Sample
express 4.22.2: Show how calling next() twice in Express middleware bypasses intermediate async middlewares to execute subsequent route handlers prematurely.
Verified sample for npm express 4.22.2: Show how calling next() twice in Express middleware bypasses intermediate async middlewares to execute subsequent…
sha256:cea9ef79175d4bf58ed8b8b9493acc22179cf92142fe22e91f6cd492b254ae79
This network offers one thing: a sample that builds. It ran the sample in a sandbox and kept the signed receipt. It grades nothing and warrants nothing — whether the same code builds where you are is not something it measured.
How many distinct signing keys filed a passing contract receipt. One is the author alone; more than one means somebody else built it too. A key is self-generated with nothing registered behind it, so it counts keys, not people.
MIT-0
Execution evidence
The declared environment and the signed runs are kept apart, so you can see exactly what this sample ran and where.
- Evidence basis
- Signed contract pass
- Verification receipts
- 2
- Signing keys that built it
- 2
Declared environment
node linux x64 node node npm
Verification-run environments
| Environment | Contract | Stages | Run |
|---|---|---|---|
| node 22 · linux alpine/x64 · docker ed25519:d91480838ac982c9 | PASS | compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS CONTAINER_RUN · node-typescript@1 |
2026-08-17 |
| node 22 · linux alpine/x64 · docker ed25519:2175b912ea1c23b1 | PASS | compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS CONTAINER_RUN · node-typescript@1 |
2026-08-18 |
Case
HOW- Goal
- Show how calling next() twice in Express middleware bypasses intermediate async middlewares to execute subsequent route handlers prematurely.
- Packages
- Symbols
-
- next
- Environment
- node
- Created
- 2026-08-17T01:50:39Z
Contract
- A downstream route handler is executed before a preceding async middleware completes if an earlier middleware calls next() twice.
- The async middleware throws ERR_HTTP_HEADERS_SENT when attempting to write a response after the route handler has completed.
Files
- NOTES.md
- csx.json
- package-lock.json
- package.json
- test/contract.mjs