refactor(llm): drop the image content block until a path can honor it
ImageBlock had no production producer and every consumer dropped it: the deepseek serializer skipped it, the pi-ai converter skipped it as unrepresentable, the ACP bridge neither advertises image prompt capability nor forwards image blocks, and compact-basic charged a flat 85-token estimate and rendered an [image] placeholder. A block constructed today would silently vanish from the wire — the vocabulary advertised a capability no path honors, the silent-data-loss shape the defensive patterns warn against. The only constructors were tests pinning the skip/estimate branches. Remove ImageBlock and its ContentBlockMap entry (its cache?: CacheHint field leaves with it; CacheHint itself and the other two cache? fields are out of scope). compact-basic loses its explicit image estimate and placeholder arms (the merge-extensible default arms absorb the case); the deepseek serializer, pi-ai converter, and ACP codec already handled image in their default arms, so only their image-naming comments change. The codec's inbound rejection of ACP-protocol image prompt content stays — that guards wire content a client can send regardless of our vocabulary. Tests that constructed harness image blocks to pin the removed branches are dropped (the 85-token estimate pin) or retargeted onto plugin-added block types / other non-text blocks, which the surviving default arms own. Docs, the type-equiv pastes, and the content-block vocabulary RFC's block list and multimodal-home consequence are updated in the same change; the RFC moves to implemented/ and the index is regenerated. A real multimodal feature reintroduces image via declaration merging together with the adapter mapping, ACP advertisement, and compaction pricing that honor it.
This commit is contained in:
@@ -93,7 +93,7 @@ The web capability uses the same three-package split but folds two capabilities
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## The vocabulary (dsh-llm)
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Messages are arrays of typed **content blocks** (`text`, `reasoning`, `tool-call`, `tool-result`, `image`); the union is derived from the merge-extensible `ContentBlockMap`, so plugins can add block types via declaration merging. The same merge-extensible-map pattern is used for `MessageSource`, `FinishReason`, `TurnTrigger`, and `TurnEndReason` — typed sum types instead of strings.
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Messages are arrays of typed **content blocks** (`text`, `reasoning`, `tool-call`, `tool-result`); the union is derived from the merge-extensible `ContentBlockMap`, so plugins can add block types via declaration merging. The core set is limited to blocks every shipping path honors — multimodal content (images, audio, …) has no core block type; a feature that needs one adds it via the map in the same coordinated change that maps it in the adapters, surfaces it in the UI bridges, and prices it in compaction ([the drop-image RFC](rfc/implemented/simplification/2026-07-04-drop-image-content-block.md)). The same merge-extensible-map pattern is used for `MessageSource`, `FinishReason`, `TurnTrigger`, and `TurnEndReason` — typed sum types instead of strings.
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Streaming is a raw chunk protocol (`block-start`, `text-delta`, `reasoning-delta`, `tool-call-delta`, `block-end`, `usage`, `finish`). `BlockAssembler` is the single shared implementation that assembles chunks into blocks/messages; the loop logs raw chunks (replay fidelity) while feeding the same chunks through an assembler.
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@@ -87,11 +87,10 @@ interface ContentBlockMap {
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'reasoning': ReasoningBlock
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'tool-call': ToolCallBlock
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'tool-result': ToolResultBlock
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'image': ImageBlock
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}
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```
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The block interfaces (full fields in source): `TextBlock` (`text`), `ReasoningBlock` (thinking, distinct from visible text), `ToolCallBlock` (`id: CallId`, `name`, raw-JSON `arguments`), `ToolResultBlock` (`toolCallId`, nested `content: ContentBlock[]`, `isError?`), `ImageBlock` (`url`, `mimeType?`). `ContentBlock = ContentBlockMap[ContentBlockType]`.
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The block interfaces (full fields in source): `TextBlock` (`text`), `ReasoningBlock` (thinking, distinct from visible text), `ToolCallBlock` (`id: CallId`, `name`, raw-JSON `arguments`), `ToolResultBlock` (`toolCallId`, nested `content: ContentBlock[]`, `isError?`). `ContentBlock = ContentBlockMap[ContentBlockType]`. The core set is limited to blocks every shipping path honors — multimodal content (images, audio, …) has no core block type; a feature that needs one adds it via the merge-extensible map together with the adapter/UI/compaction support that honors it.
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A `Message` is a role plus blocks:
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@@ -59,7 +59,6 @@ interface ContentBlockMap {
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'reasoning': ReasoningBlock
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'tool-call': ToolCallBlock
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'tool-result': ToolResultBlock
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'image': ImageBlock
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}
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```
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@@ -52,7 +52,6 @@ Do NOT write one for a mechanical or local choice (a variable name, a one-file r
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| Title | First proposed |
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|---|---|
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| [Unify the agent id and the session id](proposed/simplification/2026-06-20-unify-agent-and-session-id.md) | 2026-06-20 |
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| [Drop the `image` content block until a path can honor it](proposed/simplification/2026-07-04-drop-image-content-block.md) | 2026-07-04 |
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| [Drop `GenerateOptions.prefill` and `ToolSchema.strict` — request knobs with no working end-to-end path](proposed/simplification/2026-07-04-drop-inert-request-knobs.md) | 2026-07-04 |
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| [Drop the unconsumed web observation surface — the `providers-change` event and the status methods](proposed/simplification/2026-07-04-drop-unconsumed-web-observation-surface.md) | 2026-07-04 |
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| [Fold the stdio UI helper into the stdio app](proposed/simplification/2026-07-04-fold-stdio-ui-helper.md) | 2026-07-04 |
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@@ -120,6 +119,7 @@ Do NOT write one for a mechanical or local choice (a variable name, a one-file r
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| [Stop mirroring durable boundaries as agent events](implemented/simplification/2026-06-20-remove-agent-boundary-mirror-events.md) | 2026-06-20 |
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| [Split the filesystem seam — provider text mutations plus the `dsh-fs-policy` plugin](implemented/simplification/2026-06-26-fsspec-style-fs-seam.md) | 2026-06-26 |
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| [Stop mirroring the token stream as an agent event](implemented/simplification/2026-07-02-remove-stream-chunk-mirror.md) | 2026-07-02 |
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| [Drop the `image` content block until a path can honor it](implemented/simplification/2026-07-04-drop-image-content-block.md) | 2026-07-04 |
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### Architecture
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@@ -10,12 +10,12 @@ The harness needs one internal language for messages that the loop, session log,
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## Decision
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Own it: messages are arrays of typed content blocks (`text`, `reasoning`, `tool-call`, `tool-result`, `image`), with the union derived from the merge-extensible `ContentBlockMap` so plugins add block types via declaration merging. The same merge-extensible-map pattern types every "stringly" field (`MessageSource`, `FinishReason`, `TurnTrigger`, `TurnEndReason`). Streaming is a raw chunk protocol; `BlockAssembler` is the single shared assembly implementation. Adapters translate to provider wire formats — mapping cost lives in adapters, where it belongs.
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Own it: messages are arrays of typed content blocks (`text`, `reasoning`, `tool-call`, `tool-result`), with the union derived from the merge-extensible `ContentBlockMap` so plugins add block types via declaration merging. The same merge-extensible-map pattern types every "stringly" field (`MessageSource`, `FinishReason`, `TurnTrigger`, `TurnEndReason`). Streaming is a raw chunk protocol; `BlockAssembler` is the single shared assembly implementation. Adapters translate to provider wire formats — mapping cost lives in adapters, where it belongs.
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In-session context injection (`context/message`, `steering/message`) renders as tagged user-role envelopes (the system-reminder pattern) rather than a new role, so adapters carry zero burden. Live-adapter review has since validated the tagged-envelope rendering against current DeepSeek behavior; a future provider-specific mismatch should be handled in that adapter rather than by adding a new role to the canonical content vocabulary.
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## Consequences
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- Reasoning, prefill, cache hints, and multimodal content all have a home without provider contortions.
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- Reasoning, prefill, and cache hints have a home without provider contortions. Multimodal content deliberately has NO core block type: the core set is limited to blocks every shipping path honors, and a multimodal feature adds its block type through the merge-extensible map in the same coordinated change that maps it in the adapters, surfaces it in the UI bridges, and prices it in compaction — see [the drop-image RFC](../simplification/2026-07-04-drop-image-content-block.md).
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- Every adapter pays a translation cost; the first real adapters have since validated the streaming protocol, and new adapters should continue proving their provider-specific mapping in adapter-local tests.
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- IDs that cross package boundaries are branded (`CallId`, `SessionId`, `AgentId`) — nominal typing at zero runtime cost.
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@@ -0,0 +1,27 @@
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# RFC: Drop the `image` content block until a path can honor it
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Status: implemented (proposed and accepted 2026-07-04)
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## Problem
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`ImageBlock` (`packages/llm/llm/src/types.ts`) had no production producer, and every consumer on every path DROPPED it: the deepseek adapter's serializer skipped image blocks (a documented MVP limitation), the pi-ai converter skipped them as unrepresentable, the ACP codec neither advertises image prompt capability nor forwarded image blocks outbound and REJECTS image prompt content inbound, and the compaction estimator charged a flat token constant and rendered `[image]`. An `ImageBlock` constructed then would silently vanish from the wire — the vocabulary advertised a capability no path honored, which is the silent-data-loss shape AGENTS.md's defensive patterns warn against. The only constructors anywhere were tests pinning the skip/drop/estimate branches.
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## Decision
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Remove `ImageBlock`, its `ContentBlockMap` entry (and its `cache?: CacheHint` field with it), the explicit `image` estimate/placeholder arms in compact-basic, and the image-naming comments in the deepseek serializer's, pi-ai converter's, and ACP codec's default arms — those default arms absorb the case the way they absorb any unknown block type. Updated in the same change: the vocabulary line in [architecture.md](../../../architecture.md), the block list in `packages/llm/llm/README.md`, the deepseek README's image-skip row, the pi-ai README's images-not-representable row, the compact-basic README's image-estimation and `[image]`-placeholder rows, the pastes in [core.md](../../../core-data-structures/core.md) and [llm-streaming.md](../../../core-data-structures/llm-streaming.md), and the [content-block vocabulary RFC](../architecture/2026-06-11-content-block-vocabulary.md)'s block list and multimodal-home consequence per [implemented/AGENTS.md](../AGENTS.md); the tests that constructed image blocks to exercise the removed branches were dropped (the estimate pin) or retargeted onto the merge-extensible default arms (plugin-added block types). The ACP codec's inbound rejection of image PROMPT content is unaffected — that guard is about protocol content a client can send regardless of our vocabulary, and it stays.
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## Why not keep it?
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This was the most contested cut in the batch. Multimodal input (screenshots) is a plausible near-term coding-agent feature, and the [content-block vocabulary RFC](../architecture/2026-06-11-content-block-vocabulary.md) reserved the slot deliberately. Two responses. First, `ContentBlockMap` is merge-extensible by design: a real multimodal feature reintroduces `image` in core in the same coordinated change that maps it in the adapters, advertises and renders it in ACP, and prices it in compaction — the producer and its consumers arrive together, which is how the map is meant to grow. Second, the middle option — keep the type but make adapters throw UNSUPPORTED instead of silently dropping — converts this into exactly the shape the sibling request-knobs proposal (`2026-07-04-drop-inert-request-knobs`) argues against: surface whose only implementation is rejection. Absence (a compile error at the would-be producer) is strictly clearer than either silent loss or universal throw.
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The recorded fallback, had review landed on keeping the slot: keep `ImageBlock` but replace every silent skip with a loud rejection, and document that policy in the vocabulary — the silent drop was the one state with no defender. Review landed on removal; the fallback stands as the documented alternative should the slot ever return ahead of a full feature.
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## Acceptance criteria
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- No `ImageBlock` / harness `type: 'image'` block construction outside this RFC; the codec's inbound ACP-image rejection still passes its tests.
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- Adapter/codec/compaction switches handle the case through their unknown-block default arms (pinned by the plugin-added-block tests).
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- Doc pastes, the manifest, and the architecture vocabulary list updated; `pnpm run doc-sync` green.
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## Risks
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Re-adding a core vocabulary type later touches several packages at once — but that coordinated change is the shape a real multimodal feature needs anyway (adapter mapping, ACP advertisement, compaction pricing), and none of it existed to preserve.
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@@ -1,27 +0,0 @@
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# RFC: Drop the `image` content block until a path can honor it
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Status: proposed
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## Problem
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`ImageBlock` (`packages/llm/llm/src/types.ts`) has no production producer, and every consumer on every path DROPS it: the deepseek adapter's serializer skips image blocks (a documented MVP limitation), the pi-ai converter skips them as unrepresentable, the ACP codec neither advertises image prompt capability nor forwards image blocks outbound and REJECTS image prompt content inbound, and the compaction estimator charges a flat token constant and renders `[image]`. An `ImageBlock` constructed today would silently vanish from the wire — the vocabulary advertises a capability no path honors, which is the silent-data-loss shape AGENTS.md's defensive patterns warn against. The only constructors anywhere are tests pinning the skip/drop/estimate branches.
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## Proposal
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Remove `ImageBlock`, its `ContentBlockMap` entry, the explicit `image` estimate/placeholder arms in compact-basic, and the image-naming comments in the deepseek serializer's, pi-ai converter's, and ACP codec's default arms — those default arms already absorb the case the way they absorb any unknown block type. Update the vocabulary line in [architecture.md](../../../architecture.md), the block list in `packages/llm/llm/README.md`, the deepseek README's image-skip row, the pi-ai README's images-not-representable row, the compact-basic README's image-estimation and `[image]`-placeholder rows, the pastes in [core.md](../../../core-data-structures/core.md) and [llm-streaming.md](../../../core-data-structures/llm-streaming.md), and the type-equiv manifest; amend the [content-block vocabulary RFC](../../implemented/architecture/2026-06-11-content-block-vocabulary.md)'s block list and multimodal-home consequence per [implemented/AGENTS.md](../../implemented/AGENTS.md); drop or retarget the tests that construct image blocks to exercise the removed branches. The ACP codec's inbound rejection of image PROMPT content is unaffected — that guard is about protocol content a client can send regardless of our vocabulary, and it stays.
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## Why not keep it?
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This is the most contested cut in the batch. Multimodal input (screenshots) is a plausible near-term coding-agent feature, and the [content-block vocabulary RFC](../../implemented/architecture/2026-06-11-content-block-vocabulary.md) reserved the slot deliberately. Two responses. First, `ContentBlockMap` is merge-extensible by design: a real multimodal feature reintroduces `image` in core in the same coordinated change that maps it in the adapters, advertises and renders it in ACP, and prices it in compaction — the producer and its consumers arrive together, which is how the map is meant to grow. Second, the middle option — keep the type but make adapters throw UNSUPPORTED instead of silently dropping — converts this into exactly the shape the [request-knobs RFC](2026-07-04-drop-inert-request-knobs.md) argues against: surface whose only implementation is rejection. Absence (a compile error at the would-be producer) is strictly clearer than either silent loss or universal throw.
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If review lands on keeping the slot, the fallback this RFC records is: keep `ImageBlock` but replace every silent skip with a loud rejection, and document that policy in the vocabulary — the current silent drop is the one state with no defender.
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## Acceptance criteria
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- No `ImageBlock` / harness `type: 'image'` block construction outside this RFC; the codec's inbound ACP-image rejection still passes its tests.
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- Adapter/codec/compaction switches handle the case through their unknown-block default arms (pinned by the existing plugin-added-block tests where present).
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- Doc pastes, the manifest, and the architecture vocabulary list updated; `pnpm run doc-sync` green.
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## Risks
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Re-adding a core vocabulary type later touches several packages at once — but that coordinated change is the shape a real multimodal feature needs anyway (adapter mapping, ACP advertisement, compaction pricing), and none of it exists today to preserve.
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@@ -28,4 +28,4 @@ The [content-block vocabulary RFC](../../implemented/architecture/2026-06-11-con
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## Risks
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None operational — nothing can construct these values today. The mirror-event removals (recorded in [the boundary-mirror RFC](../../implemented/simplification/2026-06-20-remove-agent-boundary-mirror-events.md) and [the stream-chunk RFC](../../implemented/simplification/2026-07-02-remove-stream-chunk-mirror.md)) touch only transient `agent/*` events, never the durable vocabulary, so there is no collision. Elsewhere in the vocabulary the admission policy already holds: `rejected`, `prompt/blocked`, and `hook/invoked`/`hook/result` each have live producers — this RFC extends the same bar to the three variants that lack one. If the [image-block RFC](2026-07-04-drop-image-content-block.md) ships first, one of the three `cache?` fields leaves with it; the two proposals are independent and compose in either order.
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None operational — nothing can construct these values today. The mirror-event removals (recorded in [the boundary-mirror RFC](../../implemented/simplification/2026-06-20-remove-agent-boundary-mirror-events.md) and [the stream-chunk RFC](../../implemented/simplification/2026-07-02-remove-stream-chunk-mirror.md)) touch only transient `agent/*` events, never the durable vocabulary, so there is no collision. Elsewhere in the vocabulary the admission policy already holds: `rejected`, `prompt/blocked`, and `hook/invoked`/`hook/result` each have live producers — this RFC extends the same bar to the three variants that lack one. If the [image-block RFC](../../implemented/simplification/2026-07-04-drop-image-content-block.md) ships first, one of the three `cache?` fields leaves with it; the two proposals are independent and compose in either order.
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