diff --git a/tools/zq.py b/tools/zq.py
index 0dc6dbc2..81757f24 100755
--- a/tools/zq.py
+++ b/tools/zq.py
@@ -38,18 +38,59 @@ Usage:
 
 A command that needs a table the current DB predates prints what to regenerate
 rather than a SQL error.
+
+The database is found via `$SYLPH_XEXDB`, else `<repo root>/sylpheed.db`. It is a
+build artefact, not a tracked file; if neither exists, zq.py says so and prints
+the command that builds one.
 """
-import duckdb, sys, signal
+import duckdb, sys, os, pathlib, signal
 
 # Output is routinely piped into `head`; without this Python prints a
 # BrokenPipeError traceback when the reader closes early.
 signal.signal(signal.SIGPIPE, signal.SIG_DFL)
 
-DB = '/home/fabi/RE - Project Sylpheed/xenia-rs/sylpheed.db'
-c = duckdb.connect(DB, read_only=True)
-H = lambda x: '0x%08x' % x
+REGEN = "sylph-xexdb dis <xex|iso> --db sylpheed.db --analyze sql"
 
-REGEN = ("xenia-rs dis <xex|iso> --db sylpheed.db --analyze sql")
+
+def _resolve_db():
+    """Locate the database: `$SYLPH_XEXDB`, else `<repo root>/sylpheed.db`.
+
+    🔴 This used to be one hardcoded absolute path, and it pointed *inside*
+    `xenia-rs` -- a repository `docs/agents/CONSOLIDATION.md` archives in Phase 5
+    and drops in Phase 7. It resolved on exactly one machine and would have
+    started failing there too, with `duckdb` raising about a missing file rather
+    than anything saying why.
+
+    The database is a build artefact of several hundred MB and is not in the
+    repository, so there is nothing to fall back *to*: if neither location has
+    one, say so and print how to build it. A default that silently resolves to
+    the wrong database is worse than no default -- see issue #16.
+    """
+    env = os.environ.get('SYLPH_XEXDB')
+    if env:
+        p = pathlib.Path(env).expanduser()
+        if not p.is_file():
+            sys.exit(f'$SYLPH_XEXDB is set but is not a file:\n  {p}')
+        return p
+    # Relative to this script, not to the caller's cwd: `zq.py` is run from
+    # wherever the investigation happens to be.
+    p = pathlib.Path(__file__).resolve().parent.parent / 'sylpheed.db'
+    if p.is_file():
+        return p
+    sys.exit(
+        f'no database found.\n'
+        f'  looked for: {p}\n'
+        f'  set $SYLPH_XEXDB to an existing one, or build it with:\n'
+        f'    {REGEN}'
+    )
+
+
+# Resolved lazily enough that `zq.py` with no command still prints its usage on
+# a machine that has no database yet.
+_WANTS_DB = len(sys.argv) > 1 and sys.argv[1] not in ('-h', '--help', 'help')
+DB = _resolve_db() if _WANTS_DB else None
+c = duckdb.connect(str(DB), read_only=True) if DB is not None else None
+H = lambda x: '0x%08x' % x
 
 
 def _need(*tables):