Strip inherited host shell env from SSH remote execution (#5142)

## Thinking Path

> - Paperclip orchestrates AI agents for zero-human companies
> - Agents executing on remote SSH hosts receive an env map built from
the host
>   process's env plus per-run additions like `PAPERCLIP_API_KEY`,
>   `PAPERCLIP_RUN_ID`, etc.
> - The env map currently includes inherited host vars by default,
including
> identity-bound ones like `PATH`, `HOME`, `USER`, `NVM_DIR`, `XDG_*` —
> variables whose values are meaningful only on the host they came from
> - Sending the host's `PATH` (containing host-only directories like a
local
> nvm install path) to a remote SSH box overrides the remote's actual
`PATH`
> and breaks command resolution. Same hazard for `HOME` (commands
looking for
> config files end up in a non-existent dir), `USER` (writes go to the
wrong
>   path), etc.
> - This PR adds `sanitizeSshRemoteEnv()` that drops inherited
identity-bound
> vars when their value matches the host process's value. Explicitly-set
> values pass through untouched, so callers that genuinely want to
override
>   remote `PATH` etc. still can — but accidental leakage from
>   `process.env` is filtered.
> - The benefit is that SSH remote execution stops corrupting the remote
> shell's environment with host-shaped paths, so commands resolve
correctly
>   against the remote PATH and config files land in the remote `HOME`

## What Changed

- New `sanitizeSshRemoteEnv(env, inheritedEnv = process.env)` in
`packages/adapter-utils/src/server-utils.ts`. The identity-bound key set
is:
    - `PATH`, `HOME`, `PWD`, `SHELL`, `USER`, `LOGNAME`
    - `NVM_DIR`, `TMPDIR`, `TMP`, `TEMP`
    - `XDG_CONFIG_HOME`, `XDG_CACHE_HOME`, `XDG_DATA_HOME`,
      `XDG_STATE_HOME`, `XDG_RUNTIME_DIR`
For any key in this set, the entry is dropped iff the env value equals
the
  inherited (host process) value. Other keys pass through unchanged.
- `readEnvValueCaseInsensitive(...)` helper handles Windows-style
  case-insensitive env var lookups.
- Wired into `resolveSpawnTarget(...)` for the SSH transport. Sandbox
and local
  paths are unaffected.
- Tests added in `server-utils.test.ts` (~50 lines) covering: matching
keys
filtered, mismatched keys preserved, non-identity keys passed through,
case
  insensitivity.

## Verification

- `pnpm --filter @paperclipai/adapter-utils test -- server-utils`
- Manual QA: run any adapter against an SSH-backed environment, confirm
remote command resolution works (e.g. `node`, `npm`, the adapter's CLI)
and
config files land in the remote user's `HOME`. Compare to the prior
behaviour
by transiently re-introducing the inherited `PATH` and watching commands
  fail with `command not found`.

## Risks

- Behavioural shift: SSH remote execution previously passed inherited
host env
  vars verbatim. Code that relied on that (e.g. a remote command somehow
  expecting the host's `PATH`) will see different behaviour. None of the
  adapter code in this repo has such a dependency.
- Edge case: if a caller explicitly sets `PATH` to the same value as the
host's
`PATH` (literally — same exact string), the sanitizer drops it as a
leak.
  In practice no caller constructs the env this way.
- Windows host: case-insensitive lookup handles `Path` vs `PATH`
correctly.
  Tested.

## Model Used

- OpenAI GPT-5.4 (reasoning effort: high) via Codex CLI
- Provider: OpenAI
- Used to author the code changes in this PR

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [ ] If this change affects the UI, I have included before/after
screenshots — N/A
- [ ] I have updated relevant documentation to reflect my changes — N/A
- [x] I have considered and documented any risks above
- [x] I will address all Greptile and reviewer comments before
requesting merge

packages/adapter-utils/src/server-utils.test.ts

@@ -12,6 +12,7 @@ import {
   renderPaperclipWakePrompt,
   runningProcesses,
   runChildProcess,
+  sanitizeSshRemoteEnv,
   shapePaperclipWorkspaceEnvForExecution,
   stringifyPaperclipWakePayload,
 } from "./server-utils.js";
@@ -61,6 +62,86 @@ describe("buildInvocationEnvForLogs", () => {
   });
 });
 
+describe("sanitizeSshRemoteEnv", () => {
+  it("drops inherited host shell identity variables for SSH remote execution", () => {
+    expect(
+      sanitizeSshRemoteEnv(
+        {
+          PATH: "/host/bin:/usr/bin",
+          HOME: "/Users/local",
+          NVM_DIR: "/Users/local/.nvm",
+          TMPDIR: "/var/folders/local/T",
+          XDG_CONFIG_HOME: "/Users/local/.config",
+          SAFE_VALUE: "visible",
+        },
+        {
+          PATH: "/host/bin:/usr/bin",
+          HOME: "/Users/local",
+          NVM_DIR: "/Users/local/.nvm",
+          TMPDIR: "/var/folders/local/T",
+          XDG_CONFIG_HOME: "/Users/local/.config",
+        },
+      ),
+    ).toEqual({
+      SAFE_VALUE: "visible",
+    });
+  });
+
+  it("preserves explicit remote overrides even for filtered key names", () => {
+    expect(
+      sanitizeSshRemoteEnv(
+        {
+          PATH: "/custom/remote/bin:/usr/bin",
+          HOME: "/home/agent",
+          TMPDIR: "/tmp",
+          SAFE_VALUE: "visible",
+        },
+        {
+          PATH: "/host/bin:/usr/bin",
+          HOME: "/Users/local",
+          TMPDIR: "/var/folders/local/T",
+        },
+      ),
+    ).toEqual({
+      PATH: "/custom/remote/bin:/usr/bin",
+      HOME: "/home/agent",
+      TMPDIR: "/tmp",
+      SAFE_VALUE: "visible",
+    });
+  });
+
+  it("filters identity keys via case-insensitive match against the inherited env", () => {
+    expect(
+      sanitizeSshRemoteEnv(
+        {
+          // Caller passed PATH in upper case while the inherited (Windows-style)
+          // host env exposes it as Path. The lookup must still treat them as
+          // equal so the leaked host PATH gets stripped.
+          PATH: "/host/bin:/usr/bin",
+          HOME: "/host/home",
+        },
+        {
+          Path: "/host/bin:/usr/bin",
+          home: "/host/home",
+        },
+      ),
+    ).toEqual({});
+  });
+
+  it("preserves explicitly-set identity keys when the inherited env disagrees in case but not in value", () => {
+    expect(
+      sanitizeSshRemoteEnv(
+        {
+          PATH: "/explicit/remote/bin",
+        },
+        {
+          Path: "/host/bin:/usr/bin",
+        },
+      ),
+    ).toEqual({ PATH: "/explicit/remote/bin" });
+  });
+});
+
 describe("materializePaperclipSkillCopy", () => {
   it("refuses to materialize into an ancestor of the source", async () => {
     const root = await fs.mkdtemp(path.join(os.tmpdir(), "paperclip-skill-copy-"));

packages/adapter-utils/src/server-utils.ts

@@ -1039,6 +1039,56 @@ function quoteForCmd(arg: string) {
   return /[\s"&<>|^()]/.test(escaped) ? `"${escaped}"` : escaped;
 }
 
+const SSH_REMOTE_ENV_IDENTITY_KEYS = new Set([
+  "PATH",
+  "HOME",
+  "PWD",
+  "SHELL",
+  "USER",
+  "LOGNAME",
+  "NVM_DIR",
+  "TMPDIR",
+  "TMP",
+  "TEMP",
+  "XDG_CONFIG_HOME",
+  "XDG_CACHE_HOME",
+  "XDG_DATA_HOME",
+  "XDG_STATE_HOME",
+  "XDG_RUNTIME_DIR",
+]);
+
+function readEnvValueCaseInsensitive(env: NodeJS.ProcessEnv, key: string): string | undefined {
+  const direct = env[key];
+  if (typeof direct === "string") return direct;
+  const upper = key.toUpperCase();
+  for (const [candidateKey, candidateValue] of Object.entries(env)) {
+    if (candidateKey.toUpperCase() === upper && typeof candidateValue === "string") {
+      return candidateValue;
+    }
+  }
+  return undefined;
+}
+
+export function sanitizeSshRemoteEnv(
+  env: Record<string, string>,
+  inheritedEnv: NodeJS.ProcessEnv = process.env,
+): Record<string, string> {
+  const sanitized: Record<string, string> = {};
+  for (const [key, value] of Object.entries(env)) {
+    const normalizedKey = key.toUpperCase();
+    if (!SSH_REMOTE_ENV_IDENTITY_KEYS.has(normalizedKey)) {
+      sanitized[key] = value;
+      continue;
+    }
+    const inheritedValue = readEnvValueCaseInsensitive(inheritedEnv, key);
+    if (typeof inheritedValue === "string" && inheritedValue === value) {
+      continue;
+    }
+    sanitized[key] = value;
+  }
+  return sanitized;
+}
+
 function resolveWindowsCmdShell(env: NodeJS.ProcessEnv): string {
   const fallbackRoot = env.SystemRoot || process.env.SystemRoot || "C:\\Windows";
   return path.join(fallbackRoot, "System32", "cmd.exe");
@@ -1064,9 +1114,9 @@ async function resolveSpawnTarget(
       spec: remote,
       command,
       args,
-      env: Object.fromEntries(
+      env: sanitizeSshRemoteEnv(Object.fromEntries(
         Object.entries(options.remoteEnv ?? {}).filter((entry): entry is [string, string] => typeof entry[1] === "string"),
-      ),
+      )),
     });
     return {
       command: sshResolved,