0.3.0

HTTP/SSE MCP servers can be now included in `session/new`

README.md

@@ -1,12 +1,14 @@
 # ACP adapter for Claude Code
 
+[![npm](https://img.shields.io/npm/v/%40zed-industries%2Fclaude-code-acp)](https://www.npmjs.com/package/@zed-industries/claude-code-acp)
+
 Use [Claude Code](https://www.anthropic.com/claude-code) from [ACP-compatible](https://agentclientprotocol.com) clients such as [Zed](https://zed.dev)!
 
 This tool implements an ACP agent by using the official [Claude Code SDK](https://docs.anthropic.com/en/docs/claude-code/sdk/sdk-overview), supporting:
 
 - Context @-mentions
 - Images
-- Tool calls
+- Tool calls (with permission requests)
 - Following
 - Edit review
 - TODO lists
@@ -26,10 +28,12 @@ To use Claude Code, open the Agent Panel and click "New Claude Code Thread" from
 
 https://github.com/user-attachments/assets/ddce66c7-79ac-47a3-ad59-4a6a3ca74903
 
-[Read the docs](https://zed.dev/docs/ai/external-agents) on External Agent support.
+Read the docs on [External Agent](https://zed.dev/docs/ai/external-agents) support.
 
 ### Other clients
 
+- Neovim via [CodeCompanion.nvim](https://codecompanion.olimorris.dev/configuration/adapters#setup-claude-code-via-acp)
+
 Setup instructions for other clients are coming soon. Feel free to [submit a PR](https://github.com/zed-industries/claude-code-acp/pulls) to add yours!
 
 #### Installation
@@ -37,13 +41,13 @@ Setup instructions for other clients are coming soon. Feel free to [submit a PR]
 Install the adapter from `npm`:
 
 ```bash
-$ npm install @zed-industries/claude-code-acp
+npm install @zed-industries/claude-code-acp
 ```
 
 You can then use `claude-code-acp` as a regular ACP agent:
 
 ```
-$ ANTHROPIC_API_KEY=sk-... claude-code-acp
+ANTHROPIC_API_KEY=sk-... claude-code-acp
 ```
 
 ## License

package-lock.json

@@ -1,18 +1,18 @@
 {
   "name": "@zed-industries/claude-code-acp",
-  "version": "0.1.9",
+  "version": "0.3.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "@zed-industries/claude-code-acp",
-      "version": "0.1.9",
+      "version": "0.3.0",
       "license": "Apache-2.0",
       "dependencies": {
         "@anthropic-ai/claude-code": "^1.0.100",
         "@modelcontextprotocol/sdk": "^1.17.4",
-        "@types/express": "^5.0.3",
-        "@zed-industries/agent-client-protocol": "0.2.0-alpha.4",
+        "@zed-industries/agent-client-protocol": "0.2.0-alpha.7",
+        "diff": "^8.0.2",
         "express": "^5.1.0",
         "minimist": "^1.2.8",
         "uuid": "11.1.0"
@@ -21,6 +21,7 @@
         "claude-code-acp": "dist/index.js"
       },
       "devDependencies": {
+        "@types/express": "^5.0.3",
         "@types/minimist": "^1.2.5",
         "@types/node": "^24.3.0",
         "@types/uuid": "^10.0.0",
@@ -1276,6 +1277,7 @@
       "version": "1.19.6",
       "resolved": "https://registry.npmjs.org/@types/body-parser/-/body-parser-1.19.6.tgz",
       "integrity": "sha512-HLFeCYgz89uk22N5Qg3dvGvsv46B8GLvKKo1zKG4NybA8U2DiEO3w9lqGg29t/tfLRJpJ6iQxnVw4OnB7MoM9g==",
+      "dev": true,
       "license": "MIT",
       "dependencies": {
         "@types/connect": "*",
@@ -1296,6 +1298,7 @@
       "version": "3.4.38",
       "resolved": "https://registry.npmjs.org/@types/connect/-/connect-3.4.38.tgz",
       "integrity": "sha512-K6uROf1LD88uDQqJCktA4yzL1YYAK6NgfsI0v/mTgyPKWsX1CnJ0XPSDhViejru1GcRkLWb8RlzFYJRqGUbaug==",
+      "dev": true,
       "license": "MIT",
       "dependencies": {
         "@types/node": "*"
@@ -1319,6 +1322,7 @@
       "version": "5.0.3",
       "resolved": "https://registry.npmjs.org/@types/express/-/express-5.0.3.tgz",
       "integrity": "sha512-wGA0NX93b19/dZC1J18tKWVIYWyyF2ZjT9vin/NRu0qzzvfVzWjs04iq2rQ3H65vCTQYlRqs3YHfY7zjdV+9Kw==",
+      "dev": true,
       "license": "MIT",
       "dependencies": {
         "@types/body-parser": "*",
@@ -1330,6 +1334,7 @@
       "version": "5.0.7",
       "resolved": "https://registry.npmjs.org/@types/express-serve-static-core/-/express-serve-static-core-5.0.7.tgz",
       "integrity": "sha512-R+33OsgWw7rOhD1emjU7dzCDHucJrgJXMA5PYCzJxVil0dsyx5iBEPHqpPfiKNJQb7lZ1vxwoLR4Z87bBUpeGQ==",
+      "dev": true,
       "license": "MIT",
       "dependencies": {
         "@types/node": "*",
@@ -1342,12 +1347,14 @@
       "version": "2.0.5",
       "resolved": "https://registry.npmjs.org/@types/http-errors/-/http-errors-2.0.5.tgz",
       "integrity": "sha512-r8Tayk8HJnX0FztbZN7oVqGccWgw98T/0neJphO91KkmOzug1KkofZURD4UaD5uH8AqcFLfdPErnBod0u71/qg==",
+      "dev": true,
       "license": "MIT"
     },
     "node_modules/@types/mime": {
       "version": "1.3.5",
       "resolved": "https://registry.npmjs.org/@types/mime/-/mime-1.3.5.tgz",
       "integrity": "sha512-/pyBZWSLD2n0dcHE3hq8s8ZvcETHtEuF+3E7XVt0Ig2nvsVQXdghHVcEkIWjy9A0wKfTn97a/PSDYohKIlnP/w==",
+      "dev": true,
       "license": "MIT"
     },
     "node_modules/@types/minimist": {
@@ -1361,6 +1368,7 @@
       "version": "24.3.0",
       "resolved": "https://registry.npmjs.org/@types/node/-/node-24.3.0.tgz",
       "integrity": "sha512-aPTXCrfwnDLj4VvXrm+UUCQjNEvJgNA8s5F1cvwQU+3KNltTOkBm1j30uNLyqqPNe7gE3KFzImYoZEfLhp4Yow==",
+      "dev": true,
       "license": "MIT",
       "dependencies": {
         "undici-types": "~7.10.0"
@@ -1370,18 +1378,21 @@
       "version": "6.14.0",
       "resolved": "https://registry.npmjs.org/@types/qs/-/qs-6.14.0.tgz",
       "integrity": "sha512-eOunJqu0K1923aExK6y8p6fsihYEn/BYuQ4g0CxAAgFc4b/ZLN4CrsRZ55srTdqoiLzU2B2evC+apEIxprEzkQ==",
+      "dev": true,
       "license": "MIT"
     },
     "node_modules/@types/range-parser": {
       "version": "1.2.7",
       "resolved": "https://registry.npmjs.org/@types/range-parser/-/range-parser-1.2.7.tgz",
       "integrity": "sha512-hKormJbkJqzQGhziax5PItDUTMAM9uE2XXQmM37dyd4hVM+5aVl7oVxMVUiVQn2oCQFN/LKCZdvSM0pFRqbSmQ==",
+      "dev": true,
       "license": "MIT"
     },
     "node_modules/@types/send": {
       "version": "0.17.5",
       "resolved": "https://registry.npmjs.org/@types/send/-/send-0.17.5.tgz",
       "integrity": "sha512-z6F2D3cOStZvuk2SaP6YrwkNO65iTZcwA2ZkSABegdkAh/lf+Aa/YQndZVfmEXT5vgAp6zv06VQ3ejSVjAny4w==",
+      "dev": true,
       "license": "MIT",
       "dependencies": {
         "@types/mime": "^1",
@@ -1392,6 +1403,7 @@
       "version": "1.15.8",
       "resolved": "https://registry.npmjs.org/@types/serve-static/-/serve-static-1.15.8.tgz",
       "integrity": "sha512-roei0UY3LhpOJvjbIP6ZZFngyLKl5dskOtDhxY5THRSpO+ZI+nzJ+m5yUMzGrp89YRa7lvknKkMYjqQFGwA7Sg==",
+      "dev": true,
       "license": "MIT",
       "dependencies": {
         "@types/http-errors": "*",
@@ -1796,9 +1808,9 @@
       }
     },
     "node_modules/@zed-industries/agent-client-protocol": {
-      "version": "0.2.0-alpha.4",
-      "resolved": "https://registry.npmjs.org/@zed-industries/agent-client-protocol/-/agent-client-protocol-0.2.0-alpha.4.tgz",
-      "integrity": "sha512-l/MdK0MrvEb55/U3wAtAN/MC04YK+N6vNyakNgLsK2JTcmG54n45gXa0OZ08lYUmEvLe0shdu1dDtzlOV/Luxw==",
+      "version": "0.2.0-alpha.7",
+      "resolved": "https://registry.npmjs.org/@zed-industries/agent-client-protocol/-/agent-client-protocol-0.2.0-alpha.7.tgz",
+      "integrity": "sha512-LusOBTbhX1veoL2IwUigWcCUf4r7Wl0nFJPeXoBx3OXTWCGE5WfmUPjpXVpduegxEipqea53Q/ls5lQfyoYd3Q==",
       "license": "Apache-2.0",
       "dependencies": {
         "zod": "^3.0.0"
@@ -2215,10 +2227,9 @@
       }
     },
     "node_modules/diff": {
-      "version": "4.0.2",
-      "resolved": "https://registry.npmjs.org/diff/-/diff-4.0.2.tgz",
-      "integrity": "sha512-58lmxKSA4BNyLz+HHMUzlOEpg09FV+ev6ZMe3vJihgdxzgcwZ8VoEEPmALCZG9LmqfVoNMMKpttIYTVG6uDY7A==",
-      "dev": true,
+      "version": "8.0.2",
+      "resolved": "https://registry.npmjs.org/diff/-/diff-8.0.2.tgz",
+      "integrity": "sha512-sSuxWU5j5SR9QQji/o2qMvqRNYRDOcBTgsJ/DeCf4iSN4gW+gNMXM7wFIP+fdXZxoNiAnHUTGjCr+TSWXdRDKg==",
       "license": "BSD-3-Clause",
       "engines": {
         "node": ">=0.3.1"
@@ -4362,6 +4373,16 @@
         }
       }
     },
+    "node_modules/ts-node/node_modules/diff": {
+      "version": "4.0.2",
+      "resolved": "https://registry.npmjs.org/diff/-/diff-4.0.2.tgz",
+      "integrity": "sha512-58lmxKSA4BNyLz+HHMUzlOEpg09FV+ev6ZMe3vJihgdxzgcwZ8VoEEPmALCZG9LmqfVoNMMKpttIYTVG6uDY7A==",
+      "dev": true,
+      "license": "BSD-3-Clause",
+      "engines": {
+        "node": ">=0.3.1"
+      }
+    },
     "node_modules/type-check": {
       "version": "0.4.0",
       "resolved": "https://registry.npmjs.org/type-check/-/type-check-0.4.0.tgz",
@@ -4420,6 +4441,7 @@
       "version": "7.10.0",
       "resolved": "https://registry.npmjs.org/undici-types/-/undici-types-7.10.0.tgz",
       "integrity": "sha512-t5Fy/nfn+14LuOc2KNYg75vZqClpAiqscVvMygNnlsHBFpSXdJaYtXMcdNLpl/Qvc3P2cB3s6lOV51nqsFq4ag==",
+      "dev": true,
       "license": "MIT"
     },
     "node_modules/unpipe": {

package.json

@@ -6,7 +6,7 @@
   "bin": {
     "claude-code-acp": "./dist/index.js"
   },
-  "version": "0.1.9",
+  "version": "0.3.0",
   "description": "An ACP-compatible coding agent powered by the Claude Code SDK (TypeScript)",
   "main": "dist/index.js",
   "type": "module",
@@ -45,13 +45,14 @@
   "dependencies": {
     "@anthropic-ai/claude-code": "^1.0.100",
     "@modelcontextprotocol/sdk": "^1.17.4",
-    "@types/express": "^5.0.3",
-    "@zed-industries/agent-client-protocol": "0.2.0-alpha.4",
+    "@zed-industries/agent-client-protocol": "0.2.0-alpha.7",
+    "diff": "^8.0.2",
     "express": "^5.1.0",
     "minimist": "^1.2.8",
     "uuid": "11.1.0"
   },
   "devDependencies": {
+    "@types/express": "^5.0.3",
     "@types/minimist": "^1.2.5",
     "@types/node": "^24.3.0",
     "@types/uuid": "^10.0.0",

src/acp-agent.ts

@@ -31,7 +31,7 @@ import * as fs from "node:fs";
 import * as path from "node:path";
 import * as os from "node:os";
 import { v7 as uuidv7 } from "uuid";
-import { nodeToWebReadable, nodeToWebWritable, Pushable, sleep, unreachable } from "./utils.js";
+import { nodeToWebReadable, nodeToWebWritable, Pushable, unreachable } from "./utils.js";
 import { SessionNotification } from "@zed-industries/agent-client-protocol";
 import { createMcpServer } from "./mcp-server.js";
 import { AddressInfo } from "node:net";
@@ -86,36 +86,52 @@ export class ClaudeAcpAgent implements Agent {
           image: true,
           embeddedContext: true,
         },
+        mcpCapabilities: {
+          http: true,
+          sse: true,
+        },
       },
       authMethods: [
         {
           description: "Run `claude /login` in the terminal",
-          name: "Login with Claude CLI",
+          name: "Log in with Claude Code",
           id: "claude-login",
         },
-        {
-          description: "Anthropic API KEY",
-          name: "Use Anthropic API Key",
-          id: "anthropic-api-key",
-        },
       ],
     };
   }
   async newSession(params: NewSessionRequest): Promise<NewSessionResponse> {
+    if (
+      fs.existsSync(path.resolve(os.homedir(), ".claude.json.backup")) &&
+      !fs.existsSync(path.resolve(os.homedir(), ".claude.json"))
+    ) {
+      throw RequestError.authRequired();
+    }
+
     const sessionId = uuidv7();
     const input = new Pushable<SDKUserMessage>();
 
     const mcpServers: Record<string, McpServerConfig> = {};
     if (Array.isArray(params.mcpServers)) {
       for (const server of params.mcpServers) {
-        mcpServers[server.name] = {
-          type: "stdio",
-          command: server.command,
-          args: server.args,
-          env: server.env
-            ? Object.fromEntries(server.env.map((e) => [e.name, e.value]))
-            : undefined,
-        };
+        if ("type" in server) {
+          mcpServers[server.name] = {
+            type: server.type,
+            url: server.url,
+            headers: server.headers
+              ? Object.fromEntries(server.headers.map((e) => [e.name, e.value]))
+              : undefined,
+          };
+        } else {
+          mcpServers[server.name] = {
+            type: "stdio",
+            command: server.command,
+            args: server.args,
+            env: server.env
+              ? Object.fromEntries(server.env.map((e) => [e.name, e.value]))
+              : undefined,
+          };
+        }
       }
     }
 
@@ -134,6 +150,9 @@ export class ClaudeAcpAgent implements Agent {
       mcpServers,
       permissionPromptToolName: "mcp__acp__permission",
       stderr: (err) => console.error(err),
+      // note: although not documented by the types, passing an absolute path
+      // here works to find zed's managed node version.
+      executable: process.execPath as any,
     };
 
     const allowedTools = [];
@@ -168,10 +187,18 @@ export class ClaudeAcpAgent implements Agent {
       cancelled: false,
     };
 
-    const availableCommands = await availableSlashCommands(q);
+    getAvailableSlashCommands(q).then((availableCommands) => {
+      this.client.sessionUpdate({
+        sessionId,
+        update: {
+          sessionUpdate: "available_commands_update",
+          availableCommands,
+        },
+      });
+    });
+
     return {
       sessionId,
-      availableCommands,
     };
   }
 
@@ -274,7 +301,7 @@ export class ClaudeAcpAgent implements Agent {
   }
 }
 
-async function availableSlashCommands(query: Query): Promise<AvailableCommand[]> {
+async function getAvailableSlashCommands(query: Query): Promise<AvailableCommand[]> {
   const UNSUPPORTED_COMMANDS = [
     "add-dir",
     "agents", // Modal
@@ -310,20 +337,8 @@ async function availableSlashCommands(query: Query): Promise<AvailableCommand[]>
     "todos", // Escape Codes
     "vim", // Not needed
   ];
-
-  const commands = await Promise.race([
-    //todo: Do not use `as any` once `supportedCommands` is exposed via the typescript interface
-    (query as any).supportedCommands(),
-    sleep(5000).then(() => {
-      if (
-        fs.existsSync(path.resolve(os.homedir(), ".claude.json.backup")) &&
-        !fs.existsSync(path.resolve(os.homedir(), ".claude.json"))
-      ) {
-        throw RequestError.authRequired();
-      }
-      throw new Error("can't load supported slash commands");
-    }),
-  ]);
+  //todo: Do not use `as any` once `supportedCommands` is exposed via the typescript interface
+  const commands = await (query as any).supportedCommands();
 
   return commands
     .map((command: { name: string; description: string; argumentHint: string }) => {

src/index.ts

@@ -1,5 +1,16 @@
 #!/usr/bin/env node
 
+// stdout is used to send messages to the client
+// we redirect everything else to stderr to make sure it doesn't interfere with ACP
+console.log = console.error;
+console.info = console.error;
+console.warn = console.error;
+console.debug = console.error;
+
+process.on("unhandledRejection", (reason, promise) => {
+  console.error("Unhandled Rejection at:", promise, "reason:", reason);
+});
+
 import { runAcp as runAcp } from "./acp-agent.js";
 runAcp();
 

src/mcp-server.ts

@@ -6,6 +6,7 @@ import { z } from "zod";
 import { Server } from "node:http";
 import { ClaudeAcpAgent } from "./acp-agent.js";
 import { ClientCapabilities, TerminalOutputResponse } from "@zed-industries/agent-client-protocol";
+import * as diff from "diff";
 
 import { sleep, unreachable } from "./utils.js";
 
@@ -167,7 +168,8 @@ File editing instructions:
   - For unique lines, include only those lines.
   - For non-unique lines, include enough context to identify them.
 - Do not escape quotes, newlines, or other characters.
-- Only edit the specified file.`,
+- Only edit the specified file.
+- If the \`old_string\` value isn't found in the file, the edit won't be applied. The tool will fail and must be retried.`,
         inputSchema: {
           abs_path: z.string().describe("The absolute path to the file to read."),
           old_string: z.string().describe("The old text to replace (must be unique in the file)"),
@@ -182,56 +184,47 @@ File editing instructions:
         },
       },
       async (input) => {
-        try {
-          const session = agent.sessions[sessionId];
-          if (!session) {
-            return {
-              content: [
-                {
-                  type: "text",
-                  text: "The user has left the building",
-                },
-              ],
-            };
-          }
-
-          const { content } = await agent.readTextFile({
-            sessionId,
-            path: input.abs_path,
-          });
-
-          const { newContent, lineNumbers } = replaceAndCalculateLocation(content, [
-            {
-              oldText: input.old_string,
-              newText: input.new_string,
-              replaceAll: false,
-            },
-          ]);
-
-          await agent.writeTextFile({
-            sessionId,
-            path: input.abs_path,
-            content: newContent,
-          });
-
+        const session = agent.sessions[sessionId];
+        if (!session) {
           return {
             content: [
               {
                 type: "text",
-                text: JSON.stringify({ lineNumbers }),
-              },
-            ],
-          };
-        } catch (error: any) {
-          return {
-            content: [
-              {
-                type: "text",
-                text: "Editing file failed: " + error.message,
+                text: "The user has left the building",
               },
             ],
           };
         }
+
+        const { content } = await agent.readTextFile({
+          sessionId,
+          path: input.abs_path,
+        });
+
+        const { newContent } = replaceAndCalculateLocation(content, [
+          {
+            oldText: input.old_string,
+            newText: input.new_string,
+            replaceAll: false,
+          },
+        ]);
+
+        const patch = diff.createPatch(input.abs_path, content, newContent);
+
+        await agent.writeTextFile({
+          sessionId,
+          path: input.abs_path,
+          content: newContent,
+        });
+
+        return {
+          content: [
+            {
+              type: "text",
+              text: patch,
+            },
+          ],
+        };
       },
     );
 
@@ -239,7 +232,20 @@ File editing instructions:
       "multi-edit",
       {
         title: "Multi Edit",
-        description: `Edit a file with multiple sequential edits.`,
+        description: `Edit a file with multiple sequential edits.
+
+In sessions with mcp__acp__multi-edit always use it instead of MultiEdit as it will
+allow the user to conveniently review changes.
+
+File editing instructions:
+- The \`old_string\` param must match existing file content, including indentation.
+- The \`old_string\` param must come from the actual file, not an outline.
+- The \`old_string\` section must not be empty.
+- Be minimal with replacements:
+  - For unique lines, include only those lines.
+  - For non-unique lines, include enough context to identify them, unless you're using \`replace_all\`
+- Do not escape quotes, newlines, or other characters.
+- If any of the provided \`old_string\` values aren't found in the file, no edits will be applied. The tool will fail and must be retried.`,
         inputSchema: {
           file_path: z.string().describe("The absolute path to the file to modify"),
           edits: z
@@ -282,7 +288,7 @@ File editing instructions:
           path: input.file_path,
         });
 
-        const { newContent, lineNumbers } = replaceAndCalculateLocation(
+        const { newContent } = replaceAndCalculateLocation(
           content,
           input.edits.map((edit) => ({
             oldText: edit.old_string,
@@ -291,6 +297,8 @@ File editing instructions:
           })),
         );
 
+        const patch = diff.createPatch(input.file_path, content, newContent);
+
         await agent.writeTextFile({
           sessionId,
           path: input.file_path,
@@ -301,7 +309,7 @@ File editing instructions:
           content: [
             {
               type: "text",
-              text: JSON.stringify({ lineNumbers }),
+              text: patch,
             },
           ],
         };
@@ -379,13 +387,13 @@ File editing instructions:
         });
 
         const statusPromise = Promise.race([
-          handle.waitForExit().then(() => ({ status: "exited" as const })),
-          abortPromise.then(() => ({ status: "aborted" as const })),
+          handle.waitForExit().then((exitStatus) => ({ status: "exited" as const, exitStatus })),
+          abortPromise.then(() => ({ status: "aborted" as const, exitStatus: null })),
           sleep(input.timeout_ms).then(async () => {
             if (agent.backgroundTerminals[handle.id]?.status === "started") {
               await handle.kill();
             }
-            return { status: "timedOut" as const };
+            return { status: "timedOut" as const, exitStatus: null };
           }),
         ]);
 
@@ -396,7 +404,7 @@ File editing instructions:
             status: "started",
           };
 
-          statusPromise.then(async ({ status }) => {
+          statusPromise.then(async ({ status, exitStatus }) => {
             const bgTerm = agent.backgroundTerminals[handle.id];
 
             if (bgTerm.status !== "started") {
@@ -410,6 +418,7 @@ File editing instructions:
               pendingOutput: {
                 ...currentOutput,
                 output: stripCommonPrefix(bgTerm.lastOutput?.output ?? "", currentOutput.output),
+                exitStatus: exitStatus ?? currentOutput.exitStatus,
               },
             };
 
@@ -700,9 +709,10 @@ function toolCommandOutput(
   let toolOutput = "";
 
   switch (status) {
-    case "started": {
+    case "started":
+    case "exited": {
       if (exitStatus && (exitStatus.exitCode ?? null) === null) {
-        toolOutput += `Interrupted. `;
+        toolOutput += `Interrupted by the user. `;
       }
       break;
     }
@@ -712,7 +722,6 @@ function toolCommandOutput(
     case "timedOut":
       toolOutput += `Timed out. `;
       break;
-    case "exited":
     case "aborted":
       break;
     default: {
@@ -722,16 +731,19 @@ function toolCommandOutput(
   }
 
   if (exitStatus) {
-    if (typeof exitStatus.exitCode === "number" && exitStatus.exitCode !== 0) {
-      toolOutput += `Failed with exit code ${exitStatus.exitCode}.`;
+    if (typeof exitStatus.exitCode === "number") {
+      toolOutput += `Exited with code ${exitStatus.exitCode}.`;
     }
 
     if (typeof exitStatus.signal === "string") {
       toolOutput += `Signal \`${exitStatus.signal}\`. `;
     }
+
+    toolOutput += "Final output:\n\n";
+  } else {
+    toolOutput += "New output:\n\n";
   }
 
-  toolOutput += "Output:\n\n";
   toolOutput += commandOutput;
 
   if (truncated) {
@@ -767,7 +779,7 @@ export function replaceAndCalculateLocation(
   for (const edit of edits) {
     // Skip empty oldText
     if (edit.oldText === "") {
-      continue;
+      throw new Error(`The provided \`old_string\` is empty.\n\nNo edits were applied.`);
     }
 
     if (edit.replaceAll) {
@@ -779,6 +791,11 @@ export function replaceAndCalculateLocation(
       while (true) {
         const index = currentContent.indexOf(edit.oldText, searchIndex);
         if (index === -1) {
+          if (searchIndex === 0) {
+            throw new Error(
+              `The provided \`old_string\` does not appear in the file: "${edit.oldText}".\n\nNo edits were applied.`,
+            );
+          }
           break;
         }
 
@@ -800,7 +817,11 @@ export function replaceAndCalculateLocation(
     } else {
       // Replace first occurrence only
       const index = currentContent.indexOf(edit.oldText);
-      if (index !== -1) {
+      if (index === -1) {
+        throw new Error(
+          `The provided \`old_string\` does not appear in the file: "${edit.oldText}".\n\nNo edits were applied.`,
+        );
+      } else {
         const marker = `${markerPrefix}${markerCounter++}__`;
         markers.push(marker);
         currentContent =

src/tests/acp-agent.test.ts

@@ -2,6 +2,7 @@ import { describe, it, expect, beforeAll, afterAll } from "vitest";
 import { spawn, spawnSync } from "child_process";
 import {
   Agent,
+  AvailableCommand,
   Client,
   ClientSideConnection,
   NewSessionResponse,
@@ -47,9 +48,15 @@ describe.skipIf(!process.env.RUN_INTEGRATION_TESTS)("ACP subprocess integration"
     agent: Agent;
     files: Map<string, string> = new Map();
     receivedText: string = "";
+    resolveAvailableCommands: (commands: AvailableCommand[]) => void;
+    availableCommandsPromise: Promise<AvailableCommand[]>;
 
     constructor(agent: Agent) {
       this.agent = agent;
+      this.resolveAvailableCommands = () => {};
+      this.availableCommandsPromise = new Promise((resolve) => {
+        this.resolveAvailableCommands = resolve;
+      });
     }
 
     takeReceivedText() {
@@ -67,11 +74,18 @@ describe.skipIf(!process.env.RUN_INTEGRATION_TESTS)("ACP subprocess integration"
     async sessionUpdate(params: SessionNotification): Promise<void> {
       console.error("RECEIVED", JSON.stringify(params, null, 4));
 
-      if (
-        params.update.sessionUpdate === "agent_message_chunk" &&
-        params.update.content.type === "text"
-      ) {
-        this.receivedText += params.update.content.text;
+      switch (params.update.sessionUpdate) {
+        case "agent_message_chunk": {
+          if (params.update.content.type === "text") {
+            this.receivedText += params.update.content.text;
+          }
+          break;
+        }
+        case "available_commands_update":
+          this.resolveAvailableCommands(params.update.availableCommands);
+          break;
+        default:
+          break;
       }
     }
 
@@ -140,12 +154,14 @@ describe.skipIf(!process.env.RUN_INTEGRATION_TESTS)("ACP subprocess integration"
   it("should include available commands", async () => {
     const { client, connection, newSessionResponse } = await setupTestSession(__dirname);
 
-    expect(newSessionResponse.availableCommands).toContainEqual({
+    const commands = await client.availableCommandsPromise;
+
+    expect(commands).toContainEqual({
       name: "quick-math",
       description: "10 * 3 = 30 (project)",
       input: null,
     });
-    expect(newSessionResponse.availableCommands).toContainEqual({
+    expect(commands).toContainEqual({
       name: "say-hello",
       description: "Say hello (project)",
       input: { hint: "[name]" },
@@ -216,7 +232,7 @@ describe("tool conversions", () => {
 
     expect(toolInfoFromToolUse(tool_use, {})).toStrictEqual({
       kind: "search",
-      title: "Find */**.ts",
+      title: "Find `*/**.ts`",
       content: [],
       locations: [],
     });
@@ -638,36 +654,6 @@ describe("tool conversions", () => {
     ]);
   });
 
-  it("should extract locations from edit tool results", () => {
-    const toolUse = {
-      type: "tool_use",
-      id: "toolu_01ABC123",
-      name: "edit",
-      input: {
-        abs_path: "/Users/test/project/example.txt",
-        old_string: "old content",
-        new_string: "new content",
-      },
-    };
-
-    const toolResult = {
-      content: [
-        {
-          type: "text",
-          text: JSON.stringify({ lineNumbers: [5, 10, 15] }),
-        },
-      ],
-    };
-
-    const update = toolUpdateFromToolResult(toolResult, toolUse);
-
-    expect(update.locations).toEqual([
-      { path: "/Users/test/project/example.txt", line: 5 },
-      { path: "/Users/test/project/example.txt", line: 10 },
-      { path: "/Users/test/project/example.txt", line: 15 },
-    ]);
-  });
-
   it("should show full diff for multi edit tool", () => {
     const toolUse = {
       type: "tool_use",
@@ -722,110 +708,22 @@ describe("tool conversions", () => {
       locations: [
         {
           path: "/Users/test/project/config.json",
+          line: 1,
+        },
+        {
+          path: "/Users/test/project/config.json",
+          line: 3,
         },
       ],
       title: "Edit /Users/test/project/config.json",
     });
   });
 
-  it("should extract locations from multi-edit tool results", () => {
-    const toolUse = {
-      type: "tool_use",
-      id: "toolu_01DEF456",
-      name: "multi-edit",
-      input: {
-        file_path: "/Users/test/project/config.json",
-        edits: [
-          {
-            old_string: "version: 1.0",
-            new_string: "version: 2.0",
-            replace_all: false,
-          },
-          {
-            old_string: "enabled: false",
-            new_string: "enabled: true",
-            replace_all: true,
-          },
-        ],
-      },
-    };
-
-    const toolResult = {
-      content: [
-        {
-          type: "text",
-          text: JSON.stringify({ lineNumbers: [2, 8, 12, 20] }),
-        },
-      ],
-    };
-
-    const update = toolUpdateFromToolResult(toolResult, toolUse);
-
-    expect(update.locations).toEqual([
-      { path: "/Users/test/project/config.json", line: 2 },
-      { path: "/Users/test/project/config.json", line: 8 },
-      { path: "/Users/test/project/config.json", line: 12 },
-      { path: "/Users/test/project/config.json", line: 20 },
-    ]);
-  });
-
-  it("should handle mcp__acp__edit tool results", () => {
-    const toolUse = {
-      type: "tool_use",
-      id: "toolu_01GHI789",
-      name: "mcp__acp__edit",
-      input: {
-        abs_path: "/Users/test/project/main.py",
-        old_string: "def hello():",
-        new_string: "def hello_world():",
-      },
-    };
-
-    const toolResult = {
-      content: [
-        {
-          type: "text",
-          text: JSON.stringify({ lineNumbers: [42] }),
-        },
-      ],
-    };
-
-    const update = toolUpdateFromToolResult(toolResult, toolUse);
-
-    expect(update.locations).toEqual([{ path: "/Users/test/project/main.py", line: 42 }]);
-  });
-
-  it("should handle empty locations from edit tools", () => {
-    const toolUse = {
-      type: "tool_use",
-      id: "toolu_01JKL012",
-      name: "edit",
-      input: {
-        abs_path: "/Users/test/project/notfound.txt",
-        old_string: "nonexistent",
-        new_string: "replacement",
-      },
-    };
-
-    const toolResult = {
-      content: [
-        {
-          type: "text",
-          text: JSON.stringify({ lineNumbers: [] }),
-        },
-      ],
-    };
-
-    const update = toolUpdateFromToolResult(toolResult, toolUse);
-
-    expect(update.locations).toEqual([]);
-  });
-
-  it("should handle malformed tool results gracefully", () => {
+  it("should return empty update for successful edit result", () => {
     const toolUse = {
       type: "tool_use",
       id: "toolu_01MNO345",
-      name: "edit",
+      name: "mcp__acp__edit",
       input: {
         abs_path: "/Users/test/project/test.txt",
         old_string: "old",
@@ -840,6 +738,9 @@ describe("tool conversions", () => {
           text: "not valid json",
         },
       ],
+      tool_use_id: "test",
+      is_error: false,
+      type: "tool_result" as const,
     };
 
     const update = toolUpdateFromToolResult(toolResult, toolUse);
@@ -847,6 +748,40 @@ describe("tool conversions", () => {
     // Should return empty object when parsing fails
     expect(update).toEqual({});
   });
+
+  it("should return content update for edit failure", () => {
+    const toolUse = {
+      type: "tool_use",
+      id: "toolu_01MNO345",
+      name: "mcp__acp__edit",
+      input: {
+        abs_path: "/Users/test/project/test.txt",
+        old_string: "old",
+        new_string: "new",
+      },
+    };
+
+    const toolResult = {
+      content: [
+        {
+          type: "text",
+          text: "Failed to find `old_string`",
+        },
+      ],
+      tool_use_id: "test",
+      is_error: true,
+      type: "tool_result" as const,
+    };
+
+    const update = toolUpdateFromToolResult(toolResult, toolUse);
+
+    // Should return empty object when parsing fails
+    expect(update).toEqual({
+      content: [
+        { content: { type: "text", text: "Failed to find `old_string`" }, type: "content" },
+      ],
+    });
+  });
 });
 
 describe("escape markdown", () => {

src/tests/replace-and-calculate-location.test.ts

@@ -22,12 +22,9 @@ describe("replaceAndCalculateLocation", () => {
 
   it("should return empty line numbers array when no match found", () => {
     const content = "line 1\nline 2\nline 3";
-    const result = replaceAndCalculateLocation(content, [
-      { oldText: "notfound", newText: "replaced" },
-    ]);
-
-    expect(result.newContent).toBe(content);
-    expect(result.lineNumbers).toEqual([]);
+    expect(() => {
+      replaceAndCalculateLocation(content, [{ oldText: "notfound", newText: "replaced" }]);
+    }).toThrow('The provided `old_string` does not appear in the file: "notfound"');
   });
 
   it("should handle Windows line endings (CRLF)", () => {
@@ -89,35 +86,31 @@ describe("replaceAndCalculateLocation", () => {
   });
 
   it("should handle empty file content", () => {
-    const content = "";
-    const result = replaceAndCalculateLocation(content, [{ oldText: "text", newText: "replaced" }]);
-
-    expect(result.newContent).toBe("");
-    expect(result.lineNumbers).toEqual([]);
+    expect(() => {
+      replaceAndCalculateLocation("", [{ oldText: "text", newText: "replaced" }]);
+    }).toThrowError(
+      'The provided `old_string` does not appear in the file: "text".\n\nNo edits were applied.',
+    );
   });
 
   it("should handle empty search text", () => {
     // Test with replaceAll false (default)
     const content1 = "line 1\nline 2\nline 3";
-    const result1 = replaceAndCalculateLocation(content1, [{ oldText: "", newText: "replaced" }]);
-    expect(result1.newContent).toBe(content1);
-    expect(result1.lineNumbers).toEqual([]);
+    expect(() => {
+      replaceAndCalculateLocation(content1, [{ oldText: "", newText: "replaced" }]);
+    }).toThrowError("The provided `old_string` is empty.\n\nNo edits were applied.");
 
     // Test with replaceAll true on single line
     const content2 = "abc";
-    const result2 = replaceAndCalculateLocation(content2, [
-      { oldText: "", newText: "X", replaceAll: true },
-    ]);
-    expect(result2.newContent).toBe(content2);
-    expect(result2.lineNumbers).toEqual([]);
+    expect(() => {
+      replaceAndCalculateLocation(content2, [{ oldText: "", newText: "X", replaceAll: true }]);
+    }).toThrowError("The provided `old_string` is empty.\n\nNo edits were applied.");
 
     // Test with replaceAll true on multiline content
     const content3 = "ab\ncd";
-    const result3 = replaceAndCalculateLocation(content3, [
-      { oldText: "", newText: "X", replaceAll: true },
-    ]);
-    expect(result3.newContent).toBe(content3);
-    expect(result3.lineNumbers).toEqual([]);
+    expect(() => {
+      replaceAndCalculateLocation(content3, [{ oldText: "", newText: "X", replaceAll: true }]);
+    }).toThrowError("The provided `old_string` is empty.\n\nNo edits were applied.");
   });
 
   it("should handle single line content", () => {

src/tools.ts

@@ -140,27 +140,27 @@ export function toolInfoFromToolUse(
       const path = input?.abs_path ?? input?.file_path;
       let oldText = input.old_string ?? null;
       let newText = input.new_string ?? "";
-      let line = null;
+      let affectedLines: number[] = [];
 
-      if (path && input.old_text) {
+      if (path && oldText) {
         try {
           const oldContent = cachedFileContent[path] || "";
           const newContent = replaceAndCalculateLocation(oldContent, [
             {
-              oldText: input.old_string,
-              newText: input.new_string,
+              oldText,
+              newText,
               replaceAll: false,
             },
           ]);
           oldText = oldContent;
           newText = newContent.newContent;
-          line = newContent.lineNumbers[0];
+          affectedLines = newContent.lineNumbers;
         } catch (e) {
           console.error(e);
         }
       }
       return {
-        title: path ? `Edit ${path}` : "Edit",
+        title: path ? `Edit \`${path}\`` : "Edit",
         kind: "edit",
         content:
           input && path
@@ -173,7 +173,11 @@ export function toolInfoFromToolUse(
                 },
               ]
             : [],
-        locations: path ? [{ path, line }] : [],
+        locations: path
+          ? affectedLines.length > 0
+            ? affectedLines.map((line) => ({ line, path }))
+            : [{ path }]
+          : [],
       };
     }
 
@@ -189,6 +193,7 @@ export function toolInfoFromToolUse(
       };
       let oldTextMulti = multiInput.edits.map((edit: any) => edit.old_string).join("\n");
       let newTextMulti = multiInput.edits.map((edit: any) => edit.new_string).join("\n");
+      let affectedLines: number[] = [];
       try {
         if (multiInput.edits && multiInput.file_path) {
           const oldContent =
@@ -204,6 +209,7 @@ export function toolInfoFromToolUse(
           );
           oldTextMulti = oldContent;
           newTextMulti = newContent.newContent;
+          affectedLines = newContent.lineNumbers;
         }
       } catch (e) {
         console.error(e);
@@ -221,7 +227,11 @@ export function toolInfoFromToolUse(
             newText: newTextMulti,
           },
         ],
-        locations: input?.file_path ? [{ path: input.file_path }] : [],
+        locations: input?.file_path
+          ? affectedLines.length > 0
+            ? affectedLines.map((line) => ({ line, path: input.file_path }))
+            : [{ path: input.file_path }]
+          : [],
       };
     }
     case "mcp__acp__write": {
@@ -272,10 +282,10 @@ export function toolInfoFromToolUse(
     case "Glob": {
       let label = "Find";
       if (input.path) {
-        label += ` ${input.path}`;
+        label += ` \`${input.path}\``;
       }
       if (input.pattern) {
-        label += ` ${input.pattern}`;
+        label += ` \`${input.pattern}\``;
       }
       return {
         title: label,
@@ -424,60 +434,18 @@ export function toolInfoFromToolUse(
   }
 }
 
-export function toolUpdateFromToolResult(toolResult: any, toolUse: any | undefined): ToolUpdate {
+type ToolResult = {
+  type: "tool_result";
+  content: any;
+  tool_use_id: string;
+  is_error: boolean;
+};
+
+export function toolUpdateFromToolResult(
+  toolResult: ToolResult,
+  toolUse: any | undefined,
+): ToolUpdate {
   switch (toolUse?.name) {
-    case "mcp__acp__edit":
-    case "edit":
-    case "Edit": {
-      // Parse the line numbers from the tool result
-      if (toolResult.content && toolResult.content.length > 0) {
-        try {
-          const firstContent = toolResult.content[0];
-          const data = JSON.parse(firstContent.text || firstContent);
-          if (data.lineNumbers && Array.isArray(data.lineNumbers)) {
-            const locations: ToolCallLocation[] = data.lineNumbers.map((line: number) => ({
-              path: toolUse?.input?.abs_path || toolUse?.input?.file_path,
-              line: line,
-            }));
-            return { locations };
-          }
-        } catch (error) {
-          console.error(`Error parsing edit tool result: ${error}`);
-          // If parsing fails, return empty object
-          return {};
-        }
-      }
-      return {};
-    }
-    case "mcp__acp__multi-edit":
-    case "multi-edit":
-    case "MultiEdit": {
-      // Parse the line numbers from the tool result
-      if (toolResult.content && toolResult.content.length > 0) {
-        try {
-          const firstContent = toolResult.content[0];
-          const data = JSON.parse(firstContent.text || firstContent);
-          if (data.lineNumbers && Array.isArray(data.lineNumbers)) {
-            const locations: ToolCallLocation[] = data.lineNumbers.map((line: number) => ({
-              path: toolUse?.input?.file_path || toolUse?.input?.abs_path,
-              line: line,
-            }));
-            return { locations };
-          }
-        } catch (error) {
-          console.error(`Error parsing edit tool result: ${error}`);
-
-          // If parsing fails, return empty object
-          return {};
-        }
-      }
-      return {};
-    }
-
-    case "mcp__acp__write":
-    case "Write":
-      return {};
-
     case "Read":
     case "mcp__acp__read":
       if (Array.isArray(toolResult.content) && toolResult.content.length > 0) {
@@ -509,8 +477,20 @@ export function toolUpdateFromToolResult(toolResult: any, toolUse: any | undefin
       return {};
 
     case "mcp__acp__Bash":
-      // The bash tool already embeds a terminal
+    case "mcp__acp__edit":
+    case "edit":
+    case "Edit":
+    case "mcp__acp__multi-edit":
+    case "multi-edit":
+    case "MultiEdit":
+    case "mcp__acp__write":
+    case "Write": {
+      if (toolResult.is_error && toolResult.content?.length > 0) {
+        // Only return errors
+        return toAcpContentUpdate(toolResult.content);
+      }
       return {};
+    }
 
     case "Task":
     case "NotebookEdit":
@@ -527,31 +507,35 @@ export function toolUpdateFromToolResult(toolResult: any, toolUse: any | undefin
     case "WebSearch":
     case "Other":
     default: {
-      if (Array.isArray(toolResult.content) && toolResult.content.length > 0) {
-        return {
-          content: toolResult.content.map((content: any) => ({
-            type: "content",
-            content,
-          })),
-        };
-      } else if (typeof toolResult.content === "string" && toolResult.content.length > 0) {
-        return {
-          content: [
-            {
-              type: "content",
-              content: {
-                type: "text",
-                text: toolResult.content,
-              },
-            },
-          ],
-        };
-      }
-      return {};
+      return toAcpContentUpdate(toolResult.content);
     }
   }
 }
 
+function toAcpContentUpdate(content: any): { content?: ToolCallContent[] } {
+  if (Array.isArray(content) && content.length > 0) {
+    return {
+      content: content.map((content: any) => ({
+        type: "content",
+        content,
+      })),
+    };
+  } else if (typeof content === "string" && content.length > 0) {
+    return {
+      content: [
+        {
+          type: "content",
+          content: {
+            type: "text",
+            text: content,
+          },
+        },
+      ],
+    };
+  }
+  return {};
+}
+
 type ClaudePlanEntry = {
   content: string;
   status: "pending" | "in_progress" | "completed";