Summary

PR #2785 added several new docs pages covering ExecJS limitations, performance benchmarks, debugging, and client-vs-server rendering. Bot reviewers raised several valid concerns about ExecJS technical accuracy that require research to resolve properly. These were deferred from #2785 to avoid an endless review cycle on a docs PR.

Items to investigate

1. ExecJS runtime auto-detection — Multiple docs state "By default, ExecJS uses the Node.js runtime." However, ExecJS auto-detects via best_available and picks mini_racer/Bun before Node if installed. Verify and clarify across:

   • docs/oss/core-concepts/execjs-limitations.md:9
   • docs/oss/core-concepts/client-vs-server-rendering.md:7

2. ExecJS-on-Node process model — docs/oss/core-concepts/performance-benchmarks.md:13 describes ExecJS-on-Node as "Persistent subprocess via IPC" but ExecJS's ExternalRuntime may shell out per evaluation. Verify the actual architecture.

3. Timer polyfill behavior — docs/oss/building-features/debugging.md:68 says users will see setTimeout is not defined errors, but RubyEmbeddedJavaScript#execjs_timer_polyfills stubs these as silent no-ops. Clarify the actual failure mode.

4. SSR timing logging claim — docs/oss/core-concepts/performance-benchmarks.md:110 says "Server render time" is "logged by React on Rails when logging_on_server is enabled." But logging_on_server replays console messages, not render durations. Clarify what metrics are actually available.

5. pool_size constraint scope — docs/oss/core-concepts/execjs-limitations.md:108 says pool_size=1 is required on MRI for all ExecJS runtimes. This may only apply to mini_racer (V8 holds the GVL). With Node.js ExternalRuntime, rendering runs in a subprocess. Narrow the claim if appropriate.

Context

• PR: Docs: Add RSC landing, ExecJS limitations, debugging, and benchmarks pages #2785
• Review comments from: claude[bot], chatgpt-codex-connector[bot]
• All items require reading ExecJS source code and React on Rails' RubyEmbeddedJavaScript to verify claims

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