diff --git a/.github/workflows/bvt.yml b/.github/workflows/bvt.yml
index 946df530..0b5ab3b5 100644
--- a/.github/workflows/bvt.yml
+++ b/.github/workflows/bvt.yml
@@ -9,13 +9,13 @@ jobs:
     name: Minimum Supported Rust Version
     runs-on: ubuntu-latest
     env:
-      RUSTUP_TOOLCHAIN: "1.85.0"
-      CARGO_RESOLVER_INCOMPATIBLE_RUST_VERSIONS: fallback
+      RUSTUP_TOOLCHAIN: "1.80.0"
     steps:
       - name: Checkout
         uses: actions/checkout@v3
       - name: Install Rust
-        run: rustup toolchain install 1.85.0 --profile minimal
+        run: |
+          rustup toolchain install 1.80.0 --profile minimal
       - name: Install Protoc
         run: ./install_protoc.sh
         shell: bash
@@ -23,7 +23,9 @@ jobs:
         run: |
           cargo test --workspace --features async,sync,security_extension
           cargo test -p ttrpc --no-default-features --features sync,async,prost
+          cargo check -p ttrpc-example --examples
           cargo test --manifest-path ttrpc-codegen-prost/Cargo.toml
+          cargo check --manifest-path example-prost/Cargo.toml --examples
 
   check:
     name: Check
diff --git a/Cargo.toml b/Cargo.toml
index 7796afd4..37a0dc61 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -16,7 +16,7 @@ resolver = "2"
 
 [workspace.package]
 edition = "2018"
-rust-version = "1.85"
+rust-version = "1.80"
 license = "Apache-2.0"
 readme = "README.md"
 repository = "https://github.com/containerd/ttrpc-rust"
@@ -76,6 +76,10 @@ prost-build = { version = "0.13", optional = true }
 
 [dev-dependencies]
 ttrpc-codegen = { workspace = true }
+# Newer tempfile selects getrandom 0.4, which Cargo 1.80 cannot parse.
+tempfile = ">=3.0, <3.25"
+# Newer indexmap releases require a newer Rust/Cargo toolchain.
+indexmap = ">=2.0, <2.12"
 
 [features]
 default = ["sync","rustprotobuf"]
diff --git a/README.md b/README.md
index 8e208d6a..2169e3fe 100644
--- a/README.md
+++ b/README.md
@@ -258,7 +258,11 @@ ttrpc does not provide TLS. If you expose TCP beyond a trusted boundary, secure
 
 ## Compatibility
 
-- Runtime and code generators minimum supported Rust version: **1.85**
+- Runtime and code generators minimum supported Rust version: **1.80**
+- With Rust 1.80–1.84, a fresh dependency resolution may select transitive
+  crates requiring a newer toolchain. If needed, constrain `tempfile` to
+  `<3.25` in your application's `Cargo.toml`. For `indexmap`, use `<2.12` on
+  Rust 1.80–1.81 or `<2.14` on Rust 1.82–1.84.
 - Repository development toolchain: see [`rust-toolchain.toml`](https://github.com/containerd/ttrpc-rust/blob/master/rust-toolchain.toml)
 - Default features: `sync`, `rustprotobuf`
 - Optional features: `async`, `prost`, `security_extension` (Unix only)
diff --git a/compiler/Cargo.toml b/compiler/Cargo.toml
index 4d4867f0..64de359f 100644
--- a/compiler/Cargo.toml
+++ b/compiler/Cargo.toml
@@ -17,7 +17,8 @@ protobuf = { workspace = true }
 protobuf-codegen = { workspace = true }
 
 [dev-dependencies]
-tempfile = "3.0"
+# Newer tempfile selects getrandom 0.4, which Cargo 1.80 cannot parse.
+tempfile = ">=3.0, <3.25"
 
 [[bin]]
 name = "ttrpc_rust_plugin"
diff --git a/example-prost/Cargo.toml b/example-prost/Cargo.toml
index 29a05d97..af80b57f 100644
--- a/example-prost/Cargo.toml
+++ b/example-prost/Cargo.toml
@@ -3,6 +3,7 @@ name = "ttrpc-example-prost"
 version = "0.2.0"
 authors = ["The AntFin Kata Team <kata@list.alibaba-inc.com>"]
 edition = "2018"
+rust-version = "1.80"
 license = "Apache-2.0"
 keywords = ["ttrpc", "protobuf", "rpc", "prost"]
 description = "An example of ttrpc using the Prost backend."
@@ -25,6 +26,12 @@ rand = "0.8.5"
 [build-dependencies]
 ttrpc-codegen-prost = { version = "0.1.0", path = "../ttrpc-codegen-prost" }
 
+[dev-dependencies]
+# Newer tempfile selects getrandom 0.4, which Cargo 1.80 cannot parse.
+tempfile = ">=3.0, <3.25"
+# Newer indexmap releases require a newer Rust/Cargo toolchain.
+indexmap = ">=2.0, <2.12"
+
 [[example]]
 name = "client"
 path = "./client.rs"
diff --git a/example/Cargo.toml b/example/Cargo.toml
index 2b851c36..b95349a9 100644
--- a/example/Cargo.toml
+++ b/example/Cargo.toml
@@ -3,6 +3,7 @@ name = "ttrpc-example"
 version = "0.2.0"
 authors = ["The AntFin Kata Team <kata@list.alibaba-inc.com>"]
 edition = "2018"
+rust-version = "1.80"
 license = "Apache-2.0"
 keywords = ["ttrpc", "protobuf", "rpc"]
 readme = "README.md"
@@ -20,7 +21,9 @@ ctrlc = { version = "3.0", features = ["termination"] }
 tokio = { version = "1.0.1", features = ["signal", "time", "rt-multi-thread", "macros"] }
 async-trait = "0.1.42"
 rand = "0.8.5"
-clap = { version = "4.5.40", features = ["derive"] }
+clap = { version = ">=4.5.40, <4.6", features = ["derive"] }
+# clap 4.5 accepts clap_lex 1.1, whose 2024 edition needs newer Cargo.
+clap_lex = ">=1.0, <1.1"
 
 [[example]]
 name = "client"
diff --git a/ttrpc-codegen-prost/Cargo.toml b/ttrpc-codegen-prost/Cargo.toml
index 9d7825b0..f30be6e4 100644
--- a/ttrpc-codegen-prost/Cargo.toml
+++ b/ttrpc-codegen-prost/Cargo.toml
@@ -2,7 +2,7 @@
 name = "ttrpc-codegen-prost"
 version = "0.1.0"
 edition = "2021"
-rust-version = "1.85"
+rust-version = "1.80"
 authors = ["The Ant Group Kata Team <kata@list.alibaba-inc.com>"]
 license = "Apache-2.0"
 keywords = ["codegen", "ttrpc", "protobuf"]
@@ -24,3 +24,9 @@ prost-types = "0.13"
 prost-build = "0.13"
 proc-macro2 = "1.0"
 quote = "1.0"
+
+[dev-dependencies]
+# Newer tempfile selects getrandom 0.4, which Cargo 1.80 cannot parse.
+tempfile = ">=3.0, <3.25"
+# Newer indexmap releases require a newer Rust/Cargo toolchain.
+indexmap = ">=2.0, <2.12"
diff --git a/ttrpc-codegen/Cargo.toml b/ttrpc-codegen/Cargo.toml
index 3b69a057..ceb1a31c 100644
--- a/ttrpc-codegen/Cargo.toml
+++ b/ttrpc-codegen/Cargo.toml
@@ -20,4 +20,5 @@ protobuf-parse = { workspace = true }
 ttrpc-compiler = { workspace = true }
 
 [dev-dependencies]
-tempfile = "3"
+# Newer tempfile selects getrandom 0.4, which Cargo 1.80 cannot parse.
+tempfile = ">=3.0, <3.25"