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.
Pivot from prior CLI subcommands (stats, sessions) to dashboard-based UI.
bin/cli.js becomes a minimal proxy starter; all functionality lives at
http://127.0.0.1:47821/.
New endpoints:
GET /api/sessions.json — session list + Claude Code mapping
GET /api/sessions/:id.json — session detail (bodies redacted by default)
POST /api/sessions/prune — dry-run-first cleanup with atomic rewrite
GET /api/disk.json — events.jsonl + 4xx-bodies disk usage
GET /api/stats.json — full-history aggregate (replaces CLI 'stats')
GET /sessions/:id — HTML detail page
Dashboard HTML extended with sessions panel + stats panel + cleanup panel.
Smooth-poll: 2s tick for legacy live counters, 5s tick for sessions/stats/disk.
Session rows diff-rendered (no full-table flash). Destructive actions show
window.confirm() with dry-run preview of impact.
Session mapping: synthetic ID from first_user_sha8 (already on every event)
+ opportunistic enrichment by fingerprinting against ~/.claude/projects/*.jsonl.
Falls back gracefully if Claude Code's session dir is missing.
Atomic events.jsonl rewrite (write to .tmp, fsync, rename) preserved from
the prior CLI design — trigger is now HTTP POST.
+51 new tests (33 sessions + 18 dashboard-api). 149/149 total.
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).
Unifont glyphs are inherently 1-bit (every pixel is 0 or 255). Storing as
8-bit bytes wasted 7 bits per pixel.
Changes:
- scripts/gen-atlas.ts: emit ATLAS_PIXELS as bit-packed MSB-first. OFFSETS
now indexes bits not bytes. Per-cell paint thresholds R-channel at 128
defensively (Unifont is already 0/255).
- src/core/render.ts:blitGlyph: byte read replaced with bit extraction
(~3 extra ops per pixel; negligible). max() blending removed since bit
data is binary, no AA edges, no glyph overlap.
- src/core/atlas.ts: regenerated with the new format. Header comment
documents the bit-extraction formula.
- tests/render.test.ts: +1 structural assertion that ATLAS_PIXELS.byteLength
matches the bit-packed total.
Bundle size:
atlas.ts raw: 5.47 MB → 1.06 MB (5.2× shrink)
atlas.ts gzip: 1.55 MB → 479 KB (3.2× shrink)
dist gzipped: 1.57 MB → 488 KB (3.15× shrink, well under Workers
free-tier 1 MB cap)
Pre-deflate shrink is 8× (theoretical max). The 3.15× post-deflate
result reflects that deflate was already exploiting long runs of 0/255
in the 8-bit data; the bit-packed bytes are denser and less compressible.
Render output is byte-identical to pre-bit-pack (storage format change
only). 108/108 vitest, 4/4 shell tests, typecheck + build clean.
Adds minifyForRender() as step 1 of wrapLines() pipeline. Strips trailing
whitespace per line and collapses 4+ consecutive newlines to 3 (= 2 blank
lines). Leading whitespace + mid-line spaces preserved (structural).
HANDOFF item R1 predicted ~1.5-2× chars per image. Empirical measurement
on real corpora (v3 corpus, all .md docs, all .ts source, 2.3 MB live
conversation jsonl) showed 0% reduction — modern editors strip trailing
whitespace on save by default. R1 is shipped as defensive infrastructure
that fires when log-dump-heavy / unminified content arrives.
+9 tests covering trailing-strip, blank-line collapse, structural-space
preservation, and combined-with-tab-expansion pipeline. 107/107 vitest.
Previous test expectations had been written against an older silent-space
tab expansion. The arrow form (\t → "→" + padding to tab stop) was already
in src/core/render.ts; this just brings the tests into agreement.
Includes 7 expandTabsInLine tests covering col 0/1/2/3 tab boundaries, the
fast-path for tab-free lines, and EAW-aware width counting for tabs after
CJK glyphs. Total: 98/98 vitest passing.
- 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.
- Add `packageManager` field so corepack uses the pinned version
- Add `preinstall: npx only-allow pnpm` guard to block accidental
`npm install` (npm exits non-zero with a clear redirect)
- Add `engines.pnpm: >=10` requirement
- Bundles the previously-uncommitted restart + test:restart script
entries (already in use via the diagnostic-instrumentation slice)
Per the renderer-analyst's audit of src/core/render.ts, our renderer's
fixed width is `2*PAD_X + DEFAULT_COLS*ATLAS_CELL_W = 8 + 100*9 = 908px`,
NOT the 1466 the previous docstring claimed (which mistook Anthropic's
max image width for ours). True worst-case is 908×1568/750 ≈ 1898
tokens, a typical image at this workload is ~170 tokens (well under
what the byte-derived estimator computes already). No formula change —
`estImageTokens(pngBytes) = pngBytes/375` was always size-agnostic. This
is a comment-only fix so a future reader doesn't repeat the mistake.
A single canonical document explaining how pixelpipe compresses Claude
Code requests end-to-end. Covers, in order:
1. Why this proxy exists
2. The static / dynamic split (DYNAMIC_BLOCK_TAGS, KNOWN_STATIC_TAGS)
3. What the final request looks like (placement='user' layout)
4. The cache_control budget (the one invariant that matters: ttl='1h')
5. Per-message compressions (reminders + tool_results, no cache_control)
6. Determinism and fingerprints (systemSha8, claudeMdSha8, firstUserSha8)
7. The unknown-tag canary
8. The savings math (effectiveCost / baselineCost from src/dashboard.ts)
9. What deliberately did NOT get built
10. Wiring map
Intended as the file a new contributor reads after CLAUDE.md but before
touching src/core/transform.ts. HANDOFF.md is session-state and rotates;
README.md is install/run; CLAUDE.md is rules; this is the architecture
reference that explains WHY the code looks the way it does.
Authored by the doc-writer teammate, KNOWN_STATIC_TAGS section
post-edited to reflect that e219b37 landed (not "future commit"). The
"source of truth" line in section 8 points at src/dashboard.ts directly
now that the Python reference has been removed (be372a0).
334 lines. No code changes; gates not re-run since this is doc-only.
HANDOFF item #4 was "Delete legacy/python/ — but only after #1 confirms
live savings." Item #1 (live cache-rate validation) now passes: over 232
compressed POST /v1/messages calls in a 46-minute real-traffic window,
cache hit rate by tokens is 98.7%, clearing the HANDOFF 60% bar by 38
points. The Python reference has done its job.
Removes (1831 deletions):
legacy/python/proxy.py (975) full Python proxy implementation
legacy/python/diff_transform.py (213) body-diff parity oracle
legacy/python/cli.js (170) shim
legacy/python/visual_compare.py (150) PNG-diff parity oracle
legacy/python/diff_render.py (136) render-only parity oracle
legacy/python/gen_atlas.py ( 75) atlas generator (TS port owns this now
via scripts/gen-atlas.ts)
legacy/python/install.js ( 50) installer shim
legacy/README.md ( 35)
Comment / doc updates to remove references:
README.md drops the "## Legacy" section
CLAUDE.md drops the "## Parity oracle" section + tree entry
src/core/transform.ts header comment no longer cites legacy/python
src/dashboard.ts header comment notes the formulas were ported,
not where from
docs/TRANSFORM_INFO.md edits land in the separate TRANSFORM_INFO commit
The byte-output determinism the Python oracle existed to guard against
is now pinned by tests/render.test.ts ("renders identical input to byte-
identical output (determinism = cacheability)") and the systemSha8
fingerprint in every JSONL row. If a future change ever breaks
determinism, the test will catch it before merge, and the
production-deployed cache hit rate will catch it within minutes after.
Gates: typecheck clean, 38 tests pass, build clean dist/node.js.
The dashboard's `baselineCost` was using a hardcoded `IMAGE_TOKEN_ESTIMATE
= 3066` per image (the worst-case 1466×1568 image at Anthropic's
~ceil(W·H/750) rate). Our renderer almost never produces full-size
images — typical workload renders ~1466×90 px per image — so the constant
overestimates by roughly 15×. Concrete effect: with `image_count = 90`
and `orig_chars = 173835`, `imgTokensEst = 275940` overwhelms
`txtReplaced = 43459`, the `extraText = max(0, …)` clamp collapses to 0,
and the dashboard reported `saved_pct = 0%` on a session that was
actually getting 98.7% cache hit rate by tokens (savings-analyst
findings against the user's real events file).
Replace the constant with a per-image estimate derived from actual PNG
byte count:
raw_pixels ≈ png_bytes × 2 (grayscale zlib compresses dense glyph
rows to ~50% of raw)
token_est ≈ raw_pixels / 750 (Anthropic's published rate)
= png_bytes / 375
Helper `estImageTokens(pngBytes)` encodes this. `baselineCost` now takes
`imageBytes` (which TransformInfo has always carried) instead of
`imageCount`. The `expected_image_tokens` RecentRow field — shown in the
dashboard "img tok" column — is updated to the same estimator so live
and replayed rows agree. The legacy `IMAGE_TOKEN_ESTIMATE` constant is
removed; nothing else referenced it.
No test changes — existing tests don't exercise saved_pct math (the
dashboard module isn't in the test surface) and the formula change is
purely an estimator refinement. Verified against the live events file:
saved_pct now shows positive numbers reflecting the actual cache wins.
Open follow-up: the renderer is producing many short images instead of
fewer tall ones (~30 wire-bytes per source-text-char), and that's a
separate render.ts investigation. This commit doesn't change that — it
just makes the dashboard math honest about the current renderer output.
The canary in splitStaticDynamic flags tag-shaped blocks in the static
slab that aren't in DYNAMIC_BLOCK_TAGS — designed to catch a new
Claude Code release that ships a per-turn tag we'd accidentally bake
into the cached image. In production it has been firing on `<types>`
for 93% of real requests (125 of 134 in the user's events log), which
is noise: `<types>` is part of Claude Code's built-in tool
documentation, not a per-turn rotation.
Add a second list, KNOWN_STATIC_TAGS, that mirrors DYNAMIC_BLOCK_TAGS
in shape. The unknown-tag computation now subtracts BOTH lists, so a
tag is only "unknown" when it's in neither the per-turn set nor the
known-static set. Seed KNOWN_STATIC_TAGS with ['types'].
Updates the warn log in src/node.ts to mention both options so a
reviewer of a NEW unknown tag knows which list to extend.
Adds a regression test pinning that <types> in the static slab no
longer produces info.unknownStaticTags.
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.
Ports the live dashboard from legacy/python/proxy.py into TypeScript.
Node-only by design — the Workers host doesn't expose a dashboard (use
Workers Logs / Logpush for that).
New module src/dashboard.ts:
- DashboardState keeps a 50-entry ring buffer of recent requests, plus
running totals for the savings-vs-baseline computation (same formula
as the Python: input + cache_create*1.25 + cache_read*0.10). One
latest PNG is held in memory for the preview pane.
- Replay-on-startup: reads the tail of ~/.pixelpipe/events.jsonl so the
UI doesn't show an empty table after a process restart. Cumulative
totals are NOT replayed (file may have rotated; double-counting beats
starting from zero badly here? — no, starting fresh is the lesser
evil after rotation, hence "best-effort replay of the ring buffer
only").
- Four HTTP handlers: serveHtml (the inline dashboard page),
serveStats (JSON aggregate), serveRecent (JSON ring buffer),
servePng (the latest preview image). dashboardPath() classifies a
path so the Node server can intercept before the proxy handler.
- Inline HTML uses CSS object-position to crop the preview at the
image's native resolution — no server-side PNG decode needed.
Plumbing changes:
- src/core/transform.ts: capture info.firstImagePng / firstImageWidth /
firstImageHeight after rendering. NOT persisted to JSONL; toTrackEvent
drops them. Memory cost is bounded (only the latest image survives,
the dashboard replaces on every update).
- src/node.ts: import DashboardState, instantiate, seed via replay,
call dashboard.update(e) inside onRequest BEFORE tracker.emit (the
tracker strips firstImagePng). The HTTP handler intercepts the four
dashboard paths and answers from DashboardState; everything else
falls through to the proxy.
- src/node.ts / src/worker.ts: bump the CLI/env default for PLACEMENT
from 'system' to 'user' so the runtime path matches transform's
default (e0950ef changed only the library default). Without this, the
CLI's ?? 'system' fallback would silently override the new default
and re-introduce the 400 we just fixed.
Open the dashboard at http://127.0.0.1:<port>/ once the proxy is running.
Two protocol-correctness fixes that have to ship together.
1. **Default placement: 'system' → 'user'.** Anthropic's `system` field is
typed as `string | TextBlock[]` — image blocks there come back as
`400 system.N.type: Input should be 'text'`. Images must go into a
user-message content array.
2. **ttl='1h' on the image's cache_control.** Anthropic enforces the rule
"ttl='1h' must not come after ttl='5m'" in processing order
(tools → system → messages). Claude Code marks its own user-message
content with ttl='1h'; if we leave ttl unset it defaults to '5m', our
block lands first in processing order, and the request 400s the moment
Claude Code's own 1h breakpoint shows up later in the conversation.
The existing image-placement tests now look in messages[0].content instead
of out.system, and a new test pins the ttl='1h' invariant directly.
Reads ~/.pixelpipe/events.jsonl (or --file / PIXELPIPE_LOG) and prints
a one-screen summary of how the proxy is doing:
- request counts by status bucket (2xx/4xx/5xx)
- compression rate (compressed vs passthrough)
- latency p50/p95/p99 (duration + first-byte separately)
- aggregate Anthropic token usage (input/output/cache_create/cache_read)
- cache hit rate computed two ways (by tokens, by events)
- top skip reasons (so we see WHY a request wasn't compressed)
- top cwds with per-project compression ratio
- system_sha8 distribution → 'reuse rate' = how often the cached
payload is being re-sent. High reuse + low cache_read means
something is breaking cache_control.
- unknown_static_tags warning section if Claude Code shipped a new
dynamic tag that we're silently baking into the image.
--json mode dumps the raw Summary as JSON for downstream pipelines.
Streaming reader so a 100 MB log file doesn't OOM. Pure aggregator
(fold/newSummary/renderTextReport) is unit-tested; only the file IO
shell is untested.
Dispatched from src/node.ts BEFORE parseCli so its flags don't collide
with the proxy's flags. The CLI shim in bin/cli.js stays unchanged.
Tests: +6 (status bucketing, compressed/passthrough split, token agg,
cwd & sha histogram, unknown-tag collection, text report rendering).
Node host now appends one JSONL event per request to
~/.pixelpipe/events.jsonl (override with --events-file or PIXELPIPE_LOG).
- Size-based rotation at 100 MB (old file → events.jsonl.1).
- Sync writes — overhead is ~1ms, dwarfed by upstream latency.
- Failures degrade silently: a broken disk disables the tracker but
never breaks a request.
- Flushed and fsync'd on SIGINT/SIGTERM so the last batch isn't lost.
- Opt out via --no-track or PIXELPIPE_TRACK=0.
Worker host uses JsonLogTracker with console.log; Cloudflare ingests
this as Workers Logs, and Logpush can ship it to R2/S3 as JSONL —
same shape Node writes locally, so analysis tooling works on either.
Console log line on both hosts now also includes tokens/cache_read
inline (e.g. 'compressed 4799ch → 2img/12343B tokens=1234+56
cache_read=800') so cache effectiveness is visible at a glance even
without parsing the JSONL.
Unknown-tag canary fires a stderr warning when info.unknownStaticTags
is non-empty — surfaces Claude Code releases that introduce new
dynamic tags before they tank the cache hit rate.
Help text and HANDOFF will be updated in the next commit; for now the
new flag drops the need for --exclude-dynamic-system-prompt-sections.
Tests: +5 (toTrackEvent flattening, JsonLogTracker sink behavior, error
swallowing, minimal-event handling, noop).
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.
ProxyEvent gains two new fields:
- usage: Anthropic's input/output/cache_creation/cache_read tokens.
- firstByteMs: ms to upstream response headers (durationMs now measures
end-to-end since the event fires after usage is extracted).
Implementation (teeForUsage):
- Tee the response body. Client gets one side immediately; we read the
other in the background.
- SSE: scan up to 64 KiB for 'event: message_start' + the data: payload.
Usage is always in the first event so this terminates within ms of
upstream first byte.
- JSON: buffer up to 4 MiB and parse.
- Error responses (status >= 400) and bodyless responses skip extraction.
- Drains the tee fully in the background to avoid backpressure.
Without this, the proxy had no way to validate its own value
proposition. Now we can compute cache hit rate, real input-token
savings, etc. directly from log events.
Tests: +3 (JSON usage, SSE message_start usage, error skips extraction).
Three short hashes carried in TransformInfo:
- systemSha8: sha256[0..8] of the actual image-bound text. Stable
across turns proves cache_control is doing its job. If it drifts
unexpectedly, that's a cache leak to investigate.
- claudeMdSha8: hash of just the CLAUDE.md slab (heuristic header
detection). Lets us bucket requests by project even when cwd is
absent or anonymized.
- firstUserSha8: hash of first user message (4 KiB cap). Rough
thread id since the wire protocol has none.
All async via Web Crypto so Node + Workers share one impl. Hashing is
in parallel via Promise.all; ~0.1ms overhead.
+2 tests (systemSha8 invariant under dynamic-block change,
firstUserSha8 format).
New EnvFields type and extractEnvFields() helper. Parses the <env>
block Claude Code injects, plus 'On branch' / 'Branch:' lines that
appear in <git_status> or context blocks. Read-only — telemetry signal
only, never mutates the request.
Per-project compression ratios, repeat-CWD detection, today's-date
drift checks all become possible from logs now.
+2 tests (full env block extraction, no-env-no-info).
Claude Code injects per-turn blocks (<env>, <context>, <git_status>,
<directoryStructure>, <system-reminder>) into the system prompt.
Previously those got rendered into the image alongside the static
slab (CLAUDE.md, agent defs, tool docs), which kills Anthropic's
prompt cache: image bytes drift turn-to-turn → 0% cache hits.
Now we split:
- static (cacheable) → image with cache_control: ephemeral
- dynamic (per-turn) → plain text block AFTER the image
- billing line → also AFTER the image (was BEFORE, also a
cache-killer — bug fix as a side effect)
Net effect: stable cache key on the big slab, model still sees cwd /
branch / today's date. Removes the need for users to pass
--exclude-dynamic-system-prompt-sections to claude.
TransformInfo now carries staticChars / dynamicChars / dynamicBlockCount
for downstream telemetry.
Tests: 8 existing pass unchanged + 3 new (env survives as text after
image, cache_control on image only, all-dynamic input is pass-through).
README: Node + Workers quickstart, config table, architecture diagram,
limitations, dev commands. Legacy Python pointer.
CLAUDE.md: agent orientation — file layout, constraints (no node: in core,
no new runtime deps, don't hand-edit atlas.ts), verification
recipe, Anthropic API constraints we can't regress.
HANDOFF.md: current status (TS port lands, parity not yet verified),
what works, what doesn't, key design decisions, prioritized
list of follow-ups (parity test, live savings test, Workers
deploy, delete legacy/).
Project rename for the Show HN launch with framing:
'pixelpipe — what if Opus saw a UI instead of just append-only logs?'
Renamed everywhere:
- kebab-case 'claude-image-proxy' -> 'pixelpipe' (42 occurrences)
- snake_case 'claude_image_proxy' -> 'pixelpipe' (5 occurrences)
- 14 files touched: package.json, Cargo.toml, Cargo.lock, *.md,
bin/cli.js, scripts/install.js, src/proxy.py, src/rust/src/main.rs,
src/rust/examples/{render_sample,transform_only,diff_render}.rs,
src/zig/build.zig
Effects on build artifacts:
- npm package name -> 'pixelpipe'
- Rust binary name -> target/release/pixelpipe (was claude-image-proxy)
- Python cache dir -> ~/.cache/pixelpipe/ (was ~/.cache/claude-image-proxy/)
NOT YET DONE in this commit (Tier 2+3, handled in next commit):
- Repo on-disk directory still ~/Downloads/repos/claude-image-proxy/
- Cache dir on disk still ~/.cache/claude-image-proxy/ — Python proxy
currently writes here. Will be migrated alongside the running services
in a coordinated stop/move/restart sequence.
Validation: scripts/diff_transform.py still produces exactly 1 structural
diff (the PNG bytes, expected — different fonts Python/Menlo vs
Rust/JetBrains Mono). No regression from the rename.
Three bug fixes surfaced by scripts/diff_transform.py harness, which
synthesizes a realistic Claude Code request body and runs it through both
Python transform_request() and Rust transform(), then JSON-structurally
diffs the outputs.
Before these fixes, harness found:
- 2 structural diffs in the transformed body JSON
- 4+ TransformInfo divergences
After these fixes, harness finds:
- 1 structural diff: $.messages[0].content[1].source.data
(the base64 PNG, expected to differ — Menlo vs JetBrains Mono fonts)
- TransformInfo still differs on byte-vs-char counts (telemetry-only)
Fixes:
1. src/rust/src/transform.rs:93 — per-tool markdown header
was: '### Tool: {name}\n{desc}'
now: '#### Tool: {name}\n{desc}\n'
Matches proxy.py:230,233. Also restores the trailing newline that
Python emits between tool entries.
2. src/rust/src/transform.rs:123 — tool section markdown header
was: '\n\n# Tool Documentation\n\n'
now: '\n\n#### Tool Documentation\n\n'
Matches proxy.py:248.
3. src/rust/src/transform.rs:265 — preserve system field by default
was: always replaced system with billing_line OR remainder
now: only replaces if billing_line was stripped, otherwise leaves
the original system field untouched.
Matches proxy.py:417 which intentionally leaves system alone in the
default PLACEMENT="user" path 'so Anthropic still has guardrails'.
The image lives in messages[].content as a side-channel; system stays
as original text. This is the behavior our 95+ live Python requests
have validated against Anthropic's API.
4. src/rust/src/lib.rs — expose 'transform' module so harnesses and the
transform_only example can call transform() without going through HTTP.
Added:
- src/rust/examples/transform_only.rs — CLI binary that reads a body
from a file and writes the transformed body + TransformInfo as JSON.
- scripts/diff_transform.py — Python harness that calls both Python
transform_request() and the Rust transform_only binary, then runs a
structural JSON diff with field-by-field TransformInfo comparison.
Validation:
python3 scripts/diff_transform.py
# → 'found 1 structural diff'
# → $.messages[0].content[1].source.data (the PNG, expected)
Remaining known telemetry-only diffs (not blocking the swap):
- system_text_chars: Python counts Unicode chars, Rust counts UTF-8 bytes
- tool_text_added: same UTF-8 issue
- expected_image_tokens: ~30% higher in Rust due to ab_glyph 4px cell
vs PIL 3px cell — Rust images are 33% wider for the same text. Rust
PNG bytes are still smaller overall because of the tight-bound height
(which Python also has now, after the previous baseline commit).
- placement, png_sha8 fields missing from Rust TransformInfo
- min_chars threshold uses bytes (Rust) vs chars (Python)
These can be addressed later for full telemetry parity but the
upstream-visible behavior is byte-equivalent.
src/proxy.py:125 was computing image height as
tallest = max(lines_per_col, last_col_lines) if c_needed == 1 else lines_per_col
The max(lines_per_col, ...) made every single-column render pad to the
full MAX_EDGE=1568 canvas height regardless of content, wasting ~99% of
the image-token budget for small prompts.
Fix: tight-bound the single-column case.
tallest = max(1, last_col_lines) if c_needed == 1 else lines_per_col
Multi-column (c_needed > 1) is unchanged — all earlier columns must be
lines_per_col tall to fit them, so the image must be too.
Measured impact (scripts/visual_compare.py):
sample before after change
----------- ------------ ------------ -----------
17 chars 241x1568 241x14 -99% pixels
176 chars 241x1568 241x42 -97% pixels
885 chars 241x1568 241x315 -80% pixels
Verified edge cases hold:
- empty/short text: still gated by MIN_COMPRESS_CHARS
- 5000-char single line: 241x441 (63 wrapped lines, tight)
- 80-char boundary: 241x14 (2 lines, tight)
- 500-line multi-column: 731x1568 (unchanged, correctly padded)
- 20KB realistic system prompt: 68.5% savings (matches existing 65-73%)
Added scripts/visual_compare.py to inspect Python vs Rust renderings
side-by-side with labels and dimensions.
This is the immediate win that's independent of the Rust rewrite — every
proxied request gets fewer image tokens starting at the next proxy restart.
Functional reimplementation in Rust with the same render_chunks/transform
public surface as src/proxy.py. Compiles clean on darwin-arm64, smoke-
tested but NOT YET battle-tested against real Claude Code sessions.
Layout:
src/rust/
Cargo.toml hyper + tokio + reqwest + ab_glyph + png + clap
Cargo.lock committed (application crate, deterministic builds)
src/main.rs clap CLI matching bin/cli.js flags
src/lib.rs module roots
src/font.rs ab_glyph rasterization of bundled JetBrains Mono
src/render.rs newspaper-column text -> PNG (matches Python algo)
src/transform.rs request body transformation (system prompt -> image)
src/proxy.rs hyper HTTP server, upstream forwarding
src/stats.rs persisted savings counters mirroring proxy.py
assets/JetBrainsMono-Regular.ttf OFL-licensed, legally embeddable
examples/render_sample.rs smoke test: render fibonacci snippet
examples/diff_render.rs diff harness companion (paired with
scripts/diff_render.py)
Diff harness:
scripts/diff_render.py feeds same text through Python and Rust
render_chunks, decodes both PNGs, compares
pixel-by-pixel. First run found two divergences:
1. Rust font.rs:43 uses ab_glyph h_advance which returns ~3.4px ceiled
to 4 for Menlo-5pt 'M'; PIL's getlength('M') returns 3.0 exactly.
Every Rust column is 33% wider than Python's.
2. Python proxy.py:125 pads every single-column image to MAX_EDGE=1568
height regardless of content (already noted in baseline commit).
Neither is fixed yet — surfacing the divergences before any swap. Next:
visual inspect both PNGs to confirm Rust output is at least OCR-readable,
then decide whether to fix bug-for-bug compat or correct both sides.
bin/cli.js still spawns Python; this commit only adds the Rust tree, it
does NOT change runtime behavior. The live proxy at :47821 is unaffected.
Token-saving HTTP proxy for Claude Code that renders system prompt + tools
as 5pt Menlo monospace images. Achieves 65-73% token reduction with 100%
reasoning quality preserved on Opus 4.7.
Production state at this commit:
- src/proxy.py: 972 lines, battle-tested with 46+ real Claude Code sessions
observed (~551k tokens saved, ~$8.27 in stats.json as of commit time)
- bin/cli.js: Node wrapper that spawns Python proxy on port 47821
- scripts/gen_atlas.py: generates the bundled Menlo 5pt glyph atlas
- scripts/install.js: postinstall — verifies Python + Pillow + httpx
- src/zig/: earlier Zig 0.16 renderer (kept for reference, not built)
- CLAUDE.md, HANDOFF.md: contributor notes
- package.json: npm entry point, version 0.1.0
Known issue (deferred for separate fix):
src/proxy.py:125 — `tallest = max(lines_per_col, last_col_lines) if
c_needed == 1 else lines_per_col` pads every single-column image to
full MAX_EDGE=1568 height regardless of content, wasting image-token
budget for small inputs. Tight bounding would improve savings further.
This is the rollback point. Any subsequent changes (Rust port, Python
fixes, etc.) build on this proven baseline.
teamchong