chore(changelog): land entries as per-change fragments in changelog.d/

.github/PULL_REQUEST_TEMPLATE.md

@@ -22,8 +22,9 @@
 
 ---
 
-- [ ] `CHANGELOG.md` updated under `## Unreleased` — or this change is
-      internal-only / test-only / docs-only (apply the `no-changelog` label).
+- [ ] Changelog fragment added — `changelog.d/<slug>.<breaking|added|changed|fixed>.md`
+      (see `changelog.d/README.md`) — or this change is internal-only /
+      test-only / docs-only (apply the `no-changelog` label).
 
 <!-- AI-assisted contributions are welcome and normal here — see
      CONTRIBUTING.md for the attribution convention (footer + Co-Authored-By). -->

.github/workflows/changelog.yml

@@ -18,15 +18,20 @@ jobs:
         with:
           fetch-depth: 0
 
-      - name: Require CHANGELOG.md update when src/ changes
+      - name: Require changelog fragment when src/ changes
         run: |
           base="${{ github.event.pull_request.base.sha }}"
           head="${{ github.event.pull_request.head.sha }}"
           changed=$(git diff --name-only "$base...$head")
+          # Fragments must be *added* — a deleted or renamed fragment also
+          # appears in --name-only and must not satisfy the check.
+          added=$(git diff --name-only --diff-filter=A "$base...$head")
           echo "Changed files:"
           echo "$changed"
-          if echo "$changed" | grep -q '^src/' && ! echo "$changed" | grep -qx 'CHANGELOG.md'; then
-            echo "::error::This PR touches src/ but not CHANGELOG.md. Add an entry under 'Unreleased' (see CONTRIBUTING.md), or apply the 'no-changelog' label if the change is internal-only."
+          if echo "$changed" | grep -q '^src/' \
+             && ! echo "$added" | grep -Eq '^changelog\.d/[^/]+\.(breaking|added|changed|fixed)\.md$' \
+             && ! echo "$changed" | grep -qx 'CHANGELOG.md'; then
+            echo "::error::This PR touches src/ but carries no changelog entry. Add a fragment changelog.d/<slug>.<breaking|added|changed|fixed>.md (see CONTRIBUTING.md), or apply the 'no-changelog' label if the change is internal-only."
             exit 1
           fi
           echo "OK"

.github/workflows/ci.yml

@@ -11,16 +11,19 @@ permissions:
 
 jobs:
   build-and-test:
-    name: Build & Test (${{ matrix.os }})
+    name: Build & Test (${{ matrix.os }}, node ${{ matrix.node }})
     runs-on: ${{ matrix.os }}
     strategy:
       fail-fast: false
       # Both platforms: a package-lock.json regenerated over an existing
       # node_modules tree records only that machine's native binaries, so a
       # lock made on macOS breaks Linux installs and vice versa. Each runner
       # catches the lock the other's platform produced. Tests run on ubuntu.
+      # Node: the engines floor and current LTS — stdio flushing semantics
+      # around process exit differ between versions and platforms.
       matrix:
         os: [ubuntu-latest, macos-latest]
+        node: [20, 24]
 
     steps:
       - uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4.4.0
@@ -30,7 +33,7 @@ jobs:
       - name: Setup Node.js
         uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4.4.0
         with:
-          node-version: 20
+          node-version: ${{ matrix.node }}
 
       # npm ci installs the lock verbatim: npm >= 11 'npm install' silently
       # re-resolves platform packages missing from the lock, so only npm ci
@@ -44,6 +47,7 @@ jobs:
       - name: Build
         run: npm run build
 
+      # Tests run on both platforms: process/stdio behaviour differs (pipes
+      # are asynchronous on macOS), and ubuntu-only runs have missed that.
       - name: Test
-        if: matrix.os == 'ubuntu-latest'
         run: npm test

CHANGELOG.md

@@ -2,7 +2,9 @@
 
 Notable changes to `@animalabs/context-manager`, loosely following
 [Keep a Changelog](https://keepachangelog.com/). Entries land with the change
-that causes them — see [CONTRIBUTING.md](CONTRIBUTING.md#changelog).
+that causes them, as fragment files in [`changelog.d/`](changelog.d/) that are
+folded into a version section at release time — see
+[CONTRIBUTING.md](CONTRIBUTING.md#changelog).
 
 Releases up to and including 0.6.2 predate this file; for their contents see
 `git log` and the

CONTRIBUTING.md

@@ -50,7 +50,7 @@ plus, when applicable, **Not verified**, **Out of scope**, and
   not mere presence — a test that can't fail on the unfixed code will be
   called out, and a compression test whose fixture is too small to trigger
   the path it claims to cover is the local specialty of that failure.
-- **Changelog entry** under `## Unreleased` for anything behavior-affecting
+- **Changelog fragment** in `changelog.d/` for anything behavior-affecting
   (see below).
 
 Conventional-commit-style titles (`feat(strategy): …`, `fix(compression): …`)
@@ -88,39 +88,63 @@ that don't fail on unfixed code, or with claims the branch itself disproves.
 
 ## Changelog
 
-`CHANGELOG.md` keeps a standing `## Unreleased` section with
-`### Breaking` / `### Added` / `### Changed` / `### Fixed` subsections
-(loosely [Keep a Changelog](https://keepachangelog.com/)).
-
-- **The entry lands with the change** — same commit, or at least the same
+Changelog entries land as **fragment files** in
+[`changelog.d/`](changelog.d/) — one file per change — and are folded into
+`CHANGELOG.md` (loosely [Keep a Changelog](https://keepachangelog.com/)) at
+release time. One file per change is what keeps concurrent work from
+conflicting: when every PR edited the same `## Unreleased` section, any PR
+that outlived another merge hit a conflict in `CHANGELOG.md`; distinct files
+never do.
+
+- **Format:** `changelog.d/<slug>.<breaking|added|changed|fixed>.md`, a flat
+  file directly in `changelog.d/`, containing one or more markdown bullets
+  (`- …`) written exactly as they should appear in `CHANGELOG.md`:
+  continuation lines indent two spaces, nested bullets are fine, headings
+  and horizontal rules are refused (even indented — a heading inside a
+  fragment would corrupt the section structure). The slug just has to be
+  unique among pending fragments and filesystem-safe — the PR number works,
+  and so does the branch name with `/` replaced by `-`
+  (`54-view-composition.added.md`, `fix-retry-backoff.fixed.md`). The release
+  script scans the directory fail-closed: a subdirectory, an unrecognized
+  category suffix, or any other stray file aborts the release rather than
+  silently stranding an entry.
+
+- **The fragment lands with the change** — same commit, or at least the same
   PR. This binds direct pushes to `main` just as much as PRs. On PRs, CI
-  enforces it softly: touching `src/` without touching `CHANGELOG.md` fails
-  the `changelog` check unless the `no-changelog` label is applied.
+  enforces it softly: touching `src/` without adding a fragment (or editing
+  `CHANGELOG.md`) fails the `changelog` check unless the `no-changelog`
+  label is applied.
 - **What needs an entry:** anything a host or strategy author would notice —
   strategy behavior and option types, compression triggers and thresholds,
   token budgeting and holdback, pinning, cache-breakpoint placement, what a
   compile emits, public exports, defaults. Internal refactors, test-only,
   and docs-only changes don't.
-- **Breaking entries are audience-scoped.** Name the audience in the heading
-  (`### Breaking (host operators only)`) and cover: **who needs to act**,
+- **Breaking entries are audience-scoped.** Open the bullet by naming who
+  needs to act (`- **Host operators:** …`) and cover: **who needs to act**,
   **migration**, and **unchanged** (what readers might fear broke but
   didn't). Config that becomes *required* is the sharpest case here — an
   option that starts throwing when unset breaks every recipe that omitted
   it, and that is exactly what the "who needs to act" line is for.
-- **Keep one `## Unreleased` heading.** Add entries under the existing one;
-  don't open a second. Only the first is cut at release time, so entries
-  filed under a later heading are silently never released — the release
-  script refuses to run if it finds more than one.
+- **Editing `## Unreleased` in `CHANGELOG.md` directly still works** and is
+  merged with the fragments at release time — it remains the right place to
+  restructure pending entries, and the escape hatch for anything the
+  fragment format can't express (e.g. an audience-qualified
+  `### Breaking (host operators only)` heading, which `breaking` fragments
+  will then join). Keep one `## Unreleased` heading — the release script
+  refuses more than one, since only the first is ever cut.
 - **Releases** (maintainers): `npm version <patch|minor|major>` does the
-  whole cut — the `version` hook retitles `Unreleased` to
-  `## X.Y.Z — YYYY-MM-DD` (keeping a fresh `Unreleased` above it, and
-  refusing to release when there are no entries), then npm commits and tags.
-  `git push --follow-tags` triggers CI, which refuses a tag with no matching
-  changelog section, publishes `@animalabs/context-manager` to npm, and
-  creates the GitHub release with that section as its notes. The two release
-  jobs are independent: some consumers run github-clone checkouts, so
-  release notes must exist even when npm publish fails. Version bumps are a
-  maintainer release-time action, not part of feature PRs.
+  whole cut — the `version` hook folds the pending fragments plus any
+  entries filed directly under `Unreleased` into `## X.Y.Z — YYYY-MM-DD`
+  (subsections emitted in `### Breaking` / `### Added` / `### Changed` /
+  `### Fixed` order), deletes the consumed fragments, keeps a fresh empty
+  `Unreleased` above, and refuses to release when there is nothing to
+  release; npm then commits and tags. `git push --follow-tags` triggers CI,
+  which refuses a tag with no matching changelog section, publishes
+  `@animalabs/context-manager` to npm, and creates the GitHub release with
+  that section as its notes. The two release jobs are independent: some
+  consumers run github-clone checkouts, so release notes must exist even
+  when npm publish fails. Version bumps are a maintainer release-time
+  action, not part of feature PRs.
 
 ## Building and testing
 

changelog.d/README.md

@@ -0,0 +1,28 @@
+# Pending changelog fragments
+
+One file per change, so concurrent branches never conflict the way shared
+`CHANGELOG.md` edits do. At release time `npm version` folds every fragment
+here into the new version section of `CHANGELOG.md` and deletes it.
+
+**Name:** `<slug>.<breaking|added|changed|fixed>.md`, as a flat file directly
+in this directory. The slug just has to be unique among pending fragments and
+filesystem-safe: the PR number works, and so does the branch name with `/`
+replaced by `-` (`54-view-composition.added.md`, `fix-retry-backoff.fixed.md`). The
+release script refuses subdirectories and any other stray file here, so a
+misplaced entry fails the release loudly instead of being left out.
+
+**Content:** one or more markdown bullets, exactly as they should appear in
+`CHANGELOG.md`. Continuation lines indent two spaces (nested bullets are
+fine); headings and horizontal rules are refused even when indented, since a
+heading inside a fragment would corrupt the section structure:
+
+
+```markdown
+- `viewFilter` composes a strategy's view of the message store without
+  forking the chunker (#54). Continuation lines indent two spaces.
+```
+
+Breaking fragments open by naming who needs to act:
+`- **Host operators:** …`.
+
+See [CONTRIBUTING.md](../CONTRIBUTING.md#changelog) for what needs an entry.

changelog.d/changelog-fragments.changed.md

@@ -0,0 +1,5 @@
+- Changelog entries now land as per-change fragment files in `changelog.d/`
+  (`<slug>.<breaking|added|changed|fixed>.md`), folded into the version
+  section at release time — concurrent PRs no longer conflict in
+  `CHANGELOG.md`. Editing `## Unreleased` directly still works and is merged
+  at the same point.

package.json

@@ -23,7 +23,7 @@
     "typecheck": "tsc --noEmit",
     "pretest": "npm run build",
     "test": "node --test dist/test/*.test.js dist/test/adaptive/*.test.js",
-    "version": "node scripts/release-changelog.mjs && git add CHANGELOG.md",
+    "version": "node scripts/release-changelog.mjs && git add CHANGELOG.md changelog.d",
     "prepublishOnly": "npm run build"
   },
   "keywords": [