Update the v2 status banner and pin spawned environments to the running SDK version#2834
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…ng SDK version - README.md banner: v2 is in alpha with pre-releases published to PyPI (previously said "pre-alpha, in development"), plus the beta/stable target dates, the <2 upper-bound ask for dependents, and v1.x's maintenance-mode status. The freeze check in shared.yml now honors an override-readme-freeze label so deliberate updates like this one can land while accidental edits stay blocked. - mcp dev and mcp install spawn environments via `uv run --with mcp`, which resolves to the latest stable release rather than the version the user installed; pre-releases are never selected without an explicit pin, so with a v2 pre-release installed the spawned environment got v1 and the user's server failed to import. The requirement now pins the running version; source builds fall back to the unpinned form since dev/local versions are not published to PyPI.
maxisbey
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override-readme-freeze
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Also pin down two test contracts on the new requirement helper: the dev-version fallback preserves extras, and a user-supplied mcp[cli] coexists with the pinned requirement rather than deduplicating into it.
felixweinberger
approved these changes
Jun 11, 2026
| import pytest | ||
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| from mcp.cli.claude import get_uv_path, update_claude_config | ||
| from mcp.cli.claude import get_uv_path, mcp_requirement, update_claude_config |
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Interesting we have a Claude test but guess it's pre-existing
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yeaaa it is definitely weird, will have to think whether we add all CLIs later or something
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Two pre-alpha-release fixes in one PR, per maintainer discussion.
Motivation and Context
README banner: the front-page README.md still described v2 as "pre-alpha, in development". With
2.0.0a1about to be published, it now states the alpha status, how to install it, the beta/stable target dates, the<2upper-bound ask for dependent packages, and v1.x's maintenance-mode status. README.md is deliberately frozen onmain(it documents v1), so the freeze CI check now honors anoverride-readme-freezelabel for intentional updates like this one; accidental edits stay blocked.CLI version pinning:
mcp devandmcp installbuild commands of the formuv run --with mcp .../uv run --with mcp[cli] .... In a fresh environment an unpinnedmcprequirement resolves to the latest stable release - never a pre-release - so a user who installedmcp[cli]==2.0.0a1and ranmcp dev server.py(outside a uv project) ormcp installgot a child environment with v1 in it, and their v2 server failed withModuleNotFoundError. Themcp installcase is the worst variant: the broken command is persisted into Claude Desktop's config. Both sites now pin the requirement to the running SDK version (mcp[cli]==<version>). Source builds carry dev/local version segments that are not on PyPI, so they fall back to the unpinned form.How Has This Been Tested?
uv run --with mcp python -c "from mcp.server.mcpserver import MCPServer"resolves mcp 1.27.2 and fails the import..dev-> unpinned,+local-> unpinned), and the command-construction tests now mock the SDK version so they are deterministic across environments (the repo venv runs a dev build; CI may produce a different version).tests/cli/passes (26 tests), 100% branch coverage onsrc/mcp/cli/*, strict-no-cover clean, pyright and ruff clean.Breaking Changes
None. Claude Desktop configs written by older versions keep their unpinned form until
mcp installis re-run.Types of changes
Checklist
Additional context
A companion PR updates the v1.x branch's README with the same v2 status information, since that branch's README is what PyPI renders for the stable line.
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