diff --git a/CHANGELOG.md b/CHANGELOG.md
index 88dfe3c9..7a98906d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -46,6 +46,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   providers now report whether the value came from `--provider`, environment,
   or config. Config-sourced unsupported providers fall back to DeepSeek without
   forwarding stale keyring secrets. Thanks @cyq1017 for the PR.
+- **Exec auto-model handoff (#3148).** `codewhale exec --model auto` now
+  survives the CLI/TUI boundary by honoring the CodeWhale model env alias and
+  legacy DeepSeek model handoff before falling back to provider defaults.
+  Thanks @hongchen1993 for the PR.
 - **TUI mouse-report leak (#3063/#3067).** Strip raw SGR mouse coordinate
   tails from the composer even when `use_mouse_capture` is false, covering
   orphaned terminal reporting state after crashes or focus races.
diff --git a/crates/tui/CHANGELOG.md b/crates/tui/CHANGELOG.md
index 1949f190..f43019b0 100644
--- a/crates/tui/CHANGELOG.md
+++ b/crates/tui/CHANGELOG.md
@@ -46,6 +46,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   providers now report whether the value came from `--provider`, environment,
   or config. Config-sourced unsupported providers fall back to DeepSeek without
   forwarding stale keyring secrets. Thanks @cyq1017 for the PR.
+- **Exec auto-model handoff (#3148).** `codewhale exec --model auto` now
+  survives the CLI/TUI boundary by honoring the CodeWhale model env alias and
+  legacy DeepSeek model handoff before falling back to provider defaults.
+  Thanks @hongchen1993 for the PR.
 - **TUI mouse-report leak (#3063/#3067).** Strip raw SGR mouse coordinate
   tails from the composer even when `use_mouse_capture` is false, covering
   orphaned terminal reporting state after crashes or focus races.
diff --git a/crates/tui/src/main.rs b/crates/tui/src/main.rs
index bfb7b2db..93108c10 100644
--- a/crates/tui/src/main.rs
+++ b/crates/tui/src/main.rs
@@ -307,14 +307,6 @@ Plain `codewhale exec` is a one-shot model response. Use `--auto` for
 non-interactive filesystem/shell tool use.
 ")]
 struct ExecArgs {
-    /// Prompt to send to the model
-    #[arg(
-        value_name = "PROMPT",
-        required = true,
-        trailing_var_arg = true,
-        allow_hyphen_values = true
-    )]
-    prompt: Vec<String>,
     /// Override model for this run
     #[arg(long)]
     model: Option<String>,
@@ -349,6 +341,14 @@ struct ExecArgs {
     /// Extra text appended to the system prompt for this run.
     #[arg(long)]
     append_system_prompt: Option<String>,
+    /// Prompt to send to the model
+    #[arg(
+        value_name = "PROMPT",
+        required = true,
+        trailing_var_arg = true,
+        allow_hyphen_values = true
+    )]
+    prompt: Vec<String>,
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, ValueEnum)]
@@ -464,9 +464,21 @@ fn resolve_exec_model(config: &Config, explicit_model: Option<&str>) -> String {
         .map(str::trim)
         .filter(|model| !model.is_empty())
         .map(ToOwned::to_owned)
+        .or_else(exec_model_env_override)
         .unwrap_or_else(|| config.default_model())
 }
 
+fn exec_model_env_override() -> Option<String> {
+    ["CODEWHALE_MODEL", "DEEPSEEK_MODEL"]
+        .into_iter()
+        .find_map(|key| {
+            std::env::var(key)
+                .ok()
+                .map(|model| model.trim().to_string())
+                .filter(|model| !model.is_empty())
+        })
+}
+
 fn top_level_prompt_initial_input(parts: &[String]) -> Option<tui::InitialInput> {
     (!parts.is_empty()).then(|| tui::InitialInput::Submit(join_prompt_parts(parts)))
 }
@@ -6647,6 +6659,9 @@ mod terminal_mode_tests {
 
     #[test]
     fn exec_model_resolution_uses_provider_scoped_default() {
+        let _env_lock = crate::test_support::lock_test_env();
+        let _codewhale_model = crate::test_support::EnvVarGuard::remove("CODEWHALE_MODEL");
+        let _deepseek_model = crate::test_support::EnvVarGuard::remove("DEEPSEEK_MODEL");
         let config = Config {
             provider: Some("openrouter".to_string()),
             default_text_model: Some("deepseek/deepseek-v4-pro".to_string()),
@@ -6670,6 +6685,33 @@ mod terminal_mode_tests {
         );
     }
 
+    #[test]
+    fn exec_model_resolution_prefers_codewhale_model_env_override() {
+        let _env_lock = crate::test_support::lock_test_env();
+        let _codewhale_model = crate::test_support::EnvVarGuard::set("CODEWHALE_MODEL", " auto ");
+        let _deepseek_model =
+            crate::test_support::EnvVarGuard::set("DEEPSEEK_MODEL", "stale-deepseek-model");
+        let config = Config {
+            default_text_model: Some("deepseek/deepseek-v4-pro".to_string()),
+            ..Default::default()
+        };
+
+        assert_eq!(resolve_exec_model(&config, None), "auto");
+    }
+
+    #[test]
+    fn exec_model_resolution_uses_legacy_deepseek_model_env_override() {
+        let _env_lock = crate::test_support::lock_test_env();
+        let _codewhale_model = crate::test_support::EnvVarGuard::remove("CODEWHALE_MODEL");
+        let _deepseek_model = crate::test_support::EnvVarGuard::set("DEEPSEEK_MODEL", " auto ");
+        let config = Config {
+            default_text_model: Some("deepseek/deepseek-v4-pro".to_string()),
+            ..Default::default()
+        };
+
+        assert_eq!(resolve_exec_model(&config, None), "auto");
+    }
+
     #[test]
     fn exec_accepts_split_prompt_words_for_windows_cmd_shims() {
         let cli = parse_cli(&["codewhale", "exec", "hello", "world"]);
@@ -6680,6 +6722,17 @@ mod terminal_mode_tests {
         assert_eq!(args.prompt, vec!["hello", "world"]);
     }
 
+    #[test]
+    fn exec_keeps_model_flag_before_split_prompt_words() {
+        let cli = parse_cli(&["codewhale", "exec", "--model", "auto", "hello", "world"]);
+        let Some(Commands::Exec(args)) = cli.command else {
+            panic!("expected exec command");
+        };
+
+        assert_eq!(args.model.as_deref(), Some("auto"));
+        assert_eq!(args.prompt, vec!["hello", "world"]);
+    }
+
     #[test]
     fn exec_keeps_flags_before_split_prompt_words() {
         let cli = parse_cli(&["codewhale", "exec", "--json", "hello", "world"]);