billion-context

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Context-compression plugin — billion-context is all you need.

_{small context windows (100K is enough) · 5× fewer tokens · month-long single sessions (billions of tokens) · high compression quality}

npm install -g billion-context --prefix=~/.local

                                           

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Cache health at a glance: a healthy session keeps a 95–97% prefix-cache hit rate — compression itself costs ≤2%. Sustained lower? Check attribution with /acp or /acp-cache (see FAQ); usual causes, in order: upstream cache TTL expiry · model switch · a bili bug (please report) · other/unknown.

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📄 Paper / Preprint

• Model-Driven Incremental Hierarchical Compression: Training-Free Multi-Generational Context Management for Long-Lived Coding Agents (English, v0.2)

📝 The paper itself is open-sourced under the MIT License as part of the codebase (paper/). It is a living document — anyone may edit it; improvements are welcome via pull request.

A production-scale longitudinal study: 4.5 months, three hosts, 174,327 model calls, 18.76B cumulative input tokens (~24.7B across all hosts), zero window violations on 204,800-token models, marathon sessions of 8,584–12,049 calls.

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billion-context sits between any agent and its model API, rewriting Anthropic/OpenAI streams with acp-kernel compression. The model decides when and what to compress into high-fidelity summaries — not a hard truncation limit.

Why

Long coding sessions blow up context. Each provider charges per token, and once you pass the context window the session degrades or dies. billion-context compresses consumed conversation into layered summaries so you can run a single session for days — billions of tokens through one context window.

Unlike a host's built-in summarizer, compression here is incremental, reversible, and prefix-cache friendly: summaries are written in small ranges, can be decompressed on demand, and the cache prefix stays intact.

How it works

Agent (Claude Code / Codex / Cursor / Aider ...)
        │  you point the agent's base URL at the proxy
        ▼
┌─────────────────┐
│  billion-context│   1. parse the request (Anthropic or OpenAI shape)
│     proxy       │   2. run acp-kernel compression on the conversation
│                 │   3. inject a `compress` tool + compression philosophy
│                 │   4. forward to the real model API
│                 │   5. rewrite the streaming response
└─────────────────┘
        │
        ▼
   real model API (Anthropic / OpenAI / compatible)

Context-management tools

The proxy injects four context-management tools into the conversation; the model calls them itself as context grows, and the proxy executes compress server-side so folded ranges stay summarized in history until restored:

• compress — fold a message range into a detailed summary.
• decompress — restore a compressed range when exact details are needed again.
• search_context — keyword search over compressed summaries and visible messages.
• acp_status — context-usage overview plus which ranges are still compressible.

Which do I need?

Pick by your client:

Client	Use
pi	billion-context — bili pi (launcher) or bili plugin install pi (native); standalone billion-context-pi remains usable — details: CLIENTS.md
opencode (1.x / 2.x)	billion-context — bili opencode (launcher) or bili plugin install opencode (native); standalone opencode-acp remains usable on 1.x — full guide: OpenCode
omp	billion-context via bili omp (built-in plugin) or bili plugin install omp (self-spawning native plugin, no launcher)
dsh	bili dsh (launcher — full native plugin via --patch) or bili plugin install dsh ≡ dsh plugin --profile <name> add billion-context (one unified lane) — details: CLIENTS.md
kimi	bili plugin install kimi (self-spawning native, Kimi Code ≥ 2.0.0) or bili kimi (cert-MITM) or /bili/ prefix — details: CLIENTS.md
hermes	bili plugin install hermes (self-spawning native, Python plugin #958) or bili hermes (cert-MITM)
zcode (Z.ai / bigmodel coding plan)	bili plugin install zcode (self-spawning native, #1145) or cert-MITM via the GUI's Settings → Network or /bili/ prefix — details: CLIENTS.md
claude	bili claude (launcher) or bili plugin install claude (native posture, #964 — managed settings block + session-owned proxy; see the notes below)
codex	bili codex (launcher — the full zero-config posture) or bili plugin install codex (MCP-shell tools companion: start bili first — the shell never spawns a proxy and never routes codex's own traffic) — details: CLIENTS.md
jcode	billion-context via bili jcode (cert-MITM) or /bili/ prefix — no native mode (compiled Rust binary, no plugin seam, #962)
gemini (Gemini CLI)	bili gemini (launcher, GOOGLE_GEMINI_BASE_URL /bili/ rewrite) or /bili/ prefix — launcher-only (no in-loop tool seam, #1043)
iflow (iFlow CLI)	bili iflow (launcher, IFLOW_BASE_URL /bili/ rewrite) or /bili/ prefix
qwen (Qwen Code)	bili qwen (launcher, cert-MITM) or /bili/ prefix
antigravity (Antigravity CLI / agy, Google)	bili antigravity (launcher, CLOUD_CODE_URL /bili/ rewrite of cloudcode-pa.googleapis.com) or /bili/ prefix — no plugin seam (closed Go language_server; its user-plugin surface is additive-only, #2115) — details: CLIENTS.md
mcode (MiniMax Code)	billion-context via bili mcode (cert-MITM) or /bili/ prefix — no native mode (event hooks only, no model-request seam, #1050)
aider	billion-context via bili aider (cert-MITM) or /bili/ prefix — no native mode (shell-command-only hooks, no tool-injection seam, #1048)
copilot (GitHub Copilot CLI)	bili copilot (launcher, cert-MITM) — closed Go binary, no plugin seam (#1049)
amp (Amp CLI)	bili amp (launcher, cert-MITM) — closed Go binary, no plugin seam (#1049)
crush (Charm Crush)	bili crush (launcher, cert-MITM) — open-source Go binary, no plugin seam; built-in provider hosts whitelisted, custom base_urls auto-discovered from crush.json (#2340)
zed (Zed editor)	bili zed (launcher, cert-MITM) — open-source Rust editor, no plugin seam; reqwest honors HTTPS_PROXY, CA via SSL_CERT_FILE (Linux env probing); built-in provider hosts whitelisted, custom api_urls auto-discovered from settings.json; loopback providers (ollama/lmstudio) stay direct via NO_PROXY (#2340)
goose (Goose CLI)	bili goose (launcher) — rustls trusts no CA file, so no cert-MITM: openai/anthropic legs via OPENAI_HOST/ANTHROPIC_HOST, custom providers via a regenerated GOOSE_PATH_ROOT overlay (#1049)
everything else (no context hook)	billion-context — bili <client> (launcher, preferred) or /bili/ prefix

Native mode vs standalone extensions. The host-native plugins (bili plugin install …) and the standalone in-process extensions (billion-context-pi, opencode-acp) are mutually exclusive — both active means double compression. The installer makes the switch: it replaces the legacy entries (bare name, npm: alias, versioned, path form; array or object shape) and snapshots the original config to .bili-bak once; a project-local install is not touched — remove that one by hand. As a runtime safety net for manual installs, the native entries set BILLION_CONTEXT_NATIVE=<host> synchronously at load so a standalone extension can stand down at action time. On the pi side the marker needs billion-context-pi 0.1.72+, and the pi-native entry scans both pi settings files once its proxy is up and warns loudly when it spots a co-resident legacy entry the installer never saw — that warning is the only visible signal while an old billion-context-pi silently double-compresses.

Install

Linux / macOS — install with a user-level prefix (no sudo, no npm config changes, and bili's self-update never hits permission errors):

npm install -g billion-context --prefix=~/.local

The bili command lands in ~/.local/bin — already on PATH in most distros; if not, add export PATH="$HOME/.local/bin:$PATH" to ~/.bashrc or ~/.zshrc. On nvm or Homebrew Node the default prefix is already user-owned — a plain npm install -g billion-context works as-is. On Windows the default prefix (%APPDATA%\npm) is also user-writable — plain npm install -g billion-context.

This installs the bili command (bili-proxy is kept as an alias). Hitting EACCES with an old root-owned prefix? Reinstall with --prefix=~/.local (pass the flag again on any future npm reinstall of bili) — that is the permanent fix; avoid sudo.

Quickstart

Three ways to use it — pick one:

• Native plugin (most native): bili plugin install <client> — bili becomes a plugin inside the client; start the client as usual.
• Launcher (config-free): one bili <client> command brings up the proxy and the client together — no real config file is ever touched.
• URL change (most universal): prefix your client's baseURL with the proxy origin + /bili/.

Mechanism details behind these three options (plugin lifecycle, runtime-info protocol, injection priority) live in TECHNICAL-NOTES.md.

Ports, briefly (#1660): bili start (manual) owns 8787. Everything a lane spawns for you (native hooks, launcher lanes) lives in a separate self-managed zone starting at 18787 — collisions hop +1 and each lane remembers its drift, so zero-config installs never fight you for a port, and a deliberate bili start daemon is attached by default. An upgrade-restart that finds the previous build still draining on the lane's port waits for it to release (up to 5s) and rebinds the SAME port instead of drifting (#1723); only a genuinely occupied port hops +1 — and that hop is now logged loudly.

Option 1 — Native plugin (bili plugin install pi / omp / opencode / dsh / kimi / hermes / zcode)

The proxy lives inside the client: install once, then start the client exactly as you always do — no launcher command, no env vars, no fixed port, no URL edits. Supported today for pi, omp, opencode (1.x and 2.x), dsh, kimi, hermes and zcode:

bili plugin install pi          # registers a "billion-context" entry in pi's settings (npm form when bili itself was npm-installed)
bili plugin install omp         # registers an extensions entry in omp's config.yml (~/.omp/agent/config.yml)
bili plugin install opencode    # registers the plugin in opencode's real config + disables native auto-compaction
bili plugin install dsh         # runs 'dsh plugin --profile <name> add billion-context' for every existing profile
bili plugin install kimi        # writes $KIMI_CODE_HOME/plugins/managed/billion-context/kimi.plugin.json (+ installed.json record); per-session routing block lands in config.toml on first start (Kimi Code >= 2.0.0)
bili plugin install hermes      # copies the Python plugin into ~/.hermes/plugins/billion-context/ (+ machine-owned bili.json sidecar) and enables it via `hermes plugins enable billion-context`
bili plugin install zcode       # writes hooks.enabled + a SessionStart hook + mcp.servers.bili into ~/.zcode/cli/config.json; per-session routing lands in the bigmodel provider store on first start
bili plugin remove <client>     # undo (dsh removes through the same channel; config snapshots go to .bili-bak)

Where a client has its own plugin channel you can also install natively, skipping bili commands entirely:

• dsh: dsh plugin --profile <name> add billion-context is the very command bili plugin install dsh drives per profile (npm form only; a git checkout has no published entry — pasting a GitHub address installs source without dist/ and the bundle never loads) — same end state either way (pnpm into the profile, bundled patch layer mounted by dsh itself); remove through the same channel. See the dsh section below.
• opencode: add the bare npm name to your real config's plugin list — "plugin": ["billion-context"] (npm form only; a git checkout has no published entry). The package publishes exports["./server"] → dist/agent/opencode-native.js, so opencode loads it through its own Npm.add machinery and the plugin self-spawns exactly like the bili-installed form. Do the two things the bili installer would have done for you too: set "compaction": { "auto": false } in the same config (otherwise OpenCode's native auto-compaction double-compresses) and keep a manual backup of the file first.
• claude: this repository doubles as a Claude Code plugin marketplace — /plugin marketplace add ranxianglei/billion-context, then /plugin install billion-context@billion-context, then run /billion-context:bili-setup (it drives bili plugin install claude for you and tells you to restart). Same end state as the bili installer; the plugin ships no hooks or MCP entries of its own, so nothing double-registers.

For pi / omp / kimi / claude there is no client-side channel — bili plugin install <client> writes their config entries for you (kimi's declarative kimi.plugin.json + registry record, claude's managed settings block, …).

Notes:

• Native mode is mutually exclusive with the standalone in-process extensions (billion-context-pi, opencode-acp) — the installer swaps the entries and snapshots the original config (.bili-bak).
• pi: native installs wire in built-in subagents by default (acp_delegate / acp_delegate_wait / acp_delegate_cancel) — how to disable them while keeping context compression: Pi built-in subagents.
• OpenCode legacy sessions, V1/V2 shapes and caveats: OpenCode.
• kimi reports runtime-info at bootstrap only (static headers can't carry per-request window/model values); subagent tool calls are routed by the proxy's outbound tool-use witness ring (#1685) — no model-visible conversation id.
• hermes's native plugin is Python: it points hermes' httpx stack at the proxy via env vars after a health check and stamps per-request headers through an llm_request middleware.
• codex is the one client a plugin install cannot make self-sufficient: codex routes model traffic via env only (no config-file routing seam for the default ChatGPT-login provider — a managed model_providers block would force API-key auth and drop subscription login), and an MCP server cannot inject env into its parent. bili plugin install codex writes a single [mcp_servers.bili] block into ~/.codex/config.toml (command = node, args = dist/mcp.js) exposing the four ACP tools; at session start the shell resolves a proxy — env BILI_MCP_PROXY > the live-instance record (any lane's proxy or a bili start daemon) > the 8787 user-zone default (#1660 removed the install-time origin bake, #403) — nothing reachable → tools/list fails with -32003. So: start bili first (bili start or any client's lane proxy), export HTTPS_PROXY yourself if you also want compression, or use bili codex for the zero-config full posture. Mechanics: CLIENTS.md.
• claude has a native posture (#964): managed settings block + SessionStart hook + MCP shell; the hook rides the self-managed port zone (#1660) and re-pins the managed URL to the live origin each session, so port drift self-heals. Opt out with BILI_NATIVE_CLAUDE=0 (passthrough). Mechanics: TECHNICAL-NOTES.md. Known limitation (#2290): the Claude Desktop app's Code tab (CLAUDE_CODE_ENTRYPOINT=claude-desktop) sets its own ANTHROPIC_BASE_URL on its embedded Claude Code, overriding the managed one — desktop sessions bypass the proxy entirely while the managed block's DISABLE_AUTO_COMPACT=1 still applies, so they get neither bili compression nor native auto-compaction. The hook warns loudly at session start (and records it for bili doctor, which also flags machines where Claude Desktop is installed alongside the native lane); terminal sessions are unaffected. Field-tested 2026-10-06 (#2290): putting HTTPS_PROXY in the settings env block produced zero CONNECT traffic to a live MITM-enabled proxy on Claude Desktop 2.19675.1 / embedded CC 2.1.288 (Windows 11) — the variable reaches no network stack there, consistent with the CLI finding that CC's undici ignores proxy env vars (why bili claude uses the /bili/ base-URL rewrite instead). As of that version there is no usable routing seam on the desktop Code tab; the lane stays tracked in #2290 in case upstream changes behavior. Desktop-only users can restore native auto-compact with bili plugin remove claude.
• zcode has a native posture (#1145): managed ~/.zcode/cli/config.json block + per-session provider baseURL rewrite. Full mechanics: CLIENTS.md.
• jcode and aider have no native mode (no plugin/MCP/tool-injection seam: #962, #1048) — use bili jcode / bili aider.
• copilot, amp and goose are launcher-only (#1049); goose cannot be cert-MITMed (rustls trusts no CA file) and rides plain-HTTP base-URL redirects instead.

Option 2 — Launcher (bili pi / bili codex / bili claude / bili omp / bili opencode / bili hermes / bili dsh / bili codebuddy / bili qoder / bili trae / bili jcode / bili kimi / bili gemini / bili iflow / bili qwen / bili antigravity / bili mcode / bili aider / bili copilot / bili amp / bili goose)

The launcher wraps a client in one command: it starts a proxy on an independent port (a fresh instance is always spawned — a port is never reused), then points the client at it — certificate-based MITM where the client honors proxy/CA env vars, or an isolated /bili/ config rewrite where it doesn't. No real config file is ever edited; the client's own config is READ to discover which HTTPS upstream hosts it talks to, and those hosts are whitelisted for MITM so the proxy can TLS-terminate exactly them and blind-tunnel everything else.

bili pi                               # launch pi through the proxy — file-free (#535): env + extension registerProvider, real ~/.pi untouched
bili codex                            # launch codex through the proxy
bili claude                           # launch claude through the proxy
bili omp                              # pi-style, file-free (#535): env + extension registerProvider + compaction cancel, real ~/.omp untouched
bili opencode                         # OpenCode (1.x & 2.x): full guide in the [OpenCode](https://github.com/ranxianglei/billion-context/blob/HEAD/CLIENTS.md#opencode) section below
bili hermes                           # file-free (#535): hermes proxy env (HTTPS_PROXY + combined CA bundle via SSL_CERT_FILE) — https via CONNECT MITM, http via absolute-form forward proxy; real ~/.hermes untouched
bili dsh                              # deepseek-harness: full native plugin injected via --patch (#941) — real dsh tools, session-bound /acp + /acp-cache (plugin mode); non-loopback upstreams ride proxy envs, loopback keeps the overlay DSH_HOME rewrite (#535); dsh auto-compaction off outside web profiles, and switchable off there via a profile-level full-snapshot override of preset-standard (#1772/#2474)
bili codebuddy                        # Tencent CodeBuddy Code CLI: CODEBUDDY_BASE_URL /bili/ rewrite (OpenAI chat completions wire), budget aligned via CODEBUDDY_AUTO_COMPACT_WINDOW; real ~/.codebuddy untouched
bili qoder                            # qoder: model endpoint is hardcoded https (no /bili/ rewrite possible) — cert-MITM via HTTPS_PROXY + NODE_EXTRA_CA_CERTS, default model hosts whitelisted (#653)
bili trae                             # Trae CLI (ByteDance, closed Go binary, no base-URL override) — cert-MITM via HTTPS_PROXY + SSL_CERT_FILE, model host from TRAE_CLI_API_HOST or the default enterprise gateway (#655)
bili jcode                            # jcode (Rust agent harness) — env-only cert-MITM launch: HTTPS_PROXY + SSL_CERT_FILE, model host api.z.ai whitelisted, local loopback providers stay direct via NO_PROXY
bili kimi                             # Kimi Code CLI (Moonshot): standard proxy envs except an unconditional loopback bypass — https via cert-MITM, http via absolute-form forward proxy; loopback endpoints inventoried with a manual /bili/ hint (#757)
bili gemini                           # Gemini CLI (Google): GOOGLE_GEMINI_BASE_URL /bili/ rewrite to generativelanguage.googleapis.com (Google native wire), real ~/.gemini untouched
bili iflow                            # iFlow CLI: IFLOW_BASE_URL /bili/ rewrite to apis.iflow.cn/v1 (OpenAI chat-completions wire), real ~/.iflow untouched
bili qwen                             # Qwen Code (multi-protocol gemini-cli fork, no base-URL hook): cert-MITM via HTTPS_PROXY + NODE_EXTRA_CA_CERTS, default DashScope/Qwen model hosts whitelisted, custom relays via --mitm-domain
bili antigravity                      # Antigravity CLI (agy, Google): CLOUD_CODE_URL /bili/ rewrite of cloudcode-pa.googleapis.com (undocumented language-server env override, v2.19.1 binary-verified); wire recognized as Google native by path (#2115)
bili mcode                            # MiniMax Code CLI: same shape as kimi (proxy envs, unconditional loopback bypass, cert-MITM/absolute-form); session bound via X-Mavis-Session-Id (#1050)
bili aider                            # Aider (Python pair programmer): cert-MITM via HTTPS_PROXY + SSL_CERT_FILE/REQUESTS_CA_BUNDLE; endpoint from OPENAI_API_BASE / ANTHROPIC_BASE_URL / --openai-api-base / .aider.conf.yml (#1048)
bili copilot                          # Copilot CLI (GitHub, closed Go binary) — cert-MITM via HTTPS_PROXY + SSL_CERT_FILE, api.githubcopilot.com + per-plan subdomains whitelisted (#1049)
bili amp                              # Amp CLI (Sourcegraph, closed Go binary) — cert-MITM via HTTPS_PROXY + SSL_CERT_FILE, ampcode.com whitelisted (#1049)
bili goose                            # Goose (Block, Rust/reqwest): rustls release builds trust no CA file — openai/anthropic legs via OPENAI_HOST/ANTHROPIC_HOST, custom providers via a regenerated GOOSE_PATH_ROOT overlay (/bili/ rewrites, real config untouched) (#1049)
bili pi --mitm-domain api.foo.com     # add a domain to the MITM whitelist

Option 3 — URL change (/bili/ prefix)

Start the proxy:

bili

Then just prefix your client's existing baseURL with http://localhost:8787/bili/. The full upstream URL is embedded in the path, so the proxy knows where to forward without any config:

client baseURL before:  https://api.openai.com/v1
client baseURL after:   http://localhost:8787/bili/https://api.openai.com/v1

For more per-client configuration examples, see the web UI guide at http://localhost:8787.

Verify. With the proxy running and your config saved, check it answers and that your first real request shows compression activity in the log:

# Health check (proxy up + where it forwards)
curl -s http://localhost:8787/__bili/health
# → {"ok":true,"upstream":"https://api.anthropic.com"}

# Live session stats (after a real request)
curl -s http://localhost:8787/__bili/stats

Then send one message from your client and watch the log (~/.local/state/billion-context/bili.log, also printed to stderr). You should see a processTurn line per request, and once the conversation grows, [acp-usage] round N input=X cached=Y (cache hit Z%) + a compress event.

Client deep dives

Everything that doesn't fit in one Quickstart line — how each client's lanes attach, what gets written where, and known limitations — lives in CLIENTS.md: dsh · Kimi Code · Hermes · ZCode · Gemini family (Gemini CLI / iFlow CLI / Qwen Code / Antigravity) · cert-MITM clients that never compress (CONNECT blind tunnels, #897) · unrecognized endpoints going direct (#1290) · OpenCode (launcher / native / pure proxy, /acp status & rules, legacy opencode-acp sessions #920).

FAQ

How do I check my cache hit rate? Don't dig through logs — /acp-cache prints a text summary report right in the client, headed by a clickable Web UI link: open it for the web version of the session page — the cache hit-rate line chart plus per-break attribution:

The report has four blocks that pin things down at a glance: GRAND LEDGER (totals + hit% with an explicit HEALTHY verdict; misses decomposed into new content / compress re-pay / upstream-ttl-or-client-rewrite) · FOLD ECONOMICS (per-fold economics: net tokens saved, paid-back verdicts) · LINE ITEMS (anomalies only: hit<85% or miss≥5000). Rule of thumb: compression itself costs ≤2% — a healthy session sits at 95–97%. When you see less, the attribution tells you which of the usual suspects it was, in this order: ① upstream cache TTL expiry (shows up as stable-prefix misses — the top-spikes line names idle times), ② a model switch, ③ a bili bug (report it with the page attached), ④ other/unknown. /acp-cache [full] lists every fold & line; same report over Since #1535 the report ends with a MODEL SWITCHES section: a mid-session model change invalidates the provider's prefix cache, so the whole stable prefix is re-billed on the next request — each switch's unexplained residual (its ttl bucket minus new content) is charged to the switch instead of masquerading as TTL expiry; per-event from → to, hit %, and attributed tokens are listed (full lists every event, the summary the last 8), and the web sessions table gains a matching model-switch column. Since #2131 the same machinery fingerprints the outbound credential (a 12-hex sha256 of the authorization/x-api-key-family headers — the raw key is never stored) and attributes a key switch — the relay behind a stable URL rotated to a different account — in a dedicated KEY SWITCHES section, a key switch: line in CACHE INVALIDATION, and a 🔑 badge in the web sessions column. HTTP: GET /__bili/cache-report; the raw per-request [acp-usage] lines still land in the log file for deep dives.

What does /acp show? In clients with the native plugin (opencode, dsh), /acp renders the ACP status panel of the current conversation straight from the proxy (session, blocks, compressible ranges, usage); before the first model request it shows an idle notice instead. /acp-cache [full] prints the cache report above.

Can I query sessions and config over the web? Yes — open http://localhost:8787: an overview dashboard, session list with per-session detail, live logs, a config editor, and an upstream connectivity test. Everything is also plain JSON for scripting (/__bili/stats, /__bili/sessions, /__bili/config, …).

When does compression happen? It is model-driven: the injected context tools are called by the model as context grows, gentle growth nudges (~50K-token steps by design, adjustable via compress.nudgeGrowthTokens) prompt it along the way, and preflight fires as a hard backstop when the input alone exceeds the window (#470). Watch it live with /acp or the web UI.

Why does the first compaction wait until ~200k? Compaction does not trigger on absolute window position but on growth intervals: by default the first soft compaction fires 50k tokens past the boot content (compress.nudgeGrowthTokens, flat and window-independent). With a boot around 100k — or with the growth step set to ~100k — the first compaction may wait until ~200k. To make it fire earlier: 1) trim the system prompt, disable unneeded tools, prune skills; 2) lower compress.nudgeGrowthTokens to ~50k; 3) enable lean mode. Worked example in CONFIGURATION.md.

Is bili transparent? How do I turn it off? Unrecognized endpoints forward unchanged (CLIENTS.md), and every mode reverses cleanly: bili plugin remove <client> for native installs, stop using the launcher command / env vars / /bili/ prefix for the other two — traffic goes direct again immediately.

Where are logs and session data stored? Log: ~/.local/state/billion-context/bili.log (also mirrored to stderr); session state: ~/.local/share/billion-context/ (XDG-overridable; Windows AV exclusion #362, opt-in cleanup #1082) — full paths in CONFIGURATION.md.

Running the proxy

Flags

bili --port 9000              # change listen port
bili --host 0.0.0.0           # listen on all interfaces (see host note below)
bili --debug                 # verbose logging (also: set "debug": true in config)
bili --passthrough           # forward without compression (smoke-test mode)
bili --config ~/my-bili.json # use a different config file
bili update                  # check & install a newer version now (bypasses throttle)
bili --no-auto-update        # disable self-update for this run
bili --auto-restart-on-update   # self-restart when a new version is installed (default off)
bili --bin /path/to/client   # launcher: spawn this exact client binary instead of auto-detecting (env BILI_CLIENT_BIN)

Flags override env vars and the config file. bili --help lists them all.

Remote agents (--host)

By default the proxy binds 127.0.0.1 and only accepts loopback connections. To serve agents on other machines: bili --host 0.0.0.0 (or your LAN IP); remote agents point their model baseURL at http://<this-host>:<port>/bili/….

• MITM-mode CONNECT then also accepts remote clients — for whitelisted model hosts only. Blind tunnels to arbitrary hosts stay loopback-only, so the proxy can never be used as an open relay.
• /bili/<absolute-url> destination admission (#409): the proxy itself and link-local/metadata addresses are always denied; loopback/private destinations are allowed for local clients (self-hosted upstreams) and denied for remote clients unless listed in BILI_TUNNEL_ALLOWED_HOSTS (host or host:port, comma-separated). One exception (#1073): a local client relaying a management path (/__bili/*, /__acp/*) to a loopback IP-literal destination is forwarded unmarked; remote peers and hostname destinations keep the internal tunnel marker unconditionally, and management paths stay unreachable through the tunnel even via NAT hairpin. An absolute-form request addressed to the instance's own endpoint on a management path is served locally instead of tunneled (a forward-proxy-style health probe gets a real answer).
• There is no authentication: only do this on a trusted LAN or behind a firewall. The /__bili/ management endpoints remain loopback-only. A startup [security] warning reminds you of the above.

Debugging

bili --debug (or env ACP_DEBUG=1, or "debug": true in config — flag > env > config) logs every processTurn (tag counts, token usage), the nudge decision (growth/usage/pendingT1/shouldInject), client headers, and SSE rewrites.

Log file

All logs tee to ~/.local/state/billion-context/bili.log by default (XDG state dir) and still print to stderr. Override with "logFile" in config or ACP_LOG_FILE (off disables the file). Auto-rotates at 10 MB (bili.log.old). Per-request cache-hit stats log as [acp-usage] round N input=X cached=Y (cache hit Z%) so you can measure prefix-cache health directly from the log.

Connection lifecycle tuning (#1982)

Client-facing connections close gracefully after the final response: when the proxy initiates the close (Connection: close), it waits up to BILI_POST_RESPONSE_LINGER_MS (default 5000) for the client's close signal before releasing the socket, so pooled clients see a clean EOF instead of a possible RST from racing bytes. Related knobs: BILI_KEEP_ALIVE_TIMEOUT_MS (idle-reap budget, default 5000) and BILI_CLIENT_ERROR_BACKSTOP_MS (terminal backstop for the error-drain path, default 30000) — full semantics in CONFIGURATION.md.

Self-update

The proxy checks npm on startup and every 3 minutes; a newer version is installed in place and a notice is logged — restart bili to pick it up, unless you enable opt-in self-restart (--auto-restart-on-update flag, env ACP_AUTO_RESTART_ON_UPDATE=1, or "autoRestartOnUpdate": true in config — default OFF): with zero in-flight requests it verifies the new install, stops accepting connections, drains, spawns a replacement on the same port, and exits once it accepts connections (clients reconnect automatically; session state survives on disk). Safety gates: zero in-flight through the drain window, an install sanity check before re-exec, and a 10-minute cooldown marker so a flapping version can never loop-restart; any failure resumes the original listener and falls back to the plain reminder.

While the running process is behind the on-disk install ("stale"), the web UI shows a banner (running vs installed version, auto-restart state) and GET /__bili/status returns {version, diskVersion, stale, autoRestartOnUpdate, advisory, inFlight} for scripting (advisory is the active critical-defect entry or null, see below). Disable permanently via "autoUpdate": false in config or ACP_AUTO_UPDATE=0.

In plugin mode (bili opencode / bili pi / bili dsh — the proxy runs embedded in a long-lived host), "restart bili" means restarting the host: the embedded process cannot exit on its own, so a host left open keeps serving whatever code it started with, silently missing every fix auto-update reports as installed (#1603). Enable --auto-restart-on-update to have it self-restart at a safe point, or run /acp (OpenCode hosts today — pi/dsh coverage tracked in #2084) — the status panel appends a one-line staleness warning (running vs installed version) whenever the on-disk install is ahead of the live process.

Update visibility is silent by default since v0.1.183 (#1977): routine/recommended releases no longer render an update line on the /acp panel footer or in acp_status — only a critical-tier release surfaces there (CRITICAL UPDATE READY/AVAILABLE). The standing ways to check an installed-but-not-restarted release are the stale cues above: web UI banner, the /acp one-line warning, and GET /__bili/status. Deliberately no always-on nag; the advisory channel (#1481) remains the only auto-visible critical path.

When an install keeps failing (unwritable or host-managed dir, network error, …), auto-update no longer re-downloads and retries on every 3-minute cycle forever. After three consecutive failures it backs off exponentially (5 min → 10 → 20 …, capped at 6 h), logs a one-time actionable hint (fix permissions / npm prefix, reinstall user-level, or disable via "autoUpdate": false / ACP_AUTO_UPDATE=0), and logs nothing further about the failure while cooling down (no download, no retry line); it resumes as soon as the failure clears or a different version is targeted (#1603).

The same bounded retry now covers the owner-managed lanes the global self-update drives instead of writing the copy itself — the dsh desktop in-place copy, the dsh profile bundles, and pi's npm copy (#2192). Each lane keeps its own failure streak keyed by lane + target version, so a persistently broken desktop layout no longer re-downloads the full tarball every cycle (up to ~480 downloads/day per affected machine before the fix); three strikes arms the same exponential cooldown, and the one-time hint names the failing lane and its manual fix (dsh plugin --profile <name> add …, pi update --extension …, or recreate the desktop profile). Host-managed instances additionally check on their own slower cadence — 30 minutes plus up to 15 minutes of jitter, tracked under a separate throttle marker — instead of consuming the global 3-minute budget. Failure streaks are shared across every bili process on the machine through a small state file in the cache dir (.install-backoff.json), so several running instances don't each burn their own retry budget; a clean bili plugin update disarms the dsh profile lane immediately. The file is written atomically (tmp+rename) and every writer merges with what is already on disk, so concurrent instances cooperate instead of overwriting each other's streaks; long-lived processes re-read it when it changes, so a manual disarm by one copy is visible to the others on their next check. It is fail-safe in the retry direction — a corrupt file or jumped clock is dropped, never allowed to silence a lane for long. bili plugin update clears the dsh-profile lane's key; a repaired desktop lane clears its own key on its next successful in-place refresh.

Critical-defect advisories (forced updates)

Independent of auto-update (#1481): even with autoUpdate off, the proxy polls a small companion npm package (billion-context-advisories, published by CI from this repo's advisories/ directory) on the same 3-minute cadence. Each advisory names a semver range of broken versions (affected), the exact version to install (target — which may be older than the current one, i.e. a rollback), and a user-facing reason. When the local version falls inside affected, bili force-installs target through the self-updater's full safety chain (cross-process lock, backup + verify + rollback; source checkouts and host-managed installs are refused with manual instructions instead) and warns prominently: a one-time [advisory] ⚠️ … log line per process per advisory id, a banner on the web UI showing the reason and the exact manual upgrade command, and the active entry under advisory in /__bili/status. The check is fail-open by design: an unreachable or malformed advisory source only produces a warning — model traffic is never blocked by it. Disable via config ("advisoryCheck": false) or env (BILI_ADVISORY_CHECK=0); point at a custom document with "advisoryUrl" / BILI_ADVISORY_URL.

Configuration

The full configuration reference — config file location, top-level keys, providers, compression tuning, environment variables — lives in CONFIGURATION.md.

Config file

One JSON document at ~/.config/billion-context/billion-context.json ($XDG_CONFIG_HOME/billion-context/; override the path with BILI_CONFIG_FILE). Precedence when several sources set the same knob: CLI flag (where one exists) > env var > config file > built-in default — every env var keeps working as the override tier.

What's inside (details in CONFIGURATION.md):

• providers — per-provider routing table: upstream override, model context windows, per-provider/model compress tuning, wire-protocol declaration, compaction opt-in.
• compress — three-level compression tuning (global → provider → model): thresholds, nudge cadence, preservation rules, prompts, tiers.
• Server-level blocks — process-wide behavior, including the #2030 additions: network (timeouts / retry / keep-alive / preflight cadence), persist (session persistence format + tail), sessions (cap + GC policy), update (registry mirror + check interval), diagnostics (dumps, render-tag mode, injection switches), fakeCompletion, plus scalars codexCompact / ccrRetrievalTtlMs / decompressTmpCap and extensions mitm.handshakeTimeoutMs, compat.noCacheControl, compat.keepResponseId.

Minimal example:

{
  "network": { "upstreamTimeoutMs": 900000 },
  "persist": { "zstd": true },
  "sessions": { "gc": { "enabled": true, "maxAgeDays": 14 } }
}

Knobs people look for first:

• Upstream proxy (firewall/GFW) — routing the proxy's own outbound traffic through v2rayA/clash: full resolution order, empty-string = explicit direct, SOCKS5 rejection, both egress paths, and the mitm:// vs https:// key schemes live in CONFIGURATION.md (Server Settings → proxy; Providers → key schemes).
• Wire-compat role rewrite (compat.roles) — an upstream that rejects the developer role? Covered by CONFIGURATION.md (Server Settings → compat) — including the learn-on-failure auto-fix that needs no configuration at all.
• Signed upstreams (body-covering signatures) — a gateway whose requests carry a body-covering signature (CodeArts APIG's SDK-HMAC-SHA256, or gateway-invented headers like x-ofm-signature): the built-in scheme re-signs transparently on dsh; every other detected scheme is ALWAYS refused locally — signed requests are either re-signed+compressed or refused, never passed through unsigned — and bili keeps reminding at startup and in the web UI until it ships the scheme's re-signer (#1884/#2090). Detection rules, per-scheme overrides, and BILI_RESIGN / BILI_RESIGN_PASSTHROUGH / BILI_CODEARTS_REF live in CONFIGURATION.md (Server Settings → resign).

Pi built-in subagents

Using bili pi or the native pi plugin (bili plugin install pi) includes built-in subagent support, enabled by default: acp_delegate, acp_delegate_wait, and acp_delegate_cancel. This additional tool surface is specific to pi.

Keep only one subagent implementation enabled. If you use the built-in support, remove or disable other pi subagent plugins (for example, pi-subagents or a separately installed billion-context-pi-subagents) in both user and project settings to avoid overlapping tools, prompts, or behavior. If you prefer another subagent plugin, disable the built-in support instead. A project-scope pi-subagents install makes the built-in delegate stand down by default, but a user-scope-only install does not; do not rely on that guard for every installation.

To disable the built-in subagents while keeping context compression, merge this into ~/.config/billion-context/billion-context.json (or the file selected by BILI_CONFIG_FILE), preserving your other settings:

{
  "pi": {
    "subagents": false
  }
}

Restart pi and start a new session for the change to take effect. This disables the three delegate tools, their system-prompt section, and the fleet keyboard shortcut; context compression remains enabled. It does not disable independently installed subagent plugins. More options: subagent configuration.

How sessions work

The proxy keys compression state on the conversation value the client itself provides, verbatim (src/session-id.ts) — no hashing, no protocol/upstream/API-key dimensions (those mutate mid-conversation and orphaned state exactly when users kept talking, #280/#286). The id stays inside the proxy (state store, persistence, UI label); it is never sent upstream.

Where the value comes from, first hit wins: the plugin's x-bili-plugin-conversation (honored only alongside the x-bili-plugin marker header), then per-client headers (x-claude-code-session-id, x-grok-session-id/x-grok-conv-id, x-mavis-session-id), then generic headers (x-session-affinity, x-acp-session, x-session-id, x-opencode-session, session-id/session_id), then body fields: session_id / metadata.session_id on the Responses wire, and prompt_cache_key promoted over the content-fingerprint fallback on the Responses/OpenAI/Anthropic wires.

Client	Sends conversation id?	Source
Codex	✅ yes	body.session_id / turn-metadata thread id
OpenCode	✅ yes	x-session-affinity / x-opencode-session header (ses_…)
Claude Code	✅ yes	x-claude-code-session-id header
omp (via plugin)	✅ yes	prompt_cache_key promoted over any fingerprint (#268)
pi (bare)	❌ no	nothing → anonymous prefix affinity below

Header-less clients (pi-like): anonymous prefix affinity. With no conversation signal at all, the proxy resolves the session from the replayed history itself (src/prefix-affinity.ts, #309): a request reattaches to a stored session only when its history reproduces that session's message chain byte-exactly from position 0; otherwise it gets its own deterministic pfa-… session. Consequences (#1262): a resumed conversation reattaches to its own session (even after a proxy restart, #499); a new task with an identical opener does NOT inherit another conversation's blocks — it mints a fresh, fully separate session; a request with no usable signal at all gets an explicit 400 instead of silently colliding.

Design record and threat model: SESSION-IDENTITY.md. The message-granularity sibling (why identity is content-derived, not an assigned id) is MESSAGE-IDENTITY.md.

For upstream sticky-routing, the proxy forwards only identity values the client already supplied (e.g. a body session_id is forwarded upstream as x-session-id); it never synthesizes one itself.

Recommendation: explicit-id clients are safe to run concurrently. For header-less multi-agent use, prefer the client plugin (stamps a stable id per conversation) or pass an explicit x-acp-session header — otherwise prefix affinity still keeps distinct tasks apart (a diverged fork costs one raw resend plus a compression-ladder restart).

Derived (child) sessions inherit the parent's compressed context (#1333, #1362)

A child session (subagent/fork starting from an empty history) reports its lineage at birth — its identity registration carries parentConversationId and the proxy records a read-only derivedFrom link — so decompress / search_context fall back along the parent chain for content the child never saw itself (cycle-guarded, depth cap 8). Nothing is copied into the child, the parent is never modified; if the parent is unknown the child simply starts fresh. Per-lane parent signals (pi/omp parentSession header, OpenCode V1/V2 parentID): SESSION-IDENTITY.md. claude/codex/dsh need nothing here: they share one session id across subagents or have no child-session concept at all.

Windows: exclude the sessions dir from antivirus (#362)

The proxy rewrites each session's state file every turn of a long session; on Windows, real-time AV (Defender), the search indexer, or a sync tool (OneDrive) can lock the sessions dir mid-write, so persists fail with EPERM until the lock clears. Fix at the root: add %USERPROFILE%\.local\share\billion-context\ to your antivirus exclusions (Defender steps included) and keep sync tools off that path — CONFIGURATION.md.

Session file cleanup (#1082)

Short-lived sessions leave small state files behind that are never resumed. Cleanup is opt-in (BILI_SESSION_GC=1; off by default — session files are user data, no silent deletion policy): when enabled, bili sweeps the sessions dir at boot and hourly and deletes a file only when BOTH hold — older than BILI_SESSION_GC_MAX_AGE_DAYS (default 7 days) AND never compressed with its newest request body ≤ BILI_SESSION_GC_MAX_TOKENS tokens (default 1M) — so deletion loses nothing but bytes. CCR content stores follow their session file's lifecycle; compressed sessions are never deleted; every deletion is audit-logged. Full policy: CONFIGURATION.md.

Status

Early. Protocol handling and compression work against mock tests (500+ passing). Real-model integration testing is the next milestone. Expect rough edges.

Client-side plugins for pi / omp / opencode ship inside billion-context (dist/agent/*.js) for the cooperative-proxy path. See the "Which do I need?" section above for how billion-context, the standalone billion-context-pi, and opencode-acp relate.

Attribution requirement (one term on top of MIT)

This project is MIT-licensed plus one additional term: any product or service (commercial or open source) whose users can see or interact with it and which uses this software must attribute it — stating that it uses billion-context with a link back to this repository — on its home page, documentation, or About/Credits page. Pure server-side/embedded use satisfies this via shipped documentation. See the Additional Term at the end of LICENSE.

If you build on this project, we'd love to hear about it: open an issue (no obligation) so we can track where it's used.

License

MIT