diff --git a/CHANGELOG.md b/CHANGELOG.md
index d0b258b..e1ebd5d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changelog
 
+## 0.3.0
+
+- Auto-register a `/plugin-compaction-init` slash command that scaffolds the compaction memory file with `## Keep` and `## Discard` sections of classification rules. User-supplied arguments are appended to extend the defaults.
+
 ## 0.2.4
 
 - Normalize npm package repository metadata.
diff --git a/README.md b/README.md
index 7fa92ad..0755a9b 100644
--- a/README.md
+++ b/README.md
@@ -36,6 +36,11 @@ You can also add it manually to your global `opencode.jsonc`:
 
 Create `.opencode/compaction.md` in the project when you have project-specific context to preserve. The file is optional.
 
+### /plugin-compaction-init <instructions>
+
+- Writes the memory file at the configured `memoryFile` path with a top instruction line and `## Keep` and `## Discard` sections containing classification rules for which messages to preserve or drop.
+- **Recommended**: pass user instructions to extend the default rules with concrete topics — specific areas of discussion you want kept or dropped.
+
 ## Options
 
 | Option             | Default                                                      | Description                                                                                                |
diff --git a/src/index.ts b/src/index.ts
index 2b06710..b3fd736 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -17,6 +17,38 @@ const defaultCompletionMarker =
   "opencode-plugin-compaction-prompt: Custom compaction done.";
 const skippedCompactionMarker =
   "opencode-plugin-compaction-prompt: No custom compaction applied.";
+const initCommandName = "plugin-compaction-init";
+
+/**
+ * Builds the prompt the auto-registered `/plugin-compaction-init` slash
+ * command sends to the model. `$ARGUMENTS$` is left unsubstituted so
+ * OpenCode substitutes it at invocation time.
+ *
+ * @param memoryFile Literal path to the memory file, inserted verbatim.
+ * @returns The full command-body template.
+ */
+export function buildInitCommandTemplate(memoryFile: string): string {
+  return `You are creating the file \`${memoryFile}\` (relative to the current project root). It is a meta-classification of which messages to preserve and which to discard during session compaction, not a summary of details.
+
+Follow this format:
+
+\`\`\`
+Keep all details related to the keep topics below, and discard everything related to the discard topics below.
+
+## Keep
+
+## Discard
+\`\`\`
+
+\`## Keep\` contains one bullet per active in-progress topic. Each bullet is a **classification rule** describing how to recognize messages that discuss that topic, including its requirements, design decisions, dependency information, and ongoing discussions needed to continue the work.
+
+\`## Discard\` contains one bullet per older or already-finished topic. Each bullet is a **classification rule** describing how to recognize messages to drop — features/tasks already shipped, abandoned, or otherwise not relevant to the next session, including any debug loops or repeated fix attempts that have already concluded. Add a final catch-all bullet:
+
+- Any other older discussions not mentioned above.
+
+$ARGUMENTS$
+`;
+}
 
 function asString(value: unknown): string | undefined {
   if (typeof value !== "string") {
@@ -106,6 +138,24 @@ export const CompactionPromptPlugin: Plugin = async (
   };
 
   return {
+    config: async (cfg): Promise<void> => {
+      if (cfg.command?.[initCommandName]) {
+        await context.client.app.log({
+          body: {
+            level: "warn",
+            message: `Skipping registration of "${initCommandName}": already defined in config.`,
+            service: "opencode-plugin-compaction-prompt",
+          },
+        });
+        return;
+      }
+
+      cfg.command ??= {};
+      cfg.command[initCommandName] = {
+        description: `Create ${memoryFile} [compaction file]`,
+        template: buildInitCommandTemplate(memoryFile),
+      };
+    },
     "experimental.session.compacting": async (
       _input,
       output,
diff --git a/test/index.test.ts b/test/index.test.ts
index 7b59e05..52a0c4e 100644
--- a/test/index.test.ts
+++ b/test/index.test.ts
@@ -2,7 +2,10 @@ import { afterEach, describe, expect, test } from "bun:test";
 import { mkdir, mkdtemp, rm, writeFile } from "node:fs/promises";
 import os from "node:os";
 import path from "node:path";
-import { CompactionPromptPlugin } from "../src/index.js";
+import {
+  buildInitCommandTemplate,
+  CompactionPromptPlugin,
+} from "../src/index.js";
 
 const temporaryDirectories: string[] = [];
 
@@ -159,3 +162,105 @@ describe("CompactionPromptPlugin", () => {
     );
   });
 });
+
+describe("buildInitCommandTemplate", () => {
+  test("substitutes the configured memory file path verbatim", () => {
+    const template = buildInitCommandTemplate("docs/agent-memory.md");
+
+    expect(template).toContain("`docs/agent-memory.md`");
+    expect(template).not.toContain(".opencode/compaction.md");
+  });
+
+  test("contains the file skeleton and both section headings", () => {
+    const template = buildInitCommandTemplate(".opencode/compaction.md");
+
+    expect(template).toContain("```\nKeep all details related to");
+    expect(template).toContain("## Keep\n");
+    expect(template).toContain("## Discard\n");
+  });
+
+  test("leaves $ARGUMENTS$ unsubstituted for OpenCode to fill in", () => {
+    const template = buildInitCommandTemplate(".opencode/compaction.md");
+
+    expect(template.trimEnd().endsWith("$ARGUMENTS$")).toBe(true);
+  });
+});
+
+describe("CompactionPromptPlugin config hook", () => {
+  test("registers the plugin-compaction-init command by default", async () => {
+    const context = await createContext();
+    const hooks = await CompactionPromptPlugin(context as never);
+    const cfg: {
+      command?: Record<string, { description: string; template: string }>;
+    } = {};
+
+    await hooks.config?.(cfg as never);
+
+    expect(cfg.command?.["plugin-compaction-init"]).toBeDefined();
+    expect(
+      cfg.command?.["plugin-compaction-init"].description.length,
+    ).toBeGreaterThan(0);
+    expect(cfg.command?.["plugin-compaction-init"].template).toContain(
+      ".opencode/compaction.md",
+    );
+    expect(cfg.command?.["plugin-compaction-init"].template).toContain(
+      "## Keep",
+    );
+    expect(cfg.command?.["plugin-compaction-init"].template).toContain(
+      "## Discard",
+    );
+    expect(cfg.command?.["plugin-compaction-init"].template).toContain(
+      "$ARGUMENTS$",
+    );
+    expect(context.logs).toHaveLength(0);
+  });
+
+  test("uses the configured memoryFile in the registered template", async () => {
+    const context = await createContext();
+    const hooks = await CompactionPromptPlugin(context as never, {
+      memoryFile: "notes/agent.md",
+    });
+    const cfg: {
+      command?: Record<string, { description: string; template: string }>;
+    } = {};
+
+    await hooks.config?.(cfg as never);
+
+    expect(cfg.command?.["plugin-compaction-init"].template).toContain(
+      "`notes/agent.md`",
+    );
+    expect(cfg.command?.["plugin-compaction-init"].template).not.toContain(
+      ".opencode/compaction.md",
+    );
+  });
+
+  test("skips registration and logs a warning when the command is already defined", async () => {
+    const context = await createContext();
+    const hooks = await CompactionPromptPlugin(context as never);
+    const userTemplate = "user-provided template body";
+    const cfg: {
+      command?: Record<string, { description: string; template: string }>;
+    } = {
+      command: {
+        "plugin-compaction-init": {
+          description: "user description",
+          template: userTemplate,
+        },
+      },
+    };
+
+    await hooks.config?.(cfg as never);
+
+    expect(cfg.command?.["plugin-compaction-init"].template).toBe(userTemplate);
+    expect(context.logs).toHaveLength(1);
+    expect(context.logs[0]).toMatchObject({
+      body: {
+        level: "warn",
+        service: "opencode-plugin-compaction-prompt",
+      },
+    });
+    expect(
+      (context.logs[0] as { body?: { message?: string } }).body?.message,
+    ).toContain("plugin-compaction-init");
+  });
+});