[Bug] Tool call parsing fails with long multibyte/CJK string arguments

Bug Description
Title: Tool call "could not be parsed (retry also failed)" — frequent with long CJK/multibyte string args
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▎ Body:
▎ Environment: Claude Code CLI, model Opus 4.8 (1M context), macOS 25.5.0
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▎ Bug 1 — tool call parse failure
▎ Repeatedly hit The model's tool call could not be parsed (retry also failed), wasting a full turn. Strongly correlated with Edit calls carrying long multibyte (Chinese) string arguments containing full-width punctuation (／｜＋＝). Short calls rarely fail; long CJK Edit args fail often. Happened ~4-5 times in one session of editing a long Markdown ledger.
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▎ Bug 2 (likely intended, but disruptive) — adaptive reasoning on trivial actions
▎ Opus 4.8 spends 30s–4min ("Brewed/Churned for Ns") thinking before trivial actions (e.g. updating a number in a file), with no text output during that time. UX reads as "frozen / no output". /effort low mitigates but the default still over-thinks simple direct lookups/edits.
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▎ Expected: long multibyte tool-call args parse reliably; trivial actions shouldn't trigger deep reasoning by default.

Environment Info

• Platform: darwin
• Terminal: ghostty
• Version: 2.1.158
• Feedback ID: f570391c-ba26-416e-bf2a-b9ed8585097c

Errors

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