feat(offset): implement LogQL offset directive — shift eval window for range and instant queries

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- `offset` directive support: LogQL queries containing `rate({...}[5m] offset 1h)` now correctly shift the evaluation window backward by the offset duration. The proxy strips the `offset` clause and adjusts `start`/`end` (range queries) or `time` (instant queries) before dispatch. Multiple distinct offsets in the same query return HTTP 400.
+
 ## [1.31.4] - 2026-05-13
 
 ### Documentation

docs/KNOWN_ISSUES.md

@@ -32,7 +32,6 @@ operational caveats that still matter in the current codebase.
 | Multi-tenant Drilldown aggregation | Some Drilldown-oriented field and label surfaces still use approximate merged cardinality across tenants. Query fanout works, but merged browse surfaces are not perfect set-theory replicas of native Loki multitenancy. |
 | Wildcard tenant shorthand | `X-Scope-OrgID: *` is a proxy convenience for global/default routing. It is not a Loki-compatible all-tenants shorthand. |
 | Patterns surface | `/loki/api/v1/patterns` is optional (`-patterns-enabled`) and responses are clamped to `1000` patterns per request. |
-| `offset` directive | Silently stripped from queries; results do not reflect time shifting. Implementation requires parsing the offset value and adjusting `start`/`end` parameters before backend dispatch. See [translation-reference.md](translation-reference.md). |
 | `count_values()` aggregation | Not translatable. VictoriaLogs has no equivalent function that groups by metric values. Queries using `count_values` return a descriptive error. |
 | Log stream ordering above split interval | For queries spanning more than one windowing interval, log entries within each stream are sorted ascending by timestamp; however Grafana may display them in the requested `direction` based on the overall response. This is stable as of v1.21.1. |
 
@@ -82,6 +81,7 @@ These are not current open issues in this codebase:
 - `detected_level` inference — proxy infers level from JSON/logfmt `_msg` content when not present in stream labels (v1.20.0)
 - circuit breaker sliding window — failure counting uses a 30-second sliding window; sporadic slow-query resets no longer open the breaker (v1.18.0)
 - deterministic log stream ordering for multi-window queries — streams and per-stream values now sorted stably before response emission (v1.21.1)
+- `offset` directive — fully implemented: proxy strips the offset clause and shifts `start`/`end` (or `time` for instant queries) backward by the offset duration before backend dispatch
 
 ## Related Docs