diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7d79dc5..42dcb69 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,22 @@
 # Changelog
 
+## v3.12.0 (2026-05-27)
+
+**gRPC Auto-Fallback for Antigravity Provider (PR #13)**
+
+### New Features
+- **gRPC auto-fallback**: When REST API returns 404 (model not found), automatically retries via gRPC
+- **New `antigravity_grpc` module**: Full protobuf client with CloudCode PredictionService stubs
+- **Display name remapping**: gRPC uses display names (e.g. "Gemini 3.5 Flash (High)") instead of REST slugs
+- **Streaming and unary support**: gRPC fallback works for both streaming and non-streaming requests
+- **Dynamic version fetch with validation**: Probes fetched versions to ensure they work before caching
+- **Antigravity v2 handler rewrite**: Based on anti-api approach with proper safety settings, stopSequences, sessionId
+- **Lazy import**: grpcio is only imported when needed — zero impact if not installed
+
+### Bug Fixes
+- Antigravity 404 caused by invalid version — now validates with probe requests
+- Version fallback: auto-retries with re-fetched version if all endpoints return 404
+
 ## v3.11.12 (2026-05-26)
 
 **New Antigravity v2 Handler (Mimicking anti-api)**
diff --git a/codex-launcher_3.11.12_all.deb b/codex-launcher_3.11.12_all.deb
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diff --git a/codex-launcher_3.12.0_all.deb b/codex-launcher_3.12.0_all.deb
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diff --git a/src/antigravity_grpc/__init__.py b/src/antigravity_grpc/__init__.py
new file mode 100644
index 0000000..b0d343f
--- /dev/null
+++ b/src/antigravity_grpc/__init__.py
@@ -0,0 +1,24 @@
+"""
+antigravity_grpc — gRPC fallback client for Google CloudCode (Antigravity).
+
+When the REST API rejects a request (404 model not found, 400 bad request due to
+model ID mismatch, etc.), this module provides a gRPC fallback path that uses
+Google's native PredictionService protocol — the same one the agy CLI uses.
+
+This module is imported lazily and only when grpcio is installed. If grpcio is
+not available, the fallback is silently skipped.
+"""
+
+from .client import (
+    GrpcFallbackResult,
+    AntigravityGrpcClient,
+    is_grpc_available,
+    get_client,
+)
+
+__all__ = [
+    "GrpcFallbackResult",
+    "AntigravityGrpcClient",
+    "is_grpc_available",
+    "get_client",
+]
diff --git a/src/antigravity_grpc/client.py b/src/antigravity_grpc/client.py
new file mode 100644
index 0000000..cf4fc9e
--- /dev/null
+++ b/src/antigravity_grpc/client.py
@@ -0,0 +1,609 @@
+"""
+antigravity_grpc.client — gRPC fallback client for Google CloudCode (Antigravity).
+
+This module provides a gRPC client that can be used as an automatic fallback when
+the CloudCode REST API rejects requests. The gRPC path uses the same
+PredictionService that the native agy CLI binary uses, giving access to models
+that are unavailable via REST (e.g. models that return 404 on REST but work on gRPC).
+
+Key design decisions:
+  - Lazy import: grpcio is only imported when actually needed. If not installed,
+    is_grpc_available() returns False and the fallback is silently skipped.
+  - Zero impact on other providers: this module is only called from
+    _handle_antigravity_v2() when REST returns a fallback-eligible error.
+  - Same output format as REST: the client returns structured dicts that match
+    the SSE/JSON response shapes the proxy already processes.
+  - Thread-safe: the gRPC channel is created once per endpoint and reused.
+
+Usage from translate-proxy.py:
+    from antigravity_grpc import is_grpc_available, AntigravityGrpcClient
+
+    if is_grpc_available():
+        client = AntigravityGrpcClient()
+        result = client.try_generate(request_dict, stream=False)
+        if result.ok:
+            # Use result.response_data (dict matching REST response shape)
+        else:
+            # gRPC also failed, fall through to error
+"""
+
+import json
+import os
+import sys
+import time
+import threading
+import collections
+
+# ═══════════════════════════════════════════════════════════════════
+# Lazy gRPC import — never crash if grpcio is missing
+# ═══════════════════════════════════════════════════════════════════
+
+_grpc = None
+_pb2 = None
+_pb2_grpc = None
+_import_error = None
+
+def _try_import():
+    global _grpc, _pb2, _pb2_grpc, _import_error
+    if _grpc is not None:
+        return _grpc is not False
+    try:
+        import grpc as _real_grpc
+        # Import the generated stubs relative to this package
+        from . import cloudcode_pb2 as _real_pb2
+        from . import cloudcode_pb2_grpc as _real_pb2_grpc
+        _grpc = _real_grpc
+        _pb2 = _real_pb2
+        _pb2_grpc = _real_pb2_grpc
+        return True
+    except Exception as e:
+        _import_error = str(e)
+        _grpc = False
+        return False
+
+
+def is_grpc_available():
+    """Return True if grpcio and the generated stubs are importable."""
+    return _try_import()
+
+
+# ═══════════════════════════════════════════════════════════════════
+# gRPC endpoints for Antigravity (same hosts, different port/path)
+# ═══════════════════════════════════════════════════════════════════
+# The CloudCode gRPC service runs on the same hosts as REST but uses
+# the gRPC protocol. The agy CLI connects to:
+#   - cloudcode-pa.googleapis.com:443
+#   - daily-cloudcode-pa.googleapis.com:443
+#   - daily-cloudcode-pa.sandbox.googleapis.com:443
+
+_GRPC_ENDPOINTS = [
+    "daily-cloudcode-pa.googleapis.com:443",
+    "cloudcode-pa.googleapis.com:443",
+]
+
+_ALLOW_STAGING_ENV = "ALLOW_ANTIGRAVITY_STAGING"
+
+# ═══════════════════════════════════════════════════════════════════
+# Result type
+# ═══════════════════════════════════════════════════════════════════
+
+class GrpcFallbackResult:
+    """Result of a gRPC fallback attempt."""
+
+    __slots__ = ("ok", "response_data", "stream_chunks", "error_message",
+                 "endpoint_used", "model_used", "elapsed_s")
+
+    def __init__(self, ok=False, response_data=None, stream_chunks=None,
+                 error_message="", endpoint_used="", model_used="", elapsed_s=0.0):
+        self.ok = ok
+        self.response_data = response_data      # dict (non-streaming)
+        self.stream_chunks = stream_chunks      # list[dict] (streaming)
+        self.error_message = error_message
+        self.endpoint_used = endpoint_used
+        self.model_used = model_used
+        self.elapsed_s = elapsed_s
+
+    def __repr__(self):
+        if self.ok:
+            if self.stream_chunks is not None:
+                return f"<GrpcFallbackResult OK stream chunks={len(self.stream_chunks)}>"
+            return f"<GrpcFallbackResult OK data_keys={list(self.response_data.keys()) if self.response_data else None}>"
+        return f"<GrpcFallbackResult FAIL error={self.error_message!r}>"
+
+
+# ═══════════════════════════════════════════════════════════════════
+# JSON → Protobuf conversion helpers
+# ═══════════════════════════════════════════════════════════════════
+
+def _struct_to_protobuf(d, struct_obj=None):
+    """Convert a Python dict to a google.protobuf.Struct."""
+    from google.protobuf.struct_pb2 import Struct, Value, NullValue, ListValue
+    if struct_obj is None:
+        struct_obj = Struct()
+    if isinstance(d, dict):
+        for k, v in d.items():
+            if isinstance(v, str):
+                struct_obj.fields[k].string_value = v
+            elif isinstance(v, bool):
+                struct_obj.fields[k].bool_value = v
+            elif isinstance(v, int):
+                struct_obj.fields[k].number_value = float(v)
+            elif isinstance(v, float):
+                struct_obj.fields[k].number_value = v
+            elif isinstance(v, dict):
+                _struct_to_protobuf(v, struct_obj.fields[k].struct_value)
+            elif isinstance(v, list):
+                lst = struct_obj.fields[k].list_value
+                for item in v:
+                    if isinstance(item, str):
+                        lst.values.add().string_value = item
+                    elif isinstance(item, bool):
+                        lst.values.add().bool_value = item
+                    elif isinstance(item, (int, float)):
+                        lst.values.add().number_value = float(item)
+                    elif isinstance(item, dict):
+                        _struct_to_protobuf(item, lst.values.add().struct_value)
+                    elif item is None:
+                        lst.values.add().null_value = 0
+            elif v is None:
+                struct_obj.fields[k].null_value = 0
+    return struct_obj
+
+
+def _protobuf_struct_to_dict(struct):
+    """Convert a google.protobuf.Struct to a Python dict."""
+    from google.protobuf.struct_pb2 import Value, NullValue
+    result = {}
+    for k, v in struct.fields.items():
+        kind = v.WhichOneof("kind")
+        if kind == "null_value":
+            result[k] = None
+        elif kind == "number_value":
+            result[k] = v.number_value
+        elif kind == "string_value":
+            result[k] = v.string_value
+        elif kind == "bool_value":
+            result[k] = v.bool_value
+        elif kind == "struct_value":
+            result[k] = _protobuf_struct_to_dict(v.struct_value)
+        elif kind == "list_value":
+            result[k] = [_value_to_python(item) for item in v.list_value.values]
+        else:
+            result[k] = None
+    return result
+
+
+def _value_to_python(v):
+    """Convert a google.protobuf.Value to a Python value."""
+    kind = v.WhichOneof("kind")
+    if kind == "null_value":
+        return None
+    elif kind == "number_value":
+        return v.number_value
+    elif kind == "string_value":
+        return v.string_value
+    elif kind == "bool_value":
+        return v.bool_value
+    elif kind == "struct_value":
+        return _protobuf_struct_to_dict(v.struct_value)
+    elif kind == "list_value":
+        return [_value_to_python(item) for item in v.list_value.values]
+    return None
+
+
+def _json_parts_to_proto(parts_json):
+    """Convert a list of JSON content parts to protobuf Part messages."""
+    result = []
+    for p in parts_json:
+        if not isinstance(p, dict):
+            continue
+        part = _pb2.Part()
+
+        # Thought signature
+        sig = p.get("thoughtSignature") or p.get("thought_signature")
+        if sig:
+            part.thought_signature = sig
+
+        if p.get("thought"):
+            part.thought = True
+            if "text" in p:
+                part.text = p["text"]
+        elif "text" in p and "functionCall" not in p:
+            part.text = p["text"]
+        elif "functionCall" in p:
+            fc = p["functionCall"]
+            part.function_call.name = fc.get("name", "")
+            part.function_call.id = fc.get("id", "")
+            args = fc.get("args", fc.get("arguments", {}))
+            if isinstance(args, dict):
+                _struct_to_protobuf(args, part.function_call.args)
+            elif isinstance(args, str):
+                try:
+                    _struct_to_protobuf(json.loads(args), part.function_call.args)
+                except Exception:
+                    pass
+        elif "functionResponse" in p:
+            fr = p["functionResponse"]
+            part.function_response.name = fr.get("name", "")
+            part.function_response.id = fr.get("id", "")
+            resp = fr.get("response", {})
+            if "result" in resp:
+                result_val = resp["result"]
+                if isinstance(result_val, (dict, list)):
+                    _struct_to_protobuf({"result": result_val}, part.function_response.response)
+                else:
+                    _struct_to_protobuf({"result": str(result_val)}, part.function_response.response)
+            elif isinstance(resp, dict):
+                _struct_to_protobuf(resp, part.function_response.response)
+        elif "inlineData" in p:
+            idata = p["inlineData"]
+            import base64
+            part.inline_data.mime_type = idata.get("mimeType", "image/png")
+            b64data = idata.get("data", "")
+            part.inline_data.data = base64.b64decode(b64data) if b64data else b""
+
+        result.append(part)
+    return result
+
+
+def _json_contents_to_proto(contents_json):
+    """Convert a list of JSON content objects to protobuf Content messages."""
+    result = []
+    for c in contents_json:
+        if not isinstance(c, dict):
+            continue
+        content = _pb2.Content()
+        content.role = c.get("role", "user")
+        for part in _json_parts_to_proto(c.get("parts", [])):
+            content.parts.append(part)
+        result.append(content)
+    return result
+
+
+def _proto_candidate_to_json(candidate):
+    """Convert a protobuf Candidate to a JSON-compatible dict."""
+    content_json = {"role": candidate.content.role, "parts": []}
+    for part in candidate.content.parts:
+        p = {}
+        if part.thought_signature:
+            p["thoughtSignature"] = part.thought_signature
+        if part.thought:
+            p["thought"] = True
+            if part.text:
+                p["text"] = part.text
+        elif part.text and not part.HasField("function_call"):
+            p["text"] = part.text
+        elif part.HasField("function_call"):
+            fc = part.function_call
+            args_dict = _protobuf_struct_to_dict(fc.args) if fc.HasField("args") else {}
+            p["functionCall"] = {
+                "name": fc.name,
+                "args": args_dict,
+                "id": fc.id,
+            }
+        elif part.HasField("function_response"):
+            fr = part.function_response
+            resp_dict = _protobuf_struct_to_dict(fr.response) if fr.HasField("response") else {}
+            p["functionResponse"] = {
+                "name": fr.name,
+                "response": resp_dict,
+                "id": fr.id,
+            }
+        elif part.HasField("inline_data"):
+            import base64
+            p["inlineData"] = {
+                "mimeType": part.inline_data.mime_type,
+                "data": base64.b64encode(part.inline_data.data).decode(),
+            }
+        if p:
+            content_json["parts"].append(p)
+
+    return {
+        "content": content_json,
+        "finishReason": candidate.finish_reason,
+        "index": candidate.index,
+    }
+
+
+# ═══════════════════════════════════════════════════════════════════
+# Client
+# ═══════════════════════════════════════════════════════════════════
+
+class AntigravityGrpcClient:
+    """
+    gRPC fallback client for Google CloudCode Antigravity.
+
+    Thread-safe. Channels are cached per endpoint and reused.
+    """
+
+    def __init__(self):
+        self._channels = {}
+        self._stubs = {}
+        self._lock = threading.Lock()
+
+    def _get_channel(self, endpoint):
+        """Get or create a gRPC channel for the given endpoint."""
+        with self._lock:
+            if endpoint not in self._channels:
+                # Use secure channel with default SSL credentials
+                creds = _grpc.ssl_channel_credentials()
+                channel = _grpc.secure_channel(endpoint, creds)
+                self._channels[endpoint] = channel
+                self._stubs[endpoint] = _pb2_grpc.PredictionServiceStub(channel)
+            return self._channels[endpoint], self._stubs[endpoint]
+
+    def _build_request(self, wrapped_dict):
+        """
+        Build a GenerateContentRequest protobuf from the same wrapped dict
+        that the REST API uses.
+
+        wrapped_dict shape:
+        {
+            "project": "...",
+            "model": "...",
+            "requestType": "agent",
+            "userAgent": "antigravity/...",
+            "requestId": "agent-...",
+            "request": {
+                "contents": [...],
+                "systemInstruction": {...},
+                "generationConfig": {...},
+                "tools": [...],
+                "safetySettings": [...],
+                "toolConfig": {...},
+                "sessionId": "..."
+            }
+        }
+        """
+        req = _pb2.GenerateContentRequest()
+        req.project = wrapped_dict.get("project", "")
+        req.model = wrapped_dict.get("model", "")
+        req.request_type = wrapped_dict.get("requestType", "agent")
+        req.user_agent = wrapped_dict.get("userAgent", "")
+        req.request_id = wrapped_dict.get("requestId", "")
+
+        inner = wrapped_dict.get("request", {})
+
+        # Contents
+        for c in _json_contents_to_proto(inner.get("contents", [])):
+            req.request.contents.append(c)
+
+        # System instruction
+        si = inner.get("systemInstruction", {})
+        if si:
+            si_parts = si.get("parts", [])
+            if si.get("role"):
+                req.request.system_instruction.role = si.get("role", "user")
+            for part in _json_parts_to_proto(si_parts):
+                req.request.system_instruction.parts.append(part)
+
+        # Generation config
+        gc = inner.get("generationConfig", {})
+        if gc:
+            cfg = req.request.generation_config
+            if "maxOutputTokens" in gc:
+                cfg.max_output_tokens = int(gc["maxOutputTokens"])
+            if "temperature" in gc:
+                cfg.temperature = float(gc["temperature"])
+            if "topP" in gc:
+                cfg.top_p = float(gc["top_p" if "top_p" in gc else "topP"])
+            for ss in gc.get("stopSequences", []):
+                cfg.stop_sequences.append(ss)
+
+            # Thinking config (Gemini 3 native)
+            tc = gc.get("thinkingConfig", gc.get("thinking_config"))
+            if tc:
+                cfg.thinking_config.include_thoughts = tc.get("includeThoughts", tc.get("include_thoughts", False))
+                cfg.thinking_config.thinking_budget = int(tc.get("thinkingBudget", tc.get("thinking_budget", 8192)))
+            # Legacy thinking fields
+            if "includeThoughts" in gc and not tc:
+                cfg.thinking_config.include_thoughts = gc["includeThoughts"]
+            if "thinkingBudget" in gc and not tc:
+                cfg.thinking_config.thinking_budget = int(gc["thinkingBudget"])
+
+        # Tools
+        for tool_json in inner.get("tools", []):
+            tool = _pb2.Tool()
+            for fd_json in tool_json.get("functionDeclarations", []):
+                fd = tool.function_declarations.add()
+                fd.name = fd_json.get("name", "")
+                fd.description = fd_json.get("description", "")
+                params = fd_json.get("parameters", {})
+                if isinstance(params, dict) and params:
+                    _struct_to_protobuf(params, fd.parameters)
+            req.request.tools.append(tool)
+
+        # Safety settings
+        for ss in inner.get("safetySettings", []):
+            ss_msg = _pb2.SafetySetting()
+            ss_msg.category = ss.get("category", "")
+            ss_msg.threshold = ss.get("threshold", "OFF")
+            req.request.safety_settings.append(ss_msg)
+
+        # Tool config
+        tcfg = inner.get("toolConfig", {})
+        if tcfg:
+            fcc = tcfg.get("functionCallingConfig", {})
+            if fcc:
+                req.request.tool_config.function_calling_config.mode = fcc.get("mode", "AUTO")
+                for afn in fcc.get("allowed_function_names", []):
+                    req.request.tool_config.function_calling_config.allowed_function_names.append(afn)
+
+        # Session ID
+        sid = inner.get("sessionId", "")
+        if sid:
+            req.request.session_id = sid
+
+        return req
+
+    def try_generate(self, wrapped_dict, stream=False, access_token="",
+                     timeout_s=180):
+        """
+        Try a gRPC GenerateContent or StreamGenerateContent request.
+
+        Args:
+            wrapped_dict: The same wrapped dict used for REST requests.
+            stream: If True, use server-streaming RPC.
+            access_token: OAuth2 Bearer token for authentication.
+            timeout_s: Request timeout in seconds.
+
+        Returns:
+            GrpcFallbackResult with ok=True if successful.
+            For non-streaming: result.response_data is a dict matching
+                the REST JSON response shape.
+            For streaming: result.stream_chunks is a list of dicts matching
+                REST SSE chunk shapes.
+        """
+        if not is_grpc_available():
+            return GrpcFallbackResult(ok=False, error_message="grpcio not installed")
+
+        t0 = time.time()
+
+        # Build metadata (gRPC uses metadata instead of HTTP headers)
+        metadata = []
+        if access_token:
+            metadata.append(("authorization", f"Bearer {access_token}"))
+        ua = wrapped_dict.get("userAgent", "")
+        if ua:
+            metadata.append(("user-agent", ua))
+        metadata.append(("x-client-name", "antigravity"))
+        # Required for Google's gRPC gateway
+        metadata.append(("x-goog-api-client", "gl-node/18.18.2 fire/0.8.6 grpc/1.10.x"))
+
+        # Build endpoints list
+        endpoints = list(_GRPC_ENDPOINTS)
+        if os.environ.get(_ALLOW_STAGING_ENV, "0") == "1":
+            endpoints.append("daily-cloudcode-pa.sandbox.googleapis.com:443")
+            endpoints.append("autopush-cloudcode-pa.sandbox.googleapis.com:443")
+
+        model = wrapped_dict.get("model", "?")
+
+        last_error = ""
+        for ep in endpoints:
+            try:
+                channel, stub = self._get_channel(ep)
+                req = self._build_request(wrapped_dict)
+
+                if stream:
+                    return self._do_stream(stub, req, metadata, ep, model,
+                                           timeout_s, t0)
+                else:
+                    return self._do_unary(stub, req, metadata, ep, model,
+                                          timeout_s, t0)
+
+            except Exception as e:
+                last_error = str(e)
+                err_str = last_error.lower()
+                print(f"[antigravity-grpc] {ep} failed: {last_error[:300]}", file=sys.stderr)
+                # Don't retry on auth errors
+                if "unauthenticated" in err_str or "permission" in err_str:
+                    break
+                # Don't retry on invalid argument (model truly doesn't exist)
+                if "not_found" in err_str or "not found" in err_str:
+                    break
+                continue
+
+        elapsed = time.time() - t0
+        return GrpcFallbackResult(
+            ok=False,
+            error_message=f"All gRPC endpoints failed: {last_error}",
+            model_used=model,
+            elapsed_s=elapsed,
+        )
+
+    def _do_unary(self, stub, req, metadata, endpoint, model, timeout_s, t0):
+        """Execute a unary (non-streaming) gRPC call."""
+        response = stub.GenerateContent(
+            req,
+            metadata=metadata,
+            timeout=timeout_s,
+        )
+        elapsed = time.time() - t0
+
+        # Convert protobuf response to REST-compatible JSON shape
+        candidates_json = []
+        for candidate in response.response.candidates:
+            candidates_json.append(_proto_candidate_to_json(candidate))
+
+        # Match the REST response envelope:
+        # { "response": { "candidates": [...] } }
+        rest_shape = {
+            "response": {
+                "candidates": candidates_json,
+            }
+        }
+
+        print(f"[antigravity-grpc] {endpoint} unary OK, candidates={len(candidates_json)}, elapsed={elapsed:.1f}s", file=sys.stderr)
+
+        return GrpcFallbackResult(
+            ok=True,
+            response_data=rest_shape,
+            endpoint_used=endpoint,
+            model_used=model,
+            elapsed_s=elapsed,
+        )
+
+    def _do_stream(self, stub, req, metadata, endpoint, model, timeout_s, t0):
+        """Execute a server-streaming gRPC call."""
+        chunks = []
+        chunk_count = 0
+
+        response_iter = stub.StreamGenerateContent(
+            req,
+            metadata=metadata,
+            timeout=timeout_s,
+        )
+
+        for chunk_proto in response_iter:
+            chunk_count += 1
+            # Each chunk_proto is a StreamGenerateContentChunk
+            # which wraps a Response with candidates
+            candidates_json = []
+            for candidate in chunk_proto.response.candidates:
+                candidates_json.append(_proto_candidate_to_json(candidate))
+
+            # Match REST SSE chunk shape: { "response": { "candidates": [...] } }
+            chunk_json = {
+                "response": {
+                    "candidates": candidates_json,
+                }
+            }
+            chunks.append(chunk_json)
+
+        elapsed = time.time() - t0
+        print(f"[antigravity-grpc] {endpoint} stream OK, chunks={chunk_count}, elapsed={elapsed:.1f}s", file=sys.stderr)
+
+        return GrpcFallbackResult(
+            ok=True,
+            stream_chunks=chunks,
+            endpoint_used=endpoint,
+            model_used=model,
+            elapsed_s=elapsed,
+        )
+
+    def close(self):
+        """Close all gRPC channels."""
+        with self._lock:
+            for ep, channel in self._channels.items():
+                try:
+                    channel.close()
+                except Exception:
+                    pass
+            self._channels.clear()
+            self._stubs.clear()
+
+
+# ═══════════════════════════════════════════════════════════════════
+# Module-level singleton
+# ═══════════════════════════════════════════════════════════════════
+
+_client = None
+_client_lock = threading.Lock()
+
+def get_client():
+    """Get the module-level AntigravityGrpcClient singleton."""
+    global _client
+    with _client_lock:
+        if _client is None:
+            _client = AntigravityGrpcClient()
+        return _client
diff --git a/src/antigravity_grpc/cloudcode_pb2.py b/src/antigravity_grpc/cloudcode_pb2.py
new file mode 100644
index 0000000..45e1eb9
--- /dev/null
+++ b/src/antigravity_grpc/cloudcode_pb2.py
@@ -0,0 +1,88 @@
+# -*- coding: utf-8 -*-
+# Generated by the protocol buffer compiler.  DO NOT EDIT!
+# NO CHECKED-IN PROTOBUF GENCODE
+# source: cloudcode.proto
+# Protobuf Python Version: 6.31.1
+"""Generated protocol buffer code."""
+from google.protobuf import descriptor as _descriptor
+from google.protobuf import descriptor_pool as _descriptor_pool
+from google.protobuf import runtime_version as _runtime_version
+from google.protobuf import symbol_database as _symbol_database
+from google.protobuf.internal import builder as _builder
+_runtime_version.ValidateProtobufRuntimeVersion(
+    _runtime_version.Domain.PUBLIC,
+    6,
+    31,
+    1,
+    '',
+    'cloudcode.proto'
+)
+# @@protoc_insertion_point(imports)
+
+_sym_db = _symbol_database.Default()
+
+
+from google.protobuf import struct_pb2 as google_dot_protobuf_dot_struct__pb2
+
+
+DESCRIPTOR = _descriptor_pool.Default().AddSerializedFile(b'\n\x0f\x63loudcode.proto\x12%google.internal.cloud.code.v1internal\x1a\x1cgoogle/protobuf/struct.proto\"S\n\x07\x43ontent\x12\x0c\n\x04role\x18\x01 \x01(\t\x12:\n\x05parts\x18\x02 \x03(\x0b\x32+.google.internal.cloud.code.v1internal.Part\"\xb8\x02\n\x04Part\x12\x0e\n\x04text\x18\x01 \x01(\tH\x00\x12H\n\x0binline_data\x18\x02 \x01(\x0b\x32\x31.google.internal.cloud.code.v1internal.InlineDataH\x00\x12L\n\rfunction_call\x18\x03 \x01(\x0b\x32\x33.google.internal.cloud.code.v1internal.FunctionCallH\x00\x12T\n\x11\x66unction_response\x18\x04 \x01(\x0b\x32\x37.google.internal.cloud.code.v1internal.FunctionResponseH\x00\x12\x19\n\x11thought_signature\x18\n \x01(\t\x12\x0f\n\x07thought\x18\x0b \x01(\x08\x42\x06\n\x04\x64\x61ta\"-\n\nInlineData\x12\x11\n\tmime_type\x18\x01 \x01(\t\x12\x0c\n\x04\x64\x61ta\x18\x02 \x01(\x0c\"O\n\x0c\x46unctionCall\x12\x0c\n\x04name\x18\x01 \x01(\t\x12%\n\x04\x61rgs\x18\x02 \x01(\x0b\x32\x17.google.protobuf.Struct\x12\n\n\x02id\x18\x03 \x01(\t\"W\n\x10\x46unctionResponse\x12\x0c\n\x04name\x18\x01 \x01(\t\x12)\n\x08response\x18\x02 \x01(\x0b\x32\x17.google.protobuf.Struct\x12\n\n\x02id\x18\x03 \x01(\t\"4\n\rSafetySetting\x12\x10\n\x08\x63\x61tegory\x18\x01 \x01(\t\x12\x11\n\tthreshold\x18\x02 \x01(\t\"\xc2\x02\n\x10GenerationConfig\x12\x19\n\x11max_output_tokens\x18\x01 \x01(\x05\x12\x13\n\x0btemperature\x18\x02 \x01(\x02\x12\r\n\x05top_p\x18\x03 \x01(\x02\x12\x17\n\x0fthinking_budget\x18\x04 \x01(\x05\x12\x18\n\x10include_thoughts\x18\x05 \x01(\x08\x12\x16\n\x0estop_sequences\x18\x06 \x03(\t\x12_\n\x0fthinking_config\x18\x07 \x01(\x0b\x32\x46.google.internal.cloud.code.v1internal.GenerationConfig.ThinkingConfig\x1a\x43\n\x0eThinkingConfig\x12\x18\n\x10include_thoughts\x18\x01 \x01(\x08\x12\x17\n\x0fthinking_budget\x18\x02 \x01(\x05\"a\n\x04Tool\x12Y\n\x15\x66unction_declarations\x18\x01 \x03(\x0b\x32:.google.internal.cloud.code.v1internal.FunctionDeclaration\"e\n\x13\x46unctionDeclaration\x12\x0c\n\x04name\x18\x01 \x01(\t\x12\x13\n\x0b\x64\x65scription\x18\x02 \x01(\t\x12+\n\nparameters\x18\x03 \x01(\x0b\x32\x17.google.protobuf.Struct\"\xbd\x01\n\nToolConfig\x12h\n\x17\x66unction_calling_config\x18\x01 \x01(\x0b\x32G.google.internal.cloud.code.v1internal.ToolConfig.FunctionCallingConfig\x1a\x45\n\x15\x46unctionCallingConfig\x12\x0c\n\x04mode\x18\x01 \x01(\t\x12\x1e\n\x16\x61llowed_function_names\x18\x02 \x03(\t\"r\n\tCandidate\x12?\n\x07\x63ontent\x18\x01 \x01(\x0b\x32..google.internal.cloud.code.v1internal.Content\x12\x15\n\rfinish_reason\x18\x02 \x01(\t\x12\r\n\x05index\x18\x03 \x01(\x05\"\xad\x05\n\x16GenerateContentRequest\x12\x0f\n\x07project\x18\x01 \x01(\t\x12\r\n\x05model\x18\x02 \x01(\t\x12\x14\n\x0crequest_type\x18\x03 \x01(\t\x12\x12\n\nuser_agent\x18\x04 \x01(\t\x12\x12\n\nrequest_id\x18\x05 \x01(\t\x12[\n\x07request\x18\n \x01(\x0b\x32J.google.internal.cloud.code.v1internal.GenerateContentRequest.InnerRequest\x1a\xd7\x03\n\x0cInnerRequest\x12@\n\x08\x63ontents\x18\x01 \x03(\x0b\x32..google.internal.cloud.code.v1internal.Content\x12J\n\x12system_instruction\x18\x02 \x01(\x0b\x32..google.internal.cloud.code.v1internal.Content\x12R\n\x11generation_config\x18\x03 \x01(\x0b\x32\x37.google.internal.cloud.code.v1internal.GenerationConfig\x12:\n\x05tools\x18\x04 \x03(\x0b\x32+.google.internal.cloud.code.v1internal.Tool\x12M\n\x0fsafety_settings\x18\x05 \x03(\x0b\x32\x34.google.internal.cloud.code.v1internal.SafetySetting\x12\x46\n\x0btool_config\x18\x06 \x01(\x0b\x32\x31.google.internal.cloud.code.v1internal.ToolConfig\x12\x12\n\nsession_id\x18\x07 \x01(\t\"\xc6\x01\n\x17GenerateContentResponse\x12Y\n\x08response\x18\x01 \x01(\x0b\x32G.google.internal.cloud.code.v1internal.GenerateContentResponse.Response\x1aP\n\x08Response\x12\x44\n\ncandidates\x18\x01 \x03(\x0b\x32\x30.google.internal.cloud.code.v1internal.Candidate\"w\n\x1aStreamGenerateContentChunk\x12Y\n\x08response\x18\x01 \x01(\x0b\x32G.google.internal.cloud.code.v1internal.GenerateContentResponse.Response\".\n\x1b\x46\x65tchAvailableModelsRequest\x12\x0f\n\x07project\x18\x01 \x01(\t\"\xdb\x01\n\x1c\x46\x65tchAvailableModelsResponse\x12]\n\x06models\x18\x01 \x03(\x0b\x32M.google.internal.cloud.code.v1internal.FetchAvailableModelsResponse.ModelInfo\x1a\\\n\tModelInfo\x12\x0c\n\x04name\x18\x01 \x01(\t\x12\x14\n\x0c\x64isplay_name\x18\x02 \x01(\t\x12\x13\n\x0b\x64\x65scription\x18\x03 \x01(\t\x12\x16\n\x0e\x63ontext_window\x18\x04 \x01(\x03\"v\n\x12\x43ountTokensRequest\x12\x0f\n\x07project\x18\x01 \x01(\t\x12\r\n\x05model\x18\x02 \x01(\t\x12@\n\x08\x63ontents\x18\x03 \x03(\x0b\x32..google.internal.cloud.code.v1internal.Content\"+\n\x13\x43ountTokensResponse\x12\x14\n\x0ctotal_tokens\x18\x01 \x01(\x05\"+\n\x18RetrieveUserQuotaRequest\x12\x0f\n\x07project\x18\x01 \x01(\t\"^\n\x19RetrieveUserQuotaResponse\x12\x13\n\x0b\x64\x61ily_limit\x18\x01 \x01(\x03\x12\x13\n\x0b\x64\x61ily_usage\x18\x02 \x01(\x03\x12\x17\n\x0f\x64\x61ily_remaining\x18\x03 \x01(\x03\x32\x86\x06\n\x11PredictionService\x12\x90\x01\n\x0fGenerateContent\x12=.google.internal.cloud.code.v1internal.GenerateContentRequest\x1a>.google.internal.cloud.code.v1internal.GenerateContentResponse\x12\x9b\x01\n\x15StreamGenerateContent\x12=.google.internal.cloud.code.v1internal.GenerateContentRequest\x1a\x41.google.internal.cloud.code.v1internal.StreamGenerateContentChunk0\x01\x12\x9f\x01\n\x14\x46\x65tchAvailableModels\x12\x42.google.internal.cloud.code.v1internal.FetchAvailableModelsRequest\x1a\x43.google.internal.cloud.code.v1internal.FetchAvailableModelsResponse\x12\x84\x01\n\x0b\x43ountTokens\x12\x39.google.internal.cloud.code.v1internal.CountTokensRequest\x1a:.google.internal.cloud.code.v1internal.CountTokensResponse\x12\x96\x01\n\x11RetrieveUserQuota\x12?.google.internal.cloud.code.v1internal.RetrieveUserQuotaRequest\x1a@.google.internal.cloud.code.v1internal.RetrieveUserQuotaResponseB2Z0google.golang.org/internal/cloud/code/v1internalb\x06proto3')
+
+_globals = globals()
+_builder.BuildMessageAndEnumDescriptors(DESCRIPTOR, _globals)
+_builder.BuildTopDescriptorsAndMessages(DESCRIPTOR, 'cloudcode_pb2', _globals)
+if not _descriptor._USE_C_DESCRIPTORS:
+  _globals['DESCRIPTOR']._loaded_options = None
+  _globals['DESCRIPTOR']._serialized_options = b'Z0google.golang.org/internal/cloud/code/v1internal'
+  _globals['_CONTENT']._serialized_start=88
+  _globals['_CONTENT']._serialized_end=171
+  _globals['_PART']._serialized_start=174
+  _globals['_PART']._serialized_end=486
+  _globals['_INLINEDATA']._serialized_start=488
+  _globals['_INLINEDATA']._serialized_end=533
+  _globals['_FUNCTIONCALL']._serialized_start=535
+  _globals['_FUNCTIONCALL']._serialized_end=614
+  _globals['_FUNCTIONRESPONSE']._serialized_start=616
+  _globals['_FUNCTIONRESPONSE']._serialized_end=703
+  _globals['_SAFETYSETTING']._serialized_start=705
+  _globals['_SAFETYSETTING']._serialized_end=757
+  _globals['_GENERATIONCONFIG']._serialized_start=760
+  _globals['_GENERATIONCONFIG']._serialized_end=1082
+  _globals['_GENERATIONCONFIG_THINKINGCONFIG']._serialized_start=1015
+  _globals['_GENERATIONCONFIG_THINKINGCONFIG']._serialized_end=1082
+  _globals['_TOOL']._serialized_start=1084
+  _globals['_TOOL']._serialized_end=1181
+  _globals['_FUNCTIONDECLARATION']._serialized_start=1183
+  _globals['_FUNCTIONDECLARATION']._serialized_end=1284
+  _globals['_TOOLCONFIG']._serialized_start=1287
+  _globals['_TOOLCONFIG']._serialized_end=1476
+  _globals['_TOOLCONFIG_FUNCTIONCALLINGCONFIG']._serialized_start=1407
+  _globals['_TOOLCONFIG_FUNCTIONCALLINGCONFIG']._serialized_end=1476
+  _globals['_CANDIDATE']._serialized_start=1478
+  _globals['_CANDIDATE']._serialized_end=1592
+  _globals['_GENERATECONTENTREQUEST']._serialized_start=1595
+  _globals['_GENERATECONTENTREQUEST']._serialized_end=2280
+  _globals['_GENERATECONTENTREQUEST_INNERREQUEST']._serialized_start=1809
+  _globals['_GENERATECONTENTREQUEST_INNERREQUEST']._serialized_end=2280
+  _globals['_GENERATECONTENTRESPONSE']._serialized_start=2283
+  _globals['_GENERATECONTENTRESPONSE']._serialized_end=2481
+  _globals['_GENERATECONTENTRESPONSE_RESPONSE']._serialized_start=2401
+  _globals['_GENERATECONTENTRESPONSE_RESPONSE']._serialized_end=2481
+  _globals['_STREAMGENERATECONTENTCHUNK']._serialized_start=2483
+  _globals['_STREAMGENERATECONTENTCHUNK']._serialized_end=2602
+  _globals['_FETCHAVAILABLEMODELSREQUEST']._serialized_start=2604
+  _globals['_FETCHAVAILABLEMODELSREQUEST']._serialized_end=2650
+  _globals['_FETCHAVAILABLEMODELSRESPONSE']._serialized_start=2653
+  _globals['_FETCHAVAILABLEMODELSRESPONSE']._serialized_end=2872
+  _globals['_FETCHAVAILABLEMODELSRESPONSE_MODELINFO']._serialized_start=2780
+  _globals['_FETCHAVAILABLEMODELSRESPONSE_MODELINFO']._serialized_end=2872
+  _globals['_COUNTTOKENSREQUEST']._serialized_start=2874
+  _globals['_COUNTTOKENSREQUEST']._serialized_end=2992
+  _globals['_COUNTTOKENSRESPONSE']._serialized_start=2994
+  _globals['_COUNTTOKENSRESPONSE']._serialized_end=3037
+  _globals['_RETRIEVEUSERQUOTAREQUEST']._serialized_start=3039
+  _globals['_RETRIEVEUSERQUOTAREQUEST']._serialized_end=3082
+  _globals['_RETRIEVEUSERQUOTARESPONSE']._serialized_start=3084
+  _globals['_RETRIEVEUSERQUOTARESPONSE']._serialized_end=3178
+  _globals['_PREDICTIONSERVICE']._serialized_start=3181
+  _globals['_PREDICTIONSERVICE']._serialized_end=3955
+# @@protoc_insertion_point(module_scope)
diff --git a/src/antigravity_grpc/cloudcode_pb2_grpc.py b/src/antigravity_grpc/cloudcode_pb2_grpc.py
new file mode 100644
index 0000000..4b2e289
--- /dev/null
+++ b/src/antigravity_grpc/cloudcode_pb2_grpc.py
@@ -0,0 +1,275 @@
+# Generated by the gRPC Python protocol compiler plugin. DO NOT EDIT!
+"""Client and server classes corresponding to protobuf-defined services."""
+import grpc
+import warnings
+
+from antigravity_grpc import cloudcode_pb2 as cloudcode__pb2
+
+GRPC_GENERATED_VERSION = '1.80.0'
+GRPC_VERSION = grpc.__version__
+_version_not_supported = False
+
+try:
+    from grpc._utilities import first_version_is_lower
+    _version_not_supported = first_version_is_lower(GRPC_VERSION, GRPC_GENERATED_VERSION)
+except ImportError:
+    _version_not_supported = True
+
+if _version_not_supported:
+    raise RuntimeError(
+        f'The grpc package installed is at version {GRPC_VERSION},'
+        + ' but the generated code in cloudcode_pb2_grpc.py depends on'
+        + f' grpcio>={GRPC_GENERATED_VERSION}.'
+        + f' Please upgrade your grpc module to grpcio>={GRPC_GENERATED_VERSION}'
+        + f' or downgrade your generated code using grpcio-tools<={GRPC_VERSION}.'
+    )
+
+
+class PredictionServiceStub(object):
+    """─── Service ──────────────────────────────────────────────────────────
+
+    """
+
+    def __init__(self, channel):
+        """Constructor.
+
+        Args:
+            channel: A grpc.Channel.
+        """
+        self.GenerateContent = channel.unary_unary(
+                '/google.internal.cloud.code.v1internal.PredictionService/GenerateContent',
+                request_serializer=cloudcode__pb2.GenerateContentRequest.SerializeToString,
+                response_deserializer=cloudcode__pb2.GenerateContentResponse.FromString,
+                _registered_method=True)
+        self.StreamGenerateContent = channel.unary_stream(
+                '/google.internal.cloud.code.v1internal.PredictionService/StreamGenerateContent',
+                request_serializer=cloudcode__pb2.GenerateContentRequest.SerializeToString,
+                response_deserializer=cloudcode__pb2.StreamGenerateContentChunk.FromString,
+                _registered_method=True)
+        self.FetchAvailableModels = channel.unary_unary(
+                '/google.internal.cloud.code.v1internal.PredictionService/FetchAvailableModels',
+                request_serializer=cloudcode__pb2.FetchAvailableModelsRequest.SerializeToString,
+                response_deserializer=cloudcode__pb2.FetchAvailableModelsResponse.FromString,
+                _registered_method=True)
+        self.CountTokens = channel.unary_unary(
+                '/google.internal.cloud.code.v1internal.PredictionService/CountTokens',
+                request_serializer=cloudcode__pb2.CountTokensRequest.SerializeToString,
+                response_deserializer=cloudcode__pb2.CountTokensResponse.FromString,
+                _registered_method=True)
+        self.RetrieveUserQuota = channel.unary_unary(
+                '/google.internal.cloud.code.v1internal.PredictionService/RetrieveUserQuota',
+                request_serializer=cloudcode__pb2.RetrieveUserQuotaRequest.SerializeToString,
+                response_deserializer=cloudcode__pb2.RetrieveUserQuotaResponse.FromString,
+                _registered_method=True)
+
+
+class PredictionServiceServicer(object):
+    """─── Service ──────────────────────────────────────────────────────────
+
+    """
+
+    def GenerateContent(self, request, context):
+        """Missing associated documentation comment in .proto file."""
+        context.set_code(grpc.StatusCode.UNIMPLEMENTED)
+        context.set_details('Method not implemented!')
+        raise NotImplementedError('Method not implemented!')
+
+    def StreamGenerateContent(self, request, context):
+        """Missing associated documentation comment in .proto file."""
+        context.set_code(grpc.StatusCode.UNIMPLEMENTED)
+        context.set_details('Method not implemented!')
+        raise NotImplementedError('Method not implemented!')
+
+    def FetchAvailableModels(self, request, context):
+        """Missing associated documentation comment in .proto file."""
+        context.set_code(grpc.StatusCode.UNIMPLEMENTED)
+        context.set_details('Method not implemented!')
+        raise NotImplementedError('Method not implemented!')
+
+    def CountTokens(self, request, context):
+        """Missing associated documentation comment in .proto file."""
+        context.set_code(grpc.StatusCode.UNIMPLEMENTED)
+        context.set_details('Method not implemented!')
+        raise NotImplementedError('Method not implemented!')
+
+    def RetrieveUserQuota(self, request, context):
+        """Missing associated documentation comment in .proto file."""
+        context.set_code(grpc.StatusCode.UNIMPLEMENTED)
+        context.set_details('Method not implemented!')
+        raise NotImplementedError('Method not implemented!')
+
+
+def add_PredictionServiceServicer_to_server(servicer, server):
+    rpc_method_handlers = {
+            'GenerateContent': grpc.unary_unary_rpc_method_handler(
+                    servicer.GenerateContent,
+                    request_deserializer=cloudcode__pb2.GenerateContentRequest.FromString,
+                    response_serializer=cloudcode__pb2.GenerateContentResponse.SerializeToString,
+            ),
+            'StreamGenerateContent': grpc.unary_stream_rpc_method_handler(
+                    servicer.StreamGenerateContent,
+                    request_deserializer=cloudcode__pb2.GenerateContentRequest.FromString,
+                    response_serializer=cloudcode__pb2.StreamGenerateContentChunk.SerializeToString,
+            ),
+            'FetchAvailableModels': grpc.unary_unary_rpc_method_handler(
+                    servicer.FetchAvailableModels,
+                    request_deserializer=cloudcode__pb2.FetchAvailableModelsRequest.FromString,
+                    response_serializer=cloudcode__pb2.FetchAvailableModelsResponse.SerializeToString,
+            ),
+            'CountTokens': grpc.unary_unary_rpc_method_handler(
+                    servicer.CountTokens,
+                    request_deserializer=cloudcode__pb2.CountTokensRequest.FromString,
+                    response_serializer=cloudcode__pb2.CountTokensResponse.SerializeToString,
+            ),
+            'RetrieveUserQuota': grpc.unary_unary_rpc_method_handler(
+                    servicer.RetrieveUserQuota,
+                    request_deserializer=cloudcode__pb2.RetrieveUserQuotaRequest.FromString,
+                    response_serializer=cloudcode__pb2.RetrieveUserQuotaResponse.SerializeToString,
+            ),
+    }
+    generic_handler = grpc.method_handlers_generic_handler(
+            'google.internal.cloud.code.v1internal.PredictionService', rpc_method_handlers)
+    server.add_generic_rpc_handlers((generic_handler,))
+    server.add_registered_method_handlers('google.internal.cloud.code.v1internal.PredictionService', rpc_method_handlers)
+
+
+ # This class is part of an EXPERIMENTAL API.
+class PredictionService(object):
+    """─── Service ──────────────────────────────────────────────────────────
+
+    """
+
+    @staticmethod
+    def GenerateContent(request,
+            target,
+            options=(),
+            channel_credentials=None,
+            call_credentials=None,
+            insecure=False,
+            compression=None,
+            wait_for_ready=None,
+            timeout=None,
+            metadata=None):
+        return grpc.experimental.unary_unary(
+            request,
+            target,
+            '/google.internal.cloud.code.v1internal.PredictionService/GenerateContent',
+            cloudcode__pb2.GenerateContentRequest.SerializeToString,
+            cloudcode__pb2.GenerateContentResponse.FromString,
+            options,
+            channel_credentials,
+            insecure,
+            call_credentials,
+            compression,
+            wait_for_ready,
+            timeout,
+            metadata,
+            _registered_method=True)
+
+    @staticmethod
+    def StreamGenerateContent(request,
+            target,
+            options=(),
+            channel_credentials=None,
+            call_credentials=None,
+            insecure=False,
+            compression=None,
+            wait_for_ready=None,
+            timeout=None,
+            metadata=None):
+        return grpc.experimental.unary_stream(
+            request,
+            target,
+            '/google.internal.cloud.code.v1internal.PredictionService/StreamGenerateContent',
+            cloudcode__pb2.GenerateContentRequest.SerializeToString,
+            cloudcode__pb2.StreamGenerateContentChunk.FromString,
+            options,
+            channel_credentials,
+            insecure,
+            call_credentials,
+            compression,
+            wait_for_ready,
+            timeout,
+            metadata,
+            _registered_method=True)
+
+    @staticmethod
+    def FetchAvailableModels(request,
+            target,
+            options=(),
+            channel_credentials=None,
+            call_credentials=None,
+            insecure=False,
+            compression=None,
+            wait_for_ready=None,
+            timeout=None,
+            metadata=None):
+        return grpc.experimental.unary_unary(
+            request,
+            target,
+            '/google.internal.cloud.code.v1internal.PredictionService/FetchAvailableModels',
+            cloudcode__pb2.FetchAvailableModelsRequest.SerializeToString,
+            cloudcode__pb2.FetchAvailableModelsResponse.FromString,
+            options,
+            channel_credentials,
+            insecure,
+            call_credentials,
+            compression,
+            wait_for_ready,
+            timeout,
+            metadata,
+            _registered_method=True)
+
+    @staticmethod
+    def CountTokens(request,
+            target,
+            options=(),
+            channel_credentials=None,
+            call_credentials=None,
+            insecure=False,
+            compression=None,
+            wait_for_ready=None,
+            timeout=None,
+            metadata=None):
+        return grpc.experimental.unary_unary(
+            request,
+            target,
+            '/google.internal.cloud.code.v1internal.PredictionService/CountTokens',
+            cloudcode__pb2.CountTokensRequest.SerializeToString,
+            cloudcode__pb2.CountTokensResponse.FromString,
+            options,
+            channel_credentials,
+            insecure,
+            call_credentials,
+            compression,
+            wait_for_ready,
+            timeout,
+            metadata,
+            _registered_method=True)
+
+    @staticmethod
+    def RetrieveUserQuota(request,
+            target,
+            options=(),
+            channel_credentials=None,
+            call_credentials=None,
+            insecure=False,
+            compression=None,
+            wait_for_ready=None,
+            timeout=None,
+            metadata=None):
+        return grpc.experimental.unary_unary(
+            request,
+            target,
+            '/google.internal.cloud.code.v1internal.PredictionService/RetrieveUserQuota',
+            cloudcode__pb2.RetrieveUserQuotaRequest.SerializeToString,
+            cloudcode__pb2.RetrieveUserQuotaResponse.FromString,
+            options,
+            channel_credentials,
+            insecure,
+            call_credentials,
+            compression,
+            wait_for_ready,
+            timeout,
+            metadata,
+            _registered_method=True)
diff --git a/src/antigravity_grpc/proto/cloudcode.proto b/src/antigravity_grpc/proto/cloudcode.proto
new file mode 100644
index 0000000..cfecf0c
--- /dev/null
+++ b/src/antigravity_grpc/proto/cloudcode.proto
@@ -0,0 +1,183 @@
+// Copyright 2026 Codex Launcher Contributors
+// SPDX-License-Identifier: MIT
+//
+// CloudCode internal gRPC service definitions.
+// Reverse-engineered from the agy-core binary for Antigravity proxy fallback.
+// Service: google.internal.cloud.code.v1internal.PredictionService
+//
+// NOTE: google/api/annotations.proto is NOT imported here because it conflicts
+// with the google namespace package at runtime. The HTTP annotations are only
+// needed for Google's Envoy/gRPC-gateway and are unnecessary for our client.
+
+syntax = "proto3";
+
+package google.internal.cloud.code.v1internal;
+
+import "google/protobuf/struct.proto";
+
+option go_package = "google.golang.org/internal/cloud/code/v1internal";
+
+// ─── Reused message types ───────────────────────────────────────────
+
+message Content {
+  string role = 1;
+  repeated Part parts = 2;
+}
+
+message Part {
+  oneof data {
+    string text = 1;
+    InlineData inline_data = 2;
+    FunctionCall function_call = 3;
+    FunctionResponse function_response = 4;
+  }
+  // Thought signature for Gemini continuity
+  string thought_signature = 10;
+  // Thought part (reasoning)
+  bool thought = 11;
+}
+
+message InlineData {
+  string mime_type = 1;
+  bytes data = 2;
+}
+
+message FunctionCall {
+  string name = 1;
+  google.protobuf.Struct args = 2;
+  string id = 3;
+}
+
+message FunctionResponse {
+  string name = 1;
+  google.protobuf.Struct response = 2;
+  string id = 3;
+}
+
+message SafetySetting {
+  string category = 1;
+  string threshold = 2;
+}
+
+message GenerationConfig {
+  int32 max_output_tokens = 1;
+  float temperature = 2;
+  float top_p = 3;
+  int32 thinking_budget = 4;
+  bool include_thoughts = 5;
+  repeated string stop_sequences = 6;
+  message ThinkingConfig {
+    bool include_thoughts = 1;
+    int32 thinking_budget = 2;
+  }
+  ThinkingConfig thinking_config = 7;
+}
+
+message Tool {
+  repeated FunctionDeclaration function_declarations = 1;
+}
+
+message FunctionDeclaration {
+  string name = 1;
+  string description = 2;
+  google.protobuf.Struct parameters = 3;
+}
+
+message ToolConfig {
+  message FunctionCallingConfig {
+    string mode = 1;  // "AUTO", "ANY", "NONE", "VALIDATED"
+    repeated string allowed_function_names = 2;
+  }
+  FunctionCallingConfig function_calling_config = 1;
+}
+
+message Candidate {
+  Content content = 1;
+  string finish_reason = 2;
+  int32 index = 3;
+}
+
+// ─── GenerateContent ─────────────────────────────────────────────────
+
+message GenerateContentRequest {
+  string project = 1;
+  string model = 2;
+  string request_type = 3;
+  string user_agent = 4;
+  string request_id = 5;
+
+  message InnerRequest {
+    repeated Content contents = 1;
+    Content system_instruction = 2;
+    GenerationConfig generation_config = 3;
+    repeated Tool tools = 4;
+    repeated SafetySetting safety_settings = 5;
+    ToolConfig tool_config = 6;
+    string session_id = 7;
+  }
+
+  InnerRequest request = 10;
+}
+
+message GenerateContentResponse {
+  message Response {
+    repeated Candidate candidates = 1;
+  }
+  Response response = 1;
+}
+
+// ─── StreamGenerateContent ────────────────────────────────────────────
+
+message StreamGenerateContentChunk {
+  GenerateContentResponse.Response response = 1;
+}
+
+// ─── FetchAvailableModels ────────────────────────────────────────────
+
+message FetchAvailableModelsRequest {
+  string project = 1;
+}
+
+message FetchAvailableModelsResponse {
+  message ModelInfo {
+    string name = 1;
+    string display_name = 2;
+    string description = 3;
+    int64 context_window = 4;
+  }
+  repeated ModelInfo models = 1;
+}
+
+// ─── CountTokens ──────────────────────────────────────────────────────
+
+message CountTokensRequest {
+  string project = 1;
+  string model = 2;
+  repeated Content contents = 3;
+}
+
+message CountTokensResponse {
+  int32 total_tokens = 1;
+}
+
+// ─── RetrieveUserQuota ───────────────────────────────────────────────
+
+message RetrieveUserQuotaRequest {
+  string project = 1;
+}
+
+message RetrieveUserQuotaResponse {
+  int64 daily_limit = 1;
+  int64 daily_usage = 2;
+  int64 daily_remaining = 3;
+}
+
+// ─── Service ──────────────────────────────────────────────────────────
+
+service PredictionService {
+  rpc GenerateContent(GenerateContentRequest) returns (GenerateContentResponse);
+  rpc StreamGenerateContent(GenerateContentRequest) returns (stream StreamGenerateContentChunk);
+  rpc FetchAvailableModels(FetchAvailableModelsRequest) returns (FetchAvailableModelsResponse);
+  rpc CountTokens(CountTokensRequest) returns (CountTokensResponse);
+  rpc RetrieveUserQuota(RetrieveUserQuotaRequest) returns (RetrieveUserQuotaResponse);
+}
diff --git a/src/antigravity_grpc/proto/google/api/annotations.proto b/src/antigravity_grpc/proto/google/api/annotations.proto
new file mode 100644
index 0000000..5f0556d
--- /dev/null
+++ b/src/antigravity_grpc/proto/google/api/annotations.proto
@@ -0,0 +1,14 @@
+// Minimal google/api/annotations.proto for code generation.
+
+syntax = "proto3";
+
+package google.api;
+
+import "google/api/http.proto";
+import "google/protobuf/descriptor.proto";
+
+option go_package = "google.golang.org/genproto/googleapis/api/annotations";
+
+extend google.protobuf.MethodOptions {
+  HttpRule http = 72295728;
+}
diff --git a/src/antigravity_grpc/proto/google/api/http.proto b/src/antigravity_grpc/proto/google/api/http.proto
new file mode 100644
index 0000000..a089001
--- /dev/null
+++ b/src/antigravity_grpc/proto/google/api/http.proto
@@ -0,0 +1,18 @@
+// Minimal google/api/http.proto for code generation.
+
+syntax = "proto3";
+
+package google.api;
+
+option go_package = "google.golang.org/genproto/googleapis/api/annotations";
+
+message HttpRule {
+  string get = 1;
+  string put = 2;
+  string post = 3;
+  string delete = 4;
+  string patch = 5;
+  repeated HttpRule additional_bindings = 11;
+  string body = 7;
+  string response_body = 12;
+}
diff --git a/src/codex-launcher-gui b/src/codex-launcher-gui
index 1f61f0d..000e696 100755
--- a/src/codex-launcher-gui
+++ b/src/codex-launcher-gui
@@ -27,9 +27,10 @@ model_catalog_json = ""
 """
 
 CHANGELOG = [
-    ("3.11.12", "2026-05-26", [
-        "New Antigravity v2 handler mimicking anti-api",
-        "Safety settings, stopSequences, simplified sanitizer",
+    ("3.12.0", "2026-05-27", [
+        "gRPC auto-fallback for Antigravity (PR #13)",
+        "Dynamic version fetch with probe validation",
+        "Antigravity v2 handler rewrite (anti-api)",
     ]),
     ("3.11.10", "2026-05-26", [
         "Fix Antigravity: interleave function_call/output pairs (PR #11)",
diff --git a/src/codex_launcher_lib.py b/src/codex_launcher_lib.py
index c6c8b84..9f93125 100644
--- a/src/codex_launcher_lib.py
+++ b/src/codex_launcher_lib.py
@@ -83,12 +83,14 @@ model_catalog_json = ""
 """
 
 CHANGELOG = [
-    ("3.11.12", "2026-05-26", [
-        "New Antigravity v2 handler mimicking anti-api approach",
+    ("3.12.0", "2026-05-27", [
+        "gRPC auto-fallback for Antigravity provider (PR #13)",
+        "New antigravity_grpc module with protobuf client",
+        "REST 404 triggers gRPC fallback using display names",
+        "gRPC supports streaming and unary generate",
+        "Dynamic version fetch with probe validation",
+        "Antigravity v2 handler rewrite (anti-api approach)",
         "Safety settings, stopSequences, sessionId, requestType: agent",
-        "Simplified sanitizer preserving functionCall/functionResponse",
-        "Endpoint priority: daily-cloudcode-pa first",
-        "functionResponse uses response.result (string) format",
     ]),
     ("3.11.11", "2026-05-26", [
         "Final trimming only removes plain messages, never function_call_output",
diff --git a/src/translate-proxy.py b/src/translate-proxy.py
index 20a6794..708cc7e 100755
--- a/src/translate-proxy.py
+++ b/src/translate-proxy.py
@@ -165,6 +165,56 @@ import tempfile
 
 _IS_WINDOWS = sys.platform == "win32"
 
+# ═══════════════════════════════════════════════════════════════════
+# Lazy gRPC import for Antigravity fallback
+# ═══════════════════════════════════════════════════════════════════
+_antigravity_grpc_client = None
+_antigravity_grpc_available = None
+
+def _get_grpc_client():
+    """Lazy-load the Antigravity gRPC client. Returns None if grpcio is not installed."""
+    global _antigravity_grpc_client, _antigravity_grpc_available
+    if _antigravity_grpc_available is False:
+        return None
+    if _antigravity_grpc_client is not None:
+        return _antigravity_grpc_client
+    try:
+        # Add the src directory to sys.path so antigravity_grpc package is found
+        _src_dir = os.path.dirname(os.path.abspath(__file__))
+        if _src_dir not in sys.path:
+            sys.path.insert(0, _src_dir)
+        from antigravity_grpc import is_grpc_available, AntigravityGrpcClient, get_client
+        if is_grpc_available():
+            _antigravity_grpc_client = get_client()
+            _antigravity_grpc_available = True
+            print("[antigravity-grpc] gRPC fallback module loaded OK", file=sys.stderr)
+            return _antigravity_grpc_client
+        else:
+            _antigravity_grpc_available = False
+            print("[antigravity-grpc] grpcio available but stubs failed to load, gRPC fallback disabled", file=sys.stderr)
+            return None
+    except ImportError as e:
+        _antigravity_grpc_available = False
+        print(f"[antigravity-grpc] grpcio not installed ({e}), gRPC fallback disabled", file=sys.stderr)
+        return None
+
+# Reverse alias map: REST slug → gRPC display name
+# gRPC uses display names (e.g. "Gemini 3.5 Flash (High)") while REST uses slugs (e.g. "gemini-3-flash")
+_GRPC_REVERSE_ALIAS = {
+    "gemini-3-flash": "Gemini 3.5 Flash (High)",
+    "gemini-3.5-flash-low": "Gemini 3.5 Flash (Low)",
+    "gemini-3.1-pro-low": "Gemini 3.1 Pro (High)",
+    "claude-sonnet-4-6": "Claude Sonnet 4.6 (Thinking)",
+    "claude-opus-4-6-thinking": "Claude Opus 4.6 (Thinking)",
+    "gpt-oss-120b-medium": "GPT-OSS 120B (Medium)",
+    "gemini-2.5-flash": "Gemini 2.5 Flash",
+    "gemini-2.5-pro": "Gemini 2.5 Pro",
+    "gemini-2.5-flash-lite": "Gemini 2.5 Flash Lite",
+}
+
+# Errors from REST that should trigger gRPC fallback
+_GRPC_FALLBACK_REST_ERRORS = {404}  # Model not found via REST (model exists in gRPC but not REST)
+
 # ═══════════════════════════════════════════════════════════════════
 # Config
 # ═══════════════════════════════════════════════════════════════════
@@ -5762,7 +5812,7 @@ class Handler(http.server.BaseHTTPRequestHandler):
             _antigravity_endpoints.append("https://autopush-cloudcode-pa.sandbox.googleapis.com")
 
         body_b = json.dumps(wrapped).encode()
-        print(f"[{self._session_id}] [antigravity-v2] model={model} stream={stream} contents={len(contents)} tools={bool(gemini_tools)} project={project_id} ver={_versions[0]}", file=sys.stderr)
+        print(f"[{self._session_id}] [antigravity-v2] model={model} stream={stream} contents={len(contents)} tools={bool(gemini_tools)} project={project_id} ver={_fetched_ver}", file=sys.stderr)
         try:
             debug_path = os.path.join(_LOG_DIR, f"antigravity-v2-request-{self._session_id}.json")
             with open(debug_path, "w") as dbg:
@@ -5863,6 +5913,14 @@ class Handler(http.server.BaseHTTPRequestHandler):
                         continue
 
         if upstream is None:
+            # ─── gRPC FALLBACK ─────────────────────────────────────────
+            # If REST failed with 404 (model not available via REST API),
+            # try gRPC which supports display names and has a wider model catalog.
+            if _all_404:
+                grpc_result = self._try_grpc_fallback(wrapped, access_token, stream, tracker)
+                if grpc_result is not None:
+                    return  # gRPC succeeded, response already sent
+            # ─── END gRPC FALLBACK ─────────────────────────────────────
             return self.send_json(502, {"error": {"type": "proxy_error", "message": "All endpoints failed"}})
 
         if stream:
@@ -5870,6 +5928,190 @@ class Handler(http.server.BaseHTTPRequestHandler):
         else:
             self._forward_gemini_json(upstream, model, body, input_data)
 
+    # ═══════════════════════════════════════════════════════════════════
+    # gRPC Fallback for Antigravity
+    # ═══════════════════════════════════════════════════════════════════
+
+    def _try_grpc_fallback(self, wrapped_dict, access_token, stream, tracker=None):
+        """
+        Try gRPC fallback when REST API returns 404 (model not found).
+
+        gRPC uses display names (e.g. "Gemini 3.5 Flash (High)") instead of
+        REST slugs (e.g. "gemini-3-flash"), so models unavailable via REST
+        may work via gRPC.
+
+        Returns None if gRPC is unavailable or also failed (caller should
+        send its own error response). Returns True if gRPC succeeded and
+        the response was already sent to the client.
+        """
+        grpc_client = _get_grpc_client()
+        if grpc_client is None:
+            print(f"[{self._session_id}] [antigravity-grpc] gRPC fallback not available (grpcio not installed), skipping", file=sys.stderr)
+            return None
+
+        # gRPC uses display names, not REST slugs — remap the model ID
+        grpc_wrapped = dict(wrapped_dict)
+        rest_model = grpc_wrapped.get("model", "")
+        grpc_model = _GRPC_REVERSE_ALIAS.get(rest_model, rest_model)
+        grpc_wrapped["model"] = grpc_model
+        if grpc_model != rest_model:
+            print(f"[{self._session_id}] [antigravity-grpc] model remapped for gRPC: REST={rest_model} -> gRPC={grpc_model}", file=sys.stderr)
+
+        print(f"[{self._session_id}] [antigravity-grpc] REST 404, trying gRPC fallback with model={grpc_model} stream={stream}", file=sys.stderr)
+
+        try:
+            result = grpc_client.try_generate(
+                grpc_wrapped,
+                stream=stream,
+                access_token=access_token,
+                timeout_s=180,
+            )
+        except Exception as e:
+            print(f"[{self._session_id}] [antigravity-grpc] gRPC call exception: {e}", file=sys.stderr)
+            return None
+
+        if not result.ok:
+            print(f"[{self._session_id}] [antigravity-grpc] gRPC fallback also failed: {result.error_message}", file=sys.stderr)
+            return None
+
+        print(f"[{self._session_id}] [antigravity-grpc] gRPC fallback OK! endpoint={result.endpoint_used} model={result.model_used} elapsed={result.elapsed_s:.1f}s", file=sys.stderr)
+
+        # Process the gRPC response through the same forwarding paths as REST
+        if stream and result.stream_chunks is not None:
+            self._forward_grpc_sse(result, grpc_model)
+        elif not stream and result.response_data is not None:
+            self._forward_grpc_json(result, grpc_model)
+        else:
+            print(f"[{self._session_id}] [antigravity-grpc] unexpected result shape, no data to forward", file=sys.stderr)
+            return None
+
+        return True  # Response sent successfully via gRPC
+
+    def _forward_grpc_sse(self, grpc_result, model):
+        """
+        Forward a gRPC streaming result to the client as SSE events.
+        The gRPC result contains stream_chunks that match the REST SSE chunk shape,
+        so we can process them through the same _forward_gemini_sse logic.
+        """
+        resp_id = f"resp-{uuid.uuid4().hex[:24]}"
+        created = int(time.time())
+        self.send_response(200)
+        self.send_header("Content-Type", "text/event-stream")
+        self.send_header("Cache-Control", "no-cache")
+        self.send_header("Connection", "keep-alive")
+        self.end_headers()
+
+        full_text = ""
+        output_items = []
+        current_tool_calls = {}
+        message_started = False
+        message_id = f"msg-{uuid.uuid4().hex[:24]}"
+
+        def flush_event(event_type, data):
+            self.wfile.write(f"event: {event_type}\ndata: {json.dumps(data)}\n\n".encode())
+            self.wfile.flush()
+
+        flush_event("response.created", {"type": "response.created", "response": {"id": resp_id, "object": "response", "model": model, "status": "in_progress", "created": created, "output": []}})
+        flush_event("response.in_progress", {"type": "response.in_progress", "response": {"id": resp_id}})
+
+        # Process each gRPC chunk (same shape as REST SSE chunks)
+        for chunk in grpc_result.stream_chunks:
+            candidates = chunk.get("response", chunk).get("candidates", [])
+            if not candidates:
+                continue
+            parts = candidates[0].get("content", {}).get("parts", [])
+            for part in parts:
+                sig = _extract_gemini_sig(part)
+                if sig:
+                    if part.get("functionCall"):
+                        fc_id = part["functionCall"].get("id") or part["functionCall"].get("name")
+                        fc_name = part["functionCall"].get("name")
+                        if fc_id:
+                            _gemini_store_sig(f"fc:{fc_id}", sig)
+                        if fc_name:
+                            _gemini_store_sig(f"fc:{fc_name}", sig)
+                    _gemini_store_sig(f"turn:{resp_id}", sig)
+                if part.get("thought"):
+                    sig_from_thought = _extract_gemini_sig(part)
+                    if sig_from_thought:
+                        _gemini_store_sig(f"turn:{resp_id}", sig_from_thought)
+                    continue
+                if "text" in part and not part.get("functionCall"):
+                    text_delta = part["text"]
+                    if not text_delta:
+                        continue
+                    full_text += text_delta
+                    if not message_started:
+                        flush_event("response.output_item.added", {"type": "response.output_item.added", "output_index": 0, "item": {"type": "message", "id": message_id, "role": "assistant", "content": []}})
+                        flush_event("response.content_part.added", {"type": "response.content_part.added", "output_index": 0, "content_index": 0, "part": {"type": "output_text", "text": ""}})
+                        output_items.append({"text": True})
+                        message_started = True
+                    flush_event("response.output_text.delta", {"type": "response.output_text.delta", "output_index": 0, "content_index": 0, "delta": text_delta})
+                elif part.get("functionCall"):
+                    fc = part["functionCall"]
+                    call_id = f"call_{uuid.uuid4().hex[:24]}"
+                    args_str = json.dumps(fc.get("args", fc.get("arguments", {})))
+                    output_index = len(output_items)
+                    flush_event("response.output_item.added", {"type": "response.output_item.added", "output_index": output_index, "item": {"type": "function_call", "id": call_id, "call_id": call_id, "name": fc.get("name", ""), "arguments": ""}})
+                    flush_event("response.function_call_arguments.delta", {"type": "response.function_call_arguments.delta", "output_index": output_index, "item_id": call_id, "delta": args_str})
+                    flush_event("response.function_call_arguments.done", {"type": "response.function_call_arguments.done", "output_index": output_index, "item_id": call_id, "arguments": args_str})
+                    current_tool_calls[call_id] = fc
+                    output_items.append({"tool": True})
+
+        # Build final response
+        out = []
+        if full_text:
+            out.append({"type": "message", "id": message_id, "role": "assistant", "content": [{"type": "output_text", "text": full_text}]})
+        tool_outputs = []
+        for cid, fc in current_tool_calls.items():
+            tool_outputs.append({"type": "function_call", "id": cid, "call_id": cid, "name": fc.get("name", ""), "arguments": json.dumps(fc.get("args", fc.get("arguments", {})))})
+        out.extend(tool_outputs)
+
+        final_resp = {"id": resp_id, "object": "response", "model": model, "status": "completed", "created": created, "output": out}
+        if full_text:
+            flush_event("response.output_text.done", {"type": "response.output_text.done", "output_index": 0, "content_index": 0, "text": full_text})
+            flush_event("response.content_part.done", {"type": "response.content_part.done", "output_index": 0, "content_index": 0, "part": {"type": "output_text", "text": full_text}})
+            flush_event("response.output_item.done", {"type": "response.output_item.done", "output_index": 0, "item": out[0]})
+        for idx, item in enumerate(tool_outputs, start=(1 if full_text else 0)):
+            flush_event("response.output_item.done", {"type": "response.output_item.done", "output_index": idx, "item": item})
+        flush_event("response.completed", {"type": "response.completed", "response": final_resp})
+        self.close_connection = True
+
+        with _response_store_lock:
+            _response_store[resp_id] = final_resp
+            while len(_response_store) > _MAX_STORED:
+                _response_store.popitem(last=False)
+
+    def _forward_grpc_json(self, grpc_result, model):
+        """Forward a gRPC non-streaming result to the client as JSON."""
+        resp_id = f"resp-{uuid.uuid4().hex[:24]}"
+        created = int(time.time())
+        out = []
+        full_text = ""
+        data = grpc_result.response_data
+        candidates = data.get("response", data).get("candidates", [])
+        if candidates:
+            parts = candidates[0].get("content", {}).get("parts", [])
+            text_parts = []
+            for part in parts:
+                if part.get("thought"):
+                    continue
+                if "text" in part and not part.get("functionCall"):
+                    text_parts.append(part["text"])
+                elif part.get("functionCall"):
+                    fc = part["functionCall"]
+                    call_id = f"call_{uuid.uuid4().hex[:24]}"
+                    out.append({"type": "function_call", "id": call_id, "call_id": call_id, "name": fc.get("name", ""), "arguments": json.dumps(fc.get("args", fc.get("arguments", {})))})
+            if text_parts:
+                full_text = "".join(text_parts)
+                out.insert(0, {"type": "message", "id": f"msg-{uuid.uuid4().hex[:24]}", "role": "assistant", "content": [{"type": "output_text", "text": full_text}]})
+        resp = {"id": resp_id, "object": "response", "model": model, "status": "completed", "created": created, "output": out}
+        with _response_store_lock:
+            _response_store[resp_id] = resp
+            while len(_response_store) > _MAX_STORED:
+                _response_store.popitem(last=False)
+        self.send_json(200, resp)
+
     def _handle_gemini_oauth(self, body, model, stream, tracker=None):
         input_data = body.get("input", "")
         policy = provider_policy()
diff --git a/tests/test_antigravity_grpc.py b/tests/test_antigravity_grpc.py
new file mode 100644
index 0000000..d099133
--- /dev/null
+++ b/tests/test_antigravity_grpc.py
@@ -0,0 +1,396 @@
+#!/usr/bin/env python3
+"""
+Unit tests for the Antigravity gRPC fallback module.
+
+Tests cover:
+1. Module import and availability detection
+2. Protobuf conversion helpers (JSON <-> protobuf)
+3. Request building from wrapped REST dict
+4. Reverse alias map correctness
+5. GrpcFallbackResult type
+6. Integration: _try_grpc_fallback triggers correctly on REST 404
+"""
+
+import json
+import os
+import sys
+import unittest
+from unittest.mock import patch, MagicMock
+
+# Add src to path so we can import the antigravity_grpc package
+_src_dir = os.path.join(os.path.dirname(os.path.abspath(__file__)), "..", "src")
+if _src_dir not in sys.path:
+    sys.path.insert(0, _src_dir)
+
+
+class TestGrpcModuleAvailability(unittest.TestCase):
+    """Tests for is_grpc_available() and module loading."""
+
+    def test_is_grpc_available_returns_bool(self):
+        """is_grpc_available should return a boolean."""
+        from antigravity_grpc import is_grpc_available
+        result = is_grpc_available()
+        self.assertIsInstance(result, bool)
+
+    def test_is_grpc_available_true_when_installed(self):
+        """If grpcio is installed and stubs are loadable, should return True."""
+        from antigravity_grpc import is_grpc_available
+        # grpcio was installed at test time, so this should be True
+        self.assertTrue(is_grpc_available())
+
+    def test_client_instantiation(self):
+        """AntigravityGrpcClient should be instantiatable."""
+        from antigravity_grpc import AntigravityGrpcClient
+        client = AntigravityGrpcClient()
+        self.assertIsNotNone(client)
+
+    def test_get_client_singleton(self):
+        """get_client should return the same singleton."""
+        from antigravity_grpc import get_client
+        c1 = get_client()
+        c2 = get_client()
+        self.assertIs(c1, c2)
+
+
+class TestGrpcFallbackResult(unittest.TestCase):
+    """Tests for GrpcFallbackResult type."""
+
+    def test_default_values(self):
+        from antigravity_grpc import GrpcFallbackResult
+        r = GrpcFallbackResult()
+        self.assertFalse(r.ok)
+        self.assertIsNone(r.response_data)
+        self.assertIsNone(r.stream_chunks)
+        self.assertEqual(r.error_message, "")
+        self.assertEqual(r.endpoint_used, "")
+        self.assertEqual(r.model_used, "")
+        self.assertEqual(r.elapsed_s, 0.0)
+
+    def test_success_result(self):
+        from antigravity_grpc import GrpcFallbackResult
+        r = GrpcFallbackResult(ok=True, response_data={"response": {"candidates": []}},
+                                endpoint_used="daily-cloudcode-pa.googleapis.com:443",
+                                model_used="Gemini 3.5 Flash (High)",
+                                elapsed_s=2.5)
+        self.assertTrue(r.ok)
+        self.assertIsNotNone(r.response_data)
+        self.assertEqual(r.elapsed_s, 2.5)
+
+    def test_failure_result(self):
+        from antigravity_grpc import GrpcFallbackResult
+        r = GrpcFallbackResult(ok=False, error_message="All gRPC endpoints failed")
+        self.assertFalse(r.ok)
+        self.assertIn("failed", r.error_message)
+
+    def test_repr(self):
+        from antigravity_grpc import GrpcFallbackResult
+        r_ok = GrpcFallbackResult(ok=True, response_data={"response": {"candidates": []}})
+        self.assertIn("OK", repr(r_ok))
+        r_fail = GrpcFallbackResult(ok=False, error_message="timeout")
+        self.assertIn("FAIL", repr(r_fail))
+
+
+class TestReverseAliasMap(unittest.TestCase):
+    """Tests for the _GRPC_REVERSE_ALIAS map in translate-proxy.py."""
+
+    def test_import_reverse_alias(self):
+        """The reverse alias map should be importable from the proxy module."""
+        import importlib
+        _spec = importlib.util.spec_from_file_location(
+            "translate_proxy",
+            os.path.join(_src_dir, "translate-proxy.py"),
+        )
+        tp = importlib.util.module_from_spec(_spec)
+        _spec.loader.exec_module(tp)
+        self.assertIsInstance(tp._GRPC_REVERSE_ALIAS, dict)
+
+    def test_key_models_have_reverse_aliases(self):
+        """All key REST model slugs should have gRPC display name mappings."""
+        import importlib
+        _spec = importlib.util.spec_from_file_location(
+            "translate_proxy",
+            os.path.join(_src_dir, "translate-proxy.py"),
+        )
+        tp = importlib.util.module_from_spec(_spec)
+        _spec.loader.exec_module(tp)
+
+        required_slugs = [
+            "gemini-3-flash",
+            "gemini-3.5-flash-low",
+            "gemini-3.1-pro-low",
+            "claude-sonnet-4-6",
+            "claude-opus-4-6-thinking",
+            "gemini-2.5-flash",
+        ]
+        for slug in required_slugs:
+            self.assertIn(slug, tp._GRPC_REVERSE_ALIAS,
+                         f"Missing reverse alias for REST slug '{slug}'")
+
+    def test_reverse_alias_values_are_display_names(self):
+        """gRPC display names should contain spaces and parentheses, not hyphens."""
+        import importlib
+        _spec = importlib.util.spec_from_file_location(
+            "translate_proxy",
+            os.path.join(_src_dir, "translate-proxy.py"),
+        )
+        tp = importlib.util.module_from_spec(_spec)
+        _spec.loader.exec_module(tp)
+
+        for slug, display_name in tp._GRPC_REVERSE_ALIAS.items():
+            # Display names typically have spaces (e.g. "Gemini 3.5 Flash (High)")
+            # while slugs use hyphens (e.g. "gemini-3-flash")
+            self.assertNotEqual(slug, display_name,
+                               f"Reverse alias for '{slug}' should differ from slug (gRPC uses display names)")
+
+
+class TestProtobufConversion(unittest.TestCase):
+    """Tests for JSON -> protobuf conversion helpers."""
+
+    def test_struct_to_protobuf(self):
+        """_struct_to_protobuf should convert a simple dict to Struct."""
+        from antigravity_grpc.client import _struct_to_protobuf
+        result = _struct_to_protobuf({"key": "value", "num": 42})
+        self.assertIsNotNone(result)
+        # Verify round-trip
+        from antigravity_grpc.client import _protobuf_struct_to_dict
+        d = _protobuf_struct_to_dict(result)
+        self.assertEqual(d["key"], "value")
+        self.assertEqual(d["num"], 42.0)
+
+    def test_struct_round_trip_nested(self):
+        """Nested dicts should survive a round-trip through protobuf."""
+        from antigravity_grpc.client import _struct_to_protobuf, _protobuf_struct_to_dict
+        original = {"outer": {"inner": "hello"}, "list_val": [1, 2, 3]}
+        proto = _struct_to_protobuf(original)
+        result = _protobuf_struct_to_dict(proto)
+        self.assertEqual(result["outer"]["inner"], "hello")
+        self.assertEqual(result["list_val"], [1.0, 2.0, 3.0])
+
+    def test_json_parts_to_proto_text(self):
+        """Text parts should convert to protobuf Part with text field."""
+        from antigravity_grpc.client import _json_parts_to_proto
+        parts = _json_parts_to_proto([{"text": "Hello world"}])
+        self.assertEqual(len(parts), 1)
+        self.assertEqual(parts[0].text, "Hello world")
+
+    def test_json_parts_to_proto_function_call(self):
+        """FunctionCall parts should convert correctly."""
+        from antigravity_grpc.client import _json_parts_to_proto
+        parts = _json_parts_to_proto([{
+            "functionCall": {
+                "name": "exec_command",
+                "args": {"cmd": "ls -la"},
+                "id": "call_123"
+            }
+        }])
+        self.assertEqual(len(parts), 1)
+        self.assertTrue(parts[0].HasField("function_call"))
+        self.assertEqual(parts[0].function_call.name, "exec_command")
+        self.assertEqual(parts[0].function_call.id, "call_123")
+
+    def test_json_parts_to_proto_function_response(self):
+        """FunctionResponse parts should convert correctly."""
+        from antigravity_grpc.client import _json_parts_to_proto
+        parts = _json_parts_to_proto([{
+            "functionResponse": {
+                "name": "exec_command",
+                "response": {"result": "file1.txt"},
+                "id": "call_123"
+            }
+        }])
+        self.assertEqual(len(parts), 1)
+        self.assertTrue(parts[0].HasField("function_response"))
+        self.assertEqual(parts[0].function_response.name, "exec_command")
+
+    def test_json_contents_to_proto(self):
+        """Content objects should convert correctly."""
+        from antigravity_grpc.client import _json_contents_to_proto
+        contents = _json_contents_to_proto([
+            {"role": "user", "parts": [{"text": "Hello"}]},
+            {"role": "model", "parts": [{"text": "Hi there"}]},
+        ])
+        self.assertEqual(len(contents), 2)
+        self.assertEqual(contents[0].role, "user")
+        self.assertEqual(contents[1].role, "model")
+
+    def test_proto_candidate_to_json(self):
+        """Protobuf candidates should convert back to JSON-compatible dicts."""
+        from antigravity_grpc.client import _json_contents_to_proto, _proto_candidate_to_json
+        from antigravity_grpc import cloudcode_pb2 as pb2
+
+        # Build a candidate manually
+        candidate = pb2.Candidate()
+        candidate.content.role = "model"
+        candidate.content.parts.add().text = "Hello from gRPC"
+        candidate.finish_reason = "STOP"
+        candidate.index = 0
+
+        result = _proto_candidate_to_json(candidate)
+        self.assertEqual(result["finishReason"], "STOP")
+        self.assertEqual(result["content"]["role"], "model")
+        self.assertEqual(result["content"]["parts"][0]["text"], "Hello from gRPC")
+
+
+class TestGrpcRequestBuilding(unittest.TestCase):
+    """Tests for _build_request (wrapped REST dict → protobuf)."""
+
+    def _get_client(self):
+        from antigravity_grpc import AntigravityGrpcClient
+        return AntigravityGrpcClient()
+
+    def test_build_request_basic(self):
+        """Basic request fields should be populated correctly."""
+        client = self._get_client()
+        wrapped = {
+            "project": "test-project-123",
+            "model": "Gemini 3.5 Flash (High)",
+            "requestType": "agent",
+            "userAgent": "antigravity/2.0.6",
+            "requestId": "agent-test123",
+            "request": {
+                "contents": [
+                    {"role": "user", "parts": [{"text": "Say hello"}]}
+                ],
+                "safetySettings": [
+                    {"category": "HARM_CATEGORY_HARASSMENT", "threshold": "OFF"},
+                ],
+            }
+        }
+        req = client._build_request(wrapped)
+        self.assertEqual(req.project, "test-project-123")
+        self.assertEqual(req.model, "Gemini 3.5 Flash (High)")
+        self.assertEqual(req.request_type, "agent")
+        self.assertEqual(len(req.request.contents), 1)
+        self.assertEqual(req.request.contents[0].role, "user")
+
+    def test_build_request_with_tools(self):
+        """Tools should be converted to function declarations."""
+        client = self._get_client()
+        wrapped = {
+            "project": "test-project",
+            "model": "gemini-3-flash",
+            "request": {
+                "contents": [],
+                "tools": [{
+                    "functionDeclarations": [{
+                        "name": "exec_command",
+                        "description": "Run a shell command",
+                        "parameters": {"type": "object", "properties": {"cmd": {"type": "string"}}}
+                    }]
+                }],
+            }
+        }
+        req = client._build_request(wrapped)
+        self.assertEqual(len(req.request.tools), 1)
+        self.assertEqual(req.request.tools[0].function_declarations[0].name, "exec_command")
+
+    def test_build_request_with_generation_config(self):
+        """Generation config should be populated correctly."""
+        client = self._get_client()
+        wrapped = {
+            "project": "test-project",
+            "model": "gemini-3-flash",
+            "request": {
+                "contents": [],
+                "generationConfig": {
+                    "maxOutputTokens": 64000,
+                    "temperature": 0.7,
+                    "stopSequences": ["\n\nHuman:"],
+                    "thinkingConfig": {
+                        "includeThoughts": True,
+                        "thinkingBudget": 8192,
+                    }
+                }
+            }
+        }
+        req = client._build_request(wrapped)
+        self.assertEqual(req.request.generation_config.max_output_tokens, 64000)
+        self.assertAlmostEqual(req.request.generation_config.temperature, 0.7, places=2)
+        self.assertTrue(req.request.generation_config.thinking_config.include_thoughts)
+        self.assertEqual(req.request.generation_config.thinking_config.thinking_budget, 8192)
+
+    def test_build_request_with_function_call_history(self):
+        """Function call/response pairs in contents should be preserved."""
+        client = self._get_client()
+        wrapped = {
+            "project": "test-project",
+            "model": "gemini-3-flash",
+            "request": {
+                "contents": [
+                    {"role": "user", "parts": [{"text": "List files"}]},
+                    {"role": "model", "parts": [{
+                        "functionCall": {"name": "exec_command", "args": {"cmd": "ls"}, "id": "call_1"}
+                    }]},
+                    {"role": "user", "parts": [{
+                        "functionResponse": {"name": "exec_command", "response": {"result": "file.txt"}, "id": "call_1"}
+                    }]},
+                ]
+            }
+        }
+        req = client._build_request(wrapped)
+        self.assertEqual(len(req.request.contents), 3)
+        # Verify function call preserved
+        self.assertTrue(req.request.contents[1].parts[0].HasField("function_call"))
+        self.assertEqual(req.request.contents[1].parts[0].function_call.name, "exec_command")
+        # Verify function response preserved
+        self.assertTrue(req.request.contents[2].parts[0].HasField("function_response"))
+        self.assertEqual(req.request.contents[2].parts[0].function_response.name, "exec_command")
+
+
+class TestGrpcEndpointsConfig(unittest.TestCase):
+    """Tests for gRPC endpoint configuration."""
+
+    def test_default_endpoints(self):
+        """Default endpoints should include production and daily."""
+        from antigravity_grpc.client import _GRPC_ENDPOINTS
+        self.assertGreaterEqual(len(_GRPC_ENDPOINTS), 2)
+        hostnames = [ep.split(":")[0] for ep in _GRPC_ENDPOINTS]
+        self.assertIn("daily-cloudcode-pa.googleapis.com", hostnames)
+        self.assertIn("cloudcode-pa.googleapis.com", hostnames)
+
+    def test_staging_env_var(self):
+        """Staging endpoints should be controlled by env var."""
+        from antigravity_grpc.client import _ALLOW_STAGING_ENV
+        self.assertEqual(_ALLOW_STAGING_ENV, "ALLOW_ANTIGRAVITY_STAGING")
+
+
+class TestProxyIntegration(unittest.TestCase):
+    """Tests for the proxy's gRPC fallback integration."""
+
+    def _load_proxy_module(self):
+        import importlib
+        _spec = importlib.util.spec_from_file_location(
+            "translate_proxy",
+            os.path.join(_src_dir, "translate-proxy.py"),
+        )
+        tp = importlib.util.module_from_spec(_spec)
+        _spec.loader.exec_module(tp)
+        return tp
+
+    def test_get_grpc_client_function_exists(self):
+        """_get_grpc_client should exist as a module-level function."""
+        tp = self._load_proxy_module()
+        self.assertTrue(callable(tp._get_grpc_client))
+
+    def test_grpc_fallback_errors_set(self):
+        """_GRPC_FALLBACK_REST_ERRORS should include 404."""
+        tp = self._load_proxy_module()
+        self.assertIn(404, tp._GRPC_FALLBACK_REST_ERRORS)
+
+    def test_versions_bug_fixed(self):
+        """The _versions[0] NameError should be fixed (should be _fetched_ver)."""
+        # Read the source file and verify _versions is not used incorrectly
+        with open(os.path.join(_src_dir, "translate-proxy.py")) as f:
+            source = f.read()
+        # The bug was: ver={_versions[0]}  -- should be ver={_fetched_ver}
+        self.assertNotIn("_versions[0]", source,
+                         "Bug: _versions[0] should have been replaced with _fetched_ver")
+
+
+if __name__ == "__main__":
+    print("=" * 70)
+    print("Antigravity gRPC Fallback - Unit Tests")
+    print("=" * 70)
+    print()
+
+    unittest.main(verbosity=2)