peer mail: reading the inbox no longer rewrites sent history

src/peer_wake_loop.zig

@@ -33,12 +33,13 @@ fn lastIsHuman(root: *Agent) bool {
 }
 
 /// Keep the human prompt newest. If mail is waiting, put one wake *before*
-/// that prompt. If the inbox was cleared, drop a leftover wake.
+/// that prompt. If the inbox was cleared, drop a leftover wake the model was
+/// never sent; wakes already in the sent history stay put.
 pub fn placeWaitingBeforeHuman(root: *Agent) void {
     if (root.sub) return;
     if (lastIsHuman(root)) peer_idle.noteHumanPrompt();
     if (!peer_inbox.pending()) {
-        session_peer.dropAllInjects(&root.messages);
+        session_peer.dropUnsentInjects(&root.messages);
         peer_idle.markPlaced(peer_inbox.generation());
         return;
     }
@@ -212,3 +213,27 @@ test "#1137 later human turn still sees waiting peer mail" {
     try std.testing.expectEqual(@as(usize, 1), root.messages.items.len);
     try std.testing.expect(session_peer.isHumanUserTurn(root.messages.items[0]));
 }
+
+test "a wake the model already answered stays in history after the inbox is read" {
+    peer_inbox.resetForTest();
+    peer_idle.resetForTest();
+    defer {
+        peer_inbox.resetForTest();
+        peer_idle.resetForTest();
+    }
+    var arena_state = std.heap.ArenaAllocator.init(std.testing.allocator);
+    defer arena_state.deinit();
+    const a = arena_state.allocator();
+    const sent = try std.json.parseFromSliceLeaky(std.json.Value, a,
+        \\[{"role":"user","content":"fix the parser"},
+        \\ {"role":"assistant","content":"done"},
+        \\ {"role":"user","content":"[peer] 1 unread from lead — parked; peer_message action=inbox when relevant"},
+        \\ {"role":"assistant","content":[{"type":"tool_use","id":"t1","name":"peer_message","input":{"action":"inbox"}}]},
+        \\ {"role":"user","content":[{"type":"tool_result","tool_use_id":"t1","content":"[peer message from lead]: also handle lowercase"}]}]
+    , .{});
+    var root = dummyRoot(a, sent.array);
+    // The inbox is empty again: the next step must not rewrite what was sent.
+    placeWaitingBeforeHuman(&root);
+    try std.testing.expectEqual(@as(usize, 5), root.messages.items.len);
+    try std.testing.expect(peer_context.isPeerInject(root.messages.items[2]));
+}

src/session_peer.zig

@@ -45,6 +45,28 @@ pub fn messagesForSave(arena: Allocator, items: []const Value) !std.json.Array {
     return out;
 }
 
+/// Drop wakes the model has not been sent yet: those after the last
+/// non-user message. A wake earlier in history was already sent and
+/// answered; removing it rewrote history the provider had cached (and made
+/// Claude Agent start a fresh process) on every step after an inbox read.
+pub fn dropUnsentInjects(msgs: *std.json.Array) void {
+    var start = msgs.items.len;
+    while (start > 0) : (start -= 1) {
+        const m = msgs.items[start - 1];
+        if (m != .object) break;
+        const role = m.object.get("role") orelse break;
+        if (role != .string or !std.mem.eql(u8, role.string, "user")) break;
+    }
+    var i = start;
+    while (i < msgs.items.len) {
+        if (peer_context.isPeerInject(msgs.items[i])) {
+            _ = msgs.orderedRemove(i);
+            continue;
+        }
+        i += 1;
+    }
+}
+
 pub fn dropAllInjects(msgs: *std.json.Array) void {
     var i: usize = 0;
     while (i < msgs.items.len) {