diff --git a/README.md b/README.md
index 34070a9..6f0dba8 100644
--- a/README.md
+++ b/README.md
@@ -56,6 +56,22 @@ Or via npm:
 npx @zed-industries/codex-acp
 ```
 
+#### Options
+
+Use `--ignore-user-config` to start the adapter without loading
+`$CODEX_HOME/config.toml`. Authentication and other Codex state still use
+`CODEX_HOME`.
+
+This is useful for ACP clients that provide their own session configuration and
+want to avoid user-level hooks or MCP servers while still using the user's Codex
+login. Configuration overrides passed with `-c key=value` still apply. If your
+credential store mode is normally configured in `config.toml`, pass it
+explicitly, for example:
+
+```
+codex-acp --ignore-user-config -c cli_auth_credentials_store=auto
+```
+
 ## License
 
 Apache-2.0
diff --git a/npm/README.md b/npm/README.md
index 554dc91..2503256 100644
--- a/npm/README.md
+++ b/npm/README.md
@@ -56,6 +56,22 @@ Or via npm:
 npx @zed-industries/codex-acp
 ```
 
+#### Options
+
+Use `--ignore-user-config` to start the adapter without loading
+`$CODEX_HOME/config.toml`. Authentication and other Codex state still use
+`CODEX_HOME`.
+
+This is useful for ACP clients that provide their own session configuration and
+want to avoid user-level hooks or MCP servers while still using the user's Codex
+login. Configuration overrides passed with `-c key=value` still apply. If your
+credential store mode is normally configured in `config.toml`, pass it
+explicitly, for example:
+
+```
+codex-acp --ignore-user-config -c cli_auth_credentials_store=auto
+```
+
 ## License
 
 Apache-2.0
diff --git a/src/lib.rs b/src/lib.rs
index 595403d..397cc3b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -2,7 +2,8 @@
 #![deny(clippy::print_stdout, clippy::print_stderr)]
 
 use agent_client_protocol::ByteStreams;
-use codex_core::config::{Config, ConfigOverrides};
+use codex_config::LoaderOverrides;
+use codex_core::config::{Config, ConfigBuilder, ConfigOverrides};
 use codex_utils_cli::CliConfigOverrides;
 use std::path::PathBuf;
 use std::sync::Arc;
@@ -12,6 +13,12 @@ use tracing_subscriber::EnvFilter;
 mod codex_agent;
 mod thread;
 
+#[derive(Debug, Clone, Copy, Default)]
+pub struct RunOptions {
+    /// Do not load `$CODEX_HOME/config.toml`; auth still uses `CODEX_HOME`.
+    pub ignore_user_config: bool,
+}
+
 /// Run the Codex ACP agent.
 ///
 /// This sets up an ACP agent that communicates over stdio, bridging
@@ -23,6 +30,24 @@ mod thread;
 pub async fn run_main(
     codex_linux_sandbox_exe: Option<PathBuf>,
     cli_config_overrides: CliConfigOverrides,
+) -> std::io::Result<()> {
+    run_main_with_options(
+        codex_linux_sandbox_exe,
+        cli_config_overrides,
+        RunOptions::default(),
+    )
+    .await
+}
+
+/// Run the Codex ACP agent with explicit adapter options.
+///
+/// # Errors
+///
+/// If unable to parse the config or start the program.
+pub async fn run_main_with_options(
+    codex_linux_sandbox_exe: Option<PathBuf>,
+    cli_config_overrides: CliConfigOverrides,
+    options: RunOptions,
 ) -> std::io::Result<()> {
     // Install a simple subscriber so `tracing` output is visible.
     // Users can control the log level with `RUST_LOG`.
@@ -31,28 +56,12 @@ pub async fn run_main(
         .with_env_filter(EnvFilter::from_default_env())
         .init();
 
-    // Parse CLI overrides and load configuration
-    let cli_kv_overrides = cli_config_overrides.parse_overrides().map_err(|e| {
-        std::io::Error::new(
-            std::io::ErrorKind::InvalidInput,
-            format!("error parsing -c overrides: {e}"),
-        )
-    })?;
-
-    let config_overrides = ConfigOverrides {
-        codex_linux_sandbox_exe: codex_linux_sandbox_exe.clone(),
-        ..ConfigOverrides::default()
-    };
-
-    let config =
-        Config::load_with_cli_overrides_and_harness_overrides(cli_kv_overrides, config_overrides)
-            .await
-            .map_err(|e| {
-                std::io::Error::new(
-                    std::io::ErrorKind::InvalidData,
-                    format!("error loading config: {e}"),
-                )
-            })?;
+    let config = load_config(
+        codex_linux_sandbox_exe.clone(),
+        cli_config_overrides,
+        options,
+    )
+    .await?;
     // Apply residency requirement so the HTTP client sends the
     // x-openai-internal-codex-residency header on all requests.
     codex_login::default_client::set_default_client_residency_requirement(
@@ -72,8 +81,151 @@ pub async fn run_main(
     Ok(())
 }
 
+async fn load_config(
+    codex_linux_sandbox_exe: Option<PathBuf>,
+    cli_config_overrides: CliConfigOverrides,
+    options: RunOptions,
+) -> std::io::Result<Config> {
+    let cli_kv_overrides = cli_config_overrides.parse_overrides().map_err(|e| {
+        std::io::Error::new(
+            std::io::ErrorKind::InvalidInput,
+            format!("error parsing -c overrides: {e}"),
+        )
+    })?;
+    let config_overrides = ConfigOverrides {
+        codex_linux_sandbox_exe,
+        ..ConfigOverrides::default()
+    };
+    let loader_overrides = LoaderOverrides {
+        ignore_user_config: options.ignore_user_config,
+        ..Default::default()
+    };
+
+    ConfigBuilder::default()
+        .cli_overrides(cli_kv_overrides)
+        .harness_overrides(config_overrides)
+        .loader_overrides(loader_overrides)
+        .build()
+        .await
+        .map_err(|e| {
+            std::io::Error::new(
+                std::io::ErrorKind::InvalidData,
+                format!("error loading config: {e}"),
+            )
+        })
+}
+
 // Re-export the MCP server types for compatibility
 pub use codex_mcp_server::{
     CodexToolCallParam, CodexToolCallReplyParam, ExecApprovalElicitRequestParams,
     ExecApprovalResponse, PatchApprovalElicitRequestParams, PatchApprovalResponse,
 };
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::fs;
+    use std::path::{Path, PathBuf};
+    use uuid::Uuid;
+
+    struct TestDir(PathBuf);
+
+    impl TestDir {
+        fn new() -> std::io::Result<Self> {
+            let path = std::env::temp_dir().join(format!("codex-acp-{}", Uuid::new_v4()));
+            fs::create_dir_all(&path)?;
+            Ok(Self(path))
+        }
+
+        fn path(&self) -> &Path {
+            &self.0
+        }
+    }
+
+    impl Drop for TestDir {
+        fn drop(&mut self) {
+            drop(fs::remove_dir_all(&self.0));
+        }
+    }
+
+    async fn load_config_for_test(
+        codex_home: PathBuf,
+        raw_overrides: Vec<&str>,
+        options: RunOptions,
+    ) -> std::io::Result<Config> {
+        let cli_config_overrides = CliConfigOverrides {
+            raw_overrides: raw_overrides.into_iter().map(str::to_string).collect(),
+        };
+        let cli_kv_overrides = cli_config_overrides.parse_overrides().map_err(|e| {
+            std::io::Error::new(
+                std::io::ErrorKind::InvalidInput,
+                format!("error parsing -c overrides: {e}"),
+            )
+        })?;
+        let config_overrides = ConfigOverrides {
+            cwd: Some(codex_home.clone()),
+            ..ConfigOverrides::default()
+        };
+        let mut loader_overrides = LoaderOverrides::without_managed_config_for_tests();
+        loader_overrides.ignore_user_config = options.ignore_user_config;
+
+        ConfigBuilder::default()
+            .codex_home(codex_home)
+            .cli_overrides(cli_kv_overrides)
+            .harness_overrides(config_overrides)
+            .loader_overrides(loader_overrides)
+            .build()
+            .await
+    }
+
+    #[tokio::test]
+    async fn ignore_user_config_ignores_invalid_user_config_but_applies_cli_overrides()
+    -> std::io::Result<()> {
+        let codex_home = TestDir::new()?;
+        fs::write(
+            codex_home.path().join("config.toml"),
+            "model = \"from-user-config\"\ninvalid = [",
+        )?;
+
+        let config = load_config_for_test(
+            codex_home.path().to_path_buf(),
+            vec!["model=\"from-cli\""],
+            RunOptions {
+                ignore_user_config: true,
+            },
+        )
+        .await?;
+
+        assert_eq!(config.codex_home.as_path(), codex_home.path());
+        assert_eq!(config.model.as_deref(), Some("from-cli"));
+        Ok(())
+    }
+
+    #[tokio::test]
+    async fn ignore_user_config_does_not_load_user_notify_or_mcp_servers() -> std::io::Result<()> {
+        let codex_home = TestDir::new()?;
+        fs::write(
+            codex_home.path().join("config.toml"),
+            r#"
+notify = ["notify-send", "Codex"]
+
+[mcp_servers.user_config_server]
+command = "node"
+args = ["server.js"]
+"#,
+        )?;
+
+        let config = load_config_for_test(
+            codex_home.path().to_path_buf(),
+            vec![],
+            RunOptions {
+                ignore_user_config: true,
+            },
+        )
+        .await?;
+
+        assert_eq!(config.notify, None);
+        assert!(!config.mcp_servers.get().contains_key("user_config_server"));
+        Ok(())
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index 182167a..70c5b5f 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -3,10 +3,54 @@ use clap::Parser;
 use codex_arg0::arg0_dispatch_or_else;
 use codex_utils_cli::CliConfigOverrides;
 
+#[derive(Parser, Debug)]
+#[command(version, about = "ACP adapter for Codex")]
+struct Cli {
+    #[clap(flatten)]
+    config_overrides: CliConfigOverrides,
+
+    /// Do not load `$CODEX_HOME/config.toml`; auth still uses `CODEX_HOME`.
+    #[arg(long = "ignore-user-config", default_value_t = false)]
+    ignore_user_config: bool,
+}
+
 fn main() -> Result<()> {
     arg0_dispatch_or_else(|args| async move {
-        let cli_config_overrides = CliConfigOverrides::parse();
-        codex_acp::run_main(args.codex_linux_sandbox_exe, cli_config_overrides).await?;
+        let cli = Cli::parse();
+        codex_acp::run_main_with_options(
+            args.codex_linux_sandbox_exe,
+            cli.config_overrides,
+            codex_acp::RunOptions {
+                ignore_user_config: cli.ignore_user_config,
+            },
+        )
+        .await?;
         Ok(())
     })
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parses_ignore_user_config_with_config_overrides() {
+        let cli = Cli::parse_from([
+            "codex-acp",
+            "--ignore-user-config",
+            "-c",
+            "model=gpt-5.5",
+            "-c",
+            "cli_auth_credentials_store=auto",
+        ]);
+
+        assert!(cli.ignore_user_config);
+        assert_eq!(
+            cli.config_overrides.raw_overrides,
+            vec![
+                "model=gpt-5.5".to_string(),
+                "cli_auth_credentials_store=auto".to_string()
+            ]
+        );
+    }
+}