flaky

codex-rs/app-server/src/codex_message_processor.rs

@@ -1173,6 +1173,8 @@ impl CodexMessageProcessor {
             with_escalated_permissions: None,
             justification: None,
             arg0: None,
+            max_output_tokens: None,
+            max_output_chars: None,
         };
 
         let effective_policy = params

codex-rs/core/src/codex.rs

@@ -3058,6 +3058,8 @@ mod tests {
             with_escalated_permissions: Some(true),
             justification: Some("test".to_string()),
             arg0: None,
+            max_output_tokens: None,
+            max_output_chars: None,
         };
 
         let params2 = ExecParams {

codex-rs/core/src/context_manager/history.rs

@@ -5,6 +5,7 @@ use crate::truncate::truncate_function_output_items_with_policy;
 use crate::truncate::truncate_text;
 use codex_protocol::models::FunctionCallOutputPayload;
 use codex_protocol::models::ResponseItem;
+use codex_protocol::models::ShellToolCallParams;
 use codex_protocol::protocol::TokenUsage;
 use codex_protocol::protocol::TokenUsageInfo;
 use codex_utils_tokenizer::Tokenizer;
@@ -135,6 +136,47 @@ impl ContextManager {
         normalize::remove_orphan_outputs(&mut self.items);
     }
 
+    fn get_shell_truncation_policy(&self, call_id: &str) -> Option<TruncationPolicy> {
+        let call = self.get_call_for_call_id(call_id)?;
+        match call {
+            ResponseItem::FunctionCall { arguments, .. } => {
+                let shell_tool_call_params =
+                    serde_json::from_str::<ShellToolCallParams>(&arguments).ok()?;
+                Self::create_truncation_policy(
+                    shell_tool_call_params.max_output_tokens,
+                    shell_tool_call_params.max_output_chars,
+                )
+            }
+            _ => None,
+        }
+    }
+
+    fn create_truncation_policy(
+        max_output_tokens: Option<usize>,
+        max_output_chars: Option<usize>,
+    ) -> Option<TruncationPolicy> {
+        if let Some(max_output_tokens) = max_output_tokens {
+            Some(TruncationPolicy::Tokens(max_output_tokens))
+        } else {
+            max_output_chars.map(TruncationPolicy::Bytes)
+        }
+    }
+
+    fn get_call_for_call_id(&self, call_id: &str) -> Option<ResponseItem> {
+        self.items.iter().find_map(|item| match item {
+            ResponseItem::FunctionCall {
+                call_id: existing, ..
+            } => {
+                if existing == call_id {
+                    Some(item.clone())
+                } else {
+                    None
+                }
+            }
+            _ => None,
+        })
+    }
+
     /// Returns a clone of the contents in the transcript.
     fn contents(&self) -> Vec<ResponseItem> {
         self.items.clone()
@@ -148,13 +190,12 @@ impl ContextManager {
         let policy_with_serialization_budget = policy.mul(1.2);
         match item {
             ResponseItem::FunctionCallOutput { call_id, output } => {
-                let truncated =
-                    truncate_text(output.content.as_str(), policy_with_serialization_budget);
+                let truncation_policy_override = self.get_shell_truncation_policy(call_id);
+                let truncation_policy =
+                    truncation_policy_override.unwrap_or(policy_with_serialization_budget);
+                let truncated = truncate_text(output.content.as_str(), truncation_policy);
                 let truncated_items = output.content_items.as_ref().map(|items| {
-                    truncate_function_output_items_with_policy(
-                        items,
-                        policy_with_serialization_budget,
-                    )
+                    truncate_function_output_items_with_policy(items, truncation_policy)
                 });
                 ResponseItem::FunctionCallOutput {
                     call_id: call_id.clone(),

codex-rs/core/src/exec.rs

@@ -55,6 +55,8 @@ pub struct ExecParams {
     pub with_escalated_permissions: Option<bool>,
     pub justification: Option<String>,
     pub arg0: Option<String>,
+    pub max_output_tokens: Option<usize>,
+    pub max_output_chars: Option<usize>,
 }
 
 impl ExecParams {
@@ -100,6 +102,8 @@ pub async fn process_exec_tool_call(
         with_escalated_permissions,
         justification,
         arg0: _,
+        max_output_tokens,
+        max_output_chars,
     } = params;
 
     let (program, args) = command.split_first().ok_or_else(|| {
@@ -117,6 +121,8 @@ pub async fn process_exec_tool_call(
         timeout_ms,
         with_escalated_permissions,
         justification,
+        max_output_tokens,
+        max_output_chars,
     };
 
     let manager = SandboxManager::new();
@@ -148,6 +154,8 @@ pub(crate) async fn execute_exec_env(
         with_escalated_permissions,
         justification,
         arg0,
+        max_output_tokens,
+        max_output_chars,
     } = env;
 
     let params = ExecParams {
@@ -158,6 +166,8 @@ pub(crate) async fn execute_exec_env(
         with_escalated_permissions,
         justification,
         arg0,
+        max_output_tokens,
+        max_output_chars,
     };
 
     let start = Instant::now();
@@ -794,6 +804,8 @@ mod tests {
             with_escalated_permissions: None,
             justification: None,
             arg0: None,
+            max_output_tokens: None,
+            max_output_chars: None,
         };
 
         let output = exec(params, SandboxType::None, &SandboxPolicy::ReadOnly, None).await?;

codex-rs/core/src/model_family.rs

@@ -76,6 +76,7 @@ macro_rules! model_family {
     (
         $slug:expr, $family:expr $(, $key:ident : $value:expr )* $(,)?
     ) => {{
+        let truncation_policy = TruncationPolicy::Bytes(10_000);
         // defaults
         #[allow(unused_mut)]
         let mut mf = ModelFamily {
@@ -90,10 +91,10 @@ macro_rules! model_family {
             experimental_supported_tools: Vec::new(),
             effective_context_window_percent: 95,
             support_verbosity: false,
-            shell_type: ConfigShellToolType::Default,
+            shell_type: ConfigShellToolType::Default(truncation_policy),
             default_verbosity: None,
             default_reasoning_effort: None,
-            truncation_policy: TruncationPolicy::Bytes(10_000),
+            truncation_policy,
         };
 
         // apply overrides
@@ -138,6 +139,7 @@ pub fn find_family_for_model(slug: &str) -> Option<ModelFamily> {
     } else if slug.starts_with("gpt-3.5") {
         model_family!(slug, "gpt-3.5", needs_special_apply_patch_instructions: true)
     } else if slug.starts_with("test-gpt-5") {
+        let truncation_policy = TruncationPolicy::Tokens(10_000);
         model_family!(
             slug, slug,
             supports_reasoning_summaries: true,
@@ -150,13 +152,13 @@ pub fn find_family_for_model(slug: &str) -> Option<ModelFamily> {
                 "test_sync_tool".to_string(),
             ],
             supports_parallel_tool_calls: true,
-            shell_type: ConfigShellToolType::ShellCommand,
+            shell_type: ConfigShellToolType::ShellCommand(truncation_policy),
             support_verbosity: true,
-            truncation_policy: TruncationPolicy::Tokens(10_000),
         )
 
     // Internal models.
     } else if slug.starts_with("codex-exp-") {
+        let truncation_policy = TruncationPolicy::Tokens(10_000);
         model_family!(
             slug, slug,
             supports_reasoning_summaries: true,
@@ -168,41 +170,44 @@ pub fn find_family_for_model(slug: &str) -> Option<ModelFamily> {
                 "list_dir".to_string(),
                 "read_file".to_string(),
             ],
-            shell_type: ConfigShellToolType::ShellCommand,
+            shell_type: ConfigShellToolType::ShellCommand(truncation_policy),
             supports_parallel_tool_calls: true,
             support_verbosity: true,
-            truncation_policy: TruncationPolicy::Tokens(10_000),
+            truncation_policy: truncation_policy,
         )
 
     // Production models.
     } else if slug.starts_with("gpt-5.1-codex-max") {
+        let truncation_policy = TruncationPolicy::Tokens(10_000);
         model_family!(
             slug, slug,
             supports_reasoning_summaries: true,
             reasoning_summary_format: ReasoningSummaryFormat::Experimental,
             base_instructions: GPT_5_1_CODEX_MAX_INSTRUCTIONS.to_string(),
             apply_patch_tool_type: Some(ApplyPatchToolType::Freeform),
-            shell_type: ConfigShellToolType::ShellCommand,
+            shell_type: ConfigShellToolType::ShellCommand(truncation_policy),
             supports_parallel_tool_calls: true,
             support_verbosity: false,
-            truncation_policy: TruncationPolicy::Tokens(10_000),
+            truncation_policy: truncation_policy,
         )
     } else if slug.starts_with("gpt-5-codex")
         || slug.starts_with("gpt-5.1-codex")
         || slug.starts_with("codex-")
     {
+        let truncation_policy = TruncationPolicy::Tokens(10_000);
         model_family!(
             slug, slug,
             supports_reasoning_summaries: true,
             reasoning_summary_format: ReasoningSummaryFormat::Experimental,
             base_instructions: GPT_5_CODEX_INSTRUCTIONS.to_string(),
             apply_patch_tool_type: Some(ApplyPatchToolType::Freeform),
-            shell_type: ConfigShellToolType::ShellCommand,
+            shell_type: ConfigShellToolType::ShellCommand(truncation_policy),
             supports_parallel_tool_calls: true,
             support_verbosity: false,
-            truncation_policy: TruncationPolicy::Tokens(10_000),
+            truncation_policy: truncation_policy,
         )
     } else if slug.starts_with("gpt-5.1") {
+        let truncation_policy = TruncationPolicy::Tokens(10_000);
         model_family!(
             slug, "gpt-5.1",
             supports_reasoning_summaries: true,
@@ -212,7 +217,7 @@ pub fn find_family_for_model(slug: &str) -> Option<ModelFamily> {
             base_instructions: GPT_5_1_INSTRUCTIONS.to_string(),
             default_reasoning_effort: Some(ReasoningEffort::Medium),
             truncation_policy: TruncationPolicy::Bytes(10_000),
-            shell_type: ConfigShellToolType::ShellCommand,
+            shell_type: ConfigShellToolType::ShellCommand(truncation_policy),
             supports_parallel_tool_calls: true,
         )
     } else if slug.starts_with("gpt-5") {
@@ -220,7 +225,7 @@ pub fn find_family_for_model(slug: &str) -> Option<ModelFamily> {
             slug, "gpt-5",
             supports_reasoning_summaries: true,
             needs_special_apply_patch_instructions: true,
-            shell_type: ConfigShellToolType::Default,
+            shell_type: ConfigShellToolType::Default(TruncationPolicy::Bytes(10_000)),
             support_verbosity: true,
             truncation_policy: TruncationPolicy::Bytes(10_000),
         )
@@ -230,6 +235,7 @@ pub fn find_family_for_model(slug: &str) -> Option<ModelFamily> {
 }
 
 pub fn derive_default_model_family(model: &str) -> ModelFamily {
+    let truncation_policy = TruncationPolicy::Bytes(10_000);
     ModelFamily {
         slug: model.to_string(),
         family: model.to_string(),
@@ -242,9 +248,9 @@ pub fn derive_default_model_family(model: &str) -> ModelFamily {
         experimental_supported_tools: Vec::new(),
         effective_context_window_percent: 95,
         support_verbosity: false,
-        shell_type: ConfigShellToolType::Default,
+        shell_type: ConfigShellToolType::Default(truncation_policy),
         default_verbosity: None,
         default_reasoning_effort: None,
-        truncation_policy: TruncationPolicy::Bytes(10_000),
+        truncation_policy,
     }
 }

codex-rs/core/src/sandboxing/mod.rs

@@ -35,6 +35,8 @@ pub struct CommandSpec {
     pub timeout_ms: Option<u64>,
     pub with_escalated_permissions: Option<bool>,
     pub justification: Option<String>,
+    pub max_output_tokens: Option<usize>,
+    pub max_output_chars: Option<usize>,
 }
 
 #[derive(Clone, Debug)]
@@ -47,6 +49,8 @@ pub struct ExecEnv {
     pub with_escalated_permissions: Option<bool>,
     pub justification: Option<String>,
     pub arg0: Option<String>,
+    pub max_output_tokens: Option<usize>,
+    pub max_output_chars: Option<usize>,
 }
 
 pub enum SandboxPreference {
@@ -161,6 +165,8 @@ impl SandboxManager {
             with_escalated_permissions: spec.with_escalated_permissions,
             justification: spec.justification.clone(),
             arg0: arg0_override,
+            max_output_tokens: spec.max_output_tokens,
+            max_output_chars: spec.max_output_chars,
         })
     }
 

codex-rs/core/src/tasks/user_shell.rs

@@ -98,6 +98,8 @@ impl SessionTask for UserShellCommandTask {
             with_escalated_permissions: None,
             justification: None,
             arg0: None,
+            max_output_tokens: None,
+            max_output_chars: None,
         };
 
         let stdout_stream = Some(StdoutStream {

codex-rs/core/src/tools/events.rs

@@ -15,6 +15,8 @@ use crate::protocol::PatchApplyEndEvent;
 use crate::protocol::TurnDiffEvent;
 use crate::tools::context::SharedTurnDiffTracker;
 use crate::tools::sandboxing::ToolError;
+use crate::truncate::TruncationPolicy;
+use crate::truncate::formatted_truncate_text;
 use codex_protocol::parse_command::ParsedCommand;
 use std::collections::HashMap;
 use std::path::Path;
@@ -29,6 +31,7 @@ pub(crate) struct ToolEventCtx<'a> {
     pub turn: &'a TurnContext,
     pub call_id: &'a str,
     pub turn_diff_tracker: Option<&'a SharedTurnDiffTracker>,
+    pub override_truncation_policy: Option<&'a TruncationPolicy>,
 }
 
 impl<'a> ToolEventCtx<'a> {
@@ -37,12 +40,14 @@ impl<'a> ToolEventCtx<'a> {
         turn: &'a TurnContext,
         call_id: &'a str,
         turn_diff_tracker: Option<&'a SharedTurnDiffTracker>,
+        override_truncation_policy: Option<&'a TruncationPolicy>,
     ) -> Self {
         Self {
             session,
             turn,
             call_id,
             turn_diff_tracker,
+            override_truncation_policy,
         }
     }
 }
@@ -245,13 +250,13 @@ impl ToolEmitter {
     fn format_exec_output_for_model(
         &self,
         output: &ExecToolCallOutput,
-        ctx: ToolEventCtx<'_>,
+        truncation_policy: &TruncationPolicy,
     ) -> String {
         match self {
             Self::Shell { freeform: true, .. } => {
-                super::format_exec_output_for_model_freeform(output, ctx.turn.truncation_policy)
+                super::format_exec_output_for_model_freeform(output, *truncation_policy)
             }
-            _ => super::format_exec_output_for_model_structured(output, ctx.turn.truncation_policy),
+            _ => super::format_exec_output_for_model_structured(output, *truncation_policy),
         }
     }
 
@@ -260,9 +265,12 @@ impl ToolEmitter {
         ctx: ToolEventCtx<'_>,
         out: Result<ExecToolCallOutput, ToolError>,
     ) -> Result<String, FunctionCallError> {
+        let truncation_policy = ctx
+            .override_truncation_policy
+            .unwrap_or(&ctx.turn.truncation_policy);
         let (event, result) = match out {
             Ok(output) => {
-                let content = self.format_exec_output_for_model(&output, ctx);
+                let content = self.format_exec_output_for_model(&output, truncation_policy);
                 let exit_code = output.exit_code;
                 let event = ToolEventStage::Success(output);
                 let result = if exit_code == 0 {
@@ -274,24 +282,26 @@ impl ToolEmitter {
             }
             Err(ToolError::Codex(CodexErr::Sandbox(SandboxErr::Timeout { output })))
             | Err(ToolError::Codex(CodexErr::Sandbox(SandboxErr::Denied { output }))) => {
-                let response = self.format_exec_output_for_model(&output, ctx);
+                let response = self.format_exec_output_for_model(&output, truncation_policy);
                 let event = ToolEventStage::Failure(ToolEventFailure::Output(*output));
                 let result = Err(FunctionCallError::RespondToModel(response));
                 (event, result)
             }
             Err(ToolError::Codex(err)) => {
-                let message = format!("execution error: {err:?}");
-                let event = ToolEventStage::Failure(ToolEventFailure::Message(message.clone()));
-                let result = Err(FunctionCallError::RespondToModel(message));
+                let formatted_error = formatted_truncate_text(&err.to_string(), *truncation_policy);
+                let message = format!("execution error: {formatted_error}");
+                let event = ToolEventStage::Failure(ToolEventFailure::Message(message));
+                let result = Err(FunctionCallError::RespondToModel(formatted_error));
                 (event, result)
             }
             Err(ToolError::Rejected(msg)) => {
+                let formatted_msg = formatted_truncate_text(&msg, *truncation_policy);
                 // Normalize common rejection messages for exec tools so tests and
                 // users see a clear, consistent phrase.
-                let normalized = if msg == "rejected by user" {
+                let normalized = if formatted_msg == "rejected by user" {
                     "exec command rejected by user".to_string()
                 } else {
-                    msg
+                    formatted_msg
                 };
                 let event = ToolEventStage::Failure(ToolEventFailure::Message(normalized.clone()));
                 let result = Err(FunctionCallError::RespondToModel(normalized));

codex-rs/core/src/tools/handlers/apply_patch.rs

@@ -100,6 +100,7 @@ impl ToolHandler for ApplyPatchHandler {
                             turn.as_ref(),
                             &call_id,
                             Some(&tracker),
+                            None,
                         );
                         emitter.begin(event_ctx).await;
 
@@ -127,6 +128,7 @@ impl ToolHandler for ApplyPatchHandler {
                             turn.as_ref(),
                             &call_id,
                             Some(&tracker),
+                            None,
                         );
                         let content = emitter.finish(event_ctx, out).await?;
                         Ok(ToolOutput::Function {

codex-rs/core/src/tools/handlers/shell.rs

@@ -25,6 +25,7 @@ use crate::tools::runtimes::apply_patch::ApplyPatchRuntime;
 use crate::tools::runtimes::shell::ShellRequest;
 use crate::tools::runtimes::shell::ShellRuntime;
 use crate::tools::sandboxing::ToolCtx;
+use crate::truncate::TruncationPolicy;
 
 pub struct ShellHandler;
 
@@ -40,6 +41,8 @@ impl ShellHandler {
             with_escalated_permissions: params.with_escalated_permissions,
             justification: params.justification,
             arg0: None,
+            max_output_tokens: params.max_output_tokens,
+            max_output_chars: params.max_output_chars,
         }
     }
 }
@@ -62,6 +65,8 @@ impl ShellCommandHandler {
             with_escalated_permissions: params.with_escalated_permissions,
             justification: params.justification,
             arg0: None,
+            max_output_tokens: params.max_output_tokens,
+            max_output_chars: params.max_output_chars,
         }
     }
 }
@@ -207,6 +212,9 @@ impl ShellHandler {
             )));
         }
 
+        let override_truncation_policy =
+            create_truncation_policy(exec_params.max_output_tokens, exec_params.max_output_chars);
+
         // Intercept apply_patch if present.
         match codex_apply_patch::maybe_parse_apply_patch_verified(
             &exec_params.command,
@@ -235,6 +243,7 @@ impl ShellHandler {
                             turn.as_ref(),
                             &call_id,
                             Some(&tracker),
+                            override_truncation_policy.as_ref(),
                         );
                         emitter.begin(event_ctx).await;
 
@@ -261,6 +270,7 @@ impl ShellHandler {
                             turn.as_ref(),
                             &call_id,
                             Some(&tracker),
+                            override_truncation_policy.as_ref(),
                         );
                         let content = emitter.finish(event_ctx, out).await?;
                         return Ok(ToolOutput::Function {
@@ -292,7 +302,13 @@ impl ShellHandler {
             source,
             freeform,
         );
-        let event_ctx = ToolEventCtx::new(session.as_ref(), turn.as_ref(), &call_id, None);
+        let event_ctx = ToolEventCtx::new(
+            session.as_ref(),
+            turn.as_ref(),
+            &call_id,
+            None,
+            override_truncation_policy.as_ref(),
+        );
         emitter.begin(event_ctx).await;
 
         let req = ShellRequest {
@@ -302,6 +318,8 @@ impl ShellHandler {
             env: exec_params.env.clone(),
             with_escalated_permissions: exec_params.with_escalated_permissions,
             justification: exec_params.justification.clone(),
+            max_output_tokens: exec_params.max_output_tokens,
+            max_output_chars: exec_params.max_output_chars,
         };
         let mut orchestrator = ToolOrchestrator::new();
         let mut runtime = ShellRuntime::new();
@@ -314,7 +332,13 @@ impl ShellHandler {
         let out = orchestrator
             .run(&mut runtime, &req, &tool_ctx, &turn, turn.approval_policy)
             .await;
-        let event_ctx = ToolEventCtx::new(session.as_ref(), turn.as_ref(), &call_id, None);
+        let event_ctx = ToolEventCtx::new(
+            session.as_ref(),
+            turn.as_ref(),
+            &call_id,
+            None,
+            override_truncation_policy.as_ref(),
+        );
         let content = emitter.finish(event_ctx, out).await?;
         Ok(ToolOutput::Function {
             content,
@@ -324,6 +348,16 @@ impl ShellHandler {
     }
 }
 
+fn create_truncation_policy(
+    max_output_tokens: Option<usize>,
+    max_output_chars: Option<usize>,
+) -> Option<TruncationPolicy> {
+    if let Some(max_output_tokens) = max_output_tokens {
+        Some(TruncationPolicy::Tokens(max_output_tokens))
+    } else {
+        max_output_chars.map(TruncationPolicy::Bytes)
+    }
+}
 #[cfg(test)]
 mod tests {
     use std::path::PathBuf;

codex-rs/core/src/tools/handlers/unified_exec.rs

@@ -162,6 +162,7 @@ impl ToolHandler for UnifiedExecHandler {
                     context.turn.as_ref(),
                     &context.call_id,
                     None,
+                    None,
                 );
                 let emitter = ToolEmitter::unified_exec(
                     &command,

codex-rs/core/src/tools/router.rs

@@ -116,6 +116,8 @@ impl ToolRouter {
                             timeout_ms: exec.timeout_ms,
                             with_escalated_permissions: None,
                             justification: None,
+                            max_output_tokens: None,
+                            max_output_chars: None,
                         };
                         Ok(Some(ToolCall {
                             tool_name: "local_shell".to_string(),

codex-rs/core/src/tools/runtimes/apply_patch.rs

@@ -72,6 +72,8 @@ impl ApplyPatchRuntime {
             env: HashMap::new(),
             with_escalated_permissions: None,
             justification: None,
+            max_output_tokens: None,
+            max_output_chars: None,
         })
     }
 

codex-rs/core/src/tools/runtimes/mod.rs

@@ -15,6 +15,7 @@ pub mod unified_exec;
 
 /// Shared helper to construct a CommandSpec from a tokenized command line.
 /// Validates that at least a program is present.
+#[allow(clippy::too_many_arguments)]
 pub(crate) fn build_command_spec(
     command: &[String],
     cwd: &Path,
@@ -22,6 +23,8 @@ pub(crate) fn build_command_spec(
     timeout_ms: Option<u64>,
     with_escalated_permissions: Option<bool>,
     justification: Option<String>,
+    max_output_tokens: Option<usize>,
+    max_output_chars: Option<usize>,
 ) -> Result<CommandSpec, ToolError> {
     let (program, args) = command
         .split_first()
@@ -34,5 +37,7 @@ pub(crate) fn build_command_spec(
         timeout_ms,
         with_escalated_permissions,
         justification,
+        max_output_tokens,
+        max_output_chars,
     })
 }

codex-rs/core/src/tools/runtimes/shell.rs

@@ -33,6 +33,8 @@ pub struct ShellRequest {
     pub env: std::collections::HashMap<String, String>,
     pub with_escalated_permissions: Option<bool>,
     pub justification: Option<String>,
+    pub max_output_tokens: Option<usize>,
+    pub max_output_chars: Option<usize>,
 }
 
 impl ProvidesSandboxRetryData for ShellRequest {
@@ -147,6 +149,8 @@ impl ToolRuntime<ShellRequest, ExecToolCallOutput> for ShellRuntime {
             req.timeout_ms,
             req.with_escalated_permissions,
             req.justification.clone(),
+            req.max_output_tokens,
+            req.max_output_chars,
         )?;
         let env = attempt
             .env_for(&spec)

codex-rs/core/src/tools/runtimes/unified_exec.rs

@@ -36,6 +36,8 @@ pub struct UnifiedExecRequest {
     pub env: HashMap<String, String>,
     pub with_escalated_permissions: Option<bool>,
     pub justification: Option<String>,
+    pub max_output_tokens: Option<usize>,
+    pub max_output_chars: Option<usize>,
 }
 
 impl ProvidesSandboxRetryData for UnifiedExecRequest {
@@ -72,6 +74,8 @@ impl UnifiedExecRequest {
             env,
             with_escalated_permissions,
             justification,
+            max_output_tokens: None,
+            max_output_chars: None,
         }
     }
 }
@@ -162,6 +166,8 @@ impl<'a> ToolRuntime<UnifiedExecRequest, UnifiedExecSession> for UnifiedExecRunt
             None,
             req.with_escalated_permissions,
             req.justification.clone(),
+            req.max_output_tokens,
+            req.max_output_chars,
         )
         .map_err(|_| ToolError::Rejected("missing command line for PTY".to_string()))?;
         let exec_env = attempt

codex-rs/core/src/tools/spec.rs

@@ -8,6 +8,7 @@ use crate::tools::handlers::apply_patch::ApplyPatchToolType;
 use crate::tools::handlers::apply_patch::create_apply_patch_freeform_tool;
 use crate::tools::handlers::apply_patch::create_apply_patch_json_tool;
 use crate::tools::registry::ToolRegistryBuilder;
+use crate::truncate::TruncationPolicy;
 use serde::Deserialize;
 use serde::Serialize;
 use serde_json::Value as JsonValue;
@@ -17,7 +18,7 @@ use std::collections::HashMap;
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub enum ConfigShellToolType {
-    Default,
+    Default(TruncationPolicy),
     Local,
     UnifiedExec,
     /// Do not include a shell tool by default. Useful when using Codex
@@ -26,7 +27,7 @@ pub enum ConfigShellToolType {
     /// to customize agent behavior.
     Disabled,
     /// Takes a command as a single string to be run in the user's default shell.
-    ShellCommand,
+    ShellCommand(TruncationPolicy),
 }
 
 #[derive(Debug, Clone)]
@@ -58,7 +59,7 @@ impl ToolsConfig {
         } else if features.enabled(Feature::UnifiedExec) {
             ConfigShellToolType::UnifiedExec
         } else if features.enabled(Feature::ShellCommandTool) {
-            ConfigShellToolType::ShellCommand
+            ConfigShellToolType::ShellCommand(model_family.truncation_policy)
         } else {
             model_family.shell_type.clone()
         };
@@ -266,7 +267,7 @@ fn create_write_stdin_tool() -> ToolSpec {
     })
 }
 
-fn create_shell_tool() -> ToolSpec {
+fn create_shell_tool(truncation_policy: TruncationPolicy) -> ToolSpec {
     let mut properties = BTreeMap::new();
     properties.insert(
         "command".to_string(),
@@ -300,6 +301,24 @@ fn create_shell_tool() -> ToolSpec {
             description: Some("Only set if with_escalated_permissions is true. 1-sentence explanation of why we want to run this command.".to_string()),
         },
     );
+    match truncation_policy {
+        TruncationPolicy::Tokens(_) => {
+            properties.insert(
+                "max_output_tokens".to_string(),
+                JsonSchema::Number {
+                    description: Some("Maximum number of tokens to return from stdout/stderr. Excess tokens will be truncated".to_string()),
+                },
+            );
+        }
+        TruncationPolicy::Bytes(_) => {
+            properties.insert(
+                "max_output_chars".to_string(),
+                JsonSchema::Number {
+                    description: Some("Maximum number of characters to return from stdout/stderr. Excess characters will be truncated".to_string()),
+                },
+            );
+        }
+    }
 
     let description  = if cfg!(windows) {
         r#"Runs a Powershell command (Windows) and returns its output. Arguments to `shell` will be passed to CreateProcessW(). Most commands should be prefixed with ["powershell.exe", "-Command"].
@@ -330,7 +349,7 @@ Examples of valid command strings:
     })
 }
 
-fn create_shell_command_tool() -> ToolSpec {
+fn create_shell_command_tool(truncation_policy: TruncationPolicy) -> ToolSpec {
     let mut properties = BTreeMap::new();
     properties.insert(
         "command".to_string(),
@@ -364,6 +383,30 @@ fn create_shell_command_tool() -> ToolSpec {
             description: Some("Only set if with_escalated_permissions is true. 1-sentence explanation of why we want to run this command.".to_string()),
         },
     );
+    match truncation_policy {
+        TruncationPolicy::Tokens(_) => {
+            properties.insert(
+                "max_output_tokens".to_string(),
+                JsonSchema::Number {
+                    description: Some(
+                        "Maximum number of tokens to return. Excess output will be truncated."
+                            .to_string(),
+                    ),
+                },
+            );
+        }
+        TruncationPolicy::Bytes(_) => {
+            properties.insert(
+                "max_output_chars".to_string(),
+                JsonSchema::Number {
+                    description: Some(
+                        "Maximum number of tokens to return. Excess output will be truncated."
+                            .to_string(),
+                    ),
+                },
+            );
+        }
+    }
 
     let description = if cfg!(windows) {
         r#"Runs a Powershell command (Windows) and returns its output.
@@ -1001,8 +1044,8 @@ pub(crate) fn build_specs(
     let shell_command_handler = Arc::new(ShellCommandHandler);
 
     match &config.shell_type {
-        ConfigShellToolType::Default => {
-            builder.push_spec(create_shell_tool());
+        ConfigShellToolType::Default(truncation_policy) => {
+            builder.push_spec(create_shell_tool(*truncation_policy));
         }
         ConfigShellToolType::Local => {
             builder.push_spec(ToolSpec::LocalShell {});
@@ -1016,8 +1059,8 @@ pub(crate) fn build_specs(
         ConfigShellToolType::Disabled => {
             // Do nothing.
         }
-        ConfigShellToolType::ShellCommand => {
-            builder.push_spec(create_shell_command_tool());
+        ConfigShellToolType::ShellCommand(truncation_policy) => {
+            builder.push_spec(create_shell_command_tool(*truncation_policy));
         }
     }
 
@@ -1160,11 +1203,11 @@ mod tests {
 
     fn shell_tool_name(config: &ToolsConfig) -> Option<&'static str> {
         match config.shell_type {
-            ConfigShellToolType::Default => Some("shell"),
+            ConfigShellToolType::Default(_) => Some("shell"),
             ConfigShellToolType::Local => Some("local_shell"),
             ConfigShellToolType::UnifiedExec => None,
             ConfigShellToolType::Disabled => None,
-            ConfigShellToolType::ShellCommand => Some("shell_command"),
+            ConfigShellToolType::ShellCommand(_) => Some("shell_command"),
         }
     }
 
@@ -1926,7 +1969,7 @@ mod tests {
 
     #[test]
     fn test_shell_tool() {
-        let tool = super::create_shell_tool();
+        let tool = super::create_shell_tool(TruncationPolicy::Bytes(10_000));
         let ToolSpec::Function(ResponsesApiTool {
             description, name, ..
         }) = &tool
@@ -1956,7 +1999,7 @@ Examples of valid command strings:
 
     #[test]
     fn test_shell_command_tool() {
-        let tool = super::create_shell_command_tool();
+        let tool = super::create_shell_command_tool(TruncationPolicy::Tokens(10_000));
         let ToolSpec::Function(ResponsesApiTool {
             description, name, ..
         }) = &tool

codex-rs/core/src/unified_exec/session_manager.rs

@@ -149,6 +149,7 @@ impl UnifiedExecSessionManager {
                 turn_ref.as_ref(),
                 request.call_id,
                 None,
+                None,
             )
         };
         interaction_emitter
@@ -356,6 +357,7 @@ impl UnifiedExecSessionManager {
             entry.turn_ref.as_ref(),
             &entry.call_id,
             None,
+            None,
         );
         let emitter = ToolEmitter::unified_exec(
             &entry.command,
@@ -389,6 +391,7 @@ impl UnifiedExecSessionManager {
             context.turn.as_ref(),
             &context.call_id,
             None,
+            None,
         );
         let emitter =
             ToolEmitter::unified_exec(command, cwd, ExecCommandSource::UnifiedExecStartup, None);

codex-rs/core/tests/suite/exec.rs

@@ -37,6 +37,8 @@ async fn run_test_cmd(tmp: TempDir, cmd: Vec<&str>) -> Result<ExecToolCallOutput
         with_escalated_permissions: None,
         justification: None,
         arg0: None,
+        max_output_tokens: None,
+        max_output_chars: None,
     };
 
     let policy = SandboxPolicy::new_read_only_policy();

codex-rs/core/tests/suite/unified_exec.rs

@@ -1530,8 +1530,8 @@ async fn unified_exec_formats_large_output_summary() -> Result<()> {
     } = builder.build(&server).await?;
 
     let script = r#"python3 - <<'PY'
-for i in range(10000):
-    print("token token ")
+import sys
+sys.stdout.write("token token \n" * 500)
 PY
 "#;
 

codex-rs/exec-server/src/posix/escalate_server.rs

@@ -76,6 +76,8 @@ impl EscalateServer {
                 with_escalated_permissions: None,
                 justification: None,
                 arg0: None,
+                max_output_tokens: None,
+                max_output_chars: None,
             },
             get_platform_sandbox().unwrap_or(SandboxType::None),
             // TODO: use the sandbox policy and cwd from the calling client

codex-rs/protocol/src/models.rs

@@ -322,6 +322,10 @@ pub struct ShellToolCallParams {
     pub with_escalated_permissions: Option<bool>,
     #[serde(skip_serializing_if = "Option::is_none")]
     pub justification: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub max_output_tokens: Option<usize>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub max_output_chars: Option<usize>,
 }
 
 /// If the `name` of a `ResponseItem::FunctionCall` is `shell_command`, the
@@ -338,6 +342,10 @@ pub struct ShellCommandToolCallParams {
     pub with_escalated_permissions: Option<bool>,
     #[serde(skip_serializing_if = "Option::is_none")]
     pub justification: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub max_output_tokens: Option<usize>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub max_output_chars: Option<usize>,
 }
 
 /// Responses API compatible content items that can be returned by a tool call.
@@ -650,6 +658,8 @@ mod tests {
                 timeout_ms: Some(1000),
                 with_escalated_permissions: None,
                 justification: None,
+                max_output_tokens: None,
+                max_output_chars: None,
             },
             params
         );