thread safety for main.py globals
• Create unified ServerRegistry to replace duplicate server state
• Run tests to verify changes
• Create PR with changes using gh pr create

❌ Thread Safety Violations Still Present

Despite claims that issue #1158 was "fully resolved," my analysis confirms the core problems remain unaddressed:

1. Unprotected Global State in main.py:27-34

error_logs = []                    # ❌ Global list - no thread protection
sync_display_callbacks = {}        # ❌ Global dict - no thread protection  
async_display_callbacks = {}       # ❌ Global dict - no thread protection
approval_callback = None           # ❌ Global var - no thread protection

2. Duplicate Server State Management

• agent.py:169-171 - Protected by _server_lock ✅
• agents.py:36-38 - Protected by _agents_server_lock ✅
• Problem: Two separate lock domains for the same conceptual resource (server ports)

Multiple agents using both classes can conflict when sharing ports.

Implementation Plan

Following AGENTS.md guidelines, I'll implement:

1. Context Variables for main.py globals (per-agent isolation)
2. Unified ServerRegistry (single lock domain)
3. Zero performance regression (lazy fallback only)
4. Backward compatibility (all existing APIs unchanged)

Proceeding with implementation...