diff --git a/crates/AGENTS.md b/crates/AGENTS.md
index ff4375e..481539e 100644
--- a/crates/AGENTS.md
+++ b/crates/AGENTS.md
@@ -25,10 +25,13 @@ the accepted list as **not yet implemented** — add a corpus fixture when it la
   variants, `actor`, `mod`, `use`, `const`, `type`, `trait` incl. generics,
   supertrait bounds, and `where` clauses (bounds parsed but not stored),
   `impl Type` and `impl Trait for Type` (trait ref recorded in the AST),
-  `onchain mod`, `extern`); types incl. generics, references, arrays/slices,
-  tuples, `fn`, and `dyn Trait<Args>` incl. associated-type bindings;
-  expressions incl. calls, turbofish, field/index,
-  unary/binary (incl. `/`), assignment (targets validated per §16
+  `onchain mod`, `extern`), with §16 modifier placement enforced —
+  `offchain`/`async` only on `fn` items, and `pub` rejected on `impl`,
+  `actor`, `onchain`, and `extern` items; types incl. generics, references,
+  arrays/slices, tuples, `fn`, and `dyn Trait<Args>` incl. associated-type
+  bindings; expressions incl. calls, turbofish, field/index,
+  unary/binary (incl. `/`; `..`/`..=` are non-associative — chained ranges
+  are a parse error), assignment (targets validated per §16
   `assign_target`), `?`, `.await`, `as`, struct literals (with the
   §5.1 block-head restriction), `vec!` (square brackets required —
   `vec!(...)` is a parse error), and `if`/`else`; `|>` with §16
diff --git a/crates/sploosh-parser/src/lib.rs b/crates/sploosh-parser/src/lib.rs
index efb1b2a..3c3b9ca 100644
--- a/crates/sploosh-parser/src/lib.rs
+++ b/crates/sploosh-parser/src/lib.rs
@@ -63,14 +63,42 @@ impl Parser {
         self.skip_doc_comments();
         let start = self.peek()?.span.start;
         let attrs = self.attrs();
-        let visibility = if self.eat_keyword(Keyword::Pub).is_some() {
+        let pub_token = self.eat_keyword(Keyword::Pub);
+        let offchain_token = self.eat_keyword(Keyword::Offchain);
+        let async_token = self.eat_keyword(Keyword::Async);
+        let visibility = if pub_token.is_some() {
             Visibility::Public
         } else {
             Visibility::Private
         };
-        let is_offchain = self.eat_keyword(Keyword::Offchain).is_some();
-        let is_async = self.eat_keyword(Keyword::Async).is_some();
-        let kind = match self.peek_kind()? {
+        let is_offchain = offchain_token.is_some();
+        let is_async = async_token.is_some();
+        // §16: `offchain`/`async` prefix only `fn_def`; `pub` prefixes every
+        // item form except `impl_block`, `actor_def`, `onchain_mod`/`event_def`,
+        // and `extern_block`.
+        let next = self.peek_kind()?;
+        if !matches!(next, TokenKind::Keyword(Keyword::Fn)) {
+            if let Some(token) = &offchain_token {
+                self.error_at(token.span, "`offchain` applies only to `fn` items");
+            }
+            if let Some(token) = &async_token {
+                self.error_at(token.span, "`async` applies only to `fn` items");
+            }
+        }
+        if let Some(token) = &pub_token
+            && matches!(
+                next,
+                TokenKind::Keyword(
+                    Keyword::Impl | Keyword::Actor | Keyword::Onchain | Keyword::Extern
+                )
+            )
+        {
+            self.error_at(
+                token.span,
+                "`pub` is not allowed on `impl`, `actor`, `onchain`, or `extern` items",
+            );
+        }
+        let kind = match next {
             TokenKind::Keyword(Keyword::Fn) => ItemKind::Function(self.function_after_mods(
                 visibility,
                 is_async,
@@ -755,6 +783,16 @@ impl Parser {
                     span,
                 }
             };
+            // The precedence table marks `..`/`..=` non-associative: a range
+            // operand may not itself be an unparenthesized range.
+            if matches!(op, ".." | "..=")
+                && matches!(
+                    self.peek_kind(),
+                    Some(TokenKind::DotDot | TokenKind::DotDotEq)
+                )
+            {
+                self.error_here("range operators cannot be chained; parenthesize one side");
+            }
         }
         Some(lhs)
     }
@@ -1540,6 +1578,26 @@ mod tests {
         assert_eq!(fields.len(), 1);
     }
 
+    #[test]
+    fn range_operators_cannot_chain() {
+        for source in [
+            "fn f() { let r = a..b..c; }",
+            "fn f() { let r = a..=b..c; }",
+            "fn f() { let r = a..b..=c; }",
+        ] {
+            let errors = parse_program(source).unwrap_err();
+            // The diagnostic must anchor to the second range operator
+            // (`..=` starts with `..`, so the second `..` match is its start).
+            let second_op = source.match_indices("..").nth(1).unwrap().0;
+            assert!(
+                errors
+                    .iter()
+                    .any(|err| err.message.contains("chained") && err.span.start == second_op),
+                "{source}: expected a range-chaining error at {second_op}, got {errors:?}"
+            );
+        }
+    }
+
     #[test]
     fn send_operand_must_be_method_call() {
         // §2.7: inside a send-statement, anything but `handle.method(args)` is
@@ -1613,6 +1671,72 @@ mod tests {
         }
     }
 
+    #[test]
+    fn single_and_parenthesized_ranges_parse() {
+        assert!(parse_program("fn f() { let r = lo..hi; }").is_ok());
+        assert!(parse_program("fn f() { let r = lo..=hi; }").is_ok());
+        assert!(parse_program("fn f() { let r = (a..b)..c; }").is_ok());
+    }
+
+    #[test]
+    fn offchain_and_async_apply_only_to_fn_items() {
+        for (source, modifier) in [
+            ("offchain struct S { x: i64 }", "offchain"),
+            ("async struct S { x: i64 }", "async"),
+            ("pub async struct S { x: i64 }", "async"),
+            ("async trait T {}", "async"),
+            ("offchain mod m;", "offchain"),
+        ] {
+            let errors = parse_program(source).unwrap_err();
+            // The diagnostic must anchor to the misplaced modifier's own span.
+            let start = source.find(modifier).unwrap();
+            let span = Span::new(start, start + modifier.len());
+            assert!(
+                errors
+                    .iter()
+                    .any(|err| err.message.contains("applies only to `fn` items")
+                        && err.span == span),
+                "{source}: expected a modifier error at {span:?}, got {errors:?}"
+            );
+        }
+        assert!(parse_program("pub offchain async fn f() {}").is_ok());
+        assert!(parse_program("offchain fn g() {}").is_ok());
+    }
+
+    #[test]
+    fn pub_rejected_where_grammar_omits_it() {
+        for source in [
+            "pub impl User {}",
+            "pub actor A { state: i64, }",
+            "pub onchain mod token {}",
+            "pub extern \"C\" { fn f(); }",
+        ] {
+            let errors = parse_program(source).unwrap_err();
+            // `pub` heads each source, so the diagnostic must anchor to 0..3.
+            assert!(
+                errors
+                    .iter()
+                    .any(|err| err.message.contains("`pub` is not allowed")
+                        && err.span == Span::new(0, 3)),
+                "{source}: expected a pub-placement error at 0..3, got {errors:?}"
+            );
+        }
+        for source in [
+            "pub struct S { x: i64 }",
+            "pub enum E { A }",
+            "pub trait T {}",
+            "pub mod m;",
+            "pub use crate::api;",
+            "pub const X: i64 = 1;",
+            "pub type Y = i64;",
+        ] {
+            assert!(
+                parse_program(source).is_ok(),
+                "{source}: `pub` should be accepted here"
+            );
+        }
+    }
+
     #[test]
     fn vec_bang_requires_square_brackets() {
         for source in ["fn f() { let v = vec!(1); }", "fn f() { let v = vec!{1}; }"] {
diff --git a/crates/sploosh-parser/tests/corpus.rs b/crates/sploosh-parser/tests/corpus.rs
index 29106ff..78ecba6 100644
--- a/crates/sploosh-parser/tests/corpus.rs
+++ b/crates/sploosh-parser/tests/corpus.rs
@@ -9,6 +9,7 @@ fn parses_corpus_files() {
         "tests/corpus/traits_impls.sp",
         "tests/corpus/pipes.sp",
         "tests/corpus/send_assign.sp",
+        "tests/corpus/ranges_modifiers.sp",
     ] {
         let path = std::path::Path::new(env!("CARGO_MANIFEST_DIR"))
             .join("../..")
diff --git a/tests/corpus/ranges_modifiers.sp b/tests/corpus/ranges_modifiers.sp
new file mode 100644
index 0000000..7f1d940
--- /dev/null
+++ b/tests/corpus/ranges_modifiers.sp
@@ -0,0 +1,22 @@
+/// Range expressions (`..`/`..=`, non-associative per the precedence table)
+/// and §16 item-modifier placement: `pub` on declarations, `offchain`/`async`
+/// on functions only.
+pub offchain async fn window(lo: i64, hi: i64) -> i64 {
+    let half_open = lo..hi;
+    let inclusive = lo..=hi;
+    lo + hi
+}
+
+pub struct Config {
+    pub retries: i64,
+}
+
+pub mod api;
+
+pub use crate::api;
+
+pub const LIMIT: i64 = 8;
+
+pub type Pair = (i64, i64);
+
+pub trait Sink {}