feat(rust): add OAuth header provider (#3579)

## Summary

Add the Rust OAuth header provider for remote LanceDB connections.

This supports client credentials and Azure managed identity flows,
handles token caching and refresh, redacts secrets in Debug output, and
wires `ConnectBuilder::oauth_config()` into the remote client while
rejecting ambiguous API-key/header-provider combinations.

Cargo.lock

@@ -5384,6 +5384,7 @@ dependencies = [
  "tokenizers",
  "tokio",
  "url",
+ "urlencoding",
  "uuid",
  "walkdir",
 ]

rust/lancedb/Cargo.toml

@@ -50,7 +50,7 @@ lance-namespace = { workspace = true }
 lance-namespace-impls = { workspace = true }
 moka = { workspace = true }
 pin-project = { workspace = true }
-tokio = { version = "1.23", features = ["rt-multi-thread"] }
+tokio = { version = "1.23", features = ["rt-multi-thread", "sync"] }
 log.workspace = true
 async-trait = "0"
 bytes = "1"
@@ -75,6 +75,7 @@ reqwest = { version = "0.12.0", default-features = false, features = [
     "stream",
 ], optional = true }
 http = { version = "1", optional = true } # Matching what is in reqwest
+urlencoding = { version = "2", optional = true }
 uuid = { version = "1.7.0", features = ["v4", "v5"] }
 polars-arrow = { version = ">=0.37,<0.40.0", optional = true }
 polars = { version = ">=0.37,<0.40.0", optional = true }
@@ -93,6 +94,7 @@ semver = { workspace = true }
 anyhow = "1"
 tempfile = "3.5.0"
 random_word = { version = "0.4.3", features = ["en"] }
+tokio = { version = "1.23", features = ["io-util", "macros", "net", "rt-multi-thread", "sync"] }
 uuid = { version = "1.7.0", features = ["v4"] }
 walkdir = "2"
 aws-sdk-dynamodb = { version = "1.55.0" }
@@ -129,7 +131,13 @@ huggingface = [
     "lance-namespace-impls/dir-huggingface",
 ]
 dynamodb = ["lance/dynamodb", "aws"]
-remote = ["dep:reqwest", "dep:http", "lance-namespace-impls/rest", "lance-namespace-impls/rest-adapter"]
+remote = [
+    "dep:reqwest",
+    "dep:http",
+    "dep:urlencoding",
+    "lance-namespace-impls/rest",
+    "lance-namespace-impls/rest-adapter",
+]
 fp16kernels = ["lance-linalg/fp16kernels"]
 s3-test = []
 bedrock = ["dep:aws-sdk-bedrockruntime"]

rust/lancedb/src/connection.rs

@@ -667,6 +667,8 @@ pub struct ConnectRequest {
 pub struct ConnectBuilder {
     request: ConnectRequest,
     embedding_registry: Option<Arc<dyn EmbeddingRegistry>>,
+    #[cfg(feature = "remote")]
+    oauth_config: Option<crate::remote::OAuthConfig>,
 }
 
 #[cfg(feature = "remote")]
@@ -688,6 +690,8 @@ impl ConnectBuilder {
                 session: None,
             },
             embedding_registry: None,
+            #[cfg(feature = "remote")]
+            oauth_config: None,
         }
     }
 
@@ -776,6 +780,19 @@ impl ConnectBuilder {
         self
     }
 
+    /// Configure OAuth authentication for LanceDB Cloud/Enterprise.
+    ///
+    /// This creates an [`OAuthHeaderProvider`](crate::remote::OAuthHeaderProvider)
+    /// from the given config and sets it as the header provider. OAuth cannot
+    /// be combined with an API key or another header provider.
+    ///
+    /// Token acquisition and refresh are handled in Rust.
+    #[cfg(feature = "remote")]
+    pub fn oauth_config(mut self, config: crate::remote::OAuthConfig) -> Self {
+        self.oauth_config = Some(config);
+        self
+    }
+
     /// Provide a custom [`EmbeddingRegistry`] to use for this connection.
     pub fn embedding_registry(mut self, registry: Arc<dyn EmbeddingRegistry>) -> Self {
         self.embedding_registry = Some(registry);
@@ -921,9 +938,40 @@ impl ConnectBuilder {
         let region = options.region.ok_or_else(|| Error::InvalidInput {
             message: "A region is required when connecting to LanceDb Cloud".to_string(),
         })?;
-        let api_key = options.api_key.ok_or_else(|| Error::InvalidInput {
-            message: "An api_key is required when connecting to LanceDb Cloud".to_string(),
-        })?;
+        let api_key = match (&self.oauth_config, &options.api_key) {
+            (Some(_), None) => String::new(),
+            (Some(_), Some(_)) => {
+                return Err(Error::InvalidInput {
+                    message:
+                        "api_key and oauth_config cannot both be set when connecting to LanceDb Cloud"
+                            .to_string(),
+                });
+            }
+            (None, Some(key)) => key.clone(),
+            (None, None) => {
+                return Err(Error::InvalidInput {
+                    message:
+                        "An api_key or oauth_config is required when connecting to LanceDb Cloud"
+                            .to_string(),
+                });
+            }
+        };
+
+        if self.oauth_config.is_some() && self.request.client_config.header_provider.is_some() {
+            return Err(Error::InvalidInput {
+                message:
+                    "oauth_config and client_config.header_provider cannot both be set when connecting to LanceDb Cloud"
+                        .to_string(),
+            });
+        }
+
+        let mut client_config = self.request.client_config;
+
+        if let Some(oauth_config) = self.oauth_config {
+            let provider = crate::remote::OAuthHeaderProvider::new(oauth_config)?;
+            client_config.header_provider =
+                Some(Arc::new(provider) as Arc<dyn crate::remote::HeaderProvider>);
+        }
 
         let storage_options = StorageOptions(options.storage_options.clone());
         let internal = Arc::new(crate::remote::db::RemoteDatabase::try_new(
@@ -931,7 +979,7 @@ impl ConnectBuilder {
             &api_key,
             &region,
             options.host_override,
-            self.request.client_config,
+            client_config,
             storage_options.into(),
             self.request.read_consistency_interval,
         )?);
@@ -1240,6 +1288,83 @@ mod tests {
         assert_eq!(Some(&"EXPLICIT-VALUE".to_string()), options.get(opts_key));
     }
 
+    #[cfg(feature = "remote")]
+    #[tokio::test]
+    async fn test_connect_rejects_api_key_with_oauth_config() {
+        let oauth_config = crate::remote::OAuthConfig {
+            issuer_url: "https://issuer.example.com".to_string(),
+            client_id: "client-id".to_string(),
+            client_secret: Some("secret".to_string()),
+            scopes: vec!["scope".to_string()],
+            flow: crate::remote::OAuthFlow::ClientCredentials,
+            refresh_buffer_secs: None,
+        };
+
+        let result = ConnectBuilder::new("db://my-container/my-prefix")
+            .region("us-east-1")
+            .api_key("my-api-key")
+            .oauth_config(oauth_config)
+            .execute()
+            .await;
+
+        match result {
+            Err(Error::InvalidInput { message })
+                if message
+                    == "api_key and oauth_config cannot both be set when connecting to LanceDb Cloud" =>
+                {}
+            Err(err) => panic!("expected InvalidInput, got {err:?}"),
+            Ok(_) => panic!("expected api_key and oauth_config to be rejected"),
+        }
+    }
+
+    #[cfg(feature = "remote")]
+    #[tokio::test]
+    async fn test_connect_rejects_header_provider_with_oauth_config() {
+        #[derive(Debug)]
+        struct TestHeaderProvider;
+
+        #[async_trait::async_trait]
+        impl crate::remote::HeaderProvider for TestHeaderProvider {
+            async fn get_headers(&self) -> Result<HashMap<String, String>> {
+                Ok(HashMap::from([(
+                    "authorization".to_string(),
+                    "Bearer token".to_string(),
+                )]))
+            }
+        }
+
+        let oauth_config = crate::remote::OAuthConfig {
+            issuer_url: "https://issuer.example.com".to_string(),
+            client_id: "client-id".to_string(),
+            client_secret: Some("secret".to_string()),
+            scopes: vec!["scope".to_string()],
+            flow: crate::remote::OAuthFlow::ClientCredentials,
+            refresh_buffer_secs: None,
+        };
+        let client_config = crate::remote::ClientConfig {
+            header_provider: Some(
+                Arc::new(TestHeaderProvider) as Arc<dyn crate::remote::HeaderProvider>
+            ),
+            ..Default::default()
+        };
+
+        let result = ConnectBuilder::new("db://my-container/my-prefix")
+            .region("us-east-1")
+            .client_config(client_config)
+            .oauth_config(oauth_config)
+            .execute()
+            .await;
+
+        match result {
+            Err(Error::InvalidInput { message })
+                if message
+                    == "oauth_config and client_config.header_provider cannot both be set when connecting to LanceDb Cloud" =>
+                {}
+            Err(err) => panic!("expected InvalidInput, got {err:?}"),
+            Ok(_) => panic!("expected header_provider and oauth_config to be rejected"),
+        }
+    }
+
     #[cfg(not(windows))]
     #[tokio::test]
     async fn test_connect_relative() {

rust/lancedb/src/remote.rs

@@ -8,6 +8,7 @@
 
 pub(crate) mod client;
 pub(crate) mod db;
+pub mod oauth;
 mod retry;
 pub(crate) mod table;
 pub(crate) mod util;
@@ -20,3 +21,4 @@ const JSON_CONTENT_TYPE: &str = "application/json";
 
 pub use client::{ClientConfig, HeaderProvider, RetryConfig, TimeoutConfig, TlsConfig};
 pub use db::{RemoteDatabaseOptions, RemoteDatabaseOptionsBuilder};
+pub use oauth::{OAuthConfig, OAuthFlow, OAuthHeaderProvider};

rust/lancedb/src/remote/oauth.rs

@@ -0,0 +1,907 @@
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-FileCopyrightText: Copyright The LanceDB Authors
+
+use std::collections::HashMap;
+use std::net::IpAddr;
+use std::sync::Arc;
+use std::time::{Duration, Instant};
+
+use async_trait::async_trait;
+use log::debug;
+use reqwest::Client;
+use serde::Deserialize;
+use tokio::sync::RwLock;
+
+use crate::error::{Error, Result};
+use crate::remote::client::HeaderProvider;
+
+const DEFAULT_REFRESH_BUFFER_SECS: u64 = 300;
+const DEFAULT_TOKEN_TTL_SECS: u64 = 3600;
+const AZURE_IMDS_ENDPOINT: &str = "http://169.254.169.254/metadata/identity/oauth2/token";
+const AZURE_IMDS_API_VERSION: &str = "2018-02-01";
+
+/// OAuth authentication flow configuration.
+#[derive(Debug, Clone)]
+pub enum OAuthFlow {
+    /// Client Credentials grant (service-to-service / M2M).
+    /// Requires `client_secret` in [`OAuthConfig`].
+    ClientCredentials,
+
+    /// Azure Managed Identity via IMDS.
+    /// Works on Azure VMs, AKS, App Service, and Azure Functions.
+    /// IMDS requests bypass proxy settings because the endpoint is link-local.
+    AzureManagedIdentity {
+        /// Client ID for user-assigned managed identity.
+        /// Omit for system-assigned managed identity.
+        client_id: Option<String>,
+    },
+}
+
+/// OAuth configuration for LanceDB authentication.
+///
+/// All token acquisition and refresh is handled in the Rust layer.
+/// Python and TypeScript bindings expose this as a plain config object.
+#[derive(Clone)]
+pub struct OAuthConfig {
+    /// OIDC issuer URL or OAuth authority URL.
+    /// For Azure: `https://login.microsoftonline.com/{tenant_id}/v2.0`
+    pub issuer_url: String,
+
+    /// Application / Client ID.
+    pub client_id: String,
+
+    /// Client secret (required for `ClientCredentials`, optional for others).
+    pub client_secret: Option<String>,
+
+    /// OAuth scopes to request.
+    /// For Azure managed identity, exactly one scope or resource is required.
+    /// For example: `["api://{app_id}/.default"]`
+    pub scopes: Vec<String>,
+
+    /// Authentication flow to use.
+    pub flow: OAuthFlow,
+
+    /// Seconds before token expiry to trigger proactive refresh (default: 300).
+    /// Keep this well below the token TTL; if it is greater than or equal to
+    /// the TTL, each request refreshes the token.
+    pub refresh_buffer_secs: Option<u64>,
+}
+
+impl std::fmt::Debug for OAuthConfig {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("OAuthConfig")
+            .field("issuer_url", &self.issuer_url)
+            .field("client_id", &self.client_id)
+            .field(
+                "client_secret",
+                &self.client_secret.as_deref().map(|_| "<redacted>"),
+            )
+            .field("scopes", &self.scopes)
+            .field("flow", &self.flow)
+            .field("refresh_buffer_secs", &self.refresh_buffer_secs)
+            .finish()
+    }
+}
+
+// -- OIDC Discovery --
+
+#[derive(Clone, Debug, Deserialize)]
+struct OidcDiscovery {
+    token_endpoint: String,
+}
+
+// -- Token Response --
+
+#[derive(Deserialize)]
+struct TokenResponse {
+    access_token: String,
+    /// Token lifetime in seconds.
+    /// Some providers (Azure IMDS) return this as a string, so we accept both.
+    #[serde(default, deserialize_with = "deserialize_optional_u64_or_string")]
+    expires_in: Option<u64>,
+    #[serde(default)]
+    #[allow(dead_code)]
+    token_type: Option<String>,
+}
+
+impl std::fmt::Debug for TokenResponse {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("TokenResponse")
+            .field("access_token", &"<redacted>")
+            .field("expires_in", &self.expires_in)
+            .field("token_type", &self.token_type)
+            .finish()
+    }
+}
+
+fn deserialize_optional_u64_or_string<'de, D>(
+    deserializer: D,
+) -> std::result::Result<Option<u64>, D::Error>
+where
+    D: serde::Deserializer<'de>,
+{
+    use serde::de;
+
+    struct U64OrString;
+    impl<'de> de::Visitor<'de> for U64OrString {
+        type Value = Option<u64>;
+
+        fn expecting(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
+            formatter.write_str("an integer, an integer-valued float, a numeric string, or null")
+        }
+
+        fn visit_u64<E: de::Error>(self, v: u64) -> std::result::Result<Self::Value, E> {
+            Ok(Some(v))
+        }
+
+        fn visit_i64<E: de::Error>(self, v: i64) -> std::result::Result<Self::Value, E> {
+            if v < 0 {
+                return Err(E::custom(format!("invalid expires_in value: {v}")));
+            }
+            Ok(Some(v as u64))
+        }
+
+        fn visit_f64<E: de::Error>(self, v: f64) -> std::result::Result<Self::Value, E> {
+            if !v.is_finite() || v < 0.0 || v.fract() != 0.0 || v > u64::MAX as f64 {
+                return Err(E::custom(format!("invalid expires_in value: {v}")));
+            }
+            Ok(Some(v as u64))
+        }
+
+        fn visit_str<E: de::Error>(self, v: &str) -> std::result::Result<Self::Value, E> {
+            v.parse::<u64>().map(Some).map_err(de::Error::custom)
+        }
+
+        fn visit_none<E: de::Error>(self) -> std::result::Result<Self::Value, E> {
+            Ok(None)
+        }
+
+        fn visit_unit<E: de::Error>(self) -> std::result::Result<Self::Value, E> {
+            Ok(None)
+        }
+    }
+
+    deserializer.deserialize_any(U64OrString)
+}
+
+// -- Internal Token State --
+
+struct TokenState {
+    access_token: Option<String>,
+    expires_at: Option<Instant>,
+}
+
+impl TokenState {
+    fn new() -> Self {
+        Self {
+            access_token: None,
+            expires_at: None,
+        }
+    }
+
+    fn is_expired(&self, buffer: Duration) -> bool {
+        match (self.access_token.as_ref(), self.expires_at) {
+            (Some(_), Some(expires_at)) => Instant::now() + buffer >= expires_at,
+            (None, _) => true,
+            (Some(_), None) => true,
+        }
+    }
+
+    fn update(&mut self, resp: &TokenResponse) {
+        self.access_token = Some(resp.access_token.clone());
+        let expires_in = resp.expires_in.unwrap_or(DEFAULT_TOKEN_TTL_SECS);
+        self.expires_at = Some(Instant::now() + Duration::from_secs(expires_in));
+    }
+}
+
+#[async_trait]
+trait TokenSource: Send + Sync + std::fmt::Debug {
+    async fn fetch_token(&self) -> Result<TokenResponse>;
+}
+
+struct ClientCredentialsSource {
+    issuer_url: String,
+    client_id: String,
+    client_secret: String,
+    scopes: Vec<String>,
+    http_client: Client,
+    discovery: RwLock<Option<OidcDiscovery>>,
+}
+
+impl std::fmt::Debug for ClientCredentialsSource {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("ClientCredentialsSource")
+            .field("issuer_url", &self.issuer_url)
+            .field("client_id", &self.client_id)
+            .field("client_secret", &"<redacted>")
+            .field("scopes", &self.scopes)
+            .finish()
+    }
+}
+
+impl ClientCredentialsSource {
+    fn new(
+        issuer_url: String,
+        client_id: String,
+        client_secret: Option<String>,
+        scopes: Vec<String>,
+    ) -> Result<Self> {
+        let client_secret = client_secret.ok_or(Error::InvalidInput {
+            message: "client_secret is required for ClientCredentials flow".to_string(),
+        })?;
+        Self::validate_issuer_transport(&issuer_url)?;
+
+        let http_client = Client::builder()
+            .timeout(Duration::from_secs(30))
+            .build()
+            .map_err(|e| Error::Runtime {
+                message: format!("Failed to create HTTP client for OAuth: {e}"),
+            })?;
+
+        Ok(Self {
+            issuer_url,
+            client_id,
+            client_secret,
+            scopes,
+            http_client,
+            discovery: RwLock::new(None),
+        })
+    }
+
+    fn validate_issuer_transport(issuer_url: &str) -> Result<()> {
+        let issuer = url::Url::parse(issuer_url).map_err(|e| Error::InvalidInput {
+            message: format!("Invalid OAuth issuer_url: {e}"),
+        })?;
+
+        match issuer.scheme() {
+            "https" => Ok(()),
+            "http" if Self::is_loopback_issuer(&issuer) => Ok(()),
+            _ => Err(Error::InvalidInput {
+                message:
+                    "ClientCredentials OAuth issuer_url must use https, except for loopback hosts"
+                        .to_string(),
+            }),
+        }
+    }
+
+    fn is_loopback_issuer(issuer: &url::Url) -> bool {
+        let Some(host) = issuer.host_str() else {
+            return false;
+        };
+
+        host.eq_ignore_ascii_case("localhost")
+            || host
+                .parse::<IpAddr>()
+                .map(|addr| addr.is_loopback())
+                .unwrap_or(false)
+    }
+
+    async fn get_discovery(&self) -> Result<OidcDiscovery> {
+        {
+            let cached = self.discovery.read().await;
+            if let Some(ref disc) = *cached {
+                return Ok(disc.clone());
+            }
+        }
+
+        let mut cache = self.discovery.write().await;
+        // Double-check
+        if let Some(ref disc) = *cache {
+            return Ok(disc.clone());
+        }
+
+        let discovery_url = format!(
+            "{}/.well-known/openid-configuration",
+            self.issuer_url.trim_end_matches('/')
+        );
+
+        debug!("Fetching OIDC discovery from {}", discovery_url);
+
+        let resp = self
+            .http_client
+            .get(&discovery_url)
+            .send()
+            .await
+            .map_err(|e| Error::Runtime {
+                message: format!("Failed to fetch OIDC discovery document: {e}"),
+            })?;
+
+        if !resp.status().is_success() {
+            return Err(Error::Runtime {
+                message: format!(
+                    "OIDC discovery failed with status {}: {}",
+                    resp.status(),
+                    resp.text().await.unwrap_or_default()
+                ),
+            });
+        }
+
+        let disc: OidcDiscovery = resp.json().await.map_err(|e| Error::Runtime {
+            message: format!("Failed to parse OIDC discovery document: {e}"),
+        })?;
+
+        let result = disc.clone();
+
+        *cache = Some(disc);
+        Ok(result)
+    }
+
+    async fn get_token_endpoint(&self) -> Result<String> {
+        self.get_discovery().await.map(|disc| disc.token_endpoint)
+    }
+
+    fn scopes_string(&self) -> String {
+        self.scopes.join(" ")
+    }
+
+    async fn post_token_request(
+        &self,
+        endpoint: &str,
+        params: &[(&str, &str)],
+    ) -> Result<TokenResponse> {
+        let resp = self
+            .http_client
+            .post(endpoint)
+            .form(params)
+            .send()
+            .await
+            .map_err(|e| Error::Runtime {
+                message: format!("Token request to {endpoint} failed: {e}"),
+            })?;
+
+        if !resp.status().is_success() {
+            return Err(Error::Runtime {
+                message: format!(
+                    "Token request failed with status {}: {}",
+                    resp.status(),
+                    resp.text().await.unwrap_or_default()
+                ),
+            });
+        }
+
+        resp.json().await.map_err(|e| Error::Runtime {
+            message: format!("Failed to parse token response: {e}"),
+        })
+    }
+}
+
+#[async_trait]
+impl TokenSource for ClientCredentialsSource {
+    async fn fetch_token(&self) -> Result<TokenResponse> {
+        let token_endpoint = self.get_token_endpoint().await?;
+        let scope = self.scopes_string();
+        let params = [
+            ("grant_type", "client_credentials"),
+            ("client_id", self.client_id.as_str()),
+            ("client_secret", self.client_secret.as_str()),
+            ("scope", scope.as_str()),
+        ];
+
+        self.post_token_request(&token_endpoint, &params).await
+    }
+}
+
+struct AzureImdsSource {
+    client_id: Option<String>,
+    resource: String,
+    http_client: Client,
+}
+
+impl std::fmt::Debug for AzureImdsSource {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("AzureImdsSource")
+            .field("client_id", &self.client_id)
+            .field("resource", &self.resource)
+            .finish()
+    }
+}
+
+impl AzureImdsSource {
+    fn new(scopes: Vec<String>, client_id: Option<String>) -> Result<Self> {
+        let resource = Self::resource_from_scopes(&scopes)?;
+        let http_client = Client::builder()
+            .timeout(Duration::from_secs(30))
+            .no_proxy()
+            .build()
+            .map_err(|e| Error::Runtime {
+                message: format!("Failed to create HTTP client for Azure IMDS OAuth: {e}"),
+            })?;
+
+        Ok(Self {
+            client_id,
+            resource,
+            http_client,
+        })
+    }
+
+    fn resource_from_scopes(scopes: &[String]) -> Result<String> {
+        let [scope] = scopes else {
+            return Err(Error::InvalidInput {
+                message: "AzureManagedIdentity flow requires exactly one OAuth scope or resource"
+                    .to_string(),
+            });
+        };
+
+        Ok(scope.strip_suffix("/.default").unwrap_or(scope).to_string())
+    }
+}
+
+#[async_trait]
+impl TokenSource for AzureImdsSource {
+    async fn fetch_token(&self) -> Result<TokenResponse> {
+        let mut url = format!(
+            "{AZURE_IMDS_ENDPOINT}?api-version={AZURE_IMDS_API_VERSION}&resource={}",
+            urlencoding::encode(&self.resource),
+        );
+        if let Some(cid) = self.client_id.as_deref() {
+            url.push_str(&format!("&client_id={}", urlencoding::encode(cid)));
+        }
+
+        let resp = self
+            .http_client
+            .get(&url)
+            .header("Metadata", "true")
+            .send()
+            .await
+            .map_err(|e| Error::Runtime {
+                message: format!("Azure IMDS request failed: {e}"),
+            })?;
+
+        if !resp.status().is_success() {
+            return Err(Error::Runtime {
+                message: format!(
+                    "Azure IMDS returned status {}: {}",
+                    resp.status(),
+                    resp.text().await.unwrap_or_default()
+                ),
+            });
+        }
+
+        resp.json().await.map_err(|e| Error::Runtime {
+            message: format!("Failed to parse IMDS token response: {e}"),
+        })
+    }
+}
+
+/// OAuth header provider that manages the full token lifecycle.
+///
+/// Implements [`HeaderProvider`] to inject `Authorization: Bearer <token>`
+/// headers into every LanceDB request, with automatic token refresh.
+pub struct OAuthHeaderProvider {
+    token_source: Box<dyn TokenSource>,
+    token_state: Arc<RwLock<TokenState>>,
+    refresh_buffer: Duration,
+}
+
+impl std::fmt::Debug for OAuthHeaderProvider {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("OAuthHeaderProvider")
+            .field("token_source", &self.token_source)
+            .finish()
+    }
+}
+
+impl OAuthHeaderProvider {
+    /// Create a new OAuth header provider from configuration.
+    pub fn new(config: OAuthConfig) -> Result<Self> {
+        let OAuthConfig {
+            issuer_url,
+            client_id,
+            client_secret,
+            scopes,
+            flow,
+            refresh_buffer_secs,
+        } = config;
+
+        if scopes.is_empty() {
+            return Err(Error::InvalidInput {
+                message: "At least one OAuth scope is required".to_string(),
+            });
+        }
+
+        let refresh_buffer =
+            Duration::from_secs(refresh_buffer_secs.unwrap_or(DEFAULT_REFRESH_BUFFER_SECS));
+        let token_source: Box<dyn TokenSource> = match flow {
+            OAuthFlow::ClientCredentials => Box::new(ClientCredentialsSource::new(
+                issuer_url,
+                client_id,
+                client_secret,
+                scopes,
+            )?),
+            OAuthFlow::AzureManagedIdentity { client_id } => {
+                Box::new(AzureImdsSource::new(scopes, client_id)?)
+            }
+        };
+
+        Ok(Self {
+            token_source,
+            token_state: Arc::new(RwLock::new(TokenState::new())),
+            refresh_buffer,
+        })
+    }
+
+    /// Get a valid access token, refreshing if necessary.
+    async fn get_valid_token(&self) -> Result<String> {
+        // Fast path: check if current token is still valid
+        {
+            let state = self.token_state.read().await;
+            if !state.is_expired(self.refresh_buffer)
+                && let Some(ref token) = state.access_token
+            {
+                return Ok(token.clone());
+            }
+        }
+
+        // Slow path: acquire or refresh token
+        let mut state = self.token_state.write().await;
+
+        // Double-check after acquiring write lock
+        if !state.is_expired(self.refresh_buffer)
+            && let Some(ref token) = state.access_token
+        {
+            return Ok(token.clone());
+        }
+
+        debug!("Acquiring new OAuth token via {:?}", self.token_source);
+        let resp = self.token_source.fetch_token().await?;
+
+        state.update(&resp);
+        Ok(resp.access_token)
+    }
+}
+
+#[async_trait]
+impl HeaderProvider for OAuthHeaderProvider {
+    async fn get_headers(&self) -> Result<HashMap<String, String>> {
+        let token = self.get_valid_token().await?;
+        Ok(HashMap::from([(
+            "authorization".to_string(),
+            format!("Bearer {token}"),
+        )]))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::sync::atomic::{AtomicUsize, Ordering};
+
+    use tokio::io::{AsyncReadExt, AsyncWriteExt};
+    use tokio::net::{TcpListener, TcpStream};
+    use tokio::task::JoinHandle;
+
+    #[test]
+    fn test_token_state_expiry() {
+        let mut state = TokenState::new();
+        assert!(state.is_expired(Duration::from_secs(0)));
+
+        state.access_token = Some("tok".to_string());
+        state.expires_at = Some(Instant::now() + Duration::from_secs(600));
+        assert!(!state.is_expired(Duration::from_secs(300)));
+        assert!(state.is_expired(Duration::from_secs(601)));
+
+        state.expires_at = None;
+        assert!(state.is_expired(Duration::from_secs(0)));
+    }
+
+    #[test]
+    fn test_token_state_uses_default_expiry() {
+        let mut state = TokenState::new();
+        let response = TokenResponse {
+            access_token: "tok".to_string(),
+            expires_in: None,
+            token_type: None,
+        };
+
+        state.update(&response);
+
+        assert!(!state.is_expired(Duration::from_secs(DEFAULT_TOKEN_TTL_SECS - 1)));
+        assert!(state.is_expired(Duration::from_secs(DEFAULT_TOKEN_TTL_SECS + 1)));
+    }
+
+    #[test]
+    fn test_token_response_accepts_float_expires_in() {
+        let response: TokenResponse =
+            serde_json::from_str(r#"{"access_token":"tok","expires_in":3600.0}"#).unwrap();
+
+        assert_eq!(response.expires_in, Some(3600));
+    }
+
+    #[test]
+    fn test_token_response_rejects_negative_expires_in() {
+        let err =
+            serde_json::from_str::<TokenResponse>(r#"{"access_token":"tok","expires_in":-1}"#)
+                .unwrap_err();
+
+        assert!(err.to_string().contains("invalid expires_in value: -1"));
+    }
+
+    #[test]
+    fn test_token_response_debug_redacts_access_token() {
+        let response = TokenResponse {
+            access_token: "secret-token".to_string(),
+            expires_in: Some(3600),
+            token_type: Some("Bearer".to_string()),
+        };
+
+        let debug = format!("{response:?}");
+        assert!(!debug.contains("secret-token"));
+        assert!(debug.contains("access_token: \"<redacted>\""));
+    }
+
+    #[test]
+    fn test_scopes_string() {
+        let source = ClientCredentialsSource::new(
+            "https://login.microsoftonline.com/tenant/v2.0".to_string(),
+            "app-id".to_string(),
+            Some("secret".to_string()),
+            vec!["scope1".to_string(), "scope2".to_string()],
+        )
+        .unwrap();
+
+        assert_eq!(source.scopes_string(), "scope1 scope2");
+    }
+
+    #[test]
+    fn test_oauth_config_debug_redacts_client_secret() {
+        let config = OAuthConfig {
+            issuer_url: "https://issuer.example.com".to_string(),
+            client_id: "client-id".to_string(),
+            client_secret: Some("super-secret".to_string()),
+            scopes: vec!["scope".to_string()],
+            flow: OAuthFlow::ClientCredentials,
+            refresh_buffer_secs: None,
+        };
+
+        let debug = format!("{config:?}");
+        assert!(!debug.contains("super-secret"));
+        assert!(debug.contains("client_secret: Some(\"<redacted>\")"));
+    }
+
+    #[test]
+    fn test_oauth_header_provider_debug_redacts_client_secret() {
+        let config = OAuthConfig {
+            issuer_url: "https://issuer.example.com".to_string(),
+            client_id: "client-id".to_string(),
+            client_secret: Some("super-secret".to_string()),
+            scopes: vec!["scope".to_string()],
+            flow: OAuthFlow::ClientCredentials,
+            refresh_buffer_secs: None,
+        };
+
+        let provider = OAuthHeaderProvider::new(config).unwrap();
+        let debug = format!("{provider:?}");
+        assert!(!debug.contains("super-secret"));
+        assert!(debug.contains("client_secret: \"<redacted>\""));
+    }
+
+    #[test]
+    fn test_managed_identity_resource_from_default_scope() {
+        assert_eq!(
+            AzureImdsSource::resource_from_scopes(&["api://test/.default".to_string()]).unwrap(),
+            "api://test"
+        );
+    }
+
+    #[test]
+    fn test_managed_identity_resource_without_default_suffix() {
+        assert_eq!(
+            AzureImdsSource::resource_from_scopes(&["api://test".to_string()]).unwrap(),
+            "api://test"
+        );
+    }
+
+    #[test]
+    fn test_managed_identity_rejects_multiple_scopes() {
+        let config = OAuthConfig {
+            issuer_url: "https://login.microsoftonline.com/tenant/v2.0".to_string(),
+            client_id: "app-id".to_string(),
+            client_secret: None,
+            scopes: vec![
+                "api://test-a/.default".to_string(),
+                "api://test-b/.default".to_string(),
+            ],
+            flow: OAuthFlow::AzureManagedIdentity { client_id: None },
+            refresh_buffer_secs: None,
+        };
+        assert!(OAuthHeaderProvider::new(config).is_err());
+    }
+
+    #[tokio::test]
+    async fn test_token_endpoint_requires_discovery_success() {
+        let (issuer_url, server) = spawn_discovery_error_server().await;
+        let source = ClientCredentialsSource::new(
+            issuer_url,
+            "client-id".to_string(),
+            Some("secret".to_string()),
+            vec!["scope".to_string()],
+        )
+        .unwrap();
+
+        let err = source.get_token_endpoint().await.unwrap_err();
+        assert!(matches!(
+            err,
+            Error::Runtime { message }
+                if message.contains("OIDC discovery failed with status 503")
+        ));
+        server.await.unwrap();
+    }
+
+    #[test]
+    fn test_client_credentials_requires_secret() {
+        let config = OAuthConfig {
+            issuer_url: "https://login.microsoftonline.com/tenant/v2.0".to_string(),
+            client_id: "app-id".to_string(),
+            client_secret: None,
+            scopes: vec!["scope".to_string()],
+            flow: OAuthFlow::ClientCredentials,
+            refresh_buffer_secs: None,
+        };
+        assert!(OAuthHeaderProvider::new(config).is_err());
+    }
+
+    #[test]
+    fn test_client_credentials_rejects_insecure_non_loopback_issuer() {
+        let config = OAuthConfig {
+            issuer_url: "http://issuer.example.com".to_string(),
+            client_id: "app-id".to_string(),
+            client_secret: Some("secret".to_string()),
+            scopes: vec!["scope".to_string()],
+            flow: OAuthFlow::ClientCredentials,
+            refresh_buffer_secs: None,
+        };
+
+        let err = OAuthHeaderProvider::new(config).unwrap_err();
+        assert!(matches!(
+            err,
+            Error::InvalidInput { message }
+                if message == "ClientCredentials OAuth issuer_url must use https, except for loopback hosts"
+        ));
+    }
+
+    #[test]
+    fn test_empty_scopes_rejected() {
+        let config = OAuthConfig {
+            issuer_url: "https://login.microsoftonline.com/tenant/v2.0".to_string(),
+            client_id: "app-id".to_string(),
+            client_secret: None,
+            scopes: vec![],
+            flow: OAuthFlow::AzureManagedIdentity { client_id: None },
+            refresh_buffer_secs: None,
+        };
+        assert!(OAuthHeaderProvider::new(config).is_err());
+    }
+
+    #[tokio::test]
+    async fn test_client_credentials_token_lifecycle() {
+        let (issuer_url, token_requests, server) = spawn_oauth_server().await;
+        let config = OAuthConfig {
+            issuer_url,
+            client_id: "client-id".to_string(),
+            client_secret: Some("secret".to_string()),
+            scopes: vec!["scope".to_string()],
+            flow: OAuthFlow::ClientCredentials,
+            refresh_buffer_secs: Some(0),
+        };
+        let provider = OAuthHeaderProvider::new(config).unwrap();
+
+        let headers = provider.get_headers().await.unwrap();
+        assert_eq!(headers.get("authorization").unwrap(), "Bearer token-1");
+        assert_eq!(token_requests.load(Ordering::SeqCst), 1);
+
+        let headers = provider.get_headers().await.unwrap();
+        assert_eq!(headers.get("authorization").unwrap(), "Bearer token-1");
+        assert_eq!(token_requests.load(Ordering::SeqCst), 1);
+
+        provider.token_state.write().await.expires_at =
+            Some(Instant::now() - Duration::from_secs(1));
+
+        let headers = provider.get_headers().await.unwrap();
+        assert_eq!(headers.get("authorization").unwrap(), "Bearer token-2");
+        assert_eq!(token_requests.load(Ordering::SeqCst), 2);
+
+        server.await.unwrap();
+    }
+
+    async fn spawn_oauth_server() -> (String, Arc<AtomicUsize>, JoinHandle<()>) {
+        let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
+        let addr = listener.local_addr().unwrap();
+        let issuer_url = format!("http://{addr}");
+        let token_requests = Arc::new(AtomicUsize::new(0));
+        let server_token_requests = Arc::clone(&token_requests);
+
+        let server = tokio::spawn(async move {
+            for _ in 0..3 {
+                let (mut stream, _) = listener.accept().await.unwrap();
+                let (request_line, body) = read_http_request(&mut stream).await;
+
+                if request_line.starts_with("GET /.well-known/openid-configuration ") {
+                    let discovery = format!(r#"{{"token_endpoint":"http://{addr}/token"}}"#);
+                    write_json_response(&mut stream, "200 OK", &discovery).await;
+                } else if request_line.starts_with("POST /token ") {
+                    assert!(body.contains("grant_type=client_credentials"));
+                    assert!(body.contains("client_id=client-id"));
+                    assert!(body.contains("client_secret=secret"));
+                    assert!(body.contains("scope=scope"));
+
+                    let token_num = server_token_requests.fetch_add(1, Ordering::SeqCst) + 1;
+                    let token = format!(
+                        r#"{{"access_token":"token-{token_num}","expires_in":3600,"token_type":"Bearer"}}"#
+                    );
+                    write_json_response(&mut stream, "200 OK", &token).await;
+                } else {
+                    write_json_response(&mut stream, "404 Not Found", "{}").await;
+                }
+            }
+        });
+
+        (issuer_url, token_requests, server)
+    }
+
+    async fn spawn_discovery_error_server() -> (String, JoinHandle<()>) {
+        let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
+        let addr = listener.local_addr().unwrap();
+        let issuer_url = format!("http://{addr}");
+
+        let server = tokio::spawn(async move {
+            let (mut stream, _) = listener.accept().await.unwrap();
+            let (request_line, _) = read_http_request(&mut stream).await;
+            assert!(request_line.starts_with("GET /.well-known/openid-configuration "));
+            write_json_response(&mut stream, "503 Service Unavailable", "{}").await;
+        });
+
+        (issuer_url, server)
+    }
+
+    async fn read_http_request(stream: &mut TcpStream) -> (String, String) {
+        let mut buffer = Vec::new();
+        let mut header_end = None;
+
+        while header_end.is_none() {
+            let mut chunk = [0; 1024];
+            let read = stream.read(&mut chunk).await.unwrap();
+            assert_ne!(read, 0, "connection closed before request headers");
+            buffer.extend_from_slice(&chunk[..read]);
+            header_end = find_subsequence(&buffer, b"\r\n\r\n").map(|pos| pos + 4);
+        }
+
+        let header_end = header_end.unwrap();
+        let headers = String::from_utf8_lossy(&buffer[..header_end]).to_string();
+        let request_line = headers.lines().next().unwrap_or_default().to_string();
+        let content_length = headers
+            .lines()
+            .find_map(|line| {
+                let (name, value) = line.split_once(':')?;
+                name.eq_ignore_ascii_case("content-length")
+                    .then(|| value.trim().parse::<usize>().ok())
+                    .flatten()
+            })
+            .unwrap_or(0);
+
+        while buffer.len() < header_end + content_length {
+            let mut chunk = [0; 1024];
+            let read = stream.read(&mut chunk).await.unwrap();
+            assert_ne!(read, 0, "connection closed before request body");
+            buffer.extend_from_slice(&chunk[..read]);
+        }
+
+        let body =
+            String::from_utf8_lossy(&buffer[header_end..header_end + content_length]).to_string();
+
+        (request_line, body)
+    }
+
+    fn find_subsequence(haystack: &[u8], needle: &[u8]) -> Option<usize> {
+        haystack
+            .windows(needle.len())
+            .position(|window| window == needle)
+    }
+
+    async fn write_json_response(stream: &mut TcpStream, status: &str, body: &str) {
+        let response = format!(
+            "HTTP/1.1 {status}\r\ncontent-type: application/json\r\ncontent-length: {}\r\nconnection: close\r\n\r\n{body}",
+            body.len()
+        );
+        stream.write_all(response.as_bytes()).await.unwrap();
+    }
+}