diff --git a/.github/workflows/labels-sweep.yml b/.github/workflows/labels-sweep.yml
index defca41..760590b 100644
--- a/.github/workflows/labels-sweep.yml
+++ b/.github/workflows/labels-sweep.yml
@@ -34,6 +34,19 @@ name: labels-sweep
 on:
   workflow_call:
     inputs:
+      bootstrap:
+        description: >-
+          Bootstrap the label taxonomy before sweeping. The CALLER passes
+          this through from its own workflow_dispatch input; a called
+          workflow cannot read the caller's dispatch inputs on every forge
+          (Forgejo drops them at the workflow_call boundary — ceremony#215,
+          probe runs 6/7 vs merged runs 459/523), so the value must arrive
+          through this declared boundary, never via github.event.inputs.
+          Absent means "no": an event- or cron-woken sweep must never
+          re-upsert ~20 labels.
+        type: string
+        required: false
+        default: "no"
       pr_workflow_name:
         description: >-
           The `name:` of the consumer's PR-facing labels caller, exported
@@ -86,18 +99,21 @@ jobs:
       # papers over for `run:` steps, which composite `uses:` has no
       # equivalent of.
       #
-      # bootstrap: every trigger-driven wake arrives as workflow_dispatch
-      # too (that is how the trigger's dispatch wakes the caller), so the event
-      # name alone no longer separates the operator's manual full-board
-      # bootstrap from an event-woken sweep — the caller's `bootstrap`
-      # dispatch input does: the trigger passes "no", a bare manual
-      # dispatch defaults to "yes". A caller reached on any other event
-      # (the cron) has no input and stays "no".
+      # bootstrap: read from the DECLARED workflow_call input and nothing
+      # else. The old gate read `github.event.inputs.bootstrap` from inside
+      # this called workflow — which Forgejo leaves empty at the
+      # workflow_call boundary even though the top-level caller receives the
+      # value in both contexts (ceremony#215; probe runs 6/7 measured the
+      # boundary, merged runs 459/523 paid for it: every dispatch-woken
+      # sweep bootstrapped). The caller passes the value through
+      # `with.bootstrap`; anything not exactly "yes" is fed through for
+      # labels-reconcile's own yes|no validation to judge, so a typo refuses
+      # loudly instead of silently bootstrapping.
       - name: reconcile state + stale
         if: github.repository != 'heavy-duty/ceremony'
         uses: ./.ceremony-src/actions/labels-reconcile
         with:
-          bootstrap: ${{ github.event_name == 'workflow_dispatch' && github.event.inputs.bootstrap != 'no' && 'yes' || 'no' }}
+          bootstrap: ${{ inputs.bootstrap }}
         env:
           GH_TOKEN: ${{ github.token }}
           REPO: ${{ github.repository }}
@@ -106,7 +122,7 @@ jobs:
         if: github.repository == 'heavy-duty/ceremony'
         uses: ./actions/labels-reconcile
         with:
-          bootstrap: ${{ github.event_name == 'workflow_dispatch' && github.event.inputs.bootstrap != 'no' && 'yes' || 'no' }}
+          bootstrap: ${{ inputs.bootstrap }}
         env:
           GH_TOKEN: ${{ github.token }}
           REPO: ${{ github.repository }}
diff --git a/.github/workflows/self-labels-sweep.yml b/.github/workflows/self-labels-sweep.yml
index 94ae4a3..e2dcca3 100644
--- a/.github/workflows/self-labels-sweep.yml
+++ b/.github/workflows/self-labels-sweep.yml
@@ -44,3 +44,10 @@ jobs:
     # pr_workflow_name keeps its default: ceremony's PR-facing caller is
     # named `labels` (self-labels.yml).
     uses: ./.github/workflows/labels-sweep.yml
+    with:
+      # The dispatch input crosses the workflow_call boundary HERE, or not at
+      # all: the called workflow cannot read this caller's dispatch inputs on
+      # this forge (ceremony#215). On `schedule` the top-level context is
+      # empty, and empty maps to "no" EXPLICITLY — a cron that bootstraps is
+      # the failure kimi named before it could exist.
+      bootstrap: ${{ inputs.bootstrap || 'no' }}
diff --git a/changelog.d/215.md b/changelog.d/215.md
new file mode 100644
index 0000000..d94f219
--- /dev/null
+++ b/changelog.d/215.md
@@ -0,0 +1,29 @@
+### Fixed
+
+- The sweep's `bootstrap` value crosses the `workflow_call` boundary as a
+  declared input passed by the caller — a called workflow cannot read the
+  caller's dispatch inputs on this forge (#215).
+
+- Before the bridge, `github.event.inputs` was empty inside the called
+  workflow, so every dispatch-woken sweep bootstrapped: ~20 label upserts on
+  each board event (#215).
+
+- The caller maps an empty top-level value to `no` explicitly, so a
+  cron-woken sweep can never bootstrap; the declared input also defaults to
+  `no`, so a consumer that passes nothing gets the safe path (#215).
+
+- The gate feeds the declared input to `labels-reconcile` unchanged, so an
+  invalid value meets the action's own `yes|no` refusal instead of being
+  silently coerced (#215).
+
+- `docs/CONSUMERS.md`'s published sweep stub carries the same pass-through —
+  without it every consumer inherits the defect ceremony fixed for
+  itself (#215).
+
+### Added
+
+- `test/labels-bootstrap.test.sh` pins the bridge at every hop: the declared
+  boundary, both gate sites as the identity, no expression reading
+  `github.event.inputs`, the caller and stub pass-throughs byte-exact, and
+  the four value paths driven through the shipped expressions into the
+  action's real validator (#215).
diff --git a/docs/CONSUMERS.md b/docs/CONSUMERS.md
index e5a3d59..e5153f6 100644
--- a/docs/CONSUMERS.md
+++ b/docs/CONSUMERS.md
@@ -458,8 +458,14 @@ permissions:
 jobs:
   sweep:
     uses: heavy-duty/ceremony/.github/workflows/labels-sweep.yml@<pinned-tag>
+    with:
+      # Pass the dispatch input through the workflow_call boundary — the
+      # called workflow cannot read this caller's dispatch inputs on every
+      # forge (ceremony#215). Empty (schedule) maps to "no" explicitly, so a
+      # cron-woken sweep never re-upserts the taxonomy.
+      bootstrap: ${{ inputs.bootstrap || 'no' }}
     # If this repo's PR-facing labels caller is named anything but `labels`,
-    # pass that name: `with: { pr_workflow_name: <name> }`. The sweep exports
+    # pass that name alongside: `pr_workflow_name: <name>`. The sweep exports
     # it as SELF_WORKFLOW so the label machinery's own check entries (scope,
     # trigger) never count toward blocker:ci-red — a red trigger means "fix
     # the caller", which no PR edit can do (#208 reads it).
diff --git a/test/labels-bootstrap.test.sh b/test/labels-bootstrap.test.sh
new file mode 100755
index 0000000..f8c0158
--- /dev/null
+++ b/test/labels-bootstrap.test.sh
@@ -0,0 +1,93 @@
+#!/usr/bin/env bash
+# The bootstrap bridge across the workflow_call boundary (#215).
+#
+# The defect: a called workflow cannot read the caller's dispatch inputs on
+# this forge — `github.event.inputs.*` is empty inside `workflow_call` even
+# though the top-level caller receives the value in both contexts (probe runs
+# 6/7). The old gate read exactly that, so every dispatch-woken sweep
+# bootstrapped (runs 459/523). The fix moves the value through a DECLARED
+# `workflow_call` input, passed by the caller, with empty mapped to "no" at
+# the caller so a cron can never bootstrap.
+#
+# These cases pin the wiring at every hop and drive the four value paths
+# through the semantics of the exact expressions shipped — extracted from the
+# YAML, never retyped, so an edited expression is an edited test input.
+set -uo pipefail
+
+ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+# shellcheck source=test/harness.sh
+. "$ROOT/test/harness.sh"
+
+REUSABLE="$ROOT/.github/workflows/labels-sweep.yml"
+CALLER="$ROOT/.github/workflows/self-labels-sweep.yml"
+CONSUMERS="$ROOT/docs/CONSUMERS.md"
+
+# --- the declared boundary ---------------------------------------------------
+decl() { yq -r ".on.workflow_call.inputs.bootstrap.$1 // \"\"" "$REUSABLE"; }
+declares_boundary() { [ -n "$(yq -r '.on.workflow_call.inputs.bootstrap // ""' "$REUSABLE")" ]; }
+check "labels-sweep.yml declares bootstrap as a workflow_call input" 0 "" declares_boundary
+check "...typed string" 0 "string" decl type
+check "...defaulting to no — an absent pass-through must never bootstrap" 0 "no" \
+  decl default
+
+# --- the gate reads the declared input, and nothing else ---------------------
+gate_exprs() { yq -r '.jobs[].steps[] | select(.with.bootstrap != null) | .with.bootstrap' "$REUSABLE"; }
+gates_are_identity() {
+  [ "$(gate_exprs | sort -u)" = "\${{ inputs.bootstrap }}" ] \
+    && [ "$(gate_exprs | wc -l)" -eq 2 ]
+}
+check "both gate sites feed the DECLARED input, unchanged" 0 "" gates_are_identity
+# The forbidden context is only live inside an expression: the file NAMES it
+# in comments and in the declared input's description to explain the defect,
+# and both are prose. Matching raw text asserted on the explanation — the
+# adjacent-assertion trap this suite keeps re-learning — so the predicate is
+# scoped to `${{ … }}` bodies.
+reads_event_inputs() { grep -qE '\$\{\{[^}]*github\.event\.inputs' "$REUSABLE"; }
+check "no expression in the reusable reads github.event.inputs — the context this forge empties" 1 "" \
+  reads_event_inputs
+
+# --- the caller passes it through, empty mapped to no ------------------------
+CALLER_EXPR="$(yq -r '.jobs.sweep.with.bootstrap // ""' "$CALLER")"
+check "self-labels-sweep.yml passes with.bootstrap through the boundary" 0 "" \
+  test -n "$CALLER_EXPR"
+check "...with the exact empty-guard expression" 0 "" \
+  test "$CALLER_EXPR" = "\${{ inputs.bootstrap || 'no' }}"
+
+# The published stub must carry the same bridge, or every consumer inherits
+# the defect ceremony just fixed for itself.
+check "the CONSUMERS.md sweep stub passes bootstrap through the boundary" 0 \
+  "bootstrap: \${{ inputs.bootstrap || 'no' }}" \
+  grep -F "bootstrap: \${{ inputs.bootstrap || 'no' }}" "$CONSUMERS"
+
+# --- the four value paths, through the shipped expressions -------------------
+# Evaluate the caller expression's semantics for a given top-level value. The
+# expression is asserted byte-exact above, so modelling `x || 'no'` here is
+# modelling the string the tree actually ships, not a hope about it.
+caller_pass() { [ -n "$1" ] && printf '%s' "$1" || printf 'no'; }
+# The reusable's gate is asserted to be the identity; the value then meets
+# actions/labels-reconcile's REAL validate step, extracted and executed.
+VALIDATE="$(mktemp)"
+trap 'rm -f "$VALIDATE"' EXIT
+{
+  printf '%s\n' '#!/usr/bin/env bash'
+  yq -r '.runs.steps[] | select(.name == "validate bootstrap input") | .run' \
+    "$ROOT/actions/labels-reconcile/action.yml"
+} >"$VALIDATE"
+chmod +x "$VALIDATE"
+path() { BOOTSTRAP="$(caller_pass "$1")" bash "$VALIDATE"; }
+
+check "schedule (empty top-level context) validates as a non-bootstrap sweep" 0 "" path ""
+check "a REST event wake passing no validates as a non-bootstrap sweep" 0 "" path no
+check "a manual dispatch passing yes validates as a bootstrap" 0 "" path yes
+invalid_path() { BOOTSTRAP="maybe" bash "$VALIDATE"; }
+check "an invalid value reaches the validator UNSANITIZED and refuses" 2 \
+  "bootstrap must be 'yes' or 'no'" invalid_path
+
+# ...and the non-bootstrap/bootstrap split is what the validator's callers
+# act on: prove the two accepted values are distinguished, not merely both
+# accepted, by pinning what each resolves to after the caller pass.
+check "empty and no resolve identically — the cron can never bootstrap" 0 "" \
+  test "$(caller_pass "")" = "$(caller_pass no)"
+check "...and yes stays yes through the pass" 0 "" test "$(caller_pass yes)" = yes
+
+summary