diff --git a/docs/development/current/main/10-Now.md b/docs/development/current/main/10-Now.md
index 75709578..1c8fd42b 100644
--- a/docs/development/current/main/10-Now.md
+++ b/docs/development/current/main/10-Now.md
@@ -3,7 +3,7 @@
 ## Current Focus
 
 - Phase: `docs/development/current/main/phases/phase-29aq/README.md`
-- Next: Phase 29aq P0 (inventory, docs-first)
+- Next: Phase 29aq P1 (stdlib subset additions)
 
 ## Gate (SSOT)
 
diff --git a/docs/development/current/main/30-Backlog.md b/docs/development/current/main/30-Backlog.md
index 90d5045c..1a4cae7f 100644
--- a/docs/development/current/main/30-Backlog.md
+++ b/docs/development/current/main/30-Backlog.md
@@ -5,7 +5,7 @@ Scope: 「次にやる候補」を短く列挙するメモ。入口は `docs/dev
 
 ## Active
 
-- Phase 29aq: `docs/development/current/main/phases/phase-29aq/README.md` (Next: P0 inventory)
+- Phase 29aq: `docs/development/current/main/phases/phase-29aq/README.md` (Next: P1 subsets)
 - JoinIR regression gate SSOT: `docs/development/current/main/phases/phase-29ae/README.md`
 - CorePlan hardening (docs-first): `docs/development/current/main/phases/phase-29al/README.md`
 
diff --git a/docs/development/current/main/design/coreplan-migration-roadmap-ssot.md b/docs/development/current/main/design/coreplan-migration-roadmap-ssot.md
index 1fb301a5..1b27a8cf 100644
--- a/docs/development/current/main/design/coreplan-migration-roadmap-ssot.md
+++ b/docs/development/current/main/design/coreplan-migration-roadmap-ssot.md
@@ -34,7 +34,7 @@ Related:
 ## 1.1 Current (active)
 
 - Active phase: `docs/development/current/main/phases/phase-29aq/README.md`
-- Next step: Phase 29aq P0 (stdlib loop inventory)
+- Next step: Phase 29aq P1 (stdlib subset additions)
 
 ## 2. すでに固めた SSOT（再発防止の土台）
 
diff --git a/docs/development/current/main/phases/phase-29aq/P1-INDEXOF-PARSEINT-SPLIT-SUBSET-INSTRUCTIONS.md b/docs/development/current/main/phases/phase-29aq/P1-INDEXOF-PARSEINT-SPLIT-SUBSET-INSTRUCTIONS.md
new file mode 100644
index 00000000..b87f0d74
--- /dev/null
+++ b/docs/development/current/main/phases/phase-29aq/P1-INDEXOF-PARSEINT-SPLIT-SUBSET-INSTRUCTIONS.md
@@ -0,0 +1,91 @@
+---
+Status: Planned
+Scope: stdlib subsets (index_of/last_index_of, parse_integer, split)
+Related:
+- docs/development/current/main/phases/phase-29aq/README.md
+- docs/development/current/main/phases/phase-29ae/README.md
+---
+
+# Phase 29aq P1: stdlib subsets (index_of/last_index_of, parse_integer, split)
+
+Goal: add minimal subsets for three stdlib loops, with fixtures and gate smokes.
+Order is fixed: index_of/last_index_of → parse_integer → split.
+
+## P1-1: index_of / last_index_of (ScanWithInit)
+
+Target: `apps/lib/json_native/utils/string.hako`
+
+- `index_of(s, ch)`:
+  - loop(i < s.length())
+  - if s.substring(i, i + 1) == ch { return i }
+  - i = i + 1
+  - return -1
+- `last_index_of(s, ch)`:
+  - loop(i >= 0)
+  - if s.substring(i, i + 1) == ch { return i }
+  - i = i - 1
+  - return -1
+
+Subset policy:
+
+- ScanWithInit facts only; no new CorePlan vocabulary.
+- Return-in-loop is allowed only for immediate `return i` with literal fallback at end.
+- Facts normalize `>= 0` reverse step to existing scan shape if possible; otherwise Ok(None).
+
+Fixtures/smokes:
+
+- `apps/tests/phase29aq_string_index_of_min.hako`
+- `apps/tests/phase29aq_string_last_index_of_min.hako`
+- `tools/smokes/v2/profiles/integration/joinir/phase29aq_string_index_of_min_vm.sh`
+- `tools/smokes/v2/profiles/integration/joinir/phase29aq_string_last_index_of_min_vm.sh`
+- Wire both into `tools/smokes/v2/profiles/integration/joinir/phase29ae_regression_pack_vm.sh`
+
+## P1-2: parse_integer (Pattern2Break)
+
+Target: `apps/lib/json_native/utils/string.hako`
+
+- loop(i < s.length())
+- d = this.index_of(digits, ch)
+- if d < 0 { break }
+- acc = acc * 10 + d
+- i = i + 1
+- return acc / neg handling at end
+
+Subset policy:
+
+- Pattern2Break facts only; keep break-only (no continue).
+- Keep existing “not is_digit” normalization rules; no new UnaryOp.
+- If neg handling is present, allow a final `return 0 - acc` literal expression only.
+
+Fixtures/smokes:
+
+- `apps/tests/phase29aq_string_parse_integer_min.hako`
+- `tools/smokes/v2/profiles/integration/joinir/phase29aq_string_parse_integer_min_vm.sh`
+- Wire into `phase29ae_regression_pack_vm.sh`
+
+## P1-3: split (SplitScan)
+
+Target: `apps/lib/json_native/utils/string.hako`
+
+- loop(i <= s.length() - separator.length())
+- if s.substring(i, i + separator.length()) == separator { push segment; i = start }
+- else { i = i + 1 }
+- final push after loop
+
+Subset policy:
+
+- SplitScan facts only; no value-join handling in this phase.
+- Only allow `separator.length() > 0` path (empty separator returns early).
+- If step join/value_join is required, return Ok(None) (do not Freeze).
+
+Fixtures/smokes:
+
+- `apps/tests/phase29aq_string_split_min.hako`
+- `tools/smokes/v2/profiles/integration/joinir/phase29aq_string_split_min_vm.sh`
+- Wire into `phase29ae_regression_pack_vm.sh`
+
+## Verification (required when code lands)
+
+- `cargo build --release`
+- `./tools/smokes/v2/run.sh --profile quick`
+- `./tools/smokes/v2/profiles/integration/joinir/phase29ae_regression_pack_vm.sh`
diff --git a/docs/development/current/main/phases/phase-29aq/README.md b/docs/development/current/main/phases/phase-29aq/README.md
index 69525634..0b1ee35a 100644
--- a/docs/development/current/main/phases/phase-29aq/README.md
+++ b/docs/development/current/main/phases/phase-29aq/README.md
@@ -54,4 +54,4 @@ Plan/Composer subsets (or mark unsupported) before adding new subsets.
 
 ## Next (planned)
 
-- P1: Pick top 3 subset candidates from the table and define fixtures/smokes.
+- P1: Add stdlib subsets in priority order (index_of/last_index_of → parse_integer → split).