[Bug]: rpc couch_db:get_db_info/1 {badmatch,{error,enoent}} on database after compaction

Reproduce the failure with the empty database and compaction commands in the issue, then inspect src/couch_bt_engine.erl at line 264 and src/couch_db.erl at line 625, along with the fabric_rpc stack frames. Done means GET /test continues to return normal database information after compaction, with coverage for the reported enoent case.

Version

3.5.1

Describe the problem you're encountering

I tried to run one small single node of couchdb for personal use in docker desktop for obsidian selfhosted live sync.
During Initialization of obsidian vault with 2k .md files (~2.2mb size of obisidian vault) and uploading it to database (~6.6mb database size in fauxton ui) I encountered an http 500 error that prevents me from getting synced.
Error get fixed with reboot of couchdb container.
Noticed that GET /db queries fails with error 500, but GET\PUT /db/_local/<somestr> queries finishes with 200 and 201 and database size still grows, so uploading files is ok, but getting it back doesnt.
Noticed that this error begin to pop after couchdb decides to run auto-compaction (because of db grows??).

Tried to manually run compaction on new database to confirm and yes - after compaction database became unavailable.

Expected Behaviour

database works stable as intended without errors.

Steps to Reproduce

1. run couchdb:latest docker container with pretty much default configuration
2. create new database (leave it empty or add some data - doesn't matter)
3. run curl -H "Content-Type: application/json" -X POST http://<name>:<pass>@localhost:5984/<db-name>/_compact
4. run curl http://<name>:<pass>@localhost:5984/<db-name>

it returns {"error":"error","reason":"{badmatch,{error,enoent}}"}

if compaction is still running it will return normal json as intended with "compact_running":true value)

Your Environment

I'm running couchdb as just single node in docker.desktop under win11 (with wsl)
image: couchdb:latest
version 3.5.1

Additional Context

here is debug logs from reproduction with empty test database

curl http://gidsik:<pass>@localhost:5984/test

[notice] 2026-03-03T00:50:17.729237Z nonode@nohost <0.643.0> 0884c5319c localhost:5984 172.18.0.1 gidsik GET /test 200 ok 156

curl -H "Content-Type: application/json" -X POST http://gidsik:<pass>@localhost:5984/test/_compact

[debug] 2026-03-03T00:53:19.917826Z nonode@nohost <0.925.0> -------- Starting compaction for db "shards/80000000-ffffffff/test.1772498476" at 0
[debug] 2026-03-03T00:53:19.917847Z nonode@nohost <0.919.0> -------- Starting compaction for db "shards/00000000-7fffffff/test.1772498476" at 0
[notice] 2026-03-03T00:53:19.917873Z nonode@nohost <0.1212.0> fccfbe44c6 localhost:5984 172.18.0.1 gidsik POST /test/_compact 202 ok 1
[debug] 2026-03-03T00:53:19.920434Z nonode@nohost <0.1252.0> -------- Compaction process spawned for db "shards/00000000-7fffffff/test.1772498476"
[debug] 2026-03-03T00:53:19.920432Z nonode@nohost <0.1251.0> -------- Compaction process spawned for db "shards/80000000-ffffffff/test.1772498476"
[debug] 2026-03-03T00:53:20.185521Z nonode@nohost <0.242.0> -------- New task status for <0.1252.0>: [{changes_done,0},{database,<<"shards/00000000-7fffffff/test.1772498476">>},{phase,document_copy},{progress,0},{started_on,1772499200},{total_changes,0},{type,database_compaction},{updated_on,1772499200}]
[debug] 2026-03-03T00:53:20.205917Z nonode@nohost <0.242.0> -------- New task status for <0.1251.0>: [{changes_done,0},{database,<<"shards/80000000-ffffffff/test.1772498476">>},{phase,document_copy},{progress,0},{started_on,1772499200},{total_changes,0},{type,database_compaction},{updated_on,1772499200}]
[debug] 2026-03-03T00:53:20.361294Z nonode@nohost <0.242.0> -------- New task status for <0.1252.0>: [{changes_done,0},{database,<<"shards/00000000-7fffffff/test.1772498476">>},{phase,docid_sort},{progress,0},{started_on,1772499200},{total_changes,0},{type,database_compaction},{updated_on,1772499200}]
[debug] 2026-03-03T00:53:20.383774Z nonode@nohost <0.242.0> -------- New task status for <0.1251.0>: [{changes_done,0},{database,<<"shards/80000000-ffffffff/test.1772498476">>},{phase,docid_sort},{progress,0},{started_on,1772499200},{total_changes,0},{type,database_compaction},{updated_on,1772499200}]
[debug] 2026-03-03T00:53:20.461284Z nonode@nohost <0.242.0> -------- New task status for <0.1252.0>: [{changes_done,0},{database,<<"shards/00000000-7fffffff/test.1772498476">>},{phase,docid_copy},{progress,0},{started_on,1772499200},{total_changes,0},{type,database_compaction},{updated_on,1772499200}]
[debug] 2026-03-03T00:53:20.490932Z nonode@nohost <0.242.0> -------- New task status for <0.1251.0>: [{changes_done,0},{database,<<"shards/80000000-ffffffff/test.1772498476">>},{phase,docid_copy},{progress,0},{started_on,1772499200},{total_changes,0},{type,database_compaction},{updated_on,1772499200}]

curl http://gidsik:<pass>@localhost:5984/test

[error] 2026-03-03T00:53:22.528529Z nonode@nohost <0.1317.0> aaa3bb5814 rpc couch_db:get_db_info/1 {badmatch,{error,enoent}} [{couch_bt_engine,get_size_info,1,[{file,"src/couch_bt_engine.erl"},{line,264}]},{couch_db,get_db_info,1,[{file,"src/couch_db.erl"},{line,625}]},{fabric_rpc,with_db,3,[{file,"src/fabric_rpc.erl"},{line,376}]},{rexi_server,init_p,3,[{file,"src/rexi_server.erl"},{line,141}]}]
[error] 2026-03-03T00:53:22.528553Z nonode@nohost <0.1316.0> aaa3bb5814 rpc couch_db:get_db_info/1 {badmatch,{error,enoent}} [{couch_bt_engine,get_size_info,1,[{file,"src/couch_bt_engine.erl"},{line,264}]},{couch_db,get_db_info,1,[{file,"src/couch_db.erl"},{line,625}]},{fabric_rpc,with_db,3,[{file,"src/fabric_rpc.erl"},{line,376}]},{rexi_server,init_p,3,[{file,"src/rexi_server.erl"},{line,141}]}]
[notice] 2026-03-03T00:53:22.528732Z nonode@nohost <0.1278.0> aaa3bb5814 localhost:5984 172.18.0.1 gidsik GET /test 500 ok 2