Feature Request: Support Custom Advertised Hostname for Headless Pairing

[jacobgraf]

Summary

T3 Code should support configuring a persistent custom hostname or base URL for headless servers so that:

npx t3 pair

returns pairing information and a QR code using that hostname instead of an automatically detected IP address.

Current Behavior

On a headless Linux server, T3 Code can correctly bind to all interfaces with:

T3CODE_HOST=0.0.0.0

However, when running:

npx t3 pair

T3 Code advertises a detected IP address in the pairing information, for example:

http://10.x.x.x:3773

In environments with working internal DNS, it would be preferable to advertise something like:

http://server.internal.example:3773

The lower-level command supports specifying a custom base URL:

npx t3 auth pairing create --base-url http://server.internal.example:3773

but this does not provide the same convenient QR-code pairing experience as:

npx t3 pair

Using:

T3CODE_HOST=server.internal.example

is also not an appropriate solution because T3CODE_HOST controls the server's bind address, not just the externally advertised endpoint.

Requested Behavior

Please add a persistent configuration option for the hostname or base URL advertised by the headless server during pairing.

For example:

T3CODE_ADVERTISE_URL=http://server.internal.example:3773

or:

T3CODE_PUBLIC_URL=http://server.internal.example:3773

Then:

npx t3 pair

would continue to provide its normal pairing URL, token, and QR code, but use the configured hostname.

Alternatively, supporting this directly would also work:

npx t3 pair --base-url http://server.internal.example:3773

Ideally, both a CLI option and a persistent environment/config setting would be available.

Why This Matters

Headless servers commonly use:

• Internal DNS
• Split DNS
• VPN-provided DNS
• Reverse proxies
• Stable hostnames instead of raw IP addresses

A server's bind address and its advertised or reachable address are separate concerns.

A typical configuration should be able to look like:

T3CODE_HOST=0.0.0.0
T3CODE_ADVERTISE_URL=http://server.internal.example:3773

This keeps the server listening correctly while allowing pairing information to use the stable hostname clients are actually expected to connect to.

Expected Result

Running:

npx t3 pair

should generate the normal QR code and pairing information using the configured advertised hostname rather than forcing users to use an automatically detected IP address or a separate lower-level pairing command.