Release Codename Sequencing Specification

The codename of a CWIST LTS release is a state identifier. It carries no semantic meaning and no tier (major, minor, and so on); it follows only the alphabet's tail-in sequential propagation rule.

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1. Principles

• A codename consists of uppercase ASCII letters.
• A new letter always enters at the rightmost (tail) position.
• Each following release pushes the new letter one position to the left. Once every position holds that letter, the sequence moves on to the next letter.
• No position carries a functional meaning or a version weight.

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2. Two-letter sequence (default)

$$\text{AA} \rightarrow \text{AB} \rightarrow \text{BA} \rightarrow \text{BB} \rightarrow \text{BC} \rightarrow \text{CB} \rightarrow \text{CC} \rightarrow \text{CD} \rightarrow \dots$$

1. AA
2. AB (B enters at the tail)
3. BA (B propagates left)
4. BB (B complete)
5. BC (C enters at the tail)
6. CB (C propagates left)
7. CC (C complete)

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3. Three-letter extension

Codenames extend to three letters only when the two-letter sequence is exhausted. A three-letter codename expands the same way as the two-letter one: the new letter always enters at the tail (rightmost position) and propagates one position to the left per release until every position holds it; then the next letter enters at the tail.

$$\text{AAA} \rightarrow \text{AAB} \rightarrow \text{ABB} \rightarrow \text{BBB} \rightarrow \text{BBC} \rightarrow \text{BCC} \rightarrow \text{CCC} \rightarrow \dots$$

1. AAA
2. AAB (B enters at the tail)
3. ABB (B propagates left)
4. BBB (B complete)
5. BBC (C enters at the tail)
6. BCC (C propagates left)
7. CCC (C complete)

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4. Notation

The codename is shown next to the release identifier in build binaries and CLI output:

$ cwist --version
cwist 4.0.0-LTS (AA)

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5. API stability gate (from the v4 LTS)

Independently of the codename, from v4 on the existing public API does not change (ROADMAP.md "API stability from v4.0"). CI checks this with scripts/ci/check_api_baseline.py.

• docs/api/v4.0-api-baseline.txt records the public headers: names, function signatures (parameter names dropped) and struct/union/enum layouts.
• CI fails when the headers no longer match that file. For an intended change, regenerate it with make api-baseline and commit it in the same PR.
• Once the LTS tag v4 exists, CI also fails when a guaranteed entry from that tag's baseline is removed or changed, even with the baseline regenerated. New API passes; the experimental (WebTransport) sections are not checked.

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6. First ascent of a major version

When a major version line opens for the first time (the major number increments), the releases of that line are named sequentially from v1: v1 → v2 → v3 → v4 → …. The counter always starts at 1 and never skips.

This rule applies to every fresh major line independently: the first ascent of the next major starts again at v1, regardless of how far the previous line counted. Do not carry the previous line's counter over, and do not jump ahead (for example to a .0 style name) because an editor or autocomplete suggested it.