# drive-plugin-chunks spec delta — DTP-25 (inline-sig)

## ADDED Requirements

### Requirement: Inline hint signed over fileId ‖ bytes

`FileLocation.storageHints` entries with `kind: 'inline'` SHALL be
`{ kind: 'inline'; bytes: Uint8Array; sig: Uint8Array }` where
`sig = Ed25519-sign(driveSecretKey, fileId ‖ bytes)`. The drive
SHALL verify the signature before returning `bytes`; failure SHALL
throw `CHUNKS.INLINE_SIG_INVALID`.

The verifier SHALL be Ed25519 over the canonical concatenation
exposed by `inlineSigningInput(fileId, bytes)`. A tampered signature,
tampered bytes, replay onto a different `fileId`, or signature
produced under a different key SHALL all reject with
`CHUNKS.INLINE_SIG_INVALID`.

The `verifyInlineHint` function SHALL accept an optional
`VerifyEd25519Fn` parameter so engine-substitution scenarios where a
native verifier throws (rather than returning false) compose cleanly.
When the injected verifier throws, the implementation SHALL wrap the
exception as `CHUNKS.INLINE_SIG_INVALID` with the original error
attached as `cause`.

**Verified by:** `tests/inline-file-sig.test.ts`::"inline file with
valid sig reads successfully" AND "inline file with bad sig throws
INLINE_SIG_INVALID" AND "sig bound to fileId — replay onto a
different fileId rejects" AND "byte tamper rejects with
INLINE_SIG_INVALID" AND "rejects under a different public key" AND
"verify catch arm wraps a throwing verifier".

### Requirement: Legacy inline hints accepted with rewrite-on-write

Drives reading old-format inline entries (no `sig` field) SHALL
accept them via the `LegacyInlineHint` shape and SHALL emit a
`drive:inline:legacy` warning event. `isLegacyInlineHint(hint)` SHALL
discriminate the two wire shapes (legacy vs signed). On the next
write that touches such a hint, `upgradeLegacyInlineHint(legacy,
fileId, driveSecretKey)` SHALL produce a signed `InlineHint` so the
upgrade lands at-rest and subsequent reads no longer trigger the
legacy warning.

**Verified by:** `tests/inline-file-sig.test.ts`::"old-format inline
reads with warning AND rewrites with sig on next write" AND
"isLegacyInlineHint distinguishes signed from legacy hints".

### Requirement: Canonical signing input exposed

`inlineSigningInput(fileId: Uint8Array, bytes: Uint8Array)` SHALL
return `concat(fileId, bytes)` as a freshly-allocated `Uint8Array`.
Any consumer that wants to re-derive the bytes that are signed (for
auditing, alternate-keypath signing, or cross-checking against a
hardware signer) SHALL use this function.

**Verified by:** `tests/inline-file-sig.test.ts`::"inlineSigningInput
is the canonical fileId ‖ bytes concatenation".