diff --git a/packages/opencode/test/provider/copilot/finish-reason.test.ts b/packages/opencode/test/provider/copilot/finish-reason.test.ts
new file mode 100644
index 0000000000..f06e3c0051
--- /dev/null
+++ b/packages/opencode/test/provider/copilot/finish-reason.test.ts
@@ -0,0 +1,89 @@
+import { describe, test, expect } from "bun:test"
+import { mapOpenAICompatibleFinishReason } from "../../../src/provider/sdk/copilot/chat/map-openai-compatible-finish-reason"
+import { mapOpenAIResponseFinishReason } from "../../../src/provider/sdk/copilot/responses/map-openai-responses-finish-reason"
+
+// ---------------------------------------------------------------------------
+// mapOpenAICompatibleFinishReason (Chat API path)
+// ---------------------------------------------------------------------------
+
+describe("mapOpenAICompatibleFinishReason", () => {
+  test("maps 'stop' to 'stop'", () => {
+    expect(mapOpenAICompatibleFinishReason("stop")).toBe("stop")
+  })
+
+  test("maps 'length' to 'length'", () => {
+    expect(mapOpenAICompatibleFinishReason("length")).toBe("length")
+  })
+
+  test("maps 'content_filter' to 'content-filter'", () => {
+    expect(mapOpenAICompatibleFinishReason("content_filter")).toBe("content-filter")
+  })
+
+  test("maps 'function_call' to 'tool-calls'", () => {
+    expect(mapOpenAICompatibleFinishReason("function_call")).toBe("tool-calls")
+  })
+
+  test("maps 'tool_calls' to 'tool-calls'", () => {
+    expect(mapOpenAICompatibleFinishReason("tool_calls")).toBe("tool-calls")
+  })
+
+  test("maps null to 'unknown'", () => {
+    expect(mapOpenAICompatibleFinishReason(null)).toBe("unknown")
+  })
+
+  test("maps undefined to 'unknown'", () => {
+    expect(mapOpenAICompatibleFinishReason(undefined)).toBe("unknown")
+  })
+
+  test("maps empty string to 'unknown'", () => {
+    expect(mapOpenAICompatibleFinishReason("")).toBe("unknown")
+  })
+
+  test("maps unrecognized string to 'unknown'", () => {
+    expect(mapOpenAICompatibleFinishReason("something_else")).toBe("unknown")
+  })
+})
+
+// ---------------------------------------------------------------------------
+// mapOpenAIResponseFinishReason (Responses API path)
+// ---------------------------------------------------------------------------
+
+describe("mapOpenAIResponseFinishReason", () => {
+  test("null without function call returns 'stop'", () => {
+    expect(mapOpenAIResponseFinishReason({ finishReason: null, hasFunctionCall: false })).toBe("stop")
+  })
+
+  test("null with function call returns 'tool-calls'", () => {
+    expect(mapOpenAIResponseFinishReason({ finishReason: null, hasFunctionCall: true })).toBe("tool-calls")
+  })
+
+  test("undefined without function call returns 'stop'", () => {
+    expect(mapOpenAIResponseFinishReason({ finishReason: undefined, hasFunctionCall: false })).toBe("stop")
+  })
+
+  test("undefined with function call returns 'tool-calls'", () => {
+    expect(mapOpenAIResponseFinishReason({ finishReason: undefined, hasFunctionCall: true })).toBe("tool-calls")
+  })
+
+  test("'max_output_tokens' maps to 'length'", () => {
+    expect(mapOpenAIResponseFinishReason({ finishReason: "max_output_tokens", hasFunctionCall: false })).toBe("length")
+  })
+
+  test("'max_output_tokens' maps to 'length' even with function call", () => {
+    expect(mapOpenAIResponseFinishReason({ finishReason: "max_output_tokens", hasFunctionCall: true })).toBe("length")
+  })
+
+  test("'content_filter' maps to 'content-filter'", () => {
+    expect(mapOpenAIResponseFinishReason({ finishReason: "content_filter", hasFunctionCall: false })).toBe(
+      "content-filter",
+    )
+  })
+
+  test("unknown string without function call returns 'unknown'", () => {
+    expect(mapOpenAIResponseFinishReason({ finishReason: "something_else", hasFunctionCall: false })).toBe("unknown")
+  })
+
+  test("unknown string with function call returns 'tool-calls'", () => {
+    expect(mapOpenAIResponseFinishReason({ finishReason: "something_else", hasFunctionCall: true })).toBe("tool-calls")
+  })
+})
diff --git a/packages/opencode/test/provider/copilot/prepare-tools.test.ts b/packages/opencode/test/provider/copilot/prepare-tools.test.ts
new file mode 100644
index 0000000000..71576bb0be
--- /dev/null
+++ b/packages/opencode/test/provider/copilot/prepare-tools.test.ts
@@ -0,0 +1,114 @@
+import { describe, test, expect } from "bun:test"
+import { prepareTools } from "../../../src/provider/sdk/copilot/chat/openai-compatible-prepare-tools"
+
+describe("prepareTools", () => {
+  test("undefined tools returns all undefined", () => {
+    const result = prepareTools({ tools: undefined })
+    expect(result.tools).toBeUndefined()
+    expect(result.toolChoice).toBeUndefined()
+    expect(result.toolWarnings).toEqual([])
+  })
+
+  test("empty tools array returns all undefined", () => {
+    const result = prepareTools({ tools: [] })
+    expect(result.tools).toBeUndefined()
+    expect(result.toolChoice).toBeUndefined()
+    expect(result.toolWarnings).toEqual([])
+  })
+
+  test("converts a single function tool to OpenAI format", () => {
+    const result = prepareTools({
+      tools: [
+        {
+          type: "function",
+          name: "get_weather",
+          description: "Get weather for a city",
+          inputSchema: { type: "object", properties: { city: { type: "string" } } },
+        },
+      ],
+    })
+    expect(result.tools).toEqual([
+      {
+        type: "function",
+        function: {
+          name: "get_weather",
+          description: "Get weather for a city",
+          parameters: { type: "object", properties: { city: { type: "string" } } },
+        },
+      },
+    ])
+    expect(result.toolWarnings).toEqual([])
+  })
+
+  test("provider-defined tool emits unsupported-tool warning", () => {
+    const providerTool = {
+      type: "provider-defined" as const,
+      id: "some-provider-tool",
+      name: "provider_tool",
+      args: {},
+    }
+    const result = prepareTools({
+      tools: [providerTool],
+    })
+    expect(result.toolWarnings).toHaveLength(1)
+    expect(result.toolWarnings[0]).toEqual({
+      type: "unsupported-tool",
+      tool: providerTool,
+    })
+    // Provider-defined tools are not included in the output tools array
+    expect(result.tools).toEqual([])
+  })
+
+  test("toolChoice 'auto' passes through", () => {
+    const result = prepareTools({
+      tools: [
+        { type: "function", name: "foo", description: "test", inputSchema: {} },
+      ],
+      toolChoice: { type: "auto" },
+    })
+    expect(result.toolChoice).toBe("auto")
+  })
+
+  test("toolChoice 'none' passes through", () => {
+    const result = prepareTools({
+      tools: [
+        { type: "function", name: "foo", description: "test", inputSchema: {} },
+      ],
+      toolChoice: { type: "none" },
+    })
+    expect(result.toolChoice).toBe("none")
+  })
+
+  test("toolChoice 'required' passes through", () => {
+    const result = prepareTools({
+      tools: [
+        { type: "function", name: "foo", description: "test", inputSchema: {} },
+      ],
+      toolChoice: { type: "required" },
+    })
+    expect(result.toolChoice).toBe("required")
+  })
+
+  test("toolChoice type 'tool' converts to function format", () => {
+    const result = prepareTools({
+      tools: [
+        { type: "function", name: "my_func", description: "desc", inputSchema: {} },
+      ],
+      toolChoice: { type: "tool", toolName: "my_func" },
+    })
+    expect(result.toolChoice).toEqual({
+      type: "function",
+      function: { name: "my_func" },
+    })
+  })
+
+  test("no toolChoice returns undefined toolChoice", () => {
+    const result = prepareTools({
+      tools: [
+        { type: "function", name: "foo", description: "test", inputSchema: {} },
+      ],
+    })
+    expect(result.toolChoice).toBeUndefined()
+    expect(result.tools).toHaveLength(1)
+  })
+})