perf(context): skip O(N) calculateTokenBreakdown when tracer is disabled

[rushikeshsakharleofficial]

Summary

• Bug: render.ts eagerly evaluated env.tokenCalculator.calculateTokenBreakdown(nodes) as an argument to tracer.logEvent(...) on every API turn, even though logEvent immediately returns if (!this.enabled). JS evaluates arguments before the function call, so the O(N×parts) computation always ran.
• Fix: Added get isEnabled(): boolean to ContextTracer and guarded the two expensive calls behind if (tracer.isEnabled):
  • calculateTokenBreakdown(nodes) — iterates all nodes, calls estimateTokenCountSync per part for categorization
  • Object.fromEntries(protectionReasons) — O(N) map copy
• Both calls now execute only when GEMINI_CONTEXT_TRACE_DIR is set (tracing opt-in, off by default).

Impact: Applies to users with contextManagement.enabled: true. The generalistProfile budget is configured, so the budget branch of render() fires on every turn for those users.

Test plan

• Existing context pipeline tests pass (no behavior change when tracing disabled)
• When GEMINI_CONTEXT_TRACE_DIR is set, trace logs still contain Estimation Calibration and Protection Audit events
• Nightly perf CI should show improvement for long-conversation scenarios with context management enabled

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[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request optimizes the context rendering pipeline by ensuring that resource-intensive diagnostic operations are only performed when tracing is explicitly enabled. By checking the tracer's status before evaluating arguments for log events, the application avoids unnecessary computations on every API turn, leading to improved performance for users with context management enabled.

Highlights

• Performance Optimization: Added a guard condition to prevent expensive O(N) token breakdown calculations and map copies when the tracer is disabled.
• API Update: Introduced an isEnabled getter to the ContextTracer class to allow efficient checking of the tracing state before executing logging logic.

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[gemini-code-assist]

Code Review

The pull request introduces a check for the tracer's enabled state before logging events during the rendering process in packages/core/src/context/graph/render.ts. To support this, a new isEnabled getter was added to the ContextTracer class in packages/core/src/context/tracer.ts. I have no feedback to provide.