Your first session with Context Mode Engine

You installed Context Mode Engine, and you want to see it work. Ask your agent to run your tests or read a big web page. The big output goes to a local sandbox, and the agent reads a short reply. Then call ctx_stats, the Context Mode tool that counts bytes: it shows how many bytes stayed out of the context window. In our benchmark, a 265 KB web page is what the agent would have sent to the model; the agent read 0.4 KB instead (median of 5 runs). Your own session gives your own numbers.

Free · Local · Private · Yours to keep

Context Mode Engine is source-available under the Elastic License 2.0. Use it, copy it, change it and share it at zero cost, for as long as you follow the licence terms. It runs on your machine, sends zero usage data, and keeps your data in ~/.context-mode.

The question after install

The install is done and the doctor shows PASS. Now you ask: "How do I know it works?"

The answer takes two steps. First, give the agent a task with big output. Then, ask the agent for ctx_stats. The report shows the bytes that stayed in the sandbox and the bytes that reached the model.

To install first, use your agent's own command on the install page. Restart the agent, then run this in a terminal:

context-mode doctor

Step 1: run your tests

A test suite prints a long log. Ask your agent to run it through the sandbox and print only what you need:

Run the test suite with ctx_execute and print only the names of the tests that need a fix.

The agent writes a short script. ctx_execute runs it as you, in your project folder. Only what the script prints comes back to the agent.

In the benchmark, a vitest run of 1106 tests printed 61.4 KB. The agent read 0.4 KB. That is the median of 5 runs on an Apple M1 Pro (raw file, source on GitHub).

Or: read a big web page

Ask your agent to read a long docs page. The PreToolUse hook (a small script that runs before each tool call) sends the WebFetch call to ctx_index and ctx_search. The page goes into the local index, and the agent searches it for the part it needs.

In the benchmark, a WebFetch of a 265 KB guide page would have sent 265.4 KB to the model. The agent read 0.4 KB. That is the median of 5 runs (raw file).

What happens to the output

Each big tool call takes the same short path. Step through it below.

Step 2: read ctx_stats

Ask your agent for the numbers:

Call ctx_stats and tell me how many bytes stayed out of the context in this session.

On agents with slash commands, /ctx-stats calls the same tool for you. The report shows the bytes kept out of the context at three levels:

• Session: the work you did since the agent started.
• Project: every session in this project.
• All time: every session the Engine logged on this machine.

What you get

You see the proof in your own session: big output in, short reply out. The full output stays in the index on your machine, so the agent can search it later with ctx_search. Your context window keeps its room for your work.