diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,9 @@
+# v1.0.7.0
+
+## Non-breaking
+
+- Added a `connectdb` spec covering a `postgresql://` URI whose host segment is a percent-encoded Unix-socket directory, checked via the parsed host rather than the failure message. Found `pqi-native`'s URI parser never runs the host segment through percent-decoding, unlike every sibling component.
+
 # v1.0.6.0
 
 ## Non-breaking
diff --git a/pqi-conformance.cabal b/pqi-conformance.cabal
--- a/pqi-conformance.cabal
+++ b/pqi-conformance.cabal
@@ -1,6 +1,6 @@
 cabal-version: 3.0
 name: pqi-conformance
-version: 1.0.6.0
+version: 1.0.7.0
 category: Database, PostgreSQL, Testing
 synopsis: Differential conformance tests for pqi adapters
 description:
@@ -95,6 +95,7 @@
     Pqi.Conformance.Operation.CmdTuples
     Pqi.Conformance.Operation.Connectdb
     Pqi.Conformance.Operation.Connectdb.Rejection
+    Pqi.Conformance.Operation.Connectdb.UnixSocketUri
     Pqi.Conformance.Operation.ConnectionNeedsPassword
     Pqi.Conformance.Operation.ConnectionUsedPassword
     Pqi.Conformance.Operation.ConnectPoll
diff --git a/src/library/Pqi/Conformance/Operation/Connectdb.hs b/src/library/Pqi/Conformance/Operation/Connectdb.hs
--- a/src/library/Pqi/Conformance/Operation/Connectdb.hs
+++ b/src/library/Pqi/Conformance/Operation/Connectdb.hs
@@ -15,6 +15,7 @@
 import Pqi.Conformance.Harness
 import Pqi.Conformance.Observation
 import qualified Pqi.Conformance.Operation.Connectdb.Rejection as Rejection
+import qualified Pqi.Conformance.Operation.Connectdb.UnixSocketUri as UnixSocketUri
 import Pqi.Conformance.Prelude
 import qualified Pqi.Conformance.Reference as Reference
 import Test.Hspec
@@ -23,6 +24,7 @@
 spec :: Pqi.Adapter -> SpecWith ByteString
 spec adapter = do
   Rejection.spec adapter
+  UnixSocketUri.spec adapter
 
   describe "connectdb" do
     it "opens a usable connection" \conninfo ->
diff --git a/src/library/Pqi/Conformance/Operation/Connectdb/UnixSocketUri.hs b/src/library/Pqi/Conformance/Operation/Connectdb/UnixSocketUri.hs
new file mode 100644
--- /dev/null
+++ b/src/library/Pqi/Conformance/Operation/Connectdb/UnixSocketUri.hs
@@ -0,0 +1,44 @@
+-- | Coverage for a @postgresql:\/\/@ URI conninfo whose host segment is a
+-- percent-encoded Unix-domain socket directory (e.g. @%2ftmp%2fsome-dir@),
+-- per PostgreSQL's own URI convention:
+-- <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNSTRING-URIS>.
+--
+-- Found in @pqi-native@: @parseUri@'s host branch is never run through
+-- @pctDecode@, unlike every sibling component (user, password, database,
+-- query params), which all are. The candidate therefore treats the
+-- still-percent-encoded string as a literal hostname to resolve via DNS,
+-- instead of decoding it into the filesystem socket-directory path the URI
+-- names.
+--
+-- This is deliberately checked via 'Pqi.host' rather than
+-- 'Pqi.errorMessage': both adapters fail to connect either way (there is no
+-- such socket directory), but their failure text is produced by unrelated,
+-- adapter-specific machinery (DNS resolution vs. a filesystem check) and
+-- isn't expected to match byte-for-byte. What must match is the host each
+-- adapter parsed out of the conninfo, which is deterministic and
+-- OS\/locale-independent.
+module Pqi.Conformance.Operation.Connectdb.UnixSocketUri
+  ( spec,
+  )
+where
+
+import qualified Pqi
+import Pqi.Conformance.Harness
+import Pqi.Conformance.Prelude
+import Test.Hspec
+
+spec :: Pqi.Adapter -> SpecWith ByteString
+spec adapter =
+  describe "connectdb" do
+    describe "a URI conninfo with a percent-encoded Unix-socket host" do
+      it "decodes the host the same way the reference does" \_ ->
+        differentialConnect adapter conninfo \adapter' conninfo' -> do
+          connection <- Pqi.connectdb adapter' conninfo'
+          observedHost <- Pqi.host connection
+          Pqi.finish connection
+          pure observedHost
+  where
+    -- Points at a socket directory that doesn't exist: this test is only
+    -- about how the host segment is parsed, not about a real connection
+    -- succeeding.
+    conninfo = "postgresql://%2ftmp%2fpqi-conformance-nonexistent-socket-dir"