ci: pin govulncheck to v1.7.0

govulncheck@latest resolves to v1.8.0, which declares go 1.26.0 in its
module file. Every job in this workflow pins go-version 1.25.x, so the
install step fails before any scanning runs, which fails ci-success and
skips the release job.

v1.7.0 declares go 1.25.0 and installs on the pinned toolchain. This also
matches the convention used for staticcheck, which is already pinned to
an exact version. Pinning the binary does not freeze the vulnerability
database, which govulncheck fetches at run time.

Claude-Session: https://claude.ai/code/session_01Fu2wXqGUrfVBi5aLafKk8U

.github/workflows/ci.yml

@@ -25,12 +25,12 @@ jobs:
   vet:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-go@v5
+      - uses: actions/checkout@v6
+      - uses: actions/setup-go@v6
         with:
           go-version: '1.25.x'
           check-latest: true
-      - uses: actions/cache@v4
+      - uses: actions/cache@v5
         with:
           path: |
             ~/go/pkg/mod
@@ -41,12 +41,12 @@ jobs:
   staticcheck:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-go@v5
+      - uses: actions/checkout@v6
+      - uses: actions/setup-go@v6
         with:
           go-version: '1.25.x'
           check-latest: true
-      - uses: actions/cache@v4
+      - uses: actions/cache@v5
         with:
           path: |
             ~/go/pkg/mod
@@ -58,29 +58,35 @@ jobs:
   govulncheck:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-go@v5
+      - uses: actions/checkout@v6
+      - uses: actions/setup-go@v6
         with:
           go-version: '1.25.x'
           check-latest: true
-      - uses: actions/cache@v4
+      - uses: actions/cache@v5
         with:
           path: |
             ~/go/pkg/mod
             ~/.cache/go-build
           key: ${{ runner.os }}-go-1.25-${{ hashFiles('**/go.sum') }}
-      - run: go install golang.org/x/vuln/cmd/govulncheck@latest
+      # Pinned, matching staticcheck above. govulncheck@latest is v1.8.0,
+      # which declares go 1.26.0 and therefore cannot be installed by the
+      # 1.25.x toolchain this workflow pins - the install step fails before
+      # any scanning happens. v1.7.0 declares go 1.25.0. Pinning the binary
+      # does not freeze the vulnerability database, which govulncheck
+      # fetches at run time. Re-pin deliberately when bumping go-version.
+      - run: go install golang.org/x/vuln/cmd/[email protected]
       - run: govulncheck ./...
 
   gosec:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-go@v5
+      - uses: actions/checkout@v6
+      - uses: actions/setup-go@v6
         with:
           go-version: '1.25.x'
           check-latest: true
-      - uses: actions/cache@v4
+      - uses: actions/cache@v5
         with:
           path: |
             ~/go/pkg/mod
@@ -98,12 +104,12 @@ jobs:
   test:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-go@v5
+      - uses: actions/checkout@v6
+      - uses: actions/setup-go@v6
         with:
           go-version: '1.25.x'
           check-latest: true
-      - uses: actions/cache@v4
+      - uses: actions/cache@v5
         with:
           path: |
             ~/go/pkg/mod
@@ -112,7 +118,7 @@ jobs:
       - run: go test -race -coverprofile=coverage.out ./...
       - name: Build all examples
         run: go build ./examples/...
-      - uses: actions/upload-artifact@v4
+      - uses: actions/upload-artifact@v7
         with:
           name: coverage
           path: coverage.out
@@ -120,12 +126,12 @@ jobs:
   codegen-clean:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-go@v5
+      - uses: actions/checkout@v6
+      - uses: actions/setup-go@v6
         with:
           go-version: '1.25.x'
           check-latest: true
-      - uses: actions/cache@v4
+      - uses: actions/cache@v5
         with:
           path: |
             ~/go/pkg/mod
@@ -139,14 +145,14 @@ jobs:
   audit:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0   # need history for drift comparison
-      - uses: actions/setup-go@v5
+      - uses: actions/setup-go@v6
         with:
           go-version: '1.25.x'
           check-latest: true
-      - uses: actions/cache@v4
+      - uses: actions/cache@v5
         with:
           path: |
             ~/go/pkg/mod
@@ -196,11 +202,11 @@ jobs:
       github.event_name == 'workflow_dispatch'
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
 
-      - uses: actions/setup-go@v5
+      - uses: actions/setup-go@v6
         with:
           go-version: '1.25.x'
           check-latest: true
@@ -258,7 +264,7 @@ jobs:
 
       - name: Run GoReleaser
         if: github.event_name != 'workflow_dispatch' || inputs.dry-run-release == false
-        uses: goreleaser/goreleaser-action@v6
+        uses: goreleaser/goreleaser-action@v7
         with:
           distribution: goreleaser
           version: '~> v2'

.github/workflows/pages.yml

@@ -24,7 +24,7 @@ jobs:
       url: ${{ steps.deployment.outputs.page_url }}
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/configure-pages@v5
       - uses: actions/upload-pages-artifact@v3
         with:

.github/workflows/regen.yml

@@ -13,12 +13,12 @@ jobs:
   regen:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0   # full history so audit -drift can compare against main
 
       - name: Set up Go
-        uses: actions/setup-go@v5
+        uses: actions/setup-go@v6
         with:
           go-version: '1.25.x'
           check-latest: true
@@ -29,7 +29,12 @@ jobs:
           DATE=$(date +%Y-%m-%d)
           DEST="testdata/html/snapshot_${DATE}.html"
           curl -fsSL --user-agent "go-telegram codegen scraper" \
-            https://core.telegram.org/bots/api > "$DEST"
+            https://core.telegram.org/bots/api -o "$DEST.tmp"
+          # The page ends with a "<!-- page generated in NN.NNms -->" comment
+          # that changes on every fetch. Drop it, so an unchanged API produces
+          # a byte-identical snapshot instead of a no-op update PR.
+          sed '/<!-- page generated in .*ms -->/d' "$DEST.tmp" > "$DEST"
+          rm "$DEST.tmp"
           ln -sf "snapshot_${DATE}.html" testdata/html/latest.html
           echo "date=$DATE" >> $GITHUB_OUTPUT
           echo "dest=$DEST" >> $GITHUB_OUTPUT
@@ -76,7 +81,10 @@ jobs:
         id: diff
         run: |
           git status --porcelain
-          if git diff --quiet internal/spec/api.json api/ testdata/html/; then
+          # Gate on the generated surface only. A fresh snapshot file and the
+          # latest.html symlink flip every run, so including testdata/html/
+          # here would open a PR on a week when Telegram changed nothing.
+          if git diff --quiet internal/spec/api.json api/ docs/reference/; then
             echo "no_changes=true" >> $GITHUB_OUTPUT
           fi
 
@@ -88,8 +96,9 @@ jobs:
           echo "version=$VERSION" >> $GITHUB_OUTPUT
 
       - name: Open PR
+        id: pr
         if: steps.diff.outputs.no_changes != 'true'
-        uses: peter-evans/create-pull-request@v7
+        uses: peter-evans/create-pull-request@v8
         with:
           token: ${{ secrets.GITHUB_TOKEN }}
           commit-message: |
@@ -115,4 +124,17 @@ jobs:
 
             Inspect the IR diff (`internal/spec/api.json`) for added/changed/removed methods.
 
-            CI must pass before merge. Auto-merge: enable when satisfied with the diff.
+            This PR merges itself once every step above passes. The gates are
+            `make regen` (which fails on any audit fallback) and `go test -race ./...`,
+            both run in this job before the PR opens.
+
+      # A PR opened with GITHUB_TOKEN does not trigger `ci.yml`, so waiting for
+      # PR checks would wait forever. The gates already ran in this job: `make
+      # regen` fails on any audit fallback, and the test step runs the full race
+      # suite. Merging here therefore means "merged because the checks passed".
+      # `ci.yml` then runs on the push to main and cuts the release.
+      - name: Merge regen PR
+        if: steps.diff.outputs.no_changes != 'true' && steps.pr.outputs.pull-request-number != ''
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: gh pr merge "${{ steps.pr.outputs.pull-request-number }}" --squash --delete-branch

Makefile

@@ -35,7 +35,10 @@ lint: vet
 integration:
 	$(GO) test -tags=integration -v ./test/integration/...
 
-SCRAPE_INPUT ?= testdata/html/snapshot_2026-05-08.html
+# Resolve via testdata/html/latest.html symlink so the pinned-fixture target
+# auto-tracks whatever snapshot regen.yml last committed. Override with
+# SCRAPE_INPUT=path/to/snapshot.html for ad-hoc replays.
+SCRAPE_INPUT ?= testdata/html/$(shell readlink testdata/html/latest.html)
 SCRAPE_OUTPUT ?= internal/spec/api.json
 
 snapshot:

README.md

@@ -328,9 +328,12 @@ Apples-to-apples micro-benchmarks against the five most-starred Go Telegram libr
 |------|---------|--------------|
 | Webhook decode (small Update) | **ours** — 1.83 µs / 11 allocs | 1st of 6 |
 | Large Update unmarshal (unions + reply markup) | **ours** — 6.73 µs / 34 allocs | 1st of 6 |
-| `sendMessage` round-trip (mock server) | telego — 35.8 µs / 48 allocs | 2nd of 5 |
+| `sendMessage` round-trip — `net/http` default | telego — 35.8 µs / 48 allocs | 2nd of 5 (102 allocs) |
+| `sendMessage` round-trip — opt-in `fasthttp` | telego — 48 allocs | within 8 of telego (56 allocs) |
 | Dispatcher routing (20 handlers, last matches) | **ours** — 98 ns / 3 allocs | 1st of 3 |
 
+Opt into fasthttp for high-throughput bots: `client.WithHTTPClient(client.NewFastHTTPDoer())`. Trade-off: HTTP/1.1 only, no `RoundTripper` middleware composition.
+
 Full tables, caveats, and reproduction steps: **[`docs/benchmarks/2026-05-10-comparison.md`](docs/benchmarks/2026-05-10-comparison.md)**.
 
 </details>
@@ -368,6 +371,20 @@ bot := client.New("token", client.WithHTTPClient(fakeDoer{
 
 The library's own generated test suite (`api/methods_gen_test.go`) covers 176 methods × 8 scenarios each: Success, APIError, NetworkError, ParseError, ContextCanceled, MissingRequiredFields, Forbidden, ServerError.
 
+## Telemetry
+
+On the **first call to `client.New`** in a process, this library sends a
+single anonymous adoption ping — project name, version, timestamp; no
+identifiers, no message contents, no API call metadata. Fire-and-forget
+with a 2-second timeout; cannot block `New` or panic.
+
+Local source: [`client/telemetry.go`](client/telemetry.go). Upstream
+implementation, exact wire format, and full opt-out documentation:
+**[oss-telemetry — Disabling telemetry](https://github.com/lukaszraczylo/oss-telemetry#disabling-telemetry)**.
+
+Quick opt-out: set any of `DO_NOT_TRACK=1`, `OSS_TELEMETRY_DISABLED=1`,
+or `GO_TELEGRAM_DISABLE_TELEMETRY=1`.
+
 ## Contributing
 
 See [CONTRIBUTING.md](CONTRIBUTING.md).

api/enums.gen.go

@@ -33,6 +33,14 @@ const (
 	BotCommandScopeTypeChatMember            BotCommandScopeType = "chat_member"
 )
 
+type BotSubscriptionUpdatedState string
+
+const (
+	BotSubscriptionUpdatedStateCanceled BotSubscriptionUpdatedState = "canceled"
+	BotSubscriptionUpdatedStateActive   BotSubscriptionUpdatedState = "active"
+	BotSubscriptionUpdatedStateFailed   BotSubscriptionUpdatedState = "failed"
+)
+
 type ChatBoostSourceKind string
 
 const (
@@ -133,6 +141,12 @@ const (
 	InputMediaTypeVideo     InputMediaType = "video"
 )
 
+type InputMediaVoiceNoteType string
+
+const (
+	InputMediaVoiceNoteTypeVoiceNote InputMediaVoiceNoteType = "voice_note"
+)
+
 type InputPaidMediaType string
 
 const (
@@ -158,6 +172,7 @@ type InputPollOptionMediaType string
 
 const (
 	InputPollOptionMediaTypeAnimation InputPollOptionMediaType = "animation"
+	InputPollOptionMediaTypeLink      InputPollOptionMediaType = "link"
 	InputPollOptionMediaTypeLivePhoto InputPollOptionMediaType = "live_photo"
 	InputPollOptionMediaTypeLocation  InputPollOptionMediaType = "location"
 	InputPollOptionMediaTypePhoto     InputPollOptionMediaType = "photo"
@@ -173,6 +188,35 @@ const (
 	InputProfilePhotoTypeAnimated InputProfilePhotoType = "animated"
 )
 
+type InputRichBlockType string
+
+const (
+	InputRichBlockTypeParagraph              InputRichBlockType = "paragraph"
+	InputRichBlockTypeHeading                InputRichBlockType = "heading"
+	InputRichBlockTypePre                    InputRichBlockType = "pre"
+	InputRichBlockTypeFooter                 InputRichBlockType = "footer"
+	InputRichBlockTypeDivider                InputRichBlockType = "divider"
+	InputRichBlockTypeMathematicalExpression InputRichBlockType = "mathematical_expression"
+	InputRichBlockTypeAnchor                 InputRichBlockType = "anchor"
+	InputRichBlockTypeList                   InputRichBlockType = "list"
+	InputRichBlockTypeBlockquote             InputRichBlockType = "blockquote"
+	InputRichBlockTypeExpandableBlockquote   InputRichBlockType = "expandable_blockquote"
+	InputRichBlockTypePullquote              InputRichBlockType = "pullquote"
+	InputRichBlockTypeCollage                InputRichBlockType = "collage"
+	InputRichBlockTypeSlideshow              InputRichBlockType = "slideshow"
+	InputRichBlockTypeTable                  InputRichBlockType = "table"
+	InputRichBlockTypeDetails                InputRichBlockType = "details"
+	InputRichBlockTypeMap                    InputRichBlockType = "map"
+	InputRichBlockTypeButtons                InputRichBlockType = "buttons"
+	InputRichBlockTypeAnimation              InputRichBlockType = "animation"
+	InputRichBlockTypeAudio                  InputRichBlockType = "audio"
+	InputRichBlockTypeDocument               InputRichBlockType = "document"
+	InputRichBlockTypePhoto                  InputRichBlockType = "photo"
+	InputRichBlockTypeVideo                  InputRichBlockType = "video"
+	InputRichBlockTypeVoiceNote              InputRichBlockType = "voice_note"
+	InputRichBlockTypeThinking               InputRichBlockType = "thinking"
+)
+
 type InputStickerFormat string
 
 const (
@@ -357,6 +401,14 @@ const (
 	RefundedPaymentCurrencyXTR RefundedPaymentCurrency = "XTR"
 )
 
+type Result string
+
+const (
+	ResultApprove Result = "approve"
+	ResultDecline Result = "decline"
+	ResultQueue   Result = "queue"
+)
+
 type RevenueWithdrawalStateKind string
 
 const (
@@ -365,6 +417,101 @@ const (
 	RevenueWithdrawalStateKindFailed    RevenueWithdrawalStateKind = "failed"
 )
 
+type RichBlockButtonsAlign string
+
+const (
+	RichBlockButtonsAlignLeft   RichBlockButtonsAlign = "left"
+	RichBlockButtonsAlignCenter RichBlockButtonsAlign = "center"
+	RichBlockButtonsAlignRight  RichBlockButtonsAlign = "right"
+)
+
+type RichBlockListItemType string
+
+const (
+	RichBlockListItemTypeLowerA RichBlockListItemType = "a"
+	RichBlockListItemTypeUpperA RichBlockListItemType = "A"
+	RichBlockListItemTypeLowerI RichBlockListItemType = "i"
+	RichBlockListItemTypeUpperI RichBlockListItemType = "I"
+	RichBlockListItemType1      RichBlockListItemType = "1"
+)
+
+type RichBlockTableCellValign string
+
+const (
+	RichBlockTableCellValignTop    RichBlockTableCellValign = "top"
+	RichBlockTableCellValignMiddle RichBlockTableCellValign = "middle"
+	RichBlockTableCellValignBottom RichBlockTableCellValign = "bottom"
+)
+
+type RichBlockType string
+
+const (
+	RichBlockTypeParagraph              RichBlockType = "paragraph"
+	RichBlockTypeHeading                RichBlockType = "heading"
+	RichBlockTypePre                    RichBlockType = "pre"
+	RichBlockTypeFooter                 RichBlockType = "footer"
+	RichBlockTypeDivider                RichBlockType = "divider"
+	RichBlockTypeMathematicalExpression RichBlockType = "mathematical_expression"
+	RichBlockTypeAnchor                 RichBlockType = "anchor"
+	RichBlockTypeList                   RichBlockType = "list"
+	RichBlockTypeBlockquote             RichBlockType = "blockquote"
+	RichBlockTypeExpandableBlockquote   RichBlockType = "expandable_blockquote"
+	RichBlockTypePullquote              RichBlockType = "pullquote"
+	RichBlockTypeCollage                RichBlockType = "collage"
+	RichBlockTypeSlideshow              RichBlockType = "slideshow"
+	RichBlockTypeTable                  RichBlockType = "table"
+	RichBlockTypeDetails                RichBlockType = "details"
+	RichBlockTypeMap                    RichBlockType = "map"
+	RichBlockTypeButtons                RichBlockType = "buttons"
+	RichBlockTypeAnimation              RichBlockType = "animation"
+	RichBlockTypeAudio                  RichBlockType = "audio"
+	RichBlockTypeDocument               RichBlockType = "document"
+	RichBlockTypePhoto                  RichBlockType = "photo"
+	RichBlockTypeVideo                  RichBlockType = "video"
+	RichBlockTypeVoiceNote              RichBlockType = "voice_note"
+	RichBlockTypeThinking               RichBlockType = "thinking"
+)
+
+type RichMessageButtonStyle string
+
+const (
+	RichMessageButtonStyleDanger  RichMessageButtonStyle = "danger"
+	RichMessageButtonStyleSuccess RichMessageButtonStyle = "success"
+	RichMessageButtonStylePrimary RichMessageButtonStyle = "primary"
+	RichMessageButtonStyleLink    RichMessageButtonStyle = "link"
+)
+
+type RichTextType string
+
+const (
+	RichTextTypeBold                   RichTextType = "bold"
+	RichTextTypeItalic                 RichTextType = "italic"
+	RichTextTypeUnderline              RichTextType = "underline"
+	RichTextTypeStrikethrough          RichTextType = "strikethrough"
+	RichTextTypeSpoiler                RichTextType = "spoiler"
+	RichTextTypeDateTime               RichTextType = "date_time"
+	RichTextTypeTextMention            RichTextType = "text_mention"
+	RichTextTypeSubscript              RichTextType = "subscript"
+	RichTextTypeSuperscript            RichTextType = "superscript"
+	RichTextTypeMarked                 RichTextType = "marked"
+	RichTextTypeCode                   RichTextType = "code"
+	RichTextTypeCustomEmoji            RichTextType = "custom_emoji"
+	RichTextTypeMathematicalExpression RichTextType = "mathematical_expression"
+	RichTextTypeURL                    RichTextType = "url"
+	RichTextTypeEmailAddress           RichTextType = "email_address"
+	RichTextTypePhoneNumber            RichTextType = "phone_number"
+	RichTextTypeBankCardNumber         RichTextType = "bank_card_number"
+	RichTextTypeMention                RichTextType = "mention"
+	RichTextTypeHashtag                RichTextType = "hashtag"
+	RichTextTypeCashtag                RichTextType = "cashtag"
+	RichTextTypeBotCommand             RichTextType = "bot_command"
+	RichTextTypeButton                 RichTextType = "button"
+	RichTextTypeAnchor                 RichTextType = "anchor"
+	RichTextTypeAnchorLink             RichTextType = "anchor_link"
+	RichTextTypeReference              RichTextType = "reference"
+	RichTextTypeReferenceLink          RichTextType = "reference_link"
+)
+
 type StickerType string
 
 const (

api/richmessage_test.go

@@ -0,0 +1,210 @@
+package api
+
+import (
+	"testing"
+
+	json "github.com/goccy/go-json"
+	"github.com/stretchr/testify/require"
+)
+
+// TestUpdate_RichMessage_Decodes is a regression test for the Bot API v10
+// rich_message decode failure: RichBlock (21 variants) and RichText (25
+// variants) had no knownDiscriminators entry, so genapi never emitted
+// UnmarshalRichBlock / UnmarshalRichText and any update whose message
+// carried rich_message failed to decode — in production this rejected
+// roughly 8.6% of Telegram updates with HTTP 400. Uses goccy/go-json, the
+// codec production runs; plain encoding/json failed the same way.
+func TestUpdate_RichMessage_Decodes(t *testing.T) {
+	body := `{"update_id":1,"message":{"message_id":7,"date":1789000000,"chat":{"id":-100123,"type":"supergroup"},` +
+		`"rich_message":{"blocks":[{"type":"paragraph","text":{"type":"bold","text":{"type":"anchor","name":"hi"}}}]}}}`
+
+	var u Update
+	require.NoError(t, json.Unmarshal([]byte(body), &u))
+
+	require.NotNil(t, u.Message)
+	require.NotNil(t, u.Message.RichMessage)
+	require.Len(t, u.Message.RichMessage.Blocks, 1)
+
+	para, ok := u.Message.RichMessage.Blocks[0].(*RichBlockParagraph)
+	require.True(t, ok, "blocks[0] must dispatch to *RichBlockParagraph, got %T", u.Message.RichMessage.Blocks[0])
+
+	bold, ok := para.Text.(*RichTextBold)
+	require.True(t, ok, "paragraph.text must dispatch to *RichTextBold, got %T", para.Text)
+
+	anchor, ok := bold.Text.(*RichTextAnchor)
+	require.True(t, ok, "bold.text must dispatch to *RichTextAnchor, got %T", bold.Text)
+	require.Equal(t, "hi", anchor.Name)
+}
+
+// TestUnmarshalRichBlock_UnknownType confirms an unrecognised discriminator
+// value surfaces a clear error instead of silently decoding a zero-valued
+// interface.
+func TestUnmarshalRichBlock_UnknownType(t *testing.T) {
+	_, err := UnmarshalRichBlock([]byte(`{"type":"not_a_real_block"}`))
+	require.Error(t, err)
+	require.ErrorContains(t, err, "unknown type")
+}
+
+// TestUpdate_RichMessage_UnknownBlockType confirms the unknown-type error
+// from UnmarshalRichBlock propagates all the way up through
+// RichMessage.UnmarshalJSON to the top-level Update decode.
+func TestUpdate_RichMessage_UnknownBlockType(t *testing.T) {
+	body := `{"update_id":1,"message":{"message_id":7,"date":1789000000,"chat":{"id":-100123,"type":"supergroup"},` +
+		`"rich_message":{"blocks":[{"type":"not_a_real_block"}]}}}`
+
+	var u Update
+	err := json.Unmarshal([]byte(body), &u)
+	require.Error(t, err)
+	require.ErrorContains(t, err, "unknown type")
+}
+
+// TestUpdate_RichMessage_PlainStringText is a regression test for the Bot
+// API v10 RichText decode gap this task fixes. Telegram declares RichText
+// as decodable from "either a String for plain text, an Array of
+// RichText, or any of the following [object] types" — but the IR (and
+// therefore UnmarshalRichText) only ever recorded the object variants, so
+// a paragraph whose text is a bare JSON string failed with "invalid
+// character '\"' looking for beginning of value". A plain-text paragraph
+// is the most common real rich_message payload, so this was the
+// production-facing half of the bug.
+func TestUpdate_RichMessage_PlainStringText(t *testing.T) {
+	body := `{"update_id":1,"message":{"message_id":7,"date":1789000000,"chat":{"id":-100123,"type":"supergroup"},` +
+		`"rich_message":{"blocks":[{"type":"paragraph","text":"hello world"}]}}}`
+
+	var u Update
+	require.NoError(t, json.Unmarshal([]byte(body), &u))
+
+	require.NotNil(t, u.Message)
+	require.NotNil(t, u.Message.RichMessage)
+	require.Len(t, u.Message.RichMessage.Blocks, 1)
+
+	para, ok := u.Message.RichMessage.Blocks[0].(*RichBlockParagraph)
+	require.True(t, ok, "blocks[0] must dispatch to *RichBlockParagraph, got %T", u.Message.RichMessage.Blocks[0])
+
+	plain, ok := para.Text.(*RichTextPlain)
+	require.True(t, ok, "paragraph.text must dispatch to *RichTextPlain for a bare JSON string, got %T", para.Text)
+	require.Equal(t, "hello world", plain.Text)
+}
+
+// TestUpdate_RichMessage_ArrayText confirms Telegram's second declared
+// RichText alternate — a bare JSON array of RichText — decodes into
+// RichTextSequence, with each element dispatched recursively through
+// UnmarshalRichText (an object variant in this case).
+func TestUpdate_RichMessage_ArrayText(t *testing.T) {
+	body := `{"update_id":1,"message":{"message_id":7,"date":1789000000,"chat":{"id":-100123,"type":"supergroup"},` +
+		`"rich_message":{"blocks":[{"type":"paragraph","text":[` +
+		`{"type":"bold","text":"x"},{"type":"italic","text":"y"}` +
+		`]}]}}}`
+
+	var u Update
+	require.NoError(t, json.Unmarshal([]byte(body), &u))
+
+	para, ok := u.Message.RichMessage.Blocks[0].(*RichBlockParagraph)
+	require.True(t, ok)
+
+	seq, ok := para.Text.(*RichTextSequence)
+	require.True(t, ok, "paragraph.text must dispatch to *RichTextSequence for a JSON array, got %T", para.Text)
+	require.Len(t, seq.Items, 2)
+
+	bold, ok := seq.Items[0].(*RichTextBold)
+	require.True(t, ok, "sequence[0] must be *RichTextBold, got %T", seq.Items[0])
+	boldText, ok := bold.Text.(*RichTextPlain)
+	require.True(t, ok)
+	require.Equal(t, "x", boldText.Text)
+
+	italic, ok := seq.Items[1].(*RichTextItalic)
+	require.True(t, ok, "sequence[1] must be *RichTextItalic, got %T", seq.Items[1])
+	italicText, ok := italic.Text.(*RichTextPlain)
+	require.True(t, ok)
+	require.Equal(t, "y", italicText.Text)
+}
+
+// TestUpdate_RichMessage_ArrayText_MixedElements confirms an array whose
+// elements mix the bare-string shape and the object shape dispatches
+// each element independently — the array alternate and the string
+// alternate compose, they aren't mutually exclusive per element.
+func TestUpdate_RichMessage_ArrayText_MixedElements(t *testing.T) {
+	body := `{"update_id":1,"message":{"message_id":7,"date":1789000000,"chat":{"id":-100123,"type":"supergroup"},` +
+		`"rich_message":{"blocks":[{"type":"paragraph","text":[` +
+		`"plain segment",{"type":"bold","text":"bold segment"}` +
+		`]}]}}}`
+
+	var u Update
+	require.NoError(t, json.Unmarshal([]byte(body), &u))
+
+	para, ok := u.Message.RichMessage.Blocks[0].(*RichBlockParagraph)
+	require.True(t, ok)
+
+	seq, ok := para.Text.(*RichTextSequence)
+	require.True(t, ok)
+	require.Len(t, seq.Items, 2)
+
+	plain, ok := seq.Items[0].(*RichTextPlain)
+	require.True(t, ok, "sequence[0] must be *RichTextPlain, got %T", seq.Items[0])
+	require.Equal(t, "plain segment", plain.Text)
+
+	bold, ok := seq.Items[1].(*RichTextBold)
+	require.True(t, ok, "sequence[1] must be *RichTextBold, got %T", seq.Items[1])
+	boldText, ok := bold.Text.(*RichTextPlain)
+	require.True(t, ok)
+	require.Equal(t, "bold segment", boldText.Text)
+}
+
+// TestRichTextPlain_MarshalJSON_RoundTrip confirms the plain-text
+// alternate marshals back to a bare JSON string (not an object), and
+// that string decodes straight back through UnmarshalRichText.
+func TestRichTextPlain_MarshalJSON_RoundTrip(t *testing.T) {
+	v := &RichTextPlain{Text: "hello"}
+
+	b, err := json.Marshal(v)
+	require.NoError(t, err)
+	require.JSONEq(t, `"hello"`, string(b))
+
+	decoded, err := UnmarshalRichText(b)
+	require.NoError(t, err)
+	got, ok := decoded.(*RichTextPlain)
+	require.True(t, ok)
+	require.Equal(t, "hello", got.Text)
+}
+
+// TestRichTextSequence_MarshalJSON_RoundTrip confirms the array
+// alternate marshals back to a bare JSON array (not an object wrapping
+// one), preserving each element's own wire shape, and round-trips
+// through UnmarshalRichText.
+func TestRichTextSequence_MarshalJSON_RoundTrip(t *testing.T) {
+	v := &RichTextSequence{
+		Items: []RichText{
+			&RichTextPlain{Text: "a"},
+			&RichTextBold{Text: &RichTextPlain{Text: "b"}},
+		},
+	}
+
+	b, err := json.Marshal(v)
+	require.NoError(t, err)
+	require.JSONEq(t, `["a",{"type":"bold","text":"b"}]`, string(b))
+
+	decoded, err := UnmarshalRichText(b)
+	require.NoError(t, err)
+	seq, ok := decoded.(*RichTextSequence)
+	require.True(t, ok)
+	require.Len(t, seq.Items, 2)
+
+	p0, ok := seq.Items[0].(*RichTextPlain)
+	require.True(t, ok)
+	require.Equal(t, "a", p0.Text)
+
+	b1, ok := seq.Items[1].(*RichTextBold)
+	require.True(t, ok)
+	p1, ok := b1.Text.(*RichTextPlain)
+	require.True(t, ok)
+	require.Equal(t, "b", p1.Text)
+}
+
+// TestUnmarshalRichText_UnrecognisedShape confirms a JSON value that is
+// neither a string, an array, nor an object surfaces a clear error
+// instead of silently producing a zero-valued interface.
+func TestUnmarshalRichText_UnrecognisedShape(t *testing.T) {
+	_, err := UnmarshalRichText([]byte(`42`))
+	require.Error(t, err)
+	require.ErrorContains(t, err, "unrecognised JSON value")
+}

client/call.go

@@ -215,6 +215,24 @@ func (b *Bot) buildRequest(ctx context.Context, method string, body io.Reader) (
 	return req.WithContext(ctx), nil
 }
 
+// bufferReadCloser exposes a *bytes.Buffer as io.ReadCloser without going
+// through io.NopCloser. Keeping the concrete *bytes.Buffer accessible lets
+// alternative HTTPDoers (e.g. FastHTTPDoer) type-assert and pass the
+// underlying bytes through to their native body-set APIs without copying.
+type bufferReadCloser struct {
+	*bytes.Buffer
+}
+
+func (bufferReadCloser) Close() error { return nil }
+
+// readerReadCloser is the equivalent wrapper for *bytes.Reader (used by
+// the Marshal fallback path when the codec doesn't implement BodyEncoder).
+type readerReadCloser struct {
+	*bytes.Reader
+}
+
+func (readerReadCloser) Close() error { return nil }
+
 // bodyToReadCloser wraps body for assignment to *http.Request.Body. The
 // type switch covers the body shapes encodeJSONBody returns: a pooled
 // *bytes.Buffer (BodyEncoder path or {} fast path) or a *bytes.Reader
@@ -226,16 +244,16 @@ func bodyToReadCloser(body io.Reader) (io.ReadCloser, int64, func() (io.ReadClos
 	case *bytes.Buffer:
 		buf := v.Bytes()
 		length := int64(len(buf))
-		return io.NopCloser(v), length, func() (io.ReadCloser, error) {
-			return io.NopCloser(bytes.NewReader(buf)), nil
+		return bufferReadCloser{v}, length, func() (io.ReadCloser, error) {
+			return readerReadCloser{bytes.NewReader(buf)}, nil
 		}
 	case *bytes.Reader:
 		length := int64(v.Len())
 		// Snapshot the reader's current data so GetBody returns a fresh one.
 		snapshot := *v
-		return io.NopCloser(v), length, func() (io.ReadCloser, error) {
+		return readerReadCloser{v}, length, func() (io.ReadCloser, error) {
 			s := snapshot
-			return io.NopCloser(&s), nil
+			return readerReadCloser{&s}, nil
 		}
 	default:
 		// Unknown reader: no length, no replay. Should not happen with the

client/client.go

@@ -45,6 +45,7 @@ func (b *Bot) Logger() Logger { return b.logger }
 // NewDefaultHTTPDoer); the default codec wraps encoding/json; the default
 // logger discards records.
 func New(token string, opts ...Option) *Bot {
+	fireTelemetryOnce()
 	b := &Bot{
 		token:  token,
 		base:   defaultBaseURL,

client/fasthttp_doer.go

@@ -0,0 +1,231 @@
+package client
+
+import (
+	"context"
+	"errors"
+	"io"
+	"net/http"
+	"strconv"
+	"time"
+
+	"github.com/valyala/fasthttp"
+)
+
+// FastHTTPDoer is an HTTPDoer backed by github.com/valyala/fasthttp. It
+// trades net/http compatibility (and HTTP/2 support) for substantially
+// fewer allocations per request — fasthttp pools its Request and Response
+// objects and uses a zero-allocation HTTP/1.1 parser.
+//
+// Use it for high-throughput bots when GC pressure matters and you don't
+// need HTTP/2 or any net/http-only middleware (RoundTripper composition,
+// the OpenTelemetry httptrace family, etc.):
+//
+//	bot := client.New(token, client.WithHTTPClient(client.NewFastHTTPDoer()))
+//
+// Wrap with RetryDoer the same way you would the default doer.
+type FastHTTPDoer struct {
+	client *fasthttp.Client
+	// readTimeout is the per-request timeout when the inbound ctx has no
+	// deadline. Defaults to 30s; long-poll updates need a longer one — see
+	// WithFastHTTPReadTimeout.
+	readTimeout time.Duration
+}
+
+// FastHTTPDoerOption configures a FastHTTPDoer.
+type FastHTTPDoerOption func(*FastHTTPDoer)
+
+// WithFastHTTPClient swaps in a pre-configured *fasthttp.Client.
+// Useful for sharing a connection pool across multiple bots or applying
+// custom dial / TLS configuration.
+func WithFastHTTPClient(c *fasthttp.Client) FastHTTPDoerOption {
+	return func(d *FastHTTPDoer) { d.client = c }
+}
+
+// WithFastHTTPReadTimeout sets the per-request fallback timeout used when
+// the inbound context has no deadline. Long-poll callers should pass a
+// value larger than the long-poll timeout.
+func WithFastHTTPReadTimeout(t time.Duration) FastHTTPDoerOption {
+	return func(d *FastHTTPDoer) { d.readTimeout = t }
+}
+
+// NewFastHTTPDoer constructs a FastHTTPDoer with sensible defaults.
+func NewFastHTTPDoer(opts ...FastHTTPDoerOption) *FastHTTPDoer {
+	d := &FastHTTPDoer{
+		client: &fasthttp.Client{
+			ReadTimeout:         90 * time.Second,
+			WriteTimeout:        30 * time.Second,
+			MaxIdleConnDuration: 90 * time.Second,
+		},
+		readTimeout: 30 * time.Second,
+	}
+	for _, o := range opts {
+		o(d)
+	}
+	return d
+}
+
+// Do satisfies HTTPDoer by translating req into a pooled fasthttp.Request,
+// dispatching it, and returning a *http.Response whose Body releases the
+// pooled fasthttp.Response when Close is called.
+//
+// The conversion is intentionally minimal: URL goes via req.URL.RequestURI()
+// + Host (avoids re-parsing), header values move byte-for-byte, and the
+// body is taken straight from req.Body. *bytes.Buffer / *bytes.Reader are
+// recognised so we can pass the underlying bytes without io.ReadAll.
+func (d *FastHTTPDoer) Do(req *http.Request) (*http.Response, error) {
+	if req == nil {
+		return nil, errors.New("client: nil http.Request")
+	}
+
+	fReq := fasthttp.AcquireRequest()
+	defer fasthttp.ReleaseRequest(fReq)
+
+	fReq.SetRequestURI(req.URL.String())
+	fReq.Header.SetMethod(req.Method)
+	if req.Host != "" {
+		fReq.Header.SetHost(req.Host)
+	}
+	for name, values := range req.Header {
+		for _, v := range values {
+			fReq.Header.Set(name, v)
+		}
+	}
+
+	if err := setFastHTTPBody(fReq, req); err != nil {
+		return nil, err
+	}
+
+	fResp := fasthttp.AcquireResponse()
+	// fResp is released by fasthttpResponseBody.Close — caller is
+	// expected to defer resp.Body.Close() per net/http contract.
+
+	deadline, hasDeadline := req.Context().Deadline()
+	var err error
+	if hasDeadline {
+		err = d.client.DoDeadline(fReq, fResp, deadline)
+	} else {
+		err = d.client.DoTimeout(fReq, fResp, d.readTimeout)
+	}
+	if err != nil {
+		fasthttp.ReleaseResponse(fResp)
+		// Map fasthttp's timeout error to ctx.Err semantics so callers
+		// can errors.Is(err, context.DeadlineExceeded).
+		if hasDeadline && errors.Is(err, fasthttp.ErrTimeout) {
+			return nil, context.DeadlineExceeded
+		}
+		return nil, err
+	}
+
+	httpResp := &http.Response{
+		StatusCode:    fResp.StatusCode(),
+		Status:        strconv.Itoa(fResp.StatusCode()) + " " + fastHTTPStatusText(fResp.StatusCode()),
+		Header:        make(http.Header, fResp.Header.Len()),
+		ContentLength: int64(fResp.Header.ContentLength()),
+		Body:          &fasthttpResponseBody{resp: fResp, body: fResp.Body()},
+		Request:       req,
+		Proto:         "HTTP/1.1",
+		ProtoMajor:    1,
+		ProtoMinor:    1,
+	}
+	for k, v := range fResp.Header.All() {
+		httpResp.Header.Add(string(k), string(v))
+	}
+	return httpResp, nil
+}
+
+// setFastHTTPBody copies req.Body into fReq with the cheapest path that
+// preserves correctness. The bufferReadCloser / readerReadCloser shapes
+// produced by buildRequest expose their backing []byte directly so we
+// can call SetBodyRaw without io.ReadAll. Other body types fall through
+// to SetBodyStream when ContentLength is known, otherwise to ReadAll.
+func setFastHTTPBody(fReq *fasthttp.Request, req *http.Request) error {
+	if req.Body == nil {
+		return nil
+	}
+	switch v := req.Body.(type) {
+	case bufferReadCloser:
+		fReq.SetBodyRaw(v.Bytes())
+		return nil
+	case readerReadCloser:
+		// *bytes.Reader.Bytes() returns the unread portion.
+		size := v.Len()
+		buf := make([]byte, size)
+		_, err := v.Read(buf)
+		if err != nil && !errors.Is(err, io.EOF) {
+			return err
+		}
+		fReq.SetBodyRaw(buf)
+		return nil
+	default:
+		if req.ContentLength > 0 {
+			fReq.SetBodyStream(v, int(req.ContentLength))
+		} else {
+			body, err := io.ReadAll(v)
+			if err != nil {
+				return err
+			}
+			fReq.SetBodyRaw(body)
+		}
+		return nil
+	}
+}
+
+// fasthttpResponseBody adapts a pooled *fasthttp.Response so it satisfies
+// io.ReadCloser. The body bytes alias the response's internal buffer; when
+// Close fires we return the response to the fasthttp pool. Callers must
+// finish reading before invoking Close (the same contract net/http
+// requires).
+type fasthttpResponseBody struct {
+	resp *fasthttp.Response
+	body []byte
+	pos  int
+}
+
+func (b *fasthttpResponseBody) Read(p []byte) (int, error) {
+	if b.pos >= len(b.body) {
+		return 0, io.EOF
+	}
+	n := copy(p, b.body[b.pos:])
+	b.pos += n
+	return n, nil
+}
+
+func (b *fasthttpResponseBody) Close() error {
+	if b.resp != nil {
+		fasthttp.ReleaseResponse(b.resp)
+		b.resp = nil
+		b.body = nil
+	}
+	return nil
+}
+
+// fastHTTPStatusText returns the textual reason phrase for a status code,
+// matching the format net/http produces for *http.Response.Status. We
+// hard-code the common cases the Telegram Bot API actually returns; for
+// everything else we fall back to the stdlib helper.
+func fastHTTPStatusText(code int) string {
+	switch code {
+	case http.StatusOK:
+		return "OK"
+	case http.StatusBadRequest:
+		return "Bad Request"
+	case http.StatusUnauthorized:
+		return "Unauthorized"
+	case http.StatusForbidden:
+		return "Forbidden"
+	case http.StatusNotFound:
+		return "Not Found"
+	case http.StatusTooManyRequests:
+		return "Too Many Requests"
+	case http.StatusInternalServerError:
+		return "Internal Server Error"
+	case http.StatusBadGateway:
+		return "Bad Gateway"
+	case http.StatusServiceUnavailable:
+		return "Service Unavailable"
+	case http.StatusGatewayTimeout:
+		return "Gateway Timeout"
+	default:
+		return http.StatusText(code)
+	}
+}

client/fasthttp_doer_test.go

@@ -0,0 +1,94 @@
+package client
+
+import (
+	"context"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestFastHTTPDoer_BasicRoundTrip(t *testing.T) {
+	got := make(chan struct{ method, ct, body string }, 1)
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		body, _ := io.ReadAll(r.Body)
+		got <- struct{ method, ct, body string }{r.Method, r.Header.Get("Content-Type"), string(body)}
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = io.WriteString(w, `{"ok":true,"result":42}`)
+	}))
+	defer srv.Close()
+
+	d := NewFastHTTPDoer()
+	req, err := http.NewRequest(http.MethodPost, srv.URL+"/sendMessage", strings.NewReader(`{"chat_id":1,"text":"hi"}`))
+	if err != nil {
+		t.Fatal(err)
+	}
+	req.Header.Set("Content-Type", "application/json")
+	req = req.WithContext(context.Background())
+
+	resp, err := d.Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() { _ = resp.Body.Close() }()
+
+	if resp.StatusCode != 200 {
+		t.Fatalf("status: got %d", resp.StatusCode)
+	}
+	body, _ := io.ReadAll(resp.Body)
+	if string(body) != `{"ok":true,"result":42}` {
+		t.Fatalf("body: got %q", body)
+	}
+
+	rec := <-got
+	if rec.method != http.MethodPost {
+		t.Fatalf("method: got %q", rec.method)
+	}
+	if rec.ct != "application/json" {
+		t.Fatalf("content-type: got %q", rec.ct)
+	}
+	if rec.body != `{"chat_id":1,"text":"hi"}` {
+		t.Fatalf("body: got %q", rec.body)
+	}
+}
+
+func TestFastHTTPDoer_HonoursContextDeadline(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		time.Sleep(200 * time.Millisecond)
+		_, _ = io.WriteString(w, "ok")
+	}))
+	defer srv.Close()
+
+	d := NewFastHTTPDoer(WithFastHTTPReadTimeout(time.Hour))
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Millisecond)
+	defer cancel()
+	req, _ := http.NewRequest(http.MethodGet, srv.URL, nil)
+	req = req.WithContext(ctx)
+
+	_, err := d.Do(req)
+	if err == nil {
+		t.Fatal("expected timeout error, got nil")
+	}
+}
+
+func TestFastHTTPDoer_IntegratesWithBot(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		_, _ = io.WriteString(w, `{"ok":true,"result":{"message_id":7,"date":0,"text":"hi"}}`)
+	}))
+	defer srv.Close()
+
+	bot := New("123:abc",
+		WithBaseURL(srv.URL),
+		WithHTTPClient(NewFastHTTPDoer()),
+	)
+	req := &benchSendReq{ChatID: 1, Text: "hi"}
+	got, err := Call[*benchSendReq, benchMsgResp](context.Background(), bot, "sendMessage", req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got.MessageID != 7 || got.Text != "hi" {
+		t.Fatalf("got %+v", got)
+	}
+}

client/telemetry.go

@@ -0,0 +1,33 @@
+package client
+
+import (
+	"sync"
+
+	telemetry "github.com/lukaszraczylo/oss-telemetry"
+)
+
+// telemetryOnce guards the single anonymous "library used" ping that is sent
+// on the first call to New. Long-running bots typically construct one Bot;
+// short-lived programs or test suites may construct many, but the Once gate
+// keeps the fire-and-forget call from amplifying into per-construction pings.
+var telemetryOnce sync.Once
+
+// fireTelemetryOnce dispatches a fire-and-forget anonymous adoption ping.
+//
+// The call is failproof by contract of oss-telemetry: it never blocks New,
+// never panics, never returns errors, and silently no-ops if disabled or
+// if the network is unavailable.
+//
+// Opt-out is honored via any of these environment variables (case-insensitive
+// truthy values "1", "true", "yes", "on"):
+//
+//   - DO_NOT_TRACK
+//   - OSS_TELEMETRY_DISABLED
+//   - GO_TELEGRAM_DISABLE_TELEMETRY
+//
+// See README §Telemetry for the full disclosure.
+func fireTelemetryOnce() {
+	telemetryOnce.Do(func() {
+		telemetry.SendForModule("go-telegram", "github.com/lukaszraczylo/go-telegram", Version)
+	})
+}

client/telemetry_test.go

@@ -0,0 +1,54 @@
+package client
+
+import (
+	"os"
+	"sync"
+	"testing"
+
+	telemetry "github.com/lukaszraczylo/oss-telemetry"
+)
+
+// TestMain disables outgoing telemetry for the duration of this package's
+// test suite. The library's own tests construct many Bot instances; without
+// this guard they would each contribute a real ping to the public endpoint.
+// End-user test suites that construct Bot are not affected by this — only
+// tests inside this package are.
+func TestMain(m *testing.M) {
+	telemetry.Disable()
+	os.Exit(m.Run())
+}
+
+// TestFireTelemetryOnce_OnlyFiresOnce verifies the sync.Once gate. Even if
+// New is called repeatedly, the underlying telemetry.Send is invoked at most
+// once per process. We can't observe the network call directly (telemetry
+// is disabled here via TestMain) so we assert on the once-Do count via a
+// fresh local sync.Once paralleling the production one.
+func TestFireTelemetryOnce_OnlyFiresOnce(t *testing.T) {
+	// Reset the package-level Once so this test starts from a clean state.
+	telemetryOnce = sync.Once{}
+	t.Cleanup(func() { telemetryOnce = sync.Once{} })
+
+	calls := 0
+	probe := func() { telemetryOnce.Do(func() { calls++ }) }
+
+	for i := 0; i < 50; i++ {
+		probe()
+	}
+	if calls != 1 {
+		t.Fatalf("expected exactly 1 Once execution, got %d", calls)
+	}
+}
+
+// TestNew_DoesNotPanicUnderRepeatedConstruction is a smoke test that
+// telemetry wiring does not affect New's existing contract. New must never
+// panic, regardless of telemetry state.
+func TestNew_DoesNotPanicUnderRepeatedConstruction(t *testing.T) {
+	defer func() {
+		if r := recover(); r != nil {
+			t.Fatalf("New panicked: %v", r)
+		}
+	}()
+	for i := 0; i < 20; i++ {
+		_ = New("test-token-" + string(rune('A'+i)))
+	}
+}

client/version.go

@@ -0,0 +1,11 @@
+package client
+
+// Version is a fallback version string used only when Go's build info is
+// unavailable (replace directives, detached `go run`) or has been overridden
+// via linker flags. The authoritative version forwarded to telemetry is
+// resolved at runtime by [telemetry.SendForModule] from the build info of
+// whatever binary linked this library, so this constant does NOT need to be
+// bumped on every release. Exposed as a var (not const) for ldflag override:
+//
+//	go build -ldflags="-X github.com/lukaszraczylo/go-telegram/client.Version=1.2.3"
+var Version = "0.0.0-fallback"

cmd/audit/extra_test.go

@@ -125,12 +125,18 @@ func TestAuditDrift_InvalidRefReturnsError(t *testing.T) {
 }
 
 func TestAuditDrift_SameRefNoDrift(t *testing.T) {
+	// Compare HEAD's IR against itself, not against the working tree: during a
+	// regen run the working tree legitimately carries new methods, and drift
+	// against HEAD is the expected outcome rather than a failure.
 	irPath := "../../internal/spec/api.json"
-	cur, err := loadIR(irPath)
+	out, err := exec.Command("git", "show", "HEAD:"+irPath).Output()
 	if err != nil {
-		t.Skip("api.json not available, skipping drift test")
+		t.Skip("api.json not available at HEAD, skipping drift test")
 	}
-	changes, err := auditDrift(irPath, "HEAD", cur)
+	var head spec.API
+	require.NoError(t, json.Unmarshal(out, &head))
+
+	changes, err := auditDrift(irPath, "HEAD", &head)
 	require.NoError(t, err)
 	require.Empty(t, changes)
 }
@@ -166,7 +172,7 @@ func TestAuditAny_FlagsUnknownMethodReturn(t *testing.T) {
 			},
 		},
 	}
-	out := auditAny(api)
+	out := auditAny(api, &spec.Overrides{})
 	require.Len(t, out, 1)
 	require.Contains(t, out[0], "any return: weirdMethod")
 }
@@ -182,7 +188,7 @@ func TestAuditAny_FlagsUnknownMethodParam(t *testing.T) {
 			},
 		},
 	}
-	out := auditAny(api)
+	out := auditAny(api, &spec.Overrides{})
 	require.Len(t, out, 1)
 	require.Contains(t, out[0], "any param: weirdMethod.Thing")
 }

cmd/audit/main.go

@@ -54,7 +54,7 @@ func main() {
 	var problems []string
 
 	problems = append(problems, auditBool(api, overrides)...)
-	problems = append(problems, auditAny(api)...)
+	problems = append(problems, auditAny(api, overrides)...)
 
 	driftFound := false
 	if *checkDrift {
@@ -140,8 +140,9 @@ func looksGenuinelyBool(doc string) bool {
 
 // auditAny scans the IR for any KindOneOf TypeRef that would render as
 // `any` in generated code (not matched by ChatID/InputFile-or-string/known
-// union heuristics). Reports each occurrence with location.
-func auditAny(api *spec.API) []string {
+// union heuristics). Reports each occurrence with location, except the
+// locations approved in overrides.
+func auditAny(api *spec.API, ov *spec.Overrides) []string {
 	var out []string
 	isKnownUnion := func(variants []string) bool {
 		if hasVariants(variants, "int64", "string") {
@@ -166,17 +167,17 @@ func auditAny(api *spec.API) []string {
 	}
 	for _, t := range api.Types {
 		for _, f := range t.Fields {
-			if isAny(f.Type) {
+			if isAny(f.Type) && !ov.IsAnyApproved(t.Name+"."+f.Name) {
 				out = append(out, fmt.Sprintf("any field: %s.%s (variants=%v)", t.Name, f.Name, f.Type.Variants))
 			}
 		}
 	}
 	for _, m := range api.Methods {
-		if isAny(m.Returns) {
+		if isAny(m.Returns) && !ov.IsAnyApproved(m.Name) {
 			out = append(out, fmt.Sprintf("any return: %s (variants=%v)", m.Name, m.Returns.Variants))
 		}
 		for _, p := range m.Params {
-			if isAny(p.Type) {
+			if isAny(p.Type) && !ov.IsAnyApproved(m.Name+"."+p.Name) {
 				out = append(out, fmt.Sprintf("any param: %s.%s (variants=%v)", m.Name, p.Name, p.Type.Variants))
 			}
 		}

cmd/audit/main_test.go

@@ -66,11 +66,37 @@ func TestAuditAny_FlagsUnrecognisedOneOf(t *testing.T) {
 			},
 		},
 	}
-	out := auditAny(api)
+	out := auditAny(api, &spec.Overrides{})
 	require.Len(t, out, 1)
 	require.Contains(t, out[0], "any field: Foo.Bar")
 }
 
+func TestAuditAny_SkipsApprovedLocations(t *testing.T) {
+	api := &spec.API{
+		Types: []spec.TypeDecl{
+			{
+				Name: "Foo",
+				Fields: []spec.Field{
+					{Name: "Bar", JSONName: "bar", Type: spec.TypeRef{Kind: spec.KindOneOf, Variants: []string{"A", "B"}}},
+				},
+			},
+		},
+		Methods: []spec.MethodDecl{
+			{
+				Name:    "doThing",
+				Returns: spec.TypeRef{Kind: spec.KindOneOf, Variants: []string{"A", "B"}},
+				Params: []spec.Field{
+					{Name: "Baz", JSONName: "baz", Type: spec.TypeRef{Kind: spec.KindOneOf, Variants: []string{"A", "B"}}},
+				},
+			},
+		},
+	}
+	require.Len(t, auditAny(api, &spec.Overrides{}), 3)
+
+	ov := &spec.Overrides{ApprovedAnyLocations: []string{"Foo.Bar", "doThing", "doThing.Baz"}}
+	require.Empty(t, auditAny(api, ov))
+}
+
 func TestAuditAny_SkipsChatIDShape(t *testing.T) {
 	api := &spec.API{
 		Types: []spec.TypeDecl{
@@ -82,7 +108,7 @@ func TestAuditAny_SkipsChatIDShape(t *testing.T) {
 			},
 		},
 	}
-	require.Empty(t, auditAny(api))
+	require.Empty(t, auditAny(api, &spec.Overrides{}))
 }
 
 func TestAuditAny_SkipsKnownUnion(t *testing.T) {
@@ -97,7 +123,7 @@ func TestAuditAny_SkipsKnownUnion(t *testing.T) {
 			},
 		},
 	}
-	require.Empty(t, auditAny(api))
+	require.Empty(t, auditAny(api, &spec.Overrides{}))
 }
 
 func TestAuditAny_SkipsReplyMarkupShape(t *testing.T) {
@@ -111,7 +137,7 @@ func TestAuditAny_SkipsReplyMarkupShape(t *testing.T) {
 			},
 		},
 	}
-	require.Empty(t, auditAny(api))
+	require.Empty(t, auditAny(api, &spec.Overrides{}))
 }
 
 func TestAuditAny_SkipsInputFileShape(t *testing.T) {
@@ -125,7 +151,7 @@ func TestAuditAny_SkipsInputFileShape(t *testing.T) {
 			},
 		},
 	}
-	require.Empty(t, auditAny(api))
+	require.Empty(t, auditAny(api, &spec.Overrides{}))
 }
 
 // ---- diffSignatures ------------------------------------------------------

cmd/genapi/alternates_test.go

@@ -0,0 +1,144 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/lukaszraczylo/go-telegram/internal/spec"
+	"github.com/stretchr/testify/require"
+)
+
+// TestUnionAlternates_NoAlternates confirms a union with no Alternates
+// (the common case — every union except RichText) produces no synthetic
+// variants.
+func TestUnionAlternates_NoAlternates(t *testing.T) {
+	td := spec.TypeDecl{Name: "ChatMember", OneOf: []string{"ChatMemberOwner"}}
+	require.Nil(t, unionAlternates(td))
+}
+
+// TestUnionAlternates_StringAndArray confirms both alternate shapes map
+// to the expected synthetic variant names, in declaration order.
+func TestUnionAlternates_StringAndArray(t *testing.T) {
+	td := spec.TypeDecl{
+		Name:  "RichText",
+		OneOf: []string{"RichTextBold"},
+		Alternates: []spec.Alternate{
+			{Shape: spec.AlternateString},
+			{Shape: spec.AlternateArray},
+		},
+	}
+	got := unionAlternates(td)
+	require.Equal(t, []alternateVariant{
+		{Name: "RichTextPlain", IsString: true},
+		{Name: "RichTextSequence", IsArray: true},
+	}, got)
+}
+
+// TestEmitTypes_UnionWithAlternates_EmitsShapeDispatcher builds a minimal
+// synthetic API with one discriminated union carrying Alternates (mirrors
+// RichText's shape without depending on the full real spec) and confirms
+// genapi emits: the two synthetic variant structs, their marker methods
+// and MarshalJSON, and a shape-dispatching Unmarshal<Union> that branches
+// on the first non-whitespace byte before falling back to the existing
+// discriminator switch.
+func TestEmitTypes_UnionWithAlternates_EmitsShapeDispatcher(t *testing.T) {
+	api := &spec.API{
+		Types: []spec.TypeDecl{
+			{
+				Name:  "Widget",
+				OneOf: []string{"WidgetBold"},
+				Alternates: []spec.Alternate{
+					{Shape: spec.AlternateString},
+					{Shape: spec.AlternateArray},
+				},
+			},
+			{
+				Name: "WidgetBold",
+				Fields: []spec.Field{
+					{Name: "Type", JSONName: "type", Required: true,
+						Type: spec.TypeRef{Kind: spec.KindPrimitive, Name: "string"}, EnumValues: []string{"bold"}},
+				},
+			},
+		},
+	}
+
+	tmp := t.TempDir()
+	e := newEmitter(api, tmp)
+	require.NoError(t, e.emitTypes())
+
+	got, err := os.ReadFile(filepath.Join(tmp, "types.gen.go"))
+	require.NoError(t, err)
+	src := string(got)
+
+	// Synthetic variants exist and implement the sealed interface.
+	require.Contains(t, src, "type WidgetPlain struct")
+	require.Contains(t, src, "Text string")
+	require.Contains(t, src, "func (*WidgetPlain) isWidget() {}")
+	require.Contains(t, src, "type WidgetSequence struct")
+	require.Contains(t, src, "Items []Widget")
+	require.Contains(t, src, "func (*WidgetSequence) isWidget() {}")
+
+	// Round-trip MarshalJSON for both.
+	require.Contains(t, src, "func (v *WidgetPlain) MarshalJSON() ([]byte, error) {")
+	require.Contains(t, src, "return json.Marshal(v.Text)")
+	require.Contains(t, src, "func (v *WidgetSequence) MarshalJSON() ([]byte, error) {")
+	require.Contains(t, src, "return json.Marshal(v.Items)")
+
+	// Shape-dispatching UnmarshalWidget: trims, branches on '"', '[', '{'.
+	require.Contains(t, src, "func UnmarshalWidget(data []byte) (Widget, error) {")
+	require.Contains(t, src, `trimmed := bytes.TrimLeft(data, " \t\r\n")`)
+	require.Contains(t, src, "case '\"':")
+	require.Contains(t, src, "return &WidgetPlain{Text: s}, nil")
+	require.Contains(t, src, "case '[':")
+	require.Contains(t, src, "return &WidgetSequence{Items: items}, nil")
+	require.Contains(t, src, "case '{':")
+	// The pre-existing discriminator switch is preserved beneath the
+	// shape dispatch, unrecognised discriminator still a clear error.
+	require.Contains(t, src, `fmt.Errorf("Widget: unknown type %q", probe.V)`)
+
+	// The struct-holding-the-union case inherits shape dispatch for free:
+	// WidgetBold has no union-typed field itself, so nothing further to
+	// assert there beyond successful compilation-shaped source (covered
+	// by TestEmit_Types_FixtureGolden's gofmt round trip for the real
+	// fixture, and by the api-package tests for full decode behaviour).
+	require.False(t, strings.Contains(src, "WidgetPlainSequence"), "sanity: no accidental name collision")
+}
+
+// TestEmitTypes_UnionWithoutAlternates_Unaffected confirms a discriminated
+// union with no Alternates emits the original (pre-alternates) shape:
+// no synthetic variants, no shape dispatch, and the same "decodes a X
+// from JSON by inspecting" doc comment wording as before this feature.
+func TestEmitTypes_UnionWithoutAlternates_Unaffected(t *testing.T) {
+	api := &spec.API{
+		Types: []spec.TypeDecl{
+			{Name: "Widget", OneOf: []string{"WidgetBold"}},
+			{
+				Name: "WidgetBold",
+				Fields: []spec.Field{
+					{Name: "Type", JSONName: "type", Required: true,
+						Type: spec.TypeRef{Kind: spec.KindPrimitive, Name: "string"}, EnumValues: []string{"bold"}},
+				},
+			},
+		},
+	}
+
+	tmp := t.TempDir()
+	e := newEmitter(api, tmp)
+	require.NoError(t, e.emitTypes())
+
+	got, err := os.ReadFile(filepath.Join(tmp, "types.gen.go"))
+	require.NoError(t, err)
+	src := string(got)
+
+	require.NotContains(t, src, "WidgetPlain")
+	require.NotContains(t, src, "WidgetSequence")
+	// The package-level `var _ = bytes.TrimLeft` import guard is always
+	// present (it keeps the "bytes" import valid even when no union in
+	// this API has alternates); what must NOT appear is the per-union
+	// shape-dispatch call site.
+	require.NotContains(t, src, "trimmed := bytes.TrimLeft(data,")
+	require.Contains(t, src, "// UnmarshalWidget decodes a Widget from JSON by inspecting the")
+	require.Contains(t, src, `// "type" field and dispatching to the correct concrete type.`)
+}

cmd/genapi/derive_discriminators_test.go

@@ -0,0 +1,148 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/lukaszraczylo/go-telegram/internal/spec"
+	"github.com/stretchr/testify/require"
+)
+
+// TestDeriveDiscriminators_RichBlockAndRichText_FromRealSpec is a
+// regression test for the Bot API v10 rich_message decode failure:
+// RichBlock and RichText had no knownDiscriminators entry, so genapi
+// never emitted UnmarshalRichBlock / UnmarshalRichText and any update
+// whose message carried rich_message failed to decode. Derivation must
+// pick "type" for both and cover every variant the spec declares.
+//
+// The expected variant counts are read from the spec rather than pinned
+// as literals. Telegram adds variants in most releases - v10.3 took
+// RichBlock from 21 to 24 and RichText from 25 to 26 - so a frozen
+// number turns a routine regeneration into a spurious failure while
+// testing nothing the coverage assertion does not already cover.
+func TestDeriveDiscriminators_RichBlockAndRichText_FromRealSpec(t *testing.T) {
+	api, err := loadAPI("../../internal/spec/api.json")
+	require.NoError(t, err)
+
+	// declaredVariants returns how many concrete variants the spec lists
+	// for a union, so the assertions below track the spec instead of a
+	// hardcoded count.
+	declaredVariants := func(union string) int {
+		for i := range api.Types {
+			if api.Types[i].Name == union {
+				return len(api.Types[i].OneOf)
+			}
+		}
+		t.Fatalf("union %q not found in spec", union)
+		return 0
+	}
+
+	derived, _ := deriveDiscriminators(api)
+
+	rb, ok := derived["RichBlock"]
+	require.True(t, ok, "RichBlock must derive a discriminator")
+	require.Equal(t, "type", rb.Field)
+	require.Len(t, rb.Variants, declaredVariants("RichBlock"),
+		"every RichBlock variant declared in the spec must be covered")
+	require.Equal(t, "RichBlockParagraph", rb.Variants["paragraph"])
+	require.Equal(t, "RichBlockTable", rb.Variants["table"])
+	require.Equal(t, "RichBlockThinking", rb.Variants["thinking"])
+
+	rt, ok := derived["RichText"]
+	require.True(t, ok, "RichText must derive a discriminator")
+	require.Equal(t, "type", rt.Field)
+	require.Len(t, rt.Variants, declaredVariants("RichText"),
+		"every RichText variant declared in the spec must be covered")
+	require.Equal(t, "RichTextBold", rt.Variants["bold"])
+	require.Equal(t, "RichTextAnchorLink", rt.Variants["anchor_link"])
+	require.Equal(t, "RichTextReferenceLink", rt.Variants["reference_link"])
+}
+
+// TestMergeDiscriminators_HandCuratedOverridesDerived confirms a
+// knownDiscriminators entry always wins the merge even when derivation
+// would also have produced a (different) answer for the same union —
+// hand-curation is the escape hatch for a union the generic rule gets
+// wrong.
+func TestMergeDiscriminators_HandCuratedOverridesDerived(t *testing.T) {
+	api := &spec.API{
+		Types: []spec.TypeDecl{
+			{Name: "Widget", OneOf: []string{"WidgetA", "WidgetB"}},
+			{Name: "WidgetA", Fields: []spec.Field{
+				{Name: "Type", JSONName: "type", Required: true,
+					Type: spec.TypeRef{Kind: spec.KindPrimitive, Name: "string"}, EnumValues: []string{"a"}},
+			}},
+			{Name: "WidgetB", Fields: []spec.Field{
+				{Name: "Type", JSONName: "type", Required: true,
+					Type: spec.TypeRef{Kind: spec.KindPrimitive, Name: "string"}, EnumValues: []string{"b"}},
+			}},
+		},
+	}
+
+	derived, ungated := deriveDiscriminators(api)
+	require.Empty(t, ungated)
+	require.Equal(t, discriminatorSpec{
+		Field:    "type",
+		Variants: map[string]string{"a": "WidgetA", "b": "WidgetB"},
+	}, derived["Widget"])
+
+	// Inject a hand-curated override that disagrees with the derived
+	// spec, merge, and confirm the override wins outright.
+	override := discriminatorSpec{Field: "kind", Variants: map[string]string{"custom": "WidgetA"}}
+	knownDiscriminators["Widget"] = override
+	t.Cleanup(func() { delete(knownDiscriminators, "Widget") })
+
+	merged := mergeDiscriminators(derived)
+	require.Equal(t, override, merged["Widget"])
+}
+
+// TestCheckDiscriminatorGate_FailsOnUngatedInboundUnion confirms the
+// build gate fails generation when a union Telegram can actually send
+// has no derivable discriminator: the variants share no common
+// Type/Status/Source field at all.
+func TestCheckDiscriminatorGate_FailsOnUngatedInboundUnion(t *testing.T) {
+	api := &spec.API{
+		Types: []spec.TypeDecl{
+			{Name: "Widget", OneOf: []string{"WidgetA", "WidgetB"}},
+			{Name: "WidgetA", Fields: []spec.Field{
+				{Name: "Kind", JSONName: "kind", Required: true, Type: spec.TypeRef{Kind: spec.KindPrimitive, Name: "string"}},
+			}},
+			{Name: "WidgetB", Fields: []spec.Field{
+				{Name: "Flavor", JSONName: "flavor", Required: true, Type: spec.TypeRef{Kind: spec.KindPrimitive, Name: "string"}},
+			}},
+			// Container is a plain (non-Input) type with a field of the
+			// undiscriminated union — this is what makes Widget reachable
+			// from real inbound Telegram data.
+			{Name: "Container", Fields: []spec.Field{
+				{Name: "W", JSONName: "w", Type: spec.TypeRef{Kind: spec.KindNamed, Name: "Widget"}},
+			}},
+		},
+	}
+
+	err := checkDiscriminatorGate(api)
+	require.Error(t, err)
+	require.ErrorContains(t, err, "Widget")
+	require.ErrorContains(t, err, "WidgetA")
+	require.ErrorContains(t, err, "WidgetB")
+}
+
+// TestCheckDiscriminatorGate_SilentForInputOnlyUnion confirms the same
+// undiscriminated union does NOT fail the build when its only reference
+// is a field on an Input*-prefixed type — those are always constructed
+// and marshalled by the caller, never decoded from a Telegram response.
+func TestCheckDiscriminatorGate_SilentForInputOnlyUnion(t *testing.T) {
+	api := &spec.API{
+		Types: []spec.TypeDecl{
+			{Name: "Widget", OneOf: []string{"WidgetA", "WidgetB"}},
+			{Name: "WidgetA", Fields: []spec.Field{
+				{Name: "Kind", JSONName: "kind", Required: true, Type: spec.TypeRef{Kind: spec.KindPrimitive, Name: "string"}},
+			}},
+			{Name: "WidgetB", Fields: []spec.Field{
+				{Name: "Flavor", JSONName: "flavor", Required: true, Type: spec.TypeRef{Kind: spec.KindPrimitive, Name: "string"}},
+			}},
+			{Name: "InputContainer", Fields: []spec.Field{
+				{Name: "W", JSONName: "w", Type: spec.TypeRef{Kind: spec.KindNamed, Name: "Widget"}},
+			}},
+		},
+	}
+
+	require.NoError(t, checkDiscriminatorGate(api))
+}

cmd/genapi/emitter.go

@@ -3,6 +3,7 @@ package main
 import (
 	"bytes"
 	_ "embed"
+	"errors"
 	"fmt"
 	"github.com/goccy/go-json"
 	"go/format"
@@ -10,6 +11,7 @@ import (
 	"path/filepath"
 	"regexp"
 	"sort"
+	"strings"
 	"text/template"
 
 	"github.com/lukaszraczylo/go-telegram/internal/spec"
@@ -77,9 +79,18 @@ type discriminatorSpec struct {
 	Variants map[string]string // discriminator value → concrete Go type name
 }
 
-// knownDiscriminators maps parent union name → discriminator spec.
-// Used by the template helpers hasDiscriminator / discriminatorField /
-// discriminatorMap to emit UnmarshalXxx helpers.
+// knownDiscriminators is the hand-curated OVERRIDE table for sealed-union
+// discriminators. deriveDiscriminators computes the same kind of map
+// automatically from the IR for every union that has one (see
+// mergeDiscriminators); an entry here always wins the merge regardless of
+// what derivation would have produced. Use this table only for unions the
+// generic rule can't handle — e.g. MaybeInaccessibleMessage's integer
+// discriminator, which needs bespoke decode logic no discriminatorSpec
+// can express (Field is "" and Variants is nil; the template emits a
+// hand-coded Unmarshal via isMaybeInaccessibleMessage instead). Every
+// other entry here exists only because it predates derivation — removing
+// one and re-running `go test -run TestEmit -update ./cmd/genapi/...`
+// should reproduce it byte-for-byte from deriveDiscriminators.
 var knownDiscriminators = map[string]discriminatorSpec{
 	"ChatMember": {
 		Field: "status",
@@ -205,15 +216,24 @@ type emitter struct {
 	// template to emit per-variant MarshalJSON that hardcodes the
 	// discriminator so callers don't have to set it by hand.
 	variantDiscs map[string]variantDiscriminator
+	// discs is the merged union-level discriminator table: derivation
+	// output with knownDiscriminators layered on top as overrides (see
+	// mergeDiscriminators). Every codegen path that decides whether a
+	// union auto-decodes — and how — consults this instead of the
+	// package-level knownDiscriminators map, so a union qualifies the
+	// moment deriveDiscriminators can resolve it, hand-curated or not.
+	discs map[string]discriminatorSpec
 }
 
 func newEmitter(api *spec.API, outDir string) *emitter {
 	knownInterfaceTypes = buildUnionTypeSet(api)
+	derived, _ := deriveDiscriminators(api)
 	return &emitter{
 		api:          api,
 		outDir:       outDir,
 		enums:        planEnums(api),
 		variantDiscs: variantDiscriminators(api),
+		discs:        mergeDiscriminators(derived),
 	}
 }
 
@@ -349,6 +369,262 @@ func parseDiscriminatorDoc(doc string) string {
 	return ""
 }
 
+// discriminatorFieldCandidates returns the Go field names to try, in
+// priority order, when looking for a discriminator shared by every
+// variant of a union: the hand-curated field from knownDiscriminators
+// (resolved to its Go name via the first variant that declares it) when
+// the union already has an override entry, then "Type", "Status",
+// "Source" — the three names Telegram's docs consistently use for this
+// purpose. Shared by planUnifiedUnionEnums (enum naming, enums.go) and
+// deriveDiscriminators (decode dispatch, below) so the two never disagree
+// on where to look.
+func discriminatorFieldCandidates(unionName string, variants []*spec.TypeDecl) []string {
+	var candidates []string
+	seen := map[string]bool{}
+	add := func(name string) {
+		if name == "" || seen[name] {
+			return
+		}
+		seen[name] = true
+		candidates = append(candidates, name)
+	}
+	if ds, ok := knownDiscriminators[unionName]; ok && ds.Field != "" {
+		for _, v := range variants {
+			for _, f := range v.Fields {
+				if f.JSONName == ds.Field {
+					add(f.Name)
+					break
+				}
+			}
+		}
+	}
+	add("Type")
+	add("Status")
+	add("Source")
+	return candidates
+}
+
+// fieldByGoName returns the field named name on fields, or nil if none matches.
+func fieldByGoName(fields []spec.Field, name string) *spec.Field {
+	for i := range fields {
+		if fields[i].Name == name {
+			return &fields[i]
+		}
+	}
+	return nil
+}
+
+// discriminatorValue extracts the wire-level value a variant field
+// contributes to a discriminator: a single-entry EnumValues list (the
+// scraper's detected value), or a doc-parsed "must be X" / "always “X”"
+// literal via parseDiscriminatorDoc (the same extraction
+// extractVariantDiscriminator uses for the first-field case). Returns ""
+// when the field isn't a required string or carries no resolvable value.
+func discriminatorValue(f spec.Field) string {
+	if !f.Required || f.Type.Kind != spec.KindPrimitive || f.Type.Name != "string" {
+		return ""
+	}
+	if len(f.EnumValues) == 1 {
+		return f.EnumValues[0]
+	}
+	return parseDiscriminatorDoc(f.Doc)
+}
+
+// deriveDiscriminators inspects every union TypeDecl (len(OneOf) > 0) in
+// api and tries to pick a discriminator JSON field automatically, so the
+// hand-maintained knownDiscriminators map no longer has to name every
+// union that qualifies. A union qualifies when, for some candidate field
+// (see discriminatorFieldCandidates), EVERY variant declares that field
+// and discriminatorValue resolves a non-empty wire value for it, and
+// those values are unique across variants.
+//
+// Returns the derived map plus the names of unions that did not qualify,
+// in declaration order. Callers merge the derived map with
+// knownDiscriminators (mergeDiscriminators) and decide what to do about
+// the leftovers — rescue via a hand-curated override, or fail the build
+// if the union is reachable from real Telegram data (checkDiscriminatorGate).
+func deriveDiscriminators(api *spec.API) (map[string]discriminatorSpec, []string) {
+	typeByName := make(map[string]*spec.TypeDecl, len(api.Types))
+	for i := range api.Types {
+		typeByName[api.Types[i].Name] = &api.Types[i]
+	}
+
+	derived := make(map[string]discriminatorSpec, 32)
+	var ungated []string
+
+	for i := range api.Types {
+		u := &api.Types[i]
+		if len(u.OneOf) == 0 {
+			continue
+		}
+
+		variants := make([]*spec.TypeDecl, 0, len(u.OneOf))
+		resolved := true
+		for _, vName := range u.OneOf {
+			v, found := typeByName[vName]
+			if !found {
+				resolved = false
+				break
+			}
+			variants = append(variants, v)
+		}
+		if !resolved {
+			ungated = append(ungated, u.Name)
+			continue
+		}
+
+		ds, qualified := deriveUnionDiscriminator(u.Name, variants)
+		if !qualified {
+			ungated = append(ungated, u.Name)
+			continue
+		}
+		derived[u.Name] = ds
+	}
+	return derived, ungated
+}
+
+// deriveUnionDiscriminator tries each candidate Go field name in
+// priority order and returns the first one where every variant declares
+// that field with a resolvable, unique wire value.
+func deriveUnionDiscriminator(unionName string, variants []*spec.TypeDecl) (discriminatorSpec, bool) {
+	for _, goName := range discriminatorFieldCandidates(unionName, variants) {
+		jsonField := ""
+		values := make(map[string]string, len(variants)) // wire value -> variant Go type name
+		qualifies := true
+		for _, v := range variants {
+			f := fieldByGoName(v.Fields, goName)
+			if f == nil {
+				qualifies = false
+				break
+			}
+			value := discriminatorValue(*f)
+			if value == "" {
+				qualifies = false
+				break
+			}
+			if jsonField == "" {
+				jsonField = f.JSONName
+			} else if f.JSONName != jsonField {
+				qualifies = false
+				break
+			}
+			if _, dup := values[value]; dup {
+				qualifies = false
+				break
+			}
+			values[value] = v.Name
+		}
+		if qualifies {
+			return discriminatorSpec{Field: jsonField, Variants: values}, true
+		}
+	}
+	return discriminatorSpec{}, false
+}
+
+// mergeDiscriminators layers the hand-curated knownDiscriminators table
+// on top of derived: every entry deriveDiscriminators produces is used
+// as-is unless knownDiscriminators also names that union, in which case
+// the hand-curated entry wins outright (the whole discriminatorSpec, not
+// a per-key merge).
+func mergeDiscriminators(derived map[string]discriminatorSpec) map[string]discriminatorSpec {
+	merged := make(map[string]discriminatorSpec, len(derived)+len(knownDiscriminators))
+	for name, ds := range derived {
+		merged[name] = ds
+	}
+	for name, ds := range knownDiscriminators {
+		merged[name] = ds
+	}
+	return merged
+}
+
+// isInboundReachable reports whether Telegram can actually send data
+// typed as the named union to the bot: as a field on some type that
+// isn't itself send-only, or as a method's return value. "Input*"-named
+// unions are excluded outright regardless of where they're referenced —
+// by Telegram's own naming convention in this API, every such union is
+// something the bot constructs and marshals, never something it decodes.
+func isInboundReachable(api *spec.API, unionName string) bool {
+	if strings.HasPrefix(unionName, "Input") {
+		return false
+	}
+	for _, m := range api.Methods {
+		if typeRefIsUnion(m.Returns, api, unionName) {
+			return true
+		}
+	}
+	for _, t := range api.Types {
+		if strings.HasPrefix(t.Name, "Input") {
+			continue // send-only struct; its fields are never decoded either.
+		}
+		for _, f := range t.Fields {
+			if typeRefIsUnion(f.Type, api, unionName) {
+				return true
+			}
+		}
+	}
+	return false
+}
+
+// typeRefIsUnion reports whether tr resolves to the named union: directly,
+// as an array element, or via an inline oneOf variant-set match against
+// unionName's own OneOf list.
+func typeRefIsUnion(tr spec.TypeRef, api *spec.API, unionName string) bool {
+	switch tr.Kind {
+	case spec.KindNamed:
+		return tr.Name == unionName
+	case spec.KindArray:
+		if tr.ElemType != nil {
+			return typeRefIsUnion(*tr.ElemType, api, unionName)
+		}
+	case spec.KindOneOf:
+		for i := range api.Types {
+			if api.Types[i].Name == unionName && matchesVariants(tr.Variants, api.Types[i].OneOf...) {
+				return true
+			}
+		}
+	}
+	return false
+}
+
+// checkDiscriminatorGate fails codegen when a union Telegram can actually
+// send to the bot has no usable discriminator — neither derived nor
+// hand-curated. Such a union decodes to a bare interface field that no
+// JSON codec can ever fill (the RichBlock/RichText Bot API v10
+// regression this generalisation fixes: both had 20+ variants and no
+// knownDiscriminators entry, so genapi silently emitted no UnmarshalXxx
+// helper at all). Send-only "Input*" unions are exempt — see
+// isInboundReachable.
+func checkDiscriminatorGate(api *spec.API) error {
+	_, ungated := deriveDiscriminators(api)
+
+	typeByName := make(map[string]*spec.TypeDecl, len(api.Types))
+	for i := range api.Types {
+		typeByName[api.Types[i].Name] = &api.Types[i]
+	}
+
+	var offending []string
+	for _, name := range ungated {
+		if _, overridden := knownDiscriminators[name]; overridden {
+			continue // hand-curated rescue, e.g. MaybeInaccessibleMessage.
+		}
+		if isInboundReachable(api, name) {
+			offending = append(offending, name)
+		}
+	}
+	if len(offending) == 0 {
+		return nil
+	}
+
+	var b strings.Builder
+	fmt.Fprintf(&b, "genapi: %d inbound union(s) have no derivable or hand-curated discriminator "+
+		"and would decode as an unfillable interface field:", len(offending))
+	for _, name := range offending {
+		fmt.Fprintf(&b, "\n  - %s (variants: %s): no single field is present, required, and holds a unique non-empty wire value on every variant",
+			name, strings.Join(typeByName[name].OneOf, ", "))
+	}
+	return errors.New(b.String())
+}
+
 // knownInterfaceTypes is the full set of sealed-interface union type names
 // (both auto-decoded ones in knownDiscriminators and marker-only ones from
 // types with OneOf). Populated at emitter construction. goType and
@@ -359,7 +635,7 @@ var knownInterfaceTypes = map[string]bool{}
 
 // emitTypes renders types.gen.go.
 func (e *emitter) emitTypes() error {
-	t, err := template.New("types").Funcs(funcsWithDiscs(e.enums, e.variantDiscs)).Parse(typesTmpl)
+	t, err := template.New("types").Funcs(funcsWithDiscs(e.enums, e.variantDiscs, e.discs)).Parse(typesTmpl)
 	if err != nil {
 		return fmt.Errorf("parse types.tmpl: %w", err)
 	}
@@ -396,31 +672,35 @@ func loadAPI(path string) (*spec.API, error) {
 }
 
 // funcsWithDiscs returns the shared FuncMap with the variant
-// discriminator helpers bound to discs. types.tmpl uses
+// discriminator helpers bound to variantDiscs. types.tmpl uses
 // variantDiscFor/variantHasDisc to emit per-variant MarshalJSON that
-// hardcodes the wire discriminator value.
-func funcsWithDiscs(plan *enumPlan, discs map[string]variantDiscriminator) template.FuncMap {
-	fm := funcs(plan)
+// hardcodes the wire discriminator value. unionDiscs is the merged
+// union-level table (see mergeDiscriminators), threaded into funcs.
+func funcsWithDiscs(plan *enumPlan, variantDiscs map[string]variantDiscriminator, unionDiscs map[string]discriminatorSpec) template.FuncMap {
+	fm := funcs(plan, unionDiscs)
 	fm["variantHasDisc"] = func(name string) bool {
-		_, ok := discs[name]
+		_, ok := variantDiscs[name]
 		return ok
 	}
-	fm["variantDiscField"] = func(name string) string { return discs[name].JSONField }
-	fm["variantDiscGoField"] = func(name string) string { return discs[name].GoField }
-	fm["variantDiscValue"] = func(name string) string { return discs[name].Value }
+	fm["variantDiscField"] = func(name string) string { return variantDiscs[name].JSONField }
+	fm["variantDiscGoField"] = func(name string) string { return variantDiscs[name].GoField }
+	fm["variantDiscValue"] = func(name string) string { return variantDiscs[name].Value }
 	return fm
 }
 
 // funcs is the FuncMap shared across templates. plan is the resolved
-// enum plan; pass nil only in unit tests that don't exercise enums.
-func funcs(plan *enumPlan) template.FuncMap {
+// enum plan; pass nil only in unit tests that don't exercise enums. discs
+// is the merged union-level discriminator table (see
+// mergeDiscriminators); pass nil (or knownDiscriminators directly) in
+// unit tests that only exercise the hand-curated unions.
+func funcs(plan *enumPlan, discs map[string]discriminatorSpec) template.FuncMap {
 	return template.FuncMap{
 		"goType": goType,
 		"goField": func(parent string, f spec.Field) string {
 			return goField(plan, parent, f)
 		},
 		"goFieldP": func(methodName string, f spec.Field) string {
-			return goFieldX(plan, "", title(methodName)+"Params", f)
+			return goFieldX(plan, methodEnumParent(methodName), title(methodName)+"Params", f)
 		},
 		"docComment":  docComment,
 		"isOptional":  func(f spec.Field) bool { return !f.Required },
@@ -432,7 +712,7 @@ func funcs(plan *enumPlan) template.FuncMap {
 			return multipartFieldEntry(plan, parent, f)
 		},
 		"multipartFieldEntryP": func(methodName string, f spec.Field) string {
-			return multipartFieldEntryX(plan, "", title(methodName)+"Params", f)
+			return multipartFieldEntryX(plan, methodEnumParent(methodName), title(methodName)+"Params", f)
 		},
 		"multipartFileEntry": multipartFileEntry,
 		"returnGoType":       returnGoType,
@@ -444,20 +724,22 @@ func funcs(plan *enumPlan) template.FuncMap {
 			return plan.All()
 		},
 		"enumConstName": constName,
-		// discriminator helpers for types.tmpl
-		"hasDiscriminator": func(name string) bool { s, ok := knownDiscriminators[name]; return ok && len(s.Variants) > 0 },
+		// discriminator helpers for types.tmpl — all consult the merged
+		// table (discs), not the package-level knownDiscriminators, so a
+		// derived-only union gates exactly like a hand-curated one.
+		"hasDiscriminator": func(name string) bool { s, ok := discs[name]; return ok && len(s.Variants) > 0 },
 		"isSealedUnionReturn": func(tr spec.TypeRef) bool {
 			if tr.Kind != spec.KindNamed {
 				return false
 			}
-			s, ok := knownDiscriminators[tr.Name]
+			s, ok := discs[tr.Name]
 			return ok && len(s.Variants) > 0
 		},
 		"isSealedUnionArrayReturn": func(tr spec.TypeRef) bool {
 			if tr.Kind != spec.KindArray || tr.ElemType == nil || tr.ElemType.Kind != spec.KindNamed {
 				return false
 			}
-			s, ok := knownDiscriminators[tr.ElemType.Name]
+			s, ok := discs[tr.ElemType.Name]
 			return ok && len(s.Variants) > 0
 		},
 		"sealedUnionElemName": func(tr spec.TypeRef) string {
@@ -467,12 +749,13 @@ func funcs(plan *enumPlan) template.FuncMap {
 			return ""
 		},
 		"isMaybeInaccessibleMessage": func(name string) bool { return name == "MaybeInaccessibleMessage" },
-		"discriminatorField":         func(name string) string { return knownDiscriminators[name].Field },
-		"discriminatorMap":           func(name string) map[string]string { return knownDiscriminators[name].Variants },
+		"discriminatorField":         func(name string) string { return discs[name].Field },
+		"discriminatorMap":           func(name string) map[string]string { return discs[name].Variants },
 		// union-field helpers for per-struct UnmarshalJSON emission
-		"unionFields":   unionFieldsOf,
-		"isArrayUnion":  func(tr spec.TypeRef) bool { return hasUnionElem(tr) },
-		"unionTypeName": func(tr spec.TypeRef) string { name, _ := unionTypeFor(tr); return name },
+		"unionFields":     func(t spec.TypeDecl) []unionField { return unionFieldsOf(t, discs) },
+		"isArrayUnion":    func(tr spec.TypeRef) bool { return hasUnionElem(tr, discs) },
+		"unionTypeName":   func(tr spec.TypeRef) string { name, _ := unionTypeFor(tr, discs); return name },
+		"unionAlternates": unionAlternates,
 	}
 }
 
@@ -645,7 +928,7 @@ func returnGoElem(tr spec.TypeRef) string {
 
 // emitMethods renders methods.gen.go.
 func (e *emitter) emitMethods() error {
-	t, err := template.New("methods").Funcs(funcs(e.enums)).Parse(methodsTmpl)
+	t, err := template.New("methods").Funcs(funcs(e.enums, e.discs)).Parse(methodsTmpl)
 	if err != nil {
 		return fmt.Errorf("parse methods.tmpl: %w", err)
 	}
@@ -662,7 +945,7 @@ func (e *emitter) emitMethods() error {
 
 // emitEnums renders enums.gen.go.
 func (e *emitter) emitEnums() error {
-	t, err := template.New("enums").Funcs(funcs(e.enums)).Parse(enumsTmpl)
+	t, err := template.New("enums").Funcs(funcs(e.enums, e.discs)).Parse(enumsTmpl)
 	if err != nil {
 		return fmt.Errorf("parse enums.tmpl: %w", err)
 	}
@@ -735,11 +1018,12 @@ type unionField struct {
 }
 
 // unionFieldsOf returns the subset of t.Fields whose type is a known
-// discriminated union (directly or as array element).
-func unionFieldsOf(t spec.TypeDecl) []unionField {
+// discriminated union (directly or as array element), per discs — the
+// merged union-level discriminator table (see mergeDiscriminators).
+func unionFieldsOf(t spec.TypeDecl, discs map[string]discriminatorSpec) []unionField {
 	var out []unionField
 	for _, f := range t.Fields {
-		if u, ok := unionTypeFor(f.Type); ok {
+		if u, ok := unionTypeFor(f.Type, discs); ok {
 			out = append(out, unionField{Field: f, UnionName: u})
 		}
 	}
@@ -747,19 +1031,20 @@ func unionFieldsOf(t spec.TypeDecl) []unionField {
 }
 
 // unionTypeFor inspects a TypeRef and reports whether it (or its array
-// element) is a known discriminated union. Returns the union name and true.
-func unionTypeFor(tr spec.TypeRef) (string, bool) {
+// element) is a known discriminated union in discs. Returns the union
+// name and true.
+func unionTypeFor(tr spec.TypeRef, discs map[string]discriminatorSpec) (string, bool) {
 	switch tr.Kind {
 	case spec.KindNamed:
-		if _, ok := knownDiscriminators[tr.Name]; ok {
+		if _, ok := discs[tr.Name]; ok {
 			return tr.Name, true
 		}
 	case spec.KindArray:
 		if tr.ElemType != nil {
-			return unionTypeFor(*tr.ElemType)
+			return unionTypeFor(*tr.ElemType, discs)
 		}
 	case spec.KindOneOf:
-		if u := unionNameByVariants(tr.Variants); u != "" {
+		if u := unionNameByVariants(tr.Variants, discs); u != "" {
 			return u, true
 		}
 	}
@@ -768,8 +1053,8 @@ func unionTypeFor(tr spec.TypeRef) (string, bool) {
 
 // unionNameByVariants finds the parent union whose variant type names exactly
 // match the given variant set (order-insensitive).
-func unionNameByVariants(variants []string) string {
-	for parentName, ds := range knownDiscriminators {
+func unionNameByVariants(variants []string, discs map[string]discriminatorSpec) string {
+	for parentName, ds := range discs {
 		wanted := make([]string, 0, len(ds.Variants))
 		for _, vt := range ds.Variants {
 			wanted = append(wanted, vt)
@@ -782,14 +1067,50 @@ func unionNameByVariants(variants []string) string {
 }
 
 // hasUnionElem reports whether tr is an array whose element type is a known union.
-func hasUnionElem(tr spec.TypeRef) bool {
+func hasUnionElem(tr spec.TypeRef, discs map[string]discriminatorSpec) bool {
 	if tr.Kind != spec.KindArray || tr.ElemType == nil {
 		return false
 	}
-	_, ok := unionTypeFor(*tr.ElemType)
+	_, ok := unionTypeFor(*tr.ElemType, discs)
 	return ok
 }
 
+// alternateVariant describes one synthetic sealed-interface variant the
+// generator emits for a union's non-object wire shape (see
+// spec.Alternate): a bare-JSON-string variant, or a variant holding a
+// JSON array of the union itself. Exactly one of IsString / IsArray is
+// set. types.tmpl emits the struct, marker method, and MarshalJSON for
+// each, and Unmarshal<Union> dispatches to it by inspecting the first
+// non-whitespace byte of the wire value.
+type alternateVariant struct {
+	Name     string // synthetic Go type name, e.g. "RichTextPlain"
+	IsString bool
+	IsArray  bool
+}
+
+// unionAlternates maps a union TypeDecl's spec.Alternate entries (see
+// cmd/scrape's extractAlternates) to the synthetic Go variant
+// descriptors types.tmpl emits alongside the regular OneOf variants:
+// "<Union>Plain" for the bare-string shape, "<Union>Sequence" for the
+// array-of-<Union> shape. Returns nil for a union with no alternates,
+// which is every union except RichText as of Bot API v10 — so this is a
+// no-op for the rest of the type list.
+func unionAlternates(t spec.TypeDecl) []alternateVariant {
+	if len(t.Alternates) == 0 {
+		return nil
+	}
+	out := make([]alternateVariant, 0, len(t.Alternates))
+	for _, a := range t.Alternates {
+		switch a.Shape {
+		case spec.AlternateString:
+			out = append(out, alternateVariant{Name: t.Name + "Plain", IsString: true})
+		case spec.AlternateArray:
+			out = append(out, alternateVariant{Name: t.Name + "Sequence", IsArray: true})
+		}
+	}
+	return out
+}
+
 // matchesVariants reports whether got equals want as a set (order-insensitive).
 func matchesVariants(got []string, want ...string) bool {
 	if len(got) != len(want) {
@@ -915,15 +1236,15 @@ func buildUnionTypeSet(api *spec.API) map[string]bool {
 // used in generated test param literals. plan supplies typed-enum names
 // so a method-param sentinel for a ParseMode field becomes a typed
 // constant rather than a magic string.
-func makeSentinelValue(unionTypes map[string]bool, plan *enumPlan) func(spec.Field) string {
-	return func(f spec.Field) string {
-		return sentinelForField(f, unionTypes, plan)
+func makeSentinelValue(unionTypes map[string]bool, plan *enumPlan) func(string, spec.Field) string {
+	return func(methodName string, f spec.Field) string {
+		return sentinelForField(methodName, f, unionTypes, plan)
 	}
 }
 
-func sentinelForField(f spec.Field, unionTypes map[string]bool, plan *enumPlan) string {
-	if name := plan.FieldEnum("", f.Name); name != "" && len(f.EnumValues) > 0 {
-		return constName(name, f.EnumValues[0])
+func sentinelForField(methodName string, f spec.Field, unionTypes map[string]bool, plan *enumPlan) string {
+	if name := plan.FieldEnum(methodEnumParent(methodName), f.Name); name != "" && len(f.EnumValues) > 0 {
+		return plan.ConstFor(name, f.EnumValues[0])
 	}
 	tr := f.Type
 	switch tr.Kind {
@@ -1023,7 +1344,7 @@ func (e *emitter) emitTests() error {
 	unionTypes := buildUnionTypeSet(e.api)
 
 	// Add test-specific helpers to the shared func map.
-	fm := funcs(e.enums)
+	fm := funcs(e.enums, e.discs)
 	fm["sentinelValue"] = makeSentinelValue(unionTypes, e.enums)
 	fm["successResp"] = successResp
 

cmd/genapi/enums.go

@@ -26,15 +26,21 @@ type enumPlan struct {
 }
 
 // enumKey identifies a single Field occurrence so the emitter can look
-// up the enum name later. Parent is "" for method params (the method
-// doesn't share a Go type with the field).
+// up the enum name later. Parent is the type name for struct fields and
+// methodEnumParent(name) for method params, so two methods sharing a
+// param name never alias each other's enum (or non-enum) fields.
 func enumKey(parent, fieldName string) string { return parent + "::" + fieldName }
 
+// methodEnumParent is the enum-plan key parent for a method's params.
+// The "method:" prefix keeps it disjoint from type names.
+func methodEnumParent(methodName string) string { return "method:" + methodName }
+
 // planEnums walks the IR, decides on enum names, deduplicates, and
 // returns an enumPlan. All scraper-marked enum fields are covered.
 func planEnums(api *spec.API) *enumPlan {
 	type ref struct {
-		parent    string
+		parent    string // naming parent ("" for method params)
+		keyParent string // byField key parent (methodEnumParent(...) for method params)
 		fieldName string
 		jsonName  string
 		values    []string
@@ -52,7 +58,7 @@ func planEnums(api *spec.API) *enumPlan {
 	}
 
 	var refs []ref
-	collect := func(parent string, fields []spec.Field) {
+	collect := func(parent, keyParent string, fields []spec.Field) {
 		for _, f := range fields {
 			if len(f.EnumValues) == 0 {
 				continue
@@ -62,6 +68,7 @@ func planEnums(api *spec.API) *enumPlan {
 			}
 			refs = append(refs, ref{
 				parent:    parent,
+				keyParent: keyParent,
 				fieldName: f.Name,
 				jsonName:  f.JSONName,
 				values:    f.EnumValues,
@@ -70,13 +77,15 @@ func planEnums(api *spec.API) *enumPlan {
 		}
 	}
 	for _, t := range api.Types {
-		collect(t.Name, t.Fields)
+		collect(t.Name, t.Name, t.Fields)
 	}
 	for _, m := range api.Methods {
-		// Method params have no shared Go parent type, so we pass "" as
-		// the parent. The default-name heuristic still produces the
-		// right answer for ParseMode-style enums.
-		collect("", m.Params)
+		// Method params have no shared Go parent type, so the naming
+		// parent is "" (the default-name heuristic still produces the
+		// right answer for ParseMode-style enums), but the byField key
+		// is method-scoped so a same-named non-enum param on another
+		// method can never pick up this enum.
+		collect("", methodEnumParent(m.Name), m.Params)
 	}
 
 	// candidate name per ref (before collision resolution)
@@ -196,7 +205,7 @@ func planEnums(api *spec.API) *enumPlan {
 	}
 	for i, r := range refs {
 		name := groups[r.valueKey].name
-		plan.byField[enumKey(r.parent, r.fieldName)] = name
+		plan.byField[enumKey(r.keyParent, r.fieldName)] = name
 		_ = i
 	}
 	for vk, g := range groups {
@@ -262,32 +271,12 @@ func planUnifiedUnionEnums(api *spec.API) (map[string]enumDecl, map[string]strin
 			continue
 		}
 
-		// Build the candidate Go-name list. Priority order:
+		// Build the candidate Go-name list (shared with deriveDiscriminators
+		// in emitter.go so enum naming and decode dispatch never disagree
+		// on where to look). Priority order:
 		//  1. discriminator GoField from knownDiscriminators (resolved via JSONName);
 		//  2. "Type", "Status", "Source".
-		var candidateNames []string
-		seen := map[string]bool{}
-		add := func(name string) {
-			if name == "" || seen[name] {
-				return
-			}
-			seen[name] = true
-			candidateNames = append(candidateNames, name)
-		}
-		if ds, ok := knownDiscriminators[u.Name]; ok && ds.Field != "" {
-			// Resolve Go-name from the first variant whose field matches the JSON name.
-			for _, v := range variants {
-				for _, f := range v.Fields {
-					if f.JSONName == ds.Field {
-						add(f.Name)
-						break
-					}
-				}
-			}
-		}
-		for _, n := range []string{"Type", "Status", "Source"} {
-			add(n)
-		}
+		candidateNames := discriminatorFieldCandidates(u.Name, variants)
 
 		// Find the first candidate Go-name where every variant has a
 		// matching single-value string-enum field.
@@ -389,6 +378,18 @@ func (p *enumPlan) FieldEnum(parent, fieldName string) string {
 	return p.byField[enumKey(parent, fieldName)]
 }
 
+// ConstFor returns the collision-resolved constant identifier for value
+// within the named enum declaration. Falls back to the plain constName
+// when the declaration is unknown (unit tests with partial plans).
+func (p *enumPlan) ConstFor(enumName, value string) string {
+	if p != nil {
+		if d, ok := p.decls[enumName]; ok {
+			return d.ConstName(value)
+		}
+	}
+	return constName(enumName, value)
+}
+
 // defaultEnumName picks an initial Go enum name for a field. parse_mode
 // fields collapse to the canonical "ParseMode"; otherwise the name is
 // parent + PascalCase(jsonName).
@@ -406,6 +407,48 @@ func constName(enumName, value string) string {
 	return enumName + valuePascal(value)
 }
 
+// ConstName returns the constant identifier for value within this enum,
+// resolving case-collisions between values that Pascal-case to the same
+// identifier (e.g. RichBlockListItem.type values "a" and "A"). Colliding
+// values get a Lower/Upper prefix on the value part based on the case of
+// the value's first letter; any residual collision gets a numeric suffix.
+func (e enumDecl) ConstName(value string) string {
+	counts := map[string]int{}
+	for _, v := range e.Values {
+		counts[constName(e.Name, v)]++
+	}
+	plain := constName(e.Name, value)
+	if counts[plain] <= 1 {
+		return plain
+	}
+	cased := e.Name + casePrefix(value) + valuePascal(value)
+	// Residual collision (same value text repeated, or Lower/Upper still
+	// ambiguous): append the value's 1-based position for determinism.
+	casedCounts := map[string]int{}
+	pos := 0
+	for i, v := range e.Values {
+		if counts[constName(e.Name, v)] > 1 {
+			casedCounts[e.Name+casePrefix(v)+valuePascal(v)]++
+		}
+		if v == value {
+			pos = i + 1
+		}
+	}
+	if casedCounts[cased] > 1 {
+		return cased + itoa(pos)
+	}
+	return cased
+}
+
+// casePrefix distinguishes case-colliding enum values: "Lower" when the
+// value starts with a lowercase letter, "Upper" otherwise.
+func casePrefix(v string) string {
+	if v != "" && v[0] >= 'a' && v[0] <= 'z' {
+		return "Lower"
+	}
+	return "Upper"
+}
+
 func valuePascal(v string) string {
 	// "image/jpeg" → "ImageOfJpeg"
 	parts := strings.Split(v, "/")

cmd/genapi/enums.tmpl

@@ -8,6 +8,6 @@ package api
 type {{$e.Name}} string
 
 const (
-{{range $v := $e.Values}}	{{enumConstName $e.Name $v}} {{$e.Name}} = {{printf "%q" $v}}
+{{range $v := $e.Values}}	{{$e.ConstName $v}} {{$e.Name}} = {{printf "%q" $v}}
 {{end}})
 {{end}}

cmd/genapi/enums_collision_test.go

@@ -0,0 +1,56 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/lukaszraczylo/go-telegram/internal/spec"
+	"github.com/stretchr/testify/require"
+)
+
+// Regression: Bot API 9.x RichBlockListItem.type enumerates "a"/"A"/"i"/"I"/"1",
+// which Pascal-case to the same identifier. ConstName must disambiguate.
+func TestEnumDecl_ConstName_CaseCollision(t *testing.T) {
+	d := enumDecl{Name: "RichBlockListItemType", Values: []string{"a", "A", "i", "I", "1"}}
+	got := map[string]bool{}
+	for _, v := range d.Values {
+		n := d.ConstName(v)
+		require.False(t, got[n], "duplicate const ident %q for value %q", n, v)
+		got[n] = true
+	}
+	require.Equal(t, "RichBlockListItemTypeLowerA", d.ConstName("a"))
+	require.Equal(t, "RichBlockListItemTypeUpperA", d.ConstName("A"))
+	// Non-colliding values keep the plain name.
+	require.Equal(t, "RichBlockListItemType1", d.ConstName("1"))
+}
+
+// Regression: answerChatJoinRequestQuery has an enum param named "result";
+// answerGuestQuery has a NON-enum param also named "result". The enum plan
+// must scope method params per method so the enum never leaks onto the
+// other method's field.
+func TestPlanEnums_MethodParamsScopedPerMethod(t *testing.T) {
+	api := &spec.API{
+		Methods: []spec.MethodDecl{
+			{
+				Name: "answerChatJoinRequestQuery",
+				Params: []spec.Field{{
+					Name: "Result", JSONName: "result", Required: true,
+					Type:       spec.TypeRef{Kind: spec.KindPrimitive, Name: "string"},
+					EnumValues: []string{"approve", "decline", "queue"},
+				}},
+			},
+			{
+				Name: "answerGuestQuery",
+				Params: []spec.Field{{
+					Name: "Result", JSONName: "result", Required: true,
+					Type: spec.TypeRef{Kind: spec.KindNamed, Name: "InlineQueryResult"},
+				}},
+			},
+		},
+	}
+	plan := planEnums(api)
+	require.Equal(t, "Result",
+		plan.FieldEnum(methodEnumParent("answerChatJoinRequestQuery"), "Result"))
+	require.Empty(t,
+		plan.FieldEnum(methodEnumParent("answerGuestQuery"), "Result"),
+		"non-enum param must not inherit another method's enum")
+}

cmd/genapi/extra_test.go

@@ -280,7 +280,7 @@ func TestMultipartFieldEntry_Named_Optional(t *testing.T) {
 
 func TestUnionTypeFor_DirectNamed(t *testing.T) {
 	tr := spec.TypeRef{Kind: spec.KindNamed, Name: "ChatMember"}
-	name, ok := unionTypeFor(tr)
+	name, ok := unionTypeFor(tr, knownDiscriminators)
 	require.True(t, ok)
 	require.Equal(t, "ChatMember", name)
 }
@@ -288,26 +288,26 @@ func TestUnionTypeFor_DirectNamed(t *testing.T) {
 func TestUnionTypeFor_Array(t *testing.T) {
 	elem := spec.TypeRef{Kind: spec.KindNamed, Name: "ChatMember"}
 	tr := spec.TypeRef{Kind: spec.KindArray, ElemType: &elem}
-	name, ok := unionTypeFor(tr)
+	name, ok := unionTypeFor(tr, knownDiscriminators)
 	require.True(t, ok)
 	require.Equal(t, "ChatMember", name)
 }
 
 func TestUnionTypeFor_ArrayNilElem(t *testing.T) {
 	tr := spec.TypeRef{Kind: spec.KindArray}
-	_, ok := unionTypeFor(tr)
+	_, ok := unionTypeFor(tr, knownDiscriminators)
 	require.False(t, ok)
 }
 
 func TestUnionTypeFor_NotUnion(t *testing.T) {
 	tr := spec.TypeRef{Kind: spec.KindNamed, Name: "Message"}
-	_, ok := unionTypeFor(tr)
+	_, ok := unionTypeFor(tr, knownDiscriminators)
 	require.False(t, ok)
 }
 
 func TestUnionTypeFor_Unknown(t *testing.T) {
 	tr := spec.TypeRef{Kind: spec.Kind(99)}
-	_, ok := unionTypeFor(tr)
+	_, ok := unionTypeFor(tr, knownDiscriminators)
 	require.False(t, ok)
 }
 
@@ -321,12 +321,12 @@ func TestUnionNameByVariants_ChatMember(t *testing.T) {
 		"ChatMemberOwner", "ChatMemberAdministrator", "ChatMemberMember",
 		"ChatMemberRestricted", "ChatMemberLeft", "ChatMemberBanned",
 	}
-	name := unionNameByVariants(variants)
+	name := unionNameByVariants(variants, knownDiscriminators)
 	require.Equal(t, "ChatMember", name)
 }
 
 func TestUnionNameByVariants_Unknown(t *testing.T) {
-	name := unionNameByVariants([]string{"X", "Y", "Z"})
+	name := unionNameByVariants([]string{"X", "Y", "Z"}, knownDiscriminators)
 	require.Equal(t, "", name)
 }
 
@@ -336,24 +336,24 @@ func TestUnionNameByVariants_Unknown(t *testing.T) {
 
 func TestHasUnionElem_NonArray(t *testing.T) {
 	tr := spec.TypeRef{Kind: spec.KindNamed, Name: "ChatMember"}
-	require.False(t, hasUnionElem(tr))
+	require.False(t, hasUnionElem(tr, knownDiscriminators))
 }
 
 func TestHasUnionElem_ArrayNilElem(t *testing.T) {
 	tr := spec.TypeRef{Kind: spec.KindArray}
-	require.False(t, hasUnionElem(tr))
+	require.False(t, hasUnionElem(tr, knownDiscriminators))
 }
 
 func TestHasUnionElem_ArrayUnionElem(t *testing.T) {
 	elem := spec.TypeRef{Kind: spec.KindNamed, Name: "ChatMember"}
 	tr := spec.TypeRef{Kind: spec.KindArray, ElemType: &elem}
-	require.True(t, hasUnionElem(tr))
+	require.True(t, hasUnionElem(tr, knownDiscriminators))
 }
 
 func TestHasUnionElem_ArrayNonUnionElem(t *testing.T) {
 	elem := spec.TypeRef{Kind: spec.KindNamed, Name: "Message"}
 	tr := spec.TypeRef{Kind: spec.KindArray, ElemType: &elem}
-	require.False(t, hasUnionElem(tr))
+	require.False(t, hasUnionElem(tr, knownDiscriminators))
 }
 
 // ---------------------------------------------------------------------------
@@ -369,7 +369,7 @@ func TestUnionFieldsOf_WithUnionField(t *testing.T) {
 			{Name: "Date", JSONName: "date", Type: spec.TypeRef{Kind: spec.KindPrimitive, Name: "int64"}},
 		},
 	}
-	uf := unionFieldsOf(td)
+	uf := unionFieldsOf(td, knownDiscriminators)
 	require.Len(t, uf, 2)
 	require.Equal(t, "ChatMember", uf[0].UnionName)
 }
@@ -574,7 +574,7 @@ func TestSentinelForField(t *testing.T) {
 	}
 	for _, c := range cases {
 		t.Run(c.name, func(t *testing.T) {
-			got := sentinelForField(c.field, unionTypes, nil)
+			got := sentinelForField("testMethod", c.field, unionTypes, nil)
 			require.Contains(t, got, c.contains, "sentinelForField for %q", c.name)
 		})
 	}
@@ -621,14 +621,14 @@ func TestUnionTypeFor_OneOfVariants(t *testing.T) {
 			"ChatMemberRestricted", "ChatMemberLeft", "ChatMemberBanned",
 		},
 	}
-	name, ok := unionTypeFor(tr)
+	name, ok := unionTypeFor(tr, knownDiscriminators)
 	require.True(t, ok)
 	require.Equal(t, "ChatMember", name)
 }
 
 func TestUnionTypeFor_OneOfNoMatch(t *testing.T) {
 	tr := spec.TypeRef{Kind: spec.KindOneOf, Variants: []string{"Foo", "Bar"}}
-	_, ok := unionTypeFor(tr)
+	_, ok := unionTypeFor(tr, knownDiscriminators)
 	require.False(t, ok)
 }
 
@@ -637,7 +637,7 @@ func TestUnionTypeFor_OneOfNoMatch(t *testing.T) {
 // ---------------------------------------------------------------------------
 
 func TestFuncs_HasExpectedKeys(t *testing.T) {
-	fm := funcs(nil)
+	fm := funcs(nil, nil)
 	require.NotNil(t, fm)
 	for _, key := range []string{"goType", "docComment", "returnGoType", "unionFields"} {
 		require.NotNil(t, fm[key], "funcs() missing key %q", key)

cmd/genapi/main.go

@@ -29,6 +29,9 @@ func run(input, outdir string) error {
 	if err != nil {
 		return fmt.Errorf("load api: %w", err)
 	}
+	if err := checkDiscriminatorGate(api); err != nil {
+		return err
+	}
 	if err := os.MkdirAll(outdir, 0o750); err != nil {
 		return err
 	}

cmd/genapi/tests.tmpl

@@ -48,7 +48,7 @@ func Test_{{$mName}}_Success(t *testing.T) {
 	{{- if .Params}}
 	params := &{{$mName}}Params{
 		{{- range .Params}}{{if .Required}}
-		{{.Name}}: {{sentinelValue .}},{{end}}
+		{{.Name}}: {{sentinelValue $m.Name .}},{{end}}
 		{{- end}}
 	}
 	_, err := {{$mName}}(context.Background(), bot, params)
@@ -67,7 +67,7 @@ func Test_{{$mName}}_APIError(t *testing.T) {
 	{{- if .Params}}
 	params := &{{$mName}}Params{
 		{{- range .Params}}{{if .Required}}
-		{{.Name}}: {{sentinelValue .}},{{end}}
+		{{.Name}}: {{sentinelValue $m.Name .}},{{end}}
 		{{- end}}
 	}
 	_, err := {{$mName}}(context.Background(), bot, params)
@@ -89,7 +89,7 @@ func Test_{{$mName}}_NetworkError(t *testing.T) {
 	{{- if .Params}}
 	params := &{{$mName}}Params{
 		{{- range .Params}}{{if .Required}}
-		{{.Name}}: {{sentinelValue .}},{{end}}
+		{{.Name}}: {{sentinelValue $m.Name .}},{{end}}
 		{{- end}}
 	}
 	_, err := {{$mName}}(context.Background(), bot, params)
@@ -109,7 +109,7 @@ func Test_{{$mName}}_ParseError(t *testing.T) {
 	{{- if .Params}}
 	params := &{{$mName}}Params{
 		{{- range .Params}}{{if .Required}}
-		{{.Name}}: {{sentinelValue .}},{{end}}
+		{{.Name}}: {{sentinelValue $m.Name .}},{{end}}
 		{{- end}}
 	}
 	_, err := {{$mName}}(context.Background(), bot, params)
@@ -132,7 +132,7 @@ func Test_{{$mName}}_ContextCanceled(t *testing.T) {
 	{{- if .Params}}
 	params := &{{$mName}}Params{
 		{{- range .Params}}{{if .Required}}
-		{{.Name}}: {{sentinelValue .}},{{end}}
+		{{.Name}}: {{sentinelValue $m.Name .}},{{end}}
 		{{- end}}
 	}
 	_, err := {{$mName}}(ctx, bot, params)
@@ -177,7 +177,7 @@ func Test_{{$mName}}_Forbidden(t *testing.T) {
 	{{- if .Params}}
 	params := &{{$mName}}Params{
 		{{- range .Params}}{{if .Required}}
-		{{.Name}}: {{sentinelValue .}},{{end}}
+		{{.Name}}: {{sentinelValue $m.Name .}},{{end}}
 		{{- end}}
 	}
 	_, err := {{$mName}}(context.Background(), bot, params)
@@ -203,7 +203,7 @@ func Test_{{$mName}}_ServerError(t *testing.T) {
 	{{- if .Params}}
 	params := &{{$mName}}Params{
 		{{- range .Params}}{{if .Required}}
-		{{.Name}}: {{sentinelValue .}},{{end}}
+		{{.Name}}: {{sentinelValue $m.Name .}},{{end}}
 		{{- end}}
 	}
 	_, err := {{$mName}}(context.Background(), bot, params)

cmd/genapi/types.tmpl

@@ -7,14 +7,16 @@
 package api
 
 import (
+	"bytes"
 	"github.com/goccy/go-json"
 	"fmt"
 	"io"
 )
 
-var _ = io.Discard   // keep import even if no fields use io
-var _ = json.Marshal // keep import for UnmarshalXxx helpers
-var _ = fmt.Errorf   // keep import for UnmarshalXxx helpers
+var _ = io.Discard     // keep import even if no fields use io
+var _ = json.Marshal   // keep import for UnmarshalXxx helpers
+var _ = fmt.Errorf     // keep import for UnmarshalXxx helpers
+var _ = bytes.TrimLeft // keep import for shape-dispatching UnmarshalXxx helpers (unions with alternates)
 
 {{range .Types}}
 {{- $td := . -}}
@@ -22,6 +24,7 @@ var _ = fmt.Errorf   // keep import for UnmarshalXxx helpers
 // {{.Name}} is a union type. The following concrete variants implement
 // it:
 {{range .OneOf}}//   - {{.}}
+{{end}}{{range unionAlternates .}}//   - {{.Name}} ({{if .IsString}}bare JSON string{{else}}JSON array of {{$td.Name}}{{end}})
 {{end}}//
 {{docComment .Doc -}}
 type {{.Name}} interface{ is{{.Name}}() }
@@ -30,11 +33,67 @@ type {{.Name}} interface{ is{{.Name}}() }
 // is{{$td.Name}} is the marker method that makes {{.}} implement {{$td.Name}}.
 func (*{{.}}) is{{$td.Name}}() {}
 {{end}}
+{{range unionAlternates .}}
+// {{.Name}} implements {{$td.Name}} for the {{if .IsString}}bare JSON string{{else}}JSON array of {{$td.Name}}{{end}} wire
+// shape Telegram documents for this union, alongside its object variants.
+type {{.Name}} struct {
+{{if .IsString}}	Text string
+{{else}}	Items []{{$td.Name}}
+{{end}}}
+
+// is{{$td.Name}} is the marker method that makes {{.Name}} implement {{$td.Name}}.
+func (*{{.Name}}) is{{$td.Name}}() {}
+
+{{if .IsString}}// MarshalJSON encodes {{.Name}} back to its bare JSON string wire shape.
+func (v *{{.Name}}) MarshalJSON() ([]byte, error) {
+	return json.Marshal(v.Text)
+}
+{{else}}// MarshalJSON encodes {{.Name}} back to its bare JSON array wire shape.
+func (v *{{.Name}}) MarshalJSON() ([]byte, error) {
+	return json.Marshal(v.Items)
+}
+{{end}}
+{{end}}
 {{if hasDiscriminator .Name}}
-// Unmarshal{{.Name}} decodes a {{.Name}} from JSON by inspecting the
+{{$alts := unionAlternates .}}{{if $alts}}// Unmarshal{{.Name}} decodes a {{.Name}} from JSON. Telegram documents
+// this type as either a bare JSON string, a JSON array of {{.Name}}, or
+// an object dispatched by its "{{discriminatorField .Name}}" field;
+// leading whitespace is trimmed and the first remaining byte selects
+// the shape.
+{{else}}// Unmarshal{{.Name}} decodes a {{.Name}} from JSON by inspecting the
 // "{{discriminatorField .Name}}" field and dispatching to the correct concrete type.
-func Unmarshal{{.Name}}(data []byte) ({{.Name}}, error) {
-	var probe struct {
+{{end}}func Unmarshal{{.Name}}(data []byte) ({{.Name}}, error) {
+{{if $alts}}	trimmed := bytes.TrimLeft(data, " \t\r\n")
+	if len(trimmed) == 0 {
+		return nil, fmt.Errorf("{{.Name}}: empty JSON value")
+	}
+	switch trimmed[0] {
+{{range $alts}}{{if .IsString}}	case '"':
+		var s string
+		if err := json.Unmarshal(data, &s); err != nil {
+			return nil, fmt.Errorf("{{$td.Name}}: decoding string: %w", err)
+		}
+		return &{{.Name}}{Text: s}, nil
+{{else}}	case '[':
+		var raws []json.RawMessage
+		if err := json.Unmarshal(data, &raws); err != nil {
+			return nil, fmt.Errorf("{{$td.Name}}: decoding array: %w", err)
+		}
+		items := make([]{{$td.Name}}, 0, len(raws))
+		for i, r := range raws {
+			v, err := Unmarshal{{$td.Name}}(r)
+			if err != nil {
+				return nil, fmt.Errorf("{{$td.Name}}: decoding array[%d]: %w", i, err)
+			}
+			items = append(items, v)
+		}
+		return &{{.Name}}{Items: items}, nil
+{{end}}{{end}}	case '{':
+		// fall through to the discriminator switch below.
+	default:
+		return nil, fmt.Errorf("{{.Name}}: unrecognised JSON value starting with %q", trimmed[0])
+	}
+{{end}}	var probe struct {
 		V string `json:"{{discriminatorField .Name}}"`
 	}
 	if err := json.Unmarshal(data, &probe); err != nil {

cmd/scrape/alternates.go

@@ -0,0 +1,50 @@
+package main
+
+import (
+	"regexp"
+
+	"github.com/lukaszraczylo/go-telegram/internal/spec"
+)
+
+// altStringRE matches the scalar-string alternate clause Telegram uses
+// for union types that can also decode as plain text on the wire, e.g.
+// "a String for plain text". The trailing "for ..." clause is optional
+// and, when present, is not captured — only the shape matters. "an"
+// (rather than "a") is tolerated so a future rephrasing ("an String")
+// doesn't silently stop matching, and the word boundary keeps "Strings"
+// or "SubString" from misfiring.
+var altStringRE = regexp.MustCompile(`(?i)\ban?\s+String\b`)
+
+// altArrayRE builds the pattern that matches the self-referential array
+// alternate clause Telegram uses for recursive union types, e.g. "an
+// Array of RichText". Matching is anchored to the union's own name so a
+// doc mentioning "an Array of" some other type is never mistaken for a
+// shape alternate.
+func altArrayRE(unionName string) *regexp.Regexp {
+	return regexp.MustCompile(`(?i)\ban?\s+Array\s+of\s+` + regexp.QuoteMeta(unionName) + `\b`)
+}
+
+// extractAlternates detects Telegram's "can be either a String for
+// plain text, an Array of <Union>, or any of the following types:"
+// phrasing on a union type's doc string and returns the non-object
+// shapes it declares, in a fixed (string, then array) order regardless
+// of how the sentence orders its clauses.
+//
+// Conservative by design: callers invoke this only for types that
+// already have OneOf populated (see typeFromSection in scrape.go), and
+// it only recognises the two shapes Telegram's docs currently use for
+// this ("a String" and "an Array of <the union's own name>") — anything
+// else in the doc is ignored, so free-text mentioning "String" or
+// "Array" elsewhere in a union's description can't produce a false
+// positive for a type this pattern wasn't written for. As of Bot API
+// v10, RichText is the only union whose doc matches either pattern.
+func extractAlternates(unionName, doc string) []spec.Alternate {
+	var alts []spec.Alternate
+	if altStringRE.MatchString(doc) {
+		alts = append(alts, spec.Alternate{Shape: spec.AlternateString})
+	}
+	if altArrayRE(unionName).MatchString(doc) {
+		alts = append(alts, spec.Alternate{Shape: spec.AlternateArray})
+	}
+	return alts
+}

cmd/scrape/alternates_test.go

@@ -0,0 +1,99 @@
+package main
+
+import (
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/lukaszraczylo/go-telegram/internal/spec"
+)
+
+func TestExtractAlternates_RichTextDoc(t *testing.T) {
+	// Exact doc string as scraped from the live Bot API v10 docs page
+	// (internal/spec/api.json / testdata/html/latest.html).
+	doc := "This object represents a rich formatted text. Currently, it can be either a String for plain text, " +
+		"an Array of RichText, or any of the following types:"
+	got := extractAlternates("RichText", doc)
+	require.Equal(t, []spec.Alternate{
+		{Shape: spec.AlternateString},
+		{Shape: spec.AlternateArray},
+	}, got)
+}
+
+func TestExtractAlternates_OrderIndependent(t *testing.T) {
+	// Same two clauses, reversed, plus an extra clause in between —
+	// order and surrounding prose must not matter.
+	doc := "Currently, it can be either an Array of RichText, something else entirely, a String for plain text, " +
+		"or any of the following types:"
+	got := extractAlternates("RichText", doc)
+	require.Equal(t, []spec.Alternate{
+		{Shape: spec.AlternateString},
+		{Shape: spec.AlternateArray},
+	}, got)
+}
+
+func TestExtractAlternates_ObjectOnlyUnion_NoAlternates(t *testing.T) {
+	// RichBlock's doc is object-only: no String/Array alternate clause.
+	doc := "This object represents a block in a rich formatted message. Currently, it can be any of the following types:"
+	got := extractAlternates("RichBlock", doc)
+	require.Nil(t, got)
+}
+
+func TestExtractAlternates_ArrayOfDifferentType_NotSelfReferential(t *testing.T) {
+	// "an Array of X" only counts when X is the union's own name — an
+	// array of some other type mentioned in the doc must not match.
+	doc := "This object can be either an Array of PhotoSize or any of the following types:"
+	got := extractAlternates("RichText", doc)
+	require.Nil(t, got)
+}
+
+func TestExtractAlternates_StringOnly(t *testing.T) {
+	doc := "This object can be either a String or any of the following types:"
+	got := extractAlternates("Widget", doc)
+	require.Equal(t, []spec.Alternate{{Shape: spec.AlternateString}}, got)
+}
+
+func TestExtractAlternates_PlainTypeDoc_NoFalsePositive(t *testing.T) {
+	// Ordinary field/type prose mentioning neither shape must not match.
+	doc := "This object represents a chat photo."
+	got := extractAlternates("ChatPhoto", doc)
+	require.Nil(t, got)
+}
+
+// TestTypeFromSection_RichText_RealSnapshot grounds the extraction in the
+// real pinned docs snapshot (not just a literal fixture string): scraping
+// testdata/html/latest.html end-to-end must produce a RichText TypeDecl
+// with both alternates, matching the same live text that broke decoding
+// of plain-text and array-shaped rich_message payloads.
+func TestTypeFromSection_RichText_RealSnapshot(t *testing.T) {
+	htmlBytes, err := os.ReadFile("../../testdata/html/latest.html")
+	require.NoError(t, err)
+
+	api, err := scrape(htmlBytes)
+	require.NoError(t, err)
+
+	var richText *spec.TypeDecl
+	for i := range api.Types {
+		if api.Types[i].Name == "RichText" {
+			richText = &api.Types[i]
+			break
+		}
+	}
+	require.NotNil(t, richText, "RichText type must be present in the real docs snapshot")
+	require.Equal(t, []spec.Alternate{
+		{Shape: spec.AlternateString},
+		{Shape: spec.AlternateArray},
+	}, richText.Alternates)
+
+	// RichBlock is the control: object-only union, no alternates.
+	var richBlock *spec.TypeDecl
+	for i := range api.Types {
+		if api.Types[i].Name == "RichBlock" {
+			richBlock = &api.Types[i]
+			break
+		}
+	}
+	require.NotNil(t, richBlock)
+	require.Nil(t, richBlock.Alternates)
+}

cmd/scrape/method.go

@@ -42,7 +42,7 @@ func extractReturn(desc string) spec.TypeRef {
 			return spec.TypeRef{Kind: spec.KindArray, ElemType: &elem}
 		}},
 		// "an array of X of the sent messages is returned" (ForwardMessages/CopyMessages shape).
-		{regexp.MustCompile(`(?:[Oo]n success[,.]?\s+)?an? array of ([A-Z][A-Za-z0-9]+)(?:\s+of [^.]+?)?\s+(?:objects\s+)?(?:is|are) returned`), func(m []string) spec.TypeRef {
+		{regexp.MustCompile(`(?:[Oo]n success[,.]?\s+)?an? [Aa]rray of ([A-Z][A-Za-z0-9]+)(?:\s+of [^.]+?)?\s+(?:objects\s+)?(?:is|are) returned`), func(m []string) spec.TypeRef {
 			elem := primitiveOrNamed(m[1])
 			return spec.TypeRef{Kind: spec.KindArray, ElemType: &elem}
 		}},

cmd/scrape/method_test.go

@@ -29,6 +29,8 @@ func TestExtractReturn(t *testing.T) {
 		{"On success, an array of Message objects that were sent is returned.", spec.TypeRef{Kind: spec.KindArray, ElemType: &spec.TypeRef{Kind: spec.KindNamed, Name: "Message"}}},
 		// ForwardMessages/CopyMessages shape: "an array of X of the sent messages is returned".
 		{"On success, an array of MessageId of the sent messages is returned.", spec.TypeRef{Kind: spec.KindArray, ElemType: &spec.TypeRef{Kind: spec.KindNamed, Name: "MessageId"}}},
+		// Bot API 10.1 recapitalised the same sentence to "an Array of X".
+		{"On success, an Array of MessageId of the sent messages is returned.", spec.TypeRef{Kind: spec.KindArray, ElemType: &spec.TypeRef{Kind: spec.KindNamed, Name: "MessageId"}}},
 		// "Returns X on success" (no article) — OwnedGifts, StarAmount, Story, MenuButton, etc.
 		{"Returns the gifts received and owned by a managed business account. Returns OwnedGifts on success.", spec.TypeRef{Kind: spec.KindNamed, Name: "OwnedGifts"}},
 		{"Returns StarAmount on success.", spec.TypeRef{Kind: spec.KindNamed, Name: "StarAmount"}},

cmd/scrape/scrape.go

@@ -38,6 +38,10 @@ func typeFromSection(s section) spec.TypeDecl {
 	} else if len(s.Lists) > 0 {
 		// Union: extract variant names from <li><a>...</a></li>.
 		td.OneOf = extractListLinks(s.Lists[0])
+		// Some unions (e.g. RichText) also declare non-object wire shapes
+		// ("a String for plain text", "an Array of RichText") in the same
+		// sentence as the object-variant list; extract those too.
+		td.Alternates = extractAlternates(td.Name, td.Doc)
 	}
 	return td
 }

docs/benchmarks/2026-05-10-comparison.md

@@ -20,7 +20,7 @@
 
 - **Webhook decode** (small Update): ours is **12–20% faster** than every competitor and ties telego for the lowest alloc count (11).
 - **Large Update unmarshal** (entities + reply markup + photo array): ours is **17–34% faster** with the lowest ns/op of all six. telego edges us on alloc count (31 vs 34) at the cost of ~17% more time.
-- **API call round-trip** (mock HTTP server): telego wins (35.8 µs / 48 allocs) thanks to its `application/x-www-form-urlencoded` shortcut on simple methods; ours is **second** (39.8 µs / 102 allocs) and beats gotba, telebot, gobot.
+- **API call round-trip** (mock HTTP server): telego wins on allocs (35.8 µs / 48 allocs) because it uses fasthttp by default. We default to `net/http` (102 allocs / 39.8 µs); with the opt-in `client.NewFastHTTPDoer` we drop to 56 allocs / 6.6 KiB — within 8 of telego while keeping `*http.Request` semantics (RetryDoer, middleware, generated tests).
 - **Dispatcher routing** (20 handlers, last matches): ours is **2.5–2.8× faster than telebot and gobot** (98 ns vs 271 / 246 ns).
 
 ## How to read these numbers
@@ -67,16 +67,19 @@ Build params → POST to local `httptest.Server` returning `{"ok":true,"result":
 
 | Lib | sec/op | B/op | allocs/op |
 |-----|--------|------|-----------|
-| ours | 39.83 µs ±4% | 11.09 KiB | 102 |
+| ours (default `net/http`) | 39.83 µs ±4% | 11.09 KiB | 102 |
+| ours (opt-in `fasthttp`) | *time TBD on quiet box* | **6.62 KiB** | **56** |
 | gotba | 42.03 µs ±4% | 10.97 KiB | 125 |
 | telebot | 43.41 µs ±1% | 13.15 KiB | 139 |
 | gobot | 61.19 µs ±1% | 13.50 KiB | 176 |
-| **telego** | **35.84 µs ±1%** | **6.547 KiB** | **48** |
+| **telego** (uses fasthttp) | **35.84 µs ±1%** | **6.547 KiB** | **48** |
 | echotron | *skipped — see below* | — | — |
 
 **Notes.**
-- telego wins by sending requests as `application/x-www-form-urlencoded` form data (cheaper than JSON marshal+upload for small payloads), plus an aggressive request-pool. We send JSON over `multipart/form-data` only when needed; for the JSON case our cost lands between gotba and telego.
-- Our request path runs through a manually-constructed `*http.Request` with a pre-parsed base URL (cached on `*Bot`), and request bodies are stream-encoded into a pooled `*bytes.Buffer` via the optional `BodyEncoder` codec extension. Together those skip the `url.Parse` + `*http.Request` bookkeeping that `http.NewRequestWithContext` runs on every call.
+- The headline alloc gap to telego turned out to be transport choice: telego defaults to [`fasthttp`](https://github.com/valyala/fasthttp), which pools requests/responses and skips most of `net/http`'s bookkeeping. Most of the other libs (and us, by default) use `net/http`.
+- We ship an opt-in fasthttp doer (`client.NewFastHTTPDoer`). Plug it via `client.WithHTTPClient(client.NewFastHTTPDoer())` and per-call allocs drop from 102 to **56** — within 8 of telego despite still going through our `*http.Request`-based `HTTPDoer` interface (kept that way so `RetryDoer`, custom transports, observability middleware, and the 1428 generated tests all keep working).
+- The default stays `net/http` because fasthttp is HTTP/1.1-only, can't be composed with the `RoundTripper` middleware ecosystem, and most users don't have the throughput to notice. Bots making thousands of API calls/sec should opt in.
+- Our `net/http` request path is already minimised: manually-constructed `*http.Request` with a pre-parsed base URL (cached on `*Bot`), and request bodies stream-encoded into a pooled `*bytes.Buffer` via the optional `BodyEncoder` codec extension. Those skip the `url.Parse` + `*http.Request` bookkeeping that `http.NewRequestWithContext` runs on every call.
 - gobot's higher cost comes from per-call goroutine + channel plumbing in its dispatcher path even when called directly.
 - **echotron skip:** echotron ships built-in dual-level rate limiting (30 req/s global, 20 req/min per chat) on its unexported `lclient` field. The setters that disable it (`SetGlobalRequestLimit`, `SetChatRequestLimit`) are methods on the unexported type with no public accessor through the `API` value, so the limiter cannot be bypassed without monkey-patching. A naive run produces ~3 s/op driven entirely by the per-chat token bucket — measuring rate limiting, not the library. We skip rather than publish a misleading number. The rate limiter is a feature of echotron and worth knowing about; it just makes a microbench unfair.
 

docs/reference/client.md

@@ -32,6 +32,12 @@ Package client provides HTTP client primitives for the Telegram Bot API.
   - [func \(DefaultCodec\) Marshal\(v any\) \(\[\]byte, error\)](<#DefaultCodec.Marshal>)
   - [func \(DefaultCodec\) MarshalTo\(w io.Writer, v any\) error](<#DefaultCodec.MarshalTo>)
   - [func \(DefaultCodec\) Unmarshal\(data \[\]byte, v any\) error](<#DefaultCodec.Unmarshal>)
+- [type FastHTTPDoer](<#FastHTTPDoer>)
+  - [func NewFastHTTPDoer\(opts ...FastHTTPDoerOption\) \*FastHTTPDoer](<#NewFastHTTPDoer>)
+  - [func \(d \*FastHTTPDoer\) Do\(req \*http.Request\) \(\*http.Response, error\)](<#FastHTTPDoer.Do>)
+- [type FastHTTPDoerOption](<#FastHTTPDoerOption>)
+  - [func WithFastHTTPClient\(c \*fasthttp.Client\) FastHTTPDoerOption](<#WithFastHTTPClient>)
+  - [func WithFastHTTPReadTimeout\(t time.Duration\) FastHTTPDoerOption](<#WithFastHTTPReadTimeout>)
 - [type HTTPDoer](<#HTTPDoer>)
 - [type Logger](<#Logger>)
 - [type MultipartFile](<#MultipartFile>)
@@ -81,6 +87,16 @@ var (
 )
 ```
 
+<a name="Version"></a>Version is a fallback version string used only when Go's build info is unavailable \(replace directives, detached \`go run\`\) or has been overridden via linker flags. The authoritative version forwarded to telemetry is resolved at runtime by \[telemetry.SendForModule\] from the build info of whatever binary linked this library, so this constant does NOT need to be bumped on every release. Exposed as a var \(not const\) for ldflag override:
+
+```
+go build -ldflags="-X github.com/lukaszraczylo/go-telegram/client.Version=1.2.3"
+```
+
+```go
+var Version = "0.0.0-fallback"
+```
+
 <a name="Call"></a>
 ## func [Call](<https://github.com/lukaszraczylo/go-telegram/blob/main/client/call.go#L68>)
 
@@ -292,6 +308,72 @@ func (DefaultCodec) Unmarshal(data []byte, v any) error
 
 Unmarshal calls json.Unmarshal.
 
+<a name="FastHTTPDoer"></a>
+## type [FastHTTPDoer](<https://github.com/lukaszraczylo/go-telegram/blob/main/client/fasthttp_doer.go#L26-L32>)
+
+FastHTTPDoer is an HTTPDoer backed by github.com/valyala/fasthttp. It trades net/http compatibility \(and HTTP/2 support\) for substantially fewer allocations per request — fasthttp pools its Request and Response objects and uses a zero\-allocation HTTP/1.1 parser.
+
+Use it for high\-throughput bots when GC pressure matters and you don't need HTTP/2 or any net/http\-only middleware \(RoundTripper composition, the OpenTelemetry httptrace family, etc.\):
+
+```
+bot := client.New(token, client.WithHTTPClient(client.NewFastHTTPDoer()))
+```
+
+Wrap with RetryDoer the same way you would the default doer.
+
+```go
+type FastHTTPDoer struct {
+    // contains filtered or unexported fields
+}
+```
+
+<a name="NewFastHTTPDoer"></a>
+### func [NewFastHTTPDoer](<https://github.com/lukaszraczylo/go-telegram/blob/main/client/fasthttp_doer.go#L52>)
+
+```go
+func NewFastHTTPDoer(opts ...FastHTTPDoerOption) *FastHTTPDoer
+```
+
+NewFastHTTPDoer constructs a FastHTTPDoer with sensible defaults.
+
+<a name="FastHTTPDoer.Do"></a>
+### func \(\*FastHTTPDoer\) [Do](<https://github.com/lukaszraczylo/go-telegram/blob/main/client/fasthttp_doer.go#L75>)
+
+```go
+func (d *FastHTTPDoer) Do(req *http.Request) (*http.Response, error)
+```
+
+Do satisfies HTTPDoer by translating req into a pooled fasthttp.Request, dispatching it, and returning a \*http.Response whose Body releases the pooled fasthttp.Response when Close is called.
+
+The conversion is intentionally minimal: URL goes via req.URL.RequestURI\(\) \+ Host \(avoids re\-parsing\), header values move byte\-for\-byte, and the body is taken straight from req.Body. \*bytes.Buffer / \*bytes.Reader are recognised so we can pass the underlying bytes without io.ReadAll.
+
+<a name="FastHTTPDoerOption"></a>
+## type [FastHTTPDoerOption](<https://github.com/lukaszraczylo/go-telegram/blob/main/client/fasthttp_doer.go#L35>)
+
+FastHTTPDoerOption configures a FastHTTPDoer.
+
+```go
+type FastHTTPDoerOption func(*FastHTTPDoer)
+```
+
+<a name="WithFastHTTPClient"></a>
+### func [WithFastHTTPClient](<https://github.com/lukaszraczylo/go-telegram/blob/main/client/fasthttp_doer.go#L40>)
+
+```go
+func WithFastHTTPClient(c *fasthttp.Client) FastHTTPDoerOption
+```
+
+WithFastHTTPClient swaps in a pre\-configured \*fasthttp.Client. Useful for sharing a connection pool across multiple bots or applying custom dial / TLS configuration.
+
+<a name="WithFastHTTPReadTimeout"></a>
+### func [WithFastHTTPReadTimeout](<https://github.com/lukaszraczylo/go-telegram/blob/main/client/fasthttp_doer.go#L47>)
+
+```go
+func WithFastHTTPReadTimeout(t time.Duration) FastHTTPDoerOption
+```
+
+WithFastHTTPReadTimeout sets the per\-request fallback timeout used when the inbound context has no deadline. Long\-poll callers should pass a value larger than the long\-poll timeout.
+
 <a name="HTTPDoer"></a>
 ## type [HTTPDoer](<https://github.com/lukaszraczylo/go-telegram/blob/main/client/httpclient.go#L13-L15>)
 

examples/echo/handlers.go

@@ -26,7 +26,7 @@ func handleEcho(c *dispatch.Context, m *api.Message) error {
 	_, err := api.SendMessage(c.Ctx, c.Bot, &api.SendMessageParams{
 		ChatID:          api.ChatIDFromInt(m.Chat.ID),
 		Text:            m.Text,
-		ReplyParameters: &api.ReplyParameters{MessageID: m.MessageID},
+		ReplyParameters: &api.ReplyParameters{MessageID: &m.MessageID},
 	})
 	return err
 }

go.mod

@@ -4,13 +4,18 @@ go 1.25.0
 
 require (
 	github.com/goccy/go-json v0.10.6
+	github.com/lukaszraczylo/oss-telemetry v0.2.3
 	github.com/stretchr/testify v1.9.0
-	golang.org/x/net v0.54.0
+	github.com/valyala/fasthttp v1.71.0
+	golang.org/x/net v0.56.0
 )
 
 require (
+	github.com/andybalholm/brotli v1.2.1 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/klauspost/compress v1.18.6 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/stretchr/objx v0.5.2 // indirect
+	github.com/valyala/bytebufferpool v1.0.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

go.sum

@@ -1,15 +1,31 @@
+github.com/andybalholm/brotli v1.2.1 h1:R+f5xP285VArJDRgowrfb9DqL18yVK0gKAW/F+eTWro=
+github.com/andybalholm/brotli v1.2.1/go.mod h1:rzTDkvFWvIrjDXZHkuS16NPggd91W3kUSvPlQ1pLaKY=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/goccy/go-json v0.10.6 h1:p8HrPJzOakx/mn/bQtjgNjdTcN+/S6FcG2CTtQOrHVU=
 github.com/goccy/go-json v0.10.6/go.mod h1:oq7eo15ShAhp70Anwd5lgX2pLfOS3QCiwU/PULtXL6M=
+github.com/klauspost/compress v1.18.6 h1:2jupLlAwFm95+YDR+NwD2MEfFO9d4z4Prjl1XXDjuao=
+github.com/klauspost/compress v1.18.6/go.mod h1:cwPg85FWrGar70rWktvGQj8/hthj3wpl0PGDogxkrSQ=
+github.com/lukaszraczylo/oss-telemetry v0.2.1 h1:6ULyfzXplpdmIY/i01OPM1jeod9+L1RAhI0jtbVnJI0=
+github.com/lukaszraczylo/oss-telemetry v0.2.1/go.mod h1:+Cn78qZo8rc3T9eZt0v3oICYRdd75wORtSidc8lNjDQ=
+github.com/lukaszraczylo/oss-telemetry v0.2.3 h1:xoDtBqeZGmXj7IteiE1M5WMuzeoqag58qEleI0Cf2Ms=
+github.com/lukaszraczylo/oss-telemetry v0.2.3/go.mod h1:+Cn78qZo8rc3T9eZt0v3oICYRdd75wORtSidc8lNjDQ=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/objx v0.5.2 h1:xuMeJ0Sdp5ZMRXx/aWO6RZxdr3beISkG5/G/aIRr3pY=
 github.com/stretchr/objx v0.5.2/go.mod h1:FRsXN1f5AsAjCGJKqEizvkpNtU+EGNCLh3NxZ/8L+MA=
 github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
 github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
-golang.org/x/net v0.54.0 h1:2zJIZAxAHV/OHCDTCOHAYehQzLfSXuf/5SoL/Dv6w/w=
-golang.org/x/net v0.54.0/go.mod h1:Sj4oj8jK6XmHpBZU/zWHw3BV3abl4Kvi+Ut7cQcY+cQ=
+github.com/valyala/bytebufferpool v1.0.0 h1:GqA5TC/0021Y/b9FG4Oi9Mr3q7XYx6KllzawFIhcdPw=
+github.com/valyala/bytebufferpool v1.0.0/go.mod h1:6bBcMArwyJ5K/AmCkWv1jt77kVWyCJ6HpOuEn7z0Csc=
+github.com/valyala/fasthttp v1.71.0 h1:tepR7H+Guh9VUqxxcPggYi8R3lGUu2Rsdh+z7/FCY3k=
+github.com/valyala/fasthttp v1.71.0/go.mod h1:z1sDUvOShhXq/C9mwH/fSm1Vb71tUJwmQdgkBrBNwnA=
+github.com/xyproto/randomstring v1.0.5 h1:YtlWPoRdgMu3NZtP45drfy1GKoojuR7hmRcnhZqKjWU=
+github.com/xyproto/randomstring v1.0.5/go.mod h1:rgmS5DeNXLivK7YprL0pY+lTuhNQW3iGxZ18UQApw/E=
+golang.org/x/net v0.55.0 h1:bcvxaJn3e1U6InsFWt1JUq1aSjnRxLzT2rtD2KfkDF8=
+golang.org/x/net v0.55.0/go.mod h1:L5U2KuzuOe1lY7Z+aWVIKK6qEeJXnXV9yzGA+WCHJww=
+golang.org/x/net v0.56.0 h1:Rw8j/hFzGvJUZwNBXnAtf5sVDVt+65SK2C7IxCxZt5o=
+golang.org/x/net v0.56.0/go.mod h1:D3Ku6r+V6JROoZK144D2XfMHFcMq/0zSfLelVTCFKec=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=

internal/spec/ir.go

@@ -24,6 +24,31 @@ type TypeDecl struct {
 	// OneOf, when non-empty, indicates this type is a union and lists the concrete variant type names.
 	// Variants are emitted as concrete structs implementing a sealed interface.
 	OneOf []string `json:"one_of,omitempty"`
+	// Alternates lists non-object wire shapes this union may also decode
+	// as, in addition to the object variants in OneOf. Only populated for
+	// unions whose doc declares them (Telegram's "can be either a String
+	// for plain text, an Array of X, or any of the following types:"
+	// phrasing) — as of Bot API v10 that's RichText alone, so every other
+	// type's serialised IR is unaffected by this field's existence.
+	Alternates []Alternate `json:"alternates,omitempty"`
+}
+
+// AlternateShape enumerates the non-object wire shapes a union's
+// Alternates field records.
+type AlternateShape string
+
+const (
+	// AlternateString: the union may decode from a bare JSON string.
+	AlternateString AlternateShape = "string"
+	// AlternateArray: the union may decode from a JSON array whose
+	// elements are themselves the same union type.
+	AlternateArray AlternateShape = "array"
+)
+
+// Alternate records one non-object shape a union type may appear as on
+// the wire, beyond its OneOf object variants.
+type Alternate struct {
+	Shape AlternateShape `json:"shape"`
 }
 
 // MethodDecl describes a Telegram API method.

internal/spec/overrides.go

@@ -22,6 +22,12 @@ type Overrides struct {
 	// ApprovedBoolMethods lists methods whose returns are genuinely bool.
 	// The audit tool ignores these.
 	ApprovedBoolMethods []string `json:"approved_bool_methods,omitempty"`
+
+	// ApprovedAnyLocations lists IR locations whose union renders as `any` by
+	// design, keyed "<TypeName>.<FieldName>" for struct fields,
+	// "<methodName>.<ParamName>" for params and "<methodName>" for returns.
+	// The audit tool ignores these.
+	ApprovedAnyLocations []string `json:"approved_any_locations,omitempty"`
 }
 
 // LoadOverrides reads and parses overrides.json. Returns an empty Overrides
@@ -73,3 +79,17 @@ func (o *Overrides) IsBoolApproved(methodName string) bool {
 	}
 	return false
 }
+
+// IsAnyApproved reports whether location is on the approved `any` list.
+// See ApprovedAnyLocations for the key format.
+func (o *Overrides) IsAnyApproved(location string) bool {
+	if o == nil {
+		return false
+	}
+	for _, n := range o.ApprovedAnyLocations {
+		if n == location {
+			return true
+		}
+	}
+	return false
+}

internal/spec/overrides.json

@@ -1,6 +1,9 @@
 {
   "method_returns": {},
   "field_types": {},
+  "approved_any_locations": [
+    "InputRichMessageMedia.Media"
+  ],
   "approved_bool_methods": [
     "setWebhook",
     "deleteWebhook",

test/benchmarks/call_bench_test.go

@@ -28,7 +28,8 @@ import (
 // Telegram-format token (digits:[\w-]{35}). telego enforces this format on construction.
 const benchToken = "1234567890:ABCDEFGHIJKLMNOPQRSTUVWXYZ_ab123456"
 
-// BenchmarkCall_ours — lukaszraczylo/go-telegram.
+// BenchmarkCall_ours — lukaszraczylo/go-telegram with default net/http
+// transport. Most users land here.
 func BenchmarkCall_ours(b *testing.B) {
 	srv := shared.NewMockServer()
 	defer srv.Close()
@@ -47,6 +48,30 @@ func BenchmarkCall_ours(b *testing.B) {
 	}
 }
 
+// BenchmarkCall_ours_fasthttp — lukaszraczylo/go-telegram with the
+// opt-in fasthttp transport (client.NewFastHTTPDoer). Apples-to-apples
+// against telego, which also runs on fasthttp by default.
+func BenchmarkCall_ours_fasthttp(b *testing.B) {
+	srv := shared.NewMockServer()
+	defer srv.Close()
+	bot := client.New(benchToken,
+		client.WithBaseURL(srv.URL),
+		client.WithHTTPClient(client.NewFastHTTPDoer()),
+	)
+	ctx := context.Background()
+	b.ReportAllocs()
+	b.ResetTimer()
+	for b.Loop() {
+		_, err := api.SendMessage(ctx, bot, &api.SendMessageParams{
+			ChatID: api.ChatIDFromInt(42),
+			Text:   "hello",
+		})
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
+}
+
 // BenchmarkCall_gotba — go-telegram-bot-api/telegram-bot-api/v5.
 func BenchmarkCall_gotba(b *testing.B) {
 	srv := shared.NewMockServer()

test/benchmarks/go.mod

@@ -14,20 +14,20 @@ require (
 )
 
 require (
-	github.com/andybalholm/brotli v1.2.0 // indirect
+	github.com/andybalholm/brotli v1.2.1 // indirect
 	github.com/bytedance/gopkg v0.1.3 // indirect
 	github.com/bytedance/sonic v1.15.0 // indirect
 	github.com/bytedance/sonic/loader v0.5.0 // indirect
 	github.com/cloudwego/base64x v0.1.6 // indirect
 	github.com/goccy/go-json v0.10.6 // indirect
 	github.com/grbit/go-json v0.11.0 // indirect
-	github.com/klauspost/compress v1.18.2 // indirect
+	github.com/klauspost/compress v1.18.6 // indirect
 	github.com/klauspost/cpuid/v2 v2.2.9 // indirect
 	github.com/twitchyliquid64/golang-asm v0.15.1 // indirect
 	github.com/valyala/bytebufferpool v1.0.0 // indirect
-	github.com/valyala/fasthttp v1.69.0 // indirect
+	github.com/valyala/fasthttp v1.71.0 // indirect
 	github.com/valyala/fastjson v1.6.10 // indirect
 	golang.org/x/arch v0.0.0-20210923205945-b76863e36670 // indirect
-	golang.org/x/sys v0.39.0 // indirect
+	golang.org/x/sys v0.41.0 // indirect
 	golang.org/x/time v0.5.0 // indirect
 )

test/benchmarks/go.sum

@@ -65,8 +65,8 @@ github.com/alecthomas/template v0.0.0-20190718012654-fb15b899a751/go.mod h1:LOuy
 github.com/alecthomas/units v0.0.0-20151022065526-2efee857e7cf/go.mod h1:ybxpYRFXyAe+OPACYpWeL0wqObRcbAqCMya13uyzqw0=
 github.com/alecthomas/units v0.0.0-20190717042225-c3de453c63f4/go.mod h1:ybxpYRFXyAe+OPACYpWeL0wqObRcbAqCMya13uyzqw0=
 github.com/alecthomas/units v0.0.0-20190924025748-f65c72e2690d/go.mod h1:rBZYJk541a8SKzHPHnH3zbiI+7dagKZ0cgpgrD7Fyho=
-github.com/andybalholm/brotli v1.2.0 h1:ukwgCxwYrmACq68yiUqwIWnGY0cTPox/M94sVwToPjQ=
-github.com/andybalholm/brotli v1.2.0/go.mod h1:rzTDkvFWvIrjDXZHkuS16NPggd91W3kUSvPlQ1pLaKY=
+github.com/andybalholm/brotli v1.2.1 h1:R+f5xP285VArJDRgowrfb9DqL18yVK0gKAW/F+eTWro=
+github.com/andybalholm/brotli v1.2.1/go.mod h1:rzTDkvFWvIrjDXZHkuS16NPggd91W3kUSvPlQ1pLaKY=
 github.com/antihax/optional v1.0.0/go.mod h1:uupD/76wgC+ih3iEmQUL+0Ugr19nfwCT1kdvxnR2qWY=
 github.com/armon/circbuf v0.0.0-20150827004946-bbbad097214e/go.mod h1:3U/XgcO3hCbHZ8TKRvWD2dDTCfh9M9ya+I9JpbB7O8o=
 github.com/armon/go-metrics v0.0.0-20180917152333-f0300d1749da/go.mod h1:Q73ZrmVTwzkszR9V5SSuryQ31EELlFMUz1kKyl939pY=
@@ -275,8 +275,8 @@ github.com/julienschmidt/httprouter v1.2.0/go.mod h1:SYymIcj16QtmaHHD7aYtjjsJG7V
 github.com/julienschmidt/httprouter v1.3.0/go.mod h1:JR6WtHb+2LUe8TCKY3cZOxFyyO8IZAc4RVcycCCAKdM=
 github.com/kisielk/errcheck v1.5.0/go.mod h1:pFxgyoBC7bSaBwPgfKdkLd5X25qrDl4LWUI2bnpBCr8=
 github.com/kisielk/gotool v1.0.0/go.mod h1:XhKaO+MFFWcvkIS/tQcRk01m1F5IRFswLeQ+oQHNcck=
-github.com/klauspost/compress v1.18.2 h1:iiPHWW0YrcFgpBYhsA6D1+fqHssJscY/Tm/y2Uqnapk=
-github.com/klauspost/compress v1.18.2/go.mod h1:R0h/fSBs8DE4ENlcrlib3PsXS61voFxhIs2DeRhCvJ4=
+github.com/klauspost/compress v1.18.6 h1:2jupLlAwFm95+YDR+NwD2MEfFO9d4z4Prjl1XXDjuao=
+github.com/klauspost/compress v1.18.6/go.mod h1:cwPg85FWrGar70rWktvGQj8/hthj3wpl0PGDogxkrSQ=
 github.com/klauspost/cpuid/v2 v2.2.9 h1:66ze0taIn2H33fBvCkXuv9BmCwDfafmiIVpKV9kKGuY=
 github.com/klauspost/cpuid/v2 v2.2.9/go.mod h1:rqkxqrZ1EhYM9G+hXH7YdowN5R5RGN6NK4QwQ3WMXF8=
 github.com/konsorten/go-windows-terminal-sequences v1.0.1/go.mod h1:T0+1ngSBFLxvqU3pZ+m/2kptfBszLMUkC4ZK/EgS/cQ=
@@ -392,8 +392,8 @@ github.com/twitchyliquid64/golang-asm v0.15.1 h1:SU5vSMR7hnwNxj24w34ZyCi/FmDZTkS
 github.com/twitchyliquid64/golang-asm v0.15.1/go.mod h1:a1lVb/DtPvCB8fslRZhAngC2+aY1QWCk3Cedj/Gdt08=
 github.com/valyala/bytebufferpool v1.0.0 h1:GqA5TC/0021Y/b9FG4Oi9Mr3q7XYx6KllzawFIhcdPw=
 github.com/valyala/bytebufferpool v1.0.0/go.mod h1:6bBcMArwyJ5K/AmCkWv1jt77kVWyCJ6HpOuEn7z0Csc=
-github.com/valyala/fasthttp v1.69.0 h1:fNLLESD2SooWeh2cidsuFtOcrEi4uB4m1mPrkJMZyVI=
-github.com/valyala/fasthttp v1.69.0/go.mod h1:4wA4PfAraPlAsJ5jMSqCE2ug5tqUPwKXxVj8oNECGcw=
+github.com/valyala/fasthttp v1.71.0 h1:tepR7H+Guh9VUqxxcPggYi8R3lGUu2Rsdh+z7/FCY3k=
+github.com/valyala/fasthttp v1.71.0/go.mod h1:z1sDUvOShhXq/C9mwH/fSm1Vb71tUJwmQdgkBrBNwnA=
 github.com/valyala/fastjson v1.6.10 h1:/yjJg8jaVQdYR3arGxPE2X5z89xrlhS0eGXdv+ADTh4=
 github.com/valyala/fastjson v1.6.10/go.mod h1:e6FubmQouUNP73jtMLmcbxS6ydWIpOfhz34TSfO3JaE=
 github.com/xyproto/randomstring v1.0.5 h1:YtlWPoRdgMu3NZtP45drfy1GKoojuR7hmRcnhZqKjWU=
@@ -624,8 +624,8 @@ golang.org/x/sys v0.0.0-20220328115105-d36c6a25d886/go.mod h1:oPkhp1MJrh7nUepCBc
 golang.org/x/sys v0.0.0-20220412211240-33da011f77ad/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20220502124256-b6088ccd6cba/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.39.0 h1:CvCKL8MeisomCi6qNZ+wbb0DN9E5AATixKsvNtMoMFk=
-golang.org/x/sys v0.39.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
+golang.org/x/sys v0.41.0 h1:Ivj+2Cp/ylzLiEU89QhWblYnOE9zerudt9Ftecq2C6k=
+golang.org/x/sys v0.41.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
 golang.org/x/term v0.0.0-20210927222741-03fcf44c2211/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
 golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=

testdata/golden/types.gen.go

@@ -7,14 +7,16 @@
 package api
 
 import (
+	"bytes"
 	"fmt"
 	"github.com/goccy/go-json"
 	"io"
 )
 
-var _ = io.Discard   // keep import even if no fields use io
-var _ = json.Marshal // keep import for UnmarshalXxx helpers
-var _ = fmt.Errorf   // keep import for UnmarshalXxx helpers
+var _ = io.Discard     // keep import even if no fields use io
+var _ = json.Marshal   // keep import for UnmarshalXxx helpers
+var _ = fmt.Errorf     // keep import for UnmarshalXxx helpers
+var _ = bytes.TrimLeft // keep import for shape-dispatching UnmarshalXxx helpers (unions with alternates)
 
 // This object represents a Telegram user or bot.
 type User struct {

testdata/html/latest.html

@@ -1 +1 @@
-snapshot_2026-05-08.html
+snapshot_2026-09-14.html