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fix(mcp-sessions): require a minimum idle age before LRU eviction at capacity (#467) - #468
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October 9, 2026 01:35
…capacity (#467) LRU eviction at capacity now only evicts sessions idle for at least DEVSPACE_MCP_SESSION_LRU_MIN_IDLE_MS (default 60s, <= idle timeout), so one client cannot churn others' recently active sessions. Rejections report rejectionCause (all_in_flight | no_session_idle_min) in the mcp_session_capacity_rejected log; the HTTP response is unchanged. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
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Closes #467. LRU eviction at capacity (added in #461) now only considers sessions with no in-flight request, not pending close, and idle for at least
DEVSPACE_MCP_SESSION_LRU_MIN_IDLE_MS(default 60 000 ms). Younger sessions stay protected, so one noisy client can no longer evict other clients' recently active sessions; if no session qualifies, registration is rejected with the same 503 / -32004 as before #461.DEVSPACE_MCP_SESSION_LRU_MIN_IDLE_MS(config-file keymcpSessionLruMinIdleMs), validated as a positive integer no greater than the effective idle timeout (sameInvalid <NAME>: <value>error as the sibling settings). The unset default is clamped to the idle timeout so a short idle timeout never makes the default invalid.evictLruToLimit()andhasEvictableSession()share the rule, socanAcceptRegistration()/admitRegistration()still agree withregister().register()rejections carryrejectionCause: "all_in_flight" | "no_session_idle_min"and the registry exposescapacityRejectionCause()for the pre-check path.mcp_session_capacity_rejectedlogs it asrejectionCause. The HTTP response is unchanged.lruMinIdleMsdefaults tomin(60 s, idleTimeoutMs)when omitted, so callers that only set an idle timeout keep pre-P1: MCP session store rejects new sessions with 503 while idle sessions with no in-flight requests remain evictable #461 behavior for young sessions.no_session_idle_min,capacityRejections+1,lruEvictionsunchanged); 256 idle 90 s evicts the LRU with no rejection; exact-boundary check; all in flight rejects withall_in_flight; mixed young/in-flight case; config default, env override, config clamp, and rejection of 0, negative, non-integer, and values above the idle timeout. P1: MCP session store rejects new sessions with 503 while idle sessions with no in-flight requests remain evictable #461 tests that assumed unconditional eviction now setlruMinIdleMsexplicitly and the rejection assertions includerejectionCause.Verification:
npx tsx src/mcp-sessions.test.ts,npx tsx src/config.test.ts,npx tsx src/server.test.ts(67 pass),npm run typecheck,npm run build.🤖 Generated with Claude Code