feat: Languageインストラクションの追加

crates/manifest/src/config.rs

@@ -66,6 +66,8 @@ pub struct WorkerManifestConfig {
     #[serde(default)]
     pub instruction: Option<String>,
     #[serde(default)]
+    pub language: Option<String>,
+    #[serde(default)]
     pub max_tokens: Option<u32>,
     #[serde(default)]
     pub max_turns: Option<NonZeroU32>,
@@ -291,6 +293,7 @@ impl WorkerManifestConfig {
     fn merge(self, upper: Self) -> Self {
         Self {
             instruction: upper.instruction.or(self.instruction),
+            language: upper.language.or(self.language),
             max_tokens: upper.max_tokens.or(self.max_tokens),
             max_turns: upper.max_turns.or(self.max_turns),
             temperature: upper.temperature.or(self.temperature),
@@ -429,6 +432,10 @@ impl TryFrom<PodManifestConfig> for PodManifest {
                 .worker
                 .instruction
                 .unwrap_or_else(|| defaults::DEFAULT_INSTRUCTION.to_string()),
+            language: cfg
+                .worker
+                .language
+                .unwrap_or_else(|| defaults::WORKER_LANGUAGE.to_string()),
             max_tokens: cfg.worker.max_tokens,
             max_turns: cfg.worker.max_turns,
             temperature: cfg.worker.temperature,

crates/manifest/src/defaults.rs

@@ -33,6 +33,11 @@ pub const COMPACT_RETAINED_TOKENS: u64 = 8000;
 /// `$insomnia/` / `$user/` / `$workspace/` namespaces.
 pub const DEFAULT_INSTRUCTION: &str = "$insomnia/default";
 
+/// Default language policy used by the main worker for normal prose
+/// responses. See [`crate::WorkerManifest::language`].
+pub const WORKER_LANGUAGE: &str =
+    "match the user's language unless they explicitly request another language";
+
 /// Token budget for auto-read file contents injected into the new
 /// session after compaction. Limits how much raw file text the
 /// compact worker can pull into the compacted context via

crates/manifest/src/lib.rs

@@ -173,6 +173,12 @@ pub struct WorkerManifest {
     /// unset manifests fall through to [`defaults::DEFAULT_INSTRUCTION`].
     #[serde(default = "default_instruction")]
     pub instruction: String,
+    /// Language policy used by the main worker for normal prose responses.
+    /// Free-form so workspaces can use names like `English`, `Japanese`,
+    /// locale tags, or a policy phrase. Unset manifests fall through to
+    /// [`defaults::WORKER_LANGUAGE`].
+    #[serde(default = "default_worker_language")]
+    pub language: String,
     #[serde(default)]
     pub max_tokens: Option<u32>,
     #[serde(default)]
@@ -241,6 +247,10 @@ fn default_instruction() -> String {
     defaults::DEFAULT_INSTRUCTION.to_string()
 }
 
+fn default_worker_language() -> String {
+    defaults::WORKER_LANGUAGE.to_string()
+}
+
 impl Default for ToolOutputLimits {
     fn default() -> Self {
         Self {
@@ -689,6 +699,16 @@ model_id = "claude-sonnet-4-20250514"
         );
     }
 
+    #[test]
+    fn worker_language_defaults_and_parses() {
+        let manifest = PodManifest::from_toml(MINIMAL_REQUIRED).unwrap();
+        assert_eq!(manifest.worker.language, defaults::WORKER_LANGUAGE);
+
+        let toml = MINIMAL_REQUIRED.replace("[worker]\n", "[worker]\nlanguage = \"Japanese\"\n");
+        let manifest = PodManifest::from_toml(&toml).unwrap();
+        assert_eq!(manifest.worker.language, "Japanese");
+    }
+
     #[test]
     fn parse_worker_output_limits() {
         let toml = MINIMAL_REQUIRED.replace(