Track: upgrade to MCP 2026-07-28 protocol revision (blocked on mcp-go)

[Dumbris]

Summary

The MCP 2026-07-28 spec revision (release candidate) is a major, proxy-impacting protocol change. This issue tracks mcpproxy's upgrade. Full scope captured in spec 057-mcp-2026-upgrade (specs/057-mcp-2026-upgrade/spec.md).

⛔ Dependency gate

Implementation is BLOCKED until github.com/mark3labs/mcp-go ships 2026-07-28 support. As of 2026-05-28, pinned v0.54.0 and latest v0.54.1 both target only 2025-11-25. We do not hand-roll protocol primitives ahead of the library.

Breaking changes to address (proxy-specific)

• Sessions removed / fully stateless; */list MUST NOT vary per connection — reconcile with agent-token scoping + multiuser filtering.
• initialize/initialized removed → new server/discover RPC + per-request _meta (protocolVersion/clientInfo/clientCapabilities), both as server and client.
• New REQUIRED headers Mcp-Method, Mcp-Name, MCP-Protocol-Version — proxy must set/validate/forward both directions; -32001 HeaderMismatch.
• MRTR (input_required + inputResponses) replaces server-initiated sampling/elicitation over SSE.
• x-mcp-header param→header mirroring.
• resources/subscribe → subscriptions/listen; GET stream removed.
• Resource-not-found -32002 → -32602.

Additive opportunities

• CacheableResult (ttlMs + cacheScope) → amplifies token-savings value prop.
• Deterministic tool ordering; server:tool prefix now spec-blessed.
• Header-based routing (avoid JSON body parse); Tasks + MCP Apps extensions.
• W3C/OTel trace context in _meta → activity log; JSON Schema 2020-12 default.

Deprecations to migrate away from

roots, sampling, logging, HTTP+SSE 2024-11-05 transport (12-month window).

Next steps

1. Watch mcp-go for a 2026-07-28 release (scheduled tracking agent).
2. Re-validate spec 057 against the finalized (non-RC) spec when the gate clears.
3. Run /speckit.plan → /speckit.tasks once unblocked.

Related spec: specs/057-mcp-2026-upgrade/spec.md

[Dumbris]

⏳ Still blocked — no change (weekly check 2026-06-01)

Dependency gate: github.com/mark3labs/mcp-go latest release is v0.54.1 (May 25, 2026). LATEST_PROTOCOL_VERSION = "2025-11-25"; ValidProtocolVersions contains only 2025-11-25, 2025-06-18, 2025-03-26, 2024-11-05. The string 2026-07-28 does not appear anywhere in the types file. Library gate is not cleared.

Spec status: Still a Release Candidate. RC was announced May 21, 2026 (post: The 2026-07-28 MCP Specification Release Candidate). Final specification is scheduled to ship July 28, 2026 — no finalization post yet. No breaking detail changes since last check; confirmed RC details: Mcp-Session-Id header removed, new required headers MCP-Protocol-Version / Mcp-Method / Mcp-Name, initialize/initialized handshake eliminated (client info moves to _meta), error code -32002 → -32602, Tasks API requires migration.

Tracking: Issue #532 is open. PR #533 is open / not merged (spec doc only, awaiting library gate).

No action required this week. Will re-check next Sunday.

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[Dumbris]

⏳ Still blocked — no change (weekly check 2026-06-08)

Dependency gate: github.com/mark3labs/mcp-go latest is v0.54.1 (released May 25, 2026). LATEST_PROTOCOL_VERSION = "2025-11-25"; ValidProtocolVersions covers 2025-11-25 / 2025-06-18 / 2025-03-26 / 2024-11-05. The string "2026-07-28" does not appear anywhere in mcp/types.go. Gate is not cleared.

Spec status: MCP 2026-07-28 is still a release candidate — the most recent blog post (May 21, 2026) at blog.modelcontextprotocol.io still uses RC language. The spec is not expected to be finalized until July 28, 2026 itself. No field-name or error-code changes vs. original RC have been detected that would require editing the spec.

Project status: Issue #532 is open. PR #533 is open, not merged (note: PR title was corrected to "spec 058" in a revision, though tracked here as 057/058).

No action required yet. Next check: 2026-06-15. Implementation can begin once mcp-go ships a release where "2026-07-28" appears in ValidProtocolVersions.

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[Dumbris]

⏳ Still blocked — no change (weekly check, 2026-06-15)

Dependency gate: github.com/mark3labs/mcp-go latest is v0.54.1 (released May 25, 2026). LATEST_PROTOCOL_VERSION is still "2025-11-25"; ValidProtocolVersions contains only 2024/2025 dates. No 2026-07-28 anywhere in the codebase. Library gate is not cleared.

Spec status: The 2026-07-28 revision is still a release candidate (RC locked May 21, 2026; final ships July 28, 2026 — 43 days out). No breaking-detail changes since the RC was announced. Key breaking items remain as documented in the spec: removal of initialize/initialized handshake, session management eliminated (Mcp-Session-Id gone), new required Mcp-Method / Mcp-Name headers, MCP-Protocol-Version header replacing handshake exchange, missing-resource error code changed from -32002 → -32602.

Project status: Issue #532 open, no new comments. PR #533 open and intentionally held (June 8 triage note confirmed: "no engineer action needed now; revisit when mcp-go ships 2026-07-28 support").

Next check: 2026-06-22. Will fire earlier if mcp-go cuts a new release.

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[Dumbris]

⏳ Still blocked — no change (weekly check 2026-06-22)

Dependency gate: mcp-go latest is v0.55.0 (released 2026-06-16). LATEST_PROTOCOL_VERSION is still "2025-11-25"; ValidProtocolVersions is ["2025-11-25", "2025-06-18", "2025-03-26", "2024-11-05"]. The string "2026-07-28" does not appear anywhere in types.go. Library gate not cleared.

Spec status: The 2026-07-28 revision remains a release candidate (RC announced 2026-05-21). No blog post or changelog entry indicates it has moved to final. No breaking-detail changes detected since last check.

Project: Issue #532 is open. PR #533 is open, not merged (title now reads "spec 058" — possibly renumbered; still waiting on library).

Nothing actionable this week. Will recheck next Monday.

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[Dumbris]

⏳ Still blocked — weekly watcher check, 2026-06-29

Dependency gate (mcp-go): Latest release is v0.55.1 (2026-06-25). LATEST_PROTOCOL_VERSION in mcp/types.go is still "2025-11-25"; ValidProtocolVersions = ["2025-11-25", "2025-06-18", "2025-03-26", "2024-11-05"]. The string "2026-07-28" does not appear anywhere in the library. Gate remains blocked.

Spec status: The 2026-07-28 spec remains a Release Candidate (RC locked 2026-05-21). Final is scheduled for the date itself — July 28, 2026 (~4 weeks out). No breaking field/header/error-code changes detected vs. the RC captured in spec 057; no edits to the spec are needed this week.

Project status: Issue #532 — open. PR #533 (spec/docs) — merged 2026-06-24 (all 46 CI checks passed).

Next gate: Watch for mcp-go tag ≥ v0.56.0 with LATEST_PROTOCOL_VERSION = "2026-07-28". Expect library support to land in the ~4-week window between now and the final spec ship date.

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[Dumbris]

🟡 Movement — spec finalization imminent, library still blocked (weekly check 2026-07-06)

mcp-go gate: Latest is v0.55.1 (released 2026-06-25). LATEST_PROTOCOL_VERSION = "2025-11-25" — ValidProtocolVersions still contains only 2025-11-25, 2025-06-18, 2025-03-26, 2024-11-05. The string "2026-07-28" does not appear anywhere in the library. Gate not cleared.

Spec status: The 2026-07-28 revision is still an RC, but the final specification ships in 22 days (July 28, 2026). The official Tier-1 SDKs (Python v2, TypeScript v2, modelcontextprotocol/go-sdk v1.7.0-pre.1, C# v2 preview) have beta releases with 2026-07-28 support — mark3labs/mcp-go is not among them. No breaking detail changes since baseline: -32602 for missing-resource and Mcp-Method/Mcp-Name headers are confirmed in spec 057 already.

Project: Issue #532 open. PR #533 merged 2026-06-24.

Watch signal: With the official Go SDK beta live and the final spec ~3 weeks out, pressure on mark3labs/mcp-go to ship a compatible release should increase sharply. Recommend daily checks of mcp-go releases starting ~July 21.

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[Dumbris]

⏳ Still blocked — mcp-go v0.56.0 still targets 2025-11-25 (weekly check 2026-07-13)

mcp-go gate: Latest is v0.56.0 (released ~2026-07-09, up from v0.55.1 last week). LATEST_PROTOCOL_VERSION = "2025-11-25" — ValidProtocolVersions unchanged: 2025-11-25, 2025-06-18, 2025-03-26, 2024-11-05. The string "2026-07-28" does not appear in the library. Gate not cleared.

Spec status: Still an RC. The 2026-07-28 specification is scheduled to finalize in 15 days (July 28, 2026). No breaking-detail changes detected since last check. The official modelcontextprotocol/go-sdk has a beta with 2026-07-28 support; mark3labs/mcp-go has not yet followed.

Project: Issue #532 open. PR #533 merged 2026-06-24.

Watch signal: Spec finalization and library release are now likely within 2 weeks of each other. Daily monitoring of mcp-go releases recommended from ~July 21 onward.

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[Dumbris]

⏳ Still blocked — no change (weekly check 2026-07-20)

mcp-go gate: Latest release is v0.56.0 (2026-07-09). LATEST_PROTOCOL_VERSION remains "2025-11-25"; ValidProtocolVersions = ["2025-11-25", "2025-06-18", "2025-03-26", "2024-11-05"]. No 2026-07-28 support present. Implementation of spec 057 cannot begin yet.

Spec status: 2026-07-28 is still a Release Candidate. The most recent MCP blog post (2026-06-29) covers beta SDKs for the RC — no finalization announcement found. No breaking-detail changes noted since last check.

Issue #532: Open. PR #533: Merged 2026-06-24 (spec/docs only; implementation blocked pending mcp-go gate).

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