diff --git a/.github/workflows/integration.yml b/.github/workflows/integration.yml
index b882ca931..934fe3f3e 100644
--- a/.github/workflows/integration.yml
+++ b/.github/workflows/integration.yml
@@ -43,18 +43,17 @@ jobs:
             ~/.cargo/registry/cache/
             ~/.cargo/git/db/
             target/
+            guest/target/
           key: integration-${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
       - uses: dtolnay/rust-toolchain@nightly
 
       - name: Run example
         env:
-          RAYON_NUM_THREADS: 2
           RUSTFLAGS: "-C opt-level=3"
         run: cargo run --package ceno_zkvm --example riscv_opcodes -- --start 10 --end 11
 
       - name: Run fibonacci
         env:
-          RAYON_NUM_THREADS: 8
           RUST_LOG: debug
           RUSTFLAGS: "-C opt-level=3"
         run: cargo run --package ceno_zkvm --bin e2e -- --platform=sp1 ceno_zkvm/examples/fibonacci.elf
diff --git a/.github/workflows/lints.yml b/.github/workflows/lints.yml
index fe7367a54..207769aa8 100644
--- a/.github/workflows/lints.yml
+++ b/.github/workflows/lints.yml
@@ -49,7 +49,7 @@ jobs:
             ~/.cargo/registry/cache/
             ~/.cargo/git/db/
             target/
-            examples/target/
+            guest/target/
           key: lint-${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
 
       - name: Install cargo make
@@ -62,13 +62,13 @@ jobs:
         env:
           RUSTFLAGS: "-Dwarnings"
         run: |
-          cargo check --workspace --all-targets --exclude ceno_rt
+          cargo check --workspace --all-targets
           # We have a lot of code under #[cfg(not(debug_assertions))] and similar,
           # so we need to run cargo check in release mode, too:
-          cargo check --workspace --all-targets --exclude ceno_rt --release
+          cargo check --workspace --all-targets --release
           cargo make clippy
           # Same for clippy:
-          cargo clippy --workspace --all-targets --exclude ceno_rt --release
+          cargo clippy --workspace --all-targets --release
 
       - name: Install taplo
         run: taplo --version || cargo install taplo-cli
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index da0784782..e7d224995 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -47,7 +47,7 @@ jobs:
             ~/.cargo/registry/cache/
             ~/.cargo/git/db/
             target/
-            examples/target/
+            guest/target/
           key: tests-${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
 
       - name: Install cargo make
diff --git a/Cargo.lock b/Cargo.lock
index 865b783f5..35ff0505a 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -244,13 +244,6 @@ dependencies = [
  "tracing",
 ]
 
-[[package]]
-name = "ceno_rt"
-version = "0.1.0"
-dependencies = [
- "riscv",
-]
-
 [[package]]
 name = "ceno_zkvm"
 version = "0.1.0"
@@ -468,12 +461,6 @@ dependencies = [
  "itertools 0.10.5",
 ]
 
-[[package]]
-name = "critical-section"
-version = "1.2.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "790eea4361631c5e7d22598ecd5723ff611904e3344ce8720784c93e3d83d40b"
-
 [[package]]
 name = "crossbeam-channel"
 version = "0.5.13"
@@ -602,12 +589,6 @@ version = "0.7.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4445909572dbd556c457c849c4ca58623d84b27c8fff1e74b0b4227d8b90d17b"
 
-[[package]]
-name = "embedded-hal"
-version = "1.0.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "361a90feb7004eca4019fb28352a9465666b24f840f5c3cddf0ff13920590b89"
-
 [[package]]
 name = "encode_unicode"
 version = "1.0.0"
@@ -655,9 +636,9 @@ dependencies = [
 
 [[package]]
 name = "fastrand"
-version = "2.2.0"
+version = "2.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "486f806e73c5707928240ddc295403b1b93c96a02038563881c4a2fd84b81ac4"
+checksum = "37909eebbb50d72f9059c3b6d82c0463f2ff062c9e95845c43a6c9c0355411be"
 
 [[package]]
 name = "ff"
@@ -973,9 +954,9 @@ dependencies = [
 
 [[package]]
 name = "libc"
-version = "0.2.167"
+version = "0.2.168"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "09d6582e104315a817dff97f75133544b2e094ee22447d2acf4a74e189ba06fc"
+checksum = "5aaeb2981e0606ca11d79718f8bb01164f1d6ed75080182d3abf017e6d244b6d"
 
 [[package]]
 name = "libredox"
@@ -1416,7 +1397,7 @@ dependencies = [
  "smallvec",
  "symbolic-demangle",
  "tempfile",
- "thiserror 2.0.4",
+ "thiserror 2.0.6",
 ]
 
 [[package]]
@@ -1548,9 +1529,9 @@ dependencies = [
 
 [[package]]
 name = "redox_syscall"
-version = "0.5.7"
+version = "0.5.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9b6dfecf2c74bce2466cabf93f6664d6998a69eb21e39f4207930065b27b771f"
+checksum = "03a862b389f93e68874fbf580b9de08dd02facb9a788ebadaf4a3fd33cf58834"
 dependencies = [
  "bitflags",
 ]
@@ -1619,36 +1600,6 @@ dependencies = [
  "bytemuck",
 ]
 
-[[package]]
-name = "riscv"
-version = "0.12.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5ea8ff73d3720bdd0a97925f0bf79ad2744b6da8ff36be3840c48ac81191d7a7"
-dependencies = [
- "critical-section",
- "embedded-hal",
- "paste",
- "riscv-macros",
- "riscv-pac",
-]
-
-[[package]]
-name = "riscv-macros"
-version = "0.1.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f265be5d634272320a7de94cea15c22a3bfdd4eb42eb43edc528415f066a1f25"
-dependencies = [
- "proc-macro2",
- "quote",
- "syn 2.0.90",
-]
-
-[[package]]
-name = "riscv-pac"
-version = "0.2.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8188909339ccc0c68cfb5a04648313f09621e8b87dc03095454f1a11f6c5d436"
-
 [[package]]
 name = "rrs-succinct"
 version = "0.1.0"
@@ -1668,15 +1619,15 @@ checksum = "719b953e2095829ee67db738b3bfa9fa368c94900df327b3f07fe6e794d2fe1f"
 
 [[package]]
 name = "rustix"
-version = "0.38.41"
+version = "0.38.42"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d7f649912bc1495e167a6edee79151c84b1bad49748cb4f1f1167f459f6224f6"
+checksum = "f93dc38ecbab2eb790ff964bb77fa94faf256fd3e73285fd7ba0903b76bedb85"
 dependencies = [
  "bitflags",
  "errno",
  "libc",
  "linux-raw-sys",
- "windows-sys 0.52.0",
+ "windows-sys 0.59.0",
 ]
 
 [[package]]
@@ -1708,18 +1659,18 @@ checksum = "94143f37725109f92c262ed2cf5e59bce7498c01bcc1502d7b9afe439a4e9f49"
 
 [[package]]
 name = "serde"
-version = "1.0.215"
+version = "1.0.216"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6513c1ad0b11a9376da888e3e0baa0077f1aed55c17f50e7b2397136129fb88f"
+checksum = "0b9781016e935a97e8beecf0c933758c97a5520d32930e460142b4cd80c6338e"
 dependencies = [
  "serde_derive",
 ]
 
 [[package]]
 name = "serde_derive"
-version = "1.0.215"
+version = "1.0.216"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ad1e866f866923f252f05c889987993144fb74e722403468a4ebd70c3cd756c0"
+checksum = "46f859dbbf73865c6627ed570e78961cd3ac92407a2d117204c49232485da55e"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -1918,11 +1869,11 @@ dependencies = [
 
 [[package]]
 name = "thiserror"
-version = "2.0.4"
+version = "2.0.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2f49a1853cf82743e3b7950f77e0f4d622ca36cf4317cba00c767838bac8d490"
+checksum = "8fec2a1820ebd077e2b90c4df007bebf344cd394098a13c563957d0afc83ea47"
 dependencies = [
- "thiserror-impl 2.0.4",
+ "thiserror-impl 2.0.6",
 ]
 
 [[package]]
@@ -1938,9 +1889,9 @@ dependencies = [
 
 [[package]]
 name = "thiserror-impl"
-version = "2.0.4"
+version = "2.0.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8381894bb3efe0c4acac3ded651301ceee58a15d47c2e34885ed1908ad667061"
+checksum = "d65750cab40f4ff1929fb1ba509e9914eb756131cef4210da8d5d700d26f6312"
 dependencies = [
  "proc-macro2",
  "quote",
diff --git a/Cargo.toml b/Cargo.toml
index ead19b880..93cabd8d9 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,9 +1,8 @@
 [workspace]
-exclude = ["examples"]
+exclude = ["guest"]
 members = [
   "ceno_emul",
   "examples-builder",
-  "ceno_rt",
   "mpcs",
   "multilinear_extensions",
   "sumcheck",
@@ -54,6 +53,13 @@ tracing-subscriber = { version = "0.3", features = ["env-filter"] }
 
 [profile.dev]
 lto = "thin"
+# We are running our tests with optimizations turned on to make them faster.
+# Please turn optimizations off, when you want accurate stack traces for debugging.
+opt-level = 2
+
+[profile.dev.package."*"]
+# Set the default for dependencies in Development mode.
+opt-level = 3
 
 [profile.release]
 lto = "thin"
diff --git a/Makefile.toml b/Makefile.toml
index 4a5a93188..199a42528 100644
--- a/Makefile.toml
+++ b/Makefile.toml
@@ -1,7 +1,5 @@
 [env]
 CARGO_MAKE_EXTEND_WORKSPACE_MAKEFILE = true
-CORE = { script = ["nproc"] }
-RAYON_NUM_THREADS = "${CORE}"
 
 [tasks.tests]
 args = [
@@ -11,10 +9,7 @@ args = [
   "--bins",
   "--tests",
   "--examples",
-  "--release",
   "--workspace",
-  "--exclude",
-  "ceno_rt",
 ]
 command = "cargo"
 workspace = false
@@ -34,8 +29,6 @@ args = [
   "clippy",
   "--workspace",
   "--all-targets",
-  "--exclude",
-  "ceno_rt",
   "--",
   "-D",
   "warnings",
diff --git a/README.md b/README.md
index 82f2e8bfe..0c57ac442 100644
--- a/README.md
+++ b/README.md
@@ -33,10 +33,9 @@ Clippy and check work as usual:
 ```sh
 cargo check
 cargo clippy
+cargo build
 ```
 
-Alas, `cargo build` doesn't work. That's a known problem and we're working on it.  Please use `cargo make build` instead for now.
-
 ### Setting up self-hosted CI docker container
 
 To set up docker container for CI, you can run the following command:
diff --git a/ceno_zkvm/Makefile.toml b/ceno_zkvm/Makefile.toml
index a4965ba50..45d27cf51 100644
--- a/ceno_zkvm/Makefile.toml
+++ b/ceno_zkvm/Makefile.toml
@@ -1,9 +1,7 @@
 [env]
 CARGO_MAKE_EXTEND_WORKSPACE_MAKEFILE = true
-CORE = { script = ["nproc"] }
-RAYON_NUM_THREADS = "${CORE}"
 
 [tasks.riscv_opcodes_flamegraph]
 args = ["run", "--package", "ceno_zkvm", "--release", "--example", "riscv_opcodes"]
 command = "cargo"
-env = { "RUST_LOG" = "debug", "RAYON_NUM_THREADS" = "8" }
+env = { "RUST_LOG" = "debug" }
diff --git a/examples-builder/build.rs b/examples-builder/build.rs
index 7ea9b9628..0e8d90441 100644
--- a/examples-builder/build.rs
+++ b/examples-builder/build.rs
@@ -26,7 +26,7 @@ fn build_elfs() {
     // See git history for an attempt to do this.
     let output = Command::new("cargo")
         .args(["build", "--release", "--examples"])
-        .current_dir("../examples")
+        .current_dir("../guest/examples")
         .env_clear()
         .envs(std::env::vars().filter(|x| !x.0.starts_with("CARGO_")))
         .output()
@@ -41,11 +41,11 @@ fn build_elfs() {
             dest,
             r#"#[allow(non_upper_case_globals)]
             pub const {example}: &[u8] =
-                include_bytes!(r"{CARGO_MANIFEST_DIR}/../examples/target/riscv32im-unknown-none-elf/release/examples/{example}");"#
+                include_bytes!(r"{CARGO_MANIFEST_DIR}/../guest/target/riscv32im-unknown-none-elf/release/examples/{example}");"#
         ).expect("failed to write vars.rs");
     }
-    let input_path = "../examples/";
-    let elfs_path = "../examples/target/riscv32im-unknown-none-elf/release/examples/";
+    let input_path = "../guest/";
+    let elfs_path = "../guest/target/riscv32im-unknown-none-elf/release/examples/";
 
     println!("cargo:rerun-if-changed={input_path}");
     println!("cargo:rerun-if-changed={elfs_path}");
diff --git a/examples/.cargo/config.toml b/examples/.cargo/config.toml
deleted file mode 120000
index bade0c189..000000000
--- a/examples/.cargo/config.toml
+++ /dev/null
@@ -1 +0,0 @@
-../../ceno_rt/.cargo/config.toml
\ No newline at end of file
diff --git a/examples/Cargo.toml b/examples/Cargo.toml
deleted file mode 100644
index 85c975ac1..000000000
--- a/examples/Cargo.toml
+++ /dev/null
@@ -1,9 +0,0 @@
-[package]
-edition = "2021"
-name = "examples"
-readme = "README.md"
-resolver = "2"
-version = "0.1.0"
-
-[dependencies]
-ceno_rt = { path = "../ceno_rt" }
diff --git a/examples/rust-toolchain.toml b/examples/rust-toolchain.toml
deleted file mode 120000
index 43fe0ada6..000000000
--- a/examples/rust-toolchain.toml
+++ /dev/null
@@ -1 +0,0 @@
-../rust-toolchain.toml
\ No newline at end of file
diff --git a/ceno_rt/.cargo/config.toml b/guest/.cargo/config.toml
similarity index 100%
rename from ceno_rt/.cargo/config.toml
rename to guest/.cargo/config.toml
diff --git a/examples/Cargo.lock b/guest/Cargo.lock
similarity index 88%
rename from examples/Cargo.lock
rename to guest/Cargo.lock
index 359355930..84c6c3ab6 100644
--- a/examples/Cargo.lock
+++ b/guest/Cargo.lock
@@ -36,9 +36,9 @@ checksum = "57c0d7b74b563b49d38dae00a0c37d4d6de9b432382b2892f0574ddcae73fd0a"
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.88"
+version = "1.0.92"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7c3a7fc5db1e57d5a779a352c8cdb57b29aa4c40cc69c3a68a7fedc815fbf2f9"
+checksum = "37d3544b3f2748c54e147655edb5025752e2303145b5aefb3c3ea2c78b973bb0"
 dependencies = [
  "unicode-ident",
 ]
@@ -84,9 +84,9 @@ checksum = "8188909339ccc0c68cfb5a04648313f09621e8b87dc03095454f1a11f6c5d436"
 
 [[package]]
 name = "syn"
-version = "2.0.82"
+version = "2.0.90"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "83540f837a8afc019423a8edb95b52a8effe46957ee402287f4292fae35be021"
+checksum = "919d3b74a5dd0ccd15aeb8f93e7006bd9e14c295087c9896a110f490752bcf31"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -95,6 +95,6 @@ dependencies = [
 
 [[package]]
 name = "unicode-ident"
-version = "1.0.13"
+version = "1.0.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e91b56cd4cadaeb79bbf1a5645f6b4f8dc5bde8834ad5894a8db35fda9efa1fe"
+checksum = "adb9e6ca4f869e1180728b7950e35922a7fc6397f7b641499e8f3ef06e50dc83"
diff --git a/guest/Cargo.toml b/guest/Cargo.toml
new file mode 100644
index 000000000..0aa06be48
--- /dev/null
+++ b/guest/Cargo.toml
@@ -0,0 +1,15 @@
+[workspace]
+members = ["examples", "ceno_rt"]
+resolver = "2"
+
+[workspace.package]
+categories = ["cryptography", "zk", "blockchain", "ceno"]
+edition = "2021"
+keywords = ["cryptography", "zk", "blockchain", "ceno"]
+license = "MIT OR Apache-2.0"
+readme = "../README.md"
+repository = "https://github.com/scroll-tech/ceno"
+version = "0.1.0"
+
+[profile.release]
+lto = "thin"
diff --git a/ceno_rt/Cargo.toml b/guest/ceno_rt/Cargo.toml
similarity index 100%
rename from ceno_rt/Cargo.toml
rename to guest/ceno_rt/Cargo.toml
diff --git a/ceno_rt/README.md b/guest/ceno_rt/README.md
similarity index 100%
rename from ceno_rt/README.md
rename to guest/ceno_rt/README.md
diff --git a/ceno_rt/build.rs b/guest/ceno_rt/build.rs
similarity index 100%
rename from ceno_rt/build.rs
rename to guest/ceno_rt/build.rs
diff --git a/ceno_rt/ceno_link.x b/guest/ceno_rt/ceno_link.x
similarity index 100%
rename from ceno_rt/ceno_link.x
rename to guest/ceno_rt/ceno_link.x
diff --git a/ceno_rt/memory.x b/guest/ceno_rt/memory.x
similarity index 100%
rename from ceno_rt/memory.x
rename to guest/ceno_rt/memory.x
diff --git a/ceno_rt/src/allocator.rs b/guest/ceno_rt/src/allocator.rs
similarity index 100%
rename from ceno_rt/src/allocator.rs
rename to guest/ceno_rt/src/allocator.rs
diff --git a/ceno_rt/src/io.rs b/guest/ceno_rt/src/io.rs
similarity index 100%
rename from ceno_rt/src/io.rs
rename to guest/ceno_rt/src/io.rs
diff --git a/ceno_rt/src/lib.rs b/guest/ceno_rt/src/lib.rs
similarity index 100%
rename from ceno_rt/src/lib.rs
rename to guest/ceno_rt/src/lib.rs
diff --git a/ceno_rt/src/params.rs b/guest/ceno_rt/src/params.rs
similarity index 100%
rename from ceno_rt/src/params.rs
rename to guest/ceno_rt/src/params.rs
diff --git a/guest/examples/Cargo.toml b/guest/examples/Cargo.toml
new file mode 100644
index 000000000..397e743b1
--- /dev/null
+++ b/guest/examples/Cargo.toml
@@ -0,0 +1,13 @@
+[package]
+categories.workspace = true
+description = "Ceno RiscV guest examples"
+edition.workspace = true
+keywords.workspace = true
+license.workspace = true
+name = "examples"
+readme = "README.md"
+repository.workspace = true
+version.workspace = true
+
+[dependencies]
+ceno_rt = { path = "../ceno_rt" }
diff --git a/examples/examples/ceno_rt_alloc.rs b/guest/examples/examples/ceno_rt_alloc.rs
similarity index 100%
rename from examples/examples/ceno_rt_alloc.rs
rename to guest/examples/examples/ceno_rt_alloc.rs
diff --git a/examples/examples/ceno_rt_io.rs b/guest/examples/examples/ceno_rt_io.rs
similarity index 100%
rename from examples/examples/ceno_rt_io.rs
rename to guest/examples/examples/ceno_rt_io.rs
diff --git a/examples/examples/ceno_rt_mem.rs b/guest/examples/examples/ceno_rt_mem.rs
similarity index 100%
rename from examples/examples/ceno_rt_mem.rs
rename to guest/examples/examples/ceno_rt_mem.rs
diff --git a/examples/examples/ceno_rt_mini.rs b/guest/examples/examples/ceno_rt_mini.rs
similarity index 100%
rename from examples/examples/ceno_rt_mini.rs
rename to guest/examples/examples/ceno_rt_mini.rs
diff --git a/examples/examples/ceno_rt_panic.rs b/guest/examples/examples/ceno_rt_panic.rs
similarity index 100%
rename from examples/examples/ceno_rt_panic.rs
rename to guest/examples/examples/ceno_rt_panic.rs
diff --git a/mpcs/src/basefold.rs b/mpcs/src/basefold.rs
index 1aec0fb9d..c7eb18f71 100644
--- a/mpcs/src/basefold.rs
+++ b/mpcs/src/basefold.rs
@@ -947,8 +947,6 @@ where
         transcript: &mut impl Transcript<E>,
     ) -> Result<(), Error> {
         let timer = start_timer!(|| "Basefold::batch_verify");
-        // 	let key = "RAYON_NUM_THREADS";
-        // 	env::set_var(key, "32");
         let comms = comms.iter().collect_vec();
         let num_vars = points.iter().map(|point| point.len()).max().unwrap();
         let num_rounds = num_vars - Spec::get_basecode_msg_size_log();