From 8c3c5a4fd2f558ea79bc82ee26163b46a595d790 Mon Sep 17 00:00:00 2001
From: Mohamed Boudra <boudra.moha@gmail.com>
Date: Sun, 1 Nov 2026 17:20:51 +0100
Subject: [PATCH] fix(server): an option a session drops when opening is not
 brought back by a configured default

The opening snapshot merged defaults over the options after the session's openOptionsPatch had removed a key. Defaults now merge into what the session was given and the patch applies after.
---
 .../src/server/agent/agent-manager.test.ts    |  9 +++++++++
 .../server/src/server/agent/agent-manager.ts  | 19 +++++++++++++++++--
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/packages/server/src/server/agent/agent-manager.test.ts b/packages/server/src/server/agent/agent-manager.test.ts
index 7d555e310e..17f19cec88 100644
--- a/packages/server/src/server/agent/agent-manager.test.ts
+++ b/packages/server/src/server/agent/agent-manager.test.ts
@@ -13120,6 +13120,15 @@ describe("agent options", () => {
     expect(published.every((options) => options?.service_tier === "slow")).toBe(true);
   });
 
+  test("an option the session dropped when opening does not come back from a configured default", async () => {
+    const { manager, agentId } = await createOptionsAgent(undefined, { service_tier: null });
+
+    const agent = manager.getAgent(agentId);
+    expect(agent?.effectiveOptions).toEqual({});
+    await manager.markAgentUnread(agentId);
+    expect(toAgentPayload(manager.getAgent(agentId)!).options).toEqual({});
+  });
+
   test("an option without a control is settable through the patch and readable in the snapshot", async () => {
     const { manager, client, storage, agentId } = await createOptionsAgent();
 
diff --git a/packages/server/src/server/agent/agent-manager.ts b/packages/server/src/server/agent/agent-manager.ts
index 6c2dfa2c78..43f093cfee 100644
--- a/packages/server/src/server/agent/agent-manager.ts
+++ b/packages/server/src/server/agent/agent-manager.ts
@@ -3983,6 +3983,12 @@ export class AgentManager {
         resolvedAgentId,
         session,
         config,
+        // Defaults merge into what the session was given; what it reports it ended up with comes
+        // after, so an option it dropped does not come back from a default.
+        effectiveOptions: applyProviderOptionsPatch({
+          options: this.effectiveOptionsFor(openedConfig.provider, openedConfig.providerOptions),
+          patch: session.openOptionsPatch ?? {},
+        }),
         now,
         durableTimelineHasRows,
         background: options?.background === true,
@@ -4128,6 +4134,7 @@ export class AgentManager {
     resolvedAgentId: string;
     session: AgentSession;
     config: AgentSessionConfig;
+    effectiveOptions: ProviderOptions;
     now: Date;
     durableTimelineHasRows: boolean;
     background: boolean;
@@ -4148,7 +4155,15 @@ export class AgentManager {
         }
       | undefined;
   }): ActiveManagedAgent {
-    const { resolvedAgentId, session, config, now, durableTimelineHasRows, options } = params;
+    const {
+      resolvedAgentId,
+      session,
+      config,
+      effectiveOptions,
+      now,
+      durableTimelineHasRows,
+      options,
+    } = params;
     return {
       id: resolvedAgentId,
       provider: config.provider,
@@ -4160,7 +4175,7 @@ export class AgentManager {
       capabilities: session.capabilities,
       config,
       // What the session opened with. Provider defaults edited later reach it when it next opens.
-      effectiveOptions: this.effectiveOptionsFor(config.provider, config.providerOptions),
+      effectiveOptions,
       runtimeInfo: undefined,
       lifecycle: "initializing",
       createdAt: options?.createdAt ?? now,