Claude Code MCP reliability routing: v2.1.191 fixes the flaky agent control plane

Claude Code MCP reliability routing became a more concrete operator concern with the v2.1.191 release on June 24. The headline is not a new model or a flashy IDE feature. It is a cluster of small control-plane fixes: MCP discovery now retries transient network failures, MCP OAuth is friendlier to headless environments, managed settings can force a no-cache remote refresh, and sandbox network approvals can persist for the rest of a session. For teams running coding agents through an AI gateway, those details decide whether a long-running agent fails closed, loops on auth, or burns budget on recoverable infrastructure noise.

What happened

Anthropic's official Claude Code v2.1.191 release lists several fixes that are easy to miss if you only scan for model changes. The most important operator items are:

• MCP capability discovery for tools/list, prompts/list, and resources/list now retries transient network errors with short backoff.
• MCP OAuth discovery and token requests retry once after transient network errors, while headless environments skip the browser popup and go straight to the paste-the-URL prompt.
• Managed settings forceRemoteSettingsRefresh now works when set by MDM or file policy, and the refresh request sends Cache-Control: no-cache so proxies do not serve stale policy.
• Sandbox network permission dialogs remember hosts approved with "Yes" for the rest of the session instead of prompting again on every connection.
• Background agents that were stopped from the tasks panel no longer resurrect later.
• Streaming text updates are coalesced to 100ms, reducing CPU usage during responses by about 37%, and long-session terminal-output memory growth was reduced.

None of these changes rewrites the Claude Code product. Together, they tighten the agent control plane around the exact interfaces operators usually own: tool discovery, credential flow, policy propagation, sandbox egress, and long-session resource overhead.

Why Claude Code MCP reliability routing matters for AI engineering teams

A coding agent is only as reliable as the control plane around its tools. If an MCP server briefly drops during tools/list, the agent may interpret the missing tool as an application limitation. If OAuth discovery fails inside an SSH or CI environment, the operator may see an auth failure rather than a transient network issue. If remote settings are cached by a proxy, a fleet may run stale model restrictions or permission policy after the team believes the new policy has shipped.

That is why Claude Code MCP reliability routing should be treated as a policy topic, not a patch-note footnote. Teams that route agent sessions through shared infrastructure need to distinguish three classes of failure:

1. Recoverable control-plane noise: retry MCP discovery and OAuth once or twice before changing model route or failing the task.
2. Policy freshness failures: fail closed when managed settings cannot be refreshed, especially for model restrictions, sandbox policy, and tool permissions.
3. Runtime-resource drift: watch CPU, memory, and terminal-output growth for long sessions so agent cost is not hidden inside host overhead.

TheRouter users can map those classes to broader gateway practice through the TheRouter docs: treat agent sessions as stateful workloads with tool inventory, identity, policy version, and cost attribution, not just isolated chat completions.

The Claude Code MCP reliability routing angle

The release changes how a router or gateway should observe coding-agent sessions. A model fallback alone will not fix a missing MCP tool list, a stale remote policy, or a sandbox egress prompt that repeats every few seconds. Those are control-plane conditions, so the routing layer needs a control-plane checklist.

First, log MCP discovery separately from model requests. A failed tools/list should not be blended into generic model latency. It should be tagged as MCP availability, server URL, retry count, and final tool inventory. That lets operators know whether task failure came from model reasoning or missing tool context.

Second, include policy version and refresh status in session metadata. The forceRemoteSettingsRefresh fix matters because stale policy is one of the easiest ways for enterprise agent fleets to drift. If a gateway routes sessions by team, project, or risk tier, it should also record the managed-settings version that was active when the session began.

Third, treat sandbox network approvals as egress state. Remembering approved hosts for a session reduces prompt fatigue, but it also means the session has an evolving network allowance. Operators should reconcile that with deny-by-default egress rules and with any compliance boundary around repositories, package registries, and internal APIs.

What TheRouter users should watch or try

Start with a controlled upgrade lane rather than a fleet-wide flip. Compare v2.1.191 against your current Claude Code version on a representative long-running task that uses MCP, sandboxed commands, and background agents.

Use this quick operator checklist:

• Confirm MCP discovery failures are logged with retry count and final status.
• Test MCP OAuth in a headless or SSH environment and document the paste-the-URL path.
• Verify that managed settings refreshes bypass proxy cache and that the active policy version is visible to operators.
• Review sandbox network approvals as session-scoped egress state, not just UX convenience.
• Compare CPU and memory for a long streaming session before and after the upgrade.
• Re-read the earlier TheRouter analysis of Claude Code 2.1.186 bash auto-respond and subagent permission routing because v2.1.191 builds on the same operator theme: the agent control plane is becoming a first-class reliability surface.

The practical takeaway: Claude Code MCP reliability routing is less about changing which model answers a prompt and more about proving that tools, credentials, policy, and sandbox egress are healthy before a coding agent spends another hour on the wrong path.