fix(eve): persist text streams as deltas

[ruiconti]

Summary

Before

{ "messageDelta": "Revenue", "messageSoFar": "Revenue" }
{ "messageDelta": " increased", "messageSoFar": "Revenue increased" }
{ "messageDelta": " by 12%", "messageSoFar": "Revenue increased by 12%" }

After

{ "messageDelta": "Revenue" }
{ "messageDelta": " increased" }
{ "messageDelta": " by 12%" }

reasoning.appended and action.input.appended now have the same shape: each event persists only the new chunk plus its existing turn, step, and call coordinates. Empty tool-input starts no longer emit an append event; the first append contains actual input text.

Consumers that need text-so-far accumulate chunks in stream order. The default reducer, TUI, Slack, Chat SDK, and Next.js trace consumer now do that locally. Slack still posts final answers from message.completed; its progressive reasoning accumulator resets at reasoning completion and turn/step boundaries.

The durable event index remains the reconnect cursor, and stable event IDs deduplicate replay overlap. The protocol does not add a second text position or block-boundary mechanism.

The stream version advances from 24 to 25. The client and server normalize v21-v24 cumulative message/reasoning events and v24 tool-input offsets into the current delta-only shape. Missing deltas and append fields that contradict the declared version fail at the decode boundary. Published extensions whose capability contract changed must be rebuilt and republished.

Provider retries remain append-only: events emitted by an interrupted attempt stay durable. A later completed event can replace provisional text in replaceable consumers; the TUI now replaces its still-live block before committing the completed text. A block completed before its attempt later fails cannot be retracted without adding attempt identity.

Reproduction

The same 159-call, 414,436-event sequence was encoded with the cumulative and delta-only formats:

Measurement	Cumulative format	Delta-only format	Difference
Total serialized eve protocol	11,381,164,093 bytes	85,280,426 bytes	-11,295,883,667 bytes (-99.25%)
reasoningSoFar payload	9,666,376,952 bytes	0 bytes	-9,666,376,952 bytes
messageSoFar payload	1,629,506,715 bytes	0 bytes	-1,629,506,715 bytes

The cumulative stream was 133.46 times the delta-only size; the new stream is 0.75% of the previous size. These are serialized eve protocol bytes before Workflow framing, not billed Workflow Data Written.

Validation

The matched replay sends the same chunk sequence through the cumulative and current eve emitters and protocol encoders. The delta full branch passed 7,758 unit tests and 711 integration tests. The final TUI repair passes 298 focused TUI tests, both provider-retry integration tests, and eve typecheck; CI remains the authoritative full-commit result.

Tests cover delta accumulation and coalescing, provider retry output, legacy replay, reconnects across stream versions, malformed v25 events, and built-in client, Chat SDK, Slack, TUI, ACP, and trace consumers. The TUI regression asserts that discarded retry text is absent from the committed transcript and the recovered answer appears once.

Checklist

• This change was requested or approved by a maintainer
• I ran the relevant checks from CONTRIBUTING.md
• I added tests and documentation where relevant
• I added a changeset if this touches the published eve package
• DCO sign-off passes for every commit (git commit --signoff)

Diff size

Docs — 4 files · +112 / -8

Explains the delta-only wire format, consumer migration, reconnect semantics, and retry limitation.

Implementation — 29 files · +627 / -190

Removes cumulative snapshots and tool-input offsets, normalizes supported historical streams, validates the v25 shape, and migrates first-party consumers. Eight generated capability reports record the breaking author-facing event contract.

Tests — 30 files · +933 / -129

Covers byte scaling, accumulation, coalescing, retry behavior, legacy replay, reconnects, malformed events, and first-party consumer behavior.

[vercel]

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

Project	Deployment	Actions	Updated
eve-docs	Ready	Preview, v0	Sep 2, 2026 9:09pm UTC
eve-docs-4759	Ready	Preview, v0	Sep 2, 2026 9:09pm UTC
eve-pkg	Ready	Preview, v0	Sep 2, 2026 9:09pm UTC

[github-actions]

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

Key takeaways

• No notable deltas vs main (23a4b59).

Delta vs main (23a4b59)

Area	Metric	Baseline	Current	Delta
Package	Packed tarball	8.62 MB	8.62 MB	+2.6 kB ⚠️
Package	Unpacked publish size	32.46 MB	32.48 MB	+21.9 kB ⚠️
Package	Installed footprint	77.62 MB	77.64 MB	+21.9 kB ⚠️
Package	Published files	3769	3775	+6
Package	Installed files	7615	7621	+6
Package	Installed package instances	35	35	0
Package	Distinct installed package names	34	34	0
Package	Installed dependency edges	53	53	0
Package	Installed optional peer edges	47	47	0
Runtime	Unique function payloads	2	2	0
Runtime	Total function bytes	20.31 MB	20.32 MB	+7.9 kB ⚠️
Runtime	Public routes	18	18	0

Changed function payloads vs main (23a4b59) (2)

Function	Status	Baseline	Current	Delta	Route changes
functions/__server.func	changed	10.16 MB	10.16 MB	+4.0 kB ⚠️	none
functions/.well-known/workflow/v1/flow.func	changed	10.16 MB	10.16 MB	+4.0 kB ⚠️	none

eve init install

Metric	Baseline	Current	Delta
Installed footprint	116.06 MB	116.08 MB	+21.9 kB ⚠️
Installed packages	120	120	0
dependencies	4	4	0
devDependencies	2	2	0
Dependency package bytes	48.52 MB	48.54 MB	+21.9 kB ⚠️
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: 2026-09-02T21:09:29.791Z
• Route aliases: 18 public, 1 internal (19 total aliases)
• Vercel routes in config: 21
• Severity legend: 🔴 dominant/large, 🟠 notable, 🟡 watch, ⚪ small

Package Drill-Down

Package Details

• Package: eve@0.49.0
• Package directory: packages/eve
• Tarball: 8.62 MB (eve-0.49.0.tgz)
• Unpacked payload: 32.48 MB across 3775 published files
• Installed footprint: 77.64 MB across 7621 installed files
• Installed root package: 31.02 MB
• Installed dependencies: 46.63 MB
• Installed package instances: 35
• Distinct installed package names: 34
• Installed dependency edges: 53
• Installed optional peer edges: 47
• Runtime dependencies: 2
• Peer dependencies: 5 (4 optional)

Installed footprint is measured from an isolated temporary npm install of the packed tarball.
Graph metrics read only package.json files in package directories directly beneath a node_modules boundary, including nested boundaries. Each directory is one package instance; distinct names come from those manifests. Dependency edges count each unique name in dependencies or optionalDependencies per instance; optional peer edges count peerDependencies marked optional.

Heavy installed dependencies

• eve: 31.02 MB (39.9%)
• @rolldown/binding-linux-x64-gnu: 19.31 MB (24.9%)
• ai: 6.98 MB (9.0%)
• zod: 6.41 MB (8.3%)
• undici: 3.50 MB (4.5%)

Publish payload breakdown

Published file size
🔴 dist/src/compiled/shadcn-registry/index.js       [#############...........] 9.76 MB 30.1%
🟠 dist/src/compiled/@photon-ai/chat-adapter-ime... [###.....................] 2.27 MB 7.0%
🟠 dist/src/compiled/@ai-sdk/code-mode/index.js     [#.......................] 1.03 MB 3.2%
🟡 dist/src/compiled/@vercel/blob/index.js          [#.......................] 901.8 kB 2.8%
🟡 dist/src/compiled/_chunks/workflow/undici-Dfx... [#.......................] 512.5 kB 1.6%
🔴 Other published files                            [########################] 18.01 MB 55.4%

Installed footprint breakdown

Installed package size
🔴 eve                             [########################] 31.02 MB 39.9%
🔴 @rolldown/binding-linux-x64-gnu [###############.........] 19.31 MB 24.9%
🔴 ai                              [#####...................] 6.98 MB 9.0%
🔴 zod                             [#####...................] 6.41 MB 8.3%
🟠 undici                          [###.....................] 3.50 MB 4.5%
🟠 nitro                           [##......................] 2.41 MB 3.1%
🔴 Other installed packages        [######..................] 8.00 MB 10.3%

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	^3.1.0	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: 116.08 MB across 9517 installed files
• Installed packages: 120 total (114 transitive-only)
• dependencies: 4 direct packages totaling 48.54 MB
• devDependencies: 2 direct packages totaling 5.04 MB
• Other transitive package files: 62.50 MB

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

Heavy installed dependencies

• eve: 31.02 MB (26.7%)
• @typescript/typescript-linux-x64: 27.95 MB (24.1%)
• @rolldown/binding-linux-x64-gnu: 19.31 MB (16.6%)
• zod: 10.37 MB (8.9%)
• ai: 6.98 MB (6.0%)

Installed footprint breakdown

Installed package size
🔴 eve                              [########################] 31.02 MB 26.7%
🔴 @typescript/typescript-linux-x64 [######################..] 27.95 MB 24.1%
🔴 @rolldown/binding-linux-x64-gnu  [###############.........] 19.31 MB 16.6%
🔴 zod                              [########................] 10.37 MB 8.9%
🔴 ai                               [#####...................] 6.98 MB 6.0%
🟠 undici                           [###.....................] 3.50 MB 3.0%
🔴 Other installed packages         [#############...........] 16.94 MB 14.6%

dependencies (4)

Package	Range	Installed size	Share
@vercel/connect	1.0.0	167.9 kB	0.1%
ai	^7.0.82	6.98 MB	6.0%
eve	file:eve-0.49.0.tgz	31.02 MB	26.7%
zod	4.5.4	10.37 MB	8.9%

devDependencies (2)

Package	Range	Installed size	Share
@types/node	24.x	2.54 MB	2.2%
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     [########################] 10.16 MB 50.0%
🔴 functions/__server.func                         [########################] 10.16 MB 50.0%

Top Function Payloads

🟠 functions/.well-known/workflow/v1/flow.func • 1 public route • 10.16 MB

Metric	Value
Public routes	/.well-known/workflow/v1/flow
Runtime	nodejs24.x
Handler	index.mjs
Payload	10.16 MB
Function files	10.16 MB across 111 files
Traced dependencies	0 B
Signal	🟠 Bundled file index.mjs is 2.15 MB (21.1%)

🟠 🔎 Dependency Analysis

📦 Bundled files:

Bundled file size
🟠 index.mjs                       [##########..............] 2.15 MB 21.1%
🟡 _libs/undici.mjs                [#####...................] 980.5 kB 9.7%
🟡 _chunks/decode_jwt-Col8JOnf.mjs [###.....................] 702.6 kB 6.9%
🟡 _chunks/rename-with-retry.mjs   [###.....................] 695.6 kB 6.8%
🟡 _chunks/frames-CZ9eHShe.mjs     [###.....................] 679.1 kB 6.7%
🔴 Other bundled files             [########################] 4.96 MB 48.8%

🧾 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 • 17 public routes, 1 internal alias • 10.16 MB

Metric	Value
Public routes	/ /.well-known/workflow/v1/webhook/[token] /eve/v1/activity/[token] /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/[parentSessionId]/subagents/[callId]/[childSessionId]/stream /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 /eve/v1/task-input/[token]
Internal aliases	/__server
Runtime	nodejs24.x
Handler	index.mjs
Payload	10.16 MB
Function files	10.16 MB across 111 files
Traced dependencies	0 B
Signal	🟠 Bundled file index.mjs is 2.15 MB (21.1%)

🟠 🔎 Dependency Analysis

📦 Bundled files:

Bundled file size
🟠 index.mjs                       [##########..............] 2.15 MB 21.1%
🟡 _libs/undici.mjs                [#####...................] 980.5 kB 9.7%
🟡 _chunks/decode_jwt-Col8JOnf.mjs [###.....................] 702.6 kB 6.9%
🟡 _chunks/rename-with-retry.mjs   [###.....................] 695.6 kB 6.8%
🟡 _chunks/frames-CZ9eHShe.mjs     [###.....................] 679.1 kB 6.7%
🔴 Other bundled files             [########################] 4.96 MB 48.8%

🧾 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: 2.81 s -> 2.68 s (-121.9 ms) vs main (23a4b59).
• Timing is informational: shared GitHub runners are too variable for a hard timing budget.

Detailed phase timings vs `main (23a4b59)`

Phase	Baseline	Current	Delta
extension.check	12.7 ms	1.1 ms	-11.6 ms
project.resolve	0.4 ms	0.4 ms	0.0 ms
workspace.create	0.7 ms	0.8 ms	+0.1 ms
host.prepare	543.9 ms	475.0 ms	-68.9 ms
vercel.service-prefix.resolve	1.8 ms	1.9 ms	+0.1 ms
nitro.create	495.0 ms	484.3 ms	-10.7 ms
sandbox.prewarm	261.5 ms	247.7 ms	-13.8 ms
nitro.cache.prepare	0.2 ms	0.3 ms	+0.1 ms
nitro.prepare	0.7 ms	0.7 ms	0.0 ms
nitro.public-assets	0.7 ms	0.7 ms	0.0 ms
nitro.prerender	0.4 ms	0.5 ms	+0.1 ms
nitro.bundle	1.44 s	1.42 s	-16.9 ms
nitro.cache.write	0.3 ms	0.3 ms	0.0 ms
vercel.workflow-function.materialize	43.0 ms	42.6 ms	-0.4 ms
agent-summary.emit	0.7 ms	0.7 ms	0.0 ms
nitro.close	0.1 ms	0.1 ms	0.0 ms
output.publish	3.1 ms	3.3 ms	+0.2 ms
workspace.remove	1.9 ms	1.8 ms	-0.1 ms

[vercel]

Additional Suggestion:

Trace viewer reads removed cumulative stream fields reasoningSoFar/messageSoFar, so progressive streaming text never renders during reasoning.appended/message.appended.

[ctgowrie]

Why do we have an offset vs just using the chunk which is closer to what providers and ai sdk use?

[ruiconti]

Why do we have an offset vs just using the chunk which is closer to what providers and ai sdk use?

The reasoning was to provide a way for clients, during reconnect midstream, to distinguish if the current reasoning-delta event:

• should be appended or not e.g offset !== 0
• has skewed from current local state e.g last known offset was 13 and it received 45

But these are theoretical and not consistent with other -delta usage, so looks like a theoretical issue.