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+# RetrieX Patch 9.0e - PromptBuilder Fact-Grounding YAML-only
+
+## Scope
+
+This patch builds on Patch 9.0d.
+
+It only migrates the PromptBuilder fact-grounding rule group to YAML-only accessors:
+
+- `sections.fact_grounding_rules_label`
+- `fact_grounding.base_rules`
+- `fact_grounding.with_shop_rules`
+- `fact_grounding.without_shop_rules`
+- `fact_grounding.technical_rules`
+
+## Included changes
+
+- `src/Config/PromptBuilderConfig.php`
+  - Removes PHP fallback accessors for the fact-grounding section label and fact-grounding rule lists.
+  - Uses required YAML accessors for the migrated paths.
+
+- `config/retriex/prompt.yaml`
+  - Adds two fact-grounding base rules that still existed as PHP fallback text but were not present in YAML.
+
+## Not changed
+
+This patch does not change:
+
+- Measurement evidence guard logic
+- Role guard keywords
+- Technical product keywords
+- Accessory request keywords
+- Retrieval
+- Commerce
+- Shop matching
+- AgentRunner
+- Frontend/SSE behavior
+
+## Validation
+
+Run after applying:
+
+```bash
+php bin/console cache:clear
+php bin/console mto:agent:config:validate
+php bin/console mto:agent:config:audit-source --details
+php bin/console mto:agent:regression:test
+```
+
+Expected result:
+
+- Configuration validation remains OK.
+- Regression baseline remains OK.
+- PromptBuilderConfig fallback accessors for `fact_grounding.*` disappear from the audit.