Add --mcp-version flag to pin MCP protocol version - #320
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… version Adds a strict protocol version pin: mcpc connect --mcp-version <version> (also an mcpVersion field in mcp.json config entries) connects with exactly the requested MCP revision instead of auto-negotiating, failing loudly when the server does not support it. Modern revisions (2026-07-28) map to the SDK's pin mode; legacy revisions run the plain initialize handshake offering only the pinned version. The pin is persisted in sessions.json, survives restarts, and is shown as "(pinned)" in session info. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01DCJziR1mQfJk9XynQCwsFx
This was referenced Jul 26, 2026
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The MCP spec and TypeScript SDK use `protocolVersion` as the canonical term, so this renames the `mcpc connect --mcp-version` flag to `--protocol-version` and the mcp.json config field `mcpVersion` to `protocolVersion`. No deprecation alias — the flag was added in unreleased #320, so nothing shipped under the old name. - Internal option fields, `protocol.ts` constants/helpers, docs (README, SKILL.md, CLAUDE.md), and the changelog entry renamed to match - E2E suite renamed to `protocol-version.test.sh`; the JSON pin now appears as `_mcpc.server.protocolVersion` Refs #320 https://claude.ai/code/session_01TpJ2kbEL9zSS4baM3CGU5E Co-authored-by: Claude <noreply@anthropic.com>
jancurn
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A `protocolVersion` field in an mcp.json entry never reached the client, so `mcpc connect cfg.json:entry` auto-negotiated instead of pinning, with no error or warning — only the `--protocol-version` flag worked. `substituteEnvVars()` rebuilt each entry from a per-field allowlist and simply forgot the field. - The config copier now passes every field through and rewrites only those needing env-var substitution or URL normalization, so future `ServerConfig` fields can't be dropped the same way. - An unsupported pin from a config entry is now rejected up front with the same error as the flag, instead of failing later inside the bridge. - Unit tests for the preserved pin and unknown-field pass-through, plus e2e coverage in `basic/protocol-version.test.sh` (both protocol eras). No changelog entry: config-entry `protocolVersion` is still in `[Unreleased]` (#320), so the existing "Added" line already describes the working behaviour. Fixes #323 Refs #320 https://claude.ai/code/session_01D4Y47mxUVcz73X13R5f4sJ Co-authored-by: Claude <noreply@anthropic.com>
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Adds
--mcp-version <version>tomcpc connect(and anmcpVersionfield in mcp.json entries) to pin the MCP protocol version instead of auto-negotiating. The pin is strict: the connection fails with an actionable error unless the server agrees to exactly the requested version.{ pin }mode; legacy pins run the plaininitializehandshake offering only the pinned versionrestart) and shows as(pinned)inmcpc @sessionsrc/core/protocol.ts(CLI startup never loads the SDK); a unit test guards drift against the SDK's listRefs #314
https://claude.ai/code/session_01DCJziR1mQfJk9XynQCwsFx