sqz

Pre-injection context compression and session deduplication for AI coding agents

_{Real session stats: 3,003 compressions · 178,442 tokens saved · 24.7% avg reduction · up to 92% on output the model already has}

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AI coding agents spend most of their input tokens on tool output: build logs, test runs, git status, the same file read again after every edit. All of it goes into the context window raw, and it is re-sent on every turn after that.

sqz compresses tool output before it enters the context. Per-command formatters keep what an agent acts on (the failing test, the assertion, the file:line) and drop what it does not. Anything the model already has in context comes back as a short reference instead of the content. Source code passes through unchanged, and so do stack traces, migrations and credential lines.

cargo install sqz-cli sqz-mcp     # or: brew install ojuschugh1/sqz/sqz · npm i -g sqz-cli · pipx install sqzsqz init                          # hooks + MCP server + agent guidance for every client it finds

[sqz: a 200-line file is served in full, a re-read of lines 41-80 becomes a line-range reference, cargo test output collapses to the failure, and sqz stats shows both]

_{Real output from the release binary (assets/demo.tape). Regenerate with vhs assets/demo.tape.}

Without sqz:                              With sqz:
cat auth.py (200 lines):   1,300 tokens    1,300 tokens  (source is served in full)cargo test (1 failure):      366 tokens      185 tokens  (failure, assertion, file:line)sed -n '41,80p' auth.py:     260 tokens       35 tokens  (§ref:…:L41-80§ to the read above)git status, unchanged:       166 tokens       37 tokens  (§ref:…§)─────────────────────────────────────      ─────────────Total:                     2,092 tokens    1,557 tokens  (26% saved, nothing dropped)

Single Rust binary, deterministic, no LLM calls, works offline. Every compressed result can be recovered byte-exact with sqz expand, except output that mentions credentials, a stack trace or a migration, which sqz never caches.

[!NOTE] Name disambiguation: this repo, ojuschugh1/sqz, is an independent project and is not affiliated with any other similarly named or working tool or other compression projects that shorten "squeeze". If you installed sqz / sqz-cli / sqz-mcp from crates.io, npm, PyPI, or Homebrew, it comes from this repository.

Token Savings

24.7% average reduction across 3,003 real compressions · 13-token refs for output the model already has · 100% of agent-critical facts kept in the quality benchmark · 0% on source code, and on stack traces and credential lines

One developer's week, measured from actual sqz gain output:

$ sqz gainsqz token savings (last 7 days)──────────────────────────────────────────────────  04-13 │                              │   2,329 saved  04-14 │                              │       0 saved  04-15 │███                           │  12,954 saved  04-16 │██                            │   9,223 saved  04-17 │████                          │  14,752 saved  04-18 │██████████████████████████████│ 105,569 saved  04-19 │████████                      │  30,882 saved  04-20 │█                             │   4,334 saved──────────────────────────────────────────────────  Total: 3,003 compressions, 178,442 tokens saved (24.7% avg reduction)

Per-command compression

Single-command compression (measured via cargo test -p sqz-engine benchmarks):

Session-level with dedup

Anything the model already has in its context comes back as a reference. Measured with the release binary against a throwaway database, using the fixtures in sqz/tests/quality_bench.rs and demo/, in cl100k tokens of everything the agent sees (the reference plus sqz's one-line note on stderr):

A word on what actually repeats. A user who counted 92 of their own Claude Code sessions (script) found identical whole-file re-reads in 1 of 542 reads, and line-range re-reads in 8.4% of them. So sqz does not lead with "the same file read five times": the repeats that happen in practice are unchanged command output, line ranges of a file already read, and files re-read after a small edit, and each has its own reference type (details). Sessions with noisy command output and repeated commands see the biggest wins.

Install

Prebuilt binaries (no compiler required — works on every platform):

# macOS / Linuxcurl -fsSL https://raw.githubusercontent.com/ojuschugh1/sqz/main/install.sh | sh
# Windows (PowerShell)irm https://raw.githubusercontent.com/ojuschugh1/sqz/main/install.ps1 | iex
# Any platform via npmnpm install -g sqz-cli
# macOS / Linux via Homebrewbrew tap ojuschugh1/sqzbrew install sqz

Build from source via Cargo:

cargo install sqz-cli sqz-mcp

sqz-cli provides the sqz binary; sqz-mcp provides the MCP server. sqz-engine is a library dependency — it compiles automatically and does not need to be installed separately.

Build from source (cargo install sqz-cli) works too, but needs a C toolchain:

• Linux: build-essential (apt) or equivalent
• macOS: Xcode Command Line Tools (xcode-select --install)
• Windows: Visual Studio Build Tools with the "Desktop development with C++" workload. Without these, cargo install fails with linker link.exe not found. If you don't already have them, use the PowerShell or npm install above instead.

Then initialize:

sqz init --global     # hooks apply to every project on this machine# orsqz init              # hooks apply to just this project (.claude/settings.local.json)

--global writes to ~/.claude/settings.json (the user scope per the Anthropic scope table), so the sqz hook fires in every Claude Code session on this machine. This is the common case on first install. Your existing permissions, env, statusLine, and unrelated hooks in ~/.claude/settings.json are preserved — sqz merges its entries rather than overwriting. The entries are its hooks and two allow rules, Bash(set -o pipefail) and Bash(sqz compress --cmd *), which cover only the parts its rewrite adds. sqz does not approve commands; your own permission rules still decide. When Claude Code asks before a rewritten command, or denies it, its message quotes the rewritten command, such as set -o pipefail; git tag v0 2>&1 for git tag v0.

Plain sqz init (project scope) is useful when you want sqz active only inside one repo. If ~/.claude/settings.json already has the sqz hooks, it leaves them out of the project file, since they already run in every project.

After installing, sqz doctor checks the whole chain — binary, database, shell hook, which clients are detected vs actually routed through sqz, and whether anything was compressed recently — and prints the fix for each gap it finds. sqz doctor --fix applies those fixes. After upgrading sqz, run it once: it brings hooks and guidance an older version wrote up to date, removes hook files current sqz no longer uses and a project copy of hooks that ~/.claude/settings.json already has, points hooks whose sqz binary is gone at the running one, and notes any hook that still runs a different sqz binary. sqz uninstall removes only sqz's own entries, deletes a file only when nothing else is left in it, and ends by listing the files it kept. Without a terminal to answer its prompt it needs --yes, like sqz reset.

See what sqz would have saved, before installing any hook

If you already use Claude Code or Kiro, your transcripts are on disk. Replay them through the sqz engine and get a counterfactual estimate on your own sessions, computed locally with nothing uploaded. From the author's last week of Kiro IDE work, trimmed to the summary:

$ sqz discover --replaysqz discover — counterfactual replay (last 7 days)────────────────────────────────────────────────────────
  Kiro IDE: 35 sessions, 155 sub-agent runs, advisory
                            outputs    tokens in    avoidable    shell                     6,297    1,917,662      454,028  23.7%    file reads                4,880    7,854,071      188,239   2.4%    other MCP servers         1,547    6,717,440    4,234,128  63.0%    already through sqz         260    1,393,517            -    out of reach              4,172    1,282,285            -
  Avoidable with no help from the agent:   0 tokens  Avoidable if the agent uses every route: 4,876,395 tokens, 25.4% of all tool output  Of that, 3,816,588 is the MCP proxy's lossy first pass.

Each output is replayed the way sqz could actually have reached it on that client. Kiro can't let sqz rewrite a tool call, so the first total is zero there; on Claude Code the shell rows split into commands the hook rewrites on its own and ones it skips. The second total assumes the agent pipes shell output through sqz compress, reads files with the sqz MCP tools (lossless, so only repeats count) and runs MCP servers behind sqz-mcp proxy, and the report says how much of that is the proxy cutting long strings and arrays on first pass. Web fetches, edits and sub-agent results are out of reach on every client and are counted, not replayed.

It scans ~/.claude/projects and ~/.kiro/sessions (Kiro CLI and IDE), or point it anywhere with --transcripts PATH. Each transcript replays against a fresh throwaway cache, so dedup references never pretend to span sessions, and the report says "estimate" because that's what it is: these outputs were not compressed at the time.

Only using one agent? Pass --only (or --skip) to limit which configs are written:

sqz init --only opencode              # just OpenCode, nothing elsesqz init --only opencode,codex        # OpenCode and Codexsqz init --skip cursor,windsurf       # everything except Cursor and Windsurf

Accepted names: claude, cursor, windsurf, cline, gemini, kiro, opencode, codex. Aliases (claude-code, gemini-cli, roo, kiro-cli) also work. --only and --skip can't be combined.

Manual installation (preserve comments in your config)

sqz init round-trips your config file through a JSON parser to merge the sqz entry, which drops any comments in your opencode.jsonc (and the analogous JSON-with-comments files other tools accept). If you've commented your config carefully and want to keep them, install by hand instead.

OpenCode — two steps:

1. Drop the plugin file in place. sqz prints the generated TS to stdout so you don't have to hand-write the path-escaping logic:

   sh

   mkdir -p ~/.config/opencode/pluginssqz print-opencode-plugin > ~/.config/opencode/plugins/sqz.ts

2. Add the MCP entry to your existing opencode.jsonc yourself. Append this block inside the top-level mcp object (create the mcp object if it doesn't exist):

   jsonc

   "sqz": {  "type": "local",  "command": ["sqz-mcp", "--transport", "stdio"],  "enabled": true}

Comments in the rest of your file stay put. OpenCode auto-discovers the plugin file; no plugin array entry needed (adding one causes double-loading, see issue #10).

The same plugin file loads on OpenCode 1 and 2. OpenCode 2 does not load the plugin sqz 2.0.0 and earlier wrote, so after upgrading sqz run sqz doctor --fix (or the print-opencode-plugin line above again) to rewrite it.

Other tools: Claude Code and Gemini CLI use plain JSON configs without comment support, Cursor, Windsurf and Cline get markdown rules files, and Codex gets a TOML entry in ~/.codex/config.toml that keeps your comments, so the automated path is non-destructive there. Use sqz init --only <tool> for those. An existing .gemini/settings.json gets sqz's hook merged in; if it has comments or doesn't parse, sqz init leaves it alone and prints the entry to add by hand.

Run sqz doctor afterwards to see what was configured for each client and which integration tier it is on.

How It Works

[sqz system architecture]

On transparent clients (Claude Code, Gemini CLI, Copilot CLI, OpenCode) sqz installs a hook that rewrites shell commands so their output goes through sqz before it reaches the AI tool. On advisory clients the agent is told to pipe output through sqz compress or use the sqz MCP tools. The table below gives each client's tier.

Claude → git status → [sqz hook rewrites] → compressed output

What gets compressed:

• Shell output: per-command formatters (git, cargo, npm/pnpm/yarn/bun, pytest, ruff, mypy, go, docker ps/images, kubectl describe/apply, terraform, gradle, maven, xcodebuild, adb logcat, dotnet, grep/rg, tree, curl, and more)
• JSON: strips nulls and empty values, cuts strings over 500 characters, compact encoding, TOON format
• Logs — collapses repeated lines
• Test output — shows failures only (state-machine parsers for Rust, Go, Python, JS, JVM)

What doesn't get compressed:

• Source code: served in full on first read
• Stack traces, SQL migrations, PEM blocks and credential lines: routed to safe mode and passed through unchanged at any size, and never cached; on the shell hook a per-command formatter may still summarize the rest of a test run around them
• Your prompts and the AI's responses — controlled by the AI tool, not sqz

Supported Tools

Transparent clients have a hook that routes shell commands through sqz on its own. On advisory clients sqz saves tokens only when the agent pipes output through sqz compress or calls the sqz MCP tools; the client's built-in shell and file tools bypass it. sqz doctor shows each client's tier.

Compress Any MCP Server

sqz-mcp proxy sits between your agent and any stdio MCP server and compresses what flows back: tool results go through the full sqz pipeline (dedup refs on repeats, safe-mode for stack traces and secrets, error results untouched), and verbose tool descriptions get compacted so tools/list stops eating your context window. The proxy injects an sqz_expand tool so the agent can recover any cached original byte-exact; results that mention credentials, a stack trace or a migration are never cached.

Wrap a server by prefixing its command in your MCP config:

{  "mcpServers": {    "github": {      "command": "sqz-mcp",      "args": ["proxy", "--", "npx", "-y", "@modelcontextprotocol/server-github"]    }  }}

Flags: --lazy-tools shortens every tool description to one sentence and injects an sqz_tool_help tool that serves the full original docs on demand (some MCP servers spend 10-40k tokens on tools/list alone); --no-desc keeps descriptions verbatim; --no-cache stores nothing, so it sends no dedup refs and adds no sqz_expand tool. Works with every MCP client (Claude Code, Cursor, Windsurf, Zed, Codex, Kiro, ...) because the client just sees a normal MCP server. Full guide, including the server's own sqz_read_file / sqz_grep / sqz_list_dir tools and per-client config: MCP context compression.

CLI

sqz init --global             # Install hooks for every project on this machinesqz init                      # Install hooks for just this projectsqz init --only kiro          # Only configure Kiro (skip the rest)sqz init --only opencode      # Only configure OpenCode (skip the rest)sqz init --skip cursor        # Configure every agent except Cursorsqz init --ci                 # Also write .github/hooks/sqz.json for Copilot agent CI runssqz compress <text>           # Compress (or pipe from stdin)sqz compress --no-cache       # Compress without dedup (always full output)sqz expand <ref>              # Recover original content from a §ref:HASH§ tokensqz compact                   # Evict stale context to free tokenssqz reset                     # Clear dedup cache or compression statssqz gain                      # Show daily token savings (bar chart)sqz gain --project .          # Per-project daily gainssqz gain --days 30            # Last 30 dayssqz stats                     # Cumulative compression report (includes regret signals)sqz stats --cost              # Estimated $ saved under a prompt-cached billing modelsqz stats --breakdown         # Per-command token usage breakdownsqz stats --project .         # Stats for current project onlysqz stats --project list      # List all tracked projectssqz stats --share             # Five-line share card sized for a paste into an issue or postsqz doctor                    # Verify sqz is installed, wired into your clients, and activesqz doctor --fix              # Apply the fixes doctor prints (run once after upgrading)sqz uninstall                 # Remove sqz's hooks, guidance and MCP entries, keep the restsqz discover                  # Find missed savings (incl. your weakest-compressing commands)sqz discover --replay         # Counterfactual replay of your agent transcripts (Claude Code, Kiro)sqz recall "auth timeout"     # Full-text search everything sqz has compressedsqz resume                    # Re-inject session context after compactionsqz vizit                     # Live terminal dashboard (like htop for AI agents)sqz hook claude               # Process a PreToolUse hook (Claude Code)sqz hook claude-post          # Process a PostToolUse hook (Claude Code)sqz hook kiro                 # Legacy; Kiro now uses steering + MCP (sqz init)sqz print-opencode-plugin     # Print OpenCode plugin TS for manual installsqz proxy --port 8080         # Local endpoint: compresses an API request body and sends it back, no forwarding

Dedup Escape Hatch

When sqz sees the same content twice, it returns a compact §ref:HASH§ token instead of the full text. Most models handle this fine, but some (e.g., GLM 5.1) can't parse the ref format and loop. Four ways to work around this:

# 1. Recover original content from a refsqz expand a1b2c3d4              # prefix matchsqz expand '§ref:a1b2c3d4§'     # paste the whole token
# 2. Compress without dedup (per-invocation)echo "..." | sqz compress --no-cache
# 3. Disable dedup globally (env var)export SQZ_NO_DEDUP=1
# 3b. Or just shorten the ref freshness window (seconds, default 1800).# Useful on clients without a compaction hook; 0 disables refs.export SQZ_REF_TTL_SECS=300
# 4. MCP passthrough tool (returns input byte-exact, zero transforms)# Available via tools/list when sqz-mcp is running

Recall: search everything sqz has seen

Everything that flows through sqz is indexed locally (SQLite FTS5, on your machine, nothing leaves it). When your agent compacts its context and loses that error message from an hour ago, search for it instead of re-running the command:

$ sqz recall "connection refused"  1. [git · 2h ago]  … curl: (7) Failed to connect: >>connection refused<< on port 5432 …     full content: sqz expand 3f9a1c05e2d84b17

Agents get the same thing as the sqz_recall MCP tool.

Track Your Own Savings

Run sqz gain in your shell any time to see your own daily breakdown (see the Token Savings section above for what the output looks like), and sqz stats for the full cumulative report:

$ sqz stats  📊 sqz compression stats  ──────────────────────────────────────────────────
  178,442  tokens saved  ↓  24.7% average reduction
  Compressions           3,003  Tokens in              721,840  Tokens out             543,398  Tokens saved           178,442  Avg reduction          24.7%
  🗄️  Cache  ──────────────────────────────────────────────────  Entries                43  Size                   39.1 KB

Add --breakdown to see exactly which commands consume the most tokens:

$ sqz stats --breakdown
  🔍 Top Token Consumers  ──────────────────────────────────────────────────────────────────────  command               calls  tokens in        out    saved  ──────────────────────────────────────────────────────────────────────  dedup                   249      45541       3237      93%  stdin                    51      30851      24289      21%  auto                    132      18288       7740      58%  echo                     17       1050        558      47%  ls -la                    8        948        948       0%  cargo build               7        170        145      15%  git status                4         56          8      86%  ──────────────────────────────────────────────────────────────────────

sqz stats and sqz gain count cl100k tokens of what sqz actually printed, abbreviation legend and expand hint included. A run of one character class longer than 2 KB, such as a long separator line, is counted in 2 KB slices, which can be off by about 1% plus 4 tokens.

Honest accounting: cost and regret

Token reduction is not automatically billed-cost reduction — with provider prompt caching, most context re-transmits at a ~90% discount, and compression that drops something the agent needed costs extra turns instead (arXiv:2607.12161). sqz measures both sides instead of hand-waving:

• sqz stats --cost estimates dollars saved under a prompt-cached billing model (cache write ×1.25 once, cache read ×0.10 per subsequent turn), with every assumption printed and overridable (--price-in, --reread-turns, --cache-write-mult, --cache-read-mult). This is the conservative estimate: without caching the same savings would bill at full input price on every turn.
• sqz stats reports regret signals: quick re-runs (the agent re-produced byte-identical output within 2 minutes — the repeat bought nothing; the Claude Code PostToolUse hook never answers with a reference, so its repeats count as ordinary compressions) and ref expands (§ref§ tokens recovered to original bytes). Both are proxies for "compression dropped something the model needed." If one command keeps showing up, its formatter needs work — file an issue.

sqz's design already avoids the failure modes that study measured: compression is deterministic and query-agnostic (never invalidates provider prompt caches), only new tool output is touched (history is never rewritten), commands that follow output, run a server or background a job are left alone (on Claude Code outside bypass mode, the PreToolUse hook leaves pipelines, loops and heredocs as written and the PostToolUse hook compresses their output after a successful run), grouped lists and pipelines (Gemini CLI, Copilot CLI, Claude Code in bypass mode) skip the per-command formatters, and the 16-token net-win gate skips compressions that wouldn't pay for their own markers. A command is also left as written when its rewrite could run a different set of commands than the original. In ls ${DEST:?}; echo next, piping ls on its own would let echo next run after the failed expansion stopped the shell, and where a list goes through sqz as one group, a failed cd in cd build && make; make test would skip the group instead of only make. [image]

Per-project filtering:

sqz stats --project .           # stats for current project onlysqz stats --project list        # list all tracked projectssqz gain --project .            # daily gains for current projectsqz gain --days 30              # last 30 days instead of 7sqz gain --days 30 --project .  # combine both

Stats are stored locally in SQLite under ~/.sqz/sessions.db — nothing leaves your machine.

How Compression Works

1. Per-command formatters for the commands below:

   Ecosystem	Commands
   Git	status, log, diff, show, stash, remote, fetch, push, pull, add, commit
   Rust	cargo build/test/clippy/check/nextest
   JavaScript	npm/pnpm/yarn/bun install/audit/outdated (test and run when they fail), tsc, eslint, biome
   Python	pytest, ruff, mypy, pip
   Go	go test (incl. -json stream), go build, go vet, golangci-lint
   Cloud	terraform plan/apply/destroy/refresh/init
   Containers	docker/podman ps/images, kubectl describe/apply
   JVM	gradle build/test, maven
   Mobile	xcodebuild (build + test), adb logcat
   .NET	dotnet build/publish/test
   System	grep/rg, tree, curl/wget

   Other commands, including kubectl get and logs, gh, aws, gcloud, ls and find, go through the generic compression pipeline.

2. Table compactor — aligned-column output from tools without a dedicated formatter (ps aux, netstat, database CLIs) collapses its padding runs to two-space separators. The detector is strict — indented lines, code, YAML, and JSON never match.

3. Structural summaries: the engine has an API that reduces a code file to imports, function signatures and a call graph. The hook and MCP paths do not use it; they serve source in full.

4. Dedup cache: SHA-256 content hash, persistent across sessions. Byte-identical output the model already has = 13-token reference. A line range of a file the model already has in full (sed -n '40,80p', sqz_read_file with offset/limit) = §ref:HASH:L40-80§. A re-read after a small edit = the changed lines with one unchanged line on each side, through the sqz MCP tools (the shell hook sends the edited file again); edits spread through the file come back in full. References are only served while the original is still in context (30-minute window, tunable via SQZ_REF_TTL_SECS, reset on compaction).

5. JSON pipeline: strip nulls → drop bookkeeping fields (__v, etag, request and correlation ids) → flatten → collapse arrays → TOON encoding (lossless compact format). Fields whose value is an empty string, array or object are dropped at any depth, and strings over 500 characters are cut to their first 500 characters followed by ....

6. Safe mode: stack traces (a trace header followed by its frames), SQL DDL at the start of a line, PEM blocks and credential lines (key=value or key: value with a secret-looking key), with or without ANSI colors, skip the pipeline and pass through unchanged at any size, with only ANSI codes stripped, and are never cached. On the shell hook a per-command formatter still runs first. Its summary is used only when it keeps every line of each paragraph that holds one of them unchanged, so it may summarize the rest of a test run around a trace; otherwise the whole output passes through. Output that only mentions a password, key, trace or migration outside those structures is compressed as usual but is not cached either, so anything a lossy stage drops from it cannot be expanded.

If a stage panics, sqz compress prints the input unchanged with one line on stderr and keeps the command's exit status, and the Claude Code PostToolUse hook leaves the result as it was.

Measured quality, including what each stage drops and what it never touches: quality benchmark. For the full technical details, see docs/.

Configuration

# ~/.sqz/presets/default.toml[preset]name = "default"version = "1.0"
[compression.condense]enabled = truemax_repeated_lines = 3
[compression.strip_nulls]enabled = true
[budget]warning_threshold = 0.70default_window_size = 200000

Per-project database

Everything sqz persists (stats, dedup cache, sessions) lives in one SQLite file, ~/.sqz/sessions.db by default. Set SQZ_DB_PATH to keep it per-project instead:

# e.g. in the project's .envrc (direnv)export SQZ_DB_PATH="$PWD/.sqz/sessions.db"

Every surface honors it — the shell hook, sqz stats/gain/expand, and the MCP server (set it under env in your MCP config). Prefer absolute paths: relative values resolve against whatever directory the process runs from. The parent directory is created if missing (mode 0700, like ~/.sqz).

Privacy

• Zero telemetry — no data transmitted, no crash reports
• Fully offline — works in air-gapped environments
• All processing local

Development

git clone https://github.com/ojuschugh1/sqz.gitcd sqzcargo test --workspacecargo build --release

License

sqz is licensed under either of the Apache License, Version 2.0, or the MIT license, at your option.

Copyright 2026 Ojus Chugh

Releases up to and including 2.0.0 were published under the Elastic License 2.0.

Contributions are accepted under the Contributor License Agreement.

Links

• Documentation index
• How to stop AI coding agents from re-reading the same files
• MCP context compression
• Quality benchmark: compression ratio vs information preservation
• Context rot vs context compression
• Choosing a context compression approach
• White Paper: Pre-Injection Context Compression
• Token Savings Benchmark
• Discord
• Changelog
• MCP Registry name: mcp-name: io.github.ojuschugh1/sqz

Star History

If sqz saved you tokens today, a star helps other people find it. sqz stats --share prints your own numbers if you want to show them.

Contributors

Thanks to everyone who has contributed code, fixes, and ideas to sqz:

And to everyone who filed the detailed bug reports behind our fixes. Precise repros make this project better with every release. Want to join them? PRs are reviewed fast: see the open issues to get started.

_{Contributor grid made with contrib.rocks.}