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ADR: A2A Artifact Streaming Race Condition Fix

Status: 🟢 In-use Category: Bug Fixes & Performance Date: November 5, 2025 Signed-off-by: Sri Aradhyula <sraradhy@cisco.com>

Motivation​

Frequent warnings in platform-engineer logs:

[a2a.utils.helpers] [WARNING] [append_artifact_to_task:102]
Received append=True for nonexistent artifact index 6e0ef907-0e47-433d-9329-533ec97a1015
in task 2506c285-1c00-4203-a31c-ea86892b3235. Ignoring chunk.

Testing Strategy​

Verification Steps​

  1. Rebuild supervisor:

    docker compose -f docker-compose.dev.yaml build platform-engineer-p2p

  2. Restart services:

    docker compose -f docker-compose.dev.yaml up -d platform-engineer-p2p

  3. Test streaming query:

    # Send query that triggers ArgoCD agent
    curl -X POST http://localhost:8000 \
      -H "Content-Type: application/json" \
      -d '{
        "jsonrpc": "2.0",
        "method": "message/send",
        "params": {
          "message": {
            "role": "user",
            "parts": [{"kind": "text", "text": "Search ArgoCD for prod apps"}]
          }
        },
        "id": 1
      }'

  4. Check logs:

    docker logs platform-engineer-p2p 2>&1 | grep -i "nonexistent artifact"
    # Should return no results ✅

Expected Results​

Before Fix:

[WARNING] Received append=True for nonexistent artifact index...
[WARNING] Received append=True for nonexistent artifact index...
[WARNING] Received append=True for nonexistent artifact index...

After Fix:

[DEBUG] ✅ Streamed FIRST chunk (with 10ms buffer): Here are the...
[DEBUG] ✅ Streamed chunk to client: prod applications...
[DEBUG] ✅ Streamed chunk to client: found 18 matches...
  • Modified: ai_platform_engineering/multi_agents/platform_engineer/protocol_bindings/a2a/agent_executor.py
  • Related: ai_platform_engineering/utils/a2a_common/base_langgraph_agent_executor.py
  • Documentation: This file

  • A2A Protocol: Agent-to-Agent communication via event streaming

  • Event Queue: Asynchronous message passing between agents

  • Artifact: Container for agent response content

  • TaskArtifactUpdateEvent: Event type for streaming artifacts

  • Architecture: architecture.md