Add /v3/contracts/fast-call-read endpoint for (authorized) read only calls without cost tracking

docs/rpc/openapi.yaml

@@ -948,3 +948,72 @@ paths:
                 $ref: ./api/core-node/get-health-error.schema.json
               example:
                 $ref: ./api/core-node/get-health-error.example.json
+
+  /v3/contracts/fast-call-read/{contract_address}/{contract_name}/{function_name}:
+    post:
+      summary: Call read-only function in fast mode (no cost and memory tracking)
+      tags:
+        - Smart Contracts
+      operationId: fast_call_read_only_function
+      description: |
+        Call a read-only public function on a given smart contract without cost tracking.
+
+        **This API endpoint requires a basic Authorization header.**
+
+        The smart contract and function are specified using the URL path. The arguments and the simulated tx-sender are supplied via the POST body in the following JSON format:
+      responses:
+        "200":
+          description: Success
+          content:
+            application/json:
+              schema:
+                $ref: ./api/contract/post-call-read-only-fn.schema.json
+              examples:
+                success:
+                  $ref: ./api/contract/post-call-read-only-fn-success.example.json
+                fail:
+                  $ref: ./api/contract/post-call-read-only-fn-fail.example.json
+        "400":
+          description: Endpoint not enabled.
+        "401":
+          description: Unauthorized.
+        "408":
+          description: ExecutionTime expired.
+      parameters:
+        - name: contract_address
+          in: path
+          required: true
+          description: Stacks address
+          schema:
+            type: string
+        - name: contract_name
+          in: path
+          required: true
+          description: Contract name
+          schema:
+            type: string
+        - name: function_name
+          in: path
+          required: true
+          description: Function name
+          schema:
+            type: string
+        - name: tip
+          in: query
+          schema:
+            type: string
+          description: The Stacks chain tip to query from. If tip == latest, the query will be run from the latest
+            known tip (includes unconfirmed state).
+          required: false
+      requestBody:
+        description: map of arguments and the simulated tx-sender where sender is either a Contract identifier or a normal Stacks address, and arguments is an array of hex serialized Clarity values.
+        required: true
+        content:
+          application/json:
+            schema:
+              $ref: './entities/contracts/read-only-function-args.schema.json'
+              example:
+                sender: 'SP31DA6FTSJX2WGTZ69SFY11BH51NZMB0ZW97B5P0.get-info'
+                arguments:
+                  - '0x0011...'
+                  - '0x00231...'

stackslib/src/config/mod.rs

@@ -3719,6 +3719,13 @@ pub struct ConnectionOptionsFile {
     /// @default: [`DEFAULT_BLOCK_PROPOSAL_MAX_AGE_SECS`]
     /// @units: seconds
     pub block_proposal_max_age_secs: Option<u64>,
+
+    /// Maximum time (in seconds) that a readonly call in free cost tracking mode
+    /// can run before being interrupted
+    /// ---
+    /// @default: 30
+    /// @units: seconds
+    pub read_only_max_execution_time_secs: Option<u64>,
 }
 
 impl ConnectionOptionsFile {
@@ -3870,6 +3877,9 @@ impl ConnectionOptionsFile {
             block_proposal_max_age_secs: self
                 .block_proposal_max_age_secs
                 .unwrap_or(DEFAULT_BLOCK_PROPOSAL_MAX_AGE_SECS),
+            read_only_max_execution_time_secs: self
+                .read_only_max_execution_time_secs
+                .unwrap_or(default.read_only_max_execution_time_secs),
             ..default
         })
     }

stackslib/src/net/api/callreadonly.rs

@@ -59,7 +59,7 @@ pub struct CallReadOnlyResponse {
 
 #[derive(Clone)]
 pub struct RPCCallReadOnlyRequestHandler {
-    maximum_call_argument_size: u32,
+    pub maximum_call_argument_size: u32,
     read_only_call_limit: ExecutionCost,
 
     /// Runtime fields