refactor(security): ipaddr-free @sim/security/hostnames sub-export (removes urls.ts loopback dup)

[waleedlatif1]

What

Follow-up to #5784 (the SSRF hardening PR, now merged). Completes the @sim/security/ssrf consolidation by splitting the pure host helpers into an ipaddr-free sub-export so the last duplicate can be removed.

unwrapIpv6Brackets + isLoopbackHostname never touch ipaddr.js, but they lived in @sim/security/ssrf whose top line is import * as ipaddr from 'ipaddr.js'. That's why apps/sim/lib/core/utils/urls.ts — which is pulled into client bundles — kept its own copy of isLoopbackHostname (importing the ssrf one would have dragged ipaddr.js into the browser).

Change

• New @sim/security/hostnames — pure, zero-dependency: unwrapIpv6Brackets, isLoopbackHostname.
• ssrf.ts imports unwrapIpv6Brackets from it and re-exports both, so every existing @sim/security/ssrf consumer (desktop + server) is unchanged.
• urls.ts drops its local LOCALHOST_HOSTNAMES set + isLoopbackHostname, and its three client importers (hooks/queries/mcp, mcp/oauth/probe, mcp/oauth/url-validation) now use the single shared definition — no ipaddr.js in the client bundle.
• Tests for the pure helpers moved to hostnames.test.ts.

Behavior is equivalent for every reachable url.hostname input (bracketed IPv6 [::1] → stripped ::1; localhost/127.0.0.1 unchanged) — verified by direct execution.

Testing

@sim/security 106 · affected sim suites (urls + mcp/oauth) 45 · type-check (security + full apps/sim) · check:boundaries · check:utils · check:api-validation:strict · Biome — all green.

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
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[cursor]

PR Summary

Low Risk
Refactor with equivalent exact-match loopback behavior; no auth or SSRF logic changes beyond import paths.

Overview
Introduces @sim/security/hostnames as an ipaddr-free export for unwrapIpv6Brackets and isLoopbackHostname, so client code can share one loopback definition without pulling ipaddr.js into the browser (which blocked importing these from @sim/security/ssrf).

apps/sim drops the duplicate LOCALHOST_HOSTNAMES / isLoopbackHostname in urls.ts and switches urls.ts, MCP hooks, and MCP OAuth helpers to import from @sim/security/hostnames. @sim/security/ssrf now imports unwrapIpv6Brackets from hostnames and re-exports both helpers so existing @sim/security/ssrf consumers stay unchanged.

Unit tests for the pure helpers move from ssrf.test.ts to hostnames.test.ts.

^{Reviewed by Cursor Bugbot for commit 32bb5b3. Configure here.}

[greptile-apps]

Greptile Summary

This PR moves pure hostname checks into an ipaddr.js-free security subpath. The main changes are:

• Adds @sim/security/hostnames with loopback and IPv6 helpers.
• Keeps existing SSRF imports working through re-exports.
• Moves browser-facing callers to the dependency-free subpath.
• Removes the duplicate URL helper and moves its focused tests.

Confidence Score: 5/5

This looks safe to merge.

• No blocking issues found in the changed code.

Important Files Changed

Filename	Overview
packages/security/src/hostnames.ts	Adds dependency-free hostname helpers with behavior matching the previous implementations.
packages/security/src/ssrf.ts	Uses the extracted IPv6 helper internally and preserves the existing public API through re-exports.
packages/security/package.json	Exposes the new hostname module using the package's established subpath export pattern.
apps/sim/lib/core/utils/urls.ts	Removes the duplicate loopback implementation and delegates URL checks to the shared helper.
apps/sim/hooks/queries/mcp.ts	Moves the client-facing loopback check to the dependency-free security subpath.
apps/sim/lib/mcp/oauth/probe.ts	Uses the shared hostname helper without changing OAuth probe behavior.
apps/sim/lib/mcp/oauth/url-validation.ts	Uses the shared helper while preserving insecure URL validation behavior.
packages/security/src/hostnames.test.ts	Covers canonical loopback hosts, bracketed IPv6 input, and negative cases.

_{Reviews (1): Last reviewed commit: "refactor: split pure host helpers into @..." | Re-trigger Greptile}