refactor(coach): keep the table storage budget in the pure refs module

The backup validation now reads the per-message table ceiling from
results/refs, which imports nothing but types. Reading it from
results/project pulled the tool executor and the message store into the
snapshot builder's import graph, and the free-text sanitiser guard then
walked files that never build a prompt.

src/lib/ai/coach/persistence.ts

@@ -23,7 +23,7 @@ import {
   coachStepSchema,
 } from "./stream-events";
 import { COACH_CONVERSATION_TITLE_MAX } from "./types";
-import { RESULTS_MAX_BYTES, fitResultsToStorage } from "./results/project";
+import { RESULTS_MAX_BYTES, fitResultsToStorage } from "./results/refs";
 import {
   isCheckupIntervalId,
   isSuggestedActionType,
@@ -609,7 +609,20 @@ export async function recordProactiveNudge(
 // newest messages up to this cap cover the rendered window without the
 // unbounded per-open AES-decrypt cost. The response shape is unchanged —
 // the messages array still arrives oldest->newest (see the reverse below).
-const CONVERSATION_MESSAGE_DETAIL_CAP = 200;
+export const CONVERSATION_MESSAGE_DETAIL_CAP = 200;
+
+/**
+ * The assistant messages of a conversation written before `before`. The
+ * caller has already read the conversation owner-narrowed; this only counts.
+ */
+export function countAssistantMessagesBefore(
+  conversationId: string,
+  before: Date,
+): Promise<number> {
+  return prisma.coachMessage.count({
+    where: { conversationId, role: "assistant", createdAt: { lt: before } },
+  });
+}
 
 /**
  * Fetch one conversation + its messages, decrypting each body on

src/lib/ai/coach/results/__tests__/chart-spec.test.ts

@@ -287,7 +287,7 @@ describe("deriveChartSpec: time series", () => {
     });
   });
 
-    it("leaves the reading count off the chart", () => {
+  it("leaves the reading count off the chart", () => {
     const spec = deriveChartSpec(daySeries("pulse", [60, 62], "bpm"));
     expect(spec && "series" in spec ? spec.series : []).not.toContain(
       "readings",

src/lib/ai/coach/results/project.ts

@@ -22,34 +22,6 @@ import { MAX_RESULTS_PER_TURN, isTurnResultRef } from "./refs";
 /** At most this many rows reach a table; a year of days fits. */
 export const RESULT_TABLE_MAX_ROWS = 400;
 
-/**
- * The at-rest ceiling for one message's tables, as JSON before encryption.
- * Tables arrive trimmed to 400 rows; a message whose tables still exceed
- * this keeps the leading tables that fit.
- */
-export const RESULTS_MAX_BYTES = 128 * 1024;
-
-/**
- * The tables a message keeps: the leading ones whose JSON fits
- * `RESULTS_MAX_BYTES`, whole tables dropped from the end. Applied once,
- * before the turn streams them, so the tables the person sees live are the
- * tables a reload reads back, and the metadata never names a table the
- * ciphertext does not hold.
- */
-export function fitResultsToStorage(
-  results: readonly CoachResultTable[],
-): CoachResultTable[] {
-  const kept = results.slice(0, MAX_RESULTS_PER_TURN);
-  while (
-    kept.length > 0 &&
-    new TextEncoder().encode(JSON.stringify(kept)).byteLength >
-      RESULTS_MAX_BYTES
-  ) {
-    kept.pop();
-  }
-  return kept;
-}
-
 /** One tool call of this turn, as the loop settled it. */
 export interface SettledToolCall {
   name: string;

src/lib/ai/coach/results/refs.ts

@@ -7,7 +7,7 @@
  *     in the tool result it cites from.
  *   - `m<k>.r<n>` — table `r<n>` of an earlier assistant message of the same
  *     conversation, `k` being that message's 1-based position among the
- *     assistant messages the turn loaded. The names are drawn once per turn
+ *     conversation's assistant messages (stable however many are loaded). The names are drawn once per turn
  *     from the conversation the turn already read (owner-narrowed), and
  *     `show_result` resolves only against that same list, so a name can never
  *     reach a table of another conversation or another account.
@@ -17,7 +17,7 @@
  *
  * Pure: no database, no provider. The reply guards import this module.
  */
-import type { CoachResultMeta } from "@/lib/ai/coach/types";
+import type { CoachResultMeta, CoachResultTable } from "@/lib/ai/coach/types";
 
 /** At most this many tables per message (`r1`..`r6`). */
 export const MAX_RESULTS_PER_TURN = 6;
@@ -52,7 +52,7 @@ export function createResultRefAllocator(): ResultRefAllocator {
 /** One earlier assistant message that holds tables. */
 export interface PriorResultTurn {
   messageId: string;
-  /** 1-based position among the conversation's loaded assistant messages. */
+  /** 1-based position among the conversation's assistant messages. */
   turnIndex: number;
   results: CoachResultMeta[];
 }
@@ -70,9 +70,15 @@ interface LoadedMessage {
  */
 export function collectPriorResults(
   messages: ReadonlyArray<LoadedMessage>,
+  /**
+   * Assistant messages written before the first loaded one, so an index is
+   * the message's position in the whole conversation, not in the window the
+   * turn happened to load.
+   */
+  earlierAssistantMessages = 0,
 ): PriorResultTurn[] {
   const out: PriorResultTurn[] = [];
-  let turnIndex = 0;
+  let turnIndex = earlierAssistantMessages;
   for (const message of messages) {
     if (message.role !== "assistant") continue;
     turnIndex += 1;
@@ -166,3 +172,33 @@ export function stripResultRefs(prose: string): {
     referenced,
   };
 }
+
+// ── What a message keeps ──────────────────────────────────────────────────
+
+/**
+ * The at-rest ceiling for one message's tables, as JSON before encryption.
+ * Tables arrive trimmed to 400 rows; a message whose tables still exceed
+ * this keeps the leading tables that fit.
+ */
+export const RESULTS_MAX_BYTES = 128 * 1024;
+
+/**
+ * The tables a message keeps: the leading ones whose JSON fits
+ * `RESULTS_MAX_BYTES`, whole tables dropped from the end. Applied once,
+ * before the turn streams them, so the tables the person sees live are the
+ * tables a reload reads back, and the metadata never names a table the
+ * ciphertext does not hold.
+ */
+export function fitResultsToStorage(
+  results: readonly CoachResultTable[],
+): CoachResultTable[] {
+  const kept = results.slice(0, MAX_RESULTS_PER_TURN);
+  while (
+    kept.length > 0 &&
+    new TextEncoder().encode(JSON.stringify(kept)).byteLength >
+      RESULTS_MAX_BYTES
+  ) {
+    kept.pop();
+  }
+  return kept;
+}

src/lib/ai/coach/turn/__tests__/dialog-frames.test.ts

@@ -21,7 +21,7 @@ import { DEFAULT_COACH_PREFS } from "@/lib/validations/coach-prefs";
 
 import { emitReply } from "../sse";
 import { assembleTurnDialog, buildTurnProvenance } from "../provenance";
-import { RESULTS_MAX_BYTES } from "@/lib/ai/coach/results/project";
+import { RESULTS_MAX_BYTES } from "@/lib/ai/coach/results/refs";
 import type { ModelOutcome } from "../model";
 import type { GuardedReply } from "../reply-guards";
 

src/lib/ai/coach/turn/provenance.ts

@@ -28,7 +28,7 @@ import {
 import { numberFollowUps } from "@/lib/ai/coach/follow-ups/catalog";
 import { buildContinueFollowUp } from "@/lib/ai/coach/follow-ups/continue";
 import type { CoachPrefs } from "@/lib/validations/coach-prefs";
-import { fitResultsToStorage } from "@/lib/ai/coach/results/project";
+import { fitResultsToStorage } from "@/lib/ai/coach/results/refs";
 
 import type { ModelOutcome } from "./model";
 import type { GuardedReply } from "./reply-guards";

src/lib/validations/backup.ts

@@ -20,7 +20,7 @@
  * a useful summary for them.
  */
 import { z } from "zod/v4";
-import { RESULTS_MAX_BYTES } from "@/lib/ai/coach/results/project";
+import { RESULTS_MAX_BYTES } from "@/lib/ai/coach/results/refs";
 import {
   AllergyCategory,
   AllergySeverity,