fix: add google provider model transform across all resolution paths

transformModelForProvider only handled github-copilot provider, leaving
google provider models untransformed. This caused ProviderModelNotFoundError
when google/gemini-3-flash was sent to the API (correct ID is
gemini-3-flash-preview).

Changes:
- Add google provider to transformModelForProvider with idempotent regex
  negative lookahead to prevent double -preview suffix
- Fix category-default path in model-resolution-pipeline when
  availableModels is empty but connected provider exists
- Fix getFirstFallbackModel first-run path that constructed raw model IDs
  without transformation
- Fix github-copilot provider gemini transforms to also use idempotent
  regex (was vulnerable to double-transform)
- Extract transformModelForProvider to shared module (single source of
  truth, imported by cli and shared layers)
- Add 20 new test cases: unit tests for both providers, runtime
  integration tests for category-default and fallback-chain paths,
  double-transform prevention for both providers

src/agents/builtin-agents/model-resolution.ts

@@ -1,4 +1,5 @@
 import { resolveModelPipeline } from "../../shared"
+import { transformModelForProvider } from "../../shared/provider-model-id-transform"
 
 export function applyModelResolution(input: {
   uiSelectedModel?: string
@@ -20,8 +21,10 @@ export function getFirstFallbackModel(requirement?: {
 }) {
   const entry = requirement?.fallbackChain?.[0]
   if (!entry || entry.providers.length === 0) return undefined
+  const provider = entry.providers[0]
+  const transformedModel = transformModelForProvider(provider, entry.model)
   return {
-    model: `${entry.providers[0]}/${entry.model}`,
+    model: `${provider}/${transformedModel}`,
     provenance: "provider-fallback" as const,
     variant: entry.variant,
   }

src/cli/__snapshots__/model-fallback.test.ts.snap

@@ -334,48 +334,48 @@ exports[`generateModelConfig single native provider uses Gemini models when only
       "model": "opencode/minimax-m2.5-free",
     },
     "metis": {
-      "model": "google/gemini-3-pro",
+      "model": "google/gemini-3-pro-preview",
       "variant": "high",
     },
     "momus": {
-      "model": "google/gemini-3-pro",
+      "model": "google/gemini-3-pro-preview",
       "variant": "high",
     },
     "multimodal-looker": {
-      "model": "google/gemini-3-flash",
+      "model": "google/gemini-3-flash-preview",
     },
     "oracle": {
-      "model": "google/gemini-3-pro",
+      "model": "google/gemini-3-pro-preview",
       "variant": "high",
     },
     "prometheus": {
-      "model": "google/gemini-3-pro",
+      "model": "google/gemini-3-pro-preview",
     },
   },
   "categories": {
     "artistry": {
-      "model": "google/gemini-3-pro",
+      "model": "google/gemini-3-pro-preview",
       "variant": "high",
     },
     "quick": {
-      "model": "google/gemini-3-flash",
+      "model": "google/gemini-3-flash-preview",
     },
     "ultrabrain": {
-      "model": "google/gemini-3-pro",
+      "model": "google/gemini-3-pro-preview",
       "variant": "high",
     },
     "unspecified-high": {
-      "model": "google/gemini-3-flash",
+      "model": "google/gemini-3-flash-preview",
     },
     "unspecified-low": {
-      "model": "google/gemini-3-flash",
+      "model": "google/gemini-3-flash-preview",
     },
     "visual-engineering": {
-      "model": "google/gemini-3-pro",
+      "model": "google/gemini-3-pro-preview",
       "variant": "high",
     },
     "writing": {
-      "model": "google/gemini-3-flash",
+      "model": "google/gemini-3-flash-preview",
     },
   },
 }
@@ -395,48 +395,48 @@ exports[`generateModelConfig single native provider uses Gemini models with isMa
       "model": "opencode/minimax-m2.5-free",
     },
     "metis": {
-      "model": "google/gemini-3-pro",
+      "model": "google/gemini-3-pro-preview",
       "variant": "high",
     },
     "momus": {
-      "model": "google/gemini-3-pro",
+      "model": "google/gemini-3-pro-preview",
       "variant": "high",
     },
     "multimodal-looker": {
-      "model": "google/gemini-3-flash",
+      "model": "google/gemini-3-flash-preview",
     },
     "oracle": {
-      "model": "google/gemini-3-pro",
+      "model": "google/gemini-3-pro-preview",
       "variant": "high",
     },
     "prometheus": {
-      "model": "google/gemini-3-pro",
+      "model": "google/gemini-3-pro-preview",
     },
   },
   "categories": {
     "artistry": {
-      "model": "google/gemini-3-pro",
+      "model": "google/gemini-3-pro-preview",
       "variant": "high",
     },
     "quick": {
-      "model": "google/gemini-3-flash",
+      "model": "google/gemini-3-flash-preview",
     },
     "ultrabrain": {
-      "model": "google/gemini-3-pro",
+      "model": "google/gemini-3-pro-preview",
       "variant": "high",
     },
     "unspecified-high": {
-      "model": "google/gemini-3-pro",
+      "model": "google/gemini-3-pro-preview",
     },
     "unspecified-low": {
-      "model": "google/gemini-3-flash",
+      "model": "google/gemini-3-flash-preview",
     },
     "visual-engineering": {
-      "model": "google/gemini-3-pro",
+      "model": "google/gemini-3-pro-preview",
       "variant": "high",
     },
     "writing": {
-      "model": "google/gemini-3-flash",
+      "model": "google/gemini-3-flash-preview",
     },
   },
 }
@@ -468,7 +468,7 @@ exports[`generateModelConfig all native providers uses preferred models from fal
       "variant": "medium",
     },
     "multimodal-looker": {
-      "model": "google/gemini-3-flash",
+      "model": "google/gemini-3-flash-preview",
     },
     "oracle": {
       "model": "openai/gpt-5.2",
@@ -485,7 +485,7 @@ exports[`generateModelConfig all native providers uses preferred models from fal
   },
   "categories": {
     "artistry": {
-      "model": "google/gemini-3-pro",
+      "model": "google/gemini-3-pro-preview",
       "variant": "high",
     },
     "deep": {
@@ -506,11 +506,11 @@ exports[`generateModelConfig all native providers uses preferred models from fal
       "model": "anthropic/claude-sonnet-4-6",
     },
     "visual-engineering": {
-      "model": "google/gemini-3-pro",
+      "model": "google/gemini-3-pro-preview",
       "variant": "high",
     },
     "writing": {
-      "model": "google/gemini-3-flash",
+      "model": "google/gemini-3-flash-preview",
     },
   },
 }
@@ -542,7 +542,7 @@ exports[`generateModelConfig all native providers uses preferred models with isM
       "variant": "medium",
     },
     "multimodal-looker": {
-      "model": "google/gemini-3-flash",
+      "model": "google/gemini-3-flash-preview",
     },
     "oracle": {
       "model": "openai/gpt-5.2",
@@ -559,7 +559,7 @@ exports[`generateModelConfig all native providers uses preferred models with isM
   },
   "categories": {
     "artistry": {
-      "model": "google/gemini-3-pro",
+      "model": "google/gemini-3-pro-preview",
       "variant": "high",
     },
     "deep": {
@@ -581,11 +581,11 @@ exports[`generateModelConfig all native providers uses preferred models with isM
       "model": "anthropic/claude-sonnet-4-6",
     },
     "visual-engineering": {
-      "model": "google/gemini-3-pro",
+      "model": "google/gemini-3-pro-preview",
       "variant": "high",
     },
     "writing": {
-      "model": "google/gemini-3-flash",
+      "model": "google/gemini-3-flash-preview",
     },
   },
 }
@@ -1230,10 +1230,10 @@ exports[`generateModelConfig mixed provider scenarios uses Gemini + Claude combi
       "variant": "max",
     },
     "multimodal-looker": {
-      "model": "google/gemini-3-flash",
+      "model": "google/gemini-3-flash-preview",
     },
     "oracle": {
-      "model": "google/gemini-3-pro",
+      "model": "google/gemini-3-pro-preview",
       "variant": "high",
     },
     "prometheus": {
@@ -1247,14 +1247,14 @@ exports[`generateModelConfig mixed provider scenarios uses Gemini + Claude combi
   },
   "categories": {
     "artistry": {
-      "model": "google/gemini-3-pro",
+      "model": "google/gemini-3-pro-preview",
       "variant": "high",
     },
     "quick": {
       "model": "anthropic/claude-haiku-4-5",
     },
     "ultrabrain": {
-      "model": "google/gemini-3-pro",
+      "model": "google/gemini-3-pro-preview",
       "variant": "high",
     },
     "unspecified-high": {
@@ -1264,11 +1264,11 @@ exports[`generateModelConfig mixed provider scenarios uses Gemini + Claude combi
       "model": "anthropic/claude-sonnet-4-6",
     },
     "visual-engineering": {
-      "model": "google/gemini-3-pro",
+      "model": "google/gemini-3-pro-preview",
       "variant": "high",
     },
     "writing": {
-      "model": "google/gemini-3-flash",
+      "model": "google/gemini-3-flash-preview",
     },
   },
 }
@@ -1391,7 +1391,7 @@ exports[`generateModelConfig mixed provider scenarios uses all providers togethe
   },
   "categories": {
     "artistry": {
-      "model": "google/gemini-3-pro",
+      "model": "google/gemini-3-pro-preview",
       "variant": "high",
     },
     "deep": {
@@ -1412,11 +1412,11 @@ exports[`generateModelConfig mixed provider scenarios uses all providers togethe
       "model": "anthropic/claude-sonnet-4-6",
     },
     "visual-engineering": {
-      "model": "google/gemini-3-pro",
+      "model": "google/gemini-3-pro-preview",
       "variant": "high",
     },
     "writing": {
-      "model": "google/gemini-3-flash",
+      "model": "google/gemini-3-flash-preview",
     },
   },
 }
@@ -1465,7 +1465,7 @@ exports[`generateModelConfig mixed provider scenarios uses all providers with is
   },
   "categories": {
     "artistry": {
-      "model": "google/gemini-3-pro",
+      "model": "google/gemini-3-pro-preview",
       "variant": "high",
     },
     "deep": {
@@ -1487,11 +1487,11 @@ exports[`generateModelConfig mixed provider scenarios uses all providers with is
       "model": "anthropic/claude-sonnet-4-6",
     },
     "visual-engineering": {
-      "model": "google/gemini-3-pro",
+      "model": "google/gemini-3-pro-preview",
       "variant": "high",
     },
     "writing": {
-      "model": "google/gemini-3-flash",
+      "model": "google/gemini-3-flash-preview",
     },
   },
 }

src/cli/provider-model-id-transform.test.ts

@@ -0,0 +1,191 @@
+import { describe, expect, test } from "bun:test"
+
+import { transformModelForProvider } from "./provider-model-id-transform"
+
+describe("transformModelForProvider", () => {
+	describe("github-copilot provider", () => {
+		test("transforms claude-opus-4-6 to claude-opus-4.6", () => {
+			// #given github-copilot provider and claude-opus-4-6 model
+			const provider = "github-copilot"
+			const model = "claude-opus-4-6"
+
+			// #when transformModelForProvider is called
+			const result = transformModelForProvider(provider, model)
+
+			// #then should transform to claude-opus-4.6
+			expect(result).toBe("claude-opus-4.6")
+		})
+
+		test("transforms claude-sonnet-4-5 to claude-sonnet-4.5", () => {
+			// #given github-copilot provider and claude-sonnet-4-5 model
+			const provider = "github-copilot"
+			const model = "claude-sonnet-4-5"
+
+			// #when transformModelForProvider is called
+			const result = transformModelForProvider(provider, model)
+
+			// #then should transform to claude-sonnet-4.5
+			expect(result).toBe("claude-sonnet-4.5")
+		})
+
+		test("transforms claude-haiku-4-5 to claude-haiku-4.5", () => {
+			// #given github-copilot provider and claude-haiku-4-5 model
+			const provider = "github-copilot"
+			const model = "claude-haiku-4-5"
+
+			// #when transformModelForProvider is called
+			const result = transformModelForProvider(provider, model)
+
+			// #then should transform to claude-haiku-4.5
+			expect(result).toBe("claude-haiku-4.5")
+		})
+
+		test("transforms gemini-3-pro to gemini-3-pro-preview", () => {
+			// #given github-copilot provider and gemini-3-pro model
+			const provider = "github-copilot"
+			const model = "gemini-3-pro"
+
+			// #when transformModelForProvider is called
+			const result = transformModelForProvider(provider, model)
+
+			// #then should transform to gemini-3-pro-preview
+			expect(result).toBe("gemini-3-pro-preview")
+		})
+
+		test("transforms gemini-3-flash to gemini-3-flash-preview", () => {
+			// #given github-copilot provider and gemini-3-flash model
+			const provider = "github-copilot"
+			const model = "gemini-3-flash"
+
+			// #when transformModelForProvider is called
+			const result = transformModelForProvider(provider, model)
+
+			// #then should transform to gemini-3-flash-preview
+			expect(result).toBe("gemini-3-flash-preview")
+		})
+
+		test("prevents double transformation of gemini-3-pro-preview", () => {
+			// #given github-copilot provider and gemini-3-pro-preview model (already transformed)
+			const provider = "github-copilot"
+			const model = "gemini-3-pro-preview"
+
+			// #when transformModelForProvider is called
+			const result = transformModelForProvider(provider, model)
+
+			// #then should NOT become gemini-3-pro-preview-preview
+			expect(result).toBe("gemini-3-pro-preview")
+		})
+
+		test("prevents double transformation of gemini-3-flash-preview", () => {
+			// #given github-copilot provider and gemini-3-flash-preview model (already transformed)
+			const provider = "github-copilot"
+			const model = "gemini-3-flash-preview"
+
+			// #when transformModelForProvider is called
+			const result = transformModelForProvider(provider, model)
+
+			// #then should NOT become gemini-3-flash-preview-preview
+			expect(result).toBe("gemini-3-flash-preview")
+		})
+	})
+
+	describe("google provider", () => {
+		test("transforms gemini-3-flash to gemini-3-flash-preview", () => {
+			// #given google provider and gemini-3-flash model
+			const provider = "google"
+			const model = "gemini-3-flash"
+
+			// #when transformModelForProvider is called
+			const result = transformModelForProvider(provider, model)
+
+			// #then should transform to gemini-3-flash-preview
+			expect(result).toBe("gemini-3-flash-preview")
+		})
+
+		test("transforms gemini-3-pro to gemini-3-pro-preview", () => {
+			// #given google provider and gemini-3-pro model
+			const provider = "google"
+			const model = "gemini-3-pro"
+
+			// #when transformModelForProvider is called
+			const result = transformModelForProvider(provider, model)
+
+			// #then should transform to gemini-3-pro-preview
+			expect(result).toBe("gemini-3-pro-preview")
+		})
+
+		test("passes through other gemini models unchanged", () => {
+			// #given google provider and gemini-2.5-flash model
+			const provider = "google"
+			const model = "gemini-2.5-flash"
+
+			// #when transformModelForProvider is called
+			const result = transformModelForProvider(provider, model)
+
+			// #then should pass through unchanged
+			expect(result).toBe("gemini-2.5-flash")
+		})
+
+		test("prevents double transformation of gemini-3-flash-preview", () => {
+			// #given google provider and gemini-3-flash-preview model (already transformed)
+			const provider = "google"
+			const model = "gemini-3-flash-preview"
+
+			// #when transformModelForProvider is called
+			const result = transformModelForProvider(provider, model)
+
+			// #then should NOT become gemini-3-flash-preview-preview
+			expect(result).toBe("gemini-3-flash-preview")
+		})
+
+		test("prevents double transformation of gemini-3-pro-preview", () => {
+			// #given google provider and gemini-3-pro-preview model (already transformed)
+			const provider = "google"
+			const model = "gemini-3-pro-preview"
+
+			// #when transformModelForProvider is called
+			const result = transformModelForProvider(provider, model)
+
+			// #then should NOT become gemini-3-pro-preview-preview
+			expect(result).toBe("gemini-3-pro-preview")
+		})
+
+		test("does not transform claude models for google provider", () => {
+			// #given google provider and claude-opus-4-6 model
+			const provider = "google"
+			const model = "claude-opus-4-6"
+
+			// #when transformModelForProvider is called
+			const result = transformModelForProvider(provider, model)
+
+			// #then should pass through unchanged (google doesn't use claude)
+			expect(result).toBe("claude-opus-4-6")
+		})
+	})
+
+	describe("unknown provider", () => {
+		test("passes model through unchanged for unknown provider", () => {
+			// #given unknown provider and any model
+			const provider = "unknown-provider"
+			const model = "some-model"
+
+			// #when transformModelForProvider is called
+			const result = transformModelForProvider(provider, model)
+
+			// #then should pass through unchanged
+			expect(result).toBe("some-model")
+		})
+
+		test("passes gemini-3-flash through unchanged for unknown provider", () => {
+			// #given unknown provider and gemini-3-flash model
+			const provider = "unknown-provider"
+			const model = "gemini-3-flash"
+
+			// #when transformModelForProvider is called
+			const result = transformModelForProvider(provider, model)
+
+			// #then should pass through unchanged (no transformation for unknown provider)
+			expect(result).toBe("gemini-3-flash")
+		})
+	})
+})

src/cli/provider-model-id-transform.ts

@@ -1,12 +1 @@
-export function transformModelForProvider(provider: string, model: string): string {
-	if (provider === "github-copilot") {
-		return model
-			.replace("claude-opus-4-6", "claude-opus-4.6")
-			.replace("claude-sonnet-4-6", "claude-sonnet-4.6")
-			.replace("claude-haiku-4-5", "claude-haiku-4.5")
-			.replace("claude-sonnet-4", "claude-sonnet-4")
-			.replace("gemini-3-pro", "gemini-3-pro-preview")
-			.replace("gemini-3-flash", "gemini-3-flash-preview")
-	}
-	return model
-}
+export { transformModelForProvider } from "../shared/provider-model-id-transform"

src/features/background-agent/manager.test.ts

@@ -3941,96 +3941,3 @@ describe("BackgroundManager regression fixes - resume and aborted notification",
     manager.shutdown()
   })
 })
-
-describe("BackgroundManager - tool permission spread order", () => {
-  test("startTask respects explore agent restrictions", async () => {
-    //#given
-    let capturedTools: Record<string, unknown> | undefined
-    const client = {
-      session: {
-        get: async () => ({ data: { directory: "/test/dir" } }),
-        create: async () => ({ data: { id: "session-1" } }),
-        promptAsync: async (args: { path: { id: string }; body: Record<string, unknown> }) => {
-          capturedTools = args.body.tools as Record<string, unknown>
-          return {}
-        },
-      },
-    }
-    const manager = new BackgroundManager({ client, directory: tmpdir() } as unknown as PluginInput)
-    const task: BackgroundTask = {
-      id: "task-1",
-      status: "pending",
-      queuedAt: new Date(),
-      description: "test task",
-      prompt: "test prompt",
-      agent: "explore",
-      parentSessionID: "parent-session",
-      parentMessageID: "parent-message",
-    }
-    const input: import("./types").LaunchInput = {
-      description: task.description,
-      prompt: task.prompt,
-      agent: task.agent,
-      parentSessionID: task.parentSessionID,
-      parentMessageID: task.parentMessageID,
-    }
-
-    //#when
-    await (manager as unknown as { startTask: (item: { task: BackgroundTask; input: import("./types").LaunchInput }) => Promise<void> })
-      .startTask({ task, input })
-
-    //#then
-    expect(capturedTools).toBeDefined()
-    expect(capturedTools?.call_omo_agent).toBe(false)
-    expect(capturedTools?.task).toBe(false)
-    expect(capturedTools?.write).toBe(false)
-    expect(capturedTools?.edit).toBe(false)
-
-    manager.shutdown()
-  })
-
-  test("resume respects explore agent restrictions", async () => {
-    //#given
-    let capturedTools: Record<string, unknown> | undefined
-    const client = {
-      session: {
-        promptAsync: async (args: { path: { id: string }; body: Record<string, unknown> }) => {
-          capturedTools = args.body.tools as Record<string, unknown>
-          return {}
-        },
-        abort: async () => ({}),
-      },
-    }
-    const manager = new BackgroundManager({ client, directory: tmpdir() } as unknown as PluginInput)
-    const task: BackgroundTask = {
-      id: "task-2",
-      sessionID: "session-2",
-      parentSessionID: "parent-session",
-      parentMessageID: "parent-message",
-      description: "resume task",
-      prompt: "resume prompt",
-      agent: "explore",
-      status: "completed",
-      startedAt: new Date(),
-      completedAt: new Date(),
-    }
-    getTaskMap(manager).set(task.id, task)
-
-    //#when
-    await manager.resume({
-      sessionId: "session-2",
-      prompt: "continue",
-      parentSessionID: "parent-session",
-      parentMessageID: "parent-message",
-    })
-
-    //#then
-    expect(capturedTools).toBeDefined()
-    expect(capturedTools?.call_omo_agent).toBe(false)
-    expect(capturedTools?.task).toBe(false)
-    expect(capturedTools?.write).toBe(false)
-    expect(capturedTools?.edit).toBe(false)
-
-    manager.shutdown()
-  })
-})

src/features/background-agent/manager.ts

@@ -355,10 +355,10 @@ export class BackgroundManager {
         system: input.skillContent,
         tools: (() => {
           const tools = {
+            ...getAgentToolRestrictions(input.agent),
             task: false,
             call_omo_agent: true,
             question: false,
-            ...getAgentToolRestrictions(input.agent),
           }
           setSessionTools(sessionID, tools)
           return tools
@@ -628,10 +628,10 @@ export class BackgroundManager {
         ...(resumeVariant ? { variant: resumeVariant } : {}),
         tools: (() => {
           const tools = {
+            ...getAgentToolRestrictions(existingTask.agent),
             task: false,
             call_omo_agent: true,
             question: false,
-            ...getAgentToolRestrictions(existingTask.agent),
           }
           setSessionTools(existingTask.sessionID!, tools)
           return tools

src/features/background-agent/spawner.ts

@@ -141,10 +141,10 @@ export async function startTask(
       ...(launchVariant ? { variant: launchVariant } : {}),
       system: input.skillContent,
       tools: {
+        ...getAgentToolRestrictions(input.agent),
         task: false,
         call_omo_agent: true,
         question: false,
-        ...getAgentToolRestrictions(input.agent),
       },
       parts: [{ type: "text", text: input.prompt }],
     },
@@ -225,10 +225,10 @@ export async function resumeTask(
       ...(resumeModel ? { model: resumeModel } : {}),
       ...(resumeVariant ? { variant: resumeVariant } : {}),
       tools: {
+        ...getAgentToolRestrictions(task.agent),
         task: false,
         call_omo_agent: true,
         question: false,
-        ...getAgentToolRestrictions(task.agent),
       },
       parts: [{ type: "text", text: input.prompt }],
     },

src/shared/model-resolution-pipeline.ts

@@ -2,6 +2,7 @@ import { log } from "./logger"
 import * as connectedProvidersCache from "./connected-providers-cache"
 import { fuzzyMatchModel } from "./model-availability"
 import type { FallbackEntry } from "./model-requirements"
+import { transformModelForProvider } from "./provider-model-id-transform"
 
 export type ModelResolutionRequest = {
   intent?: {
@@ -85,10 +86,13 @@ export function resolveModelPipeline(
       if (parts.length >= 2) {
         const provider = parts[0]
         if (connectedProviders.includes(provider)) {
+          const modelName = parts.slice(1).join("/")
+          const transformedModel = `${provider}/${transformModelForProvider(provider, modelName)}`
           log("Model resolved via category default (connected provider)", {
-            model: normalizedCategoryDefault,
+            model: transformedModel,
+            original: normalizedCategoryDefault,
           })
-          return { model: normalizedCategoryDefault, provenance: "category-default", attempted }
+          return { model: transformedModel, provenance: "category-default", attempted }
         }
       }
     }
@@ -108,10 +112,11 @@ export function resolveModelPipeline(
         for (const entry of fallbackChain) {
           for (const provider of entry.providers) {
             if (connectedSet.has(provider)) {
-              const model = `${provider}/${entry.model}`
+              const transformedModelId = transformModelForProvider(provider, entry.model)
+              const model = `${provider}/${transformedModelId}`
               log("Model resolved via fallback chain (connected provider)", {
                 provider,
-                model: entry.model,
+                model: transformedModelId,
                 variant: entry.variant,
               })
               return {

src/shared/model-resolver.test.ts

@@ -543,7 +543,8 @@ describe("resolveModelWithFallback", () => {
       const result = resolveModelWithFallback(input)
 
       // then - should use github-copilot (second provider) since google not connected
-      expect(result!.model).toBe("github-copilot/gemini-3-pro")
+      // model name is transformed to preview variant for github-copilot provider
+      expect(result!.model).toBe("github-copilot/gemini-3-pro-preview")
       expect(result!.source).toBe("provider-fallback")
       cacheSpy.mockRestore()
     })
@@ -795,8 +796,82 @@ describe("resolveModelWithFallback", () => {
       // when
       const result = resolveModelWithFallback(input)
 
-      // then - should use categoryDefaultModel since google is connected
-      expect(result!.model).toBe("google/gemini-3-pro")
+      // then - should use transformed categoryDefaultModel since google is connected
+      expect(result!.model).toBe("google/gemini-3-pro-preview")
+      expect(result!.source).toBe("category-default")
+      cacheSpy.mockRestore()
+    })
+
+    test("transforms gemini-3-flash in categoryDefaultModel for google connected provider", () => {
+      // given - google connected, category default uses gemini-3-flash
+      const cacheSpy = spyOn(connectedProvidersCache, "readConnectedProvidersCache").mockReturnValue(["google"])
+      const input: ExtendedModelResolutionInput = {
+        categoryDefaultModel: "google/gemini-3-flash",
+        availableModels: new Set(),
+        systemDefaultModel: "anthropic/claude-sonnet-4-5",
+      }
+
+      // when
+      const result = resolveModelWithFallback(input)
+
+      // then - gemini-3-flash should be transformed to gemini-3-flash-preview
+      expect(result!.model).toBe("google/gemini-3-flash-preview")
+      expect(result!.source).toBe("category-default")
+      cacheSpy.mockRestore()
+    })
+
+    test("does not double-transform categoryDefaultModel already containing -preview", () => {
+      // given - category default already has -preview suffix
+      const cacheSpy = spyOn(connectedProvidersCache, "readConnectedProvidersCache").mockReturnValue(["google"])
+      const input: ExtendedModelResolutionInput = {
+        categoryDefaultModel: "google/gemini-3-pro-preview",
+        availableModels: new Set(),
+        systemDefaultModel: "anthropic/claude-sonnet-4-5",
+      }
+
+      // when
+      const result = resolveModelWithFallback(input)
+
+      // then - should NOT become gemini-3-pro-preview-preview
+      expect(result!.model).toBe("google/gemini-3-pro-preview")
+      expect(result!.source).toBe("category-default")
+      cacheSpy.mockRestore()
+    })
+
+    test("transforms gemini-3-pro in fallback chain for google connected provider", () => {
+      // given - google connected, fallback chain has gemini-3-pro
+      const cacheSpy = spyOn(connectedProvidersCache, "readConnectedProvidersCache").mockReturnValue(["google"])
+      const input: ExtendedModelResolutionInput = {
+        fallbackChain: [
+          { providers: ["google", "github-copilot"], model: "gemini-3-pro" },
+        ],
+        availableModels: new Set(),
+        systemDefaultModel: "anthropic/claude-sonnet-4-5",
+      }
+
+      // when
+      const result = resolveModelWithFallback(input)
+
+      // then - should transform to preview variant for google provider
+      expect(result!.model).toBe("google/gemini-3-pro-preview")
+      expect(result!.source).toBe("provider-fallback")
+      cacheSpy.mockRestore()
+    })
+
+    test("passes through non-gemini-3 models for google connected provider", () => {
+      // given - google connected, category default uses gemini-2.5-flash (no transform needed)
+      const cacheSpy = spyOn(connectedProvidersCache, "readConnectedProvidersCache").mockReturnValue(["google"])
+      const input: ExtendedModelResolutionInput = {
+        categoryDefaultModel: "google/gemini-2.5-flash",
+        availableModels: new Set(),
+        systemDefaultModel: "anthropic/claude-sonnet-4-5",
+      }
+
+      // when
+      const result = resolveModelWithFallback(input)
+
+      // then - should pass through unchanged
+      expect(result!.model).toBe("google/gemini-2.5-flash")
       expect(result!.source).toBe("category-default")
       cacheSpy.mockRestore()
     })

src/shared/provider-model-id-transform.ts

@@ -0,0 +1,18 @@
+export function transformModelForProvider(provider: string, model: string): string {
+	if (provider === "github-copilot") {
+		return model
+			.replace("claude-opus-4-6", "claude-opus-4.6")
+			.replace("claude-sonnet-4-6", "claude-sonnet-4.6")
+			.replace("claude-sonnet-4-5", "claude-sonnet-4.5")
+			.replace("claude-haiku-4-5", "claude-haiku-4.5")
+			.replace("claude-sonnet-4", "claude-sonnet-4")
+			.replace(/gemini-3-pro(?!-)/g, "gemini-3-pro-preview")
+			.replace(/gemini-3-flash(?!-)/g, "gemini-3-flash-preview")
+	}
+	if (provider === "google") {
+		return model
+			.replace(/gemini-3-pro(?!-)/g, "gemini-3-pro-preview")
+			.replace(/gemini-3-flash(?!-)/g, "gemini-3-flash-preview")
+	}
+	return model
+}

src/tools/delegate-task/model-selection.ts

@@ -1,5 +1,6 @@
 import type { FallbackEntry } from "../../shared/model-requirements"
 import { fuzzyMatchModel } from "../../shared/model-availability"
+import { transformModelForProvider } from "../../shared/provider-model-id-transform"
 
 function normalizeModel(model?: string): string | undefined {
   const trimmed = model?.trim()
@@ -38,7 +39,8 @@ export function resolveModelForDelegateTask(input: {
       const first = fallbackChain[0]
       const provider = first?.providers?.[0]
       if (provider) {
-        return { model: `${provider}/${first.model}`, variant: first.variant }
+        const transformedModelId = transformModelForProvider(provider, first.model)
+        return { model: `${provider}/${transformedModelId}`, variant: first.variant }
       }
     } else {
       for (const entry of fallbackChain) {