[Bug] Race condition in auth.json causes provider credentials to disappear

[randomm]

Problem

Users report that providers keep disappearing from ~/.local/share/opencode/auth.json. Investigation reveals race conditions and error handling flaws in the authentication storage system.

Root Cause Analysis

1. Non-Atomic Read-Modify-Write Pattern

Auth.set() in packages/opencode/src/auth/index.ts:

export async function set(key: string, info: Info) {
  const file = Bun.file(filepath)
  const data = await all()  // READ
  await Bun.write(file, JSON.stringify({ ...data, [key]: info }, null, 2))  // WRITE
  await fs.chmod(file.name!, 0o600)
}

Problem: Between read and write, another process can write, causing data loss.

2. Silent Failure Returns Empty Object

Auth.all() silently returns {} on any read failure:

const data = await file.json().catch(() => ({}) as Record<string, unknown>)

Problem: If file is corrupted/unreadable, next Auth.set() writes empty object + new provider, erasing all existing providers.

3. No File Locking

A Lock utility exists at util/lock.ts but is not used by the auth module. Multiple processes compete for the same file:

• CLI TUI
• Dev server (bun dev -- serve)
• Web app (via SDK)
• Desktop app
• Multiple terminal windows

4. Race Condition Timeline

Time	Process A	Process B	File State
T1	Reads: { p1, p2 }	-	{ p1, p2 }
T2	Adding p3...	Reads: { p1, p2 }	{ p1, p2 }
T3	Writes: { p1, p2, p3 }	-	{ p1, p2, p3 }
T4	Done	Writes: { p1, p2 }	{ p1, p2 } ❌ p3 lost

Key Files

File	Purpose
packages/opencode/src/auth/index.ts	Core auth.json read/write operations
packages/opencode/src/provider/auth.ts	Provider auth flow (OAuth/API key)
packages/opencode/src/util/lock.ts	Lock utility (NOT used by auth)

Suggested Fix

Option 1: Use Existing Lock Utility

import { Lock } from "../util/lock"

export async function set(key: string, info: Info) {
  const release = await Lock.write("auth")
  try {
    const file = Bun.file(filepath)
    const data = await all()
    await Bun.write(file, JSON.stringify({ ...data, [key]: info }, null, 2))
    await fs.chmod(file.name!, 0o600)
  } finally {
    release()
  }
}

Option 2: Atomic Write with Rename

export async function set(key: string, info: Info) {
  const file = Bun.file(filepath)
  const tempFile = filepath + ".tmp." + crypto.randomUUID()
  const data = await all()
  await Bun.write(tempFile, JSON.stringify({ ...data, [key]: info }, null, 2))
  await fs.chmod(tempFile, 0o600)
  await fs.rename(tempFile, filepath)  // Atomic on most filesystems
}

Option 3: Better Error Handling

export async function all(): Promise<Record<string, Info>> {
  const file = Bun.file(filepath)
  if (!await file.exists()) return {}
  
  try {
    const data = await file.json()
    // ... validation
  } catch (e) {
    log.error("Failed to read auth.json, preserving existing file", { error: e })
    throw e  // Don't silently return empty object!
  }
}

Priority

High - Data loss affecting user credentials

Reproduction

1. Open two terminal windows
2. Run bun dev in both (or bun dev + bun dev -- serve)
3. Add a provider in one terminal
4. Add a different provider in the other terminal quickly
5. Check auth.json - one provider may be missing

[randomm]

Fixed in PR #48