[Bug] Context window usage calculation inconsistency across sessions

Bug Description
It's impossible, to be honest, that just today with one session using 25% of context is similar or at least the same as the session where we have the same amount—21%—almost reaching the limits. You're doing an incredible job, but this is not fair for people like us paying for the max subscription.

Environment Info

• Platform: darwin
• Terminal: vscode
• Version: 2.1.91
• Feedback ID: d010bbe8-fd71-47bf-b60a-bfb242619ed7

Errors

[{"error":"Error: {\"stack\":\"Error: PeriodicExportingMetricReader: metrics export failed (error Error: 14 UNAVAILABLE: No connection established. Last error: Error: connect ECONNREFUSED ::1:4317. Resolution note: )\\n    at kB4._doRun (file:///Users/alexis.araujo/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:2067:60752)\\n    at process.processTicksAndRejections (node:internal/process/task_queues:103:5)\\n    at async kB4._runOnce (file:///Users/alexis.araujo/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:2067:59989)\",\"message\":\"PeriodicExportingMetricReader: metrics export failed (error Error: 14 UNAVAILABLE: No connection established. Last error: Error: connect ECONNREFUSED ::1:4317. Resolution note: )\",\"name\":\"Error\"}\n    at Cd1.error (file:///Users/alexis.araujo/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:2095:4337)\n    at zN1.error (file:///Users/alexis.araujo/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:469:10505)\n    at file:///Users/alexis.araujo/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:469:36851\n    at EK_ (file:///Users/alexis.araujo/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:469:37397)\n    at kB4._runOnce (file:///Users/alexis.araujo/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:2067:60222)\n    at process.processTicksAndRejections (node:internal/process/task_queues:103:5)","timestamp":"2026-04-03T16:48:42.600Z"},{"error":"Error: {\"stack\":\"Error: PeriodicExportingMetricReader: metrics export failed (error Error: 14 UNAVAILABLE: No connection established. Last error: Error: connect ECONNREFUSED ::1:4317. Resolution note: )\\n    at kB4._doRun (file:///Users/alexis.araujo/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:2067:60752)\\n    at process.processTicksAndRejections (node:internal/process/task_queues:103:5)\\n    at async kB4._runOnce (file:///Users/alexis.araujo/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:2067:59989)\",\"message\":\"PeriodicExportingMetricReader: metrics export failed (error Error: 14 UNAVAILABLE: No connection established. Last error: Error: connect ECONNREFUSED ::1:4317. Resolution note: )\",\"name\":\"Error\"}\n    at Cd1.error (file:///Users/alexis.araujo/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:2095:4337)\n    at zN1.error (file:///Users/alexis.araujo/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:469:10505)\n    at file:///Users/alexis.araujo/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:469:36851\n    at EK_ (file:///Users/alexis.araujo/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:469:37397)\n    at kB4._runOnce (file:///Users/alexis.araujo/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:2067:60222)\n    at process.processTicksAndRejections (node:internal/process/task_queues:103:5)","timestamp":"2026-04-03T16:49:42.601Z"},{"error":"Error: {\"stack\":\"Error: PeriodicExportingMetricReader: metrics export failed (error Error: 14 UNAVAILABLE: No connection established. Last error: Error: connect ECONNREFUSED ::1:4317. Resolution note: )\\n    at kB4._doRun (file:///Users/alexis.araujo/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:2067:60752)\\n    at process.processTicksAndRejections (node:internal/process/task_queues:103:5)\\n    at async kB4._runOnce (file:///Users/alexis.araujo/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:2067:59989)\",\"message\":\"PeriodicExportingMetricReader: metrics export failed (error Error: 14 UNAVAILABLE: No connection established. Last error: Error: connect ECONNREFUSED ::1:4317. Resolution note: )\",\"name\":\"Error\"}\n    at Cd1.error (file:///Users/alexis.araujo/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:2095:4337)\n    at zN1.error (file:///Users/alexis.araujo/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:469:10505)\n    at file:///Users/alexis.araujo/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:469:36851\n    at EK_ (file:///Users/alexis.araujo/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:469:37397)\n    at kB4._runOnce (file:///Users/alexis.araujo/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:2067:60222)\n    at process.processTicksAndRejections (node:internal/process/task_queues:103:5)","timestamp":"2026-04-03T16:50:42.601Z"},{"error":"Error: {\"stack\":\"Error: 14 UNAVAILABLE: No connection established. Last error: Error: connect ECONNREFUSED ::1:4317. Res…

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