fix(node:os): observe runtime HOME changes

[steipete]

What does this PR do?

Makes POSIX os.homedir() observe the current HOME value, matching Node when user code changes or deletes process.env.HOME after startup.

Bun's native POSIX binding read a startup-cached environment value before falling back to the passwd database. Runtime process.env and Bun.env mutations live in the JavaScript environment object, so os.homedir() kept returning the old home. The JavaScript adapter now owns the live POSIX environment lookup, including explicitly empty and whitespace-only values, while the native binding provides a passwd-only fallback. os.userInfo().homedir remains passwd-derived. Windows stays on the existing libuv binding.

Fixes #29244.

AI-assisted: yes. Codex helped isolate the environment ownership boundary, implement the patch, and design the cross-runtime regression. I reviewed the code and validation results.

How did you verify your code works?

• Bun 1.4.2 fails the focused runtime-HOME regression for the intended stale-value reason.
• Patched debug runtime: test/js/node/os/os.test.js — 55 passed, 0 failed.
• Vendored Node test-os.js and test-os-homedir-no-envvar.js both exit successfully.
• Host and x86_64-pc-windows-msvc bun_runtime Rust checks pass.
• bun run lint, targeted Prettier, cargo fmt --check, root tsc --noEmit, and git diff --check pass.
• A custom integration build at 1.4.3-canary.1+91b28c4bf contains a patch-equivalent copy of this exact change. The PR commit and integration-stack commit have the same stable patch ID.
• The prior Node-compatible node:test conformance suite plus a set/empty/whitespace/unset spawn matrix passes 7/7 under Node and 7/7 under that Bun build.
• OpenClaw's adjacent iMessage path, account, runtime, and remote-host tests pass 76/76 under that Bun build. This includes the real os.userInfo().homedir regression with whitespace-only HOME.
• A fresh independent P0-P2 review of the exact PR head found no actionable findings.

A clean full debug build of current main is independently blocked on this macOS host by existing SDK/compiler failures. The source patch passed the current-main Rust checks, and runtime validation used previously built debug and integration binaries containing the patch.

OpenClaw integration context: openclaw/openclaw#146807

[claude]

Claude Code Review

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[coderabbitai]

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• src/js/node/os.ts
• src/runtime/node/node_os.rs
• test/js/node/os/os.test.js

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• src/runtime/node/node_os.rs

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Walkthrough

The JavaScript os.homedir() implementation now uses non-Windows Bun.env.HOME values before falling back to the runtime binding. The runtime binding no longer has a HOME fast path. Tests cover HOME changes and userInfo().homedir.

Changes

Homedir behavior

Layer / File(s)	Summary
Update homedir resolution src/js/node/os.ts, src/runtime/node/node_os.rs	The JavaScript wrapper checks Bun.env.HOME on non-Windows platforms and falls back to binding.homedir(). The runtime implementation proceeds directly to passwd lookup. Windows behavior remains unchanged.
Validate environment changes test/js/node/os/os.test.js	Tests cover changed, empty, and deleted HOME values. The test also verifies that userInfo().homedir remains unchanged and restores the environment.

Suggested reviewers: robobun

Priority: ⬇️ Low

Merge Risk: ⚪ Minimal · up to 772e4

The updated homedir behavior honors current HOME values on POSIX while retaining the passwd fallback and existing Windows behavior. No actionable merge risk remains.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly and concisely describes the main change: making node:os observe runtime HOME changes.
Description check	✅ Passed	The description includes both required sections. It explains the behavior change, implementation, verification results, known build limitation, and related issue.

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[robobun]

This PR fixes #29244. Two older PRs covered the same bug. #29248 made the same change to os.ts and node_os.rs. #34629 fixed only the HOME="" and userInfo().homedir cases. I closed both in favor of this one: it is the smallest diff and it is based on current main.

I built this branch (772e4ac, debug build with ASAN, Linux x64) and checked it:

• The repro from os.homedir() uses process-start HOME snapshot instead of current process.env.HOME #29244 prints /root, /tmp/test-home, /root, the same as Node v26.3.0.
• test/js/node/os/os.test.js passes (55 tests). On bun 1.4.3-canary.1 the new test fails with Expected: "/tmp/bun-runtime-home", Received: "/root".
• The tests from Honor live $HOME mutations in os.homedir() #29248 and os: return empty-but-set $HOME from homedir(); read userInfo().homedir from passwd #34629 pass on this branch.
• The vendored Node tests test-os.js and test-os-homedir-no-envvar.js exit 0.

Two requests:

1. Add Fixes #29244 to the description, so that the merge closes the issue.

2. Consider the node:test file from Honor live $HOME mutations in os.homedir() #29248. In review there, alii asked for a test that uses node:test, so that the same file runs in Node.js. The file is test/js/node/os/os-homedir-env.test.js. Each of its 6 cases runs in a child process: HOME changed after and before require("node:os"), HOME from the parent environment, HOME="", HOME deleted (seeded with a sentinel and compared with userInfo().homedir), and userInfo().homedir after a HOME change. It passes 6/6 on this branch and on Node v26.3.0. Without the fix, 4 of 6 fail.

   git fetch https://github.com/oven-sh/bun refs/pull/29248/head
   git checkout FETCH_HEAD -- test/js/node/os/os-homedir-env.test.js

   os: return empty-but-set $HOME from homedir(); read userInfo().homedir from passwd #34629 tested one thing that neither test has: HOME set, empty, and unset when the child starts, for both os.homedir() and os.userInfo().homedir. The case below does that in the same file. It passes on this branch and on Node v26.3.0, and it fails without the fix.

   Extra case for os-homedir-env.test.js

   test("homedir() and userInfo().homedir with HOME set, empty, and unset at spawn", { skip: isWindows }, () => {
     // uv_os_homedir: HOME whenever it is present (including ""), passwd only when absent.
     // uv_os_get_passwd (userInfo().homedir): passwd regardless of HOME.
     const source = `
       const os = require("node:os");
       console.log(JSON.stringify({ homedir: os.homedir(), userInfo: os.userInfo().homedir }));
     `;
     const unset = runWithEnv(source, { HOME: undefined });
     const set = runWithEnv(source, { HOME: "/tmp/spawn-set-29244" });
     const empty = runWithEnv(source, { HOME: "" });
     const passwd = unset.userInfo;
     assert.ok(passwd.startsWith("/"));
     assert.deepStrictEqual(
       { unset, set, empty },
       {
         unset: { homedir: passwd, userInfo: passwd },
         set: { homedir: "/tmp/spawn-set-29244", userInfo: passwd },
         empty: { homedir: "", userInfo: passwd },
       },
     );
   });

   If you prefer, I can push both to this branch as one separate commit.

The change has one side effect that differs from Node, and #29248 had it too. In a Worker started with a different HOME in its env option, os.homedir() now returns the worker's value. Node returns the process value there, because libuv reads the C environment and not the worker's copy.

The Buildkite build for this PR (build 115128) is blocked until a maintainer unblocks it. CI has not run yet.

[steipete]

Addressed both points from the review:

• Added Fixes #29244 to the PR description.
• Ran the six-case node:test file from Honor live $HOME mutations in os.homedir() #29248, extended with the os: return empty-but-set $HOME from homedir(); read userInfo().homedir from passwd #34629 set/empty/unset spawn matrix and a whitespace-only HOME case. It passes 7/7 under Node and 7/7 under the custom Bun integration build 1.4.3-canary.1+91b28c4bf.

That integration build contains commit 4bcb6c80082e, whose stable patch ID is identical to this PR head (772e4acb9263). I also ran OpenClaw's adjacent iMessage CLI-path, account, runtime, and remote-host tests against it: 76/76 pass, including uses the real OS account home when HOME is whitespace-only, which was the downstream failure this fixes.

I kept the PR head unchanged: the committed focused regression already covers live assignment, empty HOME, deletion/passwd fallback, and userInfo().homedir independence. The larger Node-compatible matrix is now recorded as cross-runtime integration evidence without duplicating those subprocess cases in this minimal patch.

Fresh P0-P2 review of the exact PR head is clean. The PR description still includes the AI-assisted disclosure.