Fix agent switching cache issue

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## Unreleased
 
+- Fix agent switching (e.g. "code" → "plan") not taking effect mid-conversation for OpenAI Responses API models (openai/gpt-5.3-codex, github-copilot/gpt-5.3-codex). The static system prompt cache is now keyed per agent and invalidated on agent change.
+
 ## 0.126.0
 
 - Chat titles now re-generate at the 3rd user message using full conversation context for more accurate titles.

src/eca/features/chat.clj

@@ -612,6 +612,7 @@
                 :model-capabilities model-capabilities
                 :user-messages user-messages
                 :instructions  instructions
+                :agent agent
                 :past-messages (shared/messages-after-last-compact-marker
                                 (get-in @db* [:chats chat-id :messages] []))
                 :config  config
@@ -1009,14 +1010,17 @@
                           (f.context/agents-file-contexts db)
                           (f.context/raw-contexts->refined contexts db))
         repo-map* (delay (f.index/repo-map db config {:as-string? true}))
-        cached-static (get-in db [:chats chat-id :prompt-cache :static])
+        prompt-cache (get-in db [:chats chat-id :prompt-cache])
+        cached-static (when (= (:agent prompt-cache) agent)
+                        (:static prompt-cache))
         instructions (if cached-static
                        {:static cached-static
                         :dynamic (f.prompt/build-dynamic-instructions refined-contexts db)}
                        (let [result (f.prompt/build-chat-instructions
                                      refined-contexts rules skills repo-map*
                                      agent config chat-id all-tools db)]
-                         (swap! db* assoc-in [:chats chat-id :prompt-cache :static] (:static result))
+                         (swap! db* update-in [:chats chat-id :prompt-cache]
+                                assoc :static (:static result) :agent agent)
                          result))
         image-contents (->> refined-contexts
                             (filter #(= :image (:type %))))

src/eca/llm_api.clj

@@ -167,7 +167,7 @@
       merged)))
 
 (defn ^:private prompt!
-  [{:keys [provider model model-capabilities instructions user-messages config variant
+  [{:keys [provider model model-capabilities instructions user-messages config variant agent
            on-message-received on-error on-prepare-tool-call on-tools-called on-reason on-usage-updated on-server-web-search
            past-messages tools provider-auth sync? subagent? cancelled?]
     :or {on-error identity}}]
@@ -203,6 +203,7 @@
         (handler
          {:model real-model
           :instructions flat-instructions
+          :agent agent
           :user-messages user-messages
           :max-output-tokens max-output-tokens
           :reason? reason?
@@ -254,6 +255,7 @@
                                        extra-headers))
               base-opts {:model real-model
                          :instructions flat-instructions
+                         :agent agent
                          :user-messages user-messages
                          :max-output-tokens max-output-tokens
                          :reason? reason?
@@ -326,6 +328,7 @@
           (handler
            {:model real-model
             :instructions flat-instructions
+            :agent agent
             :user-messages user-messages
             :max-output-tokens max-output-tokens
             :web-search web-search
@@ -353,7 +356,7 @@
 (defn sync-or-async-prompt!
   [{:keys [provider model model-capabilities instructions user-messages config on-first-response-received
            on-message-received on-error on-prepare-tool-call on-tools-called on-reason on-usage-updated on-server-web-search
-           past-messages tools provider-auth refresh-provider-auth-fn variant cancelled? on-retry subagent?]
+           past-messages tools provider-auth refresh-provider-auth-fn variant cancelled? on-retry subagent? agent]
     :or {on-first-response-received identity
          on-message-received identity
          on-error identity
@@ -441,6 +444,7 @@
                               :model model
                               :model-capabilities model-capabilities
                               :instructions instructions
+                              :agent agent
                               :tools tools
                               :provider-auth (fresh-provider-auth)
                               :past-messages past-messages
@@ -476,6 +480,7 @@
                 :model model
                 :model-capabilities model-capabilities
                 :instructions instructions
+                :agent agent
                 :tools tools
                 :provider-auth (fresh-provider-auth)
                 :past-messages past-messages

src/eca/llm_providers/openai.clj

@@ -152,7 +152,7 @@
          tools)
     (and web-search (not codex?)) (conj {:type "web_search_preview"})))
 
-(defn create-response! [{:keys [model user-messages instructions reason? supports-image? api-key api-url url-relative-path
+(defn create-response! [{:keys [model user-messages instructions agent reason? supports-image? api-key api-url url-relative-path
                                 max-output-tokens past-messages tools web-search extra-payload extra-headers auth-type account-id http-client]}
                         {:keys [on-message-received on-error on-prepare-tool-call on-tools-called on-reason on-usage-updated on-server-web-search] :as callbacks}]
   (let [codex? (= :auth/oauth auth-type)
@@ -165,7 +165,7 @@
                 :input (if codex?
                          (concat [{:role "system" :content instructions}] input)
                          input)
-                :prompt_cache_key (str (System/getProperty "user.name") "@ECA")
+                :prompt_cache_key (str (System/getProperty "user.name") "@ECA" (when agent (str "/" agent)))
                 :instructions instructions
                 :tools tools
                 :include (when reason?

test/eca/features/chat_test.clj

@@ -927,3 +927,31 @@
              (h/messages)))))))
 
 
+
+(deftest prompt-cache-agent-switch-test
+  (testing "agent switching invalidates static prompt cache"
+    (h/reset-components!)
+    (h/config! {:agent {"code" {:mode "primary"} "plan" {:mode "primary"}}})
+    (let [build-calls* (atom 0)
+          api-mock (fn [{:keys [on-first-response-received on-message-received]}]
+                     (on-first-response-received {:type :text :text "ok"})
+                     (on-message-received {:type :text :text "ok"})
+                     (on-message-received {:type :finish}))
+          base-mocks {:all-tools-mock (constantly [])
+                      :api-mock api-mock
+                      :call-tool-mock (constantly nil)}]
+      (with-redefs [f.prompt/build-chat-instructions
+                    (fn [& _]
+                      (swap! build-calls* inc)
+                      {:static (str "static-" @build-calls*)
+                       :dynamic "dynamic"})]
+        (let [{:keys [chat-id]} (prompt! {:message "Hello" :agent "code"} base-mocks)]
+          (is (= 1 @build-calls*) "First call should build instructions")
+
+          (h/reset-messenger!)
+          (prompt! {:message "Hello again" :chat-id chat-id :agent "code"} base-mocks)
+          (is (= 1 @build-calls*) "Same agent reuses cached static instructions")
+
+          (h/reset-messenger!)
+          (prompt! {:message "Switch" :chat-id chat-id :agent "plan"} base-mocks)
+          (is (= 2 @build-calls*) "Different agent should rebuild instructions"))))))

test/eca/llm_providers/openai_test.clj

@@ -1,5 +1,6 @@
 (ns eca.llm-providers.openai-test
   (:require
+   [clojure.string :as string]
    [clojure.test :refer [deftest is testing]]
    [eca.client-test-helpers :refer [with-client-proxied]]
    [eca.llm-providers.openai :as llm-providers.openai]
@@ -437,3 +438,30 @@
                       :arguments {"command" "ls"}}]
                     (first @tools-called*)))
         (is (= 2 (count @requests*)))))))
+
+(deftest create-response-prompt-cache-key-agent-test
+  (testing "prompt_cache_key includes agent suffix when agent is provided"
+    (let [body* (atom nil)]
+      (with-redefs [llm-providers.openai/base-responses-request!
+                    (fn [{:keys [body on-stream]}]
+                      (reset! body* body)
+                      (on-stream "response.completed"
+                                 {:response {:output [] :usage {:input_tokens 1 :output_tokens 1}}}))]
+        (llm-providers.openai/create-response!
+         (assoc (base-provider-params) :agent "plan")
+         (base-callbacks {}))
+        (is (string/ends-with? (:prompt_cache_key @body*) "/plan")
+            "prompt_cache_key should end with /plan"))))
+
+  (testing "prompt_cache_key has no agent suffix when agent is nil"
+    (let [body* (atom nil)]
+      (with-redefs [llm-providers.openai/base-responses-request!
+                    (fn [{:keys [body on-stream]}]
+                      (reset! body* body)
+                      (on-stream "response.completed"
+                                 {:response {:output [] :usage {:input_tokens 1 :output_tokens 1}}}))]
+        (llm-providers.openai/create-response!
+         (base-provider-params)
+         (base-callbacks {}))
+        (is (not (string/includes? (:prompt_cache_key @body*) "/"))
+            "prompt_cache_key should not contain / when agent is nil")))))