D1 Import API becomes unstable after toggling Read Replication

Environment

• Wrangler: reproduced with 4.56.0, 4.82.2, and 4.85.0
• Node.js: 22
• OS: Linux
• D1 region: APAC
• Command path:

wrangler d1 execute <DB_NAME> --remote --file ./d1_file_select_probe.sql --yes

The SQL file is tiny, for example:

SELECT 5;

Bug

After enabling or disabling D1 Read Replication, wrangler d1 execute --remote --file becomes unstable even for tiny SQL files.

This command uses the D1 Import API (/import), not the normal query API (/query). The same database can still run small SQL through --command, which uses /query.

The failure appears to affect the new import/upload path. When the same file is retried and Wrangler prints:

File already uploaded. Processing.

that cached-etag path is not affected and still succeeds. Therefore, a successful retry with the same file does not prove that the fresh upload/init path has recovered.

Actual Results

UTC time	DB	Import stage	Result
2026-04-26T10:54:49Z	main DB	first /import request	60s later: 504 / 7009
2026-04-26T11:08:12Z	main DB	first /import request	60s later: 504 / 7009
2026-04-26T11:17:52Z	main DB	first /import returned 200, second /import timed out	504 / 7009
2026-04-26T11:21:19Z	probe DB	two /import requests returned 200	Import API body error: Network connection lost.

Example errors:

Upstream service unavailable [code: 7009]

✘ [ERROR] Network connection lost.

Expected

wrangler d1 execute --remote --file should reliably process tiny SQL files, or return a clear actionable error if D1 Import API is incompatible with recent Read Replication state changes.

Notes

This does not look like a SQL size/content issue. The failing files contain only SELECT N;.

I searched existing public issues/discussions and did not find the same Read Replication + D1 Import API report.

Could the D1 team confirm whether Import API has any known interaction with Read Replication enable/disable transitions?

I can provide private details if needed:

• account ID
• database IDs
• exact UTC timestamps
• sanitized Wrangler debug logs