fix(coding-agent): restart dead kernels on ensure() and read mcp>=2 tool schemas

[snimu]

Summary

Two Python-runtime defects:

• A dead kernel no longer wedges the session. IpythonKernelProvisioner.ensure() memoizes the started kernel and cleared that memo only on startup failure, dispose, or kill. A kernel that died after a successful startup (OOM kill, os._exit, crash) was handed to every later Python call forever — each one failing against a dead process until the session restarted. ensure() now drops the memo when the started kernel is no longer running, so the existing startup path (snapshot restore included) reruns on the next call. Fixes the defect reported in discussion [Bug] v0.8.0 stopped IPython kernel remains permanently cached after unexpected exit #1659.
• Skill-MCP tools advertise their real input schemas again. mcp>=2 renamed the Tool schema field to input_schema (with inputSchema as the wire alias); pydantic attribute access is by field name, so mcp_base.py's getattr(t, "inputSchema", ...) was always None and every skill-MCP tool advertised an empty {} schema — models called tools blind. The lookup now mirrors the dual lookup its sibling mcp.py already uses. Fixes the defect reported in discussion Fix: McpIntegration.list_tools() always returns empty inputSchema (#1073) #1757.

Validation

• two pins, each verified fail-unfixed: a memoized not-running kernel forces a restart (pre-fix: the dead memo is returned and no restart happens), and a Tool exposing only snake_case input_schema surfaces its schema through list_tools() (pre-fix: {})
• suites: ipython-provisioner (20) and test_mcp_base (18 via uv run python -m unittest) — green
• root npm run check passes via the pre-commit hook

LOC

Total src: +20/−5 (net +15); tests: +50/−0 (net +50).
Src +14/−5 (both point fixes; the kernel fix is a 4-line liveness check ahead of the existing memo, the schema fix mirrors the sibling module's lookup). Tests +42, changelog 1 fragment.

Linear: RES-1266 https://linear.app/primeintellect/issue/RES-1266

---

Note

Medium Risk
Touches kernel lifecycle memoization and MCP tool metadata; behavior changes on post-crash recovery and tool listing, but scope is narrow with targeted tests.

Overview
Fixes two runtime bugs where sessions could get stuck on a dead Python kernel and skill-MCP tools could advertise empty parameter schemas.

Dead kernel memo: IpythonKernelProvisioner.ensure() now clears its cached manager when startedManager.isDefunct is true (new KernelClient / ReplKernelManager flag for terminal shutdown). The next Python call goes through the normal startup path—including snapshot restore—instead of reusing a process that died after a successful boot. Managers that are merely not running but still repairing stay memoized so a second kernel does not race on the snapshot dir.

MCP tool schemas: McpIntegration._ensure_tools in mcp_base.py resolves tool parameters via input_schema first, then inputSchema, matching mcp.py and restoring real inputSchema metadata under mcp>=2 instead of always {}.

^{Reviewed by Cursor Bugbot for commit 749e216. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Fix dead kernel restart on ensure() and read input_schema for mcp>=2 tools

• Adds ReplKernelManager.isDefunct and the required KernelClient.isDefunct property so callers can detect a terminal-shutdown kernel. IpythonKernelProvisioner.ensure() now drops the memoized manager and its startup promise when defunct, forcing a fresh kernel on the next call; non-defunct managers stay memoized.
• Reworks McpIntegration._ensure_tools to read input_schema first and fall back to inputSchema for older MCP objects, keeping only dictionary schemas and substituting empty schemas otherwise.
• Risk: KernelClient implementers must now provide the read-only isDefunct property; any out-of-tree implementation missing it will fail the interface contract.

^{Macroscope summarized 749e216.}

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit b94d987. Configure here.}