fix(telegram): seed system prompt into chat history (IDENTITY.md was ignored)

handleChatMessage ran the agent via RunWithMessages(cs.Messages), but
RunWithMessages — unlike Run — does not inject the engine's system message, and
the per-chat session was seeded with only the user message. So the system prompt
(IDENTITY.md, the default, and the Telegram Quick Facts) was computed and set on
the agent but never sent to the model: fresh chats reached the LLM with no system
prompt and the agent answered as the provider's base identity (e.g. "I am
Claude"). The run/continue commands already prepend the system message before
RunWithMessages; Telegram did not.

Add seedSystemMessage() and call it before appending the user turn: prepend the
prompt for new/system-less histories, refresh messages[0] for resumed ones so
IDENTITY.md / prompt changes take effect on the next turn. Covers all message
types (text, voice, photo, commands) since they all funnel through
handleChatMessage. Add a regression test.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: jkyberneees

cmd/odek/telegram.go

@@ -931,6 +931,24 @@ func spawnChild() error {
 	return err
 }
 
+// seedSystemMessage guarantees the system prompt is messages[0].
+//
+// RunWithMessages — unlike Run — does NOT inject the engine's system message,
+// so every caller that resumes a message history must seed it (the run/continue
+// commands do the same). Without this, a fresh Telegram chat reaches the model
+// with no system prompt at all and the agent answers as the provider's base
+// identity (e.g. "I am Claude") instead of from IDENTITY.md / the default.
+//
+// New or system-less histories get the prompt prepended; resumed histories get
+// messages[0] refreshed so IDENTITY.md / prompt changes take effect next turn.
+func seedSystemMessage(messages []llm.Message, system string) []llm.Message {
+	if len(messages) == 0 || messages[0].Role != "system" {
+		return append([]llm.Message{{Role: "system", Content: system}}, messages...)
+	}
+	messages[0].Content = system
+	return messages
+}
+
 // handleChatMessage processes a user message from Telegram in a background
 // goroutine. It creates or loads the chat session, creates a TelegramApprover
 // for approval prompts, runs the agent loop with RunWithMessages, and sends
@@ -996,6 +1014,9 @@ func handleChatMessage(
 		return
 	}
 
+	// Ensure the system prompt is messages[0] before the agent runs.
+	cs.Messages = seedSystemMessage(cs.Messages, systemMessage)
+
 	// Append user message to session.
 	cs.Messages = append(cs.Messages, llm.Message{Role: "user", Content: text})
 	cs.LastActive = time.Now()

cmd/odek/telegram_identity_test.go

@@ -0,0 +1,48 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/BackendStack21/odek/internal/llm"
+)
+
+// TestSeedSystemMessage locks in the fix for the bug where Telegram chats
+// reached the model with no system prompt (RunWithMessages does not inject it),
+// causing the agent to answer as the provider's base identity ("I am Claude")
+// instead of from IDENTITY.md / the default system prompt.
+func TestSeedSystemMessage(t *testing.T) {
+	const sys = "You are Molty — AI Chief of Staff."
+
+	t.Run("new empty session prepends system", func(t *testing.T) {
+		got := seedSystemMessage(nil, sys)
+		if len(got) != 1 || got[0].Role != "system" || got[0].Content != sys {
+			t.Fatalf("got %+v", got)
+		}
+	})
+
+	t.Run("user-first history prepends system and keeps the user message", func(t *testing.T) {
+		got := seedSystemMessage([]llm.Message{{Role: "user", Content: "hi"}}, sys)
+		if len(got) != 2 {
+			t.Fatalf("want 2 messages, got %d: %+v", len(got), got)
+		}
+		if got[0].Role != "system" || got[0].Content != sys {
+			t.Errorf("messages[0] = %+v, want system %q", got[0], sys)
+		}
+		if got[1].Role != "user" || got[1].Content != "hi" {
+			t.Errorf("messages[1] = %+v, want user 'hi'", got[1])
+		}
+	})
+
+	t.Run("resumed history refreshes stale system without duplicating", func(t *testing.T) {
+		got := seedSystemMessage([]llm.Message{
+			{Role: "system", Content: "OLD PROMPT"},
+			{Role: "user", Content: "hi"},
+		}, sys)
+		if len(got) != 2 {
+			t.Fatalf("want 2 messages (no duplicate system), got %d: %+v", len(got), got)
+		}
+		if got[0].Role != "system" || got[0].Content != sys {
+			t.Errorf("messages[0] = %+v, want refreshed system %q", got[0], sys)
+		}
+	})
+}