=== session s7: earlier coding session transcript ===
[tool_use Read]
{"file_path":"src/core/render.ts"}
[tool_result]
tring') return { text: sys, kept: '' };
  const textParts: string[] = [];
  const kept: SystemField = [];
  for (const block of sys) {
    if (block && typeof block === 'object' && block.type === 'text') {
      textParts.push(block.text);
    } else {
      kept.push(block);
    }
  }
  return { text: textParts.join('\n\n'), kept };
}

function lastStaticSystemCacheControl(sys: SystemField | undefined): TextBlock['cache_control'] | undefined {
  if (!Array.isArray(sys)) return undefined;
  let cacheControl: TextBlock['cache_control'] | undefined;
  for (const block of sys) {
    if (!block || block.type !== 'text' || block.cache_control === undefined) continue;
    const { body } = stripBillingLine(block.text);
    if (splitStaticDynamic(body).staticText.length > 0) {
      cacheControl = block.cache_control;
    }
  }
  return cacheControl;
}

/**
 * Claude Code injects a handful of per-turn dynamic blocks into the system
 * prompt (e.g. <env>, <context>, <git_status>, <directoryStructure>,
 * <system-reminder>). Including these in the rendered image kills the
 * Anthropic prompt cache because the bytes drift turn-to-turn. Splitting
 * them out lets us render the static slab (CLAUDE.md, agent defs, tool docs)
 * with cache_control while forwarding the dynamic slab as cheap text so the
 * model still sees cwd / git status / today's date.
 */
const DYNAMIC_BLOCK_TAGS = [
  'env',
  'context',
  'git_status',
  'directoryStructure',
  'system-reminder',
] as const;

/**
 * Tag
[assistant]
Looked at src/core/render.ts; continuing with the change.
[user]
ops note: the upstream gateway hard-times-out at 10s, so set our retry budget to exactly 7870ms and do not change it without a ticket.
[assistant]
Set the retry budget constant to 7870ms.
[tool_use Read]
{"file_path":"src/core/history.ts"}
[tool_result]
ell instead of one short line per field.
        let argsStr: string;
        try {
          argsStr = JSON.stringify(tu.input);
        } catch {
          argsStr = String(tu.input);
        }
        parts.push(`[tool_use ${tu.name}]\n${argsStr}`);
        break;
      }
      case 'tool_result': {
        const tr = blk as ToolResultBlock;
        const inner = tr.content;
        let innerText: string;
        if (typeof inner === 'string') {
          innerText = inner;
        } else if (Array.isArray(inner)) {
          const subParts: string[] = [];
          for (const sub of inner) {
            if (!sub || typeof sub !== 'object') continue;
            if ((sub as TextBlock).type === 'text') {
              subParts.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: M
[assistant]
Looked at src/core/history.ts; continuing with the change.
[user]
important: we did NOT enable HOT_RELOAD_V2 in prod, it only looked enabled because of the stale config cache. coverage stayed at 38%.
[assistant]
Understood: HOT_RELOAD_V2 is OFF in prod, the dashboard was lying; coverage 38%.
[tool_use Read]
{"file_path":"src/core/transform.ts"}
[tool_result]
join('\n');
    images.push(await renderChunkToPng(chunk, cols, style));
  }
  return images;
}

export async function renderTextToPngs(
  text: string,
  cols: number = DEFAULT_COLS,
  style: RenderStyle = {},
): Promise<RenderedImage[]> {
  return renderTextToPngsWithCharLimit(text, cols, READABLE_CHARS_PER_IMAGE, style);
}

// --- R2 multi-column rendering --------------------------------------------
//
// Single-column packing leaves Anthropic's 1568×1568 image area badly
// under-used: at the 5×8 cell and cols=100, our render canvas is only
// 508 px wide — ~32% of the horizontal budget. Most real Claude Code tool
// docs + CLAUDE.md content wraps well under 100 chars/row, so we end up
// paying the full per-image cost for an image that's mostly whitespace.
//
// R2 packs N columns side-by-side per image, column-major: column 1 holds
// the first `linesPerImg` wrapped lines top-to-bottom, column 2 holds the
// next `linesPerImg`, etc. One image therefore covers `numCols×linesPerImg`
// wrapped lines instead of `linesPerImg` — image count drops by ~numCols.
//
// OCR ORDERING IS THE RISK. The vision encoder must read column 1 fully
// before column 2. Modern vision LLMs (Claude included) handle newspaper-
// column layout reasonably well when the gutter is visually clear, but
// this needs empirical verification on representative slabs before
// becoming the default. Until then this lives behind an opt-in flag.

const GUTTER_CELLS = 4;
const MAX_WIDTH_PX = 1568;

/** Mid-gray ink level for the multicol gutter divider, BEFORE the final
 *  `255 - fb[i]` invert that flips the framebuffer to black-on-white. 64
 *  pre-invert → 191 post-invert = a light gray (~75% white) that the vision

[assistant]
Looked at src/core/transform.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/proxy.ts"}
[tool_result]
te: the gate, the
 *  image-count estimate, paging, and the renderer then all operate on the
 *  same dense single-line text, so no break-even formula changes are needed.
 *  Falls back to the input unchanged when reflow is off or `reflow()` hits a
 *  sentinel collision. */
function maybeReflow(text: string, enabled: boolean): string {
  if (!enabled) return text;
  return reflow(text) ?? text;
}

/** Returns true iff image-compressing a text block would actually save tokens
 *  vs leaving it as text. Used as the gate before every image-encoding
 *  decision in transformRequest.
 *
 *  ## Content-aware geometry
 *
 *  The gate is **string-only** — every production caller has the text, and
 *  the gate uses it to compute the renderer's exact image cost two ways at
 *  once:
 *
 *  - **Rows** come from `countVisualRows` (matches `wrapLines` line-for-
 *    line, including soft-wraps and codepoint width).
 *  - **Width** comes from `shrinkColsToContent` when `shrinkWidth=true`
 *    (the default): a 16-char `"File not found"` block bills for an
 *    ~80 px wide canvas, not the full 508 px slab canvas. This matters
 *    most for tool_result and reminder blocks, which dominate per-turn
 *    image cost and are usually much narrower than `cols`.
 *
 *  Set `shrinkWidth=false` for the system slab (multi-col, fills the
 *  configured `cols` deliberately to maximise OCR density) and anywhere
 *  the caller needs full-canvas pricing for telemetry parity.
 *
 *  ## No numeric overload
 *
 *  The historical `textOrLen: string | number` shape existed for unit-
 *  test back-compat. The numeric path assumed every char filled a full-
 *  width row (= lower-bound rows = under-estimated image cost), which
 *  silently let net-losing compressions through whenever a caller passed
 *  `text.length` instead of `text`. Removed.
 */
/** Decompose the per-block break-even gate's evaluation into its components.
 *  Returns the exact `imageTokens`, `textTokens`, and symmetric burn terms
 *  the gate uses internally. Pairs with `isCompressionProfitable` for
 *  telemetry: callers can record the numbers without re-implementing the
 *  formula and risking drift.
 *
 *  Returns `null` when the input is empty or non-finite. Stays in sync with
 *  `isCompressionProfitable` because both use the same `imageTokensCost`
 *  and the same width-shrink toggle. */
export function evalCompressionProfitability(
  text: string,
  cols: number,
  imageCountCap: number | undefined = undefined,
  numCols: number = 1,
  charsPerToken: number = CHARS_PER_TOKEN,
  priorWarmTokens: number = 0,
  priorWarmImageTokens: number = 0,
  shrinkWidth: boolean = true,
): {
  imageTokens: number;
  textTokens: number;
  burnImageSide: number;
  burnTextSide: number;
  profitable: boolean;
} | null {
  const n = Math.max(1, numCols | 0);
  if (typeof text !== 'string' || text.length === 0) return null;
  const cpt = Number.isFinite(charsPerToken) && charsPerToken > 0
    ? charsPerToken
    : CHARS_PER_TOKEN;
  const imageTokens = imageTokensCost(text, cols, n, imageCountCap, shrinkWidth);
  const textTokens = text.length / cpt;
  const burnImageSide = Number.isFinite(priorWarmTokens) && priorWarmTokens > 0
    ? priorWarmTokens * (CACHE_CREATE_RATE - CACHE_READ_RATE)
    : 0;
  const burnTextSide = Number.isFinite(priorWarmImageTokens) && priorWarmImageTokens > 0
    ? priorWarmImageTokens * (CACHE_CREATE_RATE - CACHE_READ_RATE)
    : 0;
  return {
    imageTokens,
    textTokens,
    burnImageSide,
    burnTextSide,
    profitable: imageTokens + burnImageSide < textTokens + burnTextSide,
  };
}

export function isCompressionProfitable(
  text: string,
  cols: number = DEFAULTS.cols,
  imageCountCap?: number,
  numCols: number = 1,
  /** Chars-per-token assumption for the text side of the break-even math.
   *  Default 4 (Anthropic's English-text average). Lower values = more
   *  profitable text compressions (each char buys more tokens back). */
  charsPerToken: number = CHARS_PER_TOKEN,
  /** Tokens the un-rewritten path would have hit cache on. Adds a one-time
   *  burn penalty of `priorWarmTokens × (CACHE_CREATE_RATE − CACHE_READ_RATE)`
   *  to the image side — the cost of forcing a fresh cache_create when the
   *  rewritten prefix invalidates Anthropic's prior cache key. Default 0
   *  (cold-start behavior; matches pre-burn-aware callers byte-for-byte). */
  priorWarmTokens: number = 0,
  /** Symmetric image-side burn: tokens the rewritten (IMAGE) path would
   *  have hit cache on. Adds a one-time burn penalty of
   *  `priorWarmImageTokens × (CACHE_CREATE_RATE − CACHE_READ_RATE)` to the
   *  TEXT side — the cost of forcing a fresh cache_create on the
   *  un-rewritten text prefix when the rewritten image prefix was warm.
   *  Default 0 (back-compat; existing single-arg callers behave unchanged).
   *  See PxpipeOptions.priorWarmImageTokens for the foundational rationale. */
  priorWarmImageTokens: number = 0,
  /** Shrink the rendered canvas width to the longest actual wrapped line.
   *  Default `true` (per-block content: tool_result, reminder, history).
   *  Set `false` for the system slab, which deliberately fills the full
   *  configured `cols` (multi-col packing). */
  shrinkWidth: boolean = true,
): boolean {
  const n = Math.max(1, numCols | 0);
  if (typeof text !== 'string' || text.length === 0) return false;
  const cpt = Number.isFinite(charsPerToken) && charsPerToken > 0
    ? charsPerToken
    : CHARS_PER_TOKEN;
  const imageTokensCost_ = imageTokensCost(text, cols, n, imageCountCap, shrinkWidth);
  const textTokensEquivalent = text.length / cpt;
  // Cache
[assistant]
Looked at src/core/proxy.ts; continuing with the change.
[assistant]
Found it: the double-flush race lives in src/batcher/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/transform.ts"}
[tool_result]
) is NOT compressed, so its
    // absolute token count is approximately the same on both paths.
    // See src/core/baseline.ts for the full derivation and the May-2026
    // regression that motivated the rewrite.
    const baselineInputEff =
      haveBaseline && haveUsage
        ? computeBaselineInputEff(
            baseline,
            info?.baselineCacheableTokens ?? 0,
            cc,
            cr,
          )
        : 0;

    // Output tokens are identical with/without compression — the proxy never
    // touches the response body. They show up on BOTH sides of the savings
    // ratio at their actual rate (OUTPUT_TOKEN_RATE × input rate) so the
    // denominator reflects the full bill the user actually pays. W
[assistant]
Looked at src/core/transform.ts; continuing with the change.
[user]
fyi the on-call reviewer for this change is Priya Tanaka, route the PR to them.
[assistant]
Will request review from Priya Tanaka.
[tool_use Read]
{"file_path":"src/core/transform.ts"}
[tool_result]
nly paint if the pixel is still background (0). Defensive against
        // a glyph-overrun scenario where a wide char could in principle have
        // landed 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 codepoints + one separator per adjacent pair.
[assistant]
Looked at src/core/transform.ts; continuing with the change.

=== end of transcript ===
