Build in parallel races itself (“already working”); checklist freezes mid-build; mid-build interrupt needs Multitask workaround

Support Bug Reports
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1

Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

Three related Build Mode UX bugs that break trust in parallel builds and progress tracking. All happen while iterating a plan in Build/Plan mode, then committing to build.

Bug 1 - “Build in parallel” appears to spawn a duplicate conflicting agent

I iterate on a complicated plan with the agent (go back and forth refining recommendations) before committing. When I commit and choose the dropdown option to build in parallel, I immediately get an error-style response along the lines of: the agent is already working on that / finishing in the background.

I did not send a second prompt after clicking build in parallel. It feels like Cursor launches two parallel threads with the same instruction set; the first starts work, then the second tries to start the same work, hits a conflict, and then just waits on the background job so it can “update me” instead of joining as a real parallel worker. Parallel build does not feel like it is actually helping; it looks like a duplicate kickoff.

Bug 2 - Build checklist / todos stop updating mid-build

During the build phase, the agent issues a checklist (often ~10 items). The UI often marks only one item complete, then never updates again. When the build finishes I get a completion notification, but the checklist still stays stale. If I prompt the agent about it after the fact, it will update the list retrospectively - which is useless for gauging progress and ETA while the build is running. I rely on that list to understand where the build is.

Bug 3 - Hard to interrupt / collaborate mid-build

While a build is running, I often want to add clarifying info or correct course (either because the agent said something that triggered a thought, or because I kept thinking about the problem). Successful interrupt / mid-run collaboration is unreliable. The workaround that works for me is clicking Multitask and sending the info that way, but that is not an elegant way to collaborate on an in-progress build.

Steps to Reproduce

Bug 1

Open Plan/Build mode on a non-trivial feature.
Iterate with the agent several times refining the plan (do not build yet).
Commit to the plan and choose Build in parallel from the dropdown.
Observe: immediate conflict / “already working on that” style response without any further user action.
Bug 2

Start a build that produces a multi-item checklist/todo list.
Watch the checklist as tools complete.
Observe: list marks ~1 item done, then freezes for the rest of the run.
When build completes/notifies, checklist still not fully updated unless you ask the agent afterward.
Bug 3

Start a long build.
Try to send additional guidance / corrections in the same thread while it runs (without Multitask).
Observe: interrupt/collaboration is unreliable.
Using Multitask to send the same message works better, but feels like a workaround.

Expected Behavior

Parallel build: one coordinated parallel build that either waits for a clean handoff or spins workers that divide the plan - not a second agent that races the first and errors with “already working.”
Checklist: todos update as each item completes, and reflect final state when the build finishes.
Interrupt: a clear, reliable way to inject mid-build guidance without relying on Multitask as the primary path.

Operating System

Windows 10/11

Version Information

Version: 3.3.16 (system setup)
VSCode Version: 1.105.1
Commit: 7f0f522221d0ba220e4edb766bb3c47c08c14ab0
Date: 2026-05-06T20:40:56.501Z
Layout: glass
Build Type: Stable
Release Track: Default
Electron: 39.8.1
Chromium: 142.0.7444.265
Node.js: 22.22.1
V8: 14.2.231.22-electron.0
OS: Windows_NT x64 10.0.26200

Does this stop you from using Cursor

No - Cursor works, but with this issue

5

Hey, thanks for the detailed report. You laid out all three bugs clearly, which really helps. We already know about all three and we’re tracking them. Quick notes on each one, including what works right now:

Bug 1 - Build in parallel hits already working
This happens when you click Build while a chat turn is still running or waiting for an answer to a question AskQuestion. At that point a second agent gets spawned on the same working tree with no coordination, so you see already working. Workaround: first answer the pending question or cancel the current turn, wait until the chat settles, and only then click Build in parallel. Bug is confirmed, but there’s no fix timeline yet.

Bug 2 - checklist or todos freeze mid-build
Known gap: during parallel build, the parent agent doesn’t always move its todos from in_progress to completed as work finishes, so the list looks frozen even though the work is still going. Like you noticed, after you send a request the agent updates the list retrospectively. For real-time ETA, it’s not reliable right now. This is on our side too, no ETA yet.

Bug 3 - interrupt or collaboration mid-build
Queued messages during a running turn don’t always reliably stay in the right mode yet, so mid-run changes can be flaky. The Multitask flow you’re using is the supported way for this right now, so it’s not really a hack. It’s the workable option until we improve queued message reliability.

One request for next time: if you’re reporting multiple separate bugs, it’s better to create separate threads. That way each one maps to its own tracking and doesn’t get mixed with the others, and it’s easier for you to follow updates for each issue. If you can, please split these three into separate threads, but what you sent is already captured.

Let me know if the Bug 1 workaround doesn’t help, or if you notice anything else.