install: reported `mcp` dependency conflict on >= 10.3.0 — not reproducible from a clean env, needs reporter details

[RichardHightower]

Summary

Split out from #222, where @stevemju noted in passing:

Agent Brain: 10.2.0 (also present on main) (btw >= 10.3.0 doesn't work for me because of a mcp dependency conflicts, but that's another issue)

This is that other issue. A user is pinned to 10.2.0 and cannot upgrade, so it blocks them from picking up every fix since — including the base_url fix in #222.

Investigation so far (2026-08-30)

Could not reproduce from a clean environment. Resolutions were run with uv pip compile --python-version 3.10 (the reporter is on Python 3.10) for:

Package set	Result
agent-brain-rag==10.4.0 + agent-brain-cli==10.4.0	resolves clean
the above + agent-brain-ag-mcp==10.4.0	resolves clean
agent-brain-rag/cli/ag-mcp all ==10.3.2	resolves clean

Published metadata was also checked and is correct — no path dependencies leaked into any published wheel (a real risk given agent-brain-cli/pyproject.toml carries agent-brain-ag-mcp = { path = "../agent-brain-mcp" } for local dev, which the release process swaps to a PyPI pin):

• agent-brain-cli==10.4.0 → agent-brain-rag<11.0.0,>=10.4.0, agent-brain-uds<11.0.0,>=10.3.0
• agent-brain-ag-mcp==10.4.0 → mcp<2.0.0,>=1.27.2, agent-brain-rag<11.0.0,>=10.4.0, agent-brain-uds<11.0.0,>=10.4.0
• mcp itself declares requires_python >=3.10 at both 1.12.0 and 1.27.2, so there is no Python-version conflict.

Leading hypothesis

The conflict is environment-local, not a packaging defect: v10.4 raised the floor to mcp>=1.27.2 (Phase 67 needed mcp.server.auth). An environment that already holds an older mcp pinned by another MCP tool would fail to co-resolve, and pip's resolver reports that as a dependency conflict.

What's needed to close this

From the reporter:

1. The exact install command (pip install ... / uv pip install ..., and which packages).
2. The full resolver error text, which names the conflicting pins.
3. pip freeze | grep -i mcp from the target environment before the upgrade.
4. Whether installing into a fresh virtualenv succeeds.

Possible outcome

If confirmed as a pre-existing mcp pin, the fix is documentation (an install-troubleshooting note about the mcp>=1.27.2 floor from v10.4 and using a clean venv), not a metadata change.

[RichardHightower]

Reproduction attempt on 2026-09-19: still not reproducible from a clean environment

I ran a second matrix, this time with pip (26.2.1) instead of uv, in fresh venvs on Python 3.10.14 (the reporter's version). Each case was resolved with pip install --dry-run, and cases B and C were installed for real.

Case	Command	Result
A	pip install agent-brain-rag==10.3.0 agent-brain-cli==10.3.0 agent-brain-ag-mcp==10.3.0	resolves clean
A2	same at 10.3.1	resolves clean
B	same at 10.7.0	resolves clean, installs, pip check clean
C	install all three at 10.2.0, then pip install -U agent-brain-rag agent-brain-cli agent-brain-ag-mcp	upgrades to 10.7.0, pip check clean
F	pip install agent-brain-cli==10.3.0 agent-brain-rag==10.3.0 (no MCP package)	resolves clean
D	pip install "mcp==1.9.4" agent-brain-ag-mcp==10.3.0 (and ==10.4.0)	ResolutionImpossible
E	pip install "mcp>=2" agent-brain-ag-mcp==10.7.0 (and ==10.3.0)	ResolutionImpossible

Two more facts from the published metadata:

• agent-brain-ag-mcp declares the same mcp<2.0.0,>=1.12.0 at 10.2.0, 10.2.1, 10.3.0, 10.3.1, and 10.3.2. The floor moved to >=1.27.2 only at 10.4.0. Published metadata alone cannot explain a change in behavior between 10.2.x and 10.3.0.
• mcp 2.0.0 shipped on 2026-07-28, after this report. Any environment that now holds mcp>=2 (case E) fails to co-install every Agent Brain MCP release, because of our <2.0.0 cap. That is tracked separately as a follow-up issue.

The only failing cases are the ones where another package already pins mcp outside >=1.12.0,<2.0.0 (case D) or >=1.27.2,<2.0.0 for 10.4.0 and later (case E). The resolver error names both pins, for example:

ERROR: Cannot install agent-brain-ag-mcp==10.7.0 and mcp>=2 because these package versions have conflicting dependencies.
The conflict is caused by:
    The user requested mcp>=2
    agent-brain-ag-mcp 10.7.0 depends on mcp<2.0.0 and >=1.27.2

@stevemju, to move this forward I still need the four items from the issue body:

1. The exact install command and package list.
2. The full resolver error text (it names the conflicting pins).
3. pip freeze | grep -i mcp from the target environment before the upgrade.
4. Whether the install succeeds in a fresh virtualenv.

If there is no reply by 2026-10-03 I will close this as not reproducible. Reopen any time with the details above and I will pick it up again.