It's not an issue with the numbers, but with the casing. Execute the following:

gradle uni

Also with the following build file without any numbers the task unique is unambigously chosen:

task unique()
task uniqueA()

But when instead lowercasing the "A", the ambiguity is properly detected:

task unique1()
task uniquea()

Tested with master (2.11).

I am not sure what the expected behavior of the task name matching is. The User Guide is not very specific regarding this point (cf. 4.4. Task name abbreviation).

But "NameMatcherTest" defines a couple of valuable test cases of which "prefersFullCamelCaseMatchOverCamelCasePrefix" seems to perfectly reflect this issue:

    @Test
    public void prefersFullCamelCaseMatchOverCamelCasePrefix() {
        assertMatches("sN", "someName", "someNameWithExtra");
        assertMatches("name", "names", "nameWithExtra");  // reads like "gradlew name" only matches "names" of the tasks ["names", "nameWithExtra"]
        assertMatches("s_n", "some_name", "some_name_with_extra");
    }

Thus to me it looks like the behavior might be somewhat confusing, but at least seems to be in line with the specification.

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Problem as in description still exists with Gradle 3.2.

Moved to https://github.com/gradle/gradle/issues/1185