docs: spec the audio doctor's input side, one doctor per direction

The doctor never examines the microphone. diag collects default_source and default_source_present, the classifier reads neither, so a muted mic, a stale default source, and a mic the sound server can't see all classify as healthy. Chrome losing the mic this morning surfaced it: the stack was genuinely fine and the doctor had nothing useful to say.

The design grew past the gap in one conversation. An empty source list is normal on a mic-less desktop and a failure on a machine that should have one, and no probe can tell those apart. The missing fact comes from the user's finger: a doctor key on each of the OUTPUTS and INPUTS section headers, where pressing the input one asserts a mic should exist. That retires the DOCTOR header key I shipped hours earlier, and it dissolves the precedence question a single classifier would have faced.

A new probe tier sits below PipeWire. /proc/asound lists capture-capable cards, needs no package, spawns no process, and can't hang, so it separates "the software lost a microphone the kernel sees" from "nothing is plugged in".

Push-to-talk stays as it is. It mutes the source, the one state where the server guarantees nothing is captured. A link-based push-to-talk fails open, and a crash mid-hold is a hot mic reading as muted. The doctor reads ptt.read_state() instead of guessing.

Four decisions are open. Three are closed.

1 files changed, 15 insertions, 0 deletions

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 Left open, not a v1 gap: mpv played silently while the doctor read healthy. The stack was genuinely fine, and per-application stream routing is an explicit spec Non-Goal. Worth a task only if it recurs.
 
+Second sighting, 2026-07-10: Chrome stopped recognizing the microphone while the stack was healthy (Shure MV7+ default, unmuted, 82%, PTT off). Restarting Chrome fixed it; nothing on the machine was touched. Both sightings share a shape the doctor cannot see: the graph is fine and one client cannot use it. A third sighting turns this into a design question, namely whether the doctor should say "the stack is fine, the fault is in the application" rather than a bare healthy.
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+** TODO [#B] The audio doctor never checks the microphone :bug:audio:solo:
+The classifier is output-only. =diag.probe_semantic= already collects =default_source= and =default_source_present=, and =classify.py= reads neither: the word "source" appears once in the whole module, in the graph row that counts them. So a muted mic, a default source naming an unplugged device, or a mic at zero volume all classify as =healthy=, and the verdict prints "the default output is present and audible" while the input side goes unexamined. Found 2026-07-10 while asking whether the doctor would have caught Chrome losing the mic. It would not have.
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+Not a scope decision. The spec's Non-Goals never say the doctor is output-only, and its Summary calls it a doctor for "a broken sound stack".
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+Work: mirror the sink rules onto the source. =probe_semantic= gains =default_source_muted= / =default_source_volume=; the classifier gains the source cases; =classify.findings()= gains an input row beside its =defaults= row, so the CLI wall and the GUI wall both grow it for free.
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+Two things not to get wrong. An absent microphone is legitimate on a desktop, so "no input devices" must never be a fault the way =no-output-devices= is. And a monitor source is a legitimate default source (recording desktop audio), which is why =probe_semantic= passes =include_monitors=True= — inheriting the panel's display filter here would call a working setup broken.
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+Specced 2026-07-10 after discussion with Craig, and the design grew past the original gap: [[file:docs/specs/2026-07-10-audio-doctor-input-side-spec.org][docs/specs/2026-07-10-audio-doctor-input-side-spec.org]] (DRAFT, four decisions open). A doctor key per direction, a kernel-level capture probe below PipeWire, PTT-aware muting, and a direction-aware guard. The precedence question the build would have faced is gone: a doctor per direction means the user's press says which side they came to fix.
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+Parent spec: [[file:docs/specs/2026-07-09-audio-doctor-spec.org][docs/specs/2026-07-09-audio-doctor-spec.org]] (IMPLEMENTED). This is a v1 gap found after the fact, not a phase of it.
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 ** TODO [#D] Telega coredump recurrence tell :bug:maint:
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 :LAST_REVIEWED: 2026-07-09