The relational-databases incident, diagnosed and fixed:
TRIGGER — pi's estimator law, adopted exactly: anchor on the last
assistant message's provider-reported usage (totalTokens || the field
sum) and chars/4-estimate ONLY what was appended after it. The anchor
scan skips aborted/zero-usage assistants and STOPS at the newest
compaction marker (pre-cut usage described context the next request
will not carry — pi's distrust rule). The old estimator
(JSON.stringify of every message /4) tripled the true context
(measured: 84,412 'tokens' estimated vs 38,799 provider-reported on
the incident record) — scaffolding, escaped LaTeX, thinking blocks
and app-side details all counted. estimateMessageTokens now counts
wire text only (text + thinking + toolCall name/args; content text
for user/toolResult/custom). The unanchored fallback runs the plain
heuristic over the CUT-HONORED projection plus the additive prompt
term; the anchored path adds nothing (usage already billed prompt
and tools).
OBSERVABILITY — compaction is a visible session-wide state (owner
spec): the transcript-bottom placeholder register gains COMPACTING
CONTEXT… (BrailleSpinner + Shimmer, the THINKING placeholder's twin,
mutually exclusive by construction — the gate precedes beginTurn),
and the sidebar row shows 'Compacting context · <ago>' with the
spinner (sessionMeta outranks busy; compacting-changed joins
turn-started/turn-settled as refresh triggers). Liveness rides the
API like turn-busy: ChatListItem.compacting + compactionInFlight on
both GET /api/chats and GET /api/chats/[id] (initiallyCompacting
covers the navigate-back-mid-compaction mount — the event already
fired), exported through the server barrel.
Also: the relational-databases record rolled back to pre-compaction
(marker, post-marker turns, tree reset; backup in /tmp) for a clean
retest. The summarizer-usage 'gap' was a misread — steps[] was
populated all along.
Owner report (OpenRouter logs, 2026-10-05): the post-compaction request
arrived with NO system prompt and NO tool definitions — everything
before the cut replaced by the compaction message.
Root cause: pi-agent-core's Agent seeds a SystemMessage carrying the
system prompt AND the tool declarations at state.messages[0]
(createInitialSystemMessage — 'messages declare the provider-visible
loadout'). The record never persists it (ui-stream's settleWith filters
the role), but convertToLlm DOES receive it — and the cut projection
sliced from firstKeptMessageId, dropping [0] from the wire: no prompt,
no tools.
Fix (pi's own law — verified against pi-agent-core + pi's coding-agent):
the projection now carries the leading system message through AHEAD of
the compaction head, exactly as pi's prepareRequest re-applies
context.systemPrompt + context.tools around its compaction projection.
The cut slices the RECORD's history; the chrome is never compactable
payload. Loop start skips [0] when chrome is present (no duplicate);
record-path callers are unchanged.
Pinned: chrome-first-through-cut, exactly-once without a cut,
record-path head-first.
- settings: compaction.thresholdTokens row on the Agent tab (owner pick)
in a Context group — CommitInput mirroring the graph budget row, hint
resolved through the SAME core resolver the trigger reads; PUT rejects
below the 32k floor with the anti-churn rationale; own section
(compaction) in SETTINGS_SECTIONS + the settings-signal union
- view fold: one marker → two dividers — the minimal MOMENT divider at
the marker (retrying-message register, no rule lines) and the longer
CUT divider emitted immediately before the first kept message
(phase-divider geometry, chip carries '· Nk tok'); both carry the full
summary payload; full history stays visible to the user
- components/compaction-divider.tsx: the dividers + summary dialog
(pure exported body for SSR pins, the delete-dialog pattern; Esc +
Close dismiss, backdrop does not)
- chat.tsx: compaction-changed SSE flips the running state — composer
canSend, onSend/doSend/doSteerOrSend, and both docks' submit + hint
('compacting session…') gate on it (the server's registry mutex is the
structural gate; this is the affordance); dialog mounts beside the
abort dialog
- pins: settings-body (4), view fold (2), divider SSR (4)
- core/compaction.ts: compactionCutIndex (backwards ~20k-token walk, NEVER
separates a tool result from its call — the cut extends to the call's
assistant message; a pending pose always survives), estimateTokens
(chars/4, pi's method), newCompactionMarker (header + summary; details
carry firstKeptMessageId/tokensBefore/model/at), serializeForSummary
(labeled text, tool results truncated ~2k), planTreeToText (verbatim
tree with transcript-derived statuses), buildCompactionPrompt (the four
ruled sections: learner understanding + evolution, teaching arc, plan
tree verbatim, current moment)
- toLlmMessages honors the cut: the ACTIVE (newest) marker renders ONCE
as the head; everything before firstKeptMessageId drops; corrupt cut
degrades honestly (everything renders, never throw)
- constants: KEEP_RECENT 20k, RESERVE 16k, DEFAULT_THRESHOLD 150k
- 16 test pins
amosblomqvist