From e0f2e5ee1199c489fa60525dae0607bf1524524f Mon Sep 17 00:00:00 2001
From: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>
Date: Sun, 19 Jul 2026 02:17:05 +0000
Subject: [PATCH 1/2] feat(rust): add Vertex auth base provider

Co-Authored-By: Ishaan Jaffer <155045088+ishaan-berri@users.noreply.github.com>
---
 litellm-rust/Cargo.lock                       | 654 +++++++++++++++++-
 litellm-rust/crates/core/Cargo.toml           |   2 +
 .../core/src/providers/vertex_ai/constants.rs |   7 +
 .../core/src/providers/vertex_ai/mod.rs       |   4 +
 .../src/providers/vertex_ai/vertex_base.rs    | 368 ++++++++++
 5 files changed, 1013 insertions(+), 22 deletions(-)
 create mode 100644 litellm-rust/crates/core/src/providers/vertex_ai/constants.rs
 create mode 100644 litellm-rust/crates/core/src/providers/vertex_ai/vertex_base.rs

diff --git a/litellm-rust/Cargo.lock b/litellm-rust/Cargo.lock
index 402d16715a3..502f8edb4ba 100644
--- a/litellm-rust/Cargo.lock
+++ b/litellm-rust/Cargo.lock
@@ -2,6 +2,15 @@
 # It is not intended for manual editing.
 version = 4
 
+[[package]]
+name = "android_system_properties"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "819e7219dbd41043ac279b19830f2efc897156490d7fd6ea916720117ee66311"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "arc-swap"
 version = "1.9.2"
@@ -19,7 +28,7 @@ checksum = "9035ad2d096bed7955a320ee7e2230574d28fd3c3a0f186cbea1ff3c7eed5dbb"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.118",
 ]
 
 [[package]]
@@ -313,7 +322,7 @@ checksum = "221eaa237ddf1ca79b60d1372aad77e47f9c0ea5b3ce5099da8c61d027dc77b3"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.118",
 ]
 
 [[package]]
@@ -478,6 +487,15 @@ dependencies = [
  "hybrid-array",
 ]
 
+[[package]]
+name = "bs58"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bf88ba1141d185c399bee5288d850d63b8369520c1eafc32a0430b5b6c287bf4"
+dependencies = [
+ "tinyvec",
+]
+
 [[package]]
 name = "bumpalo"
 version = "3.20.3"
@@ -495,6 +513,9 @@ name = "bytes"
 version = "1.12.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8ae3f5d315924270530207e2a68396c3cc547f6dca3fbdca317cfb1a51edb593"
+dependencies = [
+ "serde",
+]
 
 [[package]]
 name = "bytes-utils"
@@ -530,6 +551,29 @@ version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "613afe47fcd5fac7ccf1db93babcb082c5994d996f20b8b159f2ad1658eb5724"
 
+[[package]]
+name = "chacha20"
+version = "0.10.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d524456ba66e72eb8b115ff89e01e497f8e6d11d78b70b1aa13c0fbd97540a81"
+dependencies = [
+ "cfg-if",
+ "cpufeatures 0.3.0",
+ "rand_core 0.10.1",
+]
+
+[[package]]
+name = "chrono"
+version = "0.4.45"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1aa79e62e7697b8e29b513a68abacf485adcd1fe8284a4316c5ae868e6633327"
+dependencies = [
+ "iana-time-zone",
+ "num-traits",
+ "serde",
+ "windows-link",
+]
+
 [[package]]
 name = "cmake"
 version = "0.1.58"
@@ -545,6 +589,16 @@ version = "0.5.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0c9ea0ac24bc397ab3c98583a3c9ba74fa56b09a4449bbe172b9b1ddb016027a"
 
+[[package]]
+name = "combine"
+version = "4.6.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ba5a308b75df32fe02788e748662718f03fde005016435c444eea572398219fd"
+dependencies = [
+ "bytes",
+ "memchr",
+]
+
 [[package]]
 name = "const-oid"
 version = "0.10.2"
@@ -613,6 +667,40 @@ dependencies = [
  "cmov",
 ]
 
+[[package]]
+name = "darling"
+version = "0.23.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "25ae13da2f202d56bd7f91c25fba009e7717a1e4a1cc98a76d844b65ae912e9d"
+dependencies = [
+ "darling_core",
+ "darling_macro",
+]
+
+[[package]]
+name = "darling_core"
+version = "0.23.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9865a50f7c335f53564bb694ef660825eb8610e0a53d3e11bf1b0d3df31e03b0"
+dependencies = [
+ "ident_case",
+ "proc-macro2",
+ "quote",
+ "strsim",
+ "syn 2.0.118",
+]
+
+[[package]]
+name = "darling_macro"
+version = "0.23.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ac3984ec7bd6cfa798e62b4a642426a5be0e68f9401cfc2a01e3fa9ea2fcdb8d"
+dependencies = [
+ "darling_core",
+ "quote",
+ "syn 2.0.118",
+]
+
 [[package]]
 name = "data-encoding"
 version = "2.11.0"
@@ -624,6 +712,9 @@ name = "deranged"
 version = "0.5.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7cd812cc2bc1d69d4764bd80df88b4317eaef9e773c75226407d9bc0876b211c"
+dependencies = [
+ "serde_core",
+]
 
 [[package]]
 name = "digest"
@@ -655,7 +746,7 @@ checksum = "1ac70aa55017e108007fbaf5aa0f54b021c98f92ff8af59d42eda9da96e3dd4f"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.118",
 ]
 
 [[package]]
@@ -664,6 +755,12 @@ version = "1.0.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "92773504d58c093f6de2459af4af33faa518c13451eb8f2b5698ed3d36e7c813"
 
+[[package]]
+name = "dyn-clone"
+version = "1.0.20"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d0881ea181b1df73ff77ffaaf9c7544ecc11e82fba9b5f27b262a3c73a332555"
+
 [[package]]
 name = "either"
 version = "1.16.0"
@@ -676,6 +773,16 @@ version = "1.0.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "877a4ace8713b0bcf2a4e7eec82529c029f1d0619886d18145fea96c3ffe5c0f"
 
+[[package]]
+name = "errno"
+version = "0.3.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "39cab71617ae0d63f51a36d69f866391735b51691dbda63cf6f96d042b63efeb"
+dependencies = [
+ "libc",
+ "windows-sys 0.61.2",
+]
+
 [[package]]
 name = "fastrand"
 version = "2.4.1"
@@ -709,6 +816,20 @@ version = "1.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "42703706b716c37f96a77aea830392ad231f44c9e9a67872fa5548707e11b11c"
 
+[[package]]
+name = "futures"
+version = "0.3.32"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8b147ee9d1f6d097cef9ce628cd2ee62288d963e16fb287bd9286455b241382d"
+dependencies = [
+ "futures-channel",
+ "futures-core",
+ "futures-io",
+ "futures-sink",
+ "futures-task",
+ "futures-util",
+]
+
 [[package]]
 name = "futures-channel"
 version = "0.3.32"
@@ -739,7 +860,7 @@ checksum = "e835b70203e41293343137df5c0664546da5745f82ec9b84d40be8336958447b"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.118",
 ]
 
 [[package]]
@@ -816,6 +937,82 @@ dependencies = [
  "cfg-if",
  "libc",
  "r-efi 6.0.0",
+ "rand_core 0.10.1",
+]
+
+[[package]]
+name = "google-cloud-auth"
+version = "1.12.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4595b69c95c727ac896a4f2f16d0cdaa6f547de0bc5d64dbe9201487fc3226d5"
+dependencies = [
+ "async-trait",
+ "base64",
+ "bytes",
+ "chrono",
+ "google-cloud-gax",
+ "hex",
+ "hmac",
+ "http 1.4.2",
+ "reqwest 0.13.4",
+ "rustc_version",
+ "rustls 0.23.41",
+ "rustls-pki-types",
+ "serde",
+ "serde_json",
+ "sha2 0.11.0",
+ "thiserror 2.0.18",
+ "time",
+ "tokio",
+ "url",
+]
+
+[[package]]
+name = "google-cloud-gax"
+version = "1.12.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3103a4a9013f1aed573ca56e19a9680b0211643a99ea85caf524b397d6be8be3"
+dependencies = [
+ "bytes",
+ "futures",
+ "google-cloud-rpc",
+ "google-cloud-wkt",
+ "http 1.4.2",
+ "pin-project",
+ "rand 0.10.2",
+ "serde",
+ "serde_json",
+ "thiserror 2.0.18",
+ "tokio",
+]
+
+[[package]]
+name = "google-cloud-rpc"
+version = "1.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e2162c08a89118130979ba261080e960e44cdcb2d6e2ab8ca9b1da245285d353"
+dependencies = [
+ "bytes",
+ "google-cloud-wkt",
+ "serde",
+ "serde_json",
+ "serde_with",
+]
+
+[[package]]
+name = "google-cloud-wkt"
+version = "1.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "46df1fcc3ab69164af3f4199ed21f45b5dbc56d9f03211eb4fa20116d442364b"
+dependencies = [
+ "base64",
+ "bytes",
+ "serde",
+ "serde_json",
+ "serde_with",
+ "thiserror 2.0.18",
+ "time",
+ "url",
 ]
 
 [[package]]
@@ -830,7 +1027,7 @@ dependencies = [
  "futures-sink",
  "futures-util",
  "http 0.2.12",
- "indexmap",
+ "indexmap 2.14.0",
  "slab",
  "tokio",
  "tokio-util",
@@ -849,13 +1046,19 @@ dependencies = [
  "futures-core",
  "futures-sink",
  "http 1.4.2",
- "indexmap",
+ "indexmap 2.14.0",
  "slab",
  "tokio",
  "tokio-util",
  "tracing",
 ]
 
+[[package]]
+name = "hashbrown"
+version = "0.12.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8a9ee70c43aaf417c914396645a0fa852624801b24ebb7ae78fe8272889ac888"
+
 [[package]]
 name = "hashbrown"
 version = "0.17.1"
@@ -1060,6 +1263,30 @@ dependencies = [
  "tracing",
 ]
 
+[[package]]
+name = "iana-time-zone"
+version = "0.1.65"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e31bc9ad994ba00e440a8aa5c9ef0ec67d5cb5e5cb0cc7f8b744a35b389cc470"
+dependencies = [
+ "android_system_properties",
+ "core-foundation-sys",
+ "iana-time-zone-haiku",
+ "js-sys",
+ "log",
+ "wasm-bindgen",
+ "windows-core",
+]
+
+[[package]]
+name = "iana-time-zone-haiku"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f31827a206f56af32e590ba56d5d2d085f558508192593743f16b2306495269f"
+dependencies = [
+ "cc",
+]
+
 [[package]]
 name = "icu_collections"
 version = "2.2.0"
@@ -1142,6 +1369,12 @@ dependencies = [
  "zerovec",
 ]
 
+[[package]]
+name = "ident_case"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b9e0384b61958566e926dc50660321d12159025e767c18e043daf26b70104c39"
+
 [[package]]
 name = "idna"
 version = "1.1.0"
@@ -1163,6 +1396,17 @@ dependencies = [
  "icu_properties",
 ]
 
+[[package]]
+name = "indexmap"
+version = "1.9.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bd070e393353796e801d209ad339e89596eb4c8d430d18ede6a1cced8fafbd99"
+dependencies = [
+ "autocfg",
+ "hashbrown 0.12.3",
+ "serde",
+]
+
 [[package]]
 name = "indexmap"
 version = "2.14.0"
@@ -1170,7 +1414,9 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d466e9454f08e4a911e14806c24e16fba1b4c121d1ea474396f396069cf949d9"
 dependencies = [
  "equivalent",
- "hashbrown",
+ "hashbrown 0.17.1",
+ "serde",
+ "serde_core",
 ]
 
 [[package]]
@@ -1185,6 +1431,55 @@ version = "1.0.18"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8f42a60cbdf9a97f5d2305f08a87dc4e09308d1276d28c869c684d7777685682"
 
+[[package]]
+name = "jni"
+version = "0.22.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5efd9a482cf3a427f00d6b35f14332adc7902ce91efb778580e180ff90fa3498"
+dependencies = [
+ "cfg-if",
+ "combine",
+ "jni-macros",
+ "jni-sys",
+ "log",
+ "simd_cesu8",
+ "thiserror 2.0.18",
+ "walkdir",
+ "windows-link",
+]
+
+[[package]]
+name = "jni-macros"
+version = "0.22.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a00109accc170f0bdb141fed3e393c565b6f5e072365c3bd58f5b062591560a3"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "rustc_version",
+ "simd_cesu8",
+ "syn 2.0.118",
+]
+
+[[package]]
+name = "jni-sys"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c6377a88cb3910bee9b0fa88d4f42e1d2da8e79915598f65fb0c7ee14c878af2"
+dependencies = [
+ "jni-sys-macros",
+]
+
+[[package]]
+name = "jni-sys-macros"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "38c0b942f458fe50cdac086d2f946512305e5631e720728f2a61aabcd47a6264"
+dependencies = [
+ "quote",
+ "syn 2.0.118",
+]
+
 [[package]]
 name = "jobserver"
 version = "0.1.35"
@@ -1222,7 +1517,7 @@ dependencies = [
  "futures-util",
  "litellm-core",
  "pyo3",
- "reqwest",
+ "reqwest 0.12.28",
  "serde",
  "serde_json",
  "sha2 0.10.9",
@@ -1242,8 +1537,9 @@ dependencies = [
  "aws-sigv4",
  "aws-smithy-runtime-api",
  "aws-types",
+ "google-cloud-auth",
  "rand 0.8.6",
- "reqwest",
+ "reqwest 0.12.28",
  "serde",
  "serde_json",
  "sha2 0.10.9",
@@ -1358,6 +1654,26 @@ version = "2.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9b4f627cb1b25917193a259e49bdad08f671f8d9708acfd5fe0a8c1455d87220"
 
+[[package]]
+name = "pin-project"
+version = "1.1.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2466b2336ed02bcdca6b294417127b90ec92038d1d5c4fbeac971a922e0e0924"
+dependencies = [
+ "pin-project-internal",
+]
+
+[[package]]
+name = "pin-project-internal"
+version = "1.1.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c96395f0a926bc13b1c17622aaddda1ecb55d49c8f1bf9777e4d877800a43f8b"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.118",
+]
+
 [[package]]
 name = "pin-project-lite"
 version = "0.2.17"
@@ -1471,7 +1787,7 @@ dependencies = [
  "proc-macro2",
  "pyo3-macros-backend",
  "quote",
- "syn",
+ "syn 2.0.118",
 ]
 
 [[package]]
@@ -1483,7 +1799,7 @@ dependencies = [
  "heck",
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.118",
 ]
 
 [[package]]
@@ -1512,6 +1828,7 @@ version = "0.11.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4fcb935c5bec503c2f0e306bdd3e58bb9029dcb14fa8d9ac76e3a5256ac0763e"
 dependencies = [
+ "aws-lc-rs",
  "bytes",
  "getrandom 0.3.4",
  "lru-slab",
@@ -1583,6 +1900,17 @@ dependencies = [
  "rand_core 0.9.5",
 ]
 
+[[package]]
+name = "rand"
+version = "0.10.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c7f5fa3a058cd35567ef9bfa5e75732bee0f9e4c55fa90477bef2dfcdbc4be80"
+dependencies = [
+ "chacha20",
+ "getrandom 0.4.3",
+ "rand_core 0.10.1",
+]
+
 [[package]]
 name = "rand_chacha"
 version = "0.3.1"
@@ -1621,6 +1949,32 @@ dependencies = [
  "getrandom 0.3.4",
 ]
 
+[[package]]
+name = "rand_core"
+version = "0.10.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "63b8176103e19a2643978565ca18b50549f6101881c443590420e4dc998a3c69"
+
+[[package]]
+name = "ref-cast"
+version = "1.0.26"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "216e8f773d7923bcba9ceb86a86c93cabb3903a11872fc3f138c49630e50b96d"
+dependencies = [
+ "ref-cast-impl",
+]
+
+[[package]]
+name = "ref-cast-impl"
+version = "1.0.26"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2c9283685feec7d69af75fb0e858d5e7378f33fe4fc699383b2916ab9273e03c"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 3.0.0",
+]
+
 [[package]]
 name = "regex-lite"
 version = "0.1.9"
@@ -1670,6 +2024,44 @@ dependencies = [
  "webpki-roots",
 ]
 
+[[package]]
+name = "reqwest"
+version = "0.13.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "219c5811de6525e5416c7d5d53bb656d3afdbc6c5af816e0802bcfa42dbdc1c3"
+dependencies = [
+ "base64",
+ "bytes",
+ "futures-core",
+ "http 1.4.2",
+ "http-body 1.0.1",
+ "http-body-util",
+ "hyper 1.10.1",
+ "hyper-rustls 0.27.9",
+ "hyper-util",
+ "js-sys",
+ "log",
+ "percent-encoding",
+ "pin-project-lite",
+ "quinn",
+ "rustls 0.23.41",
+ "rustls-pki-types",
+ "rustls-platform-verifier",
+ "serde",
+ "serde_json",
+ "serde_urlencoded",
+ "sync_wrapper",
+ "tokio",
+ "tokio-rustls 0.26.4",
+ "tower",
+ "tower-http",
+ "tower-service",
+ "url",
+ "wasm-bindgen",
+ "wasm-bindgen-futures",
+ "web-sys",
+]
+
 [[package]]
 name = "ring"
 version = "0.17.14"
@@ -1718,6 +2110,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6b92b125634d9b795e7beca796cc790df15a7fb38323bf3196fda83292d06b1f"
 dependencies = [
  "aws-lc-rs",
+ "log",
  "once_cell",
  "ring",
  "rustls-pki-types",
@@ -1748,6 +2141,33 @@ dependencies = [
  "zeroize",
 ]
 
+[[package]]
+name = "rustls-platform-verifier"
+version = "0.7.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "26d1e2536ce4f35f4846aa13bff16bd0ff40157cdb14cc056c7b14ba41233ba0"
+dependencies = [
+ "core-foundation",
+ "core-foundation-sys",
+ "jni",
+ "log",
+ "once_cell",
+ "rustls 0.23.41",
+ "rustls-native-certs",
+ "rustls-platform-verifier-android",
+ "rustls-webpki 0.103.13",
+ "security-framework",
+ "security-framework-sys",
+ "webpki-root-certs",
+ "windows-sys 0.61.2",
+]
+
+[[package]]
+name = "rustls-platform-verifier-android"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f87165f0995f63a9fbeea62b64d10b4d9d8e78ec6d7d51fb2125fda7bb36788f"
+
 [[package]]
 name = "rustls-webpki"
 version = "0.101.7"
@@ -1782,6 +2202,15 @@ version = "1.0.23"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9774ba4a74de5f7b1c1451ed6cd5285a32eddb5cccb8cc655a4e50009e06477f"
 
+[[package]]
+name = "same-file"
+version = "1.0.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "93fc1dc3aaa9bfed95e02e6eadabb4baf7e3078b0bd1b4d7b6b0b68378900502"
+dependencies = [
+ "winapi-util",
+]
+
 [[package]]
 name = "schannel"
 version = "0.1.29"
@@ -1791,6 +2220,30 @@ dependencies = [
  "windows-sys 0.61.2",
 ]
 
+[[package]]
+name = "schemars"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4cd191f9397d57d581cddd31014772520aa448f65ef991055d7f61582c65165f"
+dependencies = [
+ "dyn-clone",
+ "ref-cast",
+ "serde",
+ "serde_json",
+]
+
+[[package]]
+name = "schemars"
+version = "1.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a2b42f36aa1cd011945615b92222f6bf73c599a102a300334cd7f8dbeec726cc"
+dependencies = [
+ "dyn-clone",
+ "ref-cast",
+ "serde",
+ "serde_json",
+]
+
 [[package]]
 name = "sct"
 version = "0.7.1"
@@ -1857,7 +2310,7 @@ checksum = "d540f220d3187173da220f885ab66608367b6574e925011a9353e4badda91d79"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.118",
 ]
 
 [[package]]
@@ -1896,6 +2349,38 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "serde_with"
+version = "3.21.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "76a5c54c7310e7b8b9577c286d7e399ddd876c3e12b3ed917a8aabc4b96e9e8c"
+dependencies = [
+ "base64",
+ "bs58",
+ "chrono",
+ "hex",
+ "indexmap 1.9.3",
+ "indexmap 2.14.0",
+ "schemars 0.9.0",
+ "schemars 1.2.1",
+ "serde_core",
+ "serde_json",
+ "serde_with_macros",
+ "time",
+]
+
+[[package]]
+name = "serde_with_macros"
+version = "3.21.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "84d57bc0c8b9a17920c178daa6bb924850d54a9c97ab45194bb8c17ad66bb660"
+dependencies = [
+ "darling",
+ "proc-macro2",
+ "quote",
+ "syn 2.0.118",
+]
+
 [[package]]
 name = "sha1"
 version = "0.10.6"
@@ -1935,6 +2420,32 @@ version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f8fadd59c855ef2080decdef8ff161eb6661b86933c9d82e5ba29dc602a55aba"
 
+[[package]]
+name = "signal-hook-registry"
+version = "1.4.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c4db69cba1110affc0e9f7bcd48bbf87b3f4fc7c61fc9155afd4c469eb3d6c1b"
+dependencies = [
+ "errno",
+ "libc",
+]
+
+[[package]]
+name = "simd_cesu8"
+version = "1.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "11031e251abf8611c80f460e19dbdeb54a66db918e49c65a7065b46ac7aec520"
+dependencies = [
+ "rustc_version",
+ "simdutf8",
+]
+
+[[package]]
+name = "simdutf8"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e3a9fe34e3e7a50316060351f37187a3f546bce95496156754b601a5fa71b76e"
+
 [[package]]
 name = "slab"
 version = "0.4.12"
@@ -1973,6 +2484,12 @@ version = "1.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6ce2be8dc25455e1f91df71bfa12ad37d7af1092ae736f3a6cd0e37bc7810596"
 
+[[package]]
+name = "strsim"
+version = "0.11.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7da8b5736845d9f2fcb837ea5d9e2628564b3b043a70948a3f0b778838c5fb4f"
+
 [[package]]
 name = "subtle"
 version = "2.6.1"
@@ -1990,6 +2507,17 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "syn"
+version = "3.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f2fac314a64dc9a36e61a9eb4261a5e9bbfbc922b27e518af97bc32b926cf967"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-ident",
+]
+
 [[package]]
 name = "sync_wrapper"
 version = "1.0.2"
@@ -2007,7 +2535,7 @@ checksum = "728a70f3dbaf5bab7f0c4b1ac8d7ae5ea60a4b5549c8a5914361c99147a709d2"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.118",
 ]
 
 [[package]]
@@ -2042,7 +2570,7 @@ checksum = "4fee6c4efc90059e10f81e6d42c60a18f76588c3d74cb83a0b242a2b6c7504c1"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.118",
 ]
 
 [[package]]
@@ -2053,7 +2581,7 @@ checksum = "ebc4ee7f67670e9b64d05fa4253e753e016c6c95ff35b89b7941d6b856dec1d5"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.118",
 ]
 
 [[package]]
@@ -2121,6 +2649,7 @@ dependencies = [
  "libc",
  "mio",
  "pin-project-lite",
+ "signal-hook-registry",
  "socket2 0.6.4",
  "tokio-macros",
  "windows-sys 0.61.2",
@@ -2134,7 +2663,7 @@ checksum = "385a6cb71ab9ab790c5fe8d67f1645e6c450a7ce006a33de03daa956cf70a496"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.118",
 ]
 
 [[package]]
@@ -2252,7 +2781,7 @@ checksum = "7490cfa5ec963746568740651ac6781f701c9c5ea257c58e057f3ba8cf69e8da"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.118",
 ]
 
 [[package]]
@@ -2360,6 +2889,16 @@ version = "0.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5c3082ca00d5a5ef149bb8b555a72ae84c9c59f7250f013ac822ac2e49b19c64"
 
+[[package]]
+name = "walkdir"
+version = "2.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "29790946404f91d9c5d06f9874efddea1dc06c5efe94541a7d6863108e3a5e4b"
+dependencies = [
+ "same-file",
+ "winapi-util",
+]
+
 [[package]]
 name = "want"
 version = "0.3.1"
@@ -2426,7 +2965,7 @@ dependencies = [
  "bumpalo",
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.118",
  "wasm-bindgen-shared",
 ]
 
@@ -2472,6 +3011,15 @@ dependencies = [
  "wasm-bindgen",
 ]
 
+[[package]]
+name = "webpki-root-certs"
+version = "1.0.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b96554aa2acc8ccdb7e1c9a58a7a68dd5d13bccc69cd124cb09406db612a1c9b"
+dependencies = [
+ "rustls-pki-types",
+]
+
 [[package]]
 name = "webpki-roots"
 version = "1.0.8"
@@ -2481,12 +3029,74 @@ dependencies = [
  "rustls-pki-types",
 ]
 
+[[package]]
+name = "winapi-util"
+version = "0.1.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c2a7b1c03c876122aa43f3020e6c3c3ee5c05081c9a00739faf7503aeba10d22"
+dependencies = [
+ "windows-sys 0.61.2",
+]
+
+[[package]]
+name = "windows-core"
+version = "0.62.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b8e83a14d34d0623b51dce9581199302a221863196a1dde71a7663a4c2be9deb"
+dependencies = [
+ "windows-implement",
+ "windows-interface",
+ "windows-link",
+ "windows-result",
+ "windows-strings",
+]
+
+[[package]]
+name = "windows-implement"
+version = "0.60.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "053e2e040ab57b9dc951b72c264860db7eb3b0200ba345b4e4c3b14f67855ddf"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.118",
+]
+
+[[package]]
+name = "windows-interface"
+version = "0.59.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3f316c4a2570ba26bbec722032c4099d8c8bc095efccdc15688708623367e358"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.118",
+]
+
 [[package]]
 name = "windows-link"
 version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f0805222e57f7521d6a62e36fa9163bc891acd422f971defe97d64e70d0a4fe5"
 
+[[package]]
+name = "windows-result"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7781fa89eaf60850ac3d2da7af8e5242a5ea78d1a11c49bf2910bb5a73853eb5"
+dependencies = [
+ "windows-link",
+]
+
+[[package]]
+name = "windows-strings"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7837d08f69c77cf6b07689544538e017c1bfcf57e34b4c0ff58e6c2cd3b37091"
+dependencies = [
+ "windows-link",
+]
+
 [[package]]
 name = "windows-sys"
 version = "0.52.0"
@@ -2680,7 +3290,7 @@ checksum = "de844c262c8848816172cef550288e7dc6c7b7814b4ee56b3e1553f275f1858e"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.118",
  "synstructure",
 ]
 
@@ -2701,7 +3311,7 @@ checksum = "1ae7f38b72ec2a254e2b87ef277cf2cd4fb97cbebf944faa6f33354da0867930"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.118",
 ]
 
 [[package]]
@@ -2721,7 +3331,7 @@ checksum = "11532158c46691caf0f2593ea8358fed6bbf68a0315e80aae9bd41fbade684a1"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.118",
  "synstructure",
 ]
 
@@ -2761,7 +3371,7 @@ checksum = "625dc425cab0dca6dc3c3319506e6593dcb08a9f387ea3b284dbd52a92c40555"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 2.0.118",
 ]
 
 [[package]]
diff --git a/litellm-rust/crates/core/Cargo.toml b/litellm-rust/crates/core/Cargo.toml
index 65c6db7412c..f72497d4d9f 100644
--- a/litellm-rust/crates/core/Cargo.toml
+++ b/litellm-rust/crates/core/Cargo.toml
@@ -17,6 +17,7 @@ aws-sdk-sts = { version = "1.108.0", default-features = false, features = ["rust
 aws-sigv4 = { version = "1.5.1", optional = true }
 aws-types = { version = "1.4.0", optional = true }
 aws-smithy-runtime-api = { version = "1.13.0", optional = true }
+google-cloud-auth = { version = "=1.12.0", default-features = false, features = ["default-rustls-provider"], optional = true }
 
 [features]
 default = []
@@ -28,6 +29,7 @@ bedrock-auth = [
     "dep:aws-types",
     "dep:aws-smithy-runtime-api",
 ]
+vertex-auth = ["dep:google-cloud-auth"]
 
 [dev-dependencies]
 reqwest.workspace = true
diff --git a/litellm-rust/crates/core/src/providers/vertex_ai/constants.rs b/litellm-rust/crates/core/src/providers/vertex_ai/constants.rs
new file mode 100644
index 00000000000..846d54213f8
--- /dev/null
+++ b/litellm-rust/crates/core/src/providers/vertex_ai/constants.rs
@@ -0,0 +1,7 @@
+pub const VERTEXAI_PROJECT: &str = "VERTEXAI_PROJECT";
+pub const VERTEXAI_LOCATION: &str = "VERTEXAI_LOCATION";
+pub const VERTEXAI_CREDENTIALS: &str = "VERTEXAI_CREDENTIALS";
+pub const GOOGLE_APPLICATION_CREDENTIALS: &str = "GOOGLE_APPLICATION_CREDENTIALS";
+pub const GOOGLE_CLOUD_PROJECT: &str = "GOOGLE_CLOUD_PROJECT";
+pub const GOOGLE_CLOUD_QUOTA_PROJECT: &str = "GOOGLE_CLOUD_QUOTA_PROJECT";
+pub const CLOUD_PLATFORM_SCOPE: &str = "https://www.googleapis.com/auth/cloud-platform";
diff --git a/litellm-rust/crates/core/src/providers/vertex_ai/mod.rs b/litellm-rust/crates/core/src/providers/vertex_ai/mod.rs
index 3621ff6a2fd..424eaab91cd 100644
--- a/litellm-rust/crates/core/src/providers/vertex_ai/mod.rs
+++ b/litellm-rust/crates/core/src/providers/vertex_ai/mod.rs
@@ -1 +1,5 @@
+#[cfg(feature = "vertex-auth")]
+mod constants;
 pub mod ocr;
+#[cfg(feature = "vertex-auth")]
+pub mod vertex_base;
diff --git a/litellm-rust/crates/core/src/providers/vertex_ai/vertex_base.rs b/litellm-rust/crates/core/src/providers/vertex_ai/vertex_base.rs
new file mode 100644
index 00000000000..8909b2bc414
--- /dev/null
+++ b/litellm-rust/crates/core/src/providers/vertex_ai/vertex_base.rs
@@ -0,0 +1,368 @@
+//! User-directed exception: this base provider owns Google auth I/O for parity
+//! with Python's `VertexBase`; the broader core purity guidance is reconciled
+//! separately.
+
+use std::env;
+use std::fs;
+use std::path::Path;
+use std::sync::{Mutex, OnceLock};
+
+use google_cloud_auth::credentials::external_account;
+use google_cloud_auth::credentials::service_account;
+use google_cloud_auth::credentials::user_account;
+use google_cloud_auth::credentials::AccessTokenCredentials;
+use serde_json::Value;
+use sha2::{Digest, Sha256};
+
+use crate::caching::in_memory_cache::InMemoryCache;
+use crate::error::{CoreError, CoreResult};
+
+use super::constants::{
+    CLOUD_PLATFORM_SCOPE, GOOGLE_APPLICATION_CREDENTIALS, GOOGLE_CLOUD_PROJECT,
+    GOOGLE_CLOUD_QUOTA_PROJECT, VERTEXAI_CREDENTIALS, VERTEXAI_LOCATION, VERTEXAI_PROJECT,
+};
+
+static VERTEX_CREDENTIALS_CACHE: OnceLock<Mutex<InMemoryCache<AccessTokenCredentials>>> =
+    OnceLock::new();
+
+// google-cloud-auth owns async token caching and refresh; Python's single-flight machinery is intentionally not ported.
+
+#[derive(Clone, Debug, PartialEq)]
+pub enum VertexCredentialsInput {
+    Json(Value),
+    String(String),
+}
+
+#[derive(Clone, Debug, Default, PartialEq)]
+pub struct VertexAuthConfig {
+    pub credentials: Option<VertexCredentialsInput>,
+    pub location: Option<String>,
+    pub project_id: Option<String>,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum VertexAuthSource {
+    AwsWorkloadIdentity,
+    ExecutableWorkloadIdentity,
+    IdentityPoolWorkloadIdentity,
+    AuthorizedUser,
+    ServiceAccount,
+    DefaultAdc,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct VertexToken {
+    pub access_token: String,
+    pub project_id: String,
+}
+
+impl VertexAuthConfig {
+    pub fn from_environment() -> Self {
+        Self {
+            credentials: non_empty_env(VERTEXAI_CREDENTIALS)
+                .or_else(|| non_empty_env(GOOGLE_APPLICATION_CREDENTIALS))
+                .map(VertexCredentialsInput::String),
+            location: non_empty_env(VERTEXAI_LOCATION),
+            project_id: non_empty_env(VERTEXAI_PROJECT)
+                .or_else(|| non_empty_env(GOOGLE_CLOUD_PROJECT)),
+        }
+    }
+}
+
+pub fn resolve_credentials_input(
+    credentials: Option<VertexCredentialsInput>,
+) -> CoreResult<Option<Value>> {
+    let Some(credentials) = credentials else {
+        return Ok(None);
+    };
+
+    let value = match credentials {
+        VertexCredentialsInput::Json(value) => value,
+        VertexCredentialsInput::String(value) => {
+            if value.trim().is_empty() {
+                return Ok(None);
+            }
+            let path = Path::new(&value);
+            let json = if path.is_file() {
+                fs::read_to_string(path).map_err(|error| {
+                    CoreError::Auth(format!("unable to read Vertex credentials file: {error}"))
+                })?
+            } else {
+                value
+            };
+            serde_json::from_str(&json).map_err(|error| {
+                CoreError::Auth(format!("invalid Vertex credentials JSON: {error}"))
+            })?
+        }
+    };
+
+    if value.is_object() {
+        Ok(Some(value))
+    } else {
+        Err(CoreError::InvalidType {
+            expected: "object",
+            actual: crate::error::json_type_name(&value),
+        })
+    }
+}
+
+pub fn classify_auth(credentials: Option<&Value>) -> VertexAuthSource {
+    let Some(credentials) = credentials else {
+        return VertexAuthSource::DefaultAdc;
+    };
+
+    let credential_type = credentials.get("type").and_then(Value::as_str);
+    if credential_type == Some("external_account") {
+        let source = credentials
+            .get("credential_source")
+            .and_then(Value::as_object);
+        let environment_id = source
+            .and_then(|source| source.get("environment_id"))
+            .and_then(Value::as_str)
+            .unwrap_or_default();
+        if environment_id.contains("aws") {
+            return VertexAuthSource::AwsWorkloadIdentity;
+        }
+        if source.is_some_and(|source| source.contains_key("executable")) {
+            return VertexAuthSource::ExecutableWorkloadIdentity;
+        }
+        return VertexAuthSource::IdentityPoolWorkloadIdentity;
+    }
+    if credential_type == Some("authorized_user") {
+        return VertexAuthSource::AuthorizedUser;
+    }
+    VertexAuthSource::ServiceAccount
+}
+
+pub async fn resolve_token(config: VertexAuthConfig) -> CoreResult<VertexToken> {
+    let credentials = resolve_credentials_input(config.credentials)?;
+    let source = classify_auth(credentials.as_ref());
+    let project_id = project_id(config.project_id, credentials.as_ref())?;
+    let cache_key = cache_key(credentials.as_ref(), &project_id);
+    let provider = cached_credentials(&cache_key)?;
+    let provider = match provider {
+        Some(provider) => provider,
+        None => {
+            let provider = build_credentials(source, credentials)?;
+            let access_token = provider.access_token().await.map_err(|error| {
+                CoreError::Auth(format!("Google token resolution failed: {error}"))
+            })?;
+            store_credentials(cache_key, provider.clone())?;
+            return Ok(VertexToken {
+                access_token: access_token.token,
+                project_id,
+            });
+        }
+    };
+    let access_token = provider
+        .access_token()
+        .await
+        .map_err(|error| CoreError::Auth(format!("Google token resolution failed: {error}")))?;
+    Ok(VertexToken {
+        access_token: access_token.token,
+        project_id,
+    })
+}
+
+fn build_credentials(
+    source: VertexAuthSource,
+    credentials: Option<Value>,
+) -> CoreResult<AccessTokenCredentials> {
+    let scopes = [CLOUD_PLATFORM_SCOPE];
+    match source {
+        VertexAuthSource::DefaultAdc => google_cloud_auth::credentials::Builder::default()
+            .with_scopes(scopes)
+            .build_access_token_credentials()
+            .map_err(|error| CoreError::Auth(format!("Google ADC resolution failed: {error}"))),
+        VertexAuthSource::AwsWorkloadIdentity
+        | VertexAuthSource::ExecutableWorkloadIdentity
+        | VertexAuthSource::IdentityPoolWorkloadIdentity => {
+            let value = credentials.ok_or(CoreError::MissingField("credentials"))?;
+            external_account::Builder::new(value)
+                .with_scopes(scopes)
+                .build_access_token_credentials()
+                .map_err(|error| {
+                    CoreError::Auth(format!(
+                        "Google external account resolution failed: {error}"
+                    ))
+                })
+        }
+        VertexAuthSource::AuthorizedUser => {
+            let value = credentials.ok_or(CoreError::MissingField("credentials"))?;
+            user_account::Builder::new(value)
+                .with_scopes(scopes)
+                .build_access_token_credentials()
+                .map_err(|error| {
+                    CoreError::Auth(format!("Google authorized-user resolution failed: {error}"))
+                })
+        }
+        VertexAuthSource::ServiceAccount => {
+            let value = credentials.ok_or(CoreError::MissingField("credentials"))?;
+            service_account::Builder::new(value)
+                .with_access_specifier(service_account::AccessSpecifier::from_scopes(scopes))
+                .build_access_token_credentials()
+                .map_err(|error| {
+                    CoreError::Auth(format!("Google service-account resolution failed: {error}"))
+                })
+        }
+    }
+}
+
+fn project_id(explicit: Option<String>, credentials: Option<&Value>) -> CoreResult<String> {
+    let project_id = explicit
+        .filter(|value| !value.trim().is_empty())
+        .or_else(|| {
+            credentials.and_then(|value| {
+                value
+                    .get("project_id")
+                    .and_then(Value::as_str)
+                    .map(str::to_owned)
+            })
+        })
+        .or_else(|| {
+            credentials.and_then(|value| {
+                value
+                    .get("quota_project_id")
+                    .and_then(Value::as_str)
+                    .map(str::to_owned)
+            })
+        })
+        .or_else(|| non_empty_env(GOOGLE_CLOUD_PROJECT))
+        .or_else(|| non_empty_env(GOOGLE_CLOUD_QUOTA_PROJECT));
+    project_id.ok_or(CoreError::MissingField("project_id"))
+}
+
+fn cache_key(credentials: Option<&Value>, project_id: &str) -> String {
+    let mut hasher = Sha256::new();
+    if let Some(credentials) = credentials {
+        hasher.update(credentials.to_string());
+    }
+    hasher.update(project_id);
+    format!("{:x}", hasher.finalize())
+}
+
+fn cached_credentials(key: &str) -> CoreResult<Option<AccessTokenCredentials>> {
+    let cache = VERTEX_CREDENTIALS_CACHE.get_or_init(|| Mutex::new(InMemoryCache::default()));
+    let mut cache = cache
+        .lock()
+        .map_err(|_| CoreError::Auth("Vertex credential cache lock poisoned".to_string()))?;
+    Ok(cache.get_cache(key))
+}
+
+fn store_credentials(key: String, credentials: AccessTokenCredentials) -> CoreResult<()> {
+    let cache = VERTEX_CREDENTIALS_CACHE.get_or_init(|| Mutex::new(InMemoryCache::default()));
+    let mut cache = cache
+        .lock()
+        .map_err(|_| CoreError::Auth("Vertex credential cache lock poisoned".to_string()))?;
+    cache.set_cache(key, credentials, None);
+    Ok(())
+}
+
+fn non_empty_env(name: &str) -> Option<String> {
+    env::var(name).ok().filter(|value| !value.trim().is_empty())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use serde_json::json;
+
+    #[test]
+    fn classifier_preserves_external_account_dispatch_order() {
+        assert_eq!(
+            classify_auth(Some(&json!({
+                "type": "external_account",
+                "credential_source": {"environment_id": "aws1", "executable": {}}
+            }))),
+            VertexAuthSource::AwsWorkloadIdentity
+        );
+        assert_eq!(
+            classify_auth(Some(&json!({
+                "type": "external_account",
+                "credential_source": {"executable": {"command": "token"}}
+            }))),
+            VertexAuthSource::ExecutableWorkloadIdentity
+        );
+        assert_eq!(
+            classify_auth(Some(
+                &json!({"type": "external_account", "credential_source": {}})
+            )),
+            VertexAuthSource::IdentityPoolWorkloadIdentity
+        );
+    }
+
+    #[test]
+    fn classifier_covers_authorized_service_and_default_sources() {
+        assert_eq!(
+            classify_auth(Some(&json!({"type": "authorized_user"}))),
+            VertexAuthSource::AuthorizedUser
+        );
+        assert_eq!(
+            classify_auth(Some(&json!({"type": "service_account"}))),
+            VertexAuthSource::ServiceAccount
+        );
+        assert_eq!(
+            classify_auth(Some(&json!({"client_email": "test@example.com"}))),
+            VertexAuthSource::ServiceAccount
+        );
+        assert_eq!(classify_auth(None), VertexAuthSource::DefaultAdc);
+    }
+
+    #[test]
+    fn credential_input_reads_files_inline_json_and_objects() {
+        let path = std::env::temp_dir().join(format!("vertex-auth-{}.json", std::process::id()));
+        std::fs::write(&path, r#"{"type":"authorized_user"}"#).unwrap();
+        assert_eq!(
+            resolve_credentials_input(Some(VertexCredentialsInput::String(
+                path.to_string_lossy().into_owned()
+            )))
+            .unwrap(),
+            Some(json!({"type": "authorized_user"}))
+        );
+        std::fs::remove_file(path).unwrap();
+        assert_eq!(
+            resolve_credentials_input(Some(VertexCredentialsInput::String(
+                r#"{"type":"service_account"}"#.to_string()
+            )))
+            .unwrap(),
+            Some(json!({"type": "service_account"}))
+        );
+        assert_eq!(
+            resolve_credentials_input(Some(VertexCredentialsInput::Json(json!({
+                "type": "external_account"
+            }))))
+            .unwrap(),
+            Some(json!({"type": "external_account"}))
+        );
+    }
+
+    #[test]
+    fn credential_input_treats_empty_as_absent_and_rejects_invalid_json() {
+        assert_eq!(
+            resolve_credentials_input(Some(VertexCredentialsInput::String(" \n".to_string())))
+                .unwrap(),
+            None
+        );
+        assert!(matches!(
+            resolve_credentials_input(Some(VertexCredentialsInput::String("{".to_string()))),
+            Err(CoreError::Auth(_))
+        ));
+    }
+
+    #[test]
+    fn project_id_explicit_value_wins_over_credential_and_environment() {
+        let credentials = json!({"project_id": "credential-project"});
+        assert_eq!(
+            project_id(Some("explicit-project".to_string()), Some(&credentials)).unwrap(),
+            "explicit-project"
+        );
+        assert_eq!(
+            project_id(None, Some(&credentials)).unwrap(),
+            "credential-project"
+        );
+        assert_eq!(
+            project_id(None, Some(&json!({"quota_project_id": "quota-project"}))).unwrap(),
+            "quota-project"
+        );
+    }
+}

From 0ca7557ca37433c64180c5a7d25f9dce7dc7b5e8 Mon Sep 17 00:00:00 2001
From: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>
Date: Sun, 19 Jul 2026 02:39:23 +0000
Subject: [PATCH 2/2] ci(rust): cover Vertex auth feature

Co-Authored-By: Ishaan Jaffer <155045088+ishaan-berri@users.noreply.github.com>
---
 .github/workflows/test-rust.yml | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/.github/workflows/test-rust.yml b/.github/workflows/test-rust.yml
index 21e1bcb90c6..3a2c550443d 100644
--- a/.github/workflows/test-rust.yml
+++ b/.github/workflows/test-rust.yml
@@ -64,8 +64,14 @@ jobs:
       - name: Run Clippy with Bedrock auth
         run: cargo clippy -p litellm-core --all-targets --features bedrock-auth --locked -- -D warnings
 
+      - name: Run Clippy with Vertex auth
+        run: cargo clippy -p litellm-core --all-targets --features vertex-auth --locked -- -D warnings
+
       - name: Run Rust tests
         run: cargo test --workspace --locked
 
       - name: Run core tests with Bedrock auth
         run: cargo test -p litellm-core --features bedrock-auth --locked
+
+      - name: Run core tests with Vertex auth
+        run: cargo test -p litellm-core --features vertex-auth --locked