diff --git a/src/app/runtime/actions/mod.rs b/src/app/runtime/actions/mod.rs
index 114a166..2054a37 100644
--- a/src/app/runtime/actions/mod.rs
+++ b/src/app/runtime/actions/mod.rs
@@ -702,6 +702,7 @@ fn spawn_turn(state: &AppStateRest) {
         }
     };
     let context_window = crate::app::runtime::context::window::resolve(&state.app_config, &state.settings);
+    let concise_output = state.settings.concise_output;
     let (temperature, max_tokens) = crate::app::mode::effort::generation_params(
         state.misc.effort_level,
         state.settings.max_tokens,
@@ -746,6 +747,7 @@ fn spawn_turn(state: &AppStateRest) {
             max_tokens,
             abort_flag,
             hive_mind_converged,
+            concise_output,
         };
         let result = run_agent_turn(&tc, &messages, &events_q);
         if let Err(e) = result {
@@ -778,6 +780,10 @@ struct TurnCtx {
     /// of this turn — whether a hive-mind convergence already completed
     /// earlier in this session.
     hive_mind_converged: bool,
+    /// Snapshot of `Settings.concise_output` taken at the start of this
+    /// turn, so the system-prompt assembly above can read it without
+    /// `TurnCtx` needing a `Settings` reference.
+    concise_output: bool,
 }
 
 /// Build an ASCII tree of the workspace directory structure for the
@@ -964,12 +970,23 @@ fn run_agent_turn(
     // workspace tree and reads all memory files each time).
     let tree_info = generate_workspace_tree(&tc.workspace_roots);
     let memory_section = build_memory_section(&tc.ctx.memory_dir);
+    let concise_section = if tc.concise_output {
+        "\n\nWrite tersely: drop articles (a/an/the), filler words (just/really/basically/\
+         actually/simply), pleasantries (sure/certainly/of course/happy to), and hedging. \
+         Fragments are fine. Code, commands, file paths, and error text must stay byte-exact \
+         — never abbreviate or paraphrase those. Exception: for destructive-operation \
+         confirmations and security-relevant warnings, always give full detail regardless of \
+         this instruction — clarity matters more than brevity when something risky is at stake."
+    } else {
+        ""
+    };
     let system_text = format!(
-        "{}\n\n{}\n\n{}{}",
+        "{}\n\n{}\n\n{}{}{}",
         crate::resources::SYSTEM_PROMPT,
         crate::resources::SYSTEM_TOOLS,
         tree_info,
         memory_section,
+        concise_section,
     );
     if !msgs.iter().any(|m| matches!(m.role, crate::dto::chat::message::Role::System)) {
         let sys = ChatMessage::system(system_text);
diff --git a/src/model/settings.rs b/src/model/settings.rs
index 41122f7..aa6b960 100644
--- a/src/model/settings.rs
+++ b/src/model/settings.rs
@@ -50,6 +50,14 @@ pub struct Settings {
     /// entire hive-mind convergence forever.
     #[serde(default = "default_hive_mind_node_timeout_ms")]
     pub hive_mind_node_timeout_ms: u64,
+    /// Off by default. When enabled, appends an instruction to the
+    /// system prompt asking the model to write tersely — drop articles,
+    /// filler words, hedging, and pleasantries; keep code, commands, and
+    /// error text byte-exact — with an explicit exception for
+    /// destructive-operation confirmations and security warnings, which
+    /// always get full detail regardless of this setting.
+    #[serde(default)]
+    pub concise_output: bool,
 }
 
 impl Default for Settings {
@@ -71,6 +79,7 @@ impl Default for Settings {
             lsp_auto_provision: true,
             lsp_languages: Vec::new(),
             hive_mind_node_timeout_ms: default_hive_mind_node_timeout_ms(),
+            concise_output: false,
         }
     }
 }
@@ -123,6 +132,38 @@ mod tests {
         assert_eq!(settings.hive_mind_node_timeout_ms, 600_000);
     }
 
+    #[test]
+    fn concise_output_defaults_to_false() {
+        assert!(!Settings::default().concise_output);
+    }
+
+    #[test]
+    fn missing_concise_output_field_falls_back_to_default() {
+        // Simulates loading a settings.json written before this field
+        // existed — #[serde(default)] must fill it in rather than
+        // failing the whole parse.
+        let old_json = r#"{
+            "internet_mode": "Off",
+            "provider": "zen",
+            "model": "deepseek-v4-flash-free",
+            "api_keys": {},
+            "max_tokens": null,
+            "temperature": null,
+            "review_enabled": true,
+            "review_max_lessons_per_run": 5,
+            "adaptive_review_max_skip": 3,
+            "verify_command": null,
+            "verify_timeout_ms": 30000,
+            "workflow_max_concurrency": 5,
+            "session_archive_enabled": true,
+            "lsp_auto_provision": true,
+            "lsp_languages": []
+        }"#;
+        let parsed: Settings = serde_json::from_str(old_json)
+            .expect("must parse even without the new field present");
+        assert!(!parsed.concise_output);
+    }
+
     #[test]
     fn missing_hive_mind_node_timeout_field_falls_back_to_default() {
         // Simulates loading a settings.json written before this field