From 787aa10599ff89f77ba5cef9cc5fa9fe3244452c Mon Sep 17 00:00:00 2001
From: Chris Scott <99081550+chriswritescode-dev@users.noreply.github.com>
Date: Sat, 1 Aug 2026 19:46:01 -0400
Subject: [PATCH] fix(sandbox): canonicalize paths when detecting mount overlap

Mount planning mixed two path realms. Git paths come from
`git rev-parse --git-dir`/`--git-common-dir`, which are symlink-resolved,
while the worktree and `sourceProjectDir` go through `resolve()`, which
never resolves symlinks. Overlap detection is string prefix matching, so
on macOS (where /var and /tmp are symlinks to /private/...) it could not
see that /var/X is an ancestor of /private/var/X/.git.

The read-only source project mount was therefore not dropped, and the
same directory was mounted twice with conflicting permissions.

Canonicalize both operands inside `containerPathsOverlap`, the single
choke point behind every overlap check, and apply the same comparison to
the two containment guards in `detectGitMount`. Emitted hostDir and
containerDir values are unchanged: sbx mounts at the identical host path
and opencode reports unresolved host paths, while the git mounts must
keep git's resolved paths because the linked worktree records them.
---
 src/sandbox/manager.ts | 10 +++++-----
 src/sandbox/path.ts    | 10 ++++++++++
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/src/sandbox/manager.ts b/src/sandbox/manager.ts
index f636984d9..95d23cbed 100644
--- a/src/sandbox/manager.ts
+++ b/src/sandbox/manager.ts
@@ -4,7 +4,7 @@ import type { Logger, SandboxResources, SandboxMountConfig } from '../types'
 import { resolve, join, isAbsolute, posix as posixPath } from 'path'
 import { mkdirSync, existsSync, writeFileSync, chmodSync, rmSync } from 'fs'
 import { defaultGitService, type GitService } from '../utils/git-service'
-import { isSameOrDescendantPath, type SandboxMount } from './path'
+import { canonicalizePath, isSameOrDescendantPath, type SandboxMount } from './path'
 
 export interface SandboxManagerConfig {
   image: string
@@ -45,8 +45,8 @@ function normalizeContainerPath(path: string): string {
 }
 
 function containerPathsOverlap(a: string, b: string): boolean {
-  const left = normalizeContainerPath(a)
-  const right = normalizeContainerPath(b)
+  const left = normalizeContainerPath(canonicalizePath(a))
+  const right = normalizeContainerPath(canonicalizePath(b))
   return isSameOrDescendantPath(left, right) || isSameOrDescendantPath(right, left)
 }
 
@@ -279,11 +279,11 @@ export function createSandboxManager(
     const resolvedGitDir = resolve(projectDir, gitDirResult.stdout.trim())
     const resolvedCommonDir = resolve(projectDir, commonDirResult.stdout.trim())
 
-    if (!resolvedGitDir.startsWith(projectDir + '/')) {
+    if (!isSameOrDescendantPath(canonicalizePath(resolvedGitDir), canonicalizePath(projectDir))) {
       paths.add(resolvedGitDir)
     }
 
-    if (!resolvedCommonDir.startsWith(projectDir + '/')) {
+    if (!isSameOrDescendantPath(canonicalizePath(resolvedCommonDir), canonicalizePath(projectDir))) {
       paths.add(resolvedCommonDir)
     }
 
diff --git a/src/sandbox/path.ts b/src/sandbox/path.ts
index a198ec882..c02e61cab 100644
--- a/src/sandbox/path.ts
+++ b/src/sandbox/path.ts
@@ -1,9 +1,19 @@
+import { realpathSync } from 'fs'
+
 export interface SandboxMount {
   hostDir: string
   containerDir: string
   readOnly?: boolean
 }
 
+export function canonicalizePath(path: string): string {
+  try {
+    return realpathSync(path)
+  } catch {
+    return path
+  }
+}
+
 export function isSameOrDescendantPath(path: string, prefix: string): boolean {
   if (path === prefix) return true
   return path.startsWith(prefix + '/')