From 96911d7790add35799dd8bbc5fffc496b4d384dd Mon Sep 17 00:00:00 2001
From: Peter Steinberger <steipete@gmail.com>
Date: Sat, 27 Dec 2025 01:17:03 +0000
Subject: [PATCH] fix: enqueue system event on model switch

---
 CHANGELOG.md                           |  1 +
 src/auto-reply/reply.directive.test.ts | 31 ++++++++++++++++++++++++++
 src/auto-reply/reply.ts                | 18 +++++++++++++++
 3 files changed, 50 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index d92a54fc0..a22efbb66 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -41,6 +41,7 @@
 - LM Studio/Ollama replies now require <final> tags; streaming ignores content until <final> begins.
 - LM Studio responses API: tools payloads no longer include `strict: null`, and LM Studio no longer gets forced `<think>/<final>` tags.
 - Identity emoji no longer auto-prefixes replies (set `messages.responsePrefix` explicitly if desired).
+- Model switches now enqueue a system event so the next run knows the active model.
 - `process log` pagination is now line-based (omit `offset` to grab the last N lines).
 - macOS WebChat: assistant bubbles now update correctly when toggling light/dark mode.
 - macOS: avoid spawning a duplicate gateway process when an external listener already exists.
diff --git a/src/auto-reply/reply.directive.test.ts b/src/auto-reply/reply.directive.test.ts
index ab4921190..e7f364929 100644
--- a/src/auto-reply/reply.directive.test.ts
+++ b/src/auto-reply/reply.directive.test.ts
@@ -28,6 +28,7 @@ import {
   extractVerboseDirective,
   getReplyFromConfig,
 } from "./reply.js";
+import { drainSystemEvents } from "../infra/system-events.js";
 
 async function withTempHome<T>(fn: (home: string) => Promise<T>): Promise<T> {
   const base = await fs.mkdtemp(path.join(os.tmpdir(), "clawdis-reply-"));
@@ -425,6 +426,36 @@ describe("directive parsing", () => {
     });
   });
 
+  it("queues a system event when switching models", async () => {
+    await withTempHome(async (home) => {
+      drainSystemEvents();
+      vi.mocked(runEmbeddedPiAgent).mockReset();
+      const storePath = path.join(home, "sessions.json");
+
+      await getReplyFromConfig(
+        { Body: "/model Opus", From: "+1222", To: "+1222" },
+        {},
+        {
+          agent: {
+            model: "openai/gpt-4.1-mini",
+            workspace: path.join(home, "clawd"),
+            allowedModels: ["openai/gpt-4.1-mini", "anthropic/claude-opus-4-5"],
+            modelAliases: {
+              Opus: "anthropic/claude-opus-4-5",
+            },
+          },
+          session: { store: storePath },
+        },
+      );
+
+      const events = drainSystemEvents();
+      expect(events).toContain(
+        "Model switched to Opus (anthropic/claude-opus-4-5).",
+      );
+      expect(runEmbeddedPiAgent).not.toHaveBeenCalled();
+    });
+  });
+
   it("uses model override for inline /model", async () => {
     await withTempHome(async (home) => {
       const storePath = path.join(home, "sessions.json");
diff --git a/src/auto-reply/reply.ts b/src/auto-reply/reply.ts
index 04fe831cd..d8d40a373 100644
--- a/src/auto-reply/reply.ts
+++ b/src/auto-reply/reply.ts
@@ -39,6 +39,7 @@ import {
 import { logVerbose } from "../globals.js";
 import { buildProviderSummary } from "../infra/provider-summary.js";
 import { triggerClawdisRestart } from "../infra/restart.js";
+import { enqueueSystemEvent } from "../infra/system-events.js";
 import { drainSystemEvents } from "../infra/system-events.js";
 import { clearCommandLane, getQueueSize } from "../process/command-queue.js";
 import { defaultRuntime } from "../runtime.js";
@@ -546,6 +547,10 @@ export async function getReplyFromConfig(
     lookupContextTokens(model) ??
     DEFAULT_CONTEXT_TOKENS;
 
+  const initialModelLabel = `${provider}/${model}`;
+  const formatModelSwitchEvent = (label: string, alias?: string) =>
+    alias ? `Model switched to ${alias} (${label}).` : `Model switched to ${label}.`;
+
   const directiveOnly = (() => {
     if (
       !hasThinkDirective &&
@@ -639,6 +644,12 @@ export async function getReplyFromConfig(
         isDefault,
         alias: resolved.alias,
       };
+      const nextLabel = `${modelSelection.provider}/${modelSelection.model}`;
+      if (nextLabel !== initialModelLabel) {
+        enqueueSystemEvent(formatModelSwitchEvent(nextLabel, modelSelection.alias), {
+          contextKey: `model:${nextLabel}`,
+        });
+      }
     }
 
     if (sessionEntry && sessionStore && sessionKey) {
@@ -745,6 +756,13 @@ export async function getReplyFromConfig(
           }
           provider = resolved.ref.provider;
           model = resolved.ref.model;
+          const nextLabel = `${provider}/${model}`;
+          if (nextLabel !== initialModelLabel) {
+            enqueueSystemEvent(
+              formatModelSwitchEvent(nextLabel, resolved.alias),
+              { contextKey: `model:${nextLabel}` },
+            );
+          }
           contextTokens =
             agentCfg?.contextTokens ??
             lookupContextTokens(model) ??