GeezerVison

Extends #30882's model_invocable semantics to workspace skills and to stored skills created through the API.

Claude Code and Xum let skill authors set disable-model-invocation: true in SKILL.md frontmatter, so agents never pick the skill on their own and it runs only when a person invokes it. Coder Agents honored the key only when someone imported a SKILL.md file while adding a project skill (#30884).

What changes

• Workspace skills: when the pinned SKILL.md sets the key to the YAML boolean true, chatd leaves the skill out of <available-skills> before merging sources, so a listed skill with the same name keeps its bare name, and read_skill reports it as not found. The skill stays in the / menu, and invoking it still loads its body. read_skill_file serves its supporting files under the bare name or workspace/<name> and refuses its SKILL.md (case-insensitive, after path.Clean). Skills without the key behave as on the base.
• Invoked workspace skills: invoking a workspace skill now stores the pinned skill directory on the invocation part, and the prompt renders it as dir on <invoked-skill>, escaped as an attribute value. Before, only read_skill gave the model a skill's directory, and it refuses a hidden skill, so a hidden skill could not run the scripts it bundles. The part also stores the chat's workspace, and the prompt shows dir only while the chat stays bound to it, as it does for workspace file references. This changes feat: send skill invocations as structured message parts #30861's invocation code. Hook payloads drop the directory and its workspace like the body, and API responses strip both.
• Stored skills: a create request whose content sets the key and that omits model_invocable stores model_invocable = false. An explicit value wins, and PATCH is unchanged. This covers personal, organization, and project skills, which share createSkill.
• workspacesdk.SkillDisablesModelInvocation reads the key. The CreateSkillRequest.ModelInvocable doc comment, the generated API docs, and extending-agents.md (the SKILL.md format, a new "Turn off automatic use" section, and the notes on the skill index, the skill tools, and aliases) describe the new behavior.

Follow-ups

• The personal and organization skill editors have no "Agents can use it automatically" switch yet. Only the project editor from feat: show project skill actions above project chat composers #30884 has one.

Testing

• Go tests cover the parser, the turn's skill index and aliases, read_skill, read_skill_file, invocation of a hidden skill and the directory it carries (attribute escaping, no directory after the chat changes workspace, no directory in hook payloads), and the create default for personal and organization skills. Each new test fails when its code path is removed.
• Remote dogfood UAT with a real model failed rounds 1 to 3. Rounds 1 and 2 found the hidden SKILL.md still readable through read_skill_file by symlinks and stale pins, plus a bare-name lookup bug and a docs gap that round 2 fixed. Round 3 found that the content check added against those bypasses refused a listed skill's file whose own frontmatter sets the key. After round 3 we narrowed the rule to the hidden skill's SKILL.md path. The key decides what agents are offered (the index and read_skill), not which files they can read: read_file and execute already open any workspace file, so a content check in read_skill_file protected nothing and kept producing edge cases.
• Round 4 passed on c9ff25dc29f. Later commits added a behavior-neutral cleanup (cd617533c2e), one test case from the test audit (044c1e6e23a), and a comment fix (9ec3768b18b), which passed validation without another UAT round. Round 5 passed on 2b518c6c2b1, which adds the skill directory. A real model ran hidden skills' scripts from the dir on <invoked-skill>, including directories whose paths contain &, ', ", < and >, and API responses carried no directory. Merging main after feat: show project skill actions above project chat composers #30884 landed (2d7d3cb9674) did not change this PR's diff, so UAT was not rerun. 8f043b2a342, which shows the directory only while the chat stays bound to the skill's workspace, has Go tests but no UAT round.
• The doc-check skill ran in author self-check mode on 2d7d3cb9674, and 27de7f5c6d7 fixes its findings: the skill index sentence said every skill is listed, the stored-skill sentence claimed any project editor import honors the key and presented the API default as fixed, the API path came before the UI path, and some wording broke the docs style rules. The fix is docs-only, so UAT was not rerun.
• Polish and the test audit stayed inside the implementation diff. No new dependencies.
• Codex review found no major issues on 9ec3768b18b, then raised one P2 on the same head when the PR was marked ready: an invoked hidden skill gets no skill directory. A probe confirmed it, and 2b518c6c2b1 fixes it. Its earlier finding on that head (honor CODER_AGENT_EXP_SKILL_META_FILE) was refuted, because the pinned skill snapshot always reads SKILL.md. Both threads are resolved, and Codex found no major issues on 2b518c6c2b1 or on the merge 2d7d3cb9674.
• On 27de7f5c6d7, Codex raised two P2s. One was confirmed: an invoked skill's directory stayed in the prompt after the chat moved to another workspace, which a prompt test showed on that head, and 8f043b2a342 fixes it. The other was declined: on Windows, scripts\..\SKILL.md gets past the SKILL.md check in read_skill_file, but that check is not an access boundary (read_file opens any path), and Windows has more aliases (SKILL.md., SKILL.md::$DATA, SKILL~1.MD) that normalizing backslashes would not stop. On 8f043b2a342, Codex asked to bind the directory to the workspace build instead. That was declined: every workspace start is a new build with new agent IDs, so the directory would drop after each stop and start, and the pinned body and the live files can diverge without a rebuild anyway, as they do for read_skill. A later request on that head asked to limit a hidden skill's read_skill_file access to invocations in the current workspace. That was declined too: read_skill_file resolves names against the current pin for listed skills on main as well, and the key decides which skills agents are offered, not which files they can read. All four threads are resolved. a697dcd927f adds the format:"uuid" tag that TestSDKFieldsFormatted requires on the new field, and Codex found no major issues on a697dcd927f. ae70b2c533f is docs-only: it applies the doc-check suggestion to say that an invoked skill's directory is included only while the chat stays in that workspace. The author doc-check self-check found no blocking findings on it, and Codex found no major issues on ae70b2c533f.

Xum, an AI agent, opened this PR for @ibetitsmike and wrote this description.