FastCtx

Let Codex find the right code sooner.

FastCtx gives coding agents structured repository tools — read, grep, glob, replace, and an optional bash terminal — served by one local Rust binary over MCP. read can pack 1–32 known text files into one request-ordered call with exact per-file continuation parameters, while images, PDFs, and hex view remain single-file reads.

The optional terminal publishes run, run_background, job_output, job_kill, and job_list. Background jobs have no automatic timeout and survive MCP server and Codex restarts. Current-format jobs keep their complete output log and exit status addressable by job id under ~/.fastctx/jobs/. job_output is a query with a caller-chosen delay: it returns when the job ends or when wait_ms (0–240000 ms, default 30000) elapses, showing the newest output not yet seen, and names the log path and exact line numbers for anything it leaves out. Intermediate output does not end the wait. Complete appears only after a job ends; servers and watchers may never reach it. Records from the preceding segmented format remain readable but do not claim direct log coordinates or recover output their original rolling window evicted. While one server tracks jobs it started or queried, each successful text result also carries a one-line background readout of their current state and elapsed time. It refreshes only on tool calls; it is not a push notification, and nothing arrives if the caller stops. Finished entries remain until that server handles them with job_output or job_kill.

On Windows, all FastCtx-owned non-interactive children run without allocating a console window; no caller flag is required. Commands that explicitly launch a GUI or another terminal keep that visible behavior.

Finished records are retained until the current user's fastshell.job_storage_limit_mib limit evicts the oldest (default 1024 MiB); fastshell.max_running_jobs caps concurrent jobs across all FastCtx sessions for that user (default 128). job_list shows running jobs by default; explicit status="finished" exposes retained history, while fastshell.job_list_limit sets the default page size (20, valid range 1–100). All three settings take effect immediately when saved. Job commands, working directories, output logs, and exit status stay in the current user's private local directory and are never uploaded by FastCtx.

grep/glob keeps its existing automatic CPU parallelism by default. The TUI can set an explicit search.max_cpu_cores value from 1 through the engine-visible ceiling (available parallelism capped at 16); each newly started server reads it directly, without Apply or a copied environment key. Invalid values fail with a repairable diagnostic instead of being clamped or replaced. The Config screen also provides a default-No confirmation that resets every user preference while preserving the Apply ownership receipt, installed binary, host integration, and running jobs. Restoring the default history quota can evict excess finished records through the normal retention policy.

npm install --global fastctx
fastctx

For a one-off run without installing, npx fastctx opens the same control terminal.

If your npm registry is a mirror that has not synchronized this release yet, the install can fail with 404 Not Found on the platform package. Install once from the official registry:

npm install --global fastctx --registry=https://registry.npmjs.org/

This package is the launcher: it selects the matching scoped platform package (@fastctx/win32-x64, @fastctx/linux-x64, or the corresponding macOS package) locally and starts the complete binary. There is no postinstall script and no telemetry. The interactive TUI checks this exact npm package for updates before the main menu opens; the wait is strictly bounded, and a failed or timed-out check enters silently. When a newer version is installable, the update screen opens directly and asks whether to update or continue. Successful results are cached for 24 hours in machine-private storage. Transient failures stay quiet and remain available under Status. If GitHub is newer while npm is still propagating, the Update screen says so and offers retry. Updates require confirmation, install an exact version with lifecycle scripts disabled, and restart through a copied helper. A failed update restores and reopens the previous version with a warning. fastctx serve and MCP tool calls do not perform update traffic; commands run through the optional bash tools keep their normal network access.

Run fastctx in a terminal for the full-screen control UI (configuration, reset, preview, Apply, Jobs, doctor, Unapply), fastctx jobs for scriptable running-job management, or fastctx serve for the stdio MCP server. For MCP pipes the launcher proxies stdio, forwards termination signals and the native exit code, and closes the Rust server cleanly if the Node parent is killed.

The Jobs dashboard aggregates every currently running job from the current user's registry across FastCtx server and TUI instances. It groups jobs by honest source-session metadata, aligns ids and width-aware command ellipses, and shows exact start plus live elapsed time. Finished output remains available to the agent through job_output; the host does not expose conversation titles or ids to MCP, so FastCtx does not invent them.

Full documentation: https://github.com/yc-duan/fastctx