diff --git a/cli/src/guidance/skills.gen.ts b/cli/src/guidance/skills.gen.ts
index 99e5c4abdb..7e5593f13d 100644
--- a/cli/src/guidance/skills.gen.ts
+++ b/cli/src/guidance/skills.gen.ts
@@ -5265,8 +5265,9 @@ input, read by the agent.
 
 **Wire the provider field by field, or the chat cannot change its model.** Each \`provider\` field fed
 by a flow input becomes a control in the composer — a provider picker, a model list, a thinking
-slider — while a field left static is fixed and shown read-only. \`user_attachments\` works the same
-way: point it at an s3-object input and the composer gets a paperclip.
+slider — while a field left static is fixed, and the composer draws no control for it.
+\`user_attachments\` works the same way: point it at an s3-object input and the composer gets a
+paperclip.
 
 \`\`\`json
 {
diff --git a/frontend/src/lib/components/AIReasoningEffortPicker.svelte b/frontend/src/lib/components/AIReasoningEffortPicker.svelte
index 3ebf94c9bf..39b4e80011 100644
--- a/frontend/src/lib/components/AIReasoningEffortPicker.svelte
+++ b/frontend/src/lib/components/AIReasoningEffortPicker.svelte
@@ -27,7 +27,7 @@
 	let capability = $derived(
 		provider && model
 			? getReasoningCapability(provider, model)
-			: { supported: false, levels: [], canDisable: false }
+			: { supported: false, levels: [], canDisable: false, known: false }
 	)
 
 	// The token that turns reasoning off on a model that reasons by default
diff --git a/frontend/src/lib/components/copilot/ChatModelSettings.svelte b/frontend/src/lib/components/copilot/ChatModelSettings.svelte
index e60e4f1181..cb859db3ff 100644
--- a/frontend/src/lib/components/copilot/ChatModelSettings.svelte
+++ b/frontend/src/lib/components/copilot/ChatModelSettings.svelte
@@ -31,7 +31,7 @@
 	const capability = $derived(
 		reasoning
 			? getReasoningCapability(reasoning.provider, reasoning.model)
-			: { supported: false, levels: [] as string[], canDisable: false }
+			: { supported: false, levels: [] as string[], canDisable: false, known: false }
 	)
 	// Effective effort accounts for the default-on level on capable models.
 	const effective = $derived(
diff --git a/frontend/src/lib/components/copilot/reasoningRegistry.test.ts b/frontend/src/lib/components/copilot/reasoningRegistry.test.ts
index b4c935bcaa..faf6f60264 100644
--- a/frontend/src/lib/components/copilot/reasoningRegistry.test.ts
+++ b/frontend/src/lib/components/copilot/reasoningRegistry.test.ts
@@ -77,9 +77,9 @@ describe('supportsReasoning (static registry)', () => {
 		}
 		// Bedrock translates the same sentinel on its Converse path, but only for
 		// Opus 5 — AWS documents Bedrock's Sonnet 5 as always thinking.
-		expect(
-			getReasoningCapability('aws_bedrock', 'global.anthropic.claude-opus-5').canDisable
-		).toBe(true)
+		expect(getReasoningCapability('aws_bedrock', 'global.anthropic.claude-opus-5').canDisable).toBe(
+			true
+		)
 		expect(
 			resolveRequestReasoning({
 				provider: 'aws_bedrock',
@@ -189,13 +189,29 @@ describe('supportsReasoning (static registry)', () => {
 		expect(supportsReasoning('mistral', 'mistral-medium-3.5')).toBe(true)
 		expect(getReasoningCapability('mistral', 'mistral-medium-3-5').canDisable).toBe(true)
 	})
-	it('returns no levels for providers without a registry entry', () => {
+	it('returns no levels for a model its provider family has no entry for', () => {
+		// The family is known, so the `false` is an answer: codestral does not reason.
 		expect(getReasoningCapability('mistral', 'codestral-latest')).toEqual({
 			supported: false,
 			levels: [],
-			canDisable: false
+			canDisable: false,
+			known: true
 		})
 	})
+
+	// `customai` fronts any OpenAI-compatible endpoint, so `supported: false` there is an
+	// absence of rules rather than a fact about the model. A caller that shows the reader
+	// "this model cannot think" has to tell the two apart.
+	it('admits when it has no rules for the provider at all', () => {
+		expect(getReasoningCapability('customai', 'deepseek-r1')).toEqual({
+			supported: false,
+			levels: [],
+			canDisable: false,
+			known: false
+		})
+		expect(getReasoningCapability('openai', 'gpt-4o').known).toBe(true)
+		expect(getReasoningCapability('anthropic', 'claude-sonnet-5').known).toBe(true)
+	})
 	it('only offers off where the model can truly disable thinking', () => {
 		// Gemini Pro enforces a thinking floor — no off option.
 		expect(getReasoningCapability('googleai', 'gemini-2.5-pro').canDisable).toBe(false)
diff --git a/frontend/src/lib/components/copilot/reasoningRegistry.ts b/frontend/src/lib/components/copilot/reasoningRegistry.ts
index 95a00e28c8..242f6cb329 100644
--- a/frontend/src/lib/components/copilot/reasoningRegistry.ts
+++ b/frontend/src/lib/components/copilot/reasoningRegistry.ts
@@ -231,14 +231,35 @@ export type ReasoningCapability = {
 	 * level, making the switch a lie.
 	 */
 	canDisable: boolean
+	/**
+	 * Whether `supported` is an answer or an absence of one. The registry has rules per
+	 * provider family and falls through to `false` for the rest — `customai` above all,
+	 * which fronts any OpenAI-compatible endpoint and may well serve a thinking model. A
+	 * caller that presents `supported: false` as a fact must check this first, or it tells
+	 * the reader a model cannot think when all we know is that we have never heard of it.
+	 */
+	known: boolean
 }
 
+/** Provider families the registry has real rules for; everything else is a shrug. */
+const KNOWN_REASONING_FAMILIES: ReadonlySet<string> = new Set([
+	'anthropic',
+	'aws_bedrock',
+	'openai',
+	'azure_openai',
+	'openrouter',
+	'googleai',
+	'deepseek',
+	'mistral'
+])
+
 /** Resolve the reasoning capability of a model from the static registry. */
 export function getReasoningCapability(provider: AIProvider, model: string): ReasoningCapability {
 	const bareModel = stripLegacyThinkingSuffix(model)
+	const known = KNOWN_REASONING_FAMILIES.has(reasoningProviderFamily(provider, bareModel))
 	const supported = supportsReasoningStatic(provider, bareModel)
 	if (!supported) {
-		return { supported: false, levels: [], canDisable: false }
+		return { supported: false, levels: [], canDisable: false, known }
 	}
 	const family = reasoningProviderFamily(provider, bareModel)
 	const levels =
@@ -251,7 +272,7 @@ export function getReasoningCapability(provider: AIProvider, model: string): Rea
 					: family === 'openrouter'
 						? openrouterReasoningLevels(bareModel)
 						: (PROVIDER_REASONING_LEVELS[family] ?? ['low', 'medium', 'high'])
-	return { supported, levels, canDisable: canDisableReasoning(provider, bareModel) }
+	return { supported, levels, canDisable: canDisableReasoning(provider, bareModel), known }
 }
 
 /**
@@ -362,15 +383,11 @@ export function explicitOffToken(provider: AIProvider, model: string): Reasoning
 			// real off there and stays the wire form. Only the 5 family, which
 			// thinks when the field is absent, needs the explicit disable —
 			// Fable and Mythos reject it outright and get no off token at all.
-			return /claude-(opus|sonnet)-5/.test(model.toLowerCase())
-				? ANTHROPIC_OFF_SENTINEL
-				: undefined
+			return /claude-(opus|sonnet)-5/.test(model.toLowerCase()) ? ANTHROPIC_OFF_SENTINEL : undefined
 		case 'aws_bedrock':
 			// Bedrock's Sonnet 5 cannot be disabled at all, so only Opus 5 gets
 			// the sentinel; the rest keep omission.
-			return model.toLowerCase().includes('claude-opus-5')
-				? ANTHROPIC_OFF_SENTINEL
-				: undefined
+			return model.toLowerCase().includes('claude-opus-5') ? ANTHROPIC_OFF_SENTINEL : undefined
 		case 'googleai':
 			// Gemini 2.5/3 think by default (dynamic budget / level). The backend
 			// proxy maps 'none' to off on Flash, or the floor on Pro (only
diff --git a/frontend/src/lib/components/flows/conversations/FlowChatInterface.svelte b/frontend/src/lib/components/flows/conversations/FlowChatInterface.svelte
index 4cb4ded994..b19f2702f8 100644
--- a/frontend/src/lib/components/flows/conversations/FlowChatInterface.svelte
+++ b/frontend/src/lib/components/flows/conversations/FlowChatInterface.svelte
@@ -8,7 +8,8 @@
 	import Modal from '$lib/components/common/modal/Modal.svelte'
 	import SchemaForm from '$lib/components/SchemaForm.svelte'
 	import { type DynamicInput } from '$lib/utils'
-	import { type FlowModule } from '$lib/gen'
+	import { type AIProvider, type FlowModule } from '$lib/gen'
+	import { getReasoningCapability } from '$lib/components/copilot/reasoningRegistry'
 	import { useWorkspaceStorageConfigured } from '$lib/components/inputTransformEnv.svelte'
 	import { workspaceStore } from '$lib/stores'
 	import FlowChatModelSettings from './FlowChatModelSettings.svelte'
@@ -73,6 +74,21 @@
 	// chat says what to go and do instead of offering controls that write nowhere.
 	const modelGap = $derived(agentModelGap(modelWiring))
 
+	// Whether the reasoning registry has rules for the model in use. Only then does the
+	// model button show a thinking control and own the effort input; on a provider it cannot
+	// speak for — `customai` fronting any OpenAI-compatible endpoint, say — the field stays
+	// in the Configure-inputs modal rather than being hidden behind a control never drawn.
+	const effortKnown = $derived.by(() => {
+		if (!modelWiring || modelWiring.whole) return false
+		const pick = (field: 'model' | 'kind') => {
+			const name = modelWiring.fields[field]
+			return name ? effectiveInputs[name] : modelWiring.fixed[field]
+		}
+		const [kind, model] = [pick('kind'), pick('model')]
+		if (typeof kind !== 'string' || !kind || typeof model !== 'string' || !model) return false
+		return getReasoningCapability(kind as AIProvider, model).known
+	})
+
 	// LocalStorage helpers
 	const STORAGE_KEY_PREFIX = 'windmill_flow_chat_inputs_'
 
@@ -144,7 +160,7 @@
 		attachmentsTarget: () => attachmentsTarget,
 		workspace: () => chatWorkspace,
 		canAttach: () => workspaceStorage.current,
-		inputsShownInComposer: () => agentModelWiringInputs(modelWiring),
+		inputsShownInComposer: () => agentModelWiringInputs(modelWiring, effortKnown),
 		inputsSchema: () => additionalInputsSchema
 	})
 	setChatViewHost(chatHost)
@@ -162,7 +178,7 @@
 			// The paperclip's own condition, not half of it: an attachments input the composer
 			// has no editor for — no object storage in the workspace, say — stays askable here.
 			...(chatHost.supportsMessageAttachments && attachmentsTarget ? [attachmentsTarget.name] : []),
-			...agentModelWiringInputs(modelWiring)
+			...agentModelWiringInputs(modelWiring, effortKnown)
 		])
 		const properties = Object.fromEntries(
 			Object.entries(additionalInputsSchema.properties ?? {}).filter(([key]) => !promoted.has(key))
diff --git a/frontend/src/lib/components/flows/conversations/FlowChatModelSettings.svelte b/frontend/src/lib/components/flows/conversations/FlowChatModelSettings.svelte
index 61a623c4d7..389dfe7d57 100644
--- a/frontend/src/lib/components/flows/conversations/FlowChatModelSettings.svelte
+++ b/frontend/src/lib/components/flows/conversations/FlowChatModelSettings.svelte
@@ -148,21 +148,32 @@
 		}
 	})
 
+	/** Whether the registry can speak for this model at all. On a provider it has no rules
+	 * for the answer is "we do not know", and the composer neither shows a thinking control
+	 * nor touches the stored effort — the Configure-inputs modal keeps asking for it. */
+	const effortKnown = $derived(
+		!!provider &&
+			typeof model === 'string' &&
+			!!model &&
+			getReasoningCapability(provider, model).known
+	)
+
 	/**
-	 * The effort to write alongside a new model, which is `''` — the agent's "no effort" —
-	 * wherever that model has no such level. The composer owns this input, so it keeps it
-	 * runnable rather than leaving behind a level the provider would reject; the slider
-	 * shows the model cannot think, and the reader has nothing to clear by hand.
+	 * The effort to write alongside a new model: `''` — the agent's "no effort" — wherever
+	 * that model has no such level, so the composer never leaves behind a level the provider
+	 * would reject. Writes nothing where the registry cannot speak for the model, since
+	 * clearing a value on a guess would destroy the author's own default.
 	 */
-	function effortFor(nextModel: string | undefined): string {
-		if (!provider || !nextModel) return ''
-		return (
-			carriedReasoning(
-				typeof effort === 'string' ? effort : undefined,
-				explicitOffToken(provider, nextModel) ?? '',
-				getReasoningCapability(provider, nextModel)
-			) ?? ''
+	function effortPatch(nextModel: string | undefined): Partial<Record<ProviderField, any>> {
+		if (!provider || !nextModel) return {}
+		const capability = getReasoningCapability(provider, nextModel)
+		if (!capability.known) return {}
+		const carried = carriedReasoning(
+			typeof effort === 'string' ? effort : undefined,
+			explicitOffToken(provider, nextModel) ?? '',
+			capability
 		)
+		return { reasoning_effort: carried ?? '' }
 	}
 
 	function selectResource(path: string, picked: AIProvider) {
@@ -171,9 +182,10 @@
 			resource: `$res:${path}`,
 			// The models of one provider mean nothing to another, and the new list only
 			// arrives async, so there is nothing to carry the current one against — nor the
-			// effort, which only means something against a model.
+			// effort, which only means something against a model. Cleared only where the
+			// registry can speak for the new provider, for the same reason as `effortPatch`.
 			model: undefined,
-			reasoning_effort: ''
+			...(getReasoningCapability(picked, '').known ? { reasoning_effort: '' } : {})
 		})
 	}
 
@@ -222,7 +234,7 @@
 							key: m,
 							label: m,
 							selected: m === model,
-							onSelect: () => setFields({ model: m, reasoning_effort: effortFor(m) })
+							onSelect: () => setFields({ model: m, ...effortPatch(m) })
 						})),
 						loading: models.loading,
 						emptyMessage: provider ? 'No model available' : 'Pick a provider first'
@@ -232,7 +244,7 @@
 		// Offered as a slider only where the flow exposed it. When nothing is editable the
 		// menu never opens, so passing it there only names the effort on the button.
 		reasoning:
-			(effortEditable || readOnly) && provider && typeof model === 'string' && model
+			(effortEditable || readOnly) && effortKnown && provider && typeof model === 'string' && model
 				? {
 						provider,
 						model,
diff --git a/frontend/src/lib/components/flows/conversations/agentChatInputs.test.ts b/frontend/src/lib/components/flows/conversations/agentChatInputs.test.ts
index d2a025364e..00c5ec9440 100644
--- a/frontend/src/lib/components/flows/conversations/agentChatInputs.test.ts
+++ b/frontend/src/lib/components/flows/conversations/agentChatInputs.test.ts
@@ -142,11 +142,24 @@ describe('agentModelWiringInputs', () => {
 		expect(agentModelWiringInputs(wiring)).toEqual(['m'])
 	})
 
+	// The registry has rules per provider family and shrugs at the rest, so a `customai`
+	// endpoint — which may well serve a thinking model — must keep its effort input askable
+	// rather than hidden behind a slider the button never draws.
+	it('keeps a reasoning_effort input where the registry cannot speak for the model', () => {
+		const wiring = resolveAgentModelWiring([
+			agent(
+				`({ "kind": "customai", "resource": "$res:u/admin/custom", model: flow_input.m, reasoning_effort: flow_input.thinking })`
+			)
+		])
+		expect(agentModelWiringInputs(wiring, false)).toEqual(['m'])
+		expect(agentModelWiringInputs(wiring, true)?.sort()).toEqual(['m', 'thinking'])
+	})
+
 	it('hides a kind input it writes with the resource', () => {
 		const wiring = resolveAgentModelWiring([
 			agent(`({ kind: flow_input.k, resource: flow_input.r, model: flow_input.m })`)
 		])
-		expect(agentModelWiringInputs(wiring)?.sort()).toEqual(['k', 'm', 'r'])
+		expect(agentModelWiringInputs(wiring, true)?.sort()).toEqual(['k', 'm', 'r'])
 	})
 })
 
diff --git a/frontend/src/lib/components/flows/conversations/agentChatInputs.ts b/frontend/src/lib/components/flows/conversations/agentChatInputs.ts
index d2640b27c9..9e155e806e 100644
--- a/frontend/src/lib/components/flows/conversations/agentChatInputs.ts
+++ b/frontend/src/lib/components/flows/conversations/agentChatInputs.ts
@@ -294,18 +294,24 @@ export function agentModelGap(wiring: AgentModelWiring | undefined): string | un
  * resource leaves the button nothing to write it with, and hiding it would leave the run
  * without a provider kind and no way to supply one.
  *
- * `reasoning_effort` is unconditional by contrast. Once a model is chosen the button has a
- * control for it — the slider, or the row saying the model cannot think — and on a model
- * that cannot, the value is not a choice but a fact the button writes itself. Offering it in
- * the modal as well would invite setting a level the provider then rejects. Before a model
- * is chosen it is offered nowhere, which is the honest answer: an effort means nothing
- * until there is something to spend it on, and picking a model writes one.
+ * `reasoning_effort` follows the same shape, keyed on whether the reasoning registry can
+ * speak for the model in use. Where it can, the button owns the field — the slider, or the
+ * row saying the model cannot think, on which the value is not a choice but a fact the
+ * button writes itself — and offering it in the modal too would invite setting a level the
+ * provider rejects. Where it cannot (a `customai` endpoint, say, which may well serve a
+ * thinking model), the button shows no thinking control at all, so the modal has to keep
+ * asking. Before a model is chosen nothing is known either, which is the same answer.
  */
-export function agentModelWiringInputs(wiring: AgentModelWiring | undefined): string[] {
+export function agentModelWiringInputs(
+	wiring: AgentModelWiring | undefined,
+	/** Whether the registry can answer for the model in use. False when it cannot be told. */
+	effortKnown: boolean = false
+): string[] {
 	if (!wiring) return []
 	if (wiring.whole) return [wiring.whole]
-	const driven: ProviderField[] = ['resource', 'model', 'reasoning_effort']
+	const driven: ProviderField[] = ['resource', 'model']
 	if (wiring.fields.resource !== undefined) driven.push('kind')
+	if (effortKnown) driven.push('reasoning_effort')
 	return driven.map((field) => wiring.fields[field]).filter((name): name is string => !!name)
 }
 
diff --git a/frontend/src/lib/components/flows/conversations/flowChatViewHost.svelte.ts b/frontend/src/lib/components/flows/conversations/flowChatViewHost.svelte.ts
index e84a50372a..2600fa06be 100644
--- a/frontend/src/lib/components/flows/conversations/flowChatViewHost.svelte.ts
+++ b/frontend/src/lib/components/flows/conversations/flowChatViewHost.svelte.ts
@@ -135,16 +135,24 @@ function toDisplayMessage(
 }
 
 /**
- * Whether the turn a user message started came back unsuccessful. The answer is on
- * the messages that follow it, up to the next user message: an AI agent step or the
- * flow itself writes one with `success` false.
+ * Whether the turn a user message started ended without an answer.
+ *
+ * Read from the turn's last row and no other. A tool that fails mid-turn is handed back to
+ * the agent, which routinely recovers and answers, so an unsuccessful tool row says nothing
+ * about the turn — and this drives the Retry button, which in the copilot means "the request
+ * never went through" rather than "something inside it went wrong". Offering it for a turn
+ * that answered would invite running the whole flow a second time, side effects and all.
  */
 function turnFailed(messages: ChatMessage[], userIndex: number): boolean {
+	let last: ChatMessage | undefined
 	for (let i = userIndex + 1; i < messages.length; i++) {
-		if (messages[i].message_type === 'user') return false
-		if (messages[i].success === false) return true
+		const message = messages[i]
+		if (message.message_type === 'user') break
+		// Still going, so the turn has no outcome to report yet.
+		if (message.streaming || message.loading) return false
+		last = message
 	}
-	return false
+	return last?.success === false
 }
 
 /**
diff --git a/system_prompts/auto-generated/flow.md b/system_prompts/auto-generated/flow.md
index 8a2bbbdb8a..d1da49baa9 100644
--- a/system_prompts/auto-generated/flow.md
+++ b/system_prompts/auto-generated/flow.md
@@ -115,8 +115,9 @@ input, read by the agent.
 
 **Wire the provider field by field, or the chat cannot change its model.** Each `provider` field fed
 by a flow input becomes a control in the composer — a provider picker, a model list, a thinking
-slider — while a field left static is fixed and shown read-only. `user_attachments` works the same
-way: point it at an s3-object input and the composer gets a paperclip.
+slider — while a field left static is fixed, and the composer draws no control for it.
+`user_attachments` works the same way: point it at an s3-object input and the composer gets a
+paperclip.
 
 ```json
 {
diff --git a/system_prompts/auto-generated/prompts.ts b/system_prompts/auto-generated/prompts.ts
index d4245c19f9..f09f720c68 100644
--- a/system_prompts/auto-generated/prompts.ts
+++ b/system_prompts/auto-generated/prompts.ts
@@ -146,8 +146,9 @@ input, read by the agent.
 
 **Wire the provider field by field, or the chat cannot change its model.** Each \`provider\` field fed
 by a flow input becomes a control in the composer — a provider picker, a model list, a thinking
-slider — while a field left static is fixed and shown read-only. \`user_attachments\` works the same
-way: point it at an s3-object input and the composer gets a paperclip.
+slider — while a field left static is fixed, and the composer draws no control for it.
+\`user_attachments\` works the same way: point it at an s3-object input and the composer gets a
+paperclip.
 
 \`\`\`json
 {
diff --git a/system_prompts/auto-generated/skills/write-flow/SKILL.md b/system_prompts/auto-generated/skills/write-flow/SKILL.md
index 94588b3eb4..b399620eb4 100644
--- a/system_prompts/auto-generated/skills/write-flow/SKILL.md
+++ b/system_prompts/auto-generated/skills/write-flow/SKILL.md
@@ -203,8 +203,9 @@ input, read by the agent.
 
 **Wire the provider field by field, or the chat cannot change its model.** Each `provider` field fed
 by a flow input becomes a control in the composer — a provider picker, a model list, a thinking
-slider — while a field left static is fixed and shown read-only. `user_attachments` works the same
-way: point it at an s3-object input and the composer gets a paperclip.
+slider — while a field left static is fixed, and the composer draws no control for it.
+`user_attachments` works the same way: point it at an s3-object input and the composer gets a
+paperclip.
 
 ```json
 {
diff --git a/system_prompts/base/flow-base.md b/system_prompts/base/flow-base.md
index f06d90d9e8..133860b319 100644
--- a/system_prompts/base/flow-base.md
+++ b/system_prompts/base/flow-base.md
@@ -115,8 +115,9 @@ input, read by the agent.
 
 **Wire the provider field by field, or the chat cannot change its model.** Each `provider` field fed
 by a flow input becomes a control in the composer — a provider picker, a model list, a thinking
-slider — while a field left static is fixed and shown read-only. `user_attachments` works the same
-way: point it at an s3-object input and the composer gets a paperclip.
+slider — while a field left static is fixed, and the composer draws no control for it.
+`user_attachments` works the same way: point it at an s3-object input and the composer gets a
+paperclip.
 
 ```json
 {