chore: add CodeRabbit review instructions for the transaction module (hiero-ledger#1824)

Signed-off-by: Siddhartha Ganguly <gangulysiddhartha22@gmail.com>

Author: gangulysiddhartha22-cmyk

.coderabbit.yaml

@@ -277,6 +277,126 @@ reviews:
     - Payment-safe
     - Execution-consistent
     - Strictly aligned with Hedera query semantics
+  
+  # TRANSACTION REVIEW INSTRUCTIONS - CORE FOUNDATION (MOST CRITICAL MODULE)
+  transaction_review_instructions: &transaction_review_instructions |
+    You are acting as a senior maintainer and security architect reviewing the **core transaction module** in the hiero-sdk-python project.
+
+    Changes to this module affect **all 50+ transaction implementations** across the entire SDK.
+
+    NOTE:
+    - Review focus levels indicate areas requiring careful verification.
+    - They do NOT imply severity or urgency.
+    - Only recommend fixes when behavior, safety, immutability, or network compatibility is impacted.
+
+    Scope is STRICTLY LIMITED to:
+    - Changes under src/hiero_sdk_python/transaction/
+    - Interaction with _Executable base class and all transaction subclasses
+
+    ----------------------------------------------------------
+    REVIEW FOCUS 1 — BASE CLASS CONTRACT INTEGRITY (HIGH SENSITIVITY)
+    ----------------------------------------------------------
+    The Transaction base class (which inherits from _Executable) defines the contract for the entire SDK.
+
+    Verify:
+    - Abstract methods remain unchanged: build_transaction_body(), build_scheduled_body(), _get_method()
+    - Inheritance hierarchy (_Executable → Transaction → subclass) is never broken
+    - Any change to public methods (freeze, freeze_with, sign, execute, to_bytes, from_bytes, etc.) includes backwards-compatibility analysis
+
+    Flag as high-risk: signature changes or removal of lifecycle guards that would ripple to every transaction subclass.
+
+    ----------------------------------------------------------
+    REVIEW FOCUS 2 — TRANSACTION LIFECYCLE SAFETY (CRITICAL)
+    ----------------------------------------------------------
+    The freeze-sign-execute pattern with immutability guards is non-negotiable.
+
+    MUST verify:
+    - Every setter calls self._require_not_frozen()
+    - sign(), execute(), to_bytes(), _to_proto(), etc. call self._require_frozen()
+    - No code path allows mutation after freeze
+    - freeze_with(client) correctly populates _transaction_body_bytes for every node (including batch_key special case node 0.0.0)
+    - freeze() vs freeze_with() distinction is preserved
+
+    Any bypass of these guards = critical security issue.
+
+    ----------------------------------------------------------
+    REVIEW FOCUS 3 — MULTI-NODE BODY & SIGNATURE MANAGEMENT (HIGH SENSITIVITY)
+    ----------------------------------------------------------
+    Node failover and multi-signature support depend on these exact patterns.
+
+    Verify:
+    - _transaction_body_bytes: dict[AccountId, bytes] maintains one entry per node AccountId
+    - _signature_map keys off the exact body bytes (not node), enabling correct signature lookup on failover
+    - Both Ed25519 and ECDSA paths in sign() are preserved and consistent
+    - Signature accumulation works for multi-sig and batch_key scenarios
+
+    Any change that could break node failover or signature lookup must be flagged.
+
+    ----------------------------------------------------------
+    REVIEW FOCUS 4 — PROTOBUF SERIALIZATION INTEGRITY (CRITICAL)
+    ----------------------------------------------------------
+    Round-trip safety and type mapping are mandatory.
+
+    Verify:
+    - to_bytes() + from_bytes() produce identical, executable objects
+    - _get_transaction_class() type map remains complete (especially atomic_batch and all 30+ types)
+    - Proper handling of SignedTransaction → bodyBytes → TransactionBody
+    - Subclass _from_protobuf / _to_proto implementations stay aligned with Hedera protobufs
+    - TransactionId, Receipt, Record parsing (defaultdicts, HasField guards, children/duplicates) is untouched unless intentional
+
+    Missing type-map entry or broken round-trip = critical omission.
+
+    ----------------------------------------------------------
+    REVIEW FOCUS 5 — VALIDATION & ERROR HANDLING
+    ----------------------------------------------------------
+    Validation must be early, deterministic, and occur before any network call.
+
+    Verify:
+    - TypeError/ValueError raised correctly in all setters and helpers
+    - _should_retry() retryable status codes are not altered casually
+    - Proper use of PrecheckError, ReceiptStatusError, MaxAttemptsError
+    - BatchTransaction._verify_inner_transaction enforces all constraints
+
+    ----------------------------------------------------------
+    REVIEW FOCUS 6 — BATCH TRANSACTION CONSTRAINT GUIDELINES (SECURITY CRITICAL)
+    ----------------------------------------------------------
+    BatchTransaction is the atomic safety boundary.
+
+    Verify:
+    - _verify_inner_transaction rejects FreezeTransaction and nested BatchTransaction
+    - Inner transactions must be frozen + have batch_key set
+    - build_scheduled_body() always raises ValueError
+    - Protobuf packing of inner signedTransactionBytes and atomic_batch field is preserved
+    - batchify() / set_batch_key() flow does not bypass lifecycle
+
+    ----------------------------------------------------------
+    REVIEW FOCUS 7 — TEST EXPECTATIONS FOR TRANSACTION CHANGES
+    ----------------------------------------------------------
+    Changes require strong coverage:
+
+    - Unit tests for any new/modified validation, lifecycle, or serialization logic
+    - Full freeze → sign → execute (and freeze_with) lifecycle tests
+    - Serialization round-trip tests (to_bytes ↔ from_bytes)
+    - Integration/mock-server tests covering retry, node failover, error states, and BatchTransaction
+
+    ----------------------------------------------------------
+    REVIEW FOCUS 8 — EXPLICIT NON-GOALS
+    ----------------------------------------------------------
+    Do NOT:
+    - Propose large refactors unless they directly improve safety or correctness
+    - Review transaction usage outside this module
+    - Comment on style/linting unless it affects critical logic
+    - Suggest changes to token/query/schedule/contract modules (they inherit the base)
+
+    ----------------------------------------------------------
+    FINAL OBJECTIVE
+    ----------------------------------------------------------
+    Ensure the core Transaction system remains:
+    - Secure & immutable by design
+    - Failover-safe (multi-node bodies + signatures)
+    - Serialization-correct with complete type mapping
+    - Extremely safe for batching
+    - 100% backwards compatible
 
   # SCHEDULE REVIEW INSTRUCTIONS
   schedule_review_instructions: &schedule_review_instructions |
@@ -677,6 +797,8 @@ reviews:
         - Has no precedence bugs that weaken protection
     - path: "src/hiero_sdk_python/tokens/**/*.py"
       instructions: *token_review_instructions
+    - path: "src/hiero_sdk_python/transaction/**/*.py"
+      instructions: *transaction_review_instructions
     - path: "src/hiero_sdk_python/schedule/**/*.py"
       instructions: *schedule_review_instructions
 

CHANGELOG.md

@@ -8,6 +8,7 @@ This changelog is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.
 
 ### Added
 
+- Added CodeRabbit review instructions for the transaction module in `.coderabbit.yaml` (#1696)
 - Added CodeRabbit review instructions and path mapping for the schedule module (`src/hiero_sdk_python/schedule/`) in `.coderabbit.yaml` (#1698)
 
 ### Src