diff --git a/docs/docs/00200-core-concepts/00100-databases/00500-cheat-sheet.md b/docs/docs/00200-core-concepts/00100-databases/00500-cheat-sheet.md
index 4a52f82ac51..91fe874d848 100644
--- a/docs/docs/00200-core-concepts/00100-databases/00500-cheat-sheet.md
+++ b/docs/docs/00200-core-concepts/00100-databases/00500-cheat-sheet.md
@@ -753,6 +753,7 @@ ctx.sender              // Identity of caller
 ctx.connectionId        // ConnectionId | undefined
 ctx.timestamp           // Timestamp
 ctx.identity            // Module's identity
+ctx.random              // Deterministic random generator
 ```
 
 </TabItem>
@@ -764,7 +765,7 @@ ctx.Sender              // Identity of caller
 ctx.ConnectionId        // ConnectionId?
 ctx.Timestamp           // Timestamp
 ctx.Identity            // Module's identity
-ctx.Rng                 // Random number generator
+ctx.Rng                 // Deterministic random generator
 ```
 
 </TabItem>
@@ -776,7 +777,7 @@ ctx.sender()            // Identity of caller
 ctx.connection_id()     // Option<ConnectionId>
 ctx.timestamp           // Timestamp
 ctx.identity()          // Module's identity
-ctx.rng()               // Random number generator
+ctx.rng()               // Deterministic random generator
 ```
 
 </TabItem>
@@ -788,7 +789,7 @@ ctx.sender()            // Identity of caller (Identity type)
 ctx.connection_id       // std::optional<ConnectionId>
 ctx.timestamp           // Timestamp of current transaction (Timestamp type)
 ctx.identity()          // Module's own identity (Identity type)
-ctx.rng()               // Random number generator (for seeded randomness)
+ctx.rng()               // Deterministic random generator
 ```
 
 </TabItem>
diff --git a/skills/concepts/SKILL.md b/skills/concepts/SKILL.md
index 402a1a8ff18..1b73ae2d3e3 100644
--- a/skills/concepts/SKILL.md
+++ b/skills/concepts/SKILL.md
@@ -20,7 +20,7 @@ SpacetimeDB is a relational database that is also a server. It lets you upload a
 ## Critical Rules
 
 1. **Reducers are transactional.** They do not return data to callers. Use subscriptions to read data.
-2. **Reducers must be deterministic.** No filesystem, network, timers, or random. All state must come from tables.
+2. **Reducers must be deterministic.** No filesystem, network, timers, wall-clock time, or ambient randomness. Use `ReducerContext` APIs such as `ctx.timestamp` / `ctx.Timestamp` and the language-specific deterministic RNG instead.
 3. **Read data via tables/subscriptions**, not reducer return values. Clients get data through subscribed queries.
 4. **Auto-increment IDs are not sequential.** Gaps are normal, do not use for ordering. Use timestamps or explicit sequence columns.
 5. **`ctx.sender` is the authenticated principal.** Never trust identity passed as arguments.