📚 Normalize plan followup and sub-plan naming

Define derived plan naming for .agents/plans/.

Parent basename stays intact and derivatives append
--review-NN for review followups and --task-NN for
roadmap sub-plans, with no new date so ls groups them.
Document the rule in the planner skill, the in-place
vs new-file policy in make-a-plan, and examples in
the agents README.

AI-assisted-by: muse-spark-1.3-contributor

.agents/README.md

@@ -344,6 +344,25 @@ delegating when it helps), review it when the task is complex
 (`/review-plan`), implement it (`/implement-plan`), and mark progress
 on the roadmap as you land each piece.
 
+### Plan file naming (base + derivatives)
+
+Base plans live in `.agents/plans/` as `YYYY-MM-DD-<slug>.md`.
+Derived plans reuse the parent basename verbatim and append one
+suffix per level with `--`, with no new date — the parent prefix
+keeps everything adjacent in `ls`:
+
+- Review followup on implemented work:
+  `2026-09-14-paste-before-init-crash.md` →
+  `2026-09-14-paste-before-init-crash--review-01.md`
+- Roadmap sub-plan (task number from the roadmap):
+  `2026-09-20-upload-pipeline-roadmap.md` →
+  `2026-09-20-upload-pipeline-roadmap--task-01-chunk-upload.md`
+- Chained: `...--task-02-gc--review-01.md`
+
+While a plan is still unimplemented, `/make-a-plan` revises it in
+place. Once implemented and reviewed, it writes a new followup file.
+Full rules live in the `planner` skill.
+
 ## 7. Connecting `gh` CLI with a token
 
 The `create-issue` and `create-pr` flows need an authenticated `gh`

.agents/skills/make-a-plan/SKILL.md

@@ -16,8 +16,13 @@ stop — this skill needs the build agent to save the plan.
 - The user asks to plan, design, or break down a task, in any phrasing:
   "make a plan", "how would we build X", "design an approach for Y" —
   or runs `/make-a-plan`.
-- The user asks to rework or extend an existing plan (for example, after
-  review findings) — revise the saved plan file in place.
+- The user asks to rework or extend an existing plan. While the plan is
+  still unimplemented (pre-`implement-plan` iteration, e.g. after
+  `/review-plan` findings or user feedback), revise the saved plan file
+  in place. Once the plan has been implemented and reviewed (post
+  `/review-code` findings on committed work), write a new derived plan
+  file instead — never rewrite the executed plan. The `planner` skill
+   defines the derived naming (`--review-NN`, `--task-NN`).
 
 Do not use it to execute a plan — that is the `implement-plan` flow.
 
@@ -34,8 +39,11 @@ Do not use it to execute a plan — that is the `implement-plan` flow.
 3. Once all decisions are answered and the plan is final, save it verbatim to the
    announced path under `.agents/plans/` (create the directory if it does not
    exist). This step is the flow's explicit authorization to write the plan
-   file — the only write allowed here. If I later ask for changes, update the
-   saved file directly.
+   file — the only write allowed here. A fresh plan uses
+   `.agents/plans/YYYY-MM-DD-<slug>.md`; a derived plan uses the parent
+   basename plus the `planner` suffix (`--review-NN`, `--task-NN`) in its
+   own new file. If I later ask for changes to a still-unimplemented plan,
+   update the saved file directly.
 4. Present me with a clear, self-contained summary of the plan's most relevant points
    only after all required decisions have been answered. Write it for someone who knows
    only the project's high-level goal and may not know the plan's low-level context.

.agents/skills/planner/SKILL.md

@@ -153,6 +153,45 @@ Announce the save path `.agents/plans/YYYY-MM-DD-<slug>.md` (today's date,
 lowercase hyphen-separated slug, e.g. `2026-09-10-add-batch-get-profiles`;
 an explicit user path wins).
 
+### Derived plans
+
+Never invent a fresh slug when the plan derives from an existing one.
+The derived name is `<parent-basename>` plus one suffix per level,
+joined with `--` (double hyphen; single hyphens already separate
+slug words, so `--` marks where the derivation starts). The parent
+name is never edited, and no new date is added — the parent prefix
+already carries its date, which keeps parent and derivatives adjacent
+in `ls`. Record the real creation date inside the plan (`Created:`).
+
+Valid names match:
+
+```
+^\d{4}-\d{2}-\d{2}-[a-z0-9-]+(--(review-\d{2}|task-\d{2})(-[a-z0-9-]+)?)*\.md$
+```
+
+- `review-NN` — a new plan addressing findings of a `review-code` or
+  `review-plan` on already-implemented work. `NN` counts reviews of
+  that parent from `01`. Example: parent
+  `2026-09-14-paste-before-init-crash.md` →
+  `2026-09-14-paste-before-init-crash--review-01.md`,
+  then `--review-02.md`.
+- `task-NN-<short-slug>` — sub-plan for task `NN` of a high-level
+  roadmap plan. `NN` is the roadmap task number. Example: parent
+  `2026-09-20-upload-pipeline-roadmap.md` →
+  `2026-09-20-upload-pipeline-roadmap--task-01-chunk-upload.md`.
+  Levels chain: `...--task-02-gc--review-01.md`.
+
+Never use `v2`, `final`, `new`, or `fix2` as suffixes. Keep the
+optional short slug to 3-4 lowercase hyphen-separated words.
+
+Every derived plan opens its `Context` with:
+
+```markdown
+Parent: `<parent-basename>.md`
+Source: review-code over `<commit>` (branch `<branch>`) | task `NN` of roadmap `<parent-basename>.md`
+Created: YYYY-MM-DD
+```
+
 End the response by suggesting the next steps: `/review-plan` to get a second
 opinion on the plan and `/implement-plan` to execute it.