diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index ace4f94..15ee3f4 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -71,6 +71,7 @@ For guidance on writing deterministic quote tests, see [docs/deterministic-quote
 ## Documentation for contributors
 
 - **[CI Contract Checks](./docs/ci-contract-checks.md)**: Understanding the CI pipeline, running checks locally, and troubleshooting failures
+- **[Contract Function Contribution Guide](./docs/contract-function-contribution-guide.md)**: How new contract entrypoints should be placed, authorized, and emitted in the repo's existing patterns
 - **[Storage Key Invariants](./docs/storage-key-invariants.md)**: Storage model, key structure, and invariants that must be maintained across all operations
 - **[Minimum Viable Test Structure](./docs/minimum-viable-test-structure.md)**: Required test categories and example structures for new contract entrypoints
 - **[Deterministic Quote Tests](./docs/deterministic-quote-tests.md)**: Guide for writing tests for quote operations with the fixed price model
diff --git a/creator-keys/src/test.rs b/creator-keys/src/test.rs
index 2f6a77c..d39af64 100644
--- a/creator-keys/src/test.rs
+++ b/creator-keys/src/test.rs
@@ -509,6 +509,136 @@ fn test_update_creator_fee_recipient_unauthorized_reverts() {
     assert!(result.is_err());
 }
 
+#[test]
+fn test_update_creator_fee_recipient_reverts_when_current_recipient_is_not_authorized() {
+    let env = Env::default();
+    let contract_id = env.register(CreatorKeysContract, ());
+    let client = CreatorKeysContractClient::new(&env, &contract_id);
+    let creator = Address::generate(&env);
+    let current_recipient = Address::generate(&env);
+    let new_recipient = Address::generate(&env);
+    let handle = String::from_str(&env, "alice");
+
+    let profile = CreatorProfile {
+        creator: creator.clone(),
+        handle: handle.clone(),
+        supply: 0,
+        holder_count: 0,
+        fee_recipient: current_recipient.clone(),
+        registered_at: 0,
+    };
+
+    env.as_contract(&contract_id, || {
+        env.storage()
+            .persistent()
+            .set(&constants::storage::creator(&creator), &profile);
+    });
+
+    let result = client.try_update_creator_fee_recipient(&creator, &new_recipient);
+    assert!(result.is_err());
+}
+
+#[test]
+fn test_sell_key_accepts_exact_min_proceeds_boundary() {
+    let env = Env::default();
+    env.mock_all_auths();
+    let contract_id = env.register(CreatorKeysContract, ());
+    let client = CreatorKeysContractClient::new(&env, &contract_id);
+
+    let admin = Address::generate(&env);
+    let creator = Address::generate(&env);
+    let seller = Address::generate(&env);
+    let handle = String::from_str(&env, "alice");
+
+    client.set_key_price(&admin, &100);
+    client.set_fee_config(&admin, &9000, &1000);
+    client.register_creator(&creator, &handle, &None, &None, &None);
+
+    client.buy_key(&creator, &seller, &100, &None);
+    client.buy_key(&creator, &seller, &100, &None);
+
+    let quote = client.get_sell_quote(&creator, &seller).unwrap();
+    let exact_result = client.try_sell_key(&creator, &seller, &Some(quote.total_amount));
+    assert_eq!(exact_result, Ok(Ok(1)));
+
+    let second_quote = client.get_sell_quote(&creator, &seller).unwrap();
+    let slippage_result = client.try_sell_key(&creator, &seller, &Some(second_quote.total_amount + 1));
+    assert_eq!(slippage_result, Err(Ok(ContractError::SlippageExceeded)));
+}
+
+#[test]
+fn test_sell_extends_creator_ttl_after_successful_sell() {
+    let env = Env::default();
+    env.mock_all_auths();
+    let contract_id = env.register(CreatorKeysContract, ());
+    let client = CreatorKeysContractClient::new(&env, &contract_id);
+
+    let admin = Address::generate(&env);
+    let creator = Address::generate(&env);
+    let seller = Address::generate(&env);
+    let handle = String::from_str(&env, "alice");
+
+    client.set_key_price(&admin, &100);
+    client.set_fee_config(&admin, &9000, &1000);
+    client.register_creator(&creator, &handle, &None, &None, &None);
+    client.buy_key(&creator, &seller, &100, &None);
+
+    let creator_key = constants::storage::creator(&creator);
+    let initial_profile: CreatorProfile = env.as_contract(&contract_id, || {
+        env.storage().persistent().get(&creator_key).unwrap()
+    });
+    assert_eq!(initial_profile.supply, 1);
+
+    let mut ledger_info = env.ledger().get();
+    ledger_info.sequence_number = 100;
+    env.ledger().set(ledger_info);
+
+    let result = client.try_sell_key(&creator, &seller, &Some(1));
+    assert_eq!(result, Ok(Ok(0)));
+
+    let mut ledger_info = env.ledger().get();
+    ledger_info.sequence_number = CREATOR_TTL_LEDGERS + 1;
+    env.ledger().set(ledger_info);
+
+    let has_profile = env.as_contract(&contract_id, || {
+        env.storage().persistent().has(&creator_key)
+    });
+    assert!(has_profile);
+}
+
+#[test]
+fn test_failed_sell_does_not_extend_creator_ttl() {
+    let env = Env::default();
+    env.mock_all_auths();
+    let contract_id = env.register(CreatorKeysContract, ());
+    let client = CreatorKeysContractClient::new(&env, &contract_id);
+
+    let admin = Address::generate(&env);
+    let creator = Address::generate(&env);
+    let seller = Address::generate(&env);
+    let handle = String::from_str(&env, "alice");
+
+    client.set_key_price(&admin, &100);
+    client.register_creator(&creator, &handle, &None, &None, &None);
+
+    let creator_key = constants::storage::creator(&creator);
+    let mut ledger_info = env.ledger().get();
+    ledger_info.sequence_number = 100;
+    env.ledger().set(ledger_info);
+
+    let result = client.try_sell_key(&creator, &seller, &Some(1));
+    assert_eq!(result, Err(Ok(ContractError::InsufficientBalance)));
+
+    let mut ledger_info = env.ledger().get();
+    ledger_info.sequence_number = CREATOR_TTL_LEDGERS + 1;
+    env.ledger().set(ledger_info);
+
+    let has_profile = env.as_contract(&contract_id, || {
+        env.storage().persistent().has(&creator_key)
+    });
+    assert!(!has_profile);
+}
+
 // --- TTL extension tests (#396) ---
 
 #[test]
diff --git a/docs/contract-function-contribution-guide.md b/docs/contract-function-contribution-guide.md
new file mode 100644
index 0000000..7e18e0f
--- /dev/null
+++ b/docs/contract-function-contribution-guide.md
@@ -0,0 +1,56 @@
+# Contract function contribution guide
+
+This guide captures the conventions used by the `creator-keys` contract so contributors can add a new entrypoint without fighting the existing layout or CI expectations.
+
+## 1. Place the function in the right module
+
+Keep new public entrypoints in the main contract implementation in [creator-keys/src/lib.rs](../creator-keys/src/lib.rs) and group them by responsibility:
+
+- Trade entrypoints such as `buy_key` and `sell_key` belong with the trading flow near the other market operations.
+- Config entrypoints such as fee or price updates belong with the configuration helpers in the same contract implementation.
+- Read-only view methods belong near the other quote and profile read methods.
+- Admin-only mutators should stay near the other admin-facing entrypoints so the access model is easy to audit.
+
+## 2. Follow the authorization pattern
+
+Use the same auth pattern as the surrounding entrypoints:
+
+- `admin.require_auth()` for protocol-admin-only entrypoints.
+- `creator.require_auth()` for creator-owned actions.
+- `buyer.require_auth()` or `seller.require_auth()` for trade actions that are authorized by the user acting on the market.
+- Read-only methods should not call `require_auth()`.
+
+When a function needs to validate the currently authorized address, prefer the same address that the existing entrypoint uses for the relevant role rather than introducing a new authorization model.
+
+## 3. Emit events the same way
+
+New state-changing entrypoints should publish events via `env.events().publish(...)` using the centralized names and helpers in [creator-keys/src/events.rs](../creator-keys/src/events.rs).
+
+For a new event:
+
+1. Add a new event struct to [creator-keys/src/events.rs](../creator-keys/src/events.rs).
+2. Define a stable event name constant and any topic helpers there.
+3. Publish the event from the contract entrypoint after the state change is persisted.
+4. Keep field ordering stable so downstream indexers and tests remain deterministic.
+
+## 4. Add the right tests
+
+Every new contract function should include tests for:
+
+- a happy path,
+- the main error case,
+- any relevant state change or regression case.
+
+The repo's minimum test structure lives in [docs/minimum-viable-test-structure.md](./minimum-viable-test-structure.md).
+
+## 5. Run the required CI checks before opening a PR
+
+The repository CI workflow in [.github/workflows/ci.yml](../.github/workflows/ci.yml) expects:
+
+```bash
+cargo fmt --all -- --check
+cargo clippy --workspace --all-targets -- -D warnings
+cargo test --workspace
+```
+
+Run the same checks locally before pushing so the maintainer sees a passing PR.