refactor!: remove google-antigravity provider support

src/agents/pi-embedded-runner/google.test.ts

@@ -42,26 +42,6 @@ describe("sanitizeToolsForGoogle", () => {
     expectFormatRemoved(sanitized, "additionalProperties");
   });
 
-  it("strips unsupported schema keywords for google-antigravity", () => {
-    const tool = createTool({
-      type: "object",
-      patternProperties: {
-        "^x-": { type: "string" },
-      },
-      properties: {
-        foo: {
-          type: "string",
-          format: "uuid",
-        },
-      },
-    });
-    const [sanitized] = sanitizeToolsForGoogle({
-      tools: [tool],
-      provider: "google-antigravity",
-    });
-    expectFormatRemoved(sanitized, "patternProperties");
-  });
-
   it("returns original tools for non-google providers", () => {
     const tool = createTool({
       type: "object",

src/agents/pi-embedded-runner/google.ts

@@ -25,7 +25,7 @@ import {
 import type { TranscriptPolicy } from "../transcript-policy.js";
 import { resolveTranscriptPolicy } from "../transcript-policy.js";
 import { log } from "./logger.js";
-import { dropThinkingBlocks, isAssistantMessageWithContent } from "./thinking.js";
+import { dropThinkingBlocks } from "./thinking.js";
 import { describeUnknownError } from "./utils.js";
 
 const GOOGLE_TURN_ORDERING_CUSTOM_TYPE = "google-turn-ordering-bootstrap";
@@ -52,85 +52,8 @@ const GOOGLE_SCHEMA_UNSUPPORTED_KEYWORDS = new Set([
   "maxProperties",
 ]);
 
-const ANTIGRAVITY_SIGNATURE_RE = /^[A-Za-z0-9+/]+={0,2}$/;
 const INTER_SESSION_PREFIX_BASE = "[Inter-session message]";
 
-function isValidAntigravitySignature(value: unknown): value is string {
-  if (typeof value !== "string") {
-    return false;
-  }
-  const trimmed = value.trim();
-  if (!trimmed) {
-    return false;
-  }
-  if (trimmed.length % 4 !== 0) {
-    return false;
-  }
-  return ANTIGRAVITY_SIGNATURE_RE.test(trimmed);
-}
-
-export function sanitizeAntigravityThinkingBlocks(messages: AgentMessage[]): AgentMessage[] {
-  let touched = false;
-  const out: AgentMessage[] = [];
-  for (const msg of messages) {
-    if (!isAssistantMessageWithContent(msg)) {
-      out.push(msg);
-      continue;
-    }
-    const assistant = msg;
-    type AssistantContentBlock = Extract<AgentMessage, { role: "assistant" }>["content"][number];
-    const nextContent: AssistantContentBlock[] = [];
-    let contentChanged = false;
-    for (const block of assistant.content) {
-      if (
-        !block ||
-        typeof block !== "object" ||
-        (block as { type?: unknown }).type !== "thinking"
-      ) {
-        nextContent.push(block);
-        continue;
-      }
-      const rec = block as {
-        thinkingSignature?: unknown;
-        signature?: unknown;
-        thought_signature?: unknown;
-        thoughtSignature?: unknown;
-      };
-      const candidate =
-        rec.thinkingSignature ?? rec.signature ?? rec.thought_signature ?? rec.thoughtSignature;
-      if (!isValidAntigravitySignature(candidate)) {
-        // Preserve reasoning content as plain text when signatures are invalid/missing.
-        // Antigravity Claude rejects unsigned thinking blocks, but dropping them loses context.
-        const thinkingText = (block as { thinking?: unknown }).thinking;
-        if (typeof thinkingText === "string" && thinkingText.trim()) {
-          nextContent.push({ type: "text", text: thinkingText } as AssistantContentBlock);
-        }
-        contentChanged = true;
-        continue;
-      }
-      if (rec.thinkingSignature !== candidate) {
-        const nextBlock = {
-          ...(block as unknown as Record<string, unknown>),
-          thinkingSignature: candidate,
-        } as AssistantContentBlock;
-        nextContent.push(nextBlock);
-        contentChanged = true;
-      } else {
-        nextContent.push(block);
-      }
-    }
-    if (contentChanged) {
-      touched = true;
-    }
-    if (nextContent.length === 0) {
-      touched = true;
-      continue;
-    }
-    out.push(contentChanged ? { ...assistant, content: nextContent } : msg);
-  }
-  return touched ? out : messages;
-}
-
 function buildInterSessionPrefix(message: AgentMessage): string {
   const provenance = normalizeInputProvenance((message as { provenance?: unknown }).provenance);
   if (!provenance) {
@@ -284,7 +207,7 @@ export function sanitizeToolsForGoogle<
   // AND Claude models.  This field does not support JSON Schema keywords such as
   // patternProperties, additionalProperties, $ref, etc.  We must clean schemas
   // for every provider that routes through this path.
-  if (params.provider !== "google-gemini-cli" && params.provider !== "google-antigravity") {
+  if (params.provider !== "google-gemini-cli") {
     return params.tools;
   }
   return params.tools.map((tool) => {
@@ -301,7 +224,7 @@ export function sanitizeToolsForGoogle<
 }
 
 export function logToolSchemasForGoogle(params: { tools: AgentTool[]; provider: string }) {
-  if (params.provider !== "google-antigravity" && params.provider !== "google-gemini-cli") {
+  if (params.provider !== "google-gemini-cli") {
     return;
   }
   const toolNames = params.tools.map((tool, index) => `${index}:${tool.name}`);
@@ -481,10 +404,7 @@ export async function sanitizeSessionHistory(params: {
   const droppedThinking = policy.dropThinkingBlocks
     ? dropThinkingBlocks(sanitizedImages)
     : sanitizedImages;
-  const sanitizedThinking = policy.sanitizeThinkingSignatures
-    ? sanitizeAntigravityThinkingBlocks(droppedThinking)
-    : droppedThinking;
-  const sanitizedToolCalls = sanitizeToolCallInputs(sanitizedThinking, {
+  const sanitizedToolCalls = sanitizeToolCallInputs(droppedThinking, {
     allowedToolNames: params.allowedToolNames,
   });
   const repairedTools = policy.repairToolUseResultPairing

src/agents/pi-embedded-runner/model.test.ts

@@ -232,62 +232,6 @@ describe("resolveModel", () => {
     });
   });
 
-  it("builds an antigravity forward-compat fallback for claude-opus-4-6-thinking", () => {
-    mockDiscoveredModel({
-      provider: "google-antigravity",
-      modelId: "claude-opus-4-5-thinking",
-      templateModel: buildForwardCompatTemplate({
-        id: "claude-opus-4-5-thinking",
-        name: "Claude Opus 4.5 Thinking",
-        provider: "google-antigravity",
-        api: "google-gemini-cli",
-        baseUrl: "https://daily-cloudcode-pa.sandbox.googleapis.com",
-      }),
-    });
-
-    expectResolvedForwardCompatFallback({
-      provider: "google-antigravity",
-      id: "claude-opus-4-6-thinking",
-      expectedModel: {
-        provider: "google-antigravity",
-        id: "claude-opus-4-6-thinking",
-        api: "google-gemini-cli",
-        baseUrl: "https://daily-cloudcode-pa.sandbox.googleapis.com",
-        reasoning: true,
-        contextWindow: 200000,
-        maxTokens: 64000,
-      },
-    });
-  });
-
-  it("builds an antigravity forward-compat fallback for claude-opus-4-6", () => {
-    mockDiscoveredModel({
-      provider: "google-antigravity",
-      modelId: "claude-opus-4-5",
-      templateModel: buildForwardCompatTemplate({
-        id: "claude-opus-4-5",
-        name: "Claude Opus 4.5",
-        provider: "google-antigravity",
-        api: "google-gemini-cli",
-        baseUrl: "https://daily-cloudcode-pa.sandbox.googleapis.com",
-      }),
-    });
-
-    expectResolvedForwardCompatFallback({
-      provider: "google-antigravity",
-      id: "claude-opus-4-6",
-      expectedModel: {
-        provider: "google-antigravity",
-        id: "claude-opus-4-6",
-        api: "google-gemini-cli",
-        baseUrl: "https://daily-cloudcode-pa.sandbox.googleapis.com",
-        reasoning: true,
-        contextWindow: 200000,
-        maxTokens: 64000,
-      },
-    });
-  });
-
   it("builds a zai forward-compat fallback for glm-5", () => {
     mockDiscoveredModel({
       provider: "zai",

src/agents/pi-embedded-runner/run/attempt.ts

@@ -82,7 +82,6 @@ import { buildEmbeddedExtensionFactories } from "../extensions.js";
 import { applyExtraParamsToAgent } from "../extra-params.js";
 import {
   logToolSchemasForGoogle,
-  sanitizeAntigravityThinkingBlocks,
   sanitizeSessionHistory,
   sanitizeToolsForGoogle,
 } from "../google.js";
@@ -1062,10 +1061,7 @@ export async function runEmbeddedAttempt(
             sessionManager.resetLeaf();
           }
           const sessionContext = sessionManager.buildSessionContext();
-          const sanitizedOrphan = transcriptPolicy.sanitizeThinkingSignatures
-            ? sanitizeAntigravityThinkingBlocks(sessionContext.messages)
-            : sessionContext.messages;
-          activeSession.agent.replaceMessages(sanitizedOrphan);
+          activeSession.agent.replaceMessages(sessionContext.messages);
           log.warn(
             `Removed orphaned user message to prevent consecutive user turns. ` +
               `runId=${params.runId} sessionId=${params.sessionId}`,