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Stop output buffer resend in terminal_interaction stdin path #270

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Stop output buffer resend in terminal_interaction stdin path #270

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213a664
Fix O(N²) memory growth in exec_command_output_delta fallback
frozename May 8, 2026
3acb02c
Stop output buffer resend in terminal_interaction stdin path
frozename May 8, 2026
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100 changes: 48 additions & 52 deletions src/thread.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2029,8 +2029,8 @@ impl PromptState {
if let Some(active_command) = self.active_commands.get_mut(&call_id) {
let data_str = String::from_utf8_lossy(&chunk).to_string();

let update = if client.supports_terminal_output(active_command) {
ToolCallUpdate::new(
if client.supports_terminal_output(active_command) {
let update = ToolCallUpdate::new(
active_command.tool_call_id.clone(),
ToolCallUpdateFields::new(),
)
Expand All @@ -2040,27 +2040,15 @@ impl PromptState {
"terminal_id": call_id,
"data": data_str
}),
)]))
)]));
client.send_tool_call_update(update);
} else {
// Fallback path (no terminal_output capability): accumulate locally
// and emit a single ToolCallUpdate at exec_command_end. Resending the
// entire accumulated buffer per chunk is O(N²) memory and crashes the
// process on large outputs (issue #225).
active_command.output.push_str(&data_str);
let content = match active_command.file_extension.as_deref() {
Some("md") => active_command.output.clone(),
Some(ext) => format!(
"```{ext}\n{}\n```\n",
active_command.output.trim_end_matches('\n')
),
None => format!(
"```sh\n{}\n```\n",
active_command.output.trim_end_matches('\n')
),
};
ToolCallUpdate::new(
active_command.tool_call_id.clone(),
ToolCallUpdateFields::new().content(vec![content.into()]),
)
};

client.send_tool_call_update(update);
}
}
}

Expand Down Expand Up @@ -2092,15 +2080,35 @@ impl PromptState {
ExecCommandStatus::Failed | ExecCommandStatus::Declined => ToolCallStatus::Failed,
};

let supports_terminal = client.supports_terminal_output(&active_command);

let mut fields = ToolCallUpdateFields::new()
.status(status)
.raw_output(raw_output);

// For the non-terminal fallback path the per-chunk delta handler now
// accumulates silently (see exec_command_output_delta). Emit the full
// buffer here, exactly once, as a single content block. Skip the emission
// entirely when the command produced no output, so we don't surface an
// empty fenced code block to the client.
if !supports_terminal && !active_command.output.is_empty() {
let content = match active_command.file_extension.as_deref() {
Some("md") => active_command.output.clone(),
Some(ext) => format!(
"```{ext}\n{}\n```\n",
active_command.output.trim_end_matches('\n')
),
None => format!(
"```sh\n{}\n```\n",
active_command.output.trim_end_matches('\n')
),
};
fields = fields.content(vec![content.into()]);
}

client.send_tool_call_update(
ToolCallUpdate::new(
active_command.tool_call_id.clone(),
ToolCallUpdateFields::new()
.status(status)
.raw_output(raw_output),
)
.meta(client.supports_terminal_output(&active_command).then(
|| {
ToolCallUpdate::new(active_command.tool_call_id.clone(), fields).meta(
supports_terminal.then(|| {
Meta::from_iter([(
"terminal_exit".into(),
serde_json::json!({
Expand All @@ -2109,8 +2117,8 @@ impl PromptState {
"signal": null
}),
)])
},
)),
}),
),
);
}
}
Expand All @@ -2125,8 +2133,8 @@ impl PromptState {
let stdin = format!("\n{stdin}\n");
// Stream output bytes to the display-only terminal via ToolCallUpdate meta.
if let Some(active_command) = self.active_commands.get_mut(&call_id) {
let update = if client.supports_terminal_output(active_command) {
ToolCallUpdate::new(
if client.supports_terminal_output(active_command) {
let update = ToolCallUpdate::new(
active_command.tool_call_id.clone(),
ToolCallUpdateFields::new(),
)
Expand All @@ -2136,27 +2144,15 @@ impl PromptState {
"terminal_id": call_id,
"data": stdin
}),
)]))
)]));
client.send_tool_call_update(update);
} else {
// Fallback path: accumulate stdin into the active command buffer and
// defer emission to exec_command_end. Emitting per stdin event would
// re-send the entire output+stdin buffer each time and reintroduce the
// O(N²) growth fixed in the delta path.
active_command.output.push_str(&stdin);
let content = match active_command.file_extension.as_deref() {
Some("md") => active_command.output.clone(),
Some(ext) => format!(
"```{ext}\n{}\n```\n",
active_command.output.trim_end_matches('\n')
),
None => format!(
"```sh\n{}\n```\n",
active_command.output.trim_end_matches('\n')
),
};
ToolCallUpdate::new(
active_command.tool_call_id.clone(),
ToolCallUpdateFields::new().content(vec![content.into()]),
)
};

client.send_tool_call_update(update);
}
}
}

Expand Down