Breez 0.23 exposes mobile exit construction but deliberately leaves execution to the integrator

What the evidence shows

Technical and product details

1. New SDK capability

   Breez 0.23.0 exposes prepare, construct, export, and import operations through its Flutter-facing SDK. 1

   Supporting material shown on this page

   Breez 0.23 Flutter exit APIPinned source code · github.com · checked 2026-08-24

   95        let signer = breez_sdk_spark::signer::SingleKeySigner::new(signer_secret_key)
   96            .map_err(|e| SdkError::Generic(format!("Invalid signer key: {e}")))?;
   97        self.inner.unilateral_exit(request, Arc::new(signer)).await
   98    }
   99
   100    /// Builds and signs the unilateral exit with a caller-provided signer. The
   101    /// `sign_psbt` callback receives the serialized CPFP PSBT, signs the inputs

2. Execution fact

   Breez's own guide says the SDK never broadcasts. The integrator must persist the returned plan, submit zero-fee parents with CPFP children to a package-relay-capable node, wait for confirmations and CSV timelocks, resume over several days, and broadcast the final sweep. 3

   Supporting material shown on this page

   Breez 0.23 broadcast procedurePinned source code · github.com · checked 2026-08-24

   110The **fan-out** and the **sweep** are the exceptions: each pays its own fee and has no CPFP child ({{#name cpfp_tx_hex}} is unset), so you broadcast it **alone**, as an ordinary transaction, anywhere — including a public endpoint such as `POST https://mempool.space/api/tx`. Most public broadcast API
   111
   112### Wait for each step to confirm
   113
   114Within a branch you broadcast one package, wait for it to confirm, then broadcast the next. This is a mempool relay limit, not a Bitcoin consensus rule: nodes relay an unconfirmed parent with at most one unconfirmed child (the "one-parent-one-child", or 1P1C, package), so a second still-unconfirmed 

3. Mobile consequence

   These are important recovery primitives, but they are not a consumer recovery workflow. A wallet must still supply external fee UTXOs, signing, package relay, durable monitoring, retries, and usable failure handling. 23

   Supporting material shown on this page

   Breez 0.23 exit prerequisitesPinned source code · github.com · checked 2026-08-24

   11Three things are important to know before you build an exit:
   12
   13- **The exit data has to already be on the device.** Quoting and building an exit read each leaf's pre-signed transactions from local storage, so both work with the operators unreachable. What they cannot do is obtain that data: a leaf can be exited this way only once it has been synced at least onc
   14- **You pay the fees from your own UTXO.** The pre-signed transactions carry no fee, so each is fee-bumped with a child transaction (CPFP) funded by a Bitcoin UTXO you provide. That UTXO must be **native SegWit** (a witness-program script). P2WPKH and P2TR are handled by the built-in signer; any oth
   15- **You broadcast the transactions yourself.** The SDK builds and signs the full set but never broadcasts. You send them to the network over time, in order, as their timelocks mature. See [Broadcasting the transactions](#broadcast-the-transactions).

   Breez 0.23 broadcast procedurePinned source code · github.com · checked 2026-08-24

   110The **fan-out** and the **sweep** are the exceptions: each pays its own fee and has no CPFP child ({{#name cpfp_tx_hex}} is unset), so you broadcast it **alone**, as an ordinary transaction, anywhere — including a public endpoint such as `POST https://mempool.space/api/tx`. Most public broadcast API
   111
   112### Wait for each step to confirm
   113
   114Within a branch you broadcast one package, wait for it to confirm, then broadcast the next. This is a mempool relay limit, not a Bitcoin consensus rule: nodes relay an unconfirmed parent with at most one unconfirmed child (the "one-parent-one-child", or 1P1C, package), so a second still-unconfirmed 

Scope control

What this does not establish

• This corrects the earlier finding that Breez exposed no public mobile exit API. It does not diminish the new API: a prepared integrator can build a real operatorless exit. The narrower finding is that the SDK explicitly does not complete or operate that exit for a mobile user. 13

Sources and excerpts

Primary sources

The relevant details and available source-code excerpts appear alongside the claims above. This list preserves the complete original-source trail for independent verification.