Cut Claude API costs by rendering context as images

pxpipe

Cut Claude Code's input tokens by rendering bulky context as images - the same system prompt, tool docs, and history, in a fraction of the tokens.

An image's token cost is fixed by its pixel dimensions, not by how much text
is inside it. Dense content (code, JSON, tool output) packs 3.1 chars per
image-token vs ~1 char per text-token on real Claude Code traffic. The
reader is the same vision channel that Anthropic's computer use already
relies on for screenshots. pxpipe is a local proxy that uses that channel
for context: it rewrites the bulky parts of each request into compact PNGs
before it leaves your machine. At current Fable
list prices that lands as a **59-70% lower end-to-end bill** - but prices
move and workloads differ, so the durable number is the token cut itself,
measured per-request against a free count_tokens counterfactual in
~/.pxpipe/events.jsonl.

This is what the model sees instead of text:

~48k chars of system prompt + tool docs: ≈25k tokens as text, ≈2.7k image
tokens as this page. Real pipeline output; the model reads renders like this
at 100/100 (see benchmarks).

*Eight years of context growth, in characters. Every text line tops out near
~4M chars (a 1M-token window at ~4 chars/token); Grok 4.5 is shown as a
text-window point only (500K). The orange overlays are the same 1M
windows read through pxpipe images - ~19.0M chars for Fable 5 (4.8×) and ~21.3M chars for Gemini 3.6 Flash (5.3× text capacity). Density is measured from a live render at
generation time, not hand-typed: regenerate with
npx tsx scripts/gen-context-chart.ts
(source).*

Demo

Fable 5 (the default, 100/100 reader) - plain left, pxpipe right:

https://github.com/user-attachments/assets/1c8ee63a-fcd7-4958-917b-da788d718349

pxpipe counts an exact token 10/10 across 39 imaged filler files
(matches grep line-for-line), gets the multi-step ledger arithmetic right,
and ends the session at $6.06 with context to spare (73.5k/1M) vs
$42.21 at 96% full. One caveat visible in the clip: the pxpipe arm
needed a nudge to match the requested one-line output format.

Try it (30 seconds)

npx pxpipe-proxy                                  # proxy on 127.0.0.1:47821
ANTHROPIC_BASE_URL=http://127.0.0.1:47821 claude  # point Claude Code at it

Dashboard at http://127.0.0.1:47821/: tokens saved, every text→image
conversion side by side, kill switch, live model chips. Responses stream
normally - pxpipe compresses the request only, never the model's output.
Recent turns stay text; the system prompt, tool docs, and older bulk history
are imaged.

pxpipe warp

pxpipe warp -- claude          # also: cursor-agent, codex, or a shell alias

Same thing without ANTHROPIC_BASE_URL, so /remote-control, claude.ai
connectors, and first-party gates keep working. Full instructions in the
dashboard.

Offline export (no proxy)

You can render text, files, or diffs to PNG pages without running the proxy or
connecting Claude Code:

npx pxpipe-proxy export src/
cat prompt.txt | npx pxpipe-proxy export --stdin
npx pxpipe-proxy export --git

If the package is installed, use pxpipe export instead of
npx pxpipe-proxy export.

Each run writes a fresh pxpipe-export-XXXXXX/ output folder (the exact path
is printed when the command finishes) containing page-*.png, factsheet.txt,
manifest.json, and prompt.txt. Upload the PNG pages and paste the prompt
into image-upload clients such as Cursor when you want dense visual context
without running the proxy.

The honest part

• It is lossy. Exact 12-char hex strings in dense imaged content:
  13/15 on Fable 5 and 0/15 on Sol - misses are silent
  confabulations, not errors. Byte-exact values (IDs, hashes, secrets)
  must stay text; recent turns do. The factsheet selectively preserves up to
  96 recognized precision-critical tokens, not every identifier. A dedicated
  verbatim-risk guard is not built yet.
• Escape hatch: subagents on non-allowlisted models pass through as
  text - route byte-exact work there
  (CLAUDE_CODE_SUBAGENT_MODEL=claude-sonnet-4-6, or model: sonnet in
  agent frontmatter).
• Real work: SWE-bench Lite pilot 10/10 both arms at −65% request
  size; SWE-bench Pro 14/19 ON vs 15/19 OFF at −60%, verdicts agree
  18/19, and the single split re-resolved 3/3 on replication - run-to-run
  variance, not compression. Small n; receipts in eval/.
• Workload-dependent. Wins on token-dense content (1 char/token),
  loses money on sparse prose (3.5 chars/token); a profitability gate
  (calibrated on N=391 production rows) images only where the math wins.
• Client-dependent. Savings track uncached bulk the client still
  re-sends as text. Claude Code re-sends system + tools + history on
  /anthropic/messages and typically lands ~60-70%. Details and measured
  splits: docs/CACHING_AND_SAVINGS.md.

Benchmark results and receipts

Model quality

This matrix shows coverage as well as scores. — means the model was not run
on that test; it does not mean zero. Arithmetic uses novel random-number
problems. Gist, state, and never-stated probes share one corpus. Never-stated
is confabulations, so lower is better.

Native-profile cost check

Offline export of the same deterministic 454,045-character dense record corpus
through each complete profile produced:

The text estimate uses 3.7 characters/token; image tokens use each model's
provider formula and actual rendered page dimensions. These figures establish
profile cost on this corpus, not a universal workload savings rate. Sol's paid
fixtures estimated 42% while reading 7/8 exact with no unsupported inventions.

The runs use different transports and profile generations, not one identical
image geometry. Fable and Opus use Claude; Gemini uses Google AI Studio; Sol
and Grok use Codex Responses; Kimi K3 uses Cloudflare's OpenAI-compatible
transport. Current production profiles include the adjacent bounded factsheet;
historical or pure-image exceptions are identified in the linked evaluation.

Model-specific evaluations

These are not cross-model comparisons. Every unlisted model is not run.

The SWE-bench runner is Claude Code/Fable-specific; no other model has an ON/OFF
run. Gemini's positional-retrieval sweep is directional evidence, not a general
Lost-in-the-Middle result.

Capacity / density (how many chars per vision-token?)

Measured by rendering this repo’s dense fixture through the real pipeline and
pricing pixels at each family’s vision rate. Multiplier = measured
chars/vision-token ÷ 4 (prose text baseline). Not a model-quality score.

Regenerate: npx tsx scripts/gen-context-chart.ts · chart PNG
docs/assets/context-window-chars.png.

The older GSM8K result is omitted because its training-data contamination can
hide image misreads; the linked arithmetic evaluations use novel numbers.

How it works

model id ──► render profile ──► wrap/reflow bulk context ──► PNG[] + bounded factsheet

The proxy handles Anthropic Messages, OpenAI Responses and Chat Completions,
and Google generateContent requests. It rewrites eligible bulk into image
blocks and forwards the provider-native request, or bridges Anthropic Messages
to a configured OpenAI-compatible provider. On Anthropic, the static prefix and
prompt-cache boundary are preserved. Model-specific profiles control geometry,
factsheets, history retention, and profitability, so sparse prose stays text.
Events log to ~/.pxpipe/events.jsonl.

Library use (no proxy)

import { renderTextToImages, transformAnthropicMessages } from "pxpipe-proxy";

const { pages } = await renderTextToImages(toolResultText);     // pages[i].png: Uint8Array
const { body, applied, info } = await transformAnthropicMessages({
  body: requestBytes,
  model: "claude-fable-5",
});

options.keepSharp(block) pins blocks as text; options.emitRecoverable
returns the originals of imaged blocks. Pure-JS runtime (Node and
edge/Workers); @napi-rs/canvas is build-time only. Full API:
src/core/index.ts.

Development

pnpm install && pnpm test
pnpm run build                # regenerates dist/

Windows is community-supported: primary development targets macOS/Linux, and Windows-specific fixes rely on contributor PRs (thanks @makoribrian).

FAQ

Additional limitations

• PNG encoding adds latency to large requests before they leave.
• ASCII/Latin-1 well tested; CJK works but conservatively.

Research status

Current as of 2026-07-22. The broad conclusion from the 2026-07-05 pass still
holds: exact recall is limited by pixels per glyph, so rendering changes do not
eliminate errors at profitable density. A later glyph-style A/B did find a
useful local improvement: repainting K reduced Fable's H/K error from 47.2%
to 18.7% without changing geometry or token cost. It shipped, but exact control
IDs did not improve. See FINDINGS.md, 2026-07-19 entry.

Runtime canary + text re-fetch and surrogate-reader pre-flight remain untested.
The release tripwire remains a resolution sweep for each new model; a model
that reads production cells near 100% would permit higher density.

Effective-context benefits remain unproven. The production-history results
above are directional evidence, not a general context-window or long-task
accuracy claim.

Community projects

Third-party projects listed here are not maintained or supported by pxpipe.

• pxpipe-windows - Windows support for pxpipe mitm (node-forge CA in place of openssl, Task Scheduler autostart).
• OmniGlyph - A community-maintained project derived from pxpipe and used by OmniRoute.