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fix(deps): cap mcp below 2.0.0 to prevent streamable-http break - #70

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syf2211:fix/68-cap-mcp-below-2
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fix(deps): cap mcp below 2.0.0 to prevent streamable-http break#70
syf2211 wants to merge 1 commit into
knowsuchagency:mainfrom
syf2211:fix/68-cap-mcp-below-2

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@syf2211 syf2211 commented Jul 29, 2026

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Summary

Cap the mcp dependency at <2 so fresh installs no longer resolve MCP SDK 2.x, which breaks mcp2cli's streamable-http transport at import time.

Motivation

Fixes #68. MCP SDK 2.0.0 removed the streamablehttp_client alias that mcp2cli imports in three places. Because the published constraint was only mcp>=1.0, new uvx/CI environments resolve mcp 2.x and fail with:

ImportError: cannot import name 'streamablehttp_client' from 'mcp.client.streamable_http'

Stdio and SSE paths are unaffected at import time, but streamable-http users lose the transport entirely. With --transport auto, the ImportError is caught and SSE is attempted instead, producing a misleading 405 from the server.

Changes

  • Update pyproject.toml: mcp>=1.0,<2
  • Regenerate uv.lock

Full MCP SDK v2 migration (import renames and runtime surface checks) can be tracked separately.

Tests

uv run pytest -q

Result: 352 passed

Notes

  • Dependency-only hotfix; no runtime code changes.
  • Reviewed with composer-2.5: APPROVE
  • A patch release (e.g. 3.3.2) may be needed after merge so uvx mcp2cli picks up the cap.

Fixes #68

mcp 2.0.0 removed the streamablehttp_client alias that mcp2cli imports.
Without an upper bound, fresh uvx/CI installs resolve mcp 2.x and the
streamable-http transport fails at import time.

Cap the dependency at <2 until a full MCP SDK v2 migration lands.

Fixes knowsuchagency#68
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Unbounded mcp>=1.0 breaks streamable-http on the mcp 2.0.0 stable release (2026-07-28)

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