diff --git a/extension/src/codex-rollout-parser.ts b/extension/src/codex-rollout-parser.ts
index 60c7ab7..9748952 100644
--- a/extension/src/codex-rollout-parser.ts
+++ b/extension/src/codex-rollout-parser.ts
@@ -386,6 +386,7 @@ export class CodexRolloutParser {
         agent: ORCHESTRATOR_NAME,
         role,
         content: text.slice(0, MESSAGE_MAX),
+        runtime: 'codex',
       },
     })
     this.emitContextUpdate(state)
@@ -575,6 +576,7 @@ export class CodexRolloutParser {
         agent: ORCHESTRATOR_NAME,
         role: 'thinking',
         content: text.slice(0, MESSAGE_MAX),
+        runtime: 'codex',
       },
     })
     this.emitContextUpdate(state)
diff --git a/extension/test/codex-rollout-parser.test.ts b/extension/test/codex-rollout-parser.test.ts
index aac38e4..f8c695d 100644
--- a/extension/test/codex-rollout-parser.test.ts
+++ b/extension/test/codex-rollout-parser.test.ts
@@ -93,6 +93,15 @@ describe('CodexRolloutParser', () => {
     assert.equal(thinking[0].payload.content, '**Planning directory listing**')
   })
 
+  it('tags Codex transcript messages with the codex runtime', () => {
+    const { events } = runFixture()
+    const messages = events.filter(e => e.type === 'message')
+    assert.ok(messages.length > 0)
+    for (const event of messages) {
+      assert.equal(event.payload.runtime, 'codex')
+    }
+  })
+
   it('pairs function_call with function_call_output by call_id', () => {
     const { events, state } = runFixture()
     const starts = events.filter(e => e.type === 'tool_call_start' && e.payload.tool === 'exec_command')
diff --git a/web/components/agent-visualizer/canvas/draw-bubbles.ts b/web/components/agent-visualizer/canvas/draw-bubbles.ts
index dc952df..5716b29 100644
--- a/web/components/agent-visualizer/canvas/draw-bubbles.ts
+++ b/web/components/agent-visualizer/canvas/draw-bubbles.ts
@@ -1,4 +1,5 @@
 import { Agent, NODE } from '@/lib/agent-types'
+import { getMessageSenderLabel } from '@/lib/agent-runtime'
 import { COLORS, withAlpha } from '@/lib/colors'
 import { BUBBLE_MAX_W, BUBBLE_GAP, BUBBLE_MAX_LINES, AGENT_DRAW, BUBBLE_DRAW } from '@/lib/canvas-constants'
 import { bubbleAlpha } from './bubble-utils'
@@ -29,7 +30,7 @@ export function drawMessageBubblesWorld(
       const isThinking = role === 'thinking'
       const bgColor = isThinking ? COLORS.bubbleThinkingBase : role === 'user' ? COLORS.bubbleUserBase : COLORS.bubbleAssistantBase
       const textColor = isThinking ? COLORS.roleThinkingText : role === 'user' ? COLORS.roleUserText : COLORS.roleAssistantText
-      const label = isThinking ? '\uD83D\uDCAD THINKING' : role === 'user' ? 'USER' : 'CLAUDE'
+      const label = isThinking ? `\uD83D\uDCAD ${getMessageSenderLabel(role, agent.runtime)}` : getMessageSenderLabel(role, agent.runtime)
 
       // Thinking bubbles: smaller font, tighter spacing, more translucent
       const style = isThinking ? BUBBLE_DRAW.thinking : BUBBLE_DRAW.normal
diff --git a/web/components/agent-visualizer/chat-panel.tsx b/web/components/agent-visualizer/chat-panel.tsx
index f3d2dcf..24e656a 100644
--- a/web/components/agent-visualizer/chat-panel.tsx
+++ b/web/components/agent-visualizer/chat-panel.tsx
@@ -1,6 +1,6 @@
 'use client'
 
-import { CARD, Z, type AgentState } from '@/lib/agent-types'
+import { CARD, Z, type Agent, type AgentState } from '@/lib/agent-types'
 import { COLORS, getStateColor } from '@/lib/colors'
 import { TranscriptMessage } from './transcript-message'
 import type { ConversationMessage } from '@/hooks/simulation/types'
@@ -11,6 +11,7 @@ interface ChatPanelProps {
   visible: boolean
   agentName: string
   agentState: AgentState
+  agentRuntime?: Agent['runtime']
   conversation: ConversationMessage[]
   onClose: () => void
 }
@@ -19,6 +20,7 @@ export function AgentChatPanel({
   visible,
   agentName,
   agentState,
+  agentRuntime,
   conversation,
   onClose,
 }: ChatPanelProps) {
@@ -62,7 +64,7 @@ export function AgentChatPanel({
             </div>
           ) : (
             conversation.map((msg) => (
-              <TranscriptMessage key={msg.id} message={msg} />
+              <TranscriptMessage key={msg.id} message={msg} agentRuntime={agentRuntime} />
             ))
           )}
         </div>
diff --git a/web/components/agent-visualizer/index.tsx b/web/components/agent-visualizer/index.tsx
index 4fae266..43dc2fb 100644
--- a/web/components/agent-visualizer/index.tsx
+++ b/web/components/agent-visualizer/index.tsx
@@ -214,9 +214,12 @@ export function AgentVisualizer() {
   // Only compute when the transcript panel is visible to avoid O(n log n) sort every frame
   const sessionConversation = useMemo(() => {
     if (!showTranscript) return []
-    const all = Array.from(conversations.values()).flat()
+    const all = Array.from(conversations.entries()).flatMap(([agentId, msgs]) => {
+      const runtime = agents.get(agentId)?.runtime
+      return msgs.map(msg => msg.runtime ? msg : { ...msg, runtime })
+    })
     return all.sort((a, b) => a.timestamp - b.timestamp)
-  }, [conversations, showTranscript])
+  }, [agents, conversations, showTranscript])
 
   // Context menu items
   const contextMenuItems = selection.contextMenu ? (
@@ -326,6 +329,7 @@ export function AgentVisualizer() {
         visible={!!selectedAgent}
         agentName={selectedAgent?.name ?? ''}
         agentState={selectedAgent?.state ?? 'idle'}
+        agentRuntime={selectedAgent?.runtime}
         conversation={selectedConversation}
         onClose={selection.clearAgent}
       />
diff --git a/web/components/agent-visualizer/message-feed-panel.tsx b/web/components/agent-visualizer/message-feed-panel.tsx
index 3eb8d3c..bf5ae74 100644
--- a/web/components/agent-visualizer/message-feed-panel.tsx
+++ b/web/components/agent-visualizer/message-feed-panel.tsx
@@ -2,6 +2,7 @@
 
 import { useState, useEffect, useRef, useMemo, useCallback } from 'react'
 import { Agent, Z, type AgentState } from '@/lib/agent-types'
+import { getMessageSenderLabel } from '@/lib/agent-runtime'
 import { COLORS, ROLE_COLORS, getStateColor } from '@/lib/colors'
 import type { ConversationMessage } from '@/hooks/simulation/types'
 import { useClickOutside } from '@/hooks/use-click-outside'
@@ -285,6 +286,7 @@ export function MessageFeedPanel({
                       message={msg}
                       agentId={msg.agentId}
                       agentName={agents.get(msg.agentId)?.name ?? msg.agentId}
+                      agentRuntime={msg.runtime ?? agents.get(msg.agentId)?.runtime}
                       showAgent={activeTab === 'all'}
                       isSelected={selectedAgentId === msg.agentId}
                       onClick={() => { onAgentClick(msg.agentId); setExpanded(false) }}
@@ -332,10 +334,11 @@ function TabButton({ label, active, onClick, color, hasUnread }: {
 
 // ── Message Row ──
 
-function MessageRow({ message, agentId, agentName, showAgent, isSelected, onClick }: {
+function MessageRow({ message, agentId, agentName, agentRuntime, showAgent, isSelected, onClick }: {
   message: ConversationMessage
   agentId: string
   agentName: string
+  agentRuntime?: Agent['runtime']
   showAgent: boolean
   isSelected: boolean
   onClick: () => void
@@ -357,7 +360,7 @@ function MessageRow({ message, agentId, agentName, showAgent, isSelected, onClic
       {/* Header row */}
       <div className="flex items-center gap-1.5 mb-0.5">
         <span className="text-[9px] font-mono font-semibold" style={{ color: role.text + '90' }}>
-          {role.label}
+          {getMessageSenderLabel(message.type, message.runtime ?? agentRuntime)}
         </span>
         {showAgent && (
           <span className="text-[9px] font-mono" style={{ color: COLORS.textMuted }}>
diff --git a/web/components/agent-visualizer/transcript-message.tsx b/web/components/agent-visualizer/transcript-message.tsx
index 9b28829..620719b 100644
--- a/web/components/agent-visualizer/transcript-message.tsx
+++ b/web/components/agent-visualizer/transcript-message.tsx
@@ -1,6 +1,8 @@
 'use client'
 
 import { useState } from 'react'
+import type { Agent } from '@/lib/agent-types'
+import { getMessageSenderLabel } from '@/lib/agent-runtime'
 import { COLORS } from '@/lib/colors'
 import { ToolContentRenderer } from './tool-content-renderer'
 import type { ConversationMessage } from '@/hooks/simulation/types'
@@ -21,8 +23,19 @@ export function HighlightText({ text, query }: { text: string; query?: string })
   )
 }
 
-export function TranscriptMessage({ message, compact = false, searchQuery }: { message: ConversationMessage; compact?: boolean; searchQuery?: string }) {
+export function TranscriptMessage({
+  message,
+  compact = false,
+  searchQuery,
+  agentRuntime,
+}: {
+  message: ConversationMessage
+  compact?: boolean
+  searchQuery?: string
+  agentRuntime?: Agent['runtime']
+}) {
   const [expanded, setExpanded] = useState(false)
+  const runtime = message.runtime ?? agentRuntime
 
   switch (message.type) {
     case 'user':
@@ -34,7 +47,9 @@ export function TranscriptMessage({ message, compact = false, searchQuery }: { m
             border: `1px solid ${COLORS.userMsgBorder}`,
           }}
         >
-          <div className="text-[9px] mb-1 font-semibold tracking-wider" style={{ color: COLORS.userLabel }}>USER</div>
+          <div className="text-[9px] mb-1 font-semibold tracking-wider" style={{ color: COLORS.userLabel }}>
+            {getMessageSenderLabel(message.type, runtime)}
+          </div>
           <div style={{ color: COLORS.userText }} className="whitespace-pre-wrap break-words">
             <HighlightText text={message.content} query={searchQuery} />
           </div>
@@ -50,7 +65,9 @@ export function TranscriptMessage({ message, compact = false, searchQuery }: { m
             border: `1px solid ${COLORS.holoBorder08}`,
           }}
         >
-          <div className="text-[9px] mb-1 font-semibold tracking-wider" style={{ color: COLORS.assistantLabel }}>CLAUDE</div>
+          <div className="text-[9px] mb-1 font-semibold tracking-wider" style={{ color: COLORS.assistantLabel }}>
+            {getMessageSenderLabel(message.type, runtime)}
+          </div>
           <div style={{ color: COLORS.assistantText }} className="whitespace-pre-wrap break-words">
             <HighlightText text={compact ? message.content.slice(0, 200) + (message.content.length > 200 ? '...' : '') : message.content} query={searchQuery} />
           </div>
@@ -68,7 +85,9 @@ export function TranscriptMessage({ message, compact = false, searchQuery }: { m
           onClick={() => setExpanded(!expanded)}
         >
           <div className="flex items-center gap-1.5">
-            <span className="text-[9px] font-semibold tracking-wider" style={{ color: COLORS.thinkingLabel }}>THINKING</span>
+            <span className="text-[9px] font-semibold tracking-wider" style={{ color: COLORS.thinkingLabel }}>
+              {getMessageSenderLabel(message.type, runtime)}
+            </span>
             <span className="text-[9px]" style={{ color: COLORS.thinkingArrow }}>{expanded ? '▾' : '▸'}</span>
             {!expanded && (
               <span className="text-[9px] font-mono truncate opacity-50" style={{ color: COLORS.thinkingPreview }}>
diff --git a/web/hooks/simulation/handle-agent-events.ts b/web/hooks/simulation/handle-agent-events.ts
index fb134fe..d8db79a 100644
--- a/web/hooks/simulation/handle-agent-events.ts
+++ b/web/hooks/simulation/handle-agent-events.ts
@@ -30,6 +30,7 @@ export function handleAgentSpawn(
       state: 'idle',
       ...(task ? { task } : {}),
       ...(model ? { tokensMax: ctx.getContextWindowSize(model) } : {}),
+      ...(runtime ? { runtime } : {}),
     })
     return
   }
diff --git a/web/hooks/simulation/handle-message-events.ts b/web/hooks/simulation/handle-message-events.ts
index 6a89e90..31b72b3 100644
--- a/web/hooks/simulation/handle-message-events.ts
+++ b/web/hooks/simulation/handle-message-events.ts
@@ -11,6 +11,11 @@ export function handleMessage(
   const agentName = asString(payload.agent)
   const content = asString(payload.content)
   const role = typeof payload.role === 'string' ? payload.role : undefined
+  const payloadRuntime = payload.runtime === 'codex'
+    ? 'codex' as const
+    : payload.runtime === 'claude'
+      ? 'claude' as const
+      : undefined
 
   // Map role to conversation message type
   const msgType: ConversationMessage['type'] =
@@ -49,12 +54,15 @@ export function handleMessage(
         updates.state = 'thinking'
       }
     }
+    if (payloadRuntime && msgAgent.runtime !== payloadRuntime) {
+      updates.runtime = payloadRuntime
+    }
     if (Object.keys(updates).length > 0) {
       state.agents.set(agentName, { ...msgAgent, ...updates })
     }
   }
 
-  appendConversation(state.conversations, agentName, { type: msgType, content, timestamp: currentTime })
+  appendConversation(state.conversations, agentName, { type: msgType, content, timestamp: currentTime, runtime: payloadRuntime ?? msgAgent?.runtime })
 }
 
 export function handleContextUpdate(
diff --git a/web/hooks/simulation/handle-tool-events.ts b/web/hooks/simulation/handle-tool-events.ts
index fe22292..9d939cd 100644
--- a/web/hooks/simulation/handle-tool-events.ts
+++ b/web/hooks/simulation/handle-tool-events.ts
@@ -89,6 +89,7 @@ export function handleToolCallStart(
 
     appendConversation(state.conversations, agentName, {
       type: 'tool_call', content: `> ${toolName} ${args}`, timestamp: currentTime,
+      runtime: agent.runtime,
       toolName, inputData,
     })
   }
@@ -166,6 +167,7 @@ export function handleToolCallEnd(
       type: 'tool_result',
       content: `< ${result}${tokenCost ? ` (${tokenCost} tokens)` : ''}`,
       timestamp: currentTime,
+      runtime: agent.runtime,
       toolName,
     })
   }
diff --git a/web/hooks/simulation/types.ts b/web/hooks/simulation/types.ts
index eda15b7..68d17f7 100644
--- a/web/hooks/simulation/types.ts
+++ b/web/hooks/simulation/types.ts
@@ -57,6 +57,7 @@ export interface ConversationMessage {
   type: 'tool_call' | 'tool_result' | 'assistant' | 'user' | 'thinking'
   content: string
   timestamp: number
+  runtime?: Agent['runtime']
   toolName?: string
   inputData?: Record<string, unknown>
 }
diff --git a/web/lib/agent-runtime.ts b/web/lib/agent-runtime.ts
new file mode 100644
index 0000000..43988b9
--- /dev/null
+++ b/web/lib/agent-runtime.ts
@@ -0,0 +1,12 @@
+import type { Agent } from './agent-types'
+
+export function getAgentRuntimeLabel(runtime?: Agent['runtime']): string {
+  return runtime === 'codex' ? 'CODEX' : 'CLAUDE'
+}
+
+export function getMessageSenderLabel(type: string, runtime?: Agent['runtime']): string {
+  if (type === 'user') return 'USER'
+  if (type === 'thinking') return 'THINKING'
+  if (type === 'assistant') return getAgentRuntimeLabel(runtime)
+  return 'TOOL'
+}
diff --git a/web/lib/colors.ts b/web/lib/colors.ts
index 3f7c0b9..e9dadc5 100644
--- a/web/lib/colors.ts
+++ b/web/lib/colors.ts
@@ -219,10 +219,10 @@ export const COLORS = {
 
 // ─── Role Colors (message feed & bubbles) ───────────────────────────────────
 
-export const ROLE_COLORS: Record<string, { bg: string; bgSelected: string; text: string; label: string }> = {
-  assistant: { bg: COLORS.roleAssistantBg, bgSelected: COLORS.roleAssistantBgSelected, text: COLORS.roleAssistantText, label: 'CLAUDE' },
-  thinking:  { bg: COLORS.roleThinkingBg,  bgSelected: COLORS.roleThinkingBgSelected,  text: COLORS.roleThinkingText,  label: 'THINKING' },
-  user:      { bg: COLORS.roleUserBg,       bgSelected: COLORS.roleUserBgSelected,       text: COLORS.roleUserText,       label: 'USER' },
+export const ROLE_COLORS: Record<string, { bg: string; bgSelected: string; text: string }> = {
+  assistant: { bg: COLORS.roleAssistantBg, bgSelected: COLORS.roleAssistantBgSelected, text: COLORS.roleAssistantText },
+  thinking:  { bg: COLORS.roleThinkingBg,  bgSelected: COLORS.roleThinkingBgSelected,  text: COLORS.roleThinkingText },
+  user:      { bg: COLORS.roleUserBg,       bgSelected: COLORS.roleUserBgSelected,       text: COLORS.roleUserText },
 } as const
 
 // ─── Color Helper Functions ──────────────────────────────────────────────────