v0.5.0

What's Changed

Added

• Batch Invocations: New hangar_batch() tool for parallel tool execution

  • Execute multiple tool invocations in a single API call
  • Configurable concurrency (1-20 parallel workers)
  • Single-flight pattern for cold starts (one MCP server starts once, not N times)
  • Partial success handling (continue on error by default)
  • Fail-fast mode (abort on first error)
  • Per-call and global timeout support
  • Circuit breaker integration (CB OPEN = instant error)
  • Response truncation for oversized payloads (10MB per call, 50MB total)
  • Eager validation before execution
  • Full observability (batch_id, call_id, Prometheus metrics)

• SingleFlight Pattern: New SingleFlight class in infrastructure/single_flight.py

  • Ensures a function executes only once for a given key
  • Thread-safe implementation with result caching option
  • Used for cold start deduplication in batch operations

• Domain Events: New batch-related domain events

  • BatchInvocationRequested - When batch starts
  • BatchInvocationCompleted - When batch finishes
  • BatchCallCompleted - Per-call completion

• Prometheus Metrics: New batch metrics

  • mcp_hangar_batch_calls_total{result} - Total batch invocations
  • mcp_hangar_batch_size_histogram - Calls per batch distribution
  • mcp_hangar_batch_duration_seconds - Batch execution time
  • mcp_hangar_batch_concurrency_gauge - Current parallel executions
  • mcp_hangar_batch_truncations_total{reason} - Response truncations
  • mcp_hangar_batch_circuit_breaker_rejections_total{MCP server} - CB rejections
  • mcp_hangar_batch_cancellations_total{reason} - Batch cancellations

Documentation

• New guide: docs/guides/BATCH_INVOCATIONS.md

Installation

PyPI:

pip install mcp-hangar==0.5.0

Docker:

docker pull ghcr.io/mcp-hangar/mcp-hangar:0.5.0

Links

• PyPI Package
• Docker Image
• Documentation

Full Changelog: v0.4.0...v0.5.0