fix(server): implement slash command support for OpenCode harness (#169)

Add listCommands() to OpenCodeAgentSession via the OpenCode SDK's
command.list() API, and route recognized /commands through
session.command() instead of promptAsync(). This fixes issue #168
where slash commands didn't load when OpenCode was the selected harness.

packages/server/src/server/agent/providers/opencode-agent-commands.e2e.test.ts

@@ -0,0 +1,47 @@
+import { describe, test, expect, beforeEach, afterEach } from "vitest";
+import { createDaemonTestContext, type DaemonTestContext } from "../../test-utils/index.js";
+import { getFullAccessConfig } from "../../daemon-e2e/agent-configs.js";
+
+describe("opencode agent commands E2E", () => {
+  let ctx: DaemonTestContext;
+
+  beforeEach(async () => {
+    ctx = await createDaemonTestContext();
+  });
+
+  afterEach(async () => {
+    await ctx.cleanup();
+  }, 60000);
+
+  test("lists available slash commands for an opencode agent", async () => {
+    const agent = await ctx.client.createAgent({
+      ...getFullAccessConfig("opencode"),
+      cwd: "/tmp",
+      title: "OpenCode Commands Test Agent",
+    });
+
+    expect(agent.id).toBeTruthy();
+    expect(agent.provider).toBe("opencode");
+    expect(agent.status).toBe("idle");
+
+    const result = await ctx.client.listCommands(agent.id);
+
+    expect(result.error).toBeNull();
+    expect(result.commands.length).toBeGreaterThan(0);
+
+    for (const cmd of result.commands) {
+      expect(cmd.name).toBeTruthy();
+      expect(typeof cmd.description).toBe("string");
+      expect(typeof cmd.argumentHint).toBe("string");
+      expect(cmd.name.startsWith("/")).toBe(false);
+    }
+  }, 60_000);
+
+  test("returns error for non-existent agent", async () => {
+    const result = await ctx.client.listCommands("non-existent-agent-id");
+
+    expect(result.error).toBeTruthy();
+    expect(result.error).toContain("Agent not found");
+    expect(result.commands).toEqual([]);
+  }, 60_000);
+});

packages/server/src/server/agent/providers/opencode-agent-commands.real.e2e.test.ts

@@ -0,0 +1,38 @@
+import { describe, expect, test } from "vitest";
+import pino from "pino";
+
+import { isCommandAvailable } from "../provider-launch-config.js";
+import type { AgentSlashCommand } from "../agent-sdk-types.js";
+import { OpenCodeAgentClient } from "./opencode-agent.js";
+
+describe("opencode agent commands contract (real)", () => {
+  test("lists slash commands with the expected contract", async () => {
+    expect(isCommandAvailable("opencode")).toBe(true);
+
+    const client = new OpenCodeAgentClient(pino({ level: "silent" }));
+    const session = await client.createSession({
+      provider: "opencode",
+      cwd: process.cwd(),
+      modeId: "plan",
+    });
+
+    try {
+      expect(typeof session.listCommands).toBe("function");
+      const commands = await session.listCommands!();
+
+      expect(Array.isArray(commands)).toBe(true);
+      expect(commands.length).toBeGreaterThan(0);
+
+      for (const command of commands) {
+        const typed = command as AgentSlashCommand;
+        expect(typeof typed.name).toBe("string");
+        expect(typed.name.length).toBeGreaterThan(0);
+        expect(typed.name.startsWith("/")).toBe(false);
+        expect(typeof typed.description).toBe("string");
+        expect(typeof typed.argumentHint).toBe("string");
+      }
+    } finally {
+      await session.close();
+    }
+  }, 60_000);
+});

packages/server/src/server/agent/providers/opencode-agent.ts

@@ -21,6 +21,7 @@ import type {
   AgentRuntimeInfo,
   AgentSession,
   AgentSessionConfig,
+  AgentSlashCommand,
   AgentStreamEvent,
   AgentTimelineItem,
   AgentUsage,
@@ -445,7 +446,7 @@ export class OpenCodeAgentClient implements AgentClient {
       throw new Error("OpenCode session creation returned no data");
     }
 
-    return new OpenCodeAgentSession(openCodeConfig, client, session.id);
+    return new OpenCodeAgentSession(openCodeConfig, client, session.id, this.logger);
   }
 
   async resumeSession(
@@ -470,7 +471,7 @@ export class OpenCodeAgentClient implements AgentClient {
       directory: openCodeConfig.cwd,
     });
 
-    return new OpenCodeAgentSession(openCodeConfig, client, handle.sessionId);
+    return new OpenCodeAgentSession(openCodeConfig, client, handle.sessionId, this.logger);
   }
 
   async listModels(options?: ListModelsOptions): Promise<AgentModelDefinition[]> {
@@ -975,6 +976,7 @@ class OpenCodeAgentSession implements AgentSession {
   private readonly config: OpenCodeAgentConfig;
   private readonly client: OpencodeClient;
   private readonly sessionId: string;
+  private readonly logger: Logger;
   private currentMode: string = "default";
   private pendingPermissions = new Map<string, AgentPermissionRequest>();
   private abortController: AbortController | null = null;
@@ -994,10 +996,16 @@ class OpenCodeAgentSession implements AgentSession {
   private nextTurnOrdinal = 0;
   private activeForegroundTurnId: string | null = null;
 
-  constructor(config: OpenCodeAgentConfig, client: OpencodeClient, sessionId: string) {
+  constructor(
+    config: OpenCodeAgentConfig,
+    client: OpencodeClient,
+    sessionId: string,
+    logger: Logger,
+  ) {
     this.config = config;
     this.client = client;
     this.sessionId = sessionId;
+    this.logger = logger;
     this.currentMode = normalizeOpenCodeModeId(config.modeId);
   }
 
@@ -1129,23 +1137,37 @@ class OpenCodeAgentSession implements AgentSession {
       thinkingOptionId && thinkingOptionId !== "default" ? thinkingOptionId : undefined;
     const effectiveMode = normalizeOpenCodeModeId(this.currentMode);
 
-    const promptResponse = await this.client.session.promptAsync({
+    let promptResponse;
-      sessionID: this.sessionId,
+    const slashCommand = await this.resolveSlashCommandInvocation(prompt);
-      directory: this.config.cwd,
+    if (slashCommand) {
-      parts,
+      promptResponse = await this.client.session.command({
-      ...(options?.outputSchema
+        sessionID: this.sessionId,
-        ? {
+        directory: this.config.cwd,
-            format: {
+        command: slashCommand.commandName,
-              type: "json_schema" as const,
+        arguments: slashCommand.args,
-              schema: options.outputSchema as Record<string, unknown>,
+        ...(this.config.model ? { model: this.config.model } : {}),
-            },
+        ...(effectiveMode ? { agent: effectiveMode } : {}),
-          }
+        ...(effectiveVariant ? { variant: effectiveVariant } : {}),
-        : {}),
+      });
-      ...(this.config.systemPrompt ? { system: this.config.systemPrompt } : {}),
+    } else {
-      ...(model ? { model } : {}),
+      promptResponse = await this.client.session.promptAsync({
-      ...(effectiveMode ? { agent: effectiveMode } : {}),
+        sessionID: this.sessionId,
-      ...(effectiveVariant ? { variant: effectiveVariant } : {}),
+        directory: this.config.cwd,
-    });
+        parts,
+        ...(options?.outputSchema
+          ? {
+              format: {
+                type: "json_schema" as const,
+                schema: options.outputSchema as Record<string, unknown>,
+              },
+            }
+          : {}),
+        ...(this.config.systemPrompt ? { system: this.config.systemPrompt } : {}),
+        ...(model ? { model } : {}),
+        ...(effectiveMode ? { agent: effectiveMode } : {}),
+        ...(effectiveVariant ? { variant: effectiveVariant } : {}),
+      });
+    }
 
     if (promptResponse.error) {
       const errorMsg = JSON.stringify(promptResponse.error);
@@ -1335,6 +1357,20 @@ class OpenCodeAgentSession implements AgentSession {
     return this.currentMode;
   }
 
+  async listCommands(): Promise<AgentSlashCommand[]> {
+    const result = await this.client.command.list({
+      directory: this.config.cwd,
+    });
+    if (result.error || !result.data) {
+      return [];
+    }
+    return result.data.map((cmd) => ({
+      name: cmd.name,
+      description: cmd.description ?? "",
+      argumentHint: cmd.hints?.length ? cmd.hints.join(" ") : "",
+    }));
+  }
+
   async setMode(modeId: string): Promise<void> {
     this.currentMode = normalizeOpenCodeModeId(modeId);
   }
@@ -1418,6 +1454,45 @@ class OpenCodeAgentSession implements AgentSession {
       .map((p) => ({ type: "text", text: p.text }));
   }
 
+  private parseSlashCommandInput(text: string): { commandName: string; args?: string } | null {
+    const trimmed = text.trim();
+    if (!trimmed.startsWith("/") || trimmed.length <= 1) {
+      return null;
+    }
+    const withoutPrefix = trimmed.slice(1);
+    const firstWhitespaceIdx = withoutPrefix.search(/\s/);
+    const commandName =
+      firstWhitespaceIdx === -1 ? withoutPrefix : withoutPrefix.slice(0, firstWhitespaceIdx);
+    if (!commandName || commandName.includes("/")) {
+      return null;
+    }
+    const rawArgs =
+      firstWhitespaceIdx === -1 ? "" : withoutPrefix.slice(firstWhitespaceIdx + 1).trim();
+    return rawArgs.length > 0 ? { commandName, args: rawArgs } : { commandName };
+  }
+
+  private async resolveSlashCommandInvocation(
+    prompt: AgentPromptInput,
+  ): Promise<{ commandName: string; args?: string } | null> {
+    if (typeof prompt !== "string") {
+      return null;
+    }
+    const parsed = this.parseSlashCommandInput(prompt);
+    if (!parsed) {
+      return null;
+    }
+    try {
+      const commands = await this.listCommands();
+      return commands.some((command) => command.name === parsed.commandName) ? parsed : null;
+    } catch (error) {
+      this.logger.warn(
+        { err: error, commandName: parsed.commandName },
+        "Failed to resolve slash command; falling back to plain prompt input",
+      );
+      return null;
+    }
+  }
+
   private parseModel(model?: string): { providerID: string; modelID: string } | undefined {
     if (!model) {
       return undefined;