diff --git a/php-transformer/docs/contracts/result-envelope.md b/php-transformer/docs/contracts/result-envelope.md
index 2a11763..ef19381 100644
--- a/php-transformer/docs/contracts/result-envelope.md
+++ b/php-transformer/docs/contracts/result-envelope.md
@@ -10,8 +10,12 @@ Required top-level keys for successful transformations:
   "status": "success",
   "components": [],
   "block_types": [],
-  "source_reports": {},
-  "legacy_mapping": {},
+  "source_reports": {
+    "conversion_report": {
+      "schema": "blocks-engine/php-transformer/conversion-report/v1",
+      "source_format": "html"
+    }
+  },
   "blocks": [],
   "serialized_blocks": "",
   "documents": [],
@@ -42,7 +46,7 @@ The materialization plan also includes product-neutral `routes`, `navigation_lin
 
 Transformers may expose `source_reports.conversion_report` as a generic `blocks-engine/php-transformer/conversion-report/v1` projection over the same result envelope. It summarizes fallback diagnostics, source paths/selectors, artifact-local asset references, navigation candidates, presentation-gap signals, and metrics without applying product rewrite, import, routing, or visual-parity policy. For artifact compiles, `source_summary` mirrors canonical materialization counts such as `page_count`, `asset_count`, `route_count`, `navigation_link_count`, and `menu_count` so wrappers can validate report consistency without re-deriving write plans from product-specific assumptions.
 
-`components` contains inspectable component candidates discovered before materialization. `block_types` contains generated block type artifacts promoted from `block.json` roots. `legacy_mapping` is transitional metadata for consumer-owned migration mappers and is not a long-term package feature commitment.
+`components` contains inspectable component candidates discovered before materialization. `block_types` contains generated block type artifacts promoted from `block.json` roots. Canonical result envelopes must not expose `legacy_mapping`; consumer-owned migration mappers should derive compatibility data at their own boundary.
 
 `blocks` is always a list-shaped array of parsed WordPress block arrays when exposed through `TransformerResult` or `FormatBridge::toBlocks()`. `fallbacks` entries should include stable generic metadata such as `type`, `reason`, `diagnostic_code`, `source_format`, and the preserved source fragment needed by callers to inspect or replay unsupported content.
 
diff --git a/php-transformer/src/Contract/TransformerResult.php b/php-transformer/src/Contract/TransformerResult.php
index 7ee6cee..12dd087 100644
--- a/php-transformer/src/Contract/TransformerResult.php
+++ b/php-transformer/src/Contract/TransformerResult.php
@@ -76,7 +76,7 @@ public function toArray(): array
      */
     public static function assertCanonicalEnvelope(array $result, bool $requireMaterializationPlan = false): void
     {
-        foreach ( array( 'schema', 'status', 'source_reports', 'blocks', 'serialized_blocks', 'documents', 'assets', 'diagnostics', 'fallbacks', 'provenance', 'coverage', 'context', 'metrics' ) as $key ) {
+        foreach ( array( 'schema', 'status', 'components', 'block_types', 'source_reports', 'blocks', 'serialized_blocks', 'documents', 'assets', 'diagnostics', 'fallbacks', 'provenance', 'coverage', 'context', 'metrics' ) as $key ) {
             if ( ! array_key_exists($key, $result) ) {
                 throw new InvalidArgumentException(sprintf('Canonical transformer result is missing "%s".', $key));
             }
@@ -90,11 +90,31 @@ public static function assertCanonicalEnvelope(array $result, bool $requireMater
             throw new InvalidArgumentException('Canonical transformer result must not expose compatibility-only legacy_mapping.');
         }
 
+        foreach ( array( 'conversion_report', 'materialization_plan' ) as $key ) {
+            if ( array_key_exists($key, $result) ) {
+                throw new InvalidArgumentException(sprintf('Canonical transformer result must expose %s only under source_reports.', $key));
+            }
+        }
+
+        if ( ! in_array($result['status'], array( 'success', 'success_with_warnings', 'failed' ), true) ) {
+            throw new InvalidArgumentException('Canonical transformer result has an unsupported status.');
+        }
+
+        foreach ( array( 'components', 'block_types', 'blocks', 'documents', 'assets', 'diagnostics', 'fallbacks', 'provenance', 'coverage', 'context', 'metrics' ) as $key ) {
+            if ( ! is_array($result[$key]) ) {
+                throw new InvalidArgumentException(sprintf('Canonical transformer result %s must be an array.', $key));
+            }
+        }
+
         if ( ! is_array($result['source_reports']) ) {
             throw new InvalidArgumentException('Canonical transformer result source_reports must be an array.');
         }
 
         $sourceReports = $result['source_reports'];
+        if ( array_key_exists('legacy_mapping', $sourceReports) ) {
+            throw new InvalidArgumentException('Canonical transformer result source_reports must not expose compatibility-only legacy_mapping.');
+        }
+
         $conversionReport = $sourceReports['conversion_report'] ?? null;
         if ( ! is_array($conversionReport) ) {
             throw new InvalidArgumentException('Canonical transformer result is missing source_reports.conversion_report.');
@@ -104,12 +124,32 @@ public static function assertCanonicalEnvelope(array $result, bool $requireMater
             throw new InvalidArgumentException('Canonical transformer result has an unsupported conversion report schema.');
         }
 
+        if ( ! is_string($conversionReport['source_format'] ?? null) || '' === $conversionReport['source_format'] ) {
+            throw new InvalidArgumentException('Canonical transformer result conversion report is missing source_format.');
+        }
+
+        foreach ( array( 'source_summary', 'selector_summary', 'fallback_diagnostics', 'asset_refs', 'navigation_candidates', 'presentation_gaps', 'metrics' ) as $key ) {
+            if ( array_key_exists($key, $conversionReport) && ! is_array($conversionReport[$key]) ) {
+                throw new InvalidArgumentException(sprintf('Canonical transformer result conversion report %s must be an array.', $key));
+            }
+        }
+
         $artifactLike = isset($sourceReports['artifact']) || isset($sourceReports['compiled_site']) || 'artifact' === ($conversionReport['source_format'] ?? null);
         if ( $requireMaterializationPlan || $artifactLike ) {
             $materializationPlan = $sourceReports['materialization_plan'] ?? null;
             if ( ! is_array($materializationPlan) ) {
                 throw new InvalidArgumentException('Canonical artifact result is missing source_reports.materialization_plan.');
             }
+
+            if ( 'blocks-engine/php-transformer/materialization-plan/v1' !== ($materializationPlan['schema'] ?? null) ) {
+                throw new InvalidArgumentException('Canonical artifact result has an unsupported materialization plan schema.');
+            }
+
+            foreach ( array( 'pages', 'routes', 'navigation_links', 'menus', 'template_parts', 'template_part_writes', 'assets', 'theme', 'asset_rewrite_candidates', 'rewrite_candidates', 'totals' ) as $key ) {
+                if ( ! array_key_exists($key, $materializationPlan) || ! is_array($materializationPlan[$key]) ) {
+                    throw new InvalidArgumentException(sprintf('Canonical artifact result materialization plan %s must be an array.', $key));
+                }
+            }
         }
     }
 }
diff --git a/php-transformer/src/StaticSite/MaterializationPlanBuilder.php b/php-transformer/src/StaticSite/MaterializationPlanBuilder.php
index ab24c3b..702bc35 100644
--- a/php-transformer/src/StaticSite/MaterializationPlanBuilder.php
+++ b/php-transformer/src/StaticSite/MaterializationPlanBuilder.php
@@ -15,6 +15,13 @@ final class MaterializationPlanBuilder
     public function fromResult(TransformerResult|array $result): array
     {
         $data = $result instanceof TransformerResult ? $result->toArray() : $result;
+        TransformerResult::assertCanonicalEnvelope($data);
+
+        $materializationPlan = $data['source_reports']['materialization_plan'] ?? array();
+        if ( is_array($materializationPlan) && array() !== $materializationPlan ) {
+            return $materializationPlan;
+        }
+
         $compiledSite = $data['source_reports']['compiled_site'] ?? array();
         return is_array($compiledSite) ? $this->fromCompiledSite($compiledSite) : $this->emptyPlan();
     }
@@ -50,7 +57,6 @@ public function fromCompiledSite(array $compiledSite): array
             'visual_repair_css' => (string) ($visualRepair['css'] ?? ''),
             'asset_rewrite_candidates' => $assetRewriteCandidates,
             'rewrite_candidates' => $assetRewriteCandidates,
-            'products'       => is_array($compiledSite['products'] ?? null) ? $compiledSite['products'] : array(),
             'totals'         => array(
                 'pages'          => count($pages),
                 'routes'         => count($routes),
@@ -61,10 +67,6 @@ public function fromCompiledSite(array $compiledSite): array
             ),
         );
 
-        if ( array() === $plan['products'] ) {
-            unset($plan['products']);
-        }
-
         return $plan;
     }
 
diff --git a/php-transformer/tests/contract/run.php b/php-transformer/tests/contract/run.php
index 1f5cf17..3371a38 100644
--- a/php-transformer/tests/contract/run.php
+++ b/php-transformer/tests/contract/run.php
@@ -70,6 +70,16 @@ function serialize_blocks(array $blocks): string
 }
 $assert(! array_key_exists('legacy_mapping', $result), 'canonical result omits compatibility-only legacy mapping');
 $assertInvalidCanonicalEnvelope(array_merge($result, array('legacy_mapping' => array())), 'legacy_mapping', 'canonical validation rejects legacy mapping aliases');
+$assertInvalidCanonicalEnvelope(array_merge($result, array('conversion_report' => $result['source_reports']['conversion_report'])), 'only under source_reports', 'canonical validation rejects top-level conversion report aliases');
+$assertInvalidCanonicalEnvelope(array_merge($result, array('materialization_plan' => array())), 'only under source_reports', 'canonical validation rejects top-level materialization plan aliases');
+
+$invalidStatus = $result;
+$invalidStatus['status'] = 'ok';
+$assertInvalidCanonicalEnvelope($invalidStatus, 'unsupported status', 'canonical validation rejects unsupported status values');
+
+$invalidConversionReport = $result;
+$invalidConversionReport['source_reports']['conversion_report']['source_format'] = '';
+$assertInvalidCanonicalEnvelope($invalidConversionReport, 'source_format', 'canonical validation rejects conversion reports without a source format');
 
 $missingConversionReport = $result;
 unset($missingConversionReport['source_reports']['conversion_report']);
@@ -159,6 +169,17 @@ function serialize_blocks(array $blocks): string
 unset($missingMaterializationPlan['source_reports']['materialization_plan']);
 $assertInvalidCanonicalEnvelope($missingMaterializationPlan, 'source_reports.materialization_plan', 'canonical validation rejects artifact results without materialization plans');
 
+$invalidMaterializationPlan = $simple;
+$invalidMaterializationPlan['source_reports']['materialization_plan']['schema'] = 'legacy/materialization-plan/v1';
+$assertInvalidCanonicalEnvelope($invalidMaterializationPlan, 'materialization plan schema', 'canonical validation rejects materialization plans with unsupported schemas');
+
+$incompleteMaterializationPlan = $simple;
+unset($incompleteMaterializationPlan['source_reports']['materialization_plan']['routes']);
+$assertInvalidCanonicalEnvelope($incompleteMaterializationPlan, 'materialization plan routes', 'canonical validation rejects incomplete materialization plans');
+
+$rebuiltPlan = ( new MaterializationPlanBuilder() )->fromResult($simple);
+$assert($simple['source_reports']['materialization_plan'] === $rebuiltPlan, 'materialization plan builder preserves canonical plans from result envelopes');
+
 $formatResult = ( new FormatBridge() )->convertResult('# Format report', 'markdown', 'blocks')->toArray();
 TransformerResult::assertCanonicalEnvelope($formatResult);
 $assert('blocks-engine/php-transformer/conversion-report/v1' === ($formatResult['source_reports']['conversion_report']['schema'] ?? ''), 'format bridge exposes canonical conversion report');
@@ -214,14 +235,14 @@ function serialize_blocks(array $blocks): string
 $assert('text' === ($cssAssetPlanRow['content_encoding'] ?? ''), 'materialization plan asset rows expose text content encoding');
 $assert('.wp-site-blocks{min-height:100vh}' === ($cssAssetPlanRow['content'] ?? ''), 'materialization plan asset rows expose text payloads for writable assets');
 
-$productsPlan = ( new MaterializationPlanBuilder() )->fromCompiledSite(
+$neutralPlan = ( new MaterializationPlanBuilder() )->fromCompiledSite(
     array(
         'products' => array(
             array('sku' => 'shirt-001', 'name' => 'Shirt'),
         ),
     )
 );
-$assert('shirt-001' === ($productsPlan['products'][0]['sku'] ?? ''), 'materialization plan preserves compiled site products manifest when present');
+$assert(! array_key_exists('products', $neutralPlan), 'materialization plan omits product-specific manifest buckets');
 
 $fragment = $compiler->compileFragment('<main><h2>Fragment</h2><p>Copy</p></main>', 'fixture:fragment')->toArray();
 $assert('success' === $fragment['status'], 'fragment compiles successfully', (string) $fragment['status']);