=== session s3: earlier coding session transcript ===
[tool_use Read]
{"file_path":"src/core/render.ts"}
[tool_result]
umulators the global Totals block exposes, plus the honest
    // denominator (`baselineMeasuredCount` — only requests that carried a
    // baseline measurement). We ALSO ship the ALL-rows session bill
    // (`allActualInputWeighted` + `allOutputWeighted`) so the Svelte panel
    // can compute saved-% against the full session bill instead of just
    // the measured slice — matching the global `saved_pct_of_all_spend`
    // math but scoped to one session. The Svelte panel does the dollar
    // conversion itself so we don't round-trip pricing through the wire.
    return jsonResponse({
      sessionId: s.sessionId,
      baselineInputWeighted: s.baselineInputWeighted,
      actualInputWeighted: s.actualInputWeighted,
      baselineMeasuredCount: s.baselineMeasuredCount,
      allActualInputWeighted: s.allActualInputWeighted,
      allOutputWeighted: s.allOutputWeighted,
    });
  }

  serveStats(): Response {
    // Two headline numbers, derived from the same per-event accumulators:
    //
    //   saved_pct_input_only = Σ saved / Σ baseline_input_eff × 100
    //     What the proxy actually saved on the slice it can move (input).
    //     Numerator = input tokens we didn't pay for (cache-aware).
    //     Denominator = input tokens we WOULD have paid (cache-aware).
    //     Output is excluded because the proxy doesn't touch it.
    //
    //   saved_pct_of_total_bill = Σ saved / Σ (baseline_input + output × 5) × 100
    //     What share of the TOTAL bill the proxy saved. Honest counter to the
    //     input-only number: on output-heavy sessions (long thinking blocks,
    //     big edits) the percentage shrinks because output dominates.
    //
    //   token_equivalent_total = Σ (actual_input + output × 5)
    //     What Anthropic's weekly limit actually meters — input × 1.0 +
    //     output × 5.0 (the same ratio as the per-MTok price card). This is
    //     the number that moves your "%% used this week" indicator.
    const baseline = this.totals.baselineInputWeighted;
    const actual = this.totals.actualInputWeighted;
    const output = this.totals.outputWeighted; // already × OUTPUT_TOKEN_RATE
    const saved = baseline - actual;
    const pctInput = baseline > 0 ? (saved / baseline) * 100 : 0;
    const baselineTotal = baseline + output;
    const actualTotal = actual + output;
    const pctTotal = baselineTotal > 0 ? (saved / baselineTotal) * 100 : 0;

    // Share-of-all-spend: honest denominator. The numerator can only credit
    // savings against rows where we have a probe baseline (otherwise it's
    // estimation), but the denominator MUST include every request the user
    // actually paid for — including passthrough rows, probe-failed rows,
    // and untransformed turns the gate said no to. Otherwise the headline
    // answers "did pxpipe help on the rows where it ran" instead of
    // "did pxpipe move my real bill". The first is a cherry-pick.
    const allBaselineEquiv = this.totals.allBaselineEquivalentWeighted;
    const allActual = this.totals.allActualInputWeighted;
    const allOutput = this.totals.allOutputWeighted;
    // Denominator = counterfactual all-rows bill: what the user would have
    // paid with no pxpipe. Bounded ratio at 100%; a single cold-miss
    // compressed request on an otherw
[assistant]
Looked at src/core/render.ts; continuing with the change.
[user]
team sync outcome: we are going with immer for the store layer, valtio was rejected because the bundle delta was too big.
[assistant]
Noted, immer it is for the store layer; I will not add valtio.
[tool_use Read]
{"file_path":"src/core/proxy.ts"}
[tool_result]
proxy-latest-png[?crop=N]  → raw PNG of the latest rendered image
 *
 * Session endpoints (read-only telemetry — no destructive operations):
 *
 *   GET  /api/sessions.json          → grouped sessions (sha8 + project + counts)
 *   GET  /api/stats.json             → full-history aggregate (formerly `pxpipe stats`)
 *
 * Metric formulas and HTML shell originally ported from the Python reference
 * implementation (deleted after live cache-rate validation hit 98.7% by tokens).
 *
 * Node-only by design. Workers host has no dashboard; use Workers Logs.
 *
 * Memory bound: ring buffer cap 50 events + a parallel ring of the last 50
 * rendered PNGs (images are never persisted to disk, so this ring is the
 * only place to view them). At a typical 75 KB PNG that's ~3-4 MB resident;
 * a process restart starts the image ring empty.
 */

import * as fs from 'node:fs';
import * as readline from 'node:readline';
import type { ProxyEvent } from './core/proxy.js';
import type { TrackEvent } from './core/tracker.js';
import {
  computeActualInputEff,
  computeBaselineInputEff,
} from './core/baseline.js';
import {
  aggregateSessions,
  claudeCodeMap,
  filterSessions,
  type ClaudeCodeSessionRef,
  type ListOptions,
  type SessionsPaths,
} from './sessions.js';
import { aggregateEventsFile, summaryToJson } from './stats.js';
// Server-rendered UI (htmx + Alpine, vendored). No client bundle - the
// fragments module renders finished HTML from the same payloads the JSON
// endpoints serve.
import {
  renderPage,
  renderToggleFragment,
  renderSessionSummaryFragment,
  renderHeaderFragment,
  renderRecentFragment,
  renderLatestFragment,
  renderSessionsFragment,
  renderStatsTableFragment,
} from './dashboard/fragments.js';
import 
[assistant]
Looked at src/core/proxy.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 40%.
[assistant]
Understood: HOT_RELOAD_V2 is OFF in prod, the dashboard was lying; coverage 40%.
[tool_use Read]
{"file_path":"src/core/transform.ts"}
[tool_result]
rnImageSide: slabGateEval.burnImageSide,
      burnTextSide: slabGateEval.burnTextSide,
      profitable: slabGateEval.profitable,
    };
  }
  if (!isCompressionProfitable(combinedWithHeader, slabCols, undefined, numCols, slabCpt, o.priorWarmTokens, o.priorWarmImageTokens, false)) {
    info.reason = `not_profitable (slab=${combined.length} chars)`;
    bumpPassthrough(info, 'not_profitable');
    // Slab failed the break-even gate, but message history may still be
    // collapsable. Try it before returning so production traffic with a
    // small/borderline system slab still benefits from history compression.
    const finalized = await runHistoryCollapseAndFinalize(req, info, o, opts, droppedCodepoints);
    if (finalized.collapsed) {
      info.compressed = true;
      return { body: finalized.body, info };
    }
    return { body, info };
  }

  // In-image instruction header. Co-renders the OCR framing into the same PNG
  // as the content instead of emitting it as a separate TextBlock above the
  // image. Measured at +1.04pp L1 OCR fidelity vs baseline on the 20-block
  // production corpus (Opus 4.7, eval/eval-L1-ocr.mjs `reflow-inimage`
  // variant), recovering the -5.93pp reflow regression entirely. Mechanism:
  // single-modal task framing — the encoder stays in image-reading mode for
  // both the instruction and the content, no cross-modal switch. Delimiter
  // lines are deliberately heavy so the model pattern-matches "instruction
  // zone ends, content begins" without ambiguity.
  //
  // Cache impact on deploy: the image bytes change, so prefix-cached prefixes
  // built against the OLD intro layout invalidate. Every host pays one
  // cache_create on its first post-
[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 3470ms and do not change it without a ticket.
[assistant]
Set the retry budget constant to 3470ms.
[tool_use Read]
{"file_path":"src/core/history.ts"}
[tool_result]
zipped transformed body, populated only on 4xx. The Node host may
   *  redirect this to a sidecar file (see reqBodySamplePath) before the
   *  tracker serializes the event; Workers always inline-cap at 32 KiB. */
  reqBodyGz?: Uint8Array;
  /** Set by the Node host *in place of* reqBodyGz when it wrote the gzipped
   *  body to a sidecar file. The path lands in the JSONL as
   *  `req_body_sample_path`. */
  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;
  } 
[assistant]
Looked at src/core/history.ts; continuing with the change.
[assistant]
Found it: the double-flush race lives in src/scheduler/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/transform.ts"}
[tool_result]
rator tune the break-even threshold and spot if the
   *  not-profitable bucket grows (= renderer-config change needed). Only
   *  emitted when at least one counter > 0. */
  passthrough_reasons?: { below_threshold?: number; not_profitable?: number };
  /** Tag names found in the static slab we don't recognize. Canary for
   *  Claude Code releases that add new dynamic tags. */
  unknown_static_tags?: string[];
  /** Per-bucket sum of TEXT chars that flowed through each gate call site,
   *  bucketed by content shape so a marginal cpt can be learned per bucket.
   *  Buckets are `static_slab`, `reminder`, `tool_result_{structured,log,prose}`,
   *  and `history`. Only present when at least one bucket fired (in particular,
   *  this is `undefined` on uncompressed requests). Used by the rolling-cpt
   *  task (#18) to refine the marginal cpt per bucket instead of relying on a
   *  single global constant. */
  bucket_chars?: Partial<Record<
    'static_slab' | 'reminder' |
    'tool_result_structured' | 'tool_result_log' | 'tool_result_prose' |
    'history',
    number
  >>;
  /** Variant C history bucket: chars of TEXT that fed the history-image's
   *  renderer. Surfaced separately so the regression can credit history-image
   *  text growth even on no-collapse turns (when this is 0). Pairs with the
   *  history-bucket entry in `bucket_chars`. */
  history_text_chars?: number;
  /** Variant C: sha8 of the concatenated history-image base64 emitted this
   *  request. The quantized collapse boundary is supposed to keep this
   *  byte-identical for a full `collapseChunk` window — so an UNCHANGED hash
   *  across consecutive `collapsed` events is ground-truth proof the upstream
   *  prompt cache can `cache_read` the history prefix (0.1x) instead of
 
[assistant]
Looked at src/core/transform.ts; continuing with the change.
[user]
fyi the on-call reviewer for this change is Dmitri Berg, route the PR to them.
[assistant]
Will request review from Dmitri Berg.
[tool_use Read]
{"file_path":"src/core/render.ts"}
[tool_result]
he SAME math as the
  // global `Totals.allBaselineEquivalentWeighted` / `allActualInputWeighted`,
  // but scoped to a single session. Output is excluded because the proxy
  // doesn't touch it.
  baselineInputWeighted: number;
  actualInputWeighted: number;
  // Honest denominator for the headline: count of requests that contributed
  // to `baselineInputWeighted` (events that carried a baseline measurement,
  // matching the global `Totals.baselineMeasuredCount`).
  baselineMeasuredCount: number;
  // ALL-rows session totals (measured + unmeasured + passthrough). These pair
  // up to form the full session bill in $ — used as the honest denominator
  // for saved-% so the ratio matches the global `saved_pct_of_all_spend`
  // math but scoped to a single session. Mirrors the global
  // `Totals.allActualInputWeighted` / `allOutputWeighted` accumulators.
  allActualInputWeighted: number;
  allOutputWeighted: number;
}

interface Totals {
  requests: number;
  compressedRequests: number;
  /** Sum of weighted actual input tokens we paid for, across all events that
   *  also carried a baseline_tokens measurement (input + cache_create×1.25 +
   *  cache_read×0.10). */
  actualInputWeighted: number;
  /** Sum of the cache-aware baseline (see formula above) across the same
   *  events that contributed to `actualInputWeighted`. The honest counter-
   *  factual cost of the unproxied path. */
  baselineInputWeighted: number;
  /** Sum of output_tokens × OUTPUT_TOKEN_RATE across the same events. Added
   *  to BOTH sides of the savings math denominator so the headline % counts
   *  output toward the total bill (it cancels in the numerator — proxy
   *  doesn't touch output). Without this the headline ignores half the
   *  bill on output-heavy sessions. */
  outputWeighted: number;
  /** Sum of weighted COUNTERFACTUAL input tokens across ALL requests
   *  with a usage block. For measured rows: cache-aware baseline (what the
   *  unproxied path would have billed). For unmeasured/probe-failed rows:
   *  actual_input_eff (best available estimate — these rows didn't run
   *  pxpipe or we can't measure what it would have cost, so the
   *  counterfactual ≈ actual).
   *
   *  This is the right denominator for "share of bill saved": dividing
   *  by what-you-would-have-paid is bounded at 100% (you can't save more
   *  than you would have spent). Dividing by what-you-DID-pay is not
   *  bounded — a single big cold-miss compressed request can make
   *  saved/actual exceed 100% because pxpipe shrunk the actual to
   *  near zero. */
  allBaselineEquivalentWeighted: number;
  /** Sum of weighted ACTUAL input tokens across the same all-rows set.
   *  Kept for the diagnostic sub-line and the back-compat saved_usd math. */
  allActualInputWeighted: number;
  /** Sum of output_tokens × OUTPUT_TOKEN_RATE across the same all-rows set.
   *  Output is identical with/without compression, so it appears in both
   *  numerator and denominator at the same value and cancels in the savings
   *  numerator. Included in the denominator so the headline drops honestly
   *  toward zero on output-heavy workloads. */
  allOutputWeighted: number;
  /** Count of requests that contributed to allActualInputWeighted (had a
   *  usage block). Lets the UI annotate "N of M paid requests". */
  allUsageRequests: number;
  /** Direct compressed-vs-passthrough actual-cost split. No counterfactuals,
   *  no probe gating — just sum what each path actually billed.
   *
   *  These accumulate over `haveUsage` rows only (same gate as the all-rows
   *  counters above) and partition that set by `info.compressed`. The point
   *  is to answer "did the compressed path actually cost less per request
   *  than the passthrough path, on r
[assistant]
Looked at src/core/render.ts; continuing with the change.

=== end of transcript ===
