Arbor v2.4.0 — "The Agent-Native Leap"

[Anandb71]

Arbor v2.4.0 — The Agent-Native Leap

Release date: July 2026

First code-graph MCP server built for MCP 2026-07-28.

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What's New

MCP 2026-07-28 Protocol

• Protocol version 2026-07-28 with dual-version fallback for 2025-03-26 clients
• Stateless server/discover endpoint
• Response caching metadata (ttlMs, cacheScope) on list/read operations
• Extensions capability map for Tasks and MCP Apps

Tasks Extension

• tasks/get, tasks/update, tasks/cancel for long-running operations
• Background indexing returns task handles instead of errors during cold start
• Agents poll task progress while the graph builds

MCP Apps (SEP-1865)

• Interactive blast-radius graph UI (ui://arbor/blast-radius)
• Interactive architecture map UI (ui://arbor/architecture-map)
• analyze_impact and get_architecture_overview declare _meta.ui resource URIs

Streamable HTTP Transport

arbor bridge --http --port 3333

• Stateless HTTP alongside stdio
• Mcp-Method / Mcp-Name header routing
• Deploy behind load balancers for remote/enterprise use

Tool Quality

• get_blast_radius — real git-diff blast radius analysis (replaces stub)
• Pagination on search_symbols and get_map (offset, limit, hasMore)
• Async tokio stdio (replaces blocking stdin loop)

Benchmarks

• Criterion suite: cargo bench -p arbor-graph
• CI regression gate via .github/workflows/benchmarks.yml
• Updated docs/BENCHMARKS.md with token-savings methodology

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Upgrade Guide

MCP clients (Claude / Cursor) — no changes required for stdio:

claude mcp add --transport stdio --scope project arbor -- arbor bridge

HTTP clients (new):

arbor bridge --http --port 3333
# POST http://127.0.0.1:3333/mcp
# Headers: Mcp-Method: tools/call, Mcp-Name: analyze_impact

Clients on 2025-03-26 keep working. Clients on 2026-07-28 get Tasks, Apps, caching, and pagination.

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Full Changelog

Added

• MCP 2026-07-28 protocol: server/discover, _meta parsing, response caching, dual-version fallback
• Tasks extension: tasks/get, tasks/update, tasks/cancel
• MCP Apps: blast-radius graph + architecture map HTML templates
• Streamable HTTP: arbor bridge --http [--port 3333]
• Real get_blast_radius via shared arbor-graph::compute_blast_radius
• Pagination on search_symbols and get_map
• Criterion benchmarks + CI workflow

Changed

• Async MCP stdio (tokio replaces blocking stdin loop)
• MCP tool annotations: _meta.ui on analyze_impact and get_architecture_overview
• Workspace version bumped to 2.4.0

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Deferred to v2.5.0

• Parallel (rayon) indexing
• Incremental PageRank
• Unified parser pipelines
• Process-level graph daemon

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Install: cargo install arbor-graph-cli · GitHub · MCP Registry

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This discussion was created from the release Arbor v2.4.0 — "The Agent-Native Leap".