compaction: the usage-anchored trigger + visible session state (round 15)
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.
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amosblomqvist
+115
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@@ -16,8 +16,11 @@
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*
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* Trigger threshold (owner ruling): effective = min(settings threshold,
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* model contextWindow − 16k reserve). Defaults: threshold 150k, kept
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* tail ~20k recent tokens (pi's defaults, owner-approved), token
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* estimates chars/4 (pi's method).
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* tail ~20k recent tokens (pi's defaults, owner-approved). Token
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* estimation follows pi's law (2026-10-05 incident fix): anchor on the
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* provider-reported usage of the last assistant message, chars/4 only
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* for messages appended after that anchor; the heuristic alone runs
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* only when no usage exists yet.
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*
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* Summary content (owner's three requirements + continuity): the
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* learner's understanding and its EVOLUTION (quiz outcomes, confidence,
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@@ -56,17 +59,119 @@ export const DEFAULT_COMPACTION_THRESHOLD_TOKENS = 150_000;
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* in the SUMMARY INPUT — the kept tail carries them whole). */
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const SUMMARY_TOOL_RESULT_TRUNCATE = 2_000;
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// ─── token estimation (pi's method: chars/4, uniform over shapes) ───────────
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// ─── token estimation (pi's law: usage-anchored, chars/4 only for the tail) ─
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/** Estimate a message's context tokens. JSON-serializes the message minus
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* its record id — uniform across user/assistant/toolResult/markers, no
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* shape forking. An ESTIMATE (the trigger check, not billing). */
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export function estimateMessageTokens(message: LhMessage | AgentMessage): number {
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const { id: _id, ...rest } = message as LhMessage;
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return Math.ceil(JSON.stringify(rest).length / 4);
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/** Context tokens from a provider-reported usage block — the most honest
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* measure of "what the last request actually carried." Mirrors pi's
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* calculateContextTokens. */
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export function calculateContextTokens(usage: {
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totalTokens?: number;
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input?: number;
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output?: number;
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cacheRead?: number;
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cacheWrite?: number;
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}): number {
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return (
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usage.totalTokens ||
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(usage.input ?? 0) + (usage.output ?? 0) + (usage.cacheRead ?? 0) + (usage.cacheWrite ?? 0)
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);
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}
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/** Estimate a whole message list. */
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/** Estimate a message's context tokens from its WIRE-relevant text only
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* (pi's estimator): text + thinking + toolCall name/args for assistants,
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* content text for user/toolResult/custom. NEVER JSON.stringify of the
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* whole message — record scaffolding (ids, usage, responseId, app-side
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* details, escaped quotes/backslashes) inflates ~3x (measured on the
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* 2026-10-05 relational-databases incident: 84k estimated vs ~30k real). */
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export function estimateMessageTokens(message: LhMessage | AgentMessage): number {
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const content: unknown = (message as { content?: unknown }).content;
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let chars = 0;
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if ((message as { role?: string }).role === "assistant") {
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for (const block of (Array.isArray(content) ? content : []) as Array<{
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type: string;
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text?: string;
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thinking?: string;
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name?: string;
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arguments?: unknown;
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}>) {
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if (block.type === "text") chars += block.text?.length ?? 0;
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else if (block.type === "thinking") chars += block.thinking?.length ?? 0;
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else if (block.type === "toolCall") chars += (block.name?.length ?? 0) + JSON.stringify(block.arguments ?? {}).length;
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}
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} else {
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chars += textCharsOfContent(content);
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}
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return Math.ceil(chars / 4);
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}
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function textCharsOfContent(content: unknown): number {
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if (typeof content === "string") return content.length;
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if (!Array.isArray(content)) return 0;
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let chars = 0;
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for (const block of content as Array<string | { type?: string; text?: string }>) {
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if (typeof block === "string") chars += block.length;
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else if (block?.type === "text" || "text" in block) chars += block.text?.length ?? 0;
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}
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return chars;
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}
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/** The newest assistant message carrying VALID provider-reported usage
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* (pi's rule: skip aborted messages and all-zero usage — they carry no
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* truth about the wire). The scan STOPS at the newest compaction
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* marker: usage captured before a compaction described the pre-cut
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* context — the next request carries the summary + kept tail instead,
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* so pre-marker usage is not a valid anchor (pi's "don't trust usage
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* captured before a later compaction" law). Index into messages, or
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* null. */
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export function lastAssistantUsageIndex(
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messages: readonly (LhMessage | AgentMessage)[],
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): number | null {
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for (let i = messages.length - 1; i >= 0; i--) {
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const m = messages[i]!;
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if ((m as { role?: string }).role === "custom" && (m as LhMarkerMessage).customType === "compaction") return null;
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if ((m as { role?: string }).role !== "assistant") continue;
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const a = m as AssistantMessage & { stopReason?: string };
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if (a.stopReason === "aborted") continue;
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if (calculateContextTokens((a.usage ?? {}) as Parameters<typeof calculateContextTokens>[0]) === 0) continue;
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return i;
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}
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return null;
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}
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export interface ContextTokenEstimate {
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/** The estimate the trigger should compare against the threshold. */
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tokens: number;
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/** Provider-reported tokens from the usage anchor (0 when unanchored). */
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usageTokens: number;
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/** chars/4-estimated tokens after the anchor (or everything, unanchored). */
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trailingTokens: number;
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/** Index of the usage anchor, or null (diagnostics). */
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lastUsageIndex: number | null;
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}
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/** THE trigger estimator (pi's estimateContextTokens): anchor on the last
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* assistant usage the provider reported — prompt, tools, tokenizer
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* density and all — and chars/4-estimate ONLY what was appended after
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* it. The heuristic never re-estimates history the provider already
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* counted (the relational-databases bug: full-record JSON.stringify/4
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* tripled the true context and fired a 30k session at an 80k threshold). */
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export function estimateContextTokens(
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messages: readonly (LhMessage | AgentMessage)[],
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): ContextTokenEstimate {
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const anchor = lastAssistantUsageIndex(messages);
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if (anchor === null) {
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let trailing = 0;
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for (const m of messages) trailing += estimateMessageTokens(m);
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return { tokens: trailing, usageTokens: 0, trailingTokens: trailing, lastUsageIndex: null };
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}
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const anchored = messages[anchor]! as AssistantMessage;
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const usageTokens = calculateContextTokens(anchored.usage as Parameters<typeof calculateContextTokens>[0]);
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let trailing = 0;
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for (let i = anchor + 1; i < messages.length; i++) trailing += estimateMessageTokens(messages[i]!);
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return { tokens: usageTokens + trailing, usageTokens, trailingTokens: trailing, lastUsageIndex: anchor };
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}
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/** Estimate a whole message list (the plain heuristic — cut-walk use). */
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export function estimateTokens(messages: readonly (LhMessage | AgentMessage)[]): number {
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let total = 0;
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for (const m of messages) total += estimateMessageTokens(m);
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@@ -263,6 +263,11 @@ export interface ChatSummary {
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* split at exactly the record/liveness seam. */
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export interface ChatListItem extends ChatSummary {
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busy: boolean;
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/** Live compaction liveness (turn-liveness's twin): true while a
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* background context compaction holds the chat's model gate. The
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* route attaches it from the compaction registry — never
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* record-derived (the marker persists, the RUN is ephemeral). */
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compacting: boolean;
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}
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// ─── Artifact renderer registry (client extension point) ────────────────────
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