[codex] Remove legacy shell output formatting paths (#22706)

## Why

The client and tool pipeline still carried compatibility code for legacy
structured shell output. Current shell and apply_patch responses are
already plain text for model consumption, so keeping a
JSON-serialization path plus shell-item rewrite logic makes the request
formatter and tests preserve a format we do not need anymore.

## What Changed

- Removed the client-side shell output rewrite from
`core/src/client_common.rs`.
- Removed the structured exec-output formatter and the shell `freeform`
switch so tool emitters use one model-facing formatter.
- Collapsed apply_patch/shell serialization tests around the remaining
plain-text output expectations and removed duplicate one-variant
parameterized cases.
- Kept the `ApplyPatchModelOutput::ShellCommandViaHeredoc` compatibility
input shape, but no longer treats it as a separate output-format mode.

## Validation

- `cargo test -p codex-core client_common`
- `cargo test -p codex-core shell_serialization`
- `cargo test -p codex-core apply_patch_cli`
- `just fix -p codex-core`

## Documentation

No external Codex documentation update is needed.

codex-rs/core/src/client_common.rs

@@ -2,13 +2,10 @@ pub use codex_api::ResponseEvent;
 use codex_config::types::Personality;
 use codex_protocol::error::Result;
 use codex_protocol::models::BaseInstructions;
-use codex_protocol::models::FunctionCallOutputBody;
 use codex_protocol::models::ResponseItem;
 use codex_tools::ToolSpec;
 use futures::Stream;
-use serde::Deserialize;
 use serde_json::Value;
-use std::collections::HashSet;
 use std::pin::Pin;
 use std::task::Context;
 use std::task::Poll;
@@ -64,116 +61,10 @@ impl Default for Prompt {
 
 impl Prompt {
     pub(crate) fn get_formatted_input(&self) -> Vec<ResponseItem> {
-        let mut input = self.input.clone();
-
-        // when using the *Freeform* apply_patch tool specifically, tool outputs
-        // should be structured text, not json. Do NOT reserialize when using
-        // the Function tool - note that this differs from the check above for
-        // instructions. We declare the result as a named variable for clarity.
-        let is_freeform_apply_patch_tool_present = self.tools.iter().any(|tool| match tool {
-            ToolSpec::Freeform(f) => f.name == "apply_patch",
-            _ => false,
-        });
-        if is_freeform_apply_patch_tool_present {
-            reserialize_shell_outputs(&mut input);
-        }
-
-        input
+        self.input.clone()
     }
 }
 
-fn reserialize_shell_outputs(items: &mut [ResponseItem]) {
-    let mut shell_call_ids: HashSet<String> = HashSet::new();
-
-    items.iter_mut().for_each(|item| match item {
-        ResponseItem::LocalShellCall { call_id, id, .. } => {
-            if let Some(identifier) = call_id.clone().or_else(|| id.clone()) {
-                shell_call_ids.insert(identifier);
-            }
-        }
-        ResponseItem::CustomToolCall {
-            id: _,
-            status: _,
-            call_id,
-            name,
-            input: _,
-        } => {
-            if name == "apply_patch" {
-                shell_call_ids.insert(call_id.clone());
-            }
-        }
-        ResponseItem::FunctionCall { name, call_id, .. }
-            if is_shell_tool_name(name) || name == "apply_patch" =>
-        {
-            shell_call_ids.insert(call_id.clone());
-        }
-        ResponseItem::FunctionCallOutput {
-            call_id, output, ..
-        }
-        | ResponseItem::CustomToolCallOutput {
-            call_id, output, ..
-        } => {
-            if shell_call_ids.remove(call_id)
-                && let Some(structured) = output
-                    .text_content()
-                    .and_then(parse_structured_shell_output)
-            {
-                output.body = FunctionCallOutputBody::Text(structured);
-            }
-        }
-        _ => {}
-    })
-}
-
-fn is_shell_tool_name(name: &str) -> bool {
-    name == "shell"
-}
-
-#[derive(Deserialize)]
-struct ExecOutputJson {
-    output: String,
-    metadata: ExecOutputMetadataJson,
-}
-
-#[derive(Deserialize)]
-struct ExecOutputMetadataJson {
-    exit_code: i32,
-    duration_seconds: f32,
-}
-
-fn parse_structured_shell_output(raw: &str) -> Option<String> {
-    let parsed: ExecOutputJson = serde_json::from_str(raw).ok()?;
-    Some(build_structured_output(&parsed))
-}
-
-fn build_structured_output(parsed: &ExecOutputJson) -> String {
-    let mut sections = Vec::new();
-    sections.push(format!("Exit code: {}", parsed.metadata.exit_code));
-    sections.push(format!(
-        "Wall time: {} seconds",
-        parsed.metadata.duration_seconds
-    ));
-
-    let mut output = parsed.output.clone();
-    if let Some((stripped, total_lines)) = strip_total_output_header(&parsed.output) {
-        sections.push(format!("Total output lines: {total_lines}"));
-        output = stripped.to_string();
-    }
-
-    sections.push("Output:".to_string());
-    sections.push(output);
-
-    sections.join("\n")
-}
-
-fn strip_total_output_header(output: &str) -> Option<(&str, u32)> {
-    let after_prefix = output.strip_prefix("Total output lines: ")?;
-    let (total_segment, remainder) = after_prefix.split_once('\n')?;
-    let total_lines = total_segment.parse::<u32>().ok()?;
-    let remainder = remainder.strip_prefix('\n').unwrap_or(remainder);
-    Some((remainder, total_lines))
-}
-
 pub struct ResponseStream {
     pub(crate) rx_event: mpsc::Receiver<Result<ResponseEvent>>,
     /// Signals the mapper task that the consumer stopped polling before the

codex-rs/core/src/client_common_tests.rs

@@ -3,7 +3,6 @@ use codex_api::ResponsesApiRequest;
 use codex_api::TextControls;
 use codex_api::create_text_param_for_request;
 use codex_protocol::config_types::ServiceTier;
-use codex_protocol::models::FunctionCallOutputPayload;
 use pretty_assertions::assert_eq;
 
 use super::*;
@@ -166,65 +165,3 @@ fn serializes_flex_service_tier_when_set() {
         Some("flex")
     );
 }
-
-#[test]
-fn reserializes_shell_outputs_for_function_and_custom_tool_calls() {
-    let raw_output = r#"{"output":"hello","metadata":{"exit_code":0,"duration_seconds":0.5}}"#;
-    let expected_output = "Exit code: 0\nWall time: 0.5 seconds\nOutput:\nhello";
-    let mut items = vec![
-        ResponseItem::FunctionCall {
-            id: None,
-            name: "shell".to_string(),
-            namespace: None,
-            arguments: "{}".to_string(),
-            call_id: "call-1".to_string(),
-        },
-        ResponseItem::FunctionCallOutput {
-            call_id: "call-1".to_string(),
-            output: FunctionCallOutputPayload::from_text(raw_output.to_string()),
-        },
-        ResponseItem::CustomToolCall {
-            id: None,
-            status: None,
-            call_id: "call-2".to_string(),
-            name: "apply_patch".to_string(),
-            input: "*** Begin Patch".to_string(),
-        },
-        ResponseItem::CustomToolCallOutput {
-            call_id: "call-2".to_string(),
-            name: None,
-            output: FunctionCallOutputPayload::from_text(raw_output.to_string()),
-        },
-    ];
-
-    reserialize_shell_outputs(&mut items);
-
-    assert_eq!(
-        items,
-        vec![
-            ResponseItem::FunctionCall {
-                id: None,
-                name: "shell".to_string(),
-                namespace: None,
-                arguments: "{}".to_string(),
-                call_id: "call-1".to_string(),
-            },
-            ResponseItem::FunctionCallOutput {
-                call_id: "call-1".to_string(),
-                output: FunctionCallOutputPayload::from_text(expected_output.to_string()),
-            },
-            ResponseItem::CustomToolCall {
-                id: None,
-                status: None,
-                call_id: "call-2".to_string(),
-                name: "apply_patch".to_string(),
-                input: "*** Begin Patch".to_string(),
-            },
-            ResponseItem::CustomToolCallOutput {
-                call_id: "call-2".to_string(),
-                name: None,
-                output: FunctionCallOutputPayload::from_text(expected_output.to_string()),
-            },
-        ]
-    );
-}

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

@@ -116,7 +116,6 @@ pub(crate) enum ToolEmitter {
         cwd: AbsolutePathBuf,
         source: ExecCommandSource,
         parsed_cmd: Vec<ParsedCommand>,
-        freeform: bool,
     },
     ApplyPatch {
         changes: HashMap<PathBuf, FileChange>,
@@ -132,19 +131,13 @@ pub(crate) enum ToolEmitter {
 }
 
 impl ToolEmitter {
-    pub fn shell(
-        command: Vec<String>,
-        cwd: AbsolutePathBuf,
-        source: ExecCommandSource,
-        freeform: bool,
-    ) -> Self {
+    pub fn shell(command: Vec<String>, cwd: AbsolutePathBuf, source: ExecCommandSource) -> Self {
         let parsed_cmd = parse_command(&command);
         Self::Shell {
             command,
             cwd,
             source,
             parsed_cmd,
-            freeform,
         }
     }
 
@@ -328,12 +321,7 @@ impl ToolEmitter {
         output: &ExecToolCallOutput,
         ctx: ToolEventCtx<'_>,
     ) -> 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_structured(output, ctx.turn.truncation_policy),
-        }
+        super::format_exec_output_for_model(output, ctx.turn.truncation_policy)
     }
 
     pub async fn finish(

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

@@ -52,7 +52,6 @@ struct RunExecLikeArgs {
     turn: Arc<TurnContext>,
     tracker: crate::tools::context::SharedTurnDiffTracker,
     call_id: String,
-    freeform: bool,
     shell_runtime_backend: ShellRuntimeBackend,
 }
 
@@ -68,7 +67,6 @@ async fn run_exec_like(args: RunExecLikeArgs) -> Result<FunctionToolOutput, Func
         turn,
         tracker,
         call_id,
-        freeform,
         shell_runtime_backend,
     } = args;
 
@@ -162,12 +160,7 @@ async fn run_exec_like(args: RunExecLikeArgs) -> Result<FunctionToolOutput, Func
     }
 
     let source = ExecCommandSource::Agent;
-    let emitter = ToolEmitter::shell(
-        exec_params.command.clone(),
-        exec_params.cwd.clone(),
-        source,
-        freeform,
-    );
+    let emitter = ToolEmitter::shell(exec_params.command.clone(), exec_params.cwd.clone(), source);
     let event_ctx = ToolEventCtx::new(
         session.as_ref(),
         turn.as_ref(),

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

@@ -197,7 +197,6 @@ impl ToolExecutor<ToolInvocation> for ShellCommandHandler {
             turn,
             tracker,
             call_id,
-            freeform: true,
             shell_runtime_backend: self.shell_runtime_backend(),
         })
         .await

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

@@ -23,7 +23,6 @@ use codex_utils_output_truncation::TruncationPolicy;
 use codex_utils_output_truncation::formatted_truncate_text;
 use codex_utils_output_truncation::truncate_text;
 pub use router::ToolRouter;
-use serde::Serialize;
 
 // Telemetry preview limits: keep log events smaller than model budgets.
 pub(crate) const TELEMETRY_PREVIEW_MAX_BYTES: usize = 2 * 1024; // 2 KiB
@@ -60,46 +59,7 @@ pub(crate) fn tool_user_shell_type(
 
 /// Format the combined exec output for sending back to the model.
 /// Includes exit code and duration metadata; truncates large bodies safely.
-pub fn format_exec_output_for_model_structured(
-    exec_output: &ExecToolCallOutput,
-    truncation_policy: TruncationPolicy,
-) -> String {
-    let ExecToolCallOutput {
-        exit_code,
-        duration,
-        ..
-    } = exec_output;
-
-    #[derive(Serialize)]
-    struct ExecMetadata {
-        exit_code: i32,
-        duration_seconds: f32,
-    }
-
-    #[derive(Serialize)]
-    struct ExecOutput<'a> {
-        output: &'a str,
-        metadata: ExecMetadata,
-    }
-
-    // round to 1 decimal place
-    let duration_seconds = ((duration.as_secs_f32()) * 10.0).round() / 10.0;
-
-    let formatted_output = format_exec_output_str(exec_output, truncation_policy);
-
-    let payload = ExecOutput {
-        output: &formatted_output,
-        metadata: ExecMetadata {
-            exit_code: *exit_code,
-            duration_seconds,
-        },
-    };
-
-    #[expect(clippy::expect_used)]
-    serde_json::to_string(&payload).expect("serialize ExecOutput")
-}
-
-pub fn format_exec_output_for_model_freeform(
+pub fn format_exec_output_for_model(
     exec_output: &ExecToolCallOutput,
     truncation_policy: TruncationPolicy,
 ) -> String {