feat: add a built-in model provider named "oss"

codex-rs/Cargo.lock

@@ -838,6 +838,23 @@ dependencies = [
  "wiremock",
 ]
 
+[[package]]
+name = "codex-ollama"
+version = "0.0.0"
+dependencies = [
+ "async-stream",
+ "bytes",
+ "codex-core",
+ "futures",
+ "reqwest",
+ "serde_json",
+ "tempfile",
+ "tokio",
+ "toml 0.9.4",
+ "tracing",
+ "wiremock",
+]
+
 [[package]]
 name = "codex-tui"
 version = "0.0.0"
@@ -852,6 +869,7 @@ dependencies = [
  "codex-core",
  "codex-file-search",
  "codex-login",
+ "codex-ollama",
  "color-eyre",
  "crossterm",
  "image",

codex-rs/Cargo.toml

@@ -14,6 +14,7 @@ members = [
     "mcp-client",
     "mcp-server",
     "mcp-types",
+    "ollama",
     "tui",
 ]
 resolver = "2"

codex-rs/core/src/lib.rs

@@ -28,6 +28,7 @@ mod mcp_connection_manager;
 mod mcp_tool_call;
 mod message_history;
 mod model_provider_info;
+pub use model_provider_info::BUILT_IN_OSS_MODEL_PROVIDER_ID;
 pub use model_provider_info::ModelProviderInfo;
 pub use model_provider_info::WireApi;
 pub use model_provider_info::built_in_model_providers;

codex-rs/core/src/model_provider_info.rs

@@ -226,53 +226,93 @@ impl ModelProviderInfo {
     }
 }
 
+const DEFAULT_OLLAMA_PORT: u32 = 11434;
+
+pub const BUILT_IN_OSS_MODEL_PROVIDER_ID: &str = "oss";
+
 /// Built-in default provider list.
 pub fn built_in_model_providers() -> HashMap<String, ModelProviderInfo> {
     use ModelProviderInfo as P;
 
-    // We do not want to be in the business of adjucating which third-party
-    // providers are bundled with Codex CLI, so we only include the OpenAI
-    // provider by default. Users are encouraged to add to `model_providers`
-    // in config.toml to add their own providers.
-    [(
-        "openai",
-        P {
-            name: "OpenAI".into(),
-            // Allow users to override the default OpenAI endpoint by
-            // exporting `OPENAI_BASE_URL`. This is useful when pointing
-            // Codex at a proxy, mock server, or Azure-style deployment
-            // without requiring a full TOML override for the built-in
-            // OpenAI provider.
-            base_url: std::env::var("OPENAI_BASE_URL")
+    // These CODEX_OSS_ environment variables are experimental: we may
+    // switch to reading values from config.toml instead.
+    let codex_oss_base_url = match std::env::var("CODEX_OSS_BASE_URL")
+        .ok()
+        .filter(|v| !v.trim().is_empty())
+    {
+        Some(url) => url,
+        None => format!(
+            "http://localhost:{port}/v1",
+            port = std::env::var("CODEX_OSS_PORT")
                 .ok()
-                .filter(|v| !v.trim().is_empty()),
-            env_key: None,
-            env_key_instructions: None,
-            wire_api: WireApi::Responses,
-            query_params: None,
-            http_headers: Some(
-                [("version".to_string(), env!("CARGO_PKG_VERSION").to_string())]
+                .filter(|v| !v.trim().is_empty())
+                .and_then(|v| v.parse::<u32>().ok())
+                .unwrap_or(DEFAULT_OLLAMA_PORT)
+        ),
+    };
+
+    // We do not want to be in the business of adjucating which third-party
+    // providers are bundled with Codex CLI, so we only include the OpenAI and
+    // open source ("oss") providers by default. Users are encouraged to add to
+    // `model_providers` in config.toml to add their own providers.
+    [
+        (
+            "openai",
+            P {
+                name: "OpenAI".into(),
+                // Allow users to override the default OpenAI endpoint by
+                // exporting `OPENAI_BASE_URL`. This is useful when pointing
+                // Codex at a proxy, mock server, or Azure-style deployment
+                // without requiring a full TOML override for the built-in
+                // OpenAI provider.
+                base_url: std::env::var("OPENAI_BASE_URL")
+                    .ok()
+                    .filter(|v| !v.trim().is_empty()),
+                env_key: None,
+                env_key_instructions: None,
+                wire_api: WireApi::Responses,
+                query_params: None,
+                http_headers: Some(
+                    [("version".to_string(), env!("CARGO_PKG_VERSION").to_string())]
+                        .into_iter()
+                        .collect(),
+                ),
+                env_http_headers: Some(
+                    [
+                        (
+                            "OpenAI-Organization".to_string(),
+                            "OPENAI_ORGANIZATION".to_string(),
+                        ),
+                        ("OpenAI-Project".to_string(), "OPENAI_PROJECT".to_string()),
+                    ]
                     .into_iter()
                     .collect(),
-            ),
-            env_http_headers: Some(
-                [
-                    (
-                        "OpenAI-Organization".to_string(),
-                        "OPENAI_ORGANIZATION".to_string(),
-                    ),
-                    ("OpenAI-Project".to_string(), "OPENAI_PROJECT".to_string()),
-                ]
-                .into_iter()
-                .collect(),
-            ),
-            // Use global defaults for retry/timeout unless overridden in config.toml.
-            request_max_retries: None,
-            stream_max_retries: None,
-            stream_idle_timeout_ms: None,
-            requires_auth: true,
-        },
-    )]
+                ),
+                // Use global defaults for retry/timeout unless overridden in config.toml.
+                request_max_retries: None,
+                stream_max_retries: None,
+                stream_idle_timeout_ms: None,
+                requires_auth: true,
+            },
+        ),
+        (
+            BUILT_IN_OSS_MODEL_PROVIDER_ID,
+            P {
+                name: "Open Source".into(),
+                base_url: Some(codex_oss_base_url),
+                env_key: None,
+                env_key_instructions: None,
+                wire_api: WireApi::Chat,
+                query_params: None,
+                http_headers: None,
+                env_http_headers: None,
+                request_max_retries: None,
+                stream_max_retries: None,
+                stream_idle_timeout_ms: None,
+                requires_auth: false,
+            },
+        ),
+    ]
     .into_iter()
     .map(|(k, v)| (k.to_string(), v))
     .collect()

codex-rs/ollama/Cargo.toml

@@ -0,0 +1,32 @@
+[package]
+edition = "2024"
+name = "codex-ollama"
+version = { workspace = true }
+
+[lib]
+name = "codex_ollama"
+path = "src/lib.rs"
+
+[lints]
+workspace = true
+
+[dependencies]
+async-stream = "0.3"
+bytes = "1.10.1"
+codex-core = { path = "../core" }
+futures = "0.3"
+reqwest = { version = "0.12", features = ["json", "stream"] }
+serde_json = "1"
+tokio = { version = "1", features = [
+    "io-std",
+    "macros",
+    "process",
+    "rt-multi-thread",
+    "signal",
+] }
+toml = "0.9.2"
+tracing = { version = "0.1.41", features = ["log"] }
+wiremock = "0.6"
+
+[dev-dependencies]
+tempfile = "3"

codex-rs/ollama/src/client.rs

@@ -0,0 +1,255 @@
+use bytes::BytesMut;
+use futures::StreamExt;
+use futures::stream::BoxStream;
+use serde_json::Value as JsonValue;
+use std::collections::VecDeque;
+use std::io;
+
+use codex_core::WireApi;
+
+use crate::parser::pull_events_from_value;
+use crate::pull::PullEvent;
+use crate::pull::PullProgressReporter;
+use crate::url::base_url_to_host_root;
+use crate::url::is_openai_compatible_base_url;
+
+/// Client for interacting with a local Ollama instance.
+pub struct OllamaClient {
+    client: reqwest::Client,
+    host_root: String,
+    uses_openai_compat: bool,
+}
+
+impl OllamaClient {
+    pub fn from_oss_provider() -> Self {
+        #![allow(clippy::expect_used)]
+        // Use the built-in OSS provider's base URL.
+        let built_in_model_providers = codex_core::built_in_model_providers();
+        let provider = built_in_model_providers
+            .get(codex_core::BUILT_IN_OSS_MODEL_PROVIDER_ID)
+            .expect("oss provider must exist");
+        let base_url = provider
+            .base_url
+            .as_ref()
+            .expect("oss provider must have a base_url");
+        Self::from_provider(base_url, provider.wire_api)
+    }
+
+    /// Build a client from a provider definition. Falls back to the default
+    /// local URL if no base_url is configured.
+    fn from_provider(base_url: &str, wire_api: WireApi) -> Self {
+        let uses_openai_compat = is_openai_compatible_base_url(base_url)
+            || matches!(wire_api, WireApi::Chat) && is_openai_compatible_base_url(base_url);
+        let host_root = base_url_to_host_root(base_url);
+        let client = reqwest::Client::builder()
+            .connect_timeout(std::time::Duration::from_secs(5))
+            .build()
+            .unwrap_or_else(|_| reqwest::Client::new());
+        Self {
+            client,
+            host_root,
+            uses_openai_compat,
+        }
+    }
+
+    pub fn get_host(&self) -> &str {
+        &self.host_root
+    }
+
+    /// Low-level constructor given a raw host root, e.g. "http://localhost:11434".
+    #[cfg(test)]
+    fn from_host_root(host_root: impl Into<String>) -> Self {
+        let client = reqwest::Client::builder()
+            .connect_timeout(std::time::Duration::from_secs(5))
+            .build()
+            .unwrap_or_else(|_| reqwest::Client::new());
+        Self {
+            client,
+            host_root: host_root.into(),
+            uses_openai_compat: false,
+        }
+    }
+
+    /// Probe whether the server is reachable by hitting the appropriate health endpoint.
+    pub async fn probe_server(&self) -> io::Result<bool> {
+        let url = if self.uses_openai_compat {
+            format!("{}/v1/models", self.host_root.trim_end_matches('/'))
+        } else {
+            format!("{}/api/tags", self.host_root.trim_end_matches('/'))
+        };
+        let resp = self.client.get(url).send().await;
+        Ok(matches!(resp, Ok(r) if r.status().is_success()))
+    }
+
+    /// Return the list of model names known to the local Ollama instance.
+    pub async fn fetch_models(&self) -> io::Result<Vec<String>> {
+        let tags_url = format!("{}/api/tags", self.host_root.trim_end_matches('/'));
+        let resp = self
+            .client
+            .get(tags_url)
+            .send()
+            .await
+            .map_err(io::Error::other)?;
+        if !resp.status().is_success() {
+            return Ok(Vec::new());
+        }
+        let val = resp.json::<JsonValue>().await.map_err(io::Error::other)?;
+        let names = val
+            .get("models")
+            .and_then(|m| m.as_array())
+            .map(|arr| {
+                arr.iter()
+                    .filter_map(|v| v.get("name").and_then(|n| n.as_str()))
+                    .map(|s| s.to_string())
+                    .collect::<Vec<_>>()
+            })
+            .unwrap_or_default();
+        Ok(names)
+    }
+
+    /// Start a model pull and emit streaming events. The returned stream ends when
+    /// a Success event is observed or the server closes the connection.
+    pub async fn pull_model_stream(
+        &self,
+        model: &str,
+    ) -> io::Result<BoxStream<'static, PullEvent>> {
+        let url = format!("{}/api/pull", self.host_root.trim_end_matches('/'));
+        let resp = self
+            .client
+            .post(url)
+            .json(&serde_json::json!({"model": model, "stream": true}))
+            .send()
+            .await
+            .map_err(io::Error::other)?;
+        if !resp.status().is_success() {
+            return Err(io::Error::other(format!(
+                "failed to start pull: HTTP {}",
+                resp.status()
+            )));
+        }
+
+        let mut stream = resp.bytes_stream();
+        let mut buf = BytesMut::new();
+        let _pending: VecDeque<PullEvent> = VecDeque::new();
+
+        // Using an async stream adaptor backed by unfold-like manual loop.
+        let s = async_stream::stream! {
+            while let Some(chunk) = stream.next().await {
+                match chunk {
+                    Ok(bytes) => {
+                        buf.extend_from_slice(&bytes);
+                        while let Some(pos) = buf.iter().position(|b| *b == b'\n') {
+                            let line = buf.split_to(pos + 1);
+                            if let Ok(text) = std::str::from_utf8(&line) {
+                                let text = text.trim();
+                                if text.is_empty() { continue; }
+                                if let Ok(value) = serde_json::from_str::<JsonValue>(text) {
+                                    for ev in pull_events_from_value(&value) { yield ev; }
+                                    if let Some(err_msg) = value.get("error").and_then(|e| e.as_str()) {
+                                        yield PullEvent::Status(format!("error: {err_msg}"));
+                                        return;
+                                    }
+                                    if let Some(status) = value.get("status").and_then(|s| s.as_str()) {
+                                        if status == "success" { yield PullEvent::Success; return; }
+                                    }
+                                }
+                            }
+                        }
+                    }
+                    Err(_) => {
+                        // Connection error: end the stream.
+                        return;
+                    }
+                }
+            }
+        };
+
+        Ok(Box::pin(s))
+    }
+
+    /// High-level helper to pull a model and drive a progress reporter.
+    pub async fn pull_with_reporter(
+        &self,
+        model: &str,
+        reporter: &mut dyn PullProgressReporter,
+    ) -> io::Result<()> {
+        reporter.on_event(&PullEvent::Status(format!("Pulling model {model}...")))?;
+        let mut stream = self.pull_model_stream(model).await?;
+        while let Some(event) = stream.next().await {
+            reporter.on_event(&event)?;
+            if matches!(event, PullEvent::Success) {
+                break;
+            }
+        }
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #![allow(clippy::expect_used, clippy::unwrap_used)]
+    use super::*;
+
+    // Happy-path tests using a mock HTTP server; skip if sandbox network is disabled.
+    #[tokio::test]
+    async fn test_fetch_models_happy_path() {
+        if std::env::var(codex_core::spawn::CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR).is_ok() {
+            tracing::info!(
+                "{} is set; skipping test_fetch_models_happy_path",
+                codex_core::spawn::CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR
+            );
+            return;
+        }
+
+        let server = wiremock::MockServer::start().await;
+        wiremock::Mock::given(wiremock::matchers::method("GET"))
+            .and(wiremock::matchers::path("/api/tags"))
+            .respond_with(
+                wiremock::ResponseTemplate::new(200).set_body_raw(
+                    serde_json::json!({
+                        "models": [ {"name": "llama3.2:3b"}, {"name":"mistral"} ]
+                    })
+                    .to_string(),
+                    "application/json",
+                ),
+            )
+            .mount(&server)
+            .await;
+
+        let client = OllamaClient::from_host_root(server.uri());
+        let models = client.fetch_models().await.expect("fetch models");
+        assert!(models.contains(&"llama3.2:3b".to_string()));
+        assert!(models.contains(&"mistral".to_string()));
+    }
+
+    #[tokio::test]
+    async fn test_probe_server_happy_path_openai_compat_and_native() {
+        if std::env::var(codex_core::spawn::CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR).is_ok() {
+            tracing::info!(
+                "{} set; skipping test_probe_server_happy_path_openai_compat_and_native",
+                codex_core::spawn::CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR
+            );
+            return;
+        }
+
+        let server = wiremock::MockServer::start().await;
+
+        // Native endpoint
+        wiremock::Mock::given(wiremock::matchers::method("GET"))
+            .and(wiremock::matchers::path("/api/tags"))
+            .respond_with(wiremock::ResponseTemplate::new(200))
+            .mount(&server)
+            .await;
+        let native = OllamaClient::from_host_root(server.uri());
+        assert!(native.probe_server().await.expect("probe native"));
+
+        // OpenAI compatibility endpoint
+        wiremock::Mock::given(wiremock::matchers::method("GET"))
+            .and(wiremock::matchers::path("/v1/models"))
+            .respond_with(wiremock::ResponseTemplate::new(200))
+            .mount(&server)
+            .await;
+        let ollama_client = OllamaClient::from_provider(&server.uri(), WireApi::Chat);
+        assert!(ollama_client.probe_server().await.expect("probe compat"));
+    }
+}

codex-rs/ollama/src/lib.rs

@@ -0,0 +1,6 @@
+mod client;
+mod parser;
+mod pull;
+mod url;
+
+pub use client::OllamaClient;

codex-rs/ollama/src/parser.rs

@@ -0,0 +1,82 @@
+use serde_json::Value as JsonValue;
+
+use crate::pull::PullEvent;
+
+// Convert a single JSON object representing a pull update into one or more events.
+pub(crate) fn pull_events_from_value(value: &JsonValue) -> Vec<PullEvent> {
+    let mut events = Vec::new();
+    if let Some(status) = value.get("status").and_then(|s| s.as_str()) {
+        events.push(PullEvent::Status(status.to_string()));
+        if status == "success" {
+            events.push(PullEvent::Success);
+        }
+    }
+    let digest = value
+        .get("digest")
+        .and_then(|d| d.as_str())
+        .unwrap_or("")
+        .to_string();
+    let total = value.get("total").and_then(|t| t.as_u64());
+    let completed = value.get("completed").and_then(|t| t.as_u64());
+    if total.is_some() || completed.is_some() {
+        events.push(PullEvent::ChunkProgress {
+            digest,
+            total,
+            completed,
+        });
+    }
+    events
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_pull_events_decoder_status_and_success() {
+        let v: JsonValue = serde_json::json!({"status":"verifying"});
+        let events = pull_events_from_value(&v);
+        assert!(matches!(events.as_slice(), [PullEvent::Status(s)] if s == "verifying"));
+
+        let v2: JsonValue = serde_json::json!({"status":"success"});
+        let events2 = pull_events_from_value(&v2);
+        assert_eq!(events2.len(), 2);
+        assert!(matches!(events2[0], PullEvent::Status(ref s) if s == "success"));
+        assert!(matches!(events2[1], PullEvent::Success));
+    }
+
+    #[test]
+    fn test_pull_events_decoder_progress() {
+        let v: JsonValue = serde_json::json!({"digest":"sha256:abc","total":100});
+        let events = pull_events_from_value(&v);
+        assert_eq!(events.len(), 1);
+        match &events[0] {
+            PullEvent::ChunkProgress {
+                digest,
+                total,
+                completed,
+            } => {
+                assert_eq!(digest, "sha256:abc");
+                assert_eq!(*total, Some(100));
+                assert_eq!(*completed, None);
+            }
+            _ => panic!("expected ChunkProgress"),
+        }
+
+        let v2: JsonValue = serde_json::json!({"digest":"sha256:def","completed":42});
+        let events2 = pull_events_from_value(&v2);
+        assert_eq!(events2.len(), 1);
+        match &events2[0] {
+            PullEvent::ChunkProgress {
+                digest,
+                total,
+                completed,
+            } => {
+                assert_eq!(digest, "sha256:def");
+                assert_eq!(*total, None);
+                assert_eq!(*completed, Some(42));
+            }
+            _ => panic!("expected ChunkProgress"),
+        }
+    }
+}

codex-rs/ollama/src/pull.rs

@@ -0,0 +1,139 @@
+use std::collections::HashMap;
+use std::io;
+use std::io::Write;
+
+/// Events emitted while pulling a model from Ollama.
+#[derive(Debug, Clone)]
+pub enum PullEvent {
+    /// A human-readable status message (e.g., "verifying", "writing").
+    Status(String),
+    /// Byte-level progress update for a specific layer digest.
+    ChunkProgress {
+        digest: String,
+        total: Option<u64>,
+        completed: Option<u64>,
+    },
+    /// The pull finished successfully.
+    Success,
+}
+
+/// A simple observer for pull progress events. Implementations decide how to
+/// render progress (CLI, TUI, logs, ...).
+pub trait PullProgressReporter {
+    fn on_event(&mut self, event: &PullEvent) -> io::Result<()>;
+}
+
+/// A minimal CLI reporter that writes inline progress to stderr.
+pub struct CliProgressReporter {
+    printed_header: bool,
+    last_line_len: usize,
+    last_completed_sum: u64,
+    last_instant: std::time::Instant,
+    totals_by_digest: HashMap<String, (u64, u64)>,
+}
+
+impl Default for CliProgressReporter {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl CliProgressReporter {
+    pub fn new() -> Self {
+        Self {
+            printed_header: false,
+            last_line_len: 0,
+            last_completed_sum: 0,
+            last_instant: std::time::Instant::now(),
+            totals_by_digest: HashMap::new(),
+        }
+    }
+}
+
+impl PullProgressReporter for CliProgressReporter {
+    fn on_event(&mut self, event: &PullEvent) -> io::Result<()> {
+        let mut out = std::io::stderr();
+        match event {
+            PullEvent::Status(status) => {
+                // Avoid noisy manifest messages; otherwise show status inline.
+                if status.eq_ignore_ascii_case("pulling manifest") {
+                    return Ok(());
+                }
+                let pad = self.last_line_len.saturating_sub(status.len());
+                let line = format!("\r{status}{}", " ".repeat(pad));
+                self.last_line_len = status.len();
+                out.write_all(line.as_bytes())?;
+                out.flush()
+            }
+            PullEvent::ChunkProgress {
+                digest,
+                total,
+                completed,
+            } => {
+                if let Some(t) = *total {
+                    self.totals_by_digest
+                        .entry(digest.clone())
+                        .or_insert((0, 0))
+                        .0 = t;
+                }
+                if let Some(c) = *completed {
+                    self.totals_by_digest
+                        .entry(digest.clone())
+                        .or_insert((0, 0))
+                        .1 = c;
+                }
+
+                let (sum_total, sum_completed) = self
+                    .totals_by_digest
+                    .values()
+                    .fold((0u64, 0u64), |acc, (t, c)| (acc.0 + *t, acc.1 + *c));
+                if sum_total > 0 {
+                    if !self.printed_header {
+                        let gb = (sum_total as f64) / (1024.0 * 1024.0 * 1024.0);
+                        let header = format!("Downloading model: total {gb:.2} GB\n");
+                        out.write_all(b"\r\x1b[2K")?;
+                        out.write_all(header.as_bytes())?;
+                        self.printed_header = true;
+                    }
+                    let now = std::time::Instant::now();
+                    let dt = now
+                        .duration_since(self.last_instant)
+                        .as_secs_f64()
+                        .max(0.001);
+                    let dbytes = sum_completed.saturating_sub(self.last_completed_sum) as f64;
+                    let speed_mb_s = dbytes / (1024.0 * 1024.0) / dt;
+                    self.last_completed_sum = sum_completed;
+                    self.last_instant = now;
+
+                    let done_gb = (sum_completed as f64) / (1024.0 * 1024.0 * 1024.0);
+                    let total_gb = (sum_total as f64) / (1024.0 * 1024.0 * 1024.0);
+                    let pct = (sum_completed as f64) * 100.0 / (sum_total as f64);
+                    let text =
+                        format!("{done_gb:.2}/{total_gb:.2} GB ({pct:.1}%) {speed_mb_s:.1} MB/s");
+                    let pad = self.last_line_len.saturating_sub(text.len());
+                    let line = format!("\r{text}{}", " ".repeat(pad));
+                    self.last_line_len = text.len();
+                    out.write_all(line.as_bytes())?;
+                    out.flush()
+                } else {
+                    Ok(())
+                }
+            }
+            PullEvent::Success => {
+                out.write_all(b"\n")?;
+                out.flush()
+            }
+        }
+    }
+}
+
+/// For now the TUI reporter delegates to the CLI reporter. This keeps UI and
+/// CLI behavior aligned until a dedicated TUI integration is implemented.
+#[derive(Default)]
+pub struct TuiProgressReporter(CliProgressReporter);
+
+impl PullProgressReporter for TuiProgressReporter {
+    fn on_event(&mut self, event: &PullEvent) -> io::Result<()> {
+        self.0.on_event(event)
+    }
+}

codex-rs/ollama/src/url.rs

@@ -0,0 +1,39 @@
+/// Identify whether a base_url points at an OpenAI-compatible root (".../v1").
+pub(crate) fn is_openai_compatible_base_url(base_url: &str) -> bool {
+    base_url.trim_end_matches('/').ends_with("/v1")
+}
+
+/// Convert a provider base_url into the native Ollama host root.
+/// For example, "http://localhost:11434/v1" -> "http://localhost:11434".
+pub fn base_url_to_host_root(base_url: &str) -> String {
+    let trimmed = base_url.trim_end_matches('/');
+    if trimmed.ends_with("/v1") {
+        trimmed
+            .trim_end_matches("/v1")
+            .trim_end_matches('/')
+            .to_string()
+    } else {
+        trimmed.to_string()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_base_url_to_host_root() {
+        assert_eq!(
+            base_url_to_host_root("http://localhost:11434/v1"),
+            "http://localhost:11434"
+        );
+        assert_eq!(
+            base_url_to_host_root("http://localhost:11434"),
+            "http://localhost:11434"
+        );
+        assert_eq!(
+            base_url_to_host_root("http://localhost:11434/"),
+            "http://localhost:11434"
+        );
+    }
+}

codex-rs/tui/Cargo.toml

@@ -33,6 +33,7 @@ codex-common = { path = "../common", features = [
 codex-core = { path = "../core" }
 codex-file-search = { path = "../file-search" }
 codex-login = { path = "../login" }
+codex-ollama = { path = "../ollama" }
 color-eyre = "0.6.3"
 crossterm = { version = "0.28.1", features = ["bracketed-paste"] }
 image = { version = "^0.25.6", default-features = false, features = ["jpeg"] }
@@ -70,11 +71,9 @@ unicode-segmentation = "1.12.0"
 unicode-width = "0.1"
 uuid = "1"
 
-
-
 [dev-dependencies]
+chrono = { version = "0.4", features = ["serde"] }
 insta = "1.43.1"
 pretty_assertions = "1"
 rand = "0.8"
-chrono = { version = "0.4", features = ["serde"] }
 vt100 = "0.16.2"

codex-rs/tui/src/cli.rs

@@ -17,6 +17,12 @@ pub struct Cli {
     #[arg(long, short = 'm')]
     pub model: Option<String>,
 
+    /// Convenience flag to select the local open source model provider.
+    /// Equivalent to -c model_provider=oss; verifies a local Ollama server is
+    /// running.
+    #[arg(long = "oss", default_value_t = false)]
+    pub oss: bool,
+
     /// Configuration profile from config.toml to specify default options.
     #[arg(long = "profile", short = 'p')]
     pub config_profile: Option<String>,

codex-rs/tui/src/lib.rs

@@ -3,12 +3,14 @@
 // alternate‑screen mode starts; that file opts‑out locally via `allow`.
 #![deny(clippy::print_stdout, clippy::print_stderr)]
 use app::App;
+use codex_core::BUILT_IN_OSS_MODEL_PROVIDER_ID;
 use codex_core::config::Config;
 use codex_core::config::ConfigOverrides;
 use codex_core::config_types::SandboxMode;
 use codex_core::protocol::AskForApproval;
 use codex_core::util::is_inside_git_repo;
 use codex_login::load_auth;
+use codex_ollama::OllamaClient;
 use log_layer::TuiLogLayer;
 use std::fs::OpenOptions;
 use std::io::Write;
@@ -70,6 +72,11 @@ pub async fn run_main(
         )
     };
 
+    let model_provider_override = if cli.oss {
+        Some(BUILT_IN_OSS_MODEL_PROVIDER_ID.to_owned())
+    } else {
+        None
+    };
     let config = {
         // Load configuration and support CLI overrides.
         let overrides = ConfigOverrides {
@@ -77,7 +84,7 @@ pub async fn run_main(
             approval_policy,
             sandbox_mode,
             cwd: cli.cwd.clone().map(|p| p.canonicalize().unwrap_or(p)),
-            model_provider: None,
+            model_provider: model_provider_override,
             config_profile: cli.config_profile.clone(),
             codex_linux_sandbox_exe,
             base_instructions: None,
@@ -177,6 +184,23 @@ pub async fn run_main(
         eprintln!("");
     }
 
+    if cli.oss {
+        // Should maybe load the client using `config.model_provider`?
+        let ollama_client = OllamaClient::from_oss_provider();
+        let is_ollama_available = ollama_client.probe_server().await?;
+        #[allow(clippy::print_stderr)]
+        if !is_ollama_available {
+            eprintln!(
+                "Ollama server is not reachable at {}. Please ensure Ollama is running.",
+                ollama_client.get_host()
+            );
+            std::process::exit(1);
+        }
+
+        // TODO(easong): Check if the model is available, and if not, prompt the
+        // user to pull it.
+    }
+
     let show_login_screen = should_show_login_screen(&config);
     if show_login_screen {
         std::io::stdout()