diff --git a/crates/compiler/builtins/bitcode/src/dec.zig b/crates/compiler/builtins/bitcode/src/dec.zig
index d60057843c9..cd9a8515022 100644
--- a/crates/compiler/builtins/bitcode/src/dec.zig
+++ b/crates/compiler/builtins/bitcode/src/dec.zig
@@ -252,7 +252,6 @@ pub const RocDec = extern struct {
 
         if (answer.has_overflowed) {
             roc_panic("Decimal addition overflowed!", 0);
-            unreachable;
         } else {
             return answer.value;
         }
@@ -283,7 +282,6 @@ pub const RocDec = extern struct {
 
         if (answer.has_overflowed) {
             roc_panic("Decimal subtraction overflowed!", 0);
-            unreachable;
         } else {
             return answer.value;
         }
@@ -347,7 +345,6 @@ pub const RocDec = extern struct {
 
         if (answer.has_overflowed) {
             roc_panic("Decimal multiplication overflowed!", 0);
-            unreachable;
         } else {
             return answer.value;
         }
@@ -369,7 +366,7 @@ pub const RocDec = extern struct {
 
         // (n / 0) is an error
         if (denominator_i128 == 0) {
-            @panic("TODO runtime exception for dividing by 0!");
+            roc_panic("Decimal division by 0!", 0);
         }
 
         // If they're both negative, or if neither is negative, the final answer
@@ -397,7 +394,7 @@ pub const RocDec = extern struct {
             if (denominator_i128 == one_point_zero_i128) {
                 return self;
             } else {
-                @panic("TODO runtime exception for overflow when dividing!");
+                roc_panic("Decimal division overflow in numerator!", 0);
             }
         };
         const numerator_u128 = @as(u128, @intCast(numerator_abs_i128));
@@ -410,7 +407,7 @@ pub const RocDec = extern struct {
             if (numerator_i128 == one_point_zero_i128) {
                 return other;
             } else {
-                @panic("TODO runtime exception for overflow when dividing!");
+                roc_panic("Decimal division overflow in denominator!", 0);
             }
         };
         const denominator_u128 = @as(u128, @intCast(denominator_abs_i128));
@@ -422,7 +419,7 @@ pub const RocDec = extern struct {
         if (answer.hi == 0 and answer.lo <= math.maxInt(i128)) {
             unsigned_answer = @as(i128, @intCast(answer.lo));
         } else {
-            @panic("TODO runtime exception for overflow when dividing!");
+            roc_panic("Decimal division overflow!", 0);
         }
 
         return RocDec{ .num = if (is_answer_negative) -unsigned_answer else unsigned_answer };
@@ -636,7 +633,7 @@ fn mul_and_decimalize(a: u128, b: u128) i128 {
     const d = answer[0];
 
     if (overflowed == 1) {
-        @panic("TODO runtime exception for overflow!");
+        roc_panic("Decimal multiplication overflow!", 0);
     }
 
     // Final 512bit value is d, c, b, a
@@ -1216,7 +1213,7 @@ pub fn fromF64C(arg: f64) callconv(.C) i128 {
     if (@call(.always_inline, RocDec.fromF64, .{arg})) |dec| {
         return dec.num;
     } else {
-        @panic("TODO runtime exception failing convert f64 to RocDec");
+        roc_panic("Decimal conversion from f64 failed!", 0);
     }
 }
 
@@ -1225,7 +1222,7 @@ pub fn fromF32C(arg_f32: f32) callconv(.C) i128 {
     if (@call(.always_inline, RocDec.fromF64, .{arg_f64})) |dec| {
         return dec.num;
     } else {
-        @panic("TODO runtime exception failing convert f64 to RocDec");
+        roc_panic("Decimal conversion from f32!", 0);
     }
 }
 
@@ -1240,7 +1237,7 @@ pub fn exportFromInt(comptime T: type, comptime name: []const u8) void {
 
             const answer = @mulWithOverflow(this, RocDec.one_point_zero_i128);
             if (answer[1] == 1) {
-                @panic("TODO runtime exception failing convert integer to RocDec");
+                roc_panic("Decimal conversion from Integer failed!", 0);
             } else {
                 return answer[0];
             }
@@ -1266,11 +1263,15 @@ pub fn neqC(arg1: RocDec, arg2: RocDec) callconv(.C) bool {
 }
 
 pub fn negateC(arg: RocDec) callconv(.C) i128 {
-    return if (@call(.always_inline, RocDec.negate, .{arg})) |dec| dec.num else @panic("TODO overflow for negating RocDec");
+    return if (@call(.always_inline, RocDec.negate, .{arg})) |dec| dec.num else {
+        roc_panic("Decimal negation overflow!", 0);
+    };
 }
 
 pub fn absC(arg: RocDec) callconv(.C) i128 {
-    const result = @call(.always_inline, RocDec.abs, .{arg}) catch @panic("TODO overflow for calling absolute value on RocDec");
+    const result = @call(.always_inline, RocDec.abs, .{arg}) catch {
+        roc_panic("Decimal absolute value overflow!", 0);
+    };
     return result.num;
 }
 
diff --git a/crates/compiler/builtins/bitcode/src/num.zig b/crates/compiler/builtins/bitcode/src/num.zig
index c978af99e19..eb7c532dd43 100644
--- a/crates/compiler/builtins/bitcode/src/num.zig
+++ b/crates/compiler/builtins/bitcode/src/num.zig
@@ -233,7 +233,9 @@ pub fn exportCeiling(comptime F: type, comptime T: type, comptime name: []const
 pub fn exportDivCeil(comptime T: type, comptime name: []const u8) void {
     comptime var f = struct {
         fn func(a: T, b: T) callconv(.C) T {
-            return math.divCeil(T, a, b) catch @panic("TODO runtime exception for dividing by 0!");
+            return math.divCeil(T, a, b) catch {
+                roc_panic("Integer division by 0!", 0);
+            };
         }
     }.func;
     @export(f, .{ .name = name ++ @typeName(T), .linkage = .Strong });
@@ -379,8 +381,7 @@ pub fn exportAddOrPanic(comptime T: type, comptime name: []const u8) void {
         fn func(self: T, other: T) callconv(.C) T {
             const result = addWithOverflow(T, self, other);
             if (result.has_overflowed) {
-                roc_panic("integer addition overflowed!", 0);
-                unreachable;
+                roc_panic("Integer addition overflowed!", 0);
             } else {
                 return result.value;
             }
@@ -437,8 +438,7 @@ pub fn exportSubOrPanic(comptime T: type, comptime name: []const u8) void {
         fn func(self: T, other: T) callconv(.C) T {
             const result = subWithOverflow(T, self, other);
             if (result.has_overflowed) {
-                roc_panic("integer subtraction overflowed!", 0);
-                unreachable;
+                roc_panic("Integer subtraction overflowed!", 0);
             } else {
                 return result.value;
             }
@@ -622,8 +622,7 @@ pub fn exportMulOrPanic(comptime T: type, comptime W: type, comptime name: []con
         fn func(self: T, other: T) callconv(.C) T {
             const result = @call(.always_inline, mulWithOverflow, .{ T, W, self, other });
             if (result.has_overflowed) {
-                roc_panic("integer multiplication overflowed!", 0);
-                unreachable;
+                roc_panic("Integer multiplication overflowed!", 0);
             } else {
                 return result.value;
             }
diff --git a/crates/compiler/builtins/bitcode/src/panic.zig b/crates/compiler/builtins/bitcode/src/panic.zig
index 76ecd69e123..13224a67df1 100644
--- a/crates/compiler/builtins/bitcode/src/panic.zig
+++ b/crates/compiler/builtins/bitcode/src/panic.zig
@@ -2,14 +2,14 @@ const std = @import("std");
 const RocStr = @import("str.zig").RocStr;
 
 // Signals to the host that the program has panicked
-extern fn roc_panic(msg: *const RocStr, tag_id: u32) callconv(.C) void;
+extern fn roc_panic(msg: *const RocStr, tag_id: u32) callconv(.C) noreturn;
 
-pub fn panic_help(msg: []const u8, tag_id: u32) void {
+pub fn panic_help(msg: []const u8, tag_id: u32) noreturn {
     var str = RocStr.init(msg.ptr, msg.len);
     roc_panic(&str, tag_id);
 }
 
 // must export this explicitly because right now it is not used from zig code
-pub fn panic(msg: *const RocStr, alignment: u32) callconv(.C) void {
+pub fn panic(msg: *const RocStr, alignment: u32) callconv(.C) noreturn {
     return roc_panic(msg, alignment);
 }
diff --git a/crates/compiler/gen_llvm/src/llvm/lowlevel.rs b/crates/compiler/gen_llvm/src/llvm/lowlevel.rs
index ea9fbdecf35..8590762267f 100644
--- a/crates/compiler/gen_llvm/src/llvm/lowlevel.rs
+++ b/crates/compiler/gen_llvm/src/llvm/lowlevel.rs
@@ -1535,7 +1535,7 @@ fn build_int_binop<'ctx>(
                 )
                 .into_struct_value();
 
-            throw_on_overflow(env, parent, result, "integer addition overflowed!")
+            throw_on_overflow(env, parent, result, "Integer addition overflowed!")
         }
         NumAddWrap => bd.new_build_int_add(lhs, rhs, "add_int_wrap").into(),
         NumAddChecked => {
@@ -1566,7 +1566,7 @@ fn build_int_binop<'ctx>(
                 )
                 .into_struct_value();
 
-            throw_on_overflow(env, parent, result, "integer subtraction overflowed!")
+            throw_on_overflow(env, parent, result, "Integer subtraction overflowed!")
         }
         NumSubWrap => bd.new_build_int_sub(lhs, rhs, "sub_int").into(),
         NumSubChecked => {
@@ -1597,7 +1597,7 @@ fn build_int_binop<'ctx>(
                 )
                 .into_struct_value();
 
-            throw_on_overflow(env, parent, result, "integer multiplication overflowed!")
+            throw_on_overflow(env, parent, result, "Integer multiplication overflowed!")
         }
         NumMulWrap => bd.new_build_int_mul(lhs, rhs, "mul_int").into(),
         NumMulSaturated => call_bitcode_fn(
@@ -2350,7 +2350,7 @@ fn build_dec_binop<'a, 'ctx>(
             bitcode::DEC_ADD_WITH_OVERFLOW,
             lhs,
             rhs,
-            "decimal addition overflowed",
+            "Decimal addition overflowed",
         ),
         NumSub => build_dec_binop_throw_on_overflow(
             env,
@@ -2358,7 +2358,7 @@ fn build_dec_binop<'a, 'ctx>(
             bitcode::DEC_SUB_WITH_OVERFLOW,
             lhs,
             rhs,
-            "decimal subtraction overflowed",
+            "Decimal subtraction overflowed",
         ),
         NumMul => build_dec_binop_throw_on_overflow(
             env,
@@ -2366,7 +2366,7 @@ fn build_dec_binop<'a, 'ctx>(
             bitcode::DEC_MUL_WITH_OVERFLOW,
             lhs,
             rhs,
-            "decimal multiplication overflowed",
+            "Decimal multiplication overflowed",
         ),
         NumDivFrac => dec_binop_with_unchecked(env, bitcode::DEC_DIV, lhs, rhs),
 
@@ -2659,7 +2659,7 @@ fn int_neg_raise_on_overflow<'ctx>(
     throw_internal_exception(
         env,
         parent,
-        "integer negation overflowed because its argument is the minimum value",
+        "Integer negation overflowed because its argument is the minimum value",
     );
 
     builder.position_at_end(else_block);
@@ -2690,7 +2690,7 @@ fn int_abs_raise_on_overflow<'ctx>(
     throw_internal_exception(
         env,
         parent,
-        "integer absolute overflowed because its argument is the minimum value",
+        "Integer absolute overflowed because its argument is the minimum value",
     );
 
     builder.position_at_end(else_block);
diff --git a/crates/compiler/gen_wasm/src/low_level.rs b/crates/compiler/gen_wasm/src/low_level.rs
index cb66ab10c2e..dfbb8420af7 100644
--- a/crates/compiler/gen_wasm/src/low_level.rs
+++ b/crates/compiler/gen_wasm/src/low_level.rs
@@ -1382,7 +1382,7 @@ impl<'a> LowLevelCall<'a> {
             }
             NumAbs => {
                 const PANIC_MSG: &str =
-                    "integer absolute overflowed because its argument is the minimum value";
+                    "Integer absolute overflowed because its argument is the minimum value";
 
                 self.load_args(backend);
 
@@ -1446,7 +1446,7 @@ impl<'a> LowLevelCall<'a> {
             }
             NumNeg => {
                 const PANIC_MSG: &str =
-                    "integer negation overflowed because its argument is the minimum value";
+                    "Integer negation overflowed because its argument is the minimum value";
 
                 self.load_args(backend);
                 match CodeGenNumType::from(self.ret_layout) {
diff --git a/crates/compiler/test_gen/src/gen_list.rs b/crates/compiler/test_gen/src/gen_list.rs
index db6863b8daf..fc7aa3736df 100644
--- a/crates/compiler/test_gen/src/gen_list.rs
+++ b/crates/compiler/test_gen/src/gen_list.rs
@@ -2934,7 +2934,7 @@ fn list_map_with_index() {
 
 #[test]
 #[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
-#[should_panic(expected = r#"Roc failed with message: "integer addition overflowed!"#)]
+#[should_panic(expected = r#"Roc failed with message: "Integer addition overflowed!"#)]
 fn cleanup_because_exception() {
     assert_evals_to!(
         indoc!(
diff --git a/crates/compiler/test_gen/src/gen_num.rs b/crates/compiler/test_gen/src/gen_num.rs
index c6651b94164..077f81ea97c 100644
--- a/crates/compiler/test_gen/src/gen_num.rs
+++ b/crates/compiler/test_gen/src/gen_num.rs
@@ -575,7 +575,7 @@ fn various_sized_abs() {
 #[test]
 #[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
 #[should_panic(
-    expected = r#"Roc failed with message: "integer absolute overflowed because its argument is the minimum value"#
+    expected = r#"Roc failed with message: "Integer absolute overflowed because its argument is the minimum value"#
 )]
 fn abs_min_int_overflow() {
     assert_evals_to!(
@@ -799,6 +799,26 @@ fn gen_div_checked_by_zero_dec() {
     );
 }
 
+#[test]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
+#[should_panic(expected = r#"Roc failed with message: "Decimal division by 0!"#)]
+fn gen_div_dec_by_zero() {
+    assert_evals_to!("1dec / 0", RocDec::from_str_to_i128_unsafe("-1"), i128);
+}
+
+#[test]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
+#[should_panic(expected = r#"Roc failed with message: "Integer division by 0!"#)]
+fn gen_div_ceil_by_zero() {
+    assert_evals_to!(
+        r#"
+            Num.divCeil 5 0 == 0
+        "#,
+        false,
+        bool
+    );
+}
+
 #[test]
 #[cfg(any(feature = "gen-llvm", feature = "gen-dev", feature = "gen-wasm"))]
 fn gen_int_eq() {
@@ -1581,7 +1601,7 @@ fn int_negate() {
 #[test]
 #[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
 #[should_panic(
-    expected = r#"Roc failed with message: "integer negation overflowed because its argument is the minimum value"#
+    expected = r#"Roc failed with message: "Integer negation overflowed because its argument is the minimum value"#
 )]
 fn neg_min_int_overflow() {
     assert_evals_to!(
@@ -1809,7 +1829,7 @@ fn atan() {
 
 #[test]
 #[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
-#[should_panic(expected = r#"Roc failed with message: "integer addition overflowed!"#)]
+#[should_panic(expected = r#"Roc failed with message: "Integer addition overflowed!"#)]
 fn int_add_overflow() {
     assert_evals_to!(
         indoc!(
@@ -1884,7 +1904,7 @@ fn float_add_overflow() {
 
 #[test]
 #[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
-#[should_panic(expected = r#"Roc failed with message: "integer subtraction overflowed!"#)]
+#[should_panic(expected = r#"Roc failed with message: "Integer subtraction overflowed!"#)]
 fn int_sub_overflow() {
     assert_evals_to!("-9_223_372_036_854_775_808 - 1", 0, i64);
 }
@@ -1969,7 +1989,7 @@ fn float_sub_checked() {
 
 #[test]
 #[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
-#[should_panic(expected = r#"Roc failed with message: "integer multiplication overflowed!"#)]
+#[should_panic(expected = r#"Roc failed with message: "Integer multiplication overflowed!"#)]
 fn int_positive_mul_overflow() {
     assert_evals_to!(
         indoc!(
@@ -1984,7 +2004,7 @@ fn int_positive_mul_overflow() {
 
 #[test]
 #[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
-#[should_panic(expected = r#"Roc failed with message: "integer multiplication overflowed!"#)]
+#[should_panic(expected = r#"Roc failed with message: "Integer multiplication overflowed!"#)]
 fn int_negative_mul_overflow() {
     assert_evals_to!(
         indoc!(
@@ -3907,21 +3927,21 @@ fn num_abs_diff_float() {
 
 #[test]
 #[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
-#[should_panic(expected = r#"Roc failed with message: "integer subtraction overflowed!"#)]
+#[should_panic(expected = r#"Roc failed with message: "Integer subtraction overflowed!"#)]
 fn num_abs_max_overflow() {
     assert_evals_to!(r#"Num.absDiff Num.maxI64 -1"#, 0, i64);
 }
 
 #[test]
 #[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
-#[should_panic(expected = r#"Roc failed with message: "integer subtraction overflowed!"#)]
+#[should_panic(expected = r#"Roc failed with message: "Integer subtraction overflowed!"#)]
 fn num_abs_int_min_overflow() {
     assert_evals_to!(r#"Num.absDiff Num.minI64 0"#, 0, i64);
 }
 
 #[test]
 #[cfg(feature = "gen-llvm")]
-#[should_panic(expected = r#"Roc failed with message: "integer subtraction overflowed!"#)]
+#[should_panic(expected = r#"Roc failed with message: "Integer subtraction overflowed!"#)]
 fn num_abs_large_bits_min_overflow() {
     assert_evals_to!(r#"Num.absDiff Num.minI128 0"#, 0, i128);
 }
diff --git a/crates/lang_srv/debug_server.sh b/crates/lang_srv/debug_server.sh
index 5510f3d8d7d..427c81be671 100755
--- a/crates/lang_srv/debug_server.sh
+++ b/crates/lang_srv/debug_server.sh
@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/bash
 
 SCRIPT_DIR=$(cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd)
 ${SCRIPT_DIR}/../../target/debug/roc_ls "$@" 2> /tmp/roc_ls.err
diff --git a/crates/repl_wasm/README.md b/crates/repl_wasm/README.md
index be6731426cc..5f4cd8fb587 100644
--- a/crates/repl_wasm/README.md
+++ b/crates/repl_wasm/README.md
@@ -14,13 +14,14 @@ crates/repl_wasm/build-www.sh
 ### 2. Make symlinks to the generated Wasm and JS
 
 ```bash
-cd www/public
+mkdir -p www/public/repl
+cd www/public/repl
 ln -s ../../../crates/repl_wasm/build/roc_repl_wasm_bg.wasm
 ln -s ../../../crates/repl_wasm/build/roc_repl_wasm.js
 ```
 These symlinks are ignored by Git.
 
-> This is a bit different from the production build, where we copy all the files to `www/build/`. But for development, it's convenient to have just one copy of files like `www/public/repl.js`. You can make changes, reload your browser to see them, and commit them to Git, without getting mixed up between different copies of the same file.
+> This is a bit different from the production build, where we copy all the files to `www/build/`. But for development, it's convenient to have just one copy of files like `www/public/repl/repl.js`. You can make changes, reload your browser to see them, and commit them to Git, without getting mixed up between different copies of the same file.
 
 ### 3. Run a local HTTP server
 
diff --git a/flake.nix b/flake.nix
index b94a9c69e00..8652e8f9630 100644
--- a/flake.nix
+++ b/flake.nix
@@ -91,6 +91,7 @@
           wasm-pack # for repl_wasm
           jq # used in several bash scripts
           cargo-nextest # used to give more info for segfaults for gen tests
+          zls # zig language server
         ]);
 
         aliases = ''
@@ -135,7 +136,7 @@
         # You can build this package (the roc CLI) with the `nix build` command.
         packages = {
           default = rocBuild.roc-cli;
-          
+
           # all rust crates in workspace.members of Cargo.toml
           full = rocBuild.roc-full;
           # only the CLI crate = executable provided in nightly releases
diff --git a/www/.gitignore b/www/.gitignore
new file mode 100644
index 00000000000..9bc9fa870c6
--- /dev/null
+++ b/www/.gitignore
@@ -0,0 +1,2 @@
+# ignore a symlink to the wasm repl code
+public/repl
\ No newline at end of file