The dashboard headline was showing 0% saved because the math was
apples-to-oranges:
- orig_chars = static slab + tool docs ONLY (~135 KB)
- image_count = ALL images including reminders + tool_results (~33)
- txtReplaced = 135k/4 = 33.7k tokens
- imgTokensEst = 33 × 2500 = 82.5k tokens
- extraText = max(0, 33.7k - 82.5k) = 0 ← clamped negative
- baseline == paid → 'saved 0%' headline despite real savings happening
Two fixes:
1. Track 'compressedChars' separately from 'origChars'. It accumulates
only when a block actually image-renders (passes the break-even gate
AND any per-block min thresholds). Includes the static slab + all
compressed reminders + all compressed tool_results.
2. Remove the Math.max(0,...) clamp in baselineCost(). Negative savings
surface honestly — they're the signal that small-block compressions
are cost-bleeding, which the break-even gate is supposed to prevent.
Wires:
- TransformInfo.compressedChars (new field, mandatory).
- All 4 image-render success paths accumulate (static slab + reminder
+ tool_result string branch + tool_result array branch).
- TrackEvent.compressed_chars (new optional field, emitted when > 0).
- dashboard.baselineCost() takes compressedChars now; clamp removed.
- sessions.aggregateSessions() also uses compressed_chars + honest math.
229/229 tests passing. Bundle stays at 496 KB gzipped.
Post-restart, the dashboard 'tokens saved' will show real numbers
including negatives. Empirically expect ~1-5% net positive in
steady-state cache-hit traffic.
Two related improvements:
1. Per-tool_result paging / truncation. When a single tool_result would
render to more than maxImagesPerToolResult images (default 10), the
source text is truncated head+marker+tail BEFORE rendering. Classifier
picks the truncation strategy:
- structured (JSON/YAML/diff): head-only, tail is repeating elements
- log (timestamps / [LEVEL] prefixes): 60% head + 40% tail
- other (prose, dumps): same head/tail split
The marker tells the model what was elided so it can reason about the
gap: '[ pixelpipe paging: omitted N lines (K chars) ... ]'. Keeps
requests under Anthropic's 100-image-per-request cap even when a single
tool dumps a multi-megabyte log.
2. Adaptive CHARS_PER_IMAGE. Previously hardcoded at 14_100 (Unifont 10px
@ cell 5×11). Now derived at module load from ATLAS_CELL_H + render.ts
constants. When gen-atlas regenerates with a different font/size, the
break-even threshold automatically updates: at Cozette 4×7 the chars/
image jumps from 14.1k → 22.2k and the break-even drops from ~10k → ~3k.
Single source of truth in src/core/.
Wires:
- TransformOptions.maxImagesPerToolResult (default 10)
- TransformInfo.truncatedToolResults + omittedChars
- TrackEvent.truncated_tool_results + omitted_chars (emit when > 0)
- Two new exported helpers: estimateImageCount, classifyContent, truncateForBudget
- Paging fires before image-encoding at both tool_result branches
(string content and array-of-text-blocks content)
Tests: +28 paging-specific (paging.test.ts), 199/199 total green.
Bundle delta: negligible (~3 KB raw, ~1 KB gzipped). 488 KB dist gzipped.
Closes the paging-implementer worktree merge that was deferred earlier.
URGENT production-cost fix. Empirical data (orig_chars=169779, image_count=88)
showed we were paying ~220k image tokens to replace ~42k text tokens — a
net LOSS of ~178k tokens per request. Dashboard hid this via Math.max(0,...).
Two changes ship together:
1. isCompressionProfitable(textLen) gate in transform.ts. Before any
per-block image encode (static slab, reminder, tool_result), compute:
estImages × TOKENS_PER_IMAGE vs textLen / CHARS_PER_TOKEN
Compress only when the image side wins. Constants:
CHARS_PER_IMAGE = 14100 (Unifont 10px, cell 5×11, 100 cols)
CHARS_PER_TOKEN = 4
TOKENS_PER_IMAGE = 2500 (empirical, history-researcher round 3)
Result: blocks under ~10k chars stay as text. Static slab still
compresses (always above break-even).
2. Coarse thresholds bumped as fast-path:
minReminderChars 1000 → 5000
minToolResultChars 5000 → 10000
(Cover the obvious-no cases without invoking the precise check.)
3. Dashboard honesty: removed Math.max(0,...) clamp in baselineCost().
Negative savings now display as negative (no more hidden cost-bleed).
4. Telemetry: passthrough_reasons.below_threshold + .not_profitable
counters surface how often each gate fires.
After restart, dashboard 'saved' should jump from clamped-0 to a real
positive number (~1-3% on aggregate; static slab compression is the
only block consistently profitable at our current cell).
- Switch font: JetBrains Mono @ 15px → Unifont 16.0.04 @ 10px. Sparse
atlas with double-width EAW dispatch for CJK. Full BMP profile
(35,501 glyphs) covers Latin/Cyrillic/Greek/Hebrew/Arabic/CJK/Hangul
plus Letterlike, Misc Technical, Block Elements, Geometric Shapes,
Misc Symbols, Dingbats, Enclosed Alphanumerics, all box-drawing.
- Fix cell-height bug (was hardcoded 9; now probed from font metrics
via Math.ceil(maxAscent+maxDescent)). Previously clipped the top
2 rows off every CJK glyph since the original Unifont ship.
- Expand tabs to spaces with 4-column tab stops, EAW-aware. Was the
silent-drop source for 99.6% of dropped chars in production.
- Add dropped_codepoints_top telemetry (top 20 per event, only emitted
when drops > 0) so future coverage gaps surface in events.jsonl.
- Raise minToolResultChars 2000→5000 and minReminderChars 1000→2000
to stop net-losing tokens on small compressions, per ~2,500 tok/img
empirical measurement (N=33 cold-miss events).
- Fix dashboard per-image-cost formula: was pngBytes/375 (~190 tok),
now imageCount * 2500 (the measured empirical rate). Reduces the
inflated "tokens saved" headline to honest numbers.
- Schema-stub fix in compressSchemas path: preserveSchemaShell()
retains type / properties / required / enum / oneOf / anyOf / $ref /
numeric constraints recursively (depth 20), strips only descriptions
and metadata. Prevents 400 errors on first-tool-call requests.
- Capture full gzipped 4xx body + per-event req_body_sha8 for upstream
error diagnosis. Sidecar to ~/.pixelpipe/4xx-bodies/ when over 32 KB
inline cap. Workers-safe via CompressionStream + Web Crypto.
- scripts/restart.sh: pnpm-aware one-command kill+rebuild+start with
graceful SIGTERM→SIGKILL escalation, build-failure abort, port-in-use
precheck, --no-build flag for fast iteration. Shell-tested.
- Bundle 1.58 MB gzipped on Node. 91/91 vitest + 4/4 shell tests.
Tool results (Bash output, Read file contents, etc.) accumulate as the
session grows. Once produced they're static — same bytes turn after turn
— but the model gets billed for them on every call until they fall out
of cache. Image-rendering them at the source compounds the savings
across the whole conversation.
Walks ALL user messages (not just the first — that's the reminder-
compression scope) and rewrites tool_result blocks whose content is at
or above minToolResultChars (default 2000, matching legacy/python/proxy.py):
- content: string → replace with image block(s) (whole content goes)
- content: array → walk inner blocks, replace each TextBlock ≥ threshold
with image blocks; leave ImageBlocks and short text
alone
- is_error: true → leave the whole block alone. Anthropic rejects
images inside is_error tool_results
(`tool_result with is_error=true cannot contain images`).
Like reminder compression these images carry NO cache_control — the
system+tools image is our only breakpoint. The savings are 65-73% of
input tokens per compressed block on Opus 4.7.
Wire-up:
- src/core/transform.ts: TransformOptions.compressToolResults (default
true) + minToolResultChars (default 2000). TransformInfo.toolResultImgs
counter. Reuses textToImageBlocks / approxBlockBytes from commit 3.
- src/core/tracker.ts: TrackEvent.tool_result_imgs flows from the
transform info.
- src/worker.ts: COMPRESS_TOOL_RESULTS + MIN_TOOL_RESULT_CHARS env vars.
- src/node.ts: CliOpts fields, parseCli cases (--no-tool-results,
--min-tool-result-chars), help text, env-var summary, `tr+N` in the
per-request console line when tool_result_imgs > 0, and tool_results=
in the startup config summary.
Tests:
- "compresses large tool_result text content across user messages"
confirms info.toolResultImgs ≥ 1, the tool_result block's content
becomes an array of image blocks, and those images carry no
cache_control.
- "leaves is_error tool_results untouched (Anthropic forbids images
there)" confirms info.toolResultImgs is 0 and the content stays a
plain string when is_error: true.
Claude Code re-injects the same long <system-reminder> blocks (CLAUDE.md
hints, task-tools reminders, the dynamic skills list, etc.) into the
FIRST user message on every turn. They're text, so they're not part of
the system+tools image we already cache — they hit the wire fresh every
turn. This rewrite renders any reminder block ≥ minReminderChars (1000
by default, matching legacy/python/proxy.py) to PNG images placed inside
the user message content array, just like the static slab.
Why: the system+tools image is the only cache_control breakpoint we're
allowed (Anthropic caps at 4 and Claude Code uses the others). Per-block
reminder images therefore carry NO cache_control — they're per-turn
content that the model OCRs without prefix-cache benefit. The win is
token cost, not cache: reminders are 65-73% cheaper as PNG than as text,
and a typical turn has 1-3 of them.
Layout inside the first user message after compression:
[intro text] ← static (helps OCR framing)
[image block(s)] ← static; LAST has cache_control
↑ cache breakpoint (the only one)
[End of rendered context.] ← static text closer for the image
[processed existing content] ← per-turn (incl. reminder images)
Wire-up:
- src/core/transform.ts: new TransformOptions.compressReminders (default
true) + minReminderChars (default 1000). Two new helpers,
textToImageBlocks() (wraps renderTextToPngs + makeImageBlock with
no cache_control) and approxBlockBytes() (b64 → byte-count for the
imageBytes telemetry, no second base64 round-trip). The placement
='user' branch now walks `existing` and rewrites long reminders.
- src/core/tracker.ts: TrackEvent.reminder_imgs flows from
TransformInfo.reminderImgs through toTrackEvent so `pixelpipe stats`
and the dashboard can attribute compression contributions.
- src/worker.ts: COMPRESS_REMINDERS + MIN_REMINDER_CHARS env vars.
- src/node.ts: matching CliOpts, parseCli cases (--no-reminders,
--min-reminder-chars), help text, env-var summary, and `rem+N` in
the per-request console line when reminder_imgs > 0.
Tests:
- "compresses long <system-reminder> blocks in the first user message"
confirms info.reminderImgs ≥ 1, the reminder text is gone from
user-content text blocks, the user's actual prompt survives, and the
new reminder image blocks carry NO cache_control.
- "leaves short <system-reminder> blocks alone (below minReminderChars)"
confirms info.reminderImgs is 0 and the reminder text passes through
as text.
Two cheap guardrails based on architectural review:
1. Determinism test: renders the same input twice and asserts byte
equality of the produced PNGs. Without this guarantee, identical
system prompts on consecutive turns would yield different image
bytes, silently destroying the cache hit rate that justifies the
whole proxy. The test currently passes — locking it in so a future
refactor can't regress it without noticing.
2. Unknown-tag canary: splitStaticDynamic now sniffs the *static* slab
for any <tag>...</tag>-shaped block whose name isn't in
DYNAMIC_BLOCK_TAGS. Surfaced via info.unknownStaticTags and emitted
on the tracker event as unknown_static_tags. If Claude Code ships a
new per-turn tag in a future release, it'll show up in logs within
hours instead of being silently baked into the cached image (where
it would tank cache hit rate with no error).
Also adds tracker.ts (Tracker interface, TrackEvent shape,
JsonLogTracker, noopTracker, toTrackEvent normalizer). Hosts will wire
these in the next commit.
teamchong