feat(bash): add env parameter for setting environment variables

Add optional `env` parameter to the bash tool that allows passing
environment variables to the spawned process. This enables plugins
to inject environment variables like AGENT_MODE and AGENT_ID to
track whether commands are running in primary or subagent sessions.

Changes:
- Add `env` parameter to bash tool schema (z.record(z.string(), z.string()))
- Merge env vars with process.env in spawn call
- Add tests for single and multiple environment variables

Author: taxilian

packages/opencode/src/tool/bash.ts

@@ -64,6 +64,7 @@ const Parameters = z.object({
     .describe(
       "Clear, concise description of what this command does in 5-10 words. Examples:\nInput: ls\nOutput: Lists files in current directory\n\nInput: git status\nOutput: Shows working tree status\n\nInput: npm install\nOutput: Installs package dependencies\n\nInput: mkdir foo\nOutput: Creates directory 'foo'",
     ),
+  env: z.record(z.string(), z.string()).optional().describe("Environment variables to set for the command"),
 })
 
 type Part = {
@@ -487,7 +488,7 @@ export const BashTool = Tool.define("bash", async () => {
           name,
           command: params.command,
           cwd,
-          env: await shellEnv(ctx, cwd),
+          env: { ...(await shellEnv(ctx, cwd)), ...params.env },
           timeout,
           description: params.description,
         },

packages/opencode/test/tool/bash.test.ts

@@ -1097,3 +1097,43 @@ describe("tool.bash truncation", () => {
     })
   })
 })
+
+describe("tool.bash env", () => {
+  test("sets environment variables", async () => {
+    await Instance.provide({
+      directory: projectRoot,
+      fn: async () => {
+        const bash = await BashTool.init()
+        const result = await bash.execute(
+          {
+            command: "echo $TEST_VAR",
+            description: "Echo environment variable",
+            env: { TEST_VAR: "hello_world" },
+          },
+          ctx,
+        )
+        expect(result.metadata.exit).toBe(0)
+        expect(result.output).toContain("hello_world")
+      },
+    })
+  })
+
+  test("sets multiple environment variables", async () => {
+    await Instance.provide({
+      directory: projectRoot,
+      fn: async () => {
+        const bash = await BashTool.init()
+        const result = await bash.execute(
+          {
+            command: "echo $VAR1 $VAR2",
+            description: "Echo multiple environment variables",
+            env: { VAR1: "foo", VAR2: "bar" },
+          },
+          ctx,
+        )
+        expect(result.metadata.exit).toBe(0)
+        expect(result.output).toContain("foo bar")
+      },
+    })
+  })
+})