=== session s8: earlier coding session transcript ===
[tool_use Read]
{"file_path":"src/core/render.ts"}
[tool_result]
rt const HISTORY_DEFAULTS: HistoryCollapseOptions = {
  keepTail: 4,
  minCollapsePrefix: 10,
  cols: 100,
  collapseChunk: 50,
};

/** Per-request telemetry surfaced back to TransformInfo. */
export interface HistoryCollapseInfo {
  /** Number of turns collapsed into the history image. */
  collapsedTurns: number;
  /** Total chars of text that went into the history image. */
  collapsedChars: number;
  /** Number of PNG image blocks emitted for the history (≥1 if collapsed). */
  collapsedImages: number;
  /** Total PNG bytes emitted. */
  collapsedImageBytes: number;
  /** Total pixel area emitted (`Σ width × height`). Pairs with cold-miss
   *  cache_create tokens for empirical px/token derivation — same role as
   *  `info.imagePixels` in TransformInfo, accumulated here so the caller
   *  can fold history images into the same regression. */
  collapsedImagePixels: number;
  /** Why we didn't collapse — populated only when no collapse happened. */
  reason?:
    | 'no_history'
    | 'prefix_too_short'
    | 'no_closed_prefix'
    | 'not_profitable'
    | 'render_empty';
  /** Dropped codepoints from the history render, merged into the
   *  transform-wide map by the caller. */
  droppedChars: number;
  droppedCodepoints: Map<number, number>;
}


/**
 * Compute the largest index `i*` in `[0..messages.length - keepTail - 1]`
 * such that all `tool_use_id`s issued by assistant turns in `[0..i*]` are
 * matched by `tool_result`s also in `[0..i*]`. Returns `-1` if no such
 * 
[assistant]
Looked at src/core/render.ts; continuing with the change.
[assistant]
Found it: the double-flush race lives in src/retry/io.ts, the lock is released before the journal write lands.
[user]
ok fix it there, nowhere else.
[tool_use Read]
{"file_path":"src/core/proxy.ts"}
[tool_result]
psed range are dropped from the
 * rendered text — per the spec's Check 2, only the most-recent
 * assistant-with-tool_use's thinking content must round-trip bit-perfect,
 * and that turn is in the live tail by construction.
 *
 * **Cache-control**: caller controls whether the history-image carries
 * pxpipe's ephemeral breakpoint. This module returns the image blocks
 * unmarked; the caller in `transform.ts` decides placement.
 *
 * Spec source: `/tmp/pxpipe-history-compression.md` Variant C section
 * (round 3, lines 346-364 + check-3 cache-control discussion).
 */

import type { ContentBlock, ImageBlock, Message, TextBlock, ToolUseBlock, ToolResultBlock } from './types.js';
import { DENSE_CONTENT_CHARS_PER_IMAGE, DENSE_CONTENT_COLS, DENSE_RENDER_STYLE, renderTextToPngsWithCharLimit } from './render.js';
import { bytesToBase64 } from './png.js';

/** Function predicate signature for the break-even gate. Passed in by the
 *  caller (transform.ts) rather than imported here to keep `src/core/history.ts`
 *  free of a cycle with `src/core/transform.ts`. transform.ts already imports
 *  history.ts to invoke `collapseHistory`; importing back the other way would
 *  create an evaluation-order trap.
 *
 *  IMPORTANT — takes the full `text`, NOT `text.length`. The downstream
 *  `isCompressionProfitable` has two paths: a row-aware path for strings
 *  (matches renderTextToPngs() image budgeting exactly) and a looser
 *  chars-only fallback for numbers (assumes dense lines, no newlines).
 *  History text is *newline-heavy* — `--- role ---` headers, JSON args,
 *  `[tool_use]` / `[tool_result]` labels — so the chars-only estimate
 *  under-predicts image count by ~5-10× and used to let net-losers
 *  through. The 2026-05-19 production -250% savings measurement traces
 *  back to that asymmetry. Always pass the string. */
export type ProfitableFn = (text: string, cols: number) => boolean;

/** Configuration for history collapse. */
export interface HistoryCollapseOptions {
  /** Number of turns at the tail (most recent) to KEEP as text. Default 4. */
  keepTail: number;
  /** Minimum number of turns in the collapsable prefix before we attempt
   *  the rolling-window re-roll. Below this, leaving them as text costs
   *  almost nothing and the cache-amortization math doesn't work. Default 10. */
  minCollapsePrefix: number;
  /** Soft-wrap column count for the renderer. Should match the host's
   *  configured `cols` so the history image visually matches the system
   *  image. Default 100. */
  cols: number;
  /** Quantize the collapse boundary onto a fixed grid of this many
   *  messages. The collapsed prefix only advances in `collapseChunk`-sized
   *  steps, so the rendered history image stays byte-identical between
   *  steps and keeps hitting Anthropic's prompt cache instead of forcing a
   *  fresh `cache_create` (1.25x) of the whole prefix on every single turn.
   *  Set to 0 for the legacy per-turn moving boundary. Default 50. */
  collapseChunk: number;
}

export const HISTORY_DEFAULTS: HistoryCollapseOptions = {
  keepTail: 4,
  minCollapsePrefix: 10,
  cols: 100,
  collapseChunk: 50,
};

/** Per-request telemetry surfaced back to TransformInfo. */
export interface HistoryCollapseInfo {
  /** Number of turns collapsed into the history image. */
  collapsedTurns: number;
  /** Total chars of text that went into the history image. */
  collapsedChars: number;
  /** Number of PNG image blocks emitted for the history (≥1 if collapsed). */
  collapsedImages: number;
  /** Total PNG bytes emitted. */
  collapsedImageBytes: numb
[assistant]
Looked at src/core/proxy.ts; continuing with the change.
[user]
important: we did NOT enable ENABLE_SHARDING in prod, it only looked enabled because of the stale config cache. coverage stayed at 31%.
[assistant]
Understood: ENABLE_SHARDING is OFF in prod, the dashboard was lying; coverage 31%.
[tool_use Read]
{"file_path":"src/core/transform.ts"}
[tool_result]
it a single glyph from the grayscale atlas (atlas-gray.ts) onto the
 * framebuffer at pixel position (x, y). Reads coverage bytes and writes
 * `fb[idx] = Math.max(fb[idx], coverage)` so glyph ink accumulates without
 * overwriting already-inked pixels (max blending, same convention as the
 * 1-bit path which just sets 255).
 *
 * EVAL-ONLY: called only when style.aa is set. The 1-bit blitGlyph path
 * is unchanged and remains byte-identical to before.
 *
 * Returns the number of cells the glyph occupies (1 or 2), or 0 if the
 * codepoint is absent from the gray atlas.
 */
function blitGlyphGray(
  fb: Uint8Array,
  fbW: number,
  x: number,
  y: number,
  codepoint: number,
): number {
  const rank = atlasGrayRank(codepoint);
  if (rank < 0) return 0;
  const wide = ATLAS_GRAY_WIDE_FLAGS[rank] === 1;
  const srcW = wide ? 2 * ATLAS_GRAY_CELL_W : ATLAS_GRAY_CELL_W;
  // ATLAS_GRAY_OFFSETS is a BYTE offset (1 byte per pixel, unlike the bit-packed 1-bit atlas).
  const srcOff = ATLAS_GRAY_OFFSETS[rank]!;
  for (let gy = 0; gy < ATLAS_GRAY_CELL_H; gy++) {
    const dstRow = (y + gy) * fbW + x;
    const srcRow = srcOff + gy * srcW;
    for (let gx = 0; gx < srcW; gx++) {
      const coverage = ATLAS_GRAY_PIXELS[srcRow + gx]!;
      if (coverage > 0) {
        const idx = dstRow + gx;
        if (coverage > fb[idx]!) fb[idx] = coverage;
      }
    }
  }
  return wide ? 2 : 1;
}

/** Blit a glyph scaled horizontally by `scaleX` (each atlas pixel becomes
 *  `scaleX` px wide; height unchanged). Used for the enlarged ↵ marker:
 *  horizontal-only scaling keeps it from overlapping the densely-packed row
 *  below, which a uniform scale-up would corrupt. Marks `markerMask` for the
 *  red-output path. Returns cells advanced (`scaleX`, `2*scaleX` if wide). */
function blitGlyphScaled(
  fb: Uint8Array,
  markerMask: Uint8Array | null,
  fbW: number,
  fbH: number,
  x: number,
  y: number,
  codepoint: number,
  scaleX: number,
): number {
  const rank = atlasRank(codepoint);
  if (rank < 0) return 0;
  const wide = ATLAS_WIDE_FLAGS[rank] === 1;
  const srcW = wide ? 2 * ATLAS_CELL_W : ATLAS_CELL_W;
  const srcOff = ATLAS_OFFSETS[rank]!;
  for (let gy = 0; gy < ATLAS_CELL_H; gy++) {
    const py = y + gy;
    if (py >= fbH) break;
    const bitRowStart = srcOff + gy * srcW;
    for (let gx = 0; gx < srcW; gx++) {
      const bitIdx = bitRowStart + gx;
      const byte = ATLAS_PIXELS[bitIdx >>> 3]!;
      if (((byte >>> (7 - (bitIdx & 7))) & 1) === 0) continue;
      for (let sx = 0; sx < scaleX; sx++) {
        const px = x + gx * scaleX + sx;
        if (px >= fbW) break;
        const idx = py * fbW + px;
        fb[idx] = 255;
        if (markerMask) markerMask[idx] = 1;
      }
    }
  }
  return wide ? 2 * scaleX : scaleX;
}

/** Faint grey grid ink, pre-invert. 25 → post-invert 230: a light-grey rule
 *  distinct from the multicol gutter divider (pre 64 → post 191) by both
 *  shade and orientation, so a row rule is never mistaken for a column edge. */
const GRID_INK = 25;

/** Paint grid rules into the framebuffer. Rules are written only onto
 *  background pixels — glyph ink always wins — so the grid adds zero pixels
 *  to the image (no width, no height, no token cost). It exists purely to
 *  give the vision model row/column landmarks that dense reflow packing
 *  destroys. Horizontal rule: bottom pixel-row of every cell-band (one ruled
 *  lane per text row). Vertical rules: every `gridCols` columns when > 0. */
function drawGrid(
  fb: Uint8Array,
  fbW: number,
  fbH: number,
  rows: number,
  gridCols: number,
  cellH: number,
  cellW: number,
  glyphH: number = ATLAS_CELL_H,
): void {
  fo
[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 7850ms and do not change it without a ticket.
[assistant]
Set the retry budget constant to 7850ms.
[tool_use Read]
{"file_path":"src/core/render.ts"}
[tool_result]
d 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 scan of `this.sessions`.
        if (this.sessions.size > DashboardState.SESSION_CAP) {
          const firstKey = this.sessions.keys().next().value;
          if (firstKey !== undefined) this.sessions.delete(firstKey);
        }
      }
      // Reuse the same haveUsage / haveBaseline guards + the
      // baselineInputEff / actualInputEff locals computed earlier in
      // update() so the lifetime totals block (above) and the per-session
      // block (here) read the same values. Re-deriving them here would
      // duplicate the cache-aware-baseline math and invite drift.
      if (haveBaseline && haveUsage) {
        s.baselineInputWeighted += 
[assistant]
Looked at src/core/render.ts; continuing with the change.
[user]
team sync outcome: we are going with jotai for the store layer, immer was rejected because the bundle delta was too big.
[assistant]
Noted, jotai it is for the store layer; I will not add immer.
[tool_use Read]
{"file_path":"src/core/render.ts"}
[tool_result]
 turns.
  //
  // Run the lossless whitespace compactor before measuring/rendering. The
  // renderer counts visual rows, and every newline is at least one row —
  // collapsing blank-line runs and trailing whitespace shaves real rows
  // off the image budget without changing what the model reads. Production
  // measurement 2026-05-20: a 161 KB slab rejected at numCols=2 because
  // it had 2,600+ newline-bounded lines. The compactor reliably moves the
  // needle on those by 10-25%.
  const combinedRaw = [staticText, toolDocsText].filter((s) => s.length > 0).join('\n\n');
  // R3: reflow runs after compaction, before the break-even gate, so the gate
  // and renderer below both see the 
[assistant]
Looked at src/core/render.ts; continuing with the change.
[user]
fyi the on-call reviewer for this change is Soren Petrov, route the PR to them.
[assistant]
Will request review from Soren Petrov.
[tool_use Read]
{"file_path":"src/core/transform.ts"}
[tool_result]
ng region so it reads as intentional
 *  rather than as a render artifact bleeding into the margin. */
const GUTTER_DIVIDER_INSET_PX = 2;

/** Pixel width of a multi-col render canvas at the given `cols` and `numCols`. */
export function multiColWidth(cols: number, numCols: number): number {
  const n = Math.max(1, numCols | 0);
  return 2 * PAD_X + n * cols * CELL_W + (n - 1) * GUTTER_CELLS * CELL_W;
}

/** Largest `numCols` that fits within MAX_WIDTH_PX at `cols`. Useful for the
 *  CLI clamp so an over-large flag doesn't produce >1568px PNGs. */
export function maxFittingCols(cols: number): number {
  let n = 1;
  while (multiColWidth(cols, n + 1) <= MAX_WIDTH_PX) n++;
  return n;
}

async function renderMultiColChunkFromLines(
  lines: string[],
  cols: number,
  numCols: number,
  charsCovered: number,
  linesPerCol: number,
): Promise<RenderedImage> {
  const width = multiColWidth(cols, numCols);
  // Height tracks the tallest column. With column-major packing column 0 is
  // always at least as tall as later columns, so usedRows = min(lines.length, linesPerImg).
  const rowsPerCol = Math.max(1, linesPerCol | 0);
  const usedRows = Math.min(lines.length, rowsPerCol);
  const height = 2 * PAD_Y + usedRows * CELL_H;

  const fb = new Uint8Array(width * height);
  let droppedChars = 0;
  const droppedCodepoints = new Map<number, number>();

  // Column-major: lines [c*linesPerImg, (c+1)*linesPerImg) land in column c.
  const colStride = cols * CELL_W + GUTTER_CELLS * CELL_W;
  for (let c = 0; c < numCols; c++) {
    const colBaseX = PAD_X + c * colStride;
    const colStart = c * rowsPerCol;
    if (colStart >= lines.length) break;
    const colEnd = Math.min(colStart + rowsPerCol, lines.length);
    for (let r = 0; r < colEnd - colStart; r++) {
      const line = lines[colStart + r]!;
      const baseY = PAD_Y + r * CELL_H;
      let col = 0;
      for (const ch of line) {
        if (col >= cols) break;
        const codepoint = ch.codePointAt(0)!;
        const baseX = colBaseX + col * CELL_W;
        const advance = blitGlyph(fb, width, baseX, baseY, codepoint);
        if (advance === 0) {
          droppedChars++;
          droppedCodepoints.set(codepoint, (droppedCodepoints.get(codepoint) ?? 0) + 1);
          col += 1;
        } else {
          col += advance;
        }
      }
    }
  }

  // Draw a faint vertical divider in each gutter BEFORE the invert pass.
  // We're still in "ink = high, background = low" framebuffer convention here,
  // so GUTTER_DIVIDER_INK (64) lands at 255-64 = 191 after the invert — a
  // light gray on the final image. Position the line in the *center* of the
  // gutter region between columns c and c+1, with a small top/bottom inset
  // so it doesn't visually bleed into the padding rows.
  //
  // Cost: ~1568 px × 1 byte = 1568 bytes of identical mid-gray. After DEFLA
[assistant]
Looked at src/core/transform.ts; continuing with the change.

=== end of transcript ===
