From 9c64a7d4462a11674e2dea481b037b5f5d9c62fc Mon Sep 17 00:00:00 2001
From: t <t@tjp.lol>
Date: Tue, 2 Jun 2026 09:02:49 -0600
Subject: system prompt building and logging

---
 src/main.zig | 58 +++++++++++++++++++++++++++++++++++++---------------------
 1 file changed, 37 insertions(+), 21 deletions(-)

(limited to 'src/main.zig')

diff --git a/src/main.zig b/src/main.zig
index aaf86b5..20686eb 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -11,6 +11,7 @@ const session_paths = @import("session_paths.zig");
 const models_toml = @import("models_toml.zig");
 const config_file = @import("config_file.zig");
 const glob = @import("glob.zig");
+const system_prompt = @import("system_prompt.zig");
 
 // Shorthand alias for the Lua C API. The bridge module owns the actual
 // `@cImport`; we re-use it here so the smoke check uses identical types.
@@ -37,6 +38,7 @@ test {
     _ = models_toml;
     _ = config_file;
     _ = glob;
+    _ = system_prompt;
 }
 
 const Receiver = panto.provider.Receiver;
@@ -363,20 +365,18 @@ pub fn main(init: std.process.Init) !void {
     var conv = panto.conversation.Conversation.init(alloc);
     defer conv.deinit();
 
-    if (session_mgr.getEntries().len > 0) {
+    const is_resume = session_mgr.getEntries().len > 0;
+    if (is_resume) {
         // Resumed an existing session — rebuild the conversation from the
-        // log. The system prompt is part of the log.
+        // log. The system prompt is part of the log. (Reconciliation
+        // against the on-disk SYSTEM.md happens after the agent tree is
+        // staged, below.)
         conv.deinit();
         conv = try session_mgr.rebuildConversation();
         try stdout.print(
             "resumed session {s} ({d} entries)\n",
             .{ session_mgr.getSessionId()[0..@min(8, session_mgr.getSessionId().len)], session_mgr.getEntries().len },
         );
-    } else {
-        // Fresh session — install the default system prompt and record it.
-        const system_text = "You are a helpful assistant.";
-        try conv.addSystemMessage(system_text);
-        try appendSystemToSession(alloc, &session_mgr, system_text);
     }
 
     // The tool registry is owned here and referenced by the active config
@@ -405,6 +405,36 @@ pub fn main(init: std.process.Init) !void {
     );
     defer luarocks_rt.deinit();
 
+    // Source the system prompt now that the base agent tree has been
+    // staged to `$PANTO_HOME/agent` (the bootstrap above writes the
+    // bundled `SYSTEM.md` there). The prompt is sourced by convention
+    // from SYSTEM.md / APPEND_SYSTEM.md across the base/user/project
+    // layers; the base layer is `luarocks_rt.layout.agent_dir`.
+    var sp_arena = std.heap.ArenaAllocator.init(alloc);
+    defer sp_arena.deinit();
+    if (is_resume) {
+        // SYSTEM.md / APPEND_SYSTEM.md may have changed since this log was
+        // created; reconcile without rewriting history.
+        try system_prompt.reconcileResume(
+            sp_arena.allocator(),
+            io,
+            init.environ_map,
+            luarocks_rt.layout.agent_dir,
+            &conv,
+            &session_mgr,
+        );
+    } else {
+        // Fresh session — source and install the system prompt.
+        try system_prompt.seedFresh(
+            sp_arena.allocator(),
+            io,
+            init.environ_map,
+            luarocks_rt.layout.agent_dir,
+            &conv,
+            &session_mgr,
+        );
+    }
+
     // luv is installed (or already present) at this point; wire the
     // libuv-driven coroutine scheduler before any extensions get a
     // chance to register tools that might want to yield.
@@ -637,20 +667,6 @@ fn openSession(
 // Session append helpers — bridge in-memory ContentBlocks to on-disk entries.
 // -----------------------------------------------------------------------------
 
-fn appendSystemToSession(
-    alloc: std.mem.Allocator,
-    mgr: *panto.session_manager.SessionManager,
-    text: []const u8,
-) !void {
-    const blocks = try alloc.alloc(panto.session_manager.DiskContentBlock, 1);
-    blocks[0] = .{ .text = .{ .text = try alloc.dupe(u8, text) } };
-    _ = try mgr.appendMessage(
-        .{ .role = .system, .content = blocks },
-        null,
-        null,
-    );
-}
-
 fn appendUserPromptToSession(
     alloc: std.mem.Allocator,
     mgr: *panto.session_manager.SessionManager,
-- 
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