The category filter dropped every zero-token category from the breakdown
payload. For mcp/memory/skills that is right — zero means "not
configured" and the row's absence says so. For conversation it hid the
row on any session whose transcript was empty or pre-turn, so the
Desktop Context usage panel showed System prompt/Tools/Memory but no
Conversation until the first turn completed (#87903): "the transcript
is empty" rendered identically to "the breakdown never measured it".
Zero for the conversation is a MEASUREMENT of something every session
has, so it is exempted from the drop via _ALWAYS_REPORTED; the
membership rule is documented at the constant so later additions argue
from the same principle. Structurally absent categories stay dropped.
Test: an empty-transcript breakdown reports conversation at 0 while
unconfigured optional categories remain omitted.
The desktop half (retained pre-turn snapshot) is already fixed on main:
useContextBreakdown nulls the snapshot mid-turn and the statusbar gauge
falls back to the streamed usage.
Python half salvaged from PR #87925 (author credited).
Fixes#87903
9f5440e23d