Voice dictation requires unnaturally slow speech; degrades with duration; same mic works fine in Google Docs

Environment

• Claude Code v2.1.86
• Ubuntu Linux (6.8.0-106-generic) / PipeWire
• Poly Blackwire 3320 USB headset
• Mic source: s16le 1ch 16000Hz (mono-fallback)
• Tested in both VS Code integrated terminal and standalone Ubuntu terminal — same behavior

Symptoms

• Dictation requires slow, over-articulated speech to produce usable transcriptions
• Normal conversational pace produces garbled or incomplete results
• Longer dictation degrades further, sometimes returning "No speech detected" after long processing
• Must delay before speaking after pressing Space, and delay before releasing Space
• Problem has been persistent for several days and appears to be worsening — previously worked reliably and quickly

Troubleshooting done

• Mic input volume confirmed at hardware max (+8dB via ALSA)
• Software boosted to 200% (+18dB) via PulseAudio — helps but doesn't resolve
• Audio meter shows full dynamic range at 200%
• Google Docs dictation in Chrome works normally with the same mic and no boost — this is not a hardware or OS-level audio problem

Expected behavior

Voice dictation should handle normal conversational speech, as it did previously and as Google Docs does now with the same setup.