molecule-core/workspace-server/cmd/memory-backfill
Hongming Wang 656a02fae4 fix(textutil): SSOT for rune-safe string truncation, fix 3 audit-gap bugs
Closes #2962.

## Why

Six per-package `truncate` helpers had drifted into independent
re-implementations of the same idea. Three of them (delegation.go,
memory/client/client.go, memory-backfill/verify.go) used
`s[:max] + "…"` byte-slice form, which on a multi-byte codepoint at
byte `max` produces invalid UTF-8 → Postgres `text`/`jsonb` rejects
the INSERT silently → `delegation` / `activity_logs` row never lands
→ audit gap.

Three other helpers (delegation_ledger.go #2962, agent_message_writer.go
#2959, scheduler.go #2026) had each been fixed in isolation with three
slightly different rune-safe shapes — confirming this is a class of
bug, not a single instance.

## What

New package `internal/textutil` with three rune-safe functions:

- `TruncateBytes(s, maxBytes)` — byte-cap, "…" marker. Used by 5
  callers writing into byte-bounded columns / log lines.
- `TruncateBytesNoMarker(s, maxBytes)` — byte-cap, no marker. Used by
  delegation_ledger.go where the storage already conveys "preview"
  and an extra ellipsis would push the result over the column cap.
- `TruncateRunes(s, maxRunes)` — rune-cap, "…" marker. Used by
  agent_message_writer.go where the cap is in display chars (UI
  summary), not bytes.

All three guarantee `utf8.ValidString(out)` for any `utf8.ValidString(in)`.
Inputs already invalid go through `sanitizeUTF8` at the call site
boundary (scheduler.go preserved this defense-in-depth).

## Migration map

| Old | New | Behavior change |
|---|---|---|
| `delegation_ledger.truncatePreview` | `textutil.TruncateBytesNoMarker(s, 4096)` | none |
| `agent_message_writer.truncatePreviewRunes` | `textutil.TruncateRunes(s, n)` | none |
| `scheduler.truncate` | `textutil.TruncateBytes(s, n)` | "..." → "…" (3 bytes either way; single-glyph display) |
| `delegation.truncate` | `textutil.TruncateBytes(s, n)` | bug fix + ellipsis swap |
| `memory/client.truncate` | `textutil.TruncateBytes(s, n)` | bug fix |
| `memory-backfill.truncate` | `textutil.TruncateBytes(s, n)` | bug fix |

Five separate `truncate*` helpers + their per-package tests removed.
Net: 12 files / +427 / -255.

## Tests

- `internal/textutil/truncate_test.go` — 27 table-test cases + 145
  fuzz-invariant cases asserting `utf8.ValidString` and byte-cap
  invariants on every output.
- `delegation_ledger_test.go TestLedgerInsert_TruncatesOversizedPreview`
  strengthened with `capValidUTF8Matcher` so the SQL-write argument
  is asserted to be valid UTF-8 + within cap (not just `AnyArg()`).
  Mutation-tested: replacing the SSOT call with byte-slice form makes
  this test fail loud.

## Compatibility

- All callers internal; no external API surface change.
- Ellipsis swap "..." → "…": same byte budget (3 bytes), single-glyph
  display. No alerting/grep on either marker in this codebase
  (verified). Canvas renders both correctly.
- DB column widths unchanged (4096 / 80 / 200 / 256 / 300 — all
  preserved in the migrations).

## Security

Fixes a silent INSERT-failure mode that hid `activity_logs` /
`delegations` rows containing peer-controlled text. The class of input
that triggered it (CJK, emoji, accented Latin) is normal user content,
not malicious — but the symptom (audit gap) makes incident
reconstruction harder. Helper is pure-function over `string`; no
secrets / PII / auth handling involved. Untrusted input is handled
identically to before, just rune-aligned now.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
2026-05-05 23:01:21 -07:00
..
main_test.go Memory v2 fixup C1: backfill idempotency via MemoryWrite.id 2026-05-04 08:54:13 -07:00
main.go Merge pull request #2747 from Molecule-AI/fix/memory-v2-c2-backfill-verify 2026-05-04 16:08:27 +00:00
verify_test.go fix(textutil): SSOT for rune-safe string truncation, fix 3 audit-gap bugs 2026-05-05 23:01:21 -07:00
verify.go fix(textutil): SSOT for rune-safe string truncation, fix 3 audit-gap bugs 2026-05-05 23:01:21 -07:00