remotion-dev/remotion · error · RemotionException

Could not read progress for render {render_id}: {error}

Error message

Could not read progress for render {render_id}: {error}

What it means

The Python client's cancel_render_on_lambda() first reads renders/{render_id}/progress.json from S3 via get_object and parses it as JSON. Any boto3 ClientError (most commonly NoSuchKey because the object does not exist), or KeyError/TypeError/json.JSONDecodeError from a malformed body, is re-raised as RemotionException with the original error chained via 'from error'.

Source

Thrown at packages/lambda-python/remotion_lambda/remotionclient.py:640

        )
        if body_object:
            return RenderMediaResponse(
                bucket_name=body_object['bucketName'], render_id=body_object['renderId']
            )

        return None

    def cancel_render_on_lambda(self, render_id: str, bucket_name: str) -> None:
        """Cancel a render started with ``enable_cancellation=True``."""
        s3_client = self._create_s3_client()
        try:
            progress_object = s3_client.get_object(
                Bucket=bucket_name,
                Key=f"renders/{render_id}/progress.json",
            )
            progress = json.loads(progress_object['Body'].read())
        except (ClientError, KeyError, TypeError, json.JSONDecodeError) as error:
            raise RemotionException(
                f"Could not read progress for render {render_id}: {error}"
            ) from error

        if progress.get('cancellationEnabled') is not True:
            raise RemotionInvalidArgumentException(
                f"Cannot cancel render {render_id}: The render was not started "
                "with enableCancellation: true."
            )

        try:
            s3_client.put_object(
                Bucket=bucket_name,
                Key=f"renders/{render_id}/cancel.json",
                Body=json.dumps({'cancelledAt': int(time.time() * 1000)}),
                ContentType='application/json',
            )
        except ClientError as error:
            raise RemotionException(

View on GitHub (pinned to 10db9de073)

Solutions

1. Verify render_id is the exact value returned by render_media_on_lambda() - no trimming or case changes.
2. If the render already completed, cancellation is unnecessary: catch the error and treat 'NoSuchKey' in the message as already-finished.
3. Check the bucket_name and region arguments against the ones the render actually used.
4. Inspect the chained cause - the boto3 error code distinguishes NoSuchKey, AccessDenied, and NoSuchBucket, each with a different fix.

import boto3
from botocore.exceptions import ClientError

s3 = boto3.client("s3", region_name=region)
try:
    s3.head_object(Bucket=bucket_name, Key=f"renders/{render_id}/progress.json")
except ClientError as e:
    if e.response["Error"]["Code"] in ("404", "NoSuchKey", "NotFound"):
        pass  # nothing to cancel - render already finished or wrong id
    else:
        raise

from remotion_lambda.errors import RemotionException

try:
    client.cancel_render_on_lambda(render_id, bucket_name)
except RemotionException as e:
    msg = str(e)
    if "NoSuchKey" in msg:
        # render already finished or id is wrong - nothing to cancel
        return
    if "AccessDenied" in msg:
        raise RuntimeError("Cancel credentials lack S3 read/write access") from e
    raise

When it happens

Trigger: Calling cancel_render_on_lambda() with a wrong or typo'd render_id (NoSuchKey); canceling after the render already finished and cleanup deleted progress.json; passing a bucket_name/region that differs from the render's; a truncated or non-JSON body at the key (e.g. an XML error page from an S3-compatible endpoint).

Common situations: Retry logic that attempts to cancel a stale render long after it finished; render_id copied from logs with a missing character; default bucket name used while the render went to a custom bucket; MinIO/R2-style endpoints returning unexpected bodies.

Related errors

• Could not cancel render {render_id}: {error}
• Cannot cancel render {$renderId}: The render was not started
• Cannot cancel render {render_id}: The render was not started
• You have multiple buckets ({', '.join(buckets)}) in your S3
• could not read progress for render %q: %w

AI-assisted analysis of remotion-dev/remotion@10db9de073 (2026-08-22). Data as JSON: /api/errors/b2ba49960ca4933a. Report an issue: GitHub.