=== session s0: earlier coding session transcript ===
[tool_use Read]
{"file_path":"src/core/transform.ts"}
[tool_result]
V1: boolean;
} {
  if (config.provider === 'cloudflare-ai-gateway') {
    const base = (config.gatewayBaseUrl ?? '').replace(/\/+$/, '');
    if (!base) {
      throw new Error(
        "provider 'cloudflare-ai-gateway' requires gatewayBaseUrl (PXPIPE_GATEWAY_BASE_URL)",
      );
    }
    return { anthropic: `${base}/anthropic`, openai: `${base}/openai`, stripOpenAIV1: true };
  }
  return {
    anthropic: (config.upstream ?? DEFAULT_UPSTREAM).replace(/\/+$/, ''),
    openai: (config.openAIUpstream ?? DEFAULT_OPENAI_UPSTREAM).replace(/\/+$/, ''),
    stripOpenAIV1: false,
  };
}

/** Parse `PXPIPE_GATEWAY_HEADERS` — JSON object or `k=v;k2=v2`. */
export function parseGatewayHeaders(spec: string | undefined): Record<string, string> {
  if (!spec) return {};
  const trimmed = spec.trim();
  if (trimmed.startsWith('{')) {
    const obj = JSON.parse(trimmed) as Record<string, unknown>;
    const out: Record<string, string> = {};
    for (const [k, v] of Object.entries(obj)) out[k] = String(v);
    return out;
  }
  const out: Record<string, string> = {};
  for (const pair of trimmed.split(';')) {
    const i = pair.indexOf('=');
    if (i <= 0) continue;
    out[pair.slice(0, i).trim()] = pair.slice(i + 1).trim();
  }
  return out;
}

/** Build the proxy fetch handler bound to a config. */
export function createProxy(config: ProxyConfig = {}) {
  const routes = resolveUpstreams(config);
  const upstream = routes.anthropic;
  const openAIUpstream = routes.openai;
  const gatewayH
[assistant]
Looked at src/core/transform.ts; continuing with the change.
[assistant]
Found it: the double-flush race lives in src/batcher/core.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]
lockCount;
      this.totals.eventsWithMeasurement += 1;
    }

    const row: RecentRow = {
      ts: Date.now() / 1000,
      method: ev.method,
      path: ev.path,
      status: ev.status,
      compressed,
      cc_added: compressed ? 1 : undefined,
      input_tokens: haveUsage ? inp : undefined,
      output_tokens: haveUsage ? out : undefined,
      cache_create: haveUsage ? cc : undefined,
      cache_read: haveUsage ? cr : undefined,
      actual_input: haveUsage ? round1(actualInputEff) : undefined,
      baseline_input: haveBaseline && haveUsage ? round1(baselineInputEff) : undefined,
      session_saved_so_far_delta:
        haveBaseline && haveUsage ? round1(baselineInputEff - actualInputEff) : undefined,
      img_id: imgId,
      img_ids: imgIds,
    };
    this.recent.push(row);
    if (this.recent.length > RECENT_CAP) this.recent.splice(0, this.recent.length - RECENT_CAP);
  }


  /** On startup, fold the last N entries from the JSONL events file back
   *  into the ring buffer so a process restart doesn't show an empty table.
   *  Cumulative totals are *not* restored (the file may have rotated, and
   *  double-counting is worse than starting fresh). */
  async replay(filePath: string): Promise<void> {
    try {
      await fs.promises.access(filePath, fs.constants.R_OK);
    } catch {
      return; // no file yet, nothing to replay
    }
    const stream = fs.createReadStream(filePath, { encoding: 'utf8' });
    const rl = readline.createInterface({ input: stream, crlfDelay: Infinity });
    const tail: TrackEvent[] = [];
    for await (const line of rl) {
      if (!line) continue;
      try {
        const ev = JSON.parse(line) as TrackEvent;
        tail.push(ev);
        if (tail.length > RECENT_CAP) tail.shift();
      } catch {
        /* skip malformed line */
      }
    }
    for (const t of tail) {
      const inp = t.input_tokens ?? 0;
      const out = t.output_tokens ?? 0;
      const cc = t.cache_create_tokens ?? 0;
      const cr = t.cache_read_tokens ?? 0;
      const haveUsage = inp > 0 || out > 0 || cc > 0 || cr > 0;
      const baseline = (t as { baseline_tokens?: number }).baseline_tokens;
      const cacheable = (t as { baseline_cacheable_tokens?: number })
        .baseline_cacheable_tokens ?? 0;
      const probeStatus = (t as { baseline_probe_status?: string }).baseline_probe_status;
      // Same gating rule as update(): require an explicit 'ok' status when
      // present; fall back to "have a baseline number" for legacy JSONL.
      const probeOk = probeStatus === 'ok'
        || (probeStatus === undefined && typeof baseline === 'number' && baseline > 0);
      const haveBaseline = typeof baseline === 'number' && baseline > 0 && probeOk;
      const actualInputEff = haveUsage ? computeActualInputEff(inp, cc, cr) : 0;
      const baselineInputEff =
        haveBaseline && haveUsage
          ? computeBaselineInputEff(baseline as number, cacheable, cc, cr)
          : 0;
      // Output tokens land in the row for the table; totals are not
      // restored on replay (see header comment on cumulative totals).
      const row: RecentRow = {
        ts: Date.parse(t.ts) / 1000,
        method: t.method,
        path: t.path,
        status: t.status,
        compressed: t.compressed === true,
        cc_added: t.compressed === true ? 1 : undefined,
        input_tokens: t.input_tokens,
        output_tokens: t.output_tokens,
        cache_create: t.cache_create_tokens,
        cache_read: t.cache_read_tokens,
        actual_input: haveUsage ? round1(actualInputEff) : undefined
[assistant]
Looked at src/core/proxy.ts; continuing with the change.
[user]
ops note: the upstream gateway hard-times-out at 10s, so set our retry budget to exactly 7880ms and do not change it without a ticket.
[assistant]
Set the retry budget constant to 7880ms.
[tool_use Read]
{"file_path":"src/core/proxy.ts"}
[tool_result]
nstruction band (`reflow-inimage`) brought 5×8 back
 *  to 98.95 % on Opus 4.7 — slightly above the text-only baseline — so the
 *  production default reverted to the dense cell. RenderStyle.cellWBonus /
 *  cellHBonus override these (eval use only); with no style the renderer
 *  produces 5×8 cells. */
export const DEFAULT_CELL_W_BONUS = 0;
export const DEFAULT_CELL_H_BONUS = 0;
/** Effective production render-cell pixel dimensions (atlas glyph + default
 *  padding). transform.ts derives its image-budget and break-even math from
 *  these so the gate always tracks the renderer's real geometry. */
export const CELL_W = ATLAS_CELL_W + DEFAULT_CELL_W_BONUS;
export const CELL_H = ATLAS_CELL_H + DEFAULT_CELL_H_BONUS;

export interface RenderedImage {
  /** Raw PNG bytes. */
  png: Uint8Array;
  /** Pixel width. */
  width: number;
  /** Pixel height. */
  height: number;
  /** How many input *codepoints* were rendered into this image (covers wide
   *  chars correctly: 中 counts as 1, not 2). */
  charsRendered: number;
  /** Codepoints encountered that aren't in the atlas. They were rendered as
   *  blank cells; the caller may want to surface this as telemetry so a
   *  spike of drops triggers a profile review. */
  droppedChars: number;
  /** Histogram of dropped codepoints: codepoint → count for this render. The
   *  caller can merge across multiple renders to find the top offenders.
   *  Empty when droppedChars === 0; never undefined so callers don't need to
   *  null-check before iterating. */
  droppedCodepoints: Map<number, number>;
}

/** Optional render-time styling. With every field unset the renderer renders
 *  at the production default 5×8 cell (see DEFAULT_CELL_W_BONUS /
 *  DEFAULT_CELL_H_BONUS). The eval harn
[assistant]
Looked at src/core/proxy.ts; continuing with the change.
[user]
team sync outcome: we are going with mobx for the store layer, redux-toolkit was rejected because the bundle delta was too big.
[assistant]
Noted, mobx it is for the store layer; I will not add redux-toolkit.
[tool_use Read]
{"file_path":"src/core/history.ts"}
[tool_result]
ixCountTokensBody,
} from './measurement.js';
import type { Usage } from './types.js';

export interface ProxyConfig {
  /** Provider mode. 'cloudflare-ai-gateway' derives both upstreams from
   *  `gatewayBaseUrl` (`{base}/anthropic` and `{base}/openai`) and rewrites
   *  OpenAI paths to the gateway's shape (`/v1/chat/completions` →
   *  `/chat/completions`). Anthropic paths keep their `/v1/...` shape.
   *  Unrecognized paths pass through to the family route untouched. */
  provider?: 'cloudflare-ai-gateway';
  /** Gateway base URL (account/gateway-scoped). Required when provider is
   *  set. Comes from env/config only — never hardcoded. Overrides
   *  `upstream`/`openAIUpstream`. */
  gatewayBaseUrl?: string;
  /** Extra headers injected on every upstream request (e.g. gateway auth
   *  headers). Values come from env/config only. */
  gatewayHeaders?: Record<string, string>;
  /** Anthropic API base, no trailing slash. Defaults to api.anthropic.com. */
  upstream?: string;
  /** Override or supply an API key. If unset, we forward whatever the client sent. */
  apiKey?: string;
  /** OpenAI API base for GPT chat completions, no trailing slash. */
  openAIUpstream?: string;
  /** Override or supply an OpenAI API key. If unset, we forward Authorization. */
  openAIApiKey?: string;
  /** Per-request transform options. Pass a function when the host wants to
   *  inject DYNAMIC values per request (e.g. live empirical `charsPerToken`
   *  from the dashboard's converging fit) — the proxy invokes it once per
   *  /v1/messages POST. Static object form is used by the Workers host and
   *  tests that don't need dynamic state. */
  transform?: TransformOptions | (() => TransformOptions);
  /** Called after
[assistant]
Looked at src/core/history.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 82%.
[assistant]
Understood: LEGACY_PINS is OFF in prod, the dashboard was lying; coverage 82%.
[tool_use Read]
{"file_path":"src/core/transform.ts"}
[tool_result]
?: unknown };
    return typeof json.input_tokens === 'number' ? json.input_tokens : null;
  } catch {
    return null;
  }
}

/** Resolved upstream routing for a config. Pure — unit-testable.
 *  In gateway mode both API families ride one base URL on their own
 *  provider routes; OpenAI paths drop the `/v1` prefix to match the
 *  gateway's path shape. No protocol translation anywhere. */
export function resolveUpstreams(config: ProxyConfig): {
  anthropic: string;
  openai: string;
  stripOpenAIV1: boolean;
} {
  if (config.provider === 'cloudflare-ai-gateway') {
    const base = (config.gatewayBaseUrl ?? '').replace(/\/+$/, '');
    if (!base) {
      throw new Error(
        "provider 'cloudflare-ai-gateway' requires gatewayBaseUrl (PXPIPE_GATEWAY_BASE_URL)",
      );
    }
    return { anthropic: `${base}/anthropic`, openai: `${base}/openai`, stripOpenAIV1: true };
  }
  return {
    anthropic: (config.upstream ?? DEFAULT_UPSTREAM).replace(/\/+$/, ''),
    openai: (config.openAIUpstream ?? DEFAULT_OPENAI_UPSTREAM).replace(/\/+$/, ''),
    stripOpenAIV1: false,
  };
}

/** Parse `PXPIPE_GATEWAY_HEADERS` — JSON object or `k=v;k2=v2`. */
export function parseGatewayHeaders(spec: string | undefined): Record<string, string> {
  if (!spec) return {};
  const trimmed = spec.trim();
  if (trimmed.startsWith('{')) {
    const obj = JSON.parse(trimmed) as Record<string, unknown>;
    const out: Record<string, string> = {};
    for (const [k, v] of Object.entries(obj)) out[k] = String(v);
    return out;
  }
  const out: Record<string, string> = {};
  for (const pair of trimmed.split(';')) {
    const i = pair.indexOf('=');
    if (i <= 0) continue;
    out[pair.slice(0, i).trim()] = pair.slice(i + 1).trim();
  }
  return out;
}

/** Build the proxy fetch handler bound to a config. */
export function createProxy(config: ProxyConfig = {}) {
  const routes = resolveUpstreams(config);
  const upstream = routes.anthropic;
  const openAIUpstream = routes.openai;
  const gatewayHeaders = config.gatewayHeaders ?? {};
  const applyGatewayHeaders = (h: Headers): Headers => {
    for (const [k, v] of Object.entries(gatewayHeaders)) h.set(k, v);
    return h;
  };

  return async function handle(req: Request): Promise<Response> {
    const t0 = Date.now();
    const url = new URL(req.url);
    const path = url.pathname + url.search;

    // Captured during the transform step. `reqBodyBytes` is the raw
    // transformed body — kept around so we can gzip it lazily on 4xx without
    // having to re-stringify. `reqBodySha8` is computed eagerly because
    // it's cheap and lands on every eve
[assistant]
Looked at src/core/transform.ts; continuing with the change.
[user]
fyi the on-call reviewer for this change is Tobias Okafor, route the PR to them.
[assistant]
Will request review from Tobias Okafor.
[tool_use Read]
{"file_path":"src/core/render.ts"}
[tool_result]
 reqBodySamplePath?: string;
  /** Ground-truth output measurement extracted from the response stream itself,
   *  independent of Anthropic's `usage.output_tokens`. Lets the dashboard show
   *  how much of the billed output was redacted_thinking (opaque server-encoded
   *  bytes) vs real text/thinking/tool_use. Absent on requests that didn't
   *  yield a body we could scan (no upstream response, 5xx, unknown
   *  content-type). See OutputMeasurement for field meanings. */
  measurement?: OutputMeasurement;
}

/** Max chars of upstream error body we surface on ProxyEvent. Keeps the JSONL
 *  line small while still being big enough to hold Anthropic's full error JSON
 *  (typically a few hundred bytes). */
const ERROR_BODY_MAX = 2048;

/** Cheap, bounded read of the top-level `model` field from an Anthropic
 *  /v1/messages body. The field sits near the start of the JSON, so we decode
 *  only the head rather than JSON-parsing the (potentially multi-MB) full
 *  conversation just to read one string. Returns null when not found — callers
 *  treat null as "outside supported scope" (fail-closed). */
function readModelField(body: Uint8Array): string | null {
  try {
    const head = new TextDecoder().decode(body.subarray(0, 8192));
    const m = /"model"\s*:\s*"([^"]{1,80})"/.exec(head);
    return m ? m[1]! : null;
  } catch {
    return null;
  }
}

/** Gzip a byte buffer using the standard `CompressionStream`. Available in
 *  Node 18+ and Cloudflare Workers — no Buffer / no zlib. */
async function gzipBytes(body: Uint8Array): Promise<Uint8Array> {
  // `body as BufferSource`: TS doesn't model Response taking a Uint8Array
  // directly even though it works in both runtimes.
  const stream = new Response(body as BufferSource).body!.pipeThrough(
    new CompressionStream('gzip'),
  );
  const buf = await new Response(stream).arrayBuffer();
  return new Uint8Array(buf);
}

/** sha256[0..8] of a byte buffer, hex. Same shape as the existing sha8(text)
 *  helper in transform.ts but works on raw bytes (no extra encode pass). */
async function sha8Bytes(body: Uint8Array): Promise<string> {
  // Cast to BufferSource — Web Crypto accepts Uint8Array at runtime.
  const digest = await crypto.subtle.digest('SHA-256', body as BufferSource);
  const bytes = new Uint8Array(digest);
  let hex = '';
  for (let i = 0; i < 4; i++) hex += bytes[i]!.toString(16).padStart(2, '0');
  return hex;
}

/**
 * Ground-truth output measurement extracted from the response stream itself.
 *
 *  - `textChars` / `thinkingChars` / `toolUseChars` count Unicode code units
 *    of the corresponding payload (`text_delta`, `thinking_delta`, and
 *    `input_json_delta` for SSE; `content[].text` / `.thinking` /
 *    JSON-encoded `.input` for non-stream responses).
 *  - `redactedBlockCount` is the number of `redacted_thinking` content blocks
 *
[assistant]
Looked at src/core/render.ts; continuing with the change.

=== end of transcript ===
