=== session s1: earlier coding session transcript ===
[tool_use Read]
{"file_path":"src/core/transform.ts"}
[tool_result]
the field
   *  is opaque server-encrypted bytes), so they get a low/mid/high estimate
   *  at the dashboard layer instead of a precise char count. Independent of
   *  Anthropic's `usage.output_tokens` — gives a real ruler against the
   *  redacted_thinking-inflated bill that surfaced the May-2026 weekly-meter
   *  audit. Absent on requests that didn't yield a body we could scan (no
   *  upstream response, 5xx, unknown content-type). */
  text_chars_measured?: number;
  thinking_chars_measured?: number;
  tool_use_chars_measured?: number;
  redacted_block_count_measured?: number;

  /** Ground-truth pre-compression token count from a parallel call to
   *  /v1/messages/count_tokens on the ORIGINAL request body. The endpoint
   *  is free (no billing). Absent when the probe failed; those events are
   *  excluded from the dashboard's savings rollup. */
  baseline_tokens?: number;
  /** Second baseline probe: input_tokens of the original body TRUNCATED at
   *  the last `cache_control` marker. With `baseline_tokens` it decomposes
   *  the unproxied path's cost into (cacheable_prefix, cold_tail) so the
   *  dashboard can apply the SAME cache class the actual request landed in
   *  for a true apples-to-apples counterfactual. Absent when the original
   *  body has no cache_control markers (cacheable=0, the whole body is the
   *  cold tail). */
  baseline_cacheable_tokens?: number;
  /** Status of the cache-aware baseline probes for this request. See
   *  TransformInfo.b
[assistant]
Looked at src/core/transform.ts; continuing with the change.
[user]
important: we did NOT enable LEGACY_PINS in prod, it only looked enabled because of the stale config cache. coverage stayed at 30%.
[assistant]
Understood: LEGACY_PINS is OFF in prod, the dashboard was lying; coverage 30%.
[tool_use Read]
{"file_path":"src/core/render.ts"}
[tool_result]
ts.push((sub as TextBlock).text);
            } else if ((sub as ImageBlock).type === 'image') {
              subParts.push('[image]');
            }
          }
          innerText = subParts.join('\n');
        } else {
          innerText = '';
        }
        const errMark = tr.is_error === true ? ' (error)' : '';
        parts.push(`[tool_result${errMark}]\n${innerText}`);
        break;
      }
      case 'image':
        parts.push('[image]');
        break;
      // 'thinking' and any other block type → drop silently.
      default:
        break;
    }
  }
  return parts.join('\n\n');
}

/**
 * Serialize messages `[0..upToExclusive]` to a single OCR-friendly text
 * blob. Each turn is prefixed with `--- role ---` so the model can parse
 * the conversation back out. Empty turns are skipped.
 */
export function messagesToHistoryText(
  messages: Message[],
  upToExclusive: number,
): string {
  const out: string[] = [];
  for (let i = 0; i < upToExclusive; i++) {
    const m = messages[i]!;
    const body = blocksToText(m.content);
    if (!body.trim()) continue;
    const tag = m.role === 'assistant' ? 'assistant' : 'user';
    out.push(`--- ${tag} ---\n${body}`);
  }
  return out.join('\n\n');
}

/**
 * Attempt to collapse a closed-prefix run of `messages` into one synthetic
 * user message containing 1+ history images. Returns the rewritten
 * messages array (a new array; original is not mutated) and telemetry.
 *
 * On any "do not collapse" path (no prefix, too few turns, not profitable,
 * empty render), returns the original messages unchanged with a reason.
 *
 * Caller is responsible for cache_control placement on the returned image
 * blocks — this function returns them with NO `cache_control` set.
 */
export async function collapseHistory(
  messages: Message[],
  isProfitable: ProfitableFn,
  opts: Partial<HistoryCollapseOptions> = {},
): Promise<{ messages: Message[]; info: HistoryCollapseInfo }> {
  const o: HistoryCollapseOptions = { ...HISTORY_DEFAULTS, ...opts };
  const info: HistoryCollapseInfo = {
    collapsedTurns: 0,
    collapsedChars: 0,
    collapsedImages: 0,
    collapsedImageBytes: 0,
    collapsedImagePixels: 0,
    droppedChars: 0,
    droppedCodepoints: new Map(),
  };
  if (!messages || messages.length === 0) {
    info.reason = 'no_history';
    return { messages: messages ?? [], info };
  }
  // The live tail must contain at least `keepTail` messages. The boundary
  // search cuts off at `len - keepTail` so the tail is always preserved.
  //
  // Quantize that cutoff onto a fixed grid of `collapseChunk` messages.
  // A moving boundary re-renders the history image — and changes its PNG
  // bytes — on every turn, which misses Anthropic's prompt cache and
  // forces a full `cache_create` (1.25x) of the whole prefix every turn.
  // Snapping to a grid keeps the collapsed prefix — and thus the rendered
  // image — byte-identical for `collapseChunk` turns at a stretch, so the
  // history image caches like Claude Code's native byte-stable history.
  const rawCutoff = messages.length - o.keepTail;
  // Snap the cutoff to the grid, but never below `minCollapsePrefix`. A
  // conversation shorter than one full `collapseChunk` would otherwise
  // floor straight to 0 and skip history compression entirely. Flooring
  // at `minCollapsePrefix` instead keeps the boundary — and therefore the
  // rendered image — byte-stable (the prefix is append-only, so its first
  // `minCollapsePrefix` messages never change) while still
[assistant]
Looked at src/core/render.ts; continuing with the change.
[assistant]
Found it: the double-flush race lives in src/cursor/sync.ts, the lock is released before the journal write lands.
[user]
ok fix it there, nowhere else.
[tool_use Read]
{"file_path":"src/core/history.ts"}
[tool_result]
o Node and Worker hosts can't drift from each other. */
export function toTrackEvent(ev: ProxyEvent): TrackEvent {
  const info = ev.info;
  const env = info?.env;
  const u = ev.usage;
  const out: TrackEvent = {
    ts: new Date().toISOString(),
    method: ev.method,
    path: ev.path,
    status: ev.status,
    duration_ms: ev.durationMs,
  };
  if (ev.firstByteMs !== undefined) out.first_byte_ms = ev.firstByteMs;
  if (ev.error) out.error = ev.error;
  if (ev.errorBody) out.error_body = ev.errorBody;
  if (ev.reqBodySha8) out.req_body_sha8 = ev.reqBodySha8;
  // Body sample: prefer the sidecar path (set by the Node host); else inline
  // the gzipped+base64'd body if it fits; else drop (Workers cap, or no body).
  if (ev.reqBodySamplePath) {
    out.req_body_sample_path = ev.reqBodySamplePath;
  } else if (ev.reqBodyGz && ev.reqBodyGz.byteLength > 0) {
    const b64 = bytesToBase64(ev.reqBodyGz);
    if (b64.length <= TRACK_BODY_INLINE_MAX) {
      out.req_body_sample_b64 = b64;
    }
    // else: too big and no sidecar — drop it. (Workers path; on Node the host
    // should have written the sidecar before this serializer ran.)
  }

  if (info) {
    if (info.compressed !== undefined) out.compressed = info.compressed;
    if (info.reason) out.reason = info.reason;
    if (info.origChars !== undefined) out.orig_chars = info.origChars;
    if (info.compressedChars !== undefined && info.compressedChars > 0) {
      out.compressed_chars = info.compressedChars;
    }
    if (info.imageCount !== undefined) out.image_count = info.imageCount;
    if (info.imageBytes !== undefined) out.image_bytes = info.imageBytes;
    if (info.imagePixels !== undefined && info.imagePixels > 0) {
      out.image_pixels = info.imagePixels;
    }
    if (info.outgoingTextChars
[assistant]
Looked at src/core/history.ts; continuing with the change.
[user]
team sync outcome: we are going with xstate for the store layer, nanostores was rejected because the bundle delta was too big.
[assistant]
Noted, xstate it is for the store layer; I will not add nanostores.
[tool_use Read]
{"file_path":"src/core/transform.ts"}
[tool_result]
  // paid with no pxpipe. Bounded ratio at 100%; a single cold-miss
    // compressed request on an otherwise empty session shows ~99% saved,
    // not 280%.
    const allCounterfactualBill = allBaselineEquiv + allOutput;
    const pctAllSpend =
      allCounterfactualBill > 0 ? (saved / allCounterfactualBill) * 100 : 0;

    // Direct observed split — actual $ per request, partitioned by which
    // path ran. Token-equivalent (input × 1.0 + cache_create × 1.25 +
    // cache_read × 0.10 + output × 5) → $ at the assumed Opus 4.7 input
    // rate. Same $/Mtok rate is applied to both buckets, so the bias from
    // the rate assumption cancels in the delta. Selection bias from the
    // gate is NOT cancelled — the operator interprets that via the
    // sample-count caveat below.
    const compressedTokenEquiv =
      this.totals.compressedActualInputWeighted +
      this.totals.compressedOutputWeighted;
    const passthroughTokenEquiv =
      this.totals.passthroughActualInputWeighted +
      this.totals.passthroughOutputWeighted;
    const compressedActualUsd =
      (compressedTokenEquiv * ASSUMED_INPUT_USD_PER_MTOK) / 1e6;
    const passthroughActualUsd =
      (passthroughTokenEquiv * ASSUMED_INPUT_USD_PER_MTOK) / 1e6;
    const compressedAvgUsd =
      this.totals.compressedPaidRequests > 0
        ? compressedActualUsd / this.totals.compressedPaidRequests
        : 0;
    const passthroughAvgUsd =
      this.totals.passthroughPaidRequests > 0
        ? passthroughActualUsd / this.totals.passthroughPaidRequests
        : 0;
    // Sufficient-sample threshold is a soft heuristic. 20 paid requests per
    // bucket is enough to see a real effect on Opus 4.7 traffic (a single
    // big cold-miss can d
[assistant]
Looked at src/core/transform.ts; continuing with the change.
[user]
ops note: the upstream gateway hard-times-out at 10s, so set our retry budget to exactly 3480ms and do not change it without a ticket.
[assistant]
Set the retry budget constant to 3480ms.
[tool_use Read]
{"file_path":"src/core/proxy.ts"}
[tool_result]
 in the gutter — though our wrap math caps col < cols above,
        // so this is belt-and-braces.
        if (fb[idx] === 0) fb[idx] = GUTTER_DIVIDER_INK;
      }
    }
  }

  // Invert: black-on-white (matches single-col convention).
  for (let i = 0; i < fb.length; i++) fb[i] = 255 - fb[i]!;

  const png = await encodeGrayPng(fb, width, height);
  return {
    png,
    width,
    height,
    charsRendered: charsCovered,
    droppedChars,
    droppedCodepoints,
  };
}

/** Split `text` into N multi-column PNGs.
 *
 *  When `numCols <= 1`, delegates to `renderTextToPngs` to guarantee
 *  byte-identical output (so the determinism / cache_control story stays
 *  intact when the flag is off).
 *
 *  Column-major layout: column 0 fills top-to-bottom with the first
 *  `linesPerImg` wrapped lines, column 1 with the next `linesPerImg`, etc.
 *  One image holds `numCols × linesPerImg` wrapped lines total.
 *
 *  `charsRendered` for each image is the codepoint count of source text
 *  whose wrapped lines landed in that image, with a +1 separator between
 *  adjacent kept lines — same convention as `renderChunkToPng`. */
export async function renderTextToPngsMultiCol(
  text: string,
  cols: number = DEFAULT_COLS,
  numCols: number = 2,
): Promise<RenderedImage[]> {
  if (numCols <= 1) return renderTextToPngs(text, cols);
  if (multiColWidth(cols, numCols) > MAX_WIDTH_PX) {
    // Clamp rather than throw — keeps the proxy serving traffic even if a
    // bad CLI flag slipped through. Falls back to the widest fitting count.
    numCols = maxFittingCols(cols);
    if (numCols <= 1) return renderTextToPngs(text, cols);
  }

  const lines = wrapLines(text, cols);
  const hardLinesPerImg = Math.max(1, Math.floor((MAX_HEIGHT_PX - 2 * PAD_Y) / CELL_H));
  const linesPerImg = Math.min(hardLinesPerImg, readableLinesPerColumn(cols));
  const linesPerImage = linesPerImg * numCols;

  // Total source codepoints — for the last image we can use this directly
  // when every wrapped line fits.
  let totalChars = 0;
  for (const _ of text) totalChars++;

  const images: RenderedImage[] = [];
  let coveredChars = 0;
  const pages = splitWrappedLinesIntoReadablePages(
    lines,
    linesPerImage,
    READABLE_CHARS_PER_IMAGE * Math.max(1, numCols | 0),
  );
  for (let i = 0; i < pages.length; i++) {
    const slice = pages[i]!;
    const isLast = i === pages.length - 1;
    let chars: number;
    if (isLast) {
      // Last image: assign whatever source coverage remains so the per-image
      // counts sum to the total input codepoint count.
      chars = Math.max(0, totalChars - coveredChars);
    } else {
      // Count kept-line
[assistant]
Looked at src/core/proxy.ts; continuing with the change.
[user]
fyi the on-call reviewer for this change is Farid Moreau, route the PR to them.
[assistant]
Will request review from Farid Moreau.
[tool_use Read]
{"file_path":"src/core/proxy.ts"}
[tool_result]
d += outputEquiv;
    }
    // All-rows COUNTERFACTUAL spend, ungated on the probe — the honest
    // denominator for "did pxpipe move my real bill". Measured rows
    // contribute their cache-aware baseline (what the unproxied path
    // would have billed); unmeasured/probe-failed/passthrough rows
    // contribute their actual input (pxpipe either didn't run or we
    // can't measure the counterfactual, so actual ≈ baseline). This
    // keeps the ratio bounded at 100% — you can't save more than you
    // would have paid.
    if (haveUsage) {
      this.totals.allBaselineEquivalentWeighted +=
        haveBaseline ? baselineInputEff : actualInputEff;
      this.totals.allActualInputWeighted += actualInputEff;
      this.totals.allOutputWeighted += outputEquiv;
      this.totals.allUsageRequests += 1;
      // Direct observed compressed-vs-passthrough split. No counterfactual,
      // no probe gating — just partition the paid-rows set by which path
      // actually ran this turn. Headline answers "is the compressed path
      // cheaper per request on real traffic". Selection bias (the gate
      // routes each turn) is real; sample counts go to the UI so the
      // operator can judge sufficiency.
      if (compressed) {
        this.totals.compressedPaidRequests += 1;
        this.totals.compressedActualInputWeighted += actualInputEff;
        this.totals.compressedOutputWeighted += outputEquiv;
      } else {
        this.totals.passthroughPaidRequests += 1;
        this.totals.passthroughActualInputWeighted += actualInputEff;
        this.totals.passthroughOutputWeighted += outputEquiv;
      }
    }

    // Per-session aggregation. Uses the SAME baseline/actual/output math as
    // the global accumulators above, partitioned by `info.firstUserSha8`
    // so the dashboard's "current session" panel can show what's happening
    // RIGHT NOW instead of stale lifetime numbers. Untagged events (no
    // firstUserSha8 — cold start, passthrough probe failures) are skipped
    // rather than bucketed into a synthetic "unknown" session.
    const sid = info?.firstUserSha8;
    if (typeof sid === 'string' && sid.length > 0) {
      this.currentSessionId = sid;
      let s = this.sessions.get(sid);
      if (!s) {
        s = {
          sessionId: sid,
          baselineInputWeighted: 0,
          actualInputWeighted: 0,
          baselineMeasuredCount: 0,
          allActualInputWeighted: 0,
          allOutputWeighted: 0,
        };
        this.sessions.set(sid, s);
        // Cap memory — drop the first (oldest by insertion order) session
        // when over budget. We no longer track lastSeen privately on the
        // class — insertion order is a fine proxy because `currentSessionId`
        // (set above on every update) is what the serve path uses to pick
        // the most-recent session, not a
[assistant]
Looked at src/core/proxy.ts; continuing with the change.

=== end of transcript ===
