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Race condition in session prompt state management #11699
Description
Summary
The session prompt module has a race condition in its state management that can cause unexpected behavior when multiple concurrent operations access the same session.
Location
packages/opencode/src/session/prompt.ts:239-264
Issue
The start() function has a check-then-act pattern without atomicity:
function start(sessionID: string) {
const s = state()
if (s[sessionID]) return // CHECK
const controller = new AbortController()
s[sessionID] = { // ACT - race condition window between check and act
abort: controller,
callbacks: [],
}
return controller.signal
}Between the check at line 241 and the write at line 243, another concurrent call could:
- Also pass the check (sees no entry)
- Create its own entry
- Overwrite the first entry
Additionally, the loop() function at line 267-273 can push to callbacks array while the state is being modified.
Impact
- Severity: Medium
- Type: Race Condition
- Effect:
- Lost abort controllers
- Callbacks registered to wrong session
- Potential undefined access errors
Suggested Fix
Use the existing Lock utility for synchronization:
import { Lock } from "../util/lock"
const sessionLock = new Lock()
async function start(sessionID: string) {
return await Lock.write(sessionID, async () => {
const s = state()
if (s[sessionID]) return undefined
const controller = new AbortController()
s[sessionID] = {
abort: controller,
callbacks: [],
}
return controller.signal
})
}Metadata
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github-actions commentedon Feb 2, 2026
This issue might be a duplicate of existing issues. Please check:
Feel free to ignore if none of these address your specific case.
fix(session): prevent concurrent prompt() from creating duplicate use…
github-actions commentedon Apr 3, 2026
To stay organized issues are automatically closed after 90 days of no activity. If the issue is still relevant please open a new one.