fix: keep direct SSH Antigravity chat on its execution host

docs/reference/antigravity-native-chat.md

@@ -10,7 +10,10 @@ The execution host reads
 `.gemini/antigravity-cli/brain/<conversation-id>/.system_generated/logs/transcript.jsonl`.
 A hook-reported transcript path takes precedence. Existing WSL exact-path and
 host-isolation rules apply; a missing guest transcript must not fall back to a
-native host's same-named conversation.
+native host's same-named conversation. Direct SSH panes stay in the terminal:
+that connection has no native-chat transcript transport, and its absolute file
+path must never be opened on the client. Paired runtimes remain eligible because
+their own host reads the transcript. Direct SSH chat support remains unfinished.
 
 The sanitized fixture in `src/main/native-chat/__fixtures__/antigravity/` records
 these observed shapes:

src/renderer/src/components/native-chat/native-chat-availability.test.ts

@@ -90,20 +90,22 @@ describe('canToggleNativeChat', () => {
     ).toBe(false)
   })
 
-  // Why: omp discloses no hook transcript path either, so its session file is
-  // only reachable when this process can read the agent's disk.
-  it('rejects Model-A SSH omp but accepts it local and runtime-owned', () => {
-    const forConnection = (connectionId: string | null): boolean =>
-      canToggleNativeChat({
-        experimentalNativeChatEnabled: true,
-        contentType: 'terminal',
-        launchAgent: 'omp',
-        nativeChatTranscriptIsLocalReadable: isNativeChatTranscriptLocalReadable(connectionId)
-      })
-    expect(forConnection('ssh-target-1')).toBe(false)
-    expect(forConnection(null)).toBe(true)
-    expect(forConnection('runtime-ssh-env-1')).toBe(true)
-  })
+  // Direct SSH has no transcript transport, even when a hook names the remote file.
+  it.each(['omp', 'antigravity'] as const)(
+    'rejects Model-A SSH %s but accepts it local and runtime-owned',
+    (agent) => {
+      const forConnection = (connectionId: string | null): boolean =>
+        canToggleNativeChat({
+          experimentalNativeChatEnabled: true,
+          contentType: 'terminal',
+          launchAgent: agent,
+          nativeChatTranscriptIsLocalReadable: isNativeChatTranscriptLocalReadable(connectionId)
+        })
+      expect(forConnection('ssh-target-1')).toBe(false)
+      expect(forConnection(null)).toBe(true)
+      expect(forConnection('runtime-ssh-env-1')).toBe(true)
+    }
+  )
 
   it('lets an existing Model-A SSH Grok chat toggle back to terminal', () => {
     expect(

src/renderer/src/lib/native-chat-initial-view-mode.test.ts

@@ -14,7 +14,8 @@ describe('decideInitialAgentTabViewMode', () => {
         decideInitialAgentTabViewMode({
           experimentalNativeChat: true,
           openAgentTabsInChatByDefault: true,
-          agent
+          agent,
+          nativeChatTranscriptIsLocalReadable: true
         })
       ).toBe('chat')
     }
@@ -77,17 +78,20 @@ describe('decideInitialAgentTabViewMode', () => {
     ).toBe('chat')
   })
 
-  it('keeps Model-A SSH omp in the terminal view but opens it locally', () => {
-    const forConnection = (connectionId: string | null): Tab['viewMode'] =>
-      decideInitialAgentTabViewMode({
-        experimentalNativeChat: true,
-        openAgentTabsInChatByDefault: true,
-        agent: 'omp',
-        nativeChatTranscriptIsLocalReadable: isNativeChatTranscriptLocalReadable(connectionId)
-      })
-    expect(forConnection('ssh-target-1')).toBeUndefined()
-    expect(forConnection(null)).toBe('chat')
-  })
+  it.each(['omp', 'antigravity'] as const)(
+    'keeps Model-A SSH %s in the terminal view but opens it locally',
+    (agent) => {
+      const forConnection = (connectionId: string | null): Tab['viewMode'] =>
+        decideInitialAgentTabViewMode({
+          experimentalNativeChat: true,
+          openAgentTabsInChatByDefault: true,
+          agent,
+          nativeChatTranscriptIsLocalReadable: isNativeChatTranscriptLocalReadable(connectionId)
+        })
+      expect(forConnection('ssh-target-1')).toBeUndefined()
+      expect(forConnection(null)).toBe('chat')
+    }
+  )
 
   it('keeps Model-A SSH Grok in the terminal view', () => {
     expect(

src/shared/native-chat-agent-support.test.ts

@@ -34,11 +34,12 @@ describe('isNativeChatSupportedAgent', () => {
 })
 
 describe('nativeChatRequiresLocalTranscript', () => {
-  it('covers the agents whose hook discloses no transcript path', () => {
+  it('covers agents requiring a runtime-owned transcript filesystem', () => {
     // Claude/Codex report `transcript_path`; Grok and omp report only an id, so
     // native chat has to find their file on a disk this process can read.
     expect(nativeChatRequiresLocalTranscript('grok')).toBe(true)
     expect(nativeChatRequiresLocalTranscript('omp')).toBe(true)
+    expect(nativeChatRequiresLocalTranscript('antigravity')).toBe(true)
     expect(nativeChatRequiresLocalTranscript('claude')).toBe(false)
     expect(nativeChatRequiresLocalTranscript('openclaude')).toBe(false)
     expect(nativeChatRequiresLocalTranscript('codex')).toBe(false)

src/shared/native-chat-agent-support.ts

@@ -21,13 +21,13 @@ export function isNativeChatSupportedAgent(agent: string | null | undefined): bo
   return agent != null && NATIVE_CHAT_SUPPORTED_AGENTS.has(agent)
 }
 
-/** Agents whose hook discloses no transcript path (`extractAgentProviderSession`),
- *  so native chat can only reach the session file by scanning a sessions root on
- *  a disk THIS process can read. Under Model-A SSH that disk is the wrong host,
- *  so the chat view must stay closed instead of loading forever. */
+/** Agents whose chat reads require a filesystem owned by the selected runtime.
+ * Direct SSH has no transcript transport; a hook path alone is not a local file. */
 export function nativeChatRequiresLocalTranscript(agent: string | null | undefined): boolean {
   const transcriptAgent = resolveNativeChatTranscriptAgent(agent)
-  return transcriptAgent === 'grok' || transcriptAgent === 'omp'
+  return (
+    transcriptAgent === 'grok' || transcriptAgent === 'omp' || transcriptAgent === 'antigravity'
+  )
 }
 
 /** True when the agent renders a digit-commit question selector that ignores