diff --git a/CHANGELOG.md b/CHANGELOG.md
index 99894f63c..2ac7fc1a9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -304,6 +304,10 @@ ensuring data is stored with proper parameter values.
 
 - **Plan Rollback Command** (#8557): Implemented `agents plan rollback <plan-id> [<checkpoint-id>]` for checkpoint-based plan state restoration in Epic #8493. The command restores a plan's sandbox to the state captured at a given checkpoint, discarding all decisions made after that checkpoint. The checkpoint can be specified as an optional positional second argument or via the `--to-checkpoint` named option. Supports `--yes/-y` flag to skip confirmation prompts and `--format/-f` for output format selection (rich/plain/json/yaml). Included with comprehensive BDD test coverage (>= 97%) and spec-aligned output formatting showing rollback summary, changes reverted, impact analysis, and post-rollback state panels.
 
+### Fixed
+
+- **`agents actor add` enforces `--update` flag for existing actors** (#1500): Added regression tests to `features/actor_add_update_enforcement.feature` and step definitions in `features/steps/actor_add_update_enforcement_steps.py` verifying that re-adding an existing actor without `--update` fails, while re-adding with `--update` succeeds.
+
 ### Changed
 
 - **Expanded ruff lint scope to cover `.opencode/`** (#10848): The `lint` nox session
diff --git a/CONTRIBUTORS.md b/CONTRIBUTORS.md
index 5c06947aa..fe4f1a1f0 100644
--- a/CONTRIBUTORS.md
+++ b/CONTRIBUTORS.md
@@ -56,6 +56,9 @@ Below are some of the specific details of various contributions.
 * HAL 9000 has contributed the decision recording hook for the Strategize phase (issue #8522): captures every decision point with question, chosen option, alternatives, confidence, rationale, and full context snapshot for replay and correction.
 * HAL 9000 has contributed the ContextStrategy protocol and StrategyRegistry plugin registration system (PR #10590 / issue #8616): implemented the pluggable context assembly strategy protocol with proper type-safe method signatures, created the central thread-safe StrategyRegistry supporting registration, lookup, entry-point discovery, and per-strategy configuration (timeout, fragments limits, workers, circuit breaker threshold). Six built-in strategies implemented and documented: simple-keyword, semantic-embedding, breadth-depth-navigator, arce, temporal-archaeology, and plan-decision-context. Full BDD test coverage including thread safety, boundary validation, and error handling tests. (Part of Epic #8505)
 * HAL9000 has contributed automated implementation of ACMS context policy configuration loader and plan execution integration.
+* HAL 9000 has contributed automated bug fixes, security improvements, and migration safety enhancements including the migration prompt safe-default fix (#7503).
+* HAL 9000 has contributed the actor add --update flag enforcement tests and BDD coverage for issue #1500: added regression scenario tests verifying that re-adding an existing actor without `--update` fails, while re-adding with `--update` succeeds.
+
 * This project was made possible thanks to considerable donation of time, money, and resources by CleverThis, Inc.
 * HAL 9000 has contributed automated bug fixes, CLI output formatting improvements, and ongoing maintenance as part of the CleverAgents automation system.
 * HAL 9000 has contributed the pr-review-pool-supervisor tracking prefix documentation fix (#7891): aligned all documentation references from the outdated `AUTO-REV-POOL` prefix to the correct `AUTO-REV-SUP` prefix used in production.