feat: render Antigravity terminal sessions in native chat

Co-authored-by: haoliangli <haoliangli@users.noreply.github.com>

docs/reference/antigravity-native-chat.md

@@ -0,0 +1,50 @@
+# Antigravity terminal-backed Chat UI
+
+Antigravity uses the existing experimental Chat UI over its terminal and saved
+transcript. It is not a structured-session provider. The opt-in default-chat
+setting applies, and users can return to the terminal.
+
+## Transcript contract
+
+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.
+
+The sanitized fixture in `src/main/native-chat/__fixtures__/antigravity/` records
+these observed shapes:
+
+- User input is `USER_EXPLICIT/USER_INPUT` with a `USER_REQUEST` wrapper.
+- Planner responses carry text, thinking, or tool calls. Tool arguments are in `args`.
+- Tool output is a `MODEL` record with a tool-specific type such as `RUN_COMMAND`
+  or `VIEW_FILE`. It is not a `TOOL_RESULT` record.
+- A planner step marked `DONE` can precede more tool work in the same user turn.
+  The decoder therefore emits no turn-completion verdict. The existing host-owned
+  hook/status system remains authoritative.
+
+Full reads, incremental tails, and legacy journal imports reuse the same decoder.
+Unknown record types are skipped. Tool failures retain a nonzero exit code or
+`ERROR` status as an error result.
+
+## Mixed versions
+
+New hosts advertise `native-chat.antigravity.v1`. A new client's chat transport
+checks the owning host before reading or subscribing to Antigravity. An older
+host gets the existing update-runtime error; a failed capability probe gets the
+existing read error. Neither becomes a perpetual first-transcript wait.
+No stream opcode or message-block type was added.
+
+## Verification limits
+
+On macOS with installed agy 1.2.7, a resumed test conversation rendered from its
+real saved transcript, and a message submitted in the chat composer appeared in
+that transcript. Generation returned `401 ACCESS_TOKEN_TYPE_UNSUPPORTED`.
+Hooks were disabled in the isolated app profile, so pane/session metadata was
+supplied as a fixture; this did not validate actual hook delivery or live status
+transitions. Tool rendering was checked separately with the sanitized fixture.
+
+Five bounded real transcript samples supplied 309 tool/activity records; the
+corrected decoder preserved all 309. This is offline format evidence, not proof
+of a successful new model turn. Windows, Linux, WSL, SSH, paired-runtime execution,
+permission questions, and successful tool-generating turns still need live QA.

src/main/ai-vault/session-scanner-antigravity-parser.ts

@@ -120,7 +120,7 @@ function consumeAntigravityRecordLine(accumulator: SessionAccumulator, line: str
   }
 }
 
-function extractAntigravityUserRequest(content: string): string | null {
+export function extractAntigravityUserRequest(content: string): string | null {
   const opener = '<USER_REQUEST>'
   const startIndex = content.indexOf(opener)
   if (startIndex === -1) {

src/main/native-chat/__fixtures__/antigravity/README.md

@@ -0,0 +1,8 @@
+This fixture preserves the record and nested tool-call shapes observed in local
+Antigravity CLI transcripts on 2026-09-19. Conversation text, tool arguments,
+timestamps, and step numbers are replaced with harmless synthetic values.
+
+A planner step with `status: DONE` can precede a tool step and another planner
+response without a new user prompt. It does not prove completion of the user turn.
+Tool results use `source: MODEL` and their tool-specific step type; planner tool
+calls carry arguments in `args`.

src/main/native-chat/__fixtures__/antigravity/tool-turn.jsonl

@@ -0,0 +1,5 @@
+{"step_index":0,"source":"USER_EXPLICIT","type":"USER_INPUT","status":"DONE","created_at":"2026-09-19T10:00:00Z","content":"<USER_REQUEST>Inspect the sample file.</USER_REQUEST>"}
+{"step_index":1,"source":"MODEL","type":"PLANNER_RESPONSE","status":"DONE","created_at":"2026-09-19T10:00:01Z","thinking":"I will inspect the sample.","tool_calls":[{"name":"run_command","args":{"CommandLine":"printf sample","Cwd":"/workspace","WaitMsBeforeAsync":1000,"toolAction":"Inspect","toolSummary":"Read sample"}}]}
+{"step_index":2,"source":"MODEL","type":"RUN_COMMAND","status":"DONE","exit_code":0,"created_at":"2026-09-19T10:00:02Z","content":"sample"}
+{"step_index":3,"source":"SYSTEM","type":"CHECKPOINT","status":"DONE","created_at":"2026-09-19T10:00:03Z"}
+{"step_index":4,"source":"MODEL","type":"PLANNER_RESPONSE","status":"DONE","created_at":"2026-09-19T10:00:04Z","content":"The sample file contains sample."}

src/main/native-chat/agent-session-journal/journal-legacy-import.ts

@@ -22,6 +22,7 @@ import type { NativeChatBlock, NativeChatMessage } from '../../../shared/native-
 import { resolveNativeChatTranscriptAgent } from '../../../shared/native-chat-agent-support'
 import { resolveSessionFilePath, type ResolveSessionFileOptions } from '../session-file-resolver'
 import {
+  decodeAntigravityTranscriptLine,
   decodeClaudeTranscriptLine,
   decodeCodexTranscriptLine,
   decodeGrokTranscriptLine,
@@ -172,6 +173,7 @@ export async function prepareLegacyTranscriptImport(input: {
 const TRANSCRIPT_DECODERS = {
   claude: decodeClaudeTranscriptLine,
   codex: decodeCodexTranscriptLine,
+  antigravity: decodeAntigravityTranscriptLine,
   grok: decodeGrokTranscriptLine,
   omp: decodeOmpTranscriptLine
 } as const

src/main/native-chat/session-file-resolver.ts

@@ -84,6 +84,8 @@ export type ResolveSessionFileOptions = {
   grokSessionsDir?: string
   /** Override the omp sessions root (`~/.omp/agent/sessions`). */
   ompSessionsDir?: string
+  /** Antigravity CLI brain root on the execution host. */
+  antigravityBrainDir?: string
   /** Authoritative transcript path reported by the agent hook
    *  (`providerSession.transcriptPath`). When set and the file exists, it is used
    *  directly — recent Claude Code names the transcript with a UUID that differs
@@ -210,6 +212,22 @@ async function resolveSessionFileById(
       signal
     )
   }
+  if (transcriptAgent === 'antigravity') {
+    // A conversation id is one directory segment, never a caller-supplied path.
+    if (!/^[a-zA-Z0-9_-]+$/.test(trimmedId)) {
+      return null
+    }
+    return toHostReadableTranscriptPath(
+      join(
+        options.antigravityBrainDir ?? join(homedir(), '.gemini', 'antigravity-cli', 'brain'),
+        trimmedId,
+        '.system_generated',
+        'logs',
+        'transcript.jsonl'
+      ),
+      { signal }
+    )
+  }
   if (transcriptAgent === 'grok') {
     return resolveGrokSessionFile(trimmedId, options.grokSessionsDir ?? grokSessionsDir(), signal)
   }

src/main/native-chat/transcript-line-decoders-antigravity.ts

@@ -0,0 +1,123 @@
+// Antigravity (AGY) JSONL line → NativeChatMessage decoder.
+
+import type { NativeChatBlock, NativeChatMessage } from '../../shared/native-chat-types'
+import {
+  asRecord,
+  extractString,
+  parseJsonObject,
+  timestampMs
+} from '../ai-vault/session-scanner-values'
+import { extractAntigravityUserRequest } from '../ai-vault/session-scanner-antigravity-parser'
+
+const TOOL_STEP_TYPES = new Set([
+  'RUN_COMMAND',
+  'LIST_DIRECTORY',
+  'GENERIC',
+  'INVOKE_SUBAGENT',
+  'VIEW_FILE',
+  'CODE_ACTION',
+  'GREP_SEARCH',
+  'SEARCH_WEB'
+])
+
+export function decodeAntigravityTranscriptLine(
+  line: string,
+  fallbackId: string
+): NativeChatMessage | null {
+  const record = parseJsonObject(line)
+  if (!record) {
+    return null
+  }
+
+  const timestamp = parseTimestamp(record.created_at ?? record.timestamp)
+  const stepIndex =
+    typeof record.step_index === 'number'
+      ? String(record.step_index)
+      : (extractString(record.step_index) ?? extractString(record.id))
+  const id = stepIndex ?? fallbackId
+  const source = extractString(record.source)
+  const type = extractString(record.type)
+
+  if (
+    (source === 'USER_EXPLICIT' || source === 'USER') &&
+    (type === 'USER_INPUT' || type === 'REQUEST')
+  ) {
+    const rawContent = extractString(record.content) ?? ''
+    const text = extractAntigravityUserRequest(rawContent) || rawContent
+    if (!text.trim()) {
+      return null
+    }
+    return {
+      id,
+      role: 'user',
+      blocks: [{ type: 'text', text }],
+      timestamp,
+      source: 'transcript'
+    }
+  }
+
+  if (source === 'MODEL' && type === 'PLANNER_RESPONSE') {
+    const blocks: NativeChatBlock[] = []
+
+    const thinking = extractString(record.thinking)
+    if (thinking && thinking.trim()) {
+      blocks.push({ type: 'text', text: `> *Thinking:*\n${thinking}` })
+    }
+
+    const content = extractString(record.content)
+    if (content && content.trim()) {
+      blocks.push({ type: 'text', text: content })
+    }
+
+    if (Array.isArray(record.tool_calls)) {
+      for (const call of record.tool_calls) {
+        const tool = asRecord(call)
+        if (tool) {
+          const name = extractString(tool.name) ?? 'tool'
+          const input = tool.args ?? tool.arguments ?? tool.input ?? null
+          blocks.push({
+            type: 'tool-call',
+            name,
+            input
+          })
+        }
+      }
+    }
+
+    if (blocks.length === 0) {
+      return null
+    }
+
+    return {
+      id,
+      role: 'assistant',
+      blocks,
+      timestamp,
+      source: 'transcript'
+    }
+  }
+
+  // Recorded tool steps are MODEL records, not TOOL_RESULT messages.
+  if (source === 'MODEL' && type && TOOL_STEP_TYPES.has(type)) {
+    const output = extractString(record.content)
+    if (!output) {
+      return null
+    }
+    const isError =
+      record.status === 'ERROR' || (typeof record.exit_code === 'number' && record.exit_code !== 0)
+    return {
+      id,
+      role: 'tool',
+      blocks: [{ type: 'tool-result', output, ...(isError ? { isError: true } : {}) }],
+      timestamp,
+      source: 'transcript'
+    }
+  }
+
+  return null
+}
+
+function parseTimestamp(value: unknown): number | null {
+  const parsed = timestampMs(value)
+  return Number.isFinite(parsed) ? parsed : null
+}

src/main/native-chat/transcript-line-decoders.antigravity.test.ts

@@ -0,0 +1,76 @@
+import { readFileSync } from 'node:fs'
+import { describe, expect, it } from 'vitest'
+import { decodeAntigravityTranscriptLine } from './transcript-line-decoders-antigravity'
+
+const lines = readFileSync(
+  new URL('./__fixtures__/antigravity/tool-turn.jsonl', import.meta.url),
+  'utf8'
+)
+  .trim()
+  .split('\n')
+
+function decode(record: unknown) {
+  return decodeAntigravityTranscriptLine(JSON.stringify(record), 'line-1')
+}
+
+describe('Antigravity transcript records', () => {
+  it('preserves the recorded prompt, tool arguments, output, and subsequent response', () => {
+    const messages = lines.map((line, index) =>
+      decodeAntigravityTranscriptLine(line, `line-${index}`)
+    )
+    expect(messages[0]).toMatchObject({
+      role: 'user',
+      blocks: [{ type: 'text', text: 'Inspect the sample file.' }]
+    })
+    expect(messages[1]?.blocks).toContainEqual({
+      type: 'tool-call',
+      name: 'run_command',
+      input: {
+        CommandLine: 'printf sample',
+        Cwd: '/workspace',
+        WaitMsBeforeAsync: 1000,
+        toolAction: 'Inspect',
+        toolSummary: 'Read sample'
+      }
+    })
+    expect(messages[2]).toMatchObject({
+      role: 'tool',
+      blocks: [{ type: 'tool-result', output: 'sample' }]
+    })
+    expect(messages[3]).toBeNull()
+    expect(messages[4]).toMatchObject({
+      role: 'assistant',
+      blocks: [{ type: 'text', text: 'The sample file contains sample.' }]
+    })
+  })
+
+  it.each([
+    'RUN_COMMAND',
+    'VIEW_FILE',
+    'LIST_DIRECTORY',
+    'GREP_SEARCH',
+    'CODE_ACTION',
+    'GENERIC',
+    'INVOKE_SUBAGENT'
+  ])('keeps recorded %s output without treating step completion as turn completion', (type) => {
+    expect(decode({ source: 'MODEL', type, status: 'DONE', content: 'output' })).toMatchObject({
+      role: 'tool',
+      blocks: [{ type: 'tool-result', output: 'output' }]
+    })
+  })
+
+  it.each([{ status: 'ERROR' }, { status: 'DONE', exit_code: 1 }])(
+    'marks failed tool results',
+    (fields) => {
+      expect(
+        decode({ source: 'MODEL', type: 'RUN_COMMAND', content: 'failed', ...fields })?.blocks
+      ).toEqual([{ type: 'tool-result', output: 'failed', isError: true }])
+    }
+  )
+
+  it('ignores malformed, empty, and system bookkeeping records', () => {
+    expect(decodeAntigravityTranscriptLine('{', 'line')).toBeNull()
+    expect(decode({ source: 'MODEL', type: 'PLANNER_RESPONSE' })).toBeNull()
+    expect(decode({ source: 'SYSTEM', type: 'CHECKPOINT', content: 'private context' })).toBeNull()
+  })
+})

src/main/native-chat/transcript-line-decoders.ts

@@ -13,3 +13,5 @@ export { decodeClaudeTranscriptLine } from './transcript-line-decoders-claude'
 export { decodeCodexTranscriptLine } from './transcript-line-decoders-codex'
 export { decodeGrokTranscriptLine } from './transcript-line-decoders-grok'
 export { decodeOmpTranscriptLine } from './transcript-line-decoders-omp'
+
+export { decodeAntigravityTranscriptLine } from './transcript-line-decoders-antigravity'

src/main/native-chat/transcript-reader-antigravity.test.ts

@@ -0,0 +1,67 @@
+import { copyFile, mkdir, mkdtemp, rm } from 'node:fs/promises'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+import { afterEach, describe, expect, it } from 'vitest'
+import { resolveSessionFilePath } from './session-file-resolver'
+import { readNativeChatTranscript } from './transcript-reader'
+import {
+  nativeChatLineDecoderForAgent,
+  readNativeChatTranscriptTailFile
+} from './transcript-tail-reader'
+import { nativeChatTurnLifecycleDecoderForAgent } from './transcript-turn-lifecycle'
+
+let root: string | undefined
+
+afterEach(async () => {
+  if (root) {
+    await rm(root, { recursive: true, force: true })
+  }
+  root = undefined
+})
+
+async function fixture() {
+  root = await mkdtemp(join(tmpdir(), 'orca-agy-chat-'))
+  const dir = join(root, 'conversation', '.system_generated', 'logs')
+  await mkdir(dir, { recursive: true })
+  const path = join(dir, 'transcript.jsonl')
+  await copyFile(new URL('./__fixtures__/antigravity/tool-turn.jsonl', import.meta.url), path)
+  return { path, options: { antigravityBrainDir: root } }
+}
+
+describe('Antigravity native transcript reading', () => {
+  it('resolves its CLI conversation and preserves full-reader / tail-reader parity', async () => {
+    const { path, options } = await fixture()
+    expect(await resolveSessionFilePath('antigravity', 'conversation', options)).toBe(path)
+    const full = await readNativeChatTranscript('antigravity', 'conversation', options)
+    const decode = nativeChatLineDecoderForAgent('antigravity')
+    expect(decode).not.toBeNull()
+    if (!decode || !('messages' in full)) {
+      throw new Error('transcript reader unavailable')
+    }
+    const tail = await readNativeChatTranscriptTailFile(path, 20, decode)
+    expect(tail.messages).toEqual(full.messages)
+    expect(full.messages.map((message) => message.role)).toEqual([
+      'user',
+      'assistant',
+      'tool',
+      'assistant'
+    ])
+    expect(nativeChatTurnLifecycleDecoderForAgent('antigravity')).toBeNull()
+    expect(full.lifecycle).toBeUndefined()
+    expect(tail.lifecycle).toBeUndefined()
+  })
+
+  it('rejects path-shaped ids and does not substitute a native file for a WSL session', async () => {
+    const { options } = await fixture()
+    for (const id of ['../conversation', '..\\conversation', '/conversation', 'C:conversation']) {
+      expect(await resolveSessionFilePath('antigravity', id, options)).toBeNull()
+    }
+    expect(
+      await resolveSessionFilePath('antigravity', 'conversation', {
+        ...options,
+        wslDistro: 'Ubuntu'
+      })
+    ).toBeNull()
+    expect(await resolveSessionFilePath('antigravity', 'missing', options)).toBeNull()
+  })
+})

src/main/native-chat/transcript-reader.ts

@@ -9,6 +9,7 @@ import { resolveSessionFilePath, type ResolveSessionFileOptions } from './sessio
 import { openTranscriptReadStream } from './wsl-transcript-fs-access'
 import { wslTranscriptFsRefusal } from './wsl-transcript-fs-gate'
 import {
+  decodeAntigravityTranscriptLine,
   decodeClaudeTranscriptLine,
   decodeCodexTranscriptLine,
   decodeGrokTranscriptLine,
@@ -55,6 +56,9 @@ export async function readNativeChatTranscript(
   }
   try {
     const transcriptAgent = resolveNativeChatTranscriptAgent(agent)
+    if (transcriptAgent === 'antigravity') {
+      return { messages: await readTranscript(filePath, decodeAntigravityTranscriptLine) }
+    }
     if (transcriptAgent === 'claude') {
       return { messages: await readTranscript(filePath, decodeClaudeTranscriptLine) }
     }

src/main/native-chat/transcript-tail-reader.ts

@@ -6,6 +6,7 @@ import type {
 import { resolveNativeChatTranscriptAgent } from '../../shared/native-chat-agent-support'
 import { resolveSessionFilePath, type ResolveSessionFileOptions } from './session-file-resolver'
 import {
+  decodeAntigravityTranscriptLine,
   decodeClaudeTranscriptLine,
   decodeCodexTranscriptLine,
   decodeGrokTranscriptLine,
@@ -35,6 +36,9 @@ export type NativeChatLineDecoder = (line: string, fallbackId: string) => Native
 
 export function nativeChatLineDecoderForAgent(agent: AgentType): NativeChatLineDecoder | null {
   const transcriptAgent = resolveNativeChatTranscriptAgent(agent)
+  if (transcriptAgent === 'antigravity') {
+    return decodeAntigravityTranscriptLine
+  }
   if (transcriptAgent === 'claude') {
     return decodeClaudeTranscriptLine
   }

src/renderer/src/components/native-chat/native-chat-antigravity-capability.test.ts

@@ -0,0 +1,88 @@
+import { describe, expect, it, vi } from 'vitest'
+import { guardAntigravityChatTransport } from './native-chat-antigravity-capability'
+import {
+  RUNTIME_NATIVE_CHAT_READ_ERROR,
+  RUNTIME_NATIVE_CHAT_TOO_OLD
+} from './native-chat-runtime-contract'
+
+const args = {
+  agent: 'antigravity' as const,
+  sessionId: 'conversation',
+  subscriptionId: 'subscription'
+}
+
+function setup(supports: () => Promise<boolean>) {
+  const stop = vi.fn()
+  const transport = {
+    readSession: vi.fn(async () => ({ messages: [] })),
+    subscribe: vi.fn(() => stop)
+  }
+  return { transport, stop, guarded: guardAntigravityChatTransport(transport, supports) }
+}
+
+describe('Antigravity chat host capability', () => {
+  it('rejects old hosts before read or subscribe without claiming the transcript is pending', async () => {
+    const { guarded, transport } = setup(async () => false)
+    expect(await guarded.readSession('antigravity', 'conversation')).toEqual({
+      error: RUNTIME_NATIVE_CHAT_TOO_OLD
+    })
+    const onFrame = vi.fn()
+    const close = await guarded.subscribe(args, onFrame)
+    await vi.waitFor(() =>
+      expect(onFrame).toHaveBeenCalledWith({
+        type: 'snapshot',
+        messages: [],
+        hasMore: false,
+        error: RUNTIME_NATIVE_CHAT_TOO_OLD
+      })
+    )
+    expect(transport.readSession).not.toHaveBeenCalled()
+    expect(transport.subscribe).not.toHaveBeenCalled()
+    close()
+  })
+
+  it('keeps host-contact failure separate from unsupported versions', async () => {
+    const { guarded } = setup(async () => {
+      throw new Error('offline')
+    })
+    expect(await guarded.readSession('antigravity', 'conversation')).toEqual({
+      error: RUNTIME_NATIVE_CHAT_READ_ERROR
+    })
+  })
+
+  it('does not open a subscription after teardown while the probe was pending', async () => {
+    let resolve: ((supported: boolean) => void) | undefined
+    const { guarded, transport } = setup(
+      () =>
+        new Promise((done) => {
+          resolve = done
+        })
+    )
+    const close = await guarded.subscribe(args, vi.fn())
+    close()
+    resolve?.(true)
+    await Promise.resolve()
+    await Promise.resolve()
+    expect(transport.subscribe).not.toHaveBeenCalled()
+  })
+
+  it('uses supported hosts and closes their subscription once', async () => {
+    const { guarded, transport, stop } = setup(async () => true)
+    await guarded.readSession('antigravity', 'conversation')
+    expect(transport.readSession).toHaveBeenCalledWith('antigravity', 'conversation')
+    const close = await guarded.subscribe(args, vi.fn())
+    await vi.waitFor(() => expect(transport.subscribe).toHaveBeenCalledOnce())
+    close()
+    expect(stop).toHaveBeenCalledOnce()
+  })
+
+  it('leaves existing agents on their existing transport', async () => {
+    const supports = vi.fn(async () => false)
+    const { guarded, transport } = setup(supports)
+    await guarded.readSession('claude', 'conversation')
+    await guarded.subscribe({ ...args, agent: 'claude' }, vi.fn())
+    expect(transport.readSession).toHaveBeenCalledOnce()
+    expect(transport.subscribe).toHaveBeenCalledOnce()
+    expect(supports).not.toHaveBeenCalled()
+  })
+})

src/renderer/src/components/native-chat/native-chat-antigravity-capability.ts

@@ -0,0 +1,70 @@
+import type { NativeChatApi } from '../../../../preload/api-types'
+import {
+  RUNTIME_NATIVE_CHAT_READ_ERROR,
+  RUNTIME_NATIVE_CHAT_TOO_OLD
+} from './native-chat-runtime-contract'
+
+type Transport = Pick<NativeChatApi, 'readSession' | 'subscribe'>
+
+/** An older host cannot decode agy; distinguish that from a transcript awaiting its first write. */
+export function guardAntigravityChatTransport(
+  transport: Transport,
+  supports: () => Promise<boolean>
+): Transport {
+  const errorForHost = async (): Promise<string | null> => {
+    try {
+      return (await supports()) ? null : RUNTIME_NATIVE_CHAT_TOO_OLD
+    } catch {
+      return RUNTIME_NATIVE_CHAT_READ_ERROR
+    }
+  }
+  return {
+    readSession: async (agent, ...args) => {
+      const error = agent === 'antigravity' ? await errorForHost() : null
+      return error ? { error } : transport.readSession(agent, ...args)
+    },
+    subscribe: (args, onFrame) => {
+      if (args.agent !== 'antigravity') {
+        return transport.subscribe(args, onFrame)
+      }
+      let cancelled = false
+      let unsubscribe: (() => void) | undefined
+      void errorForHost()
+        .then(async (error) => {
+          if (cancelled) {
+            return
+          }
+          if (error) {
+            onFrame({ type: 'snapshot', messages: [], hasMore: false, error })
+            return
+          }
+          const stop = await Promise.resolve(
+            transport.subscribe(args, (frame) => {
+              if (!cancelled) {
+                onFrame(frame)
+              }
+            })
+          )
+          if (cancelled) {
+            stop()
+          } else {
+            unsubscribe = stop
+          }
+        })
+        .catch(() => {
+          if (!cancelled) {
+            onFrame({
+              type: 'snapshot',
+              messages: [],
+              hasMore: false,
+              error: RUNTIME_NATIVE_CHAT_READ_ERROR
+            })
+          }
+        })
+      return () => {
+        cancelled = true
+        unsubscribe?.()
+      }
+    }
+  }
+}

src/renderer/src/components/native-chat/native-chat-runtime-contract.ts

@@ -4,6 +4,9 @@ import type {
 } from '../../../../preload/api-types'
 import type { NativeChatTurnLifecycle } from '../../../../shared/native-chat-types'
 
+export const RUNTIME_NATIVE_CHAT_TOO_OLD =
+  'This remote runtime is too old to show agent chat history. Update the remote runtime to view it.'
+
 export const RUNTIME_NATIVE_CHAT_READ_ERROR = "Couldn't read agent chat from the remote runtime."
 
 export function parseRuntimeNativeChatTurnLifecycle(

src/renderer/src/components/native-chat/native-chat-session-transport.ts

@@ -1,7 +1,11 @@
+import { ANTIGRAVITY_NATIVE_CHAT_RUNTIME_CAPABILITY } from '../../../../shared/protocol-version'
+import { ensureLocalRuntimeCapabilities } from '@/runtime/local-runtime-capabilities'
+import { guardAntigravityChatTransport } from './native-chat-antigravity-capability'
 import type { NativeChatApi, NativeChatAppendedMessages } from '../../../../preload/api-types'
 import { isWebClientLocation } from '@/lib/web-client-location'
 import {
   callRuntimeRpc,
+  runtimeEnvironmentSupportsCapability,
   RuntimeRpcCallError,
   type RuntimeClientTarget
 } from '@/runtime/runtime-rpc-client'
@@ -9,7 +13,8 @@ import { isRuntimeCompatBlockError } from '@/runtime/runtime-protocol-compat'
 import {
   parseRuntimeNativeChatReadSessionResult,
   parseRuntimeNativeChatTurnLifecycle,
-  RUNTIME_NATIVE_CHAT_READ_ERROR
+  RUNTIME_NATIVE_CHAT_READ_ERROR,
+  RUNTIME_NATIVE_CHAT_TOO_OLD
 } from './native-chat-runtime-contract'
 
 /** The read/subscribe surface the live-session hook needs, decoupled from where
@@ -17,9 +22,6 @@ import {
  *  hook and everything downstream (merge, assembler, pagination) are unchanged. */
 export type NativeChatSessionTransport = Pick<NativeChatApi, 'readSession' | 'subscribe'>
 
-const RUNTIME_TOO_OLD =
-  'This remote runtime is too old to show agent chat history. Update the remote runtime to view it.'
-
 /** Backoff before re-opening a dropped runtime chat stream. Exported for tests. */
 export const RUNTIME_NATIVE_CHAT_RECONNECT_MS = 2_000
 
@@ -30,10 +32,10 @@ export const RUNTIME_NATIVE_CHAT_RECONNECT_MS = 2_000
  *  never mislabeled as a version problem (KTD-4, not catch-all). */
 export function toRuntimeNativeChatErrorMessage(err: unknown): string {
   if (err instanceof RuntimeRpcCallError && err.code === 'method_not_found') {
-    return RUNTIME_TOO_OLD
+    return RUNTIME_NATIVE_CHAT_TOO_OLD
   }
   if (isRuntimeCompatBlockError(err)) {
-    return RUNTIME_TOO_OLD
+    return RUNTIME_NATIVE_CHAT_TOO_OLD
   }
   return RUNTIME_NATIVE_CHAT_READ_ERROR
 }
@@ -268,8 +270,22 @@ function createRuntimeNativeChatTransport(environmentId: string): NativeChatSess
 export function getNativeChatSessionTransport(
   runtimeEnvironmentId: string | null
 ): NativeChatSessionTransport {
-  if (runtimeEnvironmentId && !isWebClientLocation()) {
-    return createRuntimeNativeChatTransport(runtimeEnvironmentId)
-  }
-  return localNativeChatTransport
+  const webClient = isWebClientLocation()
+  const remote = runtimeEnvironmentId && !webClient ? runtimeEnvironmentId : null
+  const transport = remote ? createRuntimeNativeChatTransport(remote) : localNativeChatTransport
+  return guardAntigravityChatTransport(transport, async () => {
+    if (remote) {
+      return runtimeEnvironmentSupportsCapability(
+        remote,
+        ANTIGRAVITY_NATIVE_CHAT_RUNTIME_CAPABILITY
+      )
+    }
+    const capabilities = webClient
+      ? (await window.api.runtime.getStatus()).capabilities
+      : await ensureLocalRuntimeCapabilities()
+    if (!capabilities) {
+      throw new Error('Runtime capabilities unavailable')
+    }
+    return capabilities.includes(ANTIGRAVITY_NATIVE_CHAT_RUNTIME_CAPABILITY)
+  })
 }

src/renderer/src/components/settings/NativeChatSupportedAgents.test.tsx

@@ -17,7 +17,8 @@ const EXPECTED_SUPPORTED_AGENTS = [
   'openclaude',
   'codex',
   'grok',
-  'omp'
+  'omp',
+  'antigravity'
 ] as const satisfies readonly TuiAgent[]
 const SUPPORTED_AGENTS_LABEL_KEY = 'auto.components.settings.NativeChatSupportedAgents.label'
 

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

@@ -7,15 +7,18 @@ import {
 import { isNativeChatTranscriptLocalReadable } from './native-chat-transcript-readability'
 
 describe('decideInitialAgentTabViewMode', () => {
-  it("returns 'chat' when native chat and the opt-in default setting are on", () => {
-    expect(
-      decideInitialAgentTabViewMode({
-        experimentalNativeChat: true,
-        openAgentTabsInChatByDefault: true,
-        agent: 'codex'
-      })
-    ).toBe('chat')
-  })
+  it.each(['codex', 'antigravity'] as const)(
+    'opens %s in chat when native chat and the opt-in default setting are on',
+    (agent) => {
+      expect(
+        decideInitialAgentTabViewMode({
+          experimentalNativeChat: true,
+          openAgentTabsInChatByDefault: true,
+          agent
+        })
+      ).toBe('chat')
+    }
+  )
 
   it('returns undefined when native chat is disabled', () => {
     expect(

src/shared/agent-session-resume.test.ts

@@ -8,6 +8,19 @@ import {
 } from './agent-session-resume'
 
 describe('agent session resume metadata', () => {
+  it('preserves the Antigravity hook transcript path for host-owned chat reads', () => {
+    expect(
+      extractAgentProviderSession('antigravity', {
+        conversationId: 'agy-conversation',
+        transcriptPath: '/workspace/brain/transcript.jsonl'
+      })
+    ).toEqual({
+      key: 'conversation_id',
+      id: 'agy-conversation',
+      transcriptPath: '/workspace/brain/transcript.jsonl'
+    })
+  })
+
   it('treats devin as a resumable TUI agent', () => {
     expect(isResumableTuiAgent('devin')).toBe(true)
   })

src/shared/agent-session-resume.ts

@@ -201,7 +201,7 @@ export function extractAgentProviderSession(
     }
     case 'antigravity': {
       const id = readSessionId(payload, ['conversationId'])
-      return id ? { key: 'conversation_id', id } : null
+      return id ? withTranscriptPath({ key: 'conversation_id', id }, payload) : null
     }
     case 'opencode':
     case 'mimo-code': {

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

@@ -1,6 +1,6 @@
 import type { TuiAgent } from './tui-agent'
 
-export type NativeChatTranscriptAgent = 'claude' | 'codex' | 'grok' | 'omp'
+export type NativeChatTranscriptAgent = 'claude' | 'codex' | 'grok' | 'omp' | 'antigravity'
 
 /** Agents whose transcripts the native chat view can parse and render, in the
  *  order the settings pane advertises them. */
@@ -9,7 +9,8 @@ export const NATIVE_CHAT_SUPPORTED_AGENT_LIST: readonly TuiAgent[] = [
   'openclaude',
   'codex',
   'grok',
-  'omp'
+  'omp',
+  'antigravity'
 ]
 
 export const NATIVE_CHAT_SUPPORTED_AGENTS: ReadonlySet<string> = new Set(
@@ -47,7 +48,7 @@ export function resolveNativeChatTranscriptAgent(
   if (agent === 'claude' || agent === 'openclaude') {
     return 'claude'
   }
-  if (agent === 'codex' || agent === 'grok' || agent === 'omp') {
+  if (agent === 'codex' || agent === 'grok' || agent === 'omp' || agent === 'antigravity') {
     return agent
   }
   return null

src/shared/protocol-version.ts

@@ -292,10 +292,13 @@ export const ELECTRON_REMOTE_RUNTIME_CLIENT_CAPABILITIES = [
 export const ANTIGRAVITY_CONFIGURED_MODEL_RUNTIME_CAPABILITY =
   'git.antigravity-configured-model.v1' as const
 
+export const ANTIGRAVITY_NATIVE_CHAT_RUNTIME_CAPABILITY = 'native-chat.antigravity.v1' as const
+
 export const ANTIGRAVITY_VISIBLE_READINESS_RUNTIME_CAPABILITY =
   'terminal.antigravity-visible-readiness.v1' as const
 
 export const RUNTIME_CAPABILITIES = [
+  ANTIGRAVITY_NATIVE_CHAT_RUNTIME_CAPABILITY,
   ANTIGRAVITY_VISIBLE_READINESS_RUNTIME_CAPABILITY,
   ANTIGRAVITY_CONFIGURED_MODEL_RUNTIME_CAPABILITY,
   'files.pathsExist',