diff --git a/packages/server/src/server/agent/providers/claude-agent.ts b/packages/server/src/server/agent/providers/claude-agent.ts
index 6a6e9c59e..39b2f7304 100644
--- a/packages/server/src/server/agent/providers/claude-agent.ts
+++ b/packages/server/src/server/agent/providers/claude-agent.ts
@@ -873,6 +873,12 @@ class ClaudeAgentSession implements AgentSession {
     this.availableModes = DEFAULT_MODES;
     this.currentMode = message.permissionMode;
     this.persistence = null;
+    // Capture actual model from SDK init message (not just the configured model)
+    if (message.model) {
+      this.lastOptionsModel = message.model;
+      // Invalidate cached runtime info so it picks up the new model
+      this.cachedRuntimeInfo = null;
+    }
   }
 
   private convertUsage(message: SDKResultMessage): AgentUsage | undefined {
diff --git a/plan.md b/plan.md
index bb52d0d88..4c82686f9 100644
--- a/plan.md
+++ b/plan.md
@@ -89,10 +89,11 @@ Hard requirement: We must get the actual runtime model, not just echo back the r
     - Fix: Update `handleSystemMessage()` to capture `message.model` as `lastOptionsModel`
     - Alternatively: Extract model name from `modelUsage` keys in `SDKResultMessage`
 
-- [ ] **Implement**: Capture actual model from Claude SDK init message.
+- [x] **Implement**: Capture actual model from Claude SDK init message.
   - In `handleSystemMessage()`, set `this.lastOptionsModel = message.model`
   - This gives us the actual model the SDK selected (not just our config)
   - Simpler than parsing modelUsage, same result
+  - **Done (2025-12-21 13:25)**: Updated `handleSystemMessage()` in `claude-agent.ts:868-882` to capture `message.model` from the SDK init message and invalidate cached runtime info. Typecheck passes.
 
 - [ ] **Test**: Verify current Codex runtime model detection works.
   - Create a Codex agent with default model