fix(eve): preserve MCP HTTP errors after failed SSE fallback - #2047
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Bundle + Package Summary:
|
| Area | Metric | Baseline | Current | Delta |
|---|---|---|---|---|
| Package | Packed tarball | 7.96 MB | 7.96 MB | +164 B |
| Package | Unpacked publish size | 29.73 MB | 29.73 MB | +250 B |
| Package | Installed footprint | 73.25 MB | 73.25 MB | +250 B |
| Package | Published files | 3182 | 3182 | 0 |
| Package | Installed files | 6892 | 6892 | 0 |
| Runtime | Unique function payloads | 2 | 2 | 0 |
| Runtime | Total function bytes | 17.12 MB | 17.12 MB | +582 B |
| Runtime | Public routes | 14 | 14 | 0 |
Changed function payloads vs main (0f359fe) (2)
| Function | Status | Baseline | Current | Delta | Route changes |
|---|---|---|---|---|---|
functions/__server.func |
changed | 8.56 MB | 8.56 MB | +291 B |
none |
functions/.well-known/workflow/v1/flow.func |
changed | 8.56 MB | 8.56 MB | +291 B |
none |
eve init install
| Metric | Baseline | Current | Delta |
|---|---|---|---|
| Installed footprint | 111.66 MB | 111.66 MB | +250 B |
| Installed packages | 121 | 121 | 0 |
| dependencies | 4 | 4 | 0 |
| devDependencies | 2 | 2 | 0 |
| Dependency package bytes | 44.22 MB | 44.22 MB | +250 B |
| devDependency package bytes | 5.04 MB | 5.04 MB | 0 B ➖ |
Build Metadata
- Preset:
vercel - Nitro:
nitro@3.0.260610-beta - Output directory:
apps/fixtures/weather-agent/.vercel/output - Build metadata timestamp: 2026-08-13T16:24:58.715Z
- Route aliases: 14 public, 1 internal (15 total aliases)
- Vercel routes in config: 17
- Severity legend: 🔴 dominant/large, 🟠 notable, 🟡 watch, ⚪ small
Package Drill-Down
Package Details
- Package:
eve@0.35.0 - Package directory:
packages/eve - Tarball: 7.96 MB (
eve-0.35.0.tgz) - Unpacked payload: 29.73 MB across 3182 published files
- Installed footprint: 73.25 MB across 6892 installed files
- Installed root package: 28.37 MB
- Installed dependencies: 44.87 MB
- Runtime dependencies: 2
- Peer dependencies: 5 (4 optional)
Installed footprint is measured from an isolated temporary npm install of the packed tarball.
Heavy installed dependencies
eve: 28.37 MB (38.7%)@rolldown/binding-linux-x64-gnu: 19.41 MB (26.5%)ai: 6.68 MB (9.1%)zod: 5.07 MB (6.9%)undici: 3.50 MB (4.8%)
Publish payload breakdown
Published file size
🔴 dist/src/compiled/shadcn-registry/index.js [#################.......] 10.19 MB 34.3%
🟠 dist/src/compiled/@photon-ai/chat-adapter-ime... [####....................] 2.42 MB 8.1%
🟠 dist/src/compiled/experimental-ai-sdk-code-mo... [##......................] 1.51 MB 5.1%
🟡 dist/src/compiled/_chunks/node/undici-CUIybhQ... [#.......................] 508.8 kB 1.7%
🟡 dist/src/compiled/_chunks/workflow/undici-CUI... [#.......................] 508.8 kB 1.7%
🔴 Other published files [########################] 14.59 MB 49.1%
Installed footprint breakdown
Installed package size
🔴 eve [########################] 28.37 MB 38.7%
🔴 @rolldown/binding-linux-x64-gnu [################........] 19.41 MB 26.5%
🔴 ai [######..................] 6.68 MB 9.1%
🔴 zod [####....................] 5.07 MB 6.9%
🟠 undici [###.....................] 3.50 MB 4.8%
🟠 nitro [##......................] 2.41 MB 3.3%
🔴 Other installed packages [#######.................] 7.80 MB 10.7%
Runtime dependencies (2)
| Package | Range | Notes |
|---|---|---|
nitro |
3.0.260610-beta |
|
undici |
8.9.0 |
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: 111.66 MB across 8768 installed files
- Installed packages: 121 total (115 transitive-only)
- dependencies: 4 direct packages totaling 44.22 MB
- devDependencies: 2 direct packages totaling 5.04 MB
- Other transitive package files: 62.39 MB
Installed footprint is measured from an isolated temporary eve init my-agent using the current packed eve tarball.
Heavy installed dependencies
eve: 28.37 MB (25.4%)@typescript/typescript-linux-x64: 27.95 MB (25.0%)@rolldown/binding-linux-x64-gnu: 19.41 MB (17.4%)zod: 9.02 MB (8.1%)ai: 6.68 MB (6.0%)
Installed footprint breakdown
Installed package size
🔴 eve [########################] 28.37 MB 25.4%
🔴 @typescript/typescript-linux-x64 [########################] 27.95 MB 25.0%
🔴 @rolldown/binding-linux-x64-gnu [################........] 19.41 MB 17.4%
🔴 zod [########................] 9.02 MB 8.1%
🔴 ai [######..................] 6.68 MB 6.0%
🟠 undici [###.....................] 3.50 MB 3.1%
🔴 Other installed packages [##############..........] 16.71 MB 15.0%
dependencies (4)
| Package | Range | Installed size | Share |
|---|---|---|---|
@vercel/connect |
0.4.3 |
141.0 kB | 0.1% |
ai |
^7.0.58 |
6.68 MB | 6.0% |
eve |
file:eve-0.35.0.tgz |
28.37 MB | 25.4% |
zod |
4.4.3 |
9.02 MB | 8.1% |
devDependencies (2)
| Package | Range | Installed size | Share |
|---|---|---|---|
@types/node |
24.x |
2.54 MB | 2.3% |
typescript |
7.0.2 |
2.50 MB | 2.2% |
Function Drill-Down
Payload Size Graph
Unique function payload size and share of total
🔴 functions/.well-known/workflow/v1/flow.func [########################] 8.56 MB 50.0%
🔴 functions/__server.func [########################] 8.56 MB 50.0%
Top Function Payloads
🟠 functions/.well-known/workflow/v1/flow.func • 1 public route • 8.56 MB
| Metric | Value |
|---|---|
| Public routes | /.well-known/workflow/v1/flow |
| Runtime | nodejs24.x |
| Handler | index.mjs |
| Payload | 8.56 MB |
| Function files | 8.56 MB across 49 files |
| Traced dependencies | 0 B |
| Signal | 🟠 Bundled file index.mjs is 1.77 MB (20.6%) |
🟠 🔎 Dependency Analysis
📦 Bundled files:
Bundled file size
🟠 index.mjs [################........] 1.77 MB 20.6%
🟠 _chunks/runtime-artifacts.mjs [##############..........] 1.64 MB 19.2%
🟡 _libs/undici.mjs [#########...............] 980.5 kB 11.5%
🟡 _chunks/sandbox.mjs [#######.................] 777.7 kB 9.1%
🟡 _chunks/frames-CTpeJYEQ.mjs [######..................] 671.5 kB 7.8%
🟠 Other bundled files [########################] 2.72 MB 31.8%
🧾 Vercel Config
{
"handler": "index.mjs",
"launcherType": "Nodejs",
"shouldAddHelpers": false,
"supportsResponseStreaming": true,
"runtime": "nodejs24.x",
"maxDuration": "max",
"experimentalTriggers": [
{
"type": "queue/v2beta",
"topic": "__eve776561746865722d6167656e74_wkf_workflow_*",
"consumer": "default",
"retryAfterSeconds": 5,
"initialDelaySeconds": 0
}
],
"environment": {
"WORKFLOW_PRECONDITION_GUARD": "1"
}
}🟠 functions/__server.func • 13 public routes, 1 internal alias • 8.56 MB
| Metric | Value |
|---|---|
| Public routes | //eve/v1/callback/[token]/eve/v1/connections/[name]/callback/[attemptId]/[token]/eve/v1/connections/[name]/callback/[token]/eve/v1/health/eve/v1/info/eve/v1/session/eve/v1/session/[sessionId]/eve/v1/session/[sessionId]/cancel/eve/v1/session/[sessionId]/clear/eve/v1/session/[sessionId]/compact/eve/v1/session/[sessionId]/reset/eve/v1/session/[sessionId]/stream |
| Internal aliases | /__server |
| Runtime | nodejs24.x |
| Handler | index.mjs |
| Payload | 8.56 MB |
| Function files | 8.56 MB across 49 files |
| Traced dependencies | 0 B |
| Signal | 🟠 Bundled file index.mjs is 1.77 MB (20.6%) |
🟠 🔎 Dependency Analysis
📦 Bundled files:
Bundled file size
🟠 index.mjs [################........] 1.77 MB 20.6%
🟠 _chunks/runtime-artifacts.mjs [##############..........] 1.64 MB 19.2%
🟡 _libs/undici.mjs [#########...............] 980.5 kB 11.5%
🟡 _chunks/sandbox.mjs [#######.................] 777.7 kB 9.1%
🟡 _chunks/frames-CTpeJYEQ.mjs [######..................] 671.5 kB 7.8%
🟠 Other bundled files [########################] 2.72 MB 31.8%
🧾 Vercel Config
{
"handler": "index.mjs",
"launcherType": "Nodejs",
"shouldAddHelpers": false,
"supportsResponseStreaming": true,
"runtime": "nodejs24.x"
}Build Timing: e2e/fixtures/agent-tools-sandbox
This is an informational timing measurement inside eve build, from preflight through publication. Output-size measurement and profile writing are excluded.
Build mode: deployable Vercel build with sandbox template prewarm included.
- Build pipeline: 2.19 s -> 2.15 s (-32.2 ms) vs
main (0f359fe). - Timing is informational: shared GitHub runners are too variable for a hard timing budget.
Detailed phase timings vs `main (0f359fe)`
| Phase | Baseline | Current | Delta |
|---|---|---|---|
extension.check |
1.2 ms | 1.2 ms | 0.0 ms |
project.resolve |
0.7 ms | 0.7 ms | 0.0 ms |
workspace.create |
0.8 ms | 0.8 ms | 0.0 ms |
host.prepare |
183.6 ms | 165.6 ms | -18.0 ms |
vercel.service-prefix.resolve |
2.5 ms | 2.6 ms | +0.1 ms |
nitro.create |
246.7 ms | 266.7 ms | +20.0 ms |
sandbox.prewarm |
336.8 ms | 299.1 ms | -37.7 ms |
nitro.cache.prepare |
0.3 ms | 0.3 ms | 0.0 ms |
nitro.prepare |
0.9 ms | 0.9 ms | 0.0 ms |
nitro.public-assets |
0.8 ms | 0.8 ms | 0.0 ms |
nitro.prerender |
0.6 ms | 0.5 ms | -0.1 ms |
nitro.bundle |
1.38 s | 1.38 s | +4.4 ms |
nitro.cache.write |
0.4 ms | 0.4 ms | 0.0 ms |
vercel.workflow-function.materialize |
26.9 ms | 26.1 ms | -0.8 ms |
agent-summary.emit |
0.6 ms | 0.5 ms | -0.1 ms |
nitro.close |
0.2 ms | 0.1 ms | -0.1 ms |
output.publish |
3.8 ms | 3.8 ms | 0.0 ms |
workspace.remove |
2.3 ms | 2.2 ms | -0.1 ms |
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HTTP-only MCP servers now surface the original Streamable HTTP initialization failure instead of a legacy SSE 404 or 405.
Why
When Streamable HTTP initialization returns 400, 404, or 405, eve retries with SSE for compatibility with older MCP servers. If that fallback also returns 404 or 405, the fallback error replaces the first failure. For HTTP-only servers, this hides the actionable response and can tell operators to use HTTP after eve already tried it.
A regression test reproduces #2042 with an HTTP 400 followed by an SSE 405. It failed on
mainbecause callers received the SSE error.Approach
Because an SSE 404 or 405 proves that the fallback transport is unavailable, rethrowing the first HTTP error should preserve the useful status and response without changing the compatibility retry policy.
The change also recognizes the AI SDK's
MCP SSE Transport Error: 405 ...message format. Other SSE failures still propagate unchanged.This proposal does not add protocol-version negotiation or an override. It makes the first HTTP failure visible so that negotiation failures can be diagnosed accurately.
Validation
main, then passed with the changepnpm --filter eve exec vitest run --config vitest.unit.config.ts src/runtime/connections/mcp-client.test.ts(44 tests)pnpm --filter eve typecheckpnpm --filter eve buildoxlintandoxfmtpnpm guard:invariantspnpm typecheckremains blocked in unrelated e2e fixtures becauseopenai/gpt-5.6-solandanthropic/claude-opus-4.6lack AI Gateway context-window metadata.