fix(capabilities): client may only narrow the seeded ceiling (audit B1)#89
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- initialize now intersects client-declared capabilities with the transport-seeded ceiling instead of replacing it; no seed fails closed to an empty set - policy mode ceiling read from the core (WalletContext.policy_mode): read_only leaves read+preview; unreachable core falls back to the transport ceiling with a warning (MCP-side filtering is advisory, enforcement lives in the core) - SSE: a second initialize can no longer change session capabilities (explicit initialized flag instead of the falsy-set guard) - sign_message: sign_type enum is ["eip191"] only, matching the documented EIP-191-only contract Spec: .claude/specs/2026-07-24-mcp-ceiling-integration.md
Review delta for PR #89: - SSE sessions are now seeded from the same operator ceiling, so the initialize intersection actually bites there too (B1 closed end-to-end; unset env keeps the historical gated-until-granted contract) - ruff format compliance (CI gate was red on tests/test_handlers.py) - test: seeded SSE session narrows client grants, keeps the stored ceiling
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Summary
Second half of closing audit B1 end-to-end (first half: rustok-org/core#96, merged as
eec38c1). The capability ceiling is now authoritative in the core; the MCP layer only reads it and can never widen it.handlers.py):initializenow intersects the client-declared capability list with the transport-seeded ceiling instead of replacing it. An operator launching withRUSTOK_MCP_CAPABILITIES=read_walletgets a session the agent cannot talk out of. No seeded ceiling fails closed to an empty set — the server seeds, the client only narrows.initializereadspolicy_modevia WalletContext (core increment 1).read_onlyleaves read+preview tools;supervised/autonomouskeep the full set while the core itself parks/denies writes. Unreachable core → transport ceiling alone with a warning — MCP-side filtering is advisory; enforcement stays in the core (no policy enforcement duplicated in this layer).initializedexplicitly.sign_messageschema matches its contract:sign_typeenum is["eip191"](it listedeip712while the description said EIP-712 is not supported).Spec:
.claude/specs/2026-07-24-mcp-ceiling-integration.mdTest plan
pytest— 195 passedruff check .— clean{read_wallet}+ client asks all →{read_wallet}; no seed → empty set (fail-closed)read_onlymode: tools/list hides execute/sign, keeps read+preview;supervisedkeeps the full setsign_typeenum ==["eip191"]