feat(binding-mcp): offer 2025-11-25 and negotiate elicitation url capability - #1820
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jfallows merged 2 commits intoJun 2, 2026
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Bump the offered MCP protocol version from 2025-06-18 to 2025-11-25 so the proxy can negotiate SEP-1036 url-mode elicitation against a compliant upstream. The south client offers 2025-11-25 and the north server responds with it; per-side down-negotiation to an older peer is preserved. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Parse the north client's initialize capabilities and serialize them to the
upstream so url-mode elicitation (SEP-1036) flows end-to-end through the proxy.
- mcp.idl: add CLIENT_ELICITATION_FORM and CLIENT_ELICITATION_URL to
McpCapabilities, carried on McpLifecycleBeginEx.capabilities.
- north server: parse capabilities.elicitation.{url} from the initialize
request (bare elicitation implies form) and stamp the bits on the lifecycle
begin instead of a fixed capability set; echo the negotiated protocol version
in the initialize response instead of always responding with the latest.
- south client: serialize capabilities back to the upstream from the bits,
emitting elicitation.url only when the north client advertised it; the cache
hydrater advertises no client capabilities.
The proxy already propagates the lifecycle capabilities north-to-south, so url
elicitation is gated per-side: the south advertises url only when the north
client supports it.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This was referenced Jun 3, 2026
jfallows
deleted the
feature/1819-binding-mcp-protocol-version-elicitation-url
branch
July 1, 2026 23:06
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Description
Enable url-mode elicitation (SEP-1036) to flow through the
mcpproxy by offeringMCP protocol 2025-11-25 and negotiating the
elicitation.urlclient capability,so the south client advertises it to upstreams only when the originating north client
supports it.
Closes #1819.
Changes
Two commits:
feat: offer MCP protocol version 2025-11-25 — bump the offered version from2025-06-18to2025-11-25across the two factories and the spec scripts; per-sidedown-negotiation to an older peer is preserved.
feat: negotiate elicitation client capabilitymcp.idl: addCLIENT_ELICITATION_FORMandCLIENT_ELICITATION_URLtoMcpCapabilities, carried on the existingMcpLifecycleBeginEx.capabilities.capabilities.elicitation.{url}from theinitializerequest (bare
elicitationimplies form) and stamps the bits on the lifecyclebegin instead of a fixed capability set; it now echoes the negotiated protocol
version in the
initializeresponse instead of always responding with the latest.capabilitiesback to the upstream from the bits,emitting
elicitation.urlonly when the north client advertised it; the cachehydrater advertises no client capabilities.
The proxy already propagates the lifecycle capabilities north-to-south, so url-mode
elicitation is gated per-side: the south advertises
urlonly when the north clientsupports it.
Notes
Independent binding-mcp enablement, off
develop(after the example-branch extractions#1812 / #1814 / #1816 / #1818). Precursor to wiring the
mcp.proxyurl-elicitation demoon the rebased example branch (#1793).
Testing
./mvnw verify -pl specs/binding-mcp.spec,runtime/binding-mcp— binding-mcp ITs (193)lifecycle.initialize.elicitation.url,lifecycle.initialize.elicitation.form,lifecycle.initialize.negotiate.🤖 Generated with Claude Code