diff --git a/Cargo.lock b/Cargo.lock
index cb57afded0..dfd3278645 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -401,8 +401,15 @@ dependencies = [
 name = "build_info"
 version = "0.0.0"
 dependencies = [
+ "build_rs_git_info",
  "inspect",
- "vergen",
+]
+
+[[package]]
+name = "build_rs_git_info"
+version = "0.0.0"
+dependencies = [
+ "anyhow",
 ]
 
 [[package]]
@@ -7575,7 +7582,6 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "743bd48c283afc0388f9b8827b976905fb217ad9e647fae3a379a9283c4def2c"
 dependencies = [
  "deranged",
- "itoa",
  "libc",
  "num-conv",
  "num_threads",
@@ -8352,6 +8358,7 @@ name = "underhill_crash"
 version = "0.0.0"
 dependencies = [
  "anyhow",
+ "build_rs_git_info",
  "fs-err",
  "futures",
  "get_protocol",
@@ -8362,7 +8369,6 @@ dependencies = [
  "tracing",
  "tracing-subscriber",
  "underhill_confidentiality",
- "vergen",
  "vmbus_async",
  "vmbus_user_channel",
  "zerocopy",
@@ -8400,13 +8406,13 @@ name = "underhill_init"
 version = "0.0.0"
 dependencies = [
  "anyhow",
+ "build_rs_git_info",
  "fs-err",
  "kmsg_defs",
  "libc",
  "log",
  "nix 0.30.1",
  "underhill_confidentiality",
- "vergen",
  "walkdir",
 ]
 
@@ -8590,18 +8596,6 @@ version = "0.2.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "accd4ea62f7bb7a82fe23066fb0957d48ef677f6eeb8215f372f52e48bb32426"
 
-[[package]]
-name = "vergen"
-version = "8.3.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2990d9ea5967266ea0ccf413a4aa5c42a93dbcfda9cb49a97de6931726b12566"
-dependencies = [
- "anyhow",
- "cfg-if",
- "rustversion",
- "time",
-]
-
 [[package]]
 name = "version_check"
 version = "0.9.5"
diff --git a/Cargo.toml b/Cargo.toml
index 735c7b45fa..91059cabad 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -95,6 +95,7 @@ pipette_protocol = { path = "petri/pipette_protocol" }
 
 # support crates
 address_filter = { path = "support/address_filter" }
+build_rs_git_info = { path = "support/build_rs_git_info" }
 arc_cyclic_builder = { path = "support/arc_cyclic_builder" }
 atomic_ringbuf = { path = "support/atomic_ringbuf" }
 cache_topology = { path = "support/cache_topology" }
@@ -553,7 +554,6 @@ typed-path = "0.11"
 uefi = "0.35.0"
 unicycle = "0.10.2"
 urlencoding = "2.1.3"
-vergen = "8.2"
 vfio-bindings = "0.4.0"
 walkdir = "2.3"
 wchar = "0.11"
diff --git a/openhcl/build_info/Cargo.toml b/openhcl/build_info/Cargo.toml
index 395fdeb7cf..7f302ce17f 100644
--- a/openhcl/build_info/Cargo.toml
+++ b/openhcl/build_info/Cargo.toml
@@ -10,7 +10,7 @@ rust-version.workspace = true
 inspect.workspace = true
 
 [build-dependencies]
-vergen = { workspace = true, features = ["git", "gitcl"] }
+build_rs_git_info.workspace = true
 
 [lints]
 workspace = true
diff --git a/openhcl/build_info/build.rs b/openhcl/build_info/build.rs
index 5a6d24149e..bf72c2b98e 100644
--- a/openhcl/build_info/build.rs
+++ b/openhcl/build_info/build.rs
@@ -4,5 +4,5 @@
 #![expect(missing_docs)]
 
 fn main() {
-    vergen::EmitBuilder::builder().all_git().emit().unwrap();
+    build_rs_git_info::emit_git_info().unwrap();
 }
diff --git a/openhcl/build_info/src/lib.rs b/openhcl/build_info/src/lib.rs
index 7c0868d411..66596b7094 100644
--- a/openhcl/build_info/src/lib.rs
+++ b/openhcl/build_info/src/lib.rs
@@ -31,12 +31,12 @@ impl BuildInfo {
         // structure to be closer to PODs.
         Self {
             crate_name: env!("CARGO_PKG_NAME"),
-            revision: if let Some(r) = option_env!("VERGEN_GIT_SHA") {
+            revision: if let Some(r) = option_env!("BUILD_GIT_SHA") {
                 r
             } else {
                 ""
             },
-            branch: if let Some(b) = option_env!("VERGEN_GIT_BRANCH") {
+            branch: if let Some(b) = option_env!("BUILD_GIT_BRANCH") {
                 b
             } else {
                 ""
diff --git a/openhcl/underhill_crash/Cargo.toml b/openhcl/underhill_crash/Cargo.toml
index 12f436e189..18f456effa 100644
--- a/openhcl/underhill_crash/Cargo.toml
+++ b/openhcl/underhill_crash/Cargo.toml
@@ -24,7 +24,7 @@ tracing-subscriber.workspace = true
 zerocopy.workspace = true
 
 [build-dependencies]
-vergen = { workspace = true, features = ["git", "gitcl"] }
+build_rs_git_info.workspace = true
 
 [lints]
 workspace = true
diff --git a/openhcl/underhill_crash/build.rs b/openhcl/underhill_crash/build.rs
index 5a6d24149e..bf72c2b98e 100644
--- a/openhcl/underhill_crash/build.rs
+++ b/openhcl/underhill_crash/build.rs
@@ -4,5 +4,5 @@
 #![expect(missing_docs)]
 
 fn main() {
-    vergen::EmitBuilder::builder().all_git().emit().unwrap();
+    build_rs_git_info::emit_git_info().unwrap();
 }
diff --git a/openhcl/underhill_crash/src/lib.rs b/openhcl/underhill_crash/src/lib.rs
index 8a0e46b42a..402eb32f55 100644
--- a/openhcl/underhill_crash/src/lib.rs
+++ b/openhcl/underhill_crash/src/lib.rs
@@ -283,7 +283,7 @@ pub fn main() -> ! {
 
     let os_version = OsVersionInfo::new();
 
-    let crate_revision = option_env!("VERGEN_GIT_SHA").unwrap_or("UNKNOWN_REVISION");
+    let crate_revision = option_env!("BUILD_GIT_SHA").unwrap_or("UNKNOWN_REVISION");
     let openhcl_version = option_env!("OPENHCL_VERSION").unwrap_or("UNKNOWN_VERSION");
 
     let os_version_major = os_version.major();
diff --git a/openhcl/underhill_init/Cargo.toml b/openhcl/underhill_init/Cargo.toml
index 8162fb32ab..d24da48313 100644
--- a/openhcl/underhill_init/Cargo.toml
+++ b/openhcl/underhill_init/Cargo.toml
@@ -19,7 +19,7 @@ nix = { workspace = true, features = ["ioctl"] }
 walkdir.workspace = true
 
 [build-dependencies]
-vergen = { workspace = true, features = ["git", "gitcl"] }
+build_rs_git_info.workspace = true
 
 [lints]
 workspace = true
diff --git a/openhcl/underhill_init/build.rs b/openhcl/underhill_init/build.rs
index 5a6d24149e..bf72c2b98e 100644
--- a/openhcl/underhill_init/build.rs
+++ b/openhcl/underhill_init/build.rs
@@ -4,5 +4,5 @@
 #![expect(missing_docs)]
 
 fn main() {
-    vergen::EmitBuilder::builder().all_git().emit().unwrap();
+    build_rs_git_info::emit_git_info().unwrap();
 }
diff --git a/openhcl/underhill_init/src/lib.rs b/openhcl/underhill_init/src/lib.rs
index 0530183f90..0c29aa7eca 100644
--- a/openhcl/underhill_init/src/lib.rs
+++ b/openhcl/underhill_init/src/lib.rs
@@ -436,8 +436,8 @@ fn do_main() -> anyhow::Result<()> {
     log::info!(
         "Initial process: crate_name={}, crate_revision={}, crate_branch={}",
         env!("CARGO_PKG_NAME"),
-        option_env!("VERGEN_GIT_SHA").unwrap_or("UNKNOWN_REVISION"),
-        option_env!("VERGEN_GIT_BRANCH").unwrap_or("UNKNOWN_BRANCH"),
+        option_env!("BUILD_GIT_SHA").unwrap_or("UNKNOWN_REVISION"),
+        option_env!("BUILD_GIT_BRANCH").unwrap_or("UNKNOWN_BRANCH"),
     );
 
     let stat_files = [
diff --git a/support/build_rs_git_info/Cargo.toml b/support/build_rs_git_info/Cargo.toml
new file mode 100644
index 0000000000..b95d1a0d5e
--- /dev/null
+++ b/support/build_rs_git_info/Cargo.toml
@@ -0,0 +1,13 @@
+# Copyright (c) Microsoft Corporation.
+# Licensed under the MIT License.
+
+[package]
+name = "build_rs_git_info"
+edition.workspace = true
+rust-version.workspace = true
+
+[dependencies]
+anyhow.workspace = true
+
+[lints]
+workspace = true
diff --git a/support/build_rs_git_info/src/lib.rs b/support/build_rs_git_info/src/lib.rs
new file mode 100644
index 0000000000..8a856f158f
--- /dev/null
+++ b/support/build_rs_git_info/src/lib.rs
@@ -0,0 +1,52 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+//! Build-script helper that emits `BUILD_GIT_SHA` and `BUILD_GIT_BRANCH`
+//! cargo environment variables by invoking the `git` CLI.
+
+use std::process::Command;
+
+fn git_output(args: &[&str]) -> anyhow::Result<String> {
+    let output = Command::new("git").args(args).output()?;
+
+    if !output.status.success() {
+        anyhow::bail!(
+            "git {:?} failed with code {:?}: {}",
+            args,
+            output.status.code(),
+            String::from_utf8_lossy(&output.stderr)
+        );
+    }
+
+    let output = String::from_utf8(output.stdout).unwrap().trim().to_owned();
+    Ok(output)
+}
+
+fn git_path(args: &[&str]) -> anyhow::Result<std::path::PathBuf> {
+    let output = git_output(args)?;
+    Ok(std::path::absolute(&output)?)
+}
+
+/// Emit git information as `cargo:rustc-env` variables so they are available via
+/// `env!()` / `option_env!()` in the consuming crate.
+pub fn emit_git_info() -> anyhow::Result<()> {
+    // Always rerun when HEAD changes (e.g. branch switch).
+    let head_path = git_path(&["rev-parse", "--git-path", "HEAD"])?;
+    println!("cargo:rerun-if-changed={}", head_path.display());
+
+    // If HEAD is a symbolic ref (i.e. points at a branch), also watch the
+    // branch ref file so we rebuild when new commits land on that branch.
+    if let Ok(head_ref) = git_output(&["symbolic-ref", "HEAD"]) {
+        // e.g. refs/heads/main → .git/refs/heads/main (or the worktree equivalent)
+        let ref_path = git_path(&["rev-parse", "--git-path", &head_ref])?;
+        println!("cargo:rerun-if-changed={}", ref_path.display());
+    }
+
+    let sha = git_output(&["rev-parse", "HEAD"])?;
+    let branch = git_output(&["rev-parse", "--abbrev-ref", "HEAD"])?;
+
+    println!("cargo:rustc-env=BUILD_GIT_SHA={sha}");
+    println!("cargo:rustc-env=BUILD_GIT_BRANCH={branch}");
+
+    Ok(())
+}