test(core): cover Anthropic partial recovery

packages/ai/test/fixtures/recordings/anthropic-recovery/accepts-a-synthetic-settled-tool-call-followed-by-continuation.json

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+{
+  "version": 1,
+  "metadata": {
+    "tags": [
+      "prefix:anthropic-recovery",
+      "provider:anthropic",
+      "protocol:anthropic-messages",
+      "tool",
+      "recovery"
+    ],
+    "name": "anthropic-recovery/accepts-a-synthetic-settled-tool-call-followed-by-continuation",
+    "recordedAt": "2026-08-22T01:52:23.916Z"
+  },
+  "interactions": [
+    {
+      "transport": "http",
+      "request": {
+        "method": "POST",
+        "url": "https://opencode.ai/zen/v1/messages",
+        "headers": {
+          "anthropic-version": "2023-06-01",
+          "content-type": "application/json"
+        },
+        "body": "{\"model\":\"claude-sonnet-4-6\",\"messages\":[{\"role\":\"user\",\"content\":[{\"type\":\"text\",\"text\":\"Look up the weather in Paris.\"}]},{\"role\":\"assistant\",\"content\":[{\"type\":\"text\",\"text\":\"I should use the weather tool.\"},{\"type\":\"tool_use\",\"id\":\"call_weather\",\"name\":\"lookup_weather\",\"input\":{\"city\":\"Paris\"}}]},{\"role\":\"user\",\"content\":[{\"type\":\"tool_result\",\"tool_use_id\":\"call_weather\",\"content\":\"sunny\"}]},{\"role\":\"user\",\"content\":[{\"type\":\"text\",\"text\":\"The previous response was interrupted. Continue from where you left off without repeating completed content.\",\"cache_control\":{\"type\":\"ephemeral\"}}]}],\"tools\":[{\"name\":\"lookup_weather\",\"description\":\"Return benign weather data for a city.\",\"input_schema\":{\"type\":\"object\",\"properties\":{\"city\":{\"type\":\"string\"}},\"required\":[\"city\"]},\"cache_control\":{\"type\":\"ephemeral\"}}],\"tool_choice\":{\"type\":\"none\"},\"stream\":true,\"max_tokens\":128,\"temperature\":0}"
+      },
+      "response": {
+        "status": 200,
+        "headers": {
+          "content-type": "text/event-stream; charset=utf-8"
+        },
+        "body": "event: message_start\ndata: {\"type\":\"message_start\",\"message\":{\"model\":\"claude-sonnet-4-6\",\"id\":\"msg_011CeGx6WkAQP5ULyRRbRwRw\",\"type\":\"message\",\"role\":\"assistant\",\"content\":[],\"stop_reason\":null,\"stop_sequence\":null,\"stop_details\":null,\"usage\":{\"input_tokens\":664,\"cache_creation_input_tokens\":0,\"cache_read_input_tokens\":0,\"cache_creation\":{\"ephemeral_5m_input_tokens\":0,\"ephemeral_1h_input_tokens\":0},\"output_tokens\":1,\"service_tier\":\"standard\",\"inference_geo\":\"global\"}}               }\n\nevent: content_block_start\ndata: {\"type\":\"content_block_start\",\"index\":0,\"content_block\":{\"type\":\"text\",\"text\":\"\"}  }\n\nevent: ping\ndata: {\"type\": \"ping\"}\n\nevent: content_block_delta\ndata: {\"type\":\"content_block_delta\",\"index\":0,\"delta\":{\"type\":\"text_delta\",\"text\":\"The\"}              }\n\nevent: content_block_delta\ndata: {\"type\":\"content_block_delta\",\"index\":0,\"delta\":{\"type\":\"text_delta\",\"text\":\" weather in Paris is currently **sunny**! It looks like a great day to enjoy the city. ☀️\"}    }\n\nevent: content_block_stop\ndata: {\"type\":\"content_block_stop\",\"index\":0       }\n\nevent: message_delta\ndata: {\"type\":\"message_delta\",\"delta\":{\"stop_reason\":\"end_turn\",\"stop_sequence\":null,\"stop_details\":null},\"usage\":{\"input_tokens\":664,\"cache_creation_input_tokens\":0,\"cache_read_input_tokens\":0,\"output_tokens\":28}       }\n\nevent: message_stop\ndata: {\"type\":\"message_stop\"    }\n\nevent: ping\ndata: {\"type\":\"ping\",\"cost\":\"0\"}\n\n"
+      }
+    }
+  ]
+}

packages/ai/test/provider/anthropic-recovery.recorded.test.ts

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+import { describe, expect } from "bun:test"
+import { Effect } from "effect"
+import { LLM, Message, ToolCallPart, ToolDefinition } from "../../src/index.js"
+import { configure } from "../../src/providers/anthropic.js"
+import { LLMClient } from "../../src/route.js"
+import { recordedTests } from "../recorded-test.js"
+
+const model = configure({
+  apiKey: process.env.ZEN_TEST_API_KEY ?? "fixture",
+  baseURL: "https://opencode.ai/zen/v1",
+}).model("claude-sonnet-4-6")
+const continuation =
+  "The previous response was interrupted. Continue from where you left off without repeating completed content."
+const lookup = ToolDefinition.make({
+  name: "lookup_weather",
+  description: "Return benign weather data for a city.",
+  inputSchema: {
+    type: "object",
+    properties: { city: { type: "string" } },
+    required: ["city"],
+  },
+})
+const recorded = recordedTests({
+  prefix: "anthropic-recovery",
+  provider: "anthropic",
+  protocol: "anthropic-messages",
+  requires: ["ZEN_TEST_API_KEY"],
+  options: { redact: { allowRequestHeaders: ["anthropic-version"] } },
+})
+
+describe("Anthropic interrupted recovery recorded", () => {
+  recorded.effect.with(
+    "accepts a synthetic settled tool call followed by continuation",
+    { tags: ["tool", "recovery"] },
+    () =>
+      Effect.gen(function* () {
+        const response = yield* LLMClient.generate(
+          LLM.request({
+            id: "recorded_anthropic_interrupted_tool_recovery",
+            model,
+            messages: [
+              Message.user("Look up the weather in Paris."),
+              Message.assistant([
+                { type: "text", text: "I should use the weather tool." },
+                ToolCallPart.make({ id: "call_weather", name: "lookup_weather", input: { city: "Paris" } }),
+              ]),
+              Message.tool({ id: "call_weather", name: "lookup_weather", result: "sunny", resultType: "text" }),
+              Message.user(continuation),
+            ],
+            tools: [lookup],
+            toolChoice: "none",
+            generation: { maxTokens: 128, temperature: 0 },
+          }),
+        )
+
+        expect(response.text.trim().length).toBeGreaterThan(0)
+      }),
+  )
+})

packages/core/test/session-anthropic-recovery.test.ts

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+import { expect, test } from "bun:test"
+import { LLM } from "@opencode-ai/ai"
+import { configure } from "@opencode-ai/ai/providers/anthropic"
+import { compileRequest } from "@opencode-ai/ai/route/client"
+import { Agent } from "@opencode-ai/core/agent"
+import { Model } from "@opencode-ai/core/model"
+import { Provider } from "@opencode-ai/core/provider"
+import { SessionMessage } from "@opencode-ai/core/session/message"
+import { toLLMMessages } from "@opencode-ai/core/session/runner/to-llm-message"
+import { DateTime, Effect } from "effect"
+
+const created = DateTime.makeUnsafe(0)
+const anthropic = Model.Ref.make({
+  id: Model.ID.make("claude-sonnet-4-6"),
+  providerID: Provider.ID.make("anthropic"),
+})
+const continuation =
+  "The previous response was interrupted. Continue from where you left off without repeating completed content."
+
+test("failed Anthropic tool history replays through the public request boundary", async () => {
+  const messages = toLLMMessages(
+    [
+      SessionMessage.User.make({
+        id: SessionMessage.ID.make("msg_user"),
+        type: "user",
+        text: "Look up the weather.",
+        time: { created },
+      }),
+      SessionMessage.Assistant.make({
+        id: SessionMessage.ID.make("msg_failed"),
+        type: "assistant",
+        agent: Agent.defaultID,
+        model: anthropic,
+        content: [
+          SessionMessage.AssistantReasoning.make({
+            type: "reasoning",
+            text: "I should use the weather tool.",
+            state: { signature: "signed-reasoning" },
+          }),
+          SessionMessage.AssistantTool.make({
+            type: "tool",
+            id: "call_weather",
+            name: "lookup_weather",
+            executed: false,
+            state: SessionMessage.ToolStateCompleted.make({
+              status: "completed",
+              input: { city: "Paris" },
+              content: [{ type: "text", text: "sunny" }],
+            }),
+            time: { created, completed: created },
+          }),
+        ],
+        finish: "error",
+        error: { type: "provider.internal", message: "Provider stream failed" },
+        time: { created, completed: created },
+      }),
+      SessionMessage.Synthetic.make({
+        id: SessionMessage.ID.make("msg_continue"),
+        type: "synthetic",
+        text: continuation,
+        time: { created },
+      }),
+    ],
+    anthropic,
+  )
+  const prepared = await Effect.runPromise(
+    compileRequest(
+      LLM.request({
+        model: configure({ apiKey: "test" }).model("claude-sonnet-4-6"),
+        messages,
+      }),
+    ),
+  )
+
+  expect(messages).toMatchObject([
+    { role: "user" },
+    {
+      role: "assistant",
+      content: [
+        { type: "text", text: "I should use the weather tool." },
+        { type: "tool-call", id: "call_weather", providerMetadata: undefined },
+      ],
+    },
+    { role: "tool", content: [{ type: "tool-result", id: "call_weather" }] },
+    { role: "user", content: [{ type: "text", text: continuation }] },
+  ])
+  expect(prepared.body.messages).toMatchObject([
+    { role: "user", content: [{ type: "text", text: "Look up the weather." }] },
+    {
+      role: "assistant",
+      content: [
+        { type: "text", text: "I should use the weather tool." },
+        { type: "tool_use", id: "call_weather", name: "lookup_weather", input: { city: "Paris" } },
+      ],
+    },
+    { role: "user", content: [{ type: "tool_result", tool_use_id: "call_weather", content: "sunny" }] },
+    { role: "user", content: [{ type: "text", text: continuation }] },
+  ])
+})