feat(dev): drain retired dev workers behind the stock Nitro contract

[ctgowrie]

Why

First implementation stage of the stock-Nitro dev-server route (parallel to #760–#778, branched off #759 as the shared foundation). Stock Nitro's dev server already ready-gates reloads and gates admissions — but RunnerManager.reload terminates the previous worker as soon as the next one attaches, resetting every admitted response and socket. That termination is the only gap between stock Nitro and eve's no-reset requirement.

What changed

• DrainedNitroDevServer: keeps the stock dev-server contract (dev:start/dev:reload/dev:error hooks, ready-gated replacement, crash restart) and adds drained replacement — the retired worker keeps serving the responses and websockets it already admitted (unbounded; a streaming turn can hold one for minutes) and is terminated once its last exchange settles, via parent-side exchange accounting. No worker-side protocol needed.
• Requests are served by the active worker throughout rebuilds (no stall), a failed candidate stays invisible behind the previous worker, and shutdown terminates immediately so open streams cannot block exit.
• Workers run on the vendored env-runner node-worker — the same runner stock Nitro uses. The class is deliberately shaped to be deleted once equivalent drain semantics land upstream in Nitro/env-runner (upstream PR to follow).

Tests

Real-server contract suite (dev-server-drain.scenario.test.ts): an admitted stream keeps flowing on the retired worker across a replacement; a kept-alive connection serves across a replacement on the same socket; crash restart; bounded shutdown with an open stream; socket-derived client address despite forged forwarding headers. Class-level suite covers failed-candidate invisibility, drain-on-last-exchange, crash restart, failed-upgrade socket destruction, and idempotent close. The pre-existing dev-server scenario passes unchanged.

Next stages

P3: transactional rebuild coordinator driving stock reloads. P4: Workflow World in the CLI process with latest-per-turn selection. Plan and test-parity matrix tracked in research/dev-stock-nitro-alignment.md (uncommitted).

🤖 Generated with Claude Code

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
eve-docs	Ready	Preview, Comment, Open in v0	Jul 14, 2026 6:51pm

2 Skipped Deployments

Project	Deployment	Actions	Updated (UTC)
eve-docs-1644	Skipped	Open in v0	Jul 14, 2026 6:51pm
eve-docs-4759	Skipped	Open in v0	Jul 14, 2026 6:51pm

[github-actions]

Bundle + Package Summary: apps/fixtures/weather-agent

Key takeaways

• No notable deltas vs main (e0b64a5).

Delta vs main (e0b64a5)

Area	Metric	Baseline	Current	Delta
Package	Packed tarball	3.65 MB	3.69 MB	+34.9 kB ⚠️
Package	Unpacked publish size	13.25 MB	13.35 MB	+105.1 kB ⚠️
Package	Installed footprint	52.51 MB	52.62 MB	+105.1 kB ⚠️
Package	Published files	2557	2572	+15
Package	Installed files	5797	5812	+15
Runtime	Unique function payloads	2	2	0
Runtime	Total function bytes	9.35 MB	9.36 MB	+12.5 kB ⚠️
Runtime	Public routes	9	9	0

Changed function payloads vs main (e0b64a5) (2)

Function	Status	Baseline	Current	Delta	Route changes
functions/.well-known/workflow/v1/flow.func	changed	5.87 MB	5.87 MB	+6.3 kB ⚠️	none
functions/__server.func	changed	3.48 MB	3.49 MB	+6.3 kB ⚠️	none

eve init install

Metric	Baseline	Current	Delta
Installed footprint	90.78 MB	90.88 MB	+105.1 kB ⚠️
Installed packages	122	122	0
dependencies	4	4	0
devDependencies	2	2	0
Dependency package bytes	27.45 MB	27.56 MB	+105.1 kB ⚠️
devDependency package bytes	5.04 MB	5.04 MB	0 B ➖

Build Metadata

• Preset: vercel
• Nitro: [email protected]
• Output directory: apps/fixtures/weather-agent/.vercel/output
• Build metadata timestamp: 2026-07-14T18:51:52.926Z
• Route aliases: 9 public, 1 internal (10 total aliases)
• Vercel routes in config: 10
• Severity legend: 🔴 dominant/large, 🟠 notable, 🟡 watch, ⚪ small

Package Drill-Down

Package Details

• Package: [email protected]
• Package directory: packages/eve
• Tarball: 3.69 MB (eve-0.24.0.tgz)
• Unpacked payload: 13.35 MB across 2572 published files
• Installed footprint: 52.62 MB across 5812 installed files
• Installed root package: 12.08 MB
• Installed dependencies: 40.54 MB
• Runtime dependencies: 1
• Peer dependencies: 5 (4 optional)

Installed footprint is measured from an isolated temporary npm install of the packed tarball.

Heavy installed dependencies

• @rolldown/binding-linux-x64-gnu: 19.13 MB (36.4%)
• eve: 12.08 MB (23.0%)
• ai: 6.39 MB (12.1%)
• zod: 5.04 MB (9.6%)
• nitro: 2.41 MB (4.6%)

Publish payload breakdown

Published file size
🟠 dist/src/compiled/experimental-ai-sdk-code-mo... [####....................] 1.51 MB 11.3%
🟡 dist/src/compiled/@vercel/sandbox/index.js       [#.......................] 622.2 kB 4.7%
🟡 dist/src/compiled/_chunks/workflow/undici-fb5... [#.......................] 502.4 kB 3.8%
🟡 dist/src/compiled/@chat-adapter/slack/index.js   [#.......................] 433.8 kB 3.2%
🟡 dist/src/compiled/_chunks/workflow/dist-Blxny... [#.......................] 277.7 kB 2.1%
🔴 Other published files                            [########################] 10.01 MB 75.0%

Installed footprint breakdown

Installed package size
🔴 @rolldown/binding-linux-x64-gnu [########################] 19.13 MB 36.4%
🔴 eve                             [###############.........] 12.08 MB 23.0%
🔴 ai                              [########................] 6.39 MB 12.1%
🔴 zod                             [######..................] 5.04 MB 9.6%
🟠 nitro                           [###.....................] 2.41 MB 4.6%
🟡 @ai-sdk/provider-utils          [#.......................] 847.4 kB 1.6%
🔴 Other installed packages        [########................] 6.73 MB 12.8%

Runtime dependencies (1)

Package	Range	Notes
nitro	3.0.260610-beta

Peer dependencies (5)

Package	Range	Notes
@opentelemetry/api	^1.0.0	optional peer
ai	catalog:
braintrust	^3.0.0	optional peer
just-bash	^3.0.0	optional peer
microsandbox	^0.5.0	optional peer

eve init install drill-down

eve init install details

• Command: eve init my-agent
• Package manager: npm
• Installed footprint: 90.88 MB across 7630 installed files
• Installed packages: 122 total (116 transitive-only)
• dependencies: 4 direct packages totaling 27.56 MB
• devDependencies: 2 direct packages totaling 5.04 MB
• Other transitive package files: 58.28 MB

Installed footprint is measured from an isolated temporary eve init my-agent using the current packed eve tarball.

Heavy installed dependencies

• @typescript/typescript-linux-x64: 27.95 MB (30.8%)
• @rolldown/binding-linux-x64-gnu: 19.13 MB (21.1%)
• eve: 12.08 MB (13.3%)
• zod: 9.00 MB (9.9%)
• ai: 6.39 MB (7.0%)

Installed footprint breakdown

Installed package size
🔴 @typescript/typescript-linux-x64 [########################] 27.95 MB 30.8%
🔴 @rolldown/binding-linux-x64-gnu  [################........] 19.13 MB 21.1%
🔴 eve                              [##########..............] 12.08 MB 13.3%
🔴 zod                              [########................] 9.00 MB 9.9%
🔴 ai                               [#####...................] 6.39 MB 7.0%
🟠 @types/node                      [##......................] 2.54 MB 2.8%
🔴 Other installed packages         [############............] 13.80 MB 15.2%

dependencies (4)

Package	Range	Installed size	Share
@vercel/connect	0.2.2	98.6 kB	0.1%
ai	^7.0.26	6.39 MB	7.0%
eve	file:eve-0.24.0.tgz	12.08 MB	13.3%
zod	4.4.3	9.00 MB	9.9%

devDependencies (2)

Package	Range	Installed size	Share
@types/node	24.x	2.54 MB	2.8%
typescript	7.0.2	2.50 MB	2.7%

Function Drill-Down

Payload Size Graph

Unique function payload size and share of total
🔴 functions/.well-known/workflow/v1/flow.func     [########################] 5.87 MB 62.7%
🟠 functions/__server.func                         [##############..........] 3.49 MB 37.3%

Top Function Payloads

🟠 functions/.well-known/workflow/v1/flow.func • 1 public route • 5.87 MB

Metric	Value
Public routes	/.well-known/workflow/v1/flow
Runtime	nodejs24.x
Handler	index.mjs
Payload	5.87 MB
Function files	5.87 MB across 36 files
Traced dependencies	0 B
Signal	🟠 Bundled file __eve_nitro_handler__.mjs is 2.18 MB (37.1%)

🟠 🔎 Dependency Analysis

📦 Bundled files:

Bundled file size
🟠 __eve_nitro_handler__.mjs       [########################] 2.18 MB 37.1%
🟡 _chunks/world-vercel.mjs        [#########...............] 826.4 kB 14.1%
🟡 _chunks/sandbox.mjs             [########................] 754.9 kB 12.9%
🟡 _libs/@ai-sdk/gateway+[...].mjs [#####...................] 430.4 kB 7.3%
🟡 _chunks/dist-Blxnyb7-.mjs       [####....................] 349.1 kB 5.9%
🟠 Other bundled files             [###############.........] 1.33 MB 22.7%

🧾 Vercel Config

{
  "handler": "index.mjs",
  "launcherType": "Nodejs",
  "shouldAddHelpers": false,
  "supportsResponseStreaming": true,
  "runtime": "nodejs24.x",
  "environment": {
    "NODE_OPTIONS": "--experimental-require-module"
  },
  "maxDuration": "max",
  "experimentalTriggers": [
    {
      "type": "queue/v2beta",
      "topic": "__eve776561746865722d6167656e74_wkf_workflow_*",
      "consumer": "default",
      "retryAfterSeconds": 5,
      "initialDelaySeconds": 0
    }
  ]
}

---

🟠 functions/__server.func • 8 public routes, 1 internal alias • 3.49 MB

Metric	Value
Public routes	/ /eve/v1/callback/[token] /eve/v1/connections/[name]/callback/[token] /eve/v1/health /eve/v1/info /eve/v1/session /eve/v1/session/[sessionId] /eve/v1/session/[sessionId]/stream
Internal aliases	/__server
Runtime	nodejs24.x
Handler	index.mjs
Payload	3.49 MB
Function files	3.49 MB across 26 files
Traced dependencies	0 B
Signal	🟠 Bundled file _chunks/runtime-artifacts.mjs is 942.0 kB (27.0%)

🟠 🔎 Dependency Analysis

📦 Bundled files:

Bundled file size
🟠 _chunks/runtime-artifacts.mjs [########################] 942.0 kB 27.0%
🟠 _chunks/world-vercel.mjs      [#####################...] 826.4 kB 23.7%
🟠 _chunks/sandbox.mjs           [###################.....] 754.9 kB 21.6%
🟡 _chunks/dist-Blxnyb7-.mjs     [#########...............] 348.1 kB 10.0%
⚪ _libs/zod.mjs                 [###.....................] 114.2 kB 3.3%
🟡 Other bundled files           [#############...........] 503.0 kB 14.4%

🧾 Vercel Config

{
  "handler": "index.mjs",
  "launcherType": "Nodejs",
  "shouldAddHelpers": false,
  "supportsResponseStreaming": true,
  "runtime": "nodejs24.x"
}

[ctgowrie]

Folded into #787 — the rebuild coordinator (originally here as a follow-up) is what gives the drained server its final shape, so the two ship as one PR. The intermediate hook-driven wiring this PR carried was deleted by that reshaping and had no standalone value.