Updating

Synaptic can update itself in place from the latest GitHub Release. The update system is opt-in: Synaptic never contacts the network or replaces the binary on its own. You either run synaptic self-update explicitly, or enable a once-a-day "update available" notice that only ever prints a one-line reminder.

This page covers the whole system. For the bare command reference see self-update in Commands; for the files and environment variables involved see Configuration.

At a glance

synaptic self-update            # check; if a newer release exists, prompt then replace
synaptic self-update --check    # report whether an update is available, then exit
synaptic self-update --yes      # update without the confirmation prompt
synaptic self-update --enable   # turn on the daily "update available" notice
synaptic self-update --disable  # turn the notice back off

Nothing here runs unless you ask for it. --enable/--disable only write a small config file and need no network.

How an update works

Running synaptic self-update performs these steps:

1. Check. Query releases/latest for ColinVaughn/Synaptic and compare the tag to the running version (a leading v is tolerated; the comparison is semantic-version aware). If the latest release is not newer, it prints Synaptic is up to date (<version>). and exits.
2. Confirm. If a newer release exists, it prints the version delta and the release notes, then asks Download and replace the current binary? [y/N]. Answer y/yes to proceed. --yes (or -y) skips this prompt for scripts.
3. Download. Fetch the prebuilt archive that matches your platform (see Platform support).
4. Verify. If the release publishes a .sha256 checksum next to the archive, the download is verified against it; a mismatch aborts the update before anything is replaced. Releases made before checksums were published have no sidecar, so verification is skipped with a printed warning rather than failing.
5. Replace. Extract the binary and atomically replace the currently running executable. The syn short alias next to it is updated too.
6. Refresh skills. Re-render every agent skill recorded in ~/.synaptic/skills.toml to the new version. Because the running process is still the old binary, this step spawns the freshly-installed one to do the rendering. Skills you have hand-edited are left untouched and reported; see Versioning and auto-refresh. Run it on its own anytime with synaptic install --refresh.

The new version takes effect the next time you run Synaptic — the already-running process keeps the old code in memory, so the command finishes with Updated to <version>. Restart synaptic to use the new version.

If anything fails (network, checksum mismatch, write error), the existing binary is left untouched: the download is verified before the swap, never overwritten in place first.

The opt-in background notice

By default Synaptic never checks for updates. Turn the reminder on with:

synaptic self-update --enable

Once enabled, ordinary commands occasionally check for a newer release in the background and, if one exists, print a single line to stderr and then continue normally:

(note) Synaptic 0.3.3 is available - run `synaptic self-update`

Properties of the background check:

• Throttled. It runs at most once every 24 hours. The timestamp of the last check is stored in the config file, so a burst of commands triggers only one check.
• Non-blocking and silent on failure. It uses a short timeout, and any network or parse error is swallowed — a flaky connection never slows down or breaks a normal command. The timestamp still advances so a failed check is not retried on every invocation.
• stderr only. The notice goes to stderr, so it never corrupts machine-readable stdout (for example a --json result or the serve MCP stream).
• Never on self-update itself. The check is skipped while you run the update command.

Turn it back off at any time:

synaptic self-update --disable

Disabling the check without changing config

Set SYNAPTIC_UPDATE_CHECK=0 to force the background check off even when the config has it enabled. This is useful in CI or any non-interactive environment:

SYNAPTIC_UPDATE_CHECK=0 synaptic query "..."

The variable only affects the background notice; it does not change what synaptic self-update does when you run it explicitly.

Checksum verification

When a release publishes a synaptic-<target>.tar.gz.sha256 (or .zip.sha256) sidecar next to its archive, self-update downloads it and verifies the SHA-256 of the downloaded archive before replacing the binary. A mismatch aborts the update. Synaptic's release workflow publishes these sidecars; releases predating that workflow have none, in which case verification is skipped with a warning so updating still works against older releases.

Platform support

self-update downloads the prebuilt archive matching your platform:

Platform	Release asset
Linux x86_64	synaptic-x86_64-unknown-linux-gnu.tar.gz
macOS Apple Silicon	synaptic-aarch64-apple-darwin.tar.gz
macOS Intel	synaptic-x86_64-apple-darwin.tar.gz
Windows x86_64	synaptic-x86_64-pc-windows-msvc.zip

On any other platform there is no prebuilt binary to install. self-update detects this, prints the Releases URL so you can download or build manually, and exits without changing anything.

Updating a source build

self-update replaces whatever binary is currently running, including one produced by cargo install --path bin/synaptic or cargo build. Note that the replacement is the default-feature prebuilt binary. If you built with extra Cargo features (for example pg, push, office, gws, media, or live-explain; see Installation and Configuration), self-updating swaps in a binary that does not have them. Rebuild from source with your features instead of self-updating in that case.

Rate limits and tokens

The check uses GitHub's anonymous REST API, which is rate-limited per IP. If you hit the limit (for example on a shared CI runner), set GITHUB_TOKEN to a token and Synaptic will send it to raise the limit. The token is optional and only used to authenticate the release lookup.

Files and variables

Path / variable	Role
~/.synaptic/update.toml	Stores enabled (the opt-in flag) and last_check (the throttle timestamp). Written by --enable/--disable. On Windows this is %USERPROFILE%\.synaptic\update.toml; with no home directory it falls back to .synaptic/update.toml in the working directory.
~/.synaptic/skills.toml	Registry of installed agent skills, read by the post-update refresh step (and synaptic install --refresh). Written by synaptic install/uninstall. See Assistant Integration.
SYNAPTIC_UPDATE_CHECK	Set to 0 to force the background notice off regardless of config.
GITHUB_TOKEN	Optional. Raises the GitHub API rate limit for the release lookup.

See Configuration for the full list of files and environment variables, and Commands for the command reference.