Compaction overhaul (#5186)

Co-authored-by: Douwe Osinga <douwe@squareup.com>
Co-authored-by: David Katz <dkatz@squareup.com>
Co-authored-by: Alex Hancock <alexhancock@block.xyz>

crates/goose/src/providers/utils.rs

@@ -1,6 +1,8 @@
 use super::base::Usage;
 use super::errors::GoogleErrorCode;
+use crate::config::paths::Paths;
 use crate::model::ModelConfig;
+use crate::providers::errors::{OpenAIError, ProviderError};
 use anyhow::Result;
 use base64::Engine;
 use regex::Regex;
@@ -12,8 +14,6 @@ use std::io::Read;
 use std::path::Path;
 use std::time::Duration;
 
-use crate::providers::errors::{OpenAIError, ProviderError};
-
 #[derive(serde::Deserialize)]
 struct OpenAIErrorResponse {
     error: OpenAIError,
@@ -461,14 +461,32 @@ pub fn emit_debug_trace<T1, T2>(
     T1: ?Sized + Serialize,
     T2: ?Sized + Serialize,
 {
-    tracing::debug!(
-        model_config = %serde_json::to_string_pretty(model_config).unwrap_or_default(),
-        input = %serde_json::to_string_pretty(payload).unwrap_or_default(),
-        output = %serde_json::to_string_pretty(response).unwrap_or_default(),
-        input_tokens = ?usage.input_tokens.unwrap_or_default(),
-        output_tokens = ?usage.output_tokens.unwrap_or_default(),
-        total_tokens = ?usage.total_tokens.unwrap_or_default(),
-    );
+    let logs_dir = Paths::in_state_dir("logs");
+
+    if let Err(e) = std::fs::create_dir_all(&logs_dir) {
+        tracing::warn!("Failed to create logs directory: {}", e);
+        return;
+    }
+
+    let log_path = |i| logs_dir.join(format!("llm_request.{}.json", i));
+
+    for i in (0..4).rev() {
+        let _ = std::fs::rename(log_path(i), log_path(i + 1));
+    }
+
+    let data = serde_json::json!({
+        "model_config": model_config,
+        "input": payload,
+        "output": response,
+        "usage": usage,
+    });
+
+    if let Err(e) = std::fs::write(
+        log_path(0),
+        serde_json::to_string_pretty(&data).unwrap_or_default(),
+    ) {
+        tracing::warn!("Failed to write log file: {}", e);
+    }
 }
 
 /// Safely parse a JSON string that may contain doubly-encoded or malformed JSON.