Document technical upgrades process

content/api/cli.md

@@ -14,7 +14,7 @@ In these commands:
 
 ## Tracking terms
 
-{{< refItem name="ota track" description="Track the current terms of services according to provided declarations. The declarations, snapshots and versions paths are defined in the configuration." example="npx ota track" />}}
+{{< refItem name="ota track" description="Track the current terms of services according to provided declarations. The declarations, snapshots and versions paths are defined in the configuration. This command automatically runs a technical upgrade pass first to apply any engine, dependency, or declaration updates before tracking." example="npx ota track" />}}
 
 > Note that the snapshots and versions will be recorded at the moment the command is executed, on top of the existing local history. If a shared history already exists and the goal is to add on top of it, that history has to be downloaded before executing that command.
 
@@ -26,6 +26,16 @@ In these commands:
 
 {{< refItem name="ota track --schedule [--services <service_id>...] [--types <terms_type>...]" description="Track terms on the schedule defined in the configuration" example="npx ota track --schedule" />}}
 
+## Applying technical upgrades
+
+{{< refItem name="ota apply-technical-upgrades" description="Apply technical upgrades by regenerating versions from existing snapshots with updated declarations/engine. This also fetches missing snapshots for newly added source documents in combined terms. Versions created during this process are labeled as technical upgrades to avoid false notifications." example="npx ota apply-technical-upgrades" />}}
+
+{{< refItem name="ota apply-technical-upgrades --help" description="Show help and available options for apply-technical-upgrades command" example="npx ota apply-technical-upgrades --help" />}}
+
+{{< refItem name="ota apply-technical-upgrades [--services <service_id>...]" description="Apply technical upgrades to specific services only" example="npx ota apply-technical-upgrades --services \"Facebook\" \"LinkedIn\"" />}}
+
+{{< refItem name="ota apply-technical-upgrades [--services <service_id>...] [--types <terms_type>...]" description="Apply technical upgrades to specific terms types of specific services only" example="npx ota apply-technical-upgrades --services \"Facebook\" \"LinkedIn\" --types \"Privacy Policy\" \"Terms of Service\"" />}}
+
 ## Validating declarations
 
 {{< refItem name="ota validate declarations [--services <service_id>...] [--types <terms_type>...]" description="Check that all declarations allow recording a snapshot and a version properly. If service IDs are provided, check only those services." example="npx ota validate declarations --services \"Facebook\" --types \"Privacy Policy\"" />}}

content/terms/explanation/technical-upgrades.md

@@ -0,0 +1,129 @@
+---
+title: "Technical upgrades"
+weight: 5
+---
+
+# Technical upgrades
+
+## What is the technical upgrades process
+
+The **technical upgrade** process creates new **versions** by re-extracting content from the **latest snapshots** when there are changes not in service terms content, but in the system that extracts them (declarations, filters, engine, or dependencies).
+
+## Why technical upgrades are important
+
+Technical upgrades solve the critical problem of **distinguishing between actual content changes and extraction improvements**.
+
+Without technical upgrades, improving a declaration would trigger false notifications. For example, if terms have sections A, B, and C but the declaration only extracted A and B, adding section C would make the next version appear to include new content, triggering a notification even though the service's terms never changed.
+
+With technical upgrades, the system re-extracts from the current snapshot using the improved declaration and creates a new version, that includes section C, marked as a technical upgrade. Next regular tracking then compares against this upgraded version, so only actual content changes trigger notifications.
+
+## How technical upgrades work
+
+For each tracked terms:
+
+1. Retrieve the latest snapshot for each source document of the terms
+2. Re-extract content using latest declarations and engine code
+3. Create a new version marked as a technical upgrade
+
+## Types of changes handled
+
+1. Declaration changes: updates to selectors, filters, or removal rules
+2. Engine changes: updates to the core extraction logic
+3. Dependency changes: updates to libraries affecting extraction (e.g., HTML-to-Markdown conversion)
+
+## Behavior for different scenarios
+
+### Selector or filter changes
+
+**Example:**
+
+```json
+// Before: missing section C
+{
+  "Privacy Policy": {
+    "fetch": "https://example.com/privacy",
+    "select": ".section-a, .section-b"
+  }
+}
+
+// After: includes all relevant sections
+{
+  "Privacy Policy": {
+    "fetch": "https://example.com/privacy",
+    "select": ".section-a, .section-b, .section-c"
+  }
+}
+```
+
+**What happens:**
+
+- Retrieves the latest snapshot
+- Re-extracts content using updated selectors and/or filters
+- Creates a new version marked as a technical upgrade
+
+### Adding new source documents to combined terms
+
+**Example:**
+
+```json
+// Before: 2 source documents
+{
+  "Community Guidelines": {
+    "combine": [
+      { "id": "main", "fetch": "https://example.com/community" },
+      { "id": "hate-speech", "fetch": "https://example.com/community/hate-speech" }
+    ]
+  }
+}
+
+// After: 3 source documents
+{
+  "Community Guidelines": {
+    "combine": [
+      { "id": "main", "fetch": "https://example.com/community" },
+      { "id": "hate-speech", "fetch": "https://example.com/community/hate-speech" },
+      { "id": "violence", "fetch": "https://example.com/community/violence" }  // NEW
+    ]
+  }
+}
+```
+
+**What happens:**
+
+- Fetches and records snapshots **only for new source documents**
+- Retrieves latest snapshots for existing source documents
+- Extracts all documents and creates one new combined version marked as a technical upgrade
+
+### Location changes
+
+**What happens:**
+
+Nothing, technical upgrades do not fetch from new locations. Location changes represent a genuine change in how the service publishes their terms and should be tracked as a regular content change.
+
+### Engine and dependency changes
+
+When you upgrade the engine or dependencies, extraction logic may change even if declarations remain the same.
+
+**Examples:**
+
+- Engine improves HTML entity decoding so ` ` entities are converted to regular spaces instead of appearing literally in versions
+- Library improves table support so complex tables preserve their structure as Markdown tables instead of being converted to plain text
+
+**What happens:**
+
+- Retrieves the latest snapshot for each terms
+- Re-extracts using updated code
+- Creates a new version marked as a technical upgrade if output differs
+
+## Technical upgrade markers
+
+Versions created during technical upgrades are marked with:
+
+- `isTechnicalUpgrade: true` in version metadata
+- Commit message specify it by starting by `Apply technical or declaration upgrade on …`
+
+## Running technical upgrades
+
+Technical upgrades run automatically with `npx ota track`.
+
+To run them separately, see the [apply-technical-upgrades command]({{< relref "api/cli#applying-technical-upgrades" >}}).