First prompts after session start are swallowed and processed with up to ~30s delay (regression after recent update)

Description

After a recent Claude Code update, the first 1–2 prompts in a new session
are processed with a significant delay — up to ~30 seconds — or appear to
be "swallowed" (no visible reaction for a while, then the response arrives).
Subsequent prompts in the same session work normally with no noticeable delay.

Steps to reproduce

1. Start claude in the terminal (new session).
2. Wait for SessionStart hooks to finish loading.
3. Send the first prompt.
4. Observe a delay of up to ~30 seconds before the response starts.
5. Send a second/third prompt — responds immediately, as before.

Expected behavior

The first prompt should be processed with the same latency as subsequent ones.

Actual behavior

The first prompt hangs for up to ~30 seconds, sometimes appearing to be
fully swallowed (no indication that the request was received).

Environment

• OS: macOS 15 (Darwin 24.6.0)
• Shell: zsh
• Regression started after a recent Claude Code update

Additional notes

Possibly related to cache initialization, plugin loading, or SessionStart hooks.