diff --git a/agents/vbw-lead.md b/agents/vbw-lead.md
index ff2cc0d0..5f19ccb1 100644
--- a/agents/vbw-lead.md
+++ b/agents/vbw-lead.md
@@ -66,6 +66,7 @@ Display: `✓ Lead: All plans written to disk`
 PLAN_NAME=$(bash "$RESOLVE_SCRIPT" plan "{phase-dir}" --plan-number {MM})
 ```
 Write the plan to `{phase-dir}/${PLAN_NAME}`. If the orchestrator did not provide `RESOLVE_SCRIPT`, fall back to `{NN}-{MM}-PLAN.md` where `{NN}` is the phase number from the directory basename and `{MM}` is the zero-padded plan number. Do NOT use `PLAN-{NN}.md` — this format is rejected by file-guard.
+**Frontmatter `plan:` value:** Set the `plan:` field to the plan number `{MM}` only (zero-padded, e.g. `01`). Do NOT write the `{NN}-{MM}` file id (e.g. `66-01`) into `plan:` — the phase is already carried by the separate `phase:` field. The execute router reconstructs the canonical `{NN}-{MM}` id from `phase:` + `plan:`, so a phase-prefixed `plan:` value misrepresents the plan id.
 Report: `Phase {NN}: {name}\nPlans: {N}\n  {plan}: {title} (wave {W}, {N} tasks)`
 
 ## Goal-Backward Methodology
diff --git a/scripts/resolve-execute-delegation-mode.sh b/scripts/resolve-execute-delegation-mode.sh
index 9e3c55ed..3f767198 100755
--- a/scripts/resolve-execute-delegation-mode.sh
+++ b/scripts/resolve-execute-delegation-mode.sh
@@ -295,7 +295,15 @@ resolve_plan_path() {
     if [ -n "$fm_phase" ] || [ -n "$fm_plan" ]; then
       fm_phase=${fm_phase:-$phase_id}
       fm_plan=${fm_plan:-$plan_part}
-      norm_fm_id=$(normalize_plan_ref "$(pad_number "$fm_phase")-$(pad_number "$fm_plan")" 2>/dev/null || true)
+      # A plan: frontmatter value may already be phase-qualified (NN-MM), the
+      # same form cross_phase_deps uses. Normalizing it directly avoids
+      # re-prepending fm_phase (which would double-prefix to NN-NN-MM and
+      # raise a spurious frontmatter_mismatch). A bare plan-number is still
+      # combined with fm_phase to build the canonical id.
+      case "$fm_plan" in
+        *-*) norm_fm_id=$(normalize_plan_ref "$fm_plan" 2>/dev/null || true) ;;
+        *)   norm_fm_id=$(normalize_plan_ref "$(pad_number "$fm_phase")-$(pad_number "$fm_plan")" 2>/dev/null || true) ;;
+      esac
       if [ -n "$norm_fm_id" ] && [ "$norm_fm_id" != "$id" ]; then
         printf 'frontmatter_mismatch:%s:declares:%s\n' "$(basename "$candidate")" "$norm_fm_id" >&2
         return 3
diff --git a/scripts/worktree-cleanup.sh b/scripts/worktree-cleanup.sh
index 4479f71a..e433031b 100755
--- a/scripts/worktree-cleanup.sh
+++ b/scripts/worktree-cleanup.sh
@@ -12,10 +12,20 @@ fi
 PHASE="$1"
 PLAN="$2"
 
+# Normalize the plan id into the canonical "<phase>-<plan>" slug so the worktree
+# dir, branch, and agent-map glob match what worktree-create.sh produced. A
+# caller may pass a bare plan number (MM) or an already phase-qualified id
+# (NN-MM); prepending PHASE to the latter would double-prefix to NN-NN-MM. Use
+# an already-qualified plan as-is, otherwise combine it with PHASE.
+case "$PLAN" in
+  *-*) SLUG="$PLAN" ;;
+  *)   SLUG="${PHASE}-${PLAN}" ;;
+esac
+
 PLANNING_DIR="${VBW_PLANNING_DIR:-.vbw-planning}"
 WORKTREES_PARENT=".vbw-worktrees"
-WORKTREE_DIR="${WORKTREES_PARENT}/${PHASE}-${PLAN}"
-BRANCH="vbw/${PHASE}-${PLAN}"
+WORKTREE_DIR="${WORKTREES_PARENT}/${SLUG}"
+BRANCH="vbw/${SLUG}"
 AGENT_WORKTREES_DIR="$PLANNING_DIR/.agent-worktrees"
 
 # Unlock the worktree if locked (locked worktrees resist single --force)
@@ -67,7 +77,7 @@ git branch -d "$BRANCH" 2>/dev/null || true
 # Clear the agent-worktree mapping entry if the directory exists
 if [ -d "$AGENT_WORKTREES_DIR" ]; then
   # Remove any JSON file matching the phase-plan pattern
-  for f in "$AGENT_WORKTREES_DIR"/*"${PHASE}-${PLAN}"*.json; do
+  for f in "$AGENT_WORKTREES_DIR"/*"${SLUG}"*.json; do
     [ -f "$f" ] && rm -f "$f" 2>/dev/null || true
   done
 fi
diff --git a/scripts/worktree-create.sh b/scripts/worktree-create.sh
index 1ae79fce..c27f30eb 100755
--- a/scripts/worktree-create.sh
+++ b/scripts/worktree-create.sh
@@ -15,8 +15,19 @@ if [ -z "$PHASE" ] || [ -z "$PLAN" ]; then
   exit 0
 fi
 
-WORKTREE_DIR=".vbw-worktrees/${PHASE}-${PLAN}"
-BRANCH="vbw/${PHASE}-${PLAN}"
+# Normalize the plan id into the canonical "<phase>-<plan>" slug. A caller may
+# pass either a bare plan number (MM) or an already phase-qualified id (NN-MM,
+# the form .execution-state.json and plan filenames use). Prepending PHASE to an
+# already-qualified id would double-prefix to NN-NN-MM (e.g. 43-43-03). Mirror
+# resolve-execute-delegation-mode.sh: use an already-qualified plan as-is,
+# otherwise combine it with PHASE.
+case "$PLAN" in
+  *-*) SLUG="$PLAN" ;;
+  *)   SLUG="${PHASE}-${PLAN}" ;;
+esac
+
+WORKTREE_DIR=".vbw-worktrees/${SLUG}"
+BRANCH="vbw/${SLUG}"
 
 # Idempotent: if worktree already exists, return its absolute path
 if [ -d "$WORKTREE_DIR" ]; then
diff --git a/scripts/worktree-merge.sh b/scripts/worktree-merge.sh
index 77326c19..3f9b1da1 100755
--- a/scripts/worktree-merge.sh
+++ b/scripts/worktree-merge.sh
@@ -14,10 +14,23 @@ if [ -z "$PHASE" ] || [ -z "$PLAN" ]; then
   exit 0
 fi
 
-BRANCH="vbw/${PHASE}-${PLAN}"
+# Normalize the plan id into the canonical "<phase>-<plan>" slug so the branch
+# matches the one worktree-create.sh produced. A caller may pass a bare plan
+# number (MM) or an already phase-qualified id (NN-MM); prepending PHASE to the
+# latter would double-prefix to NN-NN-MM. Use an already-qualified plan as-is,
+# otherwise combine it with PHASE.
+case "$PLAN" in
+  *-*) SLUG="$PLAN" ;;
+  *)   SLUG="${PHASE}-${PLAN}" ;;
+esac
+PLAN_NUM="${SLUG#*-}"
 
-# Attempt the merge
-git merge --no-ff "$BRANCH" -m "merge: phase ${PHASE} plan ${PLAN}" 2>/dev/null
+BRANCH="vbw/${SLUG}"
+
+# Attempt the merge. Suppress git's own stdout/stderr so the script honors its
+# contract of emitting exactly "clean" or "conflict" (git prints a porcelain
+# summary to stdout on success and conflict details on failure).
+git merge --no-ff "$BRANCH" -m "merge: phase ${PHASE} plan ${PLAN_NUM}" >/dev/null 2>&1
 MERGE_STATUS=$?
 
 if [ "$MERGE_STATUS" -eq 0 ]; then
diff --git a/templates/PLAN.md b/templates/PLAN.md
index a4f07144..68d58a57 100644
--- a/templates/PLAN.md
+++ b/templates/PLAN.md
@@ -1,6 +1,6 @@
 ---
 phase: {NN} # bare integer, no quotes
-plan: {plan-number}
+plan: {plan-number} # plan number only (MM, zero-padded e.g. 01) — NOT the NN-MM file id
 title: {plan-title}
 type: execute
 wave: {wave-number}
diff --git a/templates/SUMMARY.md b/templates/SUMMARY.md
index 1febb999..e14ac59e 100644
--- a/templates/SUMMARY.md
+++ b/templates/SUMMARY.md
@@ -1,6 +1,6 @@
 ---
 phase: {NN} # bare integer, no quotes
-plan: {plan-number}
+plan: {plan-number} # plan number only (MM, zero-padded e.g. 01) — NOT the NN-MM file id
 title: {plan-title}
 status: {complete|partial|failed}
 completed: {YYYY-MM-DD}
diff --git a/testing/verify-execute-delegation-routing.sh b/testing/verify-execute-delegation-routing.sh
index d2bd208c..09ca03e2 100755
--- a/testing/verify-execute-delegation-routing.sh
+++ b/testing/verify-execute-delegation-routing.sh
@@ -384,6 +384,54 @@ write_state '{"plans":[{"id":"01-02","status":"pending"}],"effort":"balanced","p
 write_plan_inline 01-02-PLAN.md 01 03 '[]'
 expect_helper_failure "frontmatter plan mismatch fails closed with invalid_dependency_graph"
 
+# issue #659: a phase-prefixed plan: frontmatter value (NN-MM, the same form
+# cross_phase_deps uses) must resolve to the canonical id instead of being
+# double-prefixed to NN-NN-MM and rejected as a spurious frontmatter_mismatch.
+make_fixture fm-phase-prefixed '"auto"' balanced
+write_state '{"plans":[{"id":"01-01","status":"pending"}],"effort":"balanced","phase_effort":"balanced"}'
+write_plan_inline 01-01-PLAN.md 01 01-01 '[]'
+out=$(run_helper)
+assert_eq "$(json_field "$out" '.delegation_mode')" "subagent" "phase-prefixed plan: frontmatter (unquoted NN-MM) resolves without frontmatter_mismatch"
+assert_json_array_eq "$(jq -c '.dependency_waves' <<< "$out")" '[["01-01"]]' "phase-prefixed plan: frontmatter maps to canonical id 01-01"
+
+make_fixture fm-phase-prefixed-quoted '"auto"' balanced
+write_state '{"plans":[{"id":"01-01","status":"pending"}],"effort":"balanced","phase_effort":"balanced"}'
+write_plan_inline 01-01-PLAN.md 01 '"01-01"' '[]'
+out=$(run_helper)
+assert_eq "$(json_field "$out" '.delegation_mode')" "subagent" "phase-prefixed plan: frontmatter (quoted \"NN-MM\") resolves without frontmatter_mismatch"
+
+# the fix must not blunt genuine-mismatch detection: a phase-prefixed value that
+# disagrees with the canonical id is still rejected.
+make_fixture fm-phase-prefixed-mismatch '"auto"' balanced
+write_state '{"plans":[{"id":"01-01","status":"pending"}],"effort":"balanced","phase_effort":"balanced"}'
+write_plan_inline 01-01-PLAN.md 01 01-02 '[]'
+expect_helper_failure "phase-prefixed frontmatter mismatch (NN-MM disagrees with id) still fails closed"
+
+# multi-digit phase symmetry (QA round 2): a 3-digit phase with a phase-prefixed
+# plan: value (100-01) must still normalize to the canonical id, not 100-100-01.
+# Guards the pad_number/normalize_plan_ref symmetry against future edits. Uses a
+# bespoke fixture because make_fixture/run_helper assume a 2-digit phase dir.
+MD_FIXTURE="$TMPDIR_BASE/fm-multidigit-phase"
+MD_PHASE_DIR="$MD_FIXTURE/.vbw-planning/phases/100-test"
+mkdir -p "$MD_PHASE_DIR" "$MD_FIXTURE/.vbw-planning/.cache"
+printf '{"prefer_teams":"auto","effort":"balanced"}\n' > "$MD_FIXTURE/.vbw-planning/config.json"
+printf '{"plans":[{"id":"100-01","status":"pending"}],"effort":"balanced","phase_effort":"balanced"}\n' > "$MD_FIXTURE/.vbw-planning/.execution-state.json"
+cat > "$MD_PHASE_DIR/100-01-PLAN.md" <<'MDPLAN'
+---
+phase: 100
+plan: "100-01"
+title: Plan 100-01
+depends_on: []
+---
+# Plan 100-01
+
+### Task 1: Work
+- **Files:** `src/file.txt`
+MDPLAN
+md_out=$(cd "$MD_FIXTURE" && "$HELPER" --phase-dir .vbw-planning/phases/100-test)
+assert_eq "$(json_field "$md_out" '.delegation_mode')" "subagent" "multi-digit phase with phase-prefixed plan: (100-01) resolves without frontmatter_mismatch"
+assert_json_array_eq "$(jq -c '.dependency_waves' <<< "$md_out")" '[["100-01"]]' "multi-digit phase-prefixed plan: maps to canonical id 100-01 (no 100-100-01 double-prefix)"
+
 # malformed execution-state / route-map schemas fail closed before spawning
 make_fixture valid-empty-plans '"auto"' balanced
 write_state '{"plans":[],"effort":"balanced","phase_effort":"balanced"}'
diff --git a/tests/worktree.bats b/tests/worktree.bats
index 7e41e0fc..f2508b4e 100644
--- a/tests/worktree.bats
+++ b/tests/worktree.bats
@@ -56,6 +56,28 @@ teardown() {
   [ "$output" = "vbw/02-03" ]
 }
 
+@test "worktree-create: phase-qualified plan id does not double-prefix (regression #659)" {
+  cd "$TEST_TEMP_DIR"
+  git init -q
+  git config user.name "VBW Test"
+  git config user.email "vbw-test@example.com"
+  echo "seed" > README.md
+  git add README.md
+  git commit -q -m "chore(init): seed"
+
+  # Callers pass the already phase-qualified plan id (the form
+  # .execution-state.json and plan filenames use). It must not become 43-43-03.
+  run bash "$SCRIPTS_DIR/worktree-create.sh" 43 43-03
+  [ "$status" -eq 0 ]
+  [[ "$output" == *".vbw-worktrees/43-03" ]]
+  [ -d ".vbw-worktrees/43-03" ]
+  [ ! -d ".vbw-worktrees/43-43-03" ]
+
+  run git -C ".vbw-worktrees/43-03" rev-parse --abbrev-ref HEAD
+  [ "$status" -eq 0 ]
+  [ "$output" = "vbw/43-03" ]
+}
+
 # ---------------------------------------------------------------------------
 # worktree-merge.sh tests
 # ---------------------------------------------------------------------------
@@ -82,6 +104,28 @@ teardown() {
   [ "$output" = "conflict" ]
 }
 
+@test "worktree-merge: phase-qualified plan id targets the un-doubled branch (regression #659)" {
+  cd "$TEST_TEMP_DIR"
+  git init -q
+  git config user.name "VBW Test"
+  git config user.email "vbw-test@example.com"
+  echo "seed" > README.md
+  git add README.md
+  git commit -q -m "chore(init): seed"
+
+  # Work to be merged lives on vbw/43-03, not vbw/43-43-03.
+  git checkout -q -b vbw/43-03
+  echo "feature" > feature.txt
+  git add feature.txt
+  git commit -q -m "feat: work"
+  git checkout -q -
+
+  run bash "$SCRIPTS_DIR/worktree-merge.sh" 43 43-03
+  [ "$status" -eq 0 ]
+  [ "$output" = "clean" ]
+  [ -f feature.txt ]
+}
+
 # ---------------------------------------------------------------------------
 # worktree-cleanup.sh tests
 # ---------------------------------------------------------------------------
@@ -222,6 +266,23 @@ teardown() {
   [ ! -f ".vbw-planning/.agent-worktrees/agent-01-01.json" ]
 }
 
+@test "worktree-cleanup: phase-qualified plan id removes the un-doubled worktree (regression #659)" {
+  cd "$TEST_TEMP_DIR"
+  mkdir -p .vbw-worktrees/43-03/.vbw-planning
+  run bash "$SCRIPTS_DIR/worktree-cleanup.sh" 43 43-03
+  [ "$status" -eq 0 ]
+  [ ! -d ".vbw-worktrees/43-03" ]
+}
+
+@test "worktree-cleanup: phase-qualified plan id clears agent-worktree JSON (regression #659)" {
+  cd "$TEST_TEMP_DIR"
+  mkdir -p .vbw-planning/.agent-worktrees
+  echo '{}' > .vbw-planning/.agent-worktrees/dev-43-03.json
+  run bash "$SCRIPTS_DIR/worktree-cleanup.sh" 43 43-03
+  [ "$status" -eq 0 ]
+  [ ! -f ".vbw-planning/.agent-worktrees/dev-43-03.json" ]
+}
+
 # ---------------------------------------------------------------------------
 # worktree-status.sh tests
 # ---------------------------------------------------------------------------