diff --git a/.opencode/plugins/ecc-hooks.ts b/.opencode/plugins/ecc-hooks.ts
index fa96b805..ff8628b5 100644
--- a/.opencode/plugins/ecc-hooks.ts
+++ b/.opencode/plugins/ecc-hooks.ts
@@ -43,6 +43,14 @@ export const ECCHooksPlugin: ECCHooksPluginFn = async ({
     return path.join(worktreePath, p)
   }
 
+  function hasProjectFile(relativePath: string): boolean {
+    try {
+      return fs.existsSync(resolvePath(relativePath))
+    } catch {
+      return false
+    }
+  }
+
   const pendingToolChanges = new Map<string, { path: string; type: "added" | "modified" }>()
   let writeCounter = 0
 
@@ -275,13 +283,8 @@ export const ECCHooksPlugin: ECCHooksPluginFn = async ({
       log("info", `[ECC] Session started - profile=${currentProfile}`)
 
       // Check for project-specific context files
-      try {
-        const hasClaudeMd = await $`test -f ${worktree}/CLAUDE.md && echo "yes"`.text()
-        if (hasClaudeMd.trim() === "yes") {
-          log("info", "[ECC] Found CLAUDE.md - loading project context")
-        }
-      } catch {
-        // No CLAUDE.md found
+      if (hasProjectFile("CLAUDE.md")) {
+        log("info", "[ECC] Found CLAUDE.md - loading project context")
       }
     },
 
@@ -400,7 +403,7 @@ export const ECCHooksPlugin: ECCHooksPluginFn = async ({
         ECC_PLUGIN: "true",
         ECC_HOOK_PROFILE: currentProfile,
         ECC_DISABLED_HOOKS: process.env.ECC_DISABLED_HOOKS || "",
-        PROJECT_ROOT: worktree || directory,
+        PROJECT_ROOT: worktreePath,
       }
 
       // Detect package manager
@@ -411,12 +414,9 @@ export const ECCHooksPlugin: ECCHooksPluginFn = async ({
         "package-lock.json": "npm",
       }
       for (const [lockfile, pm] of Object.entries(lockfiles)) {
-        try {
-          await $`test -f ${worktree}/${lockfile}`
+        if (hasProjectFile(lockfile)) {
           env.PACKAGE_MANAGER = pm
           break
-        } catch {
-          // Not found, try next
         }
       }
 
@@ -430,11 +430,8 @@ export const ECCHooksPlugin: ECCHooksPluginFn = async ({
       }
       const detected: string[] = []
       for (const [file, lang] of Object.entries(langDetectors)) {
-        try {
-          await $`test -f ${worktree}/${file}`
+        if (hasProjectFile(file)) {
           detected.push(lang)
-        } catch {
-          // Not found
         }
       }
       if (detected.length > 0) {
diff --git a/tests/opencode-plugin-hooks.test.js b/tests/opencode-plugin-hooks.test.js
new file mode 100644
index 00000000..8b23cee8
--- /dev/null
+++ b/tests/opencode-plugin-hooks.test.js
@@ -0,0 +1,137 @@
+/**
+ * Tests for the published OpenCode hook plugin surface.
+ */
+
+const assert = require("node:assert")
+const fs = require("node:fs")
+const os = require("node:os")
+const path = require("node:path")
+const { spawnSync } = require("node:child_process")
+const { pathToFileURL } = require("node:url")
+
+function runTest(name, fn) {
+  return Promise.resolve()
+    .then(fn)
+    .then(() => {
+      console.log(`  ✓ ${name}`)
+      return { passed: 1, failed: 0 }
+    })
+    .catch((error) => {
+      console.log(`  ✗ ${name}`)
+      console.error(`    ${error.stack || error.message}`)
+      return { passed: 0, failed: 1 }
+    })
+}
+
+async function loadPlugin() {
+  const repoRoot = path.join(__dirname, "..")
+  const buildResult = spawnSync("node", [path.join(repoRoot, "scripts", "build-opencode.js")], {
+    cwd: repoRoot,
+    encoding: "utf8",
+  })
+  assert.strictEqual(buildResult.status, 0, buildResult.stderr || buildResult.stdout)
+  const pluginUrl = pathToFileURL(
+    path.join(repoRoot, ".opencode", "dist", "plugins", "ecc-hooks.js")
+  ).href
+  return import(pluginUrl)
+}
+
+function createClient() {
+  const logs = []
+  return {
+    logs,
+    app: {
+      log: ({ body }) => {
+        logs.push(body)
+        return Promise.resolve()
+      },
+    },
+  }
+}
+
+function createFailingShell() {
+  const calls = []
+  const shell = (strings, ...values) => {
+    calls.push(String.raw({ raw: strings }, ...values))
+    const error = new Error("OpenCode plugin file probes must not use shell commands")
+    return {
+      then: (_resolve, reject) => reject(error),
+      text: async () => {
+        throw error
+      },
+    }
+  }
+  shell.calls = calls
+  return shell
+}
+
+async function withTempProject(files, fn) {
+  const projectDir = fs.mkdtempSync(path.join(os.tmpdir(), "ecc-opencode-plugin-"))
+  try {
+    for (const file of files) {
+      const filePath = path.join(projectDir, file)
+      fs.mkdirSync(path.dirname(filePath), { recursive: true })
+      fs.writeFileSync(filePath, "")
+    }
+    return await fn(projectDir)
+  } finally {
+    fs.rmSync(projectDir, { recursive: true, force: true })
+  }
+}
+
+async function main() {
+  console.log("\n=== Testing OpenCode plugin hooks ===\n")
+
+  const { ECCHooksPlugin } = await loadPlugin()
+  const tests = [
+    [
+      "shell.env detects project markers without shelling out to test -f",
+      async () => withTempProject(
+        ["pnpm-lock.yaml", "tsconfig.json", "pyproject.toml"],
+        async (projectDir) => {
+          const client = createClient()
+          const $ = createFailingShell()
+          const hooks = await ECCHooksPlugin({ client, $, directory: projectDir })
+
+          const env = await hooks["shell.env"]()
+
+          assert.deepStrictEqual($.calls, [], `Unexpected shell probes: ${$.calls.join(", ")}`)
+          assert.strictEqual(env.PROJECT_ROOT, projectDir)
+          assert.strictEqual(env.PACKAGE_MANAGER, "pnpm")
+          assert.strictEqual(env.DETECTED_LANGUAGES, "typescript,python")
+          assert.strictEqual(env.PRIMARY_LANGUAGE, "typescript")
+        }
+      ),
+    ],
+    [
+      "session.created checks CLAUDE.md through fs instead of shell test",
+      async () => withTempProject(["CLAUDE.md"], async (projectDir) => {
+        const client = createClient()
+        const $ = createFailingShell()
+        const hooks = await ECCHooksPlugin({ client, $, directory: projectDir })
+
+        await hooks["session.created"]()
+
+        assert.deepStrictEqual($.calls, [], `Unexpected shell probes: ${$.calls.join(", ")}`)
+        assert.ok(
+          client.logs.some((entry) => entry.message === "[ECC] Found CLAUDE.md - loading project context"),
+          "Expected CLAUDE.md detection log"
+        )
+      }),
+    ],
+  ]
+
+  let passed = 0
+  let failed = 0
+  for (const [name, fn] of tests) {
+    const result = await runTest(name, fn)
+    passed += result.passed
+    failed += result.failed
+  }
+
+  console.log(`\nPassed: ${passed}`)
+  console.log(`Failed: ${failed}`)
+  process.exit(failed > 0 ? 1 : 0)
+}
+
+main()