[Bug] Severe latency in Claude Code with long-context sessions (20min+ turn times)

Bug Description
⏺ Bug report: Severe latency in Claude Code session

Model: Opus 4.6 (1M context)
Environment: macOS, Claude Code CLI

Issue: Individual turns are taking ~20 minutes to complete, including
simple operations like writing 4 small markdown files (<2KB each) via
the Write tool. Tool calls themselves appear to execute quickly, but
there is significant delay between tool use and the next assistant
message streaming.

Context: Long-running conversation (~80k+ tokens) involving multiple
subagent calls (5 parallel general-purpose agents earlier in the
session, then 2 more debate agents). Conversation includes several
CSV reads and tool outputs that remain in context.

Expected: Small Write operations + a few-sentence response should
complete in seconds, not minutes.

Observed: ~20 minutes from user message submission to completion of
a sequence of 4 Write/Edit tool calls plus a brief summary reply.

Suspected causes (unverified):

• API/inference latency spike on Anthropic side
• Prompt cache misses on long context
• Opus 4.6 throughput under heavy load
• MCP server response delays

Happy to share session ID or /status output if useful.

Environment Info

• Platform: darwin
• Terminal: iTerm.app
• Version: 2.1.105
• Feedback ID: c52b4549-60fd-41b4-83fb-87d4023ebc75

Errors

[{"error":"Error: NON-FATAL: Lock acquisition failed for /Users/thedemings/.local/share/claude/versions/2.1.105 (expected in multi-process scenarios)\n    at bd_ (/$bunfs/root/src/entrypoints/cli.js:2334:2153)\n    at nt6 (/$bunfs/root/src/entrypoints/cli.js:2334:1233)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-04-14T03:09:25.240Z"},{"error":"Error: 1P event logging: 14 events failed to export (code=ECONNABORTED, timeout of 10000ms exceeded)\n    at queueFailedEvents (/$bunfs/root/src/entrypoints/cli.js:422:2574)\n    at async doExport (/$bunfs/root/src/entrypoints/cli.js:422:1516)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-04-14T03:44:44.693Z"},{"error":"Error: 1P event logging: 15 events failed to export (code=ECONNABORTED, timeout of 10000ms exceeded)\n    at queueFailedEvents (/$bunfs/root/src/entrypoints/cli.js:422:2574)\n    at async doExport (/$bunfs/root/src/entrypoints/cli.js:422:1516)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-04-14T03:45:04.709Z"}]