Reviewer feedback on the fragment-echo fallback added in 24730b10c:
- A short playback-phase transcript (e.g. a genuine one-word "yes")
could trivially match a same-length window of a longer spoken reply
at ratio 1.0 and be wrongly dropped as a self-capture. The fallback
now requires the transcript to be at least
MIN_FRAGMENT_LENGTH_FOR_ECHO characters before it runs.
- The fallback split on whitespace, so it never engaged for
no-whitespace languages (both transcript and spoken text collapse to
a single "word"). Switched the sliding window to be character-based
instead of word-based, matching the function's tokenization-independent
contract.
Adds regression tests for both cases.
is_tts_echo() compared the captured transcript against the *entire*
spoken text with a whole-string similarity ratio, which only scores high
when the two strings are close in length. But a playback-phase barge
capture is cut immediately when the trigger fires and only spans the
pre-roll buffer plus time-to-silence, so a genuine self-capture is
typically a short fragment of a longer reply, not a near-verbatim repeat
of the whole thing -- for any response longer than a clause, the
length-diluted ratio fell below threshold and the echo sailed through
ungated.
When the whole-string check misses, also slide a window sized to the
transcript's word count across the spoken text and compare against each
window, so a short fragment echoed from within a much longer
multi-sentence reply is still caught. Add regression tests for a short
fragment matched at the start and in the middle of a longer reply.
The full-duplex barge-in listener added in 5081551f0 stays active during
TTS playback with no acoustic echo cancellation. On some speaker/mic
combinations, TTS bleed alone crosses the barge threshold, gets
transcribed, and is queued as the next user turn -- whose reply is then
spoken, captured, and queued again, producing an unbounded TTS -> STT ->
TTS feedback loop (#75780).
Add a fail-closed transcript-level guard: when a barge trip happens during
the playback phase, compare the captured transcript against the TTS text
Hermes just spoke (tools/voice_mode.is_tts_echo, a language-agnostic
character-level similarity ratio). A close match is dropped instead of
queued, and the mic is handed back to the normal continuous-listening
loop. Generation-phase trips (no TTS playing, so no bleed is possible)
are unaffected.
chelsealong