diff --git a/crates/pty-conformance/src/bin/conformance_map.rs b/crates/pty-conformance/src/bin/conformance_map.rs
index 99372df..8883bc7 100644
--- a/crates/pty-conformance/src/bin/conformance_map.rs
+++ b/crates/pty-conformance/src/bin/conformance_map.rs
@@ -3,7 +3,7 @@
 //! comments in `tests/*.rs`), or the reason it is not portable.
 //!
 //! Usage: `cargo run -p pty-conformance --bin conformance-map [--node <checkout>] [--out <path>]`.
-//! Defaults: the checkout in `PTY_NODE_CHECKOUT` (or `/home/myobie/src/github.com/compoundingtech/pty`),
+//! Defaults: the checkout named by `PTY_NODE_CHECKOUT` (required; there is no default),
 //! output to `docs/conformance.md` at the workspace root.
 
 fn main() {
diff --git a/crates/pty-conformance/src/conformance_map_impl.rs b/crates/pty-conformance/src/conformance_map_impl.rs
index 6c25beb..132892e 100644
--- a/crates/pty-conformance/src/conformance_map_impl.rs
+++ b/crates/pty-conformance/src/conformance_map_impl.rs
@@ -274,11 +274,32 @@ pub fn run(args: Vec<String>) -> Result<(), String> {
         }
         i += 1;
     }
-    if checkout.is_none() {
-        let default = PathBuf::from("/home/myobie/src/github.com/compoundingtech/pty");
-        if default.join("tests").is_dir() {
-            checkout = Some(default);
-        }
+    // No default, and no silent degrade.
+    //
+    // This used to fall back to an absolute path on one developer's machine,
+    // and `node_suites` falls back again to the compiled-in `SUITES` list when
+    // it has no checkout — so running this with the variable unset produced a
+    // checked-in document describing a Node tree nobody named, which looked
+    // exactly as authoritative as a correct one. That is how docs/conformance.md
+    // came to say `0.12.0+500eab2` while the pinned reference in `node-ref` was
+    // `86dcc5e`, and a stale map is what a stale comparison is built on.
+    //
+    // A test may skip when its reference is missing. A generator may not guess:
+    // it writes a file that outlives the run and carries no memory of what it
+    // was made from.
+    let Some(dir) = checkout.clone() else {
+        return Err("PTY_NODE_CHECKOUT is not set, and there is no default.\n\
+             This writes docs/conformance.md from a Node checkout, and a map \
+             built from an unnamed source is worse than no map.\n\
+             Set PTY_NODE_CHECKOUT to the commit in crates/pty-conformance/node-ref, \
+             or pass --checkout <path>."
+            .to_string());
+    };
+    if !dir.join("tests").is_dir() {
+        return Err(format!(
+            "PTY_NODE_CHECKOUT is {}, which has no tests/ directory.",
+            dir.display()
+        ));
     }
 
     let mapped = scan_tests(&manifest_dir().join("tests"))?;
diff --git a/crates/pty-conformance/tests/completions.rs b/crates/pty-conformance/tests/completions.rs
index bfd353f..9e7afa4 100644
--- a/crates/pty-conformance/tests/completions.rs
+++ b/crates/pty-conformance/tests/completions.rs
@@ -22,10 +22,20 @@ fn which(bin: &str) -> Option<PathBuf> {
     if out.status.success() && !s.is_empty() { Some(PathBuf::from(s)) } else { None }
 }
 
+/// The Node checkout to compare against, or `None`.
+///
+/// **There is deliberately no fallback path.** This used to default to an
+/// absolute path on one developer's machine, which meant that when
+/// `PTY_NODE_CHECKOUT` was unset the test did not skip — it silently compared
+/// against whatever happened to be at that path. On a machine where that
+/// checkout was seven commits behind, it produced a confident failure about a
+/// completion entry that was not missing at all. CI never saw it, because the
+/// path does not exist on a runner, so there the filter returned `None` and the
+/// test skipped.
+///
+/// A test that cannot find its reference must say so. It must not guess.
 fn node_checkout_dir() -> Option<PathBuf> {
-    node_checkout()
-        .or_else(|| Some(PathBuf::from("/home/myobie/src/github.com/compoundingtech/pty")))
-        .filter(|p| p.join("completions").is_dir())
+    node_checkout().filter(|p| p.join("completions").is_dir())
 }
 
 /// node: tests/completions.test.ts:81