## What changed
- Add `[skills].max_context_tokens` to override the token budget used to render the available-skills catalog.
- Require a positive value and cap configured budgets at 10,000 tokens.
- Preserve the existing default of 2% of the model context window when the option is unset.
## Testing
- Cover configuration parsing, override behavior, the 10,000-token cap, and catalog rendering within the configured budget.
GitOrigin-RevId: f29ddcb57fc2d800c0006d03e1c33cbe3ab6272d
## Why
Skill catalogs can present shortened package locators, but callers previously had
to expand those aliases before reading a skill.
## What changed
- Resolve catalog aliases automatically when `skills.read` looks up a
model-visible executor or orchestrator skill package.
- Update skill prompts and tool documentation to tell models to pass the listed
package locator directly.
## Testing
- Exercise reading an executor skill through its shortened package locator when
the skills catalog exceeds its context budget.
GitOrigin-RevId: d1cdfd64002510b616146929deb5b7077850b951
## Why
Executor skills required a `skills.list` lookup before their contents could be
read, even when the catalog already identified the skill.
## What changed
- Render executor skill catalog entries as package locators, including shortened
locators when skill roots are aliased.
- Tell the model to pass those packages directly to `skills.read`, while keeping
`skills.list` as the fallback when no package is available.
- Use the shorter package locators when applying the skills context budget.
## Testing
Update catalog, aliasing, budget-pressure, and selected-skill coverage, including
an executor package ID containing a literal backslash.
GitOrigin-RevId: 2ace5e527dc4f29651a8f3214475ccc90d52c73f
## What changed
- Make `package` the only required argument to `skills.read`, resolving the
owning orchestrator or executor catalog automatically.
- Default omitted `resource` values to the package's main `SKILL.md`.
- Render orchestrator skills as package locators and instruct the model to read
them directly without first calling `skills.list`.
- Update skill extension and app-server coverage for direct main-resource
reads, referenced resources, aliases, and the revised tool schema.
GitOrigin-RevId: 9faf57a8d0935566a15094931eaabaa8f0613e9e
## What changed
- Move `SkillLoadOutcome` and its implicit-path indexing into
`codex-skills-extension`.
- Import shared skill types directly from `codex-skills` and keep the skill
prompt size limit with the extension renderer that uses it.
- Remove `codex-core-skills` from the Cargo workspace and dependent crates.
GitOrigin-RevId: 4e9e84909fa2f692bcc94af990bb4671affd776f
## Why
Long executor and orchestrator resource identifiers can consume enough of the
skills context budget to omit otherwise available skills.
## What changed
- Add source-aware root aliases for executor, orchestrator, and host skill
catalogs, including catalogs with a single shared root.
- Select the best combination of aliased catalogs under the shared metadata
budget while accounting for root tables and alias usage instructions.
- Explain how to expand shortened `skill://` locators and accept the resulting
description-shortening warning in app-server coverage.
## Testing
- Add rendering and production-turn coverage for singleton, executor,
orchestrator, host, and combined catalog aliases.
GitOrigin-RevId: c1bc1f3d371eae9526232674060235272cc28f16
## What changed
- Compact executor and orchestrator skill locators under metadata pressure, using provider-specific `e` and `o` aliases alongside host `r` aliases.
- Derive alias roots from executor discovery paths and orchestrator namespaces while preserving host plugin root handling.
- Centralize alias ordering, deduplication, and longest-prefix matching across skill providers.
## Testing
- Cover alias planning, cross-platform executor roots, and host plugin discovery.
GitOrigin-RevId: e7d15bd3891c08ae20170e96c4ad45c76d353707
## What changed
- Move the orchestrator skill catalog from thread context into its own
`orchestrator_skills` world-state section so unchanged catalogs remain
incremental across turns.
- Discover executor, orchestrator, and host catalogs together and render them
against one context-window-aware metadata budget, preserving executor entries
before orchestrator and host entries under pressure.
- Emit catalog metrics and budget warnings when each world-state section is
rendered.
## Testing
- Cover incremental orchestrator catalogs across production turns, combined
catalog budgeting, disabled and unavailable providers, caching, warnings, and
metrics.
GitOrigin-RevId: a0fb25d39dcaf43c978aff9da7972a1206f736e4
## What changed
- Track Agent Plugin manifests through plugin, skill, and MCP loading so their capabilities use format-specific behavior without changing legacy plugins.
- Discover only direct-child skills, exclude app and hook capabilities, isolate MCP data, and reject MCP configuration files that are non-regular or resolve outside the plugin root.
- Bound model-visible skill instructions, plugin instructions, MCP descriptions, schemas, individual tools, and the aggregate Agent Plugin MCP tool set.
- Stop MCP and OAuth redirects when Agent Plugins send configured or authorization headers, while retaining existing redirect behavior for legacy MCP servers.
## Testing
- Add coverage for capability filtering, skill discovery, isolated MCP data and reserved-path expansion, unsafe MCP configuration files, context limits, and redirect handling.
GitOrigin-RevId: c9af66b051269f3226628ca280a58d32c808c38f
## What changed
- Make the skills extension own the catalog prompt templates and rendering path.
- Remove the duplicate core fallback that injected available skills into initial context.
- Update core integration tests to install the skills extension explicitly when they expect model-visible skill context.
GitOrigin-RevId: bbe6b15c4e776a09c98b7f4166426fe4e58434ba
## Why
Host skill path aliases should follow the core skill loader's root discovery
order, independent of how catalog entries are sorted for rendering.
## What changed
- Propagate each host skill root's discovery position into its catalog entries.
- Assign `r0`, `r1`, and subsequent aliases from that position while leaving
entries without an explicit root order last.
## Testing
Added coverage for alias ordering in extension rendering and across consecutive
production turns.
GitOrigin-RevId: 9085a3843c91bf2ce78a378cf5ce4926e9c38eb8
## What changed
- Load and cache the host skill provider catalog during world-state contribution.
- Render host skill listings from that catalog with Core-compatible budgeting, while preserving Core's full prompt injection for selected host skills.
- Reuse the cached host catalog for shadow selection, including when skill listings are disabled.
- Preserve an empty Core-compatible skills fragment when every entry exceeds the metadata budget, and make budget warnings independent of the configured percentage.
## Testing
- Cover provider-backed host listings, selected-skill prompt injection, shadow selection, disabled listings, oversized prompts, empty fragments, metrics, and warnings.
GitOrigin-RevId: b6b2d8ea14386356094cff5783d121d74657e9e3
## What changed
- Allocate 2% of the resolved model context window to skill metadata without
imposing the previous 4,000-token ceiling.
- Keep the 8,000-character fallback when no context window is available.
- Extend catalog rendering coverage to verify that a 400,000-token context
window receives an 8,000-token metadata budget and includes more skills.
GitOrigin-RevId: 5120d462de22fbfe5f9c4ab0d1bb97e51950d4b2
## Why
Rendering host and executor skill catalogs independently allows their combined
metadata to exceed the skills context budget.
## What changed
- Allocate one budget across both catalogs when both contain model-visible
skills.
- Prefer retaining executor skills when budget pressure requires omissions,
while preserving an executor omission marker and reporting when all host
skills were omitted.
- Evaluate absolute and aliased host paths under the shared budget and select
the rendering that best preserves executor entries, total entries, and
descriptions, in that order.
## Testing
Added renderer and production-turn coverage for shared-budget description
shortening, host-first omission, executor omission markers, and alias selection.
GitOrigin-RevId: 30041736a76aa173cb641aa98a876a306cb437d2
## Why
Empty rendered skill catalogs skipped catalog telemetry instead of reporting
zero-valued counts.
## What changed
- Record a default render report when thread, turn-input, or executor catalog
rendering produces no fragment.
- Record zero-valued host world-state metrics when skill instructions are
enabled but no host skills are available.
- Preserve the `catalog_surface` tag so empty host and executor catalogs remain
distinguishable.
## Testing
Add coverage for empty catalog rendering and mixed nonempty-executor,
empty-host world state.
GitOrigin-RevId: f68d65806703c0ded1ece1e5ae1ffaf6d6045126
## What changed
- Add an optional `ExtensionMetrics` capability to thread, turn-input, and world-state contributors, backed by session telemetry in the host.
- Record skill counts, omissions, and truncated description characters for extension-rendered catalogs, tagged by the catalog surface.
- Preserve host session attribution on extension metrics, including the effective model for each turn, and prevent extension tags from overriding host metadata.
- Avoid duplicate host-catalog samples by recording world-state metrics only when the section is published or changes.
## Testing
- Cover metric values and surface tags, session metadata preservation, turn-level model changes, and host world-state publication behavior.
GitOrigin-RevId: 9059e521943a8f81df25a38b03692eddbc1d990d
## What changed
- Add executor authority support to `skills.list` and `skills.read` for skills from selected capability roots.
- Allow `skills.read` to load package-relative resources referenced by an executor skill while keeping reads within the selected package.
- Paginate skill listings and resource contents with bounded response sizes and stale-cursor validation.
- Resolve executor filesystems per sampling step so skill tools use the active selected capability roots.
## Testing
- Extend the app-server executor skill test to list an executor skill, read its main `SKILL.md`, and read a paginated reference resource.
- Cover visibility filtering, metadata bounds, pagination, invalid cursors, package boundaries, and resource size limits.
GitOrigin-RevId: 1b5de95d5d1b9f79c34d2879d6e67f24401e9c29
## Why
Repeated absolute path prefixes consume the bounded skill catalog and can leave
less room for descriptions or later skills.
## What changed
- Track the discovery root for host skills and render shared roots as `r0`,
`r1`, and similar aliases when doing so improves the bounded catalog.
- Include a skill-roots table and alias-aware usage instructions whenever
compact paths are selected.
- Keep absolute, authority-aware locators when aliases provide no benefit or
the catalog contains non-host skills.
## Testing
Added unit and extension coverage for unpressured catalogs, constrained shared
paths, mixed-source catalogs, and plugin-cache root selection.
GitOrigin-RevId: 4196df2c52be27338796065cb2e6434efcfac6d5
## Why
Skill catalog rendering can shorten descriptions or omit enabled skills to fit
the model context budget. Surface these reductions so users know when the
model-visible catalog has lost detail.
## What changed
- Emit a warning with the omitted skill count whenever entries do not fit.
- Warn when description shortening averages more than 100 characters per skill.
- Deduplicate executor catalog warnings across repeated world-state builds in a
turn.
## Testing
- Cover the description-shortening threshold and omission warning text.
- Verify warnings through extension and production-turn catalogs, including
per-turn deduplication.
GitOrigin-RevId: bd7fc3482e5dfd8c79072f772a2f54aa502478d9
## Why
Core-compatible skill catalog output should match the core renderer when the
metadata budget omits entries.
## What changed
- Emit the bounded-catalog omission notice only for `ExtensionCompatible`
rendering.
- Continue tracking omitted entries in `SkillRenderReport` for both policies,
even when `CoreCompatible` produces no fragment because every entry is
omitted.
## Testing
Cover policy-specific omission notices and the case where no minimum skill line
fits within the metadata budget.
GitOrigin-RevId: 79883c15a49c02ff83444ddc272030cb4ddb53c0
## What changed
- Return a `SkillRenderReport` with total, included, and omitted skill counts,
plus truncated description counts and character totals.
- Keep fragment construction separate from rendering so callers can inspect the
report even when the metadata budget is too small to emit a fragment.
## Testing
- Cover partial description truncation, fully omitted entries, and catalogs
whose omission marker does not fit the budget.
GitOrigin-RevId: e73fdbcf77ac73c7209100ff6c9b5862b6a59a54
## Why
Core-compatible catalog rendering needs to preserve the core renderer's skill
priority, including when metadata budgets omit lower-priority entries.
## What changed
- Carry each host skill's `SkillScope` into its catalog entry.
- Under `CoreCompatible`, order visible skills by system, admin, repo, and user
scope, then by name and prompt resource ID.
- Preserve insertion order under `ExtensionCompatible`.
## Testing
Add coverage for propagating host skill scope and for both rendering policies.
GitOrigin-RevId: 9594a177edb2166abf1b5719c51a46fcee000600
## What changed
When even the minimum skill catalog exceeds its metadata budget, render each
included entry without its description. This allows more skill names and
locators to fit before the remaining entries are omitted.
## Testing
Add coverage for extreme budget pressure and verify both the extension and
production-turn catalogs omit descriptions while staying within budget.
GitOrigin-RevId: 72cec10e9587beabbd3d8c6d53b931deb76824e6
## Why
Long skill descriptions can consume the catalog's metadata budget before later
skills are listed, hiding otherwise usable skills from the model.
## What changed
- Reserve space for every skill's name and locator when those minimum lines fit.
- Distribute the remaining token or character budget across descriptions in
round-robin order.
- Fall back to omitting entries only when the minimum catalog cannot fit.
## Testing
Added extension and production-turn coverage that verifies moderate budget
pressure keeps every catalog entry, shortens descriptions evenly, and avoids an
omission marker.
GitOrigin-RevId: 41971e4b47a86863b3839707b5cffcd8d83b888c
## Why
A fixed character limit does not account for the different context-window sizes supported by models.
## What changed
- Budget extension-rendered skill metadata at 2% of the resolved model context window, capped at 4,000 tokens.
- Keep the existing 8,000-character fallback when model context metadata is unavailable.
- Include the omission marker in the budget and still emit it when no skill entry fits.
- Apply the same resolved budget to executor and host skill catalogs assembled for a turn.
## Testing
- Cover proportional and capped budgets, multibyte fallback accounting, and omission-marker behavior.
- Verify through the production turn path that larger model context windows include more catalog entries without exceeding the computed budget.
GitOrigin-RevId: 4667293f1594de4dd605b32b9fa4255d26772c0f
## What changed
- Parameterize skill catalog rendering with explicit core- and extension-compatible description policies.
- Use full skill descriptions for core-compatible output, while extension-compatible output prefers `short_description` and falls back to the full description.
- Keep extension prompt and world-state rendering on the extension-compatible policy.
## Testing
- Add a renderer test covering description selection and fallback for both policies.
GitOrigin-RevId: 5382075f88c25a49a715feb0702a9ab888ec0123
## Summary
- add a false-by-default `include_skills_usage_instructions` model
metadata field
- enable the field for the bundled `gpt-5.5` model metadata
- consume the metadata in both core and extension skill rendering
- remove hardcoded legacy-model matching and its marker plumbing
## Why
Skill descriptions are used in model-visible lists: the default
available-skills catalog that supports implicit selection, and the
on-demand `skills.list` tool response used to discover orchestrator
skills. A single overlong description should not consume a
disproportionate share of either list.
Enforcing the 1024-character limit while loading or migrating skills is
the wrong boundary: it rejects otherwise-valid skills and discards
metadata that non-model consumers and full skill reads may need. Skill
metadata and `SKILL.md` content should remain intact; the cap belongs at
model-visible list rendering boundaries.
## What changed
- Preserve full `description` and `metadata.short-description` values
when loading skills.
- Preserve full external-agent command descriptions during
`source-command-*` migration instead of skipping commands solely because
their descriptions exceed 1024 characters.
- Preserve full normalized orchestrator descriptions in the underlying
skills catalog.
- Cap each description at 1024 Unicode characters when rendering the
default available-skills context in `codex-core-skills` and
`codex-skills-extension`.
- Apply the same cap when serializing descriptions in the model-visible
`skills.list` response.
- Render truncated descriptions as 1021 original characters plus `...`.
- Leave explicit `$skill` injection, `skills.read`, underlying metadata,
and on-disk `SKILL.md` files unchanged and full-fidelity.
## Implicit skill selection
Codex injects a bounded catalog containing each implicitly allowed
skill's name, description, and source locator, together with
instructions to use a skill when the task clearly matches its
description. The model makes that semantic choice; after selecting a
skill, it reads the full `SKILL.md` from its filesystem or provider
resource. Explicit `$skill` mentions remain a separate path that injects
the full skill instructions. For orchestrator skills, `skills.list`
provides bounded discovery metadata before `skills.read` returns the
full selected resource.
## Test plan
- `just test -p codex-core-skills`
- `just test -p codex-skills-extension`
- `just test -p codex-external-agent-migration`
The focused regressions verify that overlong metadata is preserved at
load and migration boundaries while default available-skills rendering
and `skills.list` output produce the 1021-character prefix plus `...`.
## Why
`ext/skills` currently depends on `codex-core` for two host concerns:
reading the concrete `Config` type and borrowing core-owned
model-context fragment types. That coupling prevents the extension from
being assembled independently above core and leaves context that belongs
to the skills feature owned by core.
This stacked PR introduces the host boundary needed for the broader
extension migration while intentionally preserving existing skills
behavior. It is stacked on #27404.
## What changed
- Adds a small public `SkillsExtensionConfig` view and makes skills
installation generic over the host config type.
- Requires the host to map its config into that view; app-server
supplies the current `Config` values.
- Moves the available-skills and selected-skill context fragment
implementations into `ext/skills`, preserving their roles, markers, and
rendered bytes.
- Removes the direct `codex-core` dependency from
`codex-skills-extension`.
- Keeps local discovery, invocation, side effects, and the
`codex-core-skills` compatibility types unchanged for later staged PRs.
## Behavior
This adds no capability and is intended to have no user-visible or
model-visible behavior change. The install API and ownership boundary
change internally; emitted skills context remains byte-for-byte
compatible.
## Validation
- Updates the skills extension integration coverage to use a host-owned
test config.
- Asserts the complete rendered catalog and selected-skill fragments,
including their roles and markers.
- `just bazel-lock-check`
- Rust tests and Clippy were not run locally per request; CI will run
them.
## Why
Hosted skills introduced by #27388 use opaque `skill://` resource
identifiers, but the skills catalog rendered every locator as a `file`
and told the model that every skill body lived on disk. That can send
the model toward filesystem tools for a resource that must instead be
read through its owning authority.
The catalog should describe how each source is accessed without changing
the underlying discovery or invocation behavior.
## What changed
- Render host skills as `file`, executor-owned skills as `environment
resource`, orchestrator-owned skills as `orchestrator resource`, and
custom-provider skills as `custom resource`.
- Update the shared no-alias guidance to describe source locators rather
than assuming every skill is stored on the host filesystem.
- Direct orchestrator resources through `skills.list` and `skills.read`,
and explicitly tell the model not to treat `skill://` identifiers as
filesystem paths.
- Preserve the existing filesystem and alias behavior for local skills.
## Scope
This PR changes only model-visible catalog rendering and guidance. It
does not change skill discovery, selection, prompt injection, provider
routing, catalog caching or refresh behavior, resource validation, or
the `skills.*` tool contract.
## Verification
- Extended skills-extension coverage for host-file and executor-resource
labels.
- Extended the no-executor app-server flow to assert
orchestrator-resource wording and non-filesystem guidance.
## Why
#27198 made the extension-owned `codex_apps` MCP connection the hosted
plugin runtime, but its `mcp/skill` resources still bypassed the skills
extension. App-server could list and read those resources through
generic MCP APIs, but a thread with no selected environment did not
expose them in the model's skills catalog or load their `SKILL.md`
through `$skill`.
Hosted skills should stay remote while using the same typed catalog,
source authority, deduplication, bounded contextual catalog, and
selected-skill prompt injection as host and executor skills. They should
not be downloaded or exposed as ambient filesystem paths.
## What changed
- Add a session-scoped `McpResourceClient` over the replaceable MCP
connection manager so resource list/read calls follow startup and
refresh replacements.
- Add a `BackendSkillProvider` that pages `codex_apps` resources,
accepts bounded and validated `mcp/skill` entries, and reads a selected
skill's `SKILL.md` through the same MCP connection.
- Register the remote provider in app-server and include it in the
skills catalog even when a thread has no selected capability roots or
executor.
- Contribute hosted skill metadata through the bounded
`AvailableSkillsInstructions` developer-context path, exclude remote
entries from per-turn catalog injection, and classify `<skills>`
messages as contextual developer content so rollback can trim and
rebuild them correctly.
## Testing
- Extend the app-server MCP resource integration test with
`environments: []` to exercise two-page discovery, filter a
non-`mcp/skill` resource, verify the escaped developer catalog entry and
user-role `<skill>` fragment containing the fetched `SKILL.md`, and
preserve generic MCP resource reads.
- Add core event-mapping coverage that classifies `<skills>` developer
messages as contextual history.
## Why
CCA is moving toward a split runtime where the orchestrator may not have
a filesystem, while executors can expose preinstalled plugins and
skills. A thread therefore needs to select capabilities without asking
app-server or core to interpret executor-owned paths through the
orchestrator's filesystem.
The longer-term model is broader than executor skills:
- A plugin is a bundle of skills, MCP servers, connectors/apps, and
hooks.
- A plugin root can be local, executor-owned, or hosted by a backend.
- Components inside one plugin can use different access and execution
mechanisms. A skill may be read from a filesystem or through backend
tools; an HTTP MCP server can run without an executor; a stdio MCP
server or hook needs an execution environment.
- Core should carry generic extension initialization data. The extension
that owns a component should discover it, expose it to the model, and
invoke it through the appropriate runtime.
This PR establishes that architecture through one complete vertical:
selecting a root on an executor, discovering the skills beneath it,
exposing those skills to the model, and reading an explicitly invoked
`SKILL.md` through the same executor.
## Contract
`thread/start` gains an experimental `selectedCapabilityRoots` field:
```json
{
"selectedCapabilityRoots": [
{
"id": "deploy-plugin@1",
"location": {
"type": "environment",
"environmentId": "workspace",
"path": "/opt/codex/plugins/deploy"
}
}
]
}
```
The root is intentionally not classified as a "plugin" or "skill" in the
API. It can point at a standalone skill, a directory containing several
skills, or a plugin containing skills and other components. This PR only
teaches the skills extension how to consume it; later extensions can
resolve MCP, connector, and hook components from the same selection.
The platform-supplied `id` is stable selection identity. The location
says which runtime owns the root and gives that runtime an opaque path.
App-server does not inspect or canonicalize the path.
## What changed
### Generic thread extension initialization
App-server converts selected roots into `ExtensionDataInit`. Core
carries that generic initialization value until the final thread ID is
known, then creates thread-scoped `ExtensionData` before lifecycle
contributors run.
This keeps `Session` and core independent of the capability-selection
contract. The initialization value is consumed during construction; it
is not retained as another long-lived `Session` field.
### Executor-backed skills
The skills extension now owns an `ExecutorSkillProvider` that:
- resolves the selected environment through `EnvironmentManager`
- discovers, canonicalizes, and reads skills through that environment's
`ExecutorFileSystem`
- contributes the bounded selected-skill catalog as stable developer
context
- reads an explicitly invoked skill body through the authority that
listed it
- warns when an environment or root is unavailable
- never falls back to the orchestrator filesystem for an executor-owned
root
Skill catalog and instruction fragments have hard byte bounds, which
also bound them below the 10K-token per-item context limit. If a
selected executor skill has the same name as a legacy local skill, the
executor selection owns that invocation and the local body is not
injected a second time.
Existing local and bundled skill loading remains in place. Omitting
`selectedCapabilityRoots` therefore preserves current local-only
behavior.
## Current semantics
- Only environment-owned locations are represented in this first
contract.
- Roots are resolved by the destination extension, not by app-server or
core.
- An unavailable executor or invalid root produces a warning and no
capabilities from that root; it does not trigger a local-filesystem
fallback.
- Selection applies to a newly started active thread.
- MCP servers, connectors, and hooks beneath a selected plugin root are
not activated yet.
- Selection is not yet persisted or inherited across resume, fork, or
subagent creation. Existing local capabilities continue to behave as
they do today in those flows.
## Planned vertical follow-ups
1. **Hosted HTTP MCP:** add an extension-backed HTTP MCP source that
works without an executor, then replace the special-purpose MCP plugins
loader with that implementation.
2. **Executor MCP:** register and execute stdio MCP servers through the
environment that owns the selected plugin root.
3. **Backend skills:** add a hosted skill source whose catalog and
bodies are accessed through extension tools rather than a filesystem.
4. **Connectors and hooks:** activate those components through their
owning extensions, using the same selected-root boundary and
component-specific runtime.
5. **Durable selection:** define the desired-selection lifecycle,
persist it, and make resume, fork, and subagent inheritance explicit
rather than accidental.
6. **Local convergence:** incrementally route existing local plugin,
skill, and MCP loading through the same extension model while preserving
current local behavior.
Each follow-up remains reviewable as an end-to-end capability. The
platform selects roots, generic thread extension data carries the
selection, and the owning extension resolves and operates its component.
## Verification
Coverage added for:
- app-server end-to-end discovery and explicit invocation of a skill
inside an executor-selected plugin root
- exclusive invocation when a selected executor skill collides with a
local skill name
- executor filesystem authority for discovery, canonicalization, and
reads
- thread extension initialization before lifecycle contributors run
- stable executor catalog context, explicit invocation, context
rebuilding, hidden skills, and preserved host/remote catalog behavior
Targeted protocol, core-skills, skills-extension, core lifecycle, and
app-server executor-skill tests were run during development.
## Why
The skills extension needs a real turn-time path before host, executor,
or remote skills can be routed through it. The previous code was mostly
a placeholder catalog/provider sketch, so there was no bounded
available-skills fragment, no source-owned `SKILL.md` read, and no place
for warnings or per-turn selection state to live.
This PR makes `ext/skills` the authority-preserving flow for listing
candidate skills and injecting only explicitly selected main prompts,
without adding more of that logic to `codex-core`.
## What changed
- Expands catalog entries with `main_prompt`, display path, short
description, dependency metadata, enabled/prompt visibility flags, and
authority/package-aware read requests.
- Replaces the placeholder `providers/*` modules with
`SkillProviderSource` and `SkillProviders`, routing list/read/search
calls by source kind and surfacing provider failures as warnings.
- Adds bounded available-skills rendering and `SKILL.md` main-prompt
truncation before the fragments enter model context.
- Resolves explicit skill selections from structured `UserInput::Skill`,
skill-file mentions, `skill://...` paths, and plain `$skill` text
mentions, then reads selected prompts through their owning provider.
- Stores mutable per-thread skills config and per-turn
catalog/selection/warning state.
- Adds `install_with_providers` so tests and future host wiring can
supply concrete providers.
## Testing
- Not run locally.
- Added `codex-rs/ext/skills/tests/skills_extension.rs` coverage for
available-catalog injection, selected prompt injection through the
owning provider, and prompt-hidden skills that remain invokable.
jif