fix(skill-mcp): use correct sessionID when registering skill MCP connections

Fixes #3021

src/tools/skill-mcp/tools.test.ts

@@ -1,4 +1,4 @@
-import { describe, it, expect, beforeEach, mock } from "bun:test"
+import { describe, it, expect, beforeEach, mock, spyOn } from "bun:test"
 import type { ToolContext } from "@opencode-ai/plugin/tool"
 import { createSkillMcpTool, applyGrepFilter } from "./tools"
 import { SkillMcpManager } from "../../features/skill-mcp-manager"
@@ -165,6 +165,34 @@ describe("skill_mcp tool", () => {
       expect(tool.description).toBeDefined()
     })
   })
+
+  describe("session resolution", () => {
+    it("uses the tool context sessionID when the fallback getter is empty", async () => {
+      // given
+      loadedSkills = [
+        createMockSkillWithMcp("test-skill", {
+          "test-server": { command: "echo", args: ["test"] },
+        }),
+      ]
+      const callToolSpy = spyOn(manager, "callTool").mockResolvedValue({ content: [] } as never)
+      const tool = createSkillMcpTool({
+        manager,
+        getLoadedSkills: () => loadedSkills,
+        getSessionID: () => "",
+      })
+
+      // when
+      await tool.execute({ mcp_name: "test-server", tool_name: "some-tool" }, mockContext)
+
+      // then
+      expect(callToolSpy).toHaveBeenCalledWith(
+        expect.objectContaining({ sessionID: mockContext.sessionID }),
+        expect.any(Object),
+        "some-tool",
+        {},
+      )
+    })
+  })
 })
 
 describe("applyGrepFilter", () => {

src/tools/skill-mcp/tools.ts

@@ -1,4 +1,5 @@
 import { tool, type ToolDefinition } from "@opencode-ai/plugin"
+import type { ToolContext } from "@opencode-ai/plugin/tool"
 import { BUILTIN_MCP_TOOL_HINTS, SKILL_MCP_DESCRIPTION } from "./constants"
 import type { SkillMcpArgs } from "./types"
 import type { SkillMcpManager, SkillMcpClientInfo, SkillMcpServerContext } from "../../features/skill-mcp-manager"
@@ -7,7 +8,7 @@ import type { LoadedSkill } from "../../features/opencode-skill-loader/types"
 interface SkillMcpToolOptions {
   manager: SkillMcpManager
   getLoadedSkills: () => LoadedSkill[]
-  getSessionID: () => string
+  getSessionID?: () => string | undefined
 }
 
 type OperationType = { type: "tool" | "resource" | "prompt"; name: string }
@@ -136,7 +137,7 @@ export function createSkillMcpTool(options: SkillMcpToolOptions): ToolDefinition
         .optional()
         .describe("Regex pattern to filter output lines (only matching lines returned)"),
     },
-    async execute(args: SkillMcpArgs) {
+    async execute(args: SkillMcpArgs, toolContext: ToolContext) {
       const operation = validateOperationParams(args)
       const skills = getLoadedSkills()
       const found = findMcpServer(args.mcp_name, skills)
@@ -156,10 +157,15 @@ export function createSkillMcpTool(options: SkillMcpToolOptions): ToolDefinition
         )
       }
 
+      const sessionID = toolContext.sessionID || getSessionID?.()
+      if (!sessionID) {
+        throw new Error("No active session available for skill MCP call.")
+      }
+
       const info: SkillMcpClientInfo = {
         serverName: args.mcp_name,
         skillName: found.skill.name,
-        sessionID: getSessionID(),
+        sessionID,
       }
 
       const context: SkillMcpServerContext = {