diff --git a/tvix/eval/docs/builtins.md b/tvix/eval/docs/builtins.md
index 4e09e0f9e..dba4c48c6 100644
--- a/tvix/eval/docs/builtins.md
+++ b/tvix/eval/docs/builtins.md
@@ -24,7 +24,7 @@ The `impl` column indicates implementation status in tvix:
 | addErrorContext               | false  | ?     |       | context |
 | all                           | false  | 2     | true  |         |
 | any                           | false  | 2     | true  |         |
-| appendContext                 | false  | ?     |       | context |
+| appendContext                 | false  | ?     |       |         |
 | attrNames                     | false  | 1     | true  |         |
 | attrValues                    | false  |       | true  |         |
 | baseNameOf                    | true   |       |       |         |
diff --git a/tvix/eval/src/builtins/mod.rs b/tvix/eval/src/builtins/mod.rs
index 048c8867a..8973a2592 100644
--- a/tvix/eval/src/builtins/mod.rs
+++ b/tvix/eval/src/builtins/mod.rs
@@ -692,6 +692,86 @@ mod pure_builtins {
         Ok(Value::attrs(NixAttrs::from_iter(elements)))
     }
 
+    #[builtin("appendContext")]
+    #[allow(non_snake_case)]
+    async fn builtin_appendContext(
+        co: GenCo,
+        origin: Value,
+        added_context: Value,
+    ) -> Result<Value, ErrorKind> {
+        // `appendContext` is a "grow" context function.
+        // It cannot remove a context element, neither replace a piece of its contents.
+        //
+        // Growing context is always a safe operation, there's no loss of dependency tracking
+        // information.
+        //
+        // This is why this operation is not prefixed by `unsafe` and is deemed *safe*.
+        // Nonetheless, it is possible to craft nonsensical context elements referring
+        // to inexistent derivations, output paths or output names.
+        //
+        // In Nix, those nonsensical context elements are partially mitigated by checking
+        // that various parameters are indeed syntatically valid store paths in the context, i.e.
+        // starting with the same prefix as `builtins.storeDir`, or ending with `.drv`.
+        // In addition, if writing to the store is possible (evaluator not in read-only mode), Nix
+        // will realize some paths and ensures they are present in the store.
+        //
+        // In this implementation, we do none of that, no syntax checks, no realization.
+        // The next `TODO` are the checks that Nix implements.
+        let mut ctx_elements: HashSet<NixContextElement> = HashSet::new();
+        let span = generators::request_span(&co).await;
+        let origin = origin
+            .coerce_to_string(
+                co,
+                CoercionKind {
+                    strong: true,
+                    import_paths: true,
+                },
+                span,
+            )
+            .await?;
+        let mut origin = origin.to_contextful_str()?;
+
+        let added_context = added_context.to_attrs()?;
+        for (context_key, context_element) in added_context.into_iter() {
+            // Invariant checks:
+            // - TODO: context_key must be a syntactically valid store path.
+            // - Perform a deep force `context_element`.
+            let context_element = context_element.to_attrs()?;
+            if let Some(path) = context_element.select("path") {
+                if path.as_bool()? {
+                    ctx_elements.insert(NixContextElement::Plain(context_key.to_string()));
+                }
+            }
+            if let Some(all_outputs) = context_element.select("allOutputs") {
+                if all_outputs.as_bool()? {
+                    // TODO: check if `context_key` is a derivation path.
+                    // This may require realization.
+                    ctx_elements.insert(NixContextElement::Derivation(context_key.to_string()));
+                }
+            }
+            if let Some(some_outputs) = context_element.select("outputs") {
+                let some_outputs = some_outputs.to_list()?;
+                // TODO: check if `context_key` is a derivation path.
+                // This may require realization.
+                for output in some_outputs.into_iter() {
+                    let output = output.to_str()?;
+                    ctx_elements.insert(NixContextElement::Single {
+                        derivation: context_key.to_string(),
+                        name: output.to_string(),
+                    });
+                }
+            }
+        }
+
+        if let Some(origin_ctx) = origin.context_mut() {
+            // FUTUREWORK(performance): avoid this clone
+            // and extend in-place.
+            *origin_ctx = origin_ctx.clone().join(&mut ctx_elements.into());
+        }
+
+        Ok(origin.into())
+    }
+
     #[builtin("hashString")]
     #[allow(non_snake_case)]
     async fn builtin_hashString(co: GenCo, algo: Value, s: Value) -> Result<Value, ErrorKind> {
diff --git a/tvix/glue/src/tests/mod.rs b/tvix/glue/src/tests/mod.rs
index 469ed17a5..e66f484e3 100644
--- a/tvix/glue/src/tests/mod.rs
+++ b/tvix/glue/src/tests/mod.rs
@@ -134,9 +134,13 @@ fn nix_eval_okay(#[files("src/tests/nix_tests/eval-okay-*.nix")] code_path: Path
 // notyetpassing; this makes the test suite much more useful for
 // regression testing, since there should always be zero non-ignored
 // failing tests.
-#[rstest]
-fn nix_eval_okay_currently_failing(
-    #[files("src/tests/nix_tests/notyetpassing/eval-okay-*.nix")] code_path: PathBuf,
-) {
-    eval_test(code_path, false)
-}
+//
+// NOTE: There's no such test anymore. `rstest` does not handle empty directories, so, we
+// just comment it for now.
+//
+// #[rstest]
+// fn nix_eval_okay_currently_failing(
+//     #[files("src/tests/nix_tests/notyetpassing/eval-okay-*.nix")] code_path: PathBuf,
+// ) {
+//     eval_test(code_path, false)
+// }
diff --git a/tvix/glue/src/tests/nix_tests/notyetpassing/eval-okay-context-introspection.exp b/tvix/glue/src/tests/nix_tests/eval-okay-context-introspection.exp
similarity index 100%
rename from tvix/glue/src/tests/nix_tests/notyetpassing/eval-okay-context-introspection.exp
rename to tvix/glue/src/tests/nix_tests/eval-okay-context-introspection.exp
diff --git a/tvix/glue/src/tests/nix_tests/notyetpassing/eval-okay-context-introspection.nix b/tvix/glue/src/tests/nix_tests/eval-okay-context-introspection.nix
similarity index 100%
rename from tvix/glue/src/tests/nix_tests/notyetpassing/eval-okay-context-introspection.nix
rename to tvix/glue/src/tests/nix_tests/eval-okay-context-introspection.nix