diff --git a/build.gradle b/build.gradle
index aa6e737..ab2278b 100644
--- a/build.gradle
+++ b/build.gradle
@@ -25,7 +25,7 @@ version = findProperty('cliVersion') ?: '0.1.0-SNAPSHOT'
 // branch instead (1.0.0-SNAPSHOT), which relix-core publishes to Central's snapshot
 // repository on every push. A release pins a released engine (checkEnginePin).
 // -PrelixEngineVersion=<v> overrides it for one build, to try a candidate engine.
-ext.relixEngineVersion = (findProperty('relixEngineVersion') ?: '1.0.0-rc11') as String
+ext.relixEngineVersion = (findProperty('relixEngineVersion') ?: '1.0.0-rc12') as String
 
 def engineIsSnapshot = relixEngineVersion.endsWith('-SNAPSHOT')
 
diff --git a/docs/command-examples/check.md b/docs/command-examples/check.md
index a38dafa..90066b0 100644
--- a/docs/command-examples/check.md
+++ b/docs/command-examples/check.md
@@ -12,7 +12,7 @@ A problem is printed on standard error, and the status is 3:
 relix check scripts/broken.relix 2>&1; echo "exit $?"
 ```
 ```
-scripts/broken.relix:1:30: error: Undefined relation: 'Ordrs'
+scripts/broken.relix:1:30: error: Undefined relation: 'Ordrs' — did you mean 'Orders'?
 exit 3
 ```
 
@@ -23,7 +23,7 @@ read:
 relix check --json scripts/broken.relix; echo "exit $?"
 ```
 ```
-{"diagnostics":[{"file":"scripts/broken.relix","line":1,"column":30,"severity":"error","message":"Undefined relation: 'Ordrs'"}]}
+{"diagnostics":[{"file":"scripts/broken.relix","line":1,"column":30,"severity":"error","message":"Undefined relation: 'Ordrs' — did you mean 'Orders'?"}]}
 exit 3
 ```
 
diff --git a/docs/command-examples/doc.md b/docs/command-examples/doc.md
index adc6a9b..319cfa7 100644
--- a/docs/command-examples/doc.md
+++ b/docs/command-examples/doc.md
@@ -16,12 +16,13 @@ SELECT <condition> (Relation)
 With no topic, `relix doc` lists the pages, as rows:
 
 ```shell
-relix doc -o tsv | head -4
+relix doc -o tsv | head -5
 ```
 ```
 topic	category	title	summary
 getting-started	guide	Getting started	Your first script — declare data, name a result, run it
 glossary	guide	Glossary	The vocabulary — relation, tuple, bag vs set, materialisation, pushdown
+operators-by-task	guide	Operators by task	The operator for each task SQL has no operator for, named in a question's words
 σ	operator	Selection	Filter rows by a condition
 ```
 
diff --git a/docs/guide/command-line/catalog.md b/docs/guide/command-line/catalog.md
index 84ae32a..868bafd 100644
--- a/docs/guide/command-line/catalog.md
+++ b/docs/guide/command-line/catalog.md
@@ -98,7 +98,7 @@ relix -e 'Customers' 2>&1; echo "exit $?"
 ```
 ```
 relix: warning: skipping ~/shop/.relix, which is not trusted; to load it: relix catalog trust ~/shop
--e:1:1: error: Undefined relation: 'Customers'
+-e:1:1: error: Undefined relation: 'Customers' (defined: Regions)
 relix: Customers is declared in ~/shop/.relix/catalog/00-sources.relix, which is not trusted; to load it: relix catalog trust ~/shop
 exit 5
 ```
diff --git a/docs/guide/command-line/commands/check.md b/docs/guide/command-line/commands/check.md
index 253c6ca..9d99481 100644
--- a/docs/guide/command-line/commands/check.md
+++ b/docs/guide/command-line/commands/check.md
@@ -52,7 +52,7 @@ A problem is printed on standard error, and the status is 3:
 relix check scripts/broken.relix 2>&1; echo "exit $?"
 ```
 ```
-scripts/broken.relix:1:30: error: Undefined relation: 'Ordrs'
+scripts/broken.relix:1:30: error: Undefined relation: 'Ordrs' — did you mean 'Orders'?
 exit 3
 ```
 
@@ -63,7 +63,7 @@ read:
 relix check --json scripts/broken.relix; echo "exit $?"
 ```
 ```
-{"diagnostics":[{"file":"scripts/broken.relix","line":1,"column":30,"severity":"error","message":"Undefined relation: 'Ordrs'"}]}
+{"diagnostics":[{"file":"scripts/broken.relix","line":1,"column":30,"severity":"error","message":"Undefined relation: 'Ordrs' — did you mean 'Orders'?"}]}
 exit 3
 ```
 
diff --git a/docs/guide/command-line/commands/doc.md b/docs/guide/command-line/commands/doc.md
index 5108066..e08bb14 100644
--- a/docs/guide/command-line/commands/doc.md
+++ b/docs/guide/command-line/commands/doc.md
@@ -53,12 +53,13 @@ SELECT <condition> (Relation)
 With no topic, `relix doc` lists the pages, as rows:
 
 ```shell
-relix doc -o tsv | head -4
+relix doc -o tsv | head -5
 ```
 ```
 topic	category	title	summary
 getting-started	guide	Getting started	Your first script — declare data, name a result, run it
 glossary	guide	Glossary	The vocabulary — relation, tuple, bag vs set, materialisation, pushdown
+operators-by-task	guide	Operators by task	The operator for each task SQL has no operator for, named in a question's words
 σ	operator	Selection	Filter rows by a condition
 ```
 
diff --git a/docs/guide/command-line/getting-started.md b/docs/guide/command-line/getting-started.md
index ec838b0..2f12143 100644
--- a/docs/guide/command-line/getting-started.md
+++ b/docs/guide/command-line/getting-started.md
@@ -204,7 +204,7 @@ message`, the shape compilers use, so an editor or a CI annotator can jump to it
 relix check scripts/broken.relix 2>&1; echo "exit $?"
 ```
 ```
-scripts/broken.relix:1:30: error: Undefined relation: 'Ordrs'
+scripts/broken.relix:1:30: error: Undefined relation: 'Ordrs' — did you mean 'Orders'?
 exit 3
 ```
 
diff --git a/docs/guide/command-line/output.md b/docs/guide/command-line/output.md
index 580ac4e..163a0e2 100644
--- a/docs/guide/command-line/output.md
+++ b/docs/guide/command-line/output.md
@@ -225,7 +225,7 @@ is not there, a database that refuses the connection — is one line beginning `
 relix -e 'SELECT amount > 100 (Ordrs)' 2>&1; echo "exit $?"
 ```
 ```
--e:1:22: error: Undefined relation: 'Ordrs'
+-e:1:22: error: Undefined relation: 'Ordrs' — did you mean 'Orders'?
 exit 3
 ```
 
diff --git a/docs/guide/command-line/pipelines.md b/docs/guide/command-line/pipelines.md
index 0b85f8d..646b4a8 100644
--- a/docs/guide/command-line/pipelines.md
+++ b/docs/guide/command-line/pipelines.md
@@ -139,7 +139,7 @@ script in a tree:
 find scripts -name '*.relix' | sort | xargs relix check 2>&1 || echo "a script has a problem"
 ```
 ```
-scripts/broken.relix:1:30: error: Undefined relation: 'Ordrs'
+scripts/broken.relix:1:30: error: Undefined relation: 'Ordrs' — did you mean 'Orders'?
 a script has a problem
 ```
 
diff --git a/src/test/java/com/darkcollective/relix/cli/command/ReportCommandsTest.java b/src/test/java/com/darkcollective/relix/cli/command/ReportCommandsTest.java
index e097d05..d10b1c1 100644
--- a/src/test/java/com/darkcollective/relix/cli/command/ReportCommandsTest.java
+++ b/src/test/java/com/darkcollective/relix/cli/command/ReportCommandsTest.java
@@ -168,7 +168,7 @@ void xargs() {
 
             assertThat(result.status()).isEqualTo(3);
             assertThat(result.out()).isEmpty();
-            assertThat(result.err()).isEqualTo("broken.relix:6:19: error: Undefined relation: 'Missing'\n");
+            assertThat(result.err()).isEqualTo("broken.relix:6:19: error: Undefined relation: 'Missing' (defined: N, Bad)\n");
         }
 
         @Test
@@ -180,7 +180,7 @@ void json() {
             assertThat(result.err()).isEmpty();
             assertThat(isJson(result.out())).as(result.out()).isTrue();
             assertThat(result.out()).isEqualTo("{\"diagnostics\":[{\"file\":\"broken.relix\",\"line\":6,"
-                    + "\"column\":19,\"severity\":\"error\",\"message\":\"Undefined relation: 'Missing'\"}]}\n");
+                    + "\"column\":19,\"severity\":\"error\",\"message\":\"Undefined relation: 'Missing' (defined: N, Bad)\"}]}\n");
         }
 
         @Test
@@ -396,7 +396,7 @@ void broken() {
             assertThat(result.status()).isEqualTo(3);
             assertThat(isJson(result.out())).as(result.out()).isTrue();
             assertThat(result.out()).contains("\"diagnostics\":[{\"severity\":\"error\","
-                    + "\"message\":\"Undefined relation: 'Missing'\",\"file\":\"broken.relix\",\"line\":6,\"column\":19}]");
+                    + "\"message\":\"Undefined relation: 'Missing' (defined: N, Bad)\",\"file\":\"broken.relix\",\"line\":6,\"column\":19}]");
         }
     }