diff --git a/.github/workflows/ql3-ci.yml b/.github/workflows/ql3-ci.yml
index 90e3ab95..edbe58aa 100644
--- a/.github/workflows/ql3-ci.yml
+++ b/.github/workflows/ql3-ci.yml
@@ -715,6 +715,7 @@ jobs:
           HEADLESS_IMAGE: qinglong3-local-application:ci-${{ matrix.image_arch }}
           CONSOLE_IMAGE: qinglong3-local-console:ci-${{ matrix.image_arch }}
           OPERATOR_IMAGE: qinglong3-local-operator:ci-${{ matrix.image_arch }}
+          QL3_LOCAL_DEPLOYMENT_DIAGNOSTICS: '1'
           TRIAL_VARIANT: ${{ inputs.local_alpha_variant }}
         run: |
           set -euo pipefail
diff --git a/packages/ql3-local-owner-cli/src/deployment/localDeploymentCli.ts b/packages/ql3-local-owner-cli/src/deployment/localDeploymentCli.ts
index 21942bac..0d0a5291 100644
--- a/packages/ql3-local-owner-cli/src/deployment/localDeploymentCli.ts
+++ b/packages/ql3-local-owner-cli/src/deployment/localDeploymentCli.ts
@@ -10,6 +10,7 @@ import {
   consumeLocalServiceManagerCutoverOutcomeCommandFile,
   consumeLocalServiceManagerLegacyRollbackCommandFile,
   inspectLocalDeploymentStatusCommandFile,
+  LocalDeploymentConfigurationError,
   preflightLocalDeploymentComposeCommandFile,
   prepareLocalServiceManagerIntentCommandFile,
   prepareLocalServiceManagerLegacyRollbackCommandFile,
@@ -282,8 +283,15 @@ async function main(argv: readonly string[]): Promise<void> {
   } catch (error) {
     const candidate = error as {
       readonly code?: unknown;
+      readonly message?: unknown;
       readonly name?: unknown;
     };
+    const diagnosticMessage =
+      process.env.QL3_LOCAL_DEPLOYMENT_DIAGNOSTICS === '1' &&
+      error instanceof LocalDeploymentConfigurationError &&
+      typeof candidate.message === 'string'
+        ? { message: candidate.message }
+        : {};
     process.stderr.write(
       `${JSON.stringify({
         code:
@@ -291,6 +299,7 @@ async function main(argv: readonly string[]): Promise<void> {
             ? candidate.code
             : 'QL3_LOCAL_DEPLOYMENT_FAILED',
         name: typeof candidate.name === 'string' ? candidate.name : 'Error',
+        ...diagnosticMessage,
       })}\n`,
     );
     process.exitCode = 1;
diff --git a/packages/ql3-local-owner-cli/test/localDeployment.test.cjs b/packages/ql3-local-owner-cli/test/localDeployment.test.cjs
index 3ed5ac36..b944564a 100644
--- a/packages/ql3-local-owner-cli/test/localDeployment.test.cjs
+++ b/packages/ql3-local-owner-cli/test/localDeployment.test.cjs
@@ -1000,6 +1000,42 @@ test('status CLI is private-command-only and emits no deployment authority', asy
   assert.equal(rejected.stderr.includes(state.deploymentRoot), false);
 });
 
+test('deployment CLI exposes configuration detail only under explicit diagnostics', (t) => {
+  const state = fixture(t, 'compose');
+  const commandPath = path.join(state.managementRoot, 'invalid-command.json');
+  fs.writeFileSync(commandPath, '{}\n', { mode: 0o600 });
+  const cli = path.resolve(
+    __dirname,
+    '../dist/deployment/localDeploymentCli.js',
+  );
+  const normal = spawnSync(
+    process.execPath,
+    [cli, 'prepare', '--command-file', commandPath],
+    { encoding: 'utf8' },
+  );
+  assert.equal(normal.status, 1);
+  assert.deepEqual(JSON.parse(normal.stderr), {
+    code: 'QL3_LOCAL_DEPLOYMENT_CONFIGURATION_INVALID',
+    name: 'LocalDeploymentConfigurationError',
+  });
+
+  const diagnostic = spawnSync(
+    process.execPath,
+    [cli, 'prepare', '--command-file', commandPath],
+    {
+      encoding: 'utf8',
+      env: { ...process.env, QL3_LOCAL_DEPLOYMENT_DIAGNOSTICS: '1' },
+    },
+  );
+  assert.equal(diagnostic.status, 1);
+  assert.deepEqual(JSON.parse(diagnostic.stderr), {
+    code: 'QL3_LOCAL_DEPLOYMENT_CONFIGURATION_INVALID',
+    name: 'LocalDeploymentConfigurationError',
+    message:
+      'Local deployment configuration is invalid: command shape is invalid',
+  });
+});
+
 test('durable status keeps live supervisor and database authority out of its module', () => {
   const source = fs.readFileSync(
     path.resolve(__dirname, '../src/deployment/localDeploymentStatus.ts'),
diff --git a/scripts/templates/ql3-local-alpha-reconciliation-rehearsal.sh b/scripts/templates/ql3-local-alpha-reconciliation-rehearsal.sh
index ec266bf3..3d0567d0 100644
--- a/scripts/templates/ql3-local-alpha-reconciliation-rehearsal.sh
+++ b/scripts/templates/ql3-local-alpha-reconciliation-rehearsal.sh
@@ -210,6 +210,8 @@ run_deploy() {
     --mount "type=bind,src=$decision_parent,dst=$decision_parent,readonly"
   [ -z "$secondary_decision_parent" ] || set -- "$@" \
     --mount "type=bind,src=$secondary_decision_parent,dst=$secondary_decision_parent,readonly"
+  [ "${QL3_LOCAL_DEPLOYMENT_DIAGNOSTICS:-0}" != 1 ] || set -- "$@" \
+    --env QL3_LOCAL_DEPLOYMENT_DIAGNOSTICS=1
   set -- "$@" "$OPERATOR_IMAGE" deploy "$subcommand" \
     --command-file "$command_root/$command_file"
   result_stage="$result_root/.$result_file.$$"