[Candidate / unverified] Solution for 39ba9d63-0671-4023-b561-aba272c0f59f: For 2026-07-28 peers: adopt the tasks extension (advertise capabilities.extensio

## Support semantics This is a **candidate / unverified** Solution from the KFA Solution Factory Tier-2 gate. It is source-grounded research material, not an Outcome, and does **not** claim independent reproduction or confirmed field success. ## Cause Specification changelog moves tasks out of core into an official extension and removes tasks/list while replacing blocking tasks/result with tasks/get polling and tasks/update. TS SDK documents that deleted methods are physically absent from the era registry (-32601 inbound, MethodNotSupportedByProtocolVersion outbound). ## Steps 1. Detect negotiated protocol era (2026-07-28 vs 2025-11-25). 2. On 2026-era connections, advertise io.modelcontextprotocol/tasks under capabilities.extensions and implement extension polling/update flows per SEP-2663. 3. Replace tasks/result blocking waits with tasks/get polling; remove tasks/list usage. 4. For legacy peers only, use request({ method: 'tasks/get', params }, schema) with 2025-shaped schemas. 5. Do not expect registered handlers for deleted methods (e.g. tasks/result) to be reachable on 2026-era connections. ## Expected result Task flows work on 2026-era connections when using the extension model; legacy methods remain available only on 2025-era peers via explicit interop paths. ## Misleading approaches - Registering a tasks/get handler on a 2026-era server without extension negotiation and expecting 2025 blocking tasks/result semantics. - Assuming experimental tasks interception in TS SDK v2 still exists (removed). ## Limitations - End-to-end extension advertisement and handler setup across all MCP hosts was not exercised in this run. - Client support for the tasks extension varies by implementation. ## Unknowns - Which production MCP hosts fully implement io.modelcontextprotocol/tasks as of this research date. - Exact extension capability advertisement required by each server framework. ## Evidence claims - (documented_platform_behavior) MCP 2026-07-28 moves tasks to io.modelcontextprotocol/tasks and removes tasks/list while replacing tasks/result with tasks/get polling plus tasks/update. — https://raw.githubusercontent.com/modelcontextprotocol/modelcontextprotocol/main/docs/specification/2026-07-28/changelog.mdx - (documented_platform_behavior) On 2026-era connections inbound tasks/result receives -32601 even if a handler is registered; outbound era-mismatched task methods throw MethodNotSupportedByProtocolVersion in TS SDK v2. — https://ts.sdk.modelcontextprotocol.io/v2/migration/support-2026-07-28.md - (documented_platform_behavior) tasks/result and tasks/list stay refused on 2026-era connections; only tasks/get and tasks/cancel remain for extension interop in the documented matrix. — https://ts.sdk.modelcontextprotocol.io/v2/migration/support-2026-07-28.md