* fix(#3418): write the codebase-drift baseline from code instead of agent prose
writeMappedCommit shipped correct and callerless, so no full map-codebase run ever wrote last_mapped_commit. The gate then read null and diffed HEAD against the empty tree, reporting every tracked file as newly added on every run.
Adds the stamp-codebase-map leaf verb and calls it from the map-codebase workflow and the execute-phase auto-remap path, replacing the prose instruction that asked the mapper agent to stamp its own output. An agent that concludes its work is already done skips a prose step silently, which is the failure the stamp exists to detect.
The gate now reports an absent or unresolvable baseline as skipped, with reason no-mapped-commit or unresolvable-mapped-commit, rather than as whole-repo drift. Files under .planning/ are excluded from the diff so the map's own commit does not read as seven new directories on the next run.
Emitted-Drift-Ack-Growth: map-codebase.md — adds the stamp_codebase_map step and its rationale, new workflow content this change requires
* test(#3418): cover the stamp writer and the absent-baseline gate
* docs(#3418): document how the drift baseline is written and skipped
* docs(#3418): note that a manual stamp reflows the map's whitespace
writeMappedCommit writes through platformWriteSync, which normalizes markdown whitespace on .md targets. Run in its workflow position the stamp lands on documents the mapper just wrote, so the normalization is folded into the same commit, but a hand-run stamp over an already-committed map reflows that map as a side effect. Reported on the issue thread.
* chore(#3418): add changeset fragment
Typed Changed to match the enhancement route the linked issue's label sets. The docs-required lint is satisfied by the ARCHITECTURE.md update already in this branch.
* fix(#3418): anchor the planning-artifact filter to the repo root
git diff --name-status prints repo-root-relative paths whatever the cwd, so computing the exclusion prefix against cwd yielded ".planning/" while git printed "sub/.planning/" and the filter silently matched nothing from a subdirectory.
* fix(#3418): derive the planning prefix from git, not from path arithmetic
Anchoring the exclusion prefix with path.relative() against `rev-parse --show-toplevel` broke on Windows, where os.tmpdir() hands back the 8.3 short form and git resolves the long one, so relative() produced a "../.." chain that matched nothing. `rev-parse --show-prefix` gives the cwd's root-relative prefix from the same producer as the diff paths, so the two sides cannot disagree.
* fix(#3418): take the planning lock around the codebase-map stamp
Stamping seven documents is seven frontmatter read-modify-writes, and two stampers can run at once: the full map-codebase run and the execute-phase auto-remap. Wrap the write loop in withPlanningLock, the same lock the other .planning/ writers take, so a concurrent pair cannot lose an update.
Also corrects the path-arithmetic comment, which read as if the Windows short-path hazard applied to the .planning half of the prefix. It applies to the rejected --show-toplevel alternative; both sides of the surviving relative() call are the same cwd string.
* fix(#3418): read HEAD and the map file list under the planning lock
The stamp resolved HEAD and listed the present codebase-map documents before it acquired the planning lock, so a stamper that then waited on the lock could write its now-stale sha over a newer one, or recreate a document deleted while it waited as a frontmatter-only stub. Both reads now happen inside the lock, matching the read-and-write-in-one-lock pattern config.cts and phase.cts already use. An empty --files value is refused as well instead of silently widening the stamp to all seven documents.
* fix(#3418): narrow the map stamp to the documents an update run refreshed
An "Update - only update specific documents" run reached the new stamp step with no --files narrowing, so the six documents the user did not select were stamped at HEAD and read as freshly mapped. The selection now threads through to --files, the same way the auto-remap path already does.
A bare --files (an unquoted empty shell variable drops the token) parsed to null, indistinguishable from an absent flag, so it skipped the empty-filter refusal and stamped all seven. Presence is now read off argv.
* fix(#3418): require the drift baseline to resolve to a commit, not any object
`git cat-file -t` exits 0 for a tree or blob sha and for a ref name, and `git diff <tree> HEAD` is valid, so an exit-code-only probe accepted a baseline that is not a commit and reported the resulting diff as real drift. Check the reported type instead of the exit code alone, which routes every non-commit stamp to the same `unresolvable-mapped-commit` skip.
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Co-authored-by: Tom Boucher <trekkie@nomorestars.com>
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