diff --git a/packages/opencode/src/core/account-paths.ts b/packages/opencode/src/core/account-paths.ts
index 93ade33..a1704a6 100644
--- a/packages/opencode/src/core/account-paths.ts
+++ b/packages/opencode/src/core/account-paths.ts
@@ -1,5 +1,6 @@
+import { realpathSync } from 'node:fs'
 import { homedir } from 'node:os'
-import { dirname, join } from 'node:path'
+import { basename, dirname, join, resolve } from 'node:path'
 
 /**
  * Where the account store lives.
@@ -37,13 +38,66 @@ export function getAccountStoragePath() {
 
 /** Derive the state-file path from the config path without reading env vars. */
 export function deriveStatePath(configPath: string): string {
-  return configPath.endsWith(ACCOUNT_FILE_NAME)
+  return basename(configPath) === ACCOUNT_FILE_NAME
     ? join(dirname(configPath), ACCOUNT_STATE_FILE_NAME)
     : `${configPath}.state.json`
 }
 
+function normalizePathForComparison(path: string, platform: NodeJS.Platform) {
+  const resolved = resolve(path)
+  return platform === 'win32' || platform === 'darwin'
+    ? resolved.toLowerCase()
+    : resolved
+}
+
+function realpathForComparison(path: string): string | undefined {
+  try {
+    return realpathSync.native(path)
+  } catch {
+    try {
+      return join(realpathSync.native(dirname(path)), basename(path))
+    } catch {
+      return undefined
+    }
+  }
+}
+
+/**
+ * Detect path aliases without requiring either file to exist. This is defense
+ * in depth: hardlinks and bind mounts can still make distinct paths share a
+ * file, because neither is distinguishable through pathname identity.
+ */
+export function accountPathsCollide(
+  configPath: string,
+  statePath: string,
+  platform: NodeJS.Platform = process.platform,
+) {
+  if (
+    normalizePathForComparison(configPath, platform) ===
+    normalizePathForComparison(statePath, platform)
+  ) {
+    return true
+  }
+
+  const configIdentity = realpathForComparison(configPath)
+  const stateIdentity = realpathForComparison(statePath)
+  return (
+    configIdentity !== undefined &&
+    stateIdentity !== undefined &&
+    normalizePathForComparison(configIdentity, platform) ===
+      normalizePathForComparison(stateIdentity, platform)
+  )
+}
+
 export function getAccountStatePath(configPath = getAccountStoragePath()) {
   const explicit = process.env.OPENCODE_OPENAI_AUTH_STATE_FILE?.trim()
-  if (explicit) return explicit
+  if (explicit) {
+    if (accountPathsCollide(configPath, explicit)) {
+      throw new Error(
+        `OPENCODE_OPENAI_AUTH_STATE_FILE resolves to the config path (${resolve(configPath)}). Set OPENCODE_OPENAI_AUTH_STATE_FILE to a different file.`,
+      )
+    }
+    return explicit
+  }
   return deriveStatePath(configPath)
 }
diff --git a/packages/opencode/src/tests/account-paths.test.ts b/packages/opencode/src/tests/account-paths.test.ts
new file mode 100644
index 0000000..fbf9afb
--- /dev/null
+++ b/packages/opencode/src/tests/account-paths.test.ts
@@ -0,0 +1,93 @@
+import { describe, expect, it } from 'bun:test'
+import { mkdirSync, mkdtempSync, symlinkSync } from 'node:fs'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+
+import {
+  accountPathsCollide,
+  deriveStatePath,
+  getAccountStatePath,
+} from '../core/account-paths.ts'
+
+describe('account path resolution', () => {
+  it('derives distinct state paths for distinct config filenames', () => {
+    const directory = '/tmp/account-paths'
+
+    expect(deriveStatePath(join(directory, 'openai-auth.json'))).toBe(
+      join(directory, 'openai-auth-state.json'),
+    )
+    expect(deriveStatePath(join(directory, 'team-openai-auth.json'))).toBe(
+      join(directory, 'team-openai-auth.json.state.json'),
+    )
+  })
+
+  it('refuses an explicit state path that resolves to the config path', () => {
+    const previousStatePath = process.env.OPENCODE_OPENAI_AUTH_STATE_FILE
+    const configPath = '/tmp/account-paths/roster.json'
+
+    try {
+      process.env.OPENCODE_OPENAI_AUTH_STATE_FILE =
+        '/tmp/account-paths/./nested/../roster.json'
+
+      expect(() => getAccountStatePath(configPath)).toThrow(
+        /OPENCODE_OPENAI_AUTH_STATE_FILE.*different file/,
+      )
+
+      process.env.OPENCODE_OPENAI_AUTH_STATE_FILE =
+        '/tmp/account-paths/roster-state.json'
+      expect(getAccountStatePath(configPath)).toBe(
+        '/tmp/account-paths/roster-state.json',
+      )
+    } finally {
+      if (previousStatePath === undefined) {
+        delete process.env.OPENCODE_OPENAI_AUTH_STATE_FILE
+      } else {
+        process.env.OPENCODE_OPENAI_AUTH_STATE_FILE = previousStatePath
+      }
+    }
+  })
+
+  it('treats case-only aliases as equal on common case-insensitive platforms', () => {
+    const root = mkdtempSync(join(tmpdir(), 'account-paths-case-'))
+    const configPath = join(root, 'auth.json')
+    const explicitStatePath = join(root, 'AUTH.JSON')
+
+    expect(accountPathsCollide(configPath, explicitStatePath, 'darwin')).toBe(
+      true,
+    )
+  })
+
+  it('falls back safely when a symlink target is broken', () => {
+    const root = mkdtempSync(join(tmpdir(), 'account-paths-broken-link-'))
+    const brokenPath = join(root, 'broken.json')
+    symlinkSync(join(root, 'missing.json'), brokenPath)
+
+    expect(
+      accountPathsCollide(join(root, 'auth.json'), brokenPath, 'linux'),
+    ).toBe(false)
+  })
+
+  it('wires symlink aliases through the state-path entry point', () => {
+    const previousStatePath = process.env.OPENCODE_OPENAI_AUTH_STATE_FILE
+    const root = mkdtempSync(join(tmpdir(), 'account-paths-wiring-'))
+    const realDirectory = join(root, 'real')
+    const aliasDirectory = join(root, 'alias')
+    const configPath = join(aliasDirectory, 'auth.json')
+    const explicitStatePath = join(realDirectory, 'auth.json')
+    mkdirSync(realDirectory)
+    symlinkSync(realDirectory, aliasDirectory, 'dir')
+
+    try {
+      process.env.OPENCODE_OPENAI_AUTH_STATE_FILE = explicitStatePath
+      expect(() => getAccountStatePath(configPath)).toThrow(
+        /OPENCODE_OPENAI_AUTH_STATE_FILE.*different file/,
+      )
+    } finally {
+      if (previousStatePath === undefined) {
+        delete process.env.OPENCODE_OPENAI_AUTH_STATE_FILE
+      } else {
+        process.env.OPENCODE_OPENAI_AUTH_STATE_FILE = previousStatePath
+      }
+    }
+  })
+})