Preserve MCP tools for Claude requests

README.md

@@ -72,9 +72,10 @@ Claude Code sends 26 captured core tools (plus user-specific MCP tools). OpenCod
 
 The bridge resolves this by:
 
-1. **Replacing OpenCode's tool definitions only for Claude-compatible targets** with Claude Code's exact wire-captured definitions — matching descriptions, JSON schemas, parameter names, and required fields.
-2. **Adding 16 Claude-only stub tools**: `AskUserQuestion`, `CronCreate`, `CronDelete`, `CronList`, `EnterPlanMode`, `EnterWorktree`, `ExitPlanMode`, `ExitWorktree`, `Monitor`, `NotebookEdit`, `PushNotification`, `RemoteTrigger`, `ScheduleWakeup`, `TaskOutput`, `TaskStop`, `WebSearch`.
-3. **Sorting all 26 tools alphabetically** to match Claude Code's ordering.
+1. **Replacing active OpenCode shared core tool definitions only for Claude-compatible targets** with Claude Code's exact wire-captured definitions — matching descriptions, JSON schemas, parameter names, and required fields.
+2. **Preserving active OpenCode custom/MCP tool definitions** so project-specific MCP servers remain available to Claude models.
+3. **Selecting Claude-only alias/stub schemas only when the matching OpenCode tool is active** (for example `question` → `AskUserQuestion`, `plan_enter` → `EnterPlanMode`).
+4. **Sorting selected tools alphabetically** to match Claude Code's ordering.
 
 If the model calls a stub tool, OpenCode's built-in error handling catches it, tells the model the tool is unavailable, and the model adapts on the next turn.
 

src/constants.ts

@@ -26,6 +26,12 @@ function detectClaudeVersion(): string {
   return "2.1.98";
 }
 
+/**
+ * Identity opencode registers this plugin under. Required: opencode refuses to
+ * load a plugin referenced by filesystem path unless its module exports an id.
+ */
+export const PLUGIN_ID = "opencode-claude-bridge";
+
 export const CLIENT_ID =
   process.env.ANTHROPIC_CLIENT_ID || "9d1c250a-e61b-44d9-88ed-5944d1962f5e";
 

src/index.test.ts

@@ -19,8 +19,11 @@ import {
 } from "./claude-tools.js";
 import { extractOAuthErrorDetail } from "./oauth.js";
 import {
+  default as pluginModule,
   deriveModelDisplayName,
   getClaudeToolsForActiveOpenCodeTools,
+  getInboundToolNameMapForActiveOpenCodeTools,
+  mapOutboundToolName,
   rewriteSystemBlocksForModel,
   shouldInjectClaudeTools,
   stripAssistantPrefillForClaude,
@@ -250,9 +253,102 @@ describe("tool schema selection", () => {
   it("does not advertise WebSearch when only a custom websearch_cited tool is active", () => {
     const out = getClaudeToolsForActiveOpenCodeTools([
       { name: "webfetch" },
-      { name: "websearch_cited" },
+      {
+        name: "websearch_cited",
+        description: "Search the web with citations",
+        input_schema: {
+          type: "object",
+          properties: { query: { type: "string" } },
+          required: ["query"],
+        },
+      },
     ]).map((tool) => tool.name).sort();
-    assert.deepEqual(out, ["WebFetch"]);
+    assert.deepEqual(out, ["WebFetch", "websearch_cited"]);
+  });
+
+  it("preserves active MCP and custom OpenCode tools", () => {
+    const customTool = {
+      name: "custom_mcp_query_record",
+      description: "Get a record by ID",
+      input_schema: {
+        type: "object",
+        properties: { recordId: { type: "string" } },
+        required: ["recordId"],
+      },
+    };
+    const out = getClaudeToolsForActiveOpenCodeTools([
+      { name: "bash", description: "OpenCode bash", input_schema: { type: "object" } },
+      customTool,
+    ]);
+
+    const bashTool = out.find((tool) => tool.name === "Bash");
+    const preservedTool = out.find((tool) => tool.name === customTool.name);
+
+    assert.ok(bashTool);
+    assert.notEqual(bashTool.description, "OpenCode bash");
+    assert.deepEqual(preservedTool, customTool);
+  });
+
+  it("preserves MCP tools that have no description", () => {
+    const out = getClaudeToolsForActiveOpenCodeTools([
+      {
+        name: "custom_mcp_get_timestamp",
+        input_schema: { type: "object", properties: {} },
+      },
+    ]);
+
+    assert.deepEqual(out, [
+      {
+        name: "custom_mcp_get_timestamp",
+        description: "",
+        input_schema: { type: "object", properties: {} },
+      },
+    ]);
+  });
+
+  it("preserves MCP tools whose names look like prefixed core tools", () => {
+    const mcpTool = {
+      name: "mcp_bash",
+      description: "Run a command through an MCP server",
+      input_schema: {
+        type: "object",
+        properties: { command: { type: "string" } },
+        required: ["command"],
+      },
+    };
+    const out = getClaudeToolsForActiveOpenCodeTools([mcpTool]);
+
+    assert.deepEqual(out, [mcpTool]);
+  });
+
+  it("preserves custom tools whose names collide with Claude core tool names", () => {
+    const customTool = {
+      name: "Bash",
+      description: "Custom Bash-like MCP tool",
+      input_schema: {
+        type: "object",
+        properties: { script: { type: "string" } },
+        required: ["script"],
+      },
+    };
+    const out = getClaudeToolsForActiveOpenCodeTools([customTool]);
+
+    assert.deepEqual(out, [customTool]);
+  });
+
+  it("maps inbound Claude core names only for active OpenCode core tools", () => {
+    assert.deepEqual(getInboundToolNameMapForActiveOpenCodeTools([
+      { name: "bash" },
+      { name: "mcp_bash", input_schema: { type: "object" } },
+    ]), { Bash: "bash" });
+    assert.deepEqual(getInboundToolNameMapForActiveOpenCodeTools([
+      { name: "Bash", input_schema: { type: "object" } },
+    ]), {});
+  });
+
+  it("maps outbound OpenCode core history but preserves MCP-prefixed names", () => {
+    assert.equal(mapOutboundToolName("bash"), "Bash");
+    assert.equal(mapOutboundToolName("mcp_bash"), "mcp_bash");
   });
 
   it("does not advertise AskUserQuestion when OpenCode did not enable question", () => {
@@ -1128,3 +1224,17 @@ describe("rewriteSystemBlocksForModel", () => {
     assert.equal(out[1].text, "no identity line here");
   });
 });
+
+describe("plugin module shape", () => {
+  it("default-exports { id, server } so opencode's loader recognises it", () => {
+    // A bare function default export sends opencode down its legacy path, where
+    // it calls every named export of this module as a plugin factory — which
+    // crashes on the helpers above and takes the whole plugin down with it.
+    assert.equal(typeof pluginModule, "object");
+    assert.equal(typeof pluginModule.server, "function");
+  });
+
+  it("carries an id, which opencode requires for path-referenced plugins", () => {
+    assert.equal(pluginModule.id, "opencode-claude-bridge");
+  });
+});

src/index.ts

@@ -24,6 +24,7 @@ import {
   DEFAULT_EFFORT,
   CLEAR_THINKING_TYPE,
   SESSION_ID,
+  PLUGIN_ID,
 } from "./constants.js";
 import {
   getClaudeTools,
@@ -33,6 +34,7 @@ import {
   extractFirstUserMessageText,
   shouldUseClaudeToolSchemas,
 } from "./claude-tools.js";
+import type { ToolDefinition } from "./claude-tools.js";
 import { createSseProcessor } from "./stream.js";
 
 // ── Types ──────────────────────────────────────────────────────────
@@ -79,18 +81,23 @@ const OUTBOUND_TOOL_NAME_MAP: Record<string, string> = {
   webfetch: "WebFetch",
   todowrite: "TodoWrite",
   skill: "Skill",
-  mcp_bash: "Bash",
-  mcp_read: "Read",
-  mcp_glob: "Glob",
-  mcp_grep: "Grep",
-  mcp_edit: "Edit",
-  mcp_write: "Write",
-  mcp_task: "Agent",
-  mcp_webfetch: "WebFetch",
-  mcp_todowrite: "TodoWrite",
-  mcp_skill: "Skill",
   question: "AskUserQuestion",
-  mcp_question: "AskUserQuestion",
+  plan_enter: "EnterPlanMode",
+  plan_exit: "ExitPlanMode",
+};
+
+const ACTIVE_TOOL_SCHEMA_NAME_MAP: Record<string, string> = {
+  bash: "Bash",
+  read: "Read",
+  glob: "Glob",
+  grep: "Grep",
+  edit: "Edit",
+  write: "Write",
+  task: "Agent",
+  webfetch: "WebFetch",
+  todowrite: "TodoWrite",
+  skill: "Skill",
+  question: "AskUserQuestion",
   plan_enter: "EnterPlanMode",
   plan_exit: "ExitPlanMode",
 };
@@ -230,21 +237,73 @@ export function shouldInjectClaudeTools(input: {
   return Array.isArray(input.tools) && input.tools.length > 0;
 }
 
+function getToolName(tool: unknown): string | undefined {
+  if (!tool || typeof tool !== "object") return undefined;
+  const name = (tool as { name?: unknown }).name;
+  return typeof name === "string" ? name : undefined;
+}
+
+function getToolInputSchema(tool: unknown): Record<string, unknown> | undefined {
+  if (!tool || typeof tool !== "object") return undefined;
+  const inputSchema = (tool as { input_schema?: unknown }).input_schema;
+  if (!inputSchema || typeof inputSchema !== "object" || Array.isArray(inputSchema)) return undefined;
+  return inputSchema as Record<string, unknown>;
+}
+
 export function getClaudeToolsForActiveOpenCodeTools(
   tools: unknown,
-): ReturnType<typeof getClaudeTools> {
+): ToolDefinition[] {
   if (!Array.isArray(tools)) return [];
-  const activeClaudeNames = new Set(
-    tools
-      .map((tool) => {
-        if (!tool || typeof tool !== "object") return undefined;
-        const name = (tool as { name?: unknown }).name;
-        if (typeof name !== "string") return undefined;
-        return OUTBOUND_TOOL_NAME_MAP[name] || name;
-      })
-      .filter((name): name is string => typeof name === "string"),
+  const claudeToolsByName = new Map(getClaudeTools().map((tool) => [tool.name, tool]));
+  const selectedToolsByName = new Map<string, ToolDefinition>();
+
+  for (const tool of tools) {
+    const name = getToolName(tool);
+    if (!name) continue;
+
+    const claudeName = ACTIVE_TOOL_SCHEMA_NAME_MAP[name];
+    if (claudeName) {
+      const claudeTool = claudeToolsByName.get(claudeName);
+      if (!claudeTool) continue;
+      selectedToolsByName.set(claudeName, claudeTool);
+      continue;
+    }
+
+    const inputSchema = getToolInputSchema(tool);
+    if (!inputSchema) {
+      console.error(
+        `[opencode-claude-bridge] Dropping active tool "${name}" — missing or invalid input_schema`,
+      );
+      continue;
+    }
+
+    const description = (tool as { description?: unknown }).description;
+    selectedToolsByName.set(name, {
+      name,
+      description: typeof description === "string" ? description : "",
+      input_schema: inputSchema,
+    });
+  }
+
+  return Array.from(selectedToolsByName.values()).sort((a, b) =>
+    a.name.localeCompare(b.name),
   );
-  return getClaudeTools().filter((tool) => activeClaudeNames.has(tool.name));
+}
+
+export function getInboundToolNameMapForActiveOpenCodeTools(
+  tools: unknown,
+): Record<string, string> {
+  if (!Array.isArray(tools)) return {};
+  const inboundToolNameMap: Record<string, string> = {};
+
+  for (const tool of tools) {
+    const name = getToolName(tool);
+    if (!name) continue;
+    const claudeName = ACTIVE_TOOL_SCHEMA_NAME_MAP[name];
+    if (claudeName) inboundToolNameMap[claudeName] = name;
+  }
+
+  return inboundToolNameMap;
 }
 
 const oauthProfileCache = new Map<string, Promise<OAuthProfile | null>>();
@@ -411,7 +470,7 @@ function deduplicatePrefix(text: string): string {
   return text;
 }
 
-function mapOutboundToolName(name: string | undefined): string | undefined {
+export function mapOutboundToolName(name: string | undefined): string | undefined {
   if (!name) return name;
   return OUTBOUND_TOOL_NAME_MAP[name] || name;
 }
@@ -664,6 +723,7 @@ const OpenCodeClaudeBridge = async ({ client }: { client: PluginClient }) => {
 
             // ── Body ──
             let body = init?.body;
+            let inboundToolNameMap = INBOUND_TOOL_NAME_MAP;
             if (body && typeof body === "string") {
               try {
                 const parsed = JSON.parse(body);
@@ -779,6 +839,7 @@ const OpenCodeClaudeBridge = async ({ client }: { client: PluginClient }) => {
                 // requests or Claude-family models on Anthropic-compatible
                 // routers such as OpenRouter.
                 if (shouldInjectClaudeTools({ model: parsed.model, requestUrl, tools: parsed.tools })) {
+                  inboundToolNameMap = getInboundToolNameMapForActiveOpenCodeTools(parsed.tools);
                   parsed.tools = getClaudeToolsForActiveOpenCodeTools(parsed.tools);
                 }
                 delete parsed.tool_choice;
@@ -890,7 +951,7 @@ const OpenCodeClaudeBridge = async ({ client }: { client: PluginClient }) => {
             // split across TCP chunks) that regex-on-raw-bytes can't
             // handle. See src/stream.ts for the processor implementation.
             const processor = createSseProcessor({
-              inboundToolNameMap: INBOUND_TOOL_NAME_MAP,
+              inboundToolNameMap,
               translateToolArgs: translateToolArgsJsonString,
             });
 
@@ -1074,4 +1135,15 @@ const OpenCodeClaudeBridge = async ({ client }: { client: PluginClient }) => {
   };
 };
 
-export default OpenCodeClaudeBridge;
+/**
+ * opencode plugin module.
+ *
+ * The `{ id, server }` shape is what opencode's plugin loader looks for. A bare
+ * function default export makes it fall back to its legacy path, which treats
+ * every named export of this module as a plugin factory and invokes it with
+ * `(input, options)` — crashing on the helpers exported here for tests.
+ */
+export default {
+  id: PLUGIN_ID,
+  server: OpenCodeClaudeBridge,
+};