Add --ledger-file arg for explicit ledger path control

Defaults to <output_dir>/run_ledger.jsonl as before.
Pass --ledger-file to read from (and write to) a specific ledger,
enabling multiple ledger files to seed different search campaigns
or merge results from separate runs.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/agent.rs

@@ -205,8 +205,12 @@ pub async fn run(cli: &Cli) -> Result<()> {
     let system = prompts::system_prompt(schema, claude.family());
     info!("model family: {}", claude.family().name());
 
+    // Resolve ledger path: explicit --ledger-file takes precedence, else <output_dir>/run_ledger.jsonl
+    let ledger_path = cli.ledger_file.clone().unwrap_or_else(|| cli.output_dir.join("run_ledger.jsonl"));
+    info!("ledger: {}", ledger_path.display());
+
     // Load prior runs from ledger and build cross-run context for iteration 1
-    let prior_summary = load_prior_summary(&cli.output_dir, &swym).await;
+    let prior_summary = load_prior_summary(&ledger_path, &swym).await;
 
     // Agent state
     let mut history: Vec<IterationRecord> = Vec::new();
@@ -412,7 +416,7 @@ pub async fn run(cli: &Cli) -> Result<()> {
                             info!("  condition audit: {}", serde_json::to_string_pretty(audit).unwrap_or_default());
                         }
                     }
-                    append_ledger_entry(&cli.output_dir, &result, &strategy);
+                    append_ledger_entry(&ledger_path, &result, &strategy);
                     results.push(result);
                 }
                 Err(e) => {
@@ -599,7 +603,7 @@ async fn run_single_backtest(
 }
 
 /// Append a ledger entry for a completed backtest so future runs can learn from it.
-fn append_ledger_entry(output_dir: &Path, result: &BacktestResult, strategy: &Value) {
+fn append_ledger_entry(ledger: &Path, result: &BacktestResult, strategy: &Value) {
     // Skip nil run_ids (error placeholders)
     if result.run_id == Uuid::nil() {
         return;
@@ -620,11 +624,10 @@ fn append_ledger_entry(output_dir: &Path, result: &BacktestResult, strategy: &Va
             return;
         }
     };
-    let path = output_dir.join("run_ledger.jsonl");
     if let Err(e) = std::fs::OpenOptions::new()
         .append(true)
         .create(true)
-        .open(&path)
+        .open(ledger)
         .and_then(|mut f| writeln!(f, "{}", line))
     {
         warn!("could not write ledger entry: {e}");
@@ -634,8 +637,8 @@ fn append_ledger_entry(output_dir: &Path, result: &BacktestResult, strategy: &Va
 /// Load the run ledger, fetch metrics via the compare endpoint, and return a compact
 /// prior-results summary string for the initial prompt.  Returns `None` if the ledger
 /// is absent, empty, or the compare call fails.
-async fn load_prior_summary(output_dir: &Path, swym: &SwymClient) -> Option<String> {
-    let path = output_dir.join("run_ledger.jsonl");
+async fn load_prior_summary(ledger: &Path, swym: &SwymClient) -> Option<String> {
+    let path = ledger;
     let contents = std::fs::read_to_string(&path).ok()?;
 
     // Parse all ledger entries

src/config.rs

@@ -118,6 +118,13 @@ pub struct Cli {
     #[arg(long, default_value = "./results")]
     pub output_dir: PathBuf,
 
+    /// Path to the run ledger JSONL file used for cross-run learning.
+    /// Defaults to <output_dir>/run_ledger.jsonl when not specified.
+    /// Pass a different path to seed a new run from a specific ledger
+    /// (e.g. a curated export from a previous campaign).
+    #[arg(long)]
+    pub ledger_file: Option<PathBuf>,
+
     /// Poll interval in seconds when waiting for backtest completion.
     #[arg(long, default_value_t = 2)]
     pub poll_interval_secs: u64,