feat: auto-remap codebase after significant phase execution (closes #2003)

agents/gsd-codebase-mapper.md

@@ -94,6 +94,19 @@ Based on focus, determine which documents you'll write:
 - `arch` → ARCHITECTURE.md, STRUCTURE.md
 - `quality` → CONVENTIONS.md, TESTING.md
 - `concerns` → CONCERNS.md
+
+**Optional `--paths` scope hint (#2003):**
+The prompt may include a line of the form:
+
+```
+--paths <p1>,<p2>,...
+```
+
+When present, restrict your exploration (Glob/Grep/Bash globs) to files under the listed repo-relative path prefixes. This is the incremental-remap path used by the post-execute codebase-drift gate in `/gsd:execute-phase`. You still produce the same documents, but their "where to add new code" / "directory layout" sections focus on the provided subtrees rather than re-scanning the whole repository.
+
+**Path validation:** Reject any `--paths` value containing `..`, starting with `/`, or containing shell metacharacters (`;`, `` ` ``, `$`, `&`, `|`, `<`, `>`). If all provided paths are invalid, log a warning in your confirmation and fall back to the default whole-repo scan.
+
+If no `--paths` hint is provided, behave exactly as before.
 </step>
 
 <step name="explore_codebase">

docs/AGENTS.md

@@ -343,18 +343,26 @@ GSD uses a multi-agent architecture where thin orchestrators (workflow files) sp
 
 | Property | Value |
 |----------|-------|
-| **Spawned by** | `/gsd-map-codebase` |
+| **Spawned by** | `/gsd-map-codebase`, post-execute drift gate in `/gsd:execute-phase` |
 | **Parallelism** | 4 instances (tech, architecture, quality, concerns) |
 | **Tools** | Read, Bash, Grep, Glob, Write |
 | **Model (balanced)** | Haiku |
 | **Color** | Cyan |
-| **Produces** | `.planning/codebase/*.md` (7 documents) |
+| **Produces** | `.planning/codebase/*.md` (7 documents, with `last_mapped_commit` frontmatter) |
 
 **Key behaviors:**
 - Read-only exploration + structured output
 - Writes documents directly to disk
 - No reasoning required — pattern extraction from file contents
 
+**`--paths <p1,p2,...>` scope hint (#2003):**
+Accepts an optional `--paths` directive in its prompt. When present, the
+mapper restricts Glob/Grep/Bash exploration to the listed repo-relative path
+prefixes — this is the incremental-remap path used by the post-execute
+codebase-drift gate. Path values that contain `..`, start with `/`, or
+include shell metacharacters are rejected. Without the hint, the mapper
+runs its default whole-repo scan.
+
 ---
 
 ### gsd-debugger

docs/ARCHITECTURE.md

@@ -467,8 +467,8 @@ Equivalent paths for other runtimes:
 │   ├── ARCHITECTURE.md
 │   └── PITFALLS.md
 ├── codebase/               # Brownfield mapping (from /gsd-map-codebase)
-│   ├── STACK.md
-│   ├── ARCHITECTURE.md
+│   ├── STACK.md            # YAML frontmatter carries `last_mapped_commit`
+│   ├── ARCHITECTURE.md     # for the post-execute drift gate (#2003)
 │   ├── CONVENTIONS.md
 │   ├── CONCERNS.md
 │   ├── STRUCTURE.md
@@ -502,6 +502,30 @@ Equivalent paths for other runtimes:
 └── continue-here.md        # Context handoff (from pause-work)
 ```
 
+### Post-Execute Codebase Drift Gate (#2003)
+
+After the last wave of `/gsd:execute-phase` commits, the workflow runs a
+non-blocking `codebase_drift_gate` step (between `schema_drift_gate` and
+`verify_phase_goal`). It compares the diff `last_mapped_commit..HEAD`
+against `.planning/codebase/STRUCTURE.md` and counts four kinds of
+structural elements:
+
+1. New directories outside mapped paths
+2. New barrel exports at `(packages|apps)/<name>/src/index.*`
+3. New migration files
+4. New route modules under `routes/` or `api/`
+
+If the count meets `workflow.drift_threshold` (default 3), the gate either
+**warns** (default) with the suggested `/gsd:map-codebase --paths …` command,
+or **auto-remaps** (`workflow.drift_action = auto-remap`) by spawning
+`gsd-codebase-mapper` scoped to the affected paths. Any error in detection
+or remap is logged and the phase continues — drift detection cannot fail
+verification.
+
+`last_mapped_commit` lives in YAML frontmatter at the top of each
+`.planning/codebase/*.md` file; `bin/lib/drift.cjs` provides
+`readMappedCommit` and `writeMappedCommit` round-trip helpers.
+
 ---
 
 ## Installer Architecture

docs/CONFIGURATION.md

@@ -166,6 +166,8 @@ All workflow toggles follow the **absent = enabled** pattern. If a key is missin
 | `workflow.pattern_mapper` | boolean | `true` | Run the `gsd-pattern-mapper` agent between research and planning to map new files to existing codebase analogs |
 | `workflow.subagent_timeout` | number | `600` | Timeout in seconds for individual subagent invocations. Increase for long-running research or execution phases |
 | `workflow.inline_plan_threshold` | number | `3` | Maximum number of tasks in a phase before the planner generates a separate PLAN.md file instead of inlining tasks in the prompt |
+| `workflow.drift_threshold` | number | `3` | Minimum number of new structural elements (new directories, barrel exports, migrations, route modules) introduced during a phase before the post-execute codebase-drift gate takes action. See [#2003](https://github.com/gsd-build/get-shit-done/issues/2003). Added in v1.39 |
+| `workflow.drift_action` | string | `warn` | What to do when `workflow.drift_threshold` is exceeded after `/gsd:execute-phase`. `warn` prints a message suggesting `/gsd:map-codebase --paths …`; `auto-remap` spawns `gsd-codebase-mapper` scoped to the affected paths. Added in v1.39 |
 
 ### Recommended Presets
 

docs/FEATURES.md

@@ -802,6 +802,45 @@
 | `TESTING.md` | Test infrastructure, coverage, patterns |
 | `INTEGRATIONS.md` | External services, APIs, third-party dependencies |
 
+**Incremental remap — `--paths` (#2003):** The mapper accepts an optional
+`--paths <p1,p2,...>` scope hint. When provided, it restricts exploration
+to the listed repo-relative prefixes instead of scanning the whole tree.
+This is the pathway used by the post-execute codebase-drift gate to refresh
+only the subtrees the phase actually changed. Each produced document carries
+`last_mapped_commit` in its YAML frontmatter so drift can be measured
+against the mapping point, not HEAD.
+
+### 27a. Post-Execute Codebase Drift Detection
+
+**Introduced by:** #2003
+**Trigger:** Runs automatically at the end of every `/gsd:execute-phase`
+**Configuration:**
+- `workflow.drift_threshold` (integer, default `3`) — minimum new
+  structural elements before the gate acts.
+- `workflow.drift_action` (`warn` | `auto-remap`, default `warn`) —
+  warn-only or spawn `gsd-codebase-mapper` with `--paths` scoped to
+  affected subtrees.
+
+**What counts as drift:**
+- New directory outside mapped paths
+- New barrel export at `(packages|apps)/*/src/index.*`
+- New migration file (supabase/prisma/drizzle/src/migrations/…)
+- New route module under `routes/` or `api/`
+
+**Non-blocking guarantee:** any internal failure (missing STRUCTURE.md,
+git errors, mapper spawn failure) logs a single line and the phase
+continues. Drift detection cannot fail verification.
+
+**Requirements:**
+- REQ-DRIFT-01: System MUST detect the four drift categories from `git diff
+  --name-status last_mapped_commit..HEAD`
+- REQ-DRIFT-02: Action fires only when element count ≥ `workflow.drift_threshold`
+- REQ-DRIFT-03: `warn` action MUST NOT spawn any agent
+- REQ-DRIFT-04: `auto-remap` action MUST pass sanitized `--paths` to the mapper
+- REQ-DRIFT-05: Detection/remap failure MUST be non-blocking for `/gsd:execute-phase`
+- REQ-DRIFT-06: `last_mapped_commit` round-trip through YAML frontmatter
+  on each `.planning/codebase/*.md` file
+
 ---
 
 ## Utility Features

docs/INVENTORY-MANIFEST.json

@@ -1,5 +1,5 @@
 {
-  "generated": "2026-04-20",
+  "generated": "2026-04-22",
   "families": {
     "agents": [
       "gsd-advisor-researcher",
@@ -110,11 +110,11 @@
       "/gsd-spike",
       "/gsd-spike-wrap-up",
       "/gsd-stats",
+      "/gsd-sync-skills",
       "/gsd-thread",
       "/gsd-ui-phase",
       "/gsd-ui-review",
       "/gsd-ultraplan-phase",
-      "/gsd-sync-skills",
       "/gsd-undo",
       "/gsd-update",
       "/gsd-validate-phase",
@@ -264,6 +264,7 @@
       "config.cjs",
       "core.cjs",
       "docs.cjs",
+      "drift.cjs",
       "frontmatter.cjs",
       "graphify.cjs",
       "gsd2-import.cjs",

docs/INVENTORY.md

@@ -354,7 +354,7 @@ The `gsd-planner` agent is decomposed into a core agent plus reference modules t
 
 ---
 
-## CLI Modules (26 shipped)
+## CLI Modules (27 shipped)
 
 Full listing: `get-shit-done/bin/lib/*.cjs`.
 
@@ -367,6 +367,7 @@ Full listing: `get-shit-done/bin/lib/*.cjs`.
 | `config.cjs` | `config.json` read/write, section initialization; imports validator from `config-schema.cjs` |
 | `core.cjs` | Error handling, output formatting, shared utilities, runtime fallbacks |
 | `docs.cjs` | Docs-update workflow init, Markdown scanning, monorepo detection |
+| `drift.cjs` | Post-execute codebase structural drift detector (#2003): classifies file changes into new-dir/barrel/migration/route categories and round-trips `last_mapped_commit` frontmatter |
 | `frontmatter.cjs` | YAML frontmatter CRUD operations |
 | `graphify.cjs` | Knowledge-graph build/query/status/diff for `/gsd-graphify` |
 | `gsd2-import.cjs` | External-plan ingest for `/gsd-from-gsd2` |

docs/USER-GUIDE.md

@@ -585,6 +585,20 @@ claude --dangerously-skip-permissions
 # (normal phase workflow from here)
 ```
 
+**Post-execute drift detection (#2003).** After every `/gsd:execute-phase`,
+GSD checks whether the phase introduced enough structural change
+(new directories, barrel exports, migrations, or route modules) to make
+`.planning/codebase/STRUCTURE.md` stale. If it did, the default behavior is
+to print a one-shot warning suggesting the exact `/gsd:map-codebase --paths …`
+invocation to refresh just the affected subtrees. Flip the behavior with:
+
+```bash
+/gsd:settings workflow.drift_action auto-remap       # remap automatically
+/gsd:settings workflow.drift_threshold 5             # tune sensitivity
+```
+
+The gate is non-blocking: any internal failure logs and the phase continues.
+
 ### Quick Bug Fix
 
 ```bash

get-shit-done/bin/gsd-tools.cjs

@@ -112,6 +112,7 @@
  *   verify artifacts <plan-file>       Check must_haves.artifacts
  *   verify key-links <plan-file>       Check must_haves.key_links
  *   verify schema-drift <phase> [--skip]  Detect schema file changes without push
+ *   verify codebase-drift                Detect structural drift since last codebase map (#2003)
  *
  * Template Fill:
  *   template fill summary --phase N    Create pre-filled SUMMARY.md
@@ -593,8 +594,10 @@ async function runCommand(command, args, cwd, raw, defaultValue) {
       } else if (subcommand === 'schema-drift') {
         const skipFlag = args.includes('--skip');
         verify.cmdVerifySchemaDrift(cwd, args[2], skipFlag, raw);
+      } else if (subcommand === 'codebase-drift') {
+        verify.cmdVerifyCodebaseDrift(cwd, raw);
       } else {
-        error('Unknown verify subcommand. Available: plan-structure, phase-completeness, references, commits, artifacts, key-links, schema-drift');
+        error('Unknown verify subcommand. Available: plan-structure, phase-completeness, references, commits, artifacts, key-links, schema-drift, codebase-drift');
       }
       break;
     }

get-shit-done/bin/lib/config-schema.cjs

@@ -37,6 +37,8 @@ const VALID_CONFIG_KEYS = new Set([
   'workflow.security_enforcement',
   'workflow.security_asvs_level',
   'workflow.security_block_on',
+  'workflow.drift_threshold',
+  'workflow.drift_action',
   'git.branching_strategy', 'git.base_branch', 'git.phase_branch_template', 'git.milestone_branch_template', 'git.quick_branch_template',
   'planning.commit_docs', 'planning.search_gitignored', 'planning.sub_repos',
   'workflow.cross_ai_execution', 'workflow.cross_ai_command', 'workflow.cross_ai_timeout',

get-shit-done/bin/lib/config.cjs

@@ -333,6 +333,17 @@ function cmdConfigSet(cwd, keyPath, value, raw) {
     error(`Invalid context value '${value}'. Valid values: ${VALID_CONTEXT_VALUES.join(', ')}`);
   }
 
+  // Codebase drift detector (#2003)
+  const VALID_DRIFT_ACTIONS = ['warn', 'auto-remap'];
+  if (keyPath === 'workflow.drift_action' && !VALID_DRIFT_ACTIONS.includes(String(parsedValue))) {
+    error(`Invalid workflow.drift_action '${value}'. Valid values: ${VALID_DRIFT_ACTIONS.join(', ')}`);
+  }
+  if (keyPath === 'workflow.drift_threshold') {
+    if (typeof parsedValue !== 'number' || !Number.isInteger(parsedValue) || parsedValue < 1) {
+      error(`Invalid workflow.drift_threshold '${value}'. Must be a positive integer.`);
+    }
+  }
+
   const setConfigValueResult = setConfigValue(cwd, keyPath, parsedValue);
   output(setConfigValueResult, raw, `${keyPath}=${parsedValue}`);
 }