[ShawnChen-Sirius]

Two things the same durable object needed different code for depending on which language opened it, and neither difference was anything the contract asked for.

One URL. The local backend answered only to local:, chdb-node only to file:, chdb-go to either — so no single namespace URL could be handed to all three. It now takes both here (chdb-node takes both as of chdb-io/chdb-node#94). A file: URL is percent-encoded and a local: path is not; that is the only difference between them.

One default database. A cold object was created in mem here and default in Node and Go. The head is authoritative once an object exists, so this never broke interop — but the same application ported between bindings addressed a differently-named table. default wins because two of three bindings already had it and it is what an unqualified statement means in chDB anyway. The contract now states it, so there is one answer rather than three implementations.

The refusal says which engine is loaded. It named the ABI it needed and nothing else, so its two causes read identically: an engine too old to have the ABI, and a new engine that the wrapper is not loading because something else owns chdb/. And the command it printed only became true with chdb-core 26.7.3 — the first release carrying the ABI that is published to PyPI. It names chdb-core rather than chdb because pip leaves a satisfied dependency alone, so upgrading chdb reports success and moves no engine.

chdb.durable needs chdb-core 26.7.2-rc.2 or newer, which added backup_database / restore_database / classify_query.
The engine loaded here reports 26.7.0.

    pip install -U chdb-core

Verified

Cross-binding recovery, contract §7.5 — the item no repository had implemented. Every writer produces a 100-row checkpointed base plus a 50-row WAL tail that is flushed and not checkpointed, so a reader has to restore the base and replay the WAL. 3×3, on the local backend and again on real AWS S3, every cell 150 rows / sum(id) 11175 / base 100 + wal 50, each reader taking the database name from head.json:

writer \ reader	Python	Node	Go
Python	✓	✓	✓
Node	✓	✓	✓
Go	✓	✓	✓

After this change all three take the same URL string and the same database name.

Also: tests/test_durable.py 50 passed against chdb-core 26.7.2-rc.2, and the whole suite again against real AWS S3 (DAO_TEST_URL=s3://…, 49 passed in 7 minutes). The refusal message was checked from where a user actually is — chdb on PyPI's newest chdb-core, 26.7.0 — and it names 26.7.0.

Two tests changed rather than being added to

test_control_statements_refused and test_reopen_honors_persisted_db both relied on the default being mem. With the default moved, the first one's USE default would have been a no-op instead of a refusal, and the second would have had nothing to disagree with. Both now name mem explicitly, which is what they were really testing.

Follow-ups, once 26.7.3 is on PyPI

• add chdb-core>=26.7.3 to the durable extra, so pip install "chdb[durable]" resolves an ABI-carrying engine deterministically
• drop the CHDB_CORE_ABI_WHEEL pin from the durable conformance step in the four wheel workflows; it exists only because no chdb-core on PyPI exported the ABI

🤖 Generated with Claude Code

Note

Standardize durable bindings on default database and add file: URL support to make_backend

• Adds the shared DEFAULT_DATABASE constant (value default) in protocol.py and switches DurableObject, Namespace, and contract docs from the old mem default to it. Persisted head data remains authoritative on reopen.
• Updates make_backend in backends/init.py to route file: URLs into the local filesystem backend, percent-decoding the path before resolution; local: and bare paths stay literal.
• Improves ABI mismatch errors in engine.py to report the loaded engine version and, for ManagedConnection, the missing required attributes.
• Adds installation docs and bumps the documented minimum chdb-core to 26.7.2-rc.2.
• Behavioral Change: cold-created durable objects without an explicit db now land in default instead of mem; existing tests that relied on the implicit mem default are updated to pass it explicitly.

^{Macroscope summarized 0dad0fc.}

[ShawnChen-Sirius]

@wudidapaopao please review this PR

[wudidapaopao]

LGTM