diff --git a/packages/opencode/src/session/instruction.ts b/packages/opencode/src/session/instruction.ts
index 86f73d0fd238..72ae4fe2c748 100644
--- a/packages/opencode/src/session/instruction.ts
+++ b/packages/opencode/src/session/instruction.ts
@@ -92,6 +92,13 @@ export namespace InstructionPrompt {
       }
     }
 
+    const rules = await Glob.scan(".opencode/rules/*.{md,mdc}", {
+      cwd: Instance.directory,
+      absolute: true,
+      include: "file",
+    }).catch(() => [])
+    rules.forEach((p) => paths.add(path.resolve(p)))
+
     if (config.instructions) {
       for (let instruction of config.instructions) {
         if (instruction.startsWith("https://") || instruction.startsWith("http://")) continue
diff --git a/packages/opencode/test/session/instruction.test.ts b/packages/opencode/test/session/instruction.test.ts
index e0bf94a9500d..a6569266d44f 100644
--- a/packages/opencode/test/session/instruction.test.ts
+++ b/packages/opencode/test/session/instruction.test.ts
@@ -168,3 +168,18 @@ describe("InstructionPrompt.systemPaths OPENCODE_CONFIG_DIR", () => {
     }
   })
 })
+
+test("loads .opencode/rules/project-rule.md as a system path", async () => {
+  await using tmp = await tmpdir({
+    init: async (dir) => {
+      await Bun.write(path.join(dir, ".opencode", "rules", "project-rule.md"), "# Project Rule\nDo not break things.")
+    },
+  })
+  await Instance.provide({
+    directory: tmp.path,
+    fn: async () => {
+      const paths = await InstructionPrompt.systemPaths()
+      expect(paths.has(path.join(tmp.path, ".opencode", "rules", "project-rule.md"))).toBe(true)
+    },
+  })
+})