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(

crates/pod/src/factory.rs

@@ -643,6 +643,7 @@ permission = "write"
         let ctx = SystemPromptContext {
             now: chrono::Utc::now(),
             cwd: &root,
+            language: manifest::defaults::WORKER_LANGUAGE,
             scope: &scope,
             tool_names: Vec::new(),
             agents_md: None,

crates/pod/src/pod.rs

@@ -879,10 +879,12 @@ impl<C: LlmClient, St: Store> Pod<C, St> {
             };
         let resident_exposure_snapshots =
             self.resident_exposure_snapshots(&resident, &resident_workflows);
+        let worker_language = worker_language(&self.manifest.worker);
         let scope_snapshot = self.scope.snapshot();
         let ctx = SystemPromptContext {
             now: chrono::Utc::now(),
             cwd: &self.pwd,
+            language: worker_language,
             scope: &scope_snapshot,
             tool_names,
             agents_md: agents_md_read.body,
@@ -2342,6 +2344,15 @@ fn memory_language(cfg: &manifest::MemoryConfig) -> &str {
         .unwrap_or(manifest::defaults::MEMORY_LANGUAGE)
 }
 
+fn worker_language(cfg: &manifest::WorkerManifest) -> &str {
+    let language = cfg.language.trim();
+    if language.is_empty() {
+        manifest::defaults::WORKER_LANGUAGE
+    } else {
+        language
+    }
+}
+
 /// Outcome of a single extract iteration. Internal to
 /// `try_post_run_extract` / `run_extract_once`.
 enum ExtractDecision {
@@ -3152,6 +3163,7 @@ mod build_summary_prompt_tests {
     fn worker_manifest_generation_settings_become_request_config() {
         let manifest = WorkerManifest {
             instruction: "unused".into(),
+            language: manifest::defaults::WORKER_LANGUAGE.into(),
             max_tokens: Some(1024),
             max_turns: None,
             temperature: Some(0.2),

crates/pod/src/prompt/system.rs

@@ -144,6 +144,8 @@ impl std::fmt::Debug for SystemPromptTemplate {
 pub struct SystemPromptContext<'a> {
     pub now: DateTime<Utc>,
     pub cwd: &'a Path,
+    /// Language policy exposed to instruction templates as `{{ language }}`.
+    pub language: &'a str,
     pub scope: &'a Scope,
     pub tool_names: Vec<String>,
     /// Project-level instructions read from the nearest `AGENTS.md`.
@@ -181,6 +183,7 @@ impl<'a> SystemPromptContext<'a> {
             Value::from(self.now.to_rfc3339_opts(SecondsFormat::Secs, true)),
         );
         root.insert("cwd".into(), Value::from(self.cwd.display().to_string()));
+        root.insert("language".into(), Value::from(self.language));
         root.insert(
             "tools".into(),
             Value::from(
@@ -328,6 +331,7 @@ mod tests {
         SystemPromptContext {
             now: fixed_now(),
             cwd,
+            language: manifest::defaults::WORKER_LANGUAGE,
             scope,
             tool_names: tools,
             agents_md,
@@ -345,6 +349,7 @@ mod tests {
         SystemPromptContext {
             now: fixed_now(),
             cwd,
+            language: manifest::defaults::WORKER_LANGUAGE,
             scope,
             tool_names: Vec::new(),
             agents_md: None,
@@ -380,6 +385,9 @@ mod tests {
         let rendered = tmpl
             .render(&ctx(dir.path(), &scope, vec!["Read".into()], None))
             .unwrap();
+        // Builtin default body must expose the language policy.
+        assert!(rendered.contains("## Language"));
+        assert!(rendered.contains("`language`: `match the user's language"));
         // Trailing section must be present.
         assert!(rendered.contains("## Working boundaries"));
         assert!(rendered.contains("Readable:"));

resources/prompts/common/language.md

@@ -0,0 +1,6 @@
+## Language
+
+- `language`: `{{ language }}`.
+- Follow this language policy for normal prose responses unless the user explicitly requests another language.
+- Preserve code identifiers, file paths, command names, logs, quoted text, and external proper nouns when translation would reduce fidelity.
+- Do not translate file contents, command output, or protocol literals unless the user asks for translation.

resources/prompts/default.md

@@ -6,4 +6,6 @@ Stay precise, edit code directly when asked, and avoid speculative refactoring.
 
 {% include "common/tool-usage" %}
 
+{% include "common/language" %}
+
 {% include "common/writing" %}