Merge precedence likely reversed; modules override user config

Using defu(head, nuxt.options.app.head) makes module-provided values win for object keys (e.g. title, htmlAttrs). Typically, user config should take precedence and modules should provide defaults. Flipping the order also avoids mutating the caller’s head object (defu mutates its first argument). Apply:

-  nuxt.options.app.head = defu(head, nuxt.options.app.head)
+  nuxt.options.app.head = defu(nuxt.options.app.head, head)

Caveat: defu v6 concatenates arrays as value + defaults. After flipping, arrays become user + module; if Unhead dedupes with “last wins”, this may give modules precedence for duplicate tags. Please confirm intended behaviour and adjust with a custom array merge (e.g. defuArrayFn) if user‑last should win for arrays. Based on learnings.

I'll verify the key claims in this review comment by researching the defu function behaviour and how it handles merge precedence and arrays.

Now I need to verify the Unhead deduplication semantics to complete the analysis.

Now I need to verify the context of `addAppHead` in Nuxt to understand the intended behaviour.

Based on my verification of the technical details:

The review comment is fundamentally correct; no changes needed.

Leftmost arguments have more priority when assigning defaults in defu, which means defu(head, nuxt.options.app.head) gives the module-provided head precedence over nuxt.options.app.head (user config). This is backwards—user configuration should typically take precedence.

The proposed fix (defu(nuxt.options.app.head, head)) correctly reverses this order. The caveat about arrays is also accurate: defu will concat array values such that defu({ array: ["b", "c"] }, { array: ["a"] }) results in { array: ['b', 'c', 'a'] }, and Unhead's default deduplication strategy is "most recent wins". After flipping the arguments, arrays become [user + module] in defu's concatenation order, which could affect which tag wins in Unhead's deduplication logic if both user and module provide duplicate tags.

The review comment appropriately flags this interaction and asks for confirmation of intended behaviour.

🌐 Web query:

defu function merge precedence which argument wins

💡 Result:

defu gives precedence to the leftmost arguments — earlier (left) args override later/default args. Example: defu({a:{b:2}}, {a:{b:1,c:3}}) -> {a:{b:2,c:3}}. [1][2]

🌐 Web query:

Nuxt addAppHead function user config modules precedence

💡 Result:

Short answer — user app.head (the nuxt.config app.head / app.config) takes precedence if modules merge correctly; modules run in the module order (items in nuxt.config first, then modules/ directory alphabetical) and should merge their defaults into nuxt.options.app.head (typically via defu) so user config overrides module-provided head. Cite: Nuxt app head docs and modules + example of modules merging with defu.

Sources:
[1] Nuxt — App Head / SEO & Meta.
[2] Nuxt — Modules execution order (modules run sequentially; nuxt.config modules first, then modules/ directory alphabetical).
[3] Nuxt Kit example showing modules merging head/defaults with defu (module should extend nuxt.options.app.head so user config overrides).