fix(web): open remote editors at the host this client connected to

[nkoynov]

Problem

"Open in VS Code" from a client on another machine links to the first host the server advertises: its Tailscale MagicDNS name from the default tailscale CLI, else <hostname>.local. The client may reach the server under a name that isn't that one, and then the editor fails with "Could not resolve hostname".

My case: the server is on two tailnets. The default CLI reports the work tailnet, so T3 advertises nixos.<work-tailnet>.ts.net. The Mac is only on the personal tailnet, paired at http://nixos:3773, and gets vscode://vscode-remote/ssh-remote+nixos.<work-tailnet>.ts.net/.... #10906 is the same failure with <hostname>.local on a cloud VM paired by its DNS name.

Change

resolveRemoteOpenState now picks the SSH host in this order:

1. The desktop SSH alias, as before.
2. The host of the route this client is connected over: the bearer route's URL, or the primary target's URL in a browser. Names and IP literals both count, and a route learned from the server counts too. The client has just reached the server at that host, so it resolves there.
3. The advertised targets, as before. This covers the cases where the connection URL doesn't name the server: T3 Connect (the URL names the relay), SSH routes (a local forward), loopback, desktop-local backends, and not connected yet.

An advertised list that is present but empty still means "no sshd", so that stays "No SSH route". The prepared connection is only used once it is connected, since it is published before its socket opens.

buildRemoteOpenUrl now handles IPv6 hosts: Remote-SSH and the JetBrains Toolbox link get the bare address (current Remote-SSH parses it; its own toAuthorityString emits it bare), and Zed gets [addr], because it parses zed://ssh/... as an ssh:// URL. The desktop shell's allowlist for Zed links accepts that bracketed host; it still rejects userinfo and host:port.

It's client-only, so it also works against older servers. If #11207 lands, its operator-configured target should go ahead of the connection host. That's a small follow-up once the configured kind exists.

Tradeoff: a client that reaches T3 through an HTTP reverse proxy or tunnel on another machine (a Cloudflare tunnel, say) now gets the proxy's hostname, which doesn't take SSH. Before, it got the first advertised host, which only works there if it's a Tailscale name the client can also reach; <hostname>.local didn't. Nothing on the client tells that case apart from the ones above, so the operator-configured target from #11207 is the way to cover it.

Scope and approval

Direction: the "prefer the hostname the client paired through" option in discussion #10326 (terryds's comment), which is where #10906 was sent when it was closed as a duplicate. No maintainer approval yet. I've added my case there (comment).

Verification

• apps/web/src/remoteOpen.test.ts: the connection host wins for names, a tailnet FQDN, IPv4 and IPv6. The fallback is still used for relay, loopback (including 127.0.0.2 and [::1]) and disconnected clients. The SSH alias still wins over a usable connection host. An empty list stays unavailable. IPv6 links for VS Code, Zed and JetBrains. Focused tests pass, along with OpenInPicker.test.tsx, lint, fmt and the typecheck.
• Rebased onto main @ df616cc (feat(editors): open remote projects in JetBrains IDEs over SSH #17271, JetBrains links) on 2026-10-08. The conflicts were in tests and the doc comment; the JetBrains link now also strips brackets from an IPv6 host.
• Before: on nightly 0.0.46-nightly.20261008.2819, the Mac desktop app paired at http://nixos:3773 gets remoteOpenTargets[0] = nixos.<work-tailnet>.ts.net, and VS Code fails with "Could not resolve hostname". With the same precedence applied server-side on a test instance of that build (a connection made with Host: nixos:3773 gets nixos first), that build's link builder produces vscode://vscode-remote/ssh-remote+nixos/..., a host the Mac has in its ssh config.
• Not checked: Cursor's own Remote-SSH or JetBrains Toolbox with an IPv6 host.

Model: Claude Opus 5.5 (1M). Harness: OpenCode in T3 Code. Reviewed by GPT-5.6 Sol via the Cursor CLI.

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📒 Files selected for processing (3)

• apps/desktop/src/electron/ElectronShell.test.ts
• apps/web/src/remoteOpen.test.ts
• packages/contracts/src/editor.ts

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📝 Walkthrough

Walkthrough

Remote-link resolution can use a reachable connected-route host before advertised hosts. Editor URL construction and Zed SSH URL validation support IPv6 hosts.

Changes

Remote link generation

Layer / File(s)	Summary
Resolve hosts from connected routes apps/web/src/remoteOpen.ts, apps/web/src/remoteOpen.test.ts	The resolver checks the connected route when choosing a remote-link host. It excludes relay, SSH, desktop-local, malformed, empty-host, and loopback routes. SSH aliases remain preferred, and usable connection hosts precede advertised hosts. Tests cover precedence, fallbacks, and local execution states.
Format and accept IPv6 editor URLs packages/contracts/src/editor.ts, apps/web/src/remoteOpen.test.ts, apps/desktop/src/electron/ElectronShell.ts, apps/desktop/src/electron/ElectronShell.test.ts	Editor URL construction accepts bracketed or unbracketed IPv6 hosts. Zed URLs use brackets, while other editor URLs encode the unbracketed host. Zed SSH URL validation accepts bracketed IPv6 hosts. Tests cover URL formatting, successful opening, and rejection cases.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix

Suggested reviewers: maria-rcks

Merge Risk

Merge Risk: 🟡 Moderate · up to 79fb8

For deployments where the client connects through an HTTP-only endpoint, remote-editor links can use that endpoint instead of the advertised SSH host and fail to connect. Address or explicitly accept this route-specific behavior before merging.

Security Architecture Review

Security architecture risk: 🔵 Low · up to 79fb8

The change preserves important URL restrictions, but reaching an environment over HTTP does not establish that the same hostname identifies its SSH server. Proxy-fronted connections can therefore send an editor to a different machine. No SSH authentication bypass or credential disclosure was established.

Retained concerns

• Low · security · inferred: The new precedence treats an authorized HTTP route hostname as the SSH destination. A non-loopback reverse proxy can serve the expected HTTP environment while its SSH service belongs to another machine, replacing the backend's advertised SSH target. This is a conditional destination-identity concern, not an established SSH authentication bypass.

Security review details

Security Blast Radius

• inferred — The demonstrated exposure is the local client's editor connection for a selected environment and workspace path. The generated URL contains no application bearer token, and this flow does not itself grant server-side execution authority.

Security Findings and Attack Paths

• inferred — For a proxy-fronted HTTP route, the new precedence can direct SSH to the proxy rather than the advertised backend. A party controlling that SSH endpoint could receive the connection attempt. Further access or disclosure depends on external editor and SSH behavior; neither credential theft nor an authorization bypass was established.

Trust Boundaries and Controls

• observed — Host reuse excludes relay, SSH-tunnel, desktop-local, invalid, empty, and loopback routes. SSH aliases retain precedence. The desktop gate still restricts editor protocols and URL authorities and rejects URL userinfo; its added tests retain rejection of Zed userinfo and an unbracketed explicit port.

Resilience and Maintainability Implications

• observed — The resolver ignores prepared routes before the connected phase and preserves an explicit no-SSH-target result. These guards limit premature destination selection, but do not resolve HTTP-to-SSH identity differences.

Hardening Proposals

• proposed — Represent an SSH destination explicitly, or provide an override for proxy-fronted HTTP routes, rather than relying solely on HTTP reachability to infer the SSH machine.

🚥 Pre-merge checks | ✅ 3 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check		The description covers the problem, implementation, scope, tradeoffs, verification, test results, and known gaps. However, the required scope approval is incomplete because it states that no maintaine…	Obtain explicit maintainer approval in the linked discussion, or document why this change qualifies for the small, focused obvious-bug exemption under the repository template.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.
Title check		The title clearly and concisely describes the main change: remote editors now open using the host to which the client connected.

Full details: Description check

Explanation

The description covers the problem, implementation, scope, tradeoffs, verification, test results, and known gaps. However, the required scope approval is incomplete because it states that no maintainer approval exists.

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Inline comments:
Review comments at @apps/web/src/remoteOpen.ts:
- Around line 120-122: Update resolveRemoteOpenState so a connection hostname is
selected only when it is explicitly present among the advertised SSH targets;
otherwise, use the advertised target. Preserve the existing connection-host
behavior when no advertised targets are provided.

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📒 Files selected for processing (5)

• apps/desktop/src/electron/ElectronShell.test.ts
• apps/desktop/src/electron/ElectronShell.ts
• apps/web/src/remoteOpen.test.ts
• apps/web/src/remoteOpen.ts
• packages/contracts/src/editor.ts

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[juliusmarminge]

Note

This comment is posted by Julius' dot

Closing for missing prior product-direction approval. resolveRemoteOpenState now prefers the connected HTTP host over advertised SSH targets by default. The PR explicitly acknowledges that this selects a non-SSH proxy/tunnel host in some existing setups and says “No maintainer approval yet.” Discussion #10326 contains contributor proposals, not maintainer agreement on that tradeoff.

The two-tailnet hostname failure is useful and remains documented there. Please obtain explicit maintainer approval for the new default precedence and proxy/tunnel behavior, then request reconsideration. The focused tests and IPv6 support do not replace that decision.