diff --git a/tests/package-load.test.ts b/tests/package-load.test.ts
new file mode 100644
index 00000000..57c06848
--- /dev/null
+++ b/tests/package-load.test.ts
@@ -0,0 +1,152 @@
+import assert from "node:assert/strict"
+import test from "node:test"
+import { execFileSync } from "node:child_process"
+import {
+    copyFileSync,
+    existsSync,
+    mkdirSync,
+    mkdtempSync,
+    readdirSync,
+    readFileSync,
+    rmSync,
+    symlinkSync,
+    writeFileSync,
+} from "node:fs"
+import { join, resolve } from "node:path"
+import { tmpdir } from "node:os"
+import { pathToFileURL } from "node:url"
+
+// opencode installs plugins into its own cache directory, where the packages
+// listed in `dependencies` are present but peers and devDependencies are not.
+// @opencode-ai/plugin is a peer, and because `tool()` is a value import the
+// import statement used to survive into dist/index.js, throw on load, and get
+// the plugin dropped by opencode's dynamic-import try/catch without surfacing
+// anything (#585).
+
+const root = resolve(import.meta.dirname, "..")
+const distEntry = join(root, "dist", "index.js")
+const repoModules = join(root, "node_modules")
+const built = existsSync(distEntry)
+
+// opencode's cache layout: runtime dependencies present, peers absent.
+const CACHE_EXCLUDED = new Set(["@opencode-ai/plugin"])
+
+function linkInstalledPackages(target: string): void {
+    mkdirSync(target, { recursive: true })
+    for (const entry of readdirSync(repoModules, { withFileTypes: true })) {
+        if (entry.name.startsWith(".")) continue
+        const source = join(repoModules, entry.name)
+        if (!entry.isDirectory() && !entry.isSymbolicLink()) continue
+
+        if (entry.name.startsWith("@")) {
+            mkdirSync(join(target, entry.name), { recursive: true })
+            for (const scoped of readdirSync(source)) {
+                if (CACHE_EXCLUDED.has(`${entry.name}/${scoped}`)) continue
+                symlinkSync(join(source, scoped), join(target, entry.name, scoped), "junction")
+            }
+            continue
+        }
+
+        symlinkSync(source, join(target, entry.name), "junction")
+    }
+}
+
+function buildCacheSandbox(): string {
+    const sandbox = mkdtempSync(join(tmpdir(), "dcp-plugin-cache-"))
+    mkdirSync(join(sandbox, "dist"), { recursive: true })
+    copyFileSync(distEntry, join(sandbox, "dist", "index.js"))
+    copyFileSync(join(root, "package.json"), join(sandbox, "package.json"))
+    linkInstalledPackages(join(sandbox, "node_modules"))
+    return sandbox
+}
+
+test("the built plugin entry has no bare @opencode-ai/plugin import", { skip: !built }, () => {
+    const source = readFileSync(distEntry, "utf8")
+    const runtimeImports = [
+        ...source.matchAll(
+            /(?:^|[;\s])(?:import|export)[^;'"]*from\s*["']@opencode-ai\/plugin["']/g,
+        ),
+    ]
+
+    assert.deepEqual(
+        runtimeImports.map((m) => m[0]),
+        [],
+        "dist/index.js still imports @opencode-ai/plugin at runtime",
+    )
+})
+
+test("the built entry loads from an opencode-style plugin cache", { skip: !built }, () => {
+    const sandbox = buildCacheSandbox()
+    try {
+        // Precondition: the sandbox really does model opencode's cache.
+        assert.equal(
+            existsSync(join(sandbox, "node_modules", "@opencode-ai", "plugin")),
+            false,
+            "sandbox must not provide the peer dependency",
+        )
+        assert.equal(
+            existsSync(join(sandbox, "node_modules", "@opencode-ai", "sdk")),
+            true,
+            "sandbox must provide the runtime dependency",
+        )
+        assert.equal(existsSync(join(sandbox, "node_modules", "@anthropic-ai", "tokenizer")), true)
+
+        const entryUrl = pathToFileURL(join(sandbox, "dist", "index.js")).href
+        const script = `import(${JSON.stringify(entryUrl)})
+                .then((m) => { console.log(m.default?.id === "opencode-dcp" ? "OK" : "NO_DEFAULT") })
+                .catch((e) => { console.log("ERR: " + e.message); process.exit(1) })`
+        const output = execFileSync(process.execPath, ["--input-type=module", "-e", script], {
+            encoding: "utf8",
+            cwd: sandbox,
+        })
+
+        assert.match(output, /OK/)
+    } finally {
+        rmSync(sandbox, { recursive: true, force: true })
+    }
+})
+
+test(
+    "the built entry keeps working when the peer dependency is available",
+    { skip: !built },
+    async () => {
+        // Guards against bundling changing behaviour: with @opencode-ai/plugin
+        // resolvable, the plugin must still register its hooks.
+        const sandbox = mkdtempSync(join(tmpdir(), "dcp-plugin-full-"))
+        try {
+            mkdirSync(join(sandbox, "dist"), { recursive: true })
+            copyFileSync(distEntry, join(sandbox, "dist", "index.js"))
+            writeFileSync(join(sandbox, "package.json"), JSON.stringify({ type: "module" }))
+            symlinkSync(repoModules, join(sandbox, "node_modules"), "junction")
+
+            const module = await import(pathToFileURL(join(sandbox, "dist", "index.js")).href)
+            assert.equal(module.default.id, "opencode-dcp")
+            assert.equal(typeof module.default.setup, "function")
+            assert.equal(typeof module.default.server, "function")
+        } finally {
+            rmSync(sandbox, { recursive: true, force: true })
+        }
+    },
+)
+
+test("tsup keeps the plugin package in the bundle", () => {
+    const config = readFileSync(join(root, "tsup.config.ts"), "utf8")
+    assert.match(
+        config,
+        /noExternal[\s\S]*"@opencode-ai\/plugin"/,
+        "tsup must bundle @opencode-ai/plugin or the load failure returns",
+    )
+})
+
+test("@opencode-ai/plugin is still declared as a peer, not a dependency", () => {
+    const pkg = JSON.parse(readFileSync(join(root, "package.json"), "utf8"))
+    assert.ok(
+        pkg.peerDependencies?.["@opencode-ai/plugin"],
+        "the peer range is what opencode resolves against",
+    )
+    assert.equal(
+        pkg.dependencies?.["@opencode-ai/plugin"],
+        undefined,
+        "bundling it makes a runtime dependency unnecessary",
+    )
+})
diff --git a/tsup.config.ts b/tsup.config.ts
index 8fb58167..9ae38a4b 100644
--- a/tsup.config.ts
+++ b/tsup.config.ts
@@ -6,5 +6,12 @@ export default defineConfig({
     dts: false,
     clean: true,
     sourcemap: true,
-    noExternal: ["jsonc-parser"], // Bundle this to fix its broken ESM imports
+    noExternal: [
+        "jsonc-parser", // Bundle this to fix its broken ESM imports
+        // tool() is a value import, not `import type`, so it survives into
+        // dist/index.js. @opencode-ai/plugin is a peer dependency and opencode
+        // installs plugins into its own cache without providing it, so the
+        // import threw before DCP ran and the plugin was dropped silently.
+        "@opencode-ai/plugin",
+    ],
 })