context-mode

Context Mode

The other half of the context problem.

Privacy & Architecture

Context Mode is not a CLI output filter or a cloud analytics dashboard. It operates at the MCP protocol layer — raw data stays in a sandboxed subprocess and never enters your context window. Web pages, API responses, file analysis, Playwright snapshots, log files — everything is processed in complete isolation.

Nothing leaves your machine. No telemetry, no cloud sync, no usage tracking, no account required. Your code, your prompts, your session data — all local. The SQLite databases live in your home directory and die when you're done.

This is a deliberate architectural choice, not a missing feature. Context optimization should happen at the source, not in a dashboard behind a per-seat subscription. Privacy-first is our philosophy — and every design decision follows from it. License →

The Problem

Every MCP tool call dumps raw data into your context window. A Playwright snapshot costs 56 KB. Twenty GitHub issues cost 59 KB. One access log — 45 KB. After 30 minutes, 40% of your context is gone. And when the agent compacts the conversation to free space, it forgets which files it was editing, what tasks are in progress, and what you last asked for.

Context Mode is an MCP server that solves both halves of this problem:

• Context Saving — Sandbox tools keep raw data out of the context window. 315 KB becomes 5.4 KB. 98% reduction.
• Session Continuity — Every file edit, git operation, task, error, and user decision is tracked in SQLite. When the conversation compacts, context-mode doesn't dump this data back into context — it indexes events into FTS5 and retrieves only what's relevant via BM25 search. The model picks up exactly where you left off. If you don't --continue, previous session data is deleted immediately — a fresh session means a clean slate.

https://github.com/user-attachments/assets/07013dbf-07c0-4ef1-974a-33ea1207637b

Install

Platforms are grouped by install complexity. Hook-capable platforms get automatic routing enforcement. Non-hook platforms need a one-time routing file copy.

Claude Code — plugin marketplace, fully automatic

Prerequisites: Claude Code v1.0.33+ (claude --version). If /plugin is not recognized, update first: brew upgrade claude-code or npm update -g @anthropic-ai/claude-code.

Install:

/plugin marketplace add mksglu/context-mode
/plugin install context-mode@context-mode

Restart Claude Code (or run /reload-plugins).

Verify:

/context-mode:ctx-doctor

All checks should show [x]. The doctor validates runtimes, hooks, FTS5, and plugin registration.

Routing: Automatic. The SessionStart hook injects routing instructions at runtime — no file is written to your project. The plugin registers all hooks (PreToolUse, PostToolUse, PreCompact, SessionStart) and 6 sandbox tools (ctx_batch_execute, ctx_execute, ctx_execute_file, ctx_index, ctx_search, ctx_fetch_and_index).

Slash Command	What it does
/context-mode:ctx-stats	Context savings — per-tool breakdown, tokens consumed, savings ratio.
/context-mode:ctx-doctor	Diagnostics — runtimes, hooks, FTS5, plugin registration, versions.
/context-mode:ctx-upgrade	Pull latest, rebuild, migrate cache, fix hooks.

Note: Slash commands are a Claude Code plugin feature. On other platforms, type ctx stats, ctx doctor, or ctx upgrade in the chat — the model calls the MCP tool automatically. See Utility Commands.

Alternative — MCP-only install (no hooks or slash commands)

claude mcp add context-mode -- npx -y context-mode

This gives you the 6 sandbox tools without automatic routing. The model can still use them — it just won't be nudged to prefer them over raw Bash/Read/WebFetch. Good for trying it out before committing to the full plugin.

Gemini CLI — one config file, hooks included

Prerequisites: Node.js 18+, Gemini CLI installed.

Install:

• Install context-mode globally:

  npm install -g context-mode
  

• Add the following to ~/.gemini/settings.json. This single file registers the MCP server and all four hooks:

  {
    "mcpServers": {
      "context-mode": {
        "command": "context-mode"
      }
    },
    "hooks": {
      "BeforeTool": [
        {
          "matcher": "run_shell_command|read_file|read_many_files|grep_search|search_file_content|web_fetch|activate_skill|mcp__plugin_context-mode",
          "hooks": [{ "type": "command", "command": "context-mode hook gemini-cli beforetool" }]
        }
      ],
      "AfterTool": [
        {
          "matcher": "",
          "hooks": [{ "type": "command", "command": "context-mode hook gemini-cli aftertool" }]
        }
      ],
      "PreCompress": [
        {
          "matcher": "",
          "hooks": [{ "type": "command", "command": "context-mode hook gemini-cli precompress" }]
        }
      ],
      "SessionStart": [
        {
          "matcher": "",
          "hooks": [{ "type": "command", "command": "context-mode hook gemini-cli sessionstart" }]
        }
      ]
    }
  }
  

• Restart Gemini CLI.

Verify:

/mcp list

You should see context-mode: ... - Connected.

Routing: Automatic. The SessionStart hook injects routing instructions at runtime — no GEMINI.md file is written to your project. All four hooks (BeforeTool, AfterTool, PreCompress, SessionStart) handle enforcement programmatically.

Why the BeforeTool matcher? It targets only tools that produce large output (run_shell_command, read_file, read_many_files, grep_search, search_file_content, web_fetch, activate_skill) plus context-mode's own tools (mcp__plugin_context-mode). This avoids unnecessary hook overhead on lightweight tools while intercepting every tool that could flood your context window.

Full config reference: configs/gemini-cli/settings.json

VS Code Copilot — hooks with SessionStart

Prerequisites: Node.js 18+, VS Code with Copilot Chat v0.32+.

Install:

• Install context-mode globally:

  npm install -g context-mode
  

• Create .vscode/mcp.json in your project root:

  {
    "servers": {
      "context-mode": {
        "command": "context-mode"
      }
    }
  }
  

• Create .github/hooks/context-mode.json:

  {
    "hooks": {
      "PreToolUse": [
        { "type": "command", "command": "context-mode hook vscode-copilot pretooluse" }
      ],
      "PostToolUse": [
        { "type": "command", "command": "context-mode hook vscode-copilot posttooluse" }
      ],
      "SessionStart": [
        { "type": "command", "command": "context-mode hook vscode-copilot sessionstart" }
      ]
    }
  }
  

• Restart VS Code.

Verify: Open Copilot Chat and type ctx stats. Context-mode tools should appear and respond.

Routing: Automatic. The SessionStart hook injects routing instructions at runtime — no copilot-instructions.md file is written to your project.

Full hook config including PreCompact: configs/vscode-copilot/hooks.json

Cursor — hooks without SessionStart

Prerequisites: Node.js 18+, Cursor with agent mode.

Install:

• Install context-mode globally:

  npm install -g context-mode
  

• Create .cursor/mcp.json in your project root (or ~/.cursor/mcp.json for global):

  {
    "mcpServers": {
      "context-mode": {
        "command": "context-mode"
      }
    }
  }
  

• Create .cursor/hooks.json (or ~/.cursor/hooks.json for global):

  {
    "version": 1,
    "hooks": {
      "preToolUse": [
        {
          "command": "context-mode hook cursor pretooluse",
          "matcher": "Shell|Read|Grep|WebFetch|Task|MCP:ctx_execute|MCP:ctx_execute_file|MCP:ctx_batch_execute"
        }
      ],
      "postToolUse": [
        {
          "command": "context-mode hook cursor posttooluse"
        }
      ]
    }
  }
  

  The preToolUse matcher is optional — without it, the hook fires on all tools.

• Copy the routing rules file. Cursor lacks a SessionStart hook, so the model needs a rules file for routing awareness:

  mkdir -p .cursor/rules
  cp node_modules/context-mode/configs/cursor/context-mode.mdc .cursor/rules/context-mode.mdc
  

• Restart Cursor or open a new agent session.

Verify: Open Cursor Settings > MCP and confirm "context-mode" shows as connected. In agent chat, type ctx stats.

Routing: Hooks enforce routing programmatically via preToolUse/postToolUse. The .cursor/rules/context-mode.mdc file provides routing instructions at session start since Cursor's sessionStart hook is currently rejected by their validator (forum report). Project .cursor/hooks.json overrides ~/.cursor/hooks.json.

Full configs: configs/cursor/hooks.json | configs/cursor/mcp.json | configs/cursor/context-mode.mdc

OpenCode — TypeScript plugin with hooks

Prerequisites: Node.js 18+, OpenCode installed.

Install:

• Install context-mode globally:

  npm install -g context-mode
  

• Add to opencode.json in your project root (or ~/.config/opencode/opencode.json for global):

  {
    "$schema": "https://opencode.ai/config.json",
    "mcp": {
      "context-mode": {
        "type": "local",
        "command": ["context-mode"]
      }
    },
    "plugin": ["context-mode"]
  }
  

  The mcp entry registers the 6 sandbox tools. The plugin entry enables hooks — OpenCode calls the plugin's TypeScript functions directly before and after each tool execution, blocking dangerous commands and enforcing sandbox routing.

• Restart OpenCode.

Verify: In the OpenCode session, type ctx stats. Context-mode tools should appear and respond.

Routing: Automatic. The plugin intercepts tool calls at runtime via tool.execute.before and tool.execute.after. No routing file is written to your project. The experimental.session.compacting hook builds resume snapshots when the conversation compacts.

Note: OpenCode's SessionStart hook is not yet available (#14808), so startup/resume session restore is not supported. Compaction recovery works fully via the plugin.

Full config: configs/opencode/opencode.json

OpenClaw / Pi Agent — native gateway plugin

Prerequisites: OpenClaw gateway running (>2026.1.29), Node.js 22+.

context-mode runs as a native OpenClaw gateway plugin, targeting Pi Agent sessions (Read/Write/Edit/Bash tools). Unlike other platforms, there's no separate MCP server — the plugin registers directly into the gateway runtime via OpenClaw's plugin API.

Install:

• Clone and install:

  git clone https://github.com/mksglu/context-mode.git
  cd context-mode
  npm run install:openclaw
  

  The installer uses $OPENCLAW_STATE_DIR from your environment (default: /openclaw). To specify a custom path:

  npm run install:openclaw -- /path/to/openclaw-state
  

  Common locations: Docker — /openclaw (the default). Local — ~/.openclaw or wherever you set OPENCLAW_STATE_DIR.

  The installer handles everything: npm install, npm run build, better-sqlite3 native rebuild, extension registration in runtime.json, and gateway restart via SIGUSR1.

• Open a Pi Agent session.

Verify: The plugin registers 8 hooks via api.on() (lifecycle) and api.registerHook() (commands). Type ctx stats to confirm tools are loaded.

Routing: Automatic. All tool interception, session tracking, and compaction recovery hooks activate automatically — no manual hook configuration or routing file needed.

Minimum version: OpenClaw >2026.1.29 — this includes the api.on() lifecycle fix from PR #9761. On older versions, lifecycle hooks silently fail. The adapter falls back to DB snapshot reconstruction (less precise but preserves critical state).

Full documentation: docs/adapters/openclaw.md

Codex CLI — MCP-only, no hooks

Prerequisites: Node.js 18+, Codex CLI installed.

Install:

• Install context-mode globally:

  npm install -g context-mode
  

• Add to ~/.codex/config.toml:

  [mcp_servers.context-mode]
  command = "context-mode"
  

• Copy routing instructions (Codex CLI has no hook support):

  cp node_modules/context-mode/configs/codex/AGENTS.md ./AGENTS.md
  

  For global use: cp node_modules/context-mode/configs/codex/AGENTS.md ~/.codex/AGENTS.md. Global applies to all projects. If both exist, Codex CLI merges them.

• Restart Codex CLI.

Verify: Start a session and type ctx stats. Context-mode tools should appear and respond.

Routing: Manual. The AGENTS.md file is the only enforcement method (~60% compliance). There is no programmatic interception — the model can run raw curl, read large files, or bypass sandbox tools at any time. Hook support PRs #2904 and #9796 were closed without merge.

Antigravity — MCP-only, no hooks

Prerequisites: Node.js 18+, Antigravity installed.

Install:

• Install context-mode globally:

  npm install -g context-mode
  

• Add to ~/.gemini/antigravity/mcp_config.json:

  {
    "mcpServers": {
      "context-mode": {
        "command": "context-mode"
      }
    }
  }
  

• Copy routing instructions (Antigravity has no hook support):

  cp node_modules/context-mode/configs/antigravity/GEMINI.md ./GEMINI.md
  

• Restart Antigravity.

Verify: In an Antigravity session, type ctx stats. Context-mode tools should appear and respond.

Routing: Manual. The GEMINI.md file is the only enforcement method (~60% compliance). There is no programmatic interception. Auto-detected via MCP protocol handshake (clientInfo.name) — no manual platform configuration needed.

Full configs: configs/antigravity/mcp_config.json | configs/antigravity/GEMINI.md

Kiro — hooks with steering file

Prerequisites: Node.js 18+, Kiro with MCP enabled (Settings > search "MCP").

Install:

• Install context-mode globally:

  npm install -g context-mode
  

• Add to .kiro/settings/mcp.json in your project (or ~/.kiro/settings/mcp.json for global):

  {
    "mcpServers": {
      "context-mode": {
        "command": "context-mode"
      }
    }
  }
  

• Create .kiro/hooks/context-mode.json:

  {
    "name": "context-mode",
    "description": "Context-mode hooks for context window protection",
    "hooks": {
      "preToolUse": [
        { "matcher": "*", "command": "context-mode hook kiro pretooluse" }
      ],
      "postToolUse": [
        { "matcher": "*", "command": "context-mode hook kiro posttooluse" }
      ]
    }
  }
  

• Copy routing instructions. Kiro's agentSpawn (SessionStart) is not yet implemented, so the model needs a routing file at session start:

  cp node_modules/context-mode/configs/kiro/KIRO.md ./KIRO.md
  

• Restart Kiro.

Verify: Open the Kiro panel > MCP Servers tab and confirm "context-mode" shows a green status indicator. In chat, type ctx stats.

Routing: Hooks enforce routing programmatically via preToolUse/postToolUse. The KIRO.md file provides routing instructions since agentSpawn (SessionStart equivalent) is not yet wired. Tool names appear as @context-mode/ctx_batch_execute, @context-mode/ctx_search, etc. Auto-detected via MCP protocol handshake.

Full configs: configs/kiro/mcp.json | configs/kiro/agent.json | configs/kiro/KIRO.md

Zed — MCP-only, no hooks

Prerequisites: Node.js 18+, Zed installed.

Install:

• Install context-mode globally:

  npm install -g context-mode
  

• Add to ~/.config/zed/settings.json (Windows: %APPDATA%\Zed\settings.json):

  {
    "context_servers": {
      "context-mode": {
        "command": {
          "path": "context-mode"
        }
      }
    }
  }
  

  Note: Zed uses "context_servers" and "command": { "path": "..." } syntax, not "mcpServers" or "command": "..." like other platforms.

• Copy routing instructions (Zed has no hook support):

  cp node_modules/context-mode/configs/zed/AGENTS.md ./AGENTS.md
  

• Restart Zed (or save settings.json — Zed auto-restarts context servers on config change).

Verify: Open the Agent Panel (Cmd+Shift+A), go to settings, and check the indicator dot next to "context-mode" — green means active. Type ctx stats in the agent chat.

Routing: Manual. The AGENTS.md file is the only enforcement method (~60% compliance). There is no programmatic interception. Tool names appear as mcp:context-mode:ctx_batch_execute, mcp:context-mode:ctx_search, etc. Auto-detected via MCP protocol handshake.

Pi Coding Agent — extension with full hook support

Prerequisites: Node.js 18+, Pi Coding Agent installed.

Install:

• Clone the extension:

  git clone https://github.com/mksglu/context-mode.git ~/.pi/extensions/context-mode
  cd ~/.pi/extensions/context-mode
  npm install
  

• Add to ~/.pi/settings/mcp.json (or .pi/settings/mcp.json for project-level):

  {
    "mcpServers": {
      "context-mode": {
        "command": "node",
        "args": ["~/.pi/extensions/context-mode/node_modules/context-mode/start.mjs"]
      }
    }
  }
  

• Restart Pi.

Verify: In a Pi session, type ctx stats. Context-mode tools should appear and respond.

Routing: Automatic. The extension registers all key lifecycle events (tool_call, tool_result, session_start, session_before_compact), providing full session continuity and routing enforcement.

Build Prerequisites ^{(CentOS, RHEL, Alpine)}

Context Mode uses better-sqlite3 on Node.js, which ships prebuilt native binaries for most platforms. On glibc >= 2.31 systems (Ubuntu 20.04+, Debian 11+, Fedora 34+, macOS, Windows), npm install works without any build tools.

Bun users: No native compilation needed. Context Mode automatically detects Bun and uses the built-in bun:sqlite module via a compatibility adapter. better-sqlite3 and all its build dependencies are skipped entirely.

On older glibc systems (CentOS 7/8, RHEL 8, Debian 10), prebuilt binaries don't load and better-sqlite3 automatically falls back to compiling from source via prebuild-install || node-gyp rebuild --release. This requires a C++20 compiler (GCC 10+), Make, and Python with setuptools.

CentOS 8 / RHEL 8 (glibc 2.28):

dnf install -y gcc-toolset-10-gcc gcc-toolset-10-gcc-c++ make python3 python3-setuptools
scl enable gcc-toolset-10 'npm install -g context-mode'

CentOS 7 / RHEL 7 (glibc 2.17):

yum install -y centos-release-scl
yum install -y devtoolset-10-gcc devtoolset-10-gcc-c++ make python3
pip3 install setuptools
scl enable devtoolset-10 'npm install -g context-mode'

Alpine Linux:

Alpine prebuilt binaries (musl) are available in better-sqlite3 v12.8.0+. With the ^12.6.2 dependency range, npm install resolves to the latest 12.x and works without build tools on Alpine. If you pin an older version:

apk add build-base python3 py3-setuptools
npm install -g context-mode

Tools

Tool	What it does	Context saved
ctx_batch_execute	Run multiple commands + search multiple queries in ONE call.	986 KB → 62 KB
ctx_execute	Run code in 11 languages. Only stdout enters context.	56 KB → 299 B
ctx_execute_file	Process files in sandbox. Raw content never leaves.	45 KB → 155 B
ctx_index	Chunk markdown into FTS5 with BM25 ranking.	60 KB → 40 B
ctx_search	Query indexed content with multiple queries in one call.	On-demand retrieval
ctx_fetch_and_index	Fetch URL, detect content type (HTML/JSON/text), chunk and index.	60 KB → 40 B
ctx_stats	Show context savings, call counts, and session statistics.	—
ctx_doctor	Diagnose installation: runtimes, hooks, FTS5, versions.	—
ctx_upgrade	Upgrade to latest version from GitHub, rebuild, reconfigure hooks.	—

How the Sandbox Works

Each ctx_execute call spawns an isolated subprocess with its own process boundary. Scripts can't access each other's memory or state. The subprocess runs your code, captures stdout, and only that stdout enters the conversation context. The raw data — log files, API responses, snapshots — never leaves the sandbox.

Eleven language runtimes are available: JavaScript, TypeScript, Python, Shell, Ruby, Go, Rust, PHP, Perl, R, and Elixir. Bun is auto-detected for 3-5x faster JS/TS execution.

Authenticated CLIs work through credential passthrough — gh, aws, gcloud, kubectl, docker inherit environment variables and config paths without exposing them to the conversation.

When output exceeds 5 KB and an intent is provided, Context Mode switches to intent-driven filtering: it indexes the full output into the knowledge base, searches for sections matching your intent, and returns only the relevant matches with a vocabulary of searchable terms for follow-up queries.

How the Knowledge Base Works

The ctx_index tool chunks markdown content by headings while keeping code blocks intact, then stores them in a SQLite FTS5 (Full-Text Search 5) virtual table. Search uses BM25 ranking — a probabilistic relevance algorithm that scores documents based on term frequency, inverse document frequency, and document length normalization. Porter stemming is applied at index time so "running", "runs", and "ran" match the same stem. Titles and headings are weighted 5x in BM25 scoring for precise navigational queries.

When you call ctx_search, it returns relevant content snippets focused around matching query terms — not full documents, not approximations, the actual indexed content with smart extraction around what you're looking for. ctx_fetch_and_index extends this to URLs: fetch, convert HTML to markdown, chunk, index. The raw page never enters context. Use the contentType parameter to filter results by type (e.g. code or prose).

Ranking: Reciprocal Rank Fusion

Search runs two parallel strategies and merges them with Reciprocal Rank Fusion (RRF):

• Porter stemming — FTS5 MATCH with porter tokenizer. "caching" matches "cached", "caches", "cach".
• Trigram substring — FTS5 trigram tokenizer matches partial strings. "useEff" finds "useEffect", "authenticat" finds "authentication".

RRF merges both ranked lists into a single result set, so a document that ranks well in both strategies surfaces higher than one that ranks well in only one. This replaces the old cascading fallback approach where trigram results were only used if porter returned nothing.

Proximity Reranking

Multi-term queries get an additional reranking pass. Results where query terms appear close together are boosted — "session continuity" ranks passages with adjacent terms higher than pages where "session" and "continuity" appear paragraphs apart.

Fuzzy Correction

Levenshtein distance corrects typos before re-searching. "kuberntes" becomes "kubernetes", "autentication" becomes "authentication".

Smart Snippets

Search results use intelligent extraction instead of truncation. Instead of returning the first N characters (which might miss the important part), Context Mode finds where your query terms appear in the content and returns windows around those matches.

Progressive Throttling

• Calls 1-3: Normal results (2 per query)
• Calls 4-8: Reduced results (1 per query) + warning
• Calls 9+: Blocked — redirects to ctx_batch_execute

Session Continuity

When the context window fills up, the agent compacts the conversation — dropping older messages to make room. Without session tracking, the model forgets which files it was editing, what tasks are in progress, what errors were resolved, and what you last asked for.

Context Mode captures every meaningful event during your session and persists them in a per-project SQLite database. When the conversation compacts (or you resume with --continue), your working state is rebuilt automatically — the model continues from your last prompt without asking you to repeat anything.

Session continuity requires 4 hooks working together:

Hook	Role	Claude Code	Gemini CLI	VS Code Copilot	Cursor	OpenCode	OpenClaw	Codex CLI	Antigravity	Kiro	Zed	Pi
PostToolUse	Captures events after each tool call	Yes	Yes	Yes	Yes	Plugin	Plugin	--	--	Yes	--	✓ (via tool_result event)
UserPromptSubmit	Captures user decisions and corrections	Yes	--	--	--	--	--	--	--	--	--	--
PreCompact	Builds snapshot before compaction	Yes	Yes	Yes	--	Plugin	Plugin	--	--	--	--	✓ (via session_before_compact)
SessionStart	Restores state after compaction or resume	Yes	Yes	Yes	--	--	Plugin	--	--	--	--	✓ (via session_start event)
	Session completeness	Full	High	High	Partial	High	High	--	--	Partial	--	High

Note: Full session continuity (capture + snapshot + restore) works on Claude Code, Gemini CLI, VS Code Copilot, and OpenCode. Cursor captures tool events via preToolUse/postToolUse, but sessionStart is currently rejected by Cursor's validator (forum report), so session restore after compaction is not available yet. OpenCode uses the experimental.session.compacting plugin hook for compaction recovery, but SessionStart is not yet available (#14808), so startup/resume is not supported. OpenClaw uses native gateway plugin hooks (api.on()) for full session continuity. Pi Coding Agent provides high session continuity via extension hooks (tool_call, tool_result, session_start, session_before_compact). Codex CLI, Antigravity, Kiro, and Zed have no hook support in the current release, so session tracking is not available.

What gets captured

Every tool call passes through hooks that extract structured events:

Category	Events	Priority	Captured By
Files	read, edit, write, glob, grep	Critical (P1)	PostToolUse
Tasks	create, update, complete	Critical (P1)	PostToolUse
Rules	CLAUDE.md / GEMINI.md / AGENTS.md paths + content	Critical (P1)	SessionStart
Decisions	User corrections, preferences ("use X instead", "don't do Y")	High (P2)	UserPromptSubmit
Git	checkout, commit, merge, rebase, stash, push, pull, diff, status	High (P2)	PostToolUse
Errors	Tool failures, non-zero exit codes	High (P2)	PostToolUse
Environment	cwd changes, venv, nvm, conda, package installs	High (P2)	PostToolUse
MCP Tools	All mcp__* tool calls with usage counts	Normal (P3)	PostToolUse
Subagents	Agent tool invocations	Normal (P3)	PostToolUse
Skills	Slash command invocations	Normal (P3)	PostToolUse
Role	Persona / behavioral directives ("act as senior engineer")	Normal (P3)	UserPromptSubmit
Intent	Session mode classification (investigate, implement, debug)	Low (P4)	UserPromptSubmit
Data	Large user-pasted data references (>1 KB)	Low (P4)	UserPromptSubmit
User Prompts	Every user message (for last-prompt restore)	Critical (P1)	UserPromptSubmit

How sessions survive compaction

PreCompact fires
  → Read all session events from SQLite
  → Build priority-tiered XML snapshot (≤2 KB)
  → Store snapshot in session_resume table

SessionStart fires (source: "compact")
  → Retrieve stored snapshot
  → Write structured events file → auto-indexed into FTS5
  → Build Session Guide with 15 categories
  → Inject <session_knowledge> directive into context
  → Model continues from last user prompt with full working state

The snapshot is built in priority tiers — if the 2 KB budget is tight, lower-priority events (intent, MCP tool counts) are dropped first while critical state (active files, tasks, rules, decisions) is always preserved.

After compaction, the model receives a Session Guide — a structured narrative with actionable sections:

• Last Request — user's last prompt, so the model continues without asking "what were we doing?"
• Tasks — checkbox format with completion status ([x] completed, [ ] pending)
• Key Decisions — user corrections and preferences ("use X instead", "don't do Y")
• Files Modified — all files touched during the session
• Unresolved Errors — errors that haven't been fixed
• Git — operations performed (checkout, commit, push, status)
• Project Rules — CLAUDE.md / GEMINI.md / AGENTS.md paths
• MCP Tools Used — tool names with call counts
• Subagent Tasks — delegated work summaries
• Skills Used — slash commands invoked
• Environment — working directory, env variables
• Data References — large data pasted during the session
• Session Intent — mode classification (implement, investigate, review, discuss)
• User Role — behavioral directives set during the session

Detailed event data is also indexed into FTS5 for on-demand retrieval via search().

Per-platform details

Claude Code — Full session support. All 5 hook types fire, capturing tool events, user decisions, building compaction snapshots, and restoring state after compaction or --continue.

Gemini CLI — High coverage. PostToolUse (AfterTool), PreCompact (PreCompress), and SessionStart all fire. Missing UserPromptSubmit, so user decisions and corrections aren't captured — but file edits, git ops, errors, and tasks are fully tracked.

VS Code Copilot — High coverage. Same as Gemini CLI — PostToolUse, PreCompact, and SessionStart all fire. User decisions aren't captured but all tool-level events are.

Cursor — Partial coverage. Native preToolUse and postToolUse hooks capture tool events. sessionStart is documented by Cursor but currently rejected by their validator, so session restore is not available. Routing instructions are delivered via MCP server startup instead.

OpenCode — Partial. The TypeScript plugin captures PostToolUse events via tool.execute.after, but SessionStart is not yet available (#14808). Events are stored but not automatically restored after compaction.

OpenClaw / Pi Agent — High coverage. All tool lifecycle hooks (after_tool_call, before_compaction, session_start) fire via the native gateway plugin. User decisions aren't captured but file edits, git ops, errors, and tasks are fully tracked. Falls back to DB snapshot reconstruction if compaction hooks fail on older gateway versions. See docs/adapters/openclaw.md.

Codex CLI — No session support. No hooks means no event capture. Each compaction or new session starts fresh. Requires manually copying AGENTS.md to your project root.

Antigravity — No session support. Same as Codex CLI — no hooks, no event capture. Requires manually copying GEMINI.md to your project root. Auto-detected via MCP protocol handshake (clientInfo.name).

Zed — No session support. Same as Codex CLI — no hooks, no event capture. Requires manually copying AGENTS.md to your project root. Auto-detected via MCP protocol handshake (clientInfo.name).

Kiro — Partial coverage. Native preToolUse and postToolUse hooks capture tool events and enforce sandbox routing. agentSpawn (the Kiro equivalent of SessionStart) is not yet implemented, so session restore after compaction is not available. Requires manually copying KIRO.md to your project root. Auto-detected via MCP protocol handshake (clientInfo.name).

Pi Coding Agent — High coverage. The extension registers all key lifecycle events: tool_call (PreToolUse), tool_result (PostToolUse), session_start (SessionStart), and session_before_compact (PreCompact). File edits, git ops, errors, and tasks are fully tracked. Session restore after compaction works via the extension's event hooks.

Platform Compatibility

Feature	Claude Code	Gemini CLI	VS Code Copilot	Cursor	OpenCode	OpenClaw	Codex CLI	Antigravity	Kiro	Zed	Pi
MCP Server	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
PreToolUse Hook	Yes	Yes	Yes	Yes	Plugin	Plugin	--	--	Yes	--	Yes (extension)
PostToolUse Hook	Yes	Yes	Yes	Yes	Plugin	Plugin	--	--	Yes	--	Yes (extension)
SessionStart Hook	Yes	Yes	Yes	--	--	Plugin	--	--	--	--	Yes (extension)
PreCompact Hook	Yes	Yes	Yes	--	Plugin	Plugin	--	--	--	--	Yes (extension)
Can Modify Args	Yes	Yes	Yes	Yes	Plugin	Plugin	--	--	--	--	Yes (extension)
Can Block Tools	Yes	Yes	Yes	Yes	Plugin	Plugin	--	--	Yes	--	Yes (extension)
Utility Commands (ctx)	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes (/ctx-stats, /ctx-doctor)
Slash Commands	Yes	--	--	--	--	--	--	--	--	--	--
Plugin Marketplace	Yes	--	--	--	--	--	--	--	--	--	--

OpenCode uses a TypeScript plugin paradigm — hooks run as in-process functions via tool.execute.before, tool.execute.after, and experimental.session.compacting, providing the same routing enforcement and session continuity as shell-based hooks. SessionStart is not yet available (#14808), but compaction recovery works via the plugin's compacting hook.

OpenClaw runs context-mode as a native gateway plugin targeting Pi Agent sessions. Hooks register via api.on() (tool/lifecycle) and api.registerHook() (commands). All tool interception and compaction hooks are supported. See docs/adapters/openclaw.md.

Codex CLI, Antigravity, and Zed do not support hooks. They rely solely on manually-copied routing instruction files (AGENTS.md / GEMINI.md) for enforcement (~60% compliance). See each platform's install section for copy instructions. Antigravity and Zed are auto-detected via MCP protocol handshake — no manual platform configuration needed.

Kiro supports native preToolUse and postToolUse hooks for routing enforcement and tool event capture. agentSpawn (SessionStart equivalent) and stop are not yet wired. Requires manually copying KIRO.md to your project root. Kiro is auto-detected via MCP protocol handshake (clientInfo.name).

Pi Coding Agent runs context-mode as an extension with full hook support. The extension registers tool_call, tool_result, session_start, and session_before_compact events, providing high session continuity coverage. The MCP server provides the 6 sandbox tools.

Routing Enforcement

Hooks intercept tool calls programmatically — they can block dangerous commands and redirect them to the sandbox before execution. Instruction files guide the model via prompt instructions but cannot block anything. Always enable hooks where supported.

Note: Routing instruction files were previously auto-written to project directories on first session start. This was disabled to prevent git tree pollution (#158, #164). Hook-capable platforms (Claude Code, Gemini CLI, VS Code Copilot, OpenCode, OpenClaw) inject routing via hooks and need no file. Non-hook platforms (Codex, Zed, Cursor, Kiro, Antigravity) require a one-time manual copy — see each platform's install section.

Platform	Hooks	Instruction File	With Hooks	Without Hooks
Claude Code	Yes (auto)	CLAUDE.md	~98% saved	~60% saved
Gemini CLI	Yes	GEMINI.md	~98% saved	~60% saved
VS Code Copilot	Yes	copilot-instructions.md	~98% saved	~60% saved
Cursor	Yes	context-mode.mdc	~98% saved	~60% saved
OpenCode	Plugin	AGENTS.md	~98% saved	~60% saved
OpenClaw	Plugin	AGENTS.md	~98% saved	~60% saved
Codex CLI	--	AGENTS.md	--	~60% saved
Antigravity	--	GEMINI.md	--	~60% saved
Kiro	Yes	KIRO.md	~98% saved	~60% saved
Zed	--	AGENTS.md	--	~60% saved
Pi	✓	AGENTS.md	~98% saved	~60% saved

Without hooks, one unrouted curl or Playwright snapshot can dump 56 KB into context — wiping out an entire session's worth of savings.

See docs/platform-support.md for the full capability comparison.

Utility Commands

Inside any AI session — just type the command. The LLM calls the MCP tool automatically:

ctx stats       → context savings, call counts, session report
ctx doctor      → diagnose runtimes, hooks, FTS5, versions
ctx upgrade     → update from GitHub, rebuild, reconfigure hooks

From your terminal — run directly without an AI session:

context-mode doctor
context-mode upgrade

Works on all platforms. On Claude Code, slash commands (/ctx-stats, /ctx-doctor, /ctx-upgrade) are also available.

Benchmarks

Scenario	Raw	Context	Saved
Playwright snapshot	56.2 KB	299 B	99%
GitHub Issues (20)	58.9 KB	1.1 KB	98%
Access log (500 requests)	45.1 KB	155 B	100%
Context7 React docs	5.9 KB	261 B	96%
Analytics CSV (500 rows)	85.5 KB	222 B	100%
Git log (153 commits)	11.6 KB	107 B	99%
Test output (30 suites)	6.0 KB	337 B	95%
Repo research (subagent)	986 KB	62 KB	94%

Over a full session: 315 KB of raw output becomes 5.4 KB. Session time extends from ~30 minutes to ~3 hours.

Full benchmark data with 21 scenarios →

Try It

These prompts work out of the box. Run /context-mode:ctx-stats after each to see the savings.

Deep repo research — 5 calls, 62 KB context (raw: 986 KB, 94% saved)

Research https://github.com/modelcontextprotocol/servers — architecture, tech stack,
top contributors, open issues, and recent activity. Then run /context-mode:ctx-stats.

Git history analysis — 1 call, 5.6 KB context

Clone https://github.com/facebook/react and analyze the last 500 commits:
top contributors, commit frequency by month, and most changed files.
Then run /context-mode:ctx-stats.

Web scraping — 1 call, 3.2 KB context

Fetch the Hacker News front page, extract all posts with titles, scores,
and domains. Group by domain. Then run /context-mode:ctx-stats.

Large JSON API — 7.5 MB raw → 0.9 KB context (99% saved)

Create a local server that returns a 7.5 MB JSON with 20,000 records and a secret
hidden at index 13000. Fetch the endpoint, find the hidden record, and show me
exactly what's in it. Then run /context-mode:ctx-stats.

Documentation search — 2 calls, 1.8 KB context

Fetch the React useEffect docs, index them, and find the cleanup pattern
with code examples. Then run /context-mode:ctx-stats.

Session continuity — compaction recovery with full state

Start a multi-step task: "Create a REST API with Express — add routes, tests,
and error handling." After 20+ tool calls, type: ctx stats to see the session
event count. When context compacts, the model continues from your last prompt
with tasks, files, and decisions intact — no re-prompting needed.

Security

Context Mode enforces the same permission rules you already use — but extends them to the MCP sandbox. If you block sudo, it's also blocked inside ctx_execute, ctx_execute_file, and ctx_batch_execute.

Zero setup required. If you haven't configured any permissions, nothing changes. This only activates when you add rules.

{
  "permissions": {
    "deny": [
      "Bash(sudo *)",
      "Bash(rm -rf /*)",
      "Read(.env)",
      "Read(**/.env*)"
    ],
    "allow": [
      "Bash(git:*)",
      "Bash(npm:*)"
    ]
  }
}

Add this to your project's .claude/settings.json (or ~/.claude/settings.json for global rules). All platforms read security policies from Claude Code's settings format — even on Gemini CLI, VS Code Copilot, and OpenCode. Codex CLI has no hook support, so security enforcement is not available.

The pattern is Tool(what to match) where * means "anything".

Commands chained with &&, ;, or | are split — each part is checked separately. echo hello && sudo rm -rf /tmp is blocked because the sudo part matches the deny rule.

deny always wins over allow. More specific (project-level) rules override global ones.

Contributing

See CONTRIBUTING.md for the development workflow and TDD guidelines.

git clone https://github.com/mksglu/context-mode.git
cd context-mode && npm install && npm test

License

Licensed under Elastic License 2.0 (source-available). You can use it, fork it, modify it, and distribute it. Two things you can't do: offer it as a hosted/managed service, or remove the licensing notices. We chose ELv2 over MIT because MIT permits repackaging the code as a competing closed-source SaaS — ELv2 prevents that while keeping the source available to everyone.