# How to Prevent UI Freezes and Crashes During Bulk Timeline Edits via UXP API?

**URL:** <https://forums.creativeclouddeveloper.com/t/how-to-prevent-ui-freezes-and-crashes-during-bulk-timeline-edits-via-uxp-api/11882>\
**Category:** Premiere Pro\
**Tags:** bug, uxp\
**Created:** [April 29, 2026, 8:11pm UTC](https://forums.creativeclouddeveloper.com/t/how-to-prevent-ui-freezes-and-crashes-during-bulk-timeline-edits-via-uxp-api/11882 "2026-04-29T20:11:59Z")\
**Posts on this page:** 16\
**Page:** 1

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**Author:** ![euchfator](https://avatars.discourse-cdn.com/v4/letter/e/3be4f8/32.png) [@euchfator](https://forums.creativeclouddeveloper.com/u/euchfator)\
**Post date:** [April 29, 2026, 8:11pm UTC](https://forums.creativeclouddeveloper.com/t/how-to-prevent-ui-freezes-and-crashes-during-bulk-timeline-edits-via-uxp-api/11882/1 "2026-04-29T20:11:59Z")

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Hi everyone,  
I’m building a UXP plugin for Premiere Pro that auto-arranges clips on the timeline (multi-camera auto-switcher). The entry point is an async function that iterates over potentially hundreds of camera segments and places each one on the timeline.

The UXP docs say the API is asynchronous and should not block the host UI. But in practice, Premiere freezes completely for several seconds (sometimes crashes), and all clip placements appear on the timeline all at once only after the freeze ends — the UI never updates incrementally during the loop.

What the code does (simplified):

```auto
// Called once per camera segment — may run hundreds of times
async function placeClipOnTimeline({
project, editor, projectItem,
inPointSeconds, outPointSeconds,
startSeconds, videoTrackIndex, audioTrackIndex
}) {
const startTick = TickTime.createWithSeconds(startSeconds);
const inTick = TickTime.createWithSeconds(inPointSeconds);
const outTick = TickTime.createWithSeconds(outPointSeconds);

// Step 1: set in/out on the source clip
project.lockedAccess(() => {
project.executeTransaction((compoundAction) => {
compoundAction.addAction(
projectItem.createSetInOutPointsAction(inTick, outTick)
);
}, “Set Source InOut”);
});

// Step 2: overwrite (insert) at the timeline position
project.lockedAccess(() => {
project.executeTransaction((compoundAction) => {
compoundAction.addAction(
editor.createOverwriteItemAction(
projectItem, startTick, videoTrackIndex, audioTrackIndex
)
);
}, “Overwrite Clip”);
});

// Step 3: clear in/out after insertion
project.lockedAccess(() => {
project.executeTransaction((compoundAction) => {
compoundAction.addAction(
projectItem.createClearInOutPointsAction()
);
}, “Clear Source InOut”);
});

// Step 4: re-fetch track to find the inserted clip, then trim it
const track = await sequence.getVideoTrack(videoTrackIndex);
const items = await track.getItems();
const insertedClip = items[items.length - 1];
// … further trim actions via another executeTransaction
}

// Main loop
export async function autoSwitchCamera(cameraSegments) {
for (let i = 0; i < cameraSegments.length; i++) {
await placeClipOnTimeline({ /* params for segment i */ });
}
}

```

What I observe:

Premiere’s UI becomes completely unresponsive while the loop runs.

The timeline does not update incrementally — no clips appear during the freeze.

Once Premiere unfreezes, all clips appear on the timeline at once.

With 500+ segments, Premiere sometimes crashes entirely.

My questions:

Is project.lockedAccess + project.executeTransaction synchronous/blocking on the host side?

Should all three steps (set in/out → overwrite → clear in/out) be combined into a single executeTransaction so the compound action handles the sequencing internally? Already tried this but it seems like there is a race condition(?)

Is there a recommended way to yield between iterations to keep the UI responsive, or does the host lock prevent repainting regardless?

Are there a way to prevent the crash?

Any insight? would be hugely appreciated. Thanks!

​

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<div class="post-metadata">

**Author:** ![PlanarFlow](https://sea1.discourse-cdn.com/flex015/user_avatar/forums.creativeclouddeveloper.com/planarflow/32/4852_2.png) [@PlanarFlow](https://forums.creativeclouddeveloper.com/u/PlanarFlow)\
**Post date:** [April 29, 2026, 10:44pm UTC](https://forums.creativeclouddeveloper.com/t/how-to-prevent-ui-freezes-and-crashes-during-bulk-timeline-edits-via-uxp-api/11882/2 "2026-04-29T22:44:30Z")

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See [PPro segfault crash during concurrent async locked access patterns - #2 by bbb\_999](https://forums.creativeclouddeveloper.com/t/ppro-segfault-crash-during-concurrent-async-locked-access-patterns/11778/2)

I also have a plugin that does A LOT of async and locked access pattern work and have encountered this crash bug. The PPro UXP team has been notified and is working to resolve. As a short term solution, I ended up forcing ALL PPro API calls to be serialized, AND I had to reduce the number of locked access patterns as much as possible. This means combining and making my code more efficient. Seems like there is some behind the scenes async PPro API calls being done inside of UXP that we don’t have control over, hence why I had to reduce the number of locked access patterns, to reduce the chances of this race condition.

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**Author:** ![bbb\_999](https://sea1.discourse-cdn.com/flex015/user_avatar/forums.creativeclouddeveloper.com/bbb_999/32/4247_2.png) [@bbb\_999](https://forums.creativeclouddeveloper.com/u/bbb_999)\
**Post date:** [April 29, 2026, 11:02pm UTC](https://forums.creativeclouddeveloper.com/t/how-to-prevent-ui-freezes-and-crashes-during-bulk-timeline-edits-via-uxp-api/11882/3 "2026-04-29T23:02:02Z")

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We’re working on that one, right now…

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<div class="post-metadata">

**Author:** ![euchfator](https://avatars.discourse-cdn.com/v4/letter/e/3be4f8/32.png) [@euchfator](https://forums.creativeclouddeveloper.com/u/euchfator)\
**Post date:** [April 30, 2026, 4:44am UTC](https://forums.creativeclouddeveloper.com/t/how-to-prevent-ui-freezes-and-crashes-during-bulk-timeline-edits-via-uxp-api/11882/4 "2026-04-30T04:44:34Z")

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In our case, reducing the number of lockedAccess calls is difficult because the core functionality requires placing hundreds (sometimes thousands) of short clips on the timeline. Are there any additional short-term mitigation strategies you would recommend?

Also, since we are currently in the process of porting our panel from CEP to UXP, we’d like to better understand the timeline for CEP deprecation. The documentation mentions:

“CEP extensions continue to be supported; the plan is to support both CEP and UXP for a calendar year, after which we will remove support for CEP extensibility.”

Could you clarify what “a calendar year” refers to in practice? For example:  
Is this counted from Premiere Pro 25.6 release?  
Do you have a more concrete timeline for when CEP support will be fully removed?

Appreciate any guidance you can share.

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**Author:** ![PlanarFlow](https://sea1.discourse-cdn.com/flex015/user_avatar/forums.creativeclouddeveloper.com/planarflow/32/4852_2.png) [@PlanarFlow](https://forums.creativeclouddeveloper.com/u/PlanarFlow)\
**Post date:** [April 30, 2026, 6:00pm UTC](https://forums.creativeclouddeveloper.com/t/how-to-prevent-ui-freezes-and-crashes-during-bulk-timeline-edits-via-uxp-api/11882/5 "2026-04-30T18:00:08Z")

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You can reduce the number of locked access pattern calls by grouping many actions into a group of compound actions that all gets executed in the same locked access pattern. It sounds like in your case it may be worth just waiting until the PPro team has the bugfix in place though.

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**Author:** ![justin2taylor](https://sea1.discourse-cdn.com/flex015/user_avatar/forums.creativeclouddeveloper.com/justin2taylor/32/2031_2.png) [@justin2taylor](https://forums.creativeclouddeveloper.com/u/justin2taylor)\
**Post date:** [May 1, 2026, 4:15pm UTC](https://forums.creativeclouddeveloper.com/t/how-to-prevent-ui-freezes-and-crashes-during-bulk-timeline-edits-via-uxp-api/11882/6 "2026-05-01T16:15:05Z")

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This is the ideal approach with UXP Locked Access transactions, if/when possible.

If you can group actions into a single Locked Access transaction, you’ll get infinitely better performance, and the added benefit of being grouped as a single undo item in history.

We’re doing this for removing/deleting hundreds of clips at a time with success.

The limitation comes however if transactions are dependent on previous transactions requiring them to be separate.

I’ve started a separate issue for this one, requesting `Return Values for Actions` so we can group dependent actions together, instead of only independent actions, without the need for separate transactions:

> [@We need Return Values for Actions within ExecuteTransactions for Undo Groups to make sense](https://forums.creativeclouddeveloper.com/t/we-need-return-values-for-actions-within-executetransactions-for-undo-groups-to-make-sense/11849):
>
> Premiere UXP introduces the concept of creating actions and executing those actions in bulk in order to have more control over the undo history. This is a great step forward from ExtendScript which did not have undo groups, however the implementation fails to make sense in it’s current state. Currently all actions do not return any values as you would expect, so you’re only able to run bulk actions which are unrelated (e.g. delete a bunch of separate clips), while actions that are dependent on…

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<div class="post-metadata">

**Author:** ![euchfator](https://avatars.discourse-cdn.com/v4/letter/e/3be4f8/32.png) [@euchfator](https://forums.creativeclouddeveloper.com/u/euchfator)\
**Post date:** [May 25, 2026, 12:39pm UTC](https://forums.creativeclouddeveloper.com/t/how-to-prevent-ui-freezes-and-crashes-during-bulk-timeline-edits-via-uxp-api/11882/7 "2026-05-25T12:39:38Z")

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Hi, thanks for the responses , really appreciate the acknowledgment from the Adobe team.

Just wanted to follow up on the status of this bug. Is there any update on the fix for the freeze/crash issue with repeated lockedAccess + executeTransaction patterns in UXP Premiere Pro plugins? Moreover, Is there a target release version or estimated timeline for when the fix will ship? @bbb_999

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<div class="post-metadata">

**Author:** ![PlanarFlow](https://sea1.discourse-cdn.com/flex015/user_avatar/forums.creativeclouddeveloper.com/planarflow/32/4852_2.png) [@PlanarFlow](https://forums.creativeclouddeveloper.com/u/PlanarFlow)\
**Post date:** [May 25, 2026, 11:32pm UTC](https://forums.creativeclouddeveloper.com/t/how-to-prevent-ui-freezes-and-crashes-during-bulk-timeline-edits-via-uxp-api/11882/8 "2026-05-25T23:32:47Z")

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I’ll answer this for BBB since I’ve been bugging him about the same thing 😅  
This is partially fixed in the current ppro beta build. The proper full fix is still in the works. No timelines are allowed to be given.

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<div class="post-metadata">

**Author:** ![euchfator](https://avatars.discourse-cdn.com/v4/letter/e/3be4f8/32.png) [@euchfator](https://forums.creativeclouddeveloper.com/u/euchfator)\
**Post date:** [May 26, 2026, 7:15am UTC](https://forums.creativeclouddeveloper.com/t/how-to-prevent-ui-freezes-and-crashes-during-bulk-timeline-edits-via-uxp-api/11882/9 "2026-05-26T07:15:00Z")

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Thanks for the answer! Could you elaborate on what “partially fixed” means? I’ve tried it on the current beta build but it still crashed.

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<div class="post-metadata">

**Author:** ![bbb\_999](https://sea1.discourse-cdn.com/flex015/user_avatar/forums.creativeclouddeveloper.com/bbb_999/32/4247_2.png) [@bbb\_999](https://forums.creativeclouddeveloper.com/u/bbb_999)\
**Post date:** [May 26, 2026, 2:52pm UTC](https://forums.creativeclouddeveloper.com/t/how-to-prevent-ui-freezes-and-crashes-during-bulk-timeline-edits-via-uxp-api/11882/10 "2026-05-26T14:52:43Z")

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Partially fixed = We have addressed some-but-not-all instances of this crash.

No Adobe employee can ever discuss release dates, without also scheduling their own exit interview. 🙂

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<div class="post-metadata">

**Author:** ![euchfator](https://avatars.discourse-cdn.com/v4/letter/e/3be4f8/32.png) [@euchfator](https://forums.creativeclouddeveloper.com/u/euchfator)\
**Post date:** [July 14, 2026, 2:18am UTC](https://forums.creativeclouddeveloper.com/t/how-to-prevent-ui-freezes-and-crashes-during-bulk-timeline-edits-via-uxp-api/11882/11 "2026-07-14T02:18:32Z")

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Hello, I want to follow up this thread, does this issue already fixed on the newest Premiere update ( **26.3** )? Because we already update our Premiere to the latest version but the bug still persist. Thankyou in advance

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<div class="post-metadata">

**Author:** ![bbb\_999](https://sea1.discourse-cdn.com/flex015/user_avatar/forums.creativeclouddeveloper.com/bbb_999/32/4247_2.png) [@bbb\_999](https://forums.creativeclouddeveloper.com/u/bbb_999)\
**Post date:** [July 14, 2026, 4:54pm UTC](https://forums.creativeclouddeveloper.com/t/how-to-prevent-ui-freezes-and-crashes-during-bulk-timeline-edits-via-uxp-api/11882/12 "2026-07-14T16:54:10Z")

</div>

As you have found, the issue is not yet completely fixed.

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<div class="post-metadata">

**Author:** ![euchfator](https://avatars.discourse-cdn.com/v4/letter/e/3be4f8/32.png) [@euchfator](https://forums.creativeclouddeveloper.com/u/euchfator)\
**Post date:** [September 9, 2026, 4:25am UTC](https://forums.creativeclouddeveloper.com/t/how-to-prevent-ui-freezes-and-crashes-during-bulk-timeline-edits-via-uxp-api/11882/13 "2026-09-09T04:25:46Z")

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Hello, I want to follow up this thread, does this issue already fixed on the newest Premiere update ( **26.3.2** )?

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<div class="post-metadata">

**Author:** ![euchfator](https://avatars.discourse-cdn.com/v4/letter/e/3be4f8/32.png) [@euchfator](https://forums.creativeclouddeveloper.com/u/euchfator)\
**Post date:** [September 25, 2026, 7:11am UTC](https://forums.creativeclouddeveloper.com/t/how-to-prevent-ui-freezes-and-crashes-during-bulk-timeline-edits-via-uxp-api/11882/14 "2026-09-25T07:11:33Z")

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Hello, following up on this thread.

The 26.5.1 release notes include:

> _Adding hundreds of new clips to a sequence at once could cause a spike in memory usage._

Is that fix related to this issue? We’ve updated Premiere Pro to 26.5.1 and run our plugin again, and it still crashes

Could you confirm whether this crash is covered by that fix, or whether it’s a separate issue still open?

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<div class="post-metadata">

**Author:** ![bbb\_999](https://sea1.discourse-cdn.com/flex015/user_avatar/forums.creativeclouddeveloper.com/bbb_999/32/4247_2.png) [@bbb\_999](https://forums.creativeclouddeveloper.com/u/bbb_999)\
**Post date:** [September 25, 2026, 7:02pm UTC](https://forums.creativeclouddeveloper.com/t/how-to-prevent-ui-freezes-and-crashes-during-bulk-timeline-edits-via-uxp-api/11882/15 "2026-09-25T19:02:19Z")

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The problem mentioned in the release notes, is unrelated to the issue reported in this forum.

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<div class="post-metadata">

**Author:** ![Leyero](https://sea1.discourse-cdn.com/flex015/user_avatar/forums.creativeclouddeveloper.com/leyero/32/4228_2.png) [@Leyero](https://forums.creativeclouddeveloper.com/u/Leyero)\
**Post date:** [September 27, 2026, 1:08am UTC](https://forums.creativeclouddeveloper.com/t/how-to-prevent-ui-freezes-and-crashes-during-bulk-timeline-edits-via-uxp-api/11882/16 "2026-09-27T01:08:10Z")

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Looking forward to a fix of this issue.

Working with UXP in Premiere feels like a breath of fresh air on how fast it is compared CEP!