msd-core/get-shit-done/workflows/execute-phase/steps/codebase-drift-gate.md

Step: codebase_drift_gate

Post-execution structural drift detection (#2003). Runs after the last wave commits, before verification. Non-blocking by contract: any internal error here MUST fall through and continue to verify_phase_goal. The phase is never failed by this gate.

DRIFT=$(gsd-sdk query verify.codebase-drift 2>/dev/null || echo '{"skipped":true,"reason":"sdk-failed"}')

Parse JSON for: skipped, reason, action_required, directive, spawn_mapper, affected_paths, elements, threshold, action, last_mapped_commit, message.

If skipped is true (no STRUCTURE.md, missing git, or any internal error): Log one line — Codebase drift check skipped: {reason} — and continue to verify_phase_goal. Do NOT prompt the user. Do NOT block.

If action_required is false: Continue silently to verify_phase_goal.

If action_required is true AND directive is warn: Print the message field verbatim. The format is:

Codebase drift detected: {N} structural element(s) since last mapping.

New directories:
  - {path}
New barrel exports:
  - {path}
New migrations:
  - {path}
New route modules:
  - {path}

Run /gsd-map-codebase --paths {affected_paths} to refresh planning context.

Then continue to verify_phase_goal. Do NOT block. Do NOT spawn anything.

If action_required is true AND directive is auto-remap:

First load the mapper agent's skill bundle (the executor's AGENT_SKILLS from step init_context is for gsd-executor, not the mapper):

AGENT_SKILLS_MAPPER=$(gsd-sdk query agent-skills gsd-codebase-mapper)

Then spawn gsd-codebase-mapper agents with the --paths hint:

Task(
  subagent_type="gsd-codebase-mapper",
  description="Incremental codebase remap (drift)",
  prompt="Focus: arch
Today's date: {date}
--paths {affected_paths joined by comma}

Refresh STRUCTURE.md and ARCHITECTURE.md scoped to the listed paths only.
Stamp last_mapped_commit in each document's frontmatter.
${AGENT_SKILLS_MAPPER}"
)

If the spawn fails or the agent reports an error: log Codebase drift auto-remap failed: {reason} and continue to verify_phase_goal. The phase is NOT failed by a remap failure.

If the remap succeeds: log Codebase drift auto-remap completed for paths: {affected_paths} and continue to verify_phase_goal.

The two relevant config keys (continue on error / failure if either is invalid):

• workflow.drift_threshold (integer, default 3) — minimum drift elements before action
• workflow.drift_action — warn (default) or auto-remap

This step is fully non-blocking — it never fails the phase, and any exception path returns control to verify_phase_goal.