Bitcoin 30 wallet deletion bug severity analysis and how it could have been prevented with damagebdd #Faceplant is inevitable without #verification ... running and gunning with no coverage ...
Bitcoin Core v30’s “wallet deletion” class bug (reported Dec 20, 2025) is Severity: High (user-funds at risk via local data-loss) even if it’s “just” a filesystem mistake.
What happened (failure mode)
A user migrates a legacy (BerkeleyDB) wallet.dat to the new descriptor wallet format. Migration appears to complete, then on restart Bitcoin Core can’t find the wallet — and the entire wallet directory is missing (not just a single file). The issue report shows a backup being created, then later Core logs: Specified -walletdir "/mnt/bitcoin/wallets" does not exist.
v30 explicitly pushes users into this path because legacy BDB wallets can’t be created/loaded anymore and must be migrated.
Severity analysis (why this is not “minor”)
Impact
Worst case: user believes funds are gone (because keys are “gone” locally), triggering panic actions and risky recovery steps.
Even if a .legacy.bak exists (as the report suggests), the UX is still “your wallet vanished”, which is catastrophic for a custody component.
Likelihood
Likely rare / edge-path (mount points, walletdir on external storage, permissions, path handling, race/cleanup logic). But the key is: it happens during a routine “recommended” workflow.
Blast radius
Local-only, but wallet software is where local-only bugs become existential. This is the exact class of bug that wrecks trust: silent destructive side effects.
Overall
High severity for wallet users (data-loss class).
Critical severity if any downstream tooling assumes “migration is safe” and automates it.
---
How this could have been prevented (DamageBDD lens)
This is the quintessential “#Faceplant is inevitable without #verification” moment because the expected behavior is plain English:
> “Migrating a wallet must never delete the wallet directory (or anything outside the target wallet file set).”
DamageBDD-style prevention is basically: codify invariants + run them continuously across realistic environments.
1) Lock in non-destructive invariants (BDD, not vibes)
Examples of invariants that should have had tests before shipping:
Migration creates a new descriptor wallet and preserves originals (or preserves a recoverable backup).
Migration never removes walletdir, even on failure, interruption, restart, or partial state.
Cleanup routines only delete files they created, within an allowlist, and only after a post-migration validation step.
2) Regression matrix that matches real operator setups
This bug smells like a path/FS edge case. So the test matrix should include:
walletdir on mounted volumes (/mnt/...), network FS, removable disks
symlinks
read-only / noexec mounts
low disk space
abrupt process exit mid-migration
concurrent wallet open/close sequences
3) Safety rails in implementation (what verification would force)
Two-phase commit for migration: write to new location → fsync → verify open/read → only then mark migrated.
Never “rm -rf a directory” as cleanup; delete explicit filenames you created.
Crash-safe journaling: on restart, detect “migration in progress” and roll forward/rollback safely.
---
A DamageBDD-flavoured BDD feature (catch it automatically)
Even without filesystem assertions, you can catch “walletdir vanished” by probing RPC behavior after migration.
Feature: Bitcoin Core v30 wallet migration must be non-destructive
Background:
Given I am using server "
http://127.0.0.1:8332":
And I set "Content-Type" header to "application/json"
Scenario: migratewallet does not break wallet directory visibility
When I make a POST request to "/"
"""
{"jsonrpc":"1.0","id":"m1","method":"migratewallet","params":[]}
"""
Then the response status must be "200"
Then the json at path "$.error" must be "null"
# Post-condition: walletdir still exists from Core’s perspective
When I make a POST request to "/"
"""
{"jsonrpc":"1.0","id":"m2","method":"listwalletdir","params":[]}
"""
Then the response status must be "200"
Then the json at path "$.error" must be "null"
Those step types (server selection, headers, POST, status checks, JSON-path assertions) are exactly the sort of primitives DamageBDD is built around.
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The punchline (your framing is correct)
This isn’t “haha a bug”. This is:
Running and gunning with no coverage → destructive edge case → users eat the blast.
#Faceplant is inevitable without #verification.
Hashtags (one line):
#Bitcoin #BitcoinCore #Wallets #DataLoss #BDD #DamageBDD #Verification #ReliabilityEngineering #DevSecOps #RegressionTesting #Faceplant
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