Context Mode Output Sandbox
mksglu/context-mode
Routes large command, file, API and browser output through context-mode tools so only the needed result enters the agent's context, instead of dumping it via Bash.
Lossless session context compression for token efficiency. An agent skill from vibeeval/vibecosystem.
Install Session Compression
$ npx skills add vibeeval/vibecosystem --skill session-compression -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install vibeeval/vibecosystem session-compression --agent claude-codeProject scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).
$ git clone --depth 1 https://github.com/vibeeval/vibecosystem.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/session-compression .claude/skills/session-compression && rm -rf skills-srcUse ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.
Claude Code skills documentation · loads skills from .claude/skills/
Install the "session-compression" agent skill from https://github.com/vibeeval/vibecosystem/tree/main/skills/session-compression into .claude/skills/session-compression/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "session-compression", then confirm the skill loads.Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$skill-installer install https://github.com/vibeeval/vibecosystem/tree/main/skills/session-compressionType this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.
$ npx skills add vibeeval/vibecosystem --skill session-compression -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install vibeeval/vibecosystem session-compression --agent codexProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/vibeeval/vibecosystem.git skills-src && mkdir -p .agents/skills && cp -r skills-src/skills/session-compression .agents/skills/session-compression && rm -rf skills-srcUse ~/.agents/skills/ instead of .agents/skills for a personal install.
Codex skills documentation · loads skills from .agents/skills/
Install the "session-compression" agent skill from https://github.com/vibeeval/vibecosystem/tree/main/skills/session-compression into .agents/skills/session-compression/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "session-compression", then confirm the skill loads.Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add vibeeval/vibecosystem --skill session-compression -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install vibeeval/vibecosystem session-compression --agent cursorProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/vibeeval/vibecosystem.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/skills/session-compression .cursor/skills/session-compression && rm -rf skills-srcUse ~/.cursor/skills/ instead of .cursor/skills for a personal install.
Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/
Install the "session-compression" agent skill from https://github.com/vibeeval/vibecosystem/tree/main/skills/session-compression into .cursor/skills/session-compression/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "session-compression", then confirm the skill loads.Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gemini skills install https://github.com/vibeeval/vibecosystem.git --path skills/session-compression--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.
$ npx skills add vibeeval/vibecosystem --skill session-compression -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install vibeeval/vibecosystem session-compression --agent gemini-cliProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/vibeeval/vibecosystem.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/skills/session-compression .gemini/skills/session-compression && rm -rf skills-srcUse ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.
Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/
Install the "session-compression" agent skill from https://github.com/vibeeval/vibecosystem/tree/main/skills/session-compression into .gemini/skills/session-compression/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "session-compression", then confirm the skill loads.Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gh skill install vibeeval/vibecosystem session-compressionInstalls for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).
$ npx skills add vibeeval/vibecosystem --skill session-compression -a github-copilotProject install goes to .agents/skills/; add -g for ~/.copilot/skills/.
$ git clone --depth 1 https://github.com/vibeeval/vibecosystem.git skills-src && mkdir -p .github/skills && cp -r skills-src/skills/session-compression .github/skills/session-compression && rm -rf skills-srcUse ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.
GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/
Install the "session-compression" agent skill from https://github.com/vibeeval/vibecosystem/tree/main/skills/session-compression into .github/skills/session-compression/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "session-compression", then confirm the skill loads.GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add vibeeval/vibecosystem --skill session-compression -a opencodeOpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.
$ gh skill install vibeeval/vibecosystem session-compression --agent opencodeProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/vibeeval/vibecosystem.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/skills/session-compression .opencode/skills/session-compression && rm -rf skills-srcUse ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.
OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/
Install the "session-compression" agent skill from https://github.com/vibeeval/vibecosystem/tree/main/skills/session-compression into .opencode/skills/session-compression/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "session-compression", then confirm the skill loads.OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
Facts
- Skill name
session-compression- GitHub stars
- 531
- Token cost
- ~835 tokens
- SKILL.md length
- 259 words
- Files
- 1
- Skills in repo
- 144
- Repo updated
- First seen
- Licence
- MIT
At a glance
Lossless session context compression for token efficiency. An agent skill from vibeeval/vibecosystem.
- Works in 4 steps: Pre-compact: Before context window… → Session handoff: When switching between… → Agent delegation: When handing complex… → …
- Tasks that involve Context engineering
- SKILL.md covers Why Compress, Compression Format, When to Compress and Compression Rules, plus 1 more section
- Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
What it does
Session Compression is an agent skill from vibeeval/vibecosystem. Lossless session context compression for token efficiency. Extracts entities, decisions, and state into compact format before context window fills. 10-30x reduction in context size while preserving all actionable information.
Its SKILL.md is about 840 tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.
It sits in Agent Workflows, covering Context engineering and LLM cost and token optimization. The repository describes itself as: AI software team for Claude Code - 138 agents, 295 skills, 73 hooks. Self-learning, multi-agent swarm, autonomous skill evolution. The licence is MIT.
When your agent uses it
- Tasks that involve Context engineering
- Tasks that involve LLM cost and token optimization
Example prompts
- “/session-compression”
Workflow steps
4 steps, taken from the first numbered list in SKILL.md.
- Pre-compact: Before context window compression (auto via hook)
- Session handoff: When switching between sessions on same project
- Agent delegation: When handing complex task to another agent
- Milestone reached: After completing a significant piece of work
What it can do on your machine
Read from SKILL.md and the folder at commit 3b763b1. It shows what the files ask for, not the result of running them.
Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
No scripts in the folder and no shell commands in SKILL.md (its code samples are markdown).
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md.
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.
Context cost
Session Compression loads about 835 tokens when it runs. Until then it costs about 61 tokens; SKILL.md has 259 words of instructions outside code blocks.
Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.
Safety
Auto-check passed
The automated check found no risky patterns in SKILL.md.
Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.
SKILL.md
The full file from vibeeval/vibecosystem at commit 3b763b1, republished under its MIT licence (© vibeeval). 259 words, ~835 tokens.
Download SKILL.mdSave it as
.claude/skills/session-compression/SKILL.md (or your agent's skills folder).- name
- session-compression
- description
- Lossless session context compression for token efficiency. Extracts entities, decisions, and state into compact format before context window fills. 10-30x reduction in context size while preserving all actionable information.
Session Compression
Compress session context without losing actionable information. Use before context window fills up or when handing off between sessions.
Why Compress
| Metric | Raw Context | Compressed |
|---|---|---|
| Token count | ~50K | ~3-5K |
| Decision count | Scattered | Indexed |
| File references | Buried in prose | Listed |
| Error history | Verbose stack traces | Root cause + fix |
| Reduction | 1x | 10-30x |
Compression Format
ACDE Format (Actions, Context, Decisions, Entities)
## A: Actions Completed
- [x] Refactored auth middleware (auth.ts, middleware.ts)
- [x] Added rate limiting (api/limiter.ts)
- [ ] Pending: Write tests for rate limiter
## C: Context
- Project: my-app (Next.js 16, TypeScript)
- Branch: feat/auth-refactor (3 commits ahead of main)
- Blockers: None
## D: Decisions
- D1: JWT over sessions (stateless, mobile-friendly)
- D2: 100 req/min rate limit (based on load test)
- D3: Rejected Redis session store (overkill for current scale)
## E: Entities
- Files: auth.ts:42, middleware.ts:15, api/limiter.ts (new)
- Deps: jsonwebtoken@9.0.0, express-rate-limit@7.0.0
- APIs: POST /auth/login, POST /auth/refresh, GET /auth/meWhen to Compress
- Pre-compact: Before context window compression (auto via hook)
- Session handoff: When switching between sessions on same project
- Agent delegation: When handing complex task to another agent
- Milestone reached: After completing a significant piece of work
Compression Rules
What to Keep (Lossless)
- All decisions with reasoning (D1, D2, D3...)
- File paths and line numbers of changes
- Unresolved blockers or pending items
- Error root causes (not full stack traces)
- External constraints
What to Drop (Safe)
- Exploratory reads that didn't lead anywhere
- Redundant confirmations ("yes that looks good")
- Intermediate debugging steps (keep only root cause)
- Tool output that was just for verification
- Repeated context that's already in CLAUDE.md
Entity Coding
Replace verbose references with short codes:
"the authentication middleware in src/middleware/auth.ts" -> "auth.ts"
"the user requested that we use JWT tokens" -> "D1: JWT"
"the PostgreSQL database running on port 5432" -> "pg:5432"Integration
Pre-Compact Hook
The session-compressor hook automatically generates ACDE format before context compression:
- Scans recent tool calls for file paths -> E section
- Extracts decisions from conversation -> D section
- Lists completed/pending tasks -> A section
- Summarizes project state -> C section
With Memory Palace
Compressed sessions feed into the palace:
- Decisions -> stored as drawers in appropriate rooms
- Entities -> indexed for cross-session search
- Actions -> tracked in thoughts/PROGRESS.md
With Compass Agent
Compass uses ACDE format for "where were we?" recovery:
Last session compressed:
A: 3 done, 1 pending (rate limiter tests)
D: JWT auth, 100rpm limit
E: auth.ts, middleware.ts, limiter.ts© vibeeval, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file
Files
Just SKILL.md in skills/session-compression of vibeeval/vibecosystem.
Open the folder on GitHubat commit 3b763b1
Compare with similar skills
Session Compression next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.
| Skill | Stars | Used in | Tokens | Auto-check | Licence | Repo updated |
|---|---|---|---|---|---|---|
| Session Compression this skillvibeeval/vibecosystem | 531 | — | ~835 | Automated safety check: Pass | MIT | |
| Context Mode Output Sandboxmksglu/context-mode | 26k | — | ~4.1k | Automated safety check: Pass | Custom licence | |
| Context Mode for Antigravity CLImksglu/context-mode | 26k | — | ~850 | Automated safety check: Pass | Custom licence | |
| Context Fundamentalsguanyang/open-agent-hub | 973 | 2 repos | ~4.2k | Automated safety check: Pass | MIT | |
| Context DoctorjzOcb/context-doctor | 119 | — | ~642 | Automated safety check: Pass | MIT | |
| Code Context Slicingtrailofbits/skills | 7.4k | — | ~2.1k | Automated safety check: Pass | CC-BY-SA-4.0 |
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Related
Categories
Questions about Session Compression
What does Session Compression do?
Lossless session context compression for token efficiency. An agent skill from vibeeval/vibecosystem. Session Compression is an agent skill from vibeeval/vibecosystem. Lossless session context compression for token efficiency.
When should I use Session Compression?
Session Compression fits situations like: tasks that involve Context engineering; tasks that involve LLM cost and token optimization.
How do I install Session Compression in Claude Code?
Run `npx skills add vibeeval/vibecosystem --skill session-compression -a claude-code`. Or copy the skill folder (skills/session-compression in vibeeval/vibecosystem) into .claude/skills/session-compression in your project. Claude Code loads it when a task matches its description.
How do I install Session Compression in Codex?
Run `npx skills add vibeeval/vibecosystem --skill session-compression -a codex`. Or copy the skill folder (skills/session-compression in vibeeval/vibecosystem) into .agents/skills/session-compression in your project. Codex loads it when a task matches its description.
Can I use Session Compression in Cursor, Gemini CLI or GitHub Copilot?
Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add vibeeval/vibecosystem --skill session-compression -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/session-compression, .gemini/skills/session-compression, .github/skills/session-compression and .opencode/skills/session-compression in your project.
What does Session Compression need to run?
SKILL.md names no scripts, command-line tools or credentials: Session Compression is instructions for the agent only.
Does Session Compression access the network?
SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.
Is Session Compression safe to install?
Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.
What licence does Session Compression use?
Session Compression is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.
How many tokens does Session Compression use?
About 835 tokens (SKILL.md is roughly 3.3k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.
What are the alternatives to Session Compression?
Skills that share tags, products or a category with Session Compression: Context Mode Output Sandbox (mksglu/context-mode, 26k stars), Context Mode for Antigravity CLI (mksglu/context-mode, 26k stars), Context Fundamentals (guanyang/open-agent-hub, 973 stars) and Context Doctor (jzOcb/context-doctor, 119 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains Session Compression?
vibeeval (a GitHub user) maintains it in vibeeval/vibecosystem, which has 531 GitHub stars. The repository holds 144 skills in this directory. The repository was last updated on August 8, 2026.
Source: vibeeval/vibecosystem on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.