diff --git a/scripts/lint-core-spine-imports.allowlist.json b/scripts/lint-core-spine-imports.allowlist.json
index bdb738c1e..3f1ffbcb1 100644
--- a/scripts/lint-core-spine-imports.allowlist.json
+++ b/scripts/lint-core-spine-imports.allowlist.json
@@ -2,34 +2,22 @@
   "_comment": "Files allowed to import the core re-export spine during the staged retirement (issue #1268). Entries are REMOVED as each tranche migrates a leaf; the file + this lint are deleted in T-final.",
   "allow": [
     "gsd-core/bin/gsd-tools.cjs",
-    "src/agent-command-router.cts",
     "src/audit-command-router.cts",
-    "src/capability-state.cts",
-    "src/capability-writer.cts",
     "src/check-command-router.cts",
     "src/commands.cts",
     "src/config.cts",
     "src/docs.cts",
-    "src/frontmatter.cts",
     "src/gap-checker.cts",
     "src/graphify-command-router.cts",
-    "src/gsd2-import.cts",
     "src/init.cts",
     "src/intel-command-router.cts",
-    "src/learnings.cts",
-    "src/loop-resolver.cts",
-    "src/milestone.cts",
     "src/phase.cts",
     "src/profile-output.cts",
-    "src/roadmap-command-router.cts",
     "src/roadmap.cts",
     "src/state.cts",
-    "src/task-command-router.cts",
     "src/template.cts",
     "src/uat.cts",
     "src/verification.cts",
-    "src/verify.cts",
-    "src/workstream-inventory.cts",
     "src/workstream.cts"
   ]
 }
diff --git a/src/agent-command-router.cts b/src/agent-command-router.cts
index e11f415d0..71b89a7dc 100644
--- a/src/agent-command-router.cts
+++ b/src/agent-command-router.cts
@@ -7,8 +7,8 @@
  */
 
 // eslint-disable-next-line @typescript-eslint/no-require-imports
-import core = require('./core.cjs');
-const { output, error, ERROR_REASON } = core;
+import io = require('./io.cjs');
+const { output, error, ERROR_REASON } = io;
 
 // ─── Types ────────────────────────────────────────────────────────────────────
 
diff --git a/src/capability-state.cts b/src/capability-state.cts
index c410782d3..dc0c58475 100644
--- a/src/capability-state.cts
+++ b/src/capability-state.cts
@@ -17,9 +17,9 @@
  * pure, config-only resolution with no filesystem I/O.
  * cmdCapabilityState is the I/O handler.
  *
- * Dependencies (leaf modules only — no core.cjs circular risk):
+ * Dependencies (leaf modules only — no circular risk):
  *   - node:path
- *   - ./core.cjs               (output, error)
+ *   - ./io.cjs                 (output, error)
  *   - ./capability-activation.cjs (_resolveActivationValue)
  *   - ./install-profiles.cjs   (readActiveProfile, loadSkillsManifest, resolveProfile)
  *   - ./surface.cjs            (resolveSurface)
@@ -32,8 +32,8 @@ import path from 'node:path';
 import fs from 'node:fs';
 
 // eslint-disable-next-line @typescript-eslint/no-require-imports
-import core = require('./core.cjs');
-const { output: coreOutput, error: coreError } = core;
+import ioMod = require('./io.cjs');
+const { output: coreOutput, error: coreError } = ioMod;
 
 // eslint-disable-next-line @typescript-eslint/no-require-imports
 import activationMod = require('./capability-activation.cjs');
@@ -363,7 +363,7 @@ function _resolveManifest(commandsGsdDir: string, configDir: string): Map<string
 
 /**
  * Command entry point: resolve install profile, surface, and config; compute
- * capability state; emit the envelope via core.output.
+ * capability state; emit the envelope via io.output.
  *
  * Envelope: { runtimeConfigDir, warnings?: string[], capabilities: CapabilityStateEntry[] }
  *
@@ -388,7 +388,7 @@ function _resolveManifest(commandsGsdDir: string, configDir: string): Map<string
  *                         Providing a value without a next token (e.g. the flag
  *                         is last in argv with no following value) should be
  *                         caught by the caller before invoking this function.
- * @param raw              Whether to emit raw JSON (core.output raw mode)
+ * @param raw              Whether to emit raw JSON (io.output raw mode)
  * @param _options         Reserved for future use
  */
 function resolveCapabilityRuntimeState(
diff --git a/src/capability-writer.cts b/src/capability-writer.cts
index 75022bdf4..37d178b81 100644
--- a/src/capability-writer.cts
+++ b/src/capability-writer.cts
@@ -13,7 +13,7 @@
  *   - re-resolve: always calls resolveCapabilityRuntimeState for the return value
  *
  * Dependencies (leaf modules only — no circular risk):
- *   - ./core.cjs               (output, error)
+ *   - ./io.cjs                 (output, error)
  *   - ./capability-state.cjs   (resolveCapabilityRuntimeState, _resolveManifest, _resolveCommandsGsdDir)
  *   - ./surface.cjs            (readSurface, writeSurface, applySurface)
  *   - ./install-profiles.cjs   (readActiveProfile)
@@ -23,8 +23,8 @@
  */
 
 // eslint-disable-next-line @typescript-eslint/no-require-imports
-import core = require('./core.cjs');
-const { output: coreOutput, error: coreError } = core;
+import ioMod = require('./io.cjs');
+const { output: coreOutput, error: coreError } = ioMod;
 
 // eslint-disable-next-line @typescript-eslint/no-require-imports
 import capabilityStateMod = require('./capability-state.cjs');
diff --git a/src/frontmatter.cts b/src/frontmatter.cts
index 9dda57e93..53d382642 100644
--- a/src/frontmatter.cts
+++ b/src/frontmatter.cts
@@ -9,8 +9,8 @@
 import fs from 'node:fs';
 import path from 'node:path';
 // eslint-disable-next-line @typescript-eslint/no-require-imports
-import core = require('./core.cjs');
-const { output, error } = core;
+import ioMod = require('./io.cjs');
+const { output, error } = ioMod;
 import { platformReadSync as safeReadFile, platformWriteSync } from './shell-command-projection.cjs';
 
 // ─── Types ────────────────────────────────────────────────────────────────────
diff --git a/src/gsd2-import.cts b/src/gsd2-import.cts
index 2a585962c..daf0852d6 100644
--- a/src/gsd2-import.cts
+++ b/src/gsd2-import.cts
@@ -24,8 +24,8 @@ import path from 'node:path';
 import { platformWriteSync } from './shell-command-projection.cjs';
 import { formatGsdSlash, resolveRuntime } from './runtime-slash.cjs';
 // eslint-disable-next-line @typescript-eslint/no-require-imports
-import core = require('./core.cjs');
-const { output } = core;
+import ioMod = require('./io.cjs');
+const { output } = ioMod;
 
 // ─── Types ───────────────────────────────────────────────────────────────────
 
diff --git a/src/learnings.cts b/src/learnings.cts
index 6033409e2..f1e6a6e4b 100644
--- a/src/learnings.cts
+++ b/src/learnings.cts
@@ -20,8 +20,8 @@ import path from 'node:path';
 import crypto from 'node:crypto';
 import os from 'node:os';
 // eslint-disable-next-line @typescript-eslint/no-require-imports
-import core = require('./core.cjs');
-const { output, error: coreError } = core;
+import ioMod = require('./io.cjs');
+const { output, error: coreError } = ioMod;
 import { platformWriteSync } from './shell-command-projection.cjs';
 
 // ─── Types ───────────────────────────────────────────────────────────────────
diff --git a/src/loop-resolver.cts b/src/loop-resolver.cts
index 48378d1a2..c18edcc26 100644
--- a/src/loop-resolver.cts
+++ b/src/loop-resolver.cts
@@ -19,11 +19,11 @@
  * Both pure functions (resolveLoopHooks, renderLoopHooks) take explicit
  * registry/config arguments so they are trivially testable without I/O.
  *
- * Dependencies (leaf modules only — no core.cjs circular risk):
+ * Dependencies (leaf modules only — no circular risk):
  *   - node:fs / node:path  (raw config.json read for capability-key activation)
  *   - ./config-loader.cjs  (loadConfig)
  *   - ./planning-workspace.cjs  (planningDir — to locate config.json)
- *   - ./core.cjs           (output, error)
+ *   - ./io.cjs             (output, error)
  *   - loop-host-contract.cjs (CANONICAL_POINTS via LOOP_HOST_CONTRACT)
  *   - capability-registry.cjs (byLoopPoint, consumed at call time)
  */
@@ -32,8 +32,8 @@ import fs from 'node:fs';
 import path from 'node:path';
 
 // eslint-disable-next-line @typescript-eslint/no-require-imports
-import core = require('./core.cjs');
-const { output: coreOutput, error: coreError } = core;
+import ioMod = require('./io.cjs');
+const { output: coreOutput, error: coreError } = ioMod;
 
 // eslint-disable-next-line @typescript-eslint/no-require-imports
 import configLoaderModule = require('./config-loader.cjs');
@@ -284,7 +284,7 @@ interface ResolveLoopHooksResult {
  * Pure resolver: given a point, registry, and config, returns the active hooks.
  *
  * Throws if `point` is not one of the 12 canonical points (caller converts to
- * core.error). Never throws for malformed registry/hook entries — skips and
+ * io.error). Never throws for malformed registry/hook entries — skips and
  * continues.
  *
  * Ordering: steps first, then contributions, then gates. Within each array,
@@ -571,7 +571,7 @@ function renderLoopHooks(resolved: ResolveLoopHooksResult): string {
  * Command entry point: load registry + config, resolve + render, emit envelope.
  *
  * Envelope: { point, activeHooks, rendered }
- * On invalid point, emits core.error instead of throwing.
+ * On invalid point, emits io.error instead of throwing.
  *
  * Config note: FIX 1 replaced _loadMergedConfig (whole-config deep-merge) with a
  * per-hook single-key activation resolver (_resolveActivationValue). The resolver
diff --git a/src/milestone.cts b/src/milestone.cts
index 66f1f0450..b8b67a3e5 100644
--- a/src/milestone.cts
+++ b/src/milestone.cts
@@ -8,8 +8,6 @@
 
 import fs from 'node:fs';
 import path from 'node:path';
-// eslint-disable-next-line @typescript-eslint/no-require-imports -- core.cjs is an export= CommonJS module
-import core = require('./core.cjs');
 // eslint-disable-next-line @typescript-eslint/no-require-imports -- planning-workspace.cjs is an export= CommonJS module
 import planningWorkspace = require('./planning-workspace.cjs');
 // eslint-disable-next-line @typescript-eslint/no-require-imports -- frontmatter.cjs is an export= CommonJS module
@@ -18,16 +16,18 @@ import frontmatterMod = require('./frontmatter.cjs');
 import stateMod = require('./state.cjs');
 import { platformWriteSync, platformEnsureDir } from './shell-command-projection.cjs';
 import { formatGsdSlash, resolveRuntime } from './runtime-slash.cjs';
-
-const {
-  escapeRegex,
-  getMilestonePhaseFilter,
-  extractOneLinerFromBody,
-  normalizePhaseName,
-  phaseTokenMatches,
-  output,
-  error,
-} = core;
+// eslint-disable-next-line @typescript-eslint/no-require-imports
+import ioMod = require('./io.cjs');
+const { output, error } = ioMod;
+// eslint-disable-next-line @typescript-eslint/no-require-imports
+import phaseIdMod = require('./phase-id.cjs');
+const { escapeRegex, normalizePhaseName, phaseTokenMatches } = phaseIdMod;
+// eslint-disable-next-line @typescript-eslint/no-require-imports
+import roadmapParserMod = require('./roadmap-parser.cjs');
+const { getMilestonePhaseFilter, extractCurrentMilestone } = roadmapParserMod;
+// eslint-disable-next-line @typescript-eslint/no-require-imports
+import coreUtilsMod = require('./core-utils.cjs');
+const { extractOneLinerFromBody } = coreUtilsMod;
 const { planningPaths } = planningWorkspace;
 const { extractFrontmatter } = frontmatterMod;
 const { writeStateMd, stateReplaceFieldWithFallback } = stateMod;
@@ -167,7 +167,6 @@ function cmdMilestoneComplete(cwd: string, version: string, options: MilestoneCo
       }
 
       if (stateVersion && stateVersion === version) {
-        const { extractCurrentMilestone } = core;
         const roadmapContent = fs.readFileSync(roadmapPath, 'utf-8');
         const scopedContent = extractCurrentMilestone(roadmapContent, cwd);
         const phasePattern = /#{2,4}\s*Phase\s+(\d+[A-Z]?(?:\.\d+)*)\s*:\s*([^\n]+)/gi;
diff --git a/src/roadmap-command-router.cts b/src/roadmap-command-router.cts
index 2dac5f87f..d046394aa 100644
--- a/src/roadmap-command-router.cts
+++ b/src/roadmap-command-router.cts
@@ -19,8 +19,8 @@ import roadmapUpgrade = require('./roadmap-upgrade.cjs');
 import planningWorkspace = require('./planning-workspace.cjs');
 const { planningDir } = planningWorkspace;
 // eslint-disable-next-line @typescript-eslint/no-require-imports
-import core = require('./core.cjs');
-const { loadConfig } = core;
+import configLoaderMod = require('./config-loader.cjs');
+const { loadConfig } = configLoaderMod;
 
 // ─── Types ────────────────────────────────────────────────────────────────────
 
diff --git a/src/task-command-router.cts b/src/task-command-router.cts
index ff6d6bd06..45d83828d 100644
--- a/src/task-command-router.cts
+++ b/src/task-command-router.cts
@@ -9,8 +9,8 @@
 import fs from 'node:fs';
 import path from 'node:path';
 // eslint-disable-next-line @typescript-eslint/no-require-imports
-import core = require('./core.cjs');
-const { output, error, ERROR_REASON } = core;
+import ioMod = require('./io.cjs');
+const { output, error, ERROR_REASON } = ioMod;
 
 // ─── Types ────────────────────────────────────────────────────────────────────
 
diff --git a/src/verify.cts b/src/verify.cts
index 225d22e84..ad3583865 100644
--- a/src/verify.cts
+++ b/src/verify.cts
@@ -11,8 +11,6 @@ import path from 'node:path';
 import os from 'node:os';
 import { phaseVariants, buildRoadmapPhaseVariants, buildNotStartedPhaseVariants } from './validate.cjs';
 import { phaseDirNameRe, PHASE_TOKEN_FROM_DIR_RE, MILESTONE_ARCHIVE_DIR_RE, canonicalPlanStem } from './validate.cjs';
-// eslint-disable-next-line @typescript-eslint/no-require-imports -- core.cjs is an export= CommonJS module
-import core = require('./core.cjs');
 // eslint-disable-next-line @typescript-eslint/no-require-imports -- planning-workspace.cjs is an export= CommonJS module
 import planningWorkspace = require('./planning-workspace.cjs');
 // eslint-disable-next-line @typescript-eslint/no-require-imports -- frontmatter.cjs is an export= CommonJS module
@@ -31,21 +29,24 @@ import { isCanonicalPlanningFile } from './artifacts.cjs';
 // eslint-disable-next-line @typescript-eslint/no-require-imports -- agent-install-check.cjs is an export= CommonJS module
 import agentInstallCheck = require('./agent-install-check.cjs');
 const { checkAgentsInstalled } = agentInstallCheck;
-
-const {
-  loadConfig,
-  normalizePhaseName,
-  phaseTokenMatches,
-  escapeRegex,
-  findPhaseInternal,
-  getMilestoneInfo,
-  stripShippedMilestones,
-  extractCurrentMilestone,
-  output,
-  error,
-  CONFIG_DEFAULTS,
-  inspectWorktreeHealth,
-} = core;
+// eslint-disable-next-line @typescript-eslint/no-require-imports
+import ioMod = require('./io.cjs');
+const { output, error } = ioMod;
+// eslint-disable-next-line @typescript-eslint/no-require-imports
+import configLoaderMod = require('./config-loader.cjs');
+const { loadConfig, CONFIG_DEFAULTS } = configLoaderMod;
+// eslint-disable-next-line @typescript-eslint/no-require-imports
+import phaseIdMod = require('./phase-id.cjs');
+const { normalizePhaseName, phaseTokenMatches, escapeRegex, getMilestoneFromPhaseId } = phaseIdMod;
+// eslint-disable-next-line @typescript-eslint/no-require-imports
+import phaseLocatorMod = require('./phase-locator.cjs');
+const { findPhaseInternal } = phaseLocatorMod;
+// eslint-disable-next-line @typescript-eslint/no-require-imports
+import roadmapParserMod = require('./roadmap-parser.cjs');
+const { getMilestoneInfo, stripShippedMilestones, extractCurrentMilestone } = roadmapParserMod;
+// eslint-disable-next-line @typescript-eslint/no-require-imports
+import worktreeSafetyMod = require('./worktree-safety.cjs');
+const { inspectWorktreeHealth } = worktreeSafetyMod;
 
 const { planningDir } = planningWorkspace;
 const { extractFrontmatter, parseMustHavesBlock } = frontmatterMod;
@@ -1402,7 +1403,6 @@ function cmdValidateHealth(
     if (phaseConvention === 'milestone-prefixed') {
       if (fs.existsSync(roadmapPath)) {
         const roadmapContent = fs.readFileSync(roadmapPath, 'utf-8');
-        const { getMilestoneFromPhaseId } = core;
         const mismatches = checkMilestonePrefixMismatches(roadmapContent, {
           getMilestoneFromPhaseId: getMilestoneFromPhaseId,
         });
diff --git a/src/workstream-inventory.cts b/src/workstream-inventory.cts
index 9068c9d37..67a2f0edd 100644
--- a/src/workstream-inventory.cts
+++ b/src/workstream-inventory.cts
@@ -16,8 +16,8 @@
 import fs from 'node:fs';
 import path from 'node:path';
 // eslint-disable-next-line @typescript-eslint/no-require-imports
-import core = require('./core.cjs');
-const { readSubdirectories } = core;
+import coreUtilsMod = require('./core-utils.cjs');
+const { readSubdirectories } = coreUtilsMod;
 // eslint-disable-next-line @typescript-eslint/no-require-imports
 import planScan = require('./plan-scan.cjs');
 // eslint-disable-next-line @typescript-eslint/no-require-imports